Blog archive

Wed

10

Jul

2019

Latest research in football - week 22 -2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Benefits of a Challenge Approach on Match Day: Investigating Cardiovascular Reactivity in Professional Academy Soccer Players
Reference: Eur J Sport Sci. 2019 Jun 6:1-32. doi: 10.1080/17461391.2019.1629179. [Epub ahead of print]
Authors: Dixon JG, Jones MV, Turner MJ
Summary: This study assessed physiological (cardiovascular) and psychological (confidence, control, and approach focus) data in professional academy soccer players prior to performance in competitive matches. A challenge state is characterised by an increase in cardiac output (CO), and a decrease in total peripheral vascular resistance (TPR). Data were collected from 37 participants, with 19 of these providing data on two separate occasions. Performance was measured using coach and player self-ratings. Challenge reactivity was positively, and significantly, associated with performance. Participants who demonstrated blunted cardiovascular (CV) responses performed significantly worse than participants who displayed either challenge or threat reactivity. There was mixed consistency in CV reactivity for those participants whose data were collected on more than one occasion, suggesting that some participants responded differently across the competitive matches. The association between self-report data and CV responses was weak. This study supports previous research demonstrating that challenge reactivity is associated with superior performance.


#2 First-Stance Phase Force Contributions to Acceleration Sprint Performance in Semi-Professional Soccer Players
Reference: Eur J Sport Sci. 2019 Jun 6:1-23. doi: 10.1080/17461391.2019.1629178. [Epub ahead of print]
Authors: Wdowski MM, Gittoes MJR
Summary: Sprint running is a key determinant of player performance in soccer that is typically assessed and monitored using temporal methods. The aim of this study was to examine the relationship between ground reaction force kinetics at the first step and sprint running performance in soccer players in order to enhance the development of training and assessment methods. Nineteen semi-professional soccer players participated (mean ± s: age 21.1 ± 1.9 years, body mass 79.4 ± 7.3 kg and stature 1.79 ± 0.06 m). The participants completed 20 m acceleration sprint runs as timing gates recorded split times between 0-5 m, 5-10 m, 10-15 m, 15-20 m and 0-20 m. A force plate captured vertical, anteroposterior and mediolateral ground reaction force data (1000 Hz) of the first right foot strike stance phase. Ground reaction force metrics, including peak anteroposterior propulsive force (r = 0.66 to 0.751; P = 0.000 to 0.002), peak vertical ground reaction force (r = 0.456 to 0.464; P = 0.045 to 0.05), average medial-lateral/anteroposterior orientation angle (r =-0.463; P = 0.023), and average anteroposterior/vertical orientation angle (r =-0.44; P = 0.03) were correlated with one or all split times between 0-5 m, 5-10 m, 10-15 m, 15-20 m and 0-20 m. Acceleration sprint running in soccer requires minimised mediolateral and increased anteroposterior loading in the stance phase. Multi-component ground reaction force measures of the first step in acceleration sprint runs are important for developing performance assessments, and understanding force application techniques employed by soccer players.


#3 Body composition, strength static and isokinetic, and bone health: comparative study between active adults and amateur soccer players
Reference: Einstein (Sao Paulo). 2019 May 30;17(3):eAO4419. doi: 10.31744/einstein_journal/2019AO4419. [Article in English, Portuguese]
Authors: Tavares ÓM, Duarte JP, Werneck AO, Costa DC, Sousa-E-Silva P, Martinho D, Luz LGO, Morouço P, Valente-Dos-Santos J, Soles-Gonçalves R, Conde J, Casanova JM, Coelho-E-Silva MJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6533075/pdf/2317-6385-eins-17-03-eAO4419.pdf
Summary: The purpose was to compare tissue composition, total and regional bone mineral content and bone mineral density, static hand grip and knee joint isokinetic strength between amateur soccer players and Control Group. Cross-sectional study. Air displacement plethysmography was used to estimate body volume and, in turn, density. Body composition, bone mineral content and bone mineral density were assessed for the whole body and at standardized regions using dual energy X-ray absorptiometry. Static grip strength was assessed with an adjustable dynamometer, and peak torque derived from isokinetic strength dynamometer (concentric muscular knee actions at 60°/s). Magnitude of the differences between groups was examined using d-Cohen. Compared to healthy active adults, soccer players showed larger values of whole body bone mineral content (+651g; d=1.60; p<0.01). In addition, differences between groups were large for whole body bone mineral density (d=1.20 to 1.90; p<0.01): lumbar spine, i.e. L1-L4 (+19.4%), upper limbs (+8.6%) and lower limbs (+16.8%). Soccer players attained larger mean values in strength test given by static hand grip protocol (+5.6kg, d=0.99; p<0.01). Soccer adequately regulates body composition and is associated better bone health parameters (bone mineral content and density at whole-body and at particular sites exposed to mechanical loadings).


#4 Exploring simulated driving performance among varsity male soccer players
Reference: Traffic Inj Prev. 2019 Jun 5:1-6. doi: 10.1080/15389588.2019.1601715. [Epub ahead of print]
Authors: Tremblay M, Lavallière M, Albert WJ, Boudreau SR, Johnson MJ
Summary: It is documented that male athletes display riskier behaviors while driving (as well as in life in general) than female athletes and nonathletes. However, the literature has reported that athletes show better driving ability than nonathletes. This paradox between behaviors and abilities motivated the present study to further understand the collision risk of varsity athletes. The current study estimates the performance differences between varsity male soccer players and male undergraduate nonathletes on (1) a driving task and (2) three perceptual-cognitive tasks (associated with collision risk prediction; i.e., Useful Field of View [UFOV] test). Thirty-five male undergraduate students (15 varsity soccer players, 20 undergraduate nonathletes) took part in this study. Driving performance was assessed during 14 min of urban commuting using a driving simulator. While completing the simulated driving task and UFOV test, the physiological responses were monitored using an electrocardiograph (ECG) to document heart rate variability (HRV). Varsity soccer players showed more risky behaviors at the wheel compared to their nonathlete student peers. Varsity soccer players spent more time over the speed limit, committed more driving errors, and adopted fewer safe and legal behaviors. However, no difference was observed between both groups on driving skill variables (i.e., vehicle control, vehicle mobility, ecodriving). For subtests 1 and 2 of the UFOV (i.e., processing speed, divided attention), both groups performed identically (i.e., 17 ms). The nonathlete group tended to perform better on the selective attention task (i.e., subtest 3 of UFOV test; 63.2 ± 6.2 ms vs. 87.2 ± 10.7 ms, respectively; this difference was not significant, P = .76). Preventive driving measures should be enforced in this high-risk population to develop strategies for risk reduction in male team athletes.


#5 Methodological Issues in Soccer Talent Identification Research
Reference: Sports Med. 2019 Jun 3. doi: 10.1007/s40279-019-01113-w. [Epub ahead of print]
Authors: Bergkamp TLG, Niessen ASM, den Hartigh RJR, Frencken WGP, Meijer RR
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-019-01113-w.pdf
Summary: Talent identification research in soccer comprises the prediction of elite soccer performance. While many studies in this field have aimed to empirically relate performance characteristics to subsequent soccer success, a critical evaluation of the methodology of these studies has mostly been absent in the literature. In this position paper, we discuss advantages and limitations of the design, validity, and utility of current soccer talent identification research. Specifically, we draw on principles from selection psychology that can contribute to best practices in the context of making selection decisions across domains. Based on an extensive search of the soccer literature, we identify four methodological issues from this framework that are relevant for talent identification research, i.e. (1) the operationalization of criterion variables (the performance to be predicted) as performance levels; (2) the focus on isolated performance indicators as predictors of soccer performance; (3) the effects of range restriction on the predictive validity of predictors used in talent identification; and (4) the effect of the base rate on the utility of talent identification procedures. Based on these four issues, we highlight opportunities and challenges for future soccer talent identification studies that may contribute to developing evidence-based selection procedures. We suggest for future research to consider the use of individual soccer criterion measures, to adopt representative, high-fidelity predictors of soccer performance, and to take restriction of range and the base rate into account.


#6 Effects of plyometric jump training on the physical fitness of young male soccer players: Modulation of response by inter-set recovery interval and maturation status
Reference: J Sports Sci. 2019 Jun 3:1-8. doi: 10.1080/02640414.2019.1626049. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Sanchez-Sanchez J, Slimani M, Gentil P, Chelly MS, Shephard RJ
Summary: The effects of plyometric jump training on the physical fitness of male youth (age = 10-17 years) soccer players was examined in relation to inter-set recovery intervals and the maturity of the players in a single-blind, randomized-and controlled crossover trial. Jumping tests and kicking velocities were measured before (T0), after a 6 week control period (T1), after 6 weeks of plyometrics (T2), after 6 weeks of wash-out (T3), and after a further 6 weeks of plyometrics (T4). Subjects were divided into pre- and post- peak-height-velocity (PHV) groups, and were randomly assigned to 30 s or 120 s inter-set intervals during periods T2 and T4. Any changes in jumping and maximum kicking velocities during T1 and T3, had trivial effect sizes (0.01-0.15), but small to moderate improvements (effect size = 0.20-0.99) were observed in both groups during T2 and T4. Gains in pre-PHV players were similar for the two inter-set intervals, but gains in post-PHV players were greater (p < 0.05) with an inter-set recovery of 120 s than with a 30 s recovery. We conclude that plyometric jump training improves the physical fitness of adolescents, irrespective of their maturity, but that in older individuals gains are greater with a longer inter-set recovery interval.


#7 How Does the Adjustment of Training Task Difficulty Level Influence Tactical Behavior in Soccer?
Reference: Res Q Exerc Sport. 2019 Jun 3:1-14. doi: 10.1080/02701367.2019.1612511. [Epub ahead of print]
Authors: Machado JC, Barreira D, Teoldo I, Travassos B, Júnior JB, Santos JOLD, Scaglia AJ
Summary: This study aimed to investigate if player tactical skill level and age category influence team performance and player exploratory behavior in tasks with different difficulty levels. In total, 48 youth male soccer players participated in the study (U15, n = 24, mean age = 13.06 ± 1.53 years; U17, n = 24, mean age = 16.89 ± 0.11 years). Player tactical skills were evaluated through the System of Tactical Assessment in Soccer (FUT-SAT), allowing them to be organized into three groups according to tactical efficiency: Higher tactical skill level (Group 01), Intermediate tactical skill level (Group 02), and Lower tactical skill level (Group 03). Next, Group 01 and Group 03 of both categories performed six Small-Sided and Conditioned Games (SSCG) each, namely three High difficulty SSCGs and three Low difficulty SSCGs. Team performance and players' exploratory behavior were analyzed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. We found that team performance and players' exploratory behavior were influenced both by the age and tactical skill level of the players, as well as by task difficulty level. Therefore, in an attempt to improve player performance, practitioners must carefully manipulate key task constraints to adapt training task difficulty levels to player age and tactical skill level.


#8 Influence of Whole-Body Electrostimulation on the Deformability of Density-Separated Red Blood Cells in Soccer Players
Reference: Front Physiol. 2019 May 9;10:548. doi: 10.3389/fphys.2019.00548. eCollection 2019.
Authors: Filipovic A, Bizjak D, Tomschi F, Bloch W, Grau M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6530393/pdf/fphys-10-00548.pdf
Summary: Red blood cell nitric oxide synthase (RBC-NOS) dependent NO production positively affects RBC deformability which is known to improve oxygen supply to the working tissue. Whole-body electrostimulation (WB-EMS) has been shown to improve maximum strength, sprinting and jumping performance, and to increase deformability in elite soccer players during the season. The aim of the present study was to investigate whether WB-EMS affects RBC turnover which might affect overall deformability of circulating RBC by rejuvenation of the RBC population and if this might be related to improved endurance capacity. Thirty male field soccer players were assigned in either a WB-EMS group (EG, n = 10), a training group (TG, n = 10), or a control group (CG, n = 10). EG performed 3 × 10 squat jumps superimposed with WB-EMS twice per week in concurrent to 2-4 soccer training sessions and one match per week. TG only performed 3 × 10 squat jumps without EMS in addition to their soccer routine and the CG only performed the usual soccer training and match per week. Subjects were tested before (Baseline) and in week 7 (wk-7), with blood sampling before (Pre), 15-30 min after (Post), and 24 h after (24 h post) the training. Endurance capacity was determined before and directly after the training period. The key findings of the investigation indicate an increase in young RBC in the EG group along with improved overall RBC deformability, represented by decreased SS1/2:EImax Ratio. Analysis of the different RBC subfractions revealed improved RBC deformability of old RBC during study period. This improvement was not only observed in the EG but also in TG and CG. Changes in RBC deformability were not associated to altered RBC-NOS/NO signaling pathway. Endurance capacity remained unchanged during study period. In summary, the effect of WB-EMS on RBC physiology seems to be rather low and results are only in part comparable to previous findings. According to the lower training volume of the present study it can be speculated that the soccer specific training load in addition to the WB-EMS was too low to induce changes in RBC physiology.


#9 Comparison of Selected CD45+ Cell Subsets' Response and Cytokine Levels on Exhaustive Effort Among Soccer Players
Reference: J Med Biochem. 2019 May 11;38(3):256-267. doi: 10.2478/jomb-2018-0029. eCollection 2019 Jul.
Authors: Kostrzewa-Nowak D, Buryta R, Nowak R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6534948/pdf/jomb-38-256.pdf
Summary: Immunological alterations may led to the reduction in capacity and endurance levels in elite athletes by e.g. increased susceptibility to infections. There is a need to explain the impact of intensive physical effort on the CD4+ memory T cell subsets. Fourteen participants median aged 19 years old (range 17-21 years) were recruited form Pogoń Szczecin S.A., soccer club. They performed progressive efficiency test on mechanical treadmill until exhaustion twice: during preparatory phases to spring and autumn competition rounds. We examined the influence of exhaustive effort on the selected CD45+, especially CD4+ memory T cell subsets and inflammation markers determined before, just after the test and during recovery time. Significant changes in total CD45+ cells and decrease in T lymphocytes percentage after the run was observed. Significant fluctuations in T cells' distribution were related not only to the changes in Th or Tc subsets but also to increase in naïve T cell percentage during recovery. Increase in TNF-α and IL-8 post-exercise, IL-6 and IL-10 plasma levels in recovery was also found. The novel finding of our study is that the run performed on mechanical treadmill caused a significant release of CD4+ T naïve cells into circulation. Post-exercise increase in circulating NK cells is related with fast biological response to maximal effort. However, at the same time an alternative mechanism enhancing inflammation is involved.


#10 Chronic traumatic encephalopathy is a common co-morbidity, but less frequent primary dementia in former soccer and rugby players
Reference: Acta Neuropathol. 2019 Jun 1. doi: 10.1007/s00401-019-02030-y. [Epub ahead of print]
Authors: Lee EB, Kinch K, Johnson VE, Trojanowski JQ, Smith DH, Stewart W
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00401-019-02030-y.pdf
Summary: Chronic traumatic encephalopathy (CTE) is reported at high prevalence in selected autopsy case series of former contact sports athletes. Nevertheless, the contribution of CTE pathology to clinical presentation and its interaction with co-morbid neurodegenerative pathologies remain unclear. To address these issues, we performed comprehensive neuropathology assessments on the brains of former athletes with dementia and considered these findings together with detailed clinical histories to derive an integrated clinicopathological diagnosis for each case. Consecutive, autopsy-acquired brains from former soccer and rugby players with dementia were assessed for neurodegenerative pathologies using established and preliminary consensus protocols. Thereafter, next of kin interviews were conducted to obtain detailed accounts of the patient's clinical presentation and course of disease to inform a final, integrated clinicopathological diagnosis. Neuropathologic change consistent with CTE (CTE-NC) was confirmed in five of seven former soccer and three of four former rugby players' brains, invariably in combination with mixed, often multiple neurodegenerative pathologies. However, in just three cases was the integrated dementia diagnosis consistent with CTE, the remainder having alternate diagnoses, with the most frequent integrated diagnosis Alzheimer's disease (AD) (four cases; one as mixed AD and vascular dementia). This consecutive autopsy series identifies neuropathologic change consistent with preliminary diagnostic criteria for CTE (CTE-NC) in a high proportion of former soccer and rugby players dying with dementia. However, in the majority, CTE-NC appears as a co-morbidity rather than the primary, dementia causing pathology. As such, we suggest that while CTE-NC might be common in former athletes with dementia, in many cases its clinical significance remains uncertain.


#11 Enhanced sprint performance analysis in soccer: New insights from a GPS-based tracking system
Reference: PLoS One. 2019 May 31;14(5):e0217782. doi: 10.1371/journal.pone.0217782. eCollection 2019.
Authors: Reinhardt L, Schwesig R, Lauenroth A, Schulze S, Kurz E
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0217782&type=printable
Summary: The aim of this investigation was to establish the validity of a GPS-based tracking system (Polar Team Pro System, PTPS) for estimating sprint performance and to evaluate additional diagnostic indices derived from the temporal course of the movement velocity. Thirty-four male soccer players (20 ± 4 years) performed a 20 m sprint test measured by timing gates (TG), and while wearing the PTPS. To evaluate the relevance of additional velocity-based parameters to discriminate between faster and slower athletes, the median-split method was applied to the 20-m times. Practical relevance was estimated using standardized mean differences (d) between the subgroups. Differences between the criterion reference (TG) and PTPS for the 10 and 20 m splits did not vary from zero (dt10: -0.01 ± 0.07 s, P = 0.7, d < -0.1; dt20: -0.01 ± 0.08 s, P = 0.4, d < -0.2). Although subgroups revealed large differences in their sprint times (d = -2.5), the average accelerations between 5 and 20 km/h as well as 20 and 25 km/h showed merely small effects (d < 0.5). Consequently, analyses of velocity curves derived from PTPS may help to clarify the occurrence of performance in outdoor sports. Thus, training consequences can be drawn which contribute to the differentiation and individualization of sprint training.


#12 Epidemiology of injuries in professional football: a systematic review and meta-analysis
Reference: Br J Sports Med. 2019 Jun 6. pii: bjsports-2018-099577. doi: 10.1136/bjsports-2018-099577. [Epub ahead of print]
Authors: López-Valenciano A, Ruiz-Pérez I, Garcia-Gómez A, Vera-Garcia FJ, De Ste Croix M, Myer GD, Ayala F
Summary: We performed a systematic review and meta-analysis of epidemiological data of injuries in professional male football. Forty-four studies have reported the incidence of injuries in football. Two reviewers independently extracted data and assessed trial quality using the Strengthening the Reporting of Observational Studies in Epidemiology statement and Newcastle Ottawa Scale. Studies were combined in a pooled analysis using a Poisson random effects regression model. The overall incidence of injuries in professional male football players was 8.1 injuries/1000 hours of exposure. Match injury incidence (36 injuries/1000 hours of exposure) was almost 10 times higher than training injury incidence rate (3.7 injuries/1000 hours of exposure). Lower extremity injuries had the highest incidence rates (6.8 injuries/1000 hours of exposure). The most common types of injuries were muscle/tendon (4.6 injuries/1000 hours of exposure), which were frequently associated with traumatic incidents. Minor injuries (1-3 days of time loss) were the most common. The incidence rate of injuries in the top 5 European professional leagues was not different to that of the professional leagues in other countries (6.8 vs 7.6 injuries/1000 hours of exposure, respectively). Professional male football players have a substantial risk of sustaining injuries, especially during matches.


#13 Physical workload and glycemia changes during football matches in adolescents with type 1 diabetes can be comparable
Reference: Acta Diabetol. 2019 Jun 4. doi: 10.1007/s00592-019-01371-0. [Epub ahead of print]
Authors: Gawrecki A, Michalak A, Gałczyński S, Dachowska I, Zozulińska-Ziółkiewicz D, Szadkowska A
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00592-019-01371-0.pdf
Summary: The purpose was to analyze physical performance and diabetes-related outcomes in adolescents with type 1 diabetes (T1DM) during two semi-competitive football matches utilising precise physical activity monitoring. The study was conducted during an annual summer camp for adolescents with T1DM. After physical examination and glycated hemoglobin measurement, 16 adolescent players completed Cooper's 12-min running test and, in the following days, took part in two football matches while wearing heart rate (HR) monitors coupled with global positioning system (GPS) tracking. Both matches were comparable in terms of covered distances, number of sprints, achieved velocities and heart rate responses. During both games, capillary blood lactate increased significantly (Match 1: 1.75 ± 0.16-6.13 ± 1.73 mmol/l; Match 2: 1.77 ± 0.18-3.91 ± 0.63 mmol/l, p = 0.004). No significant differences in blood glucose were observed between the matches (p = 0.83) or over each match (p = 0.78). Clinically significant hypoglycemia (< 54 mg/dl) occurred in two children during the first match. None of the players experienced severe hypoglycemia. Despite similar workloads, players consumed significantly less carbohydrates during Match 2 [median difference: - 20 g (25-75%: - 40 to 0), p = 0.006]. HR monitoring and GPS-based tracking can effectively parameterize physical activity during a football match. In T1DM patients, exercise workload and glycemic changes during similar matches are comparable, which provides an opportunity to develop individual recommendations for players with T1DM.


#14 Brief in-play cooling breaks reduce thermal strain during football in hot conditions
Reference: J Sci Med Sport. 2019 May 4. pii: S1440-2440(18)31272-6. doi: 10.1016/j.jsams.2019.04.009. [Epub ahead of print]
Authors: Chalmers S, Siegler J, Lovell R, Lynch G, Gregson W, Marshall P, Jay O
Summary: The study examined if three feasible strategies involving additional in-play cooling periods attenuate the core (rectal) temperature rise during simulated football matches. Four counterbalanced experimental trials in an environmental chamber set to 35 °C ambient temperature, 55% relative humidity, and 30 °C WBGT were utilized. Twelve healthy well-trained football players completed a regular simulated match (REG), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption (COOLwater), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption and the application of an ice towel around the neck (COOLtowel), regular simulated match with an extended (+5 min; total of 20-min) half-time break (HTextended). The difference in rectal temperature change was significantly lower in the COOLwater (-0.25 °C), COOLtowel (-0.28 °C), and HTextended (-0.21 °C) trials in comparison to the REG (all p < 0.05). Exercising heart rate and session rating of perceived exertion was lower in the COOLwater (-13 bpm; -1.4 au), COOLtowel (-10 bpm; -1.3 au), and HTextended (-8 bpm; -0.9 au) trials in comparison to the REG trial (all p < 0.05). The cooling interventions did not significantly change skin temperature or thermal sensation in comparison to the REG (all p > 0.05). All three cooling interventions attenuated core body thermal strain during simulated matches. The laboratory-based study supports the use of brief in-play cooling periods as a means to attenuate the rise in core temperature during matches in hot and humid conditions.

Fri

05

Jul

2019

Latest research in football - week 21 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Activity Profiles by Position in Youth Elite Soccer Players in Official Matches
Reference: Sports Med Int Open. 2019 May 28;3(1):E19-E24. doi: 10.1055/a-0883-5540. eCollection 2019 Jan.
Authors: Pettersen SA, Brenn T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6538502/pdf/10-1055-a-0883-5540.pdf
Summary: In order to investigate activity profiles and external load patterns in elite youth soccer players, we studied high-intensity activity patterns, maximum running speed, and temporary and end-of-match decline in external load in 54 U17 players (96 match observations) over a full season of official match play. Wide midfielders covered most high-intensity running (HIR) distance (1044.2 m), most sprinting distance (224.4 m), and the highest number of accelerations (185.2); center defenders had the lowest values for these activities (10 396.8 m, 508.3 m, 85.1 m, and 119.0), respectively. Wide midfielders had the highest and center defenders had the lowest maximum speed (30.3 km·h -1 and 28.6 km·h -1 ), respectively. During the matches, players in all playing positions displayed a significant drop in HIR distance, sprinting distance, and number of accelerations. This was especially pronounced in the 5 min following the 5-min peak period and in the last 5-min period for sprinting distance. There are substantial differences in activity profiles by positions, but all players show temporary and end-of-match drop in external load. The variation in activity profiles by playing position in this study may aid in the design of training programs. The considerable end-of-match drop in external load observed raises the question of the favorability of 90 min match times for U17 players.


#2 Russian and Low-Frequency Currents Training Programs Induced Neuromuscular Adaptations in Soccer Players: Randomized Controlled Trial
Reference: J Sport Rehabil. 2019 May 29:1-25. doi: 10.1123/jsr.2018-0314. [Epub ahead of print]
Authors: Modesto KAG, de Oliveira PFA, Fonseca HG, Azevedo KP, Guzzoni V, Bottaro MF, Babault N, Durigan JLQ
Summary: Neuromuscular electrical stimulation (NMES) is widely used to induce muscular strength increase, however, no study has compared Russian current (RC) with Pulsed current (PC) effects after a training program. We studied the effects of different neuromuscular electrical stimulation (NMES) currents, Russian current (RC) and Pulsed current (PC) on the neuromuscular system after a six-week training period. Twenty-seven male soccer players (22.2±2.2 years, 74.2±10.0 kg, 177±0 cm, BMI: 23.7±2.9 kg/cm for the control group, 22.1±3.1 years, 69.7±5.7 kg, 174±0 cm, 23.0±2.5 kg/cm for the PC group, and 23.0±3.4 years, 72.1±10.7 kg,175±0 cm, 23.5±3.4 kg/cm for the RC group) were randomized into three groups: 1) control group, 2) RC (2500 Hz, burst 100 Hz, phase duration 200 μs), and 3) PC (100 Hz and 200 μs). Intervention: The experimental groups trained for six weeks, with three sessions per week with NMES. Maximal voluntary isometric contraction (MVIC) and evoked torque, muscle architecture, sensory discomfort (VAS), and electromyographic activity (EMG) were evaluated before and after the six-week period. Evoked torque increased in the RC (169.5±78.2 %, p<0.01) and PC groups (248.7±81.1 %, p<0.01). Muscle thickness and pennation angle increased in the RC (8.7±3.8 % and 16.7±9.0%, p<0.01) and PC groups (16.1±8.0 % and 27.4±11.0 %, p<0.01). The PC demonstrated lower values for VAS (38.8±17.1 %, p<0.01). There was no significant time difference for MVIC and RMS (root mean square) values (p>0.05). For all these variables, there was no difference between the RC and PC (p>0.05). Despite the widespread use of RC in clinical practice, RC and PC training programs produced similar neuromuscular adaptations in soccer players. Nonetheless, as PC generated less perceived discomfort it could be preferred after several training sessions.


#3 Commentary: Interpersonal Coordination in Soccer: Interpreting Literature to Enhance the Representativeness of Task Design, From Dyads to Teams
Reference: Front Psychol. 2019 May 14;10:1093. doi: 10.3389/fpsyg.2019.01093. eCollection 2019.
Authors: Gesbert V, Hauw D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527810/pdf/fpsyg-10-01093.pdf


#4 Oral Ingestion of Deep Ocean Minerals Increases High-Intensity Intermittent Running Capacity in Soccer Players after Short-Term Post-Exercise Recovery: A Double-Blind, Placebo-Controlled Crossover Trial
Reference: Mar Drugs. 2019 May 24;17(5). pii: E309. doi: 10.3390/md17050309.
Authors: Higgins MF, Rudkin B, Kuo CH
Download link: https://www.mdpi.com/1660-3397/17/5/309/pdf
Summary: This study examined whether deep ocean mineral (DOM) supplementation improved high-intensity intermittent running capacity after short-term recovery from an initial bout of prolonged high-intensity running in thermoneutral environmental conditions. Nine healthy recreational male soccer players (age: 22 ± 1 y; stature: 181 ± 5 cm; and body mass 80 ± 11 kg) completed a graded incremental test to ascertain peak oxygen uptake (V·O2PEAK), two familiarisation trials, and two experimental trials following a double-blind, repeated measures, crossover and counterbalanced design. All trials were separated by seven days and at ambient room temperature (i.e., 20 °C). During the 2 h recovery period after the initial ~60 min running at 75% V·O2PEAK, participants were provided with 1.38 ± 0.51 L of either deep ocean mineral water (DOM) or a taste-matched placebo (PLA), both mixed with 6% sucrose. DOM increased high-intensity running capacity by ~25% compared to PLA. There were no differences between DOM and PLA for blood lactate concentration, blood glucose concentration, or urine osmolality. The minerals and trace elements within DOM, either individually or synergistically, appear to have augmented high-intensity running capacity in healthy, recreationally active male soccer players after short-term recovery from an initial bout of prolonged, high-intensity running in thermoneutral environmental conditions.


#5 Running Performance of Soccer Players During Matches in the 2018 FIFA World Cup: Differences Among Confederations
Reference: Front Psychol. 2019 May 7;10:1044. doi: 10.3389/fpsyg.2019.01044. eCollection 2019.
Authors: Tuo Q, Wang L, Huang G, Zhang H, Liu H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6514193/pdf/fpsyg-10-01044.pdf
Summary: With the purpose of quantifying the differences in the running performance of soccer players during matches from different continental confederations, data of 1508 match observations generated from 559 players in 59 matches at the 2018 FIFA World Cup held in Russia were analyzed. Generalized mixed linear modeling was carried out to estimate the effect of confederations on each of the selected thirteen match running performance related variables (total distance covered, top speed achieved, number of sprints, distance covered and time spent in walking, jogging, low-speed running, moderate-speed running, and high-speed running), controlling the effects of match result, competition phase, and team and opponent strength. Results showed that the differences in the match running performance of UEFA and CONMEBOL players were trivial (ES between 0.04 and 0.14); players from AFC, CAF, and CONCACAF covered less total distance (ES between 0.26 and 0.54), spent less playing time, and covered less distance in jogging and low-speed running (ES between 0.20 and 0.53), whereas they spent more time walking (ES between 0.27 and 0.41) as compared with players from UEFA and CONMEBOL; top speed achieved, number of sprints made, and time spent and distance covered in the moderate- and high-speed running intensity zones by players from all confederations were similar (ES between 0.01 and 0.15), with an exception that high-speed-running distance covered by CONCACAF players was less than that by CAF players (2.0 ± 1.5 m/min vs. 2.3 ± 1.7 m/min, ES = 0.23, ±90% CL: ±0.21).


#6 Evaluating the impact of a coach development intervention for improving coaching practices in junior football (soccer): The "MASTER" pilot study
Reference: J Sports Sci. 2019 May 25:1-13. doi: 10.1080/02640414.2019.1621002. [Epub ahead of print]
Authors: Eather N, Jones B, Miller A, Morgan PJ
Summary: The aim of this pilot study was to evaluate the impact of a novel coach development intervention (MASTER) on coaching practices of football coaches. The study involved six coaches (of 10-12 year old) from one representative football club (Australia February-July 2017). The 15-week multi-component intervention included a face-to-face workshop, ongoing mentoring, modelled training sessions, peer assessments and group discussions. MASTER is underpinned by positive coaching and game-based coaching practices and aimed to educate coaches on how to implement and operationalise a number of evidence-based coaching elements. At each of baseline and immediate post-intervention coaches were filmed three times and evaluated using a modified version of the Coach Analysis Intervention System. Using linear mixed model analysis, significant changes were observed for time spent performing playing-form activities [+15.4% (95% CI 6.01-24.79)(t(15) = 3.5, P = 0.003], with significant changes in the type of interventions undertaken and the nature of feedback given to athletes. Program feasibility was examined using measures of recruitment, retention, adherence and satisfaction. Results indicate program feasibility and high coach evaluation ratings. MASTER demonstrated effectiveness for improving coaching practices of football coaches during training sessions. Further large-scale trials will build evidence for the utility of MASTER for guiding coaching practices in football and other sporting codes.


#7 Medical assessment of potential concussion in elite football: video analysis of the 2016 UEFA European championship
Reference: BMJ Open. 2019 May 30;9(5):e024607. doi: 10.1136/bmjopen-2018-024607.
Authors: Abraham KJ, Casey J, Subotic A, Tarzi C, Zhu A, Cusimano MD
Download link: https://bmjopen.bmj.com/content/bmjopen/9/5/e024607.full.pdf
Summary: The objective is to determine if suspected concussions in elite football are medically assessed according to the International Conferences on Concussion in Sport consensus statement recommendations. Potential concussive events (PCEs) were defined as direct head collision incidents resulting in the athlete being unable to immediately resume play following impact. PCEs identified and description of PCE assessment and outcome were accomplished through direct standardised observation of video footage by trained observers in 51 games played in the Men's UEFA European Championship (10 June-10 July 2016). Sixty-nine total PCEs (1.35 per match) were identified in 51 games played during the 2016 Men's UEFA European Championship. Forty-eight PCEs (69.6%) resulted in two observable signs of concussion, 13 (18.8%) resulted in three signs and 1 (1.4%) resulted in four signs in the injured athletes. Nineteen (27.5%) PCEs were medically assessed by sideline healthcare personnel while 50 (72.5%) were not. Of the 50 PCEs that were not medically assessed, 44 (88%) PCEs resulted in two or more signs of concussion among injured athletes. Of the 19 medically assessed PCEs, 8 resulted in 3 signs of concussion, and 1 resulted in 4 signs; all assessments concluded in the same-game return for the injured athletes. PCEs were frequent events in the 2016 UEFA Euro championship, but were rarely assessed concordant with the International Conferences on Concussion in Sport consensus statement recommendations. There is an imperative need to improve the assessment and management of players suspected of concussion in elite football.


#8 Effects of Adding Vertical or Horizontal Force-Vector Exercises to In-season General Strength Training on Jumping and Sprinting Performance of Youth Football Players
Reference: J Strength Cond Res. 2019 May 27. doi: 10.1519/JSC.0000000000003221. [Epub ahead of print]
Authors: Abade E, Silva N, Ferreira R, Baptista J, Gonçalves B, Osório S, Viana J
Summary: Football is characterized by short-term high-intensity triaxial activities that require optimized neuromuscular capacity. Thus, training routines must consider the direction of force application, particularly when strength exercises are performed. This study aimed to explore the effects of adding vertical or horizontal force-vector exercises to a 20-week in-season general strength training program on jumping and sprinting performance of youth football players. Twenty-four well-trained male under-17 players participated in this study and were randomly assigned to a control, vertical, or horizontal training group. Control group performed a general strength training program (free weights, eccentric-overload, and body mass exercises) once a week during 20 weeks. Vertical and horizontal groups additionally performed back-half-squat or barbell hip-thrust, respectively. Vertical group improved vertical jump (VJ) (squat jump, likely 4.5; ±4.4% and countermovement jump, likely 4.9; ±4.1%), horizontal jump (HJ) (most likely 7.5; ±2.7%), and sprint (10 m, likely -1.6; ±2.0% and 20 m, very likely -3.3; ±1.6%). The horizontal group showed unclear results in VJ; however, large improvements were observed in HJ (most likely, 13.0; ±4.8%), 10 m and 20 m (very likely -3.0; ±1.8% and most likely -3.8; ±1.0%, respectively). Back-squat and hip-thrust showed an important transference effect to both jumping and sprinting performance. If considering the effects of back-squat on VJ, hip-thrust improved HJ and sprint to a greater extent. This study reinforces the importance of performing both vertical and horizontal force-vector exercises to enhance physical performance during football in-season, even when performed only once a week.


#9 Evaluating the impact of a coach development intervention for improving coaching practices in junior football (soccer): The "MASTER" pilot study
Reference: J Sports Sci. 2019 May 25:1-13. doi: 10.1080/02640414.2019.1621002. [Epub ahead of print]
Authors: Eather N, Jones B, Miller A, Morgan PJ
Summary: The aim of this pilot study was to evaluate the impact of a novel coach development intervention (MASTER) on coaching practices of football coaches. The study involved six coaches (of 10-12 year old) from one representative football club (Australia February-July 2017). The 15-week multi-component intervention included a face-to-face workshop, ongoing mentoring, modelled training sessions, peer assessments and group discussions. MASTER is underpinned by positive coaching and game-based coaching practices and aimed to educate coaches on how to implement and operationalise a number of evidence-based coaching elements. At each of baseline and immediate post-intervention coaches were filmed three times and evaluated using a modified version of the Coach Analysis Intervention System. Using linear mixed model analysis, significant changes were observed for time spent performing playing-form activities [+15.4% (95% CI 6.01-24.79)(t(15) = 3.5, P = 0.003], with significant changes in the type of interventions undertaken and the nature of feedback given to athletes. Program feasibility was examined using measures of recruitment, retention, adherence and satisfaction. Results indicate program feasibility and high coach evaluation ratings. MASTER demonstrated effectiveness for improving coaching practices of football coaches during training sessions. Further large-scale trials will build evidence for the utility of MASTER for guiding coaching practices in football and other sporting codes.


#10 Training load and submaximal heart rate testing throughout a competitive period in a top-level male football team
Reference: J Sports Sci. 2019 May 26:1-8. doi: 10.1080/02640414.2019.1618534. [Epub ahead of print]
Authors: Rago V, Krustrup P, Martín-Acero R, Rebelo A, Mohr M
Summary: The aim of this study was to investigate training load and cardiorespiratory fitness in a top-level Spanish (LaLiga) football team (n = 17). The submaximal Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1SUB) was performed in four moments of the competitive period from early February (E1) to early May (E4). Training load was quantified using a 10-Hz global positioning system and heart rate (HR) recording (n = 837 individual training sessions), while match load was quantified using semi-automated cameras (n = 216 individual match observations). Cardiorespiratory fitness moderately improved as the season progressed (P < 0.05; effect sizes = 0.8 to 1.2). Cumulative total distance covered during training between E1 and E4 was negatively correlated with percentage of changes in mean HR during the last 30 s of Yo-Yo IR1SUB (P = 0.049; r = -0.47 [-0.71; -0.14]; moderate). HR during the last 30 s of Yo-Yo IR1SUB was negatively correlated to total distance covered during the match (P = 0.024; r = -0.56 [-0.80; -0.17]; moderate). Yo-Yo IRSUB can be used to monitor seasonal changes in cardiorespiratory fitness without the need to have players work until exhaustion. Cardiorespiratory fitness given by mean HR during the last 30 s of the test seems meaningful in relation to match performance.


#11 Attitudes, beliefs and knowledge related to doping in different categories of football players
Reference: J Sci Med Sport. 2019 May 18. pii: S1440-2440(18)31034-X. doi: 10.1016/j.jsams.2019.05.010. [Epub ahead of print]
Authors: Morente-Sánchez J, Zandonai T, Zabala Díaz M
Summary: The aim of this study was to study and compare attitudes, beliefs and knowledge about doping of footballers, from elite to under-18 categories. The descriptive exploratory design used an instrument combining a validated questionnaire (Performance Enhancement Attitude Scale: PEAS) with qualitative open-ended questions. A total of 1324 Spanish football players (average age 22.56 ± 5.62 years) from 88 football teams that ranged from elite to under-18 categories: Elite (ELI, n = 304), non-elite Professional (PRO, n = 308), top Amateur (AMA, n = 330), elite Under-18 (U18, n = 334) and elite Female (FEM, n = 48) composed the sample. PEAS overall scores (range 17-102, with higher scores representing more permissive attitudes) was 34.02 ± 11.08. The overall scores for all groups analysed were: FEM: 33.75 ± 14.73; ELI: 30.61 ± 9.91; PRO: 34.23 ± 11.13; AMA: 35.05 ± 10.35; and U18: 35.93 ± 11.50. Significant differences were observed between ELI and PRO (p < 0.001), ELI and AMA (p < 0.001), and ELI and U18 (p < 0.001). 95% of participants did not know the meaning of WADA; 97.4% did not know the Prohibited List; 5% admitted having used banned substances and 23.7% knew dopers. This study showed different an important lack of knowledge about doping and an high levels of supplement use in this sample of footballers assessed. It which clearly reinforces the idea of implementing a wide educational doping prevention programme in football environment.


#12 Acute high-intensity football games can improve children's inhibitory control & neurophysiological measures of attention
Reference: Scand J Med Sci Sports. 2019 May 24. doi: 10.1111/sms.13485. [Epub ahead of print]
Authors: Rasmussen Lind R, Beck MM, Wikman J, Malarski K, Krustrup P, Lundbye-Jensen J, Sparre Geertsen S
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13485
Summary: Recent studies suggest that a single bout of exercise can lead to transient performance improvements in specific cognitive domains in children. However, more knowledge is needed to determine the key exercise characteristics for obtaining these effects and how they translate into real-world settings. In the present study, we investigate how small-sided football games of either high or moderate-intensity affect measures of inhibitory control in a school setting. Eighty-one children (mean age 11.8, 48 boys) were randomly allocated to three groups performing 20-min of high-intensity small-sided real football games (SRF), moderate-intensity small-sided walking football games (SWF) or resting (RF). Behavioural measures of inhibitory control and neurophysiological measures of attention (P300 latency and amplitude) were obtained during a flanker task performed at baseline and 20 minutes following the intervention. Retention of declarative memory was assessed in a visual memory task 7 days after the intervention. Measures of inhibitory control improved more in children performing SRF compared to SWF 19ms, 95% CI [7, 31ms], (p=0.041). This was paralleled by larger increases in P300 amplitudes at Fz in children performing SRF compared both to RF in congruent (3.54μV, 95% CI [0.85, 6.23 μV], p=0.039) and incongruent trials (5.56μV, 95% CI [2.87, 8.25 μV], p<0.001) and compared to SWF in incongruent trials (4.10μV, 95% CI [1.41, 6.68 μV], p=0.010). No effects were found in measures of declarative memory. Together this indicate that acute high-intensity small-sided football games can transiently improve measures of inhibitory control and neurophysiological correlates of attention. Intense small-sided football games are easily implementable and can be employed by practitioners, e.g. during breaks throughout the school day.


#13 Influence of the structural components of artificial turf systems on impact attenuation in amateur football players
Reference: Sci Rep. 2019 May 23;9(1):7774. doi: 10.1038/s41598-019-44270-8.
Authors: Sánchez-Sánchez J, Gallardo-Guerrero AM, García-Gallart A, Sánchez-Sáez JA, Felipe JL, Encarnación-Martínez A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6533268/pdf/41598_2019_Article_44270.pdf
Summary: The purpose of this research was to evaluate the influence of the structural components of different 3rd generation artificial turf football field systems on the biomechanical response of impact attenuation in amateur football players. A total of 12 amateur football players (24.3 ± 3.7 years, 73.5 ± 5.5 kg, 178.3 ± 4.1 cm and 13.7 ± 4.3 years of sport experience) were evaluated on three third generation artificial turf systems (ATS) with different structural components. ATS were composed of asphalt sub-base and 45 mm of fibre height with (ATS1) and without (ATS2) elastic layer or compacted granular sub-base, 60 mm of fibre height without elastic layer (ATS3). Two triaxial accelerometers were firmly taped to the forehead and the distal end of the right tibia of each individual. The results reveal a higher force reduction on ATS3 in comparison to ATS1 (+6.24%, CI95%: 1.67 to 10.92, ES: 1.07; p < 0.05) and ATS2 (+21.08%, CI95%: 16.51 to 25.66, ES: 2.98; p < 0.05) elastic layer. Tibia acceleration rate was lower on ATS3 than ATS1 (-0.32, CI95%: -0.60 to -0.03, ES: 4.23; p < 0.05) and ATS2 (-0.35, CI95%: -0.64 to -0.06; ES: 4.69; p < 0.05) at 3.3 m/s. A very large correlation (r = 0.7 to 0.9; p < 0.05) was found between energy restitution and fibre height in both head and tibial peak acceleration and stride time. In conclusion, structural components (fibre height, infill, sub-base and elastic layer) determine the mechanical properties of artificial turf fields. A higher force reduction and lower energy restitution diminished the impact received by the player which could protect against injuries associated with impacts compared to harder artificial turf surfaces.


#14 Comparison of Static and Dynamic Balance in Male Football and Basketball Players
Reference: Foot Ankle Spec. 2019 May 23:1938640019850618. doi: 10.1177/1938640019850618. [Epub ahead of print]
Authors: Halabchi F, Abbasian L, Mirshahi M, Mazaheri R, Pourgharib Shahi MH, Mansournia MA
Summary: The aim of the present study was to compare static and dynamic balance among professional athletes in football and basketball. In this cross-sectional study, 47 professional, male football and basketball players from Pro League in Iran participated. They were divided into 3 groups. Group 1 included 16 participants with history of grade 1 or 2 single ankle sprain within the past 6 months. Group 2 included 17 participants with recurrent ankle sprain. Group 3 included 14 participants without history of ankle sprain. Static and dynamic balance were measured by the Balance Error Scoring System (BESS) and modified Star Excursion Balance Test (SEBT), respectively. For the single-leg stance on a firm surface, group 2 scored errors with a high mean value of 3.94 compared with the other 2 groups, and the difference was statistically significant (P = .03). Significant differences in BESS scores are observed on both surfaces across the tandem limb between groups 2 and 3. The measures from the SEBTs may not reflect the balance performance especially in well-trained athletes who have a better balance when performing sport-related skills. However, BESS includes static postures, and it may reflect postural deficits better than dynamic tests in the more experienced athlete.

Sun

16

Jun

2019

Latest research in football - week 20 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Relationship between Change of Direction Tests in Elite Youth Soccer Players
Reference: Sports (Basel). 2019 May 14;7(5). pii: E111. doi: 10.3390/sports7050111.
Authors: Kadlubowski B, Keiner M, Hartmann H, Wirth K, Frick U
Download link: https://www.mdpi.com/2075-4663/7/5/111/pdf
Summary: Change of direction (COD) is a performance-limiting factor in team sports. However, there are no exact definitions describing which physical abilities limit COD performance in soccer. Nevertheless, different COD tests are used or have been recommended as being equally effective in the professional practice of measuring COD performance. Therefore, the aim of this study was to evaluate the relationship between different COD tests, and to test the independence and generalizability of these COD tests in soccer. As such, 27 elite youth soccer players were randomly recruited and were tested in different COD tests (i.e., Illinois agility test (IAT), T agility test (TT), 505 agility test (505), Gewandtheitslauf (GewT), triangle test (Tri-t), and square test (SQT)). Bivariate Pearson correlation analysis was used to assess the relationships between the COD tests. The Benjamini-Hochberg method was used to control for the false discovery rate of the study at 0.05. This investigation calculated explained variances of 10% to 55% between performances in the different COD tests. This suggested that the tests covered different aspects or task-specific characteristics of the COD. Therefore, coaches and sport scientists should review and select different tests with a logical validity, based on the requirement profiles of the corresponding sport.


#2 Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes
Reference: Br J Sports Med. 2019 May 14. pii: bjsports-2018-100238. doi: 10.1136/bjsports-2018-100238. [Epub ahead of print]
Authors: McGuine T, Post E, Pfaller AY, Hetzel S, Schwarz A, Brooks MA, Kliethermes SA
Summary: There have been no large randomised controlled trials to determine whether soccer headgear reduces the incidence or severity of sport-related concussion (SRC) in US high school athletes. We aimed to determine whether headgear reduces the incidence or severity (days out from soccer) of SRCs in soccer players. 2766 participants (67% female, age 15.6±1.2) (who undertook 3050 participant years) participated in this cluster randomised trial. Athletes in the headgear (HG) group wore headgear during the season, while those in the no headgear (NoHG) group did not. Staff recorded SRC and non-SRC injuries and soccer exposures. Multivariate Cox proportional hazards models were used to examine time-to-SRC between groups, while severity was compared with a Wilcoxon rank-sum test. 130 participants (5.3% female, 2.2% male) sustained an SRC. The incidence of SRC was not different between the HG and NoHG groups for males (HR: 2.00 (0.63-6.43) p=0.242) and females (HR: 0.86 (0.54-1.36) p=0.520). Days lost from SRC were not different (p=0.583) between the HG group (13.5 (11.0-018.8) days) and the NoHG group (13.0 (9.0-18.8) days). Soccer headgear did not reduce the incidence or severity of SRC in high school soccer players.


#3 Maximum acceleration performance of professional soccer players in linear sprints: Is there a direct connection with change-of-direction ability?
Reference: PLoS One. 2019 May 14;14(5):e0216806. doi: 10.1371/journal.pone.0216806. eCollection 2019.
Authors: Loturco I, A Pereira L, T Freitas T, E Alcaraz P, Zanetti V, Bishop C, Jeffreys I
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0216806&type=printable
Summary: The purpose of this study was to examine the selective influences of the maximum acceleration capability on change of direction (COD) speed, COD deficit, linear sprint speed, sprint momentum, and loaded and unloaded vertical jump performances in forty-nine male professional soccer players (24.3 ± 4.2 years; 75.4 ± 5.4 kg; 177.9 ± 6.4 cm). Soccer players performed the assessments in the following order: 1) squat and countermovement jumps; 2) 20-m sprinting speed test; 3) Zigzag COD ability test; and 4) bar-power outputs in the jump squat exercise. Athletes were divided, using a median split analysis, into two different groups according to their maximum acceleration rates from zero to 5-m (e.g., higher and lower ACC 0-5-m). Magnitude-based inference was used to compare the differences in the physical test results between "higher" and "lower" acceleration groups. A selective influence of the maximum acceleration ability on speed-power tests was observed, as the higher acceleration group demonstrated likely to almost certain higher performances than the lower acceleration group in all measurements (effect sizes varying from 0.66 [for sprint momentum in 20-m] to 2.39 [for sprint velocity in 5-m]). Conversely, the higher acceleration group demonstrated a higher COD deficit when compared to the lower acceleration group (ES = 0.55). This indicates compromised efficiency to perform COD maneuvers in this group of players. In summary, it was observed that soccer players with higher maximum acceleration rates are equally able to jump higher, sprint faster (over short distances), and achieve higher COD velocities than their slower counterparts. However, they appear to be less efficient at changing direction, which may be related to their reduced ability to deal with greater entry and exit velocities, or counterbalance the associated mechanical consequences (i.e., greater inertia) of being faster and more powerful.


#4 Relationship Between Resting Heart Rate Variability and Intermittent Endurance Performance in Novice Soccer Players
Reference: Res Q Exerc Sport. 2019 May 13:1-7. doi: 10.1080/02701367.2019.1601666. [Epub ahead of print]
Authors: Pereira LA, Abad CCC, Leiva DF, Oliveira G, Carmo EC, Kobal R, Loturco I
Summary: This study examined the relationships between the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and resting heart rate variability (HRV) and submaximal 5'-5' test derived measures in novice male soccer players. Forty players (11.54 ± 0.58 years) from a soccer academy participated in this study, performing physical tests on two different days, separated by 48 h, as follows: (day 1) resting HRV and Yo-Yo IR1 test, and (day 2) anthropometric assessments (for peak height velocity assessment [PHV]) and the 5'-5' test. The Pearson product-moment correlation coefficient was used to determine the correlations between Yo-Yo IR1 performance and the remaining variables. A partial correlation analysis was further performed using age, stature, body mass, distance to PHV, and age at PHV as "confounders." The highest correlation score was observed between Yo-Yo IR1 performance and resting HRV, when the absolute age was used as confounder (r = 0.72; p < .05). We observed that a practical measure of parasympathetic activity at rest is largely associated with performance obtained during a traditional intermittent endurance performance test.


#5 Shorter Small-Sided Game Sets May Increase the Intensity of Internal and External Load Measures: A Study in Amateur Soccer Players
Reference: Sports (Basel). 2019 May 9;7(5). pii: E107. doi: 10.3390/sports7050107.
Authors: Clemente FM, Nikolaidis PT, Rosemann T, Knechtle B
Download link: https://www.mdpi.com/2075-4663/7/5/107/pdf
Summary: The purpose of this study was to compare internal and external load measures during two regimens (6 x 3' and 3 x 6') of a 5 vs. 5 format of play. Moreover, within-regimen changes (between sets) were also tested. Ten amateur soccer players (age: 19.8 ± 1.6 years; experience: 8.3 ± 2.1 years; height: 177.4 ± 3.8 cm; weight: 71.7 ± 4.2 kg) participated in the experiment. Internal load was measured using the CR-10 scale as the rated of perceived exertion (RPE) scale and a heart rate (HR) monitor. The measurements of total (TD), running (RD) and sprinting (SD) distances were also collected using a 10-Hz validated and reliable GPS. Comparisons between regimens revealed that the 3 x 6' regimen was significantly more intense in terms of RPE than the 6 x 3' regimen (p = 0.028; d = 0.351), although no significant differences were found in HR. Significantly greater averages of TD (p = 0.000; d = 0.871) and RD (p = 0.004; d = 0.491) were found in the 6 x 3' regimen. In both regimens, the RPE was significantly lower during the first set than in the remaining sets. On the other hand, the TD was significantly shorter in the last sets than in the earlier. In summary, the present study suggests that shorter sets may be beneficial for maintaining higher internal and external load intensities during 5 vs. 5 formats, and that a drop-in performance may occur throughout the sets in both regimens.


#6 Maximal heart rate assessment in recreational football players. A study involving a multiple testing approach
Reference: Scand J Med Sci Sports. 2019 May 21. doi: 10.1111/sms.13472. [Epub ahead of print]
Authors: Póvoas SCA, Krustrup P, Pereira R, Vieira S, Carneiro I, Magalhães J, Castagna C
Summary: This study aimed at examining the suitability of a standard treadmill test (TT), popular intermittent field tests and small-sided recreational football matches to induce maximal heart rate (HRmax ) in recreational football players. Sixty-six male sedentary untrained subjects (age 39.3±5.8 years, VO2max 41.3±6.2 ml·kg-1 ·min-1 , body mass 81.9±10.8 kg, height 173.2±6.4 cm) were evaluated. On separate occasions, the players were randomly submitted to a progressive VO2max TT, to the Yo-Yo intermittent endurance level 1 (YYIE1) and level 2 (YYIE2) tests, to the Yo-Yo intermittent recovery level 1 (YYIR1) test, and to 7v7 (43x27 m pitch, 83 m2 /player) football matches (45 min; 2-4 matches/player). To ensure data consistency, exercise HR was recorded using the same HR monitors in all the experimental conditions. A total of 73, 24, 18, 17 and 30% of players achieved HRmax during the YYIE1, YYIE2, YYIR1, TT and the small-sided football matches, respectively. The probability of achieving HRmax increased proportionally to test duration, with 7.8 min as the cut-off time. Variations in HRpeak of ±2 b. min-1 should be regarded as of practical relevance. YYIE1 HRpeak provided the most accurate estimation of a subject's individual HRmax and much higher probability of reaching HRmax . Nevertheless, the results of this study suggest caution in considering a reference test for HRmax assessment in this population. The use of confirmation tests is still highly advisable when the test duration is shorter than 7.8 min. In this regard, field tests seem to be suitable and accurate for individual HRmax assessment in recreational football players.


#7 The effect of the change of football turf on knee kinematics of adolescent male football players
Reference: J Sports Med Phys Fitness. 2019 May 20. doi: 10.23736/S0022-4707.19.09774-3. [Epub ahead of print]
Authors: Zhou B, Li B, Bai L
Summary: The aim of this study was to investigate the effect of the change of football turf on knee kinematics of adolescent male football players. Thirteen adolescent male football players were tested by a portable infrared motion analysis system based on markers. The angular displacements of flexion/extension,valgus/ varus and internal/external rotation were calculated respectively when players performed 90° shuttle running on artificial turf and natural turf. The maximum valgus angle and range of valgus/varus were larger when they were changed from artificial turf to natural turf (P<0.05). There were no significant differences in the maximum flexion angle, maximum extension angle,range of flexion/extension,maximum varus angle,maximum internal rotation angle, maximum external rotation angle and range of internal/external rotation(P>0.05). The change of football turf has a significant effect on knee kinematics of adolescent male football players.The risk of noncontact anterior cruciate ligament(ACL) injury is increased when players who are changed from artificial turf to natural turf.


#8 The Relationship Between Cognitive Functions and Sport-Specific Motor Skills in Elite Youth Soccer Players
Reference: Front Psychol. 2019 Apr 25;10:817. doi: 10.3389/fpsyg.2019.00817. eCollection 2019.
Authors: Scharfen HE, Memmert D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6494938/pdf/fpsyg-10-00817.pdf
Summary: The aim of the present study was to examine the relationship between basic cognitive functions and sport-specific motor skills in elite youth soccer players. A total of 15 elite youth soccer players aged 11-13 years performed a computer-based test battery measuring the attention window (AW), perceptual load (PL), working memory capacity (WMC), and multiple object tracking (MOT). Another set of tests was used to asses speed abilities and football-specific technical skills (sprint, change of direction, dribbling, ball control, shooting, and juggling). Spearman's correlation tests showed that the diagonal AW was positively associated with dribbling skills (rs = 0.656) which indicates that a broader AW could be beneficial for highly demanding motor skills like dribbling. WMC was positively related to dribbling (rs = 0.562), ball control (rs = 0.669), and ball juggling (rs = 0.727). Additionally, the cumulated score of all cognitive tests was positively related to the cumulated motor test score (rs = 0.614) which supports the interplay of physical and psychological skills. Our findings highlight the need for more, and especially longitudinal, studies to enhance the knowledge of cognition-motor skill relationships for talent identification, talent development, and performance in soccer.


#9 Physical and Physiological Responses during the Stop-Ball Rule During Small-Sided Games in Soccer Players
Reference: Sports (Basel). 2019 May 17;7(5). pii: E117. doi: 10.3390/sports7050117.
Authors: Halouani J, Ghattasi K, Bouzid MA, Rosemann T, Nikolaidis PT, Chtourou H, Knechtle B
Download link: https://www.mdpi.com/2075-4663/7/5/117/pdf
Summary: Small-sided games (SSGs) are a recommended training method for significant performance enhancement, and training efficiency. The stop-ball (SSG-SB) effects on physical responses (e.g., acceleration, deceleration, sprints, total distance, and indicator of workload) have not been investigated yet. This study aimed to investigate the effects of the SSG-SB compared to the small-goals SSG (SSG-SG) on physical and heart rate (HR) responses at high intensity (total distance (>18 km/h)), sprints (>18 km/h), and acceleration and deceleration (>3 m/s²) during a 4 vs. 4 SSG format in youth professional soccer players. Sixteen male elite young soccer players (mean ± SD body height, 176.5 ± 6.3 cm; age, 18.3 ± 0.7 years; body weight, 73.4 ± 7.2 kg) performed two forms of SSGs, i.e., SSG-SB or SSG-SG, for 4 × 4 min with a recovery of 2 min between sets. Data were compared using the t-test. The SSG-SB induced a significantly higher mean HR (180.0 ± 2.0 vs. 173.0 ± 3.0 beats per minute; p < 0.05) compared to the SSG-SG. Likewise, the SSG-SB was significantly higher compared to the SSG-SG for total distance (2580 ± 220.3 vs. 2230 ± 210 m; p < 0.001), player load (98.07 ± 12.5 vs. 89.4 ± 10.5; p < 0.05), sprint distance (7.9 ± 2.3 vs. 5.2 ± 2.0 m; p < 0.05), acceleration (15.6 ± 2.75 vs. 12.5 ± 1.75; p < 0.05), and deceleration (17.3 ± 3.20 vs. 14.4 ± 2.55; p < 0.05). However, no significant difference was found between the SSG-SG and the SSG-SB for maximal velocity, power, and sprints duration. This study provides new information about the effectiveness of the SSG-SB as a training stimulus for soccer.


#10 Comparative Effects of Game Profile-Based Training and Small-Sided Games on Physical Performance of Elite Young Soccer Players
Reference: J Strength Cond Res. 2019 May 27. doi: 10.1519/JSC.0000000000003225. [Epub ahead of print]
Authors: Dello Iacono A, Beato M, Unnithan V
Summary: This study was designed to investigate and compare the effects of game profile-based training (GPBT) and small-sided game (SSG) training on physical performances of elite youth soccer players during the in-season period. Twenty young soccer players (18.6 ± 0.6) were randomly assigned to either GPBT or SSG protocols performed twice a week for 8 weeks. The GPBT consisted of 2 sets of 6-10 minutes of intermittent soccer-specific circuits. The SSG training consisted of 3-5 sets of 5 vs. 5 SSGs played on a 42 × 30-m pitch. Before and after the training program, the following physical performances were assessed: repeated sprint ability, change of direction (COD), linear sprinting on 10 m and 20 m, countermovement jump, and intermittent running (YYIRL1). Significant improvements were found in all the assessed variables after both training interventions (p < 0.05). The GPBT group improved more than the SSG group in the 10-m and 20-m sprint tests by 2.4% (g = 0.4; small effect) and 4% (g = 0.9; large effect), respectively. Conversely, the SSG group jumped 4% higher (g = 0.4; small effect) and resulted 6.7% quicker than the GPBT (g = 1.5; large effect) in completing the COD task. These results suggest both GPBT and SSGs to be effective for fitness development among elite young soccer players during the competitive season. More importantly, these 2 conditioning methodologies may be considered in terms of specificity for selectively improving or maintaining specific soccer fitness-related performances in the latter phase of the season.


#11 The Experiences of Young Men, Their Families, and Their Coaches Following a Soccer and Vocational Training Intervention to Prevent HIV and Drug Abuse in South Africa
Reference: AIDS Educ Prev. 2019 Jun;31(3):224-236. doi: 10.1521/aeap.2019.31.3.224.
Authors: Swendeman D, Bantjes J, Mindry D, Stewart J, Tomlinson M, Rotheram-Borus MJ, Medich M
Summary: Young men in South Africa are at high-risk for HIV, substance abuse, and gender-based violence. This article presents qualitative results from a pilot study testing soccer leagues and vocational training to engage young-adult township men to deliver preventive interventions, including rapid HIV and alcohol/drug testing, shifting attitudes toward gender-based violence, and promoting other prosocial behaviors. Three groups participated in focus groups and in-depth interviews on experiences with the program: (1) a subset of 15 participants, (2) 15 family members, and (3) five intervention coaches. Results suggest that participants first reduced substance use on tournament days and then gradually reduced to practice days and beyond. Families suggested that "keeping young men occupied" and encouragement of prosocial behaviors was critical to risk reduction and led to increased community respect for the men. Coaches noted that behavioral and attitudinal changes were incremental and slow. The use of incentives was problematic and more research is needed to understand how incentives can be used in interventions of this nature.

Thu

30

May

2019

Latest research in football - week 19 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Acute and chronic effects of competition on ankle dorsiflexion ROM in professional football players
Reference: Eur J Sport Sci. 2019 May 9:1-10. doi: 10.1080/17461391.2019.1611930. [Epub ahead of print]
Authors: Moreno-Pérez V, Soler A, Ansa A, López-Samanes Á, Madruga-Parera M, Beato M, Romero-Rodríguez D
Summary: The aim of this study was to investigate the acute (a football match) and chronic (a whole season) effects of competition on ankle dorsiflexion ROM in professional football players. Forty football players participated in this study. Ankle dorsiflexion ROM was recorded to examine acute (pre-match, immediately post-match and 48 h post-match) and chronic (pre-season, mid-season and post-season) effects of competitive football. In addition, it was found that players had restricted mobility measures on ankle dorsiflexion as >2 cm change between baseline measures (pre-match and pre-season). The training load of all played matches was estimated using a global positioning system (GPS) and RPE. Pre-season ankle dorsiflexion ROM was greater compared to mid-season (8.1% in the dominant, and 9.6% in the non-dominant leg) and post-season (13.8% in the dominant, and 12.5% in the non-dominant leg). In addition, around 30% of all players showed restricted ankle dorsiflexion ROM values in post-season compared with pre-season. Related to acute effects, ankle dorsiflexion ROM increased after a match (5.8%) in the dominant ankle, and this value decreased (2.65%) 48 h post-match when post-match measurements in both dominant and non-dominant ankles were compared. The progressive decrease in ankle dorsiflexion ROM throughout a season can be an indicator of increased risk of injury and may be reinforce the need of prevention actions such as stretching exercises and eccentric strength training in professional football players. In addition, these findings suggest to implement specific recovery strategies aiming at minimizing alteration in ankle dorsiflexion ROM 48 h post-match.


#2 The effect of compression shorts on pain and performance in male football players with groin pain - A double blinded randomized controlled trial
Reference: Phys Ther Sport. 2019 Apr 25;38:87-95. doi: 10.1016/j.ptsp.2019.04.013. [Epub ahead of print]
Authors: Otten R, Stam S, Langhout R, Weir A, Tak I
Summary: The purpose was to investigate the effects of compression shorts on pain and performance in football players with groin pain. Thirty-four male football players with groin pain participated in this study. The effect of wearing zoned high compression shorts (ZHC-shorts), non-zoned low compression shorts (NZLC-shorts), and normal sports clothes on pain measured with the Numeric Pain Rating Scale (NPRS) and performance during the Copenhagen 5-s squeeze test (CS), the Illinois Agility test (IAT), and maximum shooting (ST). The effects of wearing ZHC versus NZLC shorts on symptoms were measured using the Hip and groin outcome score (HAGOS) during actual football activities. Wearing ZHC-shorts reduced pain during the IAT (1.4, ES = 0.58, p= <0.01) and ST (1.2, ES = 0.47, p= <0.01) compared to wearing normal sports clothes, but did not negatively affect performance. Compared to the baseline HAGOS scores a clinically significant improvement in the symptoms (9.7, ES = 0.63, p= <0.01) and sport/recreation (13.2, ES = 0.68, p = 0.01) subscales was found when wearing the ZHC-short during football activities. Wearing zoned high compression shorts could be useful in reducing groin pain in football players during their football activities.


#3 Jump height as performance indicator for the selection of youth football players to national teams
Reference: J Sports Med Phys Fitness. 2019 May 2. doi: 10.23736/S0022-4707.19.09739-1. [Epub ahead of print]
Authors: Ryman Augustsson S, Arvidsson J, Haglund E
Summary: Different jump tests such as the Countermovement Jump (CMJ), Abalakov Jump (AJ) and Standing Long Jump (SLJ) are often used in practice to evaluate muscular power and functional performance in football. These tests are also used in different selection processes and talent identification, but the significance of the tests for the selection of youth players to national teams are relatively unknown. The aim of this study was to compare jump ability between youth football players selected or not selected for the national team. In this cross-sectional study, 22 players (aged 17±2 years), 11 national players (NP) and 11 non- national players (NNP) were evaluated in three different jump tests; CMJ, AJ and SLJ. Mean scores for the tests were analysed and compared. Significant differences were found between the groups regarding jump height in favour of the NP group in both the CMJ (NP 39.9±5.0 cm vs NNP 34.2±4.9 cm, p=0.013) and the AJ (NP 47.1±5.4 vs NNP 40.9±4.7, p=0.010). No group difference was found regarding jump length in SLJ (NP 246.2±17.9 vs NNP 232.9±16.5, p=0.084). The results suggest that tests, measuring jump height, could be used as a performance indicator and part of the selection process of youth football players to national teams, whereas the use of jump length could be questioned.


#4 Anterior cruciate ligament injury risk factors in football: a narrative review
Reference: J Sports Med Phys Fitness. 2019 Apr 30. doi: 10.23736/S0022-4707.19.09563-X. [Epub ahead of print]
Authors: Bisciotti GN, Chamari K, Cena E, Bisciotti A, Bisciotti A, Corsini A, Volpi P
Summary: Anterior cruciate ligament (ACL) lesion represents one of the most dramatic injuries in a football (soccer) player's career. There are many injury risk factors related to intrinsic (non-modifiable) and/or extrinsic (modifiable) factors of ACL-injury. To date, evidence from the literature suggests that the risk of ACL-injury is multifactorial and involves biomechanical, anatomical, hormonal, and neuromuscular factors. Despite this relative complexity, the mechanisms of injury are well known and rationally classified into two categories: mechanisms of injury based on contact or on non- contact with another player, with the non-contact injury mechanisms clearly prevailing over the mechanisms of contact injury. One of the most frequent biomechanical risk factors, associated with ACL non-contact injury, is represented by the valgus knee in the pivoting and cutting movements and in the landing phase after jumping. Gender related risk factors show female populations to have a higher predisposition to ACL-injury than males However, there are still some theoretical and practical aspects that need further investigation such as; genetic risks together with the role of oestrogen and progesterone receptors in female populations, and the in vivo interaction shoe- playing surface. In particular, the genetic risk factors of ACL lesion seem to be an interesting and promising field of investigation, where considerable progress has still to be made. This narrative review provides an insight into the risk factors of ACL-injury that could be used by practitioners for preventing injury in football (soccer).


#5 Misbehavior During Penalty Kicks and Goalkeepers Holding the Ball Too Long as Trivial Offenses in Football
Reference: Front Psychol. 2019 Apr 18;10:844. doi: 10.3389/fpsyg.2019.00844. eCollection 2019.
Authors: Kolbinger O, Stöckl M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6482224/pdf/fpsyg-10-00844.pdf
Summary: Rule violations occur in every sport and the respective book of rules prescribes how match officials need to sanction them. However, there are some rule violations that are nearly never penalized, even if they are perceived by the match officials. A phenomenon that has been neglected in the scientific community so far, for which we want to introduce the term trivial offenses. This research focuses on two potential trivial offenses in football: rule violations regarding the six-seconds rule, the time a goalkeeper is allowed to control the ball with his hands, and rule violations during the performance of penalty kicks. The aim is to provide empirical proof of the existence of those trivial offenses and describe the respective patterns. For this purpose, two observation systems were constructed; one to investigate 45 games from the German Bundesliga with respect to the six-seconds rule and one to study rule violations during 618 penalty kicks from four European football leagues and one cup event. The following variables were collected: Goalkeeper, MatchLocation, Minute (representing the minute of the game), PreviousAction, CurrentScore, Time (representing the time the goalkeeper controlled the ball with his hands), and Penalization for the six-seconds study; Responsibility for infringement, Decision of the referee, and Outcome for the penalty study. Reliability tests showed almost perfect agreement for the data of both samples. On average, goalkeepers control the ball 6.0 s (SD:4.54) with their hands and the six-second rule was violated in 38.4% of the situations, none of which was penalized. This duration was significantly influenced by CurrentScore (p < 0.001), which indicates a tactical abuse of this situation. None of the investigated penalty kicks was conducted without a rule violation either. In most incidents (96.3%) outfield players from both teams as well as the goalkeeper commit offenses. The umpire only judges 2.8% of these incidents correctly, most of them by approving the scored goal. In total, this research proves the existence of trivial offenses in football and shows how methods and tools of performance analysis can serve to investigate and even solve this issue.


#6 The ball kicking speed: A new, efficient performance indicator in youth soccer
Reference: PLoS One. 2019 May 17;14(5):e0217101. doi: 10.1371/journal.pone.0217101. eCollection 2019.
Authors: Rađa A, Kuvačić G, De Giorgio A, Sellami M, Ardigò LP, Bragazzi NL, Padulo J
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0217101&type=printable
Summary: Success in different soccer skills like kicking depends on motor abilities achieved. Kicking is a soccer fundamental, which depends on many different and complex factors (technique, foot-ball interaction, ball flight, etc.). Therefore, it is important to identify players that are able to perform faster kicks using both dominant and non-dominant leg. The current study investigated some basic variables of different soccer kicking speed and their relevance to success in youth soccer academy. 119 players from the first and the second division participated to this study. They were randomly divided into age groups (U-15, U-17, and U19) and team status (first team, reserves). The diagnostic ability of the different ball kicking speed tests in capturing differences between first team players and reserves among different age categories were computed using the receiver operating characteristics analysis. Results demonstrated that first team players achieved better results when comparing to reserves in each category. In addition, differences were greater in the U-15 and the U-17 than in the U-19 age group. In conclusion, ball kicking speed could be one of the possible identification tools to evaluate players' success in youth soccer.


#7 Hamstring rate of torque development is more affected than maximal voluntary contraction after a professional soccer match
Reference: Eur J Sport Sci. 2019 May 17:1-16. doi: 10.1080/17461391.2019.1620863. [Epub ahead of print]
Authors: Grazioli R, Lopez P, Andersen LL, Machado CLF, Pinto MD, Cadore EL, Pinto RS
Summary: Match-induced fatigue of knee muscle strength and agonist-antagonist strength-ratios may affect both performance and risk of injury in soccer players. Once explosive tasks are imperative in soccer as well as hamstring strain injuries occur during high-velocity moments, rapid force capacity of this muscle group is especially important. This study evaluated the effect of match-induced fatigue on knee muscle strength and strength-ratio parameters after a single professional soccer match. Male professional soccer players (n = 16; 24.2 ± 3.9 years) were tested before and after a soccer match (56.2 ± 22.6 minutes of playing) for knee flexors (hamstring) and extensors (quadriceps) isometric peak torque (MVC) and rate of torque development (RTD) - as well as the hamstring-to-quadriceps ratio (H:Q) - at 30° of knee flexion. Knee injuries often occur at this joint angle, which is common in sprinting, pivoting, sidecutting, and jumping. Match-induced fatigue caused a left shift in the knee extensors torque-time curve with no significant change in both early (i.e. 0 to 50 ms) and late (i.e. 0 to 200 ms) RTD, and a right shift in the knee flexors torque-time curve with a decrease in early RTD (∼16%, P = 0.029) and late RTD (∼11%, P = 0.011). Knee extensors and knee flexors peak torque remained unchanged (P > 0.05). Early RTD H:Q decreased by∼24% (P = 0.027), while late RTD H:Q and MVC H:Q remained unchanged (P > 0.05). In conclusion, match-induced fatigue impaired the ability to rapidly produce force at an angle where injuries are most susceptible to occur. Important information is missed if only the traditional H:Q is considered.


#8 Age-related physical and technical match performance changes in elite soccer players
Reference: Scand J Med Sci Sports. 2019 May 17. doi: 10.1111/sms.13463. [Epub ahead of print]
Authors: Sal de Rellán-Guerra A, Rey E, Kalén A, Lago-Peñas C
Summary: The age of peak performance is likely to vary between sports and competitions, affected by the specific skills and attributes needed to succeed in the particular competition. However, no studies using modern tracking techniques have examined on the effects of age on competitive match play performance. Thus, the purpose of this study was to evaluate the effects of age on match physical and technical performance using a large-scale analysis of match performance in professional soccer players. A total of 14,546 individual match observations were undertaken in the first German league (Bundesliga) during the 2012-13, 2013-14, and 2014-15 seasons using a computerized tracking system (VISTRACK, by Impire Corp., Germany). Differences on physical and technical match performance of soccer players were analysed for the following variables: total distance covered, number of fast runs, number of sprints and percentage of successful passes. Professional soccer players aged >30 years showed a significant lower performance in the total distance covered, the number of fast runs, and the number of sprints compared with younger players (≤30 years). Conversely, the player's ability to make successful passes increased with age. These effects were observed in all positional roles except wide midfielders. These findings may help coaches and managers to better understand the effects of age on match-related physical and technical performance and may have the potential to assist in decisions such as, for example, when a new contract would be signed, the duration of the contract, the salary or when to replace or transfer a player depending on their age.


#9 Effects of Taping and Balance Exercises on Knee and Lower Extremity Function in Amateur Soccer Players: A Randomized Controlled Trial
Reference: J Sport Rehabil. 2019 May 16:1-25. doi: 10.1123/jsr.2018-0452. [Epub ahead of print]
Authors: Espí-López GV, Serra-Añó P, Cobo-Pascual D, Zarzoso M, Suso-Martí L, Cuenca-Martínez F, Inglés M
Summary: Knee injury prevention is a critical aspect in sport rehabilitation sciences and taping is a widely used technique in this field. Nevertheless, the role and effectiveness of a long-term application of Kinesio Taping on knee function, disability and injury prevention remains unclear. The objective was to determine the effect of Kinesio Taping, alone or in combination with balance exercises, on dynamic and static knee balance and flexibility. 48 male amateur soccer players were assigned to three groups: Sham KT (sKT) + BE; KT + BE; and KT in isolation. The intervention period lasted 4 weeks. Three evaluations were performed: at baseline (pre), at two weeks (mid) and at four weeks post-treatment (post). Y-Balance Test (YBT), Unipedal Stance Test (UST), the Toe Touch Test (TTT) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were utilized as main outcome measures.  Both sKT + BE and KT + BE groups achieved significant pre-post improvements in SEBT, UST and TTT. The KT group only showed significant intra-group differences in the left and right UST variable (p<0.05, d=0.76, d=0.62 respectively). The sham KT group obtained the strongest results in all physical variables. Regarding the KOOS, pre-post significant changes were found in the sham group (p<0.05, d=0.28). Both sham and real KT in combination with BE achieved significant improvements on all physical variables, and these differences were significantly greater compared to those found in the KT in isolation group, suggesting that benefits in knee function are due to the BE.


#10 Effects of Plyometric vs Optimum Power Training on Components of Physical Fitness in Young Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 May 16:1-27. doi: 10.1123/ijspp.2019-0039. [Epub ahead of print]
Authors: Ribeiro J, Teixeira L, Lemos R, Teixeira AS, Moreira V, Silva P, Nakamura FY
Summary: The current study aimed to compare the effects of plyometric (PT) vs. optimum power load (OPL) training on physical performance of young high-level soccer players. Athletes were randomly divided into PT (horizontal and vertical drills) and OPL (squat+hip thrust exercises at the load of maximum power output) interventions, applied over 7 weeks during the in-season period. Squat (SJ) and countermovement (CMJ) jumps, maximal sprint (10 and 30 m) and change of direction (COD; agility T test) were the pre-and post-training measured performance variables. Magnitude-based inference was used for within-and between-group comparisons. OPL training induced moderate improvements in vertical SJ (ES:0.97; 90%CI:0.32-1.61) and CMJ (ES:1.02; 90%CI:0.46-1.57), 30 m sprint speed (ES:1.02; 90%CI:0.09-1.95) and COD performance (ES:0.93; 90%CI:0.50-1.36). After PT training method, vertical SJ (ES:1.08; 90%CI:0.66-1.51) and CMJ (ES:0.62; 90%CI:0.18-1.06) were moderately increased, while small enhancements were noticed for 30 m sprint speed (ES:0.21; 90%CI:-0.02-0.45) and COD performance (ES:0.53; 90%CI:0.24-0.81). The 10 m sprint speed possibly increased after PT intervention (small ES: 0.25; 90%CI:-0.05-0.54), but no substantial change (small ES:0.36; 90%CI:-0.40-1.13) was noticed in OPL. For between-group analyses, the COD ability and 30 m sprint performances were possibly (small ES:0.30; 90%CI:-0.20-0.81; Δ=+1.88%) and likely (moderate ES:0.81; 90%CI:-0.16-1.78; Δ=+2.38%) more improved in the OPL than in the PT intervention, respectively. The two different training programs improved physical performance outcomes during the in-season period. However, the combination of vertically-and horizontally-based training exercises (squat+hip thrust) at optimum power zone led to superior gains in COD and 30 m linear sprint performances.


#11 Dynamic Warm-up With a Weighted Vest: Improvement of Repeated Change-of-Direction Performance in Young Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 May 16:1-28. doi: 10.1123/ijspp.2018-0800. [Epub ahead of print]
Authors: Turki O, Dhahbi W, Gueid S, Hmaied S, Souaifi M, Khalifa R
Summary: This study aims to explore the effect of 4 different warm-up strategies using weighted vests, and to determine the specific optimal recovery duration required to optimize the repeated change of direction (RCOD) performance in young soccer players. Nineteen male soccer players (age: 18±0.88 years, body-mass: 69.85±7.68 kg, body-height: 1.75±0.07 m, body-mass-index: 22.87±2.23 kg·m-2 and body-fat-percentage: 12.53±2.59 %), completed the following loaded warm-up protocols in a randomized, counterbalanced cross-over, within participants order and on separate days: weighted-vest with a loading of 5% (WUV5%), 10% (WUV10%), 15% (WUV15%) body-mass, and an unloaded condition (control). RCOD performance (total time, peak time and fatigue index) was collected during the pre-intervention phase (5 min after the dynamic stretching sequence) for baseline values and immediately (at 15ths), at the 4th and 8th min post-warm-up intervention. For each post-warm-up tested, recovery-times (i.e., 15-s, 4-min, and 8-min), both total, and peak times were faster following WUV5%, WUV10%, and WUV15%, compared to the unloaded condition (P [<0.001-0.031], d [1.28-2.31] [large]). There were no significant differences (P [0.09-1.00], d [0.03-0.72] [trivial-moderate]) in-between recovery times in both total and peak times following WUV5%, WUV10% and WUV15%. However, baseline fatigue index score was significantly worse than all other scores (P [<0.001-0.002], d [1.35-2.46] [large]) following the loaded conditions. The findings demonstrated that a dynamic loaded warm-up increases an athlete's initial RCOD performance up to the 8th min post-warm-up intervention. Therefore, strength coaches need to consider using weighted-vests during the warm-up for trained athletes in order to acutely optimize RCODs.


#12 The Increased Effectiveness of Loaded Versus Unloaded Plyometric-Jump Training in Improving Muscle Power, Speed, Change-of-Direction, and Kicking-Distance Performance in Prepubertal Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 May 16:1-25. doi: 10.1123/ijspp.2018-0866. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Sammoud S, Prieske O, Moran J, Ramirez-Campillo R, Nejmaoui A, Granacher U
Summary: This study examined the effects of loaded (LPJT) and unloaded (UPJT) plyometric jump training programmes on measures of muscle power, speed, change-of-direction and kicking-distance performance in prepubertal male soccer players. Participants (N=29) were randomly assigned to a LPJT group (n=13; age=13.0±0.7 years) using weighted vests or UPJT group (n=16; age=13.0±0.5 years) using body mass only. Before and after the intervention, tests for the assessment of proxies of muscle power (i.e., countermovement-jump [CMJ], standing-long-jump [SLJ]), speed (i.e., 5-m, 10-m, and 20-m sprint), change-of-direction (i.e., Illinois change-of-direction test [ICoDT], modified 505 agility test), and kicking-distance test were conducted. Data were analysed using magnitude-based inferences. Within-group analyses for the LPJT group showed large and very large improvements for 10-m sprint-time (effect size [ES]=2.00) and modified 505 CoD (ES=2.83) tests, respectively. For the same group, moderate improvements were observed in ICoDT (ES=0.61), 5- and 20-m sprint-time (ES=1.00 for both tests), CMJ (ES=1.00) and MKD (ES=0.90). Small enhancements in the SLJ (ES=0.50) test were apparent. Regarding the UPJT group, small improvements were observed for all tests (ES=0.33 to 0.57) except 5-m and 10-m sprint-time (ES=1.00 and 0.63, respectively). Between-group analyses favored the LPJT group for the modified 505 CoD (ES=0.61), SLJ (ES=0.50), and MKD (ES=0.57) tests, but not for 5-m sprint-time (ES=1.00). Only trivial between-group differences were shown for the remaining tests (ES=0.00 to 0.09). Overall, LPJT appears to be more effective than UPJT in improving measures of muscle power, speed, change-of-direction and kicking-distance performance in prepubertal male soccer players.

Sun

26

May

2019

Latest research in football - week 18 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Relationship of Pre-season Training Load With In-Season Biochemical Markers, Injuries and Performance in Professional Soccer Players
Reference: Front Physiol. 2019 Apr 12;10:409. doi: 10.3389/fphys.2019.00409. eCollection 2019.
Authors: Coppalle S, Rave G, Ben Abderrahman A, Ali A, Salhi I, Zouita S, Zouita A, Brughelli M, Granacher U, Zouhal H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6474299/pdf/fphys-10-00409.pdf
Summary: There is controversy in the literature in regards of the link between training load and injury rate. Thus, the aims of this non-interventional study were to evaluate relationships between pre-season training load with biochemical markers, injury incidence and performance during the first month of the competitive period in professional soccer players. Healthy professional soccer players were enrolled in this study over two pre-season periods. Data sets were available from 26 players during the first season (2014-2015) and 24 players during the second season (2015-2016) who completed two pre-season periods (6 weeks each). External training load was assessed from all athletes during training using Global Positioning System (GPS). Internal training load was monitored after each training session using rate of perceived exertion (RPE). Before and after each pre-season, blood samples were taken to determine plasma lactate dehydrogenase (LDH), creatine kinase (CK) and C-reactive protein (CRP). Injury incidence and overall performance (ranking of the team after the first five official games of the championship) were recorded for both seasons separately. There was no statistically significant difference in mean RPE values of the two-preparation periods (2737 ± 452 and 2629 ± 786 AU, p = 0.492). The correlational analysis did not reveal significant associations between internal and external training load (RPE and GPS data) and biological markers. There was a significant positive correlation between RPE and LDH during the 2015/2016 season (r = 0.974, p = 0.001). In addition, a significant negative correlation was found between total distance >20 km/h and CRP during the 2015-2016 season (r = -0.863, p = 0.027). The injury rates for the two seasons were 1.76 and 1.06 per 1000 h exposure for the 2014-2015 and 2015-2016 seasons, respectively (p = 0.127). Our study showed that pre-season training load is not associated with overall team performance. This association is most likely multifactorial and other factors (e.g., technical and tactical level of the team, opponents, environment) may play an important role for the collective team performance. Our findings may help coaches to better prepare their athletes during pre-season.


#2 Six different football shoes, one playing surface and the weather; Assessing variation in shoe-surface traction over one season of elite football
Reference: PLoS One. 2019 Apr 30;14(4):e0216364. doi: 10.1371/journal.pone.0216364. eCollection 2019.
Authors: Thomson A, Whiteley R, Wilson M, Bleakley C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0216364&type=printable
Summary: An optimal range of shoe-surface traction (grip) exists to improve performance and minimise injury risk. Little information exists regarding the magnitude of traction forces at shoe-surface interface across a full season of elite football (soccer) using common football shoes. The objective was to assess variation in shoe-surface traction of six different football shoe models throughout a full playing season in Qatar encompassing climatic and grass species variations. Football shoes were loaded onto a portable shoe-surface traction testing machine at five individual testing time points to collect traction data (rotational and translational) on a soccer playing surface across one season. Surface mechanical properties (surface hardness, soil moisture) and climate data (temperature and humidity) were collected at each testing time point. Peak rotational traction was significantly different across shoe models (F = 218, df = 5, p <0.0001), shoe outsole groups (F = 316.2, df = 2, p < .0001), and grass species (F = 202.8, df = 4, p < 0.0001). No main effect for shoe model was found for translational traction (F = 2.392, p = 0.07). The rotational (but not translational) traction varied substantially across different shoe types, outsole groups, and grass species. Highest rotational traction values were seen with soft ground outsole (screw-in metal studs) shoes tested on warm season grass. This objective data allows more informed footwear choices for football played in warm/hot climates on sand-based elite football playing surfaces. Further research is required to confirm if these findings extend across other football shoe brands.


#3 When Better Seems Bigger: Perceived Performance of Adult Professional Football Players Is Positively Associated With Perceptions of Their Body Size
Reference: Evol Psychol. 2019 Apr-Jun;17(2):1474704919841914. doi: 10.1177/1474704919841914.
Authors: Knapen JEP, Pollet TV, van Vugt M
Download link: https://journals.sagepub.com/doi/pdf/10.1177/1474704919841914
Summary: Research has shown a positive association between cues of physical formidability and perceptions of status, supporting a generic "bigger-is-better" heuristic. However, does better also lead to appraisals as bigger? Recent research suggests that the perceptual association between body size and social status can also be explained in terms of prestige. To test whether perceptions of prestige lead to higher appraisals of body size, we examined whether people apply a "better is bigger bias" (BBB) in football, where performance and body size tend to be uncorrelated. In two studies, we examined real coalitional sports groups on a national (Study 1) and team level (Study 2), and we manipulated target performance in an experimental third study. Results suggest that perceived performance significantly predicted both the perceived height (Studies 2 and 3) and perceived weight (Studies 1 and 2) of professional football players, supporting the BBB. Support for the team had a positive effect on body size estimations of the players; however, we did not find any support for winner or loser effects. We discuss these results in light of individual versus team performance and coalitional affiliation.


#4 Efficacy of using non-linear pedagogy to support attacking players' individual learning objectives in elite-youth football: A randomised cross-over trial
Reference: J Sports Sci. 2019 Apr 27:1-11. doi: 10.1080/02640414.2019.1609894. [Epub ahead of print]
Authors: Roberts SJ, Rudd JR, Reeves MJ
Summary: The present study examined the efficacy of a coaching curriculum, based on non-linear pedagogy, on improving attacking players' individual learning objectives (ILOs) in elite-youth football. Participants included 22 attacking players (i.e., centre-forwards, wide-players and attacking midfield players) from a professional football academy in England. The players were randomly appointed to both control (CON) and intervention (INT) periods following baseline measures. The INT (non-linear) and CON (linear) periods were both designed to support the ILOs provided to each player as part of the elite player performance plan. The study adopted a randomised cross-over design and ILOs considered important for attacking players (i.e., strong foot finishing, weak foot finishing, 1-v-1 and decision-making) were evaluated using the Loughborough Shooting Skill Test. The results showed significant differences for INT in 1-v-1 (P< 0.02) and decision-making (P< 0.01). However, there were no significant differences for strong foot finishing, weak foot finishing or time taken. These results support non-linear pedagogy in developing 1-v-1 game play and decision-making but not for technical shooting proficiency.


#5 Injury Prevention in Amateur Soccer: A Nation-Wide Study on Implementation and Associations with Injury Incidence
Reference: Int J Environ Res Public Health. 2019 May 7;16(9). pii: E1593. doi: 10.3390/ijerph16091593.
Authors: Gebert A, Gerber M, Pühse U, Stamm H, Lamprecht M
Download link: https://www.mdpi.com/1660-4601/16/9/1593/pdf
Summary: Prevention programmes can reduce injury risk in amateur soccer. Hence, we examined the implementation of injury prevention in the real-world context of Swiss amateur soccer. In 2004 (n = 1029), 2008 (n = 705) and 2015 (n = 1008), a representative sample of Swiss amateur soccer coaches was interviewed by telephone about the frequency of injuries in their teams, the implementation of preventive measures and the use of injury prevention programmes. In the 2015 survey, 86.1% of amateur coaches stated that injury prevention is important and 85.3% of amateur coaches reported that they would implement some kind of preventive measures. The proportion of teams which performed a prevention programme according to minimal standards remained unchanged between 2008 (21.7%) and 2015 (21.9%), although a second prevention programme was made available in 2011. Only 8.6% of the 30+/40+ league teams, which are composed as a function of age, implemented a programme. Overall, the level of implementation of prevention programmes in this real-world context is still unsatisfactory. Offering an additional programme did not lead to a higher willingness to implement such programmes among the coaches. Concerted efforts are needed to remove barriers that hinder the use of such programmes, particularly among coaches of 30+/40+ league teams.


#6 Validity and reliability of a 6-a-side small-sided game as an indicator of match-related physical performance in elite youth Brazilian soccer players
Reference: J Sports Sci. 2019 May 7:1-6. doi: 10.1080/02640414.2019.1608895. [Epub ahead of print]
Authors: Aquino R, Melli-Neto B, Ferrari JVS, Bedo BLS, Vieira LHP, Santiago PRP, Gonçalves LGC, Oliveira LP, Puggina EF
Summary: The aims of this study were: (i) to compare the external and internal load during a 6-a-side small-sided game (6v6-SSG) according to age-group; (ii) to relate these parameters between the 6v6-SSG and official matches; and (iii) to test the reliability of the 6v6-SSG. A total of 51 Brazilian youth soccer players participated in this study (U11 [n = 16]; U13 [n = 10]; U15 [n = 9]; U17 [n = 8]; U20 [n = 8]). Three experiments were conducted. Experiment A: fifty-one U11 to U20 players were submitted to 6v6-SSGs (n = 10 games; two for each age-group). Experiment B: thirty-two players were randomized to also play official matches (n = 6 matches). Experiment C: thirty-five youth players played the 6v6-SSG twice for test and retest reliability analysis. External load was obtained using Global Positioning Systems and the internal load parameter was calculated through mean heart rate. Statistical approaches showed progressive increases in all parameters according to categories (U11< U13< U15< U17< U20; p < 0.05; ES = 0.42-23.68). Even controlling for chronological age, all parameters showed likely to almost certain correlations between 6v6-SSG and official matches (r = 0.25-0.92). Collectively, the proposed protocol indicates good reliability (CV% = 2.0-12.6; TE% = 2.3-2.7%; ICC = 0.78-0.90). This research suggests that the 6v6-SSG is an alternative tool to indicate match-related physical performance in youth soccer players.


#7 Improvements in soccer specific fitness and exercise tolerance following 8 weeks of inspiratory muscle training in adolescent males
Reference: J Sports Med Phys Fitness. 2019 Apr 30. doi: 10.23736/S0022-4707.19.09578-1. [Epub ahead of print]
Authors: Najafi A, Ebrahim K, Ahmadizad S, Jahani Ghaeh Ghashlagh GR, Javidi M, Hackett D
Summary: Inspiratory muscle training has been shown to improve exercise performance, however there is limited evidence for its effectiveness in soccer players. This study investigates the effect of inspiratory muscle training on soccer-specific fitness and exercise tolerance in adolescent male players. Thirty highly trained soccer players (16-19 y) were randomly assigned into one of three groups: experimental 1 (n=10), experimental 2 (n=10) and sham-control (sham, n=10). All groups performed inspiratory muscle training twice per day and five times per week for 8 weeks. Experimental 1 performed 25-35 breaths at 55% maximal inspiratory pressure, experimental 2 performed 45-55 breaths at 40% maximal inspiratory pressure, whereas sham performed 30 breaths at 15% maximal inspiratory pressure. Measures before and after the intervention involved the Yo-Yo intermittent recovery test level 1, running-based anaerobic test, repeated high-intensity endurance test, and maximal inspiratory pressure, and spirometry. Yo-Yo intermittent recovery test level 1 distance increased for experimental groups 1 and 2 compared to sham (P = 0.012 and P = 0.031, respectively), with no difference between experimental groups. Fatigue index calculated from running-based anaerobic test improved for experimental groups 1 and 2 compared to sham (P = 0.014 and P = 0.011, respectively), with no difference between experimental groups. Exercise tolerance (i.e. blood lactate concentration, perceived exertion and perceived breathlessness) following the repeated high-intensity endurance test decreased in experimental groups 1 and 2 compared to sham (P <0.05), with no difference between experimental groups. Maximal inspiratory pressure increased for experimental groups 1 and 2 compared to sham (P = 0.000), with no difference between experimental groups. There were no changes for the spirometry measures. Improvements in soccer-specific fitness and exercise tolerance can be achieved using inspiratory muscle training protocols of varying intensities and volumes.


#8 Effects of Strength Training on Body Composition in Young Male Professional Soccer Players
Reference: Sports (Basel). 2019 May 5;7(5). pii: E104. doi: 10.3390/sports7050104.
Authors: Suarez-Arrones L, Lara-Lopez P, Torreno N, Saez de Villarreal E, Di Salvo V, Mendez-Villanueva A
Download link: https://www.mdpi.com/2075-4663/7/5/104/pdf
Summary: The present prospective cohort study investigated changes in body composition (BC) in young male football players (n = 18, 16.1 ± 0.8 years; 181.0 ± 0.1 cm; 71.3 ± 4.9 kg) after combined football and strength training (ST) during a whole in-season period (26 weeks). BC was measured at whole-body absolute and regional levels by dual-energy X-ray absorptiometry in eighteen players at the beginning and at the end of the competitive period. The ST was organized into three different session types: ST in the gym, specific ST on the field, and individual ST (weak points). The results of the present study indicated that fat-free mass (FFM) was substantially higher following the competitive period (5.1% ± 1.2%), while percentage of fat showed no changes during the competitive period. At the regional level, arms' and legs' FFM increased at the end of the season, and bone mineral content (BMC) and density (BMD) increased in arms, legs, pelvis, thoracic spine, and lumbar spine. In conclusion, within the limitation of the potential positive impact of growth and/or maturation, present results seem to indicate that an ST program that supplements football-related training sessions could be an effective option to increase FFM, BMC, and BMD at both whole-body and regional level across the competitive season in young male professional football players.


#9 Dose-Response Relationship Between External Load Variables, Body Composition, and Fitness Variables in Professional Soccer Players
Reference: Front Physiol. 2019 Apr 17;10:443. doi: 10.3389/fphys.2019.00443. eCollection 2019.
Authors: Clemente FM, Nikolaidis PT, Rosemann T, Knechtle B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6479167/pdf/fphys-10-00443.pdf
Summary: The aim of this study was to test associations between accumulated external load and changes in body composition, isokinetic strength, and aerobic capacity of soccer players. Twenty-three professional soccer players (age: 24.7 ± 2.8 years; height: 179.2 ± 6.3; experience: 9.7 ± 2.1 years) participated in this study. This pre-post study design was performed during 10 weeks from July to August of 2017 (4 weeks of pre-season and 6 weeks during the early season). Players were monitored daily by GPS technology and were assessed before and after a 10-week period in terms of body mass (BM), fat mass, lean mass, isokinetic strength at 60°/s, VO2max, and HRmax. Large-to-very large positive correlations were found between the sum of sprinting distance and % differences of BM [0.70, (-0.09;0.95)], HRmax [0.51, (-0.37;0.91)], agonist (quadriceps)/antagonist (hamstrings) left ratio [0.84, (0.27;0.97)] and agonist/antagonist right ratio [0.92, (0.58;0.99)]. Large positive correlations were found between the acceleration sum and % differences of VO2max [0.58, (-0.29;0.92)], quadriceps left peak torque [0.66, (-0.16;0.94)], hamstrings left peak torque [0.68, (-0.13;0.94)] and hamstrings right peak torque [0.62, (-0.22;0.93)]. Sprinting load was largely and positively associated with changes in knee strength asymmetries. Acceleration sum was largely and positively correlated with variations at VO2max and peak torques at hamstrings. In addition, dose-response relationships using external load variables were identified in professional soccer players.


#10 Biological maturation and match running performance: A national football (soccer) federation perspective
Reference: J Sci Med Sport. 2019 Apr 22. pii: S1440-2440(18)30984-8. doi: 10.1016/j.jsams.2019.04.007. [Epub ahead of print]
Authors: Lovell R, Fransen J, Ryan R, Massard T, Cross R, Eggers T, Duffield R
Summary: The purpose was to examine the influence of maturation and its interaction with playing position upon physical match performances in U15 footballers from a national federation. 278 male outfield players competing in a national tournament were assessed for somatic maturity and match physical performances according to playing position. Stature, sitting height, and body mass were measured and entered into an algorithm to estimate the age at peak height velocity (APHV). Players match movements were recorded by Global Positioning System devices (10 Hz), to determine peak speed, and total- (TD), low-speed running (LSR; ≤13.0 km h-1), high-speed running (HSR; 13.1-16.0 km h-1), very high-speed running (VHSR; 16.1-20.0 km h-1) and sprint distances (SPR; >20.0 km h-1) expressed relative to match exposure (m min-1). Linear-mixed models using log transformed response variables revealed a significant contribution of estimated APHV upon TD (1.01; 95% CI: 0.99-1.02 m·min-1; p < 0.001), HSR (1.05; 95% CI: 0.98-1.13 m min-1; p < 0.001) and VHSR (1.07; 95% CI: 1.00-1.14 m min-1; p = 0.047). An increase by one year in APHV was associated with an increase of 0.6, 5.4 and 6.9% in TD, HSR and VHSR respectively. No effects of APHV were observed for LSR, SPR, and peak speed. Further, no APHV effects were observed relative to players' field position. Later maturing players covered substantially more higher-intensity (HSR and VHSR) running in matches, irrespective of playing position. The greater match intensity of later maturing players may inform talent identification and athletic development processes within a national federation.


#11 Short-Term Cardiac Autonomic Recovery after a Repeated Sprint Test in Young Soccer Players
Reference: Sports (Basel). 2019 Apr 30;7(5). pii: E102. doi: 10.3390/sports7050102.
Authors: Abad CCC, Pereira LA, Zanetti V, Kobal R, Loturco I, Nakamura FY
Download link: https://www.mdpi.com/2075-4663/7/5/102/pdf
Summary: The aim of this study was to describe the time course (within 2 h post-exercise) of heart rate variability (HRV) recovery following a traditional repeated sprint ability (RSA) test applied to youth soccer players. Twenty-four young soccer players (18.4 ± 0.5 years) undertook the following assessments: (1) 10 min rest in the seated position for HRV assessment; (2) a repeated sprint ability (RSA) test; (3) passive recovery in the seated position for 10 min, immediately after finishing the RSA test and 1 h and 2 h post-RSA test. During the HRV measurements (using the natural log of root mean square difference of successive normal RR intervals-lnRMSSD) the participants were instructed to assume a comfortable sitting position, remaining awake and breathing spontaneously for 10 min. Magnitude-based inference was used in the analyses. After the RSA test, the post-1 h measure was almost certainly lower than the resting measure, but almost certainly higher than the lnRMSSD measured post-RSA test. The lnRMSSD post-2 h was likely lower than the resting lnRMSSD and very likely higher than post-1 h. In conclusion, lnRMSSD is severely depressed after performing an RSA test, and reactivation is incomplete after 2 h of passive recovery. This result should be considered by practitioners when applying successive training sessions within intervals shorter than 2 h.


#12 A comparison of the isometric force fatigue-recovery profile in two posterior chain lower limb tests following simulated soccer competition
Reference: PLoS One. 2019 May 3;14(5):e0206561. doi: 10.1371/journal.pone.0206561. eCollection 2019.
Authors: Matinlauri A, Alcaraz PE, Freitas TT, Mendiguchia J, Abedin-Maghanaki A, Castillo A, Martínez-Ruiz E, Carlos-Vivas J, Cohen DD
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0206561&type=printable
Summary: The aim was to evaluate the reliability of isometric peak force (IPF) in a novel "long-length" 90°Hip:20°Knee (90:20) strength test and to compare the simulated soccer match induced fatigue-recovery profile of IPF in this test with that of an isometric 90°Hip:90°Knee (90:90) position test. Twenty semi-professional soccer players volunteered for the study of which 14 participated in the first part of the study which assessed 90:20 reliability (age = 21.3 ± 2.5 years, height = 1.79 ± 0.07 m, body mass = 73.2 ± 8.8 kg), while 17 completed the second part of the study evaluating fatigue-recovery (age 21.2±2.4 yrs., height = 180 ± 0.09 m, body mass 73.8 ± 8.9 kg). We evaluated the inter-session reliability of IPF in two 90:20 test protocols (hands on the wall (HW); and hands on chest (HC)) both performed on two occasions, 7 days apart. We then assessed 90:20 (HC) and 90:90 IPF immediately before (PRE) and after (POST) after a simulated soccer match protocol (BEAST90mod) and 48 (+48 h) and 72 hours (+72 h) later. Part one: the 90:20 showed moderate to high overall reliability (CV's of 7.3% to 11.0%) across test positions and limbs. CV's were lower in the HW than HC in the dominant (7.3% vs 11.0%) but the opposite happened in the non-dominant limb where CV's were higher in the HW than HC (9.7% vs 7.3%). Based on these results, the HC position was used in part two of the study. Part two: 90:20 and 90:90 IPF was significantly lower POST compared to PRE BEAST90mod across all testing positions (p<0.001). IPF was significantly lower at +48 h compared to PRE in the 90:20 in both limbs (Dominant: p<0.01,Non-dominant: p≤0.05), but not in the 90:90. At +72 h, IPF was not significantly different from PRE in either test. Simple to implement posterior IPF tests can help to define recovery from competition and training load in football and, potentially, in other multiple sprint athletes. Testing posterior chain IPF in a more knee extended 90:20 position may provide greater sensitivity to fatigue at 48 h post simulated competition than testing in the 90:90 position, but also may require greater degree of familiarization due to more functional testing position.

Sun

26

May

2019

Latest research in football - week 17 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 In-season internal and external training load quantification of an elite European soccer team
Reference: PLoS One. 2019 Apr 22;14(4):e0209393. doi: 10.1371/journal.pone.0209393. eCollection 2019.
Authors: Oliveira R, Brito JP, Martins A, Mendes B, Marinho DA, Ferraz R, Marques MC
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209393&type=printable
Summary: Elite soccer teams that participate in European competitions need to have players in the best physical and psychological status possible to play matches. As a consequence of congestive schedule, controlling the training load (TL) and thus the level of effort and fatigue of players to reach higher performances during the matches is therefore critical. Therefore, the aim of the current study was to provide the first report of seasonal internal and external training load that included Hooper Index (HI) scores in elite soccer players during an in-season period. Nineteen elite soccer players were sampled, using global position system to collect total distance, high-speed distance (HSD) and average speed (AvS). It was also collected session rating of perceived exertion (s-RPE) and HI scores during the daily training sessions throughout the 2015-2016 in-season period. Data were analysed across ten mesocycles (M: 1 to 10) and collected according to the number of days prior to a one-match week. Total daily distance covered was higher at the start (M1 and M3) compared to the final mesocycle (M10) of the season. M1 (5589m) reached a greater distance than M5 (4473m) (ES = 9.33 [12.70, 5.95]) and M10 (4545m) (ES = 9.84 [13.39, 6.29]). M3 (5691m) reached a greater distance than M5 (ES = 9.07 [12.36, 5.78]), M7 (ES = 6.13 [8.48, 3.79]) and M10 (ES = 9.37 [12.76, 5.98]). High-speed running distance was greater in M1 (227m), than M5 (92m) (ES = 27.95 [37.68, 18.22]) and M10 (138m) (ES = 8.46 [11.55, 5.37]). Interestingly, the s-RPE response was higher in M1 (331au) in comparison to the last mesocycle (M10, 239au). HI showed minor variations across mesocycles and in days prior to the match. Every day prior to a match, all internal and external TL variables expressed significant lower values to other days prior to a match (p<0.01). In general, there were no differences between player positions. Conclusions: Our results reveal that despite the existence of some significant differences between mesocycles, there were minor changes across the in-season period for the internal and external TL variables used. Furthermore, it was observed that MD-1 presented a reduction of external TL (regardless of mesocycle) while internal TL variables did not have the same record during in-season match-day-minus.


#2 Comparison of Physical Fitness and Anthropometrical Profiles Among Brazilian Female Soccer National Teams From U15 to Senior Categories
Reference: J Strength Cond Res. 2019 Apr 11. doi: 10.1519/JSC.0000000000003140. [Epub ahead of print]
Authors: Ramos GP, Nakamura FY, Penna EM, Mendes TT, Mahseredjian F, Lima AM, Garcia ES, Prado LS, Coimbra CC
Summary: This study aimed to compare anthropometric and physical fitness of Brazilian female national team soccer players from the U15 to senior categories, and to compare the physical performance between selected and nonselected players. Subjects included 231 athletes (U15, n = 46, U17, n = 49, U20, n = 98, and Senior, n = 38). Body mass, height, sum of skinfolds, squat jump (SJ), countermovement jump (CMJ), 20-m linear sprint, and Yo-Yo IR1 were assessed. The U15 players were shorter than all other groups (p < 0.01) and lighter than U20 players (p < 0.01). Regarding physical tests, Senior athletes presented higher SJ compared with U20, and both showed higher CMJ and SJ compared with the U15 and U17 (p < 0.05). Senior athletes were also faster than players of all other categories in 20-m sprint (p < 0.01) and covered the greatest distance in the Yo-Yo IR1 (p < 0.05). U20 were better in the Yo-Yo IR1 than the younger groups (p < 0.05). When comparing selected and nonselected players, no differences were identified in anthropometric measures (p > 0.05). However, selected players from U17, U20, and Senior teams showed better performance in Yo-Yo IR1 than nonselected ones (p < 0.05). Finally, selected senior athletes also presented higher CMJ and SJ than nonselected players (p < 0.05). These results suggest that, although there is a tendency for maintenance in anthropometric measures from the age of 15 years, there are substantial improvements in speed, lower-body power, and aerobic capacity from U20 age group. In addition, it seems that intermittent aerobic fitness contributes to the selection of players to international tournaments in national teams.


#3 Effects of Interlimb Asymmetries on Acceleration and Change of Direction Speed: A Between-Sport Comparison of Professional Soccer and Cricket Athletes
Reference: J Strength Cond Res. 2019 Apr 16. doi: 10.1519/JSC.0000000000003135. [Epub ahead of print]
Authors: Bishop C, Read P, Brazier J, Jarvis P, Chavda S, Bromley T, Turner A
Summary: The first aim of this study was to quantify and compare asymmetries among professional soccer and cricket athletes. The second aim was to examine the association between asymmetries and performance within both groups. Professional soccer (n = 18) and cricket (n = 23) athletes performed single-leg countermovement jumps, single-leg drop jumps (SLDJs), a 10-m sprint, and 505 change of direction speed (CODS) tests. Interlimb asymmetries were calculated as a standard percentage difference, Mann-Whitney U tests conducted to establish systematic bias between groups, and Spearman's r correlations used to establish the relationship between asymmetry scores and speed and CODS performance. Soccer athletes sprinted faster, jumped higher, and had a greater reactive strength index (RSI) score than cricket athletes (p < 0.05). However, cricketers showed reduced ground contact times compared with footballers during the SLDJ (p < 0.05). The cricket group showed significantly greater jump height (asymmetry = 11.49 vs. 6.51%; p = 0.015) and RSI (asymmetry = 10.37 vs. 5.95%; p = 0.014) asymmetries compared with soccer players. These metrics were also associated with slower 505 times in the cricket group only (r = 0.56 -0.74; p < 0.01). These results show that between-limb asymmetries exhibit no association with speed and CODS in elite soccer players but are associated with reduced CODS in elite cricketers. Thus, the reduction of interlimb asymmetries may be of greater consideration when working with cricket vs. soccer athletes.


#4 Dose-Response Relationship Between Internal Training Load and Changes in Performance During the Preseason in Youth Soccer Players
Reference: J Strength Cond Res. 2019 Apr 16. doi: 10.1519/JSC.0000000000003126. [Epub ahead of print]
Authors: Figueiredo DH, Figueiredo DH, Moreira A, Gonçalves HR, Dourado AC
Summary: The aim of this study was to describe training intensity distribution based on the session rating of perceived exertion (sRPE) and heart rate (HR) methods and examine the dose-response relation between internal training load (ITL) and change in performance of 16 youth soccer players (mean ± SD age: 18.75 ± 0.68 years, height: 175.3 ± 5.5 cm, body mass: 68.7 ± 6.5 kg, and body fat: 10.7 ± 1.2%) belonging to a Brazilian first division team during a 3-week preseason. The sRPE and HR data were registered daily to calculate the ITL and the training intensity distribution, in 3 intensity zones (low, moderate, and high). The Yo-yo Intermittent Recovery Level 1 (Yo-yo IR1) was evaluated before and after experimental period. The total time spent in the low-intensity zone (HR method) was greater (p < 0.01) compared with the moderate- and high-intensity zones. No difference was observed between training intensity zones determined by the sRPE method (p > 0.05). Negative correlations were observed between weekly mean sRPE-TL (r = -0.69), Edward's-TL (r = -0.50), and change in Yo-yo IR1. Linear regression indicated that weekly mean sRPE-TL (F1;14 = 13.3; p < 0.01) and Edward's-TL (F1;14 = 4.8; p < 0.05) predicted 48.7 and 25.5% of the variance in performance change, respectively. Stepwise linear regression revealed that these 2-predictor variables (F2;13 = 18.9; p < 0.001) explained 74.5% of the variance in performance change. The results suggest that the sRPE and HR methods cannot be used interchangeably to determine training intensity distribution. Moreover, sRPE-TL seems to be more effective than the HR-based TL method to predict changes in performance in youth soccer players.


#5 Activity Profiles of Top-Class Players and Referees and Accuracy in Foul Decision-Making During Korean National League Soccer Games
Reference: J Strength Cond Res. 2019 Apr 16. doi: 10.1519/JSC.0000000000003083. [Epub ahead of print]
Authors: Joo CH, Jee H
Summary: The aims of this study were to compare the activity profiles between the top-class referees and players and elucidate the factors related to foul decision-making. Three hundred thirty-five elite-level players and referees were analyzed for distance covered during 20 matches of nationally held 2016 Korean league competitions. Distance covered by the players and referees was analyzed for the activity zones (slow walking, walking, jogging, running, high-intensity running, and sprinting) and 15-minute match periods. Mean distance between foul play and referee locations, foul plays, and 15-minute match periods were compared with the foul decision errors. Foul play and decision error rates (%) were also analyzed per segmented pitch zone. Although the total distance covered during a match and distances covered by jogging, running, and sprinting were significantly different between the players and referees, differences were within 1%. Significant differences in the distance covered before and after halftime were observed. The greatest distance between the foul play and referee locations, number of foul plays, and number of foul decision errors were observed at the 75-minute match period. Finally, the greater number of foul plays was observed in the neutral and attacking zones, and the foul decision errors were observed in the right defensive and left attacking zones 1. In conclusion, although the activity profiles may be different, referees should maintain certain level of physical fitness to match that of the players. To reduce the number of foul decision errors, factors such as match time, foul occurring location, and distance between foul play and referee locations should be considered.


#6 Are specific players more likely to be involved in high-magnitude head impacts in youth football?
Reference: J Neurosurg Pediatr. 2019 Apr 26:1-7. doi: 10.3171/2019.2.PEDS18176. [Epub ahead of print]
Authors: Gellner RA, Campolettano ET, Smith EP, Rowson S
Summary: Youth football attracts approximately 3.5 million participants every year, but concern has recently arisen about the long-term effects of experiencing repetitive head accelerations from a young age due to participation in football. The objective of this study was to quantify total involvement in high-magnitude impacts among individual players in youth football practices. The authors explored the relationship between the total number of high-magnitude accelerations in which players were involved (experienced either by themselves or by other players) during practices and the number of high-magnitude accelerations players experienced. local cohort of 94 youth football players (mean age 11.9 ± 1.5, mean body mass 50.3 ± 16.4 kg) from 4 different teams were recruited and outfitted with helmet-mounted accelerometer arrays. The teams were followed for one season each for a total of 128 sessions (practices, games, and scrimmages). All players involved in high-magnitude (greater than 40g) head accelerations were subsequently identified through analysis of practice film. Players who experienced more high-magnitude accelerations were more likely to be involved in impacts associated with high-magnitude accelerations in other players. A small subset of 6 players (6%) were collectively involved in 230 (53%) high-magnitude impacts during practice, were involved in but did not experience a high-magnitude acceleration 78 times (21% of the 370 one-sided high-magnitude impacts), and experienced 152 (30%) of the 502 high-magnitude accelerations measured. Quarterbacks/running backs/linebackers were involved in the greatest number of high-magnitude impacts in practice and experienced the greatest number of high-magnitude accelerations. Which team a player was on was an important factor, as one team showed much greater head impact exposure than all others. This study showed that targeting the most impact-prone players for individualized interventions could reduce high-magnitude acceleration exposure for entire teams. These data will help to further quantify elevated head acceleration exposure and enable data-driven interventions that modify exposure for individual players and entire teams.


#7 Bilateral Simultaneous Tibial Tubercle Avulsion in an Adolescent Football Player with Previous Bilateral Osgood-Schlatter Disease
Reference: Case Rep Orthop. 2019 Mar 24;2019:8535370. doi: 10.1155/2019/8535370. eCollection 2019.
Authors: Dalla Rosa Nogales J, Nogales Zafra JJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451814/pdf/CRIOR2019-8535370.pdf
Summary: Tibial tubercle avulsion fractures are a very uncommon injury, accounting between 0.4 and 2.7% of all epiphyseal injuries. Bilateral lesions are extremely rare with only 20 cases described in the literature. They occur more frequently in male adolescents and during sport activities that require jumping and sprinting, such as football or basketball. We report the case of a 13-year-old boy who sustained simultaneous bilateral tibial avulsion fractures on the background of a previous conservatively managed bilateral Osgood-Schlatter disease.


#8 Working Memory Training in Professional Football Players: A Small-Scale Descriptive Feasibility Study-The Importance of Personality, Psychological Well-Being, and Motivational Factors
Reference: Sports (Basel). 2019 Apr 18;7(4). pii: E89. doi: 10.3390/sports7040089.
Authors: In de Braek D, Deckers K, Kleinhesselink T, Banning L, Ponds R
Download link: https://www.mdpi.com/2075-4663/7/4/89/pdf
Summary: Working memory training (WMT) programs can improve working memory (WM). In football players, this could lead to improved performance on the pitch. Eighteen professional football players of Maatschappelijke Voetbal Vereniging Maastricht (MVV) participated and followed an online, computerized WMT program. Neuropsychological performance, psychological wellbeing, self-efficacy, and football skills (Loughborough Soccer Passing Test; LSPT) were assessed at three time points, before and after WMT and at three-month follow-up. Descriptive data are reported. Baseline characteristics were roughly similar for both groups. Participants performed better on the trained WM tasks, but performance for other neuropsychological test measures or the LSPT did not change. Low compliance rates were observed, showing differences in personality and well-being between compliers and non-compliers. WMT is not a feasible and effective strategy to improve non-trained cognitive measures and football performance. However, this study indicates that it is important to take individual characteristics into account.


#9 Are Hip Physical Examination Findings Predictive of Future Lower Body Injury Rates in Elite Adolescent Female Soccer Athletes at Minimum 5-Year Follow-Up?
Reference: J Sport Rehabil. 2019 Apr 29:1-26. doi: 10.1123/jsr.2018-0350. [Epub ahead of print]
Authors: Cheng AL, Merlo JA, Hunt D, Yemm T, Brophy RH, Prather H
Summary: While elite adolescent female soccer athletes have unique injury risk factors and management challenges, limited epidemiological data exist for this population. Describe lower body injury patterns and determine whether a screening hip physical examination is predictive of future injuries in elite adolescent female soccer athletes. One hundred seventy-seven female soccer athletes ages 10-18 years old (mean 14.6±1.8 years) completed a demographic questionnaire and screening hip physical examination which included range of motion and provocative tests. At least five years after baseline screening, athletes completed an electronic follow-up injury survey. Injury was defined as pain that interfered with sporting activity. In addition to descriptive analyses of athletes' injury profiles, associations between players' baseline demographics and subsequent injury profiles were evaluated using chi-square tests, and potential predictors of injury based on players' baseline hip examinations were evaluated using multivariable logistic regression. Ninety-four of 177 athletes (53%) were contacted for follow-up, and 88/94 (93.6%) completed the survey. With mean follow-up of 91.9±9.3 months (range 66-108 months), 42/88 (47.7%) reported sustaining a new lower body injury. The low back was the most commonly injury region (16/42, 38.1%). Almost half of all injured athletes (20/42, 47.6%) sustained overuse injuries, and 16/42 (38.1%) had an incomplete recovery. Higher body mass index and reaching menarche were associated with sustaining an injury (p=0.03 and 0.04, respectively). Athletes' baseline hip examinations were not predictive of their subsequent rate of lower body, lumbopelvic, overuse, or incomplete recovery injury (all p>0.05). Lower body injuries were common in elite adolescent female soccer athletes, with over one third of injured athletes reporting permanent negative impact of the injury on their playing ability. Baseline hip physical examinations were not associated with future injury rate.


#10 Respiratory Frequency as a Marker of Physical Effort During High-Intensity Interval Training in Soccer Players
Reference:  Int J Sports Physiol Perform. 2019 Apr 29:1-24. doi: 10.1123/ijspp.2019-0028. [Epub ahead of print]
Authors: Nicolò A, Montini M, Girardi M, Felici F, Bazzucchi I, Sacchetti M
Summary: Variables currently used in soccer training monitoring fail to represent the physiological demand of the player during movements like accelerations, decelerations and directional changes performed at high intensity. We tested the hypothesis that respiratory frequency (fR) is a marker of physical effort during soccer-related high-intensity exercise. Twelve male soccer players performed a preliminary intermittent incremental test and two shuttle-run high-intensity interval training (HIIT) protocols, in separate visits. The two HIIT protocols consisted of 12 repetitions over 9 min and differed in the work-recovery ratio (15:30s vs. 30:15s). Work rate was self-paced by participants to achieve the longest possible total distance in each HIIT protocol. Work-phase average metabolic power was higher (P < 0.001) in the 15:30s (31.7 ± 3.0 W·kg-1) compared to the 30:15s (22.8 ± 2.0 W·kg-1). Unlike heart rate and V̇O2, fR showed a fast response to the work-recovery alternation during both HIIT protocols, resembling changes in metabolic power even at supramaximal intensities. Large correlations (P < 0.001) were observed between fR and rating of perceived exertion during both 15:30s (r = 0.87) and 30:15s (r = 0.85). Our findings suggest that fR is a good marker of physical effort during shuttle-run HIIT in soccer players. These findings have implications for monitoring training in soccer and other team sports.


#11 Case Study: Muscle Atrophy, Hypertrophy and Energy Expenditure of a Premier League Soccer Player During Rehabilitation From ACL Injury
Reference: Int J Sport Nutr Exerc Metab. 2019 Apr 29:1-17. doi: 10.1123/ijsnem.2018-0391. [Epub ahead of print]
Authors: Anderson L, Close GL, Konopinksi M, Rydings D, Milsom J, Hambly C, Speakman JR, Drust B, Morton JP
Summary: Maintaining muscle mass and function during rehabilitation from anterior cruciate ligament (ACL) injury is complicated by the challenge of accurately prescribing daily energy intakes aligned to energy expenditure. Accordingly, we present a 38-week case study characterizing whole body and regional rates of muscle atrophy and hypertrophy (as inferred by assessments of fat free mass from DXA) in a professional male soccer player from the English Premier League. Additionally, in week 6 we also quantified energy intake (via the remote food photographic method) and energy expenditure using the doubly labeled water method. Mean daily energy intake (CHO: 1.9-3.2, Protein: 1.7-3.3 and Fat: 1.4-2.7 g.kg-1) and energy expenditure was 2765 ± 474 and 3178 kcal.d-1 respectively. In accordance with an apparent energy deficit, total body mass decreased by 1.9 kg during week 1-6 where FFM loss in the injured and non-injured limb was 0.9 and 0.6 kg, respectively, yet, trunk FFM increased by 0.7 kg. In weeks 7-28, the athlete was advised to increased daily CHO intake (4-6 g.kg-1) to facilitate an increased daily energy intake. Throughout this period, total body mass increased by 3.6 kg (attributable to a 2.9 and 0.7 kg increase in fat-free and fat mass, respectively). Our data suggest it may be advantageous to avoid excessive reductions in energy intake during the initial 6-8 weeks post-ACL surgery so as to limit muscle atrophy.

Fri

17

May

2019

Latest research in football - week 16 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Creatine Supplementation on Athletic Performance in Soccer Players: A Systematic Review and Meta-Analysis
Reference: Nutrients. 2019 Mar 31;11(4). pii: E757. doi: 10.3390/nu11040757.
Authors: Mielgo-Ayuso J, Calleja-Gonzalez J, Marqués-Jiménez D, Caballero-García A, Córdova A, Fernández-Lázaro D
Summary: Studies have shown that creatine supplementation increases intramuscular creatine concentrations, favoring the energy system of phosphagens, which may help explain the observed improvements in high-intensity exercise performance. However, research on physical performance in soccer has shown controversial results, in part because the energy system used is not taken into account. The main aim of this investigation was to perform a systematic review and meta-analysis to determine the efficacy of creatine supplementation for increasing performance in skills related to soccer depending upon the type of metabolism used (aerobic, phosphagen, and anaerobic metabolism). A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science, Cochrane Library, and Scopus databases until January 2019. The search included studies with a double-blind and randomized experimental design in which creatine supplementation was compared to an identical placebo situation (dose, duration, timing, and drug appearance). There were no filters applied to the soccer players' level, gender, or age. A final meta-analysis was performed using the random effects model and pooled standardized mean differences (SMD) (Hedges's g). Nine studies published were included in the meta-analysis. This revealed that creatine supplementation did not present beneficial effects on aerobic performance tests (SMD, -0.05; 95% confidence interval (CI), -0.37 to 0.28; p = 0.78) and phosphagen metabolism performance tests (strength, single jump, single sprint, and agility tests: SMD, 0.21; 95% CI, -0.03 to 0.45; p = 0.08). However, creatine supplementation showed beneficial effects on anaerobic performance tests (SMD, 1.23; 95% CI, 0.55⁻1.91; p <0.001). Concretely, creatine demonstrated a large and significant effect on Wingate test performance (SMD, 2.26; 95% CI, 1.40⁻3.11; p <0.001). In conclusion, creatine supplementation with a loading dose of 20⁻30 g/day, divided 3⁻4 times per day, ingested for 6 to 7 days, and followed by 5 g/day for 9 weeks or with a low dose of 3 mg/kg/day for 14 days presents positive effects on improving physical performance tests related to anaerobic metabolism, especially anaerobic power, in soccer players.


#2 Dietary Intake of Polish Female Soccer Players
Reference: Int J Environ Res Public Health. 2019 Mar 29;16(7). pii: E1134. doi: 10.3390/ijerph16071134.
Authors: Dobrowolski H, Włodarek D
Download link: https://www.mdpi.com/1660-4601/16/7/1134/pdf
Summary: The aim of the study was to evaluate the energy expenditure and fulfillment of nutritional needs of female soccer players. Participants in this research were 41 professional soccer players from the three Polish female soccer league levels: Ekstraleague, I League and II League. The participants had their height and body mass measured. Total Energy Expenditure was measured by means of a SenseWear Pro3 Armband device. Data related to the food-intake energy values and the consumption of macro- and micronutrients were obtained through systematic recording of results, which was conducted over a three-day-long period at the start of the competitive season. The average age of the participants was 21 ± 5 years, the average height was 167.5 ± 5 cm, and the average body mass was 62.53 ± 9.8 kg. The average energy expenditure of the participants was 2811 ± 493 kcal/day, and their average energy intake was 1476 ± 434 kcal/day. The average consumption of carbohydrates, fats, and proteins was 199 ± 20.6, 47.3 ± 20.7, and 72.3 ± 24.2 g/day, respectively. There was a prevalence of inadequate intake of potassium, calcium, magnesium, iodine, vitamins D, E and B1, and folate in the diet of the examined group. The remaining micronutrients were consumed in the prescribed amounts by at least 50% of the examined group. The participants demonstrated low energy intakes, and consequently, low consumption of macronutrients and a large number of micronutrients.


#3 Sport-Related Structural Brain Injury in High School Soccer: Epidural Hemorrhage After a "Header"
Reference: World Neurosurg. 2019 Mar 27. pii: S1878-8750(19)30878-2. doi: 10.1016/j.wneu.2019.03.198. [Epub ahead of print]
Authors: Mummareddy N, Legarreta AD, Yengo-Kahn AM, Bow HC, Solomon GS, Naftel RP, Zuckerman SL
Summary: Sport-related structural brain injury (SRSBI) is a rare but potentially catastrophic injury. Limited data exists outlining its epidemiology, pathophysiology, and outcomes. We present the case of an epidural hematoma (EDH) suffered during a high school soccer game. A 16-year-old male experienced a head-to-ball collision and head-to-head collision with another player. He denied loss of consciousness, endorsed retrograde amnesia, and complained of a minor headache. On the sidelines, he subsequently passed brief orientation and physical exertion tests. Upon returning to play, he experienced blurry vision, along with headache and nausea/vomiting. At the local hospital, he was found to have a 2.6cm right frontal EDH. After transfer to our institution, increasing somnolence was noted, prompting emergent evacuation of the EDH. His post-operative course was unremarkable, and he was discharged on post-operative day 2. At the 2-week and 3-month follow up visits, he did not express any complaints or residual deficits and was cleared for full sporting activity. This case highlights one of the few SRSBIs that have occurred in soccer. Due to their rarity and severity, a concerted effort should be made to report these cases of SRSBIs regarding mechanism, post-collision symptoms, and long-term outcomes.


#4 Travel fatigue and sleep/wake behaviors of professional soccer players during international competition
Reference: Sleep Health. 2019 Apr;5(2):141-147. doi: 10.1016/j.sleh.2018.10.013. Epub 2018 Dec 12.
Authors: Lastella M, Roach GD, Sargent C
Summary: The magnitude of travel completed by professional Australian soccer teams during domestic competition is substantial. The inclusion of Australian soccer teams into the Asian Champions league has seen additional stress placed on soccer players' training and competition schedules. For management staff, the complexity of organizing training and travel schedules during domestic competition and the Asian Champions league is challenging. Seven male professional soccer players (mean ± SD: age 25.2 ± 3.2 years, height 182.8 ± 5.2 cm, body mass 84.6 ± 7.4 kg) participated in this study which examined the sleep and fatigue levels of Australian soccer players during an intensive home and away travel schedule during the Asian Champions league. Seven male professional soccer players' (mean ± SD: age 25.2 ± 3.2 years, height 182.8 ± 5.2 cm, body mass 84.6 ± 7.4 kg) sleep/wake behavior was assessed using sleep diaries and wrist activity monitors for 19 days, including 9 days before, 5 days during, and 4 days after a home and away group stage match of the Asian Champions league. Analyses examined differences in sleep/wake behavior and fatigue levels between day type (training day, rest day, pregame, and postgame) and between sleep location (Adelaide, during flight, and Hiroshima). Sleep/wake behavior and fatigue levels were poorest the night immediately after games compared to the night before games, training days, and rest days. Soccer players' sleep/wake behaviors were disrupted during flights such that they obtained 3.6 hours less sleep during flights compared to sleep in Adelaide (7.0 ± 1.6 hours) and Hiroshima (7.0 ± 2.1 hours). The sleep/wake behaviors of professional soccer players are compromised when they are required to travel and compete in multiple matches within a short period of time.


#5 Medial collateral ligament injuries of the knee in male professional football players: a prospective three-season study of 130 cases from the UEFA Elite Club Injury Study
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Apr 4. doi: 10.1007/s00167-019-05491-6. [Epub ahead of print]
Authors: Lundblad M, Hägglund M, Thomeé C, Hamrin Senorski E, Ekstrand J, Karlsson J, Waldén M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-019-05491-6.pdf
Summary: Medial collateral ligament (MCL) injury is the single most common traumatic knee injury in football. The purpose of this study was to study the epidemiology and mechanisms of MCL injury in men's professional football and to evaluate the diagnostic and treatment methods used. Fifty-one teams were followed prospectively between one and three full seasons (2013/2014-2015/2016). Individual player exposure and time-loss injuries were recorded by the teams' medical staffs. Moreover, details on clinical grading, imaging findings and specific treatments were recorded for all injuries with MCL injury of the knee as the main diagnosis. Agreement between magnetic resonance imaging (MRI) and clinical grading (grades I-III) was described by weighted kappa. One hundred and thirty of 4364 registered injuries (3%) were MCL injuries. Most MCL injuries (98 injuries, 75%) occurred with a contact mechanism, where the two most common playing situations were being tackled (38 injuries, 29%) and tackling (15 injuries, 12%). MRI was used in 88 (68%) of the injuries, while 33 (25%) were diagnosed by clinical examination alone. In the 88 cases in which both MRI and clinical examination were used to evaluate the grading of MCL injury, 80 (92% agreement) were equally evaluated with a weighted kappa of 0.87 (95% CI 0.77-0.96). Using a stabilising knee brace in players who sustained a grade II MCL injury was associated with a longer lay-off period compared with players who did not use a brace (41.5 (SD 13.2) vs. 31.5 (SD 20.3) days, p = 0.010). Three-quarter of the MCL injuries occurred with a contact mechanism. The clinical grading of MCL injuries showed almost perfect agreement with MRI grading, in cases where the MCL injury is the primary diagnosis. Not all grade II MCL injuries were treated with a brace and may thus indicate that routine bracing should not be necessary in milder cases.


#6 Involving research-invested clinicians in data collection affects injury incidence in youth football
Reference: Scand J Med Sci Sports. 2019 Apr 2. doi: 10.1111/sms.13427. [Epub ahead of print]
Authors: Wik EH, Materne O, Chamari K, Duque JDP, Horobeanu C, Salcinovic B, Bahr R, Johnson A
Summary: It is well established that differences in injury definition and recording methodology restrict comparisons between injury surveillance programmes. There is, however, little documentation of the variation that can exist between data recorders. The aim of this study was therefore to explore the effect on reported injuries when team recorders or supervisors are involved in research. Injury data collected prospectively over five seasons for the U16, U17 and U18 age groups in a youth football (soccer) academy were used to compare different recording settings based on the research involvement of the clinicians. A research-invested team physiotherapist reported an 8.8 times greater incidence (p<0.001) of non-time-loss injuries and a 2.5 times greater incidence (p<0.001) of minimal injuries (1-3 days lost) compared to a setting where neither the team physiotherapists or the supervisor relied on the collected data for research purposes. When team physiotherapists were not invested in research themselves but were supervised by a researcher, the incidence of non-time-loss injuries and minimal injuries was 2.5 times (p<0.001) and 2.0 times greater (p<0.01) than in the non-invested setting, respectively. However, there were no differences between recording settings for overall incidence of time-loss injuries. The results from this study demonstrate that involving clinicians that are relying on the collected data for research purposes can significantly affect the reported rates of non-time-loss and minimal injuries. Time-loss injuries overall were not affected by research investment, and should therefore be preferred for comparisons between teams and seasons. This article is protected by copyright. All rights reserved.


#7 Possession in Football: More Than a Quantitative Aspect - A Mixed Method Study
Reference: Front Psychol. 2019 Mar 18;10:501. doi: 10.3389/fpsyg.2019.00501. eCollection 2019.
Authors: Casal CA, Anguera MT, Maneiro R, Losada JL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431675/pdf/fpsyg-10-00501.pdf
Summary: The aim of the present study was to identify and differentiate the factors that determine the possession times of successful and unsuccessful elite football teams, with the purpose of identifying a more effective possession model. For this, match corresponding to the round of eighth-finals, quarter-finals, semi-finals and final of the 2016 UEFA Euro France in which 2,636 offensive sequences occurred, were analyzed. Video recordings of matches were analyzed and coded post-event using systematic observation. The performance indicators recorded and analyzed were: phase; match period; type of start-up; interaction context; intention; field zone; possession time, passes, attack outcome; match status and final outcome. An ANOVA was performed to analyze data in order to study the influence of a set of variables. A Box-Cox transformation was applied on the variable explained to achieve normal conditions. A study of the main effects and significant interactions was also carried out, complemented with a set of predictions with the variables that were more significant. It is hypothesized that possession analysis from a mixed methods perspective will identify a more effective offensive playstyle. Results show how, in successful teams, possession time is influenced by: Type of start-up, intention and field zone. On the other hand, in unsuccessful teams, possession time is determined fundamentally by intention and match status. In terms of the results of the predictive models, in the case of successful teams, they will have longer possessions in the offensive zone with the score in favor and, in the defensive zone with a draw score, in both situations, initiated with the intention of progressing by means of a transition. For unsuccessful teams, possessions will be of longer duration in the defensive zone with a draw score, regardless of the type of start-up and, in the offensive zone, losing and initiating the play by means of a set ball action and winning by means of a transition. Results obtained in this work identify key factors that determine possession time in teams and allow to differentiate the possessions of successful and unsuccessful teams, identifying a more effective ball possession model. This information can be used to design a possession model with greater probabilities of success and increase the offensive performance of teams.


#8 Influence of Aerobic Power on Youth Players' Tactical Behavior and Network Properties during Football Small-Sided Games
Reference: Sports (Basel). 2019 Mar 25;7(3). pii: E73. doi: 10.3390/sports7030073.
Authors: Praça GM, Sousa RBE, Greco PJ
Download link: https://www.mdpi.com/2075-4663/7/3/73/pdf
Summary: This study aimed to compare the incidence of tactical principles, the percentage of successful tactical principles, and the network properties between higher and lower aerobic power in young football players during small-sided games. Eighteen Under-17 Brazilian players were recruited. Firstly, they performed the Yo-Yo Intermittent Recovery Test Level 2, which was used to split them into two groups with higher and lower aerobic power. In the sequence, they played three vs three small-sided games within each group. The System of Tactical Assessment in Soccer was used to analyze the tactical behavior demonstrated by measuring the incidence of tactical principles and the percentage of successful principles, while the macro variables, density and clustering coefficient from social network analysis for team sports was used to analyze players' interactions. No differences were reported for the incidence of tactical principles (p > 0.05, small or small-to-moderate effect sizes), the percentage of successful offensive principles (p = 0.122, small-to-moderate effect size), or the network variables (p > 0.05; small effect sizes). The lower aerobic power group demonstrated a higher percentage of successful defensive tactical principles (p = 0.043; small-to-moderate effect size). We concluded that aerobic power has a limited impact on player behavior, indicating that players' actions within a small-sided game are mostly constrained by other parameters.


#9 Antioxidant vitamin supplementation prevents oxidative stress but does not enhance performance in young football athletes
Reference: Nutrition. 2019 Jan 24;63-64:29-35. doi: 10.1016/j.nut.2019.01.007. [Epub ahead of print]
Authors: de Oliveira DCX, Rosa FT, Simões-Ambrósio L, Jordao AA, Deminice R
Summary: The aim of this study was to verify the effects of supplementation with antioxidants (vitamins C and E) on oxidative stress, delayed-onset muscle soreness (DOMS), and performance in football players during a recovery period after an exercise-induced oxidative stress protocol. Twenty-one football athletes were randomly assigned to two groups: placebo and antioxidant-supplemented. Supplementation was performed in a double-blind, controlled manner using vitamin C (500 mg/d) and E (400 UI/d) for 15 d. After 7 d of supplementation, athletes were submitted to an exercise-induced oxidative stress protocol consisting of plyometric jumping and strength resistance sets to exhaustion. Blood samples, performance tests, and DOMS were determined before and 24, 48, and 72 h after exercise. Antioxidant supplementation was continued during the recuperation week and for a total of 15 d. Antioxidant supplementation caused a significant increase in plasma vitamins C and E. The antioxidant supplementation could inhibit oxidative stress characterized by elevated lipid peroxidation markers malondialdehyde and total lipid peroxidation as well as reduced ratio of glutathione to oxidized glutathione promoted by exercise. Antioxidant supplementation, however, did not significantly reduce the plasma creatine kinesis concentration or DOMS during the recovery days. Likewise, supplementation with vitamin C and E did not improve lower body power, agility, or anaerobic power, nor did it provide any indication of faster muscle recovery. Antioxidant supplementation does not attenuate elevated markers of muscle damage or muscle soreness promoted by acute exercise and do not exert any ergogenic effect on football performance of young athletes, although it reduced oxidative stress.


#10 The Effects of a Physically Active Lifestyle on the Health of Former Professional Football Players
Reference: Sports (Basel). 2019 Mar 28;7(4). pii: E75. doi: 10.3390/sports7040075.
Authors: Melekoğlu T, Sezgin E, Işın A, Türk A
Summary: The purpose of this investigation was to determine if a physically active lifestyle affects the health of former football players. Sixty former professional football players aged 40⁻50 years and who ended their sports career at least ten years ago were recruited for the study and grouped into two groups based on their physical activity habits after their retirement. Health and lifestyle characteristics were collected through a questionnaire to obtain information about recreational physical activity levels, diseases, family medical history, smoking, alcohol intake and dietary habits. Furthermore, lung functions, blood parameters and cardiovascular health were evaluated. Our results showed that body weight and body fat percentage were significantly higher in retired footballers who had a sedentary lifestyle compared to those who were physically active. The absolute and predicted values for forced expiratory volume in one-second values were higher in the active group. Twelve retired athletes were found to have intraventricular conduction delay. The findings suggest that former footballers who have higher levels of physical activity have advanced body composition, respiratory functions and serum lipids compared to former footballers with less active lifestyles. It is recommended that former elite athletes should maintain physically active lifestyles to sustain their health and reduce the risk of disease and disability in the later years of life.


#11 Scaling Demands of Soccer According to Anthropometric and Physiological Sex Differences: A Fairer Comparison of Men's and Women's Soccer
Reference: Front Psychol. 2019 Apr 9;10:762. doi: 10.3389/fpsyg.2019.00762. eCollection 2019.
Authors: Pedersen AV, Aksdal IM, Stalsberg R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6465549/pdf/fpsyg-10-00762.pdf
Summary: Spectators frequently harass female soccer players, and women's soccer is frequently compared negatively to men's soccer by writers who make the comparison without the backing of any data and without taking into account anthropometric and physiological differences between the sexes. This affects female soccer players' self-confidence negatively and contributes to an undeservedly negative image of women's soccer. In the present paper, we argue that most differences between men's and women's soccer can be explained by women having to adapt to rules and regulations that are suited for men and their physical attributes. Thus, games are much more demanding for women. Furthermore, we argue that if men had to play with a degree of adaptation similar to that which women do today, they would have to alter their style of play radically. As support for our argument, we scale game demands for male and female soccer players according to anthropometric and physiological differences in order to highlight the differences, and use these to predict what would be the most appropriate adaptations. Finally, we show that our predictions are largely supported by the scarce pool of comparable data across the sexes.

Mon

13

May

2019

Latest research in football - week 15 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 And at the end, the Germans always win, don't they? An evaluation of country-specific scoring behaviour in the dying seconds of international club soccer games
Reference: PLoS One. 2019 Apr 16;14(4):e0202852. doi: 10.1371/journal.pone.0202852. eCollection 2019.
Authors: Van Den Broucke L, Baert S
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0202852&type=printable
Summary: This article contributes to the literature on performance determinants in soccer by investigating country differences in goal scoring in the dying seconds of international soccer games (i.e. in the 90th minute or later). We analyse this goal-scoring behaviour in 1,008 recent soccer games played in the Union of European Football Associations (UEFA) Champions League and Europa League. In contrast to Gary Lineker's well-known quote that "at the end, the Germans always win", no significant evidence is found for German teams scoring a goal in the dying seconds more often than other teams. Our results indicate, however, that European clubs do have an interest in learning from the end-of-game tactics used by French and Spanish clubs in recent international games as these teams were less likely to concede a goal during the dying seconds. English teams were also in this situation but only if they had an English coach.


#2 Maximum Oxygen Uptake of Male Soccer Players According to their Competitive Level, Playing Position and Age Group: Implication from a Network Meta-Analysis
Reference: J Hum Kinet. 2019 Mar 27;66:233-245. doi: 10.2478/hukin-2018-0060. eCollection 2019 Mar.
Authors: Slimani M, Znazen H, Miarka B, Bragazzi NL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458571/pdf/hukin-66-233.pdf
Summary: The aim of the present meta-analysis was to compare the maximum oxygen uptake (VO2max) characteristics of male soccer players relative to their competitive level, playing position and age group and the interaction between them. The meta-analysis was based on 16 studies, employing 2385 soccer players aged 10-39 years. Higher-level soccer players showed greater (ES = 0.58 [95% CI 0.08-1.08], SE = 0.25, var = 0.06, z = 2.29, p = 0.022) VO2max performance with respect to their lower level counterparts. Furthermore, lower VO2max values in goalkeepers than defenders (ES = 1.31 (SE 0.46) [95% CI 0.41-2.21], var = 0.21, z = 2.84, p = 0.004) and midfielders (ES = 1.37 (SE 0.41) [95% CI 0.58 to 2.17], var = 0.16, z = 3.40, p = 0.001) were found. Thus, VO2max increased significantly with age (all, p < 0.01): Under 10 versus Under 11 years, Under 11 versus Under 12 years, Under 12 versus Under 13 years, Under 13 versus Under 14 years, Under 14 versus Under 15 years and Under 16-18 versus Under 20-23 years. VO2max performance is the most powerful discriminator between higher and lower-level soccer players. These findings indicate also the need for sports scientists and conditioning professionals to take the VO2max performance of soccer players into account when designing individualized position specific training programs.


#3 Characteristics of Very High Intensity Runs of Soccer Players in Relation to their Playing Position and Playing Half in the 2013-14 Spanish La Liga Season
Reference: J Hum Kinet. 2019 Mar 27;66:213-222. doi: 10.2478/hukin-2018-0058. eCollection 2019 Mar.
Authors: Rivilla-García J, Calvo LC, Jiménez-Rubio S, Paredes-Hernández V, Muñoz A, van den Tillaar R, Navandar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458567/pdf/hukin-66-213.pdf
Summary: The objective of this study was to carry out a detailed quantitative analysis of the very high intensity runs during actual play in the 2013-2014 Spanish First Division, at a general level and according to the specific playing position and half. 380 matches of the Spanish First Division in the 2013 - 2014 season were monitored using the Mediacoach video motion analysis tool. Total distance, very high intensity (above 21 km/h) running distance and the number of runs at very high intensity of 230 players from 20 teams in the Spanish First Division were analysed. The main findings of the study were that the performance indicators at very high intensities decreased from the first half to the second half for all outfield players (covered distance: 4694 ± 538 m vs 4485 ± 437 m, sprint distance: 256 ± 72 m vs 239 ± 67 m, number of sprints: 14.3 ± 3.5 vs 13.2 ± 3.1), except the central defenders (sprint distance: 166 ± 37 vs 166 ± 40 m, number of sprints: 10.0 ± 2.1 vs 9.8 ± 3.8). Secondly, although wide defenders (9759 ± 665 m) and central midfielders (9776 ± 942 m) covered the most distance during matches, it were the wide defenders (30 ± 5), centre-forwards (28 ± 7) and wide midfielders (31 ± 8) who performed the most runs at very high intensity. Consequently, the distance they ran at these very high intensity runs followed the same pattern. Such results enable general and specific profiles by demarcation to be established based on the demands of the game at high-level competitive play.


#4 The Influence of Situational Variables on Ball Possession in the South African Premier Soccer League
Reference: J Hum Kinet. 2019 Mar 27;66:175-181. doi: 10.2478/hukin-2018-0056. eCollection 2019 Mar.
Authors: Kubayi A, Toriola A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458569/pdf/hukin-66-175.pdf
Summary: Although the influence of ball possession in soccer has been well studied in other leagues, such information is sparse concerning the South African Premier Soccer League (PSL). The purpose of this study was to assess the impact of situational variables on ball possession in the PSL. Thirty-two matches played during the 2016-2017 PSL season were analysed using a multiple-camera match analysis system (InStat®). Three situational variables (match outcome, match location, and quality of opposition) and team performance variables (percentage of ball possession, ball possession <5 s, ball possession 5-15 s, ball possession 15-45 s, and ball possession >45 s) were examined. The results showed that losing teams had the highest ball possession (52.35 ± 5.90%) compared to winning (47.65 ± 5.90%) and drawing (50.00 ± 9.98%) teams. Playing away significantly (p < 0.05) decreased ball possession by 5.21% compared to playing at home. Playing against weak opposition was associated with increased ball possession by 4.09%. Conclusively, soccer coaches should be aware of the potential role of situational variables in determining successful team performance in a league season.


#5 Characterization of the Weekly External Load Profile of Professional Soccer Teams from Portugal and the Netherlands
Reference: J Hum Kinet. 2019 Mar 27;66:155-164. doi: 10.2478/hukin-2018-0054. eCollection 2019 Mar.
Authors: Clemente FM, Owen A, Serra-Olivares J, Nikolaidis PT, van der Linden CMI, Mendes B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458578/pdf/hukin-66-155.pdf
Summary: The purpose of this study was to analyze the day-to-day variance of a typical weekly external training workload of two professional soccer teams from different countries. Twenty-nine players from two professional teams from Portugal and the Netherlands participated in this study. The players' external load was monitored for 7 weeks, by means of portable GPS devices (10 Hz, JOHAN, Noordwijk, Netherlands). Results revealed that match day -1 (MD-1), i.e. the training day before a match, had significantly (p = 0.001) less training volume (4584.50 m) than the other days. MD-5 (training five days before a match), MD-4 (four days before a match) and MD-3 (three days before a match) were the most intense (390.83, 176.90 and 247.32 m of sprinting distance, respectively) and with large volume (7062.66, 6077.30 and 6919.49 m, respectively). Interestingly, significant differences were found between clubs of different countries (p < 0.05) with the Portuguese team showing significantly higher intensity (sprinting distance) and volume (total distance) in all days with exception of MD-1 than the Dutch team. The results of this study possibly allow for the identification of different training workloads and tapering strategies between countries in relation to volume and intensity. It should be noted, however, that both clubs used a significant tapering phase in the last two days before the competition in an attempt to reduce residual fatigue accumulation.


#6 A New Approach to the Analysis of Pitch-Positions in Professional Soccer
Reference: J Hum Kinet. 2019 Mar 27;66:143-153. doi: 10.2478/hukin-2018-0067. eCollection 2019 Mar
Authors: Konefał M, Chmura P, Zając T, Chmura J, Kowalczuk E, Andrzejewski M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458575/pdf/hukin-66-143.pdf
Summary: The purpose of the study was to examine how various playing positions affected the number of (and percentage breakdowns for) physical and technical activities of soccer players in the Germany's Bundesliga. A further objective was to identify and present features distinguishing between the activities of players within the Defender, Midfielder and Forward formations. The study sample comprised 4426 individual match observations of 473 soccer players competing in the Bundesliga during the 2016/2017 domestic season. Data from the Impire AG motion analysis system, and the so-called "heat maps" it supplies, revealed areas in which players spent most time during a match, with 22 different playing positions on the pitch identified in consequence. Players in the formation comprising Defenders did not differ significantly in relation to the number of accelerations, the number of shots or the percentage of duels won. Furthermore, there were no significant differences among Midfielders in regard to total distance covered, mean running speed, the number of accelerations, the number of duels and the percentage of duels won. Likewise, Forwards did not differ in distances covered at ≥24 km/h, average running speed, the number of sprints, the number of shots, the proportion of on-target passes, the number of duels, or the percentage share of duels won. Irrespective of the formation or position on the pitch, today's game of soccer also pays great importance to the number of accelerations, as well as the number of duels engaged in, and their effectiveness.


#7 Anthropometric and Motor Characteristics of South African National Level Female Soccer Players
Reference: J Hum Kinet. 2019 Mar 27;66:121-129. doi: 10.1515/hukin-2017-0189. eCollection 2019 Mar.
Authors: Booysen MJ, Gradidge PJ, Constantinou D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458582/pdf/hukin-66-121.pdf
Summary: Data regarding anthropometric and motor characteristics of elite national level female soccer players are scarce. Determining these characteristics may likely assist in evaluating the specificity of current training programmes, identify players who might lack specific qualities deemed critical for the successful execution of their tactical roles, and benchmark norms for developing future playing talent. Therefore, the aims of this study were to describe anthropometric and motor characteristics of South African national level female soccer players (n = 37) and determine possible differences with regard to their playing position. The following measurements and tests were performed: anthropometry (body mass index and sum-of-skinfolds), the countermovement jump, sprints (10 m, 20 m and 40 m), upper body muscle endurance (push-ups) and the Yo-Yo Intermittent Recovery Test - level 1. One-way analysis of variance revealed few differences in the main outcome variables. Fischer Least Significant Difference (LSD) showed that strikers had a greater body mass index than midfielders and defenders (both p = 0.04) and goalkeepers were heavier than defenders (p = 0.02). Goalkeepers were slower than strikers and defenders over 10 m (p = 0.01; p = 0.03) and 20 m (p = 0.001; p = 0.01). Midfielders were slower than strikers over 20 m (p = 0.02), and with strikers and defenders over 40 m (both p = 0.04). Defenders performed better than goalkeepers in the upper body muscle endurance test (p = 0.02). In conclusion, both strikers and defenders require speed to win ball possession, which may explain their fast sprint times. However, the similarity of certain motor characteristics across playing positions may suggest that conditioning coaches train players similarly, irrespective of their tactical position. The authors suggest that South African fitness professionals, particularly at a club level, develop physical conditioning programs specific to each field position. Furthermore, fitness assessments should occur on a continuous basis and comparisons should be made with existing normative data in order to guide the development of players over the course of their careers.


#8 Physiological and Psychological Changes at the End of the Soccer Season in Elite Female Athletes
Reference: J Hum Kinet. 2019 Mar 27;66:99-109. doi: 10.2478/hukin-2018-0051. eCollection 2019 Mar.
Authors: Morales J, Roman V, Yáñez A, Solana-Tramunt M, Álamo J, Fíguls A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458576/pdf/hukin-66-099.pdf
Summary: This study compares and describes relationships among stress-recovery indices, the heart rate variability index, and the Cooper and Yo-Yo IR1 tests among female soccer players during the last six weeks of the competitive season. Sixteen female soccer players engaged in a pre-test of all of the variables. After having their training monitored for six weeks, a post-test was administered. The results revealed significant (p < 0.05) differences in the specific stress-recovery scales of the RESTQ-sport and in the frequency-domain variables of the HRV, although there were no significant differences in the general stress or general recovery scales. The Yo-Yo IR1 test, the Cooper test scores, and the means of the time-domain HRV variables did not exhibit any significant differences between the pre- and the post-test. The RMSSD variations exhibited very large and large correlations with the performance test and the RESTQ-sport variables, respectively. The variations in the HRV frequency-domain variables exhibited significant moderate and large correlations among the variations of the RESTQ-sport scales. Monitoring athletes at the end of the season may reveal contradictions between some variables. To help with the interpretation of these scales, some external aspects, such as athlete strain and monotony of training, should be considered.


#9 Strength Profile of Hip Abductor and Adductor Muscles in Youth Elite Soccer Players
Reference: J Hum Kinet. 2019 Mar 27;66:31-41. doi: 10.2478/hukin-2018-0069. eCollection 2019 Mar.
Authors: Karatrantou K, Gerodimos V, Katsareli E, Manouras N, Ioakimidis P, Famisis K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458577/pdf/hukin-66-031.pdf
Summary: The main objective of this study was to provide an extensive isokinetic profile of the hip joint in youth soccer players, where the literature is limited. Additionally, this study investigated the effect of age on isokinetic peak torque values of hip abductor and adductor muscles and on reciprocal muscle group torque ratios in youth soccer players at different angular velocities (30 vs. 90o/s) and muscle actions (concentric vs. eccentric). Sixty young elite male soccer players were assigned into three equal groups (n = 20): children, young adolescents and older adolescents, and performed five maximal concentric and eccentric hip-abductions and adductions at 30o/s and 90o/s. The results showed a significant increase (p < 0.05) in peak torque values from childhood to adolescence, with the exception of young adolescents vs. older adolescents where no differences were observed. The reciprocal ratios were not affected by age, but improved with an increase in angular velocity with the exception of the CON/ECC ratio that was higher at 30o/s. The data presented in this study provide an extensive isokinetic profile of hip abductor and adductor muscle strength in youth soccer players to assist both coaches and sports medicine professionals in strength monitoring and training.


#10 Effects of 7-Week Hip Thrust Versus Back Squat Resistance Training on Performance in Adolescent Female Soccer Players
Reference: Sports (Basel). 2019 Apr 3;7(4). pii: E80. doi: 10.3390/sports7040080.
Authors: González-García J, Morencos E, Balsalobre-Fernández C, Cuéllar-Rayo Á, Romero-Moraleda B
Download link: https://www.mdpi.com/2075-4663/7/4/80/pdf
Summary: Hip thrust (HT) is a loaded bridging exercise that requires more hip extension than a back squat (SQ) does, while in a back squat, triple flex extension occurs. Due to the specificity of each exercise, it is claimed that HT gains can be better transferred to actions where hip extension occurs. In addition, strength improvements during squatting can be transferred in a greater way to vertical plane movement, such as vertical jumping. However, its effects on the performance of female soccer players are unclear. For this reason, the purpose of this study was to analyze a 7-week training program on performance variables using either HT or SQ exercises in female adolescent soccer players without lifting experience (N = 24, age = 16.82 ± 1.56 years, height = 1.64 ± 0.55 cm, body mass = 58.35 ± 6.28 kg). Players were randomized into three groups: A back squat group (SQG; N = 8), hip thrust group (HTG; N = 8), and control group (CG; N = 8). Participants in the HTG and SQG joined a progressive resistance training program twice per week for 7 weeks with either HT or SQ exercises. A countermovement jump, 10-20 m sprint, T-test, and barbell velocity during HTs and SQs (with the load that represents ~60 and ~80% RM) were measured before and after the intervention. The HTG showed greater improvements in the 10-m sprint (d = 0.7), 20-m sprint (d = 0.46), T-test (d = 0.36), and barbell velocity at 80% repetition maximal (RM) (d = 0.53) and 60% RM (d = 1.02) during hip thrusts, while the SQG showed higher barbell velocity at 80% RM (d = -0.7) during back squats. These results may be useful for strength and conditioning coaches working with adolescent female soccer athletes, since both strengthening exercises improved performance in different ways due to the nature of the exercise.


#11 Fat-Free Mass and Bone Mineral Density of Young Soccer Players: Proposal of Equations Based on Anthropometric Variables
Reference: Front Psychol. 2019 Mar 29;10:522. doi: 10.3389/fpsyg.2019.00522. eCollection 2019.
Authors: Gomez-Campos R, Santi-Maria T, Arruda M, Maldonado T, Albernaz A, Schiavo M, Cossio-Bolaños M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6449479/pdf/fpsyg-10-00522.pdf
Summary: The assessment of body composition may assist in optimizing competitive efficiency and monitoring the success of training regimes for young soccer players. The purpose of this study was to determine the predictors for Fat-Free Mass (FFM) and Bone Mineral Density (BMD) of young soccer players. Also, the goal was to propose regression equations to estimate FFM and BDM through anthropometric variables. One hundred and sixty-seven young soccer players ages 10.0 to 19.9 years old were studied. Weight, height, trunk-cephalic length, right arm circumference, diameter of the humerus, and length of the foot were assessed. FFM and BDM were determined by using dual X-ray absorptiometry (DXA). Maturity status using Peak Height Velocity (PHV) was calculated. Maturity status, weight, and circumference of the relaxed arm positively related to the FFM (R 2 = 41-66%). Similarly, PHV, weight, diameter of the humerus, and length of the foot explained BDM in both groups of soccer players (goalkeepers and filed players) (R 2 = 45-82%). Six equations to predict FFM (R 2 = 62-69%) and six to predict BDM (R 2 = 69-90%) were created. Chronological age had a limited use for predicting FFM and BDM. Results suggested the use and application of the regression equations as a non-invasive alternative for everyday use in soccer clubs.


#12 Changes Over a Decade in Anthropometry and Fitness of Elite Austrian Youth Soccer Players
Reference: Front Physiol. 2019 Mar 28;10:333. doi: 10.3389/fphys.2019.00333. eCollection 2019.
Authors: Gonaus C, Birklbauer J, Lindinger SJ, Stöggl TL, Müller E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447713/pdf/fphys-10-00333.pdf
Summary: Increases in physical (e.g., high-intensity running and sprinting), technical (e.g., passing rate), and tactical (e.g., player density) aspects made elite level soccer more challenging within the past years. The aim of the study was to evaluate whether these evolutions are also been reflected in changes in anthropometric and fitness characteristics between former (2002 to 2005) and current (2012 to 2015) elite Austrian youth development center (U13 to U14) and soccer academy (U15 to U18) players. A battery of anthropometric, general and soccer-specific fitness tests was conducted annually at the end of each year. Independent t-test and Cohen's d (ES) were calculated to compare the two four-year periods (2530 vs. 2611 players) at each age group separately. Current players were significantly faster in 20 m sprint (ES = 0.26-0.50) and reaction test (ES = 0.15-0.39, except for U18), but less flexible at sit-and-reach (ES = -0.19 to -0.55), in all age categories. Whereas height (ES = 0.26-0.32), body mass (ES = 0.11-0.18) and countermovement jump (ES = 0.24-0.26) increased significantly at youth development center level, current academy players performed superior at shuttle sprint (ES = 0.21-0.59), hurdles agility run (ES = 0.24-0.49), and endurance run (ES = 0.11-0.20). These changes over time in speed, change-of-direction ability, lower-body power, coordination, and endurance were attributed to modern training approaches (e.g., modified games and change-of-direction drills) and modifications in selection politics (e.g., coaches favor speed and decision-making skills).


#13 Recovery profiles following single and multiple matches per week in professional football
Reference: Eur J Sport Sci. 2019 Apr 18:1-9. doi: 10.1080/17461391.2019.1601260. [Epub ahead of print]
Authors: Howle K, Waterson A, Duffield R
Summary: The purpose was to investigate player responses 48 h post single (SM) and multi-match (MM) weeks on two subjective and three objective outcome measures to infer recovery status. From 42 professional players over 2 seasons, outcome measures relevant to recovery status were collected 48 h following matches, as well as during pre-season training weeks as a comparative baseline. These included (1) 5-item subjective wellness questionnaire, (2) total quality recovery (TQR) scale, (3) hip adduction squeeze test, ankle knee to wall (KTW) test, and active knee extension (AKE) flexibility test. These outcome measures 48 h post-match were compared for SM (n = 79) and MM (n = 86) weeks where players completed >75 min of match time in only one (SM) or if both matches were played and had <96 h recovery (MM). Internal match load was collected from each match based on session rating of perceived exertion (sRPE) multiplied by match duration. Subjective wellness (specifically fatigue, sleep and soreness), TQR and hip adduction squeeze test were all significantly reduced following match 1 at 48 h post for both SM and MM (p < 0.05), and further reduced following match 2 in MM (p < 0.05). No other outcome measures to infer recovery showed significant differences (p > 0.05) within or between-conditions. Subjective wellness, TQR and hip adduction strength showed reduction 48 h post match for players competing in multiple matches with <96 h recovery. Therefore, these outcome measures may be of use to practitioners to assess readiness to compete during congested competition schedules.


#14 Effects of Creatine Supplementation on Athletic Performance in Soccer Players: A Systematic Review and Meta-Analysis
Reference: Nutrients. 2019 Mar 31;11(4). pii: E757. doi: 10.3390/nu11040757.
Authors: Mielgo-Ayuso J, Calleja-Gonzalez J, Marqués-Jiménez D, Caballero-García A, Córdova A, Fernández-Lázaro D
Summary: Studies have shown that creatine supplementation increases intramuscular creatine concentrations, favoring the energy system of phosphagens, which may help explain the observed improvements in high-intensity exercise performance. However, research on physical performance in soccer has shown controversial results, in part because the energy system used is not taken into account. The main aim of this investigation was to perform a systematic review and meta-analysis to determine the efficacy of creatine supplementation for increasing performance in skills related to soccer depending upon the type of metabolism used (aerobic, phosphagen, and anaerobic metabolism). A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science, Cochrane Library, and Scopus databases until January 2019. The search included studies with a double-blind and randomized experimental design in which creatine supplementation was compared to an identical placebo situation (dose, duration, timing, and drug appearance). There were no filters applied to the soccer players' level, gender, or age. A final meta-analysis was performed using the random effects model and pooled standardized mean differences (SMD) (Hedges's g). Nine studies published were included in the meta-analysis. This revealed that creatine supplementation did not present beneficial effects on aerobic performance tests (SMD, -0.05; 95% confidence interval (CI), -0.37 to 0.28; p = 0.78) and phosphagen metabolism performance tests (strength, single jump, single sprint, and agility tests: SMD, 0.21; 95% CI, -0.03 to 0.45; p = 0.08). However, creatine supplementation showed beneficial effects on anaerobic performance tests (SMD, 1.23; 95% CI, 0.55⁻1.91; p <0.001). Concretely, creatine demonstrated a large and significant effect on Wingate test performance (SMD, 2.26; 95% CI, 1.40⁻3.11; p <0.001). In conclusion, creatine supplementation with a loading dose of 20⁻30 g/day, divided 3⁻4 times per day, ingested for 6 to 7 days, and followed by 5 g/day for 9 weeks or with a low dose of 3 mg/kg/day for 14 days presents positive effects on improving physical performance tests related to anaerobic metabolism, especially anaerobic power, in soccer players.

Mon

06

May

2019

Latest research in football - week 14 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Lower Limb Assessment Score: A valid measure of hypermobility in elite football?
Reference: Phys Ther Sport. 2019 Mar 15;37:86-90. doi: 10.1016/j.ptsp.2019.03.007. [Epub ahead of print]
Authors: Paul Johnson A, Ward S, Simmonds J
Summary: This study aims to validate the Lower Limb Assessment Score against the current gold standard Beighton Scale within an adult elite footballing population to allow for future research to explore the influence of lower limb specific hypermobility on injury incidence. Thirty-six male, professional footballers aged between 18 and 37 years old participated in this study. The Sensitivity, specificity, positive predictive value, negative predictive value and Spearman's rank correlation between the LLAS and Beighton Scale were used as outcome measures. There was significant strong correlation between LLAS and Beighton Scale scores (ρ = 0.732; p < 0.001). The LLAS displayed a sensitivity of 67% and specificity of 94% when a cut off of ≥4/12 was applied to the screening data. This cut off point also yielded moderate Positive Predictive Validity (50%) and excellent Negative Predictive Validity (97%). The present study suggests that the LLAS is a valid test for identifying lower limb hypermobility within an adult male footballing population when a cut off of ≥4/12 is used.


#2 Soccer Footedness and Between-Limbs Muscle Strength: Systematic Review and Meta-Analysis
Reference: Int J Sports Physiol Perform. 2019 Apr 11:1-12. doi: 10.1123/ijspp.2018-0336. [Epub ahead of print]
Authors: DeLang MD, Rouissi M, Bragazzi NL, Chamari K, Salamh PA.
Summary: Limb dominance and consequent between-limbs muscle strength in soccer players should be explored to determine a standard musculoskeletal profile to maintain and establish during screening protocols and postinjury rehabilitation. The primary aim of this review was to identify dominant- vs non-dominant-lower-extremity muscle-strength characteristics of healthy soccer players, with secondary aims to consider available between-limbs outcome measures and directions for future research. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Five electronic databases were used for study identification with guidance from a medical librarian. Inclusion criteria consisted of studies employing a cross-sectional design assessing soccer players of all ages, genders, and levels of play that identified limb dominance and associated lower-extremity muscle strength as a main purpose of the experiment. The literature search identified 3471 articles. After screening titles, abstracts, and full texts, 17 articles were included in the review. Peak torques and hamstring-to-quadriceps ratios via isokinetic dynamometry were commonly used, and subsequent meta-analyses were conducted to yield remarkable between-limbs symmetry. Additional results of individual studies also demonstrate symmetry, except 1 article of velocity-dependent measures that reported greater strength in the dominant limb. In soccer, between-limbs muscle strength measured by maximal isokinetic dynamometry demonstrates symmetry across ages, genders, and levels of play. Future testing using alternative measures that more specifically replicate the movement demands of soccer players may further classify between-limbs characteristics.


#3 Player Migration and Soccer Performance
Reference: Front Psychol. 2019 Mar 21;10:616. doi: 10.3389/fpsyg.2019.00616. eCollection 2019.
Authors: Lago-Peñas C, Lago-Peñas S, Lago I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6440484/pdf/fpsyg-10-00616.pdf
Summary: The aim of this study is to examine the relationship between migrating soccer players and the annual ranking of the national teams according to the World Football Elo Rating. The sample includes annual data for 243 countries over the period 1994-2018. Migration is captured with the number of migrating players by country in the "big-five" leagues. The causal relationship between the two variables is examined by using Granger causality test. Four control variables are included: the political regime, per capita income, population, and regional soccer confederations. It was hypothesized that (i) the better the ranking of the national teams in the Elo rating, the higher the number of migrating players in the "big-five" leagues (shop-window hypotheses) and that (ii) while the shop-window effect takes place in the short-run, the annual Elo rating of a national team is positively affected by expatriate players in the medium or long-run, but not in the short-run (blending hypotheses). The results shed light on two crucial issues. First, causality mainly goes from national soccer performance to migrating soccer players rather than the other way around. Second, the timing of the two effects is quite different. While those players giving an outstanding performance when their national team is doing well are immediately bought by clubs from more highly ranked leagues (the shop-window effect), it takes at least 4 years for the additional skills acquired by migrated players to have a positive effect on the national soccer performance (the blending effect).


#4 Test-retest reliability of a hip strength assessment system in varsity soccer players
Reference: Phys Ther Sport. 2019 Mar 28;37:138-143. doi: 10.1016/j.ptsp.2019.03.013. [Epub ahead of print]
Authors: Desmyttere G, Gaudet S, Begon M
Summary: The purpose was to investigate test-retest reliability of a hip strength assessment system (GroinBar).  Twenty asymptomatic varsity soccer players participated in this study. Maximal isometric hip strength (adduction, abduction, internal and external rotation, flexion and extension) was assessed using the GroinBar. Intraclass correlation coefficient (ICC) and relative standard error of measurement (SEM) were calculated to evaluate reliability of peak (ICC3,1) (highest peak within 3 trials) and average peak (ICC3,3) (average of 3 trials) force and rate of force development (RFD). Hotelling's T2, were also used to compare bilateral and reciprocal ratios between dominant and non-dominant leg. ICC for both peak force and RFD values revealed moderate to good reliability (0.53-0.88 and 0.61-0.84, respectively), whereas reliability was good to excellent regarding their average values (0.77-0.95 and 0.81-0.92, respectively). SEM of average peak force and RFD values (4.1-9.4% and 8.2-13.9%, respectively) were lower than that of peak force and RFD values (5.7-13.0% and 10.7-19.1%, respectively). No significant difference was found in bilateral and reciprocal force ratios between dominant and non-dominant leg. The GroinBar is a reliable tool to assess hip muscle function in athletic populations and could be used for player screening and follow-up.


#5 A season long investigation into the effects of injury, match selection and training load on mental wellbeing in professional under 23 soccer players: A team case study
Reference: Eur J Sport Sci. 2019 Apr 6:1-7. doi: 10.1080/17461391.2019.1600586. [Epub ahead of print]
Authors: Abbott W, Brownlee TE, Harper LD, Naughton RJ, Richardson A, Clifford T
Summary: This study examined the influence of injury, match selection and training load on mental wellbeing (MW) in a squad of professional soccer players. Using a longitudinal design, twenty-five male soccer players (age, 20 ± 1 years, height, 1.80 ± 5.79 m, body mass 76.33 ± 7.52 kg) from the under 23 squad playing in the Premier League 2 division in the UK completed the Warwick-Edinburgh Mental Well-being Scale (WEMWBS) each week of the 2017/2018 season (37 weeks in total). Injury and non-selection for the match squad were the only significant predictors of MW (P < 0.05). Injury had the biggest influence on MW that was lower when injured vs. not injured (43.6 ± 5.0 vs. 49.9 ± 3.5, respectively, P = 0.001, ES = 1.48), accounting for 40% of the variation in MW. This increased to 50% when not being selected to play games was also considered. Weekly training loads measured by GPS (total distance, sprint distance and total duration) and individual player win rate did not influence MW (P > 0.05). These findings highlight the importance of monitoring MW in professional soccer players and suggest that injured players and those rarely selected for the match squad should be educated on the strategies available for managing their mental health and wellbeing.


#6 Tibial fractures following participation in recreational football: Incidence and outcome
Reference: Niger J Clin Pract. 2019 Apr;22(4):492-495. doi: 10.4103/njcp.njcp_148_18.
Authors: Nwosu C
Download link: http://www.njcponline.com/temp/NigerJClinPract224492-2331852_003851.pdf
Summary: Football is responsible for 3.5%-10% of all injuries treated in hospital, but this may reflect the popularity of the sport rather than its dangers. Young people are particularly at risk of sports injury because of high levels of exposure at a time of major physiological change. Soccer players are susceptible to a variety of injuries due to contact, aggressive tackle, and high-speed collisions. The aim of this study was to determine the pattern of presentation, treatment, and outcome of tibial fractures following participation in recreational football activity; with the hope that knowledge gained from this study will help in preventing or reducing its occurrence. This is a retrospective study of all cases of tibial fractures following participation in recreational football presenting to the Orthopedic Unit of Federal Medical Center and Surgery Department of Sir Yahaya Memorial Hospital all in Birnin Kebbi, Kebbi State, north western Nigeria; from January 2012 to December 2017. Data were extracted from the accident and emergency register, operation register, and patients' case folders on biodata, diagnosis, mechanism of injury, associated injuries, type of surgical procedure, site of surgery, date of surgery, and postoperative complications. Data collected were analyzed using the Statistical Package for Social Sciences for Windows version 22. Results were presented with descriptive statistics. In total, 37 patients were included in the study. All of them were males. The age range is from 14 to 33 years with mean age of 23.6. 17 (45.9%) of the patients are in the 21- to 30-year age group. The right tibia was affected in 34 (91.9%) patients. None of the patients used shin guard. The mechanism of injury in all the cases was direct contact. About 31 (83.8%) of the fractures were closed. Seven (18.9%) of these patients were discharged against medical advice. Nineteen (51.3%) patients were managed nonoperatively with plaster of Paris casts. Ten (27.1%) of these patients had internal fixation with locked intramedullary nail. Tibial fractures following football occur mostly in males especially adolescents and youths. The right tibia was commonly affected and most of the injuries are closed. The most common mechanism of injury was direct contact.


#7 The Effect of the "11+ Kids" on the Isokinetic Strength of Young Football Players
Reference: Int J Sports Physiol Perform. 2019 Apr 8:1-19. doi: 10.1123/ijspp.2018-0827. [Epub ahead of print]
Authors: Zarei M, Abbasi H, Daneshjoo A, Gheitasi M, Johari K, Faude O, Rommers N, Rössler R
Summary: The "11+ Kids" injury prevention programme has shown to reduce injuries and related costs in youth football players under 14 years of age. A major argument to convince coaches to use this exercise-based injury prevention programme, is a potential performance enhancement of the players. Therefore, this study investigated the effects of the "11+ Kids" programme on isokinetic strength. Two teams were randomly assigned to the intervention and control group. The intervention group replaced their warm-up by the "11+ Kids" and the control group warmed-up as usual. Two days before and after the 10-week intervention, isokinetic strength of the hip adductors and abductors, knee flexors and extensors, and ankle invertors and evertors was tested. Thirty-one players (mean age 11.5 ± 0.8 years) completed the study. The intervention group showed large improvements in all isokinetic strength measures (p < 0.001 for all measures, Cohen's d 0.8 to 1.4), whereas the control group only showed negligible to medium positive effects (p-values from 0.006 to 0.718, Cohen's d -0.1 to 0.7). The intervention was beneficial compared to the control group regarding isokinetic strength of the hip adductors (p < 0.001), knee flexors (p = 0.002), as well as ankle evertors (p < 0.001) and invertors (p = 0.005). Given the relatively short intervention period of 10 weeks, the observed improvements relate to a practically meaningful effect of the intervention. The gain in strength may improve players' performance and may contribute to a reduction of injury risk in the long-term application.


#8 Assessment of Safety and Glycemic Control During Football Tournament in Children and Adolescents With Type 1 Diabetes-Results of GoalDiab Study
Reference: Pediatr Exerc Sci. 2019 Apr 7:1-7. doi: 10.1123/pes.2018-0264. [Epub ahead of print]
Authors: Gawrecki A, Araszkiewicz A, Szadkowska A, Biegański G, Konarski J, Domaszewska K, Michalak A, Skowrońska B, Adamska A, Naskręt D, Jarosz-Chobot P, Szypowska A, Klupa T, Zozulińska-Ziółkiewicz D
Summary: The purpose was to assess glycemic control and safety of children and adolescents with type 1 diabetes participating in a 2-day football tournament. In total, 189 children with type 1 diabetes from 11 diabetes care centers, in Poland, participated in a football tournament in 3 age categories: 7-9 (21.2%), 10-13 (42.9%), and 14-17 (36%) years. Participants were qualified and organized in 23 football teams, played 4 to 6 matches of 30 minutes, and were supervised by a medical team. Data on insulin dose and glycemia were downloaded from personal pumps, glucose meters, continuous glucose monitoring, and flash glucose monitoring systems. The median level of blood glucose before the matches was 6.78 (4.89-9.39) mmol/L, and after the matches, it was 7.39 (5.5-9.87) mmol/L (P = .001). There were no episodes of severe hypoglycemia or ketoacidosis. The number of episodes of low glucose value (blood glucose ≤3.9 mmol/L) was higher during the tournament versus 30 days before: 1.2 (0-1.5) versus 0.7 (0.3-1.1) event/person/day, P < .001. Lactate levels increased during the matches (2.2 [1.6-4.0] mmol/L to 4.4 [2.6-8.5] mmol/L after the matches, P < .001). Large football tournaments can be organized safely for children with type 1 diabetes. For the majority of children, moderate mixed aerobic-anaerobic effort did not adversely affect glycemic results and metabolic safety.


#9 The effects of TeaCrine® and caffeine on endurance and cognitive performance during a simulated match in high-level soccer players
Reference: J Int Soc Sports Nutr. 2019 Apr 18;16(1):20. doi: 10.1186/s12970-019-0287-6.
Authors: Bello ML, Walker AJ, McFadden BA, Sanders DJ, Arent SM
Summary: Theacrine (1,3,7,9-tetramethyluric-acid) is a pure alkaloid with a similar structure to caffeine and acts comparably as an adenosine receptor antagonist. Early studies have shown non-habituating effects, including increases in energy and focus in response to Teacrine®, the compound containing pure theacrine. The purpose of this study was to determine and compare the effects of Teacrine® and caffeine on cognitive performance and time-to-exhaustion during a simulated soccer game in high-level male and female athletes. Male and female soccer players (N = 24; MAge = 20.96 ± 2.05y, MMaleVO2max = 55.31 ± 3.39 mL/O2/kg, MFemaleVO2max = 50.97 ± 3.90 mL/O2/kg) completed a 90-min simulated treadmill soccer match over four randomized sessions (TeaCrine®, caffeine, TeaCrine® + caffeine, placebo). Cognitive testing at halftime and end-of-game including simple reaction time (SRT), choice RT (CRT), and cognitive-load RT with distraction questions (COGRT/COGRTWrong) was performed, with a run time-to-exhaustion (TTE) at 85% VO2max following end-of-game cognitive testing. Session times and pre-exercise nutrition were controlled. RM-MANOVAs with univariate follow-ups were conducted and significance was set at P < 0.05. TTE trended towards significance in TeaCrine® and TeaCrine® + caffeine conditions compared to placebo (P < 0.052). A condition main effect (P < 0.05) occurred with faster CRT in caffeine and TeaCrine® + caffeine compared to placebo. COGRTWrong showed a significant time main effect, with better accuracy at end-of-game compared to halftime (P < 0.05). A time x condition interaction in SRT (P < 0.05) showed placebo improved from halftime to end-of-game. The 27-38% improvements in TTE reflect increased performance capacity that may have important implications for overtime scenarios. These findings suggest TeaCrine® favorably impacts endurance and the combination with caffeine provides greater benefits on cognitive function than either supplement independently.


#10 Comparison of lateral abdominal muscle thickness of young male soccer players with and without low back pain
Reference:  Int J Sports Phys Ther. 2019 Apr;14(2):273-281.
Authors: Noormohammadpour P, Mirzaei S, Moghadam N, Mansournia MA, Kordi R
Summary: While researchers have investigated low back pain (LBP) and its association with the thickness of trunk muscles in the general population, few articles have studied this relationship in athletes. The purpose was to compare the lateral abdominal muscle thickness and other possible functional risk factors in young soccer players with and without LBP. Thirty young male soccer players, with and without LBP, from the Premier League participated in this study. The thicknesses of the external oblique, internal oblique and transversus abdominis muscles were measured via musculoskeletal ultrasound imaging, bilaterally. In addition, hamstring flexibility, lumbar spine flexion range of motion, and trunk extensor muscle endurance were measured and were compared in those with and without the history of LBP. The mean age of the subjects was 17.4 (+/- 1.1) years. There was no statistically significant difference between groups (p > 0.05). Subjects with a history of LBP during their lifetime of sports participation (sports life), within the prior year, and within the prior month had statistically significant lower external oblique muscle thickness bilaterally (p<0.05). Subjects with a sports life history of LBP had lower internal oblique muscle thickness on both sides (p<0.05). Moreover, those with a sports life history of LBP had significantly less hamstring flexibility than the non-LBP group on the dominant limb (p < 0.05). In this sample group of young soccer players, abdominal muscle ultrasound measurements were different between players with and without LBP. Further longitudinal studies are needed to evaluate the role of these muscles as LBP risk factor for soccer players.


#11 The effects of training on hormonal concentrations in young soccer players
Reference: J Cell Physiol. 2019 Apr 16. doi: 10.1002/jcp.28673. [Epub ahead of print]
Authors: Muscella A, Vetrugno C, Spedicato M, Stefàno E, Marsigliante S
Summary: The purpose was to test the hypothesis that football training would be accompanied by physiological adaptations and hormonal changes, we analyzed the effects of a whole football season on physical fitness and hormonal concentrations in youth football players. Male football players (n = 29, age 16.51 ± 0.7 years) in a regional professional league and male healthy control subjects (n = 30, age 17.1 ± 1 years) participated to the study. Blood cortisol, testosterone, and growth hormone (hGH) concentrations were assayed before the beginning of the training period (T0), just after the training period (T1), at the middle of the season (T2), and at the end of the season (T3). In each period physical tests and anthropometric measurements were also performed. Results showed significant differences in basal values of cortisol, testosterone, and growth hormone (hGH) in the four time points evaluated (P < 0.01). In addition, the concentrations of hGH were higher in the soccer players group than in control subjects (P < 0.001). Between the start of the training period and the end of the football season significant differences were observed in the anthropometric characteristics and in the physical form of the football players. Furthermore, the hormonal status was significantly correlated with the indicators of the lower limb power (squat-jump [SqJ], and counter-movement-jump [CMJ]) and those of aerobic performance (Yo-Yo intermittent recovery test level 1 (YYIRT1) and maximal oxygen consumption (VO2max )).These data underscore the importance of establishing training protocols that present the potential to promote positive adaptations without, at the same time, provoking overtraining of young players.


#12 Sport Participation and Specialization Characteristics Among Pediatric Soccer Athletes
Reference: Orthop J Sports Med. 2019 Mar 27;7(3):2325967119832399. doi: 10.1177/2325967119832399. eCollection 2019 Mar.
Authors: McLeod TV, Israel M, Christino MA, Chung JS, McKay SD, Lang PJ, Bell DR; PRiSM Sports Specialization Research Interest Group, Chan CM, Crepeau A, Davis E, Fletcher AL, Laniak J, McCaffrey K, Pacicca D, Riederer M, Rizzone K, Rush JK, Zaslow T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6437330/pdf/10.1177_2325967119832399.pdf
Summary: Soccer is an increasingly popular sport for children and adolescents in the United States. Little is known about participation patterns related to sport specialization. The purpose was to investigate soccer participation levels and sport specialization characteristics among youth soccer athletes. Adolescent athletes aged between 12 and 18 years completed an online survey addressing participant demographics, sports and soccer participation history, and level of specialization. Descriptive analyses characterized participation, while chi-square and Kruskal-Wallis tests assessed the influence of specialization, sex, and grade on survey variables. Overall, 83.7% of 746 respondents participated in an organized soccer league outside of school, and 37% played in multiple leagues concurrently. Nearly three-quarters of respondents trained in soccer more than 8 months of the year, with those who participated in club soccer being more likely to train more than 8 months of the year. More respondents were classified as high specialization (37.5%), followed by moderate (35.6%) and low (28.6%) specialization. No differences between sexes were noted for level of specialization or quitting other sports to specialize in soccer, but male athletes were more likely to train more than 8 months per year compared with female athletes. Respondents in older grades (9th-10th and 11th-12th grades) were more likely to be highly specialized and quit other sports to focus on soccer. No differences between grade levels were found among respondents training more than 8 months per year. The study findings suggest that many youth soccer athletes participated in multiple teams or leagues at the same time and trained more than 8 months of the year. Characteristics including participation on a club team, level of specialization, and male sex were associated with a greater likelihood of exceeding the 8-month training recommendation.


#13 The relative age effect in European elite soccer: A practical guide to Poisson regression modelling
Reference: PLoS One. 2019 Apr 3;14(4):e0213988. doi: 10.1371/journal.pone.0213988. eCollection 2019.
Authors: Doyle JR, Bottomley PA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447143/pdf/pone.0213988.pdf
Summary: Many disciplines of scholarship are interested in the Relative Age Effect (RAE), whereby age-banding confers advantages on older members of the cohort over younger ones. Most research does not test this relationship in a manner consistent with theory (which requires a decline in frequency across the cohort year), instead resorting to non-parametric, non-directional approaches. In this article, the authors address this disconnect, provide an overview of the benefits associated with Poisson regression modelling, and two managerially useful measures for quantifying RAE bias, namely the Indices of Discrimination and Wastage. In a tutorial-like exposition, applications and extensions of this approach are illustrated using data on professional soccer players competing in the top two tiers of the "Big Five" European football leagues in the search to identify paragon clubs, leagues, and countries from which others may learn to mitigate this form of age-discrimination in the talent identification process. As with OLS regression, Poisson regression may include more than one independent variable. In this way we test competing explanations of RAE; control for unwanted sources of covariation; model interaction effects (that different clubs and countries may not all be subject to RAE to the same degree); and test for non-monotonic versions of RAE suggested in the literature.

Fri

03

May

2019

Latest research in football - week 13 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Risk diagnosis of minor muscle injuries in professional football players: when imaging cannot help out biology might
Reference: BMJ Open Sport Exerc Med. 2019 Feb 26;5(1):e000479. doi: 10.1136/bmjsem-2018-000479. eCollection 2019.
Authors: Volpi P, Chamari K, Bisciotti GN
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6407546/pdf/bmjsem-2018-000479.pdf


#2 Epidemiology of hip and groin injuries in Swedish male first football league
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Mar 20. doi: 10.1007/s00167-019-05470-x. [Epub ahead of print]
Authors: Lundgårdh F, Svensson K, Alricsson M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-019-05470-x.pdf
Summary: This study aimed to investigate the incidence, pattern, and burden of hip/groin injuries in Swedish professional male football players over five consecutive seasons. Injury history from 16 football teams in the Swedish male first football league was evaluated during five consecutive seasons. The team's medical staff recorded team exposure and time-loss injuries prospectively between 2012 and 2016. In total, 467 time-loss injuries located in the hip/groin area were recorded among 1,687 professional male football players, with an overall incidence and burden of 0.82/1,000 h and 15.6/1,000 h, respectively. There appeared to be an increased risk of hip/groin injuries during the last two seasons (2015-2016); however, the difference was not statistically significant (n.s). Recurrent injury rate was relatively low (14%), and overuse injuries accounted for the majority of injuries and absence days. Muscle injuries were the main injury type, while kicking and sprinting/running were the primary causes of injury. Goalkeepers had the lowest percentage of injuries and absence days. Hip/groin injuries are a substantial problem in football, but does not seem to be an increasing phenomenon in the Swedish male first football league. Index and overuse injuries accounted for the majority of injuries and absence days. Thus, the focus should be on preventing hip/groin injuries to lower the injury rate. These new findings should be taken into consideration when designing and implementing preventive training interventions.


#3 Network-based centrality measures and physical demands in football regarding player position: Is there a connection? A preliminary study
Reference: J Sports Sci. 2019 Mar 20:1-8. doi: 10.1080/02640414.2019.1589919. [Epub ahead of print]
Authors: Castellano J, Echeazarra I
Summary: This study's main objective is to analyse the relationship between network-based centrality measures and physical demands in elite football players. Thirty-six matches from La Liga, the Spanish league, were analysed in the 2017/18 season. The analysis of networks formed by team players passing the ball included: degree-prestige (DP), degree-centrality (DC), betweenness-centrality (BC), page-rank (PRP) and closeness-centrality (IRCC). A video-based system was used for analysing total distance (TDpos) and distance run >21Km/h (TD21pos) when the team was in possession of the ball. A magnitude-based inference and correlation analysis were applied. There were different styles of play, team-A was characterized by greater ball circulation (e.g. higher values of DP, DC, BC and IRCC) while team-B used a more direct game (lower values in centrality-metrics except with PRP). Furthermore, TDpos was higher in team-A than in team-B, but those differences disappeared for TD21pos between teams with the exception of the forwards. Finally, the correlation among centrality measures and physical performance were higher in team-B. Coaches could identify the key opponents and players who are linked to them, allowing to adjust performance strategies. Furthermore, interaction patterns between teammates can be used to identify preferential paths of cooperation and to take decisions regarding these relations in order to optimize team performance.


#4 Unison of movements in football players with different nervous systems
Reference: Rev Assoc Med Bras (1992). 2019 Feb;65(2):211-215. doi: 10.1590/1806-9282.65.2.211.
Author: Polevoy G
Download link: http://www.scielo.br/pdf/ramb/v65n2/1806-9282-ramb-65-02-0211.pdf
Summary: In this study, we investigated the effect of typological features of nervous system properties on the ability to unite the movements of young football players. A total of 36 young football players aged 11-12 years participated in this experiment. Of them, 18 were engaged in an experimental differentiated method, which is based on using the same exercise and methods for developing the ability to unite movements but with different load components; for players with a strong nervous system (9 children), the load was intensive, but for players with a weak nervous system (9 children) - the load was volumetric. The other 18 athletes made up the control group. After 8 months of the experiment, we observed positive changes in terms of the ability to unite movements in young football players. In the control group, these changes were not significant (P>0.05). In the experimental group studied according to a special method, the indicators changed considerably. The performance of football players with a strong nervous system improved from 6.4±0.2 s to 5.7±0.1 s (P<0.05), and for football players with a weak nervous system from 6.2±0.2 s to 5.6±0.2 s (P<0.05). The study proved the effectiveness of the use of the typological properties of the nervous system as a differentiated method for developing the ability to unite movements in young football players. This approach allows for the improvement of the quality of technical training of young athletes.


#5 Relationship between External Load and Perceptual Responses to Training in Professional Football: Effects of Quantification Method
Reference: Sports (Basel). 2019 Mar 17;7(3). pii: E68. doi: 10.3390/sports7030068.
Authors: Rago V, Brito J, Figueiredo P, Krustrup P, Rebelo A
Download link: https://www.mdpi.com/2075-4663/7/3/68/pdf
Summary: We examined the within-player correlation between external training load (ETL) and perceptual responses to training in a professional male football team (n = 13 outfield players) over an eight-week competitive period. ETL was collected using 10-Hz GPS, whereas perceptual responses were accessed through rating of perceived exertion (RPE) questionnaires. Moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary (fixed) and individualised speed zones (based on maximal aerobic speed and maximal sprinting speed). When ETL was expressed as actual distance covered within the training session, perceptual responses were moderately correlated to MSR and HSR quantified using the arbitrary method (p < 0.05; r = 0.53 to 0.59). However, the magnitude of correlations tended to increase when the individualised method was used (p < 0.05; r = 0.58 to 0.67). Distance covered by sprinting was moderately correlated to perceptual responses only when the individualised method was used (p < 0.05; 0.55 [0.05; 0.83] and 0.53 [0.02; 0.82]). Perceptual responses were largely correlated to the sum of distance covered within all three speed running zones, irrespective of the quantification method (p < 0.05; r = 0.58 to 0.68). When ETL was expressed as percentage of total distance covered within the training session, no significant correlations were observed (p > 0.05). Perceptual responses to training load seem to be better associated with ETL, when the latter is adjusted to individual fitness capacities. Moreover, reporting ETL as actual values of distance covered within the training session instead of percentual values inform better about players' perceptual responses to training load.


#6 Reducing risk of head injury in youth soccer: An extension of behavioral skills training for heading
Reference: J Appl Behav Anal. 2019 Mar 29. doi: 10.1002/jaba.557. [Epub ahead of print]
Authors: Quintero LM, Moore JW, Yeager MG, Rowsey K, Olmi DJ, Britton-Slater J, Harper ML, Zezenski LE
Summary: Recently, concerns regarding sport-related concussions have increased within the research literature, the media, and popular culture. One potential source of soccer-related concussions involves the purposeful striking of the ball with one's head (i.e., heading). There is currently limited research on an effective teaching method to improve safe heading technique. In the current study, Behavior Skills Training (BST) was evaluated as a method to teach correct heading techniques to youth soccer players. BST increased the percentage of correct steps for each player based on a task analysis of heading. Based on social validity questionnaires administered to players and the coach, BST was rated as an acceptable form of training. After the final training session, experienced coaches rated each player as having improved from baseline to training.


#7 Effects of season long participation on ACL volume in female intercollegiate soccer athletes
Reference: J Exp Orthop. 2019 Mar 28;6(1):12. doi: 10.1186/s40634-019-0182-8.
Authors: Myrick KM, Voss A, Feinn RS, Martin T, Mele BM, Garbalosa JC
Download link: https://jeo-esska.springeropen.com/track/pdf/10.1186/s40634-019-0182-8
Summary: The aim of this study was to characterize the volumetric changes of the anterior cruciate ligament over the course of a competitive soccer season in female athletes. Seventeen Division-I collegiate soccer players were recruited. Two data collection sessions were conducted. The first data collection occurred prior to the start of the soccer season. Each subject completed a brief questionnaire, had height and weight measured, underwent a clinical assessment of their anterior cruciate ligaments and an eight sequence magnetic resonance imagery of their knees. Contours of the anterior cruciate ligaments were outlined in sagittal T-2 weighted MR images and volumes were calculated using Medical Image Processing, Analysis, and Visualization software. Presence or absence of edema within the ligament was determined in pre and post season scans. All subjects were followed during the season to determine if a lower extremity injury had been sustained. Mean ligament volume significantly increased from preseason to postseason (p=.006). There was a 10% increase in the percentage of knees with edema pre to post season. The physical demand of a competitive soccer season in female collegiate athletes appears to cause an increase in volume of the anterior cruciate ligament. The increase in volume may be related to the accumulation of microscopic tears over the course of the season which induce inflammation and edema. The volumetric changes in the ligament may have significant clinical implications, however further studies must be done to determine the relationship between anterior cruciate ligament volume and risk of injury.


#8 Comparing accuracy between global positioning systems and ultra-wideband-based position tracking systems used for tactical analyses in soccer
Reference: Eur J Sport Sci. 2019 Mar 28:1-9. doi: 10.1080/17461391.2019.1584248. [Epub ahead of print]
Authors: Bastida-Castillo A, Gómez-Carmona CD, De La Cruz Sánchez E, Pino-Ortega J
Summary: Current studies have reported high accuracy in global positioning system (GPS) and recently developed ultra-wideband (UWB)-based tracking systems for monitoring time - motion patterns. The accuracy and reliability of both systems may be different in tactical analysis application, an aspect that has never been studied previously. The aims of the present study were: (i) to determine and compare the accuracy of GPS and UWB technologies in soccer players' positions (ii) to compare the tactical application of both systems. Following institutional ethical approval and familiarisation, 14 well-trained soccer players performed tests around five courses: (a) field perimeter, (b) halfway line, (c) centre circle, (d) perimeter of the penalty area, and (e) semicircle penalty area. Also, a small-sided game was played monitored with WIMUPRO™ to determine real and practical differences in accuracy of both systems in tactical analysis. For the GPS, the mean absolute error (N = 9445) of "x" and "y" coordinates was 41.23 ± 17.31 cm and 47.6 ± 8.97 cm, respectively. For UWB, it was 9.57 ± 2.66 cm and 7.15 ± 2.62 cm. The results of the "x" and "y" accuracy comparison were significantly lower in all cases (p < 0.05) with an ES of 0.78 and 0.95, respectively. In a real practical application, the differences of both systems reached 8.31% in typical tactical variables (ES = 0.11). In contrast to GPS-10Hz, UWB WIMUPRO™-20 Hz has been demonstrated to be an acceptable technology to estimate the position of players on the pitch with high accuracy and be a useful, automatic, and portable instrument for tactical analysis measurement.


#9 Comparative Study of Two Intervention Programmes for Teaching Soccer to School-Age Students
Reference: Sports (Basel). 2019 Mar 26;7(3). pii: E74. doi: 10.3390/sports7030074.
Authors: García-Ceberino JM, Feu S, Ibáñez SJ
Download link: https://www.mdpi.com/2075-4663/7/3/74/pdf
Summary: The objective of this study was to design and analyse the differences and/or similarities of two homogeneous intervention programmes (didactic units) based on two different teaching methods, Direct Instruction (DI) and Tactical Games Approach (TGA), for teaching school-age soccer. The sample was composed of 58 tasks, 29 for each intervention programme. The pedagogical and external Training Load (eTL) variables recorded in the Integral System for Training Tasks Analysis (SIATE) were studied. The two intervention programmes were compared using Chi-Square, Mann-Whitney U and the Adjusted Standardized Residuals statistical tests. Likewise, the strength of association of the variables under study was calculated using Cramer's Phi and Cramer's V coefficients. Both intervention programmes had the same number of tasks (n = 29), sessions (n = 12), game phases (x² = 0.000; p = 1.000), specific contents (x² = 5.311; p = 0.968) and didactic objectives, as well as different levels of eTL (U = 145.000; p = 0.000; d = 1.357); which are necessary requirements to be considered similar. The differences and/or similarities between both intervention programmes will offer teachers guidelines to develop different didactic units using the specific DI and TGA methodologies.


#10 Stress fractures of the medial malleolus in the professional soccer player demonstrate excellent outcomes when treated with open reduction internal fixation and arthroscopic spur debridement
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Mar 26. doi: 10.1007/s00167-019-05483-6. [Epub ahead of print]
Authors: Nguyen A, Beasley I, Calder J
Summary: Despite a debilitating effect on athletic performance and an incidence of up to 4% of all stress fractures, there have been only 31 documented cases of medial malleolus stress fractures (MMSF) to our knowledge in the literature. The largest series to date is presented in this study, of 16 professional soccer players undergoing uniform operative treatment. The authors attempt to justify their preferred treatment of MMSFs in the professional soccer player, with an emphasis on patient satisfaction, clinical and radiographic union, and return to high level sport. The authors aim to prove an association between lower limb varus alignment and the development of MMSFs. Sixteen professional soccer players of mean age 23.6 years were analysed. A biomechanic assessment was performed. Preoperative CT+-MRI scan were performed to assess fracture lines and the presence of anteromedial tibial and/or talar spurs; which are the likely pathognomic lesion in the development of MMSFs. All patients underwent open reduction and internal fixation with three screws, as well as arthroscopic debridement of impringement spurs, and concentrated bone marrow aspirate into the fracture site. Patients completed the Ogilvie-Harris score, and all patients had CT scans at 3 months and until union. All the patients in this cohort had causative bony spurs that were debrided at surgery. All of the cohort achieved clinical union. All patients were able to return to professional football; at the same level as prior to the injury. There was complete cohort follow up; and 81% of patients were graded as excellent and 19% as good by the Ogilvie-Harris score. We noted 50% of our cohort demonstrated varus malalignment, either genu varum or hindfoot varus. The authors conclude that open reduction and internal fixation of MMSFs with screws combined with arthroscopic spur debridement results in excellent clinical outcomes. It can be concluded that varus lower limb malalignment is a risk factor for MMSFs. Given the treatment controversy for these injuries, the results herein demonstrate that aggressive multimodal operative treatment produces excellent outcomes in high demand professional footballers. This study is the first to report a biomechanic association, which can alert the clinician to preventative measures; such as hindfoot orthoses.


#11 No Evidence of Association Between Soccer Heading and Cognitive Performance in Professional Soccer Players: Cross-Sectional Results
Reference: Front Neurol. 2019 Mar 12;10:209. doi: 10.3389/fneur.2019.00209. eCollection 2019.
Authors: Rodrigues AC, Lima MDM, de Souza LC, Furtado C, Marques CE, Gonçalves L, Lima MV, Lasmar RP, Caramelli P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6422927/
Summary: Although the scientific community has focused on the effects of concussions in contact sports, the role of subconcussive impacts, as it can occur during soccer heading, has recently gained attention, considering that it may represent an additional mechanism of cumulative brain injury. The aim of this study is to investigate the effects of soccer heading on cognitive functioning in active professional soccer players. Male soccer players (n = 44), from two soccer teams that play in the Brazilian A Series Championship, and non-athletes (n = 47), comparable in age and education, were submitted to cognitive assessment, consisting of computerized and conventional neuropsychological testing (Neupsilin battery). In the computerized cognitive assessment, soccer players performed better than controls on reaction time measures in general motor coordination, executive functioning and memory tests, and on accuracy measures in executive functioning tests. There were no significant differences between groups on the Neupsilin battery. A comparison between two sub-groups of soccer players, based on the self-reported number of headings, did not show significant differences on tests performance. No significant correlations were found between an estimate of exposure to heading during professional soccer career and cognitive performance. Our data demonstrate no evidence of cognitive impairment in soccer players, compared to non-athletes, and no association between heading exposure and performance on neuropsychological tests. Longitudinal investigations, including neuroimaging assessment, will help to clarify whether soccer heading may be associated with brain injury and cognitive dysfunction.


#12 Effect of Creatine Supplementation on the Airways of Youth Elite Soccer Players
Reference: Med Sci Sports Exerc. 2019 Mar 19. doi: 10.1249/MSS.0000000000001979. [Epub ahead of print]
Authors: Simpson AJ, Horne S, Sharp P, Sharps R, Kippelen P
Summary: Owing to its well-established ergogenic potential, creatine is a highly popular food supplement in sports. As an oral supplement, creatine is considered safe and ethical. However, no data exist on the safety of creatine on lung function in athletes. The aim of this project was to evaluate the effects of a standard course of creatine on the airways of youth elite athletes. Nineteen elite soccer players, aged 16-21yr, completed a stratified, randomized, double-blind, placebo-controlled, parallel-group trial. The creatine group (n=9) ingested 0.3 g/kg/d of creatine monohydrate (CM) for 1wk (loading phase) and 5 g/d for 7wk (maintenance phase), and the placebo group (n=10) received the same dosages of maltodextrin. Airway inflammation (assessed by exhaled nitric oxide, FENO) and airway responsiveness (to dry air hyperpnoea) were measured pre- and post-supplementation. Mild, unfavorable changes in FENO were noticed by trend over the supplementation period in the CM group only (P=0.056 for interaction, η=0.199), with a mean group change of 9 ± 13 ppb in the CM group versus -5 ± 16 ppb in the placebo group (P=0.056, d=0.695). Further, the maximum fall in forced expiratory volume in 1 sec (FEV1) after dry air hyperpnoea was larger by trend post-supplementation in the CM group compared to the placebo group: 9.7 ± 7.5% versus 4.4 ± 1.4%, respectively (P=0.070, d=0.975). These adverse effects were more pronounced when atopic players only (n=15) were considered. Based on the observed trends and medium-to-large effect sizes, we cannot exclude that creatine supplementation has an adverse effect on the airways of elite athletes, particularly in those with allergic sensitization. Further safety profiling of the ergogenic food supplement is warranted.


#13 Effect of Overload and Tapering on Individual Heart Rate Variability, Stress Tolerance, and Intermittent Running Performance in Soccer Players During a Preseason
Reference: J Strength Cond Res. 2019 Mar 20. doi: 10.1519/JSC.0000000000003127. [Epub ahead of print]
Authors: Figueiredo DH, Figueiredo DH, Moreira A, Gonçalves HR, Stanganelli LCR
Summary:  This study evaluates the weekly natural log of the root-mean-square difference of successive R-R intervals (lnRMSSDmean), its coefficient of variation (lnRMSSDcv), training load (TL), stress tolerance (ST), and changes in intermittent running performance in response to a 2-week overload (OL) followed by a 1-week taper (TP) during a preseason. Additionally, we determined the relationships between these variables. Ultra-short lnRMSSD, psychometric responses, and ratings of perceived exertion were evaluated daily among 16 under-19 soccer players. At the end of each training phase, the athletes performed the Yo-Yo Intermittent Recovery test level 1 (Yo-Yo). Group analysis showed a decrease in lnRMSSDmean and ST, increases in lnRMSSDcv, and decreases in the Yo-Yo during OL, with a return to baseline levels and a trivial increase in the Yo-Yo during TP. Small to very large correlations were found between lnRMSSDmean and lnRMSSDcv values, with changes in Yo-Yo, TL, monotony, and strain during the preseason (r values ranging from -0.27 to 0.82). No correlation was found between lnRMSSD responses and ST. During OL, athletes with decreases in lnRMSSDmean and increases in lnRMSSDcv accumulated higher perceived TL, with higher monotony and overall stress, and presented a decrease in ST and intermittent running performance, interpreted as a negative adaptation in response to the maintenance of higher TL. During TP, these responses were reversed, leading to an increase in intermittent running performance. In addition, subjective measures of ST may be used to provide early indicators of training adaptation in soccer players.


#14 Influence of Different Small-Sided Game Formats on Physical and Physiological Demands and Physical Performance in Young Soccer Players
Reference: J Strength Cond Res. 2019 Mar 15. doi: 10.1519/JSC.0000000000003114. [Epub ahead of print]
Authors: Castillo D, Rodríguez-Fernández A, Nakamura FY, Sanchez-Sanchez J, Ramirez-Campillo R, Yanci J, Zubillaga A, Raya-González J
Summary: The aim of this study was to quantify the acute impact of bout duration and individual interaction space on physical and physiological demands and on physical performance. Ten young male soccer players (age: 14.8 ± 0.6 years) from the same team playing in the National U-16 Division participated. Physical (total distance [TD]; distance covered at different speeds; and maximum velocity [Velmax]) and physiological (peak [HRpeak] and mean [HRmean] heart rate) parameters were collected for every bout during each small-sided game (SSG) format. Moreover, the effects of SSGs on horizontal jump (HJ) and 30-m sprint performances were evaluated. The SSG formats were composed of 6 players a side (including goalkeepers) and included 4 repetitions of 6 minutes in a space of 100 m (SSG1) or 200 m (SSG2) and 6 repetitions of 4 minutes in 100 m (SSG3) or 200 m (SSG4). The TD, the distance covered at different speeds, and Velmax were greater (p < 0.01, effect size [ES] = 1.25-5.95, large) in SSG2 and SSG4 than SSG1 and SSG3, respectively. Furthermore, the HRmean and HRpeak were lower (p < 0.05, ES = 1.53-2.23, large) during SSG3 than other SSGs. In addition, while a significant (p < 0.05, ES = 0.70-2.04, moderate to large) increase in SPR30 time in SSG1 and SSG3 was observed, HJ performance was not affected (p > 0.05, ES = 0.03-0.54, trivial to moderate) by any SSG format. These findings suggest increasing pitch size to induce greater physical demands and to use SSGs with smaller pitch size, and independently of the bout duration, to induce neuromuscular fatigue.

Thu

25

Apr

2019

Latest research in football - week 12 -2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Vertical Jump Performance in Hungarian Male Elite Junior Soccer Players
Reference: Res Q Exerc Sport. 2019 Mar 22:1-7. doi: 10.1080/02701367.2019.1588934. [Epub ahead of print]
Authors: Petridis L, Utczás K, Tróznai Z, Kalabiska I, Pálinkás G, Szabó T
Summary: Vertical jump is a common test to measure impulsive ability in soccer; however, limited normative data have been published on young soccer players from vertical jump measurements on a force platform. The purpose of this study was to provide normative values for three chronological age groups of male junior soccer players (U16, U17 and, U18 years). Vertical jump performance of 365 soccer players (16.4 ± 0.8 years) was assessed using a force platform measurement system. Net impulse, force, power, jump height (impulse-momentum), jump height (flight time) were reported for each age group for squat jump (SJ) and countermovement jump (CMJ). Mean values ± SD of jump height were 32.9 ± 4.1, 33.5 ± 4.0, and 33.9 ± 4.2 cm for the three age groups respectively in SJ and 36.3 ± 3.8, 37.5 ± 3.9, and 38.6 ± 4.4 cm in the CMJ. Mean values of all age groups for maximum force and maximum power were 1559 ± 211 N and 3261 ± 492 watt respectively for SJ and 1598 ± 241 N and 3287 ± 502 watt for CMJ. Based on descriptive data, percentiles were reported for all examined variables. Jump height and relative values were less sensitive discriminator variables between age groups in the studied age range, while maximum impulse, maximum force, and maximum power were more sensitive to changes in maturational status. Normative values can be used by the coaches in the interpretation and evaluation of their athletes' performance and for training and talent identification purposes.


#2 Effect of a 4-week detraining period followed by a 4-week strength program on isokinetic strength in elite youth soccer players
Reference: J Exerc Rehabil. 2019 Feb 25;15(1):67-73. doi: 10.12965/jer.1836538.269. eCollection 2019 Feb.
Authors: Vassilis S, Yiannis M, Athanasios M, Dimitrios M, Ioannis G, Thomas M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6416502/pdf/jer-15-1-67.pdf
Summary: The aim of the present study was to determine if 4 weeks of training cessation (detraining) followed by a 4-week strength training program can affect the isokinetic strength of elite youth soccer players. There were 13 players who participated in the study. The players performed anthropometric measurements and lower limb isokinetic strength measurements 3 times, before the training cessation, after the training cessation and after the 4-week strength training program. No significant differences were observed in the anthropometric and strength measurements (P>0.05) after the detraining period and after the training program (P>0.05). These results indicate that 4 weeks of detraining in elite youth soccer players does not have any significant effects according to their anthropometric characteristics and isokinetic strength of their lower limbs. Furthermore, neither the 4-week training program affected the parameters above. Perhaps, youth players can maintain the benefits of training better than adults due to their neural adaptations. The duration of the strength training program could be the reason of the lack of adaptations.


#3 The relationship between ACTN3 R577X gene polymorphism and physical performance in amateur soccer players and sedentary individuals
Reference: Biol Sport. 2019 Mar;36(1):9-16. doi: 10.5114/biolsport.2018.78900. Epub 2018 Oct 5.
Authors: Koku FE, Karamızrak SO, Çiftçi AS, Taşlıdere H, Durmaz B, Çoğulu Ö
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413569/pdf/JBS-36-78900.pdf
Summary: The aim of this study was to determine the distribution of ACTN3 R577X gene polymorphism in soccer players and sedentary individuals, and to investigate the relationship of this distribution with performance tests. A total of 100 soccer players and 101 sedentary individuals were enrolled in the study. Standing long jump and countermovement jump (with arm swing, without arm swing and repeated) scores were recorded, using a jump meter. Maximum VO2 levels were measured using a treadmill-connected cardiopulmonary exercise device, Masterscreen CPX. ACTN3 R577X polymorphism was evaluated by real-time PCR. ACTN3 R577X genotype distribution was found to be similar in soccer players and controls (p>0.05). The only statistically significant finding was a shorter countermovement jump with arm swing scores in the RR-genotyped soccer players, compared with their RX genotyped counterparts (p<0.05). In the soccer player group, RX-genotyped subjects were observed to have lower respiratory threshold values compared with RR-genotyped subjects (p<0.05). No significant correlation was detected between this distribution and performance test results. ACTN3 R577X genotype distribution was found to have no effect on sprint and endurance characteristics in amateur soccer players. The ACTN3 R577X polymorphism may not be a specific enough genetic marker to determine athletic performance in soccer.


#4 Lack of impact moderating movement adaptation when soccer players perform game specific tasks on a third-generation artificial surface without a cushioning underlay
Reference: Sports Biomech. 2019 Mar 21:1-15. doi: 10.1080/14763141.2019.1579365. [Epub ahead of print]
Authors: Lozano-Berges G, Clansey AC, Casajús JA, Lake MJ
Summary: The objective of this study was to investigate how the inclusion of a cushioning underlay in a third-generation artificial turf (3G) affects player biomechanics during soccer-specific tasks. Twelve soccer players (9 males/3 females; 22.6 ± 2.3 y) participated in this study. Mechanical impact testing of each 3G surface; without (3G-NCU) and with cushioning underlay (3G-CU) were conducted. Impact force characteristics, joint kinematics and joint kinetics variables were calculated on each surface condition during a sprint 90° cut (90CUT), a sprint 180° cut (180CUT), a drop jump (DROP) and a sprint with quick deceleration (STOP). For all tasks, greater peak resultant force, peak knee extensor moment and peak ankle dorsi-flexion moment were found in 3G-NCU than 3G-CU (p < 0.05). During 90CUT and STOP, loading rates were higher in 3G-NCU than 3G-CU (p < 0.05). During 180CUT, higher hip, knee and ankle ranges of motion were found in 3G-NCU (p < 0.05). These findings showed that the inclusion of cushioning underlay in 3G reduces impact loading forces and lower limb joint loading in soccer players across game-specific tasks. Overall, players were not attempting to reduce higher lower limb impact loading associated with a lack of surface cushioning underlay.


#5 Maturity status effects on torque and muscle architecture of young soccer players
Reference: J Sports Sci. 2019 Mar 21:1-10. doi: 10.1080/02640414.2019.1589908. [Epub ahead of print]
Authors: Cunha GDS, Vaz MA, Herzog W, Geremia JM, Leites GT, Reischak-Oliveira Á
Summary: This study investigated the effects of maturity status on knee extensor torque and vastus lateralis architecture of young soccer players. Thirty-four males aged 13-18 years were divided into two groups: pubescent (PUB, n = 15) and postpubescent (POSP, n = 19). Torque by angle interaction was established for absolute [F(2.649, 84.771) = 9.066, p < 0.05] and relative to body mass [F(2.704, 86.533) = 4.050, p < 0.05] isometric torque with the POSP group showing greater values. Muscle volume torque-angle relationship was similar between groups. Absolute, relative to body mass, and relative to muscle volume concentric and eccentric torque-velocity relationship showed a non-significant interaction but a significant group effect in favour the POSP group for absolute and concentric torque relative to body mass. Torque-angle and torque-velocity relationship normalized by body mass allometric exponents showed a non-significant interactions and group effects. Muscle thickness (3.6 ± 0.6 vs. 3.8 ± 0.6 cm), fascicle length (8.3 ± 1.4 vs. 8.9 ± 1.6 cm) and pennation angle (15.0 ± 2.3 vs. 14.3 ± 3.2 degrees) was similar between PUB and POSP groups, respectively. Maturity status did not show a significant effect on muscle architecture and on isometric and dynamic torques when allometrically normalized.


#6 Repeated Sprint Ability and Muscular Responses According to the Age Category in Elite Youth Soccer Players
Reference: Front Physiol. 2019 Mar 6;10:175. doi: 10.3389/fphys.2019.00175. eCollection 2019.
Authors: Sánchez-Sánchez J, García-Unanue J, Hernando E, López-Fernández J, Colino E, León-Jiménez M, Gallardo L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414432/pdf/fphys-10-00175.pdf
Summary: The aim of this study was to analyse the influence of age category on the performance and muscle response after a Repeated Sprint Ability (RSA) test in elite youth soccer players. 62 soccer players from three different age categories (Under 14 [n = 21], Under 16 [n = 20], and Under 18 [n = 21]) were selected to participate in this study. Players completed an RSA test (7 × 30 m) with a 20-s recovery between sprints. The muscular response to an electrical stimulus before and after the test of both the biceps femoris (BF) and the rectus femoris (RF) were evaluated using tensiomyography. A two-way ANOVA was used to analyse the differences in RSA parameters in each of the four distance-intervals (0-5; 5-25; 25-30; 0-30 m) between sprint and age category. The U14 age category (5.30 ± 0.30 s) showed higher mean sprint times than U16 (4.62 ± 0.20 s) and U18 (4.46 ± 0.17 s) throughout the entire test (p < 0.01). U16 players revealed a worse best sprints time (RSABEST) than U18 players (+0.12 s, CI95%: to 0.01 to 0.24; ES: 1.09, p = 0.03). The muscular contractile properties were similar in the three age categories analyzed (p > 0.05), although the delay time (Td) of the muscle was significantly lower after the RSA test in U16 players (-1.53 ms, CI95%: -2.607 to -0.452; ES: 0.38) and U18 players (-1.11 ms, CI95%: -2.10 to -0.12; ES: 0.22). In conclusion, this study revealed an increase in physical performance and muscle response variability after a repeated sprint ability test in the U16's and over. The fatigue induced by the RSA test did not show differences depending on the age of the players, although muscle mechanical properties were altered after the RSA test in U16 and U18 soccer players. Physical performance and muscle response can be complementary variables in managing fatigue according to the age category in soccer players.


#7 Leadership and Motivational Climate: The Relationship with Objectives, Commitment, and Satisfaction in Base Soccer Players
Reference: Behav Sci (Basel). 2019 Mar 19;9(3). pii: E29. doi: 10.3390/bs9030029.
Authors: Calvo C, Topa G
Download link: https://www.mdpi.com/2076-328X/9/3/29/pdf
Summary: The objective of the present study is to analyze non-professional soccer players' preferences regarding coach leadership style and motivational climate and to determine the relationship of these variables with players' satisfaction, sport commitment, and sport objectives. The participants were 151 players, aged between 10 and 24 years, divided into five categories: Alevín, Infantil, Cadet, Feminine, and Juvenile, all belonging to the Aragonese Soccer Federation. The participants completed questionnaires assessing their perception of their coach's leadership style, the team's motivational climate, their individual satisfaction, degree of sport commitment, and sport objectives. The results show that the leadership styles of training and instruction (M = 3.98, SD = 0.43) and positive feedback (M = 4.02, SD = 0.53) are the most valued by the players in all categories. The training and instruction leadership style had the highest correlations with task-oriented motivational climate (r = 0.40). The findings of the regression analysis show that a training and instruction leadership style and a task-oriented motivational climate significantly predict players' satisfaction (13.3%) and sport commitment (14.5%).


#8 Monitoring Training and Match Physical Load in Junior Soccer Players: Starters versus Substitutes
Reference: Sports (Basel). 2019 Mar 19;7(3). pii: E70. doi: 10.3390/sports7030070.
Authors: Dalen T, Lorås H
Download link: https://www.mdpi.com/2075-4663/7/3/70/pdf
Summary: The aim of this study was to investigate differences in the physical (locomotor activities) and physiological (Banister's training impulse) in-season training load between starters and substitutes in a well-trained junior soccer team. Physical performance variables from the Polar Team Pro system were collected and analyzed from a sample of junior soccer players (N = 18; age = 15.7 ± 0.5 years; stature, 177.9 ± 4.6 cm; body mass, 67.1 ± 5.5 kg). The study analyzed a total of 10 matches and 38 training sessions during the 2018 season with linear mixed models. The players from the starting line-ups demonstrated significantly higher average weekly physical load compared to the non-starters with respect to all variables: distance (total, running, high-speed running, and sprint) [F (1, 573) ≥ 66, p < 0.001, eta = 0.10], number of accelerations and sprints [F (1, 573) ≥ 66, p < 0.001, eta = 0.10], as well as Banister's training impulse (TRIMP) [F (1, 569) = 10, p < 0.001, eta = 0.02]. Evidence from this study indicates that a large amount of weekly accumulated high-speed running and sprint distances is related to match playing time. Therefore, weekly fitness-related adaptations in running at high speeds seem to favor the starters in a soccer team.


#9 Determinants of concussion diagnosis, symptomology, and resolution time in U.S. high school soccer players
Reference: Res Sports Med. 2019 Mar 20:1-13. doi: 10.1080/15438627.2019.1590834. [Epub ahead of print]
Authors: Chandran A, Elmi A, Young H, DiPietro L
Summary: Determinants of concussion diagnosis, symptomology, and other sequelae have not been examined in high school soccer players. Using a sample of soccer-related head/neck injuries from the NATION Surveillance Program, we evaluated potential determinants (sex, injury history, injury mechanism, setting) of concussion characteristics. A total of 378 head/neck injuries were recorded, and 189 (50.0%) injuries from this sample, resulted in a concussion diagnosis. Odds of concussion diagnosis were 84% higher among female players compared with their male counterparts, and over two-fold higher in game settings compared with practice settings. We also observed several significant symptom dependencies, such as higher odds of difficulty concentrating (OR = 5.84, 95% CI = [2.99, 11.42]) given concurrent light sensitivity. Furthermore, we identified injury mechanism as a determinant of concussion symptom resolution time. Our results suggest that determinants of soccer-related concussions and their sequelae are multifactorial, and extend the existing literature with the potential to inform clinical practice.


#10 Tracking and Comparing Self-Determined Motivation in Elite Youth Soccer: Influence of Developmental Activities, Age, and Skill
Reference: Front Psychol. 2019 Mar 5;10:304. doi: 10.3389/fpsyg.2019.00304. eCollection 2019.
Authors: Hendry DT, Crocker PRE, Williams AM, Hodges NJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411691/pdf/fpsyg-10-00304.pdf
Summary: Our aim was to determine if self-determined motivation (SDM) in elite, men's soccer changes over time and differs as a function of age, skill-grouping, and engagement in soccer play and practice. We tested predictions from the Developmental Model of Sport Participation (DMSP) regarding relations between practice and play and SDM among both elite and non-elite samples. Elite youth soccer players in the United Kingdom (n = 31; from the Under 13/U13 and U15 years age groups) completed practice history and motivation questionnaires at time 1 (T1) and ∼2 years later (T2: now U15 and U17 years). Non-elite players (n = 32; from U15 and U17 years) completed the same questionnaires at T2 only. For the elite groups, global SDM decreased over time for the current U17 group (from U15), but no change was seen for the current U15 group (from U13). Age group differences at T2 mirrored these data, with U17 players showing lower global SDM and higher controlled motivation than U15 elites. The non-elite players did not show age group differences, but elites scored higher for global SDM and autonomous motivation than non-elites. The recent hours accumulated in practice negatively correlated with global SDM in elite and non-elite groups, but play was unrelated to measures of motivation. Conclusion: Differences in SDM as a function of age and skill point toward the dynamic nature of these motivations over time, likely a result of proximity to external rewards related to professional status. Although high volumes of practice are related to lower global SDM in both skill groups, the absence of any relations between SDM and soccer play does not support a key prediction related to the DMSP.


#11 Modelling the Acceleration and Deceleration Profile of Elite-level Soccer Players
Reference: Int J Sports Med. 2019 Mar 18. doi: 10.1055/a-0853-7676. [Epub ahead of print]
Authors: Newans T, Bellinger P, Dodd K, Minahan C
Summary: The ability to change velocity rapidly is a key element of field-based sports. This study quantified the acceleration and deceleration profiles of soccer players during match play. Global positioning system measures were collected from 20 male soccer players competing in the Australian Hyundai A-League during 58 matches. Match data were organized into ten 9 min periods (i. e., P1: 0-9 min) and the time spent at moderate (1-2 m·s-2) and high (>2 m·s-2) acceleration and deceleration thresholds were quantified. Additionally, a novel deceleration: acceleration ratio was quantified to identify the transient nature of deceleration activity. Linear mixed models were used to model the acceleration and deceleration profiles. All acceleration and deceleration metrics displayed negative logarithmic curves within each half. There was no change in the ratio of high deceleration: acceleration; however, a significant increase in the ratio of moderate deceleration:acceleration was evident. Using negative logarithmic curves to illustrate the acceleration and deceleration decay provides a novel methodological approach to quantify the high-intensity actions during match play. A decrease in the time spent decelerating throughout a match may be attributed to a lack of opportunity. Practitioners can use the coefficients, intercepts, and deceleration: acceleration ratios to monitor a player's deceleration profile in match play.


#12 Relationship of Training Load with High-intensity Running in Professional Soccer Players
Reference: Int J Sports Med. 2019 Mar 18. doi: 10.1055/a-0855-3843. [Epub ahead of print]
Authors: Lee M, Mukherjee S
Summary: This study determined the training load (TL) and its relationship with high-intensity running performance across the season in professional soccer players. The TL, YoYo Intermittent Recovery Test Level 2 (YYIR 2) and repeated sprint ability (RSA) were monitored in 29 players (age 26.2±3.8 years, height 173.6±5.6 cm, body mass 68.5±8.6 kg). In the mid in-season (MS), Lucia TRIMP (TRIMPL) was inversely correlated with YYIR 2 (r=-0.6, p<0.05), with total distance (TD), work-rate (WR), low-intensity distance (LID) and player load (PL) showing correlation with YYIR 2 (r=0.81, 0.77, 0.88, 0.67; p<0.05) in the late in-season (LS). In pre-season (PS), TD, WR and moderate-intensity distance (MID) were correlated with YYIR 2 (r=0.65, 0.80, 0.83, p<0.05), whereas in early in-season (ES), TD, WR, LID were correlated with YYIR 2 performance (r=0.58, 0.67, 0.55, p<0.05). There was no significant relationship (p>0.05) between TL and RSA. The findings showed the volume, intensity and types of TL accrued influences the relationship with physical performance that suggest the significance of phase-specific monitoring of TL for maximizing performance in soccer players.


#13 A Coding System to Quantify Powerful Actions in Soccer Match Play: A Pilot Study
Reference: Res Q Exerc Sport. 2019 Mar 18:1-10. doi: 10.1080/02701367.2019.1576838. [Epub ahead of print]
Authors: Murtagh CF, Naughton RJ, McRobert AP, O'Boyle A, Morgans R, Drust B, Erskine RM
Summary: The powerful activity profile of elite soccer match play has not been documented appropriately to inform specific maximal power assessment and development criteria. The aims of the current study were to develop a reliable  soccer-specific powerful action (SSPA) notational analysis coding system that could be used to compare frequency and durations of powerful actions during elite youth soccer match play. Sixteen elite male English Premier League (EPL) Academy players (19 ± 1 yrs) were recorded by an individual camera during 16 competitive EPL U18 and U21 games. Video footage was analyzed using performance analysis software and SSPAs were coded according to the following categories: initial acceleration, leading acceleration, sprint, unilateral jump and bilateral jump. The SSPA coding system demonstrated very good inter- and intra-rater reliability (kappa coefficients ≥ 0.827). Elite youth EPL soccer players undertook significantly more initial (31 ± 9) and leading (37 ± 12) accelerations than sprints (8 ± 3; p = .014, d = 1.7, and p < .001, d = 1.7, respectively) and jumps (6 ± 5; p = .002, d = 1.7 and p < .001, d = 1.7, respectively). Players performed a significantly greater number of initial and leading accelerations with action durations below 1.5 s compared to above 1.5 s (p = .001, d = 1.6, and p = .002, d = 1.4), respectively. Our SSPA coding system provides a reliable observational instrument for quantifying the frequency and duration of powerful actions performed during elite soccer match play. In our sample of elite youth soccer players, horizontal accelerations of short duration (< 1.5 s) from different starting speeds appear the most dominant powerful action in elite youth soccer match play.


#14 Characterizing head impact exposure in youth female soccer with a custom-instrumented mouthpiece
Reference: Res Sports Med. 2019 Mar 16:1-17. doi: 10.1080/15438627.2019.1590833. [Epub ahead of print]
Authors: Miller LE, Pinkerton EK, Fabian KC, Wu LC, Espeland MA, Lamond LC, Miles CM, Camarillo DB, Stitzel JD, Urban JE
Summary: While many research efforts have focused on head impact exposure in professional soccer, there have been few studies characterizing exposure at the youth level. The aim of this study is to evaluate a new instrumentation approach and collect some of the first head impact exposure data for youth female soccer players. Athletes were instrumented with custom-fit mouthpieces that measure head impacts. Detailed video analysis was conducted to identify characteristics describing impact source (e.g., kick, header, throw). A total of 763 verified head impacts were collected over 23 practices and 8 games from 7 athletes. The median peak linear accelerations, rotational velocities, and rotational accelerations of all impacts were 9.4 g, 4.1 rad/s, and 689 rad/s2, respectively. Pairwise comparisons resulted in statistically significant differences in kinematics by impact source. Headers following a kicked ball had the highest accelerations and velocity when compared to headers from thrown or another header.


#15 Partial-body cryostimulation after training improves sleep quality in professional soccer players
Reference: BMC Res Notes. 2019 Mar 15;12(1):141. doi: 10.1186/s13104-019-4172-9.
Authors: Douzi W, Dupuy O, Theurot D, Boucard G, Dugué B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419922/pdf/13104_2019_Article_4172.pdf
Summary: The aim of the present investigation was to determine whether using cryostimulation (partial-body cryostimulation) impacts sleep quality in professional soccer players. Different exposure durations at - 180 °C were tested randomly after standardized training sessions in nine professional soccer players (no cryostimulation, 180-s exposure, two 90-s exposures separated by a 5-min rest at room temperature, and 90-s exposure), and the effects on sleep quality using 3-dimensional accelerometers worn during sleep were assessed. The number of movements during the night after partial-body cryostimulation was significantly reduced only in the 180-s exposure condition (p < 0.05, very large effect size) compared with the control condition. Partial-body cryostimulation seems to induce a positive impact on sleep quality that may be dose-dependent. Trial registration Australia and New Zealand Clinical Trials Registry (ANZCTR), ACTRN12619000330145, date of registration: 4/03/2019. Retrospectively registered.

Tue

16

Apr

2019

Latest research in football - week 11 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 A Preventive Model For Hamstring Injuries in Professional Soccer: Learning Algorithms
Reference: Int J Sports Med. 2019 Mar 14. doi: 10.1055/a-0826-1955. [Epub ahead of print]
Authors: Ayala F, López-Valenciano A, Gámez Martín JA, De Ste Croix M, Vera-Garcia FJ, García-Vaquero MDP, Ruiz-Pérez I, Myer GD
Summary: Hamstring strain injury (HSI) is one of the most prevalent and severe injury in professional soccer. The purpose was to analyze and compare the predictive ability of a range of machine learning techniques to select the best performing injury risk factor model to identify professional soccer players at high risk of HSIs. A total of 96 male professional soccer players underwent a pre-season screening evaluation that included a large number of individual, psychological and neuromuscular measurements. Injury surveillance was prospectively employed to capture all the HSI occurring in the 2013/2014 season. There were 18 HSIs. Injury distribution was 55.6% dominant leg and 44.4% non-dominant leg. The model generated by the SmooteBoostM1 technique with a cost-sensitive ADTree as the base classifier reported the best evaluation criteria (area under the receiver operating characteristic curve score=0.837, true positive rate=77.8%, true negative rate=83.8%) and hence was considered the best for predicting HSI. The prediction model showed moderate to high accuracy for identifying professional soccer players at risk of HSI during pre-season screenings. Therefore, the model developed might help coaches, physical trainers and medical practitioners in the decision-making process for injury prevention.


#2 Effects of Small-Sided Games vs. Conventional Endurance Training on Endurance Performance in Male Youth Soccer Players: A Meta-Analytical Comparison
Reference: Sports Med. 2019 Mar 13. doi: 10.1007/s40279-019-01086-w. [Epub ahead of print]
Authors: Moran J, Blagrove RC, Drury B, Fernandes JFT, Paxton K, Chaabene H, Ramirez-Campillo R
Summary: Small-sided games have been suggested as a viable alternative to conventional endurance training to enhance endurance performance in youth soccer players. This has important implications for long-term athlete development because it suggests that players can increase aerobic endurance through activities that closely resemble their sport of choice. The objectives of this meta-analysis were to compare male youth soccer players' adaptability to small-sided games vs. conventional endurance training and to establish exercise prescription guidelines for this population. The data sources utilised were Google Scholar, PubMed and Microsoft Academic. Studies were eligible for inclusion if interventions were carried out in male soccer players (aged < 18 years) and compared the effects of small-sided games and conventional endurance training on aerobic endurance performance. We defined small-sided games as "modified [soccer] games played on reduced pitch areas, often using adapted rules and involving a smaller number of players than traditional games". We defined conventional endurance training as continuous running or extensive interval training consisting of work durations > 3 min. The inverse-variance random-effects model for meta-analyses was used because it allocates a proportionate weight to trials based on the size of their individual standard errors and facilitates analysis whilst accounting for heterogeneity across studies. Effect sizes were represented by the standardised mean difference and presented alongside 95% confidence intervals. Seven studies were included in this meta-analysis. Both modes of training were effective in increasing endurance performance. Within-mode effect sizes were both of moderate magnitude [small-sided games: 0.82 (95% confidence interval 0.05, 1.60), Z = 2.07 (p = 0.04); conventional endurance training: 0.89 (95% confidence interval 0.06, 1.72), Z = 2.10 (p = 0.04)]. There were only trivial differences [0.04 (95% confidence interval - 0.36, 0.43), Z = 0.18 (p = 0.86)] between the effects on aerobic endurance performance of small-sided games and conventional endurance training. Subgroup analyses showed mostly trivial differences between the training methods across key programming variables such as set duration (≥ or < 4 min) and recovery period between sets (≥ or < 3 min). Programmes that were longer than 8 weeks favoured small-sided games [effect size = 0.45 (95% confidence interval - 0.12, 1.02), Z = 1.54 (p = 0.12)], with the opposite being true for conventional endurance training [effect size = - 0.33 (95% confidence interval - 0.79, 0.14), Z = 1.39 (p = 0.16)]. Programmes with more than 4 sets per session favoured small-sided games [effect size = 0.53 (95% confidence interval - 0.52, 1.58), Z = 0.98 (p = 0.33)] with only a trivial difference between those with 4, or fewer, sets [effect size = - 0.13 (95% confidence interval - 0.52, 0.26), Z = 0.65 (p = 0.52)]. Small-sided games are as effective as conventional endurance training for increasing aerobic endurance performance in male youth soccer players. This is important for practitioners as it means that small-sided games can allow both endurance and skills training to be carried out simultaneously, thus providing a more efficient training stimulus. Small-sided games offer the same benefits as conventional endurance training with two sessions per week, with ≥ 4 sets of 4 min of activity, interspersed with recovery periods of 3 min, recommended in this population.


#3 Management succession and success in a professional soccer team
Reference: PLoS One. 2019 Mar 13;14(3):e0212634. doi: 10.1371/journal.pone.0212634. eCollection 2019.
Authors: Kattuman P, Loch C, Kurchian C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0212634&type=printable
Summary: Research into sports team performance has shown that across many sports and league competitions, teams that change their coaches after a decline in performance do rebound, but fare no better on average than teams that have not changed their coach in a similar situation. A similar lack of succession benefits has been reported in studies of manager and CEO succession: it has not been established that changing a team's leader improves a declining team's performance. We study the effect of a change of coach on the performance of a professional soccer team. Based on rarely obtained access to a whole season (one year) of daily close observation of the team and coaching staff in practice and matches, this study uses quantitative and qualitative data to go beyond the "average" pattern reported in the literature. We document in detail how, in a single team case study over an entire season, the processes in leadership behavior changed with a change of coach, the effect this had on the state of mind of the team, how the match behaviors of the players changed, and how these changes translated into improved performance. The process effects of a leadership change on the performance of a sports team may hold insights for leader succession in management: in addition to the aggregate organizational and experience fit of the new team leader, the specific leadership processes introduced by the new leader are critical for performance effects.


#4 Prevalence and severity of traumatic dental injuries among young amateur soccer players: a screening investigation
Reference: Dent Traumatol. 2019 Mar 13. doi: 10.1111/edt.12470. [Epub ahead of print]
Authors: Qudeimat MA, AlHasan AA, AlHasan MA, Al-Khayat K, Andersson L
Summary: Traumatic dental injuries (TDI) are prevalent among soccer players. In Kuwait, no studies of TDI among soccer players have been carried out. The aim of this study was to investigate the prevalence, type, and causes of soccer-related traumatic dental injuries among 7-18-year-old amateur soccer players. All amateur soccer players who were registered in the 14 sports clubs in the country were invited to participate in this screening study. Players who were present in the club on the assigned examination day were included. The players were examined by two trained and calibrated paediatric dentists for signs of injury to the oral tissues. Injury diagnosis was made according to the Andreasen (2007) epidemiological dental injury classification. The history of any dental injury present at the time of examination was recorded. The timing and nature of any dental advice or treatment sought was also noted. Six hundred sixty-seven (48% inclusion rate) male players were included (mean age of 13.4 ± 2.6 years). In total, 213 injured teeth were observed among 169 (25%) players. The prevalence of soccer-related injuries was 11% and a greater number of injuries were observed in older players. Maxillary central incisors were the most frequently injured teeth (91%), and enamel-only fractures represented 60% of all injured teeth. Slightly more TDIs were soccer-related (44%) compared to non-soccer-related injuries (39%) and a large number of TDIs (39%) occurred inside the sports clubs. The prevalence of reported soft tissue injuries was 18%. The majority of the players (75%) did not receive dental care for their injuries. A significant number of young Kuwaiti amateur soccer players suffered TDIs. In addition, a high percentage of traumatic injuries were not treated, and there was a lack of the use of protective mouthguards.


#5 Effects of morning and nocturnal soccer matches on levels of some trace elements in young trained males
Reference: Cell Mol Biol (Noisy-le-grand). 2019 Feb 28;65(2):32-36.
Authors: Algul S, Bengu AS, Baltaci SB, Ozcelik O
Summary: The aim of this study was to comparatively evaluate effect of morning and nocturnal soccer matches induced metabolic stress on plasma levels of iron (Fe), copper (Cu) and zinc (Zn). Twenty male footballers performed two soccer matches in morning and at night on different days. Blood samples were taken before and after match. The levels of Fe, Zn and Cu were measured through an atomic absorption spectrophotometry. Metabolic stress was evaluated by altered malondialdehyde (MDA) levels that measured using High Performance Liquid Chromatography. In morning and at nocturnal soccer matches, levels of MDA (36% and 27%), Fe (37.4% and 38.9%) and Cu (34.8% and 26.8%) were all increased in all subjects, respectively. However, Zn level decreased -4.5 % in morning (n=10 subjects) and -9.4% at nocturnal (n=12 subjects) soccer matches. In addition, Cu/Zn ratio increased significantly 46.6% in morning and 36.6% at nocturnal soccer matches. Soccer match has significant effects on levels of MDA, Fe and Cu but not Zn levels. The results of this study showed that morning soccer match significantly alters levels of MDA and Cu and Cu/Zn ratio compared to nocturnal soccer match.


#6 A Comparison of Three Different Unilateral Strength Training Strategies to Enhance Jumping Performance and Decrease Inter-Limb Asymmetries in Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Mar 12:1-26. doi: 10.1123/ijspp.2018-0920. [Epub ahead of print]
Authors: Gonzalo-Skok O, Moreno-Azze A, Arjol-Serrano JL, Tous-Fajardo J, Bishop C
Summary: This study compared the effects of performing different unilateral strength training interventions on unilateral and bilateral jumping performance and their related asymmetries in young soccer players. Forty-five male young (U-17) soccer players were randomly assigned to three eccentric overload training programs: The first group executed the same volume with both legs starting with the weaker leg (SVW, n=15), the second group carried out the double volume with the weaker leg and also starting with the weaker leg (DVW, n=15), and the third group performed the same volume with both legs starting with the stronger leg (SVS, n=15). Jumping performance assessment included a single-leg horizontal jump test, a triple single-leg horizontal jump test, a bilateral countermovement (CMJ) jump test and unilateral countermovement jump test. Asymmetries were also analyzed in the unilateral jumping tests. CMJ was improved (effect size [ES]: 0.27-0.48) and CMJ asymmetry was possibly reduced (ES: 0.08-0.24) in all groups. Substantial improvements were found in triple hop (ES: 0.52-0.71) in SVW and DVW, and triple hop asymmetry was substantially decreased (ES: 0.88) in DVW. Between-group analysis showed a substantial better performance in triple hop and horizontal hop with right leg in SVW and DVW compared to SVS. Unilateral strength training programs were shown to substantially improve bilateral jumping performance, while unilateral jumping was substantially enhanced in those groups that started the training session with the weaker leg. Finally, between-limbs asymmetries in the triple hop were mainly reduced through performing the double volume with the weaker leg.


#7 The Effects of Long Sprint Ability Oriented Small-Sided Games Using Different Players-to-Pitch Area on Internal and External Load in Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Mar 12:1-23. doi: 10.1123/ijspp.2018-0645. [Epub ahead of print]
Authors: Castagna C, D'Ottavio S, Cappelli S, Póvoas SCA
Summary: The aim of this study was to examine the internal and external load imposed by Long Sprint Ability (LSA) oriented small-sided games (SSG) using different players-to-pitch area ratio (densities) in soccer players. Nineteen professional soccer players from the same soccer club (age 17.1±0.3 years, height 1.76±0.69 m, body mass 69.7±9.4 kg) participated in this study. Players performed 4x30s (150s recovery) all-out 1v1 SSG considering 300, 200 and 100 m2 per player (48h apart). Players' external-load was tracked with GPS technology (20Hz). Heart rate, blood lactate concentration (BLc) and rating of perceived exertion characterized players' internal-load. Peak BLc was assessed with a 30s all-out test on a non-motorized treadmill (NMT). SSG300 produced higher BLc than SSG200 (moderate) and SSG100 (large). The SSG300, SSG200 and SSG100 BLc were 97.8±34.8 (trivial), 74.7±24.9 (moderate) and 43.4±15.7% (large) of the NMT30s peak BLc, respectively. Players covered more distance at high-intensity during the SSG300 than in other SSG conditions (huge to very-large differences).. High-intensity deceleration distance was largely lower in SSG200 than in SSG300. SSG100 elicit very-large to huge and large to very-large lower external load values than SSG300 and SSG200, respectively. The main finding of this study showed an inverse association between ball-drill density and internal/external loads in LSA oriented SSG. The SSG300 attested to provide BLc closer to individual maximal, and thus, satisfying the all-out construct assumed for LSA development. Further studies using the SSG300 as training intervention and/or investigating other different SSG formats using the same density are warranted.


#8 Application of a Preventive Training Program Implementation Framework to Youth Soccer and Basketball Organizations
Reference: J Athl Train. 2019 Mar 11. doi: 10.4085/1062-6050-375-17. [Epub ahead of print]
Authors: Root HJ, Frank BS, Denegar CR, Casa DJ, Gregorio DI, Mazerolle SM, DiStefano LJ
Summary: Preventive training programs (PTPs) can reduce injury rates and improve neuromuscular control and sport performance. However, PTPs must be implemented correctly and consistently over time for athletes to benefit. Coaches represent the best long-term option for implementing PTPs. Youth athletes are at the optimal age for developing good habits before maturation. Although frameworks have been proposed to guide implementation efforts, little is known regarding the feasibility and real-world context of PTP implementation at the youth sport level. The aim was to evaluate the application of the 7-Step framework for promoting implementation of a preseason PTP workshop. Youth soccer and basketball organizations were utilized for this study. Organizations with at least 1 team of athletes aged 8 to 14 years were invited to participate in a free preseason coaches' education workshop on PTP implementation. The 7-Step framework was used to guide PTP education and implementation for each organization. Personnel at organizations that agreed to participate attended a single preseason workshop for coaches. Research staff were available as a resource throughout the season but did not actively implement or monitor the PTPs. Retrospective evaluation of each organization's completion of steps 1 through 5 of the 7-Step framework were used as main outcome measures.  A total of 62 youth soccer (n = 40) and basketball (n = 22) organizations were invited to participate. Twelve organizations completed steps 1 through 4 and steps 5a through 5d. The highest drop-off rate occurred during step 1, "Establishing Administrative Support". No organization completed all components of steps 1 through 5. To better understand how to successfully promote PTP adoption, we must identify the implementation steps that may present the most challenges. Because the highest drop-off rate was seen during the initial step, establishing administrative support and strengthening initial engagement are necessary to improve PTP implementation.


#9 Dissociation between changes in sprinting performance and Nordic hamstring strength in professional male football players
Reference:  PLoS One. 2019 Mar 14;14(3):e0213375. doi: 10.1371/journal.pone.0213375. eCollection 2019.
Authors: Suarez-Arrones L, Lara-Lopez P, Rodriguez-Sanchez P, Lazaro-Ramirez JL, Di Salvo V, Guitart M, Fuentes-Nieto C, Rodas G, Mendez-Villanueva A
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0213375&type=printable
Summary: The aim of the present study was to evaluate the consequence of implementing a Nordic Hamstring exercise (NHE) protocol during the first 15 to 17 weeks of the season to assess the effect on sprinting and NHE strength (NHEs) in professional football players. The study examined 50 healthy male professional football players (age 18.8±0.8yr; height 176.8±6.9cm; weight 71.3±5.7kg) belonging to 3 of the reserve squads of three Spanish La-Liga clubs divided in 2 intervention teams [Nordic-Group1 (NG-1) and Nordic-Group2 (NG-2, extensive experience in NHE)] and 1 team as a control-group (CG). NHEs and linear sprint (T5, T10, T20-m) were evaluated at the beginning of the season and at the end of an intervention period of conditioning and football training, supplemented with a NHE protocol (24 sessions for NG-1 and 22 sessions for NG-2) or without using the NHE at all (CG). Sprint times were substantially improved in all groups (ES from -2.24±0.75 to -0.60±0.37). NHEs was enhanced absolute and relative to body-mass only in NG-1 after the training period (ES from 0.84±0.32 to 0.74±0.26), while in the NG-2 there were only improvements in average NHEs relative to body-mass (ES = 0.39±0.36). The improvements in T20-m were substantially greater in NG-2 vs. NG-1, and there were no differences in sprint performance changes between NG-1 and CG. Changes in sprinting performance and NHEs were unrelated. NHEs was largely correlated with the body-mass of the players. Results indicate that the improvements in sprint are not dependent on the NHEs changes, with no relationships between NHEs and sprint performance, and between sprint changes and changes in NHEs.


#10 Developing a theory-driven framework for a football intervention for men with severe, moderate or enduring mental health problems: a participatory realist synthesis
Reference: J Ment Health. 2019 Mar 12:1-12. doi: 10.1080/09638237.2019.1581339. [Epub ahead of print]
Authors: Such E, Burton H, Copeland RJ, Davies R, Goyder E, Jeanes R, Kesterton S, Mackenzie K, Magee J
Summary: Physical activity interventions are an important adjunct therapy for people with severe to moderate and/or enduring mental health problems. Football is particularly popular for men in this group. Several interventions have emerged over the past decade and there is a need to clearly articulate how they are intended to work, for whom and in what circumstances. The aim was to develop a theory-driven framework for a football intervention for men with severe, moderate and/or enduring mental health problems using a participatory realist approach. A participatory literature review on playing football as a means of promoting mental health recovery with a realist synthesis. It included the accounts and input of 12 mental health service users and the contributions of other stakeholders including football coaches and occupational therapists. Fourteen papers were included in the review. Analysis revealed that interventional mechanisms were social connectedness, identity security, normalising experiences and positive affectivity. These supported mental health recovery. Outcomes were moderated by social stigma and several interventional factors such as over-competitiveness. The context mechanism outcome configuration framework for these interventions map well onto social models of mental health recovery and provide insight into how they work. This now requires testing.


#11 Adductor squeeze test and groin injuries in elite football players: A prospective study
Reference: Phys Ther Sport. 2019 Mar 2;37:54-59. doi: 10.1016/j.ptsp.2019.03.001. [Epub ahead of print]
Authors: Moreno-Pérez V, Travassos B, Calado A, Gonzalo-Skok O, Del Coso J, Mendez-Villanueva A
Summary: The aim was to examining the relationship between hip adductor strength and groin injury incidence during the competitive season of professional football teams. Seventy-one players volunteered to participate. In the pre-season, maximal hip adductor strength was measured by means of the isometric adductor squeeze test. Hip adductor strength, normalized by body mass, was compared between players who suffered a groin injury (n = 18) vs uninjured players (n = 53). Risk ratios (RR) were used to evaluate the likelihood of players to suffer this type of injury. Most of the reported groin injuries occurred during competitive matches (5.5 per 1000 match hours). Maximal isometric hip adductor strength was lower in the groin-injured group compared with their uninjured counterparts (429.8 ± 100 vs 564 ± 58.7 N, d = -1.58 and 5.40 ± 1.27 vs 7.71 ± 0.89 N/kg, d = -1.88, respectively). Results revealed that values of maximal isometric adductor strength lower than 465.33 N increased the probability to suffer a groin injury by 72%. Furthermore, values of force relative to body mass lower than 6.971 N/kg increased the probability to suffer a groin injury by 83%. The assessment of Hip adductor strength, in addition to other measurements, might help practitioners to determine the probability of suffering an overuse groin injuries in elite football players.


#12 Application of multivariant decision tree technique in high performance football: The female and male corner kick
Reference: PLoS One. 2019 Mar 11;14(3):e0212549. doi: 10.1371/journal.pone.0212549. eCollection 2019.
Authors: Maneiro R, Casal CA, Ardá A, Losada JL
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0212549&type=printable
Summary: The use of multidimensional statistical technique based on decision trees is of recent application in sports science. In the case of football, this technique has not yet been sufficiently proven. The aim of the present study was to search for different success models for the corners in the FIFA World Cup 2014 and FIFA Women's World Cup 2015. For this, the statistical analysis focused on the search for classification models for the different criteria considered (shot, shot between the three posts and goal), based on the creation of different decision trees that allow the most important variables to be identified quickly and efficiently. For this, 1117 corners were collected between the two competitions, performed in 116 international matches. It has been possible to establish multivariate models for the "shot" and "shot between the three posts" criteria, allowing, in some cases, to quadruple the potential for offensive success. On the other hand, we have been able to identify significant differences in the male and female model of execution. These findings suggest the need to continue deepening the study of tactical behavior in women's soccer from a multivariate perspective, and also propose a better optimization of the management and training of this type of actions for both male and female football. In addition, it has allowed to test the decision tree statistical technique in the analysis of high performance football, with satisfactory results and of great relevance in the applied field.

Thu

11

Apr

2019

Latest research in football - week 10 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Lateral foot pain due to os vesalianum pedis in a young football player; a case report and review of the current literature
Reference: Skeletal Radiol. 2019 Feb 27. doi: 10.1007/s00256-019-03190-4. [Epub ahead of print]
Authors: Aykanat F, Vincenten C, Cankus MC, Kose O, Sindel M
Summary: Os vesalianum pedis is a rare accessory ossicle located at the 5th metatarsal base. This anatomic variation is typically asymptomatic and usually detected incidentally on routine foot radiographs. However, it may be a source of lateral foot pain and rarely become symptomatic following traumatic ankle injuries such as an inversion ankle sprain. To date, seven symptomatic os vesalianum pedis cases that required surgical treatment have been reported in the current literature. Herein, a 17-year-old professional football player with a symptomatic os vesalianum pedis was presented. The ossicle was surgically removed upon failure of conservative treatment. At the sixth month, the patient returned to sport without any restriction or pain. Clinical presentation, diagnosis, and treatment options of symptomatic os vesalianum pedis were discussed with an extensive literature review.


#2 Applying the New Teaching Methodologies in Youth Football Players: Toward a Healthier Sport
Reference: Front Physiol. 2019 Feb 13;10:121. doi: 10.3389/fphys.2019.00121. eCollection 2019.
Authors: García-Angulo A, García-Angulo FJ, Torres-Luque G, Ortega-Toro E
Download link: https://www.frontiersin.org/articles/10.3389/fphys.2019.00121/full
Summary: At early ages (6-12 years), the levels of physical activity developed in sports initiation and Physical Education often fall short of optimal levels. Ecological models of education seek, among other things, to make up for this deficit by modifying the structural elements of sport, bringing play closer to the child's developmental characteristics. In this sense, Nonlinear Pedagogy is a model of active pedagogy that seeks the integral development of young players through a sport more in line with their abilities, and that for this is based on a system of constraints on the environment, the task and the player himself. However, there are no studies that analyze the effects of these methodologies on the parameters of physical activity at such an early age. The aim of this study was to analyze the impact of a learning methodology based on Nonlinear Pedagogy on health-related levels of physical activity (heart rate) in young football players (U-11). A quasi-experimental study was developed in which three tasks were applied using structural modifications of the football elements related to Nonlinear Pedagogy (modification of the number of players related to situations of inferiority, equality and numerical superiority; dimensions of the field of play). The sample studied was composed of football players, U-11 n = 32), age: 10.35 ± 0.54 years; years of experience: 2.14 ± 0.768 years. The players carried out each task for 10 min. Physical activity levels were measured by controlling heart rate using heart rate monitors (Polar Team2). The results showed very high levels of vigorous and very vigorous physical activity in all the tasks designed. These data show that the use of these new teaching methodologies has an impact on levels of physical activity in accordance with the recommended parameters.


#3 A combination of oral L-citrulline and L-arginine improved 10-min full-power cycling test performance in male collegiate soccer players: a randomized crossover trial
Reference: Eur J Appl Physiol. 2019 Feb 16. doi: 10.1007/s00421-019-04097-7. [Epub ahead of print]
Authors: Suzuki I, Sakuraba K, Horiike T, Kishi T, Yabe J, Suzuki T, Morita M, Nishimura A, Suzuki Y
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00421-019-04097-7.pdf
Summary: The purpose of the study was to investigate Oral L-citrulline (Cit) that increases plasma L-arginine (Arg) concentration and the production of nitric oxide (NO). NO dilates blood vessels and potentially improves sports performance. The combination of oral Arg and Cit (Arg + Cit) immediately and synergistically increases plasma Arg and nitrite/nitrate (NOx) concentrations more than either Cit or Arg alone. This prompted us to assess the effects of oral Arg + Cit on 10-min cycling performance in a double-blind, randomized, placebo-controlled crossover trial. Twenty-four male soccer players ingested either Cit + Arg or placebo (both 1.2 g/day each) for 6 days. On day 7, they ingested Cit + Arg 1 h before performing a 10-min full-power pedaling test on a bicycle ergometer. Plasma NOx and amino acid levels were measured before and after the test, as well as the participants' subjective perception of physical exertion. Power output was significantly greater with Cit + Arg than in the placebo group (242 ± 24 vs. 231 ± 21 W; p < 0.05). Plasma concentrations of post-exercise NOx (p < 0.05), Cit (p < 0.01) and Arg (p < 0.01) were significantly higher in the Cit + Arg than in the placebo group, whereas exercise upregulated plasma NOx concentrations in both groups (p < 0.05). Cit + Arg also gave improved post-exercise subjective perception of "leg muscle soreness" and "ease of pedaling" (both p < 0.05). Seven days of oral Citrulline (1.2 g/d) and Arginine (1.2 g/d) ingestion improved 10-min cycling performance and the perception of physical exertion in male collegiate soccer players.


#4 Fat Oxidation Rates in Professional Soccer Players
Reference: Med Sci Sports Exerc. 2019 Mar 4. doi: 10.1249/MSS.0000000000001973. [Epub ahead of print]
Authors: Randell RK, Carter JM, Jeukendrup AE, Lizarraga MA, Yanguas JI, Rollo I
Summary: Large inter-individual variation exists in maximal fat oxidation rates (MFO) and the exercise intensity at which it occurs (FATMAX). However, there is no data describing the shape of the fat oxidation curve or, if individual differences exist when tested on separate occasions. Furthermore, there is limited data on fat metabolism in professional team sport athletes. Therefore, the aim of this study was to test-retest the concavity (shape) and intercept (height) of fat oxidation curves within a group of professional soccer players. On two occasions 16 professional male soccer players completed a graded exercise test in a fasted state (≥5 h). Rates of fat oxidation were determined using indirect calorimetry. Maximal oxygen uptake (VO2max) was measured to calculate FATMAX (%VO2max). The shape of the fat oxidation curves were modelled on an individual basis using third degree polynomial. Test-by-test differences, in the shape and vertical shift of the fat oxidation curves, were established to assess within-individual variability. Average absolute MFO was 0.69 ± 0.15 g[BULLET OPERATOR]min (range 0.45 - 0.99g[BULLET OPERATOR]min). On a group level, no significant differences were found in MFO between the two tests. No differences were found (p>0.05) in the shape of the fat oxidation curves in 13/16 players (Test1 vs. Test2). There were also no differences (p>0.05) in the vertical shift of the fat oxidation curves in 10 players. In general, the shape of the fat oxidation curve does not change within an individual however the vertical shift is more susceptible to change, which may be due to training status and body composition. Understanding a player's metabolism may be of value to practitioners working within sport, with regards to personalising nutrition strategies.


#5 Adolescent characteristics of youth soccer players: do they vary with playing status in young adulthood?
Reference: Res Sports Med. 2019 Mar 6:1-12. doi: 10.1080/15438627.2019.1586704. [Epub ahead of print]
Authors: Figueiredo AJ, Coelho-E-Silva MJ, Sarmento H, Moya J, Malina RM
Summary: Adolescent characteristics of young adult soccer players (n = 35) were compared with those of youth teammates (n = 124) no longer involved in soccer. Former U-13 players active in soccer as young adults were slightly later in maturation and performed better in several functional and soccer skills than youth teammates. Former U-15 players active in soccer as young adults did not differ in maturity status from youth teammates but were chronologically older and performed better in agility and ball control. Young adult regional and national players in both age groups were rated significantly higher on the potential for success by their youth coaches, and national players were rated significantly higher than regional players. The results highlight the need for study of interactions among coaches, youth training and playing environments and the growth, maturity, functional, skill and behavioural characteristics of youth players, and how these interactions may influence persistence in soccer and later playing status.


#6 Match Fatigue Time-Course Assessment Over Four Days: Usefulness of the Hooper Index and Heart Rate Variability in Professional Soccer Players
Reference: Front Physiol. 2019 Feb 19;10:109. doi: 10.3389/fphys.2019.00109. eCollection 2019.
Authors: Rabbani A, Clemente FM, Kargarfard M, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390199/pdf/fphys-10-00109.pdf
Summary: The aims of the present study were to (a) examine recovery time-course and (b) analyze the usefulness of the Hooper-Index (wellness index) and resting heart rate variability (HRV) in professional soccer players during an in-season phase. The Hooper-Index and resting HRV were collected on matchday and on the four following days in three consecutive in-season weeks in nine players (25.2 ± 4.3-years). The usefulness of monitoring variables was assessed by (a) comparing noise (typical error, TE) to the smallest worthwhile change (SWC) (TE/SWC) and (b) comparing match-related changes (i.e., signal) to TE (i.e., signal-to-noise ratio). Between-days standardized differences in the changes of Hooper-Index and HRV were compared to the SWC using magnitude-based inferences. The magnitudes of TE were small and moderate for the Hooper-Index and HRV, respectively. The Hooper-Index showed to be more useful than HRV for monitoring match-induced fatigue as having a lower TE/SWC (3.1 versus 4.4) and a higher signal-to-noise ratio (5.5 versus 1.5). Small-to-very large [range of effect sizes, 0.48; 2.43, confidence limits (0.22; 2.91)] and moderate-to-large [-1.71; -0.61 (-2.44; -0.03)] detrimental changes in Hooper-Index and HRV, respectively, were observed on the days following matchday. While group analyses showed a similar pattern for recovery time-course, more individual players responded, similarly when tracked using the Hooper -Index compared to when they were tracked using HRV. An inverse moderate within-individual relationship was observed between changes in the Hooper index and HRV [r = -0.41, (-0.60, 0.18)]. The Hooper index is an easy-to-use, no-cost, and non-invasive monitoring tool and seems promising for tracking match-induced fatigue during in the season in professional soccer.


#7 Epidemiological profile of soccer-related injuries in a state Brazilian championship: An observational study of 2014-15 season
Reference: J Clin Orthop Trauma. 2019 Mar-Apr;10(2):374-379. doi: 10.1016/j.jcot.2018.05.006. Epub 2018 May 14.
Authors: Gaspar-Junior JJ, Onaka GM, Barbosa FSS, Martinez PF, Oliveira-Junior SA
Summary: Soccer related injuries are often reported in studies, but epidemiological research on this theme is rare in Brazil, Furthermore, the conditions in which athletes have returned to sports practice, namely, either symptomatic or asymptomatic, have been neglected in research. The aim of this study was to describe the epidemiological features of injuries among professional Brazilian soccer players in relation to location, type, mechanism, severity, recurrence, treatment and, lastly, symptoms in return to sport. 116 male professional athletes of teams from a Brazilian state championship were interviewed and information about injuries was recorded using a retrospective reported morbidity questionnaire. Data were analyzed in mean ± SD for physical characteristics and sports practice history in absolute and relative frequencies (chi-square test with Bonferroni's correction) for characterization of soccer injuries in terms of type, location, severity, recurrence and symptoms in return to sport. The numbers of injuries per athlete and per injured athlete were 0.92 and 1.43 respectively. The injuries of muscle-tendon unit and the joint types localized on lower limbs constituted the most important clinical occurrences with significant difference both in relation to other types (p < 0.05). Moderate and severe injuries were the most frequent occurrences. In relation to mechanisms for each type of injury, body contact was at least three times more responsible for injury cases. This type of mechanism was associated with a significantly greater impairment of joint structures. Concerning occurrence and recurrence of cases, the number of recurrent injuries of the muscle-tendon unit reached about 7.5% of the first-time injuries, while the number of joint recurrent injuries integrated almost 40% of the first-time cases. Significant differences between first-time injuries and recurrent injuries were found only for muscle-tendon and joint structures (p < 0.05), while significant differences among the type of injuries within each type of occurrence (first-time or recurrent injuries) were also found between muscle-tendon and joint injuries (p < 0.05). In relation to athletes with symptoms, in return to sport, 77.6% of them were treated for their injuries but more than half of them returned with symptoms still present when compared to those who returned without any symptoms. Among athletes who did not receive treatment, a lower percentage (58.3%) returned to the sport with symptoms still present. Significant associations between treatment and symptomatology were not found.


#8 Looking for Complementary Intensity Variables in Different Training Games in Football
Reference: J Strength Cond Res. 2019 Mar 5. doi: 10.1519/JSC.0000000000003025. [Epub ahead of print]
Authors: Casamichana D, Castellano J, Gómez Díaz A, Martín-García A
Summary: The main aim of this study was to identify which combination of external intensity training load (iTL) metrics capture similar or unique information for different training game (TG) formats and official matches (OMs) in football using principal component (PC) analysis. Ten metrics of iTL were collected from 24 professional male football players using global positioning technology. A total of 348, 383, 120, 127, 148, and 207 individual files for small-sided possession games, medium-sided possession games, small-sided games, medium-sided games, large-sided games, and OMs, respectively, were studied. Principal component analysis was conducted on each game format. Extraction criteria were set at an eigenvalue of greater than one. Varimax rotation mode was used to extract more than one PC. Intensity training load metrics with PC "loadings" above 0.7 were deemed to possess well-defined relationships with the extracted PC. In each TG and OM, 3 PCs were identified. For the first PC, eigenvalues for each game format ranged from 3.89 to 4.45, which explained 39-44% of the information (i.e., variance) provided by the 10 iTL metrics. For the second PC, eigenvalues ranged from 2.17 to 2.47, explaining 22-26% of iTL information. For the third PC, eigenvalues ranged from 1.41 to 1.98, explaining 14-20% of iTL information. This would suggest that TG and OM have multidimensional demands; so, the use of only a single iTL could potentially lead to an underestimation of the physical demands. Consequently, a combination of 3 iTL metrics is required during professional football game formats.


#9 Assessing the Return on Investment of Injury Prevention Procedures in Professional Football
Reference: Sports Med. 2019 Mar 6. doi: 10.1007/s40279-019-01083-z. [Epub ahead of print]
Authors: Fuller CW
Summary: The aim of this study was to develop a quick and simple screening procedure for evaluating the return on investment provided by injury prevention programmes in professional football. Injury prevention in sport has usually been considered in isolation of other management responsibilities, and interventions are published irrespective of whether their impact is worthwhile and irrespective of the return on players' time investment in the programme. This approach is naive from a business perspective and is not an approach normally adopted by commercial organisations. In professional football, the overwhelming cost associated with implementing an injury prevention programme is the players' time commitment, and the major benefit is the players' increased availability, achieved through the reduction in the number of injuries. A comparison of these time-based costs and benefits provides the basis for the evaluation process presented. Applying the evaluation process to a number of published injury prevention programmes recommended for football demonstrates that they are unlikely to provide an adequate return on investment. Researchers should focus on developing injury prevention programmes that provide an adequate return on players' time investment, otherwise there is no incentive for clubs to implement the programmes. Reporting that an injury prevention programme produces a statistically significant reduction in the incidence of injury, for example, is insufficient information. Injury prevention programmes should focus on 'at risk' players to increase the return on investment, and researchers should evaluate and report on the utility of prevention programmes within the intended sports setting.


#10 Lifelong Football Training: Effects on Autophagy and Healthy Longevity Promotion
Reference: Front Physiol. 2019 Feb 19;10:132. doi: 10.3389/fphys.2019.00132. eCollection 2019.
Authors: Mancini A, Vitucci D, Randers MB, Schmidt JF, Hagman M, Andersen TR, Imperlini E, Mandola A, Orrù S, Krustrup P, Buono P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390296/pdf/fphys-10-00132.pdf
Summary: Aging is a physiological process characterized by a progressive decline of biological functions and an increase in destructive processes in cells and organs. Physical activity and exercise positively affects the expression of skeletal muscle markers involved in longevity pathways. Recently, a new mechanism, autophagy, was introduced to the adaptations induced by acute and chronic exercise as responsible of positive metabolic modification and health-longevity promotion. However, the molecular mechanisms regulating autophagy in response to physical activity and exercise are sparsely described. We investigated the long-term adaptations resulting from lifelong recreational football training on the expression of skeletal muscle markers involved in autophagy signaling. We demonstrated that lifelong football training increased the expression of messengers: RAD23A, HSPB6, RAB1B, TRAP1, SIRT2, and HSBPB1, involved in the auto-lysosomal and proteasome-mediated protein degradation machinery; of RPL1, RPL4, RPL36, MRLP37, involved in cellular growth and differentiation processes; of the Bcl-2, HSP70, HSP90, PSMD13, and of the ATG5-ATG12 protein complex, involved in proteasome promotion and autophagy processes in muscle samples from lifelong trained subjects compared to age-matched untrained controls. In conclusion, our results indicated that lifelong football training positively influence exercise-induced autophagy processes and protein quality control in skeletal muscle, thus promoting healthy aging.


#11 The FIFA 11 programme reduces the costs associated with ankle and hamstring injuries in amateur Spanish football players: A retrospective cohort study
Reference: Eur J Sport Sci. 2019 Mar 4:1-7. doi: 10.1080/17461391.2019.1577495. [Epub ahead of print]
Authors: Nouni-Garcia R, Asensio-Garcia MR, Orozco-Beltran D, Lopez-Pineda A, Gil-Guillen VF, Quesada JA, Bernabeu Casas RC, Carratala-Munuera C
Summary: This study aimed to assess the cost-effectiveness of the "Fédération Internationale de Football Association (FIFA) 11" injury prevention programme for ankle and hamstring injuries. This retrospective cohort study included eighty-four male amateur football players aged 18-40 years. The exposed group performed the FIFA 11 protocol twice a week throughout the 2010-2011 and 2011-2012 seasons; the unexposed group performed the usual training during the 2008-2009 and 2009-2010 seasons. Lateral ankle ligament and hamstring injuries were recorded over the whole study period. We compared the mean costs associated with lateral ankle ligament and hamstring injuries in the two groups. The mean cost per player and lateral ankle injury was EUR 928 in the unexposed group versus EUR 647 in the exposed group (p = 0.19). The mean cost of hamstring injury per player was EUR 1271 in the unexposed group versus EUR 742 in the exposed group (p = 0.028). The mean total cost per player was EUR 2199 in the unexposed group versus EUR 1273 in the exposed group (p = 0.008). We concluded that the use of the FIFA 11 injury prevention programme reduced both the direct and indirect costs associated with lateral ankle ligament and hamstring injuries.

Mon

08

Apr

2019

Latest research in football - week 9 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Does maturation influence neuromuscular performance and muscle damage after competitive match-play in youth male soccer players?
Reference: Eur J Sport Sci. 2019 Feb 18:1-10. doi: 10.1080/17461391.2019.1575913. [Epub ahead of print]
Authors: De Ste Croix M, Lehnert M, Maixnerova E, Zaatar A, Svoboda Z, Botek M, Varekova R, Stastny P
Summary: Poor neuromuscular control and fatigue have been proposed as a risk factor for non-contact injuries especially around peak height velocity (PHV). This study explored the effects of competitive soccer match-play on neuromuscular performance and muscle damage in male youth soccer players. 24 youth players aged 13-16y were split into a PHV group (-0.5 to 0.5y) and post PHV group (1.0-2.5y) based on maturity off-set. Leg stiffness, reactive strength index (RSI), muscle activation, creatine kinase (CK), and muscle soreness were determined pre and post a competitive soccer match. Paired t-tests were used to explore differences pre and post competitive match play and independent sample t-tests for between groups differences for all outcome measures. There was no significant fatigue-related change in absolute and relative leg stiffness or muscle activation in both groups, except for the gastrocnemius in the post PHV group. RSI, CK and perceived muscle soreness were significantly different after soccer match-play in both groups with small to large effects observed (ES:0.41-2.82). There were no significant differences between the groups pre match-play except for absolute and relative leg stiffness (P < 0.001; ES = 1.16 and 0.63 respectively). No significant differences were observed in the fatigue related responses to competitive match play between groups except for perceived muscle soreness. The influence of competitive match-play on neuromuscular function and muscle damage is similar in male youth around the time of PHV and those post-PHV indicating that other factors must contribute to the heightened injury risk around PHV.


#2 Spikes in acute:chronic workload ratio (ACWR) associated with a 5-7 times greater injury rate in English Premier League football players: a comprehensive 3-year study
Reference: Br J Sports Med. 2019 Feb 21. pii: bjsports-2018-099422. doi: 10.1136/bjsports-2018-099422. [Epub ahead of print]
Authors: Bowen L, Gross AS, Gimpel M, Bruce-Low S, Li FX
Download link: https://bjsm.bmj.com/content/bjsports/early/2019/02/21/bjsports-2018-099422.full.pdf
Summary: We examined the relation between global positioning system (GPS)-derived workloads and injury in English Premier League football players (n=33) over three seasons. Workload and injury data were collected over three consecutive seasons. Cumulative (1-weekly, 2-weekly, 3-weekly and 4-weekly) loads in addition to acute:chronic workload ratios (ACWR) (acute workload (1-week workload)) divided by chronic workload (previous 4-week average acute workload) were classified into discrete ranges by z-scores. Relative risk (RR) for each range was then calculated between injured and non-injured players using specific GPS variables: total distance, low-intensity distance, high-speed running distance, sprint distance, accelerations and decelerations. The greatest non-contact injury risk was when the chronic exposure to decelerations was low (<1731) and the ACWR was >2.0 (RR=6.7). Non-contact injury risk was also 5-6 times higher for accelerations and low-intensity distance when the chronic workloads were categorised as low and the ACWR was >2.0 (RR=5.4-6.6), compared with ACWRs below this. When all chronic workloads were included, an ACWR >2.0 was associated with a significant but lesser injury risk for the same metrics, plus total distance (RR=3.7-3.9). We recommend that practitioners involved in planning training for performance and injury prevention monitor the ACWR, increase chronic exposure to load and avoid spikes that approach or exceed 2.0.


#3 Measurements and Coach Assessments for Efficient Talent Selection in Elite Youth Football Science or Coaches' Eye? - Both! Beneficial Collaboration of Multidimensional
Reference: J Sports Sci Med. 2019 Feb 11;18(1):32-43. eCollection 2019 Mar.
Authors: Sieghartsleitner R, Zuber C, Zibung M, Conzelmann A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370964/pdf/jssm-18-32.pdf
Summary: Due to the tremendous popularity of youth football, practitioners in this domain face the ongoing question of the most effective solutions in early talent selection. Although the scientific community has suggested multidimensional models for some time, coach assessments and motor performance tests remain common. Earlier research has determined the strengths and weaknesses within these different approaches. The current investigation directly compared the effectiveness of each approach in talent selection (coach assessment vs. motor performance tests vs. multidimensional data). A sample of 117 youth football players, their parents, and coaches participated in multidimensional measurements in the U14 age category (coach assessments, motor performance tests, psychological characteristics, familial support, training history, and biological maturation). The area under the curve (AUC [95% CI]) from receiver operating characteristic indicated the prognostic validity of each approach in predicting U19 player status five years after the assessments (professional vs. non-professional). Motor performance tests (0.71 [0.58; 0.84]) showed a lower AUC than the multidimensional data (0.85 [0.76; 0.94], p = 0.02), whilst coach assessments did not differ from the two others (.82 [.74; .90]). Further, combined talent selection approaches, especially the use of coach assessments and multidimensional data together, were significantly better at predicting U19 player status (0.93 [0.87; 0.98], p = 0.02 vs. multidimensional data only). Although certain limitations may impede further insights (summation of data, skipped use of non-linear statistics), scientific claims for using multidimensionality within talent selection were confirmed to be fruitful. In particular, the combination of the subjective coaches' eye with scientific data may buffer the mutual weaknesses of these different approaches. Future research should focus on optimizing the output of promising multidimensional models. Knowledge of detailed values relating to specific dimensions within these models and the implementation of enhanced non-linear statistics may enable further improvements in the field of talent selection.


#4 Playing football on artificial turf as a risk factor for fifth metatarsal stress fracture: a retrospective cohort study
Reference: BMJ Open. 2019 Feb 20;9(2):e022864. doi: 10.1136/bmjopen-2018-022864.
Authors: Miyamori T, Nagao M, Sawa R, Tumilty S, Yoshimura M, Saita Y, Ikeda H, Kaneko K
Download link: https://bmjopen.bmj.com/content/bmjopen/9/2/e022864.full.pdf
Summary: The fifth metatarsal stress fracture is a common injury among football players. Although several risk factors have been proposed, the association between the playing surface and development of fifth metatarsal stress fractures (MT-5) has not been evaluated. We conducted an epidemiological study using a computer-based survey to investigate the association between the playing surface and development of MT-5. This study included 1854 football players, of which 41 experienced MT-5 within the past 24 months. Baseline demographic data and the percentage of time spent playing on artificial turf and clay fields were compared between the non-MT-5 and MT-5 player groups, and the risks for development of MT-5 associated with the playing surfaces were estimated by univariate and multivariate analyses. There were significant differences in body mass index, years of play, playing categories and playing time on artificial turf between non-MT-5 and MT-5 groups (p<0.05). Generalised estimating equations analyses adjusted for multiple confounders demonstrated that relative to the risk of playing <20% of the time on each surface, the OR (OR: 95% CI) for MT-5 for playing on artificial turf >80% of the time increased (3.44: 1.65 to 7.18), and for playing on a clay field 61%-80% of the time, the OR decreased (0.25: 0.11 to 0.59). A higher percentage of playing time on an artificial turf was a risk factor for developing MT-5 in football players. This finding could be beneficial for creating strategies to prevent MT-5.


#5 Physical Fitness Characteristics of High-level Youth Football Players: Influence of Playing Position
Reference: Sports (Basel). 2019 Feb 16;7(2). pii: E46. doi: 10.3390/sports7020046.
Authors: Bujnovky D, Maly T, Ford KR, Sugimoto D, Kunzmann E, Hank M, Zahalka F
Download link: https://www.mdpi.com/2075-4663/7/2/46/pdf
Summary: The aim of this study was to determine whether the speed, agility, aerobic and anaerobic capacities of football players varied by playing positions. Elite youth football players (n = 123, age = 15.7 ± 0.5 years) who played in six different positions, as goalkeepers (GK), full backs (FB), central defenders (CD), wide midfielders (WM), central midfielders (CM), and attackers (AT), were assessed. Multivariate analysis of variances was used to compare the following variables: Linear running sprint for 5 m (S5) and 10 m (S10), flying sprint for 20 m (F20), agility 505 test with turn on the dominant (A505D) and non-dominant leg (A505N), agility K-test, Yo-Yo intermittent recovery (YYIR1) test and repeat sprint ability (RSA) test. The results showed significant influence of playing positions on linear-running sprint performance (F1,123 = 6.19, p < 0.01, ηp² = 0.23). Midfielders reached significantly higher performance levels (CM = 2.44 ± 0.08 s, WM = 2.47 ± 0.13 s) in the A505N test compared to GK (2.61 ± 0.23 s). Outfield players had significantly higher performance in both YYIR1 and RSA tests compared to GK (p < 0.01). The results of this study may provide insightful strategies for coaches and clinical practitioners for developing position-specific conditioning programs.


#6 Energy expenditure and dietary intake in professional football players in the Dutch Premier League: Implications for nutritional counselling
Reference: J Sports Sci. 2019 Feb 16:1-9. doi: 10.1080/02640414.2019.1576256. [Epub ahead of print]
Authors: Brinkmans NYJ, Iedema N, Plasqui G, Wouters L, Saris WHM, van Loon LJC, van Dijk JW
Summary: Selecting effective dietary strategies for professional football players requires comprehensive information on their energy expenditure (EE) and dietary intake. This observational study aimed to assess EE and dietary intake over a 14-day period in a representative group (n = 41) of professional football players playing in the Dutch Premier League (Eredivisie). Daily EE, as assessed by doubly labelled water, was 13.8 ± 1.5 MJ/day, representing a physical activity level (PAL) of 1.75 ± 0.13. Weighted mean energy intake (EI), as assessed by three face-to-face 24-h recalls, was 11.1 ± 2.9 MJ/day, indicating 18 ± 15% underreporting of EI. Daily EI was higher on match days (13.1 ± 4.1 MJ) compared with training (11.1 ± 3.4 MJ; P < 0.01) and rest days (10.5 ± 3.1 MJ; P < 0.001). Daily carbohydrate intake was significantly higher during match days (5.1 ± 1.7 g/kg body mass (BM)) compared with training (3.9 ± 1.5 g/kg BM; P < 0.001) and rest days (3.7 ± 1.4 g/kg BM; P < 0.001). Weighted mean protein intake was 1.7 ± 0.5 g/kg BM. Daytime distribution of protein intake was skewed, with lowest intakes at breakfast and highest at dinner. In conclusion, daily EE and PAL of professional football players are modest. Daily carbohydrate intake should be increased to maximize performance and recovery. Daily protein intake seems more than adequate, but could be distributed more evenly throughout the day.


#7 Listening to neutral or self-selected motivational music during warm-up to improve short-term maximal performance in soccer players: Effect of time of day
Reference: Physiol Behav. 2019 Feb 25. pii: S0031-9384(18)30924-7. doi: 10.1016/j.physbeh.2019.02.033. [Epub ahead of print]
Authors: Belkhir Y, Rekik G, Chtourou H, Souissi N
Summary: The present experiment examined the effects of listening to different types of music during warm-up on the diurnal variation of short-term maximal performance (STMP) in soccer players, using a 3 × 2 mixed design with factors "Condition" (warm-up with self-selected motivational-music (WUMM) vs. warm-up with neutral-music (WUNM) vs. warm-up without-music (WUWM) and "Time of Day" (07 h00 vs. 17 h00). In a random order, twelve male soccer players performed a 5-m shuttle run test after a 10 min of WUMM, a 10 min of WUNM and a 10 min WUWM at 07 h00 and 17 h00. The higher distance (HD) and total distance (TD) were measured during the test, and the rated perceived exertion (RPE) and the feelings states (FS) were obtained immediately after the warm-up and the test. The results revealed that HD and TD were higher at 17 h00 than 07 h00 in all conditions (p < .01). At 07 h00 and 17 h00, TD and HD were higher after WUMM and WUNM than WUWM and after WUMM than WUNM (p < .01). This improvement was greater at 07 h00 than 17 h00 (e.g., 6.97% vs. 5.26% for TD). Moreover, FS were more positive after WUNM than WUWM only at 07 h00, after WUMM than WUWM at the two time-of-day (p < .01), and after WUMM than WUNM at 17 h00 (p < .01). After the 5-m shuttle run test, FS were more negative and the RPE scores were higher with WUMM than WUWM at 07 h00 (p < .01). The findings suggested that STMP and feelings depend on types of music listened during a warm-up. A warm-up with self-selected motivational-music improves STMP and feelings at 07 h00 and 17 h00 with greater enhancement in the morning. However, a warm-up with neutral-music improves STMP and feelings only at 07 h00.


#8 Effects of a Soccer Tournament on the Psychohormonal States of Collegiate Female Players
Reference: J Strength Cond Res. 2019 Feb 18. doi: 10.1519/JSC.0000000000002993. [Epub ahead of print]
Authors: Broodryk A, Pienaar C, Edwards D, Sparks M
Summary: A gap exists in the literature concerning the connection between soccer players' hormonal and psychological responses when playing a tournament, or even a match, and its outcome (victory or defeat). This study evaluates the effects of a week-long tournament on the psychohormonal states of collegiate female soccer players. Eight players' cortisol (saliva sample), mood states (Incredibly Short Profile of Mood States [ISP]), and state-anxiety (state subscale of the State-Trait Anxiety Inventory) were assessed 1 hour before and 15 minutes after every game. Cortisol increased significantly after most matches, with intramatch differences observed (p < 0.05, d > 1.2). Match intensity influenced cortisol secretion, with greater secretion as intensity increased. The ISP demonstrated intramatch differences for the subscales' fatigue, depression, tension, and vigor (p < 0.05). Matches lost produced a higher total mood disturbance (TMD) index compared with matches won (p = 0.001, d = 1.4). Cortisol correlated with the TMD and various mood subscales before a winning outcome, with the ISP correlating at all times with the anxiety scores (p < 0.05). In conclusion, these results indicate that physiological and psychological variables combine to contribute to the stress response during a tournament. Focusing on high-intensity activities and minimizing fatigue are important, as both are associated with raised cortisol and negative mood states. Finally, implementing a mood questionnaire over a tournament can be beneficial, as sensitive information on players' hormonal and perceived anxiety states, which subsequently affect physical performance, can be obtained.


#8 Concurrent changes in eccentric hamstring strength and knee joint kinematics induced by soccer-specific fatigue
Reference: Phys Ther Sport. 2019 Feb 18;37:21-26. doi: 10.1016/j.ptsp.2019.02.003. [Epub ahead of print]
Author: Greig M
Summary: The purpose was to investigate the influence of soccer-specific fatigue on concurrent changes in knee joint kinematics and hamstring strength, given the increased risk of injury during the latter stages of match-play and the prevalence of knee joint and hamstring muscular injury. Ten male professional soccer players participated in this study. Reactive inversion, eversion and neutral hop tasks were completed at 15 min intervals during a soccer-specific protocol, with touchdown knee joint kinematics in the frontal and sagittal planes calculated at 200 Hz. In a separate trial, players completed maximal eccentric knee flexions at 160°·s-1 (reflecting average knee angular velocity in the functional task) at 15 min intervals, quantifying peak torque. All trials were characterized by knee varus at touchdown, with ∼4° greater mal-alignment elicited over the final 15 min of the protocol (P ≤ 0.05). Peak eccentric hamstring strength was significantly (P = 0.045) reduced throughout the 2nd half. The coincident impairment of eccentric hamstring strength and increased knee varus at touchdown predisposes the player to injury, supporting epidemiological observations. Knee varus in these elite male players is in marked contrast to the valgus associated with ACL injury risk in female players.


#9 Evaluation of an In-Ear Sensor for Quantifying Head Impacts in Youth Soccer
Reference: Am J Sports Med. 2019 Feb 25:363546519826953. doi: 10.1177/0363546519826953. [Epub ahead of print]
Authors: Sandmo SB, McIntosh AS, Andersen TE, Koerte IK, Bahr R
Summary: Wearable sensor systems have the potential to quantify head kinematic responses of head impacts in soccer. However, on-field use of sensors (eg, accelerometers) remains challenging, owing to poor coupling to the head and difficulties discriminating low-severity direct head impacts from inertial loading of the head from human movements, such as jumping and landing. The purpose of the study was to test the validity of an in-ear sensor for quantifying head impacts in youth soccer. First, the sensor was mounted to a Hybrid III headform and impacted with a linear impactor or a soccer ball. Peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV) were obtained from both systems; random and systematic errors were calculated with Hybrid III as reference. Then, 6 youth soccer players wore sensors and performed a structured training protocol, including heading and nonheading exercises; they also completed 2 regular soccer sessions. For each accelerative event recorded, PLA, PRA, and PRV outputs were compared with video recordings. Receiver operating characteristic curves were used to determine the sensor's discriminatory capacity in both on-field settings, establishing cutoff values for predicting outcomes. For the laboratory tests, the random error was 11% for PLA, 20% for PRA, and 5% for PRV; the systematic error was 11%, 19%, and 5%, respectively. For the structured training protocol, heading events resulted in higher absolute values (PLA = 15.6 g± 11.8 g) than nonheading events (PLA = 4.6 g± 1.2 g); the area under the curve was 0.98 for PLA. In regular training sessions, the area under the curve was >0.99 for PLA. A 9 g cutoff value yielded a positive predictive value of 100% in the structured training protocol versus 65% in the regular soccer sessions. The in-ear sensor displayed considerable random error and substantially overestimated head impact exposure. Despite the sensor's excellent on-field accuracy for discriminating headings from other accelerative events in youth soccer, absolute values must be interpreted with caution, and there is a need for secondary means of verification (eg, video analysis) in real-life settings. Wearable sensor systems can potentially provide valuable insights into head impact exposures in contact sports, but their limitations require careful consideration.


#10 Workload and injury incidence in elite football academy players
Reference: J Sports Sci. 2019 Mar 1:1-6. doi: 10.1080/02640414.2019.1584954. [Epub ahead of print]
Authors: Delecroix B, Delaval B, Dawson B, Berthoin S, Dupont G
Summary: The aim of this study was to prospectively analyse the relationship between workloads and injury in elite football academy players. Elite football academy players (n = 122) from under-19 (U19) and under-21 (U21) of a professional football team competing in UEFA European Cups were followed during 5 seasons. Injuries were collected and absolute workload and workload ratios (4-weeks, 3-weeks, 2-weeks and week-to-week) calculated using a rolling days method with the help of the session Rate of Perceived Exertion. There was no association between absolute workload or workload ratio with the injury incidence in the U19. In the U21, the level of cumulative absolute workloads during 3-weeks (RR = 1.39, p = 0.026) and during 4-weeks (RR = 1.40, p = 0.019) were associated with an increase in injury. There was no association between workload ratio and injury in U21. The significant link between high cumulated 3-weeks and 4 weeks workloads and injury in U21 confirmed the requirement to monitor the internal subjective workload in U21 in order to prevent injury. Further studies exploring the relationships between workload and injury are required in football academy.

Tue

26

Mar

2019

Latest research in footbal - week 8 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Finding Roles of Players in Football Using Automatic Particle Swarm Optimization-Clustering Algorithm
Reference: Big Data. 2019 Feb 15. doi: 10.1089/big.2018.0069. [Epub ahead of print]
Authors: Behravan I, Zahiri SH, Razavi SM, Trasarti R
Summary: Recently, professional team sport organizations have invested their resources to analyze their own and opponents' performance. So, developing methods and algorithms for analyzing team sports has become one of the most popular topics among data scientists. Analyzing football is hard because of its complexity, number of events in each match, and constant flow of circulation of the ball. Finding roles of players with the purpose of analyzing the performance of a team or making a meaningful comparison between players is crucial. In this article, an automatic big data clustering method, based on a swarm intelligence algorithm, is proposed to automatically cluster the data set of players' performance centers in different matches and extract different kinds of roles in football. The proposed method created using particle swarm optimization algorithm has two phases. In the first phase, the algorithm searches the solution space to find the number of clusters and, in the second phase, it finds the positions of the centroids. To show the effectiveness of the algorithm, it is tested on six synthetic data sets and its performance is compared with two other conventional clustering methods. After that, the algorithm is used to find clusters of a data set containing 93,000 objects, which are the centers of players' performance in about 4900 matches in different European leagues.


#2 Shared Knowledge and Verbal Communication in Football: Changes in Team Cognition Through Collective Training
Reference: Front Psychol. 2019 Jan 31;10:77. doi: 10.3389/fpsyg.2019.00077. eCollection 2019.
Authors: Blaser MA, Seiler R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365450/pdf/fpsyg-10-00077.pdf
Summary: One of the psychological mechanisms that contribute to effective and efficient team actions is team cognition, defined either as shared knowledge states about game situations, teammates' skills, and action probabilities or direct communication processes in the team action itself. Particularly in interactive team sports (e.g., football), characterized by highly complex, dynamic, and uncertain situations, sharing a common understanding concerning potential future actions and how to coordinate these actions may be an advantage. Otherwise, team members must communicate their thoughts and ideas on the fly, which might be impossible due to time pressure, cognitive costs or noisy environments. This study examined if shared knowledge and verbal communication change through collective training. Forty-six under-18 and under-21 youth football players performed a football task in teams of two. The task consisted of passing and running elements common in football. After a training phase, and before two testing phases, players evaluated their actions and the actions of their assigned teammate regarding action type, location, and timing. Out of these evaluations, two indices of common understanding were computed. Furthermore, verbal communication during the task was video-and audio-recorded. Data analysis showed that shared knowledge considerably increased over time and with practice. Simultaneously, overall verbal communication and verbal communication consisting of orienting information was significantly reduced. Additionally, there was a tendency for a correlation that when shared knowledge increased, orienting verbal communication decreased. Overall, the players used orienting communications the most (77%). The study revealed that shared knowledge states and verbal communication change through collective training and that there might be a relation between the level of shared knowledge and the use of orienting verbal communication. Further studies in and off the field are needed to disentangle the complex interplay of team cognitions.


#3 Echocardiographic diagnosis of congenital coronary artery abnormalities in a continuous series of adolescent football players
Reference:  Eur J Prev Cardiol. 2019 Feb 12:2047487319825520. doi: 10.1177/2047487319825520. [Epub ahead of print]
Authors: Gerling S, Loose O, Zant R, Michel H, Melter M, Gündisch C, Krutsch V, Krutsch W
Summary: Sudden cardiac death (SCD) in children and adolescents is rare. Several studies have reported a higher risk of SCD during athletic competition. High risk congenital coronary artery abnormalities are the second leading cause of SCD in young athletes in the USA. Echocardiographic assessment of coronary arteries has not been routinely used in screening programmes for junior athletes so far. All athletes underwent a standardized cardiovascular screening protocol with a medical history, a physical examination, 12-lead resting electrocardiogram and a complete transthoracic 2D-echocardiography. Two athletes (0.19%) showed a high-risk coronary artery abnormality (CAA) with a right coronary artery originating abnormal from the aorta and coursing inter-arterial. Low-risk CAAs were found in 16 athletes (1.53%). There was an ectasia of the left coronary artery (+3.9z and +4.3z) and a fistula from the left coronary artery in two cases (0.19%), respectively. In 1.05% ( n = 11) we found a high take-off (2.3-6.8 mm) and in one case (0.096%) there was a tangential take-off of the right main coronary artery. Variants of coronary arterial anatomy were identified in 335 of 1045 athletes (32.06%). Basic pre-participation screening tests including 12-lead or exercise electrocardiogram do not safely identify high-risk CAAs. In adolescent athletes an expert cardiologist is able to describe the origin and the proximal course of the coronary arteries and identify major abnormalities in most of the cases by transthoracic 2D-echocardiography.


#4 Complete Rupture of the Triceps Tendon and Ulnar Collateral Ligament of the Elbow in a 13-Year-Old Football Player: A Case Report
Reference: J Orthop Case Rep. 2018 Sep-Oct;8(5):15-18. doi: 10.13107/jocr.2250-0685.1188.
Authors: Khalil LS, Alkhelaifi K, Meta F, Lizzio VA, Shehab R, Makhni EC
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6367299/pdf/JOCR-8-15.pdf
Summary: With the increasing number of children and adolescents participating in sports, pathologies once reserved for high-level athletes are now emerging in this younger population. Distal triceps tendon tears represent an injury infrequently seen even among older, skeletally mature athletes. We report a case of distal triceps tendon tear with concomitant ulnar collateral ligament (UCL) injury in a skeletally-immature football player. This is a rare case of traumatic triceps tendon tear with UCL injury in a 13-year-old male football player during a fall and hyperextension of his elbow. Management included surgical treatment of the triceps tear with suture anchors in double row technique. The concomitant UCL injury was treated conservatively. This case suggests that this type of injury can occur in young athletes, but good prognosis can be expected with prompt management. Surgical repair of a functionally deficient triceps tendon tear and conservative management of associated UCL injury can result in returntoplay within 6 months.


#5 A Meta-Comparison of the Effects of High-Intensity Interval Training to Those of Small-Sided Games and Other Training Protocols on Parameters Related to the Physiology and Performance of Youth Soccer Players
Reference: Sports Med Open. 2019 Feb 21;5(1):7. doi: 10.1186/s40798-019-0180-5.
Authors: Kunz P, Engel FA, Holmberg HC, Sperlich B
Summary: High-intensity interval training (HIIT) is frequently employed to improve the endurance of various types of athletes. To determine whether youth soccer players may benefit from the intermittent load and time efficiency of HIIT, we performed a meta-analysis of the relevant scientific literature. Our primary objective was to compare changes in various physiological parameters related to the performance of youth soccer players in response to running-based HIIT to the effects of other common training protocols (i.e., small-sided games, technical training and soccer-specific training, or high-volume endurance training). A secondary objective was to compare specifically running-based HIIT to a soccer-specific form of HIIT known as small-sided games (SSG) in this same respect, since this latter type of training is being discussed extensively by coaches. A systematic search of the PubMed, SPORTDiscus, and Web of Science databases was performed in August of 2017 and updated during the review process in December of 2018. The criteria for inclusion of articles for analysis were as follows: (1) comparison of HIIT to SSG or some other training protocol employing a pre-post design, (2) involvement of healthy young athletes (≤ 18 years old), and (3) assessment of variables related to endurance or soccer performance. Hedges' g effect size (dppc2) and associated 95% confidence intervals for the comparison of the responses to HIIT and other interventions were calculated. Nine studies, involving 232 young soccer players (mean age 16.2 ± 1.6 years), were examined. Endurance training in the form of HIIT or SSG produced similar positive effects on most parameters assessed, including peak oxygen uptake and maximal running performance during incremental running (expressed as Vmax or maximal aerobic speed (MAS)), shuttle runs (expressed as the distance covered or time to exhaustion), and time-trials, as well as submaximal variables such as running economy and running velocity at the lactate threshold. HIIT induced a moderate improvement in soccer-related tests involving technical exercises with the soccer ball and other game-specific parameters (i.e., total distance covered, number of sprints, and number of involvements with the ball). Neuromuscular parameters were largely unaffected by HIIT or SSG. The present meta-analysis indicates that HIIT and SSG have equally beneficial impacts on variables related to the endurance and soccer-specific performance of youth soccer players, but little influence on neuromuscular performance.


#6 Caffeine Supplementation and Physical Performance, Muscle Damage and Perception of Fatigue in Soccer Players: A Systematic Review
Reference: Nutrients. 2019 Feb 20;11(2). pii: E440. doi: 10.3390/nu11020440.
Authors: Mielgo-Ayuso J, Calleja-Gonzalez J, Del Coso J, Urdampilleta A, León-Guereño P, Fernández-Lázaro D
Summary: Soccer is a complex team sport and success in this discipline depends on different factors such as physical fitness, player technique and team tactics, among others. In the last few years, several studies have described the impact of caffeine intake on soccer physical performance, but the results of these investigations have not been properly reviewed and summarized. The main objective of this review was to evaluate critically the effectiveness of a moderate dose of caffeine on soccer physical performance. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science databases from January 2007 to November 2018. The search included studies with a cross-over and randomized experimental design in which the intake of caffeine (either from caffeinated drinks or pills) was compared to an identical placebo situation. There were no filters applied to the soccer players' level, gender or age. This review included 17 articles that investigated the effects of caffeine on soccer-specific abilities (n = 12) or on muscle damage (n = 5). The review concluded that 5 investigations (100% of the number of investigations on this topic) had found ergogenic effects of caffeine on jump performance, 4 (100%) on repeated sprint ability and 2 (100%) on running distance during a simulated soccer game. However, only 1 investigation (25%) found as an effect of caffeine to increase serum markers of muscle damage, while no investigation reported an effect of caffeine to reduce perceived fatigue after soccer practice. In conclusion, a single and moderate dose of caffeine, ingested 5⁻60 min before a soccer practice, might produce valuable improvements in certain abilities related to enhanced soccer physical performance. However, caffeine does not seem to cause increased markers of muscle damage or changes in perceived exertion during soccer practice.


#7 Defining the Early, Mid, and Late Subsections of Sprint Acceleration in Division I Men's Soccer Players
Reference: J Strength Cond Res. 2019 Feb 14. doi: 10.1519/JSC.0000000000003088. [Epub ahead of print]
Authors: Bellon CR, DeWeese BH, Sato K, Clark KP, Stone MH
Summary: The purpose of this study was to investigate whether the acceleration phase of sprinting could be split into subphases specific to the competitive demands of a soccer match by comparing sprint metrics at various sprint distances in Division I men's soccer players. Twenty-three Division I men's soccer athletes completed 2 maximal-effort 20-m sprints from a standing start position through an optical measurement system. Sprint metrics measured included sprint velocity (SV), step length (SL), step frequency (SF), and ground contact time (GCT). Each metric was recorded at approximately 2.5, 6, and 12 m. Sprint metrics at each distance were compared using a 2-tailed, 1-way repeated-measures analysis of variance. The results indicated that SV, SL, and SF were statistically greater at 12 m in comparison with 6 m (p < 0.001) and 2.5 m (p < 0.001), whereas GCT was statistically shorter at 12 m compared with 6 m (p < 0.001) and 2.5 m (p < 0.001). In addition, sprint metrics at 6 m also displayed the same relationships when compared to 2.5 m, with SV, SL, and SF being statistically greater (p < 0.001) at this distance, and GCT being statistically shorter (p < 0.001) as well. These results suggest that the acceleration phase may effectively be differentiated into early, mid, and late subphases based on differences in key sprint metrics at distances of 2.5, 6, and 12 m, respectively, in Division I men's soccer athletes.


#8 Compression Stockings Used During Two Soccer Matches Improve Perceived Muscle Soreness and High-Intensity Performance
Reference: J Strength Cond Res. 2019 Feb 14. doi: 10.1519/JSC.0000000000003048. [Epub ahead of print]
Authors: Gimenes SV, Marocolo M, Pavin LN, Spigolon LMP, Barbosa Neto O, da Silva BVC, Duffield R, da Mota GR
Summary: Evidence on the use of compression stockings (CS) during soccer matches is limited. Thus, we evaluated the acute effects of CS on match-based physical performance indicators and perceptual responses during 2 consecutive soccer matches with 72-hour recovery. Twenty outfield players were randomly allocated to the CS group (20-30 mm Hg) or control group (non-CS) and performed 2 matches (5 players using CS or regular socks per team/match). Match loads {rating of perceived exertion × minutes; CS ∼830 vs. control 843 (arbitrary units [AU])} and heart rate (HR) responses (both CS and control ∼86% HRpeak) did not differ (p > 0.05) between CS and control groups. Although total distance covered did not differ (p > 0.05) between groups, CS increased distances (effect size [ES] = 0.9-1.32) in higher-speed zones (>19 km·h CS ∼550 m vs. control ∼373 m) alongside an increased number of accelerations (-50.0 to -3.0 m·s) than control (CS: 33.7 ± 11.2 vs. control: 23.8 ± 7.9; p = 0.003; ES = 1.04). Perceived recovery did not differ (p > 0.05) between groups for either match but was worse in the second match for both groups. Perceived muscle soreness increased in control after match 2 (from 3.1 ± 1.9 to 6.3 ± 1.6 AU; p < 0.0010) but did not in CS (from 2.8 ± 1.4 to 4.1 ± 1.9 AU; p = 0.6275; ES = 1.24 CS vs. control after match). Accordingly, CS use during 2 soccer matches with 72-hour recovery reduces perceived muscle soreness in the second match and increases higher-speed match running performance.


#9 Are Linear Speed and Jumping Ability Determinants of Change of Direction Movements in Young Male Soccer Players?
Reference: J Sports Sci Med. 2019 Feb 11;18(1):109-117. eCollection 2019 Mar.
Authors: Popowczak M, Rokita A, Świerzko K, Szczepan S, Michalski R, Maćkała K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370957/pdf/jssm-18-109.pdf
Summary: The study was undertaken to investigate the relationships between linear speed, change of direction, and explosive power in the lower limbs of young soccer players. We aimed to determine the variables associated with effective change-of-direction speeds (time) based on the 30-m ZigZag (cutting maneuver) under 60° (CODS1), and 30 m sprint divided into forward-backward-forward movement (CODS2). Sixty young soccer players (age: 17.4 ± 0.7 years, height: 1.76 ± 0.06 m, weight: 68.1 ± 8.9 kg) from soccer sport clubs were included. The participants performed 30-m change-of-direction sprints and 30-m backward and forward sprints. For the maximum speed evaluation, a straight-line 30-m sprint test was performed. Counter-movement jumps and standing broad jumps were used to assess jumping ability. Pearson's linear correlation and a multiple stepwise linear regression model were used to adjust for variations related to the influence of functional speed and explosive power variables, which were analyzed based on the CODS1 and CODS2 data. Our results showed that 30-m CODS2 and standing broad jumps were associated with CODS1. The variation for the 30-m change-of-direction maneuvers under 60° could be explained by the results of 30-m forward-backward-forward change-of-direction. The standing broad jump explained 10% variation for the performances in change-of-direction sprint decrements and 9% variation for the 5-m change-of-direction with the best times, whereas straight-line sprinting was related to forward-backward-forward change-of-direction. The 10-m sprint explained 50% variation of the performances in the first 10-m forward running in the CODS2 and 12% variation for 10-m backward-forward change-of-direction. The 30-m sprint explained 36% variation for 30-m forward-backward-forward change-of-direction. The 30-m sprint and overall body mass also explained 58% variation for 10-m forward-backward change-of-direction. For coaching purposes, we report that forward-backward-forward and cutting maneuver change-of-direction movements are independent and highly useful skills. This information can help to provide better training prescriptions.


#10 The Use of GPS Analysis to Quantify the Internal and External Match Demands of Semi-Elite Level Female Soccer Players during a Tournament
Reference: J Sports Sci Med. 2019 Feb 11;18(1):73-81. eCollection 2019 Mar.
Authors: Strauss A, Sparks M, Pienaar C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370966/pdf/jssm-18-73.pdf
Summary: The purpose of this study was to make use of global positioning system technology to quantify the internal and external match demands of sub-elite female soccer players. Secondly, the study aims to describe the magnitude of change of these variables within and between matches over the course of a tournament to determine the effect of player fatigue. Thirty sub-elite female soccer players were assessed throughout a local tournament. Differences in match demands within and between matches were assessed using percent difference, effect size and 90% confidence intervals. One-way ANOVA was used to compare differences in the match demands and running intensities among playing positions and Bonferroni corrections were used to determine differences where significant effects of position were observed. A paired sample t-test in conjunction with the Cohen effect size was used to compare changes in match performance. Total distance covered averaged 5917 m. Midfielders covered the greatest absolute and relative total distances, and achieved the highest low-intensity activity and player load per minute of play. Defenders covered significantly (p ≤ 0.05) less relative distance and low-intensity activity per minute of play compared to midfielders. Forwards covered the greatest distance at high-intensity, while the greatest percentage of time at high-intensity heart rate was measured among the defenders. Within match comparisons revealed that player load decreased significantly (p ≤ 0.05) in the second half (ES: 0.4). Relative distance, low-intensity activity and high-intensity activity also decreased in the second half with possibly trivial to likely small changes. Small to large differences in variables were observed throughout the tournament. The biggest magnitude of change was seen with a large decrease (ES: -1.2) in relative distance covered between match 2 and 5. Despite generally small reductions in performance measures, there is evidence that accumulated fatigue throughout a multi-day tournament would affect performance negatively.


#11 Preseason Dynamic Balance Performance in Healthy Elite Male Soccer Players
Reference: Am J Mens Health. 2019 Jan-Feb;13(1):1557988319831920. doi: 10.1177/1557988319831920.
Authors: Onofrei RR, Amaricai E, Petroman R, Surducan D, Suciu O
Download link: https://journals.sagepub.com/doi/pdf/10.1177/1557988319831920
Summary: Lower limb musculoskeletal injuries in sports are linked with balance abnormalities and altered postural control. Dynamic balance screening should be performed in order to identify athletes at risk. The purpose of the study was to evaluate the preseason dynamic balance performance and side-to-side asymmetry of healthy elite male soccer players, using modified Star Excursion Balance Test (mSEBT). Seventy-three elite soccer players (23.8 ± 5.4 years) were evaluated using the mSEBT. Normalized reach distances, side-to-side asymmetries, and composite scores were determined. The composite scores were 93.33% ± 8.99% for dominant leg and 93.36% ± 9.23% for nondominant leg. No significant differences were found between dominant and nondominant limb in any direction. The mSEBT is an easy-to-use tool to measure the dynamic balance performance in elite athletes. It can be applied successfully during preseason physical examinations. Future studies are needed to establish predictive cutoff points in order to increase mSEBT use in screening soccer players for dynamic balance abnormalities and identify those at risk for noncontact lower limb injuries.

 

Thu

21

Mar

2019

Latest research in football - week 7 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Ankle Structures of Professional Soccer (Football) Players With Proximal Diaphyseal Stress Fractures of the Fifth Metatarsal
Reference: J Foot Ankle Surg. 2019 Feb 11. pii: S1067-2516(18)30428-9. doi: 10.1053/j.jfas.2018.09.024. [Epub ahead of print]
Authors: Kizaki K, Yamashita F, Mori D, Funakoshi N
Summary: Despite a high incidence of proximal diaphyseal stress fractures of the fifth metatarsal (zone 3) in soccer (football) players, studies that examine risk factors of the fractures in professional soccer players are scarce; in particular, ankle structures have not yet been investigated. This study was designed to investigate ankle structures of professional soccer players with proximal diaphyseal stress fractures of the fifth metatarsal. We reviewed the ankle radiographs of 100 professional soccer players (stress fractures n = 15; controls n = 85) and measured the medial malleolar slip angle (MMSA), the ratio of the medial malleolar length to the width of the talar dome (MML:TD ratio), the ratio of the lateral malleolar length to the width of the TD (LML:TD ratio), and the ratio of the MML to the LML (MML:LML ratio). The MMSA (p < .01: 28.7° ± 5.8° versus 23.0° ± 4.9°) in the stress fractures was significantly wider and the MML:TD ratio (p = .08: 0.49 ± 0.08 versus 0.52 ± 0.07) had a trend to be smaller compared with the values of the controls. Logistic regression analysis revealed that a wider malleolar slip angle became a factor associated with stress fractures in professional soccer players (p < .01: odds ratio 1.27, 95% confidence interval 1.110 to 1.463). Receiver operating characteristic curve with MMSA for the stress fractures was depicted with an area under the curve of 0.778, and the suitable cut-off point was set at MMSA >27° with a positive likelihood ratio of 3.67 (95% confidence interval 2.173 to 6.188). Our study results show that a wide MMSA was associated with proximal diaphyseal stress fractures of the fifth metatarsal in professional soccer players.


#2 The acute effects of a short technique-intense training period on side-foot kick performance among elite female soccer players
Reference: J Sports Med Phys Fitness. 2019 Feb 13. doi: 10.23736/S0022-4707.19.09449-0. [Epub ahead of print]
Authors: Carlsson M, Isberg J, Nilsson J, Carlsson T
Summary: Previously, it was shown that elite soccer teams were 24% more likely to win matches if their passing effectiveness were increased by 1%. However, research interventions aiming to improve passing performance are scarce. The current study aimed to investigate the effect of a short technique-intense training period on side-foot kick performance among elite female soccer players. Four side-foot kick tests were completed before and after a training period: kicking a stationary ball using match-relevant (SBRS) and maximal ball speed (SBMS), passing the ball on the move using match-relevant ball speed (RBRS), and repeated side-foot kicks onto a rebound-box with continuously increasing passing distance (RRB). The players were assigned to either the intervention group or the control group. The training intervention consisted of six 55-min training sessions with five side-foot kick exercises. Within-group and between-group differences were investigated using paired-samples t-test and Mann-Whitney U test, respectively. The intervention group improved the performance in the RBRS and RRB tests (both P < 0.05), but no differences were found for the SBRS and SBMS tests (both P > 0.05). No improvements were found for the control group independent of test condition (all P > 0.05). Significant between-group differences were found for the RBRS and RRB tests (both P < 0.05), whereas no differences were found for the SBRS and SBMS tests (both P > 0.05). The fundamental soccer skill of passing a moving ball was improved in elite female soccer players by a short technique-intense training period.


#3 Head Injury in Soccer: From Science to the Field; summary of the head injury summit held in April 2017 in New York City, New York
Reference: Br J Sports Med. 2019 Feb 13. pii: bjsports-2018-100232. doi: 10.1136/bjsports-2018-100232. [Epub ahead of print]
Authors: Putukian M, Echemendia RJ, Chiampas G, Dvorak J, Mandelbaum B, Lemak LJ, Kirkendall D
Summary: There has been an increased focus and awareness of head injury and sport-related concussion (SRC) across all sports from the medical and scientific communities, sports organisations, legislators, the media and the general population. Soccer, in particular, has been a focus of attention due to the popularity of the game, the frequency of SRC and the hypothesised effects of repetitive heading of the ball. Major League Soccer, US Soccer and the National Women's Soccer League jointly hosted a conference entitled, 'Head Injury in Soccer: From Science to the Field', on 21-22 April 2017 in New York City, New York. The mission of this conference was to identify, discuss and disseminate evidence-based science related to the findings and conclusions of the fifth International Conference on Concussion in Sport held by the Concussion in Sport Group and apply them to the sport of soccer. In addition, we reviewed information regarding the epidemiology and mechanism of head injuries in soccer at all levels of play, data regarding the biomechanics and effects of repetitive head impacts and other soccer-specific considerations. We discussed how to release the information raised during the summit to key stakeholders including athletes, parents, coaches and healthcare providers. We identified future areas for research and collaboration to enhance the health and safety of soccer (football) players.


#4 The use of adaptive neuro-stimulation for rebalancing posture and muscular tone in a soccer team
Reference: J Sports Med Phys Fitness. 2019 Feb 12. doi: 10.23736/S0022-4707.19.09311-3. [Epub ahead of print]
Authors: Barassi G, Bellomo RG, Porreca A, Giannuzzo G, Giannandrea N, Pezzi L, Crudeli M, Visciano C, Saggini R
Summary: Posture and somatic structure could positively influence athletic gestures for their biomechanical implications. Working on neuromuscular activity, offers the possibility of intervention on postural control. The aim is demonstrating the possibility of interacting with the human body system through the spinal reflex pathway, starting from the stimulation of cutaneous receptors. In this study, developed inside the Chair in Physical and Rehabilitative Medicine, at G. d'Annunzio University, twenty soccer players were recruited. Males between 25.5 ± 10.6 years old participated in this study. Patients were divided using a single-blind criterion into two groups, each containing ten subjects. The experimental group was treated with 2 pre-set programs 4 times a week with an Adaptive Neuro-Stimulation (ANS) able to interact with cutaneous receptors through an ENF Physio® device with a range of electrical frequency of about 15-350 Hz; the placebo-controlled group received the treatment with the device switched off. Patients performed a myometric evaluation with the MyotonPRO® system and a postural one with the Rarog system at T0 before the treatment and at T1 after the four-week treatment. After our intervention, we identified an improvement in muscular tone, in particular in the hamstring muscles (17.69%, R p<0.01 / L p<0.05 ) and a rebalancing of the principal bone points in the postural system (shoulder 71%, p<0.05, hips 65.6%, p=0.056, sagittal "AP" and frontal "LL" centre of gravity, respectively 40%, p<0.05 and 52.7%, p=0.01 ). In conclusion, we could hypothesise the usefulness of an Adaptive Neuro-Stimulation to act on these parameters. Clinical rehabilitation impact - Adaptive Neuro-Stimulation could be used not only for treatment of injuries but also in the field of prevention.


#5 Plantar pressures in male adolescent soccer players and its associations with bone geometry and strength
Reference: J Sports Med Phys Fitness. 2019 Feb 12. doi: 10.23736/S0022-4707.19.09267-3. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente Á, Gómez-Bruton A, Alfaro-Santafé V, González-Agüero A, Vicente-Rodríguez G, Casajús JA
Summary: Mechanical loads exerted by soccer-specific actions increase bone remodeling activity. Nevertheless, little is known about the relationship between plantar pressure and bone structure. Therefore, the aim of this study was to compare bone geometry and strength between soccer players who exhibited different maximum values of the average pressures (MP) when performing a combination of soccer-specific tasks. Forty male adolescent soccer players (mean age 13.20.5 y) and 13 controls (mean age 13.10.9 y) participated in this study. Biofoot system was used to measure MP at the non-dominant foot during a circuit of soccer-specific tasks. Cluster analysis was performed to classify players into groups of similar MP profiles resulting two different groups as follows: 15 players with high MP (SOC-HP; mean MP: 392.768.2 kPa) and 25 with low MP (SOC-LP; mean MP: 261.049.6 kPa). Total and cortical volumetric bone mineral content (Tt.BMC/Ct.BMC), cross-sectional area (Tt.Ar/Ct.Ar), cortical thickness (Ct.Th), fracture load in X-axis, and polar strength index (SSIp) were measured at 38% of the non-dominant tibia by peripheral quantitative computed tomography. Bone geometry and strength comparisons between SOC-HP and SOC-LP were performed using analyses of covariance controlling by weight and tibia length. Greater Tt.BMC, Ct.BMC and Tt.Ar. were found in SOC-HP compared to CG (Tt.BMC: 3.22vs2.95 g, Ct.BMC: 2.95vs2.68 g, Ct.Ar: 280vs253 mm2; p<.05). Nevertheless, no significant bone geometry and strength differences were found between soccer groups and between SOC-LP and CG (p>.05). Developing high MP when training and playing soccer might be favourable to bone development.


#6 Sex-Related Hip Strength Measures Among Professional Soccer Players
Reference: J Strength Cond Res. 2019 Feb 7. doi: 10.1519/JSC.0000000000003003. [Epub ahead of print]
Authors: Hedt CA, Pearson JM, Lambert BS, McCulloch PC, Harris JD
Summary: Lower-extremity musculoskeletal injuries in soccer are common among sexes. However, it remains unknown whether differences between sexes exist with regard to absolute or relative hip strength and how these differences may relate to injury. In the current study, we performed a retrospective cross-sectional analysis of pre-season data from male (♂n = 21) and female (♀n = 19) professional United States soccer organizations. Two years of pre-season data were collected for peak strength of lower extremity and hip musculature (no duplicates used). A 2 × 2 multivariate analysis of variance was used to detect differences in hip strength between sexes and dominant compared with nondominant legs. For all significant multivariate effects indicated by Wilks lambda and follow-up univariate analysis, a Tukey's post hoc test was used for pairwise univariate comparisons. A 2-tailed independent-samples T-test was used for comparison of height, body mass, body mass index (BMI), mean leg length, and strength ratios between dominant and nondominant limbs between sexes. Type I error was set at α = 0.05 for all analyses. Height (♂183.1 ± 6.8 cm, ♀170.0 ± 5.5 cm), body mass (♂79.0 ± 8.7 kg, ♀65.1 ± 5.6 kg), BMI (♂23.5 ± 1.3 kg·m, ♀22.5 ± 1.4 kg·m), and mean leg length (♂95.5 ± 4.34 cm, ♀ 88.3 ± 3.24 cm) differed between groups (p < 0.05). Sex differences (p < 0.05) were also found for hip abduction (dominant ♂19.5 ± 3.6 kg, ♀17.3 ± 2.2 kg; nondominant ♂18.5 ± 3.7 kg, ♀16.0 ± 2.3 kg), adduction (dominant ♂19.8 ± 3.0 kg, ♀16.7 ± 2.3 kg; nondominant ♂20.1 ± 2.9 kg, ♀17.6 ± 2.9 kg), external rotation (dominant ♂21.7 ± 3.4 kg, ♀17.7 ± 2.4 kg; nondominant ♂21.6 ± 3.9 kg, ♀16.8 ± 2.1 kg), and dominant hamstring strength (♂27.9 ± 6.5 kg, ♀23.0 ± 4.9 kg). The ratio of hip internal to external rotation strength differed in the nondominant leg (♂1.1 ± 0.2, ♀0.9 ± 0.2, p < 0.05). No significant differences were found between males and females when measures were normalized to body mass. These findings provide baseline pre-season normative data for professional soccer athletes and indicate that strength differences can be expected among different sexes, but are attenuated with attention to body mass. Further research should indicate how pre-season strength measures relate to injury.


#7 Prevalence of Hamstring Strain Injury Risk Factors in Professional and Under-20 Male Football (Soccer) Players
Reference: J Sport Rehabil. 2019 Feb 12:1-23. doi: 10.1123/jsr.2018-0084. [Epub ahead of print]
Authors: Ribeiro-Alvares JB, Dornelles MP, Fritsch CG, de Lima-E-Silva FX, Medeiros TM, Severo-Silveira L, Marques VB, Baroni BM
Summary: Hamstring strain injury (HSI) is the most prevalent injury in football (soccer), and a few intrinsic factors have been associated with higher injury rates. The purpose was to describe the prevalence of the main intrinsic risk factors for HSI in professional and under-20 football players. One-hundred and one football players (52 professionals; 49 under-20) participated in this study. Anamnesis, hamstrings ultrasonography, passive straight-leg raise test, functional movement screen, and isokinetic dynamometry were performed. Eleven HSI risk factors for each leg were assessed, besides the player's age as a systemic risk factor. Reports were delivered to the coaching staff. Professionals had greater prevalence of HSI history compared to under-20 players (40% vs. 18%). No between-group differences were found for the other screening tests. Altogether, thirty percent of players had already sustained at least one HSI; 58% had history of injuries in adjacent regions; 49% had short biceps femoris fascicles; 66% and 21% had poor passive and active flexibility, respectively; 42% and 29% had deficits in functional movements and core stability, respectively; 7% and 26% presented bilateral imbalance for hamstring concentric and eccentric strength, respectively; 87% and 94% obtained low values for hamstring-to-quadriceps conventional and functional ratios, respectively. Two-thirds of players had 3 to 5 risk factors per leg. None of the players was fully free of HSI risk factors. Most football players present multiple risk factors for sustaining an HSI. Hamstring weakness is the most prevalent risk factor, but the teams should also be aware of deficits in flexibility, core stability, functional movements, and hamstring fascicle length.


#8 Hydrothermally Modified Corn Starch Ingestion Attenuates Soccer Skill Performance Decrements in the Second Half of a Simulated Soccer Match
Reference: Int J Sport Nutr Exerc Metab. 2019 Feb 12:1-26. doi: 10.1123/ijsnem.2018-0217. [Epub ahead of print]
Authors: Quinones MD, Lemon PWR
Summary: Hydrothermally modified non-GMO corn starch (HMS) ingestion may enhance endurance exercise performance via sparing carbohydrate oxidation. To determine whether similar effects occur with intermittent, high intensity exercise we investigated the effects of HMS ingestion prior to and at half time on soccer skill performance and repeated sprint ability during the later stages of a simulated soccer match. Eleven, male, university varsity, soccer players (177.7±6.8 cm, 77.3±7.9 kg, 22±3 y, 12.8±4.9 %BF, V̇O2max = 57.1±3.9 ml∙kg BM-1∙min-1) completed the match with HMS (8% CHO containing a total of 0.7 g∙kg BM-1∙h-1; 2.8 kcal∙kg BM-1∙h-1) or isoenergetic dextrose (DEX). Blood glucose was lower (p<0.001) with HMS at 15 (5.3 vs 7.7 mmol∙L-1) and 30 min (5.6 vs 8.3 mmol∙L-1) following ingestion, there were no treatment differences in blood lactate, and the respiratory exchange ratio was lower with HMS at 15 (0.84 vs 0.86, p = 0.003), 30 (0.83 vs 0.85, p = 0.004) and 45 min (0.83 vs 0.85, p = 0.007) of the first half. Repeated sprint performance was similar for both treatments (p>0.05) but soccer dribbling time was slower with DEX vs baseline (15.63 s vs 14.43 s, p < 0.05) but not so with HMS (15.04 vs 14.43 s, p > 0.05). Further, during the passing test, penalty time was reduced (4.27 s vs 7.73 s, p = 0.004) with HMS. During situations where glycogen availability is expected to become limiting, HMS ingestion pre-match and at half time could attenuate the decline in skill performance often seen late in contests.


#9 Are Soccer Players Older Now Than Before? Aging Trends and Market Value in the Last Three Decades of the UEFA Champions League
Reference: Front Psychol. 2019 Jan 28;10:76. doi: 10.3389/fpsyg.2019.00076. eCollection 2019.
Authors: Kalén A, Rey E, de Rellán-Guerra AS, Lago-Peñas C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6360147/pdf/fpsyg-10-00076.pdf
Summary: The aims of the current study were to analyze the evolution of players' age in the UEFA Champions League since the start of its modern-day format in 1992-1993 up until 2017-2018 and to determine how the players' age relates to their market value. The sample consisted of all players participating in the UEFA Champions League from the 1992-1993 to 2017-2018 seasons (n = 16062). The following variables were used in this study: players' age, number of seasons in the club, number of Champions Leagues won, team performance, and market value of the player in the season. Data were examined using a one-way ANOVA and a linear regression. The main finding of the current study is that an aging trend has occurred in the last three decades in the Champions League. A significant increase in average players' age (>1.6 years) was observed, rising from an age of 24.9 to 26.5 years. Goalkeepers and Center Backs tend to peak later than attackers, and their peak performance can last until an age of about 31 years. Finally, an inverted-U curve defines the association between market value and age, with peak value appearing in the 26-30 age range. These results provide useful information regarding at which age soccer players are likely to perform at the highest level, as well as the age they are likely to have the highest market value.


#10 Young Soccer Players With Higher Tactical Knowledge Display Lower Cognitive Effort
Reference: Percept Mot Skills. 2019 Feb 11:31512519826437. doi: 10.1177/0031512519826437. [Epub ahead of print]
Authors: Cardoso FDSL, González-Víllora S, Guilherme J, Teoldo I
Summary: The present study aimed to investigate whether the form and amount of declarative tactical knowledge (DTK) and procedural tactical knowledge (PTK) influence cognitive effort during soccer performance among young players. We assessed 36 male players from a Brazilian first-division soccer club; participants averaged 14.89 ( SD = 1.42) years of age. We evaluated DTK from video simulation tests and PTK through the System of Tactical Assessment in Soccer. We assessed cognitive effort by measures of pupil diameter using Mobile Eye Tracking-XG while players viewed soccer video scenes and made game-related play decisions. After the assessment of tactical knowledge, we categorized the sample according to players' tactical knowledge into participants with higher and lower PTK and higher and lower DTK. Subsequently, we examined the both PTK and DTK groups on cognitive effort. Our results suggest that tactical knowledge influences cognitive effort in that players with higher PTK and DTK displayed less cognitive effort during soccer performance tasks. In conclusion, we observed that PTK and DTK influenced the cognitive effort younger soccer players expended while viewing soccer scenes and making soccer performance decisions.


#11 Differences in Acceleration and High-Intensity Activities Between Small-Sided Games and Peak Periods of Official Matches in Elite Soccer Players
Reference: J Strength Cond Res. 2019 Feb 6. doi: 10.1519/JSC.0000000000003081. [Epub ahead of print]
Authors: Dalen T, Sandmæl S, Stevens TGA, Hjelde GH, Kjøsnes TN, Wisløff U
Summary: The purpose of this study was to compare whether the physical performance of players during 4 vs. 4 + goalkeeper (4 vs. 4) and 6 vs. 6 + goalkeeper (6 vs. 6) small-sided games (SSGs) is equivalent to those experienced during the most intense 5-minute period of soccer match play. Twenty-six male soccer players from an elite Norwegian league team took part. Players were monitored during 18 matches, 56 SSGs: twenty-eight 4 vs. 4 and twenty-eight 6 vs. 6 games. The ZXY Sport Tracking System was used to measure for each player the total distance covered, high-intensity running distance, sprint distance, number of accelerations, and player load (all expressed per minute). To compare the physical performance variables on players during the SSGs formats and match play, a 1-way analysis of variance with repeated measures was used. Players performed the same number of accelerations and player load in 4 vs. 4 (1.7 and 248, respectively) as in peak match (1.6 and 227, respectively), whereas in 6 vs. 6, there were 63% fewer accelerations and 15% lower player load (1.2 and 198, respectively), than in peak match. High-intensity running and sprint distance were significantly lower than mean match values in both 4 vs. 4 (4.1 and 0.2 m vs. 8.2 and 1.7 m) and 6 vs. 6 games (2.7 and 0.21 m vs. 8.2 and 1.7 m) (p < 0.05). In conclusion, only 4 vs. 4 SSGs are highly valuable, and in that, they elicit player load and accelerations to a level that is (at least) equivalent with peak periods of official match play.


#12 Effects of Plyometric Training on Physical Performance of Young Male Soccer Players: Potential Effects of Different Drop Jump Heights
Reference: Pediatr Exerc Sci. 2019 Feb 8:1-8. doi: 10.1123/pes.2018-0207. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, García-Pinillos F, Gentil P, Moran J, Pereira LA, Loturco I
Summary: The purpose was to compare the effects of plyometric drop jump (DJ) training against those induced by regular soccer training and assess the transference effect coefficient (TEC) of DJs ("trained exercises") performed from 20- (DJ20) and 40-cm (DJ40) height boxes with respect to different physical qualities (jumping, linear and change of direction speed, kicking, endurance, and maximal strength) in youth male soccer players. Participants were randomly divided into a control group (n = 20; age: 13.5 [1.9] y) and a DJ training group (n = 19; age: 13.2 [1.8] y), and trained for 7 weeks. A 2-way analysis of variance for repeated measures with the within-subject factor time (preintervention and postintervention) and between-subject factor group (intervention vs control) was performed. To calculate the TECs between the trained exercises (DJ20 and DJ40) and the physical tests, the ratio between the "result gains" (effect size [ES]) in the analyzed physical qualities and the result gains in the trained exercises were calculated. The TECs were only calculated for variables presenting an ES ≥ 0.2. Significant improvements (ES = 0.21-0.46; P < .05) were observed in the DJ training group, except in linear sprint performance. The control group improved only the maximal strength (ES = 0.28; P < .05). Significant differences were observed in all variables (ES = 0.20-0.55; P < .05) in favor of the DJ training group, except for maximal strength (group × time interaction). A plyometric training scheme based on DJs was able to significantly improve the physical performance of youth male soccer players. Overall, greater TECs were observed for DJ40 (0.58-1.28) than DJ20 (0.55-1.21).


#13 Vitamin D Supplementation and Physical Activity of Young Soccer Players during High-Intensity Training
Reference: Nutrients. 2019 Feb 6;11(2). pii: E349. doi: 10.3390/nu11020349.
Authors: Skalska M, Nikolaidis PT, Knechtle B, Rosemann TJ, Radzimiński Ł, Jastrzębska J, Kaczmarczyk M, Myśliwiec A, Dragos P, López-Sánchez GF, Jastrzębski Z
Download link: https://www.mdpi.com/2072-6643/11/2/349/pdf
Summary: The aim of this study was to confirm that vitamin D supplementation of young soccer players during eight-week high-intensity training would have a significant effect on their motion activity. The subjects were divided into two groups: the experimental one, which was supplemented with vitamin D (SG, n = 20), and the placebo group (PG, n = 16), which was not supplemented with vitamin D. All the players were subjected to the same soccer training, described as High-Intensity Interval Training (HIIT). The data of the vitamin D status, time motion parameters and heart rate were collected just before and after the intervention. A significant increase in 25(OH)D concentration (119%) was observed in the supplemented group, while the non-supplemented group showed a decrease of 8.4%. Based on the obtained results, it was found that physical activity indicators in the players were significantly improved during small-sided games at the last stage of the experiment. However, taking into account the effect of supplementation with vitamin D, there were no statistically significant differences between the placebo and the supplemented groups; thus, the effect size of the conducted experiment was trivial.

Mon

18

Mar

2019

Latest research in football - week 6 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Design, Validation, and Reliability of an Observation Instrument for Technical and Tactical Actions of the Offense Phase in Soccer
Reference: Front Psychol. 2019 Jan 24;10:22. doi: 10.3389/fpsyg.2019.00022. eCollection 2019.
Authors: Ortega-Toro E, García-Angulo A, Giménez-Egido JM, García-Angulo FJ, Palao JM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353797/pdf/fpsyg-10-00022.pdf
Summary: The use of observational methodology in the sports context provides coaches and other sports professionals with flexible tools that adapt to their needs. In collective sports, the use of these instruments is common for the technical and tactical analysis of the game. Based on the importance of data quality in these instruments, the purpose was to design, validate, and test the reliability of a mixed observational instrument of field formats and category systems to analyze technical and tactical actions in the offense phase in soccer. The instrument collects information regarding the actions with the ball, moment of the play (start, development, and end), and contextual situation for the offensive team and for the goalkeeper. The instrument design, validation, and reliability calculation were done in four stages: (a) review of the literature, (b) design the first draft of the instrument, (c) experts' qualitative and quantitative review of the instrument, and (d) observer training test (reliability calculation). The content validity was established by 12 experts (Ph.D. in sports science or soccer coach with at least of 10 years of coaching experience). The Delphi methodology was used. Experts did a quantitative (scale 0-10) and qualitative evaluation. Experts were asked about: (a) comprehension of the criteria, categorical cores, degree of openness, and their definitions, (b) pertinence of categorical cores and degree of openness, and (c) whether to include other categorical cores or degree of openness in the observation instrument. The lowest Aiken's V index was 0.91 for the categorical core "numerical situation with opponent goalkeeper." The inter- and intra-observer reliability presented good levels of agreement. The lowest Kappa index was 0.96 for the inter-reliability in the categorical core "defensive pressing lines" and was 0.98 for the intra-reliability in the categorical core "ball height (start of ball possession)," "distance of the defensive player," "ball height (end of ball possession)," "numerical situation," and "defensive pressing lines." The coefficients of the generalizability analysis showed a high level of accuracy, validity and reliability of the instrument. The results show that the instrument allows to obtain objective, valid and reliable information about the offensive phase in soccer.


#2 Change-of-direction, speed and jump performance in soccer players: a comparison across different age-categories
Reference: J Sports Sci. 2019 Feb 6:1-7. doi: 10.1080/02640414.2019.1574276. [Epub ahead of print]
Authors: Loturco I, Jeffreys I, Abad CCC, Kobal R, Zanetti V, Pereira LA, Nimphius S
Summary: This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players' specialization process.


#3 Prevalence of labrum and articular cartilage injuries of the hip on 3T magnetic resonance imaging of asymptomatic elite soccer players
Reference: Rev Esp Cir Ortop Traumatol. 2019 Feb 2. pii: S1888-4415(18)30173-5. doi: 10.1016/j.recot.2018.10.008. [Epub ahead of print] [Article in English, Spanish]
Authors: Márquez WH, Gómez-Hoyos J, Gallo JA, Espinosa B, Rivas N, Llano JF, Osorio J, Martin HD
Summary: The purpose was to establish the prevalence of lesions of the labrum and articular cartilage of the hip in asymptomatic elite soccer players by performing 3T magnetic resonance imaging. Eighty-four asymptomatic hips of 42 professional soccer players were evaluated. Male subjects older than 18 years were included. Cam and pincer deformity were defined as an alpha angle greater than 55 degrees and a lateral centre edge angle greater than 39 degrees, respectively. Labral injuries were classified with the Czerny classification and cartilage damage was classified with the Outerbridge classification. Specific statistical tests were used to establish the relationship between anatomical variances of the hip and the presence of chondral and labral injuries. FAI morphology prevalence was 25%. Abnormalities such as cam (22.5%) and labral injuries (33.8%) were found. Those cases with reported labral injury were predominantly intrasubstance damage (18.8%). Anatomical features of FAI were found to be related to lesions of the femoral cartilage (P<.001), chondrolabral damage (P=.042), or both injuries (P<.001). Asymptomatic labral or cartilaginous injuries of the hip were reported in 25% of the included professional soccer players. These injuries were associated with anatomical features of FAI.


#4 Effects of playing position, pitch location, opposition ability and team ability on the technical performance of elite soccer players in different score line states
Reference: PLoS One. 2019 Feb 5;14(2):e0211707. doi: 10.1371/journal.pone.0211707. eCollection 2019.
Authors: Redwood-Brown AJ, O'Donoghue PG, Nevill AM, Saward C, Sunderland C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0211707&type=printable
Summary: The purpose of this study was to investigate the effects of playing position, pitch location, team ability and opposition ability on technical performance variables (pass, cross, corner, free kick accuracy) of English Premier League Soccer players in difference score line states. A validated automatic tracking system (Venatrack) was used to code player actions in real time for passing accuracy, cross accuracy, corner accuracy and free kick accuracy. In total 376 of the 380 games played during the 2011-12 English premier League season were recorded, resulting in activity profiles of 570 players and over 35'000 rows of data. These data were analysed using multi-level modelling. Multi-level regression revealed a "u" shaped association between passing accuracy and goal difference (GD) with greater accuracy occurring at extremes of GD e.g., when the score was either positive or negative. The same pattern was seen for corner accuracy away from home e.g., corner accuracy was lowest when the score was close with the lowest accuracy at extremes of GD. Although free kicks were not associated with GD, team ability, playing position and pitch location were found to predict accuracy. No temporal variables were found to predict cross accuracy. A number of score line effects were present across the temporal factors which should be considered by coaches and managers when preparing and selecting teams in order to maximise performance. The current study highlighted the need for more sensitive score line definitions in which to consider score line effects.


#5 Age-related differences in flexibility in soccer players 8-19 years old
Reference: PeerJ. 2019 Jan 29;7:e6236. doi: 10.7717/peerj.6236. eCollection 2019.
Authors: Cejudo A, Robles-Palazón FJ, Ayala F, De Ste Croix M, Ortega-Toro E, Santonja-Medina F, Sainz de Baranda P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357869/pdf/peerj-07-6236.pdf
Summary: Muscle flexibility is a main component of health-related fitness and one of the basic components of fitness for the performance in some sports. Sport and health professionals require the flexibility profile of soccer to define quantitative aims in the training of flexibility. The aim of this study was to identify age-related differences in lower extremity flexibility in youth soccer players. Seventy-two young male soccer players (age: 13.0 ± 3.1 y; body mass: 50.5 ± 15.3 kg; stature 158.2 ± 16.8 cm; BMI: 19.6 ± 2.6 kg/m2) completed this study. Measures of eleven passive hip (hip extension (HE), hip adduction with hip flexed 90°(HAD-HF90°), hip flexion with knee flexed (HF-KF) and extended (HF-KE), hip abduction with hip neutral (HAB) and hip flexed 90°(HAB-HF90°), hip external (HER) and internal (HIR) rotation), knee (knee flexion (KF)) and ankle dorsiflexion (ankle dorsiflexion with knee flexed (ADF-KF) and extended (ADF-KE)) ranges of motion (ROM) were taken. Descriptive statistics were calculated for hip, knee and ankle ROM measured separately by leg (dominant and non-dominant) and age-group (U10, U12, U14, U16 and U19). The data was analysed using a one-way analysis of variance (ANOVA) to examine the interaction of 11 ROM in the different players' age-group. Generally, U10 and/or U12 soccer players obtain the highest mean value in almost all ROM evaluated (U10: HAD-HF [39.6° ± 4.3°], ADF-KE [32.3° ± 4.1°], HER [63.5° ± 5.6°] and HAB-HF90°[64.1° ± 7.5°]; U12: HE [17.7° ± 6.2°], HAB [35.6° ± 3.0], HIR [60.8° ± 4.7°] and KF [133.8° ± 7.1°]). Nonetheless, significant differences between the players' age-groups are just found in HAD-HF90°(p = .042; ES = .136), HAB (p = .001; ES = .252), HIR (p = .001; ES = .251), HER (p < .001; ES = .321) and HAB-HF90°(p < .001; ES = .376) ROM, showing a progressive and irregular decrease in these ROM until the U19 team. The findings of this study reinforce the necessity of prescribing exercises aimed at improving HAD-HF90°  ROM in U16, HAB ROM in U14, HIR ROM in U16 and U19, HER ROM in U12 and U19, and HAB-HF90°  ROM in U16 and U19 players within everyday soccer training routines.


#6 Effects of the long-term consumption of hydrogen-rich water on the antioxidant activity and the gut flora in female juvenile soccer players from Suzhou, China
Reference: Med Gas Res. 2019 Jan 9;8(4):135-143. doi: 10.4103/2045-9912.248263. eCollection 2018 Oct-Dec.
Authors: Sha JB, Zhang SS, Lu YM, Gong WJ, Jiang XP, Wang JJ, Qiao TL, Zhang HH, Zhao MQ, Wang DP, Xia H, Li ZW, Chen JL, Zhang L, Zhang CG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352569/pdf/MGR-8-135.pdf
Summary: Expending a considerable amount of physical energy inevitably leads to fatigue during both training and competition in football. An increasing number of experimental findings have confirmed the relationship between the generation and clearance of free radicals, fatigue, and exercise injury. Recently, hydrogen was identified as a new selective antioxidant with potential beneficial applications in sports. The present study evaluated the effect of 2-month consumption of hydrogen-rich water on the gut flora in juvenile female soccer players from Suzhou. As demonstrated by enzyme linked immunosorbent assay and 16S rDNA sequence analysis of stool samples, the consumption of hydrogen-rich water for two months significantly reduced serum malondialdehyde, interleukin-1, interleukin-6, tumour necrosis factor-α levels; then significantly increased serum superoxide dismutase, total antioxidant capacity levels and haemoglobin levels of whole blood. Furthermore, the consumption of hydrogen-rich water improved the diversity and abundance of the gut flora in athletes. All examined indices, including the shannon, sobs, ace, and chao indices, were higher in the control group than those proposed to result from hydrogen-rich water consumption prior to the trial, but these indices were all reversed and were higher than those in the controls after the 2-month intervention. Nevertheless, there were some differences in the gut flora components of these two groups before the trial, whereas there were no significant changes in the gut flora composition during the trial period. Thus, the consumption of hydrogen-rich water for two months might play a role modulating in the gut flora of athletes based on its selective antioxidant and anti-inflammatory activities.


#7 Effects of a multifactorial injuries prevention program in young Spanish football players
Reference: J Sports Med Phys Fitness. 2019 Feb 5. doi: 10.23736/S0022-4707.19.09219-3. [Epub ahead of print]
Authors: Chena M, Rodríguez ML, Bores AJ, Ramos-Campo DJ
Summary: The high injury rate in football has highlighted the need to research strategies that allow the modification of the dynamic risk factors. Most of the preventive proposals have focused on standardized protocols. However, the aim of this study was to evaluate the effect of a multifactorial injuries prevention program (MC-7) in Spanish football players. A total of 219 Spanish football male players aged 16-23 were studied. The study was conducted over two consecutive seasons (2012-2013, 2013-2014). The first season was the control season (SC) and the second one was the experimental season (ES). Injuries were recorded prospectively during the two seasons in accordance with the criteria established by the consensus statement. During CS the injuries were just observed, while during ES, the players participated in the MC-7: training methodology, specific warm-up protocol (FIFA 11+), basic injury recovery strategies, continuous training of coaches, conferences for parents/family and education sessions for players. The frequency of injuries was significantly reduced by 63.8% in the ES. Muscle-tendon and joint injuries were reduced by 65% and 56.7% respectively, with a significant decrease in the lower-limbs injuries. The incidence of injuries was reduced by 71.4%, with significant differences in the typology, location and severity of injuries. The rate of injury in football is reduced when multifactorial strategies are applied. Reducing the frequency and severity of injuries allowed players to greatly increase their available for sports practice.


#8 ACTN3 single nucleotide polymorphism is associated with non-contact musculoskeletal soft-tissue injury incidence in elite professional football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2019 Feb 5. doi: 10.1007/s00167-019-05381-x. [Epub ahead of print]
Authors: Clos E, Pruna R, Lundblad M, Artells R, Esquirol Caussa J
Summary: Muscle injuries are common in professional football, even though prevention protocols are being implemented. Genetics constitutes a novel field for studying intrinsic injury risks and performance. Since previous studies involving single nucleotide polymorphisms (SNPs) have shown that SNPs influence muscle injury rate, injury severity and recovery time, the aim was to study the association the SNP of ACTN3 has with those parameters in professional football players. The medical staff team recorded non-contact musculoskeletal soft-tissue injuries in 43 professional football players in 7 different seasons (2007-2012 and 2015-2016). Injury rate, injury severity and injury recovery times were established. Players were genotyped by extracting DNA from a blood sample and using a polymerase chain reaction. Injury rate was associated with the SNP of ACTN3 (p = 0.003). The 577R allele was more frequent in subjects than in a normal population by showing presence in 93% of the subjects and suggesting that it could influence football performance. No statistically significant differences in injury severity and recovery time were associated with the SNP of ACTN3. Genetics is gaining in importance when assessing injury risk and performance in professional football. ACTN3 can be regarded as a biomarker of injury susceptibility in this discipline. Identifying those players with the highest injury susceptibility through genetics could lead football teams to individualise workloads and prevention protocols.


#9 Relationships between Anxiety, Emotional Intelligence, and Motivational Climate among Adolescent Football Players
Reference: Sports (Basel). 2019 Feb 1;7(2). pii: E34. doi: 10.3390/sports7020034.
Authors: Castro-Sánchez M, Zurita-Ortega F, Ubago-Jiménez JL, González-Valero G, Chacón-Cuberos R
Summary: Emotional and motivational factors are fundamental in the context of sport, as they directly relate to sports performance and anxiety. The present study aimed to analyze the relationships between motivational climate (MC), emotional intelligence (EI), and anxiety within a sample of footballers playing at a low level. The sample was composed of 282 registered football players aged between 16 and 18 years old (16.96 ± 0.77), playing in the lower tier in the province of Jaen (Spain). Data were self-reported, with participants responding to the Perceived Motivational Climate in Sport Questionnaire (PMCSQ-2), the Schutte Self-Report Inventory (SSRI), and the State Trait Anxiety Inventory (STAI). The results showed that footballers who reported higher levels of state anxiety and trait anxiety also demonstrated lower EI and more negatively perceived and regulated their emotions. Moreover, an ego-oriented climate was associated with higher levels of anxiety, while a task-oriented climate was related to lower levels of anxiety and higher levels of EI. No relationship was identified between the emotional aspects of young footballers and holding a motivational orientation toward an ego climate. Football players who more greatly perceived a task-oriented climate had higher EI and usually reported lower levels of anxiety related to sport performance. It is therefore important to promote intrinsic motivations and develop the capacity of footballers to regulate their own emotions.


#10 A Brazilian Football Player Still on the Pitch After 10 Years of Parkinson's Disease with Severe Freezing of Gait
Reference: Mov Disord Clin Pract. 2014 Dec 6;2(1):43-44. doi: 10.1002/mdc3.12110. eCollection 2015 Mar.
Authors: Vale TC, Pedroso JL, Barsottini OG, Lees AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6353400/pdf/MDC3-2-43.pdf

Sun

03

Mar

2019

Latest research in football - week 5 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Immediate effects and one-week follow-up after neuromuscular electric stimulation alone or combined with stretching on hamstrings extensibility in healthy football players with hamstring shortening
Reference: J Bodyw Mov Ther. 2019 Jan;23(1):16-22. doi: 10.1016/j.jbmt.2018.01.017. Epub 2018 Feb 2.
Authors: Espejo-Antúnez L, Carracedo-Rodríguez M, Ribeiro F, Venâncio J, De la Cruz-Torres B, Albornoz-Cabello M
Summary: The purpose was to assess the immediate and mid-term (after 7 days) effects of electric current combined with simultaneous muscle stretching (EME technique) per comparison to the isolated use of the same current (without applying simultaneous muscle stretching), over the hamstring extensibility in football players with hamstring shortening, and to estimate the clinical benefit of the interventions according to the muscular extensibility. Forty-eight participants were randomized to receive one session of EME technique (n = 26) or one session of the electrical current (EC) alone (n = 22). The measurement of the hamstrings extensibility through the active knee test was carried out before and immediately after each intervention and one week later. A significant interaction group x time was observed (F2,84 = 7.112, p = 0.001; partial eta squared = 0.145). The hamstrings extensibility changed significantly immediately after the EME technique (147.3° ± 16.4° to 153.5° ± 14.2°, p < 0.05), but not after the EC only (144.2 ± 10.2° to 141.7 ± 7.8°, p > 0.05). One week after the intervention no significant differences were found to the baseline values in both groups. The number needed to treat to prevent one new case of hamstring shortening was 3. The combination of electric current with simultaneous stretching is an effective technique to acutely increase the hamstring extensibility of football players with hamstring shortness.


#2 Sudden cardiac death in football players: Towards a new pre-participation algorithm
Reference: Exp Ther Med. 2019 Feb;17(2):1143-1148. doi: 10.3892/etm.2018.7041. Epub 2018 Nov 30.
Authors: Mavrogeni SI, Tsarouhas K, Spandidos DA, Kanaka-Gantenbein C, Bacopoulou F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6327574/pdf/etm-17-02-1143.pdf
Summary: Athletic pre-participation screening is essential for minimizing the risk for sudden cardiac death (SCD) in athletes participating in either competitive or leisure sporting activities. The primary causes of SCD in young athletes (<35 years of age) include hypertrophic cardiomyopathy, congenital anomalies of the coronary artery and arrhythmogenic right ventricular cardiomyopathy. Other abnormalities, such as malignant arrhythmia due to blunt trauma to the chest (commotio cordis), myocarditis, valvular disease, aortic rupture (in Marfan syndrome) and ion channelopathies (catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, long or short QT syndrome), also contribute to a lesser degree to SCD. Currently, clinical assessment, electrocardiogram (ECG) and echocardiography are the cornerstones of the pre-participation athletic evaluation. However, their low sensitivity raises queries as regards the need for the application of more sophisticated modalities, such as cardiovascular magnetic resonance (CMR). CMR offers precise biventricular assessment and is greatly reproducible without the inherent limitations of echocardiography; i.e., low quality of images due to the lack of appropriate acoustic window or operator's experience. Furthermore, myocardium replacement fibrosis, indicative of patients' increased risk for future cardiac events, can be effectively detected by late gadolinium enhanced (LGE) images, acquired 15 min post-contrast injection. Finally, diffuse myocardial fibrosis not identified by LGE, can also be detected by pre-contrast (native) T1, post-contrast T1 mapping and extracellular volume images, which provide detailed information about the underlying pathophysiologic background. Therefore, CMR is recommended in all football players with a positive family or personal history of syncope or SCD, abnormal/doubtful ECG or echocardiogram.


#3 Asthma and youth soccer: an investigation into the level of asthma awareness and training among youth soccer coaches
Reference: Open Access J Sports Med. 2019 Jan 15;10:17-31. doi: 10.2147/OAJSM.S182178. eCollection 2019.
Authors: Sadasivan C, Cave A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339450/pdf/oajsm-10-017.pdf
Summary: Asthma is the most common chronic disease among children. Exercise-induced bronchoconstriction which is common in asthmatic patients also occurs in individuals with no prior asthma diagnosis. Despite this and the fact that soccer is a high ventilation sport, there are no validated asthma management protocols in place for soccer coaches. This study aims to address 1) soccer coaches' current knowledge on asthma, 2) whether there is a need for asthma-related training, and 3) any barriers to administration of such training. A total of 2,300 volunteer youth soccer coaches from the Edmonton Minor Soccer Association (EMSA) were invited to participate in completing a 22-question online survey. The survey was open for 1 month from June 8, 2018, to July 8, 2018. There was a response rate of 22% (513 of 2,300). Respondents were on average, inexperienced coaches, coached younger age groups, and approximately one-third of respondents had personal experience with asthma (either themselves or their child had asthma). 93% of respondents had not received any asthma-related training at any coaching level, whether it be from EMSA or the Alberta Soccer Association. Coaches had strong knowledge on how to treat asthma attacks, but mixed levels of knowledge on asthma attack prevention. Experienced coaches were better at identifying the number of players with asthma on their team and the number of asthma-related incidents they had encountered as coaches. Coaches demonstrated a receptive attitude toward receiving asthma-related training, with 91% of respondents saying training would be beneficial and 69% of respondents saying training should be mandatory. The results of this study indicate that soccer coaches have limited knowledge regarding asthma management, acknowledge a need for asthma-related training, and are willing to participate in and could benefit from educational interventions as it pertains to their roles as coaches.


#4 Electrocardiographic and echocardiographic evaluation of a large cohort of peri-pubertal soccer players during pre-participation screening
Reference: Eur J Prev Cardiol. 2019 Jan 29:2047487319826312. doi: 10.1177/2047487319826312. [Epub ahead of print]
Authors: Calò L, Martino A, Tranchita E, Sperandii F, Guerra E, Quaranta F, Parisi A, Nigro A, Sciarra L, Ruvo E, Casasco M, Pigozzi F
Summary: The early diagnosis of cardiac abnormalities in young athletes may be helpful not only to identify subjects potentially at risk of sudden cardiac death but also to prevent stress-related cardiac dysfunction and cardiovascular events during the life of these subjects. The aim of our study was to investigate the prevalence of cardiac abnormalities in a population of young male soccer players undergoing pre-participation screening through electrocardiogram and trans-thoracic echocardiography. All consecutive male football players undergoing pre-participation screening comprehensive of medical history, physical examination, 12-lead electrocardiogram and trans-thoracic echocardiography at the FMSI Sport Medicine Institute in Rome between January 2008-March 2009 were enrolled in the study. Overall, 2261 consecutive young athletes aged 12.4 ± 2.6 years were evaluated. Training-unrelated electrocardiogram abnormalities were observed in 65 (2.9%) athletes. Abnormal trans-thoracic echocardiography was observed in 102 athletes (4.5%), including two cases of hypertrophic cardiomyopathy, eight of mild left ventricular hypertrophy, six of mild left ventricular dilation and 17 of bicuspid aortic valve. An abnormal electrocardiogram was associated with anomalous trans-thoracic echocardiography in 11/65 (16.9%) cases. All athletes requiring sport disqualification were identified by electrocardiogram. Notably, among 2216 athletes with a normal electrocardiogram, 91 had abnormal trans-thoracic echocardiography, including six cases of left ventricular dilation and six of ventricular hypertrophy. In a wide population of peri-pubertal male athletes, evaluation of the electrocardiogram identified all cardiac diseases requiring sport disqualification. Trans-thoracic echocardiography alone allowed the identification of cardiac abnormalities potentially leading to cardiomyopathies or major cardiovascular events over time.


#5 Ecological and Construct Validity of a Repeated Sprint Test in Male Youth Soccer Players
Reference: J Strength Cond Res. 2019 Jan 23. doi: 10.1519/JSC.0000000000003047. [Epub ahead of print]
Authors: Fernandes-Da-Silva J, Castagna C, Teixeira AS, Carminatti LJ, Francini L, Póvoas SCA, Antonacci Guglielmo LG
Summary: This study aimed to examine the relationship between a repeated sprint ability (RSA) test (5 bouts of 30-m sprints interspersed by 30 seconds of recovery) and match-related physical performance in male youth soccer players. Although 60 outfield players were evaluated, only data from players who participated in the full matches (n = 39) were retained (8 central defenders, 7 external defenders, 8 central midfielders, 8 external midfielders, and 8 forwards). To verify the ecological validity of this RSA protocol, the association between the best (RSAbest) and mean (RSAmean) sprint time in the 5 × 30-m and physical match performance during friendly youth soccer games was examined. Physical match demands were assessed using global positioning system technology (10 Hz) considering distance covered in selected arbitrary speed categories. The absolute speed thresholds were the same for all the players. Players were categorized into 2 groups based on the 5 × 30-m performance: RSAmean times below (i.e., faster) and above (i.e., slower) the median value. Players with faster RSAmean times covered significantly more distance sprinting during friendly matches (606 ± 204 m, +47.0%; t = 4.953; effect size = 1.88, 1.24; 2.52, p ≤ 0.001) compared to their slower counterparts (322 ± 145 m). A large negative correlation (r = -0.63, -0.77; -0.44, p ≤ 0.001) was found between RSAbest time (4.59 ± 0.27 seconds) and match sprint distance (457 ± 229 m). Likewise, RSAmean time (4.76 ± 0.25 seconds) was also largely associated (r = -0.60, -0.75; -0.39; p ≤ 0.001) with in-game sprinting performance. The results of this study provided evidence to support the construct and ecological validity of the 5 × 30-m protocol in male youth soccer players. Furthermore, differences in 5 × 30-m performance explained the amount of sprinting activity performed during the match.


#6 Accuracy of Anthropometric Equations to Estimate DXA-Derived Skeletal Muscle Mass in Professional Male Soccer Players
Reference: J Sports Med (Hindawi Publ Corp). 2019 Jan 1;2019:4387636. doi: 10.1155/2019/4387636. eCollection 2019.
Authors: González-Mendoza RG, Gaytán-González A, Jiménez-Alvarado JA, Villegas-Balcázar M, Jáuregui-Ulloa EE, Torres-Naranjo F, López-Taylor JR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6332936/pdf/JSM2019-4387636.pdf
Summary: Several anthropometric equations that estimate skeletal muscle mass (SMM) have been published, but their applicability and accuracy among athletes are still uncertain. The purpose was to assess the accuracy of different anthropometric equations that estimate SMM in professional male soccer players, as compared to dual-energy X-ray absorptiometry (DXA) as the reference method. In this cross-sectional study, we evaluated 179 professional male soccer players aged between 18 and 37 years. Anthropometric measurements (height, body weight, skinfold thicknesses, and girths) and a DXA whole body scan were performed the same day for each participant, and SMM was estimated with nine anthropometric equations (Heymsfield, Martin, Doupe, Kerr, Drinkwater, Lee, De Rose, and two equations published by Kuriyan). To determine differences between SMM estimated with anthropometric equations and SMM evaluated with DXA, a Kruskal-Wallis test was performed using Dunn's test as post hoc. The significance level was set at p < 0.05. We calculated the mean difference and 95% limits of agreement for the analyzed equations (Equation - DXA). Only Heymsfield's and Lee's equations showed no significant differences with DXA. Heymsfield's equation had the smallest mean difference (-0.17 kg), but wider limits of agreement with DXA (-6.61 to 6.94 kg). Lee's equation had a small mean difference (1.10 kg) but narrower limits of agreement with DXA (-1.83 to 4.03 kg). In this study, the prediction equation published by Lee et al. showed the best agreement with DXA and is able to estimate SMM accurately in professional male soccer players.


#7 Management of concussion in soccer
Reference: Acta Neurochir (Wien). 2019 Jan 28. doi: 10.1007/s00701-019-03807-6. [Epub ahead of print]
Authors: Hubertus V, Marklund N, Vajkoczy P
Summary: When participating in contact sports, (mild) head trauma is a common incident-observed in both professional and amateur sports. When head trauma results in transient neurological impairment, a sports-related concussion has occurred. Acute concussion, repetitive concussions, as well as cumulative "sub-concussive" head impacts may increase the risk of developing cognitive and behavioral deficits for athletes, as well as accelerated cerebral degeneration. While this concept has been well established for classic contact sports like American Football, Rugby, or Boxing, there is still an awareness gap for the role of sports-related concussion in the context of the world's most popular sport-Soccer. Here, we review the relevance of sport-related concussion for Soccer as well as its diagnosis and management. Finally, we provide insight into future directions for research in this field. Soccer fulfills the criteria of a contact sport and is characterized by a high incidence of concussion. There is ample evidence that these events cause functional and structural cerebral disorders. Furthermore, heading, as a repeat sub-concussive impact, has been linked to structural brain changes and neurocognitive impairment. As a consequence, recommendations for the diagnosis and management of concussion in soccer have been formulated by consensus groups. In order to minimize the risk of repetitive concussion in soccer the rapid and reliable side-line diagnosis of concussion with adoption of a strict remove-from-play protocol is essential, followed by a supervised, graduated return-to-play protocol. Recent studies, however, demonstrate that adherence to these recommendations by players, coaches, clubs, and officials is insufficient, calling for stricter enforcement. In addition, future research to solidify the pathophysiological relevance of concussion for soccer athletes seems to be needed. Advanced neuroimaging and neurochemical biomarker analyses (e.g. S100β, tau and neurofilament light (NfL)) may assist in detecting concussion-related structural brain changes and selecting athletes at risk for irreversible damage. Sports-related concussion represents a genuine neurosurgical field of interest. Given the high socioeconomic relevance, neurosurgeons should get involved in prevention and management of concussion in soccer.


#8 Training Loads and RSA and Aerobic Performance Changes During the Preseason in Youth Soccer Squads
Reference: J Hum Kinet. 2018 Dec 31;65:235-248. doi: 10.2478/hukin-2018-0032. eCollection 2018 Dec.
Authors: Cetolin T, Teixeira AS, Netto AS, Haupenthal A, Nakamura FY, Guglielmo LGA, da Silva JF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341967/pdf/hukin-65-235.pdf
Summary: The aims of this study were to compare the internal training load (ITL) in soccer players of two competitive age groups (under-15 [U-15] and under-19 [U-19]) during an 8-week preseason training period and compare the associated changes in physical performance measures. Eighteen U-15 and twelve U-19 players were monitored over an 8-week period during the preseason phase. The ITL was monitored using the session rating of perceived exertion (RPE) method. Before and after the preseason period, physical performance was assessed by best (RSAbest) and mean (RSAmean) times in a repeated sprint ability (RSA) test and peak velocity derived from the Carminatti test (PVT-CAR). Total weekly ITL increased with age (U-15: 13770 ± 874 AU vs. U-19: 33584 ± 2506 AU; p < 0.001). In addition, U-19 players perceived training sessions as heavier than U-15 players (6.1 ± 0.3 vs. 5.3 ± 0.3 AU, respectively; p < 0.001). After the preseason period, very likely to almost certainly positive changes were observed for all performance measures in both age groups. However, the U-15 group had possibly superior gains in RSAbest (+1.40%, 90%CL -0.29 to 3.05, with ES = 0.35) and likely higher effects in RSAmean (+1.89%, 90%CL 0.04 to 3.70, with ES = 0.53) and PVT-CAR (+2.71%, 90%CL 0.35 to 5.01, with ES = 0.37) compared to the U-19 group. In conclusion, our findings demonstrate that the U-19 group accumulate higher total weekly ITLs than the U-15 group during the preseason phase due to longer and heavier training sessions. However, the U-15 group obtained superior gains in soccer-specific physical abilities while accumulating half the total ITLs during lighter training sessions.


#9 Relative Age Effect and Long-Term Success in the Spanish Soccer and Basketball National Teams
Reference: J Hum Kinet. 2018 Dec 31;65:197-204. doi: 10.2478/hukin-2018-0027. eCollection 2018 Dec.
Authors: López de Subijana C, Lorenzo J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341957/pdf/hukin-65-197.pdf
Summary: The aims of this study were: i) to analyze whether relative age effect occurs in the athletes of the junior national teams and professional athletes in Spain in general and in soccer and basketball, and ii) to compare the long-term success of the players selected for the junior national team between these sports. The samples for this study were Spanish professional soccer (n = 461) and basketball (n = 250) players in the 2013-2014 premier league and players from the junior Spanish soccer (i.e., n = 273; U-17: n = 107; U-19: n = 166) and basketball (i.e., n = 240; U-18: n = 120, U-16: n = 120) teams that classified to play in the European Championships (from 2004 to 2013). Junior players (42.3%) were more frequently born in the 1st quarter of the year than the professional players (30.7%) (χ2(3) = 30.07; p = .001; Vc = .157). This was found in both basketball (χ2(3) = 12.2.; p = .007; Vc = .158) and soccer (χ2(3) = 20.13; p < .001; Vc = .166). Long-term success is more frequent in soccer, where 59.9% of the juniors selected for the national team played later in the premier league, while in basketball that percentage was 39.6% (χ2(1) = 14.64; p < .001; Vc = .201). On the other hand, 79.4% and 39.8% of the professional soccer and basketball players had been previously selected for junior national teams (χ2(1) = 60.2; p < .001; Vc = .386), respectively. The talent selection process should be reviewed as players born in the second half of the year have fewer opportunities to stand out.


#10 Effects of the Pitch Surface on Displacement of Youth Players During Soccer Match-Play
Reference: J Hum Kinet. 2018 Dec 31;65:175-185. doi: 10.2478/hukin-2018-0046. eCollection 2018 Dec.
Authors: Brito Â, Roriz P, Silva P, Duarte R, Garganta J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341947/pdf/hukin-65-175.pdf
Summary: The aim of this study was to analyze the effect of different pitch surfaces (artificial turf, natural turf and dirt field) on positioning and displacement of young soccer players (age: 13.4 ± 0.5 yrs; body height: 161.82 ± 7.52 cm; body mass: 50.79 ± 7.22 kg and playing experience: 3.5 ± 1.4 yrs). Data were collected using GPS units which allowed to calculate spatial distribution variability, assessed by measuring entropy of individual distribution maps (ShannEn). Ellipsoidal areas (m2) representing players' displacement on the pitch, centred on the average players' positional coordinates, were also calculated, with axes corresponding to the standard deviations of the displacement in the longitudinal and lateral directions. Analysis of variance (ANOVA) was used to evaluate differences between pitch surfaces and across players' positions. There was significant effect in positioning (η2 = 0.146; p < 0.001) and displacement (η2 = 0.063; p < 0.05) by the players between pitch surfaces. A dirt field condition induced an increase in the players' movement variability, while players' displacement was more restricted when playing on artificial turf. Also, there were significant effects on positioning (η2 = 0.496; p < 0.001) and displacement (η2 = 0.339; p < 0.001) across players' positions. Central midfielders presented the greatest movement variability and displacement while fullbacks showed the lowest variability. Subsequently, the results may contribute to implement strategies that optimise players' performance in different surface conditions.


#11 Work-rate Analysis of Substitute Players in Professional Soccer: Analysis of Seasonal Variations
Reference: J Hum Kinet. 2018 Dec 31;65:165-174. doi: 10.2478/hukin-2018-0025. eCollection 2018 Dec.
Authors: Padrón-Cabo A, Rey E, Vidal B, García-Nuñez J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341962/pdf/hukin-65-165.pdf
Summary: The aims of this study were to evaluate physical performance of substitute players versus those replaced or completing the entire match, determine physical performance of substitute players across different playing positions and examine variations in match-related running performance in substitute players throughout the entire competitive season. The sample was composed of 943 observations of professional players who participated in the first division of the Spanish League (La Liga) during the 2014-2015 season. The players were divided into three different groups: players who completed the entire match (n = 519), players who were replaced (n = 212) and substitute players (n = 212). Substitute players covered greater distances at medium and high intensity compared to the players who played the entire match and those who were replaced. Position-specific trends indicated that attackers and central midfielder increased the distance covered at high-intensity running compared to their peers who played the whole match. During the competitive season, it was observed that substitute players attained greater match running performance during the mid-season period, allowing them to cover more distance for different variables of running performance compared to the start and end of the season.


#12 Analysis of elite soccer players' performance before and after signing a new contract
Reference: PLoS One. 2019 Jan 25;14(1):e0211058. doi: 10.1371/journal.pone.0211058. eCollection 2019.
Authors: Gómez MÁ, Lago C, Gómez MT, Furley P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347186/pdf/pone.0211058.pdf
Summary: The aim of the current study was to analyse performance differences of football players 2-years prior and the year after signing a new contract (the following year) while taking playing position, nationality, player's role, team ability, and age into account. The sample was comprised of 249 players (n = 109 defenders, n = 113 midfielders; and n = 27 forwards) from four of the major European Leagues (Bundesliga, English FA Premier League, Ligue 1, and La Liga) during the seasons 2008 to 2015. The dependent variables studied were: shooting accuracy, defense (the sum of defensive actions, tackles, blocks, and interceptions), yellow cards, red cards, passing accuracy, tackle success, and minutes played per match. Two-step cluster analysis allowed classifying the sample into three groups of defenders (national important, foreign important, and less important players) and four groups of midfielders and forwards (national important, foreign important, national less important, and foreign less important players). Magnitude Based Inference (MBI) was used to test the differences between player's performances during the years of analyses. The main results (very likely and most likely effects) showed better performance in the year prior to signing a new contract than the previous year for foreign important defenders (decreased number of red cards), national important midfielders (increased number of minutes played), foreign important forwards (increased minutes played and defense), and national important forwards (increased minutes played). In addition, performance was lower the year after signing the contract compared to the previous one for less important defenders (decreasing defense), national less important midfielders (decreased minutes played), and foreign less important forwards (decreased defense). On the other hand, the players showed better performance in defense and more minutes played the year after signing the contract for less important defenders, national less important midfielders, and foreign less important forwards. These results may assist coaches to decide on when a new contract should be signed or the duration of the contract.


#13 Assessing the Validity of the MyJump2 App for Measuring Different Jumps in Professional Cerebral Palsy Football Players: An Experimental Study
Reference: JMIR Mhealth Uhealth. 2019 Jan 30;7(1):e11099. doi: 10.2196/11099.
Authors: Coswig V, Silva AACE, Barbalho M, Faria FR, Nogueira CD, Borges M, Buratti JR, Vieira IB, Román FJL, Gorla JI
Download link: https://mhealth.jmir.org/2019/1/e11099/pdf
Summary: Vertical jumps can be used to assess neuromuscular status in sports performance. This is particularly important in Cerebral Palsy Football (CP Football) because players are exposed to high injury risk, but it may be complicated because the gold standard for assessing jump performance is scarce in field evaluation. Thus, field techniques, such as mobile apps, have been proposed as an alternative method for solving this problem. This study aims to evaluate the reliability of the measures of the MyJump2 app to assess vertical jump performance in professional CP Football. We assessed 40 male CP Football athletes (age 28.1 [SD 1.4] years, weight 72.5 [SD 6.2] kg, and height 176 [SD 4.2] cm) through the countermovement jump (CMJ) and squat jump (SJ) using a contact mat. At the same time, we assessed the athletes using the MyJump2 app. There were no significant differences between the instruments in SJ height (P=.12) and flight time (P=.15). Additionally, there were no significant differences between the instruments for CMJ in jump height (P=.16) and flight time (P=.13). In addition, it was observed that there were significant and strong intraclass correlations in all SJ variables varying from 0.86 to 0.89 (both P<.001), which was classified as "almost perfect." Similar results were observed in all variables from the CMJ, varying from 0.92 to 0.96 (both P ≤.001). We conclude that the MyJump2 app presents high validity and reliability for measuring jump height and flight time of the SJ and CMJ in CP Football athletes.


#14 Does the Environment Influence the Frequency of Concussion Incidence in Professional Football?
Reference: Cureus. 2018 Nov 23;10(11):e3627. doi: 10.7759/cureus.3627.
Authors: Haider S, Kaye-Kauderer HP, Maniya AY, Dai JB, Li AY, Post AF, Sobotka S, Adams R, Gometz A, Lovell MR, Choudhri TF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347446/pdf/cureus-0010-00000003627.pdf
Summary: Background Sports-related concussion is a major cause of mild traumatic brain injury (mTBI). It is possible that environmental factors, such as temperature, humidity, and stadium's altitude, may influence the overall incidence of concussions during a game. Purpose To examine the impact of environmental factors, such as temperature, humidity, barometric pressure, and dew point, on concussion incidence. Methods Public Broadcasting Service (PBS) FRONTLINE Concussion Watch was used to collect injury data on 32 NFL teams during regular season games from 2012 to 2015. Weather data points were collected from Weather Underground. Concussion incidence per game, the probability of a concussion during a game, and a difference in mean game-day temperature, humidity, dew point, and barometric pressure between concussion and concussion-free games were calculated. Our analysis included t-tests, analysis of variance (ANOVA), multivariate correlation tests, and logistic and Poisson regression.  Results Overall, 564 concussions were reported. There were 411 games with concussions and 549 games without concussions. We observed a significant decrease in concussion incidence with increasing temperature, both when the temperature was divided into 20oF increments or into quartiles (p = 0.005 and p = 0.002, respectively). We identified a statistically significant lower mean-game day temperature in concussion games compared to concussion-free games (p < 0.0006). We also observed a significant decrease in the incidence of concussion per game with increasing dew point. There was no significant difference in concussion incidence in barometric pressure and humidity. The logistic regression model predicted a decrease in the probability of a concussion in games with higher temperatures and dew points. Conclusions National Football League (NFL) players experienced an increased risk of concussion during football games played in colder temperatures and at lower dew points. Further research on environmental effects on concussions may aid in improving player safety in football leagues.

Sat

02

Mar

2019

Latest research in football - week 4 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Head impact magnitudes that occur from purposeful soccer heading depend on the game scenario and head impact location
Reference: Musculoskelet Sci Pract. 2019 Jan 24;40:53-57. doi: 10.1016/j.msksp.2019.01.009. [Epub ahead of print]
Authors: Harriss A, Johnson AM, Walton DM, Dickey JP
Summary: This study quantified the linear and angular kinematics that result from purposeful heading during youth soccer games, and the influence of game scenario and head impact location on these magnitudes. This observational study recruited thirty-six female soccer players (13.4 ± 0.9 years old) from three elite youth soccer teams (U13, U14, U15) and followed for an entire soccer season. Players wore wireless sensors during each game to quantify head impact magnitudes. A total of 60 regular season games (20 games per team) were video recorded, and purposeful heading events were categorized by game scenario (e.g. throw in), and head impact location (e.g. front of head). Game scenario had a statistically significant effect on the linear head acceleration, and rotational head velocity, that resulted from purposeful headers. Rotational velocity from purposeful headers varied significantly between head impact locations, with impacts to the top of the head (improper technique) resulting in larger peak rotational velocities than impacts to the front of the head (proper technique); this was also the case for the linear acceleration for punts. Our findings suggest that the magnitude for both linear and angular head impact kinematics depend on the game scenario and head impact location. Headers performed with the top of the head (improper technique) result in larger rotational velocities compared to the front of the head (proper technique). Accordingly, youth players should be educated on how to execute proper heading technique to reduce head impact accelerations.


#2 Jumping Asymmetries Are Associated With Speed, Change of Direction Speed, and Jump Performance in Elite Academy Soccer Players
Reference: J Strength Cond Res. 2019 Jan 30. doi: 10.1519/JSC.0000000000003058. [Epub ahead of print]
Authors: Bishop C, Brashill C, Abbott W, Read P, Lake J, Turner A
Summary: The aim of this study was to establish interlimb asymmetries across different age groups in elite academy male soccer players and to examine any relationships between asymmetry and measures of physical performance. Fifty-one players from an English Premier League soccer academy were split into under-23 (n = 21), under-18 (n = 14), and under-16 (n = 16) groups and performed bilateral and unilateral countermovement jumps, 5-, 10-, and 20-m sprints, and a 505 change of direction speed tests. All tests showed low variability (coefficient of variation ≤ 2.5%) and good to excellent reliability (intraclass correlation coefficient = 0.80-0.99). A 1-way analysis of variance showed that the under-23 group was significantly faster than the under-16 group during the 20-m sprint (2.90 vs. 2.98 s; p = 0.02; effect size = 0.94). No other significant differences were present between groups. Interlimb asymmetry was quantified from the single-leg countermovement jump, and no significant differences in the magnitude of asymmetry were present between groups. However, multiple significant correlations were present in each age group between asymmetry and physical performance tests, all of which were indicative of reduced athletic performance. Results from this study show that although interlimb asymmetry scores are comparable across age groups in elite academy soccer players, differences as low as 5% are associated with reduced physical performance during jumping, sprinting, and change of direction speed tasks. This study suggests the importance of monitoring jump height asymmetries in elite academy soccer players.


#3 Coaching Efficacy, Player Perceptions of Coaches' Leadership Styles, and Team Performance in Premier League Soccer
Reference: Res Q Exerc Sport. 2019 Feb 1:1-9. doi: 10.1080/02701367.2018.1563277. [Epub ahead of print]
Authors: Keatlholetswe L, Malete L
Summary: The coaching competency research has demonstrated the role of coaching efficacy and coaching behaviors on various athlete outcomes. However, athlete perceptions of these relationships and how they affect performance are less understood. This study examined if coaching efficacy is predictive of player perceptions of coaches' leadership styles, team atmosphere, and team performance in a soccer season. Fifteen male premier league soccer coaches (Mage = 45.27, SD = 6.07) and 226 players (Mage = 25.66, SD = 3.96) from Botswana participated in the study. All participants completed a background information questionnaire. Coaches completed the Coaching Efficacy Scale. Players rated their coaches' leadership styles using the Revised Leadership Scale for Sports as well as team atmosphere. Team performance was based on position in the league log and player ratings of the teams' performance. Findings showed that coaches' self-ratings on technique efficacy predicted player perceptions of the coaches' use of all six leadership styles. Game strategy efficacy predicted higher team atmosphere and team performance. Motivation efficacy was not significantly associated with player perceptions of the coaches' use of any of the leadership styles, while character building efficacy was negatively associated with the various leadership styles. Findings provide support to previous research evidence linking higher coaching efficacy, leadership styles, and team outcomes. The study expands the emergent research within the coaching competency literature that examines player perceptions of coaches' behaviors and leadership styles.


#4 The Effect of In-Season Traditional and Explosive Resistance Training Programs on Strength, Jump Height, and Speed in Recreational Soccer Players
Reference: Res Q Exerc Sport. 2019 Feb 1:1-8. doi: 10.1080/02701367.2018.1563276. [Epub ahead of print]
Authors: Griffiths B, Grant J, Langdown L, Gentil P, Fisher J, Steele J
Summary: Resistance training is often performed in a traditional training style using deliberate relatively longer repetition durations or in an explosive training style using maximal intended velocities and relatively shorter repetition durations. Both improve strength, "power" (impulsivity), and speed. This study compared explosive and traditional training over a 6-week intervention in 30 healthy young adult male recreational soccer players. Full body supervised resistance training was performed 2 times a week using 3 sets of each exercise at 80% of one repetition maximum to momentary failure. Outcomes were Smith machine squat 1 repetition maximum, 10 meter sprint time, and countermovement jump. Both groups significantly improved all outcomes based on 95% confidence intervals not crossing zero. There were no between-group differences for squat 1 RM (TRAD = 6.3[5.1 to 7.6] kg, EXP = 5.2[3.9 to 6.4] kg) or 10 meter sprint (TRAD = -0.05[-0.07 to -0.04] s, EXP = -0.05[-0.06 to -0.03] s). Explosive group had a significantly greater increase in countermovement jump compared to the traditional group (TRAD = 0.7[0.3 to 1.1] cm, EXP = 1.3[0.9 to 1.7] cm). Both the traditional training and explosive training performed to momentary failure produced significant improvements in strength, speed, and jump performance. Strength gains are similar independent of intended movement speed. However, speed and jump performance changes are marginal with resistance training.


#5 A match-day analysis of the movement profiles of substitutes from a professional soccer club before and after pitch-entry
Reference:  PLoS One. 2019 Jan 31;14(1):e0211563. doi: 10.1371/journal.pone.0211563. eCollection 2019.
Authors: Hills SP, Barrett S, Feltbower RG, Barwood MJ, Radcliffe JN, Cooke CB, Kilduff LP, Cook CJ, Russell M
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0211563&type=printable
Summary: Whilst the movement demands of players completing a whole soccer match have been well-documented, comparable information relating to substitutes is sparse. Therefore, this study profiled the match-day physical activities performed by soccer substitutes, focusing separately on the pre and post pitch-entry periods. Seventeen English Championship soccer players were monitored using 10 Hz Micromechanical Electrical Systems (MEMS) devices during 13 matches in which they participated as substitutes (35 observations). Twenty physical variables were examined and data were organised by bouts of warm-up activity (pre pitch-entry), and five min epochs of match-play (post pitch-entry). Linear mixed modelling assessed the influence of time (i.e., 'bout' and 'epoch'), playing position, and match scoreline. Substitutes performed 3±1 rewarm-up bouts∙player-1∙match-1. Compared to the initial warm-up, each rewarm-up was shorter (-19.7 to -22.9 min) and elicited less distance (-606 to -741 m), whilst relative total distances were higher (+26 to +69 m∙min-1). Relative total (+13.4 m∙min-1) and high-speed (+0.4 m∙min-1) distances covered during rewarm-ups increased (p <0.001) with proximity to pitch-entry. Players covered more (+3.2 m; p = 0.047) high-speed distance per rewarm-up when the assessed team was losing compared with when winning at the time of pitch-entry. For 10 out of 20 variables measured after pitch-entry, values reduced from 0-5 min thereafter, and substitutes covered greater (p ˂0.05) total (+67 to +93 m) and high-speed (+14 to +33 m) distances during the first five min of match-play versus all subsequent epochs. Midfielders covered more distance (+41 m) per five min epoch than both attackers (p ˂0.001) and defenders (p = 0.016). Acknowledging the limitations of a solely movement data approach and the potential influence of other match-specific factors, such findings provide novel insights into the match-day demands faced by substitute soccer players. Future research opportunities exist to better understand the match-day practices of this population.


#6 Effect of Heavy Resisted Sled Sprint Training During the Competitive Season on Sprint and Change-of-Direction Performance in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 31:1-25. doi: 10.1123/ijspp.2018-0592. [Epub ahead of print]
Authors: McMorrow BJ, Ditroilo M, Egan B
Summary: Resisted sled sprinting (RSS) is an effective tool for improving sprint performance over short distances, but the effect on change-of-direction (COD) performance is largely unknown. The present study investigated the effect of heavy RSS training during the competitive season on sprint and COD performance in professional soccer players. Over six weeks in-season, a RSS training group (n=6) performed RSS at a sled load of 30% of body mass for a total programme running distance of 800 m, while an unresisted sprint (URS) training group (n=7) performed the same distance of unresisted sprinting. A 20 m maximal sprint with split times measured at 5, 10 and 20 m, and the sprint 9-3-6-3-9 m with 180° turns COD test were performed before and after the intervention. Sprint performance (mean; 95% confidence limits; qualitative inference) was improved in both groups over 5 m (URS, 5.1%; -2.4, 12.7; likely moderate; RSS, 5.4%; 0.5, 10.4; likely moderate), 10 m (URS, 3.9%; -0.3, 8.1; very likely moderate; RSS, 5.0%; 1.8, 8.0; very likely large), and 20 m (URS, 2.0%; -0.6, 4.5; likely moderate; RSS (3.0%; 1.7, 4.4; very likely moderate). COD was improved in both groups (URS, 3.7%; 2.2, 5.2; most likely large; RSS, 3.3%; 1.6, 5.0; most likely moderate). Between-group differences were unclear. Heavy RSS or URS training matched for running distance were similarly effective at improving sprint and COD performance in professional soccer players when performed in the competitive phase of the season.


#7 Predicting Future Perceived Wellness in Professional Soccer: The Role of Preceding Load and Wellness
Reference: Int J Sports Physiol Perform. 2019 Jan 31:1-25. doi: 10.1123/ijspp.2017-0864. [Epub ahead of print]
Authors: Jaspers A, De Beéck TO, Brink MS, Frencken WGP, Staes F, Davis JJ, Helsen WF
Summary: The influence of preceding load and perceived wellness on the future perceived wellness of professional soccer players is unexamined. This paper simultaneously evaluates the external and internal load for different time frames in combination with pre-session wellness to predict future perceived wellness using machine learning techniques. Training and match data were collected from a professional soccer team. The external load was measured using global positioning system technology and accelerometry. The internal load was obtained using the RPE multiplied by duration. Predictive models were constructed using gradient boosted regression trees (GBRT) and one naive baseline method. The individual predictions of future wellness items (i.e., fatigue, sleep quality, general muscle soreness, stress levels, and mood) were based on a set of external and internal load indicators in combination with pre-session wellness. The external and internal load was computed for acute and cumulative time frames. The GBRT model's performance on predicting the reported future wellness was compared to the naive baseline's performance by means of absolute prediction error and effect size. The GBRT model outperformed the baseline for the wellness items fatigue, general muscle soreness, stress levels and mood. Additionally, only the combination of external load, internal load, and pre-session perceived wellness resulted in non-trivial effects for predicting future wellness. Including the cumulative load did not improve the predictive performances. The findings may indicate the importance of including both acute load and pre-session perceived wellness in a broad monitoring approach in professional soccer.


#8 A tactical comparison of the 4-2-3-1 and 3-5-2 formation in soccer: A theory-oriented, experimental approach based on positional data in an 11 vs. 11 game set-up
Reference: PLoS One. 2019 Jan 30;14(1):e0210191. doi: 10.1371/journal.pone.0210191. eCollection 2019.
Authors: Memmert D, Raabe D, Schwab S, Rein R
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0210191&type=printable
Summary: The presented field experiment in an 11 vs. 11 soccer game set-up is the first to examine the impact of different formations (e.g. 4-2-3-1 vs. 3-5-2) on tactical key performance indicators (KPIs) using positional data in a controlled experiment. The data were gathered using player tracking systems (1 Hz) in a standardized 11 vs. 11 soccer game. The KPIs were measured using dynamical positioning variables like Effective Playing Space, Player Length per Width ratio, Team Separateness, Space Control Gain, and Pressure Passing Efficiency. Within the experimental positional data analysis paradigm, neither of the team formations showed differences in Effective Playing Space, Team Separateness, or Space Control Gain. However, as a theory-based approach predicted, a 3-5-2 formation for the Player Length per Width ratio and Pressure Passing Efficiency exceeded the 4-2-3-1 formation. Practice task designs which manipulate team formations therefore significantly influence the emergent behavioral dynamics and need to be considered when planning and monitoring performance. Accordingly, an experimental positional data analysis paradigm is a useful approach to enable the development and validation of theory-oriented models in the area of performance analysis in sports games.


#9 Time Trends of Head Injuries Over Multiple Seasons in Professional Male Football (Soccer)
Reference: Sports Med Int Open. 2019 Jan 28;3(1):E6-E11. doi: 10.1055/a-0808-2551. eCollection 2019 Jan.
Authors: Beaudouin F, der Fünten KA, Tröß T, Reinsberger C, Meyer T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6349547/pdf/10-1055-a-0808-2551.pdf
Summary: The present study aimed to investigate time trends of head injuries and their injury mechanisms since a rule change as monitoring may help to identify causes of head injuries and may advance head injury prevention efforts. Based on continuously recorded data from the German football magazine "kicker Sportmagazin ® " as well as other media sources, a database of head injuries in the 1 st German male Bundesliga was generated comprising 11 seasons (2006/07-2016/17). Injury mechanisms were analysed from video recordings. Injury incidence rates (IR) and 95% confidence intervals (95% CI) were calculated. Time trends were analysed via linear regression. Two hundred thirty-eight match head injuries occurred (IR 1.77/1000 match hours, 95% CI 1.56-2.01). There were no significant seasonal changes, expressed as annual average year-on-year change, in IRs over the 11-year period for total head injuries (p=0.693), facial/head fractures (p=0.455), lacerations/abrasions (p=0.162), and head contusions (p=0.106). The annual average year-on-year increase for concussion was 6.4% (p=0.004). Five head injury mechanisms were identified. There were no seasonal changes in injury mechanisms over the study period. The concussion subcategory increased slightly over the seasons, which may either be a result of increasing match dynamics or raised awareness among team physicians and players.

Thu

14

Feb

2019

Latest research in football - week 3 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Resisted Sprint With Changes of Direction Training Through Several Relative Loads on Physical Performance in Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 24:1-20. doi: 10.1123/ijspp.2018-0702. [Epub ahead of print]
Authors: Rodríguez-Osorio D, Gonzalo-Skok O, Pareja-Blanco F
Summary: The purpose was to compare the effects of resisted change of direction (COD) movements, using several relative loads, on soccer players' physical performance. Fifty-four male soccer players were randomly assigned to one of the following 3 groups, which differed only in the magnitude of the external load used during the COD training: COD training without external load (COD-0; n = 16); COD training with a 12.5% body mass (BM) external load (COD-12.5; n = 19); and COD training with a 50% BM external load (COD-50; n = 19). Participants performed the specific COD training twice per week for 6 weeks. Before and after the training period a battery of tests was completed: countermovement jump (CMJ); 30 m running sprint (time in 10-m [T10], 20-m [T20] and 30-m [T30]); L-RUN test; and V-CUT test. Within-group comparisons showed substantial improvements in CMJ and T10 (likely) in COD-0, whereas CMJ, T10 and T20 were substantially enhanced (possibly to likely) in COD-50. COD-12.5 induced substantial improvements in all analyzed variables (likely to most likely). Between-groups comparisons showed better effects on all analyzed variables for COD-12.5 compared to COD-0 group (possibly to very likely), whereas COD-50 only showed possibly better effects than COD-0 on T10. In addition, COD-12.5 induced a better effect on L-RUN and V-CUT tests than COD-50 (possibly to likely). These results indicate that COD training, especially moderate load (12.5% BM) resisted COD training, may have a positive effect on COD skills, running sprint performance and jumping ability in young soccer players.


#2 The Arrowhead Agility Test: Reliability, Minimum Detectable Change, and Practical Applications in Soccer Players
Reference: J Strength Cond Res. 2019 Jan 22. doi: 10.1519/JSC.0000000000002987. [Epub ahead of print]
Authors: Rago V, Brito J, Figueiredo P, Ermidis G, Barreira D, Rebelo A
Summary: Four independent studies were conducted to examine the utility of the arrowhead agility test (AAT) to measure change of direction (COD) capacity in soccer players, specifically, (a) intersession reliability and minimum detectable change (n = 24); (b) power-dependent abilities associated with AAT performance (n = 56); and (c) fatigue sensitivity (n = 20); differences between competitive levels and age groups (n = 264). Irrespective of the AAT outcome measure (skillful side, less-skillful side, sum of both), intersession reliability and the ability to detect changes in performance were good (ICC = 0.80-0.83; CV = 1.25-2.21%; smallest worthwhile change, 0.06-0.12 >SEM, 0.01-0.03) except for the asymmetry index. A 15-m sprint explained a significant amount of variance in COD (p < 0.01; R = 0.42). Arrowhead agility test performance did not change from the prematch toward half time (p = 0.21). However, reduced COD performance was observed after an intense period in the second half and after the game, compared with prematch and half-time performance (p < 0.05; effect size [ES] = -0.85 to 0.42). Irrespective of age group, national players were more agile than regional players (p < 0.05; ES = -1.97 to -0.36). Moreover, independently of their competitive level, senior and U18 players had a better performance than U16 (p < 0.05; ES = -2.33 to -0.84), whereas no significant differences were observed between senior and U18. Percentiles were also reported in the results. The AAT is reliable to measure COD in soccer players. The test may simultaneously encompass 15-m sprint testing but should be implemented independently to countermovement jump. Furthermore, the test is sensitive to match-induced fatigue during the second half and discriminates players from different competitive levels.


#3 External Cueing Influences Drop Jump Performance in Trained Young Soccer Players
Reference: J Strength Cond Res. 2019 Jan 22. doi: 10.1519/JSC.0000000000002935. [Epub ahead of print]
Authors: Oliver JL, Barillas SR, Lloyd RS, Moore I, Pedley J
Summary: Drop jump (DJ) characteristics provide insight on power production and injury risk. The purpose of this study was to investigate the effect of external cueing on DJ characteristics in young male soccer players. Fourteen academy soccer players performed DJs with 4 different conditions, control (CONT), contact cue (CC), height cue (HC), and quiet cue (QC). Performance measures were reactive strength index (RSI), jump height, ground contact time (GCT), and take-off impulse, with injury risk reflected by impact peak, impact timing, and landing impulse. Contact cue showed a very large significant reduction in GCT (effect size [ES] > 2.0, p < 0.05), and moderate to large increase in RSI, landing impulse, and push-off impulse (ES 0.70-1.55, p < 0.05) compared with all other conditions. Contact cue also moderately increased impact peak when compared with HC and QC (ES ≥ 0.78, p < 0.05). Height cue led to a significant increase in jump height that was moderately greater than other external cues (ES ≥ 0.87, p < 0.05), but with only a small nonsignificant increase compared (ES 0.54, p > 0.05) with CONT. The data showed that all cues provided a specific response; CC reduced GCT and increased RSI, HC increased jump height, and QC reduced outcomes associated with injury risk. Height cue may be advantageous for young soccer players with a low training age because it shows a small to moderate increase in jump height without increasing injury risk. Young players may need to be safely progressed to be able to use a CC to facilitate high reactive strength without being exposed to undue injury risk.


#4 Measuring the Hip Adductor to Abductor Strength Ratio in Ice Hockey and Soccer Players: A Critically Appraised Topic
Reference: J Sport Rehabil. 2019 Jan 24:1-18. doi: 10.1123/jsr.2018-0250. [Epub ahead of print]
Author: Rodriguez R
Summary: Ice hockey and soccer are both dynamic sports that involve continuous, unpredictable play. These athletes consistently demonstrate higher rates of groin strains compared to other contact sports. Measuring the hip adductor/abductor ratio has the potential to expose at-risk players, reduce injury rates, and preserve groin health in players with chronic strains. What is the clinical utility of measuring the hip adductor/abductor ratio for pre-season and in-season ice hockey and soccer players? Three studies, all of which were prospective cohort designs, were included. One study involved assessing preseason strength and flexibility as a risk factor for adductor strains in professional ice hockey players. Another study performed in the same professional hockey team used preseason hip adductor/abductor strength ratios to screen for those players who would benefit from a strengthening intervention aimed at reducing the incidence of adductor strains. The final study, which was performed in elite U17 soccer players, assessed the effectiveness of monthly in-season strength monitoring as a guide to trigger in-season interventions to decrease injury incidence. Measuring the hip adductor/abductor strength ratio in hockey and soccer players can be a beneficial pre-season and in-season tool to predict future groin strain risk and screen for athletes who might benefit from a strengthening intervention. Evidence exists to support monitoring the hip adductor/abductor strength ratio to assess and reduce the risk of adductor strains in ice hockey and soccer players.


#5 Realistic Soccer-Specific Virtual Environment Exposes High-Risk Lower Extremity Biomechanics
Reference: J Sport Rehabil. 2019 Jan 24:1-23. doi: 10.1123/jsr.2018-0237. [Epub ahead of print]
Authors: DiCesare CA, Kiefer AW, Bonnette SH, Myer GD
Summary: Laboratory-based biomechanical analyses of sport-relevant movements such as landing and cutting have classically been used to quantify kinematic and kinetic factors in the context of injury risk, which are then used to inform targeted interventions designed to improve risky movement patterns during sport. However, the non-contextual nature of standard assessments presents challenges for assessing sport-relevant skill transfer. It may be more effective to examine injury-risk biomechanics on individuals performing sport-specific tasks within the actual sport environment, or more feasibly, within a simulated sport environment using virtual reality (VR). The purpose of this study was to examine biomechanical differences exhibited by athletes during a jump-landing task performed as part of both a standard biomechanical assessment and a sport-specific VR-based assessment.  22 female adolescent soccer athletes (age = 16.0 ± 1.4 years; height = 165.6 ± 4.9 cm; weight = 60.2 ± 11.4 kg) participated in this study. The landing performance of was analyzed for a drop vertical jump task and a VR-based, soccer-specific corner-kick scenario in which the athletes were required to jump to head a virtual soccer ball and land. Hip, knee and ankle joint kinematic differences in the frontal and sagittal planes were used as main outcome measures. Athletes exhibited reduced hip and ankle flexion, hip abduction, and frontal plane ankle excursion during landing in realistic sport scenario compared to the standard drop vertical jump task. VR-based assessments can provide a sport-specific context in which to assess biomechanical deficits that predispose athletes for lower extremity injury and offer a promising approach to better evaluate skill transfer to sport which can guide future injury prevention efforts.


#6 Associations Between Selected Training Stress Measures and Fitness Changes in Male Soccer Players
Reference: Int J Sports Physiol Perform. 2019 Jan 24:1-23. doi: 10.1123/ijspp.2018-0462. [Epub ahead of print]
Authors: Rabbani A, Kargarfard M, Castagna C, Clemente FM, Twist C
Summary: The purpose of this study was to investigate the relationship of accumulated Global Positioning System (GPS)-accelerometer-based and heart rate (HR)-based training metrics to changes in high-intensity intermittent running capacity during an in-season phase in professional soccer players. Eleven male professional players (mean ± SD, age: 27.2 ± 4.5 years) performed the 30-15 Intermittent Fitness Test (30-15IFT) before and after a five-week in-season training phase, and the final velocity (VIFT) was considered as players' high-intensity intermittent running capacity. During all sessions, Edwards' training impulse (Edwards' TRIMP), Banister's TRIMP, Z5 TRIMP, training duration, total distance covered, New Body Load (NBL), high-intensity running performance (distance covered above 14.4 km·h-1), and very high-intensity running performance (distance covered above 19.8 km·h-1) were recorded. The players' VIFT showed a most likely moderate improvement (+4.3%, 90% confidence limits [3.1; 5.5%], effect size ES, 0.70 [0.51; 0.89]). Accumulated NBL, Banister's TRIMP and Edwards' TRIMP showed large associations (r = 0.51 to 0.54) with changes in VIFT. Very large relationship was also observed between accumulated Z5 TRIMP (r= 0.72) with changes in VIFT. Large-to-nearly perfect within-individual relationships were observed between NBL and some of the other training metrics (i.e., Edwards' TRIMP, Banister's TRIMP, training duration, and total distance) in 10 out of 11 players. HR-based training metrics can be used to monitor high-intensity intermittent running capacity changes in professional soccer players. The dose-response relationship is also largely detected using accelerometer-based metrics (i.e., NBL) to track changes in high-intensity intermittent running capacity of professional soccer players.


#7 Learning to Rate Player Positioning in Soccer
Reference: Big Data. 2019 Jan 23. doi: 10.1089/big.2018.0054. [Epub ahead of print]
Authors: Dick U, Brefeld U
Summary: We investigate how to learn functions that rate game situations on a soccer pitch according to their potential to lead to successful attacks. We follow a purely data-driven approach using techniques from deep reinforcement learning to valuate multiplayer positionings based on positional data. Empirically, the predicted scores highly correlate with dangerousness of actual situations and show that rating of player positioning without expert knowledge is possible.


#8 Match Running Performance in Young Soccer Players: A Systematic Review
Reference: Sports Med. 2019 Jan 22. doi: 10.1007/s40279-018-01048-8. [Epub ahead of print]
Authors: Palucci Vieira LH, Carling C, Barbieri FA, Aquino R, Santiago PRP
Summary: To date, athletic performance has been extensively assessed in youth soccer players through laboratory and field testing. Only recently has running performance via time-motion analysis been assessed during match play. Match running data are often useful in a practical context to aid game understanding and decision making regarding training content and prescriptions. A plethora of previous reviews have collated and appraised the literature on time-motion analysis in professional senior players, but none have solely examined youth players. The aim of the present systematic review was to provide a critical appraisal and summary of the original research articles that have evaluated match running performance in young male soccer players. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, literature searches were performed in four databases: PubMed, ISI Web of Science, SPORTDiscus and SciELO. We used the following descriptors: soccer, football, young, youth, junior, physical performance, running performance, match running performance, movement patterns, time-motion analysis, distances covered, activity profile, work rate, match analysis, and match performance. Articles were included only if they were original articles written in the English language, studied populations of male children and/or adolescents (aged ≤ 20 years), were published/ahead of print on or before 31 December 2017 and showed at least one outcome measure regarding match running performance, such as total distance covered, peak game speed or indicators of activities performed at established speed thresholds. A total of 5801 records were found. After duplicates were removed and exclusion and inclusion criteria applied, 50 articles were included (n = 2615 participants). Their outcome measures were extracted and findings were synthesized. The majority of the reviewed papers covered the European continent (62%) and used global positioning systems (GPS) (64%). Measurement error of the tools used to obtain position data and running metrics was systematically overlooked among the studies. The main aims of studies were to examine differences across playing positions (20%), age groups (26%) and match halves (36%). Consistent findings pointed to the existence of positional role and age effects on match running output (using fixed running speed thresholds), but there was no clear consensus about reductions in activity over the course of match play. Congested schedules negatively affected players' running performance. While over 32% of all studies assessed the relationships between match running performance and physical capacity, biochemical markers and body composition, ~ 70% of these did not account for playing position. This review collated scientific evidence that can aid soccer conditioning professionals in understanding external match loads across youth categories. Coaches working with youth development programs should consider that data derived from a given population may not be relevant for other populations, since game rules, match format and configuration are essentially unstandardized among studies for age-matched players. Despite limited evidence, periodization training emphasizing technical-tactical content can improve match running performance. Occurrence of acute and residual impairments in the running performance of young soccer players is common. Prescription of postmatch recovery strategies, such as cold water immersion and spa treatment, can potentially help reduce these declines, although additional research is warranted. This review also highlighted areas requiring further investigation, such as the possible influence of environmental and contextual constraints and a more integrative approach combining tactical and technical data.


#9 Drop Jump Asymmetry is Associated with Reduced Sprint and Change-of-Direction Speed Performance in Adult Female Soccer Players
Reference: Sports (Basel). 2019 Jan 21;7(1). pii: E29. doi: 10.3390/sports7010029.
Authors: Bishop C, Turner A, Maloney S, Lake J, Loturco I, Bromley T, Read P
Download link: https://www.mdpi.com/2075-4663/7/1/29/pdf
Summary: Studies that examine the effects of inter-limb asymmetry on measures of physical performance are scarce, especially in adult female populations. The aim of the present study was to establish the relationship between inter-limb asymmetry and speed and change-of-direction speed (CODS) in adult female soccer players. Sixteen adult players performed a preseason test battery consisting of unilateral countermovement jump (CMJ), unilateral drop jump (DJ), 10 m, 30 m, and 505 CODS tests. Inter-limb asymmetry was calculated using a standard percentage difference equation for jump and CODS tests, and Pearson's r correlations were used to establish a relationship between asymmetry and physical performance as well as asymmetry scores themselves across tests. Jump-height asymmetry from the CMJ (8.65%) and DJ (9.16%) tests were significantly greater (p < 0.05) than asymmetry during the 505 test (2.39%). CMJ-height asymmetry showed no association with speed or CODS. However, DJ asymmetries were significantly associated with slower 10 m (r = 0.52; p < 0.05), 30 m (r = 0.58; p < 0.05), and 505 (r = 0.52⁻0.66; p < 0.05) performance. No significant relationships were present between asymmetry scores across tests. These findings suggest that the DJ is a useful test for detecting existent between-limb asymmetry that might in turn be detrimental to speed and CODS performance. Furthermore, the lack of relationships present between different asymmetry scores indicates the individual nature of asymmetry and precludes the use of a single test for the assessment of inter-limb differences.


#10 Hip Arthroscopic Management Can Improve Osteitis Pubis and Bone Marrow Edema in Competitive Soccer Players With Femoroacetabular Impingement
Reference: Am J Sports Med. 2019 Jan 21:363546518819099. doi: 10.1177/0363546518819099. [Epub ahead of print]
Authors: Saito M, Utsunomiya H, Hatakeyama A, Nakashima H, Nishimura H, Matsuda DK, Sakai A, Uchida S
Summary: There is a dearth of knowledge regarding the correlation between femoroacetabular impingement (FAI) and osteitis pubis (OP) among symptomatic soccer players. The purpose was to elucidate whether arthroscopic FAI correction is effective for young competitive soccer players with FAI combined with OP or perisymphyseal pubic bone marrow edema (BME). A total of 577 consecutive patients who underwent arthroscopic FAI correction were retrospectively reviewed with a minimum 2-year follow-up. Competitive soccer players who were professional, college, and high school athletes were included. The authors assessed the modified Harris Hip Score and Nonarthritic Hip Score preoperatively and at 6 months, 1 year, and 2 years after surgery. In addition, players were divided into groups according to radiographic evidence of OP and BME (2 groups each). Clinical outcomes, return to play, and radiographic assessments were compared between groups. Twenty-eight hips met the inclusion criteria. The median modified Harris Hip Score significantly improved after hip arthroscopy (81.4, preoperatively; 95.7 at 6 months, P = .0065; 100 at 1 year, P = .0098; 100 at 2 years, P = .013). The median Nonarthritic Hip Score also significantly improved (75.0, preoperatively; 96.3 at 6 months, P = .015; 98.8 at 1 year, P = .0029; 100 at 2 years, P = .015). Furthermore, 92.0% of players returned to play soccer at the same or higher level of competition at a median 5.5 months (range, 4-15 months); 67.8% had radiological confirmation of OP; and 35.7% had pubic BME. The alpha angle was significantly higher in pubic BME group than the no-pubic BME group (64.8° vs 59.2°, P = .027), although there was no significant difference between the OP and no-OP groups. The prevalence of tenderness of the pubic symphysis significantly decreased preoperatively (32.1%) to postoperatively (3.6%). Magnetic resonance imaging findings confirmed that pubic BME disappeared in all players at a median 11 months (range, 6-36) after initial surgery. Arthroscopic management for FAI provides favorable clinical outcomes, a high rate of return to sports, and, when present, resolution of pubic BME among competitive soccer players.


#11 Effects of Combined Surfaces vs. Single-Surface Plyometric Training on Soccer Players' Physical Fitness
Reference: J Strength Cond Res. 2019 Jan 17. doi: 10.1519/JSC.0000000000002929. [Epub ahead of print]
Authors: Ramirez-Campillo R, Álvarez C, García-Pinillos F, García-Ramos A, Loturco I, Chaabene H, Granacher U
Summary: The aim of this study was to compare the effects of a 8-week plyometric jump training (PJT) performed on different surfaces (grass, land-dirt, sand, wood, gym mat, and tartan-track) vs. a single-surface PJT (grass) on components of physical fitness (muscle power, speed, and change-of-direction speed [CODS] tasks) and sport-specific performance (i.e., maximal kicking velocity [MKV]) in male soccer players aged 11-14 years. Athletes were randomly assigned to a combined surfaces PJT (PJTc, n = 8), a single-surface PJT (PJTs, n = 8), or an active control (CON, n = 7). Although the PJT group trained on grass, the PJTc trained on 6 different surfaces and equally distributed the total jump volume according to the surface. Pre-post tests were conducted on grass. Significant main effects of time were observed for the countermovement jump, the standing-long-jump, the 20-cm drop jump, 30-m sprint time, CODS, and MKV (all p < 0.001; d = 0.53-0.87). Group × time interactions were identified for all jump tests, MKV, 30-m sprint time, and CODS (all p < 0.001; d = 0.58-0.71) in favor of PJTc. No significant pre-post changes were observed in the CON (all p > 0.05; d = 0.07-0.1). In conclusion, PJT is effective in improving physical fitness in young soccer players when conducted in combination with regular soccer training. Although general fitness testing and PJTs were performed on grass, larger physical fitness improvements were found after PJTc. Thus, PJTc is recommended, as it provides a better overload stimulus compared with more conventional training overload (e.g., increase in training volume or intensity). Future studies still have to address the underlying physiological adaptations after PJTc.


#12 Effect of deep oscillation as a recovery method after fatiguing soccer training: A randomized cross-over study
Reference: J Exerc Sci Fit. 2018 Dec;16(3):112-117. doi: 10.1016/j.jesf.2018.10.004. Epub 2018 Oct 16.
Authors: von Stengel S, Teschler M, Weissenfels A, Willert S, Kemmler W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323303/pdf/main.pdf
Summary: In soccer the recovery time between matches is often not long enough for complete restoration. Insufficient recovery can result in reduced performance and a higher risk of injuries. The purpose of this study was to evaluate the potential of Deep Oscillation (DO) as a recovery method. In a randomized crossover study including 8 male soccer players (22 ± 3.3 years) the following parameters were evaluated directly before and 48 h after a fatiguing soccer-specific exercise: Maximum isokinetic strength of the leg and hip extensors and flexors (Con-Trex® Leg Press, Physiomed, Germany), rating of perceived exertion (RPE) during isokinetic testing (Borg scale 6-20), creatine kinase (CK) serum levels and Delayed Onset Muscle Soreness (DOMS; visual analogue scale 1-10). By random allocation, half of the group performed a DO self-treatment twice daily (4 applications of 15min each), whilst the other half received no intervention. 4 weeks later a cross-over was conducted. Two-way repeated measures analysis of variance was used to compare treatment versus control. A significant treatment effect was observed for maximum leg flexion strength (p = 0.03; DO: 125 ± 206 N vs. CG: -115 ± 194; p = 0.03) and for RPE (DO: -0.13 ± 0.64; vs. CG: +1.13 ± 1.36; p = 0.03). There was a trend to better recovery for maximum leg extension strength (DO: -31 ± 165 N vs. CG: -138 ± 212; p = 0.028), CK values (DO: 72 ± 331 U/ml vs. CG: 535 ± 797 U/ml; p = 0.15) and DOMS (DO: 3.4 ± 1.5 vs. CG: 4.1 ± 2.6; p = 0.49). In the present study we found significant effects of DO on maximum leg flexion strength and perceived rate of exertion. Other variables showed a consistent trend in favour of DO compared with the control without significance. DO seems to be a promising method to accelerate the time-course of peripheral recovery of muscle which should be addressed in larger studies in future.


#13 In season adaptations to intense intermittent training and sprint interval training in sub-elite football players
Reference: Scand J Med Sci Sports. 2019 Jan 24. doi: 10.1111/sms.13395. [Epub ahead of print]
Authors: Hostrup M, Gunnarsson TP, Fiorenza M, Mørch K, Onslev J, Pedersen KM, Bangsbo J
Summary: This study investigated the in-season effect of intensified training comparing the efficacy of duration-matched intense intermittent exercise training with sprint interval training in increasing intermittent running performance, sprint ability, and muscle content of proteins related to ion handling and metabolism in football players. After the first two weeks in the season, 20 sub-elite football players completed either 10 weeks of intense intermittent training using the 10-20-30 training concept (10-20-30, n=12) or sprint interval training (SIT, n=10; work/rest-ratio: 6-s/54-s) three times weekly, with a ~20% reduction in weekly training time. Before and after the intervention, players performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and a 30-m sprint test. Furthermore, players had a muscle biopsy taken from the vastus lateralis. Yo-Yo IR1 performance increased by 330 m (95%CI: 178-482, P≤0.01) in 10-20-30, whereas no change was observed in SIT. Sprint time did not change in 10-20-30, but decreased by 0.04 s (95%CI: 0.00-0.09, P≤0.05) in SIT. Muscle content of HADHA (24%, P≤0.01), PDH-E1α (40%, P≤0.01), complex I-V of the electron transport chain (ETC) (51%, P≤0.01) and Na+ ,K+ -ATPase subunits α2 (33%, P≤0.05) and β1 (27%, P≤0.05) increased in 10-20-30, whereas content of DHPR (27%, P≤0.01) and complex I-V of the ETC (31%, P≤0.05) increased in SIT. Intense intermittent training, combining short sprints and a high aerobic load, is superior to regular sprint interval training in increasing intense intermittent running performance during a Yo-Yo IR1 test and muscle content of PDH-E1α and HADHA in sub-elite football players.

Wed

13

Feb

2019

Latest research in football - week 2 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Impact of Sports-Related Subconcussive Injuries in Soccer Players
Reference: Semin Speech Lang. 2019 Feb;40(1):57-64. doi: 10.1055/s-0038-1676365. Epub 2019 Jan 7.
Authors: Díaz-Rodríguez YI, Salvatore AP
Summary: Sports-related subconcussive impacts to the head are receiving increased interest. Recent evidence indicates that subconcussive impacts will have greater relevance across time because of the number of repetitive impacts. Soccer players are at risk of receiving at least one impact during a soccer game. The authors review the cognitive-communication functioning following subconcussive head injuries in youth and recommendations for baseline assessments and cognitive-communication dysfunctions after subconcussive impacts in youth. The review is followed by a description and discussion of a study that assessed the cognitive-communicative dysfunction in young soccer players prior to and following a series of soccer matches and recommendations for monitoring recovery of cognitive-communication.


#2 Practical Torso Cooling During Soccer-Specific Exercise in the Heat
Reference: J Athl Train. 2018 Nov;53(11):1089-1097. doi: 10.4085/1062-6050-417-17. Epub 2019 Jan 7.
Authors: Parris K, Tyler CJ
Summary: Precooling and midevent cooling of the torso using cooling vests can improve exercise performance in the heat with or without physiological changes; however, the effects of such cooling during intermittent exercise in the heat are unknown. The objective of the study was to investigate the effects of torso cooling during intermittent exercise in the heat (35°C, 50% relative humdity) on sprint performance and the physiological and perceptual responses to the exercise. Ten non-heat-acclimated, male soccer players (age = 25 ± 2 years, height = 1.77 ± 0.06 m, mass = 72.9 ± 7.6 kg) participated in this study. Two 90-minute bouts of soccer-specific intermittent running in the heat: 1 trial with a cooling vest worn during the exercise and 1 trial without a cooling vest. Each trial comprised two 45-minute periods separated by approximately 15 minutes of seated rest in cool conditions (approximately 23°C, 50% relative humdity). Peak sprint speed, rectal temperature (Tr), mean-weighted skin temperature (Tsk), heart rate (HR), rating of perceived exertion (RPE), and thermal sensation (TS) were measured every 5 minutes. Peak sprint performance was largely unaffected by the cooling vest. The Tr, Tsk, HR, RPE, and TS were unaffected in the cooling-vest trial during the first 45 minutes, but Tr rose at a slower rate in the cooling-vest trial (0.026°C.min-1 ± 0.008°C.min-1) than in the no-vest trial (0.032°C.min-1 ± 0.009°C.min-1). During the second 45-minute period, Tr, Tr rate of rise, Tsk, RPE, and TS were lower in the cooling-vest trial (Hedges g range, 0.55-0.84), but mean HR was unaffected. Wearing a cooling vest during soccer-specific intermittent running in the heat reduced physiological and perceptual strain but did not increase peak sprint speed.


#3 Bone quality in young adults with intellectual disability involved in adapted competitive football
Reference: Eur J Sport Sci. 2019 Jan 9:1-10. doi: 10.1080/17461391.2018.1563633. [Epub ahead of print]
Authors: Lizondo V, Caplliure-Llopis J, Escrivá D, De La Rubia JE, Barrios C
Summary: The objective of this study was to analyse bone quality parameters of football players with intellectual disability (ID) participating in adapted competitive football. Sixty-seven male football players with ID were studied: 22 with Down syndrome (DS) and 45 without DS. The average age was 26 years (range: 16 ̶ 50 years). A group of 25 age-matched sedentary individuals with ID (11 DS and 14 non-DS) and another group of 20 healthy participants of the same age group not involved in competitive football were comparatively analysed. There were no differences in the bone quality parameters when the healthy sedentary individuals were compared with both the sedentary and the football players with ID. However, the speed of sound (SOS), T-score, and estimated bone mineral density (BMD) were of higher values in the football players with ID than in the sedentary ID group (p < 0.05). On comparing the football players with non-DS ID with the sedentary non-DS individuals, significant differences were noted in SOS (p < 0.01), T-scores (p < 0.01), and estimated BMD (p < 0.01). Four of the 45 non-DS (8.9%) and none of the football players with DS had T-scores less than -1.5. Two of the 14 sedentary non-DS participants (14.3%) had T-scores indicating osteoporosis. In summary, the ID population actively involved in football showed higher values of bone mass parameters than their sedentary ID and healthy peers. The participants with non-DS ID showed a higher prevalence of osteoporosis than the football players with DS. Participation in sports seems to prevent bone loss in individuals with ID.


#4 Dual Kinect v2 system can capture lower limb kinematics reasonably well in a clinical setting: concurrent validity of a dual camera markerless motion capture system in professional football players
Reference: BMJ Open Sport Exerc Med. 2018 Dec 17;4(1):e000441. doi: 10.1136/bmjsem-2018-000441. eCollection 2018.
Authors: Kotsifaki A, Whiteley R, Hansen C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307561/pdf/bmjsem-2018-000441.pdf
Summary: The purpose was to determine whether a dual-camera markerless motion capture system can be used for lower limb kinematic evaluation in athletes in a preseason screening setting. Thirty-four (n=34) healthy athletes participated. Three dimensional lower limb kinematics during three functional tests: Single Leg Squat (SLS), Single Leg Jump, Modified Counter-movement Jump. The tests were simultaneously recorded using both a marker-based motion capture system and two Kinect v2 cameras using iPi Mocap Studio software. Excellent agreement between systems for the flexion/extension range of motion of the shin during all tests and for the thigh abduction/adduction during SLS were seen. For peak angles, results showed excellent agreement for knee flexion. Poor correlation was seen for the rotation movements. This study supports the use of dual Kinect v2 configuration with the iPi software as a valid tool for assessment of sagittal and frontal plane hip and knee kinematic parameters but not axial rotation in athletes.


#5 Don't Turn Blind! The Relationship Between Exploration Before Ball Possession and On-Ball Performance in Association Football
Reference: Front Psychol. 2018 Dec 10;9:2520. doi: 10.3389/fpsyg.2018.02520. eCollection 2018.
Authors: McGuckian TB, Cole MH, Jordet G, Chalkley D, Pepping GJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6295565/pdf/fpsyg-09-02520.pdf
Summary: Visual exploratory action - scanning movements expressed through left and right rotation of the head - allows perception of a surrounding environment and supports prospective actions. In the dynamically changing football environment, the extent to which exploratory action benefits a player's subsequent performance with the ball is likely influenced by how and when the exploratory action occurs. Although few studies have examined the relationship between visual exploration and on-pitch football performance, it has been reported that a higher frequency of exploratory head movement up to 10-s before receiving the ball increases the likelihood of successful performance with the ball. This study investigated the relationship between head turn frequency and head turn excursion, and how and when exploratory head movement - within 10-s before ball possession - is related to performance with the ball in 11v11 match-play. Thirty-two semi-elite football players competed in 11v11 match-play. Head turn frequency and head turn excursion before ball possession were quantified with wearable inertial measurement units, and actions with the ball were coded via notational analysis. Odds ratio calculations were conducted to determine the associations between exploration variables and on-ball performance outcomes. A total of 783 actions with the ball were analyzed. Results revealed a strong relationship between head turn frequency and head turn excursion. Further, a higher than average head turn frequency and head turn excursion before receiving the ball resulted in a higher likelihood of turning with the ball, playing a pass in the attacking direction, and playing a pass to an area that is opposite to which it was received from. The strength of these outcomes varied for different time periods before receiving the ball. When players explored their environment with higher than average head turn frequency and excursion, they used more complex action opportunities afforded by the surrounding environment. Considerations for future research and practical implications are discussed.


#6 Use of viscosupplementation for the recovery of active football players complaining of knee pain
Reference: Open Access J Sports Med. 2018 Dec 24;10:11-15. doi: 10.2147/OAJSM.S164693. eCollection 2019.
Authors: Migliore A, Giannini S, Bizzi E, Massafra U, Cassol M, Abilius MJM, Boni G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6307486/pdf/oajsm-10-011.pdf
Summary: The aim of this study is to investigate the effect of intra-articular hyaluronic acid administration in active football players complaining of knee pain after sports activity. Efficacy and safety profiles of intra-articular hyaluronic acid and time needed for football players to recover and restart sports activity were examined. Clinical data of active football players reporting knee pain after sports activity were included in this retrospective study. All patients who received an intra-articular injection at time 0 and after 2 weeks were included in the study. Patients underwent laboratory examination, knee X-ray, ultrasound, and clinical examination before receiving the intra-articular injection. Effusions or cysts were drained before injections. Lequesne index score, pain visual analog scale (VAS) score, and patient's global assessment score were recorded at time 0 (day of the first injection), 1 and 2 days after the first injection, at 2 weeks (day of the second injection), and at follow-up visits. Only data from patients completing the follow-up were analyzed. Data from 17 patients were analyzed: 16 males and one female, of which three were professional players (two males and one female) and 14 were nonprofessional players. The mean age of patients was 39.8±11.8 years. Two patients (one male and one female) showed joint effusion. Two patients reported relevant joint pain after injection that regressed without any medication. At the first week, all parameters examined indicated improvement that was maintained until the end of follow-up. One day after the first and second injection, patients reported a slight increase in pain VAS score, which was not statistically significant, and the pain resolved after 1 day. All patients successfully restarted playing after the first injection within 3.1±2.0 days and kept playing after the second injection following our indication (1 day of break). The use of a medium-molecular weight hyaluronic acid in football players affected by knee osteoarthritis seems efficacious and safe and resulted, in our experience, a stable improvement of symptoms; moreover, it allowed a rapid restart of sports activity. Larger studies on larger populations are needed to confirm these findings.


#7 The value of tibial mounted inertial measurement units to quantify running kinetics in elite football (soccer) players. A reliability and agreement study using a research orientated and a clinically orientated system
Reference: J Electromyogr Kinesiol. 2019 Jan 7;44:156-164. doi: 10.1016/j.jelekin.2019.01.001. [Epub ahead of print]
Authors: Hughes T, Jones RK, Starbuck C, Sergeant JC, Callaghan MJ
Summary: In elite football, measurement of running kinetics with inertial measurement units (IMUs) may be useful as a component of periodic health examination (PHE). This study determined the reliability of, and agreement between a research orientated IMU and clinically orientated IMU system for initial peak acceleration (IPA) and IPA symmetry index (SI) measurement during running in elite footballers. On consecutive days, 16 participants performed treadmill running at 14kmph and 18kmph. Both IMUs measured IPA and IPA SI concurrently. All measurements had good or excellent within-session reliability (intraclass correlation coefficient (ICC2,1) range = 0.79-0.96, IPA standard error of measurement (SEM) range = 0.19-0.62 g, IPA SI SEM range = 2.50-8.05%). Only the research orientated IMU demonstrated acceptable minimal detectable changes (MDCs) for IPA at 14kmph (range = 7.46-9.80%) and IPA SI at both speeds (range = 6.92-9.21%). Considering both systems, between-session IPA reliability ranged from fair to good (ICC2,1 range = 0.63-0.87, SEM range = 0.51-1.10 g) and poor to fair for IPA SI (ICC2,1 range = 0.32-0.65, SEM range = 8.07-11.18%). All MDCs were >10%. For IPA and SI, the 95% levels of agreement indicated poor between system agreement. Therefore, the use of IMUs to evaluate treadmill running kinetics cannot be recommended in this population as a PHE test to identify prognostic factors for injuries or for rehabilitation purposes.


#8 Premenstrual Syndrome, Inflammatory Status, and Mood States in Soccer Players
Reference: Neuroimmunomodulation. 2019 Jan 17:1-6. doi: 10.1159/000494559. [Epub ahead of print]
Authors: Foster R, Vaisberg M, Bachi ALL, Dos Santos JMB, de Paula Vieira R, Luna-Junior LA, Araújo MP, Parmigiano TR, Borges F, Di-Bella ZIKJ
Summary: The aim was to evaluate the relationship between the inflammatory profile and mood states in the different phases of the menstrual cycle in soccer players with and without premenstrual syndrome (PMS). Data on the menstrual cycle and mood states were collected using the Daily Symptom Report and the Brunel Mood Scale. Cytokine and stress hormone concentrations were measured in urine by flow cytometry before and after a game in the luteal phase and in the follicular phase of one menstrual cycle. In all, 59.6% of the athletes had PMS. The PMS group showed higher concentrations of interleukin (IL)-1β, IL-6, and IL-8 than the athletes without PMS. After the game, IL-6 decreased in the follicular phase and the luteal phase. The tumor necrosis factor-α levels were higher in the group without PMS during the post-game follicular phase than before the game. In the PMS group, tension was higher in the follicular phase before the game and depression was higher in the pre-game luteal phase than in the group without PMS. The PMS group also presented a negative correlation between depression and IL-10 levels in the pre-game follicular phase. Finally, in the pre-game luteal phase were found positive correlations between growth hormone and IL-10. PMS influences the inflammatory condition related to mood states and stress hormones in female soccer players.


#9 Nutrition-Related Considerations in Soccer: A Review
Reference: Am J Orthop (Belle Mead NJ). 2018 Dec;47(12). doi: 10.12788/ajo.2018.0100.
Authors: Keen R
Summary: Soccer is the world's most popular sport. As the sport has grown, so have the physical demands and the search for ways to edge out the competition with the use of sports science and nutrition. The demands, which include intense training, ≥90 minutes matches, congested fixtures, and travel, lead to increased energy and nutrient requirements, stress on the body, and risk of impaired sleep cycles. Identifying key areas to enhance a player's performance is an ongoing effort because of individual differences. Moreover, new information is being discovered via research, and advancing technology to measure performance is always evolving. This article focuses on the core nutrition principles known to lay the foundation for a better soccer player. These principles are obvious for some; however, nutrition and hydration are often undervalued, leaving the individual player with the responsibility to eat right. This review addresses the most applicable nutrition-related recommendations for soccer players.


#10 Limb Differences in Unipedal Balance Performance in Young Male Soccer Players with Different Ages
Reference: Sports (Basel). 2019 Jan 11;7(1). pii: E20. doi: 10.3390/sports7010020.
Authors: Muehlbauer T, Schwiertz G, Brueckner D, Kiss R, Panzer S
Download link: https://www.mdpi.com/2075-4663/7/1/20/pdf
Summary: In soccer, the dominant leg is frequently used for passing and kicking while standing on the non-dominant leg. Consequently, postural control in the standing leg might be superior compared to the kicking leg and is further enhanced with increasing age (i.e., level of playing experience). Unfortunately, leg differences in postural control are associated with an increased risk of injuries. Thus, we examined differences between limbs in unipedal balance performance in young soccer players at different ages. Performance in the Lower Quarter Y Balance Test (YBT-LQ) of the dominant and non-dominant leg and anthropometry was assessed in 76 young male soccer players (under-13 years [U13]: n = 19, U15: n = 14, U17: n = 21, U19: n = 22). Maximal reach distances (% leg length) and the composite scores were used for further analyses. Statistical analyses yielded no statistically significant main effects of leg or significant Leg × Age interactions, irrespective of the measure investigated. However, limb differences in the anterior reach direction were above the proposed cut-off value of >4 cm, which is indicative of increased injury risk. Further, statistically significant main effects of age were found for all investigated parameters, indicating larger reach distances in older (U19) compared to younger (U13) players (except for U15 players). Although reach differences between legs were non-significant, the value in the anterior reach direction was higher than the cut-off value of >4 cm in all age groups. This is indicative of an increased injury risk, and thus injury prevention programs should be part of the training of young soccer players.


#11 Recruiting Older Men to Walking Football: A Pilot Feasibility Study
Reference: Explore (NY). 2018 Dec 11. pii: S1550-8307(18)30194-0. doi: 10.1016/j.explore.2018.12.001. [Epub ahead of print]
Authors: McEwan G, Buchan D, Cowan D, Arthur R, Sanderson M, Macrae E
Summary: Walking football (soccer) has recently emerged as a physical activity option targeted at older males to enhance health and wellbeing. This pilot study aimed to examine the feasibility of recruiting and retaining males aged 50 years and over to an 8-week walking football programme in a professional football club. Participants were recruited via social media and assigned to an intervention group or a wait-list control group. The intervention group engaged in 1 h of walking football a week led by a community coach from the professional football club, followed by an optional social session in the club facility. Physiological and psychological outcome measures were obtained onsite at the football club facility (aiding compliance and retention) at baseline and following 8-weeks, from both groups. Semi-structured interviews were conducted after the 8-week programme and 1 year later, to explore motivations for engagement and the social impact. The opportunity to engage in football and the link to a professional football club were key attractions. All participants recruited were overweight, sedentary, exhibited blood pressures outside normal ranges, and all but two were hypertensive. Adherence to the programme was 90% over 8 weeks, and of the participants who were contacted after one year, all (n = 6) had maintained engagement in walking football. Walking football is therefore a feasible, cost-effective method of recruiting and retaining males aged 50 years and over to a physical activity programme, though attrition is to be expected.

Thu

07

Feb

2019

Latest research in football - week 1 - 2019

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Visualizing a Team's Goal Chances in Soccer from Attacking Events: A Bayesian Inference Approach
Reference: Big Data. 2018 Dec 1;6(4):271-290. doi: 10.1089/big.2018.0071. Epub 2018 Dec 13.
Authors: Whitaker GA, Silva R, Edwards D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306690/pdf/big.2018.0071.pdf
Summary: We consider the task of determining the number of chances a soccer team creates, along with the composite nature of each chance-the players involved and the locations on the pitch of the assist and the chance. We infer this information using data consisting solely of attacking events, which the authors believe to be the first approach of its kind. We propose an interpretable Bayesian inference approach and implement a Poisson model to capture chance occurrences, from which we infer team abilities. We then use a Gaussian mixture model to capture the areas on the pitch a player makes an assist/takes a chance. This approach allows the visualization of differences between players in the way they approach attacking play (making assists/taking chances). We apply the resulting scheme to the 2016/2017 English Premier League, capturing team abilities to create chances, before highlighting key areas where players have most impact.


#2 Predicting the defensive performance of individual players in one vs. one soccer games
Reference: PLoS One. 2018 Dec 31;13(12):e0209822. doi: 10.1371/journal.pone.0209822. eCollection 2018.
Authors: Wilson RS, Smith NMA, Santiago PRP, Camata T, Ramos SP, Caetano FG, Cunha SA, Sandes de Souza AP, Moura FA
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209822&type=printable
Summary: The aim of this study was to use technical skill and physical performance and coaches' rankings to predict the defensive performance of junior soccer players. Twenty-one male players (mean age 17.2 years, SD = 1.1) were recruited from the Londrina Junior Team Football Academy in Brazil. Data were collected during regular training sessions. After participants had warmed up, players were asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0-1.37 radians.m-1). In addition, four coaches were asked to rank the players from best to worst in defensive ability. Dribbling, sprinting, and coaches' rankings were then compared with defending performance as assessed in the one vs. one competitions (N = 1090 paired-trials: 40-65 trials per individual), in which they acted as defender or attacker in turn. When defending, the objective was to steal the ball or prevent the attacker from running around them with the ball into a scoring zone. Testing occurred over three days. Overall, dribbling performance (r = 0.56; P = 0.008) and coaches' ranking (r = 0.59; P = 0.004) were significantly related to defensive ability; sprinting performance was not (r = 0.20; P = 0.38). Though dribbling performance and coaches' ranking each explained 30% and 37% of the variance in defensive performance, respectively, the two predictors were not related (r = 0.27; P = 0.23), so combined these traits explained more than half the variance in defensive performance. In conclusion, the current study demonstrates that including only one metric of closed-skill performance-dribbling speed-doubles the ability of coaches to identify their best defensive players in one vs. one scenarios.


#3 Patellar and Achilles Tendon Stiffness in Elite Soccer Players Assessed Using Myotonometric Measurements
Reference: Sports Health. 2019 Jan 2:1941738118820517. doi: 10.1177/1941738118820517. [Epub ahead of print]
Authors: Cristi-Sánchez I, Danes-Daetz C, Neira A, Ferrada W, Yáñez Díaz R, Silvestre Aguirre R
Summary: Tendon overuse injuries are an issue in elite footballers (soccer players) and may affect tendon function. Achilles and patellar tendinopathy are the most frequent pathologies. Tendon stiffness, the relationship between the force applied to a tendon and the displacement exerted, may help represent tendon function. Stiffness is affected by training and pathology. Nevertheless, information regarding this mechanical property is lacking for elite soccer athletes. Achilles and patellar tendon stiffness assessed using myotonometric measurements will be greater in elite soccer athletes than in control participants. Forty-nine elite soccer athletes and 49 control participants were evaluated during the 2017 preseason. A handheld device was used to measure Achilles and patellar tendon stiffness. Dominant and nondominant limbs were assessed for both groups. A significantly stiffer patellar tendon was found for both the dominant and the nondominant limb in the elite soccer athletes compared with the control group. Nevertheless, no differences were found in Achilles tendon stiffness between groups. When comparing between playing positions in soccer athletes, no significant differences were found for both tendons. Greater patellar tendon stiffness may be related to an improvement in force transmission during muscle contraction. On the other hand, it seems that after years of professional training, Achilles tendon stiffness does not change, conserving the storing-releasing function of elastic energy. The nonsignificant differences between positions may be attributable to the years of homogeneous training that the players underwent. The present study shows another technique for measuring mechanical properties of tendons in soccer athletes that could be used in clinical settings. In the future, this technique may help clinicians choose the best exercise protocol to address impairments in tendon stiffness.


#4 Examination of Physical Characteristics and Positional Differences in Professional Soccer Players in Qatar
Reference: Sports (Basel). 2018 Dec 31;7(1). pii: E9. doi: 10.3390/sports7010009.
Authors: Wik EH, Auliffe SM, Read PJ
Download link: https://www.mdpi.com/2075-4663/7/1/9/pdf
Summary: Physical characteristics in professional soccer differ between competition levels and playing positions, and normative data aid practitioners in profiling their players to optimize performance and reduce injury risk. Given the paucity of research in Arabic soccer populations, the purpose of this study was to provide position-specific normative values for professional players competing in the Qatar Stars League. One hundred and ninety-five players completed a musculoskeletal assessment as part of an annual periodic health examination. Tests included measures of range of motion (hip, ankle, and hamstring), bilateral and unilateral jump performance, and quadriceps/hamstring (isokinetic/NordBord), hip adduction/abduction (eccentric), and groin (isometric) strength. Descriptive data were examined, and positional differences were analyzed using a one-way analysis of variance (ANOVA). Goalkeepers were significantly heavier (p < 0.01), had a higher body mass index (p < 0.05) than outfield positions and demonstrated greater absolute strength. Defenders were the strongest relative to body mass, and these differences were significant (p < 0.05) versus goalkeepers and strikers. No meaningful between-group comparisons were apparent for jumping or range of motion tests. Compared to mean values from other professional leagues, soccer players in Qatar appear to be shorter, lighter and display inferior strength and jump capacities. These data can be used to tailor training and rehabilitation programs to the specifics of the league and position in which the athletes compete.


#5 Photobiomodulation therapy as a tool to prevent hamstring strain injuries by reducing soccer-induced fatigue on hamstring muscles
Reference: Lasers Med Sci. 2019 Jan 3. doi: 10.1007/s10103-018-02709-w. [Epub ahead of print]
Authors: Dornelles MP, Fritsch CG, Sonda FC, Johnson DS, Leal-Junior ECP, Vaz MA, Baroni BM
Summary: Muscle fatigue is a potential risk factor for hamstring strain injuries in soccer players. The aim of this study was to verify the effect of photobiomodulation therapy (PBMT) on the hamstrings' muscle fatigue of soccer players during a simulated match. Twelve male amateur soccer players (~ 25 years) participated in this randomized, crossover, double-blinded, placebo-controlled trial. The volunteers were evaluated in two sessions, with a minimum 7-day interval. At each session, volunteers received either PBMT (300 J per thigh) or placebo treatment on the hamstrings prior to the simulated soccer match. Muscle strength and functional capacity were evaluated through isokinetic dynamometry and countermovement jump (CMJ) tests, respectively, before and immediately after the simulated soccer match. Players had lower reductions on hamstring eccentric peak torque [4.85% (ES = 0.31) vs. 8.72% (ES = 0.50)], hamstring-to-quadriceps torque ratio [3.60% (ES = 0.24) vs. 7.75% (ES = 0.50)], and CMJ height [1.77% (ES = 0.09) vs. 5.47% (ES = 0.32)] when treated with PBMT compared to placebo. Magnitude-based inference supports that PBMT promoted 75%, 69%, and 53% chances for beneficial effects on hamstring eccentric peak torque, hamstring-to-quadriceps torque ratio, and CMJ height, respectively, compared to placebo treatment. In conclusion, PBMT applied before a simulated soccer match proved to be effective in attenuating the hamstrings' muscle fatigue. These findings support PBMT as a promising tool to prevent hamstring strain injury in soccer players.


#6 Accelerations - a new approach to quantify physical performance decline in male elite soccer?
Reference: Eur J Sport Sci. 2019 Jan 11:1-9. doi: 10.1080/17461391.2019.1566403. [Epub ahead of print]
Authors: Dalen T, Lorås H, Hjelde GH, Kjøsnes TN, Wisløff U
Summary: The aim of the current study was (1) to investigate whether the number of accelerations is a more precise estimate of performance decline in soccer compared to distances with high-speed running (HSR) and (2) to compare changes in the number of accelerations and HSR distances across playing positions in order to examine whether the match profiles of the physical measures are consistent or demonstrate high interposition variability. The dataset includes domestic home games (N = 34) over three full seasons (2012-2014) for a team in the Norwegian Elite League. The change in the number of accelerations throughout the match demonstrates a more clear pattern compared to the distance covered by HSR. In numbers of accelerations, a systematic and linear decrease can be observed throughout the match, with 34% less accelerations from the first to the last 5-minute period of the game (6.7 vs. 4.4 accelerations). This pattern of results captures the change in the number of accelerations across all positions. HSR distance had more variability during the match. All five positions investigated displayed a similar trend in accelerations and HSR profiles after the peak periods in each half. In contrast to the absolute number of accelerations, there were major positional differences in the mean HSR distance during the match. Our data suggest a more visible performance decline in the number of accelerations from the start to the end of the game, than the decline in the distance covered by HSR distance.


#7 A Nationwide Follow-up Survey on the Effectiveness of an Implemented Neuromuscular Training Program to Reduce Acute Knee Injuries in Soccer Players
Reference: Orthop J Sports Med. 2018 Dec 21;6(12):2325967118813841. doi: 10.1177/2325967118813841. eCollection 2018 Dec.
Authors: Åman M, Larsén K, Forssblad M, Näsmark A, Waldén M, Hägglund M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6304704/pdf/10.1177_2325967118813841.pdf
Summary: A cruciate ligament (CL) injury is a severe injury in soccer. Neuromuscular training programs have a well-documented preventive effect, but there are few studies on the effectiveness of such a program at a national level. The Swedish Knee Control Program (KCP) was found to be effective in preventing CL injuries in youth female soccer players. The KCP was implemented nationwide in Sweden in 2010. The purpose was to evaluate the effectiveness of the Swedish KCP in reducing acute knee injuries in soccer players at a nationwide level. All licensed soccer players in Sweden are covered by the same insurance company. Using this insurance database, around 17,500 acute knee injuries that were reported to the insurance company between 2006 and 2015 were included in the study. By matching the number of licensed soccer players with the number of reported injuries each year, the annual incidence of knee and CL injuries was able to be calculated. To evaluate the spread of the KCP nationally, a questionnaire was sent to all 24 Swedish district football associations (FAs) with questions regarding KCP education. The number of downloads of the KCP mobile application (app) was obtained. The incidence of CL injuries decreased during the study period for both male (from 2.9 to 2.4 per 1000 player-years) and female players (from 4.9 to 3.9 per 1000 player-years). The overall incidence of knee injuries decreased in both male (from 5.6 to 4.6 per 1000 player-years) and female players (from 8.7 to 6.4 per 1000 player-years). Comparing before and after the nationwide implementation of the KCP, there was a decrease in the incidence of CL injuries by 6% (rate ratio [RR], 0.94 [95% CI, 0.89-0.98]) in male players and 13% (RR, 0.87 [95% CI, 0.81-0.92]) in female players and a decrease in the incidence of knee injuries by 8% (RR, 0.92 [95% CI, 0.89-0.96]) and 21% (RR, 0.79 [95% CI, 0.75-0.83]), respectively (P < .01 for all). This trend corresponded to a reduction of approximately 100 CL injuries each year in Sweden. A total of 21 of 24 district FAs held organized KCP educational courses during the study period. The percentage of district FAs holding KCP courses was between 46% and 79% each year. There were 101,236 downloads of the KCP app. The KCP can be considered partially implemented nationwide, and the incidence of knee and CL injuries has decreased in both sexes at a nationwide level.


#8 Cardio respiratory response: Validation of new modifications of Bruce protocol for exercise testing and training in elite Saudi triathlon and soccer players
Reference: Saudi J Biol Sci. 2019 Jan;26(1):105-111. doi: 10.1016/j.sjbs.2017.05.009. Epub 2017 May 19.
Authors: Badawy MM, Muaidi QI
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6319022/pdf/main.pdf
Summary: The Bruce protocol is the traditional method used to assess maximal fitness level, although it may have limitations, such as its short duration and large work rate increases, with very high levels of exertion that consist of speed/incline combinations. Modifications have been added to elicit similar maximal fitness achievements. The authors of this experimental trial have proposed a new treadmill protocol that allows optimal test duration in conjunction with peak oxygen consumption 'VO2max', and with appropriate patient comfort and safety during both exercise testing and training. Twenty-two elite Saudi players, comprising eleven Saudi triathlon athletes, and eleven Saudi elite soccer players, BMI, body fat mass percentage, body fat free mass percentage. cardiovascular parameter; including, absolute and relative "VO2max" as well as maximal heart rate "HR max", were assessed during a graded treadmill running modified protocol, using a Quark Cardio Pulmonary Exercise Testing Unit (CPET). Descriptive statistics were used to obtain the anthropometric characteristics, including comparisons between the means, independent sample T-test and a regression analysis, to test the association of the protocol duration and the corresponding, dependent variables. It is often difficult to achieve a high cardiorespiratory response, VO2max, without an association to high values of HR max, and peak perceived exertion. This may lead to cardiovascular risk. Our new modifications can provide a practical, valid alternative protocol to be used comfortably both during exercise testing and training, rather than performance testing only, to achieve high VO2max with minimal cardiovascular stress.


#9 Knee Angle Affects Posterior Chain Muscle Activation During an Isometric Test Used in Soccer Players
Reference: Sports (Basel). 2019 Jan 4;7(1). pii: E13. doi: 10.3390/sports7010013.
Authors: Read PJ, Turner AN, Clarke R, Applebee S, Hughes J
Download link: https://www.mdpi.com/2075-4663/7/1/13/pdf
Summary: It has been suggested that altering the knee flexion angle during a commonly used supine isometric strength test developed with professional soccer players changes preferential hamstring muscle recruitment. The aim of this study was to examine the electromyography (EMG) knee joint-angle relationship during this test, as these data are currently unknown. Ten recreational male soccer athletes (age: 28 ± 2.4 years) were recruited and performed a supine isometric strength test on their dominant leg with the knee placed at two pre-selected flexion angles (30° and 90°). The surface EMG of the gluteus maximus, biceps femoris, semitendinosus, and medial gastrocnemius was measured, in addition to the within-session reliability (intraclass correlation coefficient (ICC) and coefficient of variation (CV)). Within-session reliability showed large variation dependent upon the test position and muscle measured (CV% = 8.8⁻36.1) Absolute mean EMG activity and percentage of maximum voluntary isometric contraction (MVIC) indicated different magnitudes of activation between the two test positions; however, significant mean differences were present for the biceps femoris only with greater activation recorded at the 30° knee angle (% MVIC: 31 ± 9 vs. 22 ± 7; p = 0.002). These differences (30% mean difference) were greater than the observed typical measurement error (CV% = 13.1⁻14.3 for the 90° and 30° test positions, respectively). Furthermore, the percentage MVIC showed a trend of heightened activation of all muscles with the knee positioned at 30°, but there was also more within-subject variation, and this was more pronounced for the gluteus maximus (CV% = 36.1 vs. 19.8) and medial gastrocnemius (CV% 31 vs. 22.6). These results indicate that biceps femoris and overall posterior chain muscle activation is increased with the knee positioned at 30° of flexion; however, the 90° angle displayed less variation in performance within individual participants, especially in the gluteus maximus and medial gastrocnemius. Thus, practitioners using this test to assess hamstring muscle strength should ensure appropriate familiarisation is afforded, and then may wish to prioritise the 30° knee position.


#10 Interpersonal Coordination in Soccer: Interpreting Literature to Enhance the Representativeness of Task Design, From Dyads to Teams
Reference: Front Psychol. 2018 Dec 11;9:2550. doi: 10.3389/fpsyg.2018.02550. eCollection 2018.
Authors: Santos R, Duarte R, Davids K, Teoldo I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6297834/pdf/fpsyg-09-02550.pdf
Summary: Interpersonal coordination in soccer has become a trending topic in sports sciences, and several studies have examined how interpersonal coordination unfolds at different levels (i.e., dyads, sub-groups, teams). Investigations have largely focused on interactional behaviors at micro and macro levels through tasks from dyadic (i.e., 1 vs. 1) to team (i.e., 11 vs. 11) levels. However, as the degree of representativeness of a task depends on the magnitude of the relationship between simulated and intended environments, it is necessary to address a discussion on the correspondence between competitive and practice/experimental settings in soccer. The aims of this paper are to: (i) provide a brief description of the main concepts underlying the subject of interpersonal coordination in sports teams; (ii) demonstrate, through exemplar research findings, how interpersonal coordination in soccer unfolds at different scales; and (iii), discuss how coaches and researchers may ensure representativeness for practice and experimental tasks. We observed that papers addressing the analysis of interpersonal coordination tendencies in soccer often resort to dyadic (one vs. one) or sub-group (many vs. many) experimental tasks, instead of full-sized (11 vs. 11) games. Consequently, the extent to which such patterns reflect those observed in competition is somewhat uncertain. The design of practice and/or experimental tasks that rely on sub-phases of the game (e.g., 1 vs. 1, 4 vs. 4) should ensure the preservation of players' behavior patterns in intended match conditions (11 vs. 11). This can be accomplished by measuring the level of action fidelity of the task, ensuring correspondence and successful transfer across contexts.


#12 Use of Saliva in Alternative to Serum Sampling to Monitor Biomarkers Modifications in Professional Soccer Players
Reference: Front Physiol. 2018 Dec 20;9:1828. doi: 10.3389/fphys.2018.01828. eCollection 2018.
Authors: Francavilla VC, Vitale F, Ciaccio M, Bongiovanni T, Marotta C, Caldarella R, Todaro L, Zarcone M, Muratore R, Bellia C, Francavilla G, Mazzucco W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306404/pdf/fphys-09-01828.pdf
Summary: We aimed to investigate the correlation between serum and salivary concentrations of steroid hormones and IgA, and the variation in concentrations of these biomarkers, across a soccer competitive season in a sample of players playing for an Italian major League team. Thirty-five elite male soccer players were recruited and assessed for salivary hormones (cortisol, testosterone, T/C‰ and DHEA-S) and IgA at three different time-points: (t1) after the pre-season period and 16 official matches played; (t2) after a winter break and three official matches played; (t3) 2 days after the final match of the championship and 19 matches played. Players were also tested for blood biomarkers (ser-C, ser-T, ser-T/C‰, ser-IgA, ACTH) at two detection times (t1 and t3). Blood samples were collected immediately after saliva sampling. The Spearman's rank correlation was used to explore the correlation between blood and salivary concentrations of cortisol, free testosterone and IgA in the different time points. One-way ANOVA and permutation test were performed to explore changes by time of hormones and IgA concentrations over the competitive season. We documented a positive correlation between serum and saliva concentrations for Cortisol at t1 (+58.2%; p-value = 0.002) and t3 (+54.2%; p-value = 0.018) and for Testosterone at t1 (+42.0%; p-value = 0.033). Moreover, a positive variation was documented across the season (D = t3-t1) for Cortisol (D = +6.83; SEM = ±2.70; Var% = +37.6; p-value = 0.032), Testosterone (D = +0.33; SEM = ±0.07; Var% = +27.3; p-value = 0.002) and DHEA-S (D = +44.48; SEM = ±18.54; Var% = +82.0; p-value = 0.042), while a decrease of sal-T/C ratio and no variation in salivary IgA concentrations were reported. In conclusion, our findings support for experimental use of saliva samples to monitor steroid hormones modifications in professional soccer players across a competitive season.

Wed

06

Feb

2019

Latest research in football - week 52 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Reliability and validity of field-based fitness tests in youth soccer players
Reference: Eur J Sport Sci. 2018 Dec 27:1-12. doi: 10.1080/17461391.2018.1556739. [Epub ahead of print]
Authors: Dugdale JH, Arthur CA, Sanders D, Hunter AM
Summary: This study aimed to establish between-day reliability and validity of commonly used field-based fitness tests in youth soccer players of varied age and playing standards, and to discriminate between players without ("unidentified") or with ("identified") a direct route to professional football through their existing club pathway. Three-hundred-and-seventy-three Scottish youth soccer players (U11-U17) from three different playing standards (amateur, development, performance) completed a battery of commonly used generic field-based fitness tests (grip dynamometry, standing broad jump, countermovement vertical jump, 505 (505COD) and T-Drill (T-Test) change of direction and 10/20 m sprint tests) on two separate occasions within 7-14 days. The majority of field-based fitness tests selected within this study proved to be reliable measures of physical performance (ICC = 0.83-0.97; p < .01). However, COD tests showed weaker reliability in younger participants (ICC = 0.57-0.79; p < .01). The field-based fitness testing battery significantly discriminated between the unidentified and identified players; χ2 (7) = 101.646, p < .001, with 70.2% of players being correctly classified. We have shown field-based fitness tests to be reliable measures of physical performance in youth soccer players. However, results from the 505COD and T-Test change of direction tests may be more variable in younger players, potentially due to complex demands of these tests and the limited training age established by these players. While the testing battery selected in this study was able to discriminate between unidentified and identified players, findings were inconsistent when attempting to differentiate between individual playing standards within the "identified" player group (development vs. performance).


#2 Factors influencing hydration status during a National Collegiate Athletics Association division 1 soccer preseason
Reference: J Sci Med Sport. 2018 Dec 14. pii: S1440-2440(18)31245-3. doi: 10.1016/j.jsams.2018.12.005. [Epub ahead of print]
Authors: Sekiguchi Y, Adams WM, Curtis RM, Benjamin CL, Casa DJ
Summary: The purpose was to investigate the roles that training load and environmental conditions have on fluid balance during a collegiate men's soccer preseason. Twenty-eight male collegiate soccer players (mean±SD; age, 20±1.7y; body mass (BM), 79.9±7.3kg; height, 180.9±6.8cm; body fat, 12.7±3.1%; VO2max, 50.7±4.3ml·kg-1·min-1) participated in this study. Prior to (PRE) and following (POST) each team session, BM, percent BM loss (%BML) and hydration status was measured. Participants donned a heart rate and GPS enabled monitor to measure training load. For all team activities, ambient temperature (TAMB) and relative humidity (RH) were obtained from the nearest local weather station. Participants consumed 500mL of water as part of the team-based hydration strategy before and after training session. Stepwise linear regression was used to identify the variables that predicted %BML. Significance was set a-priori p<0.05. Total distance covered predicted %BML during all preseason activities (r2=0.253, p<0.001), with TAMB and RH further adding to the model (r2=0.302, p<0.001). %BML never exceeded 2% of BM during any one session and daily variation in BM was <1% from baseline measures. Urine specific gravity was greater than 1.020 on 12/15days and UCOL was above 4 on 13/15days, indicating a state of hypohydration. Total distance covered was the best predictor for the extent of body water losses during a collegiate preseason. While the team-based hydration strategy during preseason was successful in minimizing fluid losses during activity, participants arrived hypohydrated 80% of the time, necessitating a greater focus on daily fluid needs.


#3 Assessing the validity of a video-based decision-making assessment for talent identification in youth soccer
Reference: J Sci Med Sport. 2018 Dec 21. pii: S1440-2440(18)30435-3. doi: 10.1016/j.jsams.2018.12.011. [Epub ahead of print]
Authors: Bennett KJM, Novak AR, Pluss MA, Coutts AJ, Fransen J
Summary: The aim was to investigate the construct and discriminant validity of a video-based decision-making assessment for talent identification in youth soccer. A total of 328 academy youth soccer players (tier one, tier two, and tier three) from three developmental stages (late childhood, early adolescence, and mid-adolescence) participated in this study. The control group consisted of 59 youth athletes with no soccer experience in the last five years. Players completed a video-based decision-making assessment on an iPad, with response accuracy and response time recorded for various attacking situations (2 vs. 1, 3 vs. 1, 3 vs. 2, 4 vs. 3, and 5 vs. 3). The video-based decision-making assessment showed some construct validity. Response times were significantly faster in early and mid-adolescent players when compared to those in the late childhood group. Furthermore, an overall decline in decision-making performance (i.e. decrease in response accuracy and increase in response time) was observed from the 2 vs. 1 to the 4 vs. 3 situations. The video-based decision-making assessment lacked discriminant validity as minimal differences between academies were evident for response accuracy and response time. Only response accuracy was able to discriminate youth academy soccer players from the control group to some extent. Coaches and sporting professionals should apply caution when interpreting data from practical, video-based decision-making assessments. There is currently limited conclusive evidence supporting the effectiveness of these assessments for talent identification.


#4 Influences of Synchronized Metronome Training on Soccer Players' Timing Ability, Performance Accuracy, and Lower-Limb Kinematics
Reference: Front Psychol. 2018 Dec 7;9:2469. doi: 10.3389/fpsyg.2018.02469. eCollection 2018.
Authors: Rönnqvist L, McDonald R, Sommer M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292953/pdf/fpsyg-09-02469.pdf
Summary: Planning and performance of all complex movement requires timing, integration, and coordination between sensory-perception and motor production to be successful. Despite this, there is limited research into "if" and "how" timing training may influence movement performance in athletes. The aim of the present study was to investigate the effect of synchronized metronome training (SMT) on sensorimotor timing ability, and in view of that, if improved timing may be transferred to lower-limb movement planning, precision performance, and kinematics. The sample consisted of 24 female elite- and semi-elite soccer players, randomly assigned to receive SMT and a control group. The SMT group received 12 sessions of Interactive Metronome® (IM) training over 4 weeks. At pre- and post-test, timing-precision was assessed through hand and feet movement synchronization with rhythmic sound; and leg-movements performance accuracy, duration, and kinematics were recorded during embodied high cognitive-load stepping task (6 trials×20 s) by use of a optoelectronic motion capture system. Pre- to post-test comparisons showed significant timing improvements as an effect of the IM training. Significant pre- to post-test improvements on the stepping task performance were seen in an increasing number of accurate foot taps during the stepping task sequence and by shorter duration for the SMT-group only. No evident pre- to post-test effects of SMT on the kinematic parameters investigated were found. These findings signify that the guided attention and working-memory functioning may be positively affected by SMT training; thereby, resulting in better motor planning, performance, and movement precision. Still, independent of group and test-occasion, significant correlations were found between the participants' outcome performance differences and the kinematic parameters. It was found that a decreasing 3D movement distance and less segmented movements correlating negatively, and increasing velocity (speed) positively, with accuracy and performance duration, respectively. These findings are likely associated with inter-individual variations in the nature of higher-order cognitive processing capacity due to the highly cognitive demanding stepping task.


#5 Amyotrophic Lateral Sclerosis and soccer: an internet survey of 29 Italian players
Reference: Ann Ist Super Sanita. 2018 Oct-Dec;54(4):364-369. doi: 10.4415/ANN_18_04_14.
Authors: Vanacore N, Barbariol P, Caffari B, Lacorte E, Bacigalupo I, Spila Alegiani S
Download link: http://old.iss.it/binary/publ/cont/ANN_18_04_14.pdf
Summary: Previous epidemiological studies reported a significantly higher risk of Amyotrophic Lateral Sclerosis (ALS) in Italian male soccer players. As a consequence, sports newspapers and news agencies focused on this issue and spread the news of 51 male soccer players with a reported diagnosis of ALS. We searched news on male Italian national soccer players with a reported diagnosis of ALS quoted from January 1, 1950 to July 31, 2016 in at least two Internet web sites or in books by journalists. A total of 39 male soccer players with a reported diagnosis of ALS were identified. Subjects were born from 1905 to 1973, 32 were currently deceased, 6 were still living, while the status of 1 player was unknown. All gathered information was available for 29 soccer players. The group had a mean age at diagnosis of 45.3 ± 12.2 years, a mean age at onset of symptoms of 46.4 ± 12.1 years, and a mean age at death of 50.9 ± 12.3 years. A significant inverse correlation between year of birth and age at onset of symptoms was observed, with a younger age at onset of symptoms in soccer players born in more recent years (r = -0.65, p < 0.01). Italian male soccer players with a reported diagnosis of ALS have a significantly younger age at diagnosis when compared to other European patients with ALS. Results support a possible relationship between soccer and the risk of ALS. We believe that further research is urgently needed in this field.


#6 Dark Chocolate Intake Positively Modulates Redox Status and Markers of Muscular Damage in Elite Football Athletes: A Randomized Controlled Study
Reference: Oxid Med Cell Longev. 2018 Nov 21;2018:4061901. doi: 10.1155/2018/4061901. eCollection 2018.
Authors: Cavarretta E, Peruzzi M, Del Vescovo R, Di Pilla F, Gobbi G, Serdoz A, Ferrara R, Schirone L, Sciarretta S, Nocella C, De Falco E, Schiavon S, Biondi-Zoccai G, Frati G, Carnevale R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280237/pdf/OMCL2018-4061901.pdf
Summary: Intensive physical exercise may cause increase oxidative stress and muscular injury in elite football athletes. The aim of this study was to exploit the effect of cocoa polyphenols on oxidative stress and muscular injuries induced by intensive physical exercise in elite football players. Oxidant/antioxidant status and markers of muscle damage were evaluated in 24 elite football players and 15 controls. Furthermore, the 24 elite football players were randomly assigned to either a dark chocolate (>85% cocoa) intake (n = 12) or a control group (n = 12) for 30 days in a randomized controlled trial. Oxidative stress, antioxidant status, and muscle damage were assessed at baseline and after 30 days of chocolate intake. Compared to controls, elite football players showed lower antioxidant power and higher oxidative stress paralleled by an increase in muscle damage markers. After 30 days of dark chocolate intake, an increased antioxidant power was found in elite athletes assuming dark chocolate. Moreover, a significant reduction in muscle damage markers (CK and LDH, p < 0.001) was observed. In the control group, no changes were observed with the exception of an increase of sNox2-dp, H2O2, and myoglobin. A simple linear regression analysis showed that sNox2-dp was associated with a significant increase in muscle damage biomarker release (p = 0.001). An in vitro study also confirmed that polyphenol extracts significantly decreased oxidative stress in murine myoblast cell line C2C12-derived. These results indicate that polyphenol-rich nutrient supplementation by means of dark chocolate positively modulates redox status and reduced exercise-induced muscular injury biomarkers in elite football athletes.


#7 "Macro-structure" of developmental participation histories and "micro-structure" of practice of German female world-class and national-class football players
Reference: J Sports Sci. 2018 Dec 24:1-9. doi: 10.1080/02640414.2018.1558744. [Epub ahead of print]
Authors: Güllich A
Summary: The study examined the "micro-structure" of football practice and the "macro-structure" of participation history of female professional football players. Participants were 29 German 1st league (Bundesliga) players, 14 of whom played on the senior national team (Olympic Champion in 2016). A questionnaire recorded the players' positions, proportions of physical conditioning, drill-type skill exercises and playing forms within coach-led football practice, and the volume of coach-led practice and peer-led play, in both football and other sports, from childhood to adulthood. Analyses revealed that most athletes played various attacker and defender positions during development. National team players differed from their Bundesliga peers by less physical conditioning and greater proportions of playing forms within football practice. National team players also accumulated less total football practice until age 18 years, but more peer-led football and coach-led practice in other sports compared to their Bundesliga counterparts. Based on these variables, a binary logistic regression classified 93% of the national team and Bundesliga players correctly. Conclusion: A combination of long-term coach-led football practice involving a relatively large proportion of playing forms with considerable childhood/adolescent peer-led football play and coach-led practice in other sports may have facilitated adult performance among German female world-class football players.


#8 Comparison of head impact exposure in practice drills among multiple youth football teams
Reference: J Neurosurg Pediatr. 2018 Dec 21:1-9. doi: 10.3171/2018.9.PEDS18314. [Epub ahead of print]
Authors: Kelley ME, Espeland MA, Flood WC, Powers AK, Whitlow CT, Maldjian JA, Stitzel JD, Urban JE
Summary: Limiting contact in football practice can reduce the number of head impacts a player receives, but further research is needed to inform the modification of optimal drills that mitigate head impact exposure (HIE) while the player develops the skills needed to safely play the game. This study aimed to compare HIE in practice drills among 6 youth football teams and to evaluate the effect of a team on HIE. On-field head impact data were collected from athletes (ages 10-13 years) playing on 6 local youth football teams (teams A-F) during all practices using the Head Impact Telemetry System. Video was recorded and analyzed to verify and assign impacts to a specific drill. Drills were identified as follows: dummy/sled tackling, half install, install, install walk through, multiplayer tackle, Oklahoma, one-on-one, open field tackling, other, passing, position skill work, scrimmage, special teams, tackling drill stations, and technique. HIE was quantified in terms of impacts per player per minute (ppm) and peak linear and rotational head acceleration. Generalized linear models were used to assess differences in head impact magnitude and frequency among drills as well as among teams within the most common drills. Among 67 athlete-seasons, a total of 14,718 impacts during contact practices were collected and evaluated in this study. Among all 6 teams, the mean linear (p < 0.0001) and rotational (p < 0.0001) acceleration varied significantly among all drills. Open field tackling had significantly (p < 0.001) higher mean linear acceleration than all other drills. Multiplayer tackle had the highest mean impact rate (0.35 ppm). Significant variations in linear acceleration and impact rate were observed among teams within specific drills. Team A had the highest mean linear acceleration in install, one-on-one, and open field tackling and the highest mean impact rate in Oklahoma and position skill work. Although team A spent the greatest proportion of their practice on minimal- or no-player versus player contact drills (27%) compared to other teams, they had the highest median (20.2g) and 95th percentile (56.4g) linear acceleration in practice. Full-speed tackling and blocking drills resulted in the highest HIE. Reducing time spent on contact drills relative to minimal or no contact drills may not lower overall HIE. Instead, interventions such as reducing the speed of players engaged in contact, correcting tackling technique, and progressing to contact may reduce HIE more effectively.

Wed

30

Jan

2019

Latest research in football - week 51 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Pre-Practice Hydration Status in Soccer (Football) Players in a Cool Environment
Reference: Medicina (Kaunas). 2018 Dec 5;54(6). pii: E102. doi: 10.3390/medicina54060102.
Authors: Kiitam U, Voitkevica L, Timpmann S, Pontaga I, Ereline J, Unt E, Ööpik V
Download link: https://www.mdpi.com/1010-660X/54/6/102/pdf
Summary: Only a few studies have reported the pre-practice hydration status in soccer players (SPs) who train in a cool climate. The primary purpose of this study was to examine the hydration status of male semiprofessional SPs immediately before their regular training session in winter. The secondary purpose was to compare the urinary indices of the hydration status of Estonian and Latvian SPs. Pre-training urine samples were collected from 40 Estonian (age 22.1 ± 3.4 years, soccer training experience 13.7 ± 3.9 years) and 41 Latvian (age 20.8 ± 3.4 years, soccer training experience 13.3 ± 3.0 years) SPs and analyzed for urine specific gravity (USG). The average outdoor temperature during the sample collection period (January⁻March) was between -5.1 °C and 0.2 °C (Estonia) and -1.9 °C and -5.0 °C (Latvia). Results: The average pre-training USG of Estonian and Latvian SPs did not differ (P = 0.464). Pooling the data of Estonian and Latvian SPs yielded a mean USG value of 1.021 ± 0.007. Hypohydration (defined as a USG ≥ 1.020) was evident altogether in fifty SPs (61.7%) and one of them had a USG value greater than 1.030. Estonian and Latvian SPs do not differ in respect of USG and the prevalence of pre-training hypohydration is high in this athletic cohort. These findings suggest that SPs as well as their coaches, athletic trainers, and sports physicians should be better educated to recognize the importance of maintaining euhydration during the daily training routine in wintertime and to apply appropriate measures to avoid hypohydration.


#2 Injury Risk and Injury Burden Are Related to Age Group and Peak Height Velocity Among Talented Male Youth Soccer Players
Reference: Orthop J Sports Med. 2018 Dec 11;6(12):2325967118811042. doi: 10.1177/2325967118811042. eCollection 2018 Dec.
Authors: Bult HJ, Barendrecht M, Tak IJR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6293374/pdf/10.1177_2325967118811042.pdf
Summary: The relationship between injury risk (IR) in age groups and periods around peak height velocity (PHV) remains unclear. PHV is defined as the moment of the largest increase in body height. The purpose was to investigate injury risk and injury burden as functions of growth velocity (periods around PHV) and chronological age groupings (under 12 years [U12] to U19) in talented youth male soccer players. Cohort study; Level of evidence, 2. A total of 170 players from the youth academy of a Dutch soccer club (highest professional league: Eredivisie) were observed for 1 to 3 seasons. Injuries, exposure, PHV age, and chronological age were registered. The injury incidence density (IID) and injury burden per 1000 hours of soccer participation, with 95% CIs, were calculated for 5 PHV periods and 7 age groups. These were compared with the overall cohort results using incidence ratios (IRs) and burden ratios (BRs) with 95% CIs. The mean age at PHV was 14.4 ± 0.65 years (range, 12.8-16.5 years). The mean IID for the total cohort was 8.34 injuries per 1000 hours (95% CI, 7.71-9.02). Compared with the overall mean, a significantly higher IID was found for PHV period 4+5 (IR, 1.31 [95% CI, 1.00-1.71]; P = .049) and for the U15 group (IR, 1.49 [95% CI, 1.24-1.79]; P < .001). The overall injury burden was 58.37 injury days per 1000 hours (95% CI, 56.66-60.13). In PHV period 4+5, the injury burden was significantly higher (BR, 1.53 [95% CI, 1.39-1.68]; P < .001) when compared with the overall mean. Also, compared with the overall mean, the injury burden was higher in the U16 (BR, 1.48 [95% CI, 1.39-1.58]; P < .001), U15 (BR, 1.28 [95% CI, 1.19-1.38]; P < .001), and U17 groups (BR, 1.21 [95% CI, 1.13-1.31]; P < .001). Talented young soccer players were more prone to injuries during the 6 months after PHV (31% above overall mean) as well as in the U15 group (49% above overall mean). Based on the higher injury burden in the U16 (48%), U15 (28%), and U17 (21%) groups, we suggest that research on injury risk factors and preventive measures should primarily target these age groups. Additional interventions based on PHV may be of limited value from a screening perspective. Further research is needed on the interaction between age groups and PHV periods.


#3 Anthropometry, Physical and Movement Features, and Repeated-sprint Ability in Soccer Players
Reference: Int J Sports Med. 2018 Dec 17. doi: 10.1055/a-0781-2473. [Epub ahead of print]
Authors: Campa F, Semprini G, Júdice PB, Messina G, Toselli S
Summary: This study aimed to evaluate the associations of anthropometry, functional movement patterns (FMP) and physical performance characteristics with repeated-sprint ability (RSA) in male youth soccer players. Thirty six athletes (ages 16.6±0.5 years, BMI 22.0±1.3 kg/m2) completed the RSA test and other physical tests including countermovement jump with (CMJA) and without the help of arms (CMJ), 10-m and 20-m straight-line sprints, Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo), and functional movement screen (FMS). In addition, a battery of anthropometric variables was measured. RSA performance components such as best time (BT), mean time (MT) and sprint decrement were calculated. Results showed that measures of physical performance derived from horizontal plane in 10-m and 20-m sprints, were more strongly associated (p<0.01) with RSA performance than those obtained with CMJ or CMJA (p<0.05). High correlations (p<0.01) were found between MT, BT and Yo-Yo distance (r=-0.79, r=-0.67, respectively), as well as with FMS scores (r=-0.68, r=-0.58, respectively). Anthropometric measures, such as fat mass, upper fat area, thigh fat area, calf muscle area, and endomorphy were associated with RSA components (p<0.05). Predictors for the RSA performance identified in the stepwise multivariate analysis included Yo-Yo distance, time in sprints, FMP, and calf muscle area.


#4 Do male and female soccer players differ in helping? A study on prosocial behavior among young players
Reference: PLoS One. 2018 Dec 17;13(12):e0209168. doi: 10.1371/journal.pone.0209168. eCollection 2018.
Authors: Van Lange PAM, Manesi Z, Meershoek RWJ, Yuan M, Dong M, Van Doesum NJ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209168&type=printable
Summary: Acting prosocially can be quite challenging in one of the most salient intergroup contexts in contemporary society: Soccer. When winning is the ultimate goal, balancing self-interest with helping a fellow player in distress can be a tough decision; yet it happens. To date, we know little about what motivates soccer players to offer such help in the heat of the game. We propose that sex and what is at stake will matter in such prosocial dilemma situations. A pilot study (N = 107) indicated that female players may be more likely to help than male players, but this difference was only observed when the players are close to scoring position rather than far away from the goal (midfield). The main study (N = 366) finds that young soccer players show elevated inclinations to help in low-stakes situations, for example when their team is winning or when the outcome of the game seems pretty much decided. Contrariwise, helping intentions decline in high-stakes situations, for example when one's own team is losing, when one is close to a scoring position in the offense (rather than at the midfield), or when the outcome of the game is still uncertain. Furthermore, female players show somewhat greater inclinations to help than their male counterparts. The current data point at some differences for male and female soccer players, albeit small in effect size. In contrast, we conclude that especially quick cost-benefit judgments regarding the stakes can play a major role in decisions to help or not to help another player on the soccer field.


#5 Internal and External Loads in Training Week Before the Competition in U19 High-Level Soccer Players
Reference: J Strength Cond Res. 2018 Dec 14. doi: 10.1519/JSC.0000000000002975. [Epub ahead of print]
Authors: Martín-López Á, Mendes RS, Castillo-Rodríguez A
Summary: Nowadays, the information about the load in training sessions (TRs) and the relationship of these TRs with official competition are necessary to gain the sport success in soccer. The aim of this study was to quantify the different loads in TRs according to days before the competition (P-4, P-2, and P-1) on soccer players U19 based on their playing position and their sport success. Twenty-four male Spanish high-level players (age: 16.5 ± 0.5 years; height: 1.69 ± 0.04 m; and body mass: 63.0 ± 6.3 kg) participated in the study. They were grouped according to their playing position: external defenders, internal defenders (ID), external midfielders, internal midfielders (IM), and forwards (FO). To conduct the study, global positioning system technology was used, and a 1-way analysis of variance and Pearson correlation were performed. The main results revealed that the highest physical and physiological responses in the TRs were shown by ID, IM, and players without sport success (p < 0.05), and during P-2. In addition, sport success is predicted by the mean heart rate (R = 0.33; p < 0.001). As conclusion, players covering central positions in the playing field performed higher physical and physiological demands than players covering exterior or forward positions. Furthermore, physical and physiological responses during the TRs P-2 may be similar to the responses produced in competition match and are notably different depending on the sport success of the soccer player.


#6 The team's influence on physical and technical demands of elite goalkeepers in LaLiga: a longitudinal study in professional soccer
Reference: Res Sports Med. 2018 Dec 16:1-15. doi: 10.1080/15438627.2018.1555755. [Epub ahead of print]
Authors: Serrano C, Paredes-Hernández V, Sánchez-Sánchez J, Gallardo-Pérez J, Da Silva R, Porcel D, Colino E, García-Unanue J, Gallardo L
Summary: This study examined physical and technical demands and the influence of the team's level on elite goalkeepers' performance during six consecutive seasons in Spanish Professional Soccer League. The goalkeepers' performance data were obtained by analyzing a total of 3,874 matches using a multiple-camera computerized tracking system. The physical and technical match variables registered were: distance traveled; distance Sprinted and the number of sprints; total number of passes; successful passes; pass percentage; recovered balls; lost balls; ratio lost balls: recovered balls, and number of saves. The results showed that the number of saves made has shown a significant reduction (p < 0.001). When comparing between the teams' level, the goalkeepers of the worst classified teams showed a greater distance traveled by sprint (+3.72 m, IC95%: 1.00-6.44, ES: 0.41, p = 0.008). In conclusion, the results the influence of the team's level on the technical and physical parameters of the goalkeepers during the last six seasons


#7 Intra-seasonal variation of injury patterns among German Bundesliga soccer players
Reference: J Sci Med Sport. 2018 Dec 6. pii: S1440-2440(18)30449-3. doi: 10.1016/j.jsams.2018.12.001. [Epub ahead of print]
Authors: Leventer L, Eek F, Lames M
Summary: High fluctuations in injury-risk during the playing season in soccer have been reported. As seasons are structured in periods with homogenous loads and intensities, we investigated injury-risk over season periods, contrarily to previous studies adopting a month-based approach. Incidence-rate ratios (IRRs) for match and training injuries were compared across six consecutive seasons of German Bundesliga, divided into six periods each: Pre-season (PS), winter-break (WB), quarter 1-4: (Q1-Q4). Significant variations in injury-risk were observed for match and training injuries. IRRs in matches was 1.30 (95% CI: 1.11-1.53) times higher in Q3 and 1.53 (95% CI: 1.31-1.78) higher in Q4 compared to Q1. For training injuries, IRR peaked in Q1 and Q3 followed by a marked decrease in each subsequent quarter. Compared to Q4, IRR was 1.62 (95% CI: 1.40-1.86) times higher during Q3 and 1.78 (95% CI: 1.53-2.07) times higher in Q1. IRR was significantly higher in the competitive season compared to pre-season across match (IRR: 2.00, 95% CI: 1.30-3.00) and training (IRR: 1.27, 95% CI: 1.11-1.43) injuries. The increased match IRRs later during the season indicate that, in practice, coaches should consider putting even more emphasis on recovery in the last part of the season. Moreover, training injuries seem to indicate a carry-over effect. Further studies need to investigate how training during preparatory phases can be implemented in a way that prevents injuries during the competitive season.


#8 Changes in injury incidences and causes in Swiss amateur soccer between the years 2004 and 2015
Reference: Swiss Med Wkly. 2018 Dec 15;148:w14690. doi: smw.2018.14690. eCollection 2018 Dec 3.
Authors: Gebert A, Gerber M, Pühse U, Faude O, Stamm H, Lamprecht M
Summary: Injury prevention in amateur soccer has been promoted in recent years, but only a few studies have addressed long-term changes in injury incidence in amateur soccer. However, better knowledge of changes with respect to injury incidences and causes could make an important contribution to improving prevention strategies. The aim of this study was to investigate the long-term development of injury incidence in Swiss amateur soccer with respect to level of play, injury causes and injury characteristics. A representative sample of about 1000 Swiss amateur soccer coaches was interviewed by telephone in 2004, 2008 and 2015. They were asked to recall their last game and to report details on all injuries. For every injury, the coaches were asked to remember injury characteristics and causes. The same procedure was repeated for all games that took place during the previous 4 weeks. Additionally, all training injuries in the previous 4 weeks were recorded in detail. The incidence of game injuries decreased between the years 2004 and 2008 from 15.1 (95% confidence interval [CI] 14.2&ndash;16.0) to 13.3 (95% CI 12.4&ndash;14.2) injuries per 1000 hours, and increased between the years 2008 and 2015 to 16.5 (95% CI 15.5&ndash;17.4) injuries per 1000 hours. Between 2004 and 2015, the rate of contact injuries during games increased by 19.1%. The incidence of foul play injuries in games increased by 25.5% between 2008 and 2015. The rise in total training injury incidence between the years 2004 (2.4, 95% CI 2.2&ndash;2.7) and 2015 (2.9, 95% CI 2.6&ndash;3.1) was caused by a 22.2% higher rate of noncontact injuries. During the same period, game and training injury incidences increased across all amateur soccer leagues without exception, but these changes did not reach statistical significance. In 2015, the incidence of injuries leading to medical attention was higher than in 2004 (game 20.0%, training 37.5%). There is evidence that injury incidence in Swiss amateur soccer has increased in past years. &nbsp.


#9 The Effect of Block Versus Daily Undulating Periodization on Strength and Performance in Adolescent Football Players
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-25. doi: 10.1123/ijspp.2018-0609. [Epub ahead of print]
Authors: Gavanda S, Geisler S, Quittmann OJ, Schiffer T
Summary: Muscle mass, strength and power are important factors for performance. To improve these characteristics, periodized resistance training is used. However, there is no consensus regarding the most effective periodization model. Therefore the purpose of this study was to compare the effects of block (BLOCK) versus daily undulating periodization (DUP) on body composition, hypertrophy, strength, performance and power in adolescent American football players. Forty-seven subjects participated in this study (M±SD age = 17±0.8 years; strength training experience = 0.93±0.99 years). Pre- and post-measurements consisted of body mass (BM), fat mass (FMkg), body fat percentage (relFM), fat-free mass (FFM), muscle mass (MM) and muscle thickness of the M. vastus lateralis (VL), M. rectus femoris (RF) and M. triceps brachii (TB), one repetition maximum (1-RM) back squat (BS) and bench press (BP), countermovement jump (CMJ), estimated peak power from vertical jump performance (Wpeak), medicine ball put (MBP) and 40 yd sprint. Subjects were randomly assigned in either the BLOCK or DUP group prior to the 12 week intervention period consisting of 3 full-body sessions per week. Both groups displayed significantly higher BM (p<0.001), relFM (p=0.005), FFM (p<0.001), MM (p<0.001), RF (p<0.001), VL (p<0.001), TB (p<0.001), BS (p<0.001), BP (p<0.001), CMJ (p<0.001), Wpeak (p<0.001) and significant lower sprint times (p<0.001) following twelve weeks of resistance training with no difference between groups. Resistance training was effective to increase muscle mass, strength, power and performance in adolescent athletes. BLOCK and DUP affect anthropometric measures and physical performance equally.


#10 Transfer market activities and sportive performance in European first football leagues: A dynamic network approach
Reference: PLoS One. 2018 Dec 19;13(12):e0209362. doi: 10.1371/journal.pone.0209362. eCollection 2018.
Authors: Matesanz D, Holzmayer F, Torgler B, Schmidt SL, Ortega GJ
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0209362&type=printable
Summary: Professional football is a globalized game in which players are the most valuable assets for clubs. In this study, we explore the evolution of the football players' transfer network among 21 European first leagues between the seasons 1996/1997 and 2015/2016. From a topological point of view, we show that this network achieved an upper limit expansion around season 2007/2008, thereafter becoming more connected and dense. Using a machine learning approach based on Self-Organizing Maps and Principal Component Analysis we confirm that European competitions, such as the UEFA Champions League or UEFA Europa League, are indeed a "money game" where the clubs with the highest transfer spending achieve better sportive performance. Some clubs' transfer market activities also affect domestic performance. We conclude from our findings that the relationship between transfer spending and domestic or international sportive performance might lead to substantial inequality between clubs and leagues, while potentially creating a virtuous (vicious) circle in which these variables reinforce (weaken) each other.

Tue

22

Jan

2019

Latest research in football - week 50 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Current Soccer Footwear, Its Role in Injuries and Potential for Improvement
Reference: Sports Med Int Open. 2018 May 25;2(2):E52-E61. doi: 10.1055/a-0608-4229. eCollection 2018 Apr.
Authors: Blanchard S, Palestri J, Guer JL, Behr M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6259463/pdf/10-1055-a-0608-4229.pdf
Summary: Soccer is the most popular sport in the world and generates great financial revenue. It is also a sport whose practice has evolved considerably in terms of intensity and commitment, and in which the intrinsic risk of injury (not directly related to an interaction with the environment) is particularly high. In this context, the cleated shoe as a major component of soccer equipment may play a key role in the overexposure to injury. Soccer shoe evolution is all the more challenging, because design and mechanical structure differ in many points compared to other modern shoes developed for sports such as running, tennis and basketball. This critical review aims to elucidate the characteristics of modern soccer footwear and their possible link to soccer-specific injuries, focusing on the following areas: (1) ergonomics, comfort and proprioception; (2) shoe mechanical characteristics; (3) field surfaces and shoe design.


#2 Does a bounding exercise program prevent hamstring injuries in adult male soccer players? - A cluster -RCT
Reference: Scand J Med Sci Sports. 2018 Dec 9. doi: 10.1111/sms.13353. [Epub ahead of print]
Authors: van de Hoef PAS, Brink MSM, Huisstede BMAB, van Smeden MM, de Vries NN, Goedhart EAE, Gouttebarge VV, Backx FJGF
Summary: Although the Nordic Hamstring Exercise (NHE) prevents hamstring injury in soccer players effectively, the annual incidence of these injuries still increases. This may be because of poor long-term compliance with the program. Furthermore, the timing and amplitude of gluteal and core muscle activation seem to play an important role in hamstring injury prevention, the NHE program was not designed to improve activation of these muscles. Therefore, we propose plyometric training as an alternative to reduce hamstring injuries soccer players. The purpose was to determine the preventive effect of the Bounding Exercise Program (BEP) on hamstring injury incidence and severity in adult male amateur soccer players. Thirty-two soccer teams competing in the first-class amateur league were cluster-randomized into the intervention or control group. Both groups were instructed to perform their regular training program, and the intervention group additionally performed BEP. Information about player characteristics was gathered at baseline and exposure, hamstring injuries and BEP compliance were weekly registered during one season (2016-2017). The data of 400 players were analyzed. In total, 57 players sustained 65 hamstring injuries. The injury incidence was 1.12/1000 hours in the intervention group and 1.39/1000 hours in the control group. There were no statistically significant differences in hamstring injury incidence (OR=0.89, 95% CI 0.46-1.75) or severity between the groups (p>0.48). In this large cluster-randomized controlled trial, no evidence was found for plyometric training in its current form to reduce hamstring injuries in amateur soccer players.


#3 Professional Soccer Players' Return to Play and Performance After Operative Repair of Achilles Tendon Rupture
Reference: Orthop J Sports Med. 2018 Nov 28;6(11):2325967118810772. doi: 10.1177/2325967118810772. eCollection 2018 Nov.
Authors: Trofa DP, Noback PC, Caldwell JE, Miller JC, Greisberg JK, Ahmad CS, Vosseller JT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280612/pdf/10.1177_2325967118810772.pdf
Summary: The majority of Achilles tendon ruptures are sports related; however, no investigation has examined the impact of surgical repair for complete ruptures on professional soccer players. The purpose was to examine the return to play, playing time, and performance of professional soccer players following Achilles tendon repair. Union of European Football Associations (UEFA) and Major League Soccer (MLS) athletes who sustained a primary complete Achilles tendon rupture and were treated surgically between 1988 and 2014 were identified via public injury reports. Demographic information and performance-related statistics for the identified athletes were recorded for the season before surgery and 2 seasons after surgery and were compared with information for matched controls. Statistical analyses were used to assess differences in recorded metrics. A total of 24 athletes with Achilles ruptures met inclusion criteria, 17 (70.8%) of whom were able to return to play. On average, players had 8.3 years of professional-level experience prior to sustaining an Achilles rupture. Among athletes who returned to play, no differences were found in the number of games played or started, minutes played, or goals scored 1 year postoperatively compared with the year prior to injury. However, 2 years postoperatively, these athletes played 28.3% (P = .028) fewer minutes compared with their preoperative season, despite starting and playing in an equivalent number of games. Matched controls had baseline playing time and performance statistics similar to those of players. However, controls played and started in significantly more games and played more minutes at 1 and 2 years compared with players (P < .05). No differences were found in goals scored at any time point. This is the first investigation examining the effect of an Achilles repair on the career of professional soccer players. This is a difficult injury that most commonly occurs in veteran players and prevents 29.2% of players from returning to play despite surgical management. Additionally, athletes able to return to play were found to play fewer minutes 2 years postoperatively compared with their baseline as well as playing less at 1 and 2 years postoperatively compared with uninjured matched controls. The reduction in playing time following an Achilles repair has significant implications for professional players and teams.


#4 Changes in Echocardiographic Parameters among Beninese Soccer Referees during the Division 1 Championship in 2016
Reference: J Sports Med (Hindawi Publ Corp). 2018 Nov 7;2018:6024574. doi: 10.1155/2018/6024574. eCollection 2018.
Authors: Coffi Q, Arnaud S, Polycarpe G, Hyacinthe A, Folly M, Basile N, Murielle H, Martin HD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6247468/pdf/JSM2018-6024574.pdf
Summary: The goal of this study was to describe the echocardiographic parameters of soccer referees and to examine the changes in these parameters after a period of intensive physical exercise. We conducted a prospective study that included Beninese soccer referees. The study of the geometry and function of the left ventricle (LV) was made at the beginning and end of the national Division 1 championship, which was held during the course of 10 weeks. There were 37 referees included in this study; 20 at the national level (G1: 27.8 ± 6.6 years) and 17 at the international level (G2: 32.1 ± 6.4 years). Dimensions of the LV were normal for all the referees. At the beginning of the championship, 51.3% of the referees had a normal LV geometry, 37.8% had concentric remodelling, 2.7% had concentric hypertrophy, and 8.1% had eccentric hypertrophy. In the group of referees with normal LV geometry, a modification in concentric remodelling at the end of the championship was seen in 30% of the referees in G1, 33.3% of the referees in G2, and 31.6% of the whole sample. In the group of subjects who presented concentric LV remodelling, a modification in the normal geometry was observed in 37.5% of those in G1, in 0% of those in G2, and in 21.4% of the whole sample. The cases of LV hypertrophy showed no change regardless of the group considered. An LV ejection fraction of more than 50% and an E/E' ratio less than 8 were found in all referees. All the referees studied had normal cardiac morphology and function. The intensity of the physical load was insufficient to impact this morphology.


#5 In-season training load quantification of one-, two- and three-game week schedules in a top European professional soccer team
Reference: Physiol Behav. 2018 Dec 6. pii: S0031-9384(18)30585-7. doi: 10.1016/j.physbeh.2018.11.036. [Epub ahead of print]
Authors: Oliveira R, Brito J, Martins A, Mendes B, Calvete F, Carriço S, Ferraz R, Marques M
Summary: Top European soccer teams that play in UEFA competitions often participate in one, two- or three-games per week. Therefore, it is necessary to understand the variations in training load (TL) according to each team's competitive schedule. The aim of this study was to quantify internal and external TLs within five microcycles: M4 and M5 - one-game weeks; M1 and M3 - two-game weeks; M2 - three-game week). The sample consisted of thirteen elite soccer players. A global positioning system (GPS) was used to measure the total distance covered and distances of different exercise training zones (1-5), the session ratings of perceived exertion (s-RPE) scores and the amount of creatine kinase (CK) created during daily training sessions for the 2015-2016 in-season period. The data were analysed with respect to the number of days prior to a given match. The main results indicate that there was a significant difference in training intensity for zone 1 between M5 and M3 (4010.2 ± 103.5 and 4507.6 ± 133.0 m, respectively); a significant difference in training intensity for zone 3 between M4 and M2 (686.1 ± 42.8 and 801.2 ± 61.2 m, respectively); a significant difference in the duration of the training sessions and matches between M5 and M2 (69.2 ± 2.1 and 79.6 ± 2.3) and M1 and M2 (69.7 ± 1.0 and 79.6 ± 2.3); and finally, there was a significant difference in CK between M1 and M5 (325.5 ± 155.0 and 194.4 ± 48.9). Moreover, there was a significant decrease in TL in the last day prior to a match, for all microcycles and all variables. There was no significant difference with respect to s-RPE. This study provides the first report of daily external and internal TLs and weekly accumulated load (training sessions and match demands) during one, two, and three-game week schedules in a group of elite soccer players. Expected significant differences are found in daily and accumulated loads for within- and between-game schedules. A similar pattern is exhibited for one- and two-game week microcycles regarding the day before the match, which exhibits a decrease in all variables.


#6 Estimating fat-free mass in elite youth male soccer players: cross-validation of different field methods and development of prediction equation
Reference: J Sports Sci. 2018 Dec 11:1-8. doi: 10.1080/02640414.2018.1551045. [Epub ahead of print]
Authors: Munguía-Izquierdo D, Suárez-Arrones L, Di Salvo V, Paredes-Hernández V, Ara I, Mendez-Villanueva A
Summary: This study determined the most effective field method for quantifying fat-free mass (FFM) in elite youth male soccer players compared to dual X-ray absorptiometry (DXA) values and to develop prediction equations for FFM based on anthropometric variables. Forty-one male elite-standard youth soccer players, ages 16.2-18.0 years, undertook FFM assessments including bioelectrical impedance analysis, and different skinfold-based prediction equations. DXA provided a criterion measure of FFM. Correlation coefficients, bias, limits of agreement, and differences were used as validity measures, and regression analyses to develop soccer-specific prediction equations. Slaughter et al (1988), Durnin and Wormersley (1974), and Sarria et al (1998) equations showed the lowest biases, and no significant, standardized, and substantial differences against DXA. The new youth soccer-specific anthropometric equation explained 91% of the DXA-derived FFM variance using three circumferences, eight skinfolds, and one bone breadth. All field methods compared in this study may not be adequate for estimating FFM in elite youth male soccer players, except the equations of Slaughter et al (1988), Durnin and Wormersley (1974), and Sarria et al (1998). We recommend the use of the new soccer-specific equation proposed in this study as a valid alternative to DXA to quantify FFM among elite youth male players.


#7 Dynamic and Static Assessment of Single Leg Postural Control in Female Soccer Players
Reference: J Sport Rehabil. 2018 Dec 11:1-19. doi: 10.1123/jsr.2018-0072. [Epub ahead of print]
Authors: Meiners KM, Loudon JK
Summary: Various methods are available for assessment of static and dynamic postural stability. The purpose of this study was to investigate the relationship between dynamic postural stability as measured by the Star Excursion Balance Test (SEBT) and static postural sway assessment as measured by the Technobody™ Prokin in female soccer players. A secondary purpose was to determine side-to-side symmetry in this cohort. 18 female soccer players completed testing on the SEBT and TechnobodyTM Prokin balance device. Outcome measures were: anterior, posterior medial, and posterior lateral reaches from the SEBT and Center of Pressure (COP) in the X and Y axis and Standard Deviation of movement in the forward-backward and medial-lateral directions from the force plate on left and right legs. Bivariate correlations were determined between the 8 measures. Additionally, paired Wilcoxon Signed Ranks were performed to determine similarity between limb scores. All measures on both the SEBT and postural sway assessment were significantly correlated when comparing dominant to non-dominant lower extremities with exception of SD of movement in both X and Y axis. When correlating results of the SEBT with postural sway assessment, a significant correlation was found between SEBT right lower extremity posterior lateral reach (r=.567, p<.05) and summed SEBT (r=.486, p<.05) and the COP in the Y axis. A significant correlation was also found on the left lower extremity, with Standard Deviation of movement forward-backward and SEBT posterior medial reach (r=-.511, p<.05). Dynamic postural tests and static postural tests provide different information to the overall assessment of balance in the female soccer player. Relationship between variables differed based on the subject's lower extremity dominance.


#8 Validation study of the Functional Assessment Scale for Acute Hamstring injuries in Spanish professional soccer players
Reference: Clin Rehabil. 2018 Dec 10:269215518815540. doi: 10.1177/0269215518815540. [Epub ahead of print]
Authors: Hernández-Sanchez S, Korakakis V, Malliaropoulos N, Moreno-Perez V
Summary: The purpose of the study was to cross-culturally adapt and validate the Functional Assessment Scale for acute hamstring injury for professional Spanish-speaking soccer players. Clinical measurement study. Cross-cultural adaptation was conducted following international recommendations. Indicators of validity, reliability and responsiveness are provided. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale was administered to 165 participants: 45 professional soccer players with acute hamstring muscle injury diagnosis, 40 healthy subjects, 40 individuals at-risk for a hamstring muscle injury and 40 patients with injuries of the lower limb other than hamstring muscle injury. The Functional Assessment Scale for acute hamstring injury were main outcome measures. Spanish version of the Quality of Life Short-Form 36 questionnaire (SF-36) and the Lower Limb Functional Index (LLFI) were used as the reference measures. Cronbach's alpha (internal consistency) for the Spanish version of the Functional Assessment Scale for acute hamstring injury scale was >0.8. The intraclass correlation coefficient using the two-way random model (ICC2,1) (test-retest) was 0.993 (95% confidence interval (CI): 0.991-0.995; P < 0.05). In the exploratory factor analysis, a one-factor solution explained 85% of the variance. Subjects with hamstring muscle injury scored significantly lower than the other groups in the Spanish version of the Functional Assessment Scale for acute hamstring injury scale ( P < 0.001). The Spanish version of the Functional Assessment Scale for acute hamstring injury scale score within the hamstring muscle injury group showed moderate and significant correlations with SF-36 physical components (Spearman's rs > 0.6; P < 0.001), and LLFI score at baseline ( rs = 0.42; P < 0.01). The standard error of measurement (SEM) and minimum detectable change threshold (MDC95%) were 2.6 and 7.2 points, respectively. The responsiveness indicators have an effect size of 3.62, and the standardized response mean is 3.24. The Spanish version of the Functional Assessment Scale for acute hamstring injury scale showed satisfactory psychometric properties. It can be considered a reliable and valid instrument to assess the functional impact of acute hamstring muscle injury in professional Spanish-speaking football players.


#9 Effective But Not Adhered to: How Can We Improve Adherence to Evidence-Based Hamstring Injury Prevention in Amateur Football?
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000710. [Epub ahead of print]
Authors: van der Horst N, Hoef SV, Otterloo PV, Klein M, Brink M, Backx F
Summary: The purpose was to investigate adherence to a Nordic hamstring exercise (NHE) program in a real-world context of male amateur football, and the perceptions of end users (players) and intervention deliverers (coaches and medical staff) about adherence to this proven effective program.
Dutch amateur football. Two hundred sixty-four players, 23 coaches, and 29 medical staff from Dutch amateur football teams that participated in a national randomized controlled trial 2 years earlier. Nordic hamstring exercise program were used as the independent variable. Main outcome measures were the Nordic hamstring exercise program adherence during 2014 and 2015. Intervention or control group allocation during the trial, transfers, and personal perception about adherence to the program were also examined. Of all players, 69% reported never, 16% sometimes, 6% frequently, 5% often, and 4% always performing exercises of the NHE program. Adherence to the NHE program was higher among players who had been in the NHE arm of the previous trial and among players who had not been transferred to another club compared with players who had been transferred. Key factors in stimulating players to adhere to the NHE program were knowledge of the NHE and personal motivation. Coaches and medical staff members also mentioned personal motivation and consensus with team staff as key factors to encourage NHE adherence. Among high-level male amateur football players, adherence to an evidence-based hamstring injury-prevention program was very low. It is essential to recognize factors that stimulate or limit adherence to injury-prevention programs for effective programs to actually lead to a reduction in hamstring injuries in a real-world context.


#10 Does Night-Training Load Affect Sleep Patterns and Nocturnal Cardiac Autonomic Activity in High-Level Female Soccer Players?
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-26. doi: 10.1123/ijspp.2018-0652. [Epub ahead of print]
Authors: Costa JA, Brito J, Nakamura FY, Oliveira EM, Costa OP, Rebelo AN
Summary: The purpose was to analyse whether exercise training conducted at night disturbs sleep and affects nocturnal cardiac autonomic control in high-level female athletes. Eighteen high-level female soccer players (mean±SD; age: 20.4±2.1 years) wore actigraphs and heart rate (HR) monitors during night-sleep throughout night-training days (n=8) and resting days (n=8), for 3 consecutive weeks. This was a longitudinal study that measured internal training load, sleep, nocturnal cardiac autonomic activity, and well-being ratings prior to training sessions. Training load varied across training days (e.g., training impulse range; mean±SD; ES [95% confidence interval]: 72.9±18.8 to 138.4±29.6 a.u.; F(4,62)=32.331; ηp2=0.673 [0.001-0.16], large effect; p<0.001). However, no differences in subjective well-being ratings were observed, although ES was large. Total sleep time (training days vs. resting days: 7:17±0:47 hours vs. 7:51±0:42 hours; ES=0.742 [0.59-0.92], p=0.005; moderate effect) and sleep onset time (00:58±0:19 vs. 00:44±0:16 hours; ES=0.802 [0.68-0.94], p=0.001; moderate effect) were negatively affected after night-training. In addition, small effects were detected for wake up time, time in bed, and sleep latency (p>0.05). No differences were detected in HR variability (HRV) during sleep (range of lnRMSSD: 4.3±0.4 to 4.5±0.4 ln[ms] vs. 4.6±0.3 to 4.5±0.4 ln[ms]; F(3,52)=2.148; p>0.05; ηp2=0.112 [0.01-0.25], medium effect), but the HR during sleep was significantly higher after training days (range of HR: 56±4 to 63±7 vs. 54±4 to 57±6 b.p.m; F(2,32) = 15.956; p<0.001 ηp2=0.484 [0.20-0.63], large effect). Overall, the results indicate that exercise training conducted at night may disturb sleep and affect HR, whereas limited effects can be expected in HRV assessed during sleep in high-level female soccer players.


#11 Modelling the Prediction of the Session Rate of Perceived Exertion in Soccer: Unravelling the Puzzle of Predictive Indicators
Reference: Int J Sports Physiol Perform. 2018 Dec 20:1-22. doi: 10.1123/ijspp.2018-0698. [Epub ahead of print]
Authors: Geurkink Y, Vandewiele G, Lievens M, de Turck F, Ongenae F, Matthys SPJ, Boone J, Bourgois JG
Summary: This study aimed to predict the session Rate of Perceived Exertion (sRPE) in soccer and determine the main predictive indicators of the sRPE. A total of 70 External Load Indicators (ELIs), Internal Load Indicators (ILIs), Individual Characteristics (ICs) and Supplementary Variables (SVs) were used to build a predictive model. The analysis using Gradient Boosting Machines showed a mean absolute error (MAE) of 0.67 ± 0.09 AU and a Root Mean Squared Error (RMSE) of 0.93 ± 0.16 AU. ELIs were found to be the strongest predictors of the sRPE, accounting for 61.5% of the total normalized importance (NI), with total distance as the strongest predictor. The included ILIs and ICs accounted only for respectively 1.0% and 4.5% of the total NI. Predictive accuracy improved when including SVs such as group-based sRPE-predictions (10.5% of NI), individual deviation variables (5.8% of NI) and individual player markers (17.0% of NI). The results showed that the sRPE can be predicted quite accurately, using only a relatively limited number of training observations. ELIs are the strongest predictors of the sRPE. It is however useful to include a broad range of variables, other than ELIs, because the accumulated importance of these variables account for a reasonable component of the total normalized importance. Applications resulting from predictive modelling of the sRPE can help the coaching staff to plan, monitor and evaluate both the external and internal training load.


#12 Data-Driven Visual Performance Analysis in Soccer: An Exploratory Prototype
Reference: Front Psychol. 2018 Dec 5;9:2416. doi: 10.3389/fpsyg.2018.02416. eCollection 2018.
Authors: Benito Santos A, Theron R, Losada A, Sampaio JE, Lago-Peñas C
Download link: https://www.frontiersin.org/articles/10.3389/fpsyg.2018.02416/full
Summary: In soccer, understanding of collective tactical behavior has become an integral part in sports analysis at elite levels. Evolution of technology allows collection of increasingly larger and more specific data sets related to sport activities in cost-effective and accessible manner. All this information is minutely scrutinized by thousands of analysts around the globe in search of answers that can in the long-term help increase the performance of individuals or teams in their respective competitions. As the volume of data increases in size, so does the complexity of the problem and the need for suitable tools that leverage the cognitive load involved in the investigation. It is proven that visualization and computer-vision techniques, correctly applied to the context of a problem, help data analysts focus on the relevant information at each stage of the process, and generally lead to a better understanding of the facts that lie behind the data. In the current study, we presented a software prototype capable of assisting researchers and performance analysts in their duty of studying group collective behavior in soccer games and trainings. We used geospatial data acquired from a professional match to demonstrate its capabilities in two different case studies. Furthermore, we successfully proved the efficiency of the different visualization techniques implemented in the prototype and demonstrated how visual analysis can effectively improve some of the basic tasks employed by sports experts on their daily work, complementing more traditional approaches.


#13 When Something Is at Stake: Differences in Soccer Performance in 11 vs. 11 During Official Matches and Training Games
Reference: J Strength Cond Res. 2019 Jan;33(1):167-173. doi: 10.1519/JSC.0000000000002936.
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Training games are used to mimic the official match, but differ in playing duration and a consequence of winning or losing. Anxiety levels, crowd pressure, and the intention to win are examples of constraints present in the match, but absent or less prevalent in training. The aim is, therefore, to compare soccer performance in official matches with 11 vs. 11 training games. Six elite youth soccer teams played 5 official matches and 15 training games. Soccer performance, defined as a combination of game characteristics (game duration, transitions, and ball possession duration) and physical (distance covered, high-intensity distance, and sprints), technical (passing), and team tactical performance (inter-team and intra-team distances) and corresponding interaction patterns, was determined with video footage and positional data (local position measurement system). Soccer performance in official matches differed from similar training games, in a way that players covered more distance, sprinted more often, but game pace was lower and players made more mistakes. In addition, team width was smaller and length-per-width ratio larger and teams were tighter coupled in official matches. 11 vs. 11 training games can be used to mimic the match, in particular the team tactical performance. Coaches could increase physical and technical representativeness of training games by raising the stakes and increasing the consequence of winning or losing.


#14 The influence of short-term fixture congestion on position specific match running performance and external loading patterns in English professional soccer
Reference: J Sports Sci. 2018 Dec 18:1-9. doi: 10.1080/02640414.2018.1558563. [Epub ahead of print]
Authors: Jones RN, Greig M, Mawéné Y, Barrow J, Page RM
Summary: The aim of the current study was to investigate positional specific physical performance and external load responses to short term fixture congestion in English professional soccer. A total of 515 match observations were categorised as G1: the first game in a week with >4 days following a previous game, G2: the second game in a week played <4 days since G1, and G3: the third game in a week played with <4 days between each of the previous games. Global positioning system and accelerometer-based metrics were partitioned into fifteen-minute epochs. These data were then analysed using a linear mixed model to assess both the within and between game positional differences. Total, low-intensity (<4.0 m·s-1), medium-intensity (MID; 4.0-5.5 m·s-1), and sprint distance (>7.0 m·s-1) were significantly different across games. No between game positional differences were identified; however, within match position specific differences were observed for measures of MID and HID. No significant differences were evident for accelerometer derived metrics between games or across positions. The current data suggests that the use of fifteen minute within game epochs enables the detection of alterations in physical output during congested schedules. The observed within game positional differences has implications for player specific conditioning and squad rotation strategies.

Sun

06

Jan

2019

Latest research in football - week 49 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Football Compared with Usual Care in Men with Prostate Cancer (FC Prostate Community Trial): A Pragmatic Multicentre Randomized Controlled Trial
Reference: Sports Med. 2018 Dec 1. doi: 10.1007/s40279-018-1031-0. [Epub ahead of print]
Authors: Bjerre ED, Brasso K, Jørgensen AB, Petersen TH, Eriksen AR, Tolver A, Christensen JF, Poulsen MH, Madsen SS, Østergren PB, Borre M, Krustrup P, Johansen C, Rørth M, Midtgaard J
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-1031-0.pdf
Summary: Physical activity has been shown to mitigate the unwanted psychological and physiological side effects of prostate cancer treatments, but sustainable exercise possibilities are limited. Our objective was to examine whether football in a real-world setting (i.e., local football clubs) was safe and feasible in practice and could improve quality of life, mitigate decline in muscle mass and bone density, and increase fat mass in patients with prostate cancer. In this pragmatic, multicentre, parallel randomized controlled trial, men diagnosed with prostate cancer were recruited from five Danish urological departments. Men (N = 214) diagnosed with prostate cancer were randomly allocated, using random generated lists (block size 4-8) stratified for center and androgen-deprivation therapy status, to either 1 h of football twice weekly in a local football club or to usual care, which was a 15- to 30-min telephone session covering their options for physical activity or free-of-charge rehabilitation delivered as standard in Denmark. Allocation was concealed from the trial investigator performing the randomization, but-given the nature of the intervention-this was not possible for personnel and participants. Assessments were performed at baseline, 12 weeks, and 6 months. The primary outcome was mean change difference in prostate cancer-specific quality of life at 12 weeks. Secondary outcomes were body composition, 12-Item Short Form Health Survey (SF-12) physical and mental health, and safety-reported as fractures, falls, and serious adverse events. Attrition was 1 and 3% at 12 weeks, and 5% and 5% at 6 months for the usual care and football groups, respectively. Prostate cancer-specific quality of life was equal between groups at 12 weeks (mean difference + 1.9 points, 95% confidence interval [CI] -1.0-4.8; P = 0.20) and at 6 months (+ 0.5 points, 95% CI -2.8-3.8; P = 0.76). Fractures were equally distributed, with two fractures in the usual care group and one in the football group. Likewise, body composition outcomes were equal. Mental health improved after 6 months of football (mean difference + 2.7 points, 95% CI 0.8-4.6; P = 0.006). In this trial, community-based football was a feasible exercise strategy for men with prostate cancer. Football did not improve prostate cancer-specific quality of life but did improve mental health; the clinical significance of this is unclear.


#2 Faster physical performance recovery with cold water immersion is not related to lower muscle damage level in professional soccer players
Reference: J Therm Biol. 2018 Dec;78:184-191. doi: 10.1016/j.jtherbio.2018.10.001. Epub 2018 Oct 12.
Authors: Bouzid MA, Ghattassi K, Daab W, Zarzissi S, Bouchiba M, Masmoudi L, Chtourou H
Summary: The aim of the present study was to assess the effects of cold water immersion (CWI) after an intermittent test on the recovery kinetic of physical performance, muscle damage and perceived muscle soreness in professionals soccer players. In a randomized design, eight soccer players completed the Loughborough Intermittent Shuttle Test followed by 10 min of either CWI (10C°) or thermoneutral water immersion (TWI) (28C°). Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 m sprint: SP), muscle damage parameter (creatine kinase: CK) and perceived muscle soreness were assessed at baseline, 0 h, 24 h, 48 h and 72 h after the intermittent test. After the test, a decrease was observed in SJ and in CMJ at 0 h, 24 h, 48 h and 72 h with TWI (p < 0.05) and only at 0 h for SJ with CWI (p < 0.05). SP decreased at 24 h and 48 h after the test with TWI (p < 0.05) and only at 24 h with CWI (p < 0.05). MVC, CK activity and perceived muscle soreness increased in both condition after the test and returned to baseline levels 72 h after the test with TWI (p < 0.05) and at 48 h with CWI (p < 0.05). For the correlation between physical performance and muscle damage parameters in CWI session, the statistical analysis didn't reveal any significant link between CK and SJ, CMJ, MVC or SP values (p > 0.05). The results suggest that CWI immediately after an intermittent test reduces muscle damage and perceived muscle soreness, and accelerate recovery of physical performance in professional soccer players. However, the faster recovery of physical performance seems not be related to the lower level of muscle damage induced by CWI.


#3 Use of Individual Relative Thresholds to Assess Acceleration in Young Soccer Players According to Initial Speed
Reference: J Strength Cond Res. 2018 Nov 29. doi: 10.1519/JSC.0000000000002902. [Epub ahead of print]
Authors: Martínez-Cabrera FI, Núñez-Sánchez FJ, Losada J, Otero-Esquina C, Sánchez H, De Hoyo M
Summary: The aims of the current study were (a) to analyze the characteristics of acceleration efforts using individual relative thresholds according to the initial speed during official matches in elite young soccer players according to player position and (b) to compare the differences between absolute and relative thresholds in assessing high-intensity acceleration. Player acceleration profiles were assessed using an individual relative threshold based on their acceleration capacity at different initial speeds (standing, 6, 10.8, and 15 km·h), and the number of accelerations (>75% of the maximal acceleration) performed during soccer matches was divided into 3 categories attending to the initial speed. (S1 = 0-7 km·h; S2 = 7.1-14 km·h; and S3 = ≥14.1 km·h). Within-group analyses showed that the number of accelerations performed in each category was higher when the effort started from a static or walking position than at moderate- or high-intensity running (S1 > S2 > S3; very likely to almost certain). Between-group analyses revealed substantial differences between some playing positions according to initial speed. In S1 and S3, central defenders had the lowest number of accelerations (likely to almost certain), whereas midfielders had the greatest number of high-intensity accelerations in S1 and S2. There were also substantial differences between the other playing positions (possibly to almost certain). Regarding relative and absolute thresholds (>3 m·s), the results showed that absolute threshold overestimated the number of high-intensity accelerations compared with the individual relative threshold in S1 and underestimated the results in S2 and S3 (almost certain). The use of an individual relative threshold to measure acceleration demands allows to distinguish between the numbers of accelerations in function of the initial speed and playing positions. In addition, the absolute acceleration threshold could overestimate or underestimate the acceleration demands in young soccer players as a function of the initial speed. Then, the absolute acceleration thresholds should be taken with caution in the assessment of acceleration activities.


#4 Ingesting a 12% Carbohydrate-Electrolyte Beverage Before Each Half of a Soccer-Match Simulation Facilitates Retention of Passing Performance and Improves High-Intensity Running Capacity in Academy Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Dec 3:1-28. doi: 10.1123/ijsnem.2018-0214. [Epub ahead of print]
Authors: Rodriguez-Giustiniani P, Rollo I, Witard OC, Galloway SDR
Summary: This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60 g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed and high-intensity running capacity. Eighteen elite academy (age 18±2 y) soccer players ingested two 250 mL doses (pre-exercise and at half-time) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomised cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean % difference (95% CI): 9 (3-15)) and non-dominant (mean % difference (95% CI): 13 (6-20)) feet was better maintained during the SMS on CHO-E (p<0.05), with passing speed better maintained in the non-dominant foot (mean % difference (95% CI): 5.3 (0.7 to 9.9), p=0.032). High-intensity running capacity was greater in CHO-E vs. placebo (mean % difference (95% CI): 13 (6 to 20), p=0.010). Capillary blood glucose concentration was higher in CHO-E than placebo at half-time (CHO-E: 5.8±0.5 mM vs. placebo: 4.1±0.4 mM, p=0.001) and following the high-intensity running capacity test (CHO-E: 4.9±0.4 mM vs. placebo: 4.3±0.4 mM, p=0.001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the non-dominant foot, and improves subsequent high-intensity running capacity.


#5 Ruptured Extensor Pollicis Longus Tendon After a Nondisplaced Distal Radius Fracture in a Young Adult Soccer Player
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000708. [Epub ahead of print]
Authors: Bogart R, Vidlock K
Summary: Forearm fractures of the distal radius are one of the most common fractures seen in the upper extremity, and they represent approximately 1/6 of fractures treated in the emergency department. Forearm fractures are associated with a rare but known complication of a delayed ruptured extensor pollicis longus (EPL) tendon. This sequela is more commonly seen in adults after a nondisplaced distal radius fracture, with much variability in the incidence ranging from 0.07% to 5%. By contrast, this complication in the pediatric population is almost exclusively seen after a displaced or unstable fracture necessitating surgical correction with open reduction and internal fixation.


#6 Postural Control Deficits After Repetitive Soccer Heading
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000709. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Rose WC, Glutting JJ, Kaminski TW
Summary: The objective was to determine the acute effects of repetitive soccer heading on postural control. One hundred sixty participants, including youth (age = 13.0 ± 0.8 years), high school (age = 17.2 ± 1.0 years), and collegiate (age = 20.2 ± 1.3 years) male and female soccer players, participated in this study. Participants in the soccer heading group performed 12 soccer headers (initial velocity = 11.2 m/s). Postural control testing was performed both before (PRE) and immediately after (POST) the purposeful soccer headers. Control participants performed postural control testing PRE and POST a 15-minute wait period. During postural control testing, participants were asked to stand on the MobileMat (Tekscan Inc, Boston, Massachusetts) for two 2-minute intervals with their hands on their hips and their feet together with one eyes-open and one eyes-closed trial. Using the center-of-pressure data, 95% area, sway velocity, and ApEn were calculated. Multilevel linear models were used to analyze the effects of age, sex, group, condition, and concussion history simultaneously. Participants in the soccer heading group had significantly higher sway velocity POST than participants in the control group after controlling for age, sex, concussion history, condition, and PRE (t = -3.002; P = 0.003; 95% confidence interval, -0.482 to -0.100). There were no significant differences from PRE to POST for 95% area, M/L ApEn, and A/P ApEn. Repetitive soccer heading does not affect most postural control measures, even among youth athletes. However, sway velocity increased after heading relative to control participants independent of age, sex, and concussion history.


#7 A Match-Derived Relative Pitch Area Facilitates the Tactical Representativeness of Small-Sided Games for the Official Soccer Match
Reference: J Strength Cond Res. 2018 Dec 13. doi: 10.1519/JSC.0000000000002978. [Epub ahead of print]
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Small-sided games (SSGs) are a promising training format in soccer to replicate (situations of) the official match across all age groups. Typically, SSGs are played on a smaller relative pitch area (RPA; i.e., <150 m) than the match (320 m RPA), which results in different tactical demands. To create a more precise replication of tactical match demands in SSGs with less than 11 players per team, a match-derived RPA (320 m) may be considered because this affords a similar playing area per player. In addition, subgroup analysis is necessary to deal with the different number of players in match and SSGs. Therefore, this study aims to investigate tactical demands of matches and various SSGs-with a different number of players and played on 320 m RPA-in talented youth soccer players. Twelve elite soccer teams in 4 age categories (under-13, under-15, under-17, and under-19) played official matches and 4 vs. 4 + goalkeepers (GKs), 6 vs. 6 + GKs, and 8 vs. 8 + GKs. Positional data were collected to calculate tactical variables (interpersonal distances, length, width, and surface areas) for all players and for 2- and 4-player subgroups. Corresponding tactical variability (coefficients of variation expressed as percentages) was determined for all players. Results demonstrated that in each age category, with an increase in number of players, team distances increased and tactical variability decreased. Subgroup analyses revealed similar team distances in matches and SSGs with the exception of larger interpersonal distances in 4 vs. 4 + GKs than the match in under-13, under-15, and under-17. Match-derived RPA in SSGs facilitates the tactical representativeness for the match. Soccer coaches can use such SSGs for an optimal tactical match preparation.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.


#8 A 9-months multidisciplinary rehabilitation protocol based on early post-operative mobilization following a chronic-degenerative patellar tendon rupture in a professional soccer player: a case report
Reference: Eur J Phys Rehabil Med. 2018 Dec 14. doi: 10.23736/S1973-9087.18.05479-5. [Epub ahead of print]
Authors: Vitale JA, Banfi G, Belli E, Negrini F, La Torre A
Summary: Isolated patellar tendon rupture (PTR) is the final stage of a long-standing tendon chronic degeneration. PTR requires immediate repair in order to avoid important muscle retraction and tendon fibrosis. The aim was to describe the effects of a rehabilitation protocol after chronic-degenerative PTR on subjective functional outcomes, knee range of motion (ROM), size, and strength in a professional football player. A 26-years-old football player who experienced RPT after a 3-year history of proximal patellar tendinopathy. After early surgical repair of the tendon, the athlete underwent a 9-months multidisciplinary rehabilitation program, based on early post-operative mobilization. Early knee mobilization and gradual controlled load from the second week determined a large increase in flexion ROM, muscular strength and trophy over the weeks by the athlete. Early surgical repair of PTR together with an early knee mobilization program demonstrated excellent results after a 9-months follow-up.


#9 Comparative Analysis of Load Profile between Small-Sided Games and Official Matches in Youth Soccer Players
Reference: Sports (Basel). 2018 Dec 12;6(4). pii: E173. doi: 10.3390/sports6040173.
Authors: Gómez-Carmona CD, Gamonales JM, Pino-Ortega J, Ibáñez SJ
Download link: https://www.mdpi.com/2075-4663/6/4/173/pdf
Summary: The purposes of the present study are: (a) to characterize the external (eTL) and internal load (iTL) of official matches and small-sided games (SSGs) in relation to their objective, (b) to compare demands between SSG, and (c) to analyze the SSG requirements in relation to official matches during a one-month competition period. Twenty under-18 national-level soccer players were recorded using WIMUTM inertial devices (RealTrack Systems, Almeria, Spain) during four official matches and 12 training sessions where four SSGs with different objectives were performed: (SSG1) keeping the ball; (SSG2) keeping the ball and progressing; (SSG3) keeping the ball, progressing and ending in mini-goals; and (SSG4) keeping the ball, progressing and ending in an official goal with a goalkeeper. Statistical analysis included Kruskall-Wallis' H and Mann-Whitney's U with Cohen's d effect size. The SSGs presented walking and jogging intensity movements (0.7⁻7 to 7⁻14 km/h), with a 5-to-8 %HIA (high intensity activity, >16 km/h), where low intensity accelerations, decelerations and impacts were predominant (1⁻2.5 m/s²; 5⁻7 G), and %HRMAX (maximum heart rate percentage) was between 70⁻90%. Only SSG4 presented similar demands to competition, finding differences between SSGs (p < 0.05; d = 1.40 - 0.36). In conclusion, the objective of the SSGs directly influenced the demands on the players in training sessions. For this reason, it is important to monitor demands for designing specific training sessions.


#10 Spatiotemporal and Kinetic Determinants of Sprint Acceleration Performance in Soccer Players
Reference: Sports (Basel). 2018 Dec 9;6(4). pii: E169. doi: 10.3390/sports6040169.
Authors: Murata M, Takai Y, Kanehisa H, Fukunaga T, Nagahara R
Dowload link: https://www.mdpi.com/2075-4663/6/4/169/pdf
Summary: We aimed to elucidate spatiotemporal and kinetic determinants of sprint acceleration performance in soccer players. Thirty-seven male soccer players performed 60-m sprints. The spatiotemporal variables and ground reaction impulses were calculated over a 50-m distance. When controlling the influence of stature and body mass, change in running speed was correlated with the step length at the 1st⁻4th step section (r = 0.695), step frequency from the 9th to 20th step sections (r = 0.428 to 0.484), braking impulse during the 17th⁻20th step section (r = 0.328), propulsive impulse from the 1st to 8th step sections (r = 0.738 and 0.379), net anteroposterior impulse for all step sections (r = 0.384 to 0.678), and vertical impulse from the 9th⁻12th step section and thereafter (r = -0.355 to -0.428). These results confirmed that an effective acceleration is probably accomplished by a greater step length originated in greater propulsive impulse during the initial acceleration phase (to the 8th step), a higher step frequency through smaller vertical impulse and smaller braking impulse during the middle and later acceleration phases (from the 9th step), as well as greater net anteroposterior impulse during the entire acceleration phase.


#11 Positional Differences in GPS Outputs and Perceived Exertion During Soccer Training Games and Competition
Reference: J Strength Cond Res. 2018 Nov;32(11):3222-3231. doi: 10.1519/JSC.0000000000002387.
Authors: Abbott W, Brickley G, Smeeton NJ
Summary: Soccer training games are popular training modalities, allowing technical, tactical, and physical aspects to be trained simultaneously. Small (SSGs), medium (MSGs), and large training games (LSGs) elicit differing physical demands. To date, no research has investigated physical and perceived demands of training games on soccer playing positions relative to competitive demands. In addition, previous research has referenced average competitive intensities, ignoring peak demands of competition. The current aim was to investigate the effect of training game formats on average and peak physical outputs produced by soccer playing positions. Physical and perceptual data from 22 competitive matches and 39 training game sessions were collected for 46 U23 professional players using 10-Hz global positioning system (GPS) and 100-Hz accelerometer devices (MinimaxX version 4.0; Catapult Innovations, Melbourne, Australia). Data analyzed included GPS-derived distance, speed, acceleration, deceleration, and rating of perceived exertion (RPE). Two-way between-subjects analyses of variance were used to compare average and peak GPS metrics, and RPE, between training games and competition for playing positions. Despite eliciting significantly higher average total distances compared with competition (p < 0.01), LSGs produced significantly lower peak total distance relative to the competition (p < 0.01). For very high-speed running and sprinting, LSGs elicited similar average intensities to competition; however, peak intensities were significantly lower than competition (p < 0.01). Medium training games and LSGs produced significantly higher average and peak moderate-intensity explosive distances than competition (p < 0.01). Results indicate the importance of analyzing relative to peak competitive demands, instead of focusing solely on average demands. The study demonstrates that specific game formats can overload the competitive demands of playing positions and provide an individualized training stimulus.


#12 Pre-season Fitness Level and Injury Rate in Professional Soccer - A Prospective Study
Reference: Sports Med Int Open. 2018 Aug 22;2(3):E84-E90. doi: 10.1055/a-0631-9346. eCollection 2018 Jun.
Authors: Eliakim E, Doron O, Meckel Y, Nemet D, Eliakim A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6225967/pdf/10-1055-a-0631-9346.pdf
Summary: The aim of the present study was to assess prospectively the effect of pre-season fitness on injury rate during the competitive season among professional soccer players. Thirty-one players participated in the study during two consecutive competitive seasons (2015-16 and 2016-17; a squad of 22 players in each season). During the 6-week pre-season training period (8 training sessions and a friendly match every week, 14-18 training hours/week) there was a significant improvement in VO 2 max, a significant increase in ideal and total sprint time and no change in vertical jump, flexibility and repeated sprint-test performance decrement. During the two consecutive seasons, 28 injuries were recorded. Ten injuries were classified as mild (missing 3-7 days of practice/match), 8 as moderate (missing 8-28 days) and 10 as severe (missing >28 days). The rate of match injuries was higher (9.4 per 1000 match hours) compared to practice injuries (4.7 per 1000 training hours). Most injuries were overuse injuries (72%) of the lower limbs (71%). Most of match injuries occurred during the last 15 min of each half. There were no differences in fitness characteristics in the beginning of pre-season training between injured and non-injured players. However, improvements in VO 2 max during the pre-season training period were significantly lower among injured players (0.9±5.5%) compared to non-injured players (10.4±6.5%, p<0.05). Our results emphasize the importance of pre-season training in professional soccer players not only for improvement in fitness but also for injury prevention during the following competitive season.

Sun

06

Jan

2019

Latest research in football - week 48 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Foot and Ankle Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0096.
Authors: Feria-Arias E, Boukhemis K, Kreulen C, Giza E
Download link: https://www.amjorthopedics.com/node/378448/pdf
Summary: The ankle is one of the most commonly injured joints in soccer and represents a significant cost to the healthcare system. The ligaments that stabilize the ankle joint determine its biomechanics-alterations of which result from various soccer-related injuries. Acute sprains are among the most common injury in soccer players and are generally treated conservatively, with emphasis placed on secondary prevention to reduce the risk for future sprains and progression to chronic ankle instability. Repetitive ankle injuries in soccer players may cause chronic ankle instability, which includes both mechanical ligamentous laxity and functional changes. Chronic ankle pathology often requires surgery to repair ligamentous damage and remove soft-tissue or osseous impingement. Proper initial treatment, rehabilitation, and secondary prevention of ankle injuries can limit the amount of time lost from play and avoid negative long-term sequelae (eg, osteochondral lesions, arthritis). On the other hand, high ankle sprains portend a poorer prognosis and a longer recovery. These injuries will typically require surgical stabilization. Impingement-like syndromes of the ankle can undergo an initial trial of conservative treatment; when this fails, however, soccer players respond favorably to arthroscopic debridement of the lesions causing impingement. Finally, other pathologies (eg, stress fractures) are highly encouraged to be treated with surgical stabilization in elite soccer players.


#2 Female Soccer Players With Anterior Cruciate Ligament Reconstruction Have a Higher Risk of New Knee Injuries and Quit Soccer to a Higher Degree Than Knee-Healthy Controls
Reference: Am J Sports Med. 2018 Nov 27:363546518808006. doi: 10.1177/0363546518808006. [Epub ahead of print]
Authors: Fältström A, Kvist J, Gauffin H, Hägglund M
Summary: Many patients with anterior cruciate ligament (ACL) reconstruction who return to sport suffer new ACL injuries or quit sports soon after returning. The purpose was to prospectively follow a cohort of female soccer players with primary unilateral ACL reconstruction and matched knee-healthy controls from the same soccer teams to compare (1) the rate of new traumatic and nontraumatic knee injuries and other injuries, (2) the proportion of players who quit soccer, and (3) player-reported activity level and satisfaction with activity level and knee function. A total of 117 active female soccer players (mean ± SD age, 19.9 ± 2.5 years) 18.9 ± 8.7 months after ACL reconstruction and 119 knee-healthy female soccer players (19.5 ± 2.5 years) matched from the same teams were prospectively followed for 2 years for new knee injuries, other injuries, soccer playing level, activity level according to the Tegner Activity Scale, and satisfaction with activity level and knee function. Players with ACL reconstruction had a higher rate of new ACL injuries (n = 29 vs 8; 19 vs 4 per 100 player years; rate ratio [RR], 4.82; 95% CI, 2.20-10.54; P < .001), other traumatic knee injuries (29 vs 16 per 100 player years; RR, 1.84; 95% CI, 1.16-2.93; P < .01), and nontraumatic knee injuries (33 vs 9 per 100 player years; RR, 3.62; 95% CI, 2.11-6.21; P < .001) as compared with controls. There was no difference in the rate of other (not knee) injuries (43 vs 48 per 100 player years; RR, 0.90; 95% CI, 0.65-1.23; P = .494). During the 2-year follow-up, 72 (62%) players with ACL reconstruction quit soccer, as opposed to 43 (36%) controls ( P = .001). The median Tegner Activity Scale score decreased in both groups ( P < .001) but more for the ACL-reconstructed group ( P < .015). Female soccer players with ACL reconstruction had nearly a 5-fold-higher rate of new ACL injuries and a 2- to 4-fold-higher rate of other new knee injuries, quit soccer to a higher degree, and reduced their activity level to a greater extent as compared with knee-healthy controls.


#3 There Is No Such Thing as an International Elite Under-9 Soccer Player
Reference: J Sports Sci Med. 2018 Nov 20;17(4):686-688. eCollection 2018 Dec.
Authors: Kirkland A, O'Sullivan M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243622/pdf/jssm-17-686.pdf


#4 Establishing the Reliability and Limits of Meaningful Change of Lower Limb Strength and Power Measures during Seated Leg Press in Elite Soccer Players
Reference: J Sports Sci Med. 2018 Nov 20;17(4):539-546. eCollection 2018 Dec.
Authors: Redden J, Stokes K, Williams S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243620/pdf/jssm-17-539.pdf
Summary: Measurement of lower limb strength, power and asymmetries of soccer players is important for monitoring physical development and injury risk. The aim of the present study was to establish the reliability and limits of meaningful change of single and double leg maximal strength, power and bilateral imbalance measures in elite soccer players using a pneumatic resistance based seated leg press. Thirteen participants undertook an incremental resistance leg press test on three separate testing days within a seven day period. Paired t-tests established no significant differences (p > 0.156) between consecutive tests, whilst 'good' reliability (intraclass correlation coefficient-ICC >0.762) and acceptable typical percentage errors (< 6.9%) were observed for maximal resistance, velocity and force pushed as well as average and peak power outputs. Imbalance variables accounting for left and right leg average power output across all repetitions were established as the most reliable imbalance variables, with 'good' reliability (ICC > 0.874) and absolute typical error values of 2.1%. Imbalance variables calculated using peak power output or average power output from the last 4 repetitions resulted in weaker reliability (ICC < 0.657) and significant differences between tests, and therefore were considered less suitable for applied use. Subsequently, to better inform the practitioner, limits of meaningful change were calculated for all strength, power and imbalance variables. The current study shows that lower limb strength, and power output variables and average imbalance measures of soccer players assessed through a seated leg press protocol show acceptable levels of reliability, and provides practitioners with limits of meaningful change around parameters to better evaluate test results.


#5 Motivation counteracts fatigue-induced performance decrements in soccer passing performance
Reference: J Sports Sci. 2018 Nov 24:1-8. doi: 10.1080/02640414.2018.1548919. [Epub ahead of print]
Authors: Barte JCM, Nieuwenhuys A, Geurts SAE, Kompier MAJ
Summary: Recent theories suggest that negative effects of fatigue on performance are determined by perception of effort and motivation rather than being directly caused by reaching physiological limits. In the current experiment, the influence of motivation on fatigue-induced decrements in soccer performance was experimentally investigated. Sixty amateur soccer players performed a validated soccer-passing test before and after a fatigue protocol. Results showed that players' motivation and performance decreased after the fatigue protocol for players in the control group. In contrast, players in the motivation group (i.e., with motivation experimentally induced after the fatigue protocol) were able to uphold their motivation and increase their performance. These results indicate that motivation plays a crucial role in performance under fatigue, as fatigue-induced decrements in soccer passing performance can be counteracted by high levels of motivation. Future research may explore the limits of this counteracting effect and extend findings to other relevant performance aspects.


#6 Dribbling speed along curved paths predicts attacking performance in match-realistic one vs. one soccer games
Reference: J Sports Sci. 2018 Nov 23:1-8. doi: 10.1080/02640414.2018.1544110. [Epub ahead of print]
Authors: Wilson RS, Smith NMA, Ramos SP, Giuliano Caetano F, Aparecido Rinaldo M, Santiago PRP, Cunha SA, Moura FA
Summary: This study assessed whether a new, closed-skill dribbling or sprinting task could predict attacking performance in soccer. Twenty-five male players were recruited from the Londrina Junior Team Football Academy in Brazil and asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0-1.37 radians.m-1). These measures were then validated using a realistic one vs. one competition in which each player acted as attacker or defender in turn (N = 1330 bouts). Sprinting (ICC = 0.96) and dribbling (ICC = 0.97) performances were highly repeatable for individual players. Average dribbling speed decreased non-linearly with increasing circuit curvature (F = 239.5; P < 0.001) from 5.19 ± 0.11 ms-1 on the straightest path to 2.13 ± 0.03 ms-1 on the curviest. Overall, dribbling but not sprinting performance predicted attacking success in the one vs. one competition, explaining more than 50% of the variation in attacking success alone (rp = 0.70; P < 0.001). In conclusion, our new closed-skill dribbling assessment is a valid and reliable protocol to predict a soccer player's success in attacking performance in one vs. one situation, and can be used to identify talented players.


#7 Career Termination of Portuguese Elite Football Players: Comparison between the Last Three Decades
Reference: Sports (Basel). 2018 Nov 28;6(4). pii: E155. doi: 10.3390/sports6040155.
Authors: Carapinheira A, Mendes P, Guedes Carvalho P, Torregrossa M, Travassos B
Download link: https://www.mdpi.com/2075-4663/6/4/155/pdf
Summary: The aim of this study was to explore the process of career termination of elite soccer players, comparing the quality and the resources to support career termination over the last three decades. To this end, was developed a questionnaire defined by four sections: (a) biographical data, (b) athletic career, (c) quality of career termination and (d) available resources at the moment of career termination. Ninety male former elite Portuguese soccer players participated in this study. The results highlighted a decrease in the length of athletic career as football players and an increase in the number of years as youth players over the last 30 years. The results also revealed that the quality of career termination was difficult. The analysis of resources for career termination revealed an increase in a high level of education over the years. Despite the evolution in the level athletes' education in the last three decades, the athletic career termination remained difficult and it was reported that they did not plan their career termination. In line with previous studies, the results highlight that the lack of plans for career termination is one of the most important factors that constrain the quality of career transition.


#8 Changes in Cortisol and Immunoglobulin a Concentrations in Referees during a Professional Football Match
Reference: J Sports Sci Med. 2018 Nov 20;17(4):689-690. eCollection 2018 Dec.
Authors: Kokaly M, Peñailillo L, Villagrán C, Mackay K, Jannas S, Deldicque L, Zbinden-Foncea H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243613/pdf/jssm-17-689.pdf


#9 Decline in Match Running Performance in Football is affected by an Increase in Game Interruptions
Reference: J Sports Sci Med. 2018 Nov 20;17(4):662-667. eCollection 2018 Dec.
Authors: Linke D, Link D, Weber H, Lames M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243615/pdf/jssm-17-662.pdf
Summary: This study quantified the contribution of game interruptions to the fatigue-related declines in match running performance over the course of a football match. Using a semi-automatic multiple camera system, the running activity of 792 individual German Bundesliga performances was divided into pre-defined 15-minute intervals and subsequently analysed under two prerequisites: with (effective playing time) and without (total playing time) consideration of game interruptions. Results showed a significant decline in effective playing time over the course of a match, from 66.3% of the total playing time in the first 15 minutes to 55.9% in the final 15 minutes of a match. Under consideration of the total playing time, match running performances decreased by 24.2% on average; considering the effective playing time, they decreased on average by only 10.2%. It can, therefore, be concluded that more than half (57.9%) of the commonly reported decline in match running performance cannot be assigned to physical fatigue, but rather to an increase in game interruptions as the game progresses. In conclusion, this study demonstrated for the first time that the decline in players' match running performance during football matches is substantially amplified by a proven increase in game interruptions, indicating that there may be a tendency among practitioners to overestimate fatigue-induced performance declines.


#10 Positional Differences in the Most Demanding Passages of Play in Football Competition
Reference: J Sports Sci Med. 2018 Nov 20;17(4):563-570. eCollection 2018 Dec.
Authors: Martín-García A, Casamichana D, Díaz AG, Cos F, Gabbett TJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243617/pdf/jssm-17-563.pdf
Summary: The aim of this investigation was to determine the position and duration specific activity of the most demanding passages of play in football players. Global positioning system data were collected from twenty-three football players across a competitive season. A total of 605 individual match files were analysed. Players were categorised based on positional groups; full-back (FB), central defender (CD), midfielder (MF), wide midfielders (WMF) and forwards (FW). The most demanding passage of a match play was analysed using a rolling average method, where maximal values were calculated for four different time durations (1', 3', 5' and 10') using distance (m·min-1), high metabolic load distance (HMLD) and average metabolic power (AMP) as variables of interest. Using distance as the criterion variable, MF and WMF positions covered greater distance, and fewer sprinting meters (>7.0 m·s-1, m·min-1). With HMLD as the criterion variable, the values for WMF and MF positions were higher than the CD and FW positions. The MF and WMF positions performed more high-intensity accelerations and decelerations when the criterion variable was AMP. These results provide an understanding of the most demanding passages of play to inform training practices for specific football playing positions.


#11 Orhtopedic injuries in mens’s professional soccer in brazil: Prospective comparison of two consecutive seasons 2017/2016
Reference: Acta Ortop Bras. 2018;26(5):338-341. doi: 10.1590/1413-785220182605194940.
Authors: de Moraes ER, Arliani GG, Lara PHS, da Silva EHR, Pagura JR, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6220654/pdf/1809-4406-aob-26-05-0338.pdf
Summary: The purpose was to compare the incidence and characteristics of injuries sustained in two consecutive seasons of the São Paulo State Football Championship. Prospective study performed using an electronic form previously developed by the Medical Committee of the São Paulo State Football Federation, sent to the physicians responsible for the tournament's series A1 and A2 teams, after each round. 17.63 injuries sustained per 1000 hours of matches in the A1 series and 14.91 injuries sustained per 1000 hours of matches in the A2 series. Incidence of injuries per 1000 hours of matches decreased from 24.16 to 17.63 in the A1 series (p<0.037) and from 19.10 to 14.01 in the A2 series (p<0.064). External defenders suffered most injuries, while muscular injuries were most common and lower limbs, the most affected areas. Most injuries occurred between 30 and 45 minutes of the match and only 11.9% of the injuries required surgery. Prevalence and frequency of injuries decreased between seasons. Most injuries were sustained in the lower limbs; strains were the most common injuries, followed by strains and contusions; MRIs were the most frequently requested exams and most injuries were classified as moderate (8-28 days).


#12 Effects of Strength Training Program and Infrared Thermography in Soccer Athletes Injuries
Reference: Sports (Basel). 2018 Nov 19;6(4). pii: E148. doi: 10.3390/sports6040148.
Authors: Menezes P, Rhea MR, Herdy C, Simão R
Download link: https://www.mdpi.com/2075-4663/6/4/148/pdf
Summary: The purpose of this investigation was to examine the effects of a periodized strength training program and the use of infrared thermography (IRT) in injuries mapping in under 20-year-old (U-20) soccer players. In this study, 26 professional soccer players participated in strength training (ST) twice a week and were tested with IRT consistently across the 1-year. Strength, vertical jump, heat differences and injuries were tracked and analyzed. Results: 69 injuries occurred during 12 months of tracking; most identified injuries were: contusions, sprains, strains to the thigh (n = 16), ankle (n = 15) and knee (n = 12). Differences (>7 °C) in IRT patterns were noted among injured and non-injured athletes. Significant improvements in strength (p < 0.005) were found for vertical jump, bench press, front lat pull down, shoulder press, leg press, leg curl and squat. Number of injuries decreased from 23 (33.3%) to 14 (20.3%) when early year rates were compared to late year (p < 0.005). Combined ST and IRT represent useful strategies for reducing injuries among U-20 soccer players.


#13 Can professional football clubs deliver a weight management programme for women: a feasibility study
Reference: BMC Public Health. 2018 Dec 3;18(1):1330. doi: 10.1186/s12889-018-6255-2.
Authors: Bunn C, Donnachie C, Wyke S, Hunt K, Brennan G, Lennox J, Maclean A, Gray CM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6276211/pdf/12889_2018_Article_6255.pdf
Summary: Levels of obesity remain high in the UK. The Football Fans in Training (FFIT) randomised controlled trial (RCT) demonstrated that a 12-week, gender-sensitised weight management, physical activity and healthy eating group programme delivered through professional football clubs helped men aged 35-65 years with BMI at least 28 kg/m2 lose a clinically-significant amount of weight. We aimed to test the feasibility of a minimally-adapted FFIT programme for delivery to women by assessing recruitment and completion rates; determining if the programme content and delivery required further refinement; and evaluating the potential of FFIT for Women to deliver improvements in weight and other clinical, behavioural and psychological outcomes. A feasibility study of the FFIT for Women programme including before-and-after measurements of clinical (weight, waist, body mass index [BMI], blood pressure) behavioural (self-reported physical activity, food and alcohol intake) and psychological (self-esteem, positive and negative affect, physical and mental HRQoL) outcomes at five professional football clubs. Post-programme focus groups assessed acceptability of the programme format, content and style of delivery for women. Recruitment across the five clubs resulted in 123 women aged 35-65 years with BMI at least 28 kg/m2 taking part in the study. The mean weight (95.3 kg) and BMI (36.6 kg/m2) of the cohort were both suggestive of high risk of future disease. Of 123 women who started the programme, 94 (76%) completed it; 72 (58.5%) returned for 12-week follow-up measurements. Participants compared FFIT for Women favourably to commercial weight loss programmes and emphasised the importance of the programme's physical activity content. They also spoke positively about group dynamics, suggested that the approach to food was less restrictive than in other weight loss approaches, and broadly enjoyed the football setting. Mean weight loss was 2.87 kg (95% CI 2.09, 3.65, p ≤ 0.001). Mean waist reduction was 3.84 cm (2.92, 4.77, p ≤ 0.001). In this evaluation, FFIT for Women was feasible, acceptable and demonstrated potential as a weight loss programme. Our findings suggest the programme has the potential to produce outcomes that are on a par with existing commercial and state-funded offerings.

Sat

05

Jan

2019

Latest research in football - week 47 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 High-Intensity Demands of 6-a-Side Small-Sided Games and 11-a-Side Matches in Youth Soccer Players
Reference: Pediatr Exerc Sci. 2018 Nov 30:1-6. doi: 10.1123/pes.2018-0122. [Epub ahead of print]
Authors: Goto H, King JA
Summary: The purposes of the present study were to examine high-intensity running distance during 6-a-side small-sided games (SSGs) and 11-a-side matches (11M) in youth soccer players using speed and metabolic power approaches and the magnitude of difference between the high-intensity running distance calculated with the 2 approaches. A total of 11 outfield players (age = 16.3 [0.6] y) performed SSGs with 3 pitch sizes (small SSG [SSGS], medium SSG, and large SSG [SSGL]) and 11M. A Global Positioning System (15 Hz) was employed to calculate total distance covered, distance covered at a speed ≥4.3 m·s-1 (TS), and metabolic power of ≥20 W·kg-1 (TP). The total distance covered increased from SSGS through to SSGL (P < .001) and was greater during 11M and SSGL compared with other SSGs (P < .01). TS and TP increased from SSGS (TS vs TP = 98 [55] vs 547 [181] m) through to SSGL (538 [167] vs 1050 [234] m; P < .001). TS and TP during 11M (370 [122] vs 869 [233] m) was greater than SSGS (P < .001 for both) and less than SSGL (P < .05 for both). The magnitude of difference between TS and TP (as a percentage) was lower with an increase in pitch size during SSGs and was greater in SSGS (615% [404%]; P < .001), medium SSG (195% [76%]; P < .05), and smaller in SSGL (102% [33%]; P < .01) compared with 11M (145% [53%]). SSGs can replicate the high-intensity demands of 11M and the speed approach underestimates the high-intensity demands of SSGs and 11M compared with the metabolic power approach.


#2 Injury prevalence and risk factors in a Greek team's professional football (soccer) players: a three consecutive seasons survey
Reference: Res Sports Med. 2018 Nov 30:1-13. doi: 10.1080/15438627.2018.1553779. [Epub ahead of print]
Authors: Smpokos E, Mourikis C, Theos C, Linardakis M
Summary: This study investigated the prevalence and risk factors of injuries on a cohort of 123 Greek team's professional football players during three consecutive seasons, 2015/16-to-2017/18. Injuries were assessed and regression analysis was used to evaluate the potential risk factors. Three-quarters of the players were recorded as injured with 2.3 injuries/injured player, and the injury incidence was 55 injuries/1,000 match-playing-exposure-hours. The mean rehabilitation days were 29.3/injured player (95%CI 22.4-36.8) and 13.0/injury (95%CI 8.6-17.4). The majority of injured players has been found to have moderate-to-major/severe injuries and most of the injuries were traumatic than overuse (p < 0.05). The number of injuries were related to the recurrence of injury (beta = 0.646, p < 0.001) and the rehabilitations days (beta = 0.271, p < 0.001). High prevalence of injuries was found as the recurrence of injury and rehabilitation days were their main predictive risk factors. In order to reduce the risk of injuries, continuous effort is required in the rehabilitation of players.


#3 ACL injury incidence, severity and patterns in professional male soccer players in a Middle Eastern league
Reference: BMJ Open Sport Exerc Med. 2018 Oct 23;4(1):e000461. doi: 10.1136/bmjsem-2018-000461. eCollection 2018.
Authors: Rekik RN, Tabben M, Eirale C, Landreau P, Bouras R, Wilson MG, Gillogly S, Bahr R, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6241976/pdf/bmjsem-2018-000461.pdf
Summary: The purpose was to ascertain ACL injury incidence, severity (injury burden) and patterns (contact/non-contact and reinjuries) in a professional male football league in the Middle East over five consecutive seasons. Prospective epidemiological study reporting ACL injuries in professional male soccer players in the Qatar Stars League, with complete matches/training exposure over five seasons (2013-2014 to 2017-2018), corresponding to 2243 player seasons and 729 team months. 37 complete ACL ruptures occurred in 37 players during 486 951  hours of player exposure. The overall ACL injury rate was 0.076 injuries/1000  hours of exposure (season range 0.045-0.098). Injury incidence during matches and training was 0.41 and 0.04 injuries/1000  hours of exposure, respectively. Match injury incidence was greater than that of training (OR 11.8, 95%  CI 6.21 to 23.23, p<0.001). Average injury-related time-loss following ACL injury was 225 days±65 (range 116-360). Overall injury burden was 16.3 days lost/1000  hours of exposure. The overall ACL injury rate in professional male soccer players competing in the Middle East was 0.076 injuries/1000  hours of exposure, match injury incidence was greater than training, while the average ACL time-loss was 225 days.


#4 Normative Data of the Wingate Anaerobic Test in 1 Year Age Groups of Male Soccer Players
Reference: Front Physiol. 2018 Nov 15;9:1619. doi: 10.3389/fphys.2018.01619. eCollection 2018.
Authors: Nikolaidis PT, Matos B, Clemente FM, Bezerra P, Camões M, Rosemann T, Knechtle B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6249309/pdf/fphys-09-01619.pdf
Summary: The Wingate anaerobic test (WAnT) has been used extensively to evaluate performance in soccer, however, a comprehensive sport-specific normative database has not been available so far. Therefore, the main aim of the present study was to develop norms of the main indices of the WAnT with regards to age in soccer. A secondary aim was to examine the relationship of WAnT with two common field tests, 20 m sprint and vertical jump, and study the variation of this relationship by age and playing position. Hundred and ninety five male soccer players (age 18.1 ± 4.9 years) performed the WAnT, and a sub-sample of 190 soccer players (age 19.4 ± 5.1 years) performed 20 m sprint, squat (SJ) and countermovement jump (CMJ). Age was related very largely with peak power (R 2 = 0.57) and mean power of the WAnT (R 2 = 0.60) when they were expressed in W, and largely (R 2 = 0.41 and R2 = 0.33, respectively) when they were expressed in W.kg-1, whereas it did not relate with fatigue index. After being adjusted for age, a relationship of SJ (B = 3.91, 90% CI: 2.49, 5.32; R 2 = 0.26), CMJ (B = 3.59, 90% CI: 2.22, 4.95; R 2 = 0.24) and 20 m sprint (B = -0.06, 90% CI: -0.10; -0.01; R 2 = 0.19) with peak power of the WanT was observed. In summary, Ppeak and Pmean were related very largely to age, especially during adolescence, and percentile norms of these indices were developed for 1-year age groups from 11 to 21 years old and for a single adult age group (22-39 years old). These findings on the largest dataset of soccer players ever studied would be expected to offer a practical tool to the members of the sports medicine team (e.g., exercise physiologists, fitness trainers, and coaches) working with them.


#5 Sprint Mechanical Properties of Female and Different Aged Male Top-Level German Soccer Players
Reference: Sports (Basel). 2018 Nov 28;6(4). pii: E161. doi: 10.3390/sports6040161.
Authors: Baumgart C, Freiwald J, Hoppe MW
Download link: https://www.mdpi.com/2075-4663/6/4/161/pdf
Summary: This study compared the sprint mechanical properties of female and different aged male top-level soccer players. A total of 14 adult females (FEM) and 115 different aged male field players, competing at German top levels, participated in this study. The males belonged to teams of under 12, 13, 14, 15, 17, 19, and 23 years (U 12⁻23) and professionals (PRO). All players were tested for a 30 m linear sprint. From timing gate derived sprint times, force-velocity and power-velocity relationships, as well as theoretical maximum running velocity, force, and power data were computed by an inverse dynamic approach applied to the center of mass. The approach was optimized for taking the starting time into account, which is a progress in the present research field, when aiming to compute sprint mechanical properties by different methodological approaches under field conditions. Sprint mechanical properties of FEM were lower than those of PRO. Compared to other age groups, sprint mechanical properties of FEM were similar to those of U 14 and U 15. An increase in sprint mechanical properties was found from U 12 to U 17. The study shows that sprint mechanical properties differ according to gender and age in top-level soccer players.


#6 Combination of Agility and Plyometric Training Provides Similar Training Benefits as Combined Balance and Plyometric Training in Young Soccer Players
Reference: Front Physiol. 2018 Nov 13;9:1611. doi: 10.3389/fphys.2018.01611. eCollection 2018.
Authors: Makhlouf I, Chaouachi A, Chaouachi M, Ben Othman A, Granacher U, Behm DG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243212/pdf/fphys-09-01611.pdf
Summary: Studies that combined balance and resistance training induced larger performance improvements compared with single mode training. Agility exercises contain more dynamic and sport-specific movements compared with balance training. Thus, the purpose of this study was to contrast the effects of combined balance and plyometric training with combined agility and plyometric training and an active control on physical fitness in youth. Fifty-seven male soccer players aged 10-12 years participated in an 8-week training program (2 × week). They were randomly assigned to a balance-plyometric (BPT: n = 21), agility-plyometric (APT: n = 20) or control group (n = 16). Measures included proxies of muscle power [countermovement jump (CMJ), triple-hop-test (THT)], muscle strength [reactive strength index (RSI), maximum voluntary isometric contraction (MVIC) of handgrip, back extensors, knee extensors], agility [4-m × 9-m shuttle run, Illinois change of direction test (ICODT) with and without the ball], balance (Standing Stork, Y-Balance), and speed (10-30 m sprints). Significant time × group interactions were found for CMJ, hand grip MVIC force, ICODT without a ball, agility (4 m × 9 m), standing stork balance, Y-balance, 10 and 30-m sprint. The APT pre- to post-test measures displayed large ES improvements for hand grip MVIC force, ICODT without a ball, agility test, CMJ, standing stork balance test, Y-balance test but only moderate ES improvements with the 10 and 30 m sprints. The BPT group showed small (30 m sprint), moderate (hand grip MVIC, ICODTwithout a ball) and large ES [agility (4 m × 9 m) test, CMJ, standing stork balance test, Y-balance] improvements, respectively. In conclusion, both training groups provided significant improvements in all measures. It is recommended that youth incorporate balance exercises into their training and progress to agility with their strength and power training.


#7 Use of Musculoskeletal Ultrasound and Regenerative Therapies in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0093.
Authors: Centurion AJ, Youmans H, Zeini IM
Download link: https://www.amjorthopedics.com/article/use-musculoskeletal-ultrasound-and-regenerative-therapies-soccer-1
Summary: Improvements in ultrasound technology have increased the popularity and use of ultrasound as a diagnostic and therapeutic modality for many soccer-related musculoskeletal (MSK) injuries. As a dynamic imaging modality, ultrasound offers increased accuracy and efficacy with minimally invasive procedures, such as guided injections, percutaneous tenotomy, and regenerative therapies, in the clinical setting. Emerging evidence indicates that regenerative therapies, such as platelet-rich-plasma (PRP), mesenchymal stem cells, and amniotic products, are a promising treatment for many MSK injuries and are gaining popularity among professional athletes. PRP is a safe treatment for a number of MSK conditions and has been included in the standard of care. However, conflicting evidence on return-to-play timeframes and efficacy in certain MSK conditions have led to inconsistent recommendations on indications for use, dose, and timing of treatment. Mesenchymal stem cell therapy, while promising, lacks high-level evidence of efficacy despite its increasing use among athletes. Currently, no data are available regarding the outcome of the use of amniotic products for the treatment of injuries in athletes. Furthermore, preparation of many regenerative therapies eclipses the concept of minimal manipulation and is subject to US Food and Drug Administration phase I to III trials. High-level research on regenerative medicine therapies should be continuously conducted to establish their clinical efficacy and safety data.


#8 Upper Extremity Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0091.
Authors: Marom N, Williams RJ 3rd
Download link: https://www.amjorthopedics.com/article/upper-extremity-injuries-soccer
Summary: Upper limb injuries in soccer represent only a marginal portion of injuries, however this is mainly true for outfield players. Goalkeepers are reported to have up to 5 times more upper extremity injuries, many of them requiring substantial time-loss for treatment and rehabilitation. The most common upper extremity injury locations are the shoulder/clavicle followed by the hand/finger/thumb, elbow, wrist, forearm, and upper arm. The mechanism of injury, presentation, physical examination, and imaging features all play a significant role in reaching the correct diagnosis. Taking to consideration the position the player plays and his demands will also enable tailoring the optimal treatment plan that allows timely and safe return to play. This article discusses common upper extremity injuries observed in soccer players, focusing on proper diagnosis and optimal management.


#9 The Three H's: Head, Heart, and Heat Considerations in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0087.
Authors: Whipple MT, Baggish AL, Pieroth EM, Chiampas GT
Download link: https://www.amjorthopedics.com/article/three-hs-head-heart-and-heat-considerations-soccer
Summary: Soccer requires significant physical conditioning and endurance, as well as the physicality required for contact play. In order to keep athletes safe, it is important that coaches, medical staff, and the players themselves are educated on the most common dangers to their health that they may encounter on a soccer pitch. This article aims to review the current literature and recommendations on concussion, cardiovascular considerations, and heat-related illness as they relate to competitive soccer, with a goal of educating all those who help to keep athletes healthy and competing to their full potential.


#10 The Effect of Playing Position on Injury Risk in Male Soccer Players: Systematic Review of the Literature and Risk Considerations for Each Playing Position
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0092.
Authors: Della Villa F, Mandelbaum BR, Lemak LJ
Download link: https://www.amjorthopedics.com/node/371449/pdf
Summary: Soccer (football) is a complex contact sport with a substantial risk of injury. As injury surveillance is the first step of the injury prevention paradigm, soccer epidemiology is well reported in the existing literature, but less is known about the actual role of player position on the general injury risk. The goal of this study is to present the existing evidence regarding the influence of player's position on general injury risk in male soccer. A systematic review of the Medline database was carried out. Only English written studies on male soccer and citing playing position as a possible determinant of injury risk were included. One hundred and two full texts were evaluated for eligibility, and 11 studies were selected for the qualitative synthesis. Of the 11 studies included in the systematic review, 5 didn't find any significant correlation with between player's position and general injury risk, while the remaining 6 studies found player's position to be correlated with injury risk, with mixed findings depending on each study. The most consistent finding was a tendency for goalkeepers (GKs) to sustain less injuries compared to outfield players. When considering only the studies reporting just the match injury risk, forwards seemed to be at higher risk, even if there wasn't a complete agreement. Few studies have evaluated a possible effect of playing position on general injury risk in male soccer. There is no agreement if weather or not different playing positions are associated to a higher injury risk. GKs seem to be at lower risk of injury when compared to outfield players.


#11 Soccer or Football Medicine? Global Sports Medicine for a Global Game
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0089.
Authors: Osbahr DC
Download link: https://www.amjorthopedics.com/node/366226/pdf


#12 Knee Injuries in Elite Level Soccer Players
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0088.
Authors: Roth TS, Osbahr DC
Download link: https://www.amjorthopedics.com/node/365357/pdf
Summary: As one of the most popular sports in the world, soccer injury rates involving the knee continue to rise. An alarming trend of knee injuries, including increased anterior cruciate ligament ruptures, underscores the need to review our current understanding of these injuries in soccer players. This article includes a critical review of the epidemiology of knee injuries in soccer, anterior cruciate ligament and other ligamentous injuries, cartilage and meniscal injury, post-traumatic osteoarthritis, as well as current prevention initiatives.


#13 Hip and Core Muscle Injuries in Soccer
Reference: Am J Orthop (Belle Mead NJ). 2018 Oct;47(10). doi: 10.12788/ajo.2018.0094.
Authors: Sherman B, Chahla J, Hutchinson W, Gerhardt M
Download link: https://www.amjorthopedics.com/node/371702/pdf
Summary: Soccer is the most popular sport in the world and has the fourth highest number of sports injuries. Hip and groin injuries account for 14% of soccer injuries and can be difficult to recognize and treat as they often require a high level of suspicion and advanced imaging. Groin pain can be separated into 3 categories: (1) defined clinical entities for groin pain (adductor-related, iliopsoas-related, inguinal-related [sports hernias/athletic pubalgia], and pubic-related groin pain), (2) hip-related groin pain (hip morphologic abnormalities, labral tears, and chondral injuries), and (3) other causes of groin pain. Conservative approaches are typically the first line of treatment, but operative intervention has been reported to result in higher rates of return to sport in athletes with hip-related and inguinal-related groin pain injuries. In patients with concurrent hip-related and inguinal-related groin pain, the failure to recognize the relationship and treat both conditions may result in lower rates of return to sport. Preseason screening programs can identify high-risk athletes, who may benefit from a targeted prevention program. Further study on exercise therapy, early surgical intervention, and potential biologic intervention are needed to determine the most effective methods of preventing groin injuries in athletes.

Sat

05

Jan

2019

Latest research in football - week 46 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effect of a Habitual Late-Evening Physical Task on Sleep Quality in Neither-Type Soccer Players
Reference: Front Physiol. 2018 Nov 6;9:1582. doi: 10.3389/fphys.2018.01582. eCollection 2018.
Authors: Vitale JA, Banfi G, La Torre A, Bonato M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6232308/pdf/fphys-09-01582.pdf
Summary: The aim of this study was to investigate objective and subjective sleep quality, daytime tiredness and sleepiness in response to a late-evening high intensity interval training (HIIT) session in neither-type soccer players that habitually trained late in the day. This is the first study that considered both athletes' chronotype and habitual training time as crucial factors when assessing sleep quality in relation to an evening physical task. In this longitudinal, prospective, observational study, 14 Italian soccer players were recruited (mean age: 26.1 ± 4.5 years; height: 1.81 ± 0.06 m; weight: 78.9 ± 6.1 kg) and performed an extra-routine 4 × 4-min HIIT session at 09:00 p.m. Players used to train always between 09:00 and 11:00 p.m during the competitive season. All subjects wore an actigraph to evaluate their objective sleep parameters and a sleep diary was used to record subjective values of sleep quality, daytime tiredness, and daytime sleepiness. All data were analyzed as: the mean of the two nights before (PRE), the night after (POST 1), and the mean of the two nights after (POST 2) the extra-routine HIIT session. The subjects' chronotype was assessed by the morningness-eveningness questionnaire (MEQ). All players were classified as N-types (mean MEQ score: 49.4 ± 3.7). None of the actigraph parameters nor the subjective values of sleep quality, tiredness, and sleepiness showed significant changes in PRE, POST 1, and POST 2. The results of our study added more information regarding sleep quality outcomes in response to a late-evening HIIT session. Athletic trainers and medical staff should always control for chronotype and habitual training time when assessing variations to sleep quality in athletes.


#2 Match outcome and running performance in different intensity ranges among elite soccer players
Reference: Biol Sport. 2018 Jun;35(2):197-203. doi: 10.5114/biolsport.2018.74196. Epub 2018 Mar 31.
Authors: Chmura P, Konefał M, Chmura J, Kowalczuk E, Zając T, Rokita A, Andrzejewski M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234309/pdf/JBS-35-74196.pdf
Summary: The monitoring of players' work-rate profiles during competition is now feasible through computer-aided motion analysis. The aim of the present study was to examine how various playing positions and match outcomes (i.e. won, drawn, lost) affect the total distance, and the distances covered at different intensities, by soccer players in Germany's Bundesliga. Match performance data were collected for 556 soccer players competing in the Bundesliga during the 2014/15, 2015/16 and 2016/17 domestic seasons. A total of 13 039 individual match observations were made of outfield players (goalkeepers excluded). The analysis was carried out using an IMPIRE AG motion analysis system, with records of all players' movements in all the 918 matches. The recorded variables included total distance covered [km] and distance covered at intensities in the ranges below 11 km/h, 11-14 km/h, 14-17 km/h, 17-21 km/h, 21-24 km/h, and above 24 km/h. In won matches, as opposed to drawn and lost matches, the wide midfielders and forwards ran a significantly longer distance, primarily covered at intensities of 21-23.99 and above 24 km/h (p ≤ 0.05). The analysis of full-backs, central defenders and central midfielders in won matches - as opposed to drawn and lost matches - in turn reveals that players ran a significantly shorter distance, most likely to be covered at intensities of 17-20.99 and 21-23.99 km/h (p ≤ 0.05). The results of the present study emphasise the importance of match outcome and playing positions during the assessment of physical aspects of soccer performance.


#3 The "FIFA 11+" injury prevention program improves body stability in child (10 year old) soccer players
Reference: Biol Sport. 2018 Jun;35(2):153-158. doi: 10.5114/biolsport.2018.71604. Epub 2017 Nov 23.
Authors: Gatterer H, Lorenzi D, Ruedl G, Burtscher M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234308/pdf/JBS-35-71604.pdf
Summary: The suitability of the FIFA 11+ prevention programme to improve selected performance outcomes in children aged < 14 years has not been established yet. This study aimed to investigate the effects of the FIFA 11+ programme on jump ability and stability in 10-year-old child soccer players. Sixteen young soccer players (aged 10 years) were randomly assigned to a conventional or a FIFA 11+ warm-up group. During a 5-week training period with 2 sessions per week the FIFA 11+ group warmed up with the 11+ programme, whereas the control group subjects performed their usual warm-up programme (e.g. running exercises with dribbling and/or passing techniques included). After the warm-up, both groups performed the same training exercises during each session. Before and after the training period, standing long jump performance and body stability (S3 Check, unstable uniaxial platform) were assessed. Significant improvements in the stability index were found in both groups (5.6±1.1 to 3.5±1.0 and 5.5±0.8 to 4.0±1.5 for the FIFA 11+ and the control group, respectively, p<0.001, partial η²=0.886 for the training effect of the analysis of variance) with likely (qualitative inference analysis) greater improvements in the FIFA 11+ group compared to the control group (p=0.078, partial η²=0.205 for the training x group interaction effect of the analysis of variance). Training had no effect on standing long jump performance (p>0.05). Data indicate that in 10-year-old soccer players the FIFA 11+ programme may have the potential to improve stability. Thus, the FIFA 11+ programme might contribute to injury prevention and possibly to better soccer performance as well. This might especially apply if the programme is performed over a longer period and/or with more weekly training sessions. Based on the present results the inclusion of such a programme within the training practice of the child soccer player can be recommended.


#4 Physiological responses, fatigue and perception of female soccer players in small-sided games with different pitch size and sport surfaces
Reference: Biol Sport. 2018 Sep;35(3):291-299. doi: 10.5114/biolsport.2018.77829. Epub 2018 Aug 27.
Authors: López-Fernández J, Sánchez-Sánchez J, Rodríguez-Cañamero S, Ubago-Guisado E, Colino E, Gallardo L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224843/pdf/JBS-35-77829.pdf
Summary: The aim of this research was to evaluate the influence of game surface and pitch size on the physiological responses, jump performance and perceptions of sub-elite female soccer players playing four-a-side games. Sixteen sub-elite female soccer players were divided into four groups of four players each. Three small-sided games (SSGs; pitch size: 400 m2, 600 m2 and 800 m2) were played on three surfaces (dirt [DT], artificial turf [AT] and natural grass [NG]). Players' heart rate (HR) was monitored during each game. Before and after each SSG, participants performed two counter-movement jumps (CMJs) and answered a questionnaire based on visual analogue scales (VASs) to indicate their perception of the effort required on each surface. DT obtained lower outputs for most variables. In the SSG 600 mean HR was higher on NG than AT (+3.31 %HRmax; p = 0.029), but players' overall satisfaction with both surfaces was similar (p>0.05). The SSG 400 received the lowest ratings for most variables, whereas the SSG 600 resulted in higher mean HR than SSG 800 [NG (+9.14 b.p.m.; p = 0.001); AT (+7.32 b.p.m.; p = 0.014)]. No surface differences in CMJ performance were found. In conclusion, a higher internal load can be achieved on NG, whereas DT is not recommended for playing soccer. Moreover, the internal load on players in SSGs can be controlled by manipulating pitch size, but over-large pitches may entail a reduction in the physiological profile of female soccer players.


#5 Effects of preconditioning hamstring resistance exercises on repeated sprinting-induced muscle damage in female soccer players
Reference: Biol Sport. 2018 Sep;35(3):269-275. doi: 10.5114/biolsport.2018.77827. Epub 2018 Aug 27.
Authors: Chen CH, Chen YS, Wang YT, Tseng WC, Ye X.
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224846/pdf/JBS-35-77827.pdf
Summary: The purpose was to examine whether adding preconditioning hamstring resistance exercises to a regular warm-up prior to a repeated sprinting exercise provides protection against the sprinting-induced muscle damage. Ten female soccer players (mean ± SD age: 21.3 ± 4.5yrs; height: 171.34 ± 8.29 cm; weight: 68.53 ± 11.27 kg) participated in this study. After the familiarization visit, the subjects completed three separate randomly sequenced experimental visits, during which three different warm-up interventions were performed before the muscle-damaging protocol (12 sets of 30-m maximal repeated sprints): 1. Regular running and static stretching (Control); 2. Control with hyperextensions (HE); 3. Control with single leg Romanian deadlift (SLRD). Before (Pre), immediately (Post0), 24 hours (24hr), and 48 hours after (48hr) the sprints, hamstring muscle thickness, muscle stiffness, knee flexion eccentric peak torque, knee extension concentric peak torque, and functional hamstring to quadriceps ratios were measured. Repeated sprints have induced muscle damage (e.g., an average of 42% knee flexion eccentric strength reduction) in all three conditions. After the SLRD, hamstring muscle thickness decreased from 24hr to 48hr (p < 0.001). Additionally, muscle stiffness and eccentric strength for the SLRD showed no difference from baseline at 24hr and 48hr, respectively. When compared with the SLRD at 48hr, the muscle stiffness and the eccentric strength were greater and lower, respectively, in other protocols. The SLRD protocol had protective effect on sprinting-induced muscle damage markers than other protocols. Athletes whose competitions/training are densely scheduled may take advantage of this strategy to facilitate muscle recovery.


#6 Effect of the 11+ injury prevention programme on fundamental movement patterns in soccer players
Reference: Biol Sport. 2018 Sep;35(3):229-236. doi: 10.5114/biolsport.2018.74636. Epub 2018 Apr 1.
Authors: Rey E, Padrón-Cabo A, Penedo-Jamardo E, González-Víllora S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224851/pdf/JBS-35-74636.pdf
Summary: No studies have assessed whether changes in an individual's fundamental movement patterns can be achieved with the 11+ prevention programme in soccer players. The aim of this study was to assess the effect of the 11+ compared with a standard warm-up on fundamental movement patterns using the Functional Movement Screen (FMS) in amateur male soccer players. Twenty-three male soccer players (age: 24.7±.3.8 years; height: 1.77±0.58 m; body mass: 73.9±6.2 kg) were randomly assigned to the 11+ (n= 12) or control (n= 11) group. The intervention programme had to be carried out 3 times a week over 6 weeks. The 11+ warm-up lasted ~25 minutes and was conducted before starting regular practice, replacing the team's standard warm-up. The control group warmed up with standard jogging, ball exercises, and active stretching to match the duration of the 11+. Within-group analysis revealed significant improvements in the FMS total score in the 11+ (+10.51%; d= 0.83) and control group (+7.99%; d= 0.68) from pre-test to post-test. In the between-group analysis, there were no significant differences between groups. At the post-test a significantly greater number of players in the 11+ group exhibited a score that improved to above the injury threshold (≤14) (p= 0.046). This study suggests that regular implementation of the 11+ injury prevention programme may not produce additional improvements in fundamental movement patterns other than those produced by a standard warm-up.


#7 Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles measured using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement study in elite football (soccer) players
Reference:  J Electromyogr Kinesiol. 2018 Nov 10;44:21-30. doi: 10.1016/j.jelekin.2018.11.005. [Epub ahead of print]
Authors: Hughes T, Jones RK, Starbuck C, Picot J, Sergeant JC, Callaghan MJ
Download link: https://reader.elsevier.com/reader/sd/pii/S1050641118303419?token=E1B0B5B18BD00B5331DDA5375C0DF58DA9AE8FE7C4A0F44DCC209E6B906A0DE3B9EB9779AA1722C2D3EB313DB6B74A08
Summary: During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using 2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation coefficient (ICC) range = 0.27-0.83, standard error of measurement (SEM) range = 2.12-6.23°, minimal detectable change (MDC) range = 5.87-17.26°). Between-sessions, ATA reliability was good for both systems (ICCs = 0.70-0.74, SEMs = 1.64-7.53°, MDCs = 4.55-7.01°), while IMU RTA and 2D FPPA reliability ranged from poor to good (ICCs = 0.39-0.72, SEMs = 2.60-5.99°, MDCs = 7.20-16.61°). All limits of agreement exceeded a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not useful surrogates for 2D video FPPA measures in this population.


#8 Exploring how playing football with different age groups affects tactical behaviour and physical performance
Reference: Biol Sport. 2018 Jun;35(2):145-153. doi: 10.5114/biolsport.2018.71603. Epub 2017 Nov 23.
Authors: Figueira B, Gonçalves B, Masiulis N, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234305/pdf/JBS-35-71603.pdf
Summary: The study aimed to compare footballers' performances when playing with teammates and opponents from the same age group with performances when playing with teammates and opponents of different age groups. Three football matches were played: i) under-15 (U15) players played with each other; ii) under-17 (U17) players played with each other; and iii) players under the age of 15 and 17 played with each other in two equivalent mixed age teams. The players' physical performance was measured using the distances covered at different speed categories and tactical behaviour was assessed using several positioning-derived variables. The results showed that, when playing in the mixed age condition, the U15 players increased the distance covered in sprinting intensity (18.1%; ±21.1%) and the U17 players increased the distance covered in jogging zones (6.8%; ±6.5%). The intra-team movement synchronization in longitudinal and lateral displacements was higher when U15 players confronted peers of the same age, in the first half (-13.4%; ±2.0%, -20.3%; ±5.7% respectively), and when U17 players confronting the mixed group, in both halves (-16.9%; ±2.5%, 9.8%; ±4.0% and 7.9%; ±5.7%, 10.6% ±4.4%, respectively). The differences between age groups and the mixed condition may be connected with the level of players' tactical expertise and adaptive positioning according to the dynamic environmental information. In general, these results suggest that mixing the age groups may be useful to promote a wider range of training session stimuli in these young football players.


#9 Elite football teams that do not have a winter break lose on average 303 player-days more per season to injuries than those teams that do: a comparison among 35 professional European teams
Reference: Br J Sports Med. 2018 Nov 15. pii: bjsports-2018-099506. doi: 10.1136/bjsports-2018-099506. [Epub ahead of print]
Authors: Ekstrand J, Spreco A, Davison M
Summary: The purpose was to compare injury rates among professional men's football teams that have a winter break in their league season schedule with corresponding rates in teams that do not. 56 football teams from 15 European countries were prospectively followed for seven seasons (2010/2011-2016/2017)-a total of 155 team-seasons. Individual training, match exposure and time-loss injuries were registered. Four different injury rates were analysed over four periods within the season, and linear regression was performed on team-level data to analyse the effect of winter break on each of the injury rates. Crude analyses and analyses adjusted for climatic region were performed. 9660 injuries were reported during 1 447 011 exposure hours. English teams had no winter break scheduled in the season calendar: the other European teams had a mean winter break scheduled for 10.0 days. Teams without a winter break lost on average 303 days more per season due to injuries than teams with a winter break during the whole season (p<0.001). The results were similar across the three periods August-December (p=0.013), January-March (p<0.001) and April-May (p=0.050). Teams without a winter break also had a higher incidence of severe injuries than teams with a winter break during the whole season (2.1 severe injuries more per season for teams without a winter break, p=0.002), as well as during the period January-March (p=0.003). A winter break was not associated with higher team training attendance or team match availability. Climatic region was also associated with injury rates. The absence of a scheduled winter break was associated with a higher injury burden, both before and during the two periods following the time that many European teams take a winter break. Teams without a winter break (English clubs) had a higher incidence of severe injuries following the time of the year that other teams (other European clubs) had their scheduled break.


#10 Cardiovascular incidents in male professional football players with negative preparticipation cardiac screening results: an 8-year follow-up
Reference: Br J Sports Med. 2018 Nov 15. pii: bjsports-2018-099845. doi: 10.1136/bjsports-2018-099845. [Epub ahead of print]
Authors: Berge HM, Andersen TE, Bahr R
Summary: Preparticipation cardiac screening of athletes aims to detect cardiovascular disease at an early stage to prevent sudden cardiac arrests and deaths. Few studies have described the cardiovascular outcomes in athletes classified as negative on screening.  The purpose was to identify cardiovascular incidents in a cohort of male professional football players who were cleared to play after a negative screening result. This is a retrospective 8-year follow-up study of 595 professional male football players in Norway who underwent preparticipation cardiac screening by experienced cardiologists, including electrocardiography (ECG) and echocardiography, in 2008. We performed a media search to identify sudden cardiovascular incidents between January 2008 and February 2016. Incidents were cross-checked with medical records. Six of the 595 players (1%), all classified as negative on cardiac screening, experienced severe cardiovascular incidents during follow-up. Retrospective review revealed abnormal ECG findings in one case, not recognised at the time of screening. Three players suffered a sudden cardiac arrest (all resuscitated successfully), one a myocardial infarction, one a transient ischaemic attack and one atrial flutter. Three of the players ignored chest pain, paresis, dyspnoea or near-syncope, two completed a match with symptoms before seeking medical assistance, one player's symptoms were misinterpreted and received inappropriate treatment initially, and two players were discharged from hospital without proper follow-up, despite having serious cardiovascular symptoms. A comprehensive preparticipation cardiac screening did not identify a subset of 6 of 595 players who experienced subsequent cardiovascular incidents as being at risk. It is important to remind athletes that a normal cardiac screening exam does not protect against all cardiac diseases. Timely reporting of symptoms is essential.

Tue

01

Jan

2019

Latest research in football - week 45 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 The Within-Subject Correlation Between Salivary IgA and Measures of Training Load in Elite Football Players
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-11. doi: 10.1123/ijspp.2018-0455. [Epub ahead of print]
Authors: Figueiredo P, Nassis GP, Brito J
Summary: The purpose was to quantify the association between salivary secretory immunoglobulin A (sIgA) and training load in elite football players. Data were obtained in four consecutive days during the preparation camp for the Rio 2016 Olympic Games. Saliva samples of 18 elite male football players were collected prior to breakfast. The session rating of perceived exertion (s-RPE) and external training load metrics from GPS were recorded. Within-subject correlation coefficients between training load and sIgA concentration, and magnitude of relationships were calculated. sIgA presented moderate to large negative correlations with s-RPE (r=-0.39), total distance covered (r=-0.55), accelerations (r=-0.52) and decelerations (r=-0.48). Trivial to small associations were detected between sIgA and distance covered per minute (r=0.01), high-speed distance (r=-0.23) and number of sprints (r=-0.18). sIgA displayed a likely moderate decrease from day 1 to day 2 (d=-0.7) but increased on day 3 (d=0.6). The training load variables had moderate to very large rises from day 1 to day 2 (d=0.7 to 3.2), but lowered from day 2 to day 3 (d=-5.0 to -0.4), except for distance per minute (d=0.8) and sprints (unclear). On day 3, all training load variables had small to large increments compared with day 1 (d=0.4 to1.5), with exception of accelerations (d=-0.8) and decelerations (unclear). In elite football sIgA might be more responsive to training volume rather than intensity. External load such as GPS-derived variables presented stronger association with sIgA compared with s-RPE. Salivary IgA can be used as an additional objective tool in monitoring football players.


#2 The Influence of Hamstring Muscle Peak Torque and Rate Of Torque Development for Sprinting Performance in Football Players: A Cross-Sectional Study
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-27. doi: 10.1123/ijspp.2018-0464. [Epub ahead of print]
Authors: Ishøi L, Aagaard P, Nielsen MF, Thornton KB, Krommes KK, Hölmich P, Thorborg K
Summary: This cross-sectional study aimed to investigate the association between hamstring muscle peak torque and rapid force capacity (rate of torque development: RTD) versus sprint performance in elite youth football players. Thirty elite academy youth football players (16.75 ± 1.1 years, 176.9 ± 6.7 cm, 67.1 ± 6.9 kg) were included. Isometric peak torque (Nm/kg) and early (0-100 ms) and late (0-200 ms) phase RTD (RTD100, RTD200) (Nm/s/kg) of the hamstring muscles were obtained as independent predictor variables. Sprint performance was assessed during a 30-m sprint trial. Mechanical sprint variables (maximal horizontal force production (FH0) (N/kg); maximal theoretical velocity (V0) (m/s); maximal horizontal power output (Pmax) (W/kg)) and sprint split times (0-5 m; 0-15 m; 0-30 m; 15-30 m) (s) were derived as dependent variables. Subsequently, linear regression analysis was conducted for each pair of dependent and independent variables. Positive associations were observed between hamstring RTD100 and FH0 (r2=0.241, p=0.006) and Pmax (r2=0.227, p=0.008). Furthermore, negative associations were observed between hamstring RTD100 and 0-5 m (r2=0.206, p=0.012), 0-15 m (r2=0.217, p=0.009) and 0-30 m sprint time (r2=0.169, p=0.024). No other associations were observed. The present data indicate that early-phase (0-100 ms) rapid force capacity of the hamstring muscles plays an important role for the acceleration capacity in elite youth football players. In contrast, no associations were observed between hamstring muscle function and maximal sprint velocity. This indicates that strength training focusing on improving early-phase hamstring rate of force development may contribute to enhance sprint acceleration performance in this athlete population.


#3 Circulation, Cell-free DNA for Monitoring Player Load in Professional Football
Reference: Int J Sports Physiol Perform. 2018 Nov 14:1-27. doi: 10.1123/ijspp.2018-0756. [Epub ahead of print]
Authors: Haller N, Ehlert T, Schmidt S, Ochmann D, Sterzing B, Grus F, Simon P
Authors: Player monitoring in elite sports settings is becoming increasingly important. Beside questionnaire based methods, biomarkers, such as circulating, cell-free DNA (cfDNA) are sug-gested for load monitoring. cfDNA concentrations were shown to increase dependent on total distance covered in football and was associated with overtraining in weightlifters. Thus, the objective of this study was to examine whether cfDNA is feasible as a monitoring tool in elite football players. We collected capillary blood samples from 22 male elite football players over 4 months of a regular season. Sampling was conducted the day before, one day after or several days after regular season games and/or training. In addition, each player filled in a Visual-Analogue-Scale questionnaire (VAS) including the items "general perceived exer-tion", "muscular fatigue" and "mental fatigue". Performance during training and games was tracked by the Catapult system (training) and with the OPTA system (games), respectively. cfDNA values were significantly elevated in players the day after regular season games (1.4-fold; p=0.0004) in line with the scores of the VAS. Both parameters showed sig-nificantly higher values during midweek game weeks. While cfDNA concentrations correlated with training data, the VAS was correlated with the tracking of the season games. However, cfDNA and VAS did not correlate with each other. Here we show that cfDNA concentrations at rest and VAS scores are influenced by previous load in professional football players. Future studies will reveal whether cfDNA might serve as a practically applicable marker for player load in football players.


#4 Towards the use of multidimensional performance indicators in football small-sided games: the effects of pitch orientation
Reference: J Sports Sci. 2018 Nov 14:1-8. doi: 10.1080/02640414.2018.1543834. [Epub ahead of print]
Authors: Folgado H, Bravo J, Pereira P, Sampaio J
Summary: This study aimed to compare youth football players' performance during two small-sided games with different pitch orientation: i) 40x30m and ii) 30x40m formats. Twenty under-15 players (age = 14.1 ± 0.5 years) participated in nine GK+4vs4+GK situations in each format, with the duration of six minutes each. Positional data were collected using individual GPS units, and computed for tactical and physical performance indicators. The SSG were video recorded, using notational analysis for collecting technical indicators. A novel method that incorporates time dependent notational information with spatiotemporal data was used to compute multidimensional parameters. Standardised effect sizes and non-clinical magnitude-based inferences were used to compare formats. Results showed that players covered more distance at higher intensities, presented more passes and dribbles and were more synchronised in the longitudinal axis while playing in the 40x30m pitch. In the 30x40m pitch, results showed a lower distance between team centroids, higher number of shots, more lateral passes and a wider team positioning. Multidimensional indicators, as players position and distance to the closest defender while shooting, revealed a more constant distance between attacker and defender in the 40x30m pitch. These results highlight the importance of integrating information from different indicators for a contextually valid information.


#5 Analysis of the PPARD Gene Expression Level Changes in Football Players in Response to the Training Cycle
Reference: Balkan J Med Genet. 2018 Oct 29;21(1):19-25. doi: 10.2478/bjmg-2018-0008. eCollection 2018 Jun.
Authors: Domańska-Senderowska D, Snochowska A, Szmigielska P, Jastrzębski Z, Jegier A, Kiszałkiewicz J, Dróbka K, Jastrzębska J, Pastuszak-Lewandoska D, Cięszczyk P, Maciejewska-Skrendo A, Zmijewski P, Brzeziańska-Lasota E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231314/pdf/bjmg-21-019.pdf
Summary: The PPARD gene codes protein that belongs to the peroxisome proliferator-activated receptor (PPAR) family engaged in a variety of biological processes, including lipid metabolism in muscle cells. In this study, we assess the relationship between PPARD gene expression lipid metabolism parameters and the variation of the PPARD gene expression before (T1) and after 12 hours of training (T2) sessions in a group of football players. Peripheral blood lymphocytes were obtained from 22 football players (17.5±0.7 years, 178±0.7 cm, 68.05±9.18 kg). The PPARD gene expression, analyzed by quantitative polymerase chain reaction (qPCR), was significantly higher after T2 (p = 0.0006). Moreover, at the end of the training cycle, there was a significant decrease in relative fat tissue (FAT) (%) (p = 0.01) and absolute FAT (kg) (p = 0.01). A negative correlation was observed between absolute FAT (kg) and PPARD gene expression level in T2 (p = 0.03). The levels of cholesterol and triglyceride (TG) fractions were not significantly different (p >0.05) before and after training. No significant relationship between PPARD expression and cholesterol or TG levels was found. We found that physical training affects PPARD expression. Moreover, the negative correlation between PPARD expression and absolute FAT (kg) level may be indicative of the contribution of PPARD in metabolic adaptation to increased lipid uptake that can be used to control the body composition of athletes.


#5 Tattoos among elite football players during the 2018 FIFA World Cup Russia
Reference: J Eur Acad Dermatol Venereol. 2018 Nov 13. doi: 10.1111/jdv.15338. [Epub ahead of print]
Authors: Kluger N, Samimi M
Download link: J Eur Acad Dermatol Venereol. 2018 Nov 13. doi: 10.1111/jdv.15338. [Epub ahead of print]
Summary: Currently 10 to 30% of the general population has tattoos. Professional athletes harbor visible tattoos during sports events and advertisement. Motivations for tattoos may include body embellishment, expression of personal values or group affiliation. Tattoos may bolster ego, be the expression of physical strength and of traits of aggression and rebelliousness. We wondered whether being tattooed reflects players' performance and discipline. We investigated this hypothesis among elite football players during the 2018 FIFA World Cup.


#6 High incidence of hip and knee arthroplasty in former professional, male football players
Reference: J Sports Med Phys Fitness. 2018 Nov 8. doi: 10.23736/S0022-4707.18.08962-4. [Epub ahead of print]
Authors: Volpi P, Quaglia A, Carimati G, Petrillo S, Bisciotti GN
Summary: The purpose of this study was to estimate the incidence of hip and knee arthroplasty in Italian male professional football (soccer) players who have played for a minimum 10 years in the Italian major football leagues. The study group was formed by 104 male professional football players who were interviewed to evaluate the incidence of hip and knee arthroplasty. The data were collected through a questionnaire and the results collected were compared with a control group of 100 volunteers matched for age, weight and height, who did not present orthopaedic diseases but had never practiced sport. In the study group, 26 subjects (25 %) underwent hip and knee arthroplasty at an average mean age of 62.1 + 6 years. The frequency of arthroplasty was: 13.5% for the hip, 5.8% for the knee and 5.8% for both hip and knee. In the control group, the incidence of arthroplasty was 1% for the knee and no subjects presented hip arthroplasty. Italian male, former professional football players present a higher than normal incidence of hip and knee arthroplasty. Further studies are necessary to understand the pathological pathways underlying the ethiology of hip and knee osteoarthritis in male populations of former professional football players in order to develop effective preventive programmes to reduce the percentage of arthroplasties.


#7 Stepovers and Signal Detection: Response Sensitivity and Bias in the Differentiation of Genuine and Deceptive Football Actions
Reference: Front Psychol. 2018 Oct 29;9:2043. doi: 10.3389/fpsyg.2018.02043. eCollection 2018.
Authors: Jackson RC, Barton H, Ashford KJ, Abernethy B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6215843/pdf/fpsyg-09-02043.pdf
Summary: The ability to differentiate genuine and deceptive actions was examined using a combination of spatial and temporal occlusion to examine sensitivity to lower body, upper body, and full body sources of visual information. High-skilled and low-skilled association football players judged whether a player genuinely intended to take the ball to the participant's left or right or intended to step over the ball then take it in the other direction. Signal detection analysis was used to calculate measures of sensitivity (d') in differentiating genuine and deceptive actions and bias (c) toward judging an action to be genuine or deceptive. Analysis revealed that high-skilled players had higher sensitivity than low-skilled players and this was consistent across all spatial occlusion conditions. Low-skilled players were more biased toward judging actions to be genuine. Receiver Operating Characteristic (ROC) curves revealed that accuracy on deceptive trials in the lower body and full body conditions most accurately classified participants as high-skilled or low-skilled. The results highlight the value of using signal detection analysis in studies of deceptive actions. They suggest that information from the lower body or upper body was sufficient for differentiating genuine and deceptive actions and that global information concurrently derived from these sources was not necessary to support the expert advantage.


#8 Effectiveness of Field-Based Resistance Training Protocols on Hip Muscle Strength Among Young Elite Football Players
Reference: Clin J Sport Med. 2018 Oct 29. doi: 10.1097/JSM.0000000000000649. [Epub ahead of print]
Authors: Kohavi B, Beato M, Laver L, Freitas TT, Chung LH, Dello Iacono A
Summary: The objective of this study was to examine the effects of an 8-week progressive resistance training program on hip joint muscles' strength measures, using the Copenhagen adduction (CA) and the sliding hip (SH) exercises. Forty-two young male football athletes (age 17.5 ± 1.1 years; height 178.3 ± 3.2 cm; body mass 66.1 ± 8.6 kg) allocated to a CA, SH, and matched control (C) group participated in this study. Maximal eccentric strength test for the hip adductor (EHAD) and maximal eccentric strength test for the hip abductor (EHAB) muscles, and the relative EHAD/EHAB ratio assessed through a break test in the side-lying position. No significant differences between groups were found at baseline for any of the assessed variables (all P > 0.053). The CA group had a significant strength increase in the right and left leg (d = 2.11, d = 1.9, respectively). The SH group also had a significant strength increase in the right and left leg (d = 1.68 and d = 1.67, respectively). The CA group presented EHAD/EHAB improvements in the right and left leg (d = 0.84 and d = 1.14, respectively). The SH group also presented EHAD/EHAB improvements in the right and left leg (d = 1.34 and d = 1.44, respectively). Both exercises' protocols were effective in inducing significant increases on EHAD, EHAB, and EHAD/EHAB ratio when compared with the control group. Practitioners should be aware of the training effectiveness of both protocols.


#9 Recommendations for hamstring injury prevention in elite football: translating research into practice
Reference: Br J Sports Med. 2018 Nov 9. pii: bjsports-2018-099616. doi: 10.1136/bjsports-2018-099616. [Epub ahead of print]
Authors: Buckthorpe M, Wright S, Bruce-Low S, Nanni G, Sturdy T, Gross AS, Bowen L, Styles B, Della Villa S, Davison M, Gimpel M
Download link: https://bjsm.bmj.com/content/bjsports/early/2018/11/09/bjsports-2018-099616.full.pdf

Tue

01

Jan

2019

Latest research in football - week 44 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Variation in the Correlation Between Heart Rate and Session Rating of Perceived Exertion-Based Estimations of Internal Training Load in Youth Soccer Players
Reference: Pediatr Exerc Sci. 2018 Oct 28:1-8. doi: 10.1123/pes.2018-0033. [Epub ahead of print]
Authors: Vahia D, Kelly A, Knapman H, Williams CA
Summary: When exposed to the same external load, players receive different internal loads, resulting in varied adaptations in fitness. In adult soccer, internal training load is measured using heart rate (HR) and session rating of perceived exertion (sRPE) scales, but these have been underutilized in youth soccer. This study investigated the in-season variation in correlation between HR and sRPE estimations of training load for adolescent soccer players. Fifteen male professional adolescent players were monitored for 7 months. Within-participant correlations and Bland-Altman agreement plots for HR and sRPE were calculated for each month to analyze variation over the season and for individual players to analyze the validity of the scale. The monthly correlations ranged from r = .60 to r = .73 (P < .05) and the overall correlation was r = .64 (95% confidence interval, .60-.68; P < .001). Bland-Altman plots showed an agreement of methods. Results showed consistently large correlations for all months. sRPE is a consistent method of measure of internal training load for the entire season for youth soccer players. Validity analysis found no bias in sRPE measurements when compared with HR for all players in the study.


#2 Mental Fatigue in Football: Is it Time to Shift the Goalposts? An Evaluation of the Current Methodology
Reference: Sports Med. 2018 Nov 2. doi: 10.1007/s40279-018-1016-z. [Epub ahead of print]
Authors: Thompson CJ, Fransen J, Skorski S, Smith MR, Meyer T, Barrett S, Coutts AJ
Summary: Research in football for a long time has focused on the physical nature of fatigue as opposed to its mental aspects. However, since 2016, six original articles have investigated the effects of induced mental fatigue in football on isolated physical, skill and decision-making performance tests, along with physical, technical and tactical performance outcomes in small-sided games. Whilst these studies have overall shown a negative impact of mental fatigue on task performance, this current opinion aims to critically examine the methodological approach to this problem, most notably the lack of ecological validity when inducing mental fatigue and the present approach to measuring mental fatigue using visual analogue scales (VAS). It is suggested that future research on mental fatigue in football may benefit from the use of surveys/interviews to understand the true cognitive demands of elite football players. Additionally, future research should aim to reduce the reliance on using VAS to measure mental fatigue as results from this tool may be confounded by several response biases. In conclusion, this article highlights the need for mentally fatiguing tasks that adequately represent football-associated mental fatigue and assessments of mental fatigue that minimise the confounding effect of response bias.


#3 A systematic review on small-sided games in football players: Acute and chronic adaptations
Reference: J Sports Sci. 2018 Oct 29:1-29. doi: 10.1080/02640414.2018.1535821. [Epub ahead of print]
Authors: Bujalance-Moreno P, Latorre-Román PÁ, García-Pinillos F
Summary: Small-sided games (SSG) are played on a small pitch, often using modified rules and involving a smaller number of players. This article aimed to critically analyse the literature to determine how small-sided games affect the performance of football players in the short- and long term. Electronic databases were searched for literature dating from January 2000 to July 2018. The methodological quality of the studies was evaluated using the modified Downs and Black Quality Index (cross-sectional studies) and the Physiotherapy Evidence Database (PEDro) scale (intervention studies). Fifty-three studies, 44 cross-sectional and 9 intervention studies, met the inclusionary criteria for review. Most of the cross-sectional studies focused on describing the differences between SSG protocols, whereas 4 studies focused on making a comparison between "interval" and "continuous" SSG training regimes. On the other hand, intervention studies focused on making a comparison between SSG-based protocols and high-intensity intermittent training (HIIT)-based running protocols, in addition to determine the effect of a SSG-based training programme alone. SSG-based football plans (2 to 4 SSG sessions per week) show athletic performance improvements in football players by improving sprint, repeated sprint ability (RSA) and change of direction (COD) along with muscular and physiological adaptation.


#4 Player Tracking Data Analytics as a Tool for Physical Performance Management in Football: A Case Study from Chelsea Football Club Academy
Reference: Sports (Basel). 2018 Oct 26;6(4). pii: E130. doi: 10.3390/sports6040130.
Authors: De Silva V, Caine M, Skinner J, Dogan S, Kondoz A, Peter T, Axtell E, Birnie M, Smith B
Summary: Global positioning system (GPS) based player movement tracking data are widely used by professional football (soccer) clubs and academies to provide insight into activity demands during training and competitive matches. However, the use of movement tracking data to inform the design of training programmes is still an open research question. The objective of this study is to analyse player tracking data to understand activity level differences between training and match sessions, with respect to different playing positions. This study analyses the per-session summary of historical movement data collected through GPS tracking to profile high-speed running activity as well as distance covered during training sessions as a whole and competitive matches. We utilise 20,913 data points collected from 53 football players aged between 18 and 23 at an elite football academy across four full seasons (2014⁻2018). Through ANOVA analysis and probability distribution analysis, we compare the activity demands, measured by the number of high-speed runs, the amount of high-speed distance, and distance covered by players in key playing positions, such as Central Midfielders, Full Backs, and Centre Forwards. While there are significant positional differences in physical activity demands during competitive matches, the physical activity levels during training sessions do not show positional variations. In matches, the Centre Forwards face the highest demand for High Speed Runs (HSRs), compared to Central Midfielders and Full Backs. However, on average the Central Midfielders tend to cover more distance than Centre Forwards and Full Backs. An increase in high-speed work demand in matches and training over the past four seasons, also shown by a gradual change in the extreme values of high-speed running activity, was also found. This large-scale, longitudinal study makes an important contribution to the literature, providing novel insights from an elite performance environment about the relationship between player activity levels during training and match play, and how these vary by playing position.


#5 Fitness effects of one year soccer training of 8-10 and 10-12 years old school children
Reference: J Sports Med Phys Fitness. 2018 Oct 31. doi: 10.23736/S0022-4707.18.08612-7. [Epub ahead of print]
Authors: Michailidis Y, Metaxas TI, Stefanidis P, Christoulas K
Summary: The purpose of the study was to investigate the effect of one year soccer training on physical fitness performance, of U10 and U12 youth levels. 28, 10-year-old and 28, 12-year-old children participated in the study. In the U12 group, 19 children participated only in the physical fitness sessions at school (control group - CG) and 9 children in four extra soccer trainings (Soccer group - SG). In the U10 group, 11 children participated only in the physical fitness sessions at school (control group - CG) and 17 children in four extra soccer trainings (Soccer group - SG). Height, body weight, body fat, standing long jump, 30 m sprint, sit and reach test, abdominal test and Yo-Yo IE1 tests were performed at the beginning and at the end of the season. School physical education programs and soccer training cannot affect anthropometric characteristics like body fat and body mass index. Soccer groups improve their performances at all fitness tests (p<0.05). The U10 control group didn't increase its performance in abdominal test and the U12 level control group didn't improve in the abdominal test nor Yo-Yo IE1 test. Soccer groups in all ages indicated greater improvements than control groups (p<0.05). In conclusion soccer training four times per week can improve the physical fitness of U10 and U12 children's.


#6 Prevalence of vitamin D deficiency amongst soccer athletes and effects of 8 weeks supplementation
Reference: J Sports Med Phys Fitness. 2018 Oct 31. doi: 10.23736/S0022-4707.18.08551-1. [Epub ahead of print]
Authors: Teixeira P, Santos AC, Casalta-Lopes J, Almeida M, Loureiro J, Ermida V, Caldas J, Fontes-Ribeiro C
Summary: High prevalence of vitamin D deficiency is well known around the world in risk populations. Although less is known about the athletic population, some studies report vitamin D deficiency amongst athletic population and adequate vitamin D levels are crucial for athletic population as it can prevent injuries such as stress fractures and might even have ergogenic effects for example on muscle function. The main objectives were to evaluate the basal serum levels of 25(OH)D and calcium in professional soccer athletes on the latitude 40 ̊N, to evaluate the effects in 25(OH)D and calcium serum levels following supplementation of 1667 IU/day of cholecalciferol during a period of 8 weeks and evaluate eventual toxicity arising from it. 28 professional athletes were evaluated according to the skin type. Basal serum levels of 25(OH)D and calcium were evaluated during winter months. Athletes were then supplemented with cholecalciferol 25.000 IU every two weeks. Serum levels of 25(OH)D and calcium were evaluated after supplementation. 25(OH)D initially ranged between 9.9 ng/mL and 32.9 ng/mL with a median of 19.2 IQR 7.24 ng/mL. A statistically significant inverse correlation exists between vitamin D deficiency and the Fitzpatrick scale (ρ= - 0,555 p=0.003). After 8 weeks, 25(OH)D ranged between 10.6 ng/mL and 43.4 ng/mL with a median of 33.2 ng/mL IQR 6.1 ng/mL. We verified a statistically significant increase of serum 25(OH) D levels (11.74 ± 5.988; IC95% [9,02; 14,47]; p<0,001. In addition, there was a statistically significant reduction of calcium: -0,36 ± 0,457; IC95% [- 0,57; -0,15]; p=0,002. Professional athletes have a high prevalence of vitamin D. Supplementation with cholecalciferol in winter months during 8 weeks is safe and effective in raising 25(OH)D serum levels. However, it may not be sufficient for athletes to reach adequate vitamin D levels.


#7 Changes in Transcranial Sonographic Measurement of the Optic Nerve Sheath Diameter in Non-concussed Collegiate Soccer Players Across a Single Season
Reference: Cureus. 2018 Aug 3;10(8):e3090. doi: 10.7759/cureus.3090.
Authors: Sadrameli SS, Wong MS, Kabir R, Wiese JR, Podell K, Volpi JJ, Gadhia RR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207277/pdf/cureus-0010-00000003090.pdf
Summary: Introduction Bedside ultrasound measurement of the optic nerve sheath diameter (ONSD) is emerging as a non-invasive technique to evaluate and predict raised intracranial pressure (ICP) in both children and adults. The prognostic value of increased ONSD on brain computed tomography (CT) scan has previously been correlated with increased intensive care unit (ICU) mortality in patients with severe traumatic brain injury (TBI). Previous studies have also evaluated the association between high-contact sports, such as soccer, and TBI; however, the related changes in ONSD are still unknown. The aim of this study was to evaluate for the natural evolution of changes in ONSD in athletes who participate in high-contact sports. Methods In this prospective observational study, volunteers from a collegiate women's soccer team underwent the measurement of ONSD with transcranial Doppler (TCD). ONSDs were measured during the initial visit during the pre-season period and again at the three-month follow-up. A single experienced neuro-sonographer performed all measurements to eliminate any operator bias. Results Twenty-four female college soccer players between the ages of 18 and 23 were included in this analysis. Mean ONSD during the initial pre-season clinic visit and the three-month follow-up were 4.14±0.6 mm and 5.02±0.72 mm, respectively (P < 0.0001). A two-tailed t-test analysis was performed, which resulted in a t-value of 4.76 and P < 0.00001. The average ONSD measured during the post-season follow-up showed a 21.3% increase compared to the baseline. Conclusion The evaluation of high-contact sports athletes is limited due to the lack of objective radiologic and diagnostic tools. Moreover, in an athlete suffering a concussion, return-to-play decisions are heavily dependent on the symptoms reported by the athletes. In our analysis of collegiate women's soccer players, active participation in soccer competitions and practice may be associated with an increase in ONSD, independent of concussions. Further studies are underway to evaluate the clinical significance of these findings as well as possible correlations between concussions and changes in ONSD.


#8 Changes in Sport Nutrition Knowledge, Attitudes/Beliefs and Behaviors Following a Two-Year Sport Nutrition Education and Life-Skills Intervention among High School Soccer Players
Reference: Nutrients. 2018 Nov 2;10(11). pii: E1636. doi: 10.3390/nu10111636.
Authors: Patton-Lopez MM, Manore MM, Branscum A, Meng Y, Wong SS
Download link: https://www.mdpi.com/2072-6643/10/11/1636/pdf
Summary: The purpose of this study was to examine the impact of a sport nutrition education and life-skills intervention on sport nutrition knowledge (SNK), attitudes/beliefs and dietary behaviors relevant to sport nutrition among high school (HS) soccer players. Three assessments were done over the 2-year intervention (baseline = time 1, end year 1 = time 2, end year 2 = time 3). Participants (n = 217; females = 64%; Latino = 47.5%; 14.9 ± 0.9-year; 46.5% National School Breakfast/Lunch Program) were assigned to an intervention group (IG, n = 153; 9 schools) or comparison group (CG, n = 64; 4 schools) based on geographical location. Differences over time were examined based on group, sex, socioeconomic status (SES) and race/ethnicity. The IG increased SNK scores by ~10% (time 1 = 51.6%; time 3 = 60.9%; p ≤ 0.001), with the greatest change in the female IG vs. CG and no differences in male IG vs. CG. Daily breakfast consumption was 53.7% in both groups. IG players were 3 times more likely (95%CI = 2.59, 7.77) to report trying to eat for performance (IG = 48.7% vs. CG = 30.2%). By time 3, IG players were less likely to report that 'diet met nutritional requirements' (31.6%) compared to CG (47.6%). For IG, the consumption of lunch (≥5-days/week) did not change (92.2⁻93.4%), but declined in the CG (90.6%) (p = 0.04). No other differences by sub-population (race/ethnicity, SES) were observed. Our findings indicate that HS athletes are motivated to learn and improve diet behaviors, and benefit from team-based nutrition interventions. Future interventions should consider delivery of curriculum/experiential learning during a defined training period, with messages reinforced with supports at home, school and athletic settings.


#9 Effects of the pitch configuration design on players' physical performance and movement behaviour during soccer small-sided games
Reference: Res Sports Med. 2018 Nov 5:1-16. doi: 10.1080/15438627.2018.1544133. [Epub ahead of print]
Authors: Coutinho D, Gonçalves B, Santos S, Travassos B, Wong DP, Sampaio J
Summary: This study aimed to identify the effects of different pitch configurations on youth players positional and physical performances. Forty players participated in a Gk + 5vs5 + Gk small-sided game under four conditions: regular condition (regular), pitch with the direction of competitive matches; sided condition (sided), goals were changed to width; different pitch orientation (≠orientation), performed in side-to-side line compared to competitive matches; dynamic pitch (dynamic), boundaries were randomly changed every minute by: regular pitch; decrease 6 m width; diamond shape. The following variables were considered: players' effective playing space, distance between teammates' dyads time spent synchronized, average speed and a ratio between the distance covered at different intensities and distance covered while recovering. Overall, players exhibited better performances in pitches that are more representative of the environmental information seen during competitive matches (regular and ≠orientation). However, coaches may also use different boundary conditions to promote the players' ability to adapt to different context information.


#10 Chronic Ingestion of Sodium and Potassium Bicarbonate, with Potassium, Magnesium and Calcium Citrate Improves Anaerobic Performance in Elite Soccer Players
Reference: Nutrients. 2018 Nov 1;10(11). pii: E1610. doi: 10.3390/nu10111610.
Authors: Chycki J, Golas A, Halz M, Maszczyk A, Toborek M, Zajac A
Download link: https://www.mdpi.com/2072-6643/10/11/1610/pdf
Summary: Anaerobic power and anaerobic capacity significantly influence performance in many sport disciplines. These include prolonged sprints in athletics, swimming, or cycling, and other high intensity intermittent sports, such as soccer or basketball. Considering the association of exercise-induced acidosis and fatigue, the ingestion of potential buffering agents such as sodium bicarbonate, has been suggested to attenuate metabolic acidosis and improve anaerobic performance. Since elite soccer players cover from 200 to 350 m while sprinting, performing 40⁻60 all out sprints during a game, it seems that repeated sprint ability in soccer players is among the key components of success. In our experiment, we evaluated the effectiveness of chronic supplementation with sodium and potassium bicarbonate, fortified with minerals, on speed and speed endurance in elite soccer players. Twenty-six soccer players participated in the study. The subjects were randomly divided into two groups. The experimental group was supplemented with sodium bi-carbonate and potassium di-carbonate fortified with minerals, while the control group received a placebo. The athletes were tested at baseline and after nine days of supplementation. Anaerobic performance was evaluated by the Repeated Anaerobic Sprint Test (RAST) protocol which involved 6 × 30 m max sprints, separated by 10 s of active recovery. Resting, post ingestion and post exercise concentrations of HCO₃- and blood pH were measured as well as lactate concentration. The current investigation demonstrated a significant increase in RAST performance of elite soccer players supplemented with sodium and potassium bicarbonate along with calcium phosphate, potassium citrate, and magnesium citrate ingested twice a day over a nine-day training period. The improvements in anaerobic performance were caused by increased resting blood pH and bicarbonate levels.


#11 Epidemiology of injury in English Professional Football players: A cohort study
Reference: Phys Ther Sport. 2018 Oct 29;35:18-22. doi: 10.1016/j.ptsp.2018.10.011. [Epub ahead of print]
Authors: Jones A, Jones G, Greig N, Bower P, Brown J, Hind K, Francis P
Summary: The purpose was to estimate the current incidence and location of injury in English professional football. Professional football players (243 players from 10 squads (24.3 ± 4.21 per squad)) competing in the English Football League and National Conference took part in this study. Injury incidence, training and match exposure were collected in accordance with the international consensus statement on football injury epidemiology. 473 injuries were reported. The estimated incidence of injury was, 9.11 injuries/1000 h of football related activity. There was a higher incidence of injury during match play (24.29/1000 h) compared to training (6.84/1000 h). The thigh was the most common site of injury (31.7%), muscle strains accounted for 41.2% of all injuries. The hamstrings were the most frequently strained muscle group, accounting for 39.5% of all muscle strains and 16.3% of all injuries. Moderate severity injuries (8-28 days) were the most common (44.2%). Incidence of injury has increased over the last 16 years with muscle strains remaining the most prevalent injury. The hamstrings remain the most commonly injured muscle group.


#12 Evidence for a Role of ACTN3 R577X Polymorphism in Football Player's Career Progression
Reference: Int J Sports Med. 2018 Nov 6. doi: 10.1055/a-0753-4973. [Epub ahead of print]
Authors: Coelho DB, Pimenta EM, Rosse IC, de Castro BM, Becker LK, de Oliveira EC, Carvalho MRS, Garcia ES
Summary: The aim was to investigate a possible role of the ACTN3 R577X polymorphism in a Brazilian football player's career progression. 2 questions were formulated: 1. Does ACTN3 polymorphism affect the probability of an individual being a professional football player? 2. Does this polymorphism affect the progression of the athlete throughout his career? The study included 353 players from first division Brazilian football clubs in the following categories: under-14 (U-14), U-15, U-17, U-20, and professional (PRO). The control group (CON) was composed of 100 healthy non-athletes. The chi-squared test was used to assess differences between the allele and genotype frequencies. Comparing football categories, the XX genotype was less frequent among professional players than in the U-20 (p<0.05) or the U-15 category (p<0.05). The RX genotype also presented more frequently in the PRO category than the U-14 category (p<0.05). Moreover, a trend towards a higher frequency of the RX genotype and a lower frequency of the XX genotype was observed in the professional category compared to U-20. These results suggest that the genotype in the ACTN3 polymorphism affects the probability of a football player progressing throughout his career and becoming professional, meaning that playing football selects against the ACTN3 XX genotype.


#13 MRI characteristics of adductor longus lesions in professional football players and prognostic factors for return to play
Reference: Eur J Radiol. 2018 Nov;108:52-58. doi: 10.1016/j.ejrad.2018.09.018. Epub 2018 Sep 17.
Authors: Pezzotta G, Pecorelli A, Querques G, Biancardi S, Morzenti C, Sironi S
Summary: The purpose was to correctly define through Magnetic Resonance Imaging (MRI), diagnosis, staging and prognosis of the adductor longus (AL) acute lesions and to identify a correlation between Return to Play (RTP) and sport-related injury predisposing conditions and complications. Twenty professional football players with acute groin pain and clinical suspicion of AL injury subsequent to sport's activity were evaluated. MRI examinations were performed by one and reviewed by other two radiologists with more than 10 years of experience. Lesions were stratified according to both Munich consensus statement and British Athletics Muscle Injury Classification (BAMIC). Patients were monitored until clinical recovery occurred. According to the Munich consensus statement, 75% of lesions were defined as type 3 and 25%as type 4; while according to the BAMIC, 45% were considered as Grade 1, 20% as Grade 2, 10% as Grade 3, and 25% as Grade 4. RTP was 1-2 weeks for minor lesions (45%), 4-6 weeks for moderate lesions (30%), and more than 6 weeks for complete lesions (25%). Both BAMIC and Munich consensus significantly correlated with RTP (R = 0.958 and 0.974, respectively). The extent of gap was the only independent prognosticator of RTP always present in all three different models of multivariate analysis (p < 0.006, p < 0.002, and p < 0.001, respectively). MRI represents the gold standard imaging technique for the evaluation of AL due to its ability not only to recognize but also to classify acute lesions and define patient's prognosis. MRI is also useful to detect potential predisposing conditions and complications, which may correlate with RTP.

Sat

29

Dec

2018

Latest research in football - week 43 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Bone mineral density in lifelong trained male football players compared with young and elderly untrained men
Reference: J Sport Health Sci. 2018 Apr;7(2):159-168. doi: 10.1016/j.jshs.2017.09.009. Epub 2017 Sep 20.
Authors: Hagman M, Helge EW, Hornstrup T, Fristrup B, Nielsen JJ, Jørgensen NR, Andersen JL, Helge JW, Krustrup P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180542/pdf/main.pdf
Summary: The purpose of the present controlled cross-sectional study was to investigate proximal femur and whole-body bone mineral density (BMD), as well as bone turnover profile, in lifelong trained elderly male football players and young elite football players compared with untrained age-matched men. One hundred and forty healthy, non-smoking men participated in the study, including lifelong trained football players (FTE, n = 35) aged 65-80 years, elite football players (FTY, n = 35) aged 18-30 years, as well as untrained age-matched elderly (UE, n = 35) and young (UY, n = 35) men. All participants underwent a regional dual-energy X-ray Absorptiometry (DXA) scan of the proximal femur and a whole-body DXA scan to determine BMD. From a resting blood sample, the bone turnover markers (BTMs) osteocalcin, carboxy-terminal type-1 collagen crosslinks (CTX-1), procollagen type-1 amino-terminal propeptide (P1NP), and sclerostin were measured. FTE had 7.3%-12.9% higher (p < 0.05) BMD of the femoral neck, wards, shaft, and total proximal femur in both legs compared to UE, and 9.3%-9.7% higher (p < 0.05) BMD in femoral trochanter in both legs compared to UY. FTY had 24.3%-37.4% higher (p < 0.001) BMD in all femoral regions and total proximal femur in both legs compared to UY. The whole-body DXA scan confirmed these results, with FTE showing similar whole-body BMD and 7.9% higher (p < 0.05) leg BMD compared to UY, and with FTY having 9.6% higher (p < 0.001) whole-body BMD and 18.2% higher (p < 0.001) leg BMD compared to UY. The plasma concentration of osteocalcin, CTX-1, and P1NP were 29%, 53%, and 52% higher (p < 0.01), respectively, in FTY compared to UY. BMD of the proximal femur and whole-body BMD are markedly higher in lifelong trained male football players aged 65-80 years and young elite football players aged 18-30 years compared to age-matched untrained men. Elderly football players even show higher BMD in femoral trochanter and leg BMD than untrained young despite an age difference of 47 years.

 


#2 A rare case of non-contact salter harris type 2 fracture of distal femur during a football match
Reference: Med J Malaysia. 2018 Oct;73(5):342-343.
Authors: Razzi M, Nordin A
Download link: http://www.e-mjm.org/2018/v73n5/distal-femoral-physeal-fractures.pdf
Summary: Distal femoral physeal fractures in adolescents are often due to high velocity injuries. We present an unusual case of a non-contact distal femoral physeal fracture that occurred during a football match. A torsional force had been directed at the fracture site occurring at the growth plate causing a transverse fracture rather than a spiral fracture. It is important to be aware that such fractures can occur despite little or no evidence of contact. These type of injuries should also be treated as an emergency to reduce the risk of further complications.


#3 Using Network Science to Analyse Football Passing Networks: Dynamics, Space, Time, and the Multilayer Nature of the Game
Reference: Front Psychol. 2018 Oct 8;9:1900. doi: 10.3389/fpsyg.2018.01900. eCollection 2018.
Authors: Buldú JM, Busquets J, Martínez JH, Herrera-Diestra JL, Echegoyen I, Galeano J, Luque J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6186964/pdf/fpsyg-09-01900.pdf


#4 Multilevel modelling of longitudinal changes in isokinetic knee extensor and flexor strength in adolescent soccer players
Reference: Ann Hum Biol. 2018 Oct 31:1-4. doi: 10.1080/03014460.2018.1521470. [Epub ahead of print]
Authors: Duarte JP, Valente-Dos-Santos J, Costa D, Coelho-E-Silva MJ, Deprez D, Philippaerts R, Lenoir M, Vaeyens R, Malina RM
Summary: The purpose of the study was to model the longitudinal development of knee extension (KE) and flexion (KF) strength in adolescent soccer players. A mixed-longitudinal sample composed of 67 soccer players aged 11.0-13.9 years at baseline was followed on three-to-five occasions over 5 years. Stature, body mass and several skinfold thicknesses were measured. Fat mass was estimated from skinfolds and fat-free mass (FFM) derived. Skeletal age was estimated with the TW2-RUS protocol. An isokinetic dynamometer was used to obtain peak torque of KE and KF from concentric assessments at an angular velocity of 180°/s. Multilevel random effects regression analyses were performed. Among youth soccer players aged 11-16 years, isokinetic strength of the knee muscle groups was reasonably predicted from chronological age (CA), stature and FFM: KE = -66.170 + 5.353 × (CA) + 0.594 × (CA2) + 0.552 × (stature) + 1.414 × (FFM), and KF = -9.356 + 2.708 × (CA) + 1.552 × (FFM). In conclusion, CA per se accounted for annual increments of 5.4 Nm in KE and 2.7 Nm in KF.


#5 Artificial neural networks and player recruitment in professional soccer
Reference: PLoS One. 2018 Oct 31;13(10):e0205818. doi: 10.1371/journal.pone.0205818. eCollection 2018.
Authors: Barron D, Ball G, Robins M, Sunderland C
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205818&type=printable
Summary: The aim was to objectively identify key performance indicators in professional soccer that influence outfield players' league status using an artificial neural network. Mean technical performance data were collected from 966 outfield players' (mean SD; age: 25 ± 4 yr, 1.81 ±) 90-minute performances in the English Football League. ProZone's MatchViewer system and online databases were used to collect data on 347 indicators assessing the total number, accuracy and consistency of passes, tackles, possessions regained, clearances and shots. Players were assigned to one of three categories based on where they went on to complete most of their match time in the following season: group 0 (n = 209 players) went on to play in a lower soccer league, group 1 (n = 637 players) remained in the Football League Championship, and group 2 (n = 120 players) consisted of players who moved up to the English Premier League. The models created correctly predicted between 61.5% and 78.8% of the players' league status. The model with the highest average test performance was for group 0 v 2 (U21 international caps, international caps, median tackles, percentage of first time passes unsuccessful upper quartile, maximum dribbles and possessions gained minimum) which correctly predicted 78.8% of the players' league status with a test error of 8.3%. To date, there has not been a published example of an objective method of predicting career trajectory in soccer. This is a significant development as it highlights the potential for machine learning to be used in the scouting and recruitment process in a professional soccer environment.


#6 Oculomotor dynamics in skilled soccer players: The effects of sport expertise and strenuous physical effort
Reference: Eur J Sport Sci. 2018 Oct 31:1-9. doi: 10.1080/17461391.2018.1538391. [Epub ahead of print]
Authors: Zwierko T, Jedziniak W, Florkiewicz B, Stępiński M, Buryta R, Kostrzewa-Nowak D, Nowak R, Popowczak M, Woźniak J
Summary: The ability to quickly locate objects within the visual field has a significant influence on athletic performance. Saccades are conjugate eye movements responsible for the rapid shift that brings a new part of the visual field into foveal vision. The aim of this study was to investigate the effects of sport expertise and intense physical effort on saccade dynamics during a free-viewing visual search task in skilled soccer players. Two groups of male subjects participated in this study: 18 soccer players and 18 non-athletes as the control group. Two sessions of visual search tasks without a sport-specific design were employed. Eye movements during the visual search tasks were recorded binocularly. Between pre- and post-test sessions, athletes performed a maximal incremental treadmill test. Cardiorespiratory parameters were measured continuously. Capillary lactate samples were collected. Pre-test findings indicated that athletes, in comparison to non-athletes, achieve higher values of the following characteristics of saccades (1) average acceleration, (2) acceleration peak, (3) deceleration peak, and (4) average velocity. An increase in post-test saccade duration and a decrease in post-test saccade velocity was observed in athletes due to the strenuous physical effort in relation to the pre-test state. Athletes may transfer high saccadic function efficiency to non-specific visual stimuli. The findings partially confirm that physical exertion can reduce oculomotor efficiency in athletes.


#7 Accumulation of high magnitude acceleration events predicts cerebrovascular reactivity changes in female high school soccer athletes
Reference: Brain Imaging Behav. 2018 Oct 30. doi: 10.1007/s11682-018-9983-0. [Epub ahead of print]
Authors: Svaldi DO, Joshi C, McCuen EC, Music JP, Hannemann R, Leverenz LJ, Nauman EA, Talavage TM
Summary: Mitigating the effects of repetitive exposure to head trauma has become a major concern for the general population, given the growing body of evidence that even asymptomatic exposure to head accelerations is linked with increased risk for negative life outcomes and that risk increases as exposure is prolonged over many years. Among women's sports, soccer currently exhibits the highest growth in participation and reports the largest number of mild traumatic brain injuries annually, making female soccer athletes a relevant population in assessing the effects of repetitive exposure to head trauma. Cerebrovascular biomarkers may be useful in assessing the effects of repetitive head trauma, as these are thought to contribute directly to neurocognitive symptoms associated with mild traumatic brain injury. Here we use fMRI paired with a hypercapnic breath hold task along with monitoring of head acceleration events, to assess the relationship between cerebrovascular brain changes and exposure to repetitive head trauma over a season of play in female high school soccer athletes. We identified longitudinal changes in cerebrovascular reactivity that were significantly associated with prolonged accumulation to high magnitude (> 75th percentile) head acceleration events. Findings argue for active monitoring of athletes during periods of exposure to head acceleration events, illustrate the importance of collecting baseline (i.e., pre-exposure) measurements, and suggest modeling as a means of guiding policy to mitigate the effects of repetitive head trauma.


#8 Are oral health and fixed orthodontic appliances associated with sports injuries and postural stability in elite junior male soccer players?
Reference: BMC Sports Sci Med Rehabil. 2018 Oct 20;10:16. doi: 10.1186/s13102-018-0105-5. eCollection 2018.
Authors: Solleveld H, Flutter J, Goedhart A, VandenBossche L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6196014/pdf/13102_2018_Article_105.pdf
Summary: Dental caries and periodontitis are associated with elevated levels of pro-inflammatory cytokines which may trigger muscle fatigue during exercise, a strong risk factor for sports injuries. Fixed orthodontic appliances (FOA) may cause poor oral health and may disturb proprioceptive inputs of the stomatognathic system. This study aims to explore associations of poor oral health and of use of a FOA with injury frequency and postural stability. One hundred eighty seven Belgian elite junior male soccer players, aged 12-17 years, completed a self-report questionnaire asking about injuries in the past year, oral health problems, use of a FOA, demographics and sports data, and stood in unipedal stance with eyes closed on a force plate to assess postural stability. Ordinal logistic regression with number of injuries in the past year as ordinal dependent variable and dental caries and/or gum problems, age and player position as covariates, showed that participants who reported dental caries and/or gum problems and never had had a FOA reported significant more injuries in the past year compared to the reference group of participants who reported no oral health problems and never had had a FOA (adjusted OR = 2.45; 95% CI, 1.19-5.05; p = 0.015). A 2 (temporomandibular joint problems) × 2 (FOA) × 2 (age) ANOVA with postural stabilities as dependent variables, showed a significant FOA x age interaction for the non-dominant (standing) leg. Post-hoc t-tests showed a significant better postural stability for the non-dominant leg (and a trend for the dominant leg) for the older compared with the younger participants in the non-FOA group (p = .002, ES = 0.61), while no age differences were found in the FOA-group. These results indicate that poor oral health may be an injury risk factor and that a FOA may hinder the development of body postural stability.


#9 Physical and technical differences between domestic and foreign soccer players according to playing positions in the China Super League
Reference: Res Sports Med. 2018 Oct 30:1-12. doi: 10.1080/15438627.2018.1540005. [Epub ahead of print]
Authors: Gai Y, Leicht AS, Lago C, Gómez MÁ
Summary: Physical demands and technical skills of different playing positions within soccer match-play have been rarely studied in competitions from Asia that have unique restrictions that limit the number of foreign players per team. Therefore, the aims of this study were to identify the technical and physical differences between domestic and foreign soccer players according to playing-positions in the China Super League (CSL); and to classify domestic and foreign players (best/worst) based on their match performance characteristics. Data were provided by Amisco Sports Analysis Services (n = 3468 observations). Discriminant and ANOVA analyses showed important differences between domestic and foreign players in the CSL in terms of physical and technical performance indicators for various playing positions. The unique match performance profiles of domestic and foreign players within the CSL highlighted important features for coaches and managers to improve the recruitment process within a league that implements a restrictive foreign player policy.


#10 The First Decade of Web-Based Sports Injury Surveillance: Descriptive Epidemiology of Injuries in US High School Boys' Soccer (2005-2006 Through 2013-2014) and National Collegiate Athletic Association Men's Soccer (2004-2005 Through 2013-2014)
Reference: J Athl Train. 2018 Sep;53(9):893-905. doi: 10.4085/1062-6050-166-17.
Authors: Kerr ZY, Putukian M, Chang CJ, DiStefano LJ, Currie DW, Pierpoint LA, Knowles SB, Wasserman EB, Dompier TP, Comstock RD, Marshall SW
Summary: The advent of Web-based sports injury surveillance via programs such as the High School Reporting Information Online system and the National Collegiate Athletic Association Injury Surveillance Program has aided the acquisition of boys' and men's soccer injury data. The purpose was to describe the epidemiology of injuries sustained in high school boys' soccer in the 2005-2006 through 2013-2014 academic years and collegiate men's soccer in the 2004-2005 through 2013-2014 academic years using Web-based sports injury surveillance. Online injury surveillance from soccer teams of high school boys (annual average = 100) and collegiate men (annual average = 41) were utilized. Boys' or men's soccer players who participated in practices and competitions during the 2005-2006 through 2013-2014 academic years in high school and the 2004-2005 through 2013-2014 academic years in college, respectively. Athletic trainers collected time-loss (≥24 hours) injury and exposure data. Injury rates per 1000 athlete-exposures (AEs), injury rate ratios (IRRs) with 95% confidence intervals (CIs), and injury proportions by body site and diagnosis were calculated as main outcome measures. High School Reporting Information Online documented 2912 time-loss injuries during 1 592 238 AEs; the National Collegiate Athletic Association Injury Surveillance Program documented 4765 time-loss injuries during 686 918 AEs. The injury rate was higher in college than in high school (6.94 versus 1.83/1000 AEs; IRR = 3.79; 95% CI = 3.62, 3.97). Injury rates increased with smaller school size for high schools and were higher in Division I than in Divisions II and III. The injury rate was higher during competitions than during practices in both high school (IRR = 3.55; 95% CI = 3.30, 3.83) and college (IRR = 3.45; 95% CI = 3.26, 3.65). Most injuries were to the lower extremity. However, concussion was a common injury, particularly in collegiate goalkeepers and at all positions for high school players. Concussions accounted for more than one-fifth of injuries in high school games. Injury-prevention interventions should be tailored to reflect variations in the incidence and type of injury by level of competition, event type, and position.

Sun

23

Dec

2018

Latest research in footbal - week 42 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Muscle Damage-Based Recovery Strategies Can Be Supported by Predictive Capacity of Specific Global Positioning System Accelerometry Parameters Immediately a Post-Soccer Match-Load
Reference: J Strength Cond Res. 2018 Oct 22. doi: 10.1519/JSC.0000000000002922. [Epub ahead of print]
Authors: da Silva CD, Machado G, Fernandes AA, Teoldo I, Pimenta EM, Marins JCB, Garcia ES
Summary: Soccer match-load can be linked to recovery kinetic markers. However, match variability hinders the magnitude of relationship between parameters of interest. Therefore, we examined the correlation between 21 global positioning system accelerometry (GPS-A) parameters and changes in serum creatine kinase (CK) concentrations, muscle soreness (MS), and perceptive recovery quality (PRQ) assessed at baseline (1 h before) and post (0 minute, 2, 4, and 24 hours) a standardized 90-minute match-simulation in 12 university players. Global positioning system accelerometry (15 Hz) data were tested as manufacturer and configurable thresholds. Four GPS-A parameters showed moderate to very large correlations with CK changes at all time points (average speed [avgSP, r = 0.75 to r = 0.84]; running symmetry foot strikes [RSfst, r = 0.53-0.63]; running series [RunS, r = 0.53-0.61]; and acceleration distance [AccD ≥ 1.5 m·s; r = 0.46-0.61]). Sprint count (≥2 m·s), AccD (≥2.5 m·s) and speed exertion (SpEx) had a moderate to large correlation (r = 0.46-0.56) with CK changes from 2 to 24 hours. Changes in MS at 0 minute had large correlation with avgSP (r = 0.53) and moderate with deceleration distance (≥-2 and ≥-3 m·s; r = 0.47, r = 0.48, respectively). The PRQ changes had moderate inverse correlation with avgSP at 0 minute (r = -0.39) and SpEx at 2 h (r = -0.69). Our results suggest that during a simulated soccer protocol with a standard workload, only the avgSP has practical application for predicting CK changes over 24 hours, allowing for a decision-making toward a postgame recovery based on previously known CK cutoff points. Global positioning system accelerometry parameters and subjective variables did not demonstrate relevant correlation.


#2 Influence of Night Soccer Matches on Sleep in Elite Players
Reference: J Strength Cond Res. 2018 Oct 22. doi: 10.1519/JSC.0000000000002906. [Epub ahead of print]
Authors: Nédélec M, Dawson B, Dupont G
Summary: This study examined the impact of night matches on the sleep/wake behavior of elite soccer players participating in the UEFA Champions League and French Ligue 1. A mixed method approach was used, combining objective sleep assessment with wrist activity monitors, and a survey to ascertain the sleep complaints after night matches (kick off after 18:00 hours). Most players (90%) indicated worse sleep in the nights after evening matches than after training days. Objective time in bed (-01:39 hours; effect size [ES] = 1.7; p < 0.001) and total sleep time (-01:32 hours; ES = 1.4; p < 0.001) were both lower after night matches than after training days. Night matches had a marked influence on sleep quantity later that night, both objectively and subjectively. The survey revealed that players may not have appropriate methods for better managing their sleep after night matches. It is yet to be determined whether players may benefit from individualized sleep interventions in these circumstances.


#3 Movement Economy in Soccer: Current Data and Limitations
Reference: Sports (Basel). 2018 Oct 23;6(4). pii: E124. doi: 10.3390/sports6040124.
Authors: Dolci F, Hart NH, Kilding A, Chivers P, Piggott B, Spiteri T
Summary: Soccer is an intermittent team-sport, where performance is determined by a myriad of psychological, technical, tactical, and physical factors. Among the physical factors, endurance appears to play a key role into counteracting the fatigue-related reduction in running performance observed during soccer matches. One physiological determinant of endurance is movement economy, which represents the aerobic energy cost to exercise at a given submaximal velocity. While the role of movement economy has been extensively examined in endurance athletes, it has received little attention in soccer players, but may be an important factor, given the prolonged demands of match play. For this reason, the current review discusses the nature, impact, and trainability of movement economy specific to soccer players. A summary of current knowledge and limitations of movement economy in soccer is provided, with an insight into future research directions, to make this important parameter more valuable when assessing and training soccer players' running performance.

#4 Seasonal Changes in the Physical Performance of Elite Youth Female Soccer Players
Reference: J Strength Cond Res. 2018 Oct 24. doi: 10.1519/JSC.0000000000002943. [Epub ahead of print]
Authors: Emmonds S, Sawczuk T, Scantlebury S, Till K, Jones B
Author information
Summary: This study investigated the seasonal change in physical performance of 113 (Under 10: U10 [n = 20], U12 [n = 30], U14 [n = 31], and U16 [n = 32]) elite youth female soccer players. Players completed testing pre-, mid-, and post-season, including speed (10- and 30-m sprint), change of direction (CoD; 505 test), power (countermovement jump [CMJ]), strength (isometric midthigh pull), and aerobic capacity (Yo-Yo intermittent recovery test level 1 [YYIRL1]). A general linear model was used to evaluate the change in physical characteristics and the influence of covariates (baseline performance; change in maturity status) on each characteristic across the season. U10's speed and CoD performance decreased from pre-post season, whereas relative strength likely improved. U12's relative strength very likely improved; however, 10-m sprint performance decreased. Relative strength likely decreased, whereas 30-m sprint and CoD time very likely improved in U14's. U16's likely improved relative strength, CMJ, and 10-m sprint, and very likely improved 30-m sprint and CoD from pre-post season. U12-U16's improved YYIRL1 performance pre-post season. Strength and conditioning coaches working with U10-U12 players should look to develop speed, lower-body power, and CoD ability as part of structured strength and conditioning sessions as well as within warm-ups before pitch-based sessions. With U14-U16 players' manipulation of small-sided games combined with short-duration high-intensity running drills may provide an efficient training stimulus to develop the aerobic system while concurrently developing technical/tactical skills. Findings of this study provide a basis for the implementation of strategies to enhance the long-term athletic development of youth female soccer players.


#5 The influence of different exercise intensities on kicking accuracy and velocity in soccer players
Reference: J Sport Health Sci. 2017 Dec;6(4):462-467. doi: 10.1016/j.jshs.2015.10.001. Epub 2015 Oct 20.
Authors: Ferraz R, van den Tillar R, Marques MC
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189251/pdf/main.pdf
Summary: The aim of this study was to investigate the influence of different exercise intensities induced by a soccer specific protocol on kicking performance in soccer players. Twelve semi-professional male soccer players participated in this study and performed maximal instep kicks before and after the implementation of an exercise protocol to determine the influence of different intensities upon kicking ball velocity and the target-hitting accuracy. Analysis of variance designs with repeated measures showed that maximal ball velocity was affected only after the most intense circuit (F(6, 66) = 2.3; p = 0.041; η 2 = 0.18), while accuracy was not affected in the protocol (F(6, 66) = 0.19; p = 0.98; η 2 = 0.02). Low and moderate intensities did not affect accuracy or kicking ball velocity. These findings suggest that kicking ball velocity is influenced by high-exercise intensities. Low and moderate exercise intensities do not affect the performance of the kick, and intensity does not influence accuracy. Otherwise, it is possible that other mechanisms (not only physiological) may influence players during the exercise.


#6 Effects of soccer training on health-related physical fitness measures in male adolescents
Reference: J Sport Health Sci. 2018 Apr;7(2):169-175. doi: 10.1016/j.jshs.2017.10.009. Epub 2018 Jan 3.
Authors: Hammami A, Randers MB, Kasmi S, Razgallah M, Tabka Z, Chamari K, Bouhlel E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180556/pdf/main.pdf
Summary: The aims of this study were to (1) investigate the health-related physical fitness profile of untrained adolescent boys in comparison to adolescent soccer players, (2) determine the intensity and enjoyment of 6 v 6 and 4 v 4 small-sided games, and (3) evaluate the health-related effects of a short-period of soccer training in the untrained group. Forty-one adolescent boys (untrained, n = 24: age = 15.9 ± 0.6 years; trained, n = 17: age = 15.7 ± 0.7 years) were recruited. For Purpose 1, the players (n = 17) and the untrained (n = 24) boys were tested for speed, jumping power, postural balance, flexibility, and aerobic capacity. After baseline testing, Purposes 2 and 3 were addressed by randomly assigning the untrained boys to either a soccer-training group (small-sided games, 2 sessions per week for 8 weeks) or to a control group, followed by identical retesting. At baseline, physical fitness was higher (p < 0.001) in trained players than in untrained for aerobic fitness, sprinting, jumping power, and postural balance. Small-sided games using 6 v 6 or 4 v 4 elicited similar heart rate (HR) (mean:  ~ 85% peak heart rate, HRpeak), rate of perceived exertion, and enjoyment responses. Over 8 weeks, the between-group analysis revealed that soccer training had a large beneficial effect on postural balance (45%) when compared with control group with unclear effects on other fitness parameters. Adolescent soccer players had markedly higher physical fitness compared with untrained adolescents. Small-sided soccer games practiced by untrained adolescents elicited high exercise intensity. While 8 weeks of twice-weekly soccer training sessions induced significant improvement in postural balance, the short duration of the study was not sufficient to result in between-group differences in sprint and jump performance or aerobic fitness.


#7 Injuries in Spanish female soccer players
Reference: J Sport Health Sci. 2018 Apr;7(2):183-190. doi: 10.1016/j.jshs.2016.09.002. Epub 2016 Sep 21.
Authors: Del Coso J, Herrero H, Salinero JJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6180559/pdf/main.pdf
Summary: Epidemiologic research to learn the incidence, type, location, and severity of female soccer injuries and the risk factors for sustaining a sport injury is the first step in developing preventive policies. The aim of this study was to analyze the incidence of injuries in the population of female soccer players in Spain. The injuries incurred by 25,397 female soccer players were registered by the medical staff of the Spanish Football Federation during 1 season. A standardized medical questionnaire was used to classify the injury according to type, severity, location, and injury mechanism. A total of 2108 injuries was reported with an incidence of 0.083 injuries per player per season. Most injuries were in the lower limbs (74.0%), mainly affecting knee (30.4%) and ankle joints (17.9%). The proportion of injuries derived from contact with another player was higher during matches (33.7%) than during training (11.4%; p < 0.001). Noncontact injuries were classified as severe more frequently than were contact injuries (51.0% vs. 42.6%; p < 0.001). A higher incidence of injury was found in adult soccer players (≥18 years) vs. their counterparts younger than18 years (0.094 vs. 0.072 injuries per player per year, respectively; p < 0.001). There were no differences between age groups in any other injury variable (e.g., type, mechanism, location, or severity; p > 0.05). Most female soccer injuries were located at the knee and ankle; the injury mechanism determined the playing time lost; and the player's age did not affect injury characteristics.


#8 Training load and schedule are important determinants of sleep behaviours in youth-soccer players
Reference: Eur J Sport Sci. 2018 Oct 24:1-9. doi: 10.1080/17461391.2018.1536171. [Epub ahead of print]
Authors: Whitworth-Turner CM, Di Michele R, Muir I, Gregson W, Drust B
Summary: The current study examined how sleep may be influenced by the scheduling of training and match load within 10 youth-soccer players. Sleep was measured over a 14-day in-season period using a commercially available wireless sleep monitor. Each collected sleep variable; lights out, sleep latency, total sleep time wake after sleep onset and final awakening, was compared for the specific day within the training schedule (e.g. match day [MD], day after match [MD + 1]) and to training/match load (high-speed distance (>5.5 m/s) [HSD] and rating of perceived exertion. The data were analysed using mixed models and effect sizes, to describe the magnitude of effects that training schedule and training load may have on sleep. A reduction of sleep duration was observed on the day after the match (MD + 1) in relation to the training days preceding the match (MD-2: -65 min, ES: 0.89 ± 0.79; MD-1 -61 min, ES: 0.82 ± 0.64) and reduction on match day (+45 min; ES: 1.91 ± 1.69). This may suggest youth-soccer players actively change their sleep scheduling behaviours in relation to the imposed soccer schedule. Increased high-speed running (for every 100 m) showed a small increase to total sleep time (+9 min; ES: 0.48 ± 0.31). This may suggest that increases in training load may be associated with small increases in sleep quantity. Such observations may highlight that the type of day and the associated load within the training microcycle may have important consequences for sleep within youth-soccer players.


#9 The acute effects of plyometric and sled towing stimuli with and without caffeine ingestion on vertical jump performance in professional soccer players
Reference: J Int Soc Sports Nutr. 2018 Oct 22;15(1):51. doi: 10.1186/s12970-018-0258-3.
Authors: Guerra MA Jr, Caldas LC, De Souza HL, Vitzel KF, Cholewa JM, Duncan MJ, Guimarães-Ferreira L
Download link: https://jissn.biomedcentral.com/track/pdf/10.1186/s12970-018-0258-3
Summary: Post-activation potentiation (PAP) is the phenomenon by which muscular performance is enhanced in response to a conditioning stimulus. PAP has typically been evidenced via improved counter movement jump (CMJ) performance. This study examined the effects of PAP, with and without prior caffeine ingestion, on CMJ performance. Twelve male professional soccer players (23 ± 5 years) performed two trials of plyometric exercises and sled towing 60 min after placebo or caffeine ingestion (5 mg.kg- 1) in a randomized, counterbalanced and double-blinded design. CMJ performance was assessed at baseline and 1, 3 and 5 min after the conditioning stimulus (T1, T3 and T5, respectively). Two way ANOVA main effects indicated a significant difference in jump height after the PAP protocol (F[3, 11] = 14.99, P < 0.001, partial η2 = 0.577). Analysis also indicated a significant difference in CMJ performance across conditions, with caffeine eliciting a greater response (F[1, 11] = 10.12, P = 0.009, partial η2 = 0.479). CMJ height was increased at T1, T3 and T5 in caffeine condition (5.07%, 5.75% and 5.40%, respectively; P < 0.01) compared to baseline. In the placebo condition, jump performance was increased at T3 (4.94%; P < 0.01) only. Jump height was higher in caffeine condition on T1, T3 and T5 (P < 0.05) but not on baseline (P > 0.05) compared to placebo. The results of this study suggest that acute plyometric and sled towing stimuli enhances jump performance and that this potentiation is augmented by caffeine ingestion in male soccer players.


#10 5-Hydroxymethylfurfural and Alpha-Ketoglutaric Acid as an Ergogenic Aid During Intensified Soccer Training: A Placebo Controlled Randomized Study
Reference: J Diet Suppl. 2018 Oct 22:1-12. doi: 10.1080/19390211.2018.1494662. [Epub ahead of print]
Authors: Gatterer H, Böcksteiner T, Müller A, Simi H, Krasser C, Djukic R, Schroth R, Wallner D
Summary: Intensified training may lead to fatigue or even a state of overreaching with temporary reductions in performance. Any aid helping to prevent these consequences and to better tolerate such a training regime would be of great importance. 5-hydroxymethylfurfural (5-HMF) and α-ketoglutaric acid (α-KG) supplementation has been suggested to support favorable training outcomes but its effectiveness to facilitate adaptations during an intensified training period has never been investigated. During an in-season competition break (2 weeks), seventeen young outfield soccer players (age:14.7 ± 0.4 yr) performed a 9-day lasting shock microcyle including 5-7 repeated sprint exercise sessions in addition to the regular training (∼6 sessions/wk) and match (1-2 matches/wk) schedule. Before the training period a treadmill test to exhaustion, a YOYO intermittent recovery level 2 (YYIR2) and a repeated sprint ability (RSA) test were performed. The treadmill test was repeated 3 days after the shock microcycle whereas the YYIR2 and the RSA test on day 10 after the training. Magnitude based inference analysis showed likely positive effects of the 5-HMF/α-KG compared to the control group for changes in the maximal running velocity (+0.3 ± 0.7 vs. -0.3 ± 0.8 km/h) and running velocity at lactate turn-point 1 (+0.2 ± 0.4 vs. -0.2 ± 0.6) and lactate turn-point 2 (+0.4 ± 0.4 vs. -0.2 ± 0.6 km/h, for the 5-HMF/α-KG and placebo group, respectively). Training improved YYIR2 performance (+180 ± 67 vs. +200 ± 168m) and RSA (mean time: -0.1 ± 0.1 vs. -0.1 ± 0.1s, for the 5-HMF/α-KG and placebo group, respectively) in both groups and to the same extent. In conclusion, an in-season shock microcyle including repeated sprint training improves YYIR2 performance and RSA in youth soccer players. Supplementation with 5-HMF/α-KG did not modify training adaptations but led to likely positive exercise performance responses shortly after the intensified training regime.


#11 The association between physical performance and match-play activities of field and assistants soccer referees
Reference: Res Sports Med. 2018 Oct 20:1-15. doi: 10.1080/15438627.2018.1534117. [Epub ahead of print]
Authors: Castillo D, Cámara J, Lozano D, Berzosa C, Yanci J
Author information
Summary: The aims of this study were to compare the external and internal match responses and fitness performance of national field referees (FRs) and assistant referees (ARs), and to examine the relationships between these fitness measures and physical and physiological responses during match play. Forty-four national soccer match officials (e.g. FRs and ARs) participated in this study. The distance covered and the VO2max in Yo-Yo Intermittent recovery test (YYIR1) and the 30 m sprint test correlated with high speed and high intensity activities during match play in FRs (r = -0.48-0.63, moderate to large, very likely to most likely, p < 0.05). In addition, YYIR1 performance was related to high accelerations (r = 0.41, moderate, likely, p < 0.05) and high decelerations (r = 0.44, moderate, very likely, p < 0.05) for FRs. Better sprint and cardiovascular fitness could be relevant to the performance of FRs during match play.


#12 Analyzing the Components of Emotional Competence of Football Coaches: A Qualitative Study from the Coaches' Perspective
Reference: Sports (Basel). 2018 Oct 23;6(4). pii: E123. doi: 10.3390/sports6040123.
Authors: Lee H, Wäsche H, Jekauc D
Summary: Emotional Competence (EC) is regarded as a fundamental skill for sports coaches. However, the applications of EC in football coaching are not well understood. This study analyzed the specific emotional processes football coaches experience. We interviewed 18 football coaches and analyzed the interview transcripts by using a systematic analysis process based on Grounded Theory principles. We derived a model from this analysis that comprises a four-phase process: emotional triggers, emotional experiences, emotion regulation strategies, and emotional consequences. In this model, we identified four categories which act as triggers of emotions in football coaches. These emotions can be positive or negative and are manifested at three levels. However, the coaches vary in their capability to perceive emotions. Our model also shows that coaches' emotion regulation strategies influence the effect of emotional experiences. Experienced emotions promote consequences with psychological and social implications for coaches and may influence their perception of future situations. In short, the process seems to be circular. This finding suggests that the ability to deal with emotions is an important aspect for football coaches.


#13 Modelling home advantage for individual teams in UEFA Champions League football
Reference: J Sport Health Sci. 2017 Sep;6(3):321-326. doi: 10.1016/j.jshs.2015.12.008. Epub 2015 Dec 24.
Authors: Goumas C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189255/pdf/main.pdf
Summary: Home advantage (HA) is well documented in a wide range of team sports including association football (soccer). Although much attention has been paid to differences in the overall magnitude of HA between football competitions and across time, few studies have investigated HA at the team level. A novel method of estimating HA for individual teams, based solely on home performance, was used to compare HA between the highest performing teams and countries in the Union of European Football Associations (UEFA) Champions League over a 10-year period (2003/2004 to 2012/2013). Away disadvantage (AD) was also estimated based on each team's performance away from home. Poisson regression analysis was used to estimate covariate adjusted HA and AD in terms of the percentage of goals scored at home (HA) and conceded away from home (AD). When controlling for differences in team ability, HA did not vary significantly between the 13 selected teams. There was evidence (p < 0.1), however, of between-team variation in AD, ranging from 45% (away advantage) to 68% (away disadvantage). When teams were grouped into the 11 selected countries, both HA and AD varied significantly (p < 0.02) between countries: HA ranged from 52% for Turkish teams to 70% for English teams, while AD ranged from 52% (France) to 67% (Turkey). Differences in style of play and tactical approaches to home and away matches may explain some of the variation in HA and AD between teams from different countries.

Thu

20

Dec

2018

Latest research in football - week 41 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 Skeletal maturity and oxygen uptake in youth soccer controlling for concurrent size descriptors
Reference: PLoS One. 2018 Oct 18;13(10):e0205976. doi: 10.1371/journal.pone.0205976. eCollection 2018.
Authors: Teixeira AS, Guglielmo LGA, Fernandes-da-Silva J, Konarski JM, Costa D, Duarte JP, Conde J, Valente-Dos-Santos J, Coelho-E-Silva MJ, Malina RM
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205976&type=printable
Summary: Interrelationships among skeletal maturity status, body size, ventilator thresholds (VT) and peak oxygen uptake (VO2peak) were considered in 47 adolescent male soccer players aged 12.5-15.4 years. Body mass, stature, and the triceps and subscapular skinfolds were measured. The latter were used to estimate fat mass and fat-free mass. Skeletal age was assessed with the Fels method. VO2peak and VO2 at the first (VT1) and second (VT2) ventilatory thresholds were determined during an incremental maximal exercise test on a motorized treadmill. Ratio standards and allometric models were used in the analysis. Scaling exponents suggested linearity for all combinations between size descriptors and physiological variables, except between log-transformed values of VT1 and body mass (mL·kg-0.801·min, 95%CI: 0.649 to 0.952). Early maturing players attained greater values than players classified as "on-time" in skeletal maturity for the three ventilatory parameters expressed in absolute terms (d ranged from 0.65 to 0.71). The differences were attenuated after normalizing for mass descriptors using ratio standards and scaled variables (d ranged from 0.00 to 0.31). The results suggested significant variability between maturity groups when moving from VT1 to maximal metabolic conditions expressed by unit of stature (VT1: t = -2.413, p = 0.02, d = 0.60; VT2: t = -2.488, p = 0.02, d = 0.65; VO2peak: t = -2.475, p = 0.02, d = 0.65). Skeletal maturity status and associated variation in overall body size affects VT1, VT2 and VO2peak. The observed scaling of ventilatory outputs for body size may be related to the better running economy and smaller body size of average maturing athletes.


#2 Life skills development and enjoyment in youth soccer: The importance of parental behaviours
Reference: J Sports Sci. 2018 Oct 17:1-7. doi: 10.1080/02640414.2018.1530580. [Epub ahead of print]
Authors: Mossman GJ, Cronin LD
Summary: This study investigated the relationships between parental behaviours and players' life skills development and enjoyment within youth soccer. In total, 317 players (Mage = 12.83, SD = 1.70, age range = 10-16 years) completed a survey assessing parental behaviours (praise and understanding, directive behaviour, and pressure), perceived life skills development (teamwork, goal setting, time management, emotional skills, interpersonal communication, social skills, leadership, and problem solving and decision making), and enjoyment of soccer. Multiple regression analyses found that praise and understanding was the key contributor to the outcome variables, making the largest unique contribution to teamwork, goal setting, leadership, and total life skills. Directive behaviour made the largest unique contribution to emotional skills, and problem solving and decision making; whereas pressure made the largest unique contribution to participants' time management and social skills. In practice, the results suggest that parents should display praise and understanding behaviours, which were the main contributor to players' development of life skills within soccer.


#3 In-season eccentric-overload training in elite soccer players: Effects on body composition, strength and sprint performance
Reference: PLoS One. 2018 Oct 16;13(10):e0205332. doi: 10.1371/journal.pone.0205332. eCollection 2018.
Authors: Suarez-Arrones L, Saez de Villarreal E, Núñez FJ, Di Salvo V, Petri C, Buccolini A, Maldonado RA, Torreno N, Mendez-Villanueva A
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0205332&type=printable
Summary: The aim of this study was to describe the changes in body composition, strength and sprint performance in response to an entire competitive season of football training supplemented with 2 inertial eccentric-overload training sessions a week in young male professional soccer players. Whole body and regional composition (assessed using dual-energy X-ray absorptiometry), power output in half-squat and 40-m sprinting performance were evaluated in fourteen players. The eccentric-overload training consisted of training sessions a week of 1-2 sets of 10 exercises of upper-body and core (Day 1) and lower-body (Day 2), during the entire competitive season (27 weeks). Whole body fat mass decreased (-6.3 ± 3.6%, ES = -0.99 ± 0.54) substantially while lean mass increased (2.5 ± 0.8%, ES = 0.25 ± 0.09), with some regional differences. There was a substantial increase in half-squat power output (from 3% to 14%, ES from 0.45 to 1.73) and sprint performance (from 1.1% to 1.8%, ES from -0.33 to -0.44), however performance changes were not correlated with changes in body composition. A combined soccer and eccentric-overload training program was able to promote positive changes in body composition and physical factors relevant to both on-field performance and injury prevention in elite soccer players.


#4 Effects of Prolonging Eccentric Phase Duration in Parallel Back-Squat Training to Momentary Failure on Muscle Cross-Sectional Area, Squat One Repetition Maximum, and Performance Tests in University Soccer Players
Reference: J Strength Cond Res. 2018 Oct 12. doi: 10.1519/JSC.0000000000002838. [Epub ahead of print]
Authors: Shibata K, Takizawa K, Nosaka K, Mizuno M
Summary: This study aimed to compare 2 squat training programs repeated until momentary failure with different eccentric phase duration (2 seconds vs. 4 seconds) on the changes in muscle cross-sectional area, squat 1 repetition maximum (1RM), squat jump (SJ), and countermovement jump (CMJ) height, agility (T-test), and Yo-Yo intermittent recovery test (YY-IR2). Male university soccer players (19.9 ± 0.9 years, 172.2 ± 3.8 cm, 66.1 ± 6.6 kg) were randomly assigned to one of the 2 groups; CON for 2 seconds and ECC for 4 seconds (C2/E4, n = 11) or CON for 2 seconds and ECC for 2 seconds (C2/E2, n = 11). They performed parallel back-squat exercises twice a week for 6 weeks using 75% 1RM weight to momentary failure in each set for 3 sets with each protocol. Outcome measurements were taken before (Pre) and after 3 (Mid; 1RM, SJ, and CMJ only), and at 6 weeks (Post). One repetition maximum increased more (p < 0.05) for C2/E2 (Pre: 95.9 ± 12.2 kg, Mid: 108.2 ± 15.4 kg, Post: 113.6 ± 14.8 kg) than C2/E4 (95.5 ± 12.9 kg, 102.7 ± 15.6 kg, 105.5 ± 14.9 kg, respectively). Cross-sectional area (50% of the thigh length: 3.5 ± 2.8%), SJ (6.7 ± 8.9%) and CMJ height (6.3 ± 8.6%) increased similarly between C2/E2 and C2/E4, but no significant changes in T-test or YY-IR2 were evident in either group. These results suggest that increasing the ECC phase duration during squat exercises does not produce greater training effects when compared with a shorter ECC phase-duration program with momentary failure.


#5 Altered brain microstructure in association with repetitive subconcussive head impacts and the potential protective effect of jugular vein compression: a longitudinal study of female soccer athletes
Reference: Br J Sports Med. 2018 Oct 15. pii: bjsports-2018-099571. doi: 10.1136/bjsports-2018-099571. [Epub ahead of print]
Authors: Myer GD, Barber Foss K, Thomas S, Galloway R, DiCesare CA, Dudley J, Gadd B, Leach J, Smith D, Gubanich P, Meehan WP 3rd, Altaye M, Lavin P, Yuan W
Summary:  The purpose was to (1) quantify white matter (WM) alterations in female high school athletes during a soccer season and characterise the potential for normalisation during the off-season rest period, (2) determine the association between WM alterations and exposure to repetitive subconcussive head impacts, and (3) evaluate the efficacy of a jugular vein compression collar to prevent WM alterations associated with head impact exposure. Diffusion tensor imaging (DTI) data were prospectively collected from high school female soccer participants (14-18 years) at up to three time points over 9 months. Head impacts were monitored using accelerometers during all practices and games. Participants were assigned to a collar (n=24) or non-collar group (n=22). The Tract-Based Spatial Statistics approach was used in the analysis of within-group longitudinal change and between-group comparisons. DTI analyses revealed significant pre-season to post-season WM changes in the non-collar group in mean diffusivity (2.83%±2.46%), axial diffusivity (2.58%±2.34%) and radial diffusivity (3.52%±2.60%), but there was no significant change in the collar group despite similar head impact exposure. Significant correlation was found between head impact exposure and pre-season to post-season DTI changes in the non-collar group. WM changes in the non-collar group partially resolved at 3 months off-season follow-up. Microstructural changes in WM occurred during a season of female high school soccer among athletes who did not wear the collar device. In comparison, there were no changes in players who wore the collar, suggesting a potential prophylactic effect of the collar device in preventing changes associated with repetitive head impacts. In those without collar use, the microstructural changes showed a reversal towards normal over time in the off-season follow-up period.


#6 Hip and Groin Injuries Among Collegiate Male Soccer Players: The 10-Year Epidemiology, Incidence, and Prevention
Reference: Orthopedics. 2018 Oct 15:1-6. doi: 10.3928/01477447-20181010-01. [Epub ahead of print]
Authors: Tummala SV, Chhabra A, Makovicka JL, Patel KA, Hartigan DE
Summary: The physical and demanding style of play in soccer places these athletes at an elevated risk for hip and groin injuries. Several studies have examined hip and groin injuries in professional and youth soccer in European countries, but few have involved American counterparts. Hip injury data were analyzed retrospectively from the National Collegiate Athletic Association Injury Surveillance Program for the 2004 to 2014 academic years for collegiate men's soccer. This study found that hip and groin injuries among collegiate male soccer players were most often new injuries (87.8%; n=527) that were noncontact in nature (77.3%; n=464) and resulted in time loss of less than 7 days (67.5%; n=405). Hip injuries were significantly more likely during the pre-season (5.72 per 1000 athlete exposures) relative to in-season (injury proportion ratio, 1.64; 95% confidence interval, 1.39-1.94) and post-season (injury proportion ratio, 1.69; 95% confidence interval, 1.18-2.41). Further, they were more likely in competition relative to practice (injury proportion ratio, 2.33; 95% confidence interval, 1.98-2.74). The most common injuries were adductor strains (46.5%; n=279) followed by hip flexor strains (27.3%; n=164) and hip contusions (10.8%; n=65). Among these injuries, adductor (73.1%; n=204) and hip flexor (59.8%; n=98) strains were more commonly noncontact related and occurred in practice, whereas hip contusions were due to contact and during competition. The study of the complex and lingering nature of hip and groin injuries in soccer players is critical because these injuries not only are prevalent but also have multifactorial risks associated with coexisting pathologies that make them difficult to prevent and treat effectively.


#7 Psychological talent predictors in youth soccer: A systematic review of the prognostic relevance of psychomotor, perceptual-cognitive and personality-related factors
Reference: PLoS One. 2018 Oct 15;13(10):e0205337. doi: 10.1371/journal.pone.0205337. eCollection 2018.
Authors: Murr D, Feichtinger P, Larkin P, O'Connor D, Höner O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6188900/pdf/pone.0205337.pdf
Summary: Within the multidimensional nature of soccer talent, recently there has been an increasing interest in psychological characteristics. The aim of this present research was to systematically review the predictive value of psychological talent predictors and provide better comprehension of the researchers' methodological approaches and the empirical evidence for individual factors (i.e., psychomotor, perceptual-cognitive and personality-related). Results highlighted heterogeneous study designs (e.g., participants, measurement methods, statistical analyses) which may limit the comparability of studies' findings. Analyzing the number of included studies, psychomotor (n = 10) and personality-related factors (n = 8) received more consideration within the literature than perceptual-cognitive factors (n = 4). In regard to empirical evidence, dribbling (0.47 ≤ d ≤ 1.24), ball control (0.57 ≤ d ≤ 1.28) and decision-making (d = 0.81) demonstrated good predictive values as well as the achievement motives hope for success (0.27 ≤ d ≤ 0.74) and fear of failure (0.21 ≤ d ≤ 0.30). In conclusion, there is growing acceptance of the need for more complex statistical analyses to predict future superior performance based on measures of current talent. New research addresses the necessity for large-scale studies that employ multidisciplinary test batteries to assess youth athletes at different age groups prospectively.


#8 Not Every Pass Can Be an Assist: A Data-Driven Model to Measure Pass Effectiveness in Professional Soccer Matches
Reference: Big Data. 2018 Sep 21. doi: 10.1089/big.2018.0067. [Epub ahead of print]
Authors: Goes FR, Kempe M, Meerhoff LA, Lemmink KAPM
Summary: In professional soccer, nowadays almost every team employs tracking technology to monitor performance during trainings and matches. Over the recent years, there has been a rapid increase in both the quality and quantity of data collected in soccer resulting in large amounts of data collected by teams every single day. The sheer amount of available data provides opportunities as well as challenges to both science and practice. Traditional experimental and statistical methods used in sport science do not seem fully capable to exploit the possibilities of the large amounts of data in modern soccer. As a result, tracking data are mainly used to monitor player loading and physical performance. However, an interesting opportunity exists at the intersection of data science and sport science. By means of tracking data, we could gain valuable insights in the how and why of tactical performance during a soccer match. One of the most interesting and most frequently occurring elements of tactical performance is the pass. Every team has around 500 passing interactions during a single game. Yet, we mainly judge the quality and effectiveness of a pass by means of observational analysis, and whether the pass reaches a teammate. In this article, we present a new approach to quantify pass effectiveness by means of tracking data. We introduce two new measures that quantify the effectiveness of a pass by means of how well a pass disrupts the opposing defense. We demonstrate that our measures are sensitive and valid in the differentiation between effective and less effective passes, as well as between the effective and less effective players. Furthermore, we use this method to study the characteristics of the most effective passes in our data set. The presented approach is the first quantitative model to measure pass effectiveness based on tracking data that are not linked directly to goal-scoring opportunities. As a result, this is the first model that does not overvalue forward passes. Therefore, our model can be used to study the complex dynamics of build-up and space creation in soccer.


#9 Basal Mild Dehydration Increase Salivary Cortisol After a Friendly Match in Young Elite Soccer Players
Reference: Front Physiol. 2018 Sep 26;9:1347. doi: 10.3389/fphys.2018.01347. eCollection 2018.
Authors: Castro-Sepulveda M, Ramirez-Campillo R, Abad-Colil F, Monje C, Peñailillo L, Cancino J, Zbinden-Foncea H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168646/pdf/fphys-09-01347.pdf
Summary: A soccer match induce changes in physiological stress biomarkers as testosterone (T), cortisol (C), and testosterone:cortisol (T:C) ration. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to soccer match. The role of hydration status before the match in this biomarkers has not yet been reported. The aim of this study was to compare the salivary T, C, and the T:C ratio responses after two friendly matches in well-hydrated and mild-dehydrated (MD) elite young male soccer player. Seventeen players (age, 16.8 ± 0.4 years; VO2max 57.2 ± 3.6 ml/kg-1/min-1) were divided into two teams. Before the matches the athletes were assessed for hydration level by the urine specific gravity method and divided for the analysis into well-hydrated (WH; n = 9; USG < 1.010 g/mL-1) and mild-dehydrated (MD; n = 8; USG 1.010 to 1.020 g/mL-1) groups. Hormones were collected before and after each match by saliva samples. The mean (HRmean) and maximal (HRmax) heart rate were measured throughout the matches. A two-way ANOVA was used to compare T, C, and T:C between and within groups. Similar HRmean (WH, 83.1 ± 4.7%; MD, 87.0 ± 4.1; p = 0.12) and HRmax (WH, 93.2 ± 4.4%; MD, 94.7 ± 3.7%; p = 0.52) were found for both groups during the matches. No differences were found before the matches in the T (p = 0.38), C (p = 66), nor T:C (p = 0.38) between groups. No changes within groups were found after matches in neither group for T (WH, p = 0.20; MD, p = 0.36), and T:C (WH, p = 0.94; MD, p = 0.63). Regarding the C, only the MD group showed increases (28%) after the matches (MD, p = 0.03; WH, p = 0.13). In conclusion MD group exacerbate the C response to friendly matches in elite young male soccer players, suggesting that dehydration before match may be an added stress to be considered.


#10 Can compression stockings reduce the degree of soccer match-induced fatigue in females?
Reference: Res Sports Med. 2018 Oct 14:1-14. doi: 10.1080/15438627.2018.1527335. [Epub ahead of print]
Authors: Pavin LN, Leicht AS, Gimenes SV, da Silva BVC, Simim MAM, Marocolo M, da Mota GR
Summary: Soccer-induced fatigue and performance are different between the sexes. The effect of compression stockings (CS) use on fatigue during the soccer match in females is unknown. Thus, we evaluated the impact of CS use during a female soccer match on match-induced fatigue. Twenty soccer players were randomly allocated to two groups (n = 10 for each group): CS and Control (regular socks), and equally distributed within two teams. At rest (baseline 48-h before the match) and immediately post-match, we assessed agility T-test, standing heel-rise test and YoYo Intermittent Endurance Test level 2 (YoYoIE2) performance. Effort during the match (heart rate and rating of perceived exertion) was similar (p > 0.05) between groups. The YoYoIE2 performance was decreased post-match (p < 0.05) equally for both groups. Otherwise, the CS group exhibited a greater post-match performance (p < 0.05) for the agility T-test and heel-rise test (large effect sizes). Therefore, we conclude that the use of CS during an amateur female soccer match resulted in less match-induced fatigue.


#11 Acute and chronic effects of soccer game on the retinal vessel diameters in middle-aged adults
Reference: J Sports Med Phys Fitness. 2018 Oct 10. doi: 10.23736/S0022-4707.18.09164-8. [Epub ahead of print]
Authors: Solianik R, Streckis V, Imbrasiene D, Paunksnis A
Summary: Although changes in retinal vessel diameter is a new biomarker for the evaluation of cardiovascular risk factors, limited information is available regarding the effects of endurance exercises on retinal microcirculation. Thus, we aimed to evaluate both chronic and acute effects of soccer game on the diameters of retinal vessels in middle-aged players. Retinal vessel diameters were measured in 12 middle-aged amateur players (44.4 ± 7.0 years of age) with more than four years of soccer playing experience and 12 age matched sedentary adults (49.7 ± 7.1 years of age). In soccer players, diameters were also measured immediately after the soccer game. Cardiovascular risk profiles (anthropometry and body composition and blood pressure (BP)) and physical activity levels were also measured. Soccer players had wider retinal vessels than controls (P<0.05), resulting in greater arteriolar-to-venular diameter ratio (AVR) (P<0.05). Greater sports-related physical activity, lower body mass index (BMI) and fat mass were observed for soccer players compared to the controls (P<0.05), whereas BP did not differ. Physical activity level correlated positively with temporal retinal arteriolar (TRA) diameter and with AVR (P<0.05), whereas TRA diameter correlated negatively with BMI and fat mass (P<0.05). A significant correlation between temporal retinal venule (TRV) diameter and TRA diameter (P<0.05) was observed. The acute soccer game increased BP (P<0.05) and induced TRV dilatation (P<0.05). In middle-aged amateur soccer players, improvement of the retinal microcirculation was observed. Cardiovascular risk factors and physical inactivity were associated with adverse retinal microvascular alterations. In terms of acute effects, soccer play causes venular, but not arteriolar dilatation for middle-aged adults.


#12 Modulation of macrophage polarization by level-1 Yo-Yo intermittent recovery test in young football players
Reference: Medicine (Baltimore). 2018 Oct;97(42):e12739. doi: 10.1097/MD.0000000000012739.
Authors: Chiu CJ, Chi CW, Hsieh HR, Huang YC, Wu HJ, Chen YJ
Download link: https://pdfs.journals.lww.com/md-journal/2018/10190/Modulation_of_macrophage_polarization_by_level_1.21.pdf?token=method|ExpireAbsolute;source|Journals;ttl|1540669179803;payload|mY8D3u1TCCsNvP5E421JYK6N6XICDamxByyYpaNzk7FKjTaa1Yz22MivkHZqjGP4kdS2v0J76WGAnHACH69s21Csk0OpQi3YbjEMdSoz2UhVybFqQxA7lKwSUlA502zQZr96TQRwhVlocEp/sJ586aVbcBFlltKNKo+tbuMfL73hiPqJliudqs17cHeLcLbV/CqjlP3IO0jGHlHQtJWcICDdAyGJMnpi6RlbEJaRheGeh5z5uvqz3FLHgPKVXJzddFRrD2hcIwdDP9eSnSkfs8tQHGPCNVqu4yfd7VFcCxs=;hash|S8jVxvqAc5VVdXOn9m+AOA==
Summary: The aim of this study was to examine the effect of the level-1 Yo-Yo intermittent recovery test (YYIRT1) on polarization of macrophages in young football players.Fourteen male football players (19.9 ± 1.4 years old) were enrolled in this study. YYIRT1 was performed with 20-meter shuttle runs at increasing speeds and 10-second active recovery in a 5-meter distance between runs till exhaustion. Fasting blood samples were collected before and immediately after YYIRT1. Analysis for macrophage polarization by flow cytometry, reactive oxygen species (ROS) by flow cytometry, biochemical parameters by chemical reactions, and serum cytokines by ELISA were performed. The rating of perceived exertion (RPE) and cardiovascular parameters were recorded.The time to exhaustion was 714.1 ± 114.4 seconds. The oxygen uptake ((Equation is included in full-text article.)) was 48.7 ± 5.6 mL/min/kg, RPE scale was 19 ± 1, resting heart rate and maximal heart rate were 64.9 ± 8.8 beat/min and 181.9 ± 9.3 beat/min, respectively, indicating a high level of cardiopulmonary fitness. The expression of macrophage-specific CD14 and M1 marker HLA-ABC, but not M2 marker CD206, was down-regulated after YYIRT1. The intracellular ROS levels in macrophages had no significant change. In biochemical profile, the serum levels of lactic dehydrogenase (LDH), a marker of muscle damage, increased after YYIRT1 whereas no significant alteration was noted in creatine phosphokinase (CPK), blood urine nitrogen, creatinine, aspartate transaminase (AST), alanine transaminase (ALT), and C-reactive protein. The serum levels of interleukin (IL)-6, IL-10 and tumor necrosis factor (TNF)-α had no significant change.The YYIRT1 may induce muscle damage accompanied by modulation of macrophage polarization toward suppression of M1 phenotype in young football players.


#13 Cam morphology in young male football players mostly develops before proximal femoral growth plate closure: a prospective study with 5-year follow-up
Reference: Br J Sports Med. 2018 Oct 15. pii: bjsports-2018-099328. doi: 10.1136/bjsports-2018-099328. [Epub ahead of print]
Authors: van Klij P, Heijboer MP, Ginai AZ, Verhaar JAN, Waarsing JH, Agricola R
Summary: Cam morphology is not completely understood. The aim of this study was threefold: (1) to investigate if cam morphology development is associated with growth plate status; (2) to examine whether cam morphology continues to develop after growth plate closure; and (3) to qualitatively describe cam morphology development over 5-year follow-up. Academy male football players (n=49) participated in this prospective 5-year follow-up study (baseline 12-19 years old). Anteroposterior and frog-leg lateral views were obtained at baseline (142 hips), 2.5-year (126 hips) and 5-year follow-up (98 hips). Cam morphology on these time points was defined as: (A) visual scores of the anterior head-neck junction, classified as: (1) normal, (2) flattening, and (3) prominence; and (B) alpha angle ≥60°.Proximal femoral growth plates were classified as open or closed. Cam morphology development was defined as every increase in visual score and/or increase in alpha angle from <60° to ≥60°, between two time points. This resulted in 224 measurements for cam morphology development analysis. Cam morphology development was significantly associated with open growth plates based on visual score (OR: 10.03, 95% CI 3.49 to 28.84, p<0.001) and alpha angle (OR: 2.85, 95% CI 1.18 to 6.88, p=0.020). With both definitions combined, cam developed in 104 of 142 hips during follow-up. Of these 104 hips, cam developed in 86 hips (82.7%) with open growth plate and in 18 hips (17.3%) with a closed growth plate. Cam morphology developed from 12 to 13 years of age until growth plate closure around 18 years. Cam morphology of the hip is more likely to develop with an open growth plate.


#14 The Effect of Blurred Perceptual Training on the Decision Making of Skilled Football Referees
Reference: Front Psychol. 2018 Sep 27;9:1803. doi: 10.3389/fpsyg.2018.01803. eCollection 2018.
Authors: van Biemen T, Koedijker J, Renden PG, Mann DL
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170623/pdf/fpsyg-09-01803.pdf
Summary: When judging ambiguous foul situations in football (soccer), referees must attune to the kinematic characteristics inherent in genuine fouls to ensure that they can (i) recognize when a foul has taken place, and (ii) discriminate the presence of deceptive intent on the part of the tackled player. The aim of this study was to determine whether perceptual training that removes superficial visual information would improve the decision-making performance of football referees. Two groups of skilled referees judged ambiguous foul situations on video before and after a training intervention that involved adjudicating foul situations. During the training phase, participants in a blurred-footage training group watched digitally altered, blurred videos that removed superficial visual information, whilst participants in a normal-footage control group viewed the same videos without blur (i.e., with the superficial information present). We hypothesized that blurred-training would train referees to ignore superficial visual information and instead focus on the basic kinematic movements that would better reveal the true nature of the inter-personal interaction. Consistent with this idea, training with blurred footage resulted in a positive change in response accuracy from pre to post-test when compared with normal-footage training. This improvement could not be explained on the basis of changes in response time or bias, but instead reflected a change in the sensitivity to genuine fouls. These findings provide a promising indication of the potential efficacy of blurred-footage training for referees to attune to the kinematic information that characterizes a foul. Blurred training might offer an innovative means of enhancing the decision-making performance of football referees via perceptual training.

Sun

04

Nov

2018

Latest research in football - week 40 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Cardio-respiratory values during recovery from exercise in soccer Spanish leagues
Reference: Physiol Meas. 2018 Oct 11;39(10):105003. doi: 10.1088/1361-6579/aae0e8.
Authors: Ramos-Álvarez JJ, Maffulli N, Bragazzi NL, Ardigò LP, Jiménez-Herranz E, Naranjo-Ortiz C, Padulo J, Calderón Montero FJ
Download link: http://iopscience.iop.org/article/10.1088/1361-6579/aae0e8/pdf
Summary: In this cross-sectional study, we compared Spanish division one (n  =  114) and division two (n  =  80) soccer players in terms of their cardio-respiratory response during recovery following a maximum laboratory effort test. Following the maximum laboratory effort protocol, we measured oxygen consumption ([Formula: see text]), heart rate (HR), and ventilation ([Formula: see text]) during recovery. Over the first 60 s of recovery, no significant differences were seen in either [Formula: see text] (28.7 versus 28.3 ml/kg/m, in division one and two players, respectively), HR, or [Formula: see text] (p  >  0.05). After 90 s, however, significant differences appeared between the players of the two divisions (p  <  0.01), although not among playing positions. Significant differences in [Formula: see text] (21.1 versus 26.0 ml/kg/m, in division one and two players, respectively) and HR were still apparent at 180 s into the recovery period. The change in professional soccer players' cardio-respiratory values over the recovery period following maximum effort are independent of the position played, but are associated with the division in which a player competes. Second division players show significantly higher [Formula: see text] and HR values than first division players at 180 s into the recovery period. These differences might influence performance in soccer and in other athletes whose sports require intermittent bouts of maximum effort and consequently times to repeat high-intensity efforts as short as possible.


#2 Lower limb injury prevention programs in youth soccer: a survey of coach knowledge, usage, and barriers
Reference: J Exp Orthop. 2018 Oct 11;5(1):43. doi: 10.1186/s40634-018-0160-6.
Authors: Mawson R, Creech MJ, Peterson DC, Farrokhyar F, Ayeni OR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6179968/pdf/40634_2018_Article_160.pdf
Summary: Participation in youth soccer carries a significant risk of injury, most commonly non-contact injuries of the lower extremity. A growing body of research supports the use of neuromuscular interventions by teams to prevent such injuries, yet the uptake of these recommendations by soccer teams remains largely unexplored. The purposes of the study were to determine (1) the level of awareness by youth coaches of injury prevention programs and their efficacy; (2) the number of youth coaches that use these interventions; and (3) barriers and potential facilitators to implementing a sustainable injury prevention program. Four hundred eighteen coaches of male and female youth soccer teams were emailed an online blinded survey. This survey consisted of 26 questions covering coaches' demographics, level of training, experience with injuries among players, and use of injury prevention programs. Question development was guided by the RE-AIM Sports Setting Matrix in combination with findings from the literature review and expert experience from orthopaedic surgeons specializing in sport medicine. Of the 418 coaches contacted, 101 responded. Only 29.8% of respondents used an injury prevention program in the prior soccer season. Coaches that had completed one or more coaching courses were more likely to use an intervention. Of those that did not already use an intervention, coaches agreed or strongly agreed that they would consider using one if it could be used in place of the warm up and take no more than 20 min (74.0%), if they could access information about the exercises (84.0%), and if the exercises could be properly demonstrated (84.0%). Additionally, 84% of coaches that did not already use an intervention agreed or strongly agreed that knowing that interventions may reduce a player's risk of injury by 45% would affect whether they would use one. This study suggests that the current use and awareness of injury prevention programs is limited by a lack of communication and education between sporting associations and coaches, as well as perceived time constraints. The results also suggest that improving coaching education of injury prevention could increase the frequency of intervention use.


#3 Low Doses of Caffeine: Enhancement of Physical Performance in Elite Adolescent Male Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Oct 9:1-21. doi: 10.1123/ijspp.2018-0536. [Epub ahead of print]
Authors: Ellis M, Noon M, Myers T, Clarke N
Summary: Large doses of ~6 mg·kg-1 body mass have improved performance during intermittent running, jumping, and agility protocols. However, there are sparse data on low doses of caffeine, especially in elite adolescent soccer players. Fifteen elite youth soccer players (177.3±4.8 cm, 66.9±7.9 kg and 16±1 y) participated in the study, consuming 1, 2, or 3 mg·kg-1 caffeine in a gelatin capsule or a 2-mg·kg-1 placebo in a single-blind, randomized, crossover study design. Testing consisted of a 20-m sprint, arrowhead agility (change of direction [CoD] right or left), countermovement jump (CMJ), and Yo-Yo Intermittent Recovery Test Level-1 (Yo-Yo IR1). Post-exercise CMJ performance was assessed as participants exited the Yo-Yo IR1. Data were analyzed using a Bayesian multilevel regression model to provide explained variance and probabilities of improvement (p=%). 3 mg·kg-1 caffeine presented the highest probabilities of change compared with placebo across a range of tests (mean ± SD, p= %). Times for 20-m sprint were 3.15±0.10s vs 3.18±0.09s (p=73%), CoD-R times were 8.43±0.24s vs 8.55±0.25s (p=99%), CoD-L times were 8.44±0.22s vs 8.52±0.18s (p=85%), Yo-Yo IR1 distance was 2440±531m vs 2308±540m (p=15%), and preexercise CMJ height was 41.6±7.2cm vs 38±8.5cm (p=96%). Postexercise CMJ was higher with 3 mg·kg-1 than with placebo (42.3±8cm vs 36.6±8cm [p=100%]). Doses of 1 or 2 mg·kg-1 caffeine also demonstrated the ability to enhance performance but were task dependent. Low doses of caffeine improve performance but are dose and task dependent. A dose of 3 mg·kg-1 caffeine improved performance across the majority of tests with potential to further improve postexercise CMJ height.


#4 The efficacy of lower limb screening tests in predicting PlayerLoad within a professional soccer academy
Reference: J Sport Rehabil. 2018 Oct 9:1-20. doi: 10.1123/jsr.2018-0175. [Epub ahead of print]
Authors: Bowen C, Weaver K, Relph N, Greig M
Summary: Training exposure has been associated with injury epidemiology in elite youth soccer, where lower limb musculoskeletal screening is commonly used to highlight injury risk. However, there has been little consideration of the relationship between lower limb screening and the loading response to soccer activities. The purpose was to quantify the efficacy of using screening tests to predict the loading elicited in soccer-specific activities, and to develop a hierarchical ordering of musculoskeletal screening tests to identify test redundancy and inform practice. 21 elite male soccer players aged 15.7 ± 0.9 years participated in this study. Players completed a battery of five screening tests (knee to wall, hip internal rotation, adductor squeeze, single leg hop, anterior reach), and a 25min standardised soccer session with a GPS unit placed at C7 to collect multi-planar PlayerLoad data. Baseline data on each screening test, along with uni-axial PlayerLoad in the medio-lateral, anterio-posterior and vertical planes were utilized as outcome measures. Stepwise hierarchical modelling of the screening tests revealed that dominant leg knee to wall distance was the most prevalent and powerful predictor of multi-planar PlayerLoad, accounting for up to 42% of variation in uni-axial loading. The adductor squeeze test was the least powerful predictor of PlayerLoad. Of note, one player who incurred a knee injury within three weeks of testing had shown a 20% reduction in knee to wall distance compared with peers, and elicited 23% greater PlayerLoad, supporting the hierarchical model. There was some evidence of redundancy in the screening battery, with implications for clinical choice. Hierarchical ordering and a concurrent case study highlight dominant leg knee to wall distance as the primary predictor of multi-axial loading in soccer. This has implications for the design and interpretation of screening data in elite youth soccer.


#5 Differences in Sprint Mechanical Force-Velocity Profile Between Trained Soccer and Futsal Players
Reference: Int J Sports Physiol Perform. 2018 Oct 9:1-21. doi: 10.1123/ijspp.2018-0402. [Epub ahead of print]
Authors: Jiménez-Reyes P, García-Ramos A, Cuadrado-Peñafiel V, Párraga-Montilla JA, Morcillo-Losa JA, Samozino P, Morin JB
Summary: This study aimed to compare the sprint mechanical force-velocity (F-V) profile between soccer and futsal players. A secondary aim was, within each sport, to study the differences in sprint mechanical F-V profile between sexes and players of different levels. 102 soccer players (63 men) and 77 futsal players (49 men) that were competing from the elite to amateur levels in the Spanish league participated in this investigation. The testing procedure consisted of 3 unloaded maximal 40-m sprints. The velocity-time data recorded by a radar device was used to calculate the variables of the sprint acceleration F-V profile (maximal theoretical force [F0], maximal theoretical velocity [V0], maximal power [Pmax], decrease in the ratio of horizontal-to-resultant force [DRF], and maximal ratio of horizontal-to-resultant force [RFpeak]). Futsal players showed a higher F0 than soccer players (effect size [ES] range: 0.11 to 0.74), while V0 (ES range: -0.48 to -1.15) and DRF (ES range: -0.75 to -1.45) was higher for soccer players. No significant differences were observed between soccer and futsal players for Pmax (ES range: -0.43 to 0.19) and RFpeak (ES range: -0.49 to 0.30). Men and high-level players presented an overall enhanced F-V profile compared to women and their lower-level counterparts, respectively. The higher F0 and lower V0 of futsal players could be caused by the specific game's demand (larger number of accelerations but of shorter distances compared to soccer). These results show that the sprint mechanical F-V profile is able to distinguish between soccer and futsal players.


#6 The temporal pattern of recovery in eccentric hamstring strength post-soccer specific fatigue
Reference: Res Sports Med. 2018 Oct 8:1-12. doi: 10.1080/15438627.2018.1523168. [Epub ahead of print]
Authors: Rhodes D, McNaughton L, Greig M
Summary: Eccentric hamstring strength is an aetiological risk factor for soccer injury. The temporal pattern of recovery post-exercise is critical in injury management. 18 male professional soccer players completed baseline assessments of eccentric hamstring strength at isokinetic speeds of 60, 150 and 300°· s-1. Post SAFT90 measures were repeated immediately, + 24 hrs, + 48 hrs and + 72 hrs. Main effects for recovery time and testing speed in average torque (AvT), peak torque (PT) and the corresponding angle (Ɵ) were supplemented by regression modelling to describe the temporal pattern of recovery. A main effect for isokinetic testing speed was observed in PT and AvT. A main effect for recovery time highlighted greater strength pre-exercise, with a quadratic pattern to temporal recovery highlighting minima achieved at between 40-48 hrs. Strength parameters are not fully recovered until 96 hrs post soccer specific fatigue, with implications for training design and injury management, particularly within fixture-congested periods.


#7 Manual therapy and early return to sport in football players with adductor-related groin pain: A prospective case series
Reference: Physiother Theory Pract. 2018 Oct 11:1-10. doi: 10.1080/09593985.2018.1531096. [Epub ahead of print]
Authors: Tak I PhD, MScPT, Langhout R MMT PT, Bertrand B MScPT, Barendrecht M MPTS, Stubbe J PhD, Kerkhoffs G PhD, MD, Weir A PhD, MBBS
Summary: The purpose was to study the clinical course including return to sport success rates of football players with adductor-related groin pain (ARGP) after manual therapy of the adductor muscles. Thirty-four football players with ARGP with median pre-injury Tegner scores of 9 (IQR 25-75: 9-9) were treated with manual therapy of the adductor muscles. Main outcome measures were numeric pain rating scale (NPRS), Hip and Groin Outcome Score (HAGOS) and global perceived effect (GPE) for treatment and patient satisfaction at 2, 6 and 12 weeks. Return to sport was documented. Pain during (NPRS 7 (6-8) and after (NPRS 8 (6-8) sports decreased to NPRS 1 (0.2-3) and 1 (0.8-3), respectively (p < 0.001). Within 2 weeks 82% of the players returned to pre-injury playing levels with improved (p < 0.001) HAGOS subscale scores. Eighty-five percent reported clinically relevant improvement, 82% reported to be satisfied. At 12 weeks, 88% had returned to pre-injury playing levels. HAGOS showed symptoms were still present. Early return to sport seems possible and safe after manual therapy of the adductor muscles in football players with ARGP in the short term. While the majority of injured football players return to sport within two weeks, caution is advised regarding effectiveness as hip and groin symptoms were still present and no control groups were available.


#8 Effects of pitch spatial references on players' positioning and physical performances during football small-sided games
Reference: J Sports Sci. 2018 Oct 11:1-7. doi: 10.1080/02640414.2018.1523671. [Epub ahead of print]
Authors: Coutinho D, Gonçalves B, Travassos B, Abade E, Wong DP, Sampaio J
Summary: The aim of this study was to identify the effects of adding spatial references during football small-sided games in youth players' tactical and physical performance. Twelve under-15 players performed a Gk+ 6v6+ Gk game under two playing conditions: (i) without spatial references (CONTROL condition); (ii) with spatial references, by dividing equally the pitch into three corridors and three sectors (experimental situation, LINES). Players' positional data was used to compute time-motion and tactical-related variables. The results revealed that performance under LINES situation increased the regularity in the zones occupied (~14%, Cohen's d: 0.5; ±0.3; p = 0.003) and in the distance between teammates' dyads (~19%, 0.9; ±0.2; p < 0.001). Oppositely, LINES condition decreased the longitudinal synchronization of players' displacements (0.4; ±0.2; p = 0.002), players' average speed (0.5; ±0.3; p = 0.002) and distance covered at lower (0.9; ±0.3; p < 0.001) and moderate speed (0.5; ±0.3; p < 0.001). Adding spatial references seems to promote a more structured pattern of play and increase positional regularity. However, coaches should be aware that this constraint may decrease the synchronization between players. Overall, these findings may be generalized to most invasion team sports.


#9 Top 50 most-cited articles in medicine and science in football
Reference: BMJ Open Sport Exerc Med. 2018 Oct 1;4(1):e000388. doi: 10.1136/bmjsem-2018-000388. eCollection 2018.
Authors: Brito J, Nassis GP, Seabra AT, Figueiredo P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6173236/pdf/bmjsem-2018-000388.pdf
Summary: The purpose was to conduct a comprehensive mapping analysis to the scientific literature published in football aiming to identify the areas of bigger interest and potential for further exploration. The data were obtained by a search conducted on the Web of Science. Articles were listed based on citation frequency. We used an open-source bibliometrix R-package for the comprehensive bibliometric analyses. The number of citations per article ranged from 251 to 869 (median 323; IQR 125). The yearly number of citations ranged from 8 to 54 (median 26; IQR 11). Most of the articles (76%) were of level III of evidence, 10% were level II and 14% were level IV. Within the top 50 most-cited articles, 40 articles were original research (37 observational and 3 experimental studies), 9 were review articles and 1 was a thesis. From the 40 original research articles, 50% involved elite players, 73% were exclusive to male players and 80% involved adult players only. The topic area with the highest number of articles was sports medicine (44%), followed by training and testing (32%), performance analysis (14%) and physiology (10%). No study within the top 50 was devoted to biomechanics, nutrition, sport psychology, coaching or social sciences. The lack of experimental studies within the top 50 most-cited articles in football clearly underpins how far we still are from establishing the theoretical and methodological guidelines for the applied science and medicine in football.


#10 Effect of the Fatigue on the Physical Performance in Different Small-Sided Games in Elite Football Players
Reference: J Strength Cond Res. 2018 Oct 5. doi: 10.1519/JSC.0000000000002858. [Epub ahead of print]
Authors: Calderón Pellegrino G, Paredes-Hernández V, Sánchez-Sánchez J, García-Unanue J, Gallardo L
Summary: Football players need to be able to perform high-intensity efforts of short duration with brief recovery periods. The aim of this study was to analyze the influence of the pitch dimension on high-intensity actions and the effect of a repeated sprint ability (RSA) test on the physical performance in different 4-against-4 (4v4) small-sided games (SSG) dimensions. Sixteen U-18 elite football players performed an RSA test between two 4v4 SSGs (pre and post) to induce fatigue and compare physical data. Speed, sprint number, accelerations, sprint distance, total distance covered, and total distance covered of the players at different intensities were evaluated in 3 different SSGs (125, 150, 250, and 300 m). Results revealed a significant detriment of physical performance in the 125-m SSG after RSA, mostly in number of sprints (-6.56; confidence interval [CI] 95%: -10.13 to -3.00; effect size [ES]: 1.13 p < 0.001), accelerations (-2.69; CI 95%: -5.13 to -0.24; ES: 0.68; p = 0.032), and sprint distance (-65.44 m; CI 95%: -103.73 to -27.16; ES: 1.20; p = 0.001). In bigger SSGs (250 and 300 m), higher distance at high intensity was covered and Vmax, Vmean, and sprint distance were greater. In summary, accelerations, sprint number, and fatigue were higher in smaller pitches, and higher velocities were reached in bigger SSGs. Football players should be aware that changes in pitch size can modify the physical performance on high-intensity actions in SSGs.

Sun

04

Nov

2018

Latest research in football - week 39 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Examination of Physical Fitness Parameters Between Professional and Amateur Greek Soccer Players During the Transition Period
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002770. [Epub ahead of print]
Authors: Bekris E, Pidoulas G, Pidoulas P, Gissis I, Katis A, Komsis S
Summary: The aim of the study was to compare physical fitness parameters between professional and amateur soccer players of different levels. The sample consisted of 381 soccer players divided in 4 experimental groups: first division professional players (n = 115), second division professional players (n = 70), third division semiprofessional players (n = 93), and amateur soccer players (n = 103). Players were tested for several physiological parameters at the end of the transition period. Analysis of variance showed significantly lower body fat and increased maximum oxygen consumption (V[Combining Dot Above]O2max) and velocity of maximum oxygen consumption (vV[Combining Dot Above]O2max) values for first division professional players compared with the other experimental groups (p < 0.05). Similarly, first division professional players showed higher performance during squat jump and countermovement jump test compared with the other experimental groups (p < 0.05). Significant differences on flexibility test were observed between amateur players and the other group (p < 0.05). The results of the study indicated that Greek soccer players at the highest level overcome in almost all the underexamination physiological parameters probably because of less absence from training and better implementation of training programs during the transition period.


#2 Individualizing Acceleration in English Premier League Academy Soccer Players
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002875. [Epub ahead of print]
Authors: Abbott W, Brickley G, Smeeton NJ, Mills S
Summary: Global thresholds are typically used to band acceleration dependent on intensity. However, global thresholds do not account for variation in individual capacities, failing to quantify true intensity of acceleration. Previous research has investigated discrepancies in high-speed distance produced using global and individual speed thresholds, not yet investigated for acceleration. The current aim was to investigate discrepancies between global and individual thresholds when quantifying acceleration tasks. Acceleration data were recorded for 31 professional soccer players, using 10-Hz Global positioning systems devices. Distances traveled performing low-, moderate-, and high-intensity acceleration were calculated for athletes using global and individual thresholds. Global acceleration thresholds for low-, moderate-, and high-intensity acceleration were classified as 1-2, 2-3, and >3 m·s, respectively, with individual thresholds classified as 25-50%, 50-75%, and >75% of maximum acceleration, respectively. Athletes were grouped low (LO), medium (ME), or high (HI) maximum accelerative capacity, determined using 3 maximal 40-m linear sprints. Two-way mixed-design analyses of variance were used to analyze differences in acceleration distances produced between analysis methods and athlete groups. No significant differences were identified between analysis methods for LO. For ME, no significant differences were demonstrated for low intensity. Moderate- and high-intensity acceleration distances were significantly higher for global compared with individual analysis method (p < 0.01). For HI, significantly higher acceleration distances were produced for all acceleration intensities using global thresholds (p < 0.01). Significant differences identified between analysis methods suggest practitioners must apply caution when using global thresholds. Global thresholds do not account for individual capacities and may provide an inaccurate representation of relative intensity of acceleration tasks.


#3 Operative Treatment of Proximal Rectus Femoris Injuries in Professional Soccer Players: A Series of 19 Cases
Reference: Orthop J Sports Med. 2018 Oct 2;6(10):2325967118798827. doi: 10.1177/2325967118798827. eCollection 2018 Oct.
Authors: Lempainen L, Kosola J, Pruna R, Puigdellivol J, Ranne J, Orava S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168727/pdf/10.1177_2325967118798827.pdf
Summary: Proximal rectus femoris (PRF) tears are relatively rare injuries among top-level athletes. PRF injuries can be avulsions of both tendon heads (direct and reflected heads) or of a single head, and some have a tendency to progress to recurrent injuries. The purpose was to describe a series of operatively treated PRF ruptures in professional soccer players. Nineteen cases of PRF injuries (18 patients, 1 bilateral) in professional soccer players who were treated surgically were retrospectively reviewed. Perioperative findings with return-to-play data were recorded. Of the PRF injuries, 10 total avulsions (both heads) and 9 single-head tears were seen on magnetic resonance imaging and were later confirmed during surgery. All 18 patients returned to their preinjury level of play (mean follow-up, 2.8 years [range, 1-11 years]). The repair of PRF tears in professional soccer players yielded good results and allowed all patients to return to their preinjury level of play.


#4 Relationship Between Heart Rate Variability and Acute: Chronic Load Ratio Throughout a Season in NCAA D1 Men's Soccer Players
Reference: J Strength Cond Res. 2018 Oct 4. doi: 10.1519/JSC.0000000000002853. [Epub ahead of print]
Authors: Sekiguchi Y, Huggins RA, Curtis RM, Benjamin CL, Adams WM, Looney DP, West CA, Casa DJ
Summary: The purpose of this study was twofold: (a) to examine the relationship between heart rate variability (HRV) and acute:chronic workload ratio (ACWR)-based training load (TL) metrics and (b) to examine relationships across various A:C ratio-based TL metrics. Heart rate variability in 23 male college soccer players (mean ± SD; age, 21 ± 1 years; body mass, 80.3 ± 5.8 kg; height, 181.9 ± 6.5 cm; %body fat, 11.9 ± 2.0%; and V[Combining Dot Above]O2max, 51.9 ± 5.0 ml·kg·min) was measured at 5 time points: week(W)1, W3, W7, W12, and W14 during the 2015 NCAA men's soccer season. Heart rate variability was calculated from beat to beat intervals using a heart rate monitor. Players donned a global position satellite-enabled device that measured the following TL metrics: session time (ST), Player Load (PL), PL·min, and total distance (TD). Acute:chronic workload ratio was calculated for each TL metric: ACWR-based ST (ACWRST), ACWR-based PL (ACWRPL), ACWR-based PL·min (ACWRPLM), and ACWR-based TD (ACWRTD): ACWR = week average TLs/mo average (30 ± 1 days) TLs. Relationships between HRV and ACWR-based each TL metric were evaluated using mixed effects models. Tukey pairwise comparisons were used to examine differences between types of ACWR-based TL metrics. An increase in ACWRST significantly reduced HRV throughout a season (-7.4 ± 3.6 m·s; p = 0.04). There were significant differences between ACWRPLM and ACWRST, ACWRPL and ACWRTD at W1, ACWRPLM and ACWRST at W3 (p < 0.05). In conclusion, ACWRST, ACWRPL, and ACWRTD were significantly different from ACWRPLM. ACWRST was found to significantly predict HRV; higher ACWRST was significantly associated with lower HRV. Therefore, tracking of the ACWR using ST may help to optimize athlete's physiological state throughout a season.


#5 The effects of a calf pump device on second half performance of a simulated soccer match in competitive youth players
Reference: J Sports Sci. 2018 Oct 4:1-9. doi: 10.1080/02640414.2018.1522947. [Epub ahead of print]
Authors: Béliard S, Cassirame J, Ennequin G, Coratella G, Tordi N
Summary: During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT90). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters.


#6 Does Early Recruitment Predict Greater Physical Performance in Academy Soccer Players?
Reference: Sports (Basel). 2018 Sep 30;6(4). pii: E108. doi: 10.3390/sports6040108.
Authors: Hertzog M, Paul DJ, Nassis GP, Silva JR
Summary: The purpose of this longitudinal study was to investigate whether recruitment status influences neuromuscular and endurance performances in academy soccer players over a 2-year training period (from Under-16 to Under-18). Thirty-seven male soccer players from an elite academy were selected and divided in two cohorts according to their recruitment status: Early Recruitment group (ER; n = 16), training and competing for the academy since Under-14 and Under-15 age groups, and; Late Recruitment group (LR; n = 21) included in the academy training process at Under-16. Squat (SJ) and countermovement jump with (CMJwA) and without arms swing (CMJ), 10-m sprint time, and Vam-Eval test (MAV) were performed in three successive occasions always pre-season (Under-16, Under-17 and Under-18 age groups, T1, T2, and T3 respectively). A two-way (recruitment status × time) analysis of variance with repeated measurements was performed as well as the magnitude of difference using both effect size and magnitude-based inferences. There was no difference between ER and LR for MAV, 10 m-sprint, and SJ from T1 to T3. However, LR players presented non-significant small and possibly greater improvement in CMJ (ES = 0.4) and CMJwA (ES = 0.4) than ER players at T2. These data indicate that early recruitment is not likely to result in greater physical performance improvement at the age of 18.


#7 Relationship of Absolute and Relative Lower-Body Strength to Predictors of Athletic Performance in Collegiate Women Soccer Players
Reference: Sports (Basel). 2018 Sep 29;6(4). pii: E106. doi: 10.3390/sports6040106.
Authors: Andersen E, Lockie RG, Dawes JJ
Summary: The purpose of this study was to investigate the relationships between absolute and relative lower-body strength on predictors of athletic performance among Division II collegiate women's soccer players. Archived pre-season testing data for seventeen (n = 17) female National Collegiate Athletics Association (NCAA) Division II soccer players were analyzed, including: vertical jump, 3RM back squat, 505-agility, modified T-test, 10 m and 30 m sprint, and 20 m multistage fitness test (20 m MSFT). Relative strength was calculated based on the estimated 1RM back squat divided by the athlete's body mass. Significant correlations were discovered between absolute lower-body strength and 505-agility (Right: r = -0.51, p < 0.05; Left: r = -0.59, p < 0.05), modified T-test (r = -0.55, p < 0.05), 10 m and 30 m (r = -0.59, p < 0.05; r = -0.54, p < 0.05), and sprint performance. Relative lower-body strength showed significant correlations with vertical jump (r = 0.54, p < 0.05), 505-agility (Right: r = -0.58, p < 0.05; Left: r = -0.67, p < 0.01), modified T-test (r = -0.75, p < 0.01), 10 m and 30 m (r = -0.59 p < 0.05; r = -0.67, p < 0.01), and the 20 m MSFT (r = 0.58, p < 0.05). These results indicate that strength and conditioning coaches should emphasize the development of absolute and relative lower-body strength with their players to improve power, agility, and speed performance.


#8 Effects of the '11+ Kids' injury prevention programme on severe injuries in children's football: a secondary analysis of data from a multicentre cluster-randomised controlled trial
Reference: Br J Sports Med. 2018 Oct 2. pii: bjsports-2018-099062. doi: 10.1136/bjsports-2018-099062. [Epub ahead of print]
Authors: Beaudouin F, Rössler R, Aus der Fünten K, Bizzini M, Chomiak J, Verhagen E, Junge A, Dvorak J, Lichtenstein E, Meyer T, Faude O
Summary: The purpose of the study was to assess the effects of the injury prevention programme '11+ Kids' on reducing severe injuries in 7 to 13 year old football (soccer) players. Football clubs (under-9, under-11 and under-13 age groups) from the Czech Republic, Germany, the Netherlands and Switzerland were cluster-randomised (clubs) into an intervention (INT) and a control group (CON). INT replaced their usual warm-up by '11+ Kids' two times a week. CON followed their regular training regime. Match and training exposure and injury characteristics were recorded and injury incidence rates (IRs) and 95% CIs calculated. For the present analysis, only severe injuries (absence from training/match ≥28 days) were considered. Hazard ratios (HR) were calculated using extended Cox models. The overall IR of severe injuries per 1000 football hours was 0.33 (95% CI 0.25 to 0.43) in CON and 0.15 (95% CI 0.10 to 0.23) in INT. There was a reduction of severe overall (HR 0.42, 95% CI 0.24 to 0.72), match (0.41, 0.17 to 0.95) and training injuries (0.42, 0.21 to 0.86) in INT. The injury types that were prevented the most were: other bone injuries 66%, fractures 49% and sprains and ligament injuries 37%. Severe injuries located at the knee (82%), hip/groin (81%), the foot/toe (80%) and the ankle (65%) were reduced tremendously. '11+ Kids' has a large preventive effect on severe injuries by investing only 15 to 20 min per training session. The present results should motivate coaches to implement effective injury prevention programmes such as the '11+ Kids' in children's football.


#9 Jumping performance based on duration of rehabilitation in female football players after anterior cruciate ligament reconstruction
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Sep 28. doi: 10.1007/s00167-018-5154-5. [Epub ahead of print]
Authors: Arundale AJH, Kvist J, Hägglund M, Fältström A
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-018-5154-5.pdf
Summary: The purpose was to determine if female football players who had longer durations of rehabilitation, measured in months, after anterior cruciate ligament reconstruction would have lower tuck jump scores (fewer technique flaws) and smaller asymmetries during drop vertical jump landing. One-hundred-and-seventeen female football players, aged 16-25 years, after primary unilateral ACL reconstruction (median 16 months, range 6-39) were included. Athletes reported the duration of rehabilitation they performed after anterior cruciate ligament reconstruction. Athletes also performed the tuck jump and drop vertical jump tests. Outcome variables were: tuck jump score, frontal plane knee motion and probability of peak knee abduction moment during drop vertical jump landing. There was no difference in tuck jump score based on duration of rehabilitation (n.s.). No interaction (n.s.), difference between limbs (n.s.), or duration of rehabilitation (n.s.) was found for peak knee abduction moment during drop vertical jump landing. No interaction (n.s.) or difference between limbs (n.s.) was found for frontal plane knee motion, but there was a difference based on duration of rehabilitation (P = 0.01). Athletes with > 9 months of rehabilitation had more frontal plane knee motion (medial knee displacement) than athletes with < 6 months (P = 0.01) or 6-9 months (P = 0.03). As there was no difference in tuck jump score or peak knee abduction moment based on duration of rehabilitation, the results of this study press upon clinicians the importance of using objective measures to progress rehabilitation and clear athletes for return to sport, rather than time alone.

Fri

02

Nov

2018

Latest research in football - week 38 - 2018

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Physical responses of professional soccer players during 4 vs. 4 small-sided games with mini-goals according to rule changes
Reference: Biol Sport. 2018 Mar;35(1):75-81. doi: 10.5114/biolsport.2018.70754. Epub 2017 Oct 12.
Authors: Giménez JV, Liu H, Lipińska P, Szwarc A, Rompa P, Gómez MA
Summary: The aim of this study was to investigate the influence of the number of ball touches authorised per game (one touch [T1], two touches [T2], and free touches [FT]) on the players' physical responses throughout the bouts in 4 vs 4 soccer small-sided games (SSGs) with mini-goals (without a goalkeeper). Fourteen professional Polish players (age 23.2±2.7 years, height 177.9±6.1 cm, weight: 73.2±6.9 kg, body fat 12.6±2%, playing experience: 14±5 years) completed nine series of 4 vs 4 SSGs. Each trial included three series of SSGs with a game duration of 4 minutes on an equal sized pitch (30x24 m; 720 m2; individual occupied area per player=90 m2). Differences in physical responses and time-motion characteristics of players were measured with the Global Positioning System (GPS) and assessed using a repeated measures ANOVA to compare the three game conditions and the magnitude-based inference to evaluate the pairwise comparison effects. The results showed that only the variables distance covered at low speed, time walking, time at low speed, and accelerations of >4 m/s² were statistically significantly different among game conditions. The pairwise comparisons only identified significant effects for distance covered at low speed (between FT and T2), for time walking (between FT and T1), for time at moderate and low speed (between FT and T2), and for accelerations of >4 m/s² (between FT and T1). The players' performances are affected by the ball touch constraint during SSGs with mini-goals. The results provide useful information for training and task design that replicate specific physical demands (i.e., accelerations of >4 m/s², time walking or running at a lower speed).


#2 Associations between wellness and internal and external load variables in two intermittent small-sided soccer games
Reference: Physiol Behav. 2018 Sep 17. pii: S0031-9384(18)30619-X. doi: 10.1016/j.physbeh.2018.09.008. [Epub ahead of print]
Authors: Clemente FM
Summary: The purpose of this study was to test the associations between wellness and internal and external load variables during two intermittent small-sided games (SSGs). Ten male amateur soccer players (age: 19.8±1.6 years; experience: 8.3±2.1 years; height: 177.4±3.8 cm; weight: 71.7±4.2 kg) voluntarily participated in this study. The 5 × 5 format was played in 3 × 6 min and 6 × 3 min regimens. Muscle soreness (DOMS), stress, fatigue, and sleep quality were rated before each session. Perceived exertion (RPE); mean heart rate (HRmean); total (TD), jogging (JD), running (RD), and sprinting (SD) distances; player's training load (PTL); and total accelerations (TAc) were monitored during SSGs. In the case of the 3 × 6' regimen, large negative correlations between DOMS and TD (-0.68, [-0.89; -0.20]), JD (-0.66, [-0.89; -0.17]) and SD (-0.63, [-0.88; -0.12]) were found, and very large negative correlations between DOMS and PTL (-0.84, [-0.95; -0.53]) were found. Very large (-0.73, [-0.91; -0.30] and large (-0.61, [-0.87; -0.09]) negative correlations between DOMS and HRmean and PTL, respectively, were observed during the 6 × 3' regimen. Regarding the associations between load variables, during the 6 × 3' regimen, RPE was very largely correlated with TD (0.77, [0.37; 0.93]), JD (0.70, [0.25; 0.90]) and largely correlated with TAc (0.67, [0.19; 0.89]). In the 3 × 6' regimen, large correlations were found between RPE and SD (0.62, [0.10; 0.87]) and TAc (0.61, [0.09; 0.87]). Overall, PTL was nearly perfectly correlated with TD (0.96, [0.86; 0.99]) and JD (0.94, [0.81; 0.98]), very largely correlated with TAc (0.87, [0.61; 0.96]), and largely correlated with RD (0.72, [0.29; 0.91]). The results of this study suggest that wellness status may influence workload in SSGs; in particular, DOMS may be moderately-to-largely detrimental to both internal and external load variables. Moreover, it was confirmed that RPE is moderately-to-largely correlated to objectively measured external load variables.


#3 Influence of contextual variables and the pressure to keep category on physical match performance in soccer players
Reference: PLoS One. 2018 Sep 20;13(9):e0204256. doi: 10.1371/journal.pone.0204256. eCollection 2018.
Authors: García-Unanue J, Pérez-Gómez J, Giménez JV, Felipe JL, Gómez-Pomares S, Gallardo L, Sánchez-Sánchez J
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0204256&type=printable
Summary: Previous studies have analysed the influence of contextual variables on performance and physical demands in soccer. However, the points needed to remain in the category have been an element that has not been analysed previously. The aim of the present study was to investigate the influence of match location, match period, strength of the opponent and the points required to keep category on physical performance in professional soccer players. Fourteen Spanish second B Division League matches played by a professional football team were analysed during the 2016/17 season using GPS devices. The 10 main players of each match used the GPS throughout the match. The variables of Total Distance (m), High Intensity Distance (m), High intensity Accelerations (n), Sprint Time (s) and Sprint Distance (m) were analysed. The most notable differences are found in Total Distance covered. Away games accumulated significantly more distance than those played at home, but only in the second half (+230.65 m, IC95%: 21.94 to 438.19, ES: 0.46, p = 0.031). There are no differences depending on the strength of the opponent. However, players covered greater distances during the first half in those matches that were played furthest from salvation (+235.86 m, 95% CI: 49.03 to 422.70, ES: 0.51, p = 0.014). Total Distance is the main parameter affected by situational variables. In addition, the pressure of being further away from saving the category increases the distance covered by players in a game.


#4 Heading in soccer increases serum neurofilament light protein and SCAT3 symptom metrics
Reference: BMJ Open Sport Exerc Med. 2018 Aug 27;4(1):e000433. doi: 10.1136/bmjsem-2018-000433. eCollection 2018.
Authors: Wallace C, Smirl JD, Zetterberg H, Blennow K, Bryk K, Burma J, Dierijck J, Wright AD, van Donkelaar P
Download link: https://bmjopensem.bmj.com/content/bmjosem/4/1/e000433.full.pdf
S