Blog archive

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
Summary: The purpose was to determine the effect of heading a soccer ball on serum neurofilament light (NF-L) protein, plasma tau protein and symptom metrics including total number of symptoms reported and symptom severity scores on the Standardized Concussion Assessment Tool- 3rd edition (SCAT3). Eleven male collegiate soccer players were recruited to take part in three experimental conditions including heading, sham and control conditions. Participants were required to perform 40 headers in 20 min in the heading condition, and control 40 soccer balls directed at them with their hands, chest or thigh in the sham condition. No ball contact was made during the control condition. Blood sampling and SCAT3 symptom assessments were completed prior to and 1 hour following conditions. A subset of participants returned 3 weeks following the heading condition for blood sampling. NF-L was elevated at 1 hour (p=0.004) and 1 month (p=0.04) following the heading condition, and at 1 hour (p=0.02) following the control condition. Tau levels remained unchanged following all conditions. The total number of symptoms (TS) and symptom severity (SS) scores from the SCAT3 were both elevated following the heading condition (p=0.01 and p=0.03, respectively). Both TS and SS decreased following sham (p=0.04 and p=0.04) and control conditions (p=0.04 and p=0.04). An acute bout of soccer heading is associated with increased NF-L concentrations at 1 hour and 1 month following the session and can lead to symptoms commonly reported following sport-related concussion.


#5 How sprinters accelerate beyond the velocity plateau of soccer players: waveform analysis of ground reaction forces
Reference: Scand J Med Sci Sports. 2018 Sep 19. doi: 10.1111/sms.13302. [Epub ahead of print]
Authors: Colyer SL, Nagahara R, Takai Y, Salo AIT
Summary: Forces applied to the ground during sprinting are vital to performance. This study aimed to understand how specific aspects of ground reaction force waveforms allow some individuals to continue to accelerate beyond the velocity plateau of others. Twenty-eight male sprint specialists and 24 male soccer players performed maximal-effort 60-m sprints. A 54-force-plate system captured ground reaction forces, which were used to calculate horizontal velocity profiles. Touchdown velocities of steps were matched (8.00, 8.25 and 8.50 m·s-1 ) and the subsequent ground contact forces were analysed. Mean forces were compared across groups and statistical parametric mapping (t-tests) assessed for differences between entire force waveforms. When individuals contacted the ground with matched horizontal velocity, ground contact durations were similar. Despite this, sprinters produced higher average horizontal power (15.7-17.9 W·kg-1 ) than the soccer players (7.9-11.9 W·kg-1 ). Force waveforms did not differ in the initial braking phase (0-~20% of stance). However, sprinters attenuated eccentric force more in the late braking phase and produced a higher anteroposterior component of force across the majority of the propulsive phase, for example from 31-82% and 92-100% of stance at 8.5 m·s-1 . At this velocity, resultant forces were also higher (33-83% and 86-100% of stance) and the force vector was more horizontally orientated (30-60% and 95-98% of stance) in the sprinters. These findings illustrate the mechanisms which allowed the sprinters to continue accelerating beyond the soccer players' velocity plateau. Moreover, these force production demands provide new insight regarding athletes' strength and technique training requirements to improve acceleration at high velocity.


#6 Outcome after Combined Lateral Extra-articular Tenodesis and Anterior Cruciate Ligament Revision in Professional Soccer Players
Reference: J Knee Surg. 2018 Sep 18. doi: 10.1055/s-0038-1672120. [Epub ahead of print]
Authors: Alessio-Mazzola M, Formica M, Russo A, Sanguineti F, Capello AG, Lovisolo S, Felli L
Summary: We report the functional outcome after combined anterior cruciate ligament (ACL) reconstruction and lateral extra-articular tenodesis (LET) for ACL re-rupture and high-grade pivot shift in professional soccer players. For this retrospective review, the medical records of 24 professional soccer players were analyzed. The mean age at surgery was 23.8 ± 4.2 years and the mean follow-up was 42.2 ± 16.9 months. Pre- and postoperative assessment included the KT-1000 Lachman test, pivot shift test, International Knee Documentation Committee (IKDC) subjective knee evaluation, Tegner activity scale (TAS), and Lysholm score. The rate of return to sports and the level of play at final follow-up were recorded. ACL revision was performed with an autologous bone-patellar tendon-bone autograft or a hamstring graft. LET was performed using an extra-articular MacIntosh procedure as modified by Arnold-Coker. Anterior-posterior laxity was significantly reduced at the final clinical assessment (p < 0.0001): 22 patients (91.7%) had a negative pivot shift and 2 (8.3%) had residual glide (+), with significant improvement (p < 0.0001). The mean subjective IKDC and Lysholm score improved from 69.5 ± 11.1 (range: 56-90) to 88.4 ± 8.9 (range: 62.1-100) and from 58.1 ± 11.7 (range: 33-72) to 97.4 ± 3.2 (range: 88-100), respectively, with significant improvement (p  < 0.0001) over preoperative values. The overall failure rate was 8.3%. There were no differences between mean preinjury and final TAS scores (p > 0.05). The rate of return to sports at the same level was 91.7% and the mean time to return to sports was 9.2 ± 2.2 months. Mid-term functional outcome after combined extra-articular reconstruction and ACL revision surgery was satisfactory, with a reduction in residual postoperative rotatory instability and degree of pivot shift.


#7 Efficacy of Injury Prevention Training Is Greater for High-Risk vs Low-Risk Elite Female Youth Soccer Players
Reference: Am J Sports Med. 2018 Sep 18:363546518795677. doi: 10.1177/0363546518795677. [Epub ahead of print]
Authors: De Ste Croix M, Hughes J, Ayala F, Taylor L, Datson N
Summary: The efficacy of robustness training for high- versus low-risk individuals within high-risk groups is currently unknown. The purpose was to explore the efficacy of robustness training on injury risk factors among female youth soccer players and to examine if high-risk athletes are greater responders to such training. A total of 125 elite youth female soccer players on the English FA talent pathway were randomly selected into a training group (n = 71) or a control group (n = 54). Relative leg stiffness, 2-dimensional knee valgus and knee flexion range of motion from a single-legged countermovement jump, and probability of high knee abduction moment (pKAM) risk were all determined before and after a 16-week robustness training program. For further analysis, participants in the training group were split into groups based on risk: high risk (pKAM >0.80, n = 33) and low risk (pKAM <0.55, n = 33). Magnitude-based inferences were used to explore differences between the control and intervention groups and the high- and low-risk groups. Magnitude-based inferences demonstrated significant beneficial effects in the training group for knee valgus, pKAM, and leg stiffness as compared with the control group. The control group demonstrated possible worthwhile differences in knee flexion range of motion as compared with the intervention group. The high-risk group demonstrated likely/very likely worthwhile differences versus the low-risk group for all parameters. Robustness training induces significant beneficial improvements in injury risk factors among female youth soccer players. The beneficial effects of this multidimensional program are greater for those classified as high risk.


#8 Functional Movement Patterns and Body Composition of High-Level Volleyball, Soccer and Rugby Players
Reference: J Sport Rehabil. 2018 Sep 17:1-20. doi: 10.1123/jsr.2018-0087. [Epub ahead of print]
Authors: Campa F, Piras A, Raffi M, Toselli S
Summary: Sports practice leads athletes to develop a specific body composition, coordination patterns and basic motor skills based on the different tactical and physical needs. This study aimed to present and compare a wide range of functional movement patterns and body composition (BC) parameters of high-level male athletes playing different sports, and to determine if there was a relationship between the parameters examined. Thirty volleyball, twenty-five soccer and thirty rugby players (age 25.9±5.0 years, BMI 25.6±4.1 kg/m2) participated in this study. Functional movement patterns and anthropometric measurements were collected by a physician specifically trained. BMI, fat mass, fat free mass, upper arm muscle and fat area, calf muscle and fat area, thigh muscle and fat area, and functional movement screen (FMS) scores. In addition to considering the FMS total score, we separated the screen into 3 parts: FMSmove, FMSflex and FMSstab. The rugby players showed a higher number of asymmetrical and dysfunctional movements than the other athletes (p <0.01), while the highest scores in FMSflex were obtained by the volleyball players (p <0.01). Additionally, most of the asymmetrical and painful movements in the athletes were measured on the shoulder mobility test. Muscle and fat areas differed significantly among the athletes (p <0.05). Significant associations were found between movement patterns and several BC variables. In particular, large negative correlations were measured between percentage of fat mass (r = -0.616; p <0.01), upper arm fat area (r = -0.519; p <0.01) and FMS total score. Functional movement patterns and BC differ in athletes according to the sport practiced. Furthermore, reaching an optimal BC is essential to achieve a satisfactory quality of movement.


#9 The Effect of a 20-Week Corrective Exercise Programme on Functional Movement Patterns in Youth Elite Male Soccer Players
Reference: J Sport Rehabil. 2018 Sep 17:1-18. doi: 10.1123/jsr.2018-0039. [Epub ahead of print]
Authors: Campa F, Spiga F, Toselli S
Summary: Poor functional movement patterns negatively affect the ability to perform fundamental movements with precision and efficiency, increasing injury risk in athletes. The purpose was to examine the effect of a 20-week corrective exercise programme during the competitive season on functional movement patterns in youth elite male soccer players. 65 youth elite male soccer players (age 15.89 ± 0.53 years; weight 67.42 ± 6.78 kg; stature 175.20 ± 6.34 cm) participated in this study. Two of four teams were randomly selected to take part in the corrective programme. Thus, the players were placed into two groups: corrective exercise programme (CEP) and control group (CON). Functional movement screen (FMS) was used to assess the presence of dysfunctional, asymmetrical and painful movements in the players before and after the intervention period. In addition to considering the FMS total score (FMStotal), we separated the screen into 3 parts: FMSmove, FMSflex and FMSstab. A repeated measures ANOVA was conducted to determine the effectiveness of the training programme on FMS scores. The chi-square (χ2) test was performed to determine whether there were significant changes in the frequencies of asymmetric and dysfunctional movements after 20 weeks. No athlete experienced severe injuries during the intervention period. There was a significant group by time interaction (P < 0.01) for FMStotal, FMSmove and FMSstab, in which only the CEP increased their scores after the intervention period (P < 0.05). A χ2 analysis showed a significant (P < 0.05) decrease in asymmetric and dysfunctional movements at the follow-up in CEP, while these changes were not observed in CON. Youth elite soccer players demonstrate a high prevalence of asymmetric movements during FMS testing, but their functional movement patterns can be improved during the competitive season following a specific corrective exercise programme.


#10 Leg strength and power in Polish striker soccer players
Reference: Acta Bioeng Biomech. 2018;20(2):109-116
Authors: Buśko K, Górski M, Nikolaidis PT, Mazur-Różycka J, Łach P, Staniak Z, Gajewski J
Summary: The main goal of the present study was to examine muscle strength and power of dominant and non-dominant leg, knee extensors and flexors, and their correlations with jumping performances in soccer players. A secondary aim was to evaluate muscle sense. 31 male professional strikers (age 20.9 ± 2.3 years, body mass 75.1 ± 6.6 kg, body height 179.5 ± 4.7 cm) participated in the study. The power output of lower extremities and the height of rise of the body mass centre during vertical jumps were measured using a force plate. The maximum muscle torque of the flexors and extensors of the knee were measured under isometric conditions using a special isometric torquemeter. Force sense was measured in isometric conditions in two tests: (a) fifty percent of the maximal voluntary contraction was set as a value of target force and the participants were instructed to reproduce the target force, (b) the participants attempted to develop a torque reproducing a sine course within the range of 10 to 50% of MVC performed. A direct relationship was observed between the peak muscle torque in knee extensors developed during isokinetic contraction at all velocities and power and height of three types of vertical jumps ( p <0.05). No correlation was observed between jumping performance and muscle torque under isometric condition. No differences were found in strength and jumping abilities as well as in force sense between dominant and non-dominant legs. This study offered a comprehensive and complete evaluation of leg muscle strength, sense and power, with the use of using force plate and isokinetic dynamometry.


#11 Nordic Hamstring Strength of Highly Trained Youth Football Players and Its Relation to Sprint Performance
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002800. [Epub ahead of print]
Authors: Markovic G, Sarabon N, Boban F, Zoric I, Jelcic M, Sos K, Scappaticci M
Summary: We aimed to characterize Nordic hamstring (NH) strength and bilateral NH strength asymmetry in highly trained youth footballers and to investigate the relationship between NH strength and sprint performance. Twenty-two adult and 133 highly trained youth footballers in the age groups U12-U18 participated in this study. Eccentric hamstring strength was assessed using the NH device. Youth footballers (n = 119) also performed 20-m sprint test. Age-related changes in absolute and relative NH strength, and bilateral NH strength asymmetry were analyzed using 1-way analysis of variance. The linear relationship between relative NH strength and sprint performance was established using a Pearson correlation analysis. Significant age-related increases (F = 3.6-18.9; all p < 0.01) in NH strength were reported for all units except N·kg (F = 1.9; p = 0.08). The largest differences in absolute NH strength were seen between U15 and U16 groups. Bilateral NH strength asymmetry varied from 8 to 16% (F = 1.8; p = 0.09) across all age groups. A large correlation between NH strength and sprint performance was observed (r = -0.52; p < 0.01). Our results indicate that NH strength increases nonlinearly with players' age, with the highest values observed in U16 group. Furthermore, bilateral NH strength asymmetry varied nonsignificantly between 8 and 16%. Finally, 27% of variance of sprint performance of youth footballers could be explained by relative NH strength. The reported NH strength data could be used as normative standards during testing and training of youth football players. Present results also suggest that coaches should pay close attention to eccentric hamstring function in youth footballers.


#12 Venous versus capillary sampling for total creatine kinase assay: Effects of a simulated football match
Reference: PLoS One. 2018 Sep 20;13(9):e0204238. doi: 10.1371/journal.pone.0204238. eCollection 2018.
Authors: de Oliveira DCX, Frisselli A, de Souza EG, Stanganelli LCR, Deminice R
Download link: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0204238&type=printable
Summary: Capillary rather than venipuncture may be a simpler and less invasive blood collection protocol that would increase the number of potential sampling tests. However, if capillary sampling can be used as an alternative to venipuncture to determine changes in plasma, total creatine kinase (CK) activity in response to a football training session is poorly known. This study aims to determine whether capillary blood sampling would provide representative measures of total CK activity compared to venipuncture in response to a football training session-induced elevated CK plasma levels. Twenty-two players from an under-19 football team performed a simulated football match with 11 players on each team for 90 minutes total duration (two halves of 45 minutes with 15 minutes rest between). Venous and ear lobe capillary blood samples were collected before and after (24h and 48h) the training session. Athletes retested for three consecutive days after exercise during the recovery week. The simulated match significantly increased (P< 0.05) total CK activity as determined in both venous (1.7-fold) and capillary (1.9-fold) blood sampling. Total CK activity determined using capillary samples demonstrated significant correlation (r = 0.85; P < 0.01) and an elevated concordance Lin index (pc = 0.80) when compared to venous sampling total CK. The Bland-Altman plot showed capillary sampling CK overestimated venous CK levels by 130 U/L (61%), with moderated variance and low bias. Our results demonstrated that capillary sampling for total CK activity assay may be considered a reliable alternative to venipuncture to determine changes in plasma total CK activity in response to a football training session.


#13 Motivational Climate in Youth Football Players
Reference: Behav Sci (Basel). 2018 Sep 15;8(9). pii: E83. doi: 10.3390/bs8090083.
Authors: Castro-Sánchez M, Zurita-Ortega F, Ubago-Jiménez JL, Ramírez-Granizo IA, Chacón-Cuberos R
Download link: www.mdpi.com/2076-328X/8/9/83/pdf
Summary:  In recent decades, the psychology of sport has gained special relevance in this field, due to the influence of psychological variables on sports performance and the regularity of sports practice. The aim of this research is to analyse the motivational climate of footballers. This study uses a descriptive cross-sectional design on a sample of 156 adolescent football players, using an ad-hoc questionnaire for the recording of socio-demographic variables and the PMCSQ-2 questionnaire on motivational climate in sport. The results of the present investigation indicate that footballers are more oriented towards task than ego, sportsmen who compete in Honor Division being the those who are more oriented towards ego and those of National Division being more oriented towards task. The main conclusion of this research is those who are the motivational climate is related to the division in which the players compete.


#14 Comparative Effects of Tensioning and Sliding Neural Mobilization on Static Postural Control and Lower Limb Hop Testing in Football Players
Reference: J Sport Rehabil. 2018 Sep 17:1-24. doi: 10.1123/jsr.2017-0374. [Epub ahead of print]
Authors: Ferreira J, Bebiano A, Raro D, Martins J, Silva AG
Summary: Context Sliding and tensioning neural mobilization are used to restore normal function of the nervous system, but impose different stresses to it. Particularly, sliding induces greater nerve excursion than tensioning. Conceivably, they might impact nervous system function differently. Objective To compare the effects of tensioning neural mobilization versus sliding neural mobilization of the dominant lower limb on static postural control and hop testing. Design Randomized, parallel and double blinded trial. Setting/Participants Thirty-seven football players. Intervention(s) Participants were randomized into two groups: sliding neural mobilization (n=18) or tensioning neural mobilization (n=19) targeting the tibial nerve. Main Outcome Measures Static postural sway was assessed with a force plate and functional performance with hop tests. Measurements were taken at baseline, after the intervention and at 30 minutes follow up. Results There was a significant effect of time for the center of pressure total displacement and velocity (p<0.05), for the single leg hop test (p<0.05), the 6 meters timed hop test (p<0.05) and the crossover hop test (p<0.05), but no significant effect of the intervention. Conclusion Sliding and tensioning neural mobilization improved postural control and hop testing in football players, and improvements remained 30 minutes after the intervention. Additional research examining the influence of neural mobilization on sensory motor impairments, postural control and functional performance is needed.

Fri

02

Nov

2018

Latest research in football - week 37 - 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 Dynamic balance asymmetries in pre-season injury-prevention screening in healthy young soccer players using the Modified Star Excursion Balance Test-a pilot study
Reference: J Phys Ther Sci. 2018 Sep;30(9):1141-1144. doi: 10.1589/jpts.30.1141. Epub 2018 Sep 4.
Authors: Gkrilias P, Zavvos A, Fousekis K, Billis E, Matzaroglou C, Tsepis E
Summary: The purpose of this preliminary study was to investigate whether young players with no history of injury, have developed early asymmetries in dynamic balance ability tested via the recommended for screening in sports, Modified Star Excursion Balance Test (MSEBT). Twenty-four young healthy male soccer players participated in the study having at least 4 years of systematic soccer training. The Waterloo Footedness Questionnaire was used to discriminate the stability dominant leg (STAB) from the non-stability dominant leg (NSTAB). Dynamic balance was assessed via the MSEBT. Participants, after familiarization, made 3 attempts in each direction for both legs: a) Anterior (AN), b) Posterolateral (PL) and c) Posteromedial (PM). The sole statistically significant performance asymmetry was in the PL direction, in favor of the STAB (94.5 ± 13.3 cm vs. 98.1 ± 10.4 cm). The results of this pilot study showed a potential for developing dynamic balance asymmetries, in soccer players at the age of 13-14 years. Since asymmetry was significant in only one direction, further long term monitoring would be helpful to evaluate whether this is a growing functional deficit, potentially involving any of the other two directions of testing or if it is alleviated with increasing training age. These asymmetries could comprise an injury risk factor.


#2 Energy Balance Coexists With Disproportionate Macronutrient Consumption Across Pretraining, During Training, and Posttraining Among Indian Junior Soccer Players
Reference: Pediatr Exerc Sci. 2018 Sep 12:1-10. doi: 10.1123/pes.2017-0276. [Epub ahead of print]
Authors: Cherian KS, Sainoji A, Nagalla B, Yagnambhatt VR
Summary: The purpose was to evaluate energy expenditure, energy intake, and nutrient adequacy of Indian junior soccer players. Forty junior national-level soccer players (Under-12 and Under-16 age groups) were assessed for 3-day weighed food records and 3-day energy expenditure. Energy and nutrient intake was analyzed from food records, and energy expenditure was measured using a portable metabolic analyzer and activity records. Nutrient adequacy was determined by comparing intake with prevailing recommendations. Players exhibited no significant difference between energy intake (boys = 3062 [340.9] and girls = 2243 [320.3] kcal·d-1) and expenditure (boys = 2875 [717.3] and girls = 2442 [350.3] kcal·d-1). Across age groups, the Under-12 boys showed positive energy balance as against energy deficits in Under-16. Girls showed energy deficits, although not significant. There were 58% of girls showing energy availability <30 kcal·kg-1 fat-free mass, of which 37% were Under-16 players. Carbohydrates contributed to >60% of energy expenditure among 95.2% boys and 73.7% girls. Among 52.4% boys and 47.4% girls, <25% of energy expenditure was contributed by fat. More than 95% players consumed <1 g·kg-1 carbohydrates pretraining and 100% of them consumed >1.2 g·kg-1 carbohydrates posttraining. Junior soccer players consumed more than recommended carbohydrates in the diet, although not aligning with the pretraining, during training, and posttraining meal requirements. Considering the energy deficits observed among Under-16 players, a suitable dietary modification is warranted.


#3 Effects of Plyometric and Directional Training on Physical Fitness Parameters in Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-22. doi: 10.1123/ijspp.2018-0545. [Epub ahead of print]
Authors: Michailidis Y, Tabouris A, Metaxas T
Summary: The aim of this study is to investigate whether the combination of a soccer training session, plyometric training (PT) and change of direction (COD) exercises would enhance soccer ability to a greater extent than training on its own in youth soccer players. Thirty-one youth players participated in this study (age 12±0.8 years). Players were randomly separated into 2 groups: control group (CG, n=14) and intervention group (INTG) which performed extra PT and COD exercises (INTG, n=17). The duration of the training program was 6 weeks. Sprint 10m, 30m, countermovement jump (CMJ), squat jump (SJ), long jump (LJ), multiple 5-bound (5MB), T-test, and YO-YO intermitted endurance test 1 (YYIET1) were measured pre and post of the training program. The performance in acceleration, T-test and LJ improved in both groups (P=0.03, P=0.002 and P=0.001, respectively). SJ performance increased in INTG (15.2 %, P=0.003) and slightly decreased in CG (P=0.003). The performances of the 2 groups differed significantly in SJ and LJ (P=0.003 and P=0.038, respectively). This study supports that a short-term combined program of PT and COD exercises can improve jumping ability, acceleration, and endurance parameters in youth soccer players. The small training effect could be explained when taking into account the level of the participants, the duration of the program and the low volume of COD exercises that were used.


#4 Presleep Casein Protein Ingestion: Acceleration of Functional Recovery in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-24. doi: 10.1123/ijspp.2018-0385. [Epub ahead of print]
Authors: Abbott W, Brett A, Cockburn E, Clifford T
Summary: This study examined whether consuming casein protein (CP) before sleep would enhance recovery after a night-time soccer match in professional players. In a randomized, crossover design, ten professional soccer players from the reserve squad of a team in the highest tier of English soccer consumed 40 g of CP or 40 g of carbohydrates (CON) 30 min pre-sleep after a soccer match (kick off 19:00). To assess recovery, countermovement jump (CMJ) height, reactive strength index (RSI), muscle soreness (MS), and the adapted Brief Assessment of Mood Questionnaire (BAM+) were measured before, 12, 36 and 60 h after each match. Dietary intake across the testing period was also recorded. There were unclear differences in external load in the matches and dietary intake between CON and CP. CP had a most likely and likely beneficial effect on CMJ recovery at 12 and 36 h post-match (CP -1.6; ±1.2% vs. CON -6.6; ±1.7%; -4.1; ±2.3% vs. -0.4; ±1.1%, respectively). RSI recovery was most likely enhanced with CP at 12 and 36 h post-match and muscle soreness, as measured with a visual analogue scale (mm), was most likely greater in CON vs. CP at 12 h post (72; ±17 vs. 42; ±20 mm). BAM+ was possibly lower in CON at 36 h post but unaffected at other time points. Pre-sleep CP accelerates functional recovery in professional soccer players and therefore provides a practical means of attenuating performance deficits in the days after a match.


#5 Determining the Relationship Between Internal Load Markers and Non-Contact Injuries in Young Elite Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-19. doi: 10.1123/ijspp.2018-0466. [Epub ahead of print]
Authors: Raya-González J, Nakamura FY, Castillo D, Yanci J, Fanchini M
Summary: The purpose was to examine the association and predictive ability of internal load markers with regards to non-contact injuries in young elite soccer players. Twenty-two soccer players (18.6 ± .6 years) who competed in the Spanish U19 League participated in the study. During a full season, non-contact injuries were recorded and, using session rating of perceived exertion (s-RPE), internal weekly load (sum of load of all training sessions and matches for each week) and acute:chronic workload ratio (typically, acute = current week and chronic = rolling 4 week average) were calculated. A Generalized Estimating Equation analysis was used to examine association of weekly and acute:chronic load ratio markers with a non-contact injury in the subsequent week. Load variables were also analyzed for predictive ability with Receiver Operating Characteristic (ROC) curve and area under the curve (AUC). No association was found for weekly load (CI 1.00, .99 to 1.00) and acute:chronic load ratio (CI .16, .01 to 1.84) with respect to injury occurrence. In addition, the analyzed load markers showed poor ability to predict injury occurrence (AUC<.50). The results of this study suggest that internal load markers are not associated with non-contact injuries in young soccer players and present poor predictive capacity with regards to the latter.


#6 Physical Characteristics of Elite Youth Female Soccer Players Characterized by Maturity Status
Reference: J Strength Cond Res. 2018 Sep 7. doi: 10.1519/JSC.0000000000002795. [Epub ahead of print]
Authors: Emmonds S, Scantlebury S, Murray E, Turner L, Robsinon C, Jones B
Summary: The purpose of this study was to investigate the influence of maturity status on the physical characteristics of youth female soccer players. One hundred fifty-seven players from 3 elite soccer academies in England completed assessments of anthropometry, strength (isometric midthigh pull), lower-body power (countermovement jump [CMJ]), aerobic capacity (Yo-Yo intermittent recovery test level 1), change of direction (CoD: 505-left/right), and speed (10 and 30 m). Each player was classified into 1 of 6 maturity groups based on their estimated years from peak height velocity (YPHV). Magnitude-based inferences were used to assess for the practical significance between consecutive groups. Speed, CoD time, CMJ, and aerobic capacity were all possibly most likely better in more mature players. However, there was a likely difference in relative peak force between maturity groups -0.5 YPHV (27.13 ± 4.24 N·Kg) and 0.5 YPHV (24.62 ± 3.70 N·Kg), which was associated with a likely difference in 10-m sprint time (-0.5 YPHV: 2.00 ± 0.12 vs. 0.5 YPHV 2.08 ± 0.16 seconds) and unclear changes in CMJ and CoD time. Findings provide novel comparative data for this cohort relative to maturity status and can be used by strength and conditioning coaches to inform the design of training programs for youth female soccer players. Strength and conditioning coaches should be aware that youth female soccer players may experience a decrease in relative strength around peak height velocity, which may impact upon the speed, CoD time, and CMJ of players.


#7 Post-football Gonathrosis: Injuries and Surgeries are A Risk
Reference: Cureus. 2018 Jul 10;10(7):e2953. doi: 10.7759/cureus.2953.
Authors: Ali Khan MM, Siddiqui AA, Yaqoob U, Yaqub MD, Khan OJ, -Ul-Haq F
Summary: Football is one of the most popular sports in the world. Many studies have shown there is a high incidence of gonarthrosis in football players. The reason for this increase is said to be injuries to the meniscus, the anterior cruciate ligament (ACL) and the resulting surgeries. The incidence is significantly increased in players with knee injuries. The knee is also the most commonly injured site in football and the most common cause of surgery in football players. Together these injuries, particularly of the ACL or meniscus and the resulting surgeries, increase the risk of developing gonarthrosis in post-football years.


#8 Validity of Session Rating of Perceived Exertion Assessed via the CR100® Scale to Track Internal Load in Elite Youth Football Players
Reference: Int J Sports Physiol Perform. 2018 Sep 11:1-14. doi: 10.1123/ijspp.2018-0432. [Epub ahead of print]
Authors: Naidu SA, Fanchini M, Cox A, Smeaton J, Hopkins WG, Serpiello FR
Summary: The purpose of the study was to assess the convergent validity of the Borg CR100® scale to track internal training load (TL) in youth football players. Nineteen youth football players (age 15 ± 1 y, height 175.9 ± 12.3 cm, body mass 69 ± 15.4 kg) were monitored for 27 sessions, including training and games. Internal training load was assessed via session rating of perceived exertion (sRPE) and two heart rate (HR)-based methods; Banister's training impulse (TRIMP) and Edwards' TL. The correlations between sRPE and HR-based TL, the differences in individual player intercepts and slopes, and the differences between types of sessions (training vs. games) were assessed using a general linear mixed model with magnitude-based inferences. Correlations between sRPE and Banister's TRIMP were very large at overall group level (r=0.77, 90% confidence limits (CL) 0.72 to 0.80), and individual level (range 0.70 - 0.95). Correlations between sRPE and Edwards' TL were very large at overall group level (r=0.84, 90% CL 0.82 to 0.86), and large to very large at individual level (range 0.64 - 0.93). A very likely small difference was found in the comparison between games and training sessions for the relationship between sRPE and Banister's TRIMP. The Borg CR100® scale is a valid method for monitoring training load in youth football players.


#9 There are more football injury prevention reviews than randomised controlled trials. Time for more RCT action!
Reference: Br J Sports Med. 2018 Sep 10. pii: bjsports-2018-099373. doi: 10.1136/bjsports-2018-099373. [Epub ahead of print]
Authors: Bricca A, Juhl CB, Bizzini M, Andersen TE, Thorborg K


#10 Quantification of a Professional Football Team's External Load Using a Microcycle Structure
Reference: J Strength Cond Res. 2018 Sep 7. doi: 10.1519/JSC.0000000000002816. [Epub ahead of print]
Authors: Martín-García A, Gómez Díaz A, Bradley PS, Morera F, Casamichana D
Summary: The aims of this study were to (a) determine the external load of a football team across playing position and relative to competition for a structured microcycle and (b) examine the loading and variation the day after competition for players with or without game time. Training and match data were obtained from 24 professional football players who belonging to the reserve squad of a Spanish La Liga club during the 2015/16 season using global positioning technology (n = 37 matches and n = 42 training weeks). Training load data were analyzed with respect to the number of days before or after a match (match day [MD] minus or plus). Training load metrics declined as competition approached (MD-4 > MD-3 > MD-2 > MD-1; p < 0.05; effect sizes [ES]: 0.4-3.1). On the day after competition, players without game time demonstrated greater load in a compensatory session (MD + 1C) that replicated competition compared with a recovery session (MD + 1R) completed by players with game time (MD + 1C > MD + 1R; p < 0.05; ES: 1.4-1.6). Acceleration and deceleration metrics during training exceeded 50% of that performed in competition for MD + 1C (80-86%), MD-4 (71-72%), MD-3 (62-69%), and MD-2 (56-61%). Full backs performed more high-speed running and sprint distance than other positions at MD-3 and MD-4 (p < 0.05; ES: 0.8-1.7). The coefficient of variation for weekly training sessions ranged from ∼40% for MD-3 and MD-4 to ∼80% for MD + 1R. The data demonstrate that the external load of a structured microcycle varied substantially based on the players training day and position. This information could be useful for applied sports scientists when trying to systematically manage load, particularly compensatory conditioning for players without game time.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.


#11 Normative Data and Physical Determinants of Multiple Sprint Sets in Young Soccer Players Aged 11-18 Years: Effect of Maturity Status
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002810. [Epub ahead of print]
Authors: Selmi MA, Sassi RH, Yahmed MH, Giannini S, Perroni F, Elloumi M
Summary: The aims of the study were: (a) to establish normative data for repeated-sprint sets (RSS) test based on the maturity status (age at peak height velocity [PHV]) and (2) to investigate the relationship between anthropometrical variables (stature, sitting height, body mass, and body fat percentage), RSS (2 × 5 × 20 m with 15-second recovery between sprints and 1-minute recovery between sets), and fitness tests {squat jump, countermovement jump, standing long jump, standing triple jump, 5-jump test, and 20-m shuttle run (multistage shuttle run test [MSRT])}. Young male soccer players (n = 262; age: 14.5 ± 2.9 years) were evaluated and classified into 4 groups according to their maturity status: pre-PHV, circum-PHV1, circum-PHV2, post-PHV. An analysis of variance and Bonferroni post hoc were used to determine maturity group differences (p ≤ 0.05), whereas Pearson's correlation was used between variables. Repeated-sprint sets' indices (sum of sprint times [SST] and best sprint time [BST]) were significantly different between the maturity groups. Significant correlations between SST with body mass (from -0.73 to -0.33) and MSRT (from -0.49 to -0.30) among each maturity group were found. With the different maturity groups, correlations between SST (s), BST (s), and vertical jump (cm) (r = -0.63 to -0.25 and r = -0.68 to -0.23) and horizontal jump (m) (r = -0.70 to -0.38 and r = -0.63 to -0.43) were observed. Repeated-sprint sets' values improve during maturation of young soccer players and the correlations between RSS and fitness tests vary through the maturity groups. This information could be useful for the coach to identify talent and to prescribe specific physical training to improve performance.


#12 Effects of Two Different Tapering Protocols on Fitness and Physical Match Performance in Elite Junior Soccer Players
Reference: J Strength Cond Res. 2018 Sep 19. doi: 10.1519/JSC.0000000000002861. [Epub ahead of print]
Authors: Krespi M, Sporiš G, Trajković N
Summary: The purpose of this study was to determine the effects of 2 different tapering protocols on fitness and physical match performance in elite junior soccer players. One-hundred fifty-eight elite junior soccer players (mean age: 17.1 ± 0.79 years; mean height: 177.9 ± 6.64 cm; mean body mass: 71.3 ± 7.96 kg; and mean body mass index: 22.5 ± 1.66 kg·m) were randomly assigned to 2 groups: an exponential (n = 79) and a linear tapering (n = 79) group. Training sessions were conducted 3 times per week for 8 weeks. After 4 weeks of training and 4 weeks of tapering, participants were assessed in terms of body composition, physical fitness, and distance covered within a match. Both groups showed similar changes for body composition. The exponential group showed better improvement than the linear group in the 5- and 30-m sprints, countermovement jump, and V[Combining Dot Above]O2max (p < 0.05). The exponential tapering group had larger changes (p < 0.05) than the linear group in medium running (8-13 km·h) (6%; effect size = 0.26 compared with 5.5%; effect size = 0.22) and sprinting (>18 km·h) (26%; effect size = 0.72 compared to 21.7%; effect size = 0.60). The results show that exponential tapering produced better effects on speed, power, and endurance abilities than the linear protocol. Our results confirmed the reports of others that suggest that volume is the optimal variable to manipulate while maintaining both the intensity and the frequency of sessions.

Thu

01

Nov

2018

Latest research in football - week 36 - 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 King-Devick test normative reference values and internal consistency in youth football and soccer athletes
Reference: Scand J Med Sci Sports. 2018 Aug 28. doi: 10.1111/sms.13286. [Epub ahead of print]
Authors: Moran RN, Covassin T
Summary: The King-Devick (K-D) test has gained popularity as a sideline concussion assessment tool, comprising of visual tracking and saccadic eye movements. However, limited normative data exists for youth athletes under the age of 13. The purpose of this study was to establish normative reference values and examine the internal consistency of the K-D test in youth athletes. The K-D test was administered to 422 youth football and soccer athletes prior to their respective season. The average K-D score was 54.29±11.5 seconds. Across the two trials, 55% of participants committed at least one error. Overall, the K-D test demonstrated a high internal consistency (Cronbach α = 0.92) when administered at baseline. Inter-item correlations revealed a moderate to strong relationship between test cards and trials (r range= 0.71 to 0.95; p<0.001), along with test cards and baseline K-D time (r range= 0.85 to 0.94; p<0.001). Although the K-D test was consistent during baseline testing, the high percentage of errors at baseline makes the K-D test questionable for post-concussion comparisons.


#2 Epidemiological Findings of Soccer Injuries During the 2017 Gold Cup
Reference: Orthop J Sports Med. 2018 Aug 20;6(8):2325967118791754. doi: 10.1177/2325967118791754. eCollection 2018 Aug.
Authors: Chahla J, Sherman B, Cinque M, Miranda A, Garrett WE, Chiampas G, O'Malley H, Gerhardt MB, Mandelbaum BR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6102768/pdf/10.1177_2325967118791754.pdf
Summary: Surveillance programs are vital to analyze the cause and nature of lesions and ultimately establish protocols of action to lower injury rates. The purpose of the study was to evaluate the adherence of team doctors to an electronic surveillance system and determine the incidence and characteristics of injuries among soccer players participating in the 2017 Gold Cup.All data were collected from the electronic medical reports submitted during each match of the 2017 Gold Cup. Twelve teams participated in the tournament (each with 23  the team physician after each injury. Each report contained the player's number, the exact time of injury (minute of play), the location and diagnosis of injury as indicated by a previously defined code, and its severity in terms of the number of days of absence from training and match play. The electronic reporting system had a response rate of 100.0%, with 97.2% of questions answered completely. The mean age of injured players was 27 years (range, 21-35 years) and was not statistically significantly different from the overall mean player age (P > .05). There were no significant differences in the frequency of injuries when analyzed by player position (P = .743). The overall rate of injuries was 1.04 per match, with the most common injuries being contusions (42.3%), sprains (7.7%), strains (7.7%), and fractures (7.7%). These injuries were more commonly the result of contact (75.0%) than noncontact (25.0%) mechanisms (P < .001). Injuries most commonly occurred between the 60th and 75th minute of play when comparing all 15-minute time intervals (P = .004). This study supports the use of electronic injury reporting, which demonstrated a high level of adherence among an international cohort of team physicians and has significant potential for improving injury surveillance and tracking responses to prevention programs. Injury rates in the Gold Cup were similar to those in previous studies and demonstrated the highest rates late in the second half of the game, specifically between the 60th and 75th minute of play.


#3 Altered lower limb kinematics and muscle activities in soccer players with chronic ankle instability
Reference: Phys Ther Sport. 2018 Aug 9;34:28-35. doi: 10.1016/j.ptsp.2018.08.003. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Koumura T, Fujimoto A, Yoshida N, Miyakawa S
Summary: The purpose was to examine the lower limb kinematics and muscle activities in diagonal single-leg rebound jump in soccer players with chronic ankle instability (CAI). Thirty male collegiate soccer players participated: 15 with CAI were compared with 15 without CAI, matched by physical description. In the diagonal single-leg rebound jump, participants stood on one leg on a 30-cm high box, hopped down diagonally (45°) onto a force plate, and jumped vertically as high as possible with hands on their hips. Hip, knee, and ankle kinematics were acquired using a motion capture system. The activity of the gluteus medius, hip adductor, and lower leg muscles was recorded using electromyography. Jump performance was calculated using a force plate. The CAI group had (i) decreased hip adduction, knee flexion, external rotation, and dorsiflexion angle; (ii) reduced hip adductor and peroneus muscle activations; and (iii) reduced jump height and short flight time. Male collegiate soccer players with CAI showed altered kinematics and muscle activities during a diagonal single-leg rebound jump; this may adversely affect rebound jump performance.


#4 Match-Play and Performance Test Responses of Soccer Goalkeepers: A Review of Current Literature
Reference: Sports Med. 2018 Aug 24. doi: 10.1007/s40279-018-0977-2. [Epub ahead of print]
Authors: White A, Hills SP, Cooke CB, Batten T, Kilduff LP, Cook CJ, Roberts C, Russell M
Summary: Goalkeepers are typically the last defensive line for soccer teams aiming to minimise goals being conceded, with match rules permitting ball handling within a specific area. Goalkeepers are also involved in initiating some offensive plays, and typically remain in close proximity to the goal line while covering ~ 50% of the match distances of outfield players; hence, the competitive and training demands of goalkeepers are unique to their specialised position. Indeed, isolated performance tests differentiate goalkeepers from outfield players in multiple variables. With a view to informing future research, this review summarised currently available literature reporting goalkeeper responses to: (1) match play (movement and skilled/technical demands) and (2) isolated performance assessments (strength, power, speed, aerobic capacity, joint range of motion). Literature searching and screening processes yielded 26 eligible records and highlighted that goalkeepers covered ~ 4-6 km on match day whilst spending ~ 98% of time at low-movement intensities. The most decisive moments are the 2-10 saves·match-1 performed, which often involve explosive actions (e.g. dives, jumps). Whilst no between-half performance decrements have been observed in professional goalkeepers, possible transient changes over shorter match epochs remain unclear. Isolated performance tests confirm divergent profiles between goalkeepers and outfield players (i.e. superior jump performance, reduced [Formula: see text]2max values, slower sprint times), and the training of soccer goalkeepers is typically completed separately from outfield positions with a focus primarily on technical or explosive drills performed within confined spaces. Additional work is needed to examine the physiological responses to goalkeeper-specific training and match activities to determine the efficacy of current preparatory strategies.


#5 Return to Competition After Surgery for Herniated Lumbar Disc in Professional Football Players
Reference: Clin J Sport Med. 2018 Aug 28. doi: 10.1097/JSM.0000000000000662. [Epub ahead of print]
Authors: Tencone F, Minetto MA, Tomaello L, Giannini A, Roi GS
Summary: The purpose was to investigate the prevalence and outcomes of surgery for lumbar disc herniation in professional football players. A period of 10 seasons of the Italian Football First League (Serie A) was retrospectively investigated. Thirty-three teams (for a total of 1960 players) took turns in the 10 seasons, and 42 team doctors were requested to provide information about the number of players who underwent surgery for lumbar disc herniation. Prevalence and match incidence of the lumbar discectomy, proportion of players returning to competition after surgery, recovery time and preintervention and postintervention number of appearances in official matches were analyzed. Eleven players underwent the surgical intervention during the considered period. The prevalence of the surgical treatment was 0.6%, whereas the match incidence was 0.09 cases/1000 match hours. All players returned to competitions 6.0 (3.5-7.7) months after surgery, with no significant difference between different roles. The number of appearances in official matches was comparable during the seasons before and after surgery. The lumbar discectomy must be considered a rare surgical procedure performed in professional football players. All players returned to competitions after surgery. The postintervention number of appearances in official matches was comparable with the preintervention one.


#6 Early return to playing professional football following fixation of 5th metatarsal stress fractures may lead to delayed union but does not increase the risk of long-term non-union
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 28. doi: 10.1007/s00167-018-5104-2. [Epub ahead of print]
Authors: Miller D, Marsland D, Jones M, Calder J
Summary: 5th metatarsal stress fractures are frequently encountered in professional football. There is concern that early return to play following intra-medullary screw fixation may lead to an increased risk of delayed union. The purpose of the study was to assess whether an early return to play after surgical fixation of 5th metatarsal fractures in professional football players is a risk factor for delayed union and the effect of this on the ultimate clinical outcome. Retrospective review of prospectively collected data of a series of 37 professional football players following intramedullary screw fixation of 5th metatarsal stress fractures. End points included time of return to play and to radiological union of the fracture. At a minimum follow-up of 24 months the mean return to play was 10.5 weeks and mean time to complete radiological union was 12.7 weeks. Return to play at 8 weeks or less resulted in a higher risk of delayed radiological union (24% at 3 months), but this neither prevented the athlete from continuing to play football nor did it affect the ultimate risk of non-union (3% overall). A re-fracture occurred in 1 patient (3%) at 10 months who previously had complete radiographic union at 9 weeks. Intramedullary screw fixation of 5th metatarsal stress fractures leads to a predictable time of return to play and a low rate of non-union. If players return to play at 8 weeks or less a persistent line may be expected in up to a quarter of patients. However, if asymptomatic this radiological finding does not mean that athletes must avoid playing football as ultimately a good outcome is expected with low rates of non-union and refracture.


#7 Injury incidence in semi-professional football claims for increased need of injury prevention in elite junior football
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 25. doi: 10.1007/s00167-018-5119-8. [Epub ahead of print]
Authors: Loose O, Fellner B, Lehmann J, Achenbach L, Krutsch V, Gerling S, Jansen P, Angele P, Nerlich M, Krutsch W
Summary: Injuries are a common occurrence in football. Sufficient epidemiological data are available in professional football but not in salaried semi-professional football. This study investigates the injury incidence at different levels of semi-professional football with focus on junior football. The data were based on injury reports provided by players and medical staff over the 2015-2016 season, which corresponded to the consensus statement for data samples in football. This study investigated the injury incidence and prevalence of five skill levels of semi-professional football (the fourth to the seventh league and elite junior football). 1130 players had sustained 2630 injuries over the 2015-2016 season. The overall injury incidence was 9.7 per 1000 h football exposure; prevalence with at least one injury was 79%. The highest overall injury incidence in elite junior football was 10.4 in 1000 h football exposure. The fifth league had the lowest incidence with 9.0 in 1000 h football (p < 0.05). Traumatic injuries most often occurred in the fourth league (3.9 in 1000 h football). The body areas most affected by traumatic injury were knees, ankles and thighs. Elite junior players had a significantly higher incidence of overuse complaints (7.4 in 1000 h football) than the fourth league (5.4, p = 0.005). The body areas most affected by overuse complaints were the lower back, thigh and groin. No differences were found between the different positions on field. Salaried semi-professional football involves a high overall injury incidence. The highest incidence, particularly of overuse injuries, was seen in elite junior football. These findings should be incorporated in specific injury prevention training or screenings beginning in junior football.


#8 Neurocognitive Performance of 425 Top-Level Football Players: Sport-specific Norm Values and Implications
Reference: Arch Clin Neuropsychol. 2018 Aug 25. doi: 10.1093/arclin/acy056. [Epub ahead of print]
Authors: Prien A, Junge A, Brugger P, Straumann D, Feddermann-Demont N
Summary: Concussion diagnosis and management in sports largely relies on neurocognitive testing. In the absence of baseline assessment, only norm values of the general population are available for comparison with scores of concussed athletes. To evaluate whether (elite) sport specific norm values are needed, cognitive performance was compared between top-level football players and the general population. Cognitive performance of 425 top-level football players was evaluated using the computerized test battery CNS Vital Signs. Players were split into two age groups (15-19 and 20-29 years) and test results were compared with a norm sample (n = 268) by means of age-standardized scores using Cohen's d effect size statistics. The younger age group outperformed the norm sample in all domains, with small to moderate effects on tests of processing speed (d = 0.58, 95% CI = 0.31,0.85), cognitive flexibility (d = 0.27, 95% CI = 0.01,0.53) and psychomotor speed (d = 0.97, 95% CI = 0.69,1.24). In the older age group, no differences were found on four out of six domains; a moderate positive effect was found for psychomotor speed (d = 0.74, 95% CI = 0.54,0.93), a small negative effect for reaction time (d = -0.47, 95% CI = -0.66,-0.28). Relative to the norm, older football players scored lower than younger football players on all test domains. Cognitive performance of elite football players may be different from the general population. It is recommended to use football-specific norm scores for comparison with test results of concussed players, and to choose an adequate control group when investigating effects of contact sport on cognition. Studies with older/retired football players are needed to further analyze potential sport-specific age effects.


#9 Match Related Time Course of Perceived Recovery in Youth Football Players
Reference: Int J Sports Physiol Perform. 2018 Aug 30:1-16. doi: 10.1123/ijspp.2017-0521. [Epub ahead of print]
Authors: Paul DJ, Tomazoli G, Nassis GP
Summary: The aim of the study was to i) examine the reproducibility of the perceived recovery scale (PRS) in football players ii) describe the time course of the PRS in response to a football match. Methods Twenty trained youth players (mean ± SD; age 16.2 ± 1.2 y, height 1.75 ± 0.07 m, body mass 64.0 ± 7.8 kg) took part in the study. PRS was collected - 2 hrs, - 30 mins before and +15 mins, +3 hrs and +24 hrs after an international football match. Players were categorised into two groups based on their playing time (≤45 and 90 mins). Reproducibility of the PRS was high (ICC = 0.83, TE = 0.59, CV = 9.9%) between the two pre-match measures. Overall, PRS was lower at +15 mins (4.0 ± 1.5, p< 0.01; ES=2.2) and + 3 hrs (4.7 ± 1.6, p< 0.01; ES=1.5) compared to -30 mins (7.1 ± 1.3), while +15 mins was lower than +24 hrs (6.1 ± 1.3, p<0.01; ES=1.5). No differences between groups for PRS scores at any of the time points. The perceived recovery scale is a reproducible method for monitoring perceptions of recovery to football activity and sensitive to time course changes relating to a match. The scale is an easy and efficient tool that can be used to monitor an aspect of recovery.


#10 Accurate Prediction Equation to Assess Body Fat in Male and Female Adolescent Football Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Aug 30:1-23. doi: 10.1123/ijsnem.2018-0099. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente Á, Gómez-Bruton A, González-Agüero A, Vicente-Rodríguez G, Casajús JA
Summary: The aims of this study were (a) to determine which of the most used anthropometric equations was the most accurate to estimate percentage of body fat (%BF), (b) to develop a new specific anthropometric equation, and (c) to validate this football-specific equation. A total of 126 (13.3±0.6 y) football players (86 males) participated in the present study. Participants were divided into two groups: 98 players were included in the assessment of existing equations and in the development of the new prediction equation; and 28 were used to validate it. %BF was measured with dual-energy X-ray absorptiometry (DXA) and also estimated with six different %BF anthropometric equations: Johnston, Slaughter, Carter, Faulkner, Deurenberg and Santi-Maria. Paired t-tests were used to analyze differences between methods. A football-specific equation was developed by a stepwise linear-regression. The existing anthropometric equations showed significant bias for %BF when compared to DXA (p<.001; constant error [CE] ranged from -4.57 to 9.24%; standard error of estimate [SEE] ranged from 2.46 to 4.20). On the other hand, the developed football-specific equation was %BF = 11.115 + 0.775(triceps skinfold) + 0.193(iliac-crest skinfold) - 1.606(sex). The developed equation demonstrated neither %BF differences (p=.121; CE=0.57%; SEE=0.36) when compared to DXA, presenting a high cross-validation prediction power (R2=0.85). Published anthropometric equations were not accurate to estimate %BF in adolescent football players. Due to the fact that the developed football-specific equation showed neither differences nor heteroscedasticity when compared to DXA, this equation is recommended to assess %BF in adolescent football players.


#11 Comparative effects of single vs. double weekly plyometric training sessions on jump, sprint and COD abilities of elite youth football players
Reference: J Sports Med Phys Fitness. 2018 Aug 28. doi: 10.23736/S0022-4707.18.08804-7. [Epub ahead of print]
Authors: Bianchi M, Coratella G, Dello Iacono A, Beato M
Summary: Plyometrics are widely implemented as training methodology for enhancing functional sports performance. Although several studies have analysed the plyometrics effects due to training plans with a frequency of 2-3 times a week, few of them provided evidence supporting an equal efficiency of similar training programs implementing lower training frequency such as one training session a week. Twenty-one players (elite academy, Switzerland) were included in the current study (mean ± SD; age 17 ± 0.8 years, weight 70.1 ± 6.4 kg, height 177.4 ± 6.2 cm). This study used a randomised pre-post parallel group trial design. The participants were assigned to either a low-volume plyometric training group (LPG = 10 participants) or a high-volume plyometric training group (HPG = 11 participants). A long jump test, a single-leg triple hop test, sprint (10, 30 and 40 m) and 505 change of directions (COD) test were performed. Exercise-induced meaningful changes in performance for both LPG and HPG occurred after the training. LPG and HPG reported improvements in long jump (ES=1.0 and 0.77), triple hop right (ES=0.32 and 0.28), triple hop left (ES=0.46 and 0.32), 10 m sprint (ES=0.62 and 1.0). Both LPG and HPG are effective training modalities inducing benefits in jump and sprint tests for elite young football players. Fitness coaches and sports scientists could integrate their training plans with the protocols described in this study.


#12 Prediction of Attendance Demand in European Football Games: Comparison of ANFIS, Fuzzy Logic, and ANN
Reference: Comput Intell Neurosci. 2018 Aug 7;2018:5714872. doi: 10.1155/2018/5714872. eCollection 2018.
Authors: Şahin M, Erol R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109553/pdf/CIN2018-5714872.pdf
Summary: An artificial neural network (ANN), adaptive neurofuzzy inference system (ANFIS) models, and fuzzy rule-based system (FRBS) models are developed to predict the attendance demand in European football games, in this paper. To determine the most successful method, each of the methods is analyzed under different situations. The Elman backpropagation, feed-forward backpropagation, and cascade-forward backpropagation network types are developed to determine the outperforming ANN model. The backpropagation and hybrid optimization methods are used for training fuzzy inference system (FIS) to determine the outperforming ANFIS model. The fuzzy logic model is developed after experimenting different forms of membership functions. To this end, the data of 236 soccer games are used to train the ANN and ANFIS models, and 2017/2018 season's data of these clubs are used to test all of the models. The results of all models are compared with each other and real past data. To assess the performance of each model, two error measures that are Mean Absolute Percent Error (MAPE) and Mean Absolute Deviation (MAD) are implemented. These measures reveal that the ANN model that has Elman network type outperforms the other models. Finally, the results emphasize that the proposed ANN model can be effectively used for prediction purposes.


#13 Exercise loading for cardiopulmonary assessment and evaluation of endurance in amputee football players
Reference: J Phys Ther Sci. 2018 Aug;30(8):960-965. doi: 10.1589/jpts.30.960. Epub 2018 Jul 24.
Authors: Mikami Y, Fukuhara K, Kawae T, Sakamitsu T, Kamijo Y, Tajima H, Kimura H, Adachi N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110228/pdf/jpts-30-960.pdf
Summary: It is difficult for amputees to perform conventional cardiopulmonary exercise testing. Values were determined for two-legged, one-legged, and two-armed exercise testing in healthy adult males (Study 1), for comparison with preliminary measurements of endurance in amputee football players (Study 2). In Study 1, cardiopulmonary exercise testing was performed in healthy adult males. Correlations between oxygen uptake in two-legged and one-legged/two-armed exercise were calculated and a comparison was made between one-legged exercise and two-armed exercise for each measured value. In Study 2, cardiopulmonary exercise testing was performed on male amputee football players using a two-arm-driven ergometer. The measured values obtained for healthy adult males and amputee football players were compared. In Study 1, peak work rate and peak heart rate values of healthy participants were significantly higher in two-armed exercise than in one-legged exercise. The correlation between peak oxygen uptake values for two-legged and one-legged exercise was decreased. In Study 2, peak work rate of two-armed exercise was significantly higher in amputee football players than in healthy participants.  Study 1 suggested that musculoskeletal factors might have greater significance for one-legged exercise than for two-armed exercise. Study 2 suggested that para-sports, including amputee football, may contribute to physical strength and health maintenance in lower leg amputees.

Sun

28

Oct

2018

Latest research in football - week 35 - 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 Relative Age Effect in the 10 Best Leagues of Male Professional Football of the Union of European Football Associations (UEFA)
Reference: J Sports Sci Med. 2018 Aug 14;17(3):409-416. eCollection 2018 Sep.
Authors: Yagüe JM, de la Rubia A, Sánchez-Molina J, Maroto-Izquierdo S, Molinero O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090398/pdf/jssm-17-409.pdf
Summary: The aim of the present research was to observe the relative age effect on professional soccer players of the ten best leagues of the Union of European Football Associations (UEFA), according to the IFFHS (International Federation of Football History and Statistics). The sample consisted of 5201 professional players who participated in the professional leagues during the 2016-2017 season. The birth date of each player was classified in four quartiles (Q1, Q2, Q3 and Q4). The frequencies (fr) and percentages (%) of the birth quartiles were analyzed. The chi square test (X2) and degrees of freedom (gl) were performed to check the differences in the intergroup distribution. Likewise, odd ratios were calculated for the different quartiles, where Q4 was the reference group according to the different leagues studied, playing positions (goalkeeper, defender, midfielder and forward) and classification (first four places, half-of the table and four last places). To calculate the size of the effect on the nominal variables, the Cramer V test was carried out. The results confirmed a greater representation of players born in Q1 and Q2, indicating statistically significant values (p < 0.05) for all the leagues studied, except in the Eerste Klasse A (Belgium). This significance was repeated for the demarcation variables in the field, with a greater effect in the case of the midfielders. Finally, the RAE also affected the three groups according to teams´ classification. The conclusions confirm the effect of the RAE in the sample studied, which would require a review of the talent selection processes in football in order to balance the chances of success of players born at the end of the year.


#2 Is Plantar Loading Altered During Repeated Sprints on Artificial Turf in International Football Players?
Reference: J Sports Sci Med. 2018 Aug 14;17(3):359-365. eCollection 2018 Sep.
Authors: Girard O, Millet GP, Thomson A, Brocherie F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090389/pdf/jssm-17-359.pdf
Summary: We compared fatigue-induced changes in plantar loading during the repeated anaerobic sprint test over two distinct distance intervals. Twelve international male football outfield players (Qatar Football Association) completed 6 × 35-m sprints (10 s of active recovery) on artificial turf with their football boots. Insole plantar pressure distribution was continuously recorded and values (whole foot and under 9 foot zones) subsequently averaged and compared over two distinct distance intervals (0-17.5 m vs. 17.5-35 m). Sprint times increased (p <0.001) from the first (4.87 ± 0.13 s) to the last (5.63 ± 0.31 s) repetition, independently of the distance interval. Contact area (150 ± 23 vs. 158 ± 19 cm2; -5.8 ± 9.1%; p = 0.032), maximum force (1910 ± 559 vs. 2211 ± 613 N; -16.9 ± 18.2%; p = 0.005) and mean pressure (154 ± 41 vs. 172 ± 37 kPa; -13.9 ± 19.0%; p = 0.033) for the whole foot were lower at 0-17.5 m vs. 17.5-35 m, irrespectively of sprint number. There were no main effects of sprint number or any significant interactions for any plantar variables of the whole foot. The distance interval × sprint number × foot region interaction on relative loads was not significant. Neither distance interval nor fatigue modified plantar pressure distribution patterns. Fatigue led to a decrement in sprint time but no significant change in plantar pressure distribution patterns across sprint repetitions.


#3 Time-use and environmental determinants of dropout from organized youth football and tennis
Reference: BMC Public Health. 2018 Aug 16;18(1):1022. doi: 10.1186/s12889-018-5919-2.
Authors: Deelen I, Ettema D, Kamphuis CBM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6097310/pdf/12889_2018_Article_5919.pdf
Summary: Many adolescents drop out of organized sports. Lack of motivation and competing priorities are known as important reasons for dropout. However, time use factors as well as environmental determinants have been largely neglected in the current literature on dropout from youth sports. The aim of this study is to investigate how (changes in) time use and characteristics of the physical environment determine dropout from football and tennis among adolescents. Data on time use and background characteristics were collected through online surveys in 2015 and 2016 among adolescents aged 13-21 (N = 2555), including both the dropped outs and those who still continued membership of their football or tennis clubs. Physical environmental determinants (travel distance to the sports club, and neighbourhood density) were measured objectively. Binary logistic regression analyses were carried out for football and tennis separately to examine the associations between time use (time spent on various activities and changes related to the school and job situation), and environmental factors on the probability of dropping out from sports. Time spent on sports outside the context of the sports club, and time spent on social or voluntary activities at the sports club was positively associated with continuing being football and tennis members. Tennis players who changed schools or participated in two sports at the same time had a higher probability of dropping out, whereas tennis players who travelled greater distances from home to the tennis club were less likely to drop out. Determinants of dropout differed between football and tennis. However, time use variables were important predictors of dropout from football as well as tennis, whereas environmental determinants hardly contributed to the prediction of dropout. To keep youths involved in organized sports, this study recommends that sports professionals should: 1) offer flexibility in training and competition schedules, 2) stimulate participation in social activities and voluntary work at the sports club, 3) pay special attention to their needs and preferences, and 4) encourage possibilities to practice and play sports outside of regular training hours, for instance at the sports club or at playgrounds or parks in the neighbourhood.


#4 The effect of playing status, maturity status, and playing position on the development of match skills in elite youth football players aged 11-18 years: A mixed-longitudinal study
Reference: Eur J Sport Sci. 2018 Aug 17:1-12. doi: 10.1080/17461391.2018.1508502. [Epub ahead of print]
Authors: Saward C, Morris JG, Nevill ME, Sunderland C
Summary: This mixed-longitudinal study examined the development of match skills in elite male youth footballers (aged 11-18 years), while considering the effect of playing status, maturity status, and playing position. Across two seasons, 126 elite male youth footballers were assessed in 1-10 competitive matches (401 player-matches). For each match, the on-the-ball actions of each player were recorded using a notation system. The match skills observed were frequencies of successful passes, on-target shots, dribbles, crosses, clearances, and tackles/blocks/interceptions. Multilevel Poisson analysis was used to model the development of players, with regard to each match skill. Modelling revealed significant (p < .05) age-related changes in the frequency of several match skills. That is, dribbles increased, on-target shots, crosses and tackles/blocks/interceptions decreased, whereas changes in successful passes were position-specific. Players retained by an academy performed more dribbles compared to released players (p < .05) (e.g. retained vs. released 18-year-old centre forward = 4.1 vs. 2.0 dribbles per hour), and retained defenders performed more tackles/blocks/interceptions than released defenders (p < .05) (e.g. retained vs. released 18-year-old, on-time maturing centre back = 12.5 vs. 10.2 tackles/blocks/interceptions per hour). Moreover, compared to on-time maturing players, early maturing players performed more tackles/blocks/interceptions (p < .05) (e.g. on-time vs. early maturing retained 18-year-old centre back = 12.5 vs. 15.2 tackles/blocks/interceptions per hour). Playing position affected all match skills (p < .05). The developmental profiles of match skills presented here may support experts in identifying and developing talented footballers across a wide age range, while considering the influence of maturity status and playing position.


#5 Evaluation of Muscle Injuries in Professional Football Players: Does Coach Replacement Affect the Injury Rate?
Reference: Clin J Sport Med. 2018 Aug 15. doi: 10.1097/JSM.0000000000000640. [Epub ahead of print]
Authors: Dönmez G, Kudaş S, Yörübulut M, Yıldırım M, Babayeva N, Torgutalp ŞŞ
Summary: The objective was to assess the incidence and characteristics of muscle injuries in professional football players and to assess if coach dismissal may be related with muscle injuries within 1-month period from the dismissal. One hundred eighteen male football players from the Turkis first league participated in this study. Data on time-loss muscle injuries confirmed using magnetic resonance imaging were recorded, including type, body part, duration, and lay-off time, and training session and match exposure times. The muscle injury rate was evaluated at 2 weeks and 30 days after coach dismissal. In total, 124 muscle injuries were recorded, with injury incidences of 2.3 muscle injuries per 1000 hours of exposure overall, 1.2 in training sessions, and 13.6 in matches. Injury time loss ranged from 3 to 67 days (median, 13 days). Eighteen percent of the injuries (n = 23) were recurrent; no association was found between recurrence rate and the player's age or position (P = 0.15, P = 0.27, respectively). Recurrent injuries caused more severe injuries (26.1%, P = 0.02) and longer median lay-off time (P = 0.01). During the study, teams A and B replaced 7 and 3 coaches, respectively. The injury incidence increased to 5.3 per 1000 hours of exposure in the 2 weeks after the coach dismissal, and decreased to 4.5 within 1 month of coach dismissal. Given the link between coach dismissal and increased rates of muscle strain injuries, increased attentiveness to preventing muscle injuries during coaching transitions and to the impact of new training regimens is required by trainers and medical teams.


#6 Overuse injuries are prevalent in children's competitive football: a prospective study using the OSTRC Overuse Injury Questionnaire
Reference: Br J Sports Med. 2018 Aug 14. pii: bjsports-2018-099218. doi: 10.1136/bjsports-2018-099218. [Epub ahead of print]
Authors: Leppänen M, Pasanen K, Clarsen B, Kannus P, Bahr R, Parkkari J, Haapasalo H, Vasankari T
Summary: The purpose was to investigate the prevalence and burden of overuse injuries in children's football as well as player characteristics and their association with overuse injury risk. This investigation is based on the control arm (10 clubs) of a randomised controlled trial investigating prevention of injuries in youth football. We conducted a prospective 20-week follow-up study on overuse injuries among Finnish football players (n=733, aged 9-14 years). Each week, we sent a text message to players' parents to ask if the player had sustained any injury during the past week. Players with overuse problem were interviewed over the phone using an overuse injury questionnaire. The main outcome measures were prevalence of all overuse injuries and substantial overuse injuries (those leading to moderate or severe reductions in participation or performance) and injury severity. The average response rate was 95%. In total, 343 players (46.8%) reported an overuse problem while in the study. The average weekly prevalence of all overuse problems and substantial overuse problems was 12.8% and 6.0%, respectively. Injuries affecting the knee had the highest weekly prevalence (5.7% and 2.4% for all and substantial knee problems, respectively). Girls had a higher likelihood of knee problems (OR 2.70; 95% CI 1.69 to 4.17), whereas boys had a higher likelihood of heel problems (OR 2.82; 95% CI 1.07 to 7.44). The likelihood of reporting an overuse problem increased with age (OR 1.21; 95% CI 1.00 to 1.47). Overuse injuries are prevalent in children's competitive football. Knee overuse injuries represent the greatest burden on participation and performance.


#7 Communication quality between the medical team and the head coach/manager is associated with injury burden and player availability in elite football clubs
Reference: Br J Sports Med. 2018 Aug 13. pii: bjsports-2018-099411. doi: 10.1136/bjsports-2018-099411. [Epub ahead of print]
Authors: Ekstrand J, Lundqvist D, Davison M, D'Hooghe M, Pensgaard AM
Download link: https://bjsm.bmj.com/content/bjsports/early/2018/08/21/bjsports-2018-099411.full.pdf
Summary: We investigated medical staff interpretations and descriptions of internal communication quality in elite football teams to determine whether internal communication was correlated with injuries and/or player availability at training and matches. Medical staff from 36 elite football clubs across 17 European countries produced 77 reports at four postseason meetings to provide their perceptions of internal communications in their teams. They also recorded data on individual players' exposure to football and time-loss injuries. The injury burden and incidence of severe injuries were significantly higher in teams with low quality of communication between the head coach/manager and the medical team (scores of 1-2 on a 5-point Likert scale) compared with teams with moderate or high-quality scores (scores of 3-5; p=0.008 for both). Teams with low scores had 4%-5% lower training attendance (76% vs 83%, p=0.001) and less availability at matches (82% vs 88%, p=0.004) compared with teams with moderate or high communication quality scores. The quality of internal communication within a team was correlated with injury rates, training attendance and match availability.


#8 An Augmented Perceptual-Cognitive Intervention Using a Pattern Recall Paradigm With Junior Soccer Players
Reference: Front Psychol. 2018 Aug 23;9:1260. doi: 10.3389/fpsyg.2018.01260. eCollection 2018.
Authors: Schorer J, Schapschröer M, Fischer L, Habben J, Baker J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6115512/pdf/fpsyg-09-01260.pdf
Summary: In sport, perceptual skill training software is intended to assist tactical training in the field. The aim of this field study was to test whether "laboratory-based" pattern recall training would augment tactical skill training performed on the field. Twenty-six soccer players between 14 and 16 years of age from a single team participated in this study and were divided into three groups. The first received field training on a specific tactical skill plus cognitive training sessions on the pattern recall task. The second performed only the field training while the third group served as a control group and had field training on other topics. The task on the pre-, post-, and retention-tests was to recall specific soccer patterns displayed on a computer screen. Results showed significant changes between pre- and post-test performance. There was no significant interaction between groups and tests but the effect size was large. From pre- to retention-test, there was a significant difference between tests and an interaction between groups and tests, but no main effect difference between groups. On the basis of significance testing only retention was affected by the additional training, however, descriptive results and effect sizes from pre- to post-test were as expected and suggested there were learning benefits. Together these results indicate that augmented perceptual-cognitive training might be beneficial, but some limitations in our study design (e.g., missing field test, missing placebo group, etc.) need to be improved in future work.


#9 Effect of a 6-week supervised detraining period on bone metabolism markers and their association with ergometrics and components of the hypothalamic-pituitary-gonadal (HPG) axis in professional male soccer players
Reference: J Bone Miner Metab. 2018 Sep 5. doi: 10.1007/s00774-018-0947-7. [Epub ahead of print]
Authors: Koundourakis NE, Androulakis N, Dermitzaki E, Venihaki M, Margioris AN
Summary: The aim of this study was to examine the effect of a supervised 6-week detraining period on bone metabolism markers, and their association with ergometrics, and components of the hypothalamic-pituitary-gonadal (HPG) axis in elite male professional soccer players. Sixty-seven soccer players (mean age ± SD 23.4 ± 5.2 years) that were following a supervised training program participated in this study. Players were tested twice: immediately after the conclusion of the competition period, and following the detraining period, for the determination of bone-turnover rates, ergometrics, and components of the HPG-axis. The detraining period resulted in significant reduction in osteocalcin [OC] (p < 0.001), C-terminal propeptide of collagen type-I [CICP] (p = 0.002), and bone-alkaline-phosphatase [b-ALP] (p < 0.001) values, while C-terminal telopeptide [CTX] was increased (p < 0.001). No significant relationships were apparent between bone biomarkers and body weight, body-fat %, total testosterone, free testosterone, estradiol, follicle-stimulating hormone, and luteinizing hormone in both experimental sessions (p > 0.05). Similarly, despite the deterioration in ergometrics after detraining (all p < 0.001), no significant correlations were evident (p > 0.05) between bone biomarkers and maximal oxygen consumption, squat jump, countermovement jump, and 20 m sprint performance, and also between % change of bone biomarkers and ergometrics, apart from a weak relationship (p = 0.041) between OC and VO2max of questionable value. Our results suggest that the 6-week soccer off-season detraining period in our study negatively affected bone physiology as reflected by the suppression of bone-formation rate and a parallel induction of bone resorption. The cause of this acute alteration of bone-turnover rates is not related to the examined components of the HPG-axis, although parallels is not associated with the changes in ergometrics.


#10 Epidemiology of Upper Extremity Soccer Injuries Among High School- and College-Aged Players in the United States: An Analysis of the 1999-2016 NEISS Database
Reference: Sports Health. 2018 Sep 5:1941738118795483. doi: 10.1177/1941738118795483. [Epub ahead of print]
Authors: Durand WM, Goodman AD, Giglio P, Etzel C, Owens BD
Summary: Although lower extremity injuries are more common than upper extremity injuries in high school- and college-aged soccer players, upper extremity injuries may be equally severe. The epidemiology of upper extremity injuries is poorly characterized in this population.  The authors hypothesis that upper extremity injuries are an important contributor to soccer-related morbidity among high school- and college-aged players. The National Electronic Injury Surveillance System (NEISS) is a nationally representative sample of 100 hospital emergency departments (EDs). Each record contains demographic and injury information. Records from 1999 to 2016 were analyzed, including patients between the ages of 14 and 23 years with a soccer-related injury sustained at school or during an athletic event. A total of 1,299,008 high school- or college-aged patients presented to the ED for a soccer-related injury from 1999 to 2016, of which 20.4% were in the upper extremity. Patients were predominantly male (58.0%) and high school-aged (81.4%). Males constituted a greater proportion of upper extremity injuries when compared with other injury locations (63.5% male for upper extremity). Upper extremity injuries were more likely to be fractures (43.7% vs 13.9%) and dislocations (7.1% vs 3.4%) and less likely to be strains/sprains (27.8% vs 56.6%). Males suffered more shoulder dislocations (81.8% males among patients with shoulder dislocation vs 57.8% among those with other injuries), finger dislocations (72.0% vs 58.0%), upper arm fractures (74.9% vs 57.6%), and forearm fractures (68.3% vs 57.3%). Upper extremity injuries are frequent in high school- and college-aged soccer players presenting to the ED. Efforts to reduce soccer-related injuries should include strategies targeting the upper extremity, perhaps reducing the incidence of high-energy falls. Efforts to reduce soccer-related injuries should include strategies targeting upper extremity injuries, particularly among males and college-aged players.


#11 Pathogenic Factors Associated With Osgood-Schlatter Disease in Adolescent Male Soccer Players: A Prospective Cohort Study
Reference: Orthop J Sports Med. 2018 Aug 28;6(8):2325967118792192. doi: 10.1177/2325967118792192. eCollection 2018 Aug.
Authors: Watanabe H, Fujii M, Yoshimoto M, Abe H, Toda N, Higashiyama R, Takahira N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6113738/pdf/10.1177_2325967118792192.pdf
Summary: A previous cross-sectional study reported that pathogenic factors associated with Osgood-Schlatter disease (OSD) in adolescent athletes include increased quadriceps muscle tightness, lower leg malalignment, and development of apophysitis in the tibial tuberosity. The purpose was to confirm these pathogenic factors associated with OSD in a longitudinal study with regard to physical function and performance. In this study, 37 boys (mean age, 10.2 ± 0.4 years) were recruited from 2 soccer teams at an elementary school. This cohort study was conducted over an observation period of 1 year, with measurements recorded at baseline, followed by screening for OSD every 6 months. Variables evaluated at baseline included physical function (morphometry, joint flexibility, and lower extremity alignment), presence of Sever disease, and kicking motion. Pathogenic factors associated with OSD in the support leg of adolescent male soccer players included height, weight, body mass index, quadriceps femoris muscle tightness in the kicking and support legs, and gastrocnemius muscle tightness, soleus muscle tightness, and medial longitudinal arch in the support leg. Additional factors included a diagnosis of Sever disease and distance from the lateral malleolus of the support leg's fibula to the center of gravity during kicking. The onset of OSD was found to be affected by many factors, including developmental stage, physical attributes, and pre-existing apophysitis. In particular, a diagnosis of Sever disease and backward shifting of the center of gravity during kicking increased the risk of the subsequent onset of OSD, suggesting that these factors are very important as a possible focus for interventions.


#12 Inter-individual Variability in Responses to 7 Weeks of Plyometric Jump Training in Male Youth Soccer Players
Reference: Front Physiol. 2018 Aug 20;9:1156. doi: 10.3389/fphys.2018.01156. eCollection 2018.
Authors: Ramirez-Campillo R, Alvarez C, Gentil P, Moran J, García-Pinillos F, Alonso-Martínez AM, Izquierdo M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6109752/pdf/fphys-09-01156.pdf
Summary: The purpose of this study was to compare the inter-individual variability in the effects of plyometric jump training (PJT) on measures of physical fitness (sprint time, change of direction speed, countermovement jump, 20- and 40-cm drop jump reactive strength index, multiple five bounds distance, maximal kicking distance, and 2.4-km time trial) in youth soccer players who completed a PJT program versus players who completed soccer training only. In a single-blinded study, participants aged between 10 and 16 years were randomly divided into a PJT group (n = 38) and a control group (n = 38). The experimental group participated in a PJT program twice weekly for 7 weeks, whereas the control group continued with their regular soccer training sessions. Between-group differences were examined using a Mann-Whitney U test. Nonresponders where defined as individuals who failed to demonstrate any beneficial change that was greater than two times the typical error of measurement from zero. The results indicated that the mean group improvement for all physical fitness measures was greater (p < 0.05) in the PJT group (Δ = 0.4 to 23.3%; ES = 0.04 to 0.58) than in the control group (Δ = 0.1 to 3.8%; ES = 0.02 to 0.35). In addition, a significantly greater (p < 0.05) number of responders across all dependent variables was observed in the PJT group (from 4 up to 33 responders) than in the control group (from 0 up to 9 responders). In conclusion, compared to soccer training only, PJT induced greater physical fitness improvements in youth soccer players, with a greater number of responders for all the physical fitness tests related to jumping, speed, change of direction speed, endurance, and kicking technical ability.


#13 Heart Rate and Perceived Experience Differ Markedly for Children in Same- versus Mixed-Gender Soccer Played as Small- and Large-Sided Games
Reference: Biomed Res Int. 2018 Aug 5;2018:7804642. doi: 10.1155/2018/7804642. eCollection 2018.
Authors: Póvoas S, Randers MB, Krustrup P, Larsen MN, Pereira R, Castagna C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6098911/pdf/BMRI2018-7804642.pdf
Summary: This study examines heart rate (HR) and perceived experience during same- versus mixed-gender soccer played as small- (SSG) and large-sided (LSG) games. HR, rating of perceived exertion (RPE), and fun scores were determined in 134 pupils (50 girls, 84 boys) randomly assigned to same- and mixed-genders formats playing 2x15-min of SSG (2v2, 4v4) and LSG (12v12) in a random order (~50 m2/player). HR was lower (p≤0.03) for girls when playing together with boys than when playing alone (71±10 versus 77±7%HRmax), while being similar for boys playing mixed- or same-gender games (74±7 versus 77±4%HRmax). Boys perceived less fun when playing together with girls than when playing alone (4.4±2.3 versus 6.3±2.3, p<0.001). Irrespective of gender, higher (p<0.001) HRmean, %time>80%HRmax, and RPE were observed during 2v2 (78±9%HRmax, 43±33%, 5.5±2.5) and 4v4 (76±9%HRmax, 39±32%, 5.5±2.7) than during 12v12 (70±10%HRmax, 23±27%, 3.8±2.9). Cardiovascular strain was lower for girls when playing together with boys than when playing alone in LSG. SSG were more intense than LSG when girls played mixed-gender games and when boys played mixed- and same-gender games. When boys played mixed-gender games, SSG were considered more fun than LSG. Physical education teachers and coaches should consider gender and game format differences when using soccer.

Thu

25

Oct

2018

Latest research in football - week 34 - 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 Changes in biomechanical knee injury risk factors across two collegiate soccer seasons using the 11+ prevention program
Reference: Scand J Med Sci Sports. 2018 Aug 17. doi: 10.1111/sms.13278. [Epub ahead of print]
Authors: Arundale AJH, Silvers-Granelli HJ, Marmon A, Zarzycki R, Dix C, Snyder-Mackler L
Summary: The 11+ injury prevention program effectively reduces injuries in high school aged female soccer player, but the mechanism of the 11+ is unknown, particularly whether it impacts biomechanical risk factors associated with knee injuries. The purpose was to report the changes in hip and knee biomechanics with use of the 11+ over two soccer seasons. Two collegiate women's soccer teams performed the 11+ for two soccer seasons. A control team was followed for one season. Athletes performed motion analysis of a drop vertical jump during preseason and postseason. Both groups had meaningful increases in peak knee abduction angle over the first season, and there were no meaningful changes in peak knee abduction moment over either season. The control group had bilateral decreases in knee flexion angle. The program did not seem to systematically impact biomechanical risk factors associated with knee injuries, with increase in peak knee abduction angle no bilateral changes in frontal or transverse hip motion. The 11+ may have mitigated clinically meaningful decreases in knee flexion, however as ACL injuries do not occur purely in the sagittal plane, it is unclear the impact of these changes. The results of this study indicate that the 11+ may require some modifications to impact landing biomechanics and potentially risky movement patterns, particularly when used in collegiate women over multiple seasons


#2 Timing Training in Female Soccer Players: Effects on Skilled Movement Performance and Brain Responses
Reference: Front Hum Neurosci. 2018 Aug 2;12:311. doi: 10.3389/fnhum.2018.00311. eCollection 2018.
Authors: Sommer M, Häger CK, Boraxbekk CJ, Rönnqvist L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082929/pdf/fnhum-12-00311.pdf
Summary: Although trainers and athletes consider "good timing skills" critical for optimal sport performance, little is known in regard to how sport-specific skills may benefit from timing training. Accordingly, this study investigated the effects of timing training on soccer skill performance and the associated changes in functional brain response in elite- and sub-elite female soccer players. Twenty-five players (mean age 19.5 years; active in the highest or second highest divisions in Sweden), were randomly assigned to either an experimental- or a control group. The experimental group (n = 12) was subjected to a 4-week program (12 sessions) of synchronized metronome training (SMT). We evaluated effects on accuracy and variability in a soccer cross-pass task. The associated brain response was captured by functional magnetic resonance imaging (fMRI) while watching videos with soccer-specific actions. SMT improved soccer cross-pass performance, with a significant increase in outcome accuracy, combined with a decrease in outcome variability. SMT further induced changes in the underlying brain response associated with observing a highly familiar soccer-specific action, denoted as decreased activation in the cerebellum post SMT. Finally, decreased cerebellar activation was associated with improved cross-pass performance and sensorimotor synchronization. These findings suggest a more efficient neural recruitment during action observation after SMT. To our knowledge, this is the first controlled study providing behavioral and neurophysiological evidence that timing training may positively influence soccer-skill, while strengthening the action-perception coupling via enhanced sensorimotor synchronization abilities, and thus influencing the underlying brain responses.


#3 Somatotype Hormone Levels and Physical Fitness in Elite Young Soccer Players over a Two-Year Monitoring Period
Reference: J Sports Sci Med. 2018 Aug 14;17(3):455-464. eCollection 2018 Sep.
Authors: Hammami MA, Ben Abderrahman A, Rhibi F, Nebigh A, Coppalle S, Ravé G, Tabka Z, Zouhal H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090385/pdf/jssm-17-455.pdf
Summary: The effect of two soccer-training seasons on the growth, development and somatotype hormone concentrations of elite youth soccer players were evaluated. Eighteen elite soccer players and 18 age-matched non-athletic control subjects participated in the study. Anthropometric-measurements, aerobic and anaerobic performance tests and serum concentrations of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), and growth hormone (GH) were assessed at 5 time points across two competitive seasons. Soccer players revealed higher GH, IGF-1 and IGFBP-3 than the control group across all-time points. Significant moderate correlations were observed only in soccer players between hormonal concentrations (IGF-1 and IGFBP-3) and the jumping tests (r = 0.45-0.48; p < 0.01). Somatotropic axis hormones, anthropometric and physical parameters increased to a greater degree with growth and soccer training combined compared to growth alone. Results from this investigation revealed that intense training did not impair growth or development in these young soccer players across 2-year period.


#4 Effects of Spatiotemporal Constraints and Age on the Interactions of Soccer Players when Competing for Ball Possession
Reference: J Sports Sci Med. 2018 Aug 14;17(3):379-391. eCollection 2018 Sep.
Authors: Menuchi MRTP, Moro ARP, Ambrósio PE, Pariente CAB, Araújo D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090386/pdf/jssm-17-379.pdf
Summary: Although there are several descriptions of interpersonal coordination in soccer teams, little is known about how such coordination is influenced by space and time constraints. In this study, we analyzed variations in interpersonal coordination under different marking intensities and across different age groups. Marking intensity was manipulated by changing the players' game space and time of ball possession in a conditioned soccer game known as rondo. Five participants in each age category (U13, U15, U17, and U20) performed rondo tasks in four experimental conditions, in a total of 134 trials. The dependent variables considered were pass performance and eco-physical variables capturing the player-environment coupling, such as coupling of the marking between players. Our results demonstrate that in soccer: (1) markers and passers are tightly coupled; (2) the marker-passer coupling emerges from a flexible and adaptive exchange of passes; (3) the marker-passer coupling is stronger in markings of higher intensity and older age groups. Thus, the interactions between soccer players in marking can be analyzed as an emerging and self-organized process in the context of group performance.


#5 Behaviours of shooter and goalkeeper interact to determine the outcome of soccer penalties
Reference: Scand J Med Sci Sports. 2018 Aug 15. doi: 10.1111/sms.13276. [Epub ahead of print]
Authors: Hunter AH, Angilletta MJ Jr, Wilson RS
Summary: During a soccer penalty, the shooter's strategy and the goalkeeper's strategy interact to determine the outcome. However, most models of penalty success overlook its interactive nature. Here, we quantified aspects of shooter and goalkeeper strategies that interact to influence the outcome of soccer penalties - namely, how the speed of the shot affects the goalkeeper's leave-time or shot-blocking success, and the effectiveness of deceptive strategies. We competed 7 goalkeepers and 17 shooters in a series of penalty shootout competitions with a total of 1278 shot taken. Each player was free to use any strategy within the rules of a penalty shot and game-like pressure was created via monetary incentive for goal-scoring (or blocking). We found that faster shots lead to earlier leave-times and were less likely blocked by goalkeepers, and-unlike most previous studies-that deceptive shooting strategies did not decrease the likelihood goalkeepers moved in the correct direction. To help identify optimal strategies for shooter's and goalkeepers, we generated distributions and mathematical functions sport scientist can use to develop more comprehensive models of penalty success.


#6 Recreational soccer as sport medicine for middle-aged and older adults: a systematic review
Reference: BMJ Open Sport Exerc Med. 2018 Aug 9;4(1):e000336. doi: 10.1136/bmjsem-2017-000336. eCollection 2018.
Authors: Luo H, Newton RU, Ma'ayah F, Galvão DA, Taaffe DR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6089298/pdf/bmjsem-2017-000336.pdf
Summary: Strategies to prevent or attenuate the age-related decline in physical and physiological function and reduce chronic disease risk factors are of clinical importance. The objective was to examine the health benefits of recreational soccer in middle-aged and older adults. All available records up until 9 June 2017 in PubMed, Web of Science, SPORTDiscus, MEDLINE, Embase, CINAHL Plus, PsycINFO and Cochrane Library databases were utilize.  Eligibility criteria for selecting studies were: All randomised trials with or without a control group (randomised controlled trials or randomised uncontrolled trials) and non-randomised controlled trials that used recreational soccer, which includes small-sided soccer games, as the sole or principal intervention, and reported relevant effects in untrained/sedentary, healthy or unhealthy adults aged 40 years and above were included. Five trials described in 13 articles were included, which scored 6-9 out of 12 points on the modified Delphi quality rating scale. The duration was from 12 to 52 weeks, with various frequencies, volumes and game formats performed both outdoors and indoors with men and women. The trials indicate that recreational soccer may result in improvement in cardiovascular function, body composition and functional ability, although no significant changes were observed in postural balance. Recreational soccer should be considered an alternative exercise modality for untrained, healthy or unhealthy middle-aged and older adults of both sexes to maintain an active lifestyle and mitigate a wide array of physical and physiological age-related changes.


#7 Effects of short-term in-season break detraining on repeated-sprint ability and intermittent endurance according to initial performance of soccer player
Reference: PLoS One. 2018 Aug 15;13(8):e0201111. doi: 10.1371/journal.pone.0201111. eCollection 2018.
Authors: Rodríguez-Fernández A, Sánchez-Sánchez J, Ramirez-Campillo R, Rodríguez-Marroyo JA, Villa Vicente JG, Nakamura FY
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0201111&type=printable
Summary: The objective was to better understand the detraining effects in soccer, the purpose of the study was to analyse if performance level of soccer players modulate repeated-sprint ability (RSA) and intermittent endurance changes during 2-weeks of detraining (i.e., in-season break). Seventeen professional and sixteen young elite soccer players of two different teams performed, before and after 2-weeks of detraining, the RSA test and the Yo-Yo Intermittent Recovery Test, level 1 (YYIR1). Before detraining, professional players perform better (p < 0.05) RSA best time (RSAbest) than young players. A decrease (p < 0.05) in RSAbest, RSA total time (RSAtotal) and mean time (RSAmean) performance was observed in both teams, without changes in RSA fatigue index (Sdec). No significant changes in distance covered during YYIR1 was observed in any team. Before detraining, faster players from both teams (FG) (following the median split technique, soccer players with RSAbest ≤ 3.95 s) performed better (p < 0.01) in RSAtotal, RSAmean and RSAbest, but worse (p < 0.01) in Sdec. Although FG and the slower players (SG, RSAbest > 3.95 s) showed a worse (p < 0.05) RSAtotal, RSAbest and RSAmean performance after detraining (ES = 1.5, 1.4 and 2.9; ES = 0.6, 1.2 and 0.6; for FG and SG, respectively), the deterioration was greater in the FG for RSAbest (p < 0.05) and RSAtotal (ES = 1.46). After detraining, FG improved (p < 0.05) Sdec performance. In conclusion, a 2-week in-season break (detraining) period induced a worse RSA, with no effect on intermittent endurance in professional and elite young soccer players, with greater detrimental effects on RSAtotal and RSAbest in FG. In addition, Sdec does not seem to be sensitive to changes in RSA after a 2-week in-season break.


#8 Enhancing motor learning of young soccer players through preventing an internal focus of attention: The effect of shoes colour
Reference: PLoS One. 2018 Aug 15;13(8):e0200689. doi: 10.1371/journal.pone.0200689. eCollection 2018.
Authors: De Giorgio A, Sellami M, Kuvacic G, Lawrence G, Padulo J, Mingardi M, Mainolfi L
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0200689&type=printable
Summary: The purpose of this research was to assess how the motor learning skills in 7-years old soccer players can be improved by preventing an internal focus of attention via the use coloured shoes. We painted the classic black soccer shoes in six areas corresponding to six regions of the foot with which it is possible to interact with the ball. Thirty-four 7-years-old soccer players were randomized to two groups (Coloured n = 17 and Black, n = 17) to perform four basic football manoeuvres/tasks: reception (RECP), passing (PASS), ball management (MAGT), and shooting (SHOT). We found highly significant differences (P<0.001) in all four performance tests: mean(sd) RECP: 0.82(0.07) vs. 0.45(0.12); PASS: 0.85(0.07) vs. 0.47(0.09); MAGT: 0.91(0.09); SHOT: 1.00(1.00) vs. 0.44(0.16). Colored shoes appear to draw children's attention away from body centered cues without explicit verbal communications. We propose that this cognitive adaptation enhanced the technical gesture by preventing the negative processes associated with action constraining when adopting an internal focus attention (perhaps by allowing the foot to adapt to surfaces and movements more naturally than conditions that promote a focus on the body movement). Consequently, this type of coloured footwear could be used during childhood to allow children to enhance the performance of basic football exercises through preventing action constraining and promoting intuitive (non-body centered) action knowledge.


#9 Electromyographic analysis of hip adductor muscles in soccer instep and side-foot kicking
Reference: Sports Biomech. 2018 Aug 13:1-12. doi: 10.1080/14763141.2018.1499800. [Epub ahead of print]
Authors: Watanabe K, Nunome H, Inoue K, Iga T, Akima H
Summary: A possible link between soccer-specific injuries, such as groin pain and the action of hip adductor muscles has been suggested. This study aimed to investigate neuromuscular activation of the adductor magnus (AM) and longus (AL) muscles during instep and side-foot soccer kicks. Eight university soccer players performed the two types of kick at 50%, 75% and 100% of the maximal ball speed. Surface electromyography (EMG) was recorded from the AM, AL, vastus lateralis (VL) and biceps femoris (BF) muscles of both kicking and supporting legs and the kicking motions were three-dimensionally captured. In the kicking leg, an increase in surface EMG with an increase in ball speed during instep kicking was noted in the AM muscle (p < 0.016), but not in AL, VL or BF muscles (p > 0.016). In the supporting leg, surface EMG of both AM and AL muscles was significantly increased with an increase in the ball speed before ball impact during both instep and side-foot kicks (p < 0.016). These results suggest that hip adductor muscles markedly contribute to either the kicking or supporting leg to emphasise the action of soccer kicks.


#10 Meniscal fixation is a successful treatment for hypermobile lateral meniscus in soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 11. doi: 10.1007/s00167-018-5080-6. [Epub ahead of print]
Authors: Steinbacher G, Alentorn-Geli E, Alvarado-Calderón M, Barastegui D, Álvarez-Díaz P, Cugat R
Summary: The purpose was to report the outcomes (subjective function, return to play, complications and reoperations) of arthroscopic all-inside meniscal fixation in a large sample of soccer players with hypermobile lateral meniscus. Between 2010 and 2015, 55 patients undergoing surgical treatment for hypermobile lateral meniscus at Mutualidad Catalana de Futbolistas (Barcelona, Spain) were identified. Patients with open physes, associated injuries, discoid meniscus, or clinical follow-up less than 6 months were excluded. Once identified, all patients were contacted over the phone to collect cross-sectional data on International Knee Documentation Committee (IKDC) score, postoperative Tegner score, and postoperative visual analogue scale (VAS) for pain. In addition, complications and reoperations were retrospectively collected. Forty-six cases (in 45 patients) with a mean (SD) age of 26.3 (9.5) years and mean (SD; range) follow-up of 43 (19.5; 8-73) months were included. The pre- and post-operative median (range) Tegner score was 9 (6-9) and 8 (0-9), respectively. Compared to the preoperative period, the postoperative Tegner score was equal in 27/46 (59%) cases and lower in 16/46 (35%) cases (3 missing values). Return to play was possible in 38/46 (82%) cases, from which 27/46 (59%) corresponded to the same pre-injury activity level. Postoperatively, the median (range) VAS for pain was 1 (0-9), and the mean (SD) subjective IKDC was 86.2 (16.7). Three of the 46 cases (6.5%) required a reoperation because of pain in one patient (meniscal suture failure) and meniscal tear in two patients. All-inside meniscal fixation is a successful treatment for hypermobile lateral meniscus, which allows acceptable return to play and good function in soccer players at a low reoperation rate. However, according to the present cross-sectional case series, players should be advised that return to the same pre-injury activity level is achieved in only 27 of 46 (59%) of the cases. Surgeons facing with the difficult problem of hypermobile lateral meniscus in soccer players should consider meniscus fixation as an easy and successful option.


#11 Attitudes and Experiences of Men with Prostate Cancer on Risk in the Context of Injuries Related to Community-based Football - A Qualitative Study
Reference: J Aging Phys Act. 2018 Aug 17:1-24. doi: 10.1123/japa.2018-0089. [Epub ahead of print]
Authors: Rørth M, Tjørnhøj-Thomsen T, Cormie P, Oliffe JL, Midtgaard J
Summary: While football training may be a potent strategy for health promotion in older men, the considerable risk of injuries may constitute a barrier for referral of clinical populations. The current study explored the attitudes of men with prostate cancer on risk in the context of injuries related to participating in a community-based football program. Four videotaped focus group interviews, and three individual in-depth telephone interviews were carried out with men with prostate cancer (n=35; mean age 68.8). Thematic networks technique was used to derive the global theme Injury-induced reinforced masculinity comprising five sub-themes: "Part of the game", "A good story to tell", "Like boys again", "An old, carefree body", and "Camaraderie". Collectively, these themes explained how football injuries may reflect masculine ideals in some men with prostate cancer. The study indicates that injuries are largely acceptable to men with prostate cancer, especially those in search of a means for expressing their masculinity.

Wed

24

Oct

2018

Latest research in football - week 33 - 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 Speed synchronization, physical workload and match-to-match performance variation of elite football players
Reference: PLoS One. 2018 Jul 24;13(7):e0200019. doi: 10.1371/journal.pone.0200019. eCollection 2018.
Authors: Gonçalves B, Coutinho D, Travassos B, Folgado H, Caixinha P, Sampaio J
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0200019&type=printable
Summary: This study aimed to: (i) examine whether the speed synchronization and physical performance of an elite football team changed between the first and the second half, using match time blocks of 15-min, and (ii) explore the match-to-match variation of players' speed synchronization performance. Twenty-eight outfield elite footballers participated in 51 official matches. Positional data were gathered and used to calculate the total distance covered as a physical workload indicator. For all the outfield teammate dyad combinations (45 pairs), it was processed the percentage of time that players' speed was synchronized during walking, jogging and running using relative phase (Hilbert Transform). Also, the match-to-match variation of the players' speed synchronization, expressed in coefficient of variation was computed. The differences in the total distance covered from all players within the different match's time block periods revealed a moderate decrease in the distance covered in the last 15-min of the match compared to the first 15-min (-6.5; ±1.07%, most likely: change in means with 95% confidence limits). However, when compared the last minutes from both halves a small increase was observed (2.7; ±1.2%, likely) from first to second half. The synchronization of the players' speed displacements revealed small to moderate decreases in the % of synchronization in the second half periods for the jogging and running speed, while the opposite was found for the walking speed (~13 to 24% more, most likely). The playing position analysis for the walking zone showed similar trends between the groups, with small to moderate higher values in the second half, with the exception of [30'-45'] vs [75'-90'] in the midfielder's dyads and in [15'-30'] vs [60'-75'] match periods for forwards. Similar trend was found during the running speed, in which small to moderate higher synchronization was found during the first half periods, with the exception of [15'-30'] vs [60'-75'] and [30'-45'] vs [75'-90'] in midfielder's dyads. Regarding to the match-to-match variation of the players' speed synchronization, overall results showed small to moderate increases in coefficient of variation during jogging and running displacements from the beginning to the end of the match (32.1; ±13.2% increase in jogging and 26.2; ±10.5% in running, both comparisons most likely). The higher distance covered during most of the first half periods and the higher dyadic synchronization at high speeds might have limited players' performance in the second half. In addition, the decrease trend in speed synchronization during the second half periods might have resulted from accumulated muscular and mental fatigue towards the match. Within, the match-to-match variation in tactical-related variables increased across the match duration, with especial focus in the midfielder dyads. Dyadic speed synchronization might provide relevant information concerning the individual and collective performance.


#2 Kinematic and kinetic analysis of the goalkeeper's diving save in football
Reference: J Sports Sci. 2018 Jul 23:1-9. doi: 10.1080/02640414.2018.1499413. [Epub ahead of print]
Authors: Ibrahim R, Kingma I, de Boode VA, Faber GS, van Dieën JH
Summary: Kinetics and full body kinematics were measured in ten elite goalkeepers diving to save high and low balls at both sides of the goal, aiming to investigate their starting position, linear and angular momentum, and legs' contribution to end-performance. Our results showed that goalkeepers adopted a starting position with a stance width of 33 ± 1% of leg length, knee flexion angle of 62 ± 18° and hip flexion angle of 63 ± 18°. The contralateral leg contributed more than the ipsilateral leg to COM velocity (p < 0.01), both for the horizontal (2.7 ± 0.1 m·s-1 versus 1.2 ± 0.1 m·s-1) and for the vertical component (3.1 ± 0.3 m·s-1 versus 0.4 ± 0.2 m·s-1). Peak horizontal and peak angular momenta were significantly larger (p < 0.01) for low dives than for high dives with a mean difference of 55 kg·m·s-1 and 9 kg·m2·s-1, respectively. In addition, peak vertical momentum was significantly larger (p < 0.01) for high dives with a mean difference between dive heights of 113 kg·m·s-1. Coaches need to highlight horizontal lateral skills and exercises (e.g. sideward push-off, sideward jumps), with emphasis on pushing-off with the contralateral leg, when training and assessing goalkeeper's physical performance.


#3 High knee loading in male adolescent pre-professional football players: Effects of a targeted training programme
Reference: J Sci Med Sport. 2018 Jul 5. pii: S1440-2440(18)30320-7. doi: 10.1016/j.jsams.2018.06.016. [Epub ahead of print]
Authors: Lagas IF, Meuffels DE, Visser E, Groot FP, Reijman M, Verhaar JAN, de Vos RJ
Summary: The objective was to assess whether targeted neuromuscular exercises can decrease knee loading of adolescent pre-professional footballers with high knee loading as identified with the field-based Drop Vertical Jump Test (DVJT). We undertook a prospective controlled trial, conducted between August and November 2016 at Erasmus Medical Centre, The Netherlands. Pre-professional football players (aged 14-21years) were evaluated at baseline and after 12weeks follow-up with the field-based DVJT. The field-based DVJT is a standardised test in which a player drops from a box and jumps up immediately after landing; knee load is calculated based on five parameters. Players with high knee load (probability≥0.75) from one club performed regular training(control group), and players with high knee load from another other club performed targeted neuromuscular exercises for 12weeks (intervention group). The difference of change in knee load between both groups after 12weeks was the primary outcome measure. Of 107 eligible players, 75 had a high knee loading. Knee loading decreased in both groups after 12weeks of training, but change in probability of high knee load was not significantly different between both groups (95% Confidence Interval [-0.012-0.082], p=0.139). Targeted neuromuscular exercises had no additional effect in decreasing knee loading of adolescent male pre-professional football players compared to regular training.


#4 Implicit learning increases shot accuracy of football players when making strategic decisions during penalty kicking
Reference: Hum Mov Sci. 2018 Jul 18;61:72-80. doi: 10.1016/j.humov.2018.07.004. [Epub ahead of print]
Authors: Navarro M, van der Kamp J, Schor P, Savelsbergh GJP
Summary: Implicit learning has been proposed to improve athletes' performance in dual-task situations. Yet, only a few studies tested this with a sports-relevant dual-task. Hence, the current study aimed to compare the effects of implicit and explicit training methods on penalty kicking performance. Twenty skilled football players were divided in two training groups and took part in a practice phase to improve kicking accuracy (i.e., without a goalkeeper) and in a post-test in order to check penalty kick performance (i.e., accuracy including a decision to kick to the side opposite the goalkeeper's dive). Results found that the implicit and explicit training method resulted in similar levels of decision-making, but after implicit training this was achieved with higher kicking accuracy. Additionally, applications for football players and coaches are discussed.


#5 Osteogenic impact of football training in 55- to 70-year-old women and men with prediabetes
Reference: Scand J Med Sci Sports. 2018 Jul 26. doi: 10.1111/sms.13252. [Epub ahead of print]
Authors: Skoradal MB, Helge EW, Jørgensen NR, Mortensen J, Weihe P, Krustrup P, Mohr M
Summary: The effects of football training on bone health were examined in 55- to 70-year-old sedentary women and men with prediabetes. Patients (n = 50) with prediabetes (age; 61 ± 9 years, BMI 29.7 ± 0.6 kg/m2 , body fat content; 37 ± 1%, VO2max ; 22.7 ± 0.8 mL/min/kg and mean arterial pressure; 104 ± 3 mm Hg) were randomized into a football training group (FTG; n = 27, 14 women) and a control group (CON; n = 23, 11 women). At baseline, 73% and 24% were diagnosed with femur osteopenia and osteoporosis, respectively. FTG performed football training twice weekly 30-60-minute sessions in 16 weeks, and both FTG and CON received professional dietary advice. Pre- and post-intervention whole-body and regional bone mineral content (BMC) and density (BMD) were determined with DXA-scans, and venous blood samples were drawn and analyzed for plasma bone turnover markers. Change scores were greater (P < 0.05) in FTG compared to CON in leg BMD (0.023 ± 0.005 vs -0.004 ± 0.001 g/cm2 ) and in leg BMC (32 ± 8 vs -4 ± 6 g). Between-group changes in favor of FTG (P < 0.05) also occurred in the femur neck BMD (3.2%) and femur shaft BMD (2.5%). Whole-body BMC and BMD were unchanged in both groups during the intervention. In FTG, resting plasma osteocalcin, P1NP, and CTX-1 rose (P < 0.05) by 23 ± 8, 52 ± 9 and 38 ± 7%, with greater change scores (P < 0.05) than in CON. Finally, P1NP (formation)/CTX-1 (resorption) ratio increased (P < 0.05) in FTG (127 ± 15 vs 150 ± 11) from pre- to post-intervention, with no change in CON (124 ± 12 and 123 ± 12). In conclusion, football training provides a powerful osteogenic stimulus and improves bone health in 55- to 70-year-old women and men diagnosed with prediabetes.


#6 Comparison of the lumbopelvic rhythm among adolescent soccer players with and without low back pain
Reference: Int J Sports Phys Ther. 2018 Apr;13(2):171-176.
Authors: Tojima M, Torii S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6063066/pdf/ijspt-13-171.pdf
Summary: Hip-spine incoordination can cause low back pain (LBP) in adolescents. Hip-spine coordination, including the lumbopelvic rhythm (LPR) and the lumbar-hip ratio (LHR), can be used to assess lower limb and spine function. However, there are no reports of the values of LPR or LHR in adolescent soccer players with and without LBP. The purpose of this study was to clarify the effect of LBP on LPR and LHR during trunk extension among adolescent soccer players. One hundred and nine adolescent soccer players were recruited and divided into two groups, one with and one without LBP. Using three-dimensional motion analysis, participants range of motion (ROM) of the lumbar spine (LS) and hip during trunk and hip extension was measured to calculate the LPR and LHR. Paired, two-tailed t-tests were used to compare the LS and hip ROM between the non-LBP and LBP groups, two-way repeated measures analysis of variance was used to compare time with the non-LBP and LBP groups for LHR, and linear prediction was used to describe the LPR. The maximum LS ROM in the LBP group was significantly less than that in the non-LBP group by 6.6 ° (p = .005). There was no difference in the maximum hip ROM between the groups (p = .376). The LHR did not change during trunk extension (F [4, 428] = 1.840, p = .120), the mean LHR was 4.6 in the non-LBP group and 3.7 in the LBP group, and there was no difference between the groups (p = .320). The linear function of the LPR indicated, that when the hip joint was extended by 1 °, the LS extended by 3.2 ° in the non-LBP group (R2 = .997, p < .001) and 2.8 ° in the LBP group (R2 = .999, p < .001). LBP inhibited lumbar motion relative to hip extension as LPR was smaller in the LBP group than in the non-LBP group. However, there was no difference between the groups in LHR because inter-individual variability affected the LHR.


#7 Foot and Soccer Referees': A Pilot Study Searching "Performance" Throughout Prevention
Reference: Front Physiol. 2018 Jul 25;9:1009. doi: 10.3389/fphys.2018.01009. eCollection 2018.
Authors: Gianturco L, Bodini BD, Gianturco V, Pregliasco FE, Cascio M, Serafin A, Turiel M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6069454/pdf/fphys-09-01009.pdf
Summary: Soccer refereeing is a "not-conventional" sport in which aerobic workload is prevalent. Along the years, several studies have attempted to define best markers of referees' performance. Many studies focused their attention on field tests and their relationship with aerobic power. Instead, in this study, starting by a medical assessment satisfying the FIFA 11+ criteria for injuries prevention, we have investigated the foot of soccer referees and we have also wanted to find possible and/or unexpected improvements in performance. As performance marker, we have used the referral field test for soccer referees that is internationally validated and known as Yo-Yo test (YYiR1). While standardized foot posture index (FPI) questionnaire was used for screening foot referees conditions (40 young, all men by sex, with mean age 23.47 ± 4.36). Analyzing collected data, we have demonstrated by means of Read-Cressie Chi square test that neutral FPI is an important favor item affecting YYiR1 results. Further studies will be necessary in order to confirm our pilot investigation.


#8 Outcomes of Cardiac Screening in Adolescent Soccer Players
Reference: N Engl J Med. 2018 Aug 9;379(6):524-534. doi: 10.1056/NEJMoa1714719.
Authors: Malhotra A, Dhutia H, Finocchiaro G, Gati S, Beasley I, Clift P, Cowie C, Kenny A, Mayet J, Oxborough D, Patel K, Pieles G, Rakhit D, Ramsdale D, Shapiro L, Somauroo J, Stuart G, Varnava A, Walsh J, Yousef Z, Tome M, Papadakis M, Sharma S
Summary: Reports on the incidence and causes of sudden cardiac death among young athletes have relied largely on estimated rates of participation and varied methods of reporting. We sought to investigate the incidence and causes of sudden cardiac death among adolescent soccer players in the United Kingdom. From 1996 through 2016, we screened 11,168 adolescent athletes with a mean (±SD) age of 16.4±1.2 years (95% of whom were male) in the English Football Association (FA) cardiac screening program, which consisted of a health questionnaire, physical examination, electrocardiography, and echocardiography. The FA registry was interrogated to identify sudden cardiac deaths, which were confirmed with autopsy reports. During screening, 42 athletes (0.38%) were found to have cardiac disorders that are associated with sudden cardiac death. A further 225 athletes (2%) with congenital or valvular abnormalities were identified. After screening, there were 23 deaths from any cause, of which 8 (35%) were sudden deaths attributed to cardiac disease. Cardiomyopathy accounted for 7 of 8 sudden cardiac deaths (88%). Six athletes (75%) with sudden cardiac death had had normal cardiac screening results. The mean time between screening and sudden cardiac death was 6.8 years. On the basis of a total of 118,351 person-years, the incidence of sudden cardiac death among previously screened adolescent soccer players was 1 per 14,794 person-years (6.8 per 100,000 athletes). Diseases that are associated with sudden cardiac death were identified in 0.38% of adolescent soccer players in a cohort that underwent cardiovascular screening. The incidence of sudden cardiac death was 1 per 14,794 person-years, or 6.8 per 100,000 athletes; most of these deaths were due to cardiomyopathies that had not been detected on screening. (Funded by the English Football Association and others.).


#9 Nesfatin-1 and irisin levels in response to the soccer matches performed in morning, afternoon and at night in young trained male subjects
Reference: Cell Mol Biol (Noisy-le-grand). 2018 Jul 30;64(10):130-133.
Authors: Ozcelik O, Algul S, Yilmaz B
Summary: This study aimed to investigate the potential effects of acute soccer matches performed in morning, afternoon and at night on both nesfatin-1 and irisin levels in trained subjects. Total of 20 male subjects performed in soccer matches at three different times of day: morning, afternoon, and night. Pre- and post-match venous blood samples were taken, and levels of both nesfatin-1 and irisin were analysed using the enzyme-linked immunosorbent assay (ELISA). Following all matches, the subjects' irisin levels increased significantly in all subjects (p &lt; 0.0001). Nesfatin-1 levels were also increased after the matches; however, the increase was statistically significant for morning (P=0.01) and night-time (p=0.009). The subjects' nesfatin-1 levels did not increase in all subjects and decrease of nesfatin-1 levels observed in some subjects after matches. This study finds that soccer matches performed different workout times have strong stimulatory effects on irisin levels in all subjects but nesfatin-1 response varied among the subjects and it did not change significantly in afternoon match.


#10 Are soccer matches dangerous for patients with heart disease? The HeartAtaque trial - a prospective pilot study
Reference: Rev Port Cardiol. 2018 Aug;37(8):645-653. doi: 10.1016/j.repc.2017.09.024. Epub 2018 May 22.
Authors: Martins JL, Adrega T, Santos L, Afreixo V, Viana J, Santos J
Summary: Behavioral and emotional factors are triggers of cardiovascular events (CVEs). It is uncertain whether soccer fans, particularly individuals with coronary artery disease (CAD), are at increased risk for CVEs. The purpose was to assess the effect of watching soccer matches in patients with known CAD on the incidence of CVEs according to the match result. We prospectively assessed 82 male soccer fans with a history of acute coronary syndrome during 23 matches of the 2015/2016 season. Each individual was assessed by Holter monitoring on the day of their team's match and on the control day. The primary endpoint was the composite of death, stroke, reinfarction, angina or sustained arrhythmia. Secondary endpoints assessed were episodes of non-sustained supraventricular or ventricular arrhythmia and mean heart rate (HR). Participants' mean age was 61±10 years. Compared with the control day, despite a significant increase in HR (p<0.001) that was independent of the result (p>0.97), the number of CVEs did not differ according to the result (p>0.05). Moreover, the number of non-sustained episodes of supraventricular and ventricular arrhythmia did not differ when stratified according to the match result (p>0.05). The match result was not associated with a difference in incidence of CVEs in patients with a past history of CAD, with ischemic and arrhythmic substrate, who watched soccer matches on television.


#11 Longevity and cardiovascular mortality of Polish elite football players
Reference: Kardiol Pol. 2018 Aug 9. doi: 10.5603/KP.a2018.0173. [Epub ahead of print]
Authors: Gajda J, Śmigielski W, Śmigielski J, Pakos E, Drygas W
Download link: https://ojs.kardiologiapolska.pl/kp/article/download/KP.a2018.0173/9831
Summary: Despite the wide popularity of football, there is a paucity of scientific evidence explaining the relationship between being a competitive footballer and life expectancy AIM: The study analyses and compares cause-specific mortality between Polish elite footballers (men) and the general male population. A retrospective method of analysis is employed to study a sample of 455 elite footballers who died between 1990 and 2015. The cause of death was established based on the official statistics of Polish Central Statistical Office. The comparative sample consists of men in the general male population in Poland who died in the sampled period being at least 25 years of age at the time of death. The mean age at death turned out to be higher for footballers than controls (70.2 vs 67.4 years). Cardiovascular diseases were a more common cause of death among footballers than in the general male population in both the under 65-group and the above- 65-group (46.9% to 32.3% and 61.3% to 53.3%, respectively). A closer analysis of cause-specific cardiovascular mortality revealed that acute myocardial infarction caused more deaths (OR=1.31; CI 95%: [1.02-1.68]) and hypertensive disease less deaths (OR=0.20; CI 95%: [0.05-0.79]) among athletes than in the general male population. The study results point to excess cardiovascular mortality among Polish elite footballers. A trend analysis has shown, however, that its level is falling.


#12 The Use of Microtechnology to Quantify the Peak Match Demands of the Football Codes: A Systematic Review
Reference: Sports Med. 2018 Aug 7. doi: 10.1007/s40279-018-0965-6. [Epub ahead of print]
Authors: Whitehead S, Till K, Weaving D, Jones B
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0965-6.pdf
Summary: Quantifying the peak match demands within the football codes is useful for the appropriate prescription of external training load. Wearable microtechnology devices can be used to identify the peak match demands, although various methodologies exist at present. This systematic review aimed to identify the methodologies and microtechnology-derived variables used to determine the peak match demands, and to summarise current data on the peak match demands in the football codes. A systematic search of electronic databases was performed from earliest record to May 2018; keywords relating to microtechnology, peak match demands and football codes were used. Twenty-seven studies met the eligibility criteria. Six football codes were reported: rugby league (n = 7), rugby union (n = 5), rugby sevens (n = 4), soccer (n = 6), Australian Football (n = 2) and Gaelic Football (n = 3). Three methodologies were identified: moving averages, segmental and 'ball in play'. The moving averages is the most commonly used (63%) and superior method, identifying higher peak demands than other methods. The most commonly used variables were relative distance covered (63%) and external load in specified speed zones (57%). This systematic review has identified moving averages to be the most appropriate method for identifying the peak match demands in the football codes. Practitioners and researchers should choose the most relevant duration-specific period and microtechnology-derived variable for their specific needs. The code specific peak match demands revealed can be used for the prescription of conditioning drills and training intensity.


#13 Different neuromuscular parameters influence dynamic balance in male and female football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Aug 7. doi: 10.1007/s00167-018-5088-y. [Epub ahead of print]
Authors: López-Valenciano A, Ayala F, De Ste Croix M, Barbado D, Vera-Garcia FJ
Summary: The purpose of the study was to analyse the relationship between several parameters of neuromuscular performance with unilateral dynamic balance measured through the Y-Balance test, as well as to determine the possible sex-related differences. The Y-Balance test, isokinetic (concentric and eccentric) knee flexion and extension strength, isometric hip abduction and adduction strength, lower extremity joint range of motion (ROM) (hip, knee and ankle) and core stability were assessed in male (n = 88) and female (n = 44) professional football players. A stepwise multivariate linear least square regression with backward elimination analysis was carried out to identify a group of factors that were independently associated with balance performance in both sexes. Passive hip flexion and ankle dorsiflexion with knee flexed ROM were the main factors that retained a significant association to dominant (R2 = 23.1) and non-dominant (R2  = 33.5) balance scores for males. For females, core stability, hip abduction isometric peak torque, passive hip abduction and ankle dorsiflexion with knee flexed ROM variables retained a significant association with balance scores for both, dominant (R2 = 38.2) and non-dominant (R2 = 46.9) legs. Training interventions aimed at improving or maintaining unilateral dynamic balance in male football players should include, among other things, stretching exercises for the posterior chain of the lower extremity. However, females should also include exercises for strength and mobility of the hip abductors and core stability (especially in the frontal plane). This knowledge would allow clinicians and sport practitioners to develop more effective and tailored unilateral dynamic balance training interventions in male and female football players, possibly improving performance and reducing the risk of injury.

Fri

19

Oct

2018

Hamburger SV team warm-up

The footage below shows the pre-match warm-up of the Hamburger SV players before their game against SV Darmstadt '98.

Thu

18

Oct

2018

Latest research in football - week 32 - 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 Age-Matched Z-Scores for Longitudinal Monitoring of Center of Pressure Speed in Single-Leg Stance Performance in Elite Male Youth Soccer Players
Reference: J Strength Cond Res. 2018 Jul 26. doi: 10.1519/JSC.0000000000002765. [Epub ahead of print]
Authors: Huurnink A, Fransz DP, de Boode VA, Kingma I, van Dieën JH
Summary: Coordination of corrective motor actions is considered important for soccer performance and injury prevention. A single-leg stance (SLS) test assesses the integrity and proficiency of the sensorimotor control system, quantified by center of pressure averaged speed (COPspeed). We aimed to provide age-matched z-scores for COPspeed in elite male youth soccer players. Second, we assessed a threshold for abnormal long-term change in performance, i.e., critical difference (CD). In a youth academy program, 133 soccer players of 9-18 years were tested twice for both legs (2 repetitions), and one repetition follow-up was conducted at 5.8 months (SD 2.7). Linear regression between age and COPspeed was performed to provide age-matched z-scores. Variance of differences in z-scores at baseline and between sessions was used to estimate the CD up to 5 repetitions. Intraclass correlation coefficients (ICCs) were assessed within and between sessions. The age significantly affected COPspeed (p < 0.0001), with lower values in older players (95% confidence interval; 3.45-9.17 to 2.88-5.13 cm·s, for 9 and 18 years, respectively). The z-score CD ranged from 1.72 (one repetition) to 1.34 (5 repetitions). The ICC of z-scores was 0.88 within session and 0.81 between sessions. In conclusion, the SLS performance in elite male youth soccer players improves with age. We determined age-matched z-scores of COPspeed, which reliably determined performance according to age. The CD allows for detection of abnormal variations in COPspeed to identify players with a (temporary) deterioration of sensorimotor function. This could be applied to concussion management, or to detect underlying physical impairments.


#2 Profiling the Responses of Soccer Substitutes: A Review of Current Literature
Reference: Sports Med. 2018 Jul 26. doi: 10.1007/s40279-018-0962-9. [Epub ahead of print]
Authors: Hills SP, Barwood MJ, Radcliffe JN, Cooke CB, Kilduff LP, Cook CJ, Russell M
Summary: Depending upon competition regulations, the laws of soccer allow between three and an unlimited number of substitutions that can be made on either a permanent or rolling basis. Substitutes are typically introduced to minimise/offset the effects of fatigue, alter tactics, replace players deemed as underperforming or injured, and/or give playing time to youth players or to squad members returning from injury. While the match-day practices of substitutes include participation in the pre-match warm-up, and sporadic periods of rewarm-up activity, it is currently unclear as to whether these pre-entry preparations facilitate optimal match performance thereafter. Acknowledging the contextual factors that possibly influence substitutes' performance, this review summarises the presently available literature on soccer substitutes, and makes recommendations for future research. Literature searching and screening yielded 13 studies, which have typically focused on characterising: (1) the patterns, including timing, of substitutes' introduction; (2) indices of match-performance; and (3) the emotional experiences of soccer substitutes. The majority of substitutions occur after the first-half has ended (i.e. at half-time or during the second-half), with introduced players exceeding the second-half physical performances of those who started the match. Observations of progressive improvements in running performance as playing time increases, and findings that substitutes mostly experience negative emotions, highlight the potential inadequacies of pre-match preparations, and present future research opportunities. Additional work is therefore needed to confirm these findings and to determine the efficacy of current preparation strategies, thereby providing opportunities to assess then address substitutes' pre-pitch entry preparations, on-field performance and emotional responses.


#3 Leg Fracture Associated with Synostosis of Interosseous Membrane During Running in A Soccer Player
Reference: Transl Med UniSa. 2018 Mar 31;17:1-5. eCollection 2017 Jul.
Authors: Oliva F, Buharaja R, Iundusi R, Tarantino U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6056250/pdf/tm-17-01.pdf
Summary: Leg fractures may occur frequently in sport injuries but it is very rare to find this kind of injury associated with interosseous membrane synostosis. This case report describes a unique case of 42 B1.2 fracture of the leg associated with an interosseous membrane synostosis and literature review on Pubmed, Google scholar and Medscape. A 26 year old male amateur soccer player came to our attention at the emergency room after a fall while he was running without any direct trauma following a referred ankle sprain. X-ray and CT scan of the left leg showed a comminuted displaced fracture of the lower middle third of tibial and peroneus diaphysis, and moreover, a fracture of peroneal malleolus associated with a bone bridge between the tibia and fibula. The patient was treated with a surgical osteosynthesis the day after trauma. We think that the interosseous membrane plays an important role in biomechanics of the leg even during running. To our knowledge, this is the first case reported which show the fractures of the tibia and fibula associated with an ipsilateral synostosis of the interosseous membrane.


#4 Dynamics of Recovery of Physiological Parameters After a Small-Sided Game in Women Soccer Players
Reference: Front Physiol. 2018 Jul 11;9:887. doi: 10.3389/fphys.2018.00887. eCollection 2018.
Authors: Mascarin RB, De Andrade VL, Barbieri RA, Loures JP, Kalva-Filho CA, Papoti M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6050376/pdf/fphys-09-00887.pdf
Summary: Training methods based on small-sided game (SSG) seem to promote physiological and tactical benefits for soccer players as they present characteristics more specific to the game. Thus, the main objective of the present study was to analyze the hormonal, biochemical, and autonomic parameters in an acute manner and the recovery dynamics (up to 72 h after) in a SSG. Thirteen professional female soccer players participated in the study (18.8 ± 0.8 years, body mass 59.4 ± 6.2 kg, and height 1.68 ± 0.05 m). During and after the SSG session (4 min × 4 min separated by 3 min of passive interval and 120 m2 coverage per player), autonomic modulation was analyzed in the time and frequency domains using heart rate variability, and blood samples (5 ml) were collected before (0 h) and after (10 min and 24, 48, 72 h) the SSG for biochemical and hormonal analysis. The SSG induced an increase effect for LF (low frequency) (92,52%; Very likely increase) and a decrease effect for HF (high frequency) values (-65,72%; Very likely decrease), after 10 min of recovery. The LF/HF increase after 10 min of recovery (386,21%; Very likely increase). The RMSSD (square root of the mean squared differences of the successive N-N intervals) and pNN50 (measure of the number of adjacent NN intervals which differ by more than 50 ms) values presented a decrease effect 10 min after SSG (61,38%; Very likely decrease and-90%; Very likely decrease). The CK (creatine kinase) values presented no changes 10 min after SSG. The LDH (lactate dehydrogenase) values presented an increase effect 10 min after the SSG (19,22%; Likely increase). Both testosterone and cortisol concentrations presented the same behavior after SSG, where no alterations were observed with after 10 min (<0,37%; Most likely trivial). The SSG promoted significant cardiovascular stress that was restored within the first 24 h of recovery. Parasympathetic parameters continued to increase while sympathetic parameters declined significantly during the 72 h of recovery. In addition, the reduced game did not alter biochemical or hormonal responses during the 72 h.


#5 Effective injury forecasting in soccer with GPS training data and machine learning
Reference: PLoS One. 2018 Jul 25;13(7):e0201264. doi: 10.1371/journal.pone.0201264. eCollection 2018.
Authors: Rossi A, Pappalardo L, Cintia P, Iaia FM, Fernàndez J, Medina D
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0201264&type=printable
Summary: Injuries have a great impact on professional soccer, due to their large influence on team performance and the considerable costs of rehabilitation for players. Existing studies in the literature provide just a preliminary understanding of which factors mostly affect injury risk, while an evaluation of the potential of statistical models in forecasting injuries is still missing. In this paper, we propose a multi-dimensional approach to injury forecasting in professional soccer that is based on GPS measurements and machine learning. By using GPS tracking technology, we collect data describing the training workload of players in a professional soccer club during a season. We then construct an injury forecaster and show that it is both accurate and interpretable by providing a set of case studies of interest to soccer practitioners. Our approach opens a novel perspective on injury prevention, providing a set of simple and practical rules for evaluating and interpreting the complex relations between injury risk and training performance in professional soccer.


#6 Mixed-methods pre-match cooling improves simulated soccer performance in the heat
Reference: Eur J Sport Sci. 2018 Jul 24:1-10. doi: 10.1080/17461391.2018.1498542. [Epub ahead of print]
Authors: Aldous JWF, Chrismas BCR, Akubat I, Stringer CA, Abt G, Taylor L
Summary: This investigation examined the effects of three pre-match and half-time cooling manoeuvres on physical performance and associated physiological and perceptual responses in eight University soccer players during a non-motorised treadmill based individualised soccer-specific simulation [intermittent soccer performance test (iSPT)] at 30°C. Four randomised experimental trials were completed; following 30-min (pre-match) and 15-min (half-time) cooling manoeuvres via (1) ice slurry ingestion (SLURRY); (2) ice-packs placed on the quadriceps and hamstrings (PACKS); (3) mixed-methods (MM; PACKS and SLURRY concurrently); or no-cooling (CON). In iSPT first half, a moderate increase in total (Mean ± Standard Deviation: 108 ± 57 m, qualitative inference: most likely, Cohen's d: 0.87, 90%CL: ±0.31), high-speed (56 ± 46 m, very likely, 0.68 ± 0.38) and variable run (15 ± 5 m, very likely, 0.81 ± 0.47) distance covered was reported in MM compared with CON. Additionally, pre-match reductions in thermal sensation (-1.0 ± 0.5, most likely, -0.91 ± 0.36), rectal (-0.6 ± 0.1°C, very likely, -0.86 ± 0.35) and skin temperature (-1.1 ± 0.3°C, very likely, -0.88 ± 0.42) continued throughout iSPT first half. Physical performance during iSPT first half was unaltered in SLURRY and PACKS compared to CON. Rectal temperature was moderately increased in SLURRY at 45-min (0.2 ± 0.1°C, very likely, 0.67 ± 0.36). Condition did not influence any measure in iSPT second half compared to CON. Only MM pre-match cooling augmented physical performance during iSPT first half, likely due to peripheral and central thermoregulatory factors favourably influencing first half iSPT performance. Further practical half-time cooling manoeuvres which enhance second half performance are still required.


#7 Association Between the Force-Velocity Profile and Performance Variables Obtained in Jumping and Sprinting in Elite Female Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jul 24:1-21. doi: 10.1123/ijspp.2018-0233. [Epub ahead of print]
Authors: Marcote-Pequeño R, García-Ramos A, Cuadrado-Peñafiel V, González-Hernández JM, Gómez MÁ, Jiménez-Reyes P
Summary: The aims of this study were (I) to quantify the magnitude of the association between the same variables of the force-velocity (FV) profile and the performance variables (unloaded squat jump [SJ] height and 20 m sprint time) obtained during the jumping and sprinting testing procedures, and (II) to determine which mechanical capacity (i.e., maximum force [F0], maximum velocity [V0] or maximum power [Pmax]) presents the highest association with the performance variables. The FV profile of 19 elite female soccer players (age: 23.4±3.8 years, height: 166.4±5.6 cm, body mass: 59.7±4.7 kg) was determined during the jumping and sprinting tasks. The F0, V0, FV slope, Pmax, and FV imbalance (difference respect to the optimal FV profile in jumping and the decrease in the ratio of horizontal force production in sprinting) were determined for each task. Very large correlations between both tasks were observed for Pmax (r= 0.75) and the performance variables (r= -0.73), moderate correlations for V0 (r= 0.49), while the F0 (r= -0.14), the FV slope (r= -0.09), and the FV imbalance (r= 0.07) were not significantly correlated between both tasks. The Pmax obtained during each specific task was the mechanical capacity most correlated with its performance variable (r= 0.84 in jumping and r= 0.99 in sprinting). The absence of significant correlations between some of the FV relationship parameters suggests that for an individualized training prescription based on the FV profile both jumping and sprinting testing procedures should be performed with elite female soccer players.


#8 Acute Avulsion of the Iliac Crest Apophysis in an Adolescent Indoor Soccer
Reference: J Belg Soc Radiol. 2015 Dec 30;99(2):20-24. doi: 10.5334/jbr-btr.876.
Author: Coulier B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6032651/pdf/jbsr-99-2-876.pdf
Summary: We report a typical case of acute avulsion of the anterior iliac crest apophysis diagnosed in an indoor football player. The injury occurred as a result of a sudden twist of the trunk while kicking. Plain radiographs made the diagnosis. Complementary CT with 3D reconstructions was preferred to ultrasound because of the very strong habitus - 110 kilograms for 1,73 meter - of the 15-year old adolescent. CT confirmed that occult chronic mechanical stress on the iliac apophysis had preceded the acute avulsion and also emphasized the crucial role of the tensor fascia lata in the mechanism of the injury. The patient was successfully treated conservatively. The case is presented with a short review of the literature.


#9 Can Squat Jump Performance Differentiate Starters vs. Nonstarters in Division I Female Soccer Players?
Reference: J Strength Cond Res. 2018 Aug;32(8):2348-2355. doi: 10.1519/JSC.0000000000002053.
Authors: Magrini MA, Colquhoun RJ, Sellers JH, Conchola EC, Hester GM, Thiele RM, Pope ZK, Smith DB
Summary: Although soccer is predominately an endurance sport, high velocity movements may be an important indicator of athletic success. The purpose of this investigation was to establish whether squat jumps (SJs) can differentiate starters from nonstarters with a female collegiate division I soccer team. Eighteen female division I soccer athletes were separated into 2 groups: 9 starters (age: 19.5 ± 1.0; mass = 64.8 ± 11.5 kg; height = 167.5 ± 7.7 cm; games started = 18.2 ± 4.7; and minutes played = 1633.8 ± 478.2 minutes) and 9 nonstarters (age: 19.4 ± 1.4 years; mass = 63.3 ± 4.2 kg; height = 164.7 ± 6.8 cm; games started 0.7 ± 1.3; and minutes played 158.2 ± 269.3 minutes). Each athlete performed 3 maximal SJs at a starting knee angle of 110° without arm swing. Each participant's SJ height, mean power (MP), peak power (PP), mean velocity (MV), and peak velocity (PV) were measured during each attempt by a linear position transducer. No statistically significant differences (p ≥ 0.05) in MP and PP between the starters and nonstarters were observed. However, starters performed significantly better than nonstarters in SJ height (p = 0.002), MV (p = 0.025), and PV (p = 0.015). In addition, SJ height was strongly correlated with MV (r = 0.628) and PV (r = 0.647). These findings suggest that SJ height, MV, and PV may be important variables for discriminating differences between starters and nonstarters in division I female soccer athletes and a strong indicator of explosive performance.


#10 Quantified Soccer Using Positional Data: A Case Study
Reference: Front Physiol. 2018 Jul 6;9:866. doi: 10.3389/fphys.2018.00866. eCollection 2018.
Authors: Pettersen SA, Johansen HD, Baptista IAM, Halvorsen P, Johansen D
Download link:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6043664/pdf/fphys-09-00866.pdf
Summary: Performance development in international soccer is undergoing a silent revolution fueled by the rapidly increasing availability of athlete quantification data and advanced analytics. Objective performance data from teams and individual players are increasingly being collected automatically during practices and more recently also in matches after FIFA's 2015 approval of wearables in electronic performance and tracking systems. Some clubs have even started collecting data from players outside of the sport arenas. Further algorithmic analysis of these data might provide vital insights for individual training personalization and injury prevention, and also provide a foundation for evidence-based decisions for team performance improvements. This paper presents our experiences from using a detailed radio-based wearable positioning data system in an elite soccer club. We demonstrate how such a system can detect and find anomalies, trends, and insights vital for individual athletic and soccer team performance development. As an example, during a normal microcycle (6 days) full backs only covered 26% of the sprint distance they covered in the next match. This indicates that practitioners must carefully consider to proximity size and physical work pattern in microcycles to better resemble match performance. We also compare and discuss the accuracy between radio waves and GPS in sampling tracking data. Finally, we present how we are extending the radio-based positional system with a novel soccer analytics annotation system, and a real-time video processing system using a video camera array. This provides a novel toolkit for modern forward-looking soccer coaches that we hope to integrate in future studies.


#11 Acute high-intensity exercise test in soccer athletes affects salivary biochemical markers
Reference: Free Radic Res. 2018 Jul 20:1-6. doi: 10.1080/10715762.2018.1481288. [Epub ahead of print]
Authors: Rodrigues de Araujo V, Lisboa P, Boaventura G, Caramez F, Pires L, Oliveira E, Moura E, Casimiro-Lopes G
Summary: Saliva has been reported as a potential biological fluid for biochemical monitoring. This study investigated salivary markers of exercise intensity, oral mucosal immunity, and redox homeostasis in soccer athletes subjected to an acute high-intensity interval exercise (HIIE) protocol characterised by a repeated sprint ability test. Thirty-two professional soccer athletes were recruited and saliva aliquots were collected at rest and immediately after HIIE protocol. When compared with pre-test values we observed that HIIE protocol induced moderate changes for total protein (p = .015; effect size (ES) = 0.51; smallest worthwhile change (SWC)factor = 5.7) and for cortisol levels (p < .0001; ES = 0.49; SWCfactor = 3.9). Lactate levels showed very large changes (p < .000; ES = 1.35; SWCfactor  = 10.8), while Ig-A alterations were considered unclear. Besides, transferrin changes were trivial and maintained its levels at rest and after HIIE below the proposed threshold of 0.5 mg/dL. Regarding redox homeostasis we observed unclear effects for TBARs, MDA, GSH, GSSG, CAT, and SOD while uric acid showed large decreases (p = .005; ES = 0.80; SWCfactor  = -5.4). HIIE protocol as a physical test conducted in soccer athletes increased salivary concentration of exercise intensity markers, such as lactate, total protein, and cortisol, but did not affect Ig-A levels. Redox homeostasis in saliva seems to be more related with uric acid levels as a possible key factor TBARs homeostasis.

Wed

17

Oct

2018

Hamburger SV Goalkeeper Warm-up

As the title proposes, the video below shows the pre-march warm-up of the HSV goalkeeper.

 

The footage was taken before the game against SV Darmstadt '98 (2nd German division).

Tue

16

Oct

2018

Latest research in football - week 31 - 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 Validity of the RSA-RANDOM Test for Young Soccer Players
Reference: Int J Sports Med. 2018 Jul 19. doi: 10.1055/a-0637-2094. [Epub ahead of print]
Authors: Martin V, Sanchez-Sanchez J, Ramírez-Campillo R, Nakamura FY, Gonzalo-Skok O
Summary: The present study aimed to examine the reliability, usefulness, responsiveness, age-related differences and construct validity of a novel decision-making RSA test (RSA-RANDOM test) in young soccer players. Twenty-five young male soccer players performed the RSA-RANDOM test on 2 occasions separated by 5-7 days to assess test-retest reliability and determine a priori usefulness. Furthermore, the same players executed the RSA-RANDOM test 4 times throughout the season to analyse responsiveness. Forty-five players (U-13 to U-17) were evaluated in such test to examine age-related differences. Finally, 9 players were used to determine the construct validity of the test. Reliability scores showed a high intraclass correlation coefficient (ICC=0.88 to 0.90) and low coefficient of variation (CV=1.0-1.2%). The responsiveness of the RSA-RANDOM test was good, as the typical short- (1.2-1.9%), mid- (1.4-2.4%) and long-term (2.3-3.2%) changes in RSA-RANDOM performance were higher than the CV. Age-related differences analysis showed better RSA-RANDOM performance as age increased in young soccer players. Low (r=-0.50) to moderate (r=-0.75) relationships were found between the RSA-RANDOM test variables (RSA best and mean times) with high-intensity and total distance covered, respectively. A novel decision-making RSA test (RSA-RANDOM) has shown to be reliable and valid in young soccer players.


#2 Prior Knowledge of the Grading Criteria Increases Functional Movement Screen Scores in Youth Soccer Players
Reference: J Strength Cond Res. 2018 Jul 17. doi: 10.1519/JSC.0000000000002724. [Epub ahead of print]
Authors: Bryson A, Arthur R, Easton C
Summary: We sought to determine whether familiarity with the grading criteria of the Functional Movement Screen (FMS) impacted the outcome score in elite youth soccer players. Thirty-two trained male youth soccer players (aged 17 ± 1 years) participated in a randomized control trial. Participants were randomly assigned to evenly sized control and experimental groups, who each completed the FMS on 2 separate occasions. Participants in the experimental group were provided the FMS grading criteria between their first and second screens. Time-synchronized video footage was used to grade the FMS using standardized criteria. Structured interviews were then conducted with selected participants (n = 4) in the experimental group to establish athletes' perception of the FMS. The experimental group had a large increase in overall FMS score from the first to the second screen in comparison with the control group (Δ2.0 ± 1.0, p < 0.001, d = 1.3). Scores for the deep squat, hurdle step, and rotary stability tests components of the FMS all increased in the experimental group in comparison with the control group (p < 0.05). Thematic analysis of the interview data suggested that the participants in the experimental group improved their understanding between good and poor technique during the FMS. These findings support the notion that FMS scores are influenced by awareness of the grading criteria. As a consequence, the FMS may not be suitable for objectively predicting injury in youth soccer players.


#3 Articular and peri-articular hip lesions in soccer players. The importance of imaging in deciding which lesions will need surgery and which can be treated conservatively?
Reference: Eur J Radiol. 2018 Aug;105:227-238. doi: 10.1016/j.ejrad.2018.06.012. Epub 2018 Jun 20.
Authors: Di Pietto F, Chianca V, Zappia M, Romano S
Summary: Soccer is one of the most popular sports worldwide engaging millions of participants each year. During play, injuries occur rather frequently and most of them involve the hip joint and the surrounding structure. In professional athletes, injuries are often complex scenarios and in the case of misdiagnosis, patients' return to play is delayed or it may progress to a more serious injury with consequent damage for their career and for the soccer team. The most frequent articular pathologies are Femoro-acetabular impingement and labral tears. Stress fracture, avulsion, ischiofemoral impingement, subspine impingement, athletic pubalgia, muscle injuries and Morel-Levallèe lesion are the most frequent hip peri-articular pathologies whereas snapping hip may be both intra- or extra-articular pathology. With an increasing number of football players, the radiologist plays a crucial role in the detection and characterization of the extent of the injuries. This article reviews the current imaging concepts frequently seen in injuries around the hips of professional football players focusing in particular on the most suitable therapeutic approaches, whether surgical or conservative.


#4 Relative Age Effect, Biological Maturation, and Coaches' Efficacy Expectations in Young Male Soccer Players
Reference: Res Q Exerc Sport. 2018 Jul 17:1-7. doi: 10.1080/02701367.2018.1486003. [Epub ahead of print]
Authors: Peña-González I, Fernández-Fernández J, Moya-Ramón M, Cervelló E
Summary: The talent identification and selection process in young male soccer players is mainly focused on anthropometrics and physical performance, but social factors are also considered in this process. The purpose of this study was to test the existence of the relative age effect and its possible influence on anthropometrics and physical performance and to analyze coaches' efficacy expectations. Data for 564 young male soccer players (Mage = 13.7 ± 1.5 years; Mweight = 53.7 ± 11.6 kg; Mheight = 160.2 ± 11.6 cm) included their birth quartile, maturity status, anthropometrics, a physical test battery, and coaches' efficacy expectations. Early-born players were overrepresented (p < .05). Early-born players were not statistically taller, heavier, or better at physical performance (p > .05) when maturation and chronological age were controlled as confounding factors. However, coaches expected more from early-born players (p < .05), and the inferential analysis showed likely to very likely worthwhile differences between the coaches' expectations for players born in the first quartile of the year and those born in the fourth quartile of the year. Anthropometrical and physical performance variables were not affected by birth quartile, and coaches' efficacy expectations were related to the relative age effect.


#5 Effect of Dehydration on Passing Decision Making in Soccer Athletes
Reference: Res Q Exerc Sport. 2018 Jul 17:1-8. doi: 10.1080/02701367.2018.1488026. [Epub ahead of print]
Authors: Fortes LS, Nascimento-Júnior JRA, Mortatti AL, Lima-Júnior DRAA, Ferreira MEC
Summary: It seems that dehydration may impair decision-making performance in athletes. This study aimed to investigate the influence of dehydration on passing decision-making performance in soccer players. Participants were 40 male soccer players (Mage = 22.3 ± 2.3 years) who agreed to participate in the study and were randomly assigned to the following conditions: control (CON), dehydration (DEH), and euhydration (EUH). The players played in 2 games of 90 min in duration (2 45-min halves) followed by 2 15-min halves (overtime) with and without proper hydration. The Game Performance Assessment Instrument (GPAI) was considered for the analysis of passing decision making. The GPAI analysis indicated effective reduction in the decision-making index in the DEH condition compared with the EUH and CON conditions, F(2, 38) = 31.4, p < .05, ES = 0.8. In conclusion, dehydration may be considered a mediating factor in the passing decision-making performance of male soccer athletes.


#6 Altered landing mechanics are shown by male youth soccer players at different stages of maturation
Reference: Phys Ther Sport. 2018 Jul 7;33:48-53. doi: 10.1016/j.ptsp.2018.07.001. [Epub ahead of print]
Authors: Read PJ, Oliver JL, Myer GD, De Ste Croix MBA, Belshaw A, Lloyd RS
Summary: Examine the effects of maturation on single leg jumping performance in elite male youth soccer players. 347 male youth players classified as either pre, circa or post-peak height velocity (PHV) participated in this study. Single leg countermovement jump (SLCMJ) height, peak vertical landing forces (pVGRF), knee valgus and trunk side flexion were used as outcome measures. Vertical jump height and absolute pVGRF increased with each stage of maturation (p < 0.001; d = 0.85-2.35). Relative to body weight, significantly higher landing forces were recorded on the left leg in circa versus post-PHV players (p < 0.05; d = -0.40). Knee valgus reduced with maturation but the only notable between-group differences were shown in post-PHV players (p < 0.05; d = 0.67); however, greater ipsilateral lateral trunk flexion angles was also present and these differences were significantly increased relative to circa-PHV players (p < 0.05; d = 0.85). Periods of rapid growth are associated with landing kinetics which may heighten injury risk. While reductions in knee valgus were displayed with maturation; a compensatory strategy of greater trunk lateral flexion was evident in post-PHV players and this may increase the risk of injury.


#7 Alternative assessment of knee joint muscle balance of soccer players through total work-based hamstring: quadriceps ratios
Reference: Eur J Sport Sci. 2018 Jul 14:1-7. doi: 10.1080/17461391.2018.1495271. [Epub ahead of print]
Authors: Minozzo F, Lopez P, Machado CLF, Wilhelm EN, Grazioli R, Pinto RS
Summary: Isokinetic hamstring-to-quadriceps (H:Q) ratios are frequently used to assess knee muscle strength imbalances and risk of injuries/re-injuries. The use of peak torque (PT) or total work (TW) to estimate joint stability may lead to different results because of the differences between these two neuromuscular variables. Thus, the current study aimed to compare the conventional and functional H:Q ratios calculated by PT and TW. Ninety-three male professional soccer players from Brazilian first division teams performed isokinetic concentric and eccentric contractions of the quadriceps and the hamstrings at 60°/s. Muscle strength balance was calculated using the conventional torque ratio (CTR) and conventional work ratio (CWR), functional torque ratio (FTR) and functional work ratio (FWR) were highly and moderately correlated between them (r = 0.83 and r = 0.73, respectively). The Wilcoxon statistical test revealed significant differences between CTR and CWR, as well as FTR and FWR (p < 0.05). T-test demonstrated significant differences in mean CTR-CWR and FTR-FWR, whereas Bland-Altman plots showed non-consistent bias. In addition, the chi-square test demonstrated significant differences between players below the conventional reference values and functional reference values (p < 0.001). In conclusion, TW ratios seem to provide distinct and additional information regarding the H:Q strength balance in professional soccer players. Moreover, taking into account that TW captures torque information throughout the entire range of motion, it is possible that TW ratios represent a more comprehensive assessment of muscle strength imbalance.


#8 Injuries in girls' soccer and basketball: a comparison of high schools with and without athletic trainers
Reference: Inj Epidemiol. 2018 Jul 16;5(1):29. doi: 10.1186/s40621-018-0159-6.
Authors: Pierpoint LA, LaBella CR, Collins CL, Fields SK, Dawn Comstock R
Download link: https://link.springer.com/content/pdf/10.1186%2Fs40621-018-0159-6.pdf
Summary: Sports injuries impose physical and economic burdens on high school athletes, yet only 37% of high schools have access to a fulltime certified athletic trainer (AT). Although intuitively there are multiple benefits of AT coverage, research demonstrating the measurable effect of AT coverage on rates and patterns of injury is limited. Our objective was to investigate the epidemiology of girls' basketball and soccer injuries in high schools with and without an AT. We compared data captured by two similar sports injury surveillance systems during the 2006/07-2008/09 academic years. High School Reporting Information Online (RIO) included a national sample of schools with ATs, and the Sports Injury Surveillance System (SISS) included a sample of Chicago public high schools without ATs. Overall injury rates were higher in schools without ATs than schools with ATs in girls' soccer (RR: 1.73, 95% CI: 1.51-2.00) and basketball (RR: 1.22, 95% CI: 1.03-1.45). Recurrent injury rates were even higher in schools without ATs compared to schools with ATs in soccer (RR: 6.00 95% CI: 4.54-7.91) and basketball (RR: 2.99, 95% CI: 2.12-4.14). Conversely, concussion rates were higher in schools with ATs than schools without ATs in soccer (RR: 8.05, 95% CI: 2.00-32.51) and basketball (RR: 4.50, 95% CI: 1.43-14.16). Other injury patterns were similar between the two samples. This study demonstrated the effectiveness of AT coverage of high school girls' soccer and basketball, both in reducing overall and recurrent injury rates and in identifying athletes with concussions. Future studies should evaluate the effect of ATs on other high school sports and on youth sports to determine if these findings are generalizable across sports and age groups.


#9 Laterality Influences Agility Performance in Elite Soccer Players
Reference: Front Physiol. 2018 Jun 29;9:807. doi: 10.3389/fphys.2018.00807. eCollection 2018.
Authors: Zouhal H, Abderrahman AB, Dupont G, Truptin P, Le Bris R, Le Postec E, Coppalle S, Ravé G, Brughelli M, Bideau B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033993/pdf/fphys-09-00807.pdf
Summary: Laterality (i.e., handedness, footedness, and eyedness) could have an impact on highly repeated soccer movements and thus, could influence performance. The purpose of this study was to examine the laterality of high-level football players and its effects on 180° left and right U-turn movements. Handedness, footedness, and eyedness were determined in 72 elite football players (EFP, 18.2 ± 2.2 years) from the Stade Rennais Football Club (French League 1) and 9 amateur football players (AFP, 19.6 ± 2.1 years). Players performed a visual-motor task on a synthetic pitch consisting of 180° left and right rotations as fast as possible in response to a visual light on a computer screen. Movement times and reactive times for each left and right rotation were recorded with an accelerometer and video display. Laterality profiles showed a majority (χ2 = 9.42, df = 2, p = 0.031) of crossed formulas (i.e., dominant leg or hand is controlateral to the dominant eye) for EFP (53 ± 7%) and a majority of non-crossed formulas for AFP (63 ± 9%). Reaction times were significantly faster (p = 0.028, effect size = 0.148, trivial) in EFP right-eyed (568.2 ± 55.5 ms) than in AFP (610.0 ± 43.9 ms). For the left rotation and for right-footed players, movement times were significantly different (p = 0.043, effect size = 0.413, small) between EFP (1.15 ± 0.07 s) and AFP (1.17 ± 0.07 s). A significant difference (p < 0.033) was observed between footedness and rotation movement times in the EFP. Our results showed that laterality profiles differed between EFP and AFP. Hence, in EFP, reaction times depended on the side of the visual stimulus. Moreover, leg laterality of EFP influenced 180° left or right rotation speed. Our results indicate the importance of determining laterality in soccer players and identifying deficits in performance when turning.


#10 Mediating Effects of Parents' Coping Strategies on the Relationship Between Parents' Emotional Intelligence and Sideline Verbal Behaviors in Youth Soccer
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):153-162. doi: 10.1123/jsep.2017-0318. Epub 2018 Jul 14.
Authors: Teques P, Calmeiro L, Martins H, Duarte D, Holt NL
Summary: The overall purpose of this study was to examine the mediating effects of parents' coping strategies on the relationship between parents' emotional intelligence and sideline verbal behaviors during their children's soccer games. Participants were 232 parents (120 mothers and 110 fathers) of youth soccer players age 9-13 years. Observations in situ were carried out at 30 soccer games during a soccer tournament. At the end of the game, parents were approached and asked to complete the Emotional Intelligence Scale and the Brief COPE scale. Structural-equation-modeling analyses revealed that adaptive and maladaptive coping mediated the relationship between regulation of emotion and parents' praise/encouragement, and negative and derogatory comments during the game. In addition, game result moderated the relationships between emotional intelligence, coping strategies, and parent behaviors. Emotional regulation and adaptive coping may promote desirable parent sideline behaviors and reduce undesirable behaviors.


#11 Goalkeepers' Reputations Bias Shot Placement in Soccer Penalties
Reference: J Sport Exerc Psychol. 2018 Jun 1;40(3):128-134. doi: 10.1123/jsep.2017-0358. Epub 2018 Jul 14.
Authors: Müller F, Best JF, Cañal-Bruland R
Summary: Research has demonstrated that in addition to minor changes in goalkeepers' position or height, goalkeeper reputation seems to influence penalty takers' shot placement. However, this evidence is based on correlative designs. Here, the authors experimentally manipulated both height and reputation to examine their causal impact on actual shot placement. Penalty takers performed kicks facing goalkeepers of different height (tall vs. short) and reputation (high vs. low) projected on a life-size screen. Results showed that tall goalkeepers were judged as taller than short goalkeepers. Likewise, high-reputation goalkeepers were judged as taller than low-reputation goalkeepers. An important finding was that reputation also influenced shot placement. When facing high-reputation goalkeepers, penalty takers aimed farther away from the goalkeeper and missed the goal more often. It follows that reputation affects both height estimates of goalkeepers and, most important, shot placement. Consequently, manipulating perceived reputation of goalkeepers provides an avenue for sport professionals to subtly influence shot placement of penalty takers.


#12 Physical growth in young Chilean football players: Proposal of percentiles based on chronological and biological age
Reference: Arch Argent Pediatr. 2018 Aug 1;116(4):e508-e514. doi: 10.5546/aap.2018.eng.e508. [Article in English, Spanish; Abstract available in Spanish from the publisher]
Authors: Carrasco López S, Gómez-Campos R, Méndez Cornejo J, Morales L, Urra-Albornoz C, Cossio-Bolañosb M
Download link: http://www.sap.org.ar/docs/publicaciones/archivosarg/2018/v116n4a10e.pdf
Summary: The aim were to a) To compare physical growth to the 2012 American standard from the Centers for Disease Control and Prevention (CDC); b) to analyze physical growth by chronological and biological age; c) to propose physical growth charts based on chronological and biological age. Methodology. A descriptive (cross-sectional) study was conducted in young Chilean football players based on weight, standing height, and sitting height. These were compared to the CDC- 2012 standard. Percentiles were developed using the LMS method. A total of 642 young Chilean football players aged 13.0-18.9 years were studied. Their body weight was lower than that of the CDC standard from 13.0 to 18.9 years old (p < 0.05), whereas their height showed no significant differences in the initial age categories (13.0- 13.9 and 14.0-14.9 years). Differences started to be observed as of 15.0 years old up to 18.9 years old (p < 0.05). In relation to chronological age, weight explained 31%; standing height, 16%; and sitting height, 0.09%, whereas in relation to biological age, weight explained 51%; standing height, 40%; and sitting height, 54%. Percentiles were developed based on chronological and biological age. These youth showed different physical growth patterns compared to the CDC-2012 standard. Their assessment reflects better explanatory percentages for biological age than for chronological age. The proposed percentiles may be an alternative to keep track of the physical growth patterns of young football players in sports settings in the short, medium, and long term.


#13 Mechanisms of acute adductor longus injuries in male football players: a systematic visual video analysis
Reference: Br J Sports Med. 2018 Jul 13. pii: bjsports-2018-099246. doi: 10.1136/bjsports-2018-099246. [Epub ahead of print]
Authors: Serner A, Mosler AB, Tol JL, Bahr R, Weir A
Summary: Change of direction and kicking have been described as the main actions resulting in adductor longus injury. Video descriptions of inciting events are lacking. The purpose was to perform a standardised visual video analysis of a series of acute adductor longus injuries in football. Video footage was reviewed by players, and assessed independently by five sports medicine professionals. Inciting events were described and categorised using standardised scoring, including playing situation, player/opponent behaviour, movement and body positions. Videos of acute adductor longus injuries in 17 professional male football players were analysed. Most injuries occurred in non-contact situations (71%), following a quick reaction to a change in play (53%). Injury actions were: change of direction (35%), kicking (29%), reaching (24%) and jumping (12%). Change of direction and reaching injuries were categorised as closed chain movements (59%), characterised by hip extension and abduction with external rotation. Kicking and jumping injuries were categorised as open chain (41%), characterised by a change from hip extension to hip flexion, and hip abduction to adduction, with external rotation. Acute adductor longus injuries in football occur in a variety of situations. Player actions can be categorised into closed (change of direction and reaching) and open (kicking and jumping) chain movements involving triplanar hip motion. A rapid muscle activation during a rapid muscle lengthening appears to be the fundamental injury mechanism for acute adductor longus injuries.

Mon

08

Oct

2018

Latest research in football - week 30 - 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 competence-supportive and competence-thwarting role of athlete leaders: An experimental test in a soccer context
Reference: PLoS One. 2018 Jul 11;13(7):e0200480. doi: 10.1371/journal.pone.0200480. eCollection 2018.
Authors: Fransen K, Vansteenkiste M, Vande Broek G, Boen F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6040764/pdf/pone.0200480.pdf
Summary: The aim of this experiment was to study the growth-promoting and adverse impact of athlete leaders' competence-supportive and-thwarting behavior on the motivation and performance of team members. Male soccer players (N = 144; MAge = 14.2) were allocated to ad-hoc teams of five soccer players. These teams participated in two sessions, being randomly exposed to an athlete leader who acted either competence-supportive, competence-thwarting, or neutral during the second session. When the athlete leader was competence-supportive (versus competence-thwarting), his teammates' intrinsic motivation and performance increased (versus decreased) compared with the control condition. The leader's impact on intrinsic motivation was fully accounted for by team members' competence satisfaction. These findings recommend coaches to invest in the competence-supportive power of their athlete leaders to establish an optimally motivating and performance-enhancing team environment.


#2 Match Running Performance of Elite Soccer Players: V[Combining Dot Above]O2max and Players Position Influences
Reference: J Strength Cond Res. 2018 Jul 9. doi: 10.1519/JSC.0000000000002646. [Epub ahead of print]
Author: Metaxas TI
Summary: The aims of this study were (a) to assess the relationship between laboratory-measured VO2max with total distance covered in a soccer match, (b) to assess the relationship between laboratory-measured VO2max with the distance covered at a different running intensity in a soccer match, (c) to quantify different intensity running in various playing positions, and (d) to determine the differences of running performance between halves. Analyzed match running performance of the Greek elite (n = 14) soccer players using a global positioning system within the second division professional league. No correlation was found between VO2max and match running performance at any velocity. The players covered greater distances in the first half at all speed levels except walking. In the first half, they covered a greater distance than in the second half (1,533 vs. 1,297 m, p < 0.001; 879 vs. 708 m, p < 0.001; 433 vs. 359 m, p < 001; 185 vs. 152 m, p < 0.01; 81.4 vs. 65.5 m, p < 0.001) when jogging, running, high-intensity running, fast running, sprint and total, respectively. Wide players covered greater distances at fast running (p < 0.001) and sprint zone than the players who played at the axon of the field (348 vs. 297 and 186 vs. 113 m, respectively). In addition, midfielders covered a greater distance at high-intensity running zone and at fast running zone than the defenders and forwards (1,768 vs. 1,372 m, p < 0.01 and 1,768 vs. 1,361 m, p < 0.01; 686 vs. 878 m, p < 0.01 and 709 vs. 878 m, p < 0.05, respectively). The results demonstrate that match running performance and the distance covered depends on the tactical role of each player in the team. These data provide valuable information for coaches regarding the running profile of the Greek elite soccer players that could be used to design a more effective training program.


#3 Relationships Between Eccentric and Concentric Knee Strength Capacities and Maximal Linear Deceleration Ability in Male Academy Soccer Players
Reference: J Strength Cond Res. 2018 Jul 9. doi: 10.1519/JSC.0000000000002739. [Epub ahead of print]
Authors: Harper DJ, Jordan AR, Kiely J
Summary: The purpose of this study was to investigate the relationships between maximal linear deceleration ability, and knee flexor (KF) and knee extensor (KE) strength. Fourteen male academy soccer players completed a 30-m linear sprint, a maximal linear deceleration test, and eccentric and concentric KF and KE contractions in both dominant leg (DL) and nondominant leg (NDL) at slower (60°·s) and faster (180°·s) angular velocities on an isokinetic dynamometer. Maximal linear deceleration ability was evaluated using distance-to-stop (DEC-DTS) and time-to-stop (DEC-TTS), with isokinetic peak torque representing KF and KE strength capacity. Relationships were established using Pearson's correlation coefficients (r) with magnitude-based inferences used to describe the uncertainty in the correlation. Both concentric KE and KF strength at 180°·s in the NDL had the highest correlations with deceleration ability (r = -0.76 and r = -0.78, respectively). In the DL, concentric KE and KF strength at 180°·s also had very likely large correlations with deceleration ability (r = -0.54 and -0.55, respectively). All correlations between eccentric KF strength and deceleration ability were unclear. At 180°·s, correlations between eccentric KE strength and deceleration ability were also unclear; however, at 60°·s, both DL (r = -0.63 to -0.64) and NDL (r = -0.54 to -0.55) had very likely large correlations with deceleration ability. These findings provide novel insights into the unilateral KF and KE strength capacities underpinning the ability to decelerate rapidly from high-sprint velocities.


#4 Creative decision making and visual search behavior in skilled soccer players
Reference: PLoS One. 2018 Jul 10;13(7):e0199381. doi: 10.1371/journal.pone.0199381. eCollection 2018.
Authors: Roca A, Ford PR, Memmert D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039007/pdf/pone.0199381.pdf
Summary: The ability to produce creative solutions is a key part of expert performance. The aim of this study was to identify the visual search behaviors that underpin superior creative performance of skilled soccer players during simulated 11-a-side match play. Players (N = 44) were required to interact with a representative life-size video-based simulation of attacking situations whilst in possession of the ball. Clips were occluded at a key moment and they were required to play the ball in response to each situation presented. Moreover, they were required to name other additional actions they could execute for each situation. Creative performance on the task was measured using the three criteria of originality, flexibility, and fluency of decisions. Visual search behaviors were examined using a portable eye-movement registration system. Players were classified as most- (n = 11) or least-creative (n = 11) based on their performance on the representative task. The most-creative players produced more appropriate, original, flexible, and fluid decisions compared to least-creative players. The creativity-based differences in judgment were underpinned by differences in visual search strategy. Most-creative players employed a broader attentional focus including more fixations of shorter duration and towards more informative locations of the display compared with least-creative players. Moreover, most-creative players detected teammates in threatening positions earlier in the attacking play. Creative performance is underpinned by different underlying visual processes when compared to less-creative performance, which appears to be crucial in facilitating more creative solutions.


#5 Association between trunk pain and lower extremity pain among youth soccer players: a cross-sectional study
Reference: BMC Sports Sci Med Rehabil. 2018 Jul 6;10:13. doi: 10.1186/s13102-018-0102-8. eCollection 2018.
Authors: Sogi Y, Hagiwara Y, Yabe Y, Sekiguchi T, Momma H, Tsuchiya M, Kuroki K, Kanazawa K, Koide M, Itaya N, Yoshida S, Yano T, Itoi E, Nagatomi R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035452/pdf/13102_2018_Article_102.pdf
Summary: Soccer is a high-intensity sport with a high injury rate. Among youth soccer players, lower extremity pain is a major problem that could be associated with trunk function. This study investigated the association between lower extremity pain and trunk pain among youth soccer players. A cross-sectional study involving youth soccer players participating in the Miyagi Amateur Sports Association was conducted using a self-reported questionnaire. A multiple logistic regression analysis was used to examine the association between trunk pain and lower extremity pain. Covariates were sex, age, body mass index, height increase, number of days of training per week, practice time per day on weekdays or weekends, competition levels, frequency of participation in games, and previous injuries. The final study population comprised 1139 youth soccer players (age, 6-15 years; male, 94.2%). Lower extremity pain with concomitant trunk pain occurred in 61.8% (42/68). Trunk pain was significantly associated with lower extremity pain (adjusted odds ratio [OR], 6.82; 95% confidence interval [CI], 3.99-11.67). Back pain and hip pain were significantly associated with knee pain (adjusted OR [95% CI]: 7.63 [3.70-15.76] and 3.84 [1.89-7.83], respectively), ankle pain (adjusted OR [95% CI]: 9.03 [4.42-18.44] and 5.43 [2.77-10.62], respectively), and both knee and ankle pain (adjusted OR [95% CI]: 13.67 [6.01-31.09] and 5.98 [2.56-13.97], respectively). Trunk pain was associated with lower extremity pain among youth soccer players. Clinicians and coaches should consider comorbidities while treating those players.


#6 Influence of Situational Variables, Team Formation, and Playing Position on Match Running Performance and Social Network Analysis in Brazilian Professional Soccer Players
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002725. [Epub ahead of print]
Authors: Aquino R, Carling C, Palucci Vieira LH, Martins G, Jabor G, Machado J, Santiago P, Garganta J, Puggina E
Summary: The purpose of this study was to investigate the independent and interactive effects of situational variables, opposition team formation, and playing position on running performance and network analysis in Brazilian professional soccer players (n = 22). Global positioning system technology was used to determine total distance covered, mean speed, maximum running speed, and distance covered in 6 speed ranges. Social network analysis was used to assess interpersonal coordination (team interactions characterized as successful passes [n = 3,033] between teammates). Observations of match running performance (n = 129) and network analysis (n = 108) were obtained. The main results were: (a) no interactive effects between team formation and playing position were observed for running and network variables (unclear to possibly); (b) matches played at home or against "weaker" opponents presented greater running demands and individual/global metrics of network analysis (likely to almost certain); (c) match outcome demonstrated influence only for running performance; matches in which the reference team won resulted in higher values than in matches lost; (d) when the reference team competed in 1-4-4-2 formation, this resulted in greater running demands than 1-4-2-3-1 formation (likely to almost certain); (e) reduced values of running performance variables were reported in central defenders compared with other positions. Central/external midfielders reported greater closeness/betweenness centrality, outdegree, and eigenvector compared with central/external defenders and forwards (likely to almost certain). The results from this study provide practical information to potentially impact on physical, tactical, and technical training.


#7 Isometric Midthigh Pull Characteristics in Elite Youth Male Soccer Players: Comparisons by Age and Maturity Offset
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002673. [Epub ahead of print]
Authors: Morris RO, Jones B, Myers T, Lake J, Emmonds S, Clarke ND, Singleton D, Ellis M, Till K
Summary: The purpose of this study was to (a) provide comparative isometric midthigh pull (IMTP) force-time characteristics for elite youth soccer players and (b) determine the effect of age and maturation on IMTP force-time characteristics. Elite male youth soccer players (U12 n = 51; U13 n = 54; U14 n = 56; U15 n = 45; U16 n = 39; and U18 n = 48) across 3 maturity offset groups (Pre n = 117; circa n = 84; and Post-peak height velocity n = 92) performed 2 maximal IMTP trials on a portable force platform (1,000 Hz). Absolute and relative values for peak force (PF) and impulse over 100 and 300 ms were analyzed. A full Bayesian regression model was used to provide probable differences similar to that of a frequentist p value. Advanced age and maturation resulted in superior IMTP force-time characteristics. Peak force demonstrated high probabilities of a difference between all consecutive age groups (p > 0.95). For absolute and relative impulse (100 and 300 ms), only 2 consecutive age groups (U14-15's and U16-18's) demonstrated high probabilities of a difference (p > 0.95) with large effects (d = 0.59-0.93). There were high probable differences between all maturity offset groups for PF and impulse with medium to large effects (d = 0.56-3.80). These were also reduced when expressed relative to body mass (relative PF and relative impulse). This study provides comparative IMTP force-time characteristics of elite male youth soccer players. Practitioners should consider individual maturation status when comparing players given the impact this has on force expression.


#8 Running Intensities in Elite Youth Soccer by Age and Position
Reference: J Strength Cond Res. 2018 Jul 4. doi: 10.1519/JSC.0000000000002728. [Epub ahead of print]
Authors: Duthie GM, Thornton HR, Delaney JA, Connolly DR, Serpiello FR
Summary: The purpose of this investigation was to examine differences between the peak running speed, acceleration, and metabolic power of elite youth soccer across a range of age levels by position. Ninety-six elite junior soccer players were assessed between 2015 and 2017. Ninety-six elite junior soccer players (at time of match: age, 15.8 ± 0.9 years; body mass, 69.1 ± 8.0 kg) were assessed during 61 games within the 2015, 2016, and 2017 season, for a total of 441 individual match observations (4.8 ± 3.3 matches per player, range 1-13). Participants were classified by age group: under 15 (U15, n = 121, 14.7 ± 0.3 years), under 16 (U16, n = 176, 15.8 ± 0.3 years), or under 17 (U17, n = 144, 16.7 ± 0.4 years), and according to their playing position: Attacker (ATT), Defender (DEF), Mid-Fielder (MID), or Wide (WIDE). Participants wore global positioning system units during each match, where speed (m·min), acceleration/deceleration (m·s), and metabolic power (Pmet) were established. A 1- to 10-minute moving average was applied to establish the intercept (c) and slope (n) of running intensity variables as a power law y = cx relationship. Linear mixed models were used to examine differences in the intercept and slope between age group and player position. There were no substantial differences in peak (intercept) or decline (slope) in running intensity between playing levels. Several differences were observed in the peak running speeds (m·min), particularly peak running speeds of ATT and DEF being substantially lower than the MID. Despite variability between positions, we suggest that the magnitude of these differences would not warrant the prescription of different running intensities across positions at the elite junior level. These findings describe the peak running intensities of elite junior soccer, useful in the monitoring and prescription of training to ensure that players are prepared for the most demanding periods of competition.


#9 Influence of opponent standard on activity profile and fatigue development during preseasonal friendly soccer matches: a team study
Reference: Res Sports Med. 2018 Jul 9:1-12. doi: 10.1080/15438627.2018.1492400. [Epub ahead of print]
Authors: Rago V, Silva J, Mohr M, Randers M, Barreira D, Krustrup P, Rebelo A
Summary: We examined the influence of competitive standard of the opponent on activity profile and fatigue during preseason friendly soccer matches. Time motion analysis was performed in a male professional soccer team (N = 14) during six friendly games played against professional, semi-professional and amateur-level opponents (PL, SPL and AL). The reference team covered higher acceleration distance, acceleration and deceleration > 2 m· s-2 distance against PL than AL (ES = 0.77 to 0.91). Acceleration and deceleration distance > 2 m· s-2 was also higher (ES = 0.66 to 0.84) against SPL than AL. Greater decreases in total distance, distance> 16 km· h-1 and > 22 km· h-1, total acceleration and deceleration, acceleration and deceleration distance > 2 m· s-2 (ES = 0.84 to 2.20) were also observed during PL compared to AL opponent. Playing against a stronger opponent seems to be more physically demanding, with special emphasis on events related with change of velocity (accelerations and decelerations). Declines in physical performance appear more evident against a higher opponent.


#10 Monitoring collegiate soccer players during a congested match schedule: Heart rate variability versus subjective wellness measures
Reference: Physiol Behav. 2018 Jul 5;194:527-531. doi: 10.1016/j.physbeh.2018.07.001. [Epub ahead of print]
Authors: Rabbani A, Baseri MK, Reisi J, Clemente FM, Kargarfard M
Summary: The aims of this study were a) to examine within-group changes of wellness and heart rate variability measures and b) to compare their sensitivity to a congested match schedule in collegiate soccer players (n = 8). Wellness (Hooper index and its subsets) and heart rate variability (Ln rMSSD, SDNN) measures were assessed after selected low-load (training sessions) and high-load (a congested match schedule) phases. Session rating of perceived exertion (sRPE) was computed for training and match sessions. A very likely large difference in accumulated sRPE was observed between low-load and high-load phases (+148.4%, 90% confidence interval CI [87.3; 229.5%]); effect size, ES, 2.16 [1.49; 2.82]. While the Hooper index showed an almost certainly moderate increase (+49.8%, [33.9; 67.5%]), ES, 1.05 [0.76; 1.34], heart rate variability measures (i.e., Ln rMSSD and SDNN) only changed with a possible trivial effect (range -2.1; 8.2%, [-7.1; 16.7%]), ES, -0.15; 0.15 [-0.50; 0.44]. The Hooper index showed a moderately higher sensitivity than Ln rMSSD to a congested match schedule (34.7%, [26.9; 41.6%], ES, 0.81 [0.60; 1.03]). Relationships between changes in the Hooper index and some of its subsets (∆Hooper index, ∆sleep, and ∆fatigue), with changes in mean sRPE (∆sRPE) were very large (range r = 0.72; 0.89). However, small associations were observed between changes in heart rate variability (∆Ln rMSSD, and ∆SDNN) and ∆sRPE (range r = -0.21; 0.10). This study suggests the use of subjective wellness indices, instead of heart rate variability measures, to monitor collegiate soccer players during congested match schedules.

Mon

08

Oct

2018

Latest research in football - week 29 - 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 Influence of intense training cycle and psychometric status on technical and physiological aspects performed during the small-sided games in soccer players
Reference: Res Sports Med. 2018 Jul 3:1-12. doi: 10.1080/15438627.2018.1492398. [Epub ahead of print]
Authors: Selmi O, Marzouki H, Ouergui I, BenKhalifa W, Bouassida A
Summary: The study investigated the effect of intense training cycle (IT) of early season preparation period (SPP) and psychological status on technical and physiological parameters during small-sided games (SSG) and the relationships between these variables. Sixteen professional soccer players participated in the study (mean±SD: age: 24.5±4.1). Training load (TL), Total quality recovery (TQR) and well-being indices were performed daily. TL increased progressively (%TL=31.56 [AU]). Physiological variables did not change after IT and were not influenced by well-being indices and TQR. Technical aspects were negatively altered after IT (p<0.05). TL was significantly correlated with successful passes (r=-0.57, p=0.02), interceptions (r=-0.83, p<0.001) and lost balls (r=0.73, p=0.002). Well-being and TQR were related to successful passes, interceptions and lost passes [(r=-0.55, p=0.03; r=-0.75, p=0.001; r=-0.69, p=0.004); (r=0.54, p=0.03; r=-0.76, p=0.001; r=-0.69, p=0.004), respectively]. TL, Well-being indices and TQR represent a useful strategy for coaches to control technical aspects in soccer players during SPP.


#2 Effects of traditional balance and slackline training on physical performance and perceived enjoyment in young soccer players
Reference: Res Sports Med. 2018 Jul 2:1-12. doi: 10.1080/15438627.2018.1492392. [Epub ahead of print]
Authors: Trecroci A, Cavaggioni L, Lastella M, Broggi M, Perri E, Iaia FM, Alberti G
Summary: The aim of this study was to evaluate the effects of 12-week balance and slackline training programs on physical performance and perceived enjoyment scale in young soccer players. Forty-one preadolescent soccer players were assigned to two experimental groups performing traditional balance (BLT) or slackline training (SLT), and a control group. Pre-post assessment encompassed Balance Error Scoring System (BESS), Star Excursion Balance test (SEBT), sprint with 90° turns (S90), and countermovement jump (CMJ). The rate of perceived enjoyment scale (PACES) was applied at the end of the experimental period. SLT and BLT improved similarly in BESS, SEBT and S90. No changes were detected in the CMJ. Regarding PACES score, SLT presented significantly higher values than BLT. Young athletes may benefit from a motivating training approach, thus, a designed program based on slackline drills should be preferable to improve physical performance in terms of balance and change of direction ability in preadolescent soccer players.


#3 Contextual factors on physical demands in professional women's soccer: Female Athletes in Motion study
Reference: Eur J Sport Sci. 2018 Jul 1:1-6. doi: 10.1080/17461391.2018.1491628. [Epub ahead of print]
Authors: Vescovi JD, Falenchuk O
Summary: The aim of this study was to examine the impact of contextual factors on relative locomotor and metabolic power distances during professional female soccer matches. Twenty-eight players (forwards, n = 4; midfielders, n = 12; defenders, n = 12) that competed in a 90-min home and away match (regular season only). The generalised estimating equations (GEE) was used to evaluate relative locomotor and metabolic power distances for three contextual factors: location (home vs. away), type of turf (natural vs. artificial), and match outcome (win, loss and draw). No differences were observed for home vs. away matches. Moderate-intensity running (20.0 ± 1.0 m min-1 and 16.4 ± 0.9 m min-1), high-intensity running (8.6 ± 0.4 m min-1 and 7.3 ± 0.4 m min-1) and high-metabolic power (16.3 ± 0.5 m min-1 and 14.4 ± 0.5 m min-1) distances were elevated on artificial turf compared to natural grass, respectively. Relative sprint distance was greater during losses compared with draws (4.3 ± 0.4 m min-1 and 3.4 ± 0.3 m min-1). Overall physical demands of professional women's soccer were not impacted by match location. However, the elevation of moderate and high-intensity demands while playing on artificial turf may have implications on match preparations as well as recovery strategies.


#4 Exercise training in overweight and obese children: Recreational football and high-intensity interval training provide similar benefits to physical fitness
Reference: Scand J Med Sci Sports. 2018 Jul 6. doi: 10.1111/sms.13241. [Epub ahead of print]
Authors: Cvetković N, Stojanović E, Stojiljković N, Nikolić D, Scanlan AT, Milanović Z
Summary: This study compared the effects of recreational football and high-intensity interval training (HIIT) on body composition, muscular fitness, and cardiorespiratory fitness in overweight and obese children. Forty-two overweight/obese males aged 11-13 years [body mass index (BMI) >20.5 kg/m2 ] were randomly assigned to a recreational football training group (n = 14; 157.9 ± 5.8 cm; 63.7 ± 12.6 kg), HIIT group (n = 14; 163.8 ± 9.4 cm; 71.5 ± 10.5 kg), or nontraining control group (n = 14; 162.7 ± 9.3 cm; 67.4 ± 16.1 kg). Physical fitness components were measured at baseline and after 12 weeks of training at the same time of the day and under similar conditions, including body composition, muscular fitness (lower-body power, change-of-direction speed, and flexibility), and cardiovascular fitness (Yo-Yo Intermittent Endurance test distance, resting heart rate, and blood pressure). Lean body mass (4.3%, ES = 0.40; 95% CI: -0.48, 1.29; P = .382) and muscle mass 4.4% (ES = 0.40; 95% CI: -0.48, 1.29; P = .378) very likely increased in the recreational football group, while possible improvements were observed in the HIIT group (lean body mass: 2.5%, ES = 0.22; 95% CI: -0.62, 1.06; P = .607, muscle mass: 2.8%, ES = 0.23; 95% CI: -0.61, 1.07; P = .594). Only trivial increases were observed in the control group for lean body mass (0.5%, ES = 0.05; 95% CI: -0.70, 0.79; P = .906) and muscle mass (1.1%, ES = 0.09; 95% CI: -0.65, 0.83; P = .814). Significant differences were found between the recreational football and control groups in post-training body mass (P = .034) and body mass index (P = .017). Body fat very likely decreased in the recreational football group (-7.7%, ES = -0.41; 95% CI: -1.29, 0.48; P = .376) and possibly decreased in the HIIT group (-5.2%, ES = -0.22; 95% CI: -1.05, 0.62; P = .607), with a trivial reduction in the control group (-1.1%, ES = -0.04; 95% CI: -0.78, 0.70; P = .914). Very likely increases in lower-body power were evident in the recreational football (17.0%, ES = 0.76; 95% CI: -0.15, 1.66; P = .107) and control groups (16.1%, ES = 0.55; 95% CI: -0.20, 1.31; P = .156), while small improvements were observed in the HIIT group (6.0%, ES = 0.24; 95% CI: -0.60, 1.08; P = .580, possible). Likely to most likely improvements in Yo-Yo Intermittent Endurance test performance and change-of-direction speed were noted in the recreational football group (Yo-Yo: 79.8%, ES = 1.09; 95% CI: 0.16, 2.03; P = .025, change-of-direction speed: -10.6%, ES = -1.05; 95% CI: -1.98, -0.12; P = .031) and the HIIT group (Yo-Yo: 81.2%, ES = 1.03; 95% CI: 0.15, 1.92; P = .025, change-of-direction speed: -5.4%, ES = -0.91; 95% CI: -1.79, -0.04; P = .045). Diastolic blood pressure likely decreased in the recreational football (-8.6%, ES = -0.74; 95% CI: -1.64, 0.17; P = .116) and HIIT groups (-9.8%, ES = -0.57; 95% CI: -1.40, 0.30; P = .195), with a possible increase in the control group (1.2%, ES = 0.21; 95% CI: -0.53, 0.96; P = .068). Recreational football and HIIT elicited improvements in all muscular and cardiorespiratory fitness measures. In contrast, the control group, which performed only physical education classes, increased body mass, BMI, and fat mass. Therefore, additional activities such as recreational football or HIIT might counter the prevalence of overweight and obesity in children.


#5 Bowlegs and Intensive Football Training in Children and Adolescents
Reference: Dtsch Arztebl Int. 2018 Jun 15;115(24):401-408. doi: 10.3238/arztebl.2018.0401.
Authors: Thaller PH, Fürmetz J, Chen F, Degen N, Manz KM, Wolf F.
Summary: In many countries around the world, football (association football, or "soccer" predominantly in North America) is the sport most commonly played by children and adolescents. It is widely thought that football players are more likely to develop genu varum (bowlegs); an association with knee arthritis also seems likely. The goals of this systematic review and meta-analysis are to provide an overview of the available evidence on genu varum after intensive soccer training in childhood and adolescence, and to discuss the possible pathogenetic mechanisms. We systematically searched the PubMed, Medline, Embase, and Coch- rane Library databases for studies of the relation between leg axis development and intensive football playing during the growing years. Controlled studies employing the intercondylar distance (ICD) as the target variable were evaluated in a meta-analysis, with the mean difference as a measure of effect strength. This meta-analysis included 3 studies with a total of 1344 football players and 1277 control individuals. All three studies individually showed a signifi- cant difference in the mean ICD values of the two groups. The pooled effect esti- mator for the mean difference was 1.50 cm (95% confidence interval [0.53; 2.46]). Two further studies that could not be included in the meta-analysis had similar con- clusions. Asymmetrical, varus muscle forces and predominantly varus stress on the osseous growth plates neighboring the knee joint, especially during the prepubertal growth spurt, seem to be the cause of this phenomenon. Intensive soccer playing during the growing years can promote the devel- opment of bowlegs (genu varum) and, in turn, increase the risk of knee arthritis. Phy- sicians should inform young athletes and their parents of this if asked to advise about the choice of soccer as a sport for intensive training. It cannot be concluded, however, that football predisposes to bowlegs when played merely as a leisure activity.


#6 The Impact of an External Load of Football Equipment on Dynamic Balance as Assessed by the Modified Star Excursion Balance Test
Reference: Int J Exerc Sci. 2018 Jun 1;11(4):797-805. eCollection 2018.
Authors: Denehey T, Marshall T, Spaccarotella K, Andzel W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033501/pdf/ijes-11-4-797.pdf
Summary: Ankle sprains are common injuries, especially for football players, and may result in ankle instability, which can limit performance and increase injury risk. Ankle stability return to play criteria is often assessed under loaded conditions, even though previous research suggests loaded conditions affect dynamic balance. The purpose of this study was to evaluate dynamic balance under loaded conditions. A modified Star Excursion Balance Test (SEBT), incorporating anterior, posterior medial and posterior lateral reach directions under the loaded condition of NCAA Division III football equipment was evaluated. Thirty male collegiate football players completed the modified SEBT under loaded and non-loaded conditions. Scores for the three reach directions on the SEBT were computed for loaded and non-loaded conditions. Repeated measures ANOVA was used to compare reach directions under loaded and non-loaded. Under loaded conditions, participants had significantly shorter posterior lateral reach distances for the left (98.05 ± 12.73 cm vs. 89.30 ± 10.45 cm, p = 0.00) and right (103.77 ± 12.78 cm vs. 99.07 ± 13.50 cm, p = 0.00) legs and significantly shorter reach distances for the right leg in both the anterior direction (84.58 ± 5.64 cm vs. 80.57 ± 13.73 cm, p = 0.02) and composite dynamic balance score (105.99 ± 12.99 vs. 102.30 ± 14.28, p = 0.009). The addition of 6.2 kg of external load significantly affected dynamic balance assessed by the modified Star Balance Excursion Test. These findings suggest that return to support assessments should involve sport-specific conditions when determining readiness of return to play.


#7 Effects of Football Simulated Fatigue on Neuromuscular Function and Whole-body Response to Disturbances in Balance
Reference: Scand J Med Sci Sports. 2018 Jul 7. doi: 10.1111/sms.13261. [Epub ahead of print]
Authors: Behan FP, Willis S, Pain MTG, Folland JP
Summary: The effect of football specific fatigue on explosive neuromuscular performance and dynamic balance has received little attention in the literature despite the potential consequences for injury risk. This study aimed to investigate the effect of fatigue induced by simulated football match-play on maximal and explosive knee flexor (KF) and knee extensor (KE) torque, and thus the maximal and explosive KF/KE ratio, as well as the effect of fatigue induced by simulated football match-play on whole-body response to disturbances in balance. Fifteen male team sports players (mean ± SD: age 24.2±4.2 years; stature 1.79±0.09 m; body mass, 77.3±10.7 kg) underwent ~90 minutes of the modified Loughborough Intermittent Shuttle Test (LIST; fatiguing exercise condition) or seated rest (control condition) on separate days. Maximal and explosive isometric KF and KE voluntary torque (MVT/ EVT) were assessed pre and post condition. Maximal and explosive KF/KE ratios were calculated. Centre of mass (COM) response (displacement) to unexpected anterior and posterior platform perturbations were also assessed pre and post condition. Football simulated fatigue resulted in reduced KF (15%) and KE (12%) MVT (p≤0.002) but was not found to reduce EVT of either muscle group, or explosive KF/KE ratio. Football simulated fatigue resulted in impaired balance response (11% increase in COM displacement) to unexpected perturbation in the posterior (p=0.002) but not the anterior direction. Impaired response to dynamic disturbances in balance, rather than explosive torque or changes in muscle balance (H/Q ratios) may be a contributory factor towards increased injury risk in the latter portion of football games, and likely highlights the influence of fatigue on sensory/proprioceptive processes.


#8 Football training over 5 years is associated with preserved femoral bone mineral density in men with prostate cancer
Reference: Scand J Med Sci Sports. 2018 Jul 12. doi: 10.1111/sms.13242. [Epub ahead of print]
Authors: Uth J, Fristrup B, Haahr RD, Brasso K, Helge JW, Rørth M, Midtgaard J, Helge EW, Krustrup P
Summary: This study investigated the association between long-term adherence to football training and retaining bone mineralization and physical capacity in men with prostate cancer (PCa) managed with androgen deprivation therapy (ADT). Patients completing follow-up at 32 weeks in the FC Prostate Randomized Controlled Trial (RCT) in 2012 or 2013 were invited to 5-year follow-up assessments in May 2017 (n = 30). Changes in physiological outcomes over time between the football participants (FTG) and nonparticipants (CON) were examined. Twenty-two men accepted the invitation of which 11, aged 71.3 ± 3.8 years, had continued to play self-organized football 1.7 (SD 0.5) times per week for 4½ years (±8 months). At 5 years, right femoral neck bone mineral density (BMD) had improved significantly in the FTG compared to CON (P = .028). No other significant between-group differences were observed. In FTG, RHR decreased by 4.3 bpm (P = .009) with no changes in CON. Muscle mass, knee-extensor muscle strength, VO2 max, and postural balance decreased in both groups. In FTG, the fraction of training time with HR between 80%-90% or >90% of HRmax was 29.9% (SD 20.6) and 22.8% (SD 28.7), respectively. Average distance covered during 3 × 20 minutes of football training was 2524 m (SD 525). Football training over a 5-year period was associated with preserved femoral neck BMD in elderly men with PCa managed on ADT. Intensity during football training was >80% of HRmax for 51% of training time after 5 years. Body composition and physical capacity deteriorated over 5 years regardless of football participation.


#9 Heading and unintentional head impacts have opposing associations with Patient Reported Outcomes in amateur soccer players
Reference: Res Sports Med. 2018 Jul 13:1-11. doi: 10.1080/15438627.2018.1492396. [Epub ahead of print]
Authors: Hunter LE, Ifrah C, Zimmerman ME, Kim M, Lipton RB, Stewart WF, Lipton ML
Summary: The effects of soccer-related head impacts, beyond overt concussions, on Patient Reported Outcomes (PROs) have not been explored to date. Generalized estimating equations were employed to determine the association between soccer-related head impacts (headers in the prior 2 weeks, unintentional head impacts in the prior 2 weeks, headers in the prior 12 months and lifetime concussions) on PROs including depression, anxiety, sleep disturbance and sleep impairment. Compared to players with no unintentional head impacts in the prior 2 weeks, players with one unintentional exposure reported more symptoms of anxiety (p = 0.002) and players with 2+ exposures reported more symptoms of depression (p = 0.006) and anxiety (p < 0.001). In contrast, players in the 3rd Quartile of 12 mo. headers reported less anxiety (p = 0.001), sleep disturbance (p = 0.002) and sleep impairment (p < 0.001) compared to those in the 1st quartile. Unintentional head impacts are associated with worse PROs while more headers are paradoxically associated with better PROs.


#10 Development of an Educational Program for Non-Professional Soccer Coaches in Charge of Community-Based Soccer in Men with Prostate Cancer: a Qualitative Study
Reference: Sports Med Open. 2018 Jul 13;4(1):31. doi: 10.1186/s40798-018-0147-y.
Authors: Bjerre ED, Leth M, Hammer NM, Midtgaard J
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0147-y
Summary: While clinical trials have demonstrated the benefits of structured exercise for prostate cancer survivors, few attempts have been made to investigate and implement sustainable community-based exercise programs supporting adoption of long-term physical activity behavior. Against this background, the aims of this study was to explore the perspectives of experts and stakeholders on the development of a training course and intervention manual used to support the delivery of community-based soccer training in men with prostate cancer (the FC Prostate Community [FCPC] trial). A two-step qualitative design including triangulation of methods, data sources, and researchers. Step 1 comprised key informant interviews with clinical and scientific experts (n = 4). Step 2 included stakeholder focus group interviews with nurses (n = 5), non-professional soccer coaches and club representatives (n = 5), and prostate cancer survivors (n = 7). Four themes emerged from the analysis of the key informant interviews: The Coach's Qualifications, Structure of the Training, Prevention of Injuries, and A Non-Patient Environment, which informed development of the training course and intervention manual. The stakeholders added the importance of clarifying the Responsibility of the Coach, the value of Positive Competition, and Social Inclusion of the prostate cancer survivors in the club. Based on these results, we present the final templates for the training course and intervention manual. No general set of rules or safety measures to promote or optimize the delivery of community-based exercise in cancer survivors is recommended. However, the general principles related to the necessary clarification of the coach's responsibility in relation to the prevention and management of injuries and participant adherence through a non-patient environment may be transferable to the training and education of other groups of lay persons in charge of delivering exercise interventions to other clinical subpopulations in a non-hospital setting.


#11 Association between knee-to-hip flexion ratio during single-leg vertical landings, and strength and range of motion in professional soccer players
Reference: Sports Biomech. 2018 Jul 12:1-10. doi: 10.1080/14763141.2018.1494207. [Epub ahead of print]
Authors: Leporace G, Tannure M, Zeitoune G, Metsavaht L, Marocolo M, Souto Maior A
Summary: The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = -0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.

Sun

23

Sep

2018

Latest research in football - week 28 - 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 Knee osteoarthritis in professional football is related to severe knee injury and knee surgery
Reference: Inj Epidemiol. 2018 Jun 18;5(1):26. doi: 10.1186/s40621-018-0157-8.
Authors: Gouttebarge V, Aoki H, Kerkhoffs GMMJ
Download link: https://link.springer.com/content/pdf/10.1186%2Fs40621-018-0157-8.pdf
Summary: As a consequence of severe knee injuries, knee osteoarthritis (OA) seems prevalent in retired professional footballers. However, some epidemiological data remain missing, for instance whether knee OA is also prevalent in current professional footballers, whether knee OA is associated with knee injuries and surgeries, and whether knee OA leads to a lower level of functioning. Therefore, three research questions were answered: (i) what is the prevalence of knee osteoarthritis (OA) among current and retired professional footballers? (ii) is severe knee injury or knee surgery associated with knee OA among current and retired professional footballers? (iii) what are the consequences of knee OA on physical knee function among current and retired professional footballers? An observational study based on a cross-sectional design by means of questionnaires was conducted. Participants were current and retired professional footballers recruited by the World Players' Union (FIFPro). Information about severe knee injury and knee OA was gathered (medical record or team doctor), while physical knee function was assessed through a validated scale. A total of 1360 participants (964 current and 396 retired professional footballers) were enrolled in the study (response rate of 54%). Prevalence of knee OA was 13% among current players and 28% among retired players (p < 0.01), being higher among older players. Current and retired professional footballers were nearly twice as likely to suffer from knee OA by every additional severe knee injury and by every additional knee surgery (risk ratio: 1.72-1.96; p < 0.01). Current and retired professional footballers with knee OA reported a lower level of physical knee function than current and retired players without OA (p < 0.01), their physical knee function being also lower than reference values (adult population, young athletic population and amateur footballers). The prevalence of knee OA was higher among retired than among current professional footballers and reached up to 40%, leading to negative consequences for their physical knee function. Current and retired professional footballers were nearly twice as likely to suffer from knee OA by every additional severe knee injury and by every additional knee surgery incurred during their career. Management of knee OA should be prioritized among professional footballers, especially to prevent the worsening of the condition during their retirement years.


#2 Match Demands of National Collegiate Athletic Association Division I Men's Soccer
Reference: J Strength Cond Res. 2018 Jul 2. doi: 10.1519/JSC.0000000000002719. [Epub ahead of print]
Authors: Curtis RM, Huggins RA, Looney DP, West CA, Fortunati A, Fontaine GJ, Casa DJ
Summary: This study aimed to profile positional movement characteristics of National Collegiate Athletic Association (NCAA) Division I male soccer players. Eighteen Division I male soccer players were monitored using global positioning systems, inertial movement, and heart rate (HR) technology during 24 matches over a full competitive season (N = 235 observations). Positional groups were classified as either a forward (F), center midfield (CM), wide midfield (WM), or defender (D). Movement was profiled by locomotor (walking [0-7.19 km·h], jogging [7.20-14.39 km·h], running [14.40-21.59 km·h], and sprinting [>21.6 km·h]), and acceleration/deceleration characteristics (low intensity [0-1.99 m·s], moderate intensity [2-3.99 m·s], and high intensity [>4 m·s]). Players averaged distances of 9,367 ± 2,149 m per match at speeds of 91 ± 20 m·min and physiological intensities of 78 ± 8 %HRmax. Center midfields demonstrated the highest average speeds (97 ± 20 m·min) and covered the most distance (9,941 ± 2,140 m). Wide midfields accumulated the most sprint distance (391 ± 145 m) and high-intensity accelerations (129 ± 30 n)/decelerations (96 ± 24 n). Several practically meaningful differences exist between positions for internal and external load metrics. Match loads seen in NCAA Division I soccer vary from reports of professional soccer; however, the effects of match regulation, structure, and congestion, which are unique to NCAA soccer, require further investigation. Physical and physiological load monitoring of NCAA soccer may aid coaches and practitioners in the periodization of training programs leading up to and during a competitive soccer season. These data speak to the necessity for examining both internal and external loads by position.


#3 Promoting additional activity in youth soccer: a half-longitudinal study on the influence of autonomy-supportive coaching and basic psychological need satisfaction
Reference: J Sports Sci. 2018 Jul 5:1-9. doi: 10.1080/02640414.2018.1495394. [Epub ahead of print]
Authors: Gjesdal S, Wold B, Ommundsen Y
Summary: This study investigated the relationships between perceptions of coach autonomy support, basic psychological need satisfaction and the frequency at which youth soccer players engage in additional soccer activity outside of team sessions. We employed structural equation modelling to test a two-wave (T1 and T2) half-longitudinal study to see if basic psychological need satisfaction mediated the relationship between coach autonomy support and additional soccer activity across a competitive season. The sample consisted of 527 youth soccer players, aged 10-15 years. Results revealed moderate to strong temporal stability for autonomy, competence, relatedness and frequency of additional soccer activity. Furthermore, no support is offered for mediation as T1 coach autonomy support was not related to any of the three basic needs at T2 when accounting for their T1 levels. However, a positive relationship between T1 autonomy and T2 additional soccer activity emerged. This suggests that those who experience high levels of autonomy in the team setting at the start of the season report an increased frequency of additional activity at the end of the season. Results are discussed in light of the Self-Determination Theory and the Trans-Contextual Model.


#4 The effect of two different speed endurance training protocols on a multiple shuttle run performance in young elite male soccer players
Reference: Res Sports Med. 2018 Jul 4:1-14. doi: 10.1080/15438627.2018.1492402. [Epub ahead of print]
Authors: Vitale JA, Povia V, Vitale ND, Bassani T, Lombardi G, Giacomelli L, Banfi G, La Torre A
Summary: There is not enough evidence on the impact of different speed endurance training regimes on footballers' ability to perform multiple shuttle run performance. This study examined the effect of 4 weeks of speed endurance maintenance (SEM) and speed endurance production (SEP) training on the 5-meter multiple shuttle run test (5-m MST) performance in young elite soccer players. A parallel two-groups, longitudinal design was used. Fifteen players were divided to either SEM (8 repetitions of 20-s all-out sprint interspersed with 40 s of recovery) or SEP (8 repetitions of 20-s all-out bout interspersed with 120 s of recovery) training group. SEM improved the ability to tolerate fatigue and maintained the performance development during the 5-m MST while SEP increased only the 1st sprint showing, simultaneously, an increased fatigue index and performance decrement. The selection of which training regimes to prioritize should be based on the players' characteristics and individual game requirements Abbreviations: SEP: Speed Endurance Production; SEM: Speed Endurance Maintenance; PRE: Baseline; POST: End of experimental protocol; 5-m MST: 5-meters Multiple Shuttle Run Test; TD: Total Distance; FI: Fatigue Index; MSTdec: Percentage Decrement Score; BMI: Body Mass Index.


#5 Recreational soccer practice among adults, in Brazilian capitals, 2011-2015
Reference: Epidemiol Serv Saude. 2018 Jul 2;27(2):e2017284. doi: 10.5123/S1679-49742018000200013. [Article in English, Portuguese; Abstract available in Portuguese from the publisher]
Authors: Lima DF, Piovani VGS, Lima LA
Download link: http://www.scielo.br/pdf/ress/v27n2/en_2237-9622-ress-27-02-e2017284.pdf
Summary: The aim of the study was to describe the profile of recreational adult soccer players who lived in the Brazilian capitals in the period from 2011 to 2015. A sample of adults were interviewed by the Surveillance System for Risk and Protective Factors for Chronic Diseases by Telephone Survey - VIGITEL (2011 to 2015). 11.812 adults (11.375 men and 437 women) pointed to soccer as their main leisure physical exercise, with higher prevalence in the North region (32%) and lower in the South region (10%) of the country; the average reduction of soccer players 3.4% for every 5 years over age (95%CI 2.9;4.1); from 2011 to 2015, there was decrease in the number of soccer players, -1.4% per year (95%CI -0,7;2,2). Tthe practice of soccer was predominantly male, presented an inverse relationship with the increase of age, more prevalent in the Northern region and less prevalent in the Southern region.


#6 Left ventricular function during exercise in trained pre-adolescent soccer players
Reference: Scand J Med Sci Sports. 2018 Jul 3. doi: 10.1111/sms.13258. [Epub ahead of print]
Authors: Unnithan VB, Rowland TW, George K, Lord R, Oxborough D
Summary: It is unclear, what the underlying cardiovascular mechanisms are that give rise to the high level of aerobic fitness seen in youth soccer players. The aim of the study was to evaluate global and regional markers of systolic and diastolic function in a group of pre-adolescent soccer players during an incremental exercise test. Twenty-two, male soccer players (SP) from two professional soccer clubs (age: 12.0 ± 0.3 years) volunteered for the study. Fifteen recreationally active boys (CON), of similar age (age: 11.7 ± 0.2 years) were also recruited. All boys underwent a cycle ergometer test to exhaustion. Cardiac dimensions were determined using M-mode echocardiography. During submaximal and maximal exercise, continuous-wave Doppler ultrasound techniques were used to derive stroke volume (SVIndex). Tissue-Doppler imaging was used to quantify systolic (S'adj) and diastolic function (E; E'adj and E/E') at rest and both submaximal and maximal exercise intensities. Speckle tracking echocardiography was used to determine peak longitudinal ε at submaximal exercise intensities. SP demonstrated significantly (P ≤ 0.05) greater peak VO2 values than CON (SP: 48.0 ± 5.0 vs CON: 40.1 ± 7.5 mL·kg-1 ·min-1 ). Allometrically scaled to body surface area left ventricular end-diastolic volume (LVEDV) was larger (P ≤ 0.05) in the SP (51.3 ± 9.0) compared to CON (44.6 ± 5.8 mL·BSA1.5 ). At the same relative, submaximal exercise intensities, the SP demonstrated greater SVIndex, cardiac output (QIndex) and E. No differences were noted for peak longitudinal ε during submaximal exercise. Factors that augment pre-load and LV volume appear to determine the superior aerobic fitness seen in the soccer players.


#7 Operative Outcomes of Grade 3 Turf Toe Injuries in Competitive Football Players
Reference: Foot Ankle Int. 2018 Jun 1:1071100718775967. doi: 10.1177/1071100718775967. [Epub ahead of print]
Authors: Smith K, Waldrop N
Summary: Turf toe is a term used to describe a hyperextension injury to the first metatarsophalangeal joint. Although the vast majority of turf toe injuries can be treated successfully without operative intervention, there are instances where surgery is required to allow the athlete to return to play. Although there is a plethora of literature on turf toe injuries and nonoperative management, there are currently few reports on operative outcomes in athletes. We obtained all cases of turf toe repair according to the ICD-10 procedural code. The inclusion criteria included: age greater than 16, turf toe injury requiring operative management and at least a varsity level high school football player. The charts were reviewed for age, BMI, level of competition, injury mechanism, football position, setting of injury and playing surface. In addition, we recorded the specifics of the operative procedure, a listing of all injured structures, the implants used and the great toe range of motion at final follow-up visit. The AOFAS Hallux score and VAS was used postoperatively as our outcome measures. Our patient population included 15 patients. The average follow-up time was 27.5 months. The average patient was 19.3 years old with a body mass index of 32.3. The average playing time missed was 16.5 weeks. The average dorsiflexion range of motion at the final follow-up was 42.3 degrees. At final follow-up, the average AOFAS Hallux score was 91.3. The average VAS pain score was 0.7 at rest and 0.8 with physical activity. Complete turf toe injuries are often debilitating and may require operative management to restore a pain-free, stable, and functional forefoot. This study represents the largest cohort of operatively treated grade 3 turf toe injuries in the literature and demonstrates that good clinical outcomes were achieved with operative repair.


#8 Load distribution on the foot and lofstrand crutches of amputee football players
Reference: Gait Posture. 2018 Jun 9;64:169-173. doi: 10.1016/j.gaitpost.2018.06.008. [Epub ahead of print]
Authors: Tatar Y, Gercek N, Ramazanoglu N, Gulmez I, Uzun S, Sanli G, Karagozoglu C, Cotuk HB
Summary: Amputee football is a worldwide popular sport with positive physical and psychological effects on the disabled. Amputee players use their hands dominantly for locomotion. However, the effect of using upper extremity which is not accommodated to loading is not very well known. The objective of this study was to determine the load distribution of amputee football players during walking, running and kicking the ball. This study was conducted with 15 certified amputee football players (age 24.5 ± 5.8 years, body weight 62.3 ± 10.9 kg, height 171.6 ± 7.7 cm). The loads on their non-amputated lower extremity were measured with F-Scan mobile system sensors inserted in their shoes, and the loads on their upper extremities were measured with F-Grip system sensors affixed to the gloves. The participants were asked to walk, run and kick the ball using Lofstrand Crutches. The maximum loading on the upper extremities during walking, running and kicking the ball varied between 111% and 175% of the body weight. While loading during walking and running was similar, the loading on the upper extremity during kicking the ball exceeded that of walking by 58.1% and running by 47.4%. The maximum loading on the non-amputated lower extremity varied between 134% and 196% of the body weight. Loading during running was 46.2% higher than that of walking. The loading on the foot during kicking the ball was 45.7% higher than that of walking. The loading on the foot during running and kicking were similar. Walking-running-kicking the ball with LC resulted in unusual loading particularly on the upper extremity. During running, the increased loading was transferred to the foot rather than the hands. During kicking, the loading increased extremely and was mainly transferred to the hands. The frequent repetition of kicking during the game may therefore increase the incidence of upper extremity injuries.

Sun

23

Sep

2018

Latest research in football - week 27 - 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 Demands of a Women's College Soccer Season
Reference: Sports (Basel). 2018 Feb 23;6(1). pii: E16. doi: 10.3390/sports6010016.
Authors: Gentles JA, Coniglio CL, Besemer MM, Morgan JM, Mahnken MT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969200/pdf/sports-06-00016.pdf
Summary: The purpose of this study was to use GPS, accelerometers, and session rating of perceived exertion (sRPE) to examine the demands of a Division II women's soccer team. Data was collected on 25 collegiate Division II women's soccer players over an entire regular season (17 matches and 24 practices). ZephyrTM BioHarnesses (BHs) were used to collect tri-axial acceleration information and GPS derived variables for all matches and practices. Acceleration data was used to calculate Impulse Load, a measure of mechanical load that includes only locomotor related accelerations. GPS was used to quantify total distance and distance in six speed zones. Internal Training Loads were assessed via sRPE. Mean Impulse Load, total distance, and sRPE during match play was 20,120 ± 8609 N·s, 5.48 ± 2.35 km, and 892.50 ± 358.50, respectively. Mean Impulse Load, total distance, and sRPE during practice was 12,410 ± 4067 N·s, 2.95 ± 0.95 km, and 143.30 ± 123.50, respectively. Several very large to nearly perfect correlations were found between Impulse Load and total distance (r = 0.95; p < 0.001), Impulse Load and sRPE (r = 0.84; p < 0.001), and total distance and sRPE (r = 0.82; p < 0.001). This study details the mechanical demands of Division II women's soccer match play. This study also demonstrates that Impulse Load is a good indicator of total distance.



#2 Seasonal Variations in Physical Fitness and Performance Indices of Elite Soccer Players
Reference: Sports (Basel). 2018 Feb 13;6(1). pii: E14. doi: 10.3390/sports6010014.
Authors: Meckel Y, Doron O, Eliakim E, Eliakim A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969193/pdf/sports-06-00014.pdf
Summary: The aim of the study was to investigate seasonal variations in fitness and performance indices of professional male soccer players. Eighteen professional male soccer players (age range 22⁻32 years) completed three similar sets of tests at three stages of the season: before preseason; after preseason and the middle of the competitive in-season. A significant decrease in body mass and percent fat was found during the preseason. A significant improvement (p < 0.05) was found in the vertical jump (preseason: 37.0 ± 5.3, post-preseason: 39.0 ± 4.8, mid-season: 40.3 ± 5.5 cm), the 4 × 10-m agility test (preseason: 8.1 ± 0.2, post-preseason: 7.9 ± 0.2, mid-season: 8.1 ± 0.3 s), flexibility (preseason: 45.2 ± 8.8, post-preseason: 48.2 ± 7.0, mid-season: 49.9 ± 6.9 cm) and aerobic capacity (preseason: 52.7 ± 6.6, post-preseason: 56.4 ± 6.0, mid-season: 57.4 ± 5.4 mL/kg/min) during preseason, with no further change during mid-season. Repeated sprint test (RST) (6 × 30-m) performance indices showed significant deterioration (p < 0.05) in ideal sprint time (IS; preseason: 21.8 ± 1.0, post-preseason: 23.0 ± 0.8, mid-season: 23.2 ± 0.8 s) and total sprint time (TS; preseason: 22.5 ± 0.7, post-preseason: 23.5 ± 0.6, mid-season: 23.8 ± 0.6 s) during preseason, with no further changes during mid-season. However, performance decrement (PD) significantly decreased during the preseason with no change during mid-season. The findings suggest that while power training was probably responsible for the anaerobic fitness improvement, the high-volume training led to improvement in aerobic fitness during the preseason. However, the low-intensity aerobic-type training, coupled with the high total training load, may have led to fatigue and decreases in IS and TS during the preseason.


#3 The Influence of Playing Position and Contextual Factors on Soccer Players' Match Differential Ratings of Perceived Exertion: A Preliminary Investigation
Reference: Sports (Basel). 2018 Feb 12;6(1). pii: E13. doi: 10.3390/sports6010013.
Authors: Barrett S, McLaren S, Spears I, Ward P, Weston M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969182/pdf/sports-06-00013.pdf
Summary: (1) Background: Differential RPE (dRPE) separates scores for breathlessness (RPE-B), leg muscle exertion (RPE-L) and technical/cognitive exertion (RPE-T). Limited information for dRPE is available in soccer match play, yet these measurements may help inform practitioners training and recovery strategies. This preliminary study investigated the effects of playing position and contextual factors on elite soccer players' dRPE. (2) Methods: Thirty-two male English Premier League players recorded dRPE scores 15⁻30 min post-match for RPE-B, RPE-L, and RPE-T. Data were analysed using linear mixed models, with magnitude-based inferences subsequently applied. (3) Results: Overall, the mean ± SD for the dRPE were 63 ± 23 arbitrary units (au) (RPE-B), 67 ± 22 au (RPE-L), and 60 ± 24 au (RPE-T). Full Backs reported substantially higher RPE-B, RPE-L and RPE-T when compared to all other positions. Substantially higher RPE-T scores were reported for matches played against Top teams compared to Bottom (10 au; 90% Confidence Interval 5 to 15 au) and Middle (10 au; 4 to 15 au) ranked teams. The effects of match result and location on dRPE were not substantial. (4) Conclusions: Positional differences were observed following soccer match play for RPE-B, RPE-L and RPE-T. Full backs had substantially higher dRPE then any other position, with all players reporting increased RPE-T when playing teams at the Top of the league. These findings can help practitioners monitor internal load responses and support the prescription of training and recovery sessions.


#4 Relationships and Predictive Capabilities of Jump Assessments to Soccer-Specific Field Test Performance in Division I Collegiate Players
Reference: Sports (Basel). 2016 Dec 3;4(4). pii: E56. doi: 10.3390/sports4040056.
Authors: Lockie RG, Stage AA, Stokes JJ, Orjalo AJ, Davis DL, Giuliano DV, Moreno MR, Risso FG, Lazar A, Birmingham-Babauta SA, Tomita TM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968899/pdf/sports-04-00056.pdf
Summary: Leg power is an important characteristic for soccer, and jump tests can measure this capacity. Limited research has analyzed relationships between jumping and soccer-specific field test performance in collegiate male players. Nineteen Division I players completed tests of: leg power (vertical jump (VJ), standing broad jump (SBJ), left- and right-leg triple hop (TH)); linear (30 m sprint; 0⁻5 m, 5⁻10 m, 0⁻10, 0⁻30 m intervals) and change-of-direction (505) speed; soccer-specific fitness (Yo-Yo Intermittent Recovery Test Level 2); and 7 × 30-m sprints to measure repeated-sprint ability (RSA; total time (TT), performance decrement (PD)). Pearson's correlations (r) determined jump and field test relationships; stepwise regression ascertained jump predictors of the tests (p < 0.05). All jumps correlated with the 0⁻5, 0⁻10, and 0⁻30 m sprint intervals (r = -0.65⁻-0.90). VJ, SBJ, and left- and right-leg TH correlated with RSA TT (r = -0.51⁻-0.59). Right-leg TH predicted the 0⁻5 and 0⁻10 m intervals (R² = 0.55⁻0.81); the VJ predicted the 0⁻30 m interval and RSA TT (R² = 0.41⁻0.84). Between-leg TH asymmetry correlated with and predicted left-leg 505 and RSA PD (r = -0.68⁻0.62; R² = 0.39⁻0.46). Improvements in jumping ability could contribute to faster speed and RSA performance in collegiate soccer players.


#5 Coalitional Physical Competition : Acute Salivary Steroid Hormone Responses among Juvenile Male Soccer Players in Hong Kong
Reference: Hum Nat. 2018 Jun 16. doi: 10.1007/s12110-018-9321-7. [Epub ahead of print]
Authors: McHale TS, Chee WC, Chan KC, Zava DT, Gray PB
Summary: A large body of research links testosterone and cortisol to male-male competition. Yet, little work has explored acute steroid hormone responses to coalitional, physical competition during middle childhood. Here, we investigate testosterone, dehydroepiandrosterone (DHEA), androstenedione, and cortisol release among ethnically Chinese boys in Hong Kong (N = 102), aged 8-11 years, during a soccer match (n = 84) and an intrasquad soccer scrimmage (n = 81), with 63 participants competing in both treatments. The soccer match and intrasquad soccer scrimmage represented out-group and in-group treatments, respectively. Results revealed that testosterone showed no measurable change. DHEA increased during both treatments in the majority of participants and the degree of change had no relation to independent variables (e.g., performance, age, treatment, outcome) or covariate measures (Body Mass Index, Pubertal Development Scale). Most boys experienced androstenedione increases during match play, but no significant differences during the intrasquad soccer scrimmage competitions. The magnitude of change differed significantly between treatments and was positively associated with age. These latter findings suggest boys' androstenedione responses may be sensitive to competitor type (i.e., unknown competitors vs. peers). For most subjects, cortisol significantly increased during match play, decreased during the intrasquad soccer scrimmage, and differed significantly between treatments, suggesting each treatment promoted a different psychological state among competitors. Cortisol/DHEA molar ratio decreased during the intrasquad scrimmage, suggestive of a more relaxed mental state. These data shed new light on potential proximate mechanisms associated with coalitional competition among prepubescent boys, with relevance to adrenarche and life history theory.


#6 Prevalence of femoroacetabular impingement and effect of training frequency on aetiology in paediatric football players
Reference: Hip Int. 2018 Jun 1:1120700018781939. doi: 10.1177/1120700018781939. [Epub ahead of print]
Authors: Polat G, Arzu U, Dinç E, Bayraktar B
Summary: The aim of this study was to determine the prevalence of asymptomatic radiographic findings of femoroacetabular impingement (FAI) in paediatric football players in different age groups and to investigate aetiological factors. Paediatric male athletes between 10 and 17 years of age from 8 soccer teams were recruited. In addition to an annual control check-up, anteroposterior pelvis and frog-leg radiographs as well as the curriculum vitae of the athletes, their injuries, and real-time complaints were recorded. The alpha angle, lateral centre-edge angle, Tönnis angle, and collodiaphyseal angle were measured and morphological abnormalities were noted. There were 214 male football players with a mean age of 13.4 ± 3.2 years included in the study. In the morphological analysis of hips, there was FAI in 30% of the athletes. In the analysis of FAI prevalence in 3 subgroups based on age (Group 1: 10-12 years [ n = 25], Group 2: 13-15 years [ n = 104], Group 3: 16-17 years [ n = 85]), there was 0% FAI in Group 1, 19.1% in Group 2 and 60% in Group 3. In the analysis of aetiological factors, there was no significant difference between the right and left hips of players regarding alpha angles and FAI prevalence. However, the prevalence of FAI was higher in players who had been playing football for 3 years or more and who had been training for 12.5 hours/week or more. Training for 12.5 hours or more per week in paediatric football players doubled the risk development of FAI morphology.


#7 Return to play, performance and career duration after ACL rupture: a case-control study in in the five biggest football nations in Europe
Reference: Scand J Med Sci Sports. 2018 Jun 21. doi: 10.1111/sms.13245. [Epub ahead of print]
Authors: Niederer D, Engeroff T, Wilke J, Vogt L, Banzer W
Summary: A media-based collection and further analysis of relative return to play (RTP) rates and the corresponding quality of play after anterior cruciate ligament (ACL) rupture in top level football was the aim of our study. In the 5-year case-control study, male players from the first two leagues of the five European countries top leagues, who sustained a total ACL rupture during the season 2010/11 and/or 2011/12, were included. For them and a matched control sample (ratio 1:2), data were retrieved from the publicly available and validated media-based platforms (transfermarkt.de & whoscored. com) until the end of season 2016/17. Injury and return to play-specific data were calculated as rate ratios (RR) to compare the injured and matched control athletes rates and as a survival analysis (log-rank-test; career duration). Overall, 132 ACL-injuries in 125 players occurred. The RTP rate was 98.2%, the RTP to same level was 59.4%. Five years post RTP, 69.9% of the ACL group were still engaged in football (RR = 87%), 40.9% at the same level (RR = 72%). Survival analysis revealed a systematic group difference in career duration compared to controls (Cox-Mantel's Chi² =5.8; p= .016). Game performance (scoring points, p < .001; rates/number of completed passes, p = .048; and minutes played, p < .001) was lower in the ACL athletes than in the matching group in the RTP and post RTP seasons. Although absolute and relative RTP rates after ACL reconstruction are high in professional football, career duration and performance quality are lower than in the reference group. This article is protected by copyright. All rights reserved.


#8 Effects of Training and Competition Load on Neuromuscular Recovery, Testosterone, Cortisol, and Match Performance During a Season of Professional Football
Reference: Front Physiol. 2018 Jun 7;9:668. doi: 10.3389/fphys.2018.00668. eCollection 2018.
Authors: Rowell AE, Aughey RJ, Hopkins WG, Esmaeili A, Lazarus BH, Cormack SJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6000155/pdf/fphys-09-00668.pdf
Summary: Training load and other measures potentially related to match performance are routinely monitored in team-sport athletes. The aim of this research was to examine the effect of training load on such measures and on match performance during a season of professional football. Training load was measured daily as session duration times perceived exertion in 23 A-League football players. Measures of exponentially weighted cumulative training load were calculated using decay factors representing time constants of 3-28 days. Players performed a countermovement jump for estimation of a measure of neuromuscular recovery (ratio of flight time to contraction time, FT:CT), and provided a saliva sample for measurement of testosterone and cortisol concentrations 1-day prior to each of 34 matches. Match performance was assessed via ratings provided by five coaching and fitness staff on a 5-point Likert scale. Effects of training load on FT:CT, hormone concentrations and match performance were modeled as quadratic predictors and expressed as changes in the outcome measure for a change in the predictor of one within-player standard deviation (1 SD) below and above the mean. Changes in each of five playing positions were assessed using standardization and magnitude-based inference. The largest effects of training were generally observed in the 3- to 14-day windows. Center defenders showed a small reduction in coach rating when 14-day a smoothed load increased from -1 SD to the mean (-0.31, ±0.15; mean, ±90% confidence limits), whereas strikers and wide midfielders displayed a small increase in coach rating when load increased 1 SD above the mean. The effects of training load on FT:CT were mostly unclear or trivial, but effects of training load on hormones included a large increase in cortisol (102, ±58%) and moderate increase in testosterone (24, ±18%) in center defenders when 3-day smoothed training load increased 1 SD above the mean. A 1 SD increase in training load above the mean generally resulted in substantial reductions in testosterone:cortisol ratio. The effects of recent training on match performance and hormones in A-League football players highlight the importance of position-specific monitoring and training.


#9 In-Season Variations in Head Impact Exposure among Youth Football Players
Reference: J Neurotrauma. 2018 Jun 19. doi: 10.1089/neu.2018.5699. [Epub ahead of print]
Authors: Urban JE, Kelley ME, Espeland MA, Davenport EM, Whitlow CT, Powers AK, Maldjian JA, Stitzel JD
Summary: Head impact exposure (HIE) is often summarized by the total exposure measured during the season and does not indicate how the exposure was accumulated, or how it varied during the season. Therefore, the objective of this study is to compare HIE during preseason, the first and second halves of the regular season, and playoffs in a sample of youth football players (n=119, ages 9-13). Athletes were divided into one of four exposure groups based on quartiles computed from the distribution of risk-weighted cumulative exposure (RWECP). Mean impacts per session and mean 95th percentile linear and rotational acceleration in practices and games were compared across the four exposure groups and time frames using mixed effects models. Within games, the mean 95th percentile accelerations for the entire sample ranged from 47.2 g and 2331.3 rad/s2 during preseason to 52.1 g and 2533.4 rad/s2 during the second half of regular season. Mean impacts per practice increased from preseason to the second half of regular season and declined into playoffs among all exposure groups; however, the variation between time frames was not greater than 2 impacts per practice. Time of season had a significant relationship with mean 95th percentile linear and rotational acceleration in games (both p=0.01) but not with practice accelerations or impacts/session. The in-practice mean levels of 95th percentile linear and rotational acceleration remained fairly constant across the four time frames, but in games these changed over time depending on exposure group (interactions p<0.05). The results of this study improve our understanding of in-season variations in HIE in youth football and may inform important opportunities for future interventions.


#10 The "Football is Medicine" platform-scientific evidence, large-scale implementation of evidence-based concepts and future perspectives
Reference: Scand J Med Sci Sports. 2018 Jun 19. doi: 10.1111/sms.13220. [Epub ahead of print]
Authors: Krustrup P, Williams CA, Mohr M, Hansen PR, Helge EW, Elbe AM, de Sousa M, et al.
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13220

Sun

23

Sep

2018

Latest research in football - week 26 - 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 Validity of External:Internal Training Load Ratios in Rested and Fatigued Soccer Players
Reference: Sports (Basel). 2018 May 19;6(2). pii: E44. doi: 10.3390/sports6020044.
Authors: Akubat I, Barrett S, Sagarra ML, Abt G
Summary: The purpose was to examine the relationship of external:internal training load ratios with fitness and assess the impact of fatigue. Ten soccer players performed a lactate threshold test followed by two soccer simulations (BEAST90mod) 48 h apart. Recovery (TQR) and muscle soreness (DOMS) was measured before each trial. Internal Training load (TL) (iTRIMP) and external load total distance (TD), high intensity distance (HID), PlayerLoad&trade; (PL) mean metabolic power (MMP) high metabolic power distance (HP) were collected for each trial and external:internal ratios produced. The relationships between ratios and velocity at lactate threshold (vLT) and velocity at Onset of Blood Lactate Accumulation (vOBLA) were examined in both trials along with changes in ratios. Total Quality of Recovery and DOMS showed large changes. There were trivial to large decreases in TL from trial 1 to 2. Moderate increases in ratios for TD:iTRIMP, PL:iTRIMP and MMP:iTRIMP were seen but only small/trivial for HP:iTRIMP and HID:iTRIMP. In rested conditions all ratios show large relationships with vLT and vOBLA. However vLT vs. HID:iTRIMP; PL:iTRIMP; HP:iTRIMP and vOBLA vs. TD:iTRIMP; PL:iTRIMP; MMP:iTRIMP became weaker under fatigue. Acute changes in the ratios have implications for the use of ratios as fitness measures but also as indicators of fatigue.


#2 Non-Linear Resistance Training Program Induced Power and Strength but Not Linear Sprint Velocity and Agility Gains in Young Soccer Players
Reference: Sports (Basel). 2018 May 14;6(2). pii: E43. doi: 10.3390/sports6020043.
Authors: Barbalho M, Gentil P, Raiol R, Del Vecchio FB, Ramirez-Campillo R, Coswig VS
Summary: The present study evaluated the effects of resistance training (RT) following a non-linear periodization model in the physical fitness of young soccer athletes. Young soccer players (n = 23) were allocated into two groups: an RT group (RTG), and the control group (CON). The RTG underwent 15 weeks of non-linear RT periodization in three weekly sessions in addition to their specific soccer training. The CON continued performing the specific soccer training. Before and after the training period, all of the subjects performed one-repetition maximum (RM) tests for speed, agility, and power (vertical and horizontal jump). The RTG obtained significant gains in one-RM tests (before 64.1 ± 5.8 kg, after 79.1 ± 3.3 kg) and power (vertical jump (before 56 ± 2.7 cm, after 61.3 ± 1.7 cm) and horizontal jump (before 184.5 ± 5.5 cm, after 213.6 ± 3.2 cm)). In contrast, the CON group presented a non-significant increase in one-RM tests and horizontal jump, and a significant reduction in vertical jump (before 55.4 ± 2.2 cm, after 51.3 ± 1.5 cm). Neither group presented significant gains in speed (CON: p = 0.27; RTG: p = 0.72) and agility (CON: p = 0.19; RTG: p = 0.58). Our data suggest that non-linear RT should be inserted into the routine of young soccer athletes for improving strength and power without impairing speed and agility.


#3 Directional Change Mediates the Physiological Response to High-Intensity Shuttle Running in Professional Soccer Players
Reference: Sports (Basel). 2018 Apr 24;6(2). pii: E39. doi: 10.3390/sports6020039.
Authors: Tang R, Murtagh C, Warrington G, Cable T, Morgan O, O'Boyle A, Burgess D, Morgans R, Drust B
Summary: The purpose of this study was to investigate the influence that different frequencies of deceleration and acceleration actions had on the physiological demands in professional soccer players. Thirteen players were monitored via microelectromechanical devices during shuttle running protocols which involved one, three, or seven 180 degree directional changes. Heart rate exertion (HRE) (1.1 ± 0.7) and rating of perceived exertion (RPE) (5 ± 1) were significantly higher for the protocol which included seven directional changes when compared to the protocols which included one (HRE 0.5 ± 0.3, ES = 1.1, RPE 3 ± 0, ES = 2.7) or three (HRE 0.5 ± 0.2, ES = 1.1, RPE 3 ± 1, ES = 1.9) directional changes (p < 0.05). The gravitational force (g-force) as measured through accelerometry (ACC) also showed a similar trend when comparing the seven (8628.2 ± 1630.4 g) to the one (5888.6 ± 1159.1 g, ES = 1.9) or three (6526.9 ± 1257.6 g, ES = 1.4) directional change protocols (p < 0.05). The results of this study suggest that increasing the frequency of decelerations and accelerations at a high intensity running (HIR) speed alters the movement demands and elevates the physiological responses in professional players. This data has implications for the monitoring of physical performance and implementation of training drills.


#4 The Influence of Fatigued Core Muscles on Head Acceleration during Headers in Soccer
Reference: Sports (Basel). 2018 Apr 11;6(2). pii: E33. doi: 10.3390/sports6020033.
Authors: Becker S, Frohlich M, Kelm J, Ludwig O
Summary: The core muscles play a central role in stabilizing the head during headers in soccer. The objective of this study was to examine the influence of a fatigued core musculature on the acceleration of the head during jump headers and run headers. Acceleration of the head was measured in a pre-post-design in 68 soccer players (age: 21.5 ± 3.8 years, height: 180.0 ± 13.9 cm, weight: 76.9 ± 8.1 kg). Data were recorded by means of a telemetric 3D acceleration sensor and with a pendulum header. The treatment encompassed two exercises each for the ventral, lateral, and dorsal muscle chains. The acceleration of the head between pre- and post-test was reduced by 0.3 G (p = 0.011) in jump headers and by 0.2 G (p = 0.067) in run headers. An additional analysis of all pretests showed an increased acceleration in run headers when compared to stand headers (p < 0.001) and jump headers (p < 0.001). No differences were found in the sub-group comparisons: semi-professional vs. recreational players, offensive vs. defensive players. Based on the results, we conclude that the acceleration of the head after fatiguing the core muscles does not increase, which stands in contrast to postulated expectations. More tests with accelerated soccer balls are required for a conclusive statement.


#5 Relationships between Linear Speed and Lower-Body Power with Change-of-Direction Speed in National Collegiate Athletic Association Divisions I and II Women Soccer Athletes
Reference: Sports (Basel). 2018 Apr 4;6(2). pii: E30. doi: 10.3390/sports6020030.
Authors: Lockie RG, Dawes JJ, Jones MT
Summary: This study investigated relationships that linear speed and lower-body power have on change-of-direction (COD) speed in collegiate women soccer players. Data from two Division I (n = 39) and one Division II (n = 18) schools were analyzed. Subjects were assessed in: power (vertical jump (VJ); jump height, peak anaerobic power measured in watts (PAPw), power-to-body mass ratio (P:BM); linear speed (10-m sprint); and COD speed (modified T-test (MTT), 505, COD deficit). Independent samples T-tests derived significant between-group differences, with effect sizes (d) calculated. Pearson&rsquo;s correlations determined relationships between COD speed, linear speed, and power, with regression equations calculated. Division I players demonstrated superior 505, COD deficit, VJ height, PAPw, and P:BM (d = 1.09⁻2.21). Division II players were faster in the MTT (d = 1.51). For all players, the 505 correlated with the 10-m sprint (r = 0.39⁻0.53) and VJ height (r = -0.65⁻0.66), while the COD deficit related to the 10-m sprint (r = -0.77⁻0.82). The regression data supported these results. Division I players were superior in the 505 and COD deficit, and expressed their power in the 180 deg; 505 task. Division II players should enhance lower-body power and the ability to perform 180 deg; direction changes.


#6 Inevitable Relative Age Effects in Different Stages of the Selection Process among Male and Female Youth Soccer Players
Reference: Sports (Basel). 2018 Mar 31;6(2). pii: E29. doi: 10.3390/sports6020029.
Authors: Lagestad P, Steen I, Dalen T
Summary: The relative age effect (RAE) in the selection of young soccer players is a well-known phenomenon. The purpose of this study was to examine the relative age effect existing despite strategies that have been implemented to avoid its presence in the selection process. We also aimed to investigate the RAE during the three different selection stages for B13, B14 (boys), and G13, G14 (girls), and gender differences in the RAE. This was achieved by collecting data from everyone who played soccer in Troendelag, and data that would illuminate the RAE during the three stages of selection for the regional teams of the 2015/2016 season. Mann⁻Whitney U-tests and Chi-square tests were used as statistical methods. The main finding of this study is that, despite the intention to reduce RAE in the selection process according to the criterion that at least 40% of the players should be born in the second half of the year, both the early-born boys and girls are more likely to be selected. The results also show that the RAE occurs gradually, and the longer the players are in the selection process the more prominent it is. This study highlights the importance of being aware of the RAE when selecting young players.


#7 Relationships between Sprint Ability and Endurance Capacity in Soccer Referees
Reference: Sports (Basel). 2018 Mar 30;6(2). pii: E28. doi: 10.3390/sports6020028.
Authors: Sanchez-Garcia M, Sanchez-Sanchez J, Rodriguez-Fernandez A, Solano D, Castillo D
Summary: The aim of this study was to analyze the association between sprint ability and endurance capacity in soccer referees. Twenty-three Spanish officials participated in this study. Each referee undertook, in this order, a 40 m linear straight sprinting test (40 m Sprint) and the Yo⁻Yo intermittent recovery level 1 test (YYIR1) interspersed with a 8 min of self-administered rest. The results in the 40 m Sprint test showed that the time spent by referees was 5.56 ± 0.27 s and achieved a maximum velocity of 31.46 ± 2.85 km·h-1. Furthermore, during the YYIR1 the referees covered 1213.91 ± 432.26 m. The distance covered at YYIR1 was moderately correlated to the velocity achieved in the 40 m Sprint test (r = -0.404, p < 0.05). These results suggest that the ability to reach high speeds is a limiting factor in YYIR1 performance.


#8 The Impact of 120 Minutes of Match-Play on Recovery and Subsequent Match Performance: A Case Report in Professional Soccer Players
Reference: Sports (Basel). 2018 Mar 13;6(1). pii: E22. doi: 10.3390/sports6010022.
Authors: Winder N, Russell M, Naughton RJ, Harper LD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969194/pdf/sports-06-00022.pdf
Summary: The influence of a match including extra-time (ET) on subsequent 90 min match performance and recovery has not been investigated. Four professional soccer players played in three competitive matches in a 7-day period: matches one (MD1) and three (MD3) lasted 90 min and match 2 (MD2) lasted 120 min (i.e., included ET). Physical (total and high-intensity (HI) distance covered, accelerations and decelerations, and mechanical load) and technical performances (pass and dribble accuracy) were analyzed throughout match-play. Subjective measures of recovery and countermovement jump (CMJ) height were made 36⁻42 h post-match. Post-MD2, there were very or most likely harmful effects of ET on CMJ height (-6 ± 9%), muscle soreness (+18 ± 12%), and fatigue (+27 ± 4%) scores, and overall wellness score (-13 ± 5%) compared to post-MD1. Furthermore, there were very likely harmful effects on muscle soreness (+13 ± 14%), wellness scores (-8 ± 10%), and CMJ height (-6 ± 9%) post-MD3 vs. post-MD1. There was a possibly harmful effect of ET on HI distance covered during MD3, along with reductions in pass (-9.3%) and dribble (-12.4%) accuracy. An ET match negatively impacted recovery 36 h post-match. Furthermore, in some players, indices of performance in a 90 min match played 64 h following ET were compromised, with subsequent recovery also adversely affected.


#9 Can Genetics Predict Sports Injury? The Association of the Genes GDF5, AMPD1, COL5A1 and IGF2 on Soccer Player Injury Occurrence
Reference: Sports (Basel). 2018 Mar 5;6(1). pii: E21. doi: 10.3390/sports6010021.
Authors: McCabe K, Collins C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969195/pdf/sports-06-00021.pdf
Summary: Genetics plays an integral role in athletic performance and is increasingly becoming recognised as an important risk factor for injury. Ankle and knee injuries are the most common injuries sustained by soccer players. Often these injuries result in players missing training and matches, which can incur significant costs to clubs. This study aimed to identify genotypes associated with ankle and knee injuries in soccer players and how these impacted the number of matches played. 289 soccer players, including 46 professional, 98 semi-professional and 145 amateur players, were genetically tested. Ankle and knee injuries and the number of matches played were recorded during the 2014/15 season. Four genes were assessed in relation to injury. Genotypes found to be associated with injury included the TT (nucleobase) genotype of the GDF5 gene, TT and CT (nucleobase) genotypes of AMPD1 gene, TT genotype of COL5A1 and GG (nucleobase) genotype of IGF2 gene. These genes were also associated with a decrease in the number of matches played.

Thu

30

Aug

2018

Latest research in football - week 25,5 - 2018

As in previous literature update, here are the rest of the Basel publications.

#1 Seasonal Variation of Agility, Speed and Endurance Performance in Young Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 4;5(1). pii: E12. doi: 10.3390/sports5010012.
Authors: Dragijsky M, Maly T, Zahalka F, Kunzmann E, Hank M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969008/pdf/sports-05-00012.pdf
Summary: The aim of this study was to investigate changes in the linear running speed (LRS) for 30 m, change of direction speed (CODS), and endurance in young elite Czech soccer players. The following tests were conducted to assess CODS and endurance: Agility 505 turning toward the dominant (A505DL) and non-dominant lower limb (A505NL); Illinois Agility Test (IAT); and intermittent test (Yo-Yo IRT1). During the soccer season, we investigated performance at the following time periods: the start (t₁) and the end of the pre-season period (t₂); during (t₃) and at the end of the competitive period (t₄). Repeated measurement analysis of variance revealed a significant effect of time period on selected fitness parameters (p < 0.05). Post hoc analysis for test A505DL revealed significant improvements of performance at t₃ (2.71 ± 0.08 s) and t₄ (2.72 ± 0.06 s) compared to t₁ (2.81 ± 0.09 s). A505NL was significantly different between t₁ (2.83 ± 0.09 s) and t₂ (2.76 ± 0.09 s), t₃ (2.7 ± 0.07 s) and t₄ (2.71 ± 0.09 s). Performance of CODS at t₁ for the IAT (18.82 ± 0.56 s) was significantly lower (p < 0.05) than any other time period (t₂ = 18.52 ± 0.63 s, t₃ = 17.94 ± 0.51 s, t₄ = 17.89 ± 0.66 s). The power of LRS was significantly different at t₃ (4.99 ± 0.15 s), and t₄ (4.98 ± 0.17 s) compared to t₁ (5.15 ± 0.21 s), and t₂ (5.07 ± 0.14 s). For the Yo-Yo IRT1 test, we observed a significant increase in performance between t₁ (625.26 ± 170.34 m), t₂ (858.95 ± 210.55 m), and t₃ (953.68 ± 229.88 m). These results show the impact of soccer season time period on young soccer player performance and may further serve as a basis for comparison with similar research conducted by peers. These results may aid sports practice for clinicians, conditioning coaches, soccer coaches and physiotherapeutic coaches.


#2 Seasonal Variation of Agility, Speed and Endurance Performance in Young Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 4;5(1). pii: E12. doi: 10.3390/sports5010012.
Authors: Dragijsky M, Maly T, Zahalka F, Kunzmann E, Hank M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969008/pdf/sports-05-00012.pdf
Summary: The aim of this study was to investigate changes in the linear running speed (LRS) for 30 m, change of direction speed (CODS), and endurance in young elite Czech soccer players. The following tests were conducted to assess CODS and endurance: Agility 505 turning toward the dominant (A505DL) and non-dominant lower limb (A505NL); Illinois Agility Test (IAT); and intermittent test (Yo-Yo IRT1). During the soccer season, we investigated performance at the following time periods: the start (t₁) and the end of the pre-season period (t₂); during (t₃) and at the end of the competitive period (t₄). Repeated measurement analysis of variance revealed a significant effect of time period on selected fitness parameters (p < 0.05). Post hoc analysis for test A505DL revealed significant improvements of performance at t₃ (2.71 ± 0.08 s) and t₄ (2.72 ± 0.06 s) compared to t₁ (2.81 ± 0.09 s). A505NL was significantly different between t₁ (2.83 ± 0.09 s) and t₂ (2.76 ± 0.09 s), t₃ (2.7 ± 0.07 s) and t₄ (2.71 ± 0.09 s). Performance of CODS at t₁ for the IAT (18.82 ± 0.56 s) was significantly lower (p < 0.05) than any other time period (t₂ = 18.52 ± 0.63 s, t₃ = 17.94 ± 0.51 s, t₄ = 17.89 ± 0.66 s). The power of LRS was significantly different at t₃ (4.99 ± 0.15 s), and t₄ (4.98 ± 0.17 s) compared to t₁ (5.15 ± 0.21 s), and t₂ (5.07 ± 0.14 s). For the Yo-Yo IRT1 test, we observed a significant increase in performance between t₁ (625.26 ± 170.34 m), t₂ (858.95 ± 210.55 m), and t₃ (953.68 ± 229.88 m). These results show the impact of soccer season time period on young soccer player performance and may further serve as a basis for comparison with similar research conducted by peers. These results may aid sports practice for clinicians, conditioning coaches, soccer coaches and physiotherapeutic coaches.


#3 Functional Assessment and Injury Risk in a Professional Soccer Team
Reference: Sports (Basel). 2017 Jan 22;5(1). pii: E9. doi: 10.3390/sports5010009.
Authors: Gomez-Piqueras P, Gonzalez-Villora S, Sainz de Baranda Andujar MDP, Contreras-Jordan OR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969000/pdf/sports-05-00009.pdf
Summary: At the last World Conference on Sport and Physical Therapy celebrated in Bern (Switzerland, 2015), it was confirmed that the functional skills of an athlete are a very important variable to be considered in the recovery of an injury. On the other hand, its use as a predictive risk tool still lacks solid evidence. The purpose of this study was to determine whether a battery of functional tests (FPT) could be used as a preliminary measure for the season in order to identify the injury risk in a professional soccer team in the Spanish Second Division B League. Fifty-two soccer players (ages of 25.3 ± 4.6 years, 10.33% ± 0.9% fat) were functionally assessed during two seasons (2012⁻2013 and 2013⁻2014) and analyzed from an injury perspective. A total of 125 injuries were recorded. The sample was grouped based on the number of injuries and the required absence days. Except for the bipodal vertical jump (CMJ), none of the functional tests revealed differences among the groups. The correlation study between the functional condition and the suffered injuries did not show any significant results.


#4 Soccer and Relative Age Effect: A Walk among Elite Players and Young Players
Reference: Sports (Basel). 2017 Jan 11;5(1). pii: E5. doi: 10.3390/sports5010005.
Authors: Sierra-Diaz MJ, Gonzalez-Villora S, Pastor-Vicedo JC, Serra-Olivares J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969014/pdf/sports-05-00005.pdf
Summary: Grouping people according to chronological age is popular in fields such as education and sport. Athletes who are born in the first months of the year usually have cognitive and physical development differences in contrast to those born in the last months of the same year. That is why competitive teams tend to select older players more often than youngsters. Age differences between athletes born in the same year as well as an over-representation of older players are known as the Relative Age Effect. This effect is extensively described in young and elite team sports such as basketball, volleyball or, ice-hockey, as well as in soccer. The purpose of this study is to examine the state-of-the-art of the Relative Age Effect in youth and elite soccer players. This review summarizes recent research articles on the Relative Age Effect related to competitive soccer from 2010 to 2016. The systematic literature search was conducted in four databases: SPORTDiscus, Medline, EBSCO host and Google Scholar. Although causes and final solutions have not been clearly achieved yet, it is necessary to continue investigating this phenomenon in order to provide a starting point for future research.


#5 Goal Format in Small-Sided Soccer Games: Technical Actions and Offensive Scenarios of Prepubescent Players
Reference: Sports (Basel). 2016 Nov 25;4(4). pii: E53. doi: 10.3390/sports4040053.
Authors: Pulling C, Twitchen A, Pettefer C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968898/pdf/sports-04-00053.pdf
Summary: The aim of this study was to investigate the influence of the number of goal-posts and the positioning of goal-posts used within small-sided games on the frequency of technical actions and offensive scenarios performed by prepubescent players within soccer. The participants were eight male prepubescent soccer players (12.1 ± 0.5 years). The participants were video recorded for 20 min playing four different formats of 4v4 small-sided games: (1) standard two goal game; (2) four goal game, one goal in each corner; (3) two goal game with goal-posts positioned 9.14 m/10 yd infield, scoring only through the back of the goal; (4) four goal-game, one goal positioned 9.14 m/10 yd infield in each corner, scoring through either the front or back of each goal. Chi-squared tests of independence were utilized to statistically explore the impact of the different small-sided game formats. There were significant associations (p < 0.05) observed between the different small-sided game formats and the frequency of turns, dribbles, shots, goals and overlaps performed. For example, players performed more turns in small-sided game format two and more shots during small-sided game format four. It is suggested coaches should consider using a variation of the number and positioning of goal-posts in small-sided games as an effective training tool in the development of prepubescent soccer players. This will enable coaches to vary the focus of sessions, and develop specific technical and tactical actions within a situation similar to that of real match-play.


#6 Relationship between Procedural Tactical Knowledge and Specific Motor Skills in Young Soccer Players
Reference: Sports (Basel). 2016 Nov 17;4(4). pii: E52. doi: 10.3390/sports4040052.
Authors: Aquino R, Marques RFR, Petiot GH, Goncalves LGC, Moraes C, Santiago PRP, Puggina EF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968894/pdf/sports-04-00052.pdf
Summary: The purpose of this study was to investigate the association between offensive tactical knowledge and the soccer-specific motor skills performance. Fifteen participants were submitted to two evaluation tests, one to assess their technical and tactical analysis. The motor skills performance was measured through four tests of technical soccer skills: ball control, shooting, passing and dribbling. The tactical performance was based on a tactical assessment system called FUT-SAT (Analyses of Procedural Tactical Knowledge in Soccer). Afterwards, technical and tactical evaluation scores were ranked with and without the use of the cluster method. A positive, weak correlation was perceived in both analyses (rho = 0.39, not significant p = 0.14 (with cluster analysis); and rho = 0.35; not significant p = 0.20 (without cluster analysis)). We can conclude that there was a weak association between the technical and the offensive tactical knowledge. This shows the need to reflect on the use of such tests to assess technical skills in team sports since they do not take into account the variability and unpredictability of game actions and disregard the inherent needs to assess such skill performance in the game.


#7 Comparıson of the Heart Rate and Blood Lactate Responses of Different Small Sided Games in Young Soccer Players
Reference: Sports (Basel). 2016 Sep 29;4(4). pii: E48. doi: 10.3390/sports4040048.
Authors: Koklu Y, Alemdaroglu U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968902/pdf/sports-04-00048.pdf
Summary: The purpose of this study was to compare the percentage of maximum heart rate (%HRmax), blood lactate (La-), and rating of perceived exertion (RPE, CR-10) responses across different formats of small-sided games (SSG) in elite young soccer players. Fourteen players (average age 16.7 ± 0.6 years; height 177.6 ± 4.1 cm; body mass 66.3 ± 4.7 kg; average training age 6.7 ± 1.6 years; percentage of body fat 8.4 ± 2.6%) volunteered to perform the YoYo intermittent recovery test (level 1) and eight bouts of soccer drills including 2-a-side, 3-a-side, and 4-a-side games without goalkeepers in random order at two-day intervals. Heart rates were monitored throughout the SSGs, whereas the RPE and venous blood lactate were determined at the end of the last bout of each SSG. The differences in La-, %HRmax, and RPE either across the different SSGs or between the bouts were identified using 3 × 8 (games × exercise bouts) two-way analysis of variance with repeated measures. Significant differences were found in terms of La-, RPE, and %HRmax among the different types of SSG (p ≤ 0.05). 3-a-side and 4-a-side games elicited significantly higher responses than 2-a-side games in terms of %HRmax (p ≤ 0.05), whereas 4-a-side games resulted in significantly lower La- and RPE responses compared to 2-a-side and 3-a-side games. The results of this study show that physiological responses differ according to the numbers of players involved in small-sided games. Therefore, it can be concluded that 3-a-side and 4-a-side games could be more effective in improving high intensity aerobic performance than 2-a-side games, which in turn are more appropriate for developing anaerobic performance.


#8 Physiological Characteristics of Incoming Freshmen Field Players in a Men's Division I Collegiate Soccer Team
Reference: Sports (Basel). 2016 Jun 8;4(2). pii: E34. doi: 10.3390/sports4020034.
Authors: Lockie RG, Davis DL, Birmingham-Babauta SA, Beiley MD, Hurley JM, Stage AA, Stokes JJ, Tomita TM, Torne IA, Lazar A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968924/pdf/sports-04-00034.pdf
Summary: Freshmen college soccer players will have lower training ages than their experienced teammates (sophomores, juniors, seniors). How this is reflected in field test performance is not known. Freshmen (n = 7) and experienced (n = 10) male field soccer players from the same Division I school completed soccer-specific tests to identify potential differences in incoming freshmen. Testing included: vertical jump (VJ), standing broad jump, and triple hop (TH); 30-m sprint, (0⁻5, 5⁻10, 0⁻10, and 0⁻30 m intervals); 505 change-of-direction test; Yo-Yo Intermittent Recovery Test Level 2 (YYIRT2); and 6 × 30-m sprints to measure repeated-sprint ability. A MANOVA with Bonferroni post hoc was conducted on the performance test data, and effect sizes and z-scores were calculated from the results for magnitude-based inference. There were no significant between-group differences in the performance tests. There were moderate effects for the differences in VJ height, left-leg TH, 0⁻5, 0⁻10 and 0⁻30 m sprint intervals, and YYIRT2 (d = 0.63⁻1.18), with experienced players being superior. According to z-score data, freshmen had meaningful differences below the squad mean in the 30-m sprint, YYIRT2, and jump tests. Freshmen soccer players may need to develop linear speed, high-intensity running, and jump performance upon entering a collegiate program.


#9 Heart Rate Responses during Small Sided Games and Official Match-Play in Soccer
Reference: Sports (Basel). 2016 May 30;4(2). pii: E31. doi: 10.3390/sports4020031.
Authors: Asci A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968916/pdf/sports-04-00031.pdf
Summary: Small sided games (SSGs) are a match specific type of training. In addition, there is an insufficient number of studies that compare heart rate (HR) responses of SSGs and official match-play (OM). The purpose of this study was to investigate the heart rate responses during SSGs and OM in young soccer players. Twenty-two male soccer players (mean ± SD; age 17.4 ± 0.9 years, height 174.9 ± 6.6 cm, body weight 67.7 ± 8.1 kg) volunteered to participate in this study. The first session included anthropometric measurements and a maximum running test (RT). Following the RT session, all players participated in five different randomly ordered SSG sessions (3-, 4-, 5-, 7- and 9-a-side with goalkeepers). OMs were also monitored in the fourth week of the study. A one-way multivariate repeated-measures analysis of variance (MANOVA) was then conducted to evaluate the differences between the SSGs and OM. The results showed that 3-a-side elicited significantly higher HR and %HRmax than other SSGs and OM, whereas 9-a-side resulted in significantly lower HR and %HRmax compared to other SSG formats and OM (p < 0.05). In conclusion, 3-a-side, 4-a-side and 5-a-side SSG formats provide players with the opportunity to spend sufficient proportion of time spent in high intensity zones that are specific to match demands.


#10 Relationship of Two Vertical Jumping Tests to Sprint and Change of Direction Speed among Male and Female Collegiate Soccer Players
Reference: Sports (Basel). 2016 Feb 16;4(1). pii: E11. doi: 10.3390/sports4010011.
Authors: McFarland IT, Dawes JJ, Elder CL, Lockie RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968930/pdf/sports-04-00011.pdf
Summary: In collegiate level soccer acceleration, maximal velocity and agility are essential for successful performance. Power production is believed to provide a foundation for these speed qualities. The purpose of this study was to determine the relationship of change of direction speed, acceleration, and maximal velocity to both the counter movement jump (CMJ) and squat jump (SJ) in collegiate soccer players. Thirty-six NCAA Division II soccer players (20 males and 16 females) were tested for speed over 10 and 30 m, CODS (T-test, pro agility) and power (CMJ, SJ). Independent t-tests (p ≤ 0.05) were used to derive gender differences, and Pearson's correlations (p ≤ 0.05) calculated relationships between the different power and speed tests. Female subjects displayed moderate-to-strong correlations between 30 m, pro agility and T-test with the CMJ (r = -0.502 to -0.751), and SJ (r = -0.502 to -0.681). Moderate correlations between 10 and 30 m with CMJ (r = -0.476 and -0.570) and SJ (r = -0.443 and -0.553, respectively) were observed for males. Moderate to strong relationships exist between speed and power attributes in both male and female collegiate soccer players, especially between CMJ and maximal velocity. Improving stretch shortening cycle (SSC) utilization may contribute to enhanced sport-specific speed.

#11 Effect of New Zealand Blackcurrant Extract on Performance during the Running Based Anaerobic Sprint Test in Trained Youth and Recreationally Active Male Football Players
Reference: Sports (Basel). 2017 Sep 15;5(3). pii: E69. doi: 10.3390/sports5030069.
Authors: Godwin C, Cook MD, Willems MET
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968969/pdf/sports-05-00069.pdf
Summary: It was observed previously that New Zealand blackcurrant (NZBC) extract reduced slowing of the maximal 15 m sprint speed during the Loughborough Intermittent Shuttle Test. We examined the effect of NZBC extract on the performance of the Running Based Anaerobic Sprint Test (RAST, 6 × 35-m sprints with 10 seconds passive recovery) in trained youth and recreationally active football players. Fifteen recreationally active (University team) (age: 20 ± 1 years, height: 174 ± 19 cm, body mass: 80 ± 13 kg) and nine trained youth players (English professional club) (age: 17 ± 0 years, height: 178 ± 8 cm, body mass: 69 ± 9 kg, mean ± SD) participated in three testing sessions. Prior to the RASTs, participants consumed two capsules of NZBC extract (600 mg∙day-1 CurraNZ®) or placebo (P) for 7 days (double blind, randomised, cross-over design, wash-out at least 14 days). Ability difference between groups was shown by sprint 1 time. In the placebo condition, trained youth players had faster times for sprint 1 (5.00 ± 0.05 s) than recreationally active players (5.42 ± 0.08 s) (p < 0.01). In trained youth players, there was a trend for an effect of NZBC extract (p = 0.10) on the slowing of the sprint 1 time. NZBC extract reduced slowing of the sprint 5 time (P: 0.56 ± 0.22 s; NZBC: 0.35 ± 0.25, p = 0.02) and this was not observed in recreationally active players (P: 0.57 ± 0.48 s; NZBC: 0.56 ± 0.33, p = 0.90). For fatigue index, expressed as a % change in fastest sprint time, there was a strong trend to be lower in both trained youth and recreationally active players combined by NZBC extract (P: -13 ± 7%; NZBC: -11 ± 6%, p = 0.06) with 12 participants (five trained youth) experiencing less fatigue. New Zealand blackcurrant extract seems to benefit repeated sprint performance only in trained football players.


#12 Body Composition Evaluation Issue among Young Elite Football Players: DXA Assessment
Reference: Sports (Basel). 2017 Feb 23;5(1). pii: E17. doi: 10.3390/sports5010017.
Authors: Leao C, Simoes M, Silva B, Clemente FM, Bezerra P, Camoes M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969018/pdf/sports-05-00017.pdf
Summary: Accurate assessment of body composition is an important issue among athletes. Different methodologies generate controversial results, leading to a deep uncertainty on individual exercise prescriptions. Thus, this study aims to identify the differences between field methods, such as bioelectrical impedance (BIA) and skinfold assessment, with a clinical method, highly accurate, dual-energy X-ray absorptiometry (DXA), among elite young football players. Thirty-eight male football players with a mean (sd) age of 16.7 (0.87) years, involved in the Portuguese national competition of U16 (n = 13) and U19 (n = 25), were evaluated and objective measures of body composition, muscle strength and football skills were collected by trained specialists. Body composition was assessed using BIA (Tanita BC-418, Tanita Corp., Tokyo, Japan), in agreement with all the evaluation premises. Additionally, all athletes were evaluated using the clinical method DXA (Hologic Inc., Waltham, MA, USA). Among the U19 athletes, three skinfold sites (SKF) were assessed: chest, abdomin and thigh. The Spearman correlation coefficients and the mean difference between methods were calculated. The agreement between both methods was analyzed using Bland-Altman plots. Among the evaluated athletes, lower mean values of body fat % were found using BIA as a method of body composition assessment compared with DXA (12.05 vs. 15.58 for U16; 11.97 vs. 14.16 for U19). Despite the moderate correlation between methods (r = 0.33) to estimate the percentage of total fat, the median of the difference (DXA vs. BIA) was relevant in clinical terms, with 2.90% and 1.47% for U16 and U19 athletes, respectively. Stronger correlations were found between the sum of the SKF and DXA fat estimation (r = 0.68). The Bland-Altman plots showed a clear underestimation in the evaluations using the BIA, namely among athletes with better body composition profiles (8%⁻12% of fat). Using BIA, an underestimation of body fat assessment was observed among 94.5% of the athletes with less than 12% body fat mass. Among the evaluated athletes, fat mass was underestimated at a median value of 2.21% using BIA in comparison with DXA. The sum of the SKF showed a stronger correlation with the reference method (DXA) (r = 0.68) than BIA.


#13 Content Validity and Psychometric Properties of the Nomination Scale for Identifying Football Talent (NSIFT): Application to Coaches, Parents and Players
Reference: Sports (Basel). 2017 Jan 1;5(1). pii: E2. doi: 10.3390/sports5010002.
Authors: Prieto-Ayuso A, Pastor-Vicedo JC, Contreras-Jordan O
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969006/pdf/sports-05-00002.pdf
Summary: The identification of football talent is a critical issue both for clubs and the families of players. However, despite its importance in a sporting, economic and social sense, there appears to be a lack of instruments that can reliably measure talent performance. The aim of this study was to design and validate the Nomination Scale for Identifying Football Talent (NSIFT), with the aim of optimising the processes for identifying said talent. The scale was first validated through expert judgment, and then statistically, by means of an exploratory factor analysis (EFA), confirmatory factor analysis (CFA), internal reliability and convergent validity. The results reveal the presence of three factors in the scale's factor matrix, with these results being confirmed by the CFA. The scale revealed suitable internal reliability and homogeneity indices. Convergent validity showed that it is teammates who are best able to identify football talent, followed by coaches and parents. It can be concluded that the NSIFT is suitable for use in the football world. Future studies should seek to confirm these results in different contexts by means of further CFAs.


#14 The Effect of Recovery Duration on Technical Proficiency during Small Sided Games of Football
Reference: Sports (Basel). 2016 Jul 8;4(3). pii: E39. doi: 10.3390/sports4030039.
Authors: McLean S, Kerherve H, Naughton M, Lovell GP, Gorman AD, Solomon C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968888/pdf/sports-04-00039.pdf
Summary: The aim of this study was to determine the effect of increasing the duration of the recovery periods separating serial bouts of small sided games (SSG) of football on technical skills (TS). Twelve semi-professional footballers (mean ± SD; age 21 ± 3 years; VO2peak 64 ± 7 mL∙min∙kg-1; playing experience 15 ± 3 years) completed two SSG sessions, consisting of 3 vs. 3 players and 6 bouts of 2 min, separated by either 30 s recovery (REC-30) or 120 s recovery (REC-120). Sixteen TS, including passing, possession, and defensive related variables, and exercise intensity (heart rate, rating of perceived exertion, time motion descriptors) during the bouts were measured. Repeated measures ANOVA were used to determine differences between-conditions, for TS. The number of successful tackles was significantly higher, and the average time each team maintained possession was significantly lower in REC-120 compared to REC-30. There were no significant differences for all other TS variables, or exercise intensity measures between REC-30 and REC-120. Overall, a four-fold increase in the duration of recovery separating SSG bouts did not alter the technical skill execution of players. The experience and skill level of the players, combined with an apparent regulation of effort through pacing, may have assisted in the maintenance of technical skill execution.


#15 Analysis of Physiological, Technical, and Tactical Analysis during a Friendly Football Match of Elite U19
Reference: Sports (Basel). 2016 Jun 16;4(2). pii: E35. doi: 10.3390/sports4020035.
Authors: Ortega JI, Evangelio C, Clemente FM, Martins FML, Gonzalez-Villora S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968927/pdf/sports-04-00035.pdf
Summary: The main objective was to analyze a friendly match of youth elite soccer players identifying the variance of tactical and physiological response parameters during the game. In addition, detecting the impact of both halves on player performance. For the purposes of this study twenty-two U19 players were analyzed playing 11v11. Activity profile, heart rate (HR and HRmax), grouped in five different zones were analyzed via Bluetooth technology, technical performance was analyzed by the Team Sport Assessment Procedure (TSAP), and tactical performance was measured by Social Network Analysis. A comparison of heart rate responses showed significant main effects in the halves (p = 0.001; η p 2 = 0.623). A comparison between tactical position and technical performance had significant main effects (p = 0.001; η p 2 = 0.390). Tactical position showed statistically significant effects on tactical prominence (p = 0.002; η p 2 = 0.296). Therefore, fatigue is a component distinguished in technical/tactical parameters, such as volume of play and efficiency index. Results suggest that fatigue effects may constrain technical performance and, for that reason, the use of instruments to monitor the fatigue effect during matches may be suggested.


#16 "You're Not Born with Talent" Talented Girls' and Boys' Perceptions of Their Talents as Football Players
Reference: Sports (Basel). 2016 Jan 27;4(1). pii: E6. doi: 10.3390/sports4010006.
Authors: Saether SA, Mehus I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968932/pdf/sports-04-00006.pdf
Summary: Generally in sports, there is a strong assumption of a connection between skill level in young age and adulthood. Studies have mainly focused on the coaches' understanding and role in identifying and developing talent. In this article we turn our attention towards the athletes' perspectives, interviewing talented young football players (five boys and five girls) about their perceptions of their own talent and development. The objective of the article is to investigate how boys and girls perceive their talent and to discuss how various perceptions influence coaching practice in talent development. We introduce the following questions: (a) do the players use a static or dynamic perception of their own talent and (b) do the players consider specific or general skills to be most important in their skill development? Results show that the boys have a more static perception of talent compared to the girls. Furthermore, the boys in this study stress the importance of highly specified skills. The girls have a more balanced view on what is important, but tend to stress the importance of basic skills. The study suggests two potential implications. First, the coaches should be aware of the possible vulnerability following players' static perception of talent. Second, an exclusive focus on specified skills might make for less optimal preparation for the changing demands young players meet when moving through the different levels of play on their way to high level football. In future research it would be interesting to investigate how players with a lower skill level, not yet regarded as talent, perceive their talent and skill development.


#17 Effects of Video-Based Visual Training on Decision-Making and Reactive Agility in Adolescent Football Players
Reference: Sports (Basel). 2015 Dec 31;4(1). pii: E1. doi: 10.3390/sports4010001.
Authors: Nimmerichter A, Weber NJR, Wirth K, Haller A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968940/pdf/sports-04-00001.pdf
Summary: This study investigated the trainability of decision-making and reactive agility via video-based visual training in young athletes. Thirty-four members of a national football academy (age: 14.4 ± 0.1 years) were randomly assigned to a training (VIS; n = 18) or a control group (CON; n = 16). In addition to the football training, the VIS completed a video-based visual training twice a week over a period of six weeks during the competition phase. Using the temporal occlusion technique, the players were instructed to react on one-on-one situations shown in 40 videos. The number of successful decisions and the response time were measured with a video-based test. In addition, the reactive-agility sprint test was used. VIS significantly improved the number of successful decisions (22.2 ± 3.6 s vs. 29.8 ± 4.5 s; p < 0.001), response time (0.41 ± 0.10 s vs. 0.31 ± 0.10 s; p = 0.006) and reactive agility (2.22 ± 0.33 s vs. 1.94 ± 0.11 s; p = 0.001) pre- vs. post-training. No significant differences were found for CON. The results have shown that video-based visual training improves the time to make decisions as well as reactive agility sprint-time, accompanied by an increase in successful decisions. It remains to be shown whether or not such training can improve simulated or actual game performance.

Thu

30

Aug

2018

Latest research in football - week 25 - 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 Short-Term Plyometric Jump Training Improves Repeated-Sprint Ability in Prepuberal Male Soccer Players
Reference: J Strength Cond Res. 2018 Jun 14. doi: 10.1519/JSC.0000000000002703. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Fernandez-Fernandez J, Sammoud S, Bouguezzi R, Prieske O, Granacher U
Summary: This study examined the effects of a short-term (i.e., 8 weeks) combined horizontal and vertical plyometric jump training (PJT) program in combination with regular soccer-specific training as compared with soccer-specific training only on jump and change of direction (CoD) performances, speed, and repeated-sprint ability (RSA) in prepuberal male soccer players. Twenty-four players were recruited and randomly assigned to either a PJT group (PJTG; n = 13; 12.7 ± 0.2 years) or an active control group (CONG; n = 11; 12.7 ± 0.2 years). The outcome measures included tests for the assessment of jump performance (drop jump from 20- to 40-cm height [DJ20 and DJ40] and 3-hop test [THT]), speed (20-m sprint), CoD (T-test), and RSA (20-m repeated shuttle sprint). Data were analyzed using magnitude-based inferences. Within-group analyses revealed large performance improvements in the T-test (d = -1.2), DJ20 (d = 3.7), DJ40 (d = 3.6), THT (d = 0.6), and the RSAtotal (d = -1.6) in the PJTG. Between-group analyses showed greater performance improvements in the T-test (d = -2.9), 20-m sprint time (d = -2.0), DJ20 (d = 2.4), DJ40 (d = 2.0), THT (d = 1.9), RSAbest (d = -1.9), and the RSAtotal (d = -1.9) in the PJTG compared with CONG. Eight weeks of an in-season PJT in addition to regular soccer-specific training induced larger increases in measures of physical fitness in prepuberal male soccer players compared with regular soccer-specific training only. More specifically, PJT was effective in improving RSA performance.


#2 Fitness Monitoring in Elite Soccer Players: Group vs. Individual Analyses
Reference: J Strength Cond Res. 2018 Jun 14. doi: 10.1519/JSC.0000000000002700. [Epub ahead of print]
Authors: Rabbani A, Kargarfard M, Twist C
Summary: The aims of this study were to (a) examine changes in group and individual HR measures during a submaximal warm-up test, and (b) investigate the relationship between accumulated internal training loads and HR changes during an in-season phase among elite soccer players (n = 14). Before and after an in-season phase (24 days), exercise HR (HRex) and HR recovery (HRR) expressed either as the number of beats recovered (HRR60s) or as the mean HR (HRpost1) during 1 minute of recovery were analyzed. Heart rate measures were expressed as the % of maximal HR. Session rating of perceived exertion (sRPE) was computed for all training/match sessions. Group and individual HR changes were analyzed using magnitude-based inferences. Pearson correlation coefficients were also used to examine the relationships. Group analyses of HR changes revealed there were possibly to likely trivial changes in all HR measures. When analyzing individual data, no substantial change was observed for HRR60s%. However, substantial changes in HRex% and HRpost1% were observed for 4/14 and 5/14 players, respectively. The relationships between HRex% and HRpost1% were nearly perfect (r = 0.90, confidence limits [0.82-0.95]). The associations between changes in HRex% and HRpost1% were also nearly perfect (r = 0.92, 0.80-0.97). A very large inverse correlation was observed between HRex% and accumulated sRPE (r = -0.75, -0.44 to -0.90). This study highlights the value of conducting individual vs. group aerobic fitness monitoring. This study also showed the importance of how HRR is reported when aerobic fitness monitoring of elite soccer players.


#3 Segmental decompressive fasciotomy for acute non-traumatic compartment syndrome in a professional soccer player: case report
Reference: Rev Bras Ortop. 2018 Feb 15;53(2):244-247. doi: 10.1016/j.rboe.2018.02.001. eCollection 2018 Mar-Apr.
Authors: Baumfeld D, Pereira AL, Lage CFG, Miura GM, Gomes YVT, Nery C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001402/pdf/main.pdf
Summary: Acute compartment syndrome in athletes is a rare orthopedic emergency associated with strenuous exercise. It is often diagnosed late and can lead to severe complications and high morbidity. This report describes the case of a young soccer player with acute compartment syndrome with no history of trauma, diagnosed and treated 24 h after the onset of symptoms, through minimally invasive decompressive fasciotomy, with good postoperative evolution.


Seems like I have missed those ones last year (strange,but anyway just in case), here they are!

#4 Balance Performance as Observed by Center-of-Pressure Parameter Characteristics in Male Soccer Athletes and Non-Athletes
Reference: Sports (Basel). 2017 Nov 8;5(4). pii: E86. doi: 10.3390/sports5040086.
Authors: Thompson LA, Badache M, Cale S, Behera L, Zhang N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969037/pdf/sports-05-00086.pdf
Summary: Static balance has a relevant influence on athletic performance as well as on reducing the risk of injury. The main goal of this study was to assess soccer athlete versus non-athlete balance performance via displacement and velocity parameters extracted from the center-of-pressure (COP) position time series. In order to accomplish our goal, we investigated standing balance in two male groups with unimpaired balance: non-athletes (n = 12) and collegiate varsity soccer athletes (n = 12). In order to make the standing balancing task more or less difficult, we altered participant base-of-support, as well as vision, yielding static (quiet stance) test conditions increasing in difficulty. From the COP position time series, displacement and velocity parameters were computed and plotted as a function of increasing test condition difficulty level. COP parameters showed steeper increases with increased test difficulty in non-athletes compared to athletes; this demonstrated athletes' better ability to control their balance. We concluded that balance performance could be characterized via COP displacement and velocity response curves. This study lends new insights into how COP parameters can be utilized to determine and characterize improvements in balance between un-impaired subject populations (athletes versus non-athletes).


#5 Executive Function and the P300 after Treadmill Exercise and Futsal in College Soccer Players
Reference: Sports (Basel). 2017 Sep 26;5(4). pii: E73. doi: 10.3390/sports5040073.
Authors: Won J, Wu S, Ji H, Smith JC, Park J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969040/pdf/sports-05-00073.pdf
Summary: Although a body of evidence demonstrates that acute exercise improves executive function, few studies have compared more complex, laboratory-based modes of exercise, such as soccer that involve multiple aspects of the environment. Twelve experienced soccer players (24.8 ± 2 years) completed three counterbalanced 20 min sessions of (1) seated rest; (2) moderate intensity treadmill exercise; and (3) a game of futsal. Once heart rate returned to within 10% of pre-activity levels, participants completed the Stroop Color Word Conflict Task while reaction time (RT) and P300 event-related potentials were measured. Reaction time during Stroop performance was significantly faster following the futsal game and treadmill exercise compared to the seated rest. The P300 amplitude during Stroop performance was significantly greater following futsal relative to both treadmill and seated-rest conditions. These findings suggest that single bouts of indoor soccer among college-aged soccer players, compared to treadmill and seated-rest conditions, may engender the greatest effect on brain networks controlling attention allocation and classification speed during the performance of an inhibitory control task. Future research is needed to determine if cognitively engaging forms of aerobic exercise may differentially impact executive control processes in less experienced and older adult participants.


#6 Effects of Heart Rate vs. Speed-Based High Intensity Interval Training on Aerobic and Anaerobic Capacity of Female Soccer Players
Reference: Sports (Basel). 2017 Aug 4;5(3). pii: E57. doi: 10.3390/sports5030057.
Authors: Arazi H, Keihaniyan A, EatemadyBoroujeni A, Oftade A, Takhsha S, Asadi A, Ramirez-Campillo R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968964/pdf/sports-05-00057.pdf
Summary: The purpose of this study was to compare the effects of two types of high-intensity interval training (HIIT) programs on aerobic and anaerobic capacity of female soccer players. Regional-level female athletes were randomly divided into heart rate-based HIIT (n = 8; age 23.4 ± 1.1 year) and speed-based HIIT groups (n = 8; age 23.4 ± 1.3 year). Athletes trained three days per week for six weeks. Before and after training, each athlete's performance was assessed directly through the Hoff test, 30-15 Intermittent Fitness Test (VIFT), and repeated-sprint ability test (RAST); maximal oxygen consumption (VO₂max), power and fatigue were estimated indirectly. Both experimental groups improved power, fatigue index and VO₂max after training (p < 0.05). It was noteworthy that the speed-based group had greater gains in minimal power (effect size (ES): 3.99 vs. 0.75), average power (ES: 2.23 vs. 0.33), and fatigue index (ES: 2.53 vs. 0.17) compared to heart rate-based group (p < 0.05). In conclusion, both heart rate-based and speed-based HIIT induced meaningful improvements in power, VO₂max, and fatigue index in female soccer players, although the speed-based HIIT group achieved greater gains in power and fatigue index compared to the heart rate-based group.


#7 The Role of Eccentric Strength in 180° Turns in Female Soccer Players
Reference: Sports (Basel). 2017 Jun 17;5(2). pii: E42. doi: 10.3390/sports5020042.
Authors: Jones PA, Thomas C, Dos'Santos T, McMahon JJ, Graham-Smith P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968983/pdf/sports-05-00042.pdf
Summary: Previous studies have reported an association between eccentric strength (ECC-STR) and change of direction (COD) ability. Little is known about how ECC-STR facilitates COD maneuvers. The aim of this study was to examine the role of ECC-STR during a 180° COD task in 18 female soccer players. Each player performed six trials of a 180° COD task whereby three-dimensional motion data from 10 Qualisys Pro-Reflex infrared cameras (240 Hz) and ground reaction forces (GRFs) from two AMTI force platforms (1200 Hz) were collected. Relative eccentric knee extensor (ECC-EXT) and flexor (ECC-FLEX) peak torque was collected from both limbs at 60°·s-1 using a Kin Com isokinetic dynamometer. Large correlations were revealed between COD performance (time to complete 5 m approach, 180° turn, 5 m return) and ECC-EXT (R = -0.674) and ECC-FLEX (R = -0.603). Moderate to large correlations were observed between approach velocity (AV) and COD performance (R = -0.484) and ECC-EXT (R = 0.724). Stronger participants (n = 9) recorded significantly (p < 0.05) faster AV (4.01 ± 0.18 vs. 3.74 ± 0.24 m·s-1, d = 1.27) and a greater reduction in velocity (-1.55 ± 0.17 vs. -1.37 ± 0.21 m·s-1, d = -0.94) during penultimate contact than weaker (n = 9) subjects. Greater ECC-STR is associated with faster COD performance in female soccer players, as stronger players are better able to decelerate during penultimate contact from faster approach velocities.


#8 Nutrition and Supplementation in Soccer
Reference: Sports (Basel). 2017 May 12;5(2). pii: E28. doi: 10.3390/sports5020028.
Authors: Oliveira CC, Ferreira D, Caetano C, Granja D, Pinto R, Mendes B, Sousa M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968974/pdf/sports-05-00028.pdf
Summary: Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).


#9 Detection and Selection of Behavioral Patterns Using Theme: A Concrete Example in Grassroots Soccer
Reference: Sports (Basel). 2017 Mar 13;5(1). pii: E20. doi: 10.3390/sports5010020.
Authors: Amatria M, Lapresa D, Arana J, Anguera MT, Jonsson GK
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969010/pdf/sports-05-00020.pdf
Summary: Observational methodology provides a rigorous yet flexible framework for capturing behaviors over time to allow for the performance of subsequent diachronic analyses of the data captured. Theme is a specialized software program that detects hidden temporal behavioral patterns (T-patterns) within data sets. It is increasingly being used to analyze performance in soccer and other sports. The aim of this study was to show how to select and interpret T-patterns generated by the application of three "quantitative" sort options in Theme and three "qualitative" filters established by the researchers. These will be used to investigate whether 7-a-side (F7) or 8-a-side (F8) soccer is best suited to the learning and skills development needs of 7- and 8-year-old male soccer players. The information contained in the T-patterns generated allowed us to characterize patterns of play in children in this age group. For both formats, we detected technical-tactical behaviors showing that children of this age have difficulty with first-touch actions and controlling the ball after a throw-in. We also found that ball control followed by a pass or a shot at the goal are common in the central corridor of the pitch. Further, depth of play is achieved by ball control, followed by dribbling and a pass or shot. In F8, we saw that depth of play was achieved through ball control, followed by dribbling and passing of one or more opponents leading to a pass or shot. However, in F7, we saw that players succeeded in advancing from their goal area to the rival goal area through a sequence of actions.


#10 Functional Movement Screen Scores and Physical Performance among Youth Elite Soccer Players
Reference: Sports (Basel). 2017 Feb 21;5(1). pii: E16. doi: 10.3390/sports5010016.
Authors: Silva B, Clemente FM, Camoes M, Bezerra P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969015/pdf/sports-05-00016.pdf
Summary: This study had two main objectives: (1) to determine if differences in Functional Movement Screen (FMS) scores exist between two levels of competition; and (2) to analyze the association between FMS individual and overall scores and physical performance variables of lower-limb power (jumps), repeated sprint ability and shot speed. Twenty-two Under 16 (U16) and twenty-six Under 19 (U19) national competitive soccer players participated in this study. All participants were evaluated according to anthropometrics, FMS, jump performance, instep kick speed and anaerobic performance. There were no significant differences in the individual FMS scores between competitive levels. There were significant negative correlations between hurdle step (right) and Running-based Anaerobic Sprint Test (RAST) power average ( ρ = -0.293; p = 0.043) and RAST fatigue index (RAST FatIndex) ( ρ = -0.340; p = 0.018). The hurdle step (left) had a significant negative correlation to squat jump (SJ) ( ρ = -0.369; p = 0.012). Rotary stability had a significant negative correlation to RAST fatigue index (Right: ρ = -0.311; p = 0.032. Left: ρ = -0.400; p = 0.005). The results suggest that individual FMS scores may be better discriminants of performance than FMS total score and established minimal association between FMS scores and physical variables. Based on that, FMS may be suitable for the purposes of determining physical function but not for discriminating physical performance.


#11 Differences in the Dominant and Non-Dominant Knee Valgus Angle in Junior Elite and Amateur Soccer Players after Unilateral Landing
Reference: Sports (Basel). 2017 Feb 13;5(1). pii: E14. doi: 10.3390/sports5010014.
Authors: Ludwig O, Simon S, Piret J, Becker S, Marschall F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969013/pdf/sports-05-00014.pdf
Summary: More than 70% of all knee injuries in soccer occur in non-contact situations. It is known that increased lower limb dynamic knee valgus is associated with such situations. Little has been found out about differences in knee kinematics of the dominant (kicking) and non-dominant (supporting) leg during a single leg landing. A total of 114 male adolescent soccer players (age 14.6 ± 1.1 years) from elite (N = 66) and amateur soccer clubs (N = 48) performed a single leg drop landing down from a box. For each leg, the two-dimensional dynamic knee valgus angle (DKVA) was calculated. Paired t-tests were used to statistically determine significant differences between dominant and non-dominant leg DKVA, and t-tests were calculated between the two performance groups. Statistically significant differences (p < 0.05) were identified for the DKVA between the dominant and non-dominant leg for both amateur and elite players, showing a greater DKVA for the dominant leg. Group differences for the DKVA between amateur and elite players were not found, neither for the dominant, nor for the non-dominant leg. It can be concluded that the non-dominant leg showed more stable dynamics than the dominant leg during unilateral landing regardless of the player's performance level. This could be due to adaptions to sport-specific requirements. Therefore, it is recommended that programs to prevent knee injuries among soccer players consider the dynamics of each leg individually.

Tue

07

Aug

2018

Latest research in football - week 24 - 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 Sex Differences in Physical Capacities of German Bundesliga Soccer Players
Reference: J Strength Cond Res. 2018 Jun 20. doi: 10.1519/JSC.0000000000002662. [Epub ahead of print]
Authors: Cardoso de Araujo M, Baumgart C, Jansen CT, Freiwald J, Hoppe MW
Summary: Sex differences in physical capacities of elite soccer players have received limited attention. Therefore, this study investigated sex differences in linear and nonlinear sprint, squat and countermovement jump, core endurance, as well as incremental and intermittent endurance capacities in German Bundesliga soccer players. A total of 76 field players (29 women) were tested for the mentioned anaerobic- and aerobic-related physical capacities in a noninterventional cross-sectional design. The largest sex differences were evident in the explosive- and intermittent endurance-related capacities, with women presenting largely to extremely largely lower values in sprints, jumps, and intermittent endurance (effect size [ES] ≥1.77, p < 0.01). The differences in the total core endurance, running velocity at 2 and 4 mmol·L capillary blood lactate (v2 and v4), maximal heart rate (HR) (ES ≤ 0.72, p ≥ 0.06), and distance covered during the incremental endurance test (ES = 1.09, p = 0.01) were trivially to moderately lower for women. However, women had small to moderately higher ventral and dorsal core endurance (ES ≤ 0.69, p ≥ 0.07) and largely higher relative HR at the lactate thresholds (ES ≥ 1.54, p < 0.01). The individual data of female players showed more variability. Some individual data of women overlapped those of men, most evident in the total core endurance and v2. The findings indicate that there are sex differences in physical capacities according to the underlying amount of anaerobic and aerobic energy supply. The sex specificities should be considered to optimize training and testing procedures for soccer players.


#2 Developmental Changes in Isometric Strength: Longitudinal Study in Adolescent Soccer Players
Reference: Int J Sports Med. 2018 Jun 20. doi: 10.1055/s-0044-100389. [Epub ahead of print]
Authors: Duarte JP, Valente-Dos-Santos J, Coelho-E-Silva MJ, Malina RM, Deprez D, Philippaerts R, Lenoir M, Vaeyens R
Summary: This study aimed to examine longitudinal changes in isometric strength of the knee extensors (ImKE) and knee flexors (ImKF) at 30° and 60°. The sample was composed of 67 players aged 11.0-13.9 years at baseline over five years. Stature, body mass, skinfolds, and isometric strength (ImKE30°, ImKF30°, ImKE60° and ImKF60°) were measured. Fat mass and fat-free mass (FFM) were derived from skinfolds. Skeletal age was obtained using TW2 RUS. Multilevel random effects regression analyses extracted developmental polynomial models. An annual increment on chronological age (CA) corresponded to 5.6 N (ImKE30°: ), 2.7 N (ImKF30°: ), 4.6 N (ImKE60°: ) and 1.5 N (ImKF60°). An increment of 1 kg in FFM predicted isometric strength as follows: 1.2 N (ImKE30°), 2.1 N (ImKF30°), 3.1 N (ImKE60°) and 2.0 N (ImKF60°). The following equations were obtained: ImKE30°=5.759×CA+1.163×FFM; ImKF30°=-19.369+2.691×CA+0.693×CA2+2.108×FFM; ImKE60°=4.553×CA+3.134×FFM; and, ImKF60°=-19.669+1.544×CA+2.033×FFM. Although skeletal maturity had a negligible effect on dependent variables, age and body size, based on FFM, were relevant longitudinal predictors. During adolescence, systematic assessment of knee extensors and knee flexors are strongly recommended to prevent impairment of knee muscle groups.


#3 Assessing Cardiorespiratory Fitness of Soccer Players: Is Test Specificity the Issue?-A Review.
Reference: Sports Med Open. 2018 Jun 19;4(1):28. doi: 10.1186/s40798-018-0134-3.
Authors: Jemni M, Prince MS, Baker JS
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0134-3
Summary: It is important that players and coaches have access to objective information on soccer player's physical status for team selection and training purposes. Physiological tests can provide this information. Physiological testing in laboratories and field settings are very common, but both methods have been questioned because of their specificity and accuracy respectively. Currently, football players have their direct aerobic fitness assessed in laboratories using treadmills or cycle ergometers, whilst indirect measures (using estimation of aerobic performance) are performed in the field, typically comprising multiple shuttle runs back and forth over a set distance. The purpose of this review is to discuss the applied techniques and technologies used for evaluating soccer players' health and fitness variables with a specific focus on cardiorespiratory testing. A clear distinction of the functionality and the specificity between the field tests and laboratory tests is well established in the literature. The review findings prioritize field tests over laboratory tests, not only for commodity purpose but also for motivational and specificity reasons. Moreover, the research literature suggests a combination of various tests to provide a comprehensive assessment of the players. Finally, more research needs to be conducted to develop a specific and comprehensive test model through the combination of various exercise modes for soccer players.


#4 Correlation between Match Performance and Field Tests in Professional Soccer Players
Reference: J Hum Kinet. 2018 Jun 13;62:213-219. doi: 10.1515/hukin-2017-0171. eCollection 2018 Jun.
Authors: Redkva PE, Paes MR, Fernandez R, da-Silva SG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006532/pdf/hukin-62-213.pdf
Summary: The aim of this study was to investigate possible correlations between aerobic and anaerobic fitness (in field tests) with performance during a 90 min friendly match, through the following variables: total distance covered, maximal running speed, number of high-intensity actions and number of sprints. Eighteen professional soccer players from a Brazilian elite team (age 23 ± 3 years, body mass 77.5 ± 8.9 kg) participated in the study. The athletes performed a Yo-Yo Endurance Test (aerobic fitness) and a Running Anaerobic Sprint Test (six maximal 35 m efforts separated by 10 s of passive recovery, anaerobic fitness). Data were collected during friendly matches using a GPS with 5 Hz technology. To establish the correlation between the variables determined during the matches, the Pearson correlation coefficient was used (significance level of p ≤ 0.05). A high correlation was found between distance covered in the Yo-Yo endurance test and total distance covered (r = 0.72; p < 0.05), number of high-intensity actions (r = 0.78; p < 0.05) and number of sprints (r = 0.88; p < 0.01) in the soccer matches. The RAST variables did not relate to the standards set during the matches (p < 0.05). From the results of the present study, it may be concluded that there is no correlation between RAST and friendly match data variables. However, better results in the Yo-Yo endurance test correlate with total distance, number of high-intensity actions and sprints during matches.


#5 The Impact of Nonlinear Pedagogy on Decision-Making and Execution in Youth Soccer Players According to Game Actions
Reference: J Hum Kinet. 2018 Jun 13;62:185-198. doi: 10.1515/hukin-2017-0169. eCollection 2018 Jun.
Authors: Praxedes A, Del Villar F, Pizarro D, Moreno A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006529/pdf/hukin-62-185.pdf
Summary: The aim of this study was to analyze the effect of a teaching program, based on Non-Linear Pedagogy, on decision-making and performance in youth soccer players as a function of the type of play action. Our participants were 19 players from the U12 age category. The teaching program, which was based on the application of modified games characterized by a numerical superiority in attack, was used for 14 training sessions. This program was conducted in two phases (preparation-for-intervention and intervention). Decision-making and execution for pass and dribbling actions were evaluated through the Game Performance Evaluation Tool. The results showed significant differences in favour of the experimental group in decision-making (p < .000) and the execution of passes (p = .003) after the intervention. However, such differences were not found for dribbling (decision-making, p = .402 and execution, p = .143). These findings demonstrate the effectiveness of this type of program for teaching actions with a high tactical component, such as the pass, and a different approach must be considered in actions with a high technical component, such as dribbling. It is necessary to continue developing studies in this line to clarify these issues.


#6 Seasonal Body Composition Variation Amongst Elite European Professional Soccer Players: An Approach of Talent Identification
Reference: J Hum Kinet. 2018 Jun 13;62:177-184. doi: 10.1515/hukin-2017-0132. eCollection 2018 Jun.
Authors: Owen AL, Lago-Penas C, Dunlop G, Mehdi R, Chtara M, Dellal A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006533/pdf/hukin-62-177.pdf
Summary: The primary aim of the investigation was to study the seasonal changes in body composition in elite European soccer players and identify key playing positional differences. Twenty-two players (age = 24 ± 3.7 years, body height = 180.45 ± 5.12 cm, body mass = 76.66 ± 5.34 kg) were tested. Players' mass (kg), lean body mass (LBM), fat free mass (FFM), fat mass (FM), muscle girths (MG) and sum of 8 skinfolds (mm) were measured across 5 time points (T0 = Start of pre-season training; T1 = End of pre-season training; T2 = Mid-season; T3 = End of mid-season break; T4 = End of season). Players were divided into their tactical positional roles for analysis. The specific positions they were divided into included defenders (n = 8), midfielders (n = 8) and forwards (n = 6). Assessment of training and matchplay exposure were also recorded. Sites-4, Sites-7, Sites-8 and Fat Mass decreased dramatically from T0 to T1 and T2 in all playing positions (p < 0.01), while no remarkable differences were found between T2, T3 and T4. Except for defenders, calf girth and lean mass were higher in T2, T3 and T4 compared to T0 and T1 (p < 0.01). Midfielders were found to be leaner than forwards and defenders in all data collection time point sessions. Defenders showed higher values in calf girth and lean body mass than midfielders and forwards. It can be concluded from this investigation that there are large variances n positional body composition profiles amongst professional European soccer players. Furthermore, significant changes are prevalent and occur across the season from LBM, FFM, MG and skinfold assessment amongst European elite level soccer players.


#7 Soccer Small-Sided Games Activities Vary According to the Interval Regime and their Order of Presentation within the Session
Reference: J Hum Kinet. 2018 Jun 13;62:167-175. doi: 10.1515/hukin-2017-0168. eCollection 2018 Jun.
Authors: Sanchez-Sanchez J, Ramirez-Campillo R, Carretero M, Martin V, Hernandez D, Nakamura FY
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006548/pdf/hukin-62-167.pdf
Summary: In order to investigate the physical demands of widely used in soccer small-sided games (SSGs), we compared game variations performed under different interval (fixed or variable) and timing regimens (beginning or end of a training session). Twelve male players wore GPS devices during the SSGs to record total distance, relative distance, distance at different speeds, and maximum velocity variables. Four variations of SSGs (4x4) were randomly applied: beginning of a training session with fixed and variable recovery, or end of a training session with fixed and variable recovery. During the beginning or end of a training session settings with fixed recovery duration, 2-min of playing and 2-min of recovery were provided. During the beginning and end of a training session settings with variable recovery, athletes kept playing until a goal was scored, or up to 2-min if no goals were scored. Results were analysed using MANOVA. Total distance and relative distance were higher in the beginning compared to end of training sessions for both fixed and variable recovery duration (small to moderate effect sizes). Distance at various speed ranges (i.e., 13-18 km/h and >18 km/h) was higher (p ≤ 0.01) at the beginning than at the end of training sessions with variable recovery. In addition, distance >18 km/h was higher at the beginning of a training session with variable recovery than fixed recovery and at the end of a training session with variable recovery than fixed recovery. In conclusion, several physical demand characteristics are affected by the moment of SSG application, while others respond to the recovery regime during SSGs, thus providing indications to the coaches to prescribe the intended training intensity by manipulating the context.


#8 Changes in Effective Playing Space when Considering Sub-Groups of 3 to 10 Players in Professional Soccer Matches
Reference: J Hum Kinet. 2018 Jun 13;62:145-155. doi: 10.1515/hukin-2017-0166. eCollection 2018 Jun.
Authors: Goncalves B, Folgado H, Coutinho D, Marcelino R, Wong D, Leite N, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006547/pdf/hukin-62-145.pdf
Summary: Success in soccer is much dependent on how players and teams create and restrict space and time. In match situations, players constitute small sub-groups to improve their collective synchronization and achievement of specific goals. This study aimed to identify changes in the effective playing space (EPS, defined as the smallest polygonal area delimited by the peripheral outfield players) when considering sub-groups of 3 to 10 players. Twenty outfield professional players participated in this study. The EPS, its regularity pattern (measured by the approximate entropy), coefficient of variation and players' mean speed were calculated for sub-groups of 3, 4, 5, 6, 7, 8, 9 and 10 players, considering the smallest inter-player distance as the criterion. The EPS presented a most likely increase with a higher number of players, especially considering the transition from 3 to 4 players (~440% of variation, very large). As the EPS increased with the number of players, the correspondent regularity presented a trend of a most likely increase (from EPS3 vs. EPS4: ~25%, very large; to EPS9 vs. EPS10: ~11%, moderate). The mean speed results suggest that players may achieve different states of collective coordination, mainly between ~6 to 8 km.h-1. Overall, three different match scenarios should require additional attention when aiming to design more match transferable tasks: i) transition from EPS3 to EPS4; ii) transition from EPS4 up to EPS8; and iii) transition from EPS8 to EPS9. These results help to understand match self-organized behaviours and, consequently, allow to optimize task characteristics in practice sessions.


#9 The Reliability of Technical and Tactical Tagging Analysis Conducted by a Semi-Automatic VTS in Soccer
Reference: J Hum Kinet. 2018 Jun 13;62:103-110. doi: 10.1515/hukin-2017-0162. eCollection 2018 Jun.
Authors: Beato M, Jamil M, Devereux G
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006549/pdf/hukin-62-103.pdf
Summary: The Video Tracking multiple cameras system (VTS) is a technology that records two-dimensional position data (x and y) at high sampling rates (over 25 Hz). The VTS is of great interest because it can record external load variables as well as collect technical and tactical parameters. Performance analysis is mainly focused on physical demands, yet less attention has been afforded to technical and tactical factors. Digital.Stadium® VTS is a performance analysis device widely used at national and international levels (i.e. Italian Serie A, Euro 2016) and the reliability evaluation of its technical tagging analysis (e.g. shots, passes, assists, set pieces) could be paramount for its application at elite level competitions, as well as in research studies. Two professional soccer teams, with 30 male players (age 23 ± 5 years, body mass 78.3 ± 6.9 kg, body height 1.81 ± 0.06 m), were monitored in the 2016 season during a friendly match and data analysis was performed immediately after the game ended. This process was then replicated a week later (4 operators conducted the data analysis in each week). This study reports a near perfect relationship between Match and its Replication. R2 coefficients (relationships between Match and Replication) were highly significant for each of the technical variables considered (p < 0.001). In particular, a high score of interclass correlation and a small coefficient of variation were reported. This study reports meaningless differences between Match and its Replication (intra-day reliability). We concluded that the semi-automatic process behind the Digital.Stadium® VTS was more than capable of recording technical tagging data accurately.


#10 Changes in Injury Risk Mechanisms after Soccer-Specific Fatigue in Male Youth Soccer Players
Reference: J Hum Kinet. 2018 Jun 13;62:33-42. doi: 10.1515/hukin-2017-0157. eCollection 2018 Jun.
Authors: Lehnert M, Croix MS, Xaverova Z, Botek M, Varekova R, Zaatar A, Lastovicka O, Stastny P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006546/pdf/hukin-62-033.pdf
Summary: The aim of this study was to examine the acute effects of soccer specific fatigue on muscular and neuromuscular function in male youth soccer players. Elite soccer players (n = 20; age 15.7 ± 0.5 y; body height 177.75 ± 6.61 cm; body mass 67.28 ± 8.29 kg) were measured before and after soccer specific exercise (SAFT90). The reactive strength index (RSI) was determined by a drop jump test, leg stiffness (LS) by a 20 sub-maximal two-legged hopping test, and a functional hamstring to quadriceps strength ratio from isokinetic concentric and eccentric strength of the dominant and non-dominant leg (measured at angular velocities of 1.05 rad · s-1 and 3.14 rad · s-1). Metabolic response to the SAFT90 was determined by blood lactate and perceived exertion was assessed by the Borg scale. After simulated match play, a significant decrease in absolute LS (t = 4.411; p < 0.001; ω2 = 0.48) and relative LS (t = 4.326; p < 0.001; ω2 = 0.49) was observed and the RSI increased significantly (t = 3.806; p = 0.001; ω2 = 0.40). A reduction in LS found after the SAFT90 indicates possible reduction in dynamic knee stabilization. However, if we consider the changes in other observed variables, the present study did not clearly confirm that fatigue induced by a soccer specific protocol increased the risk of ACL and hamstring injury. This may be attributed to the simulated rather than actual match play used in the present study.


#11 Age and maturity related differences in motor coordination among male elite youth soccer players
Reference: J Sports Sci. 2018 Jun 18:1-8. doi: 10.1080/02640414.2018.1488454. [Epub ahead of print]
Authors: Rommers N, Mostaert M, Goossens L, Vaeyens R, Witvrouw E, Lenoir M, D'Hondt E
Summary: This study investigated differences in generic and soccer specific motor coordination, as well as speed and agility depending on age and maturity in elite youth soccer players (U10-U15, N = 619). Measurements included body height, body weight and sitting height to estimate age at peak height velocity (APHV); three Körperkoordinationstest für Kinder subtests (i.e. jumping sideways (JS), moving sideways (MS), balancing backwards (BB)) to assess generic motor coordination; the UGent dribbling test for soccer specific motor coordination; a 5m/30m sprint and T-test for speed and agility, respectively. Age specific z-scores of the predicted APHV identified players as earlier, on time or later maturing. (M)ANOVA analyses showed significant age by maturity interaction effects for the speed and agility test cluster, revealing maturity related differences in U14 and U15 players. Next to an overall higher performance with age for all test clusters (η2 0.080-0.468), earlier maturing players outperformed their later maturing peers in 5m/30m sprinting. The opposite was seen for JS and BB. So, players' maturity status should be taken into account to adequately value performance in talent identification. Also, the focus on characteristics that appear to be minimally biased by an earlier maturational timing (i.e. motor coordination) should be increased.

Fri

03

Aug

2018

Latest research in football - week 23 - 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 Occurrence of Repeated High Acceleration Ability (RHAA) in Elite Youth Football
Reference: Int J Sports Med. 2018 Jun 5. doi: 10.1055/a-0608-4738. [Epub ahead of print]
Authors: Serpiello FR, Duthie GM, Moran C, Kovacevic D, Selimi E, Varley MC
Summary: The aim of the present study was to investigate the occurrence of Repeated High-Acceleration Ability (RHAA) bouts in elite youth football games using 10-Hz GPS devices and two relative thresholds derived from players' actual maximal acceleration. Thirty-six outfield soccer players (age 14.9±0.6 years) participated in the study. Players wore 10-Hz GPS units during 41 official games. High accelerations were defined as efforts commencing above a threshold corresponding to 70% (T70%) or 80% (T80%) of the average 5-m acceleration obtained during a 40-m sprint test; RHAA bouts were defined as ≥3 efforts with ≤45 s recovery between efforts. Results were analysed via generalised linear mixed model and magnitude-based inferential statistics. On average, 8.0±4.6 and 5.1±3.5 bouts were detected in an entire game using T70% and T80%, respectively. When all positions were analysed together, there was a very-likely small difference in the number of RHAA bouts between first and second half for T70% and T80%, respectively. RHAA bouts occur frequently in elite youth football, with small differences between halves and between playing positions within the first or second half in most variables assessed.


#2 Importance of Reactive Agility and Change of Direction Speed in Differentiating Performance Levels in Junior Soccer Players: Reliability and Validity of Newly Developed Soccer-Specific Tests
Reference: Front Physiol. 2018 May 15;9:506. doi: 10.3389/fphys.2018.00506. eCollection 2018.
Authors: Pojskic H, Aslin E, Krolo A, Jukic I, Uljevic O, Spasic M, Sekulic D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5962722/pdf/fphys-09-00506.pdf
Summary: Agility is a significant determinant of success in soccer; however, studies have rarely presented and evaluated soccer-specific tests of reactive agility (S_RAG) and non-reactive agility (change of direction speed - S_CODS) or their applicability in this sport. The aim of this study was to define the reliability and validity of newly developed tests of the S_RAG and S_CODS to discriminate between the performance levels of junior soccer players. The study consisted of 20 players who were involved at the highest national competitive rank (all males; age: 17.0 ± 0.9 years), divided into three playing positions (defenders, midfielders, and forwards) and two performance levels (U17 and U19). Variables included body mass (BM), body height, body fat percentage, 20-m sprint, squat jump, countermovement jump, reactive-strength-index, unilateral jump, 1RM-back-squat, S_CODS, and three protocols of S_RAG. The reliabilities of the S_RAG and S_CODS were appropriate to high (ICC: 0.70 to 0.92), with the strongest reliability evidenced for the S_CODS. The S_CODS and S_RAG shared 25-40% of the common variance. Playing positions significantly differed in BM (large effect-size differences [ES]; midfielders were lightest) and 1RM-back-squat (large ES; lowest results in midfielders). The performance levels significantly differed in age and experience in soccer; U19 achieved better results in the S_CODS (t-test: 3.61, p < 0.05, large ES) and two S_RAG protocols (t-test: 2.14 and 2.41, p < 0.05, moderate ES). Newly developed tests of soccer-specific agility are applicable to differentiate U17 and U19 players. Coaches who work with young soccer athletes should be informed that the development of soccer-specific CODS and RAG in this age is mostly dependent on training of the specific motor proficiency.


#3 The Betting Odds Rating System: Using soccer forecasts to forecast soccer
Reference: PLoS One. 2018 Jun 5;13(6):e0198668. doi: 10.1371/journal.pone.0198668. eCollection 2018.
Authors: Wunderlich F, Memmert D
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0198668&type=printable
Summary: Betting odds are frequently found to outperform mathematical models in sports related forecasting tasks, however the factors contributing to betting odds are not fully traceable and in contrast to rating-based forecasts no straightforward measure of team-specific quality is deducible from the betting odds. The present study investigates the approach of combining the methods of mathematical models and the information included in betting odds. A soccer forecasting model based on the well-known ELO rating system and taking advantage of betting odds as a source of information is presented. Data from almost 15.000 soccer matches (seasons 2007/2008 until 2016/2017) are used, including both domestic matches (English Premier League, German Bundesliga, Spanish Primera Division and Italian Serie A) and international matches (UEFA Champions League, UEFA Europe League). The novel betting odds based ELO model is shown to outperform classic ELO models, thus demonstrating that betting odds prior to a match contain more relevant information than the result of the match itself. It is shown how the novel model can help to gain valuable insights into the quality of soccer teams and its development over time, thus having a practical benefit in performance analysis. Moreover, it is argued that network based approaches might help in further improving rating and forecasting methods.


#4 Data concerning isometric lower limb strength of dominant versus not-dominant leg in young elite soccer players
Reference: Data Brief. 2018 Jan 31;17:414-418. doi: 10.1016/j.dib.2018.01.022. eCollection 2018 Apr.
Authors: Rouissi M, Chtara M, Bragazzi NL, Haddad M, Chamari K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5988318/pdf/main.pdf
Summary: The present data article describes the isometric lower limb strength of dominant leg versus not-dominant leg measured with handheld dynamometer (HHD) in a sample of 31 young elite soccer players (age 16.42 ± 0.45 years; height 169.00 ± 0.50 cm; leg length 94.80 ± 3.32 cm; body-mass 67.04 ± 5.17 kg).


#5 The Construct Validity of the CODA and Repeated Sprint Ability Tests in Football Referees
Reference: Int J Sports Med. 2018 Jun 14. doi: 10.1055/a-0577-4073. [Epub ahead of print]
Authors: Riiser A, Andersen V, Castagna C, Arne Pettersen S, Saeterbakken A, Froyd C, Ylvisaker E, Naess Kjosnes T, Fusche Moe V
Summary: As of 2017, the international football federation introduced the change of direction ability test (CODA) and the 5×30 m sprint test for assistant referees (ARs) and continued the 6×40 m sprint test for field referees (FRs) as mandatory tests. The aim of this study was to evaluate the association between performance in these tests and running performance during matches at the top level in Norway. The study included 9 FRs refereeing 21 matches and 19 ARs observed 53 times by a local positioning system at three stadiums during the 2016 season. Running performance during matches was assessed by high-intensity running (HIR) distance, HIR counts, acceleration distance, and acceleration counts. For the ARs, there was no association between the CODA test with high-intensity running or acceleration (P>0.05). However, the 5×30 m sprint test was associated with HIR count during the entire match (E -12.9, 95% CI -25.4 to -0.4) and the 5-min period with the highest HIR count (E -2.02, 95% CI -3.55 to -0.49). For the FRs, the 6×40 m fitness test was not associated with running performance during matches (P>0.05). In conclusion, performance in these tests had weak or no associations with accelerations or HIR in top Norwegian referees during match play.


#6 The effects of an enrichment training program for youth football attackers
Reference: PLoS One. 2018 Jun 13;13(6):e0199008. doi: 10.1371/journal.pone.0199008. eCollection 2018.
Authors: Coutinho D, Santos S, Goncalves B, Travassos B, Wong DP, Schollhorn W, Sampaio J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5999098/pdf/pone.0199008.pdf
Summary: The aim of this study was to identify the effects of a complementary training program based on differential learning approach in the physical, technical, creative and positioning performance of youth football attackers. Fifteen players were allocated into the control (U15C = 9, age: 13.9±0.5 years; U17C = 6, age: 16.1±0.7 years) and the experimental (U15E = 9, age: 14.2±0.8 years; U17E = 6, age: 15.8±0.5 years) groups. The experimental groups participated in 10-weeks of a complementary training program based on differential learning approach to improve physical literacy and players' tactical behavior. Variables studied encompassed: motor (vertical jump, speed and repeated change-of direction), technical (pass, dribble and shot), creative (fluency, attempts, versatility) and positioning-related variables (stretch index, spatial exploration index and regularity of the lateral and longitudinal movements). Results revealed that U15E improved both the jump and repeated change-of-direction performance, while the U17E have only improved the jump performance. The U15E showed improvements in all technical variables (small to large effects), and in the fluency and versatility (moderate effects), while the U17 have only improved the successful shots (large effects). From a positional perspective, there was a moderate increase in the stretch index, and decreased longitudinal and lateral regularity (small to moderate effects) in the U15E compared to the U15C. In turn, the U17E revealed a moderate increase of the spatial exploration index and a small decrease in the stretch index. Overall, the results suggest that the complementary training program was effective for the development of the overall performance of the U15E attackers, while more time and/or variability may be needed for older age groups. Nevertheless, the overall higher values found in experimental groups, may suggest that this type of complementary training program improves performance.


#7 The Adductor Strengthening Programme prevents groin problems among male football players: a cluster-randomised controlled trial
Reference: Br J Sports Med. 2018 Jun 10. pii: bjsports-2017-098937. doi: 10.1136/bjsports-2017-098937. [Epub ahead of print]
Authors: Haroy J, Clarsen B, Wiger EG, Oyen MG, Serner A, Thorborg K, Holmich P, Andersen TE, Bahr R
Summary: Groin injuries represent a considerable problem in male football. Previous groin-specific prevention programmes have not shown a significant reduction in groin injury rates. An exercise programme using the Copenhagen Adduction exercise increases hip adduction strength, a key risk factor for groin injuries. However, its preventive effect is yet to be tested. The aim of the study was to evaluate the effect of a single-exercise approach, based on the Copenhagen Adduction exercise, on the prevalence of groin problems in male football players. 35 semiprofessional Norwegian football teams were cluster-randomised into an intervention group (18 teams, 339 players) and a control group (17 teams, 313 players). The intervention group performed an Adductor Strengthening Programme using one exercise, with three progression levels, three times per week during the preseason (6-8 weeks), and once per week during the competitive season (28 weeks). The control group were instructed to train as normal. The prevalence of groin problems was measured weekly in both groups during the competitive season using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. The average prevalence of groin problems during the season was 13.5% (95% CI 12.3% to 14.7%) in the intervention group and 21.3% (95% CI 20.0% to 22.6%) in the control group. The risk of reporting groin problems was 41% lower in the intervention group (OR 0.59, 95% CI 0.40 to 0.86, p=0.008). The simple Adductor Strengthening Programme substantially reduced the self-reported prevalence and risk of groin problems in male football players.


#8 Football is medicine: it is time for patients to play!
Reference: Br J Sports Med. 2018 Jun 9. pii: bjsports-2018-099377. doi: 10.1136/bjsports-2018-099377. [Epub ahead of print]
Authors: Krustrup P, Krustrup BR
Download link: http://bjsm.bmj.com/content/bjsports/early/2018/06/09/bjsports-2018-099377.full.pdf


#9 Are There Differences in Elite Youth Soccer Player Work Rate Profiles in Congested vs. Regular Match Schedules?
Reference: J Strength Cond Res. 2018 Jun 21. doi: 10.1519/JSC.0000000000002702. [Epub ahead of print]
Authors: Zanetti V, Carling C, Aoki MS, Bradley PS, Moreira A
Summary: Official international tournaments in which youth soccer players participate can involve very congested schedules. Yet, no information regarding physical and technical match performance during congested vs. regular (noncongested) cycles is available. In this study, accelerations, decelerations, mean metabolic power (MP), and technical performance (offensive and defensive variables) were compared across very congested match (VCM; 10 international matches played over 3 successive days, including 2 days with 2 consecutive matches separated by a 4- to 5-hour interval) and 10 regular (noncongested match [NCM]) match periods in elite male Under 15 (U15, n = 11) and Under 17 (U17, n = 13) soccer players. Players wore a 15-Hz Global Positioning System unit with a 100-Hz triaxial accelerometer. The session rating of perceived exertion (RPE) were assessed 30 minutes after match. Results showed a higher number of accelerations per minute observed in VCM vs. NCM (U15; 2.27 ± 0.35 vs. 2.12 ± 0.23; effect size [ES] = 0.49; U17; 2.27 ± 0.41 vs. 2.01 ± 0.31; ES = 0.69). Decelerations per minute were higher during VCM (U15; 1.99 ± 0.27 vs. 1.84 ± 0.25; ES = 0.55; and U17; 1.98 ± 0.35 vs. 1.80 ± 0.27; ES = 0.56). Mean MP was higher in the VCM (U15; 0.42 ± 0.06 vs. 0.37 ± 0.02; ES = 1.08; U17; 0.46 ± 0.03 vs. 0.30 ± 0.03; ES = 1.94). Technical actions per minute were higher in the VCM for U17 (ES = 1.60 and 1.37, for offensive and defensive performance, respectively) but lower (during VCM) for U15 (ES = 3.59 and 0.28, for offensive and defensive performance). U15 reported a higher session RPE in the VCM (7.9 ± 0.5 AUs vs. 6.9 ± 0.5 AUs). The findings suggest that running activity in these youth players was unaffected overall in tournaments with congested schedules, and that the intensity of match-play was actually greater than in regular match schedules.


#10 Personality and Risk Taking in Sports: A Focus on Unintentional and Intentional Head Impacts in Amateur Soccer Players
Reference: Clin J Sport Med. 2018 Jun 21. doi: 10.1097/JSM.0000000000000627. [Epub ahead of print]
Authors: Levitch CF, Ifrah C, Kim M, Stewart WF, Lipton RB, Zimmerman ME, Lipton ML
Summary: In soccer, unintentional and intentional (heading) head impacts are associated with concussive symptoms and cognitive dysfunction. We examined whether personality traits were associated with these behaviors in soccer players. Participants completed study visits at the Albert Einstein College of Medicine. A total of 307 adult amateur soccer players, recruited from New York City and the surrounding area, completed 737 HeadCount-2w questionnaires. Personality traits (intellect/imagination, conscientiousness, extraversion, agreeableness, and neuroticism) were assessed with the Mini-International Personality Item Pool questionnaire at the baseline study visit were used as predictor variables. Main outcome variables were an online questionnaire (HeadCount-2w) to ascertain frequency of intentional head impacts and occurrence of unintentional head impacts every 3 to 6 months. Generalized estimating equations repeated-measures regressions determined whether personality predicted unintentional and intentional impacts. Personality traits were not associated with unintentional head impact(s) or frequency of intentional head impacts. These findings have important clinical implications, suggesting that personality is not driving the association between high levels of unintentional and intentional head impacts and worse neuropsychological functioning and concussive symptoms.


#11 Does Man Marking Influence Running Outputs and Intensity During Small-Sided Soccer Games?
Reference: J Strength Cond Res. 2018 Jun 20. doi: 10.1519/JSC.0000000000002668. [Epub ahead of print]
Authors: Aasgaard M, Kilding AE
Summary: Small-sided games (SSGs) are considered an effective training tool for physical development in soccer. Small-sided games can be modified in several ways to manipulate the physical demands to best match the game demands, player characteristics, and session objectives. The aim of this study was to compare the physiological, perceptual, and Global Positioning System (GPS)-derived time-motion characteristics of man marking (MM) vs. non-man marking (NMM) in 2v2, 3v3, and 4v4 SSGs. In an acute crossover design, 8 amateur soccer players (mean age ± SD: 23.6 ± 3.3 years) played 2v2, 3v3, and 4v4 SSGs consisting of 4 × 4-minute bouts, with 2-minute passive recovery. During all SSGs, players wore a heart rate (HR) monitor and GPS unit and reported their rating of perceived exertion (RPE). Average percent HR (%HRave) induced small to moderate effects with MM compared with NMM (%Δ = 1-2.7%; effect size [ES] = 0.22-0.65). Comparisons between MM formats indicated a decrease in %HRave with increased player numbers (%Δ = 1.6-3.5%; ES = 0.39-0.86). Perceptual load increased with MM compared with NMM (%Δ = 6.7-17.6%; ES = 0.66-2.09), whereas increases in player numbers (MM only) reduced RPE output (%Δ = 9.4-24.3%; ES = 1.14-3.61). Time-motion characteristics revealed substantially greater total distance covered in MM irrespective of player number (%Δ = 6.8-14.7%; ES = 1.34-2.82). There were very likely increases in distances covered at striding (13.1-17.8 km·h) (%Δ: 23.4-33.2; ES = 2.42-4.35) and high-intensity running (HIR) (17.9-21 km·h) (%Δ: 47.3-104; ES = 0.91-1.68) for MM compared with NMM irrespective of player number. In conclusion, MM substantially elevated perceptual load and distances from striding to HIR regardless of player number, whereas differences between NMM and MM for internal load remain unclear. Use of MM may allow coaches to condition for particularly demanding phases of the game and prescription of larger SSG formats to increase distance covered at higher velocities.

Wed

25

Jul

2018

Latest research in football - week 22 - 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 Prevention of Ankle Sprain Injuries in Youth Soccer and Basketball: Effectiveness of a Neuromuscular Training Program and Examining Risk Factors
Reference: Clin J Sport Med. 2017 Jun 29. doi: 10.1097/JSM.0000000000000462. [Epub ahead of print]
Authors: Owoeye OBA, Palacios-Derflingher LM, Emery CA
Summary: The primary objective of this study was to examine the effectiveness of a neuromuscular training (NMT) warm-up program in reducing the risk of ankle sprain injury (ASI) in youth soccer and basketball. The secondary objective included the evaluation of risk factors for ASI. Male and female youth (11-18 years) soccer and basketball players (n = 2265) in Alberta, Canada participated in this study. Ankle sprain injury was the primary outcome and was recorded using a validated prospective injury surveillance system consistent in all studies. The primary exposure of interest was NMT warm-up, which included aerobic, strength, agility, and balance components. Multivariable Poisson regression, controlling for clustering by team and offset for exposure hours, was used to estimate incidence rate ratios (IRRs) with 95% confidence intervals (CIs), with considerations for confounding and effect modification and evaluating all covariates as potential risk factors. A total of 188 ASIs were reported in 171 players. Neuromuscular training significantly reduced the risk of ASI [IRR = 0.68 (95% CI; 0.46-0.99)]. Independent risk factors for ASI included previous ASI [IRR = 1.98 (95% CI; 1.38-2.81)] and participation in basketball versus soccer [IRR = 1.83 (95% CI; 1.18-2.85)]. Sex, age, body mass index, and previous lower extremity injury (without previous ASI) did not predict ASI (P > 0.05). Exposure to an NMT program is significantly protective for ASI in youth soccer and basketball. Risk of ASI in youth basketball is greater than soccer, and players with a history of ASI are at greater risk


#2 Patellar tendon properties distinguish elite from non-elite soccer players and are related to peak horizontal but not vertical power
Reference: Eur J Appl Physiol. 2018 Jun 2. doi: 10.1007/s00421-018-3905-0. [Epub ahead of print]
Authors: Murtagh CF, Stubbs M, Vanrenterghem J, O'Boyle A, Morgans R, Drust B, Erskine RM
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00421-018-3905-0.pdf
Summary: The purpose was to investigate potential differences in patellar tendon properties between elite and non-elite soccer players, and to establish whether tendon properties were related to power assessed during unilateral jumps performed in different directions. Elite (n = 16; age 18.1 ± 1.0 years) and non-elite (n = 13; age 22.3 ± 2.7 years) soccer players performed vertical, horizontal-forward and medial unilateral countermovement jumps (CMJs) on a force plate. Patellar tendon (PT) cross-sectional area, elongation, strain, stiffness, and Young's modulus (measured at the highest common force interval) were assessed with ultrasonography and isokinetic dynamometry. Elite demonstrated greater PT elongation (6.83 ± 1.87 vs. 4.92 ± 1.88 mm, P = 0.011) and strain (11.73 ± 3.25 vs. 8.38 ± 3.06%, P = 0.009) than non-elite soccer players. Projectile range and peak horizontal power during horizontal-forward CMJ correlated positively with tendon elongation (r = 0.657 and 0.693, P < 0.001) but inversely with Young's modulus (r = - 0.376 and - 0.402; P = 0.044 and 0.031). Peak medial power during medial CMJ correlated positively with tendon elongation (r = 0.658, P < 0.001) but inversely with tendon stiffness (r = - 0.368, P = 0.050). Not only does a more compliant patellar tendon appear to be an indicator of elite soccer playing status but it may also facilitate unilateral horizontal-forward and medial, but not vertical CMJ performance. These findings should be considered when prescribing talent selection and development protocols related to direction-specific power in elite soccer players.


#3 Workload and non-contact injury incidence in elite football players competing in European leagues
Reference: Eur J Sport Sci. 2018 Jun 2:1-8. doi: 10.1080/17461391.2018.1477994. [Epub ahead of print]
Authors: Delecroix B, McCall A, Dawson B, Berthoin S, Dupont G
Summary: The aim of this study was to analyse the relationship between absolute and acute:chronic workload ratios and non-contact injury incidence in professional football players and to assess their predictive ability. Elite football players (n = 130) from five teams competing in European domestic and confederation level competitions were followed during one full competitive season. Non-contact injuries were recorded and using session rate of perceived exertion (s-RPE) internal absolute workload and acute:chronic (A:C) workload ratios (4-weeks, 3-weeks, 2-weeks and week-to-week) were calculated using a rolling days method. The relative risk (RR) of non-contact injury was increased (RR = 1.59, CI95%: 1.18-2.15) when a cumulative 4-week absolute workload was greater than 10629 arbitrary units (AU) in comparison with a workload between 3745 and 10628 AU. When the 3-week absolute workload was more than 8319 AU versus between 2822 and 8318 AU injury risk was also increased (RR= 1.46, CI95% 1.08-1.98). Injury incidence was higher when the 4-week A:C ratio was <0.85 versus >0.85 (RR = 1.31, CI95%: 1.02-1.70) and with a 3-week A:C ratio >1.30 versus <1.30 (RR = 1.37, CI95%: 1.05-1.77). Importantly, none of the A:C workload combinations showed high sensitivity or specificity. In elite European footballers, using internal workload (sRPE) revealed that cumulative workloads over 3 and 4 weeks were associated with injury incidence. Additionally, A:C workloads, using combinations of 2, 3 and 4 weeks as the C workloads were also associated with increased injury risk. No A:C workload combination was appropriate to predict injury.


#4 Hip and groin injury is the most common non-time-loss injury in female amateur football
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Jun 2. doi: 10.1007/s00167-018-4996-1. [Epub ahead of print]
Authors: Langhout R, Weir A, Litjes W, Gozeling M, Stubbe JH1, Kerkhoffs G, Tak I
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00167-018-4996-1.pdf
Summary: Hip and groin injuries in football are problematic due to their high incidence and risk of chronicity and recurrence. The use of only time-loss injury definitions may underestimate the burden of hip and groin injuries. Little is known about hip and groin injury epidemiology in female football. The first aim of this study was to examine the within-season (2014-2015) prevalence of total injury with and without time-loss in female amateur football players. The second aim was to study the within-season and preseason (2015-2016) prevalence of hip/groin injuries with and without time-loss. The third aim was to study the association between the duration of hip and groin injury in the 2014-2015 season and the severity of hip/groin problems during the 2015-2016 preseason. During the preseason, 434 Dutch female amateur football players completed an online questionnaire based on the previous season and current preseason. The hip and groin outcome score (HAGOS) was used to assess the severity of hip and groin injuries. The hip/groin (17%), knee (14%), and ankle (12%) were the most frequent non-time-loss injury locations. The ankle (22%), knee (18%), hamstring (11%), thigh (10%), and hip/groin (9%) were the most common time-loss injury locations. The previous season prevalence of total injury was 93%, of which non-time-loss injury was 63% and time-loss injury was 37%. The prevalence of hip/groin injury was 40%, non-time-loss hip/groin injury was 36% and time-loss hip/groin injury was 11%. The preseason prevalence of hip/groin injury was 27%, non-time-loss hip/groin injury was 25%, and time-loss hip/groin injury was 4%. Players with longstanding hip/groin injury (> 28 days) in the previous season had lower HAGOS scores at the next preseason than players with short-term (1-7 days) or no hip/groin injury (p < 0.001). From all players with hip/groin injury from the previous season, 52% also sustained hip/groin injury in the following preseason, of which 73% were recurrent and 27% were chronic hip/groin injuries. Injury risk, and especially non-time-loss hip and groin injury risk, is high in female amateur football. Three-quarters of the players with longstanding hip and groin injuries in the previous season have residual problems at the start of the following season.


#5 Distribution of Arsenic and Risk Assessment of Activities on Soccer Pitches Irrigated with Arsenic-Contaminated Water
Reference: Int J Environ Res Public Health. 2018 May 24;15(6). pii: E1060. doi: 10.3390/ijerph15061060.
Authors: Martinez-Villegas N, Hernandez A, Meza-Figueroa D, Sen Gupta B
Download link: www.mdpi.com/1660-4601/15/6/1060/pdf
Summary: The aim of this research was to estimate the risk of human exposure to arsenic due to sporting activities in a private soccer club in Mexico, where arsenic-contaminated water was regularly used for irrigation. For this purpose, the total concentration in the topsoil was considered for risk assessment. This was accomplished through three main objectives: (1) measuring arsenic concentrations in irrigation water and irrigated soils, (2) determining arsenic spatial distribution in shallow soils with Geographical Information Systems (GIS) using geostatistical analysis, and (3) collecting field and survey data to develop a risk assessment calculation for soccer activities in the soccer club. The results showed that the average arsenic concentrations in shallow soils (138.1 mg/kg) were 6.2 times higher than the Mexican threshold for domestic soils (22 mg/kg). Furthermore, dermal contact between exposed users and contaminated soils accounted for a maximum carcinogenic risk value of 1.8 &times; 10&minus;5, which is one order of magnitude higher than the recommended risk value, while arsenic concentrations in the irrigation water were higher (6 mg/L) than the WHO&rsquo;s permissible threshold in drinking water, explaining the contamination of soils after irrigation. To the best of our knowledge, this is the first risk study regarding dermal contact with arsenic following regular grass irrigation with contaminated water in soccer pitches.


#6 Modeling of relationships between physical and technical activities and match outcome in elite German soccer players
Reference: J Sports Med Phys Fitness. 2018 Jun 7. doi: 10.23736/S0022-4707.18.08506-7. [Epub ahead of print]
Authors: Konefal M, Chmura P, Kowalczuk E, Figueiredo AJ, Sarmento H, Rokita A, Chmura J, Andrzejewski M
Summary: The aim of this study was to determine what physical and technical activities of soccer players in different pitch positions affect significantly the match outcome of professional German soccer players; as well as to examine whether differences in physical and technical activities increase or reduce the probability of a match being won. The study sample comprised 4393 individual match observations of 350 soccer players competing in the Bundesliga during the 2014/2015 domestic season. Analysis was confined to outfield players (other than goalkeepers) who completed entire matches, and was carried out using the Impire AG motion analysis system. The selection of physical and technical activities to be used in predictive models was achieved using the lasso method. The odds ratio revealed that an mean running speed in the second half that was greater by 0.1 km/h was associated with a 27.0% improvement in the odds of a match being won (OR=1.27; 95% CI: 1.17 to 1.38) (forwards), 15.7% (OR=1.16; 95% CI: 1.09 to 1.23) (wide midfielders), and 10.0% (OR=1.10; 95% CI: 1.04 to 1.17) (central midfielders). Furthermore, in the case of wide midfielders, a significant variable was the distance covered at > 24 km/h, with an increase of 0.1 km associated with odds of winning the game improved by 31.7% (OR=1.32; 95% CI: 1.05 to 1.66). Match outcome is affected significantly where peak and mean running speeds in the second half of the match are greater, and where longer distances are covered at speeds in excess of 24 km/h.


#7 Professional soccer is associated with radiographic cam and pincer hip morphology
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Jun 6. doi: 10.1007/s00167-018-5008-1. [Epub ahead of print]
Authors: Falotico GG, Arliani GG, Yamada AF, Fernandes ADRC, Ejnisman B, Cohen M
Summary: Femoroacetabular impingement (FAI) syndrome is characterized by a triad: symptoms, clinical signs and imaging findings. Some individuals, especially athletes, have only imaging alterations. The objective of this study was to evaluate the prevalence of cam and pincer morphology in professional soccer players compared with a control group of non-athletes and to investigate the association between the age at which players start playing competitive soccer more than three times per week and duration of the soccer career with the prevalence of these radiographic findings. The prevalence of cam and pincer morphology in sixty professional adult male soccer players and thirty-two male controls was determined using pelvic anteroposterior radiography. Data were recorded for all hips and correlated with the age at which the players started competitive soccer practice and with the duration of their soccer career. The prevalence of morphological FAI in the soccer players was 92.5% versus 28.1% in the controls (p < 0.001). The duration of the soccer career was positively correlated with the alpha angle (p = 0.033) and negatively correlated with the retroversion index (p = 0.009). The age at which competitive play began was inversely correlated with the alpha angle (p < 0.001). The study showed a high prevalence of cam and pincer morphology in Brazilian professional soccer players compared with controls. The duration of the soccer career was associated with an increased alpha angle and a decreased retroversion index, and the age at which competitive soccer participation began was negatively associated with alpha angle values. Finally, this manuscript provides data about the association between greater exposure to soccer and cam and pincer morphological changes in the hip; specifically, cam morphology was more common in patients who began participating in sports at earlier ages. This information serves as an alert for coaches of youth teams to manage the training load in youth athletes.


#8 Injury rate and prevention in elite football: let us first search within our own hearts
Reference: Br J Sports Med. 2018 Jun 2. pii: bjsports-2018-099267. doi: 10.1136/bjsports-2018-099267. [Epub ahead of print]
Authors: Buchheit M, Eirale C, Simpson BM, Lacome M


#9 How the Experimental Setting Influences Representativeness: A Review of Gaze Behavior in Football Penalty Takers
Reference: Front Psychol. 2018 May 8;9:682. doi: 10.3389/fpsyg.2018.00682. eCollection 2018.
Authors: Kurz J, Munzert J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5952262/pdf/fpsyg-09-00682.pdf
Summary: This article reviews research on the gaze behavior of penalty takers in football. It focuses on how artificial versus representative experimental conditions affect gaze behavior in this far-aiming task. Findings reveal that-irrespective of the representativeness of the experimental conditions-different instructions regarding the aiming strategy and different threat conditions lead to different gaze patterns. Results also reveal that the goal size and the distance to the goal did not affect the gaze behavior. Moreover, it is particularly run-up conditions that lead to differences. These can be either artificial or more natural. During a natural run-up, penalty takers direct their gaze mainly toward the ball. When there is no run-up, they do not direct their gaze toward the ball. Hence, in order to deliver generalizable results with which to interpret gaze strategies, it seems important to use a run-up with a minimum length that is comparable to that in a real-life situation.


#10 Creatine kinase, neuromuscular fatigue, and the contact codes of football: A systematic review and meta-analysis of pre- and post-match differences
Reference: Eur J Sport Sci. 2018 Jun 5:1-11. doi: 10.1080/17461391.2018.1480661. [Epub ahead of print]
Authors: Hagstrom AD, Shorter KA
Summary: Physiological or performance tests are routinely utilised to assess athletes' recovery. At present, the ideal tool to assess recovery remains unknown. Therefore, the aim of this systematic review was to examine the change in creatine kinase (CK) and neuromuscular function as measured via a countermovement jump (CMJ) following a match in the contact codes of football. A comprehensive search of databases was undertaken with RevMan (V 5.3) used for statistical analysis. Our results demonstrated that CK pre- versus post-match (standardised mean difference (SMD) = 0.90, 95% CI = 0.50 to 1.31, p < .0001), CK pre- versus 24 h post-match (SMD = 1.50, 95% CI = 1.12 to 1.88, p < .00001), and CK pre- versus 48 h post-match all increased significantly (SMD = 0.90, 95% CI = 0.50 to 1.31, p < .0001), while CMJ peak power (PP) pre- versus post-match (SMD = -0.59, 95% CI = -1.12 to -0.06, p = .03), and pre- versus 24 h post-match (SMD = -0.80, 95% CI = -1.31 to -0.28, p = .002) decreased significantly. There was a significant relationship between the change in CK and the change in CMJ PP from immediately pre to immediately post (r = -0.924, p = .025), and between CMJ immediately following a match and 24 h CK change (r = -0.983, p = .017). In conclusion, CK levels increase and performance in the CMJ decreases following a match of a contact code of football. The identification of this relationship may allow coaching staff to implement a standalone measure of recovery.


#11 Lunacy revisited - the myth of the full moon: are football injuries related to the lunar cycle?
Reference: Chronobiol Int. 2018 Jun 6:1-6. doi: 10.1080/07420528.2018.1483943. [Epub ahead of print]
Authors: Yousfi N, Rekik RN, Eirale C, Whiteley R, Farooq A, Tabben M, Gillogly S, Bahr R, Chamari K
Summary: Previous literature suggests that human behaviour and physiology are somehow altered by the moon-cycle, with particular emphasis on poorer sleep quality and increased aggressive behaviour during full moon. The latter variables can negatively impact athletes' recovery and increase the likelihood of injury resulting from collision with another athlete. Therefore, the current study aimed to investigate the association between the lunar cycle and injury risk in professional football players (soccer). We monitored injuries and player exposure in the premier professional league in Qatar during four consecutive seasons (2013-2014 through 2016-2017). Acute (sudden-onset traumatic) injuries (n = 1184; 587 from contact with another player and 597 without player contact) recorded during matches and training were classified according to the lunar cycle characteristics on the date of injury: (i) moon illumination, (ii) lunar distance from earth and (iii) tidal coefficient, acquired from the lunar calendar and tide tables. We used a Poisson regression model to examine the relationship between injury risk and lunar cycle characteristics. We did not detect any association between injury risk and moon illumination, earth-to-moon distance or tidal coefficient, not for all acute injuries, nor for contact and non-contact injuries when examined separately. The findings suggest that the full moon or new moon or the gravitational pull have no effect on football injuries. Thus, organisers need not consult moon or tide tables when planning future event schedules.

Sun

08

Jul

2018

Latest research in football - week 21 - 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 Commotio Cordis in a Professional Soccer Player: Value of MRI in Unraveling Myocardial Damage
Reference: Circ Cardiovasc Imaging. 2018 Jun;11(6):e007848. doi: 10.1161/CIRCIMAGING.118.007848.
Authors: Zeldetz V, Greenberg S, Zeller L, Zahger D, Shalev A


#2 No Effect of Generalized Joint Hypermobility on Injury Risk in Elite Female Soccer Players: Response
Reference: Am J Sports Med. 2018 Jun;46(7):NP28-NP29. doi: 10.1177/0363546518773721.
Authors: Thijs KM, Blokland D, Backx FJG, Goedhart EA, Huisstede BMA.
Download link: http://journals.sagepub.com/doi/pdf/10.1177/0363546518773721


#3 Injuries in formal and informal non-professional soccer - an overview of injury context, causes, and characteristics
Reference: Eur J Sport Sci. 2018 May 29:1-9. doi: 10.1080/17461391.2018.1475507. [Epub ahead of print]
Authors: Gebert A, Gerber M, Puhse U, Gassmann P, Stamm H, Lamprecht M
Summary: The objective of this study is to analyse context, causes, and characteristics of injuries in non-professional soccer. Therefore, a retrospective telephone survey was carried out with persons who were injured while playing soccer and who reported this accident to the Swiss National Accident Insurance Fund (Suva). Based on these data, an analysis of 708 soccer injuries was performed. The findings show that 30.1% of the injuries occurred during informal soccer play, and 75.4% of the injured persons were soccer club members. 53.0% of all injuries were caused by contact and 29.5% by foul play. Foul play was not associated with injury severity. With respect to injury severity, twisting/turning and being tackled by an opponent were identified as the most influental injury causes. Moreover, the risk of being severely injured was particularly high players of the 30+/40+ amateur leagues. In conclusion, the findings highlight that 30+/40+ league players are a major target group for the prevention of severe soccer injuries. Soccer clubs may constitute an appropriate multiplier for implementing prevention strategies such as fair play education, healthy play behaviours, and prevention programmes. Finally, a better understanding of injury situations leading to severe injuries is needed to improve injury prevention.


#4 Countermovement Jump Recovery in Professional Soccer Players Using an Inertial Sensor
Reference: Int J Sports Physiol Perform. 2018 May 29:1-23. doi: 10.1123/ijspp.2018-0131. [Epub ahead of print]
Authors: McHugh MP, Clifford T, Abbott W, Kwiecien SY, Kremenic IJ, DeVita JJ, Howatson G
Summary: The purpose of this study was to assess the utility of an inertial sensor for assessing recovery in professional soccer players. In a randomized, crossover design, 11 professional soccer players wore shorts fitted with phase change material (PCM) cooling packs or uncooled packs (control) for 3 h after a 90 minute match. Countermovement jump (CMJ) performance was assessed simultaneously with an inertial sensor and an optoelectric system, pre match, and 12, 36 and 60 h post match. Inertial sensor metrics were flight height, jump height, low force, countermovement distance, force at low point, rate of eccentric force development, peak propulsive force, maximum power, and peak landing force. The only optoelectric metric was flight height. CMJ decrements, and effect of PCM cooling were assessed with repeated measures ANOVA. Jump heights were also compared between devices. For the inertial sensor data there were decrements in CMJ height on the days after matches (88±10% of baseline at 36 h P=0.012, effect size 1.2, for control condition) and accelerated recovery with PCM cooling (105±15% of baseline at 36 h, P=0.018 vs. control, effect size 1.1). Flight heights were strongly correlated between devices (r=0.905, P<0.001) but inertial sensor values were 1.8±1.8 cm lower (P=0.008). Low force during countermovement was increased (P=0.031) and landing force was decreased (P=0.043) after matches, but neither were affected by the PCM cooling intervention. Other CMJ metrics were unchanged after matches. This small portable inertial sensor provides a practical means of assessing recovery in soccer players.


#5 Neuromechanical response to passive cyclic loading of the ACL in non-professional soccer players: A pilot study
Reference: Phys Ther Sport. 2018 May 15;32:187-193. doi: 10.1016/j.ptsp.2018.05.013. [Epub ahead of print]
Authors: Nuccio S, Labanca L, Rocchi JE, Macaluso A, Sbriccoli P
Summary: The purpose was to investigate the effects of passive cyclic loading (CYC) on anterior tibial translation (ATT), knee extensor and flexor muscle strength and activation in soccer players. Functional Assessment Laboratory; Participants: Eight healthy competitive soccer players. The knee of the dominant limb was subjected to 10 min of CYC at 200 N force. ATT was measured before and after CYC. Percentage of variation was used to estimate ACL creep. Knee extension and flexion maximal voluntary contractions (MVCs) were assessed both before and after CYC. EMG amplitudes of both Biceps Femoris (BF) and Vastus Lateralis (VL) were recorded during both MVCs and CYC. There was a 20.7% increase in ATT after CYC application (p<0.001). Post-CYC agonist and antagonist BF activations were 37.7% and 18.4% lower than pre-CYC ones during MVCs (p<0.05). BF EMG activity in the last 30s of CYC was 19.9% higher than in the first 30s (p<0.05). The increased ATT and the variations in neuromuscular activation of the BF in response to loading may expose the knee at higher injury risk by increasing joint instability. Further studies are required to thoroughly investigate these aspects in both laboratory and real-field settings.


#6 Scheduling of Eccentric Lower-limb Injury Prevention Exercises during the Soccer micro-cycle: Which day of the week?
Reference: Scand J Med Sci Sports. 2018 May 24. doi: 10.1111/sms.13226. [Epub ahead of print]
Authors: Lovell R, Whalan M, Marshall PW, Sampson JA, Siegler JC, Buchheit M
Summary: Scheduling eccentric-based injury prevention programs (IPP) during the common 6-day micro-cycle in Soccer is challenged by recovery and tapering phases. This study profiled muscle damage, neuromuscular performance, and perceptual responses to a lower-limb eccentric-based IPP administered 1 (MD+1) versus 3 days (MD+3) post-match. 18 semi-professional players were monitored daily during 3 in-season 6-day micro-cycles, including weekly competitive fixtures. Capillary creatine kinase concentration (CK), posterior lower limb isometric peak force (PF), counter-movement jump (CMJ) performance, and muscle soreness were assessed 24 h prior to match-day (baseline), and every 24 h up to 120 h post-match. The IPP consisted of lunges, single stiff leg dead-lifts, single leg-squats and Nordic hamstring exercises. Performing the IPP on MD+1 attenuated the decline in CK normally observed following match-play (CON: 142%; MD+3: 166%; small differences). When IPP was delivered on MD+3, CK was higher versus CON and MD+1 trials on both MD+4 (MD+3: 260%; CON: 146%; MD+1: 151%; moderate differences) and MD+5 (MD+3: 209%; CON: 125%; MD+1: 127%; small differences). Soreness ratings were not exacerbated when the IPP was delivered on MD+1, but when prescribed on MD+3, hamstring soreness ratings remained higher on MD+4 and MD+5 (small differences). No between trial differences were observed for PF and CMJ. Administering the IPP in the middle of the micro-cycle (MD+3) increased measures of muscle damage and soreness, which remained elevated on the day prior to the next match (MD+5). Accordingly, IPP should be scheduled early in the micro-cycle, to avoid compromising preparation for the following match.


#7 Hamstring-to-Quadriceps Torque Ratios of Professional Male Soccer Players: A Systematic Review
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002609. [Epub ahead of print]
Authors: Baroni BM, Ruas CV, Ribeiro-Alvares JB, Pinto RS
Summary: The goal of this review was to determine the isokinetic hamstring-to-quadriceps (H/Q) torque ratios of professional male soccer players. Systematic searches were independently carried out by 2 researchers in 7 electronic databases. Only studies with teams from the first or second national leagues were included. From these studies, we extracted the players' H/Q conventional (concentric/concentric) and/or functional (eccentric/concentric) ratios. The initial search resulted in 2,128 articles that were filtered to 30 articles (1,727 players) meeting the inclusion criteria. The H/Q conventional ratio was assessed in 27 studies (1,274 players), whereas the H/Q functional ratio was assessed in 15 studies (1,082 players). The H/Q conventional ratio mean scores of professional male soccer players were close to 60% when tested at low to intermediate angular velocities (12°·s = 52 ± 7%; 30°·s = 52 ± 8%; 60°·s = 65 ± 12%; 90°·s = 57 ± 6%; 120°·s = 65 ± 16%; 180°·s = 67 ± 17%) and around 70-80% at fast angular velocities (240°·s = 80 ± 40%; 300°·s = 70 ± 15%; 360°·s = 80 ± 13%). The H/Q functional ratio mean scores of professional male soccer players were close to 80% at 60°·s (79 ± 19%), around 100-130% at intermediate to fast angular velocities (120°·s = 127 ± 42%; 180°·s = 96 ± 19%; 240°·s = 109 ± 22%; 300°·s = 123 ± 18%), and near or above 130% when angular testing velocities were mixed (eccentric hamstring < concentric quadriceps; 30/240°·s = 132 ± 26%; 60/180°·s = 129 ± 20%; 60/240°·s = 153 ± 30%). In conclusion, considering the tested isokinetic angular velocity, professional male soccer players do not meet the traditional reference landmarks used to assess the strength balance between quadriceps and hamstring muscles (i.e., 60 and 100% for H/Q conventional and functional ratios, respectively), which supports a need for specific reference values according to the angular velocity selected for testing H/Q torque ratios.


#8 Acupuncture techniques in professional football
Reference: Unfallchirurg. 2018 Jun;121(6):450-454. doi: 10.1007/s00113-018-0500-0. [Article in German]
Authors: Pfab F, Sommer B, Haser C
Summary: The number of scientific studies about acupuncture has increased significantly during recent years. Acupuncture can be used as an evidence-based adjunct therapy for a variety of indications in professional football. This review summarizes various acupuncture techniques and related techniques for utilization in the field of professional soccer. Besides knee, shoulder, spinal, elbow and postoperative pain, scientific meta-analyses also point towards the effectiveness of acupuncture in ankle sprains, allergic rhinoconjunctivitis and nausea. Dry needling is an emerging option for treatment of myofascial trigger points and could potentially result in improved prevention of muscular injuries and enhancement of muscular performance.


#9 Position specific player load during match-play in a professional football club
Reference: PLoS One. 2018 May 24;13(5):e0198115. doi: 10.1371/journal.pone.0198115. eCollection 2018.
Authors: Baptista I, Johansen D, Seabra A, Pettersen SA
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0198115&type=printable
Summary: There is a rapid growing body of knowledge regarding physical aspects of a football match due to studies using computer-assisted motion analysis. The present study used time-motion analysis and triaxial-accelerometers to obtain new insights about differences in physical profiles of elite football players across playing-positions. Player performance data in 23 official home matches from a professional football club, during two seasons were collected for analysis. Eighteen players from five different playing positions (central backs: n = 3; full-backs: n = 5; central midfielders: n = 6; wide midfielders: n = 3; and central forwards: n = 4), performing a total of 138 observations. A novel finding was that central backs and central midfielders had significantly lower work-rate in sprints, decelerations and accelerations than full-backs, wide midfielders and central forwards (p<0.001). Furthermore, wide midfielders and full-backs performed significantly more turns (>90°) than central backs. The most common distance covered in high-intensity runs (≥19.8 km·h-1) for central backs, central midfielders, wide midfielders and central forwards was 1-5 m, but for full-backs was 6-10 m. This may help coaches in developing individualized training programs to meet the demands of each position in match-play.


#10 Normative Quadriceps and Hamstring Muscle Strength Values for Female, Healthy, Elite Handball and Football Players
Reference: J Strength Cond Res. 2018 May 23. doi: 10.1519/JSC.0000000000002579. [Epub ahead of print]
Authors: Risberg MA, Steffen K, Nilstad A, Myklebust G, Kristianslund E, Moltubakk MM, Krosshaug T
Summary: This study presents normative values for isokinetic knee extension and flexion muscle strength tests in 350 elite, female, handball (n = 150) and football (n = 200) players. Isokinetic concentric muscle strength tests at 60°·sec were recorded bilaterally using a dynamometer. Peak torque (in Newton meter [N·m]), body mass normalized peak torque (N·m·kg), and hamstring to quadriceps ratio (H:Q ratio) for dominant and nondominant legs were recorded. The female elite players were 20.9 ± 4.0 years, started playing at the elite level at the age of 18.2 ± 2.7 years, with a mean of 9.7 ± 2.2 hours of weekly in-season training. Handball players demonstrated greater quadriceps muscle strength compared with football players (11.0%) (p < 0.001), also when normalized to body mass (4.1%) (p = 0.012), but not for weight-adjusted hamstring muscle strength. The H:Q ratio was higher on the dominant compared with the nondominant leg for handball players only (p = 0.012).The H:Q ratio was significantly lower for handball players (0.58) compared with football players (0.60) (p < 0.02). These normative values for isokinetic knee extension and flexion torques of healthy, elite, female handball and football players can be used to set rehabilitation goals for muscle strength after injury and enable comparison with uninjured legs. Significantly greater quadriceps muscle strength was found for handball players compared with football players, also when normalized to body mass.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.


#11 WAVE~Ripples for Change Obesity Two-Year Intervention in High School Soccer Players: Process Evaluation, Best Practices, and Youth Engagement
Reference: Nutrients. 2018 Jun 1;10(6). pii: E711. doi: 10.3390/nu10060711.
Authors: Meng Y, Wong SS, Manore MM, Patton-Lopez M
Download link: www.mdpi.com/2072-6643/10/6/711/pdf
Summary: This paper reports the process data on program fidelity, best practices for intervention implementation, youth and coach engagement, and youth application of knowledge and skills for the two-year WAVE~Ripples for Change (WAVE) obesity prevention intervention program focused on healthy eating, physical activity, and life skills with high school (HS) soccer players aged 14⁻19 years. Internal (staff: n = 7; volunteers: n = 27) and external (youth: n = 100; coaches: n = 9) stakeholders were interviewed/ surveyed. Staff rated program fidelity as high (94%), as did volunteers (85%). Best practices included coach encouragement for athlete participation, use of on-line consent for enrollment, building relationships with HS staff to complete assessments, sending text reminders, and providing incentives. Study results showed an enrollment rate of 72%, completion of baseline assessments of 89⁻98%, attendance of sports nutrition lessons in Year 1 and Year 2 of 90% and 39%, respectively, and team-building workshop (TBW) attendance of 25⁻31%. Activities exceeding youth expectations (>90%) included, (1) activities with their soccer team; (2) the TBW-cooking; and (3) sports nutrition lessons. The obesity prevention skills most applied by youth were obtained from the TBW-gardening and harvesting (49%), the TBW-cooking (43%), and sports nutrition lessons (44%). Coaches also rated the sports nutrition lessons highly and reported increased awareness for hydration/fueling during sport by the athletes. Using sport teams/clubs to engage youth in obesity prevention is a feasible model for future study.

Sun

08

Jul

2018

Latest research in football - week 20 - 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 Risk Factors for Groin Injury and Symptoms in Elite Level Soccer Players: A Cohort Study in the Dutch Professional Leagues
Reference: J Orthop Sports Phys Ther. 2018 May 23:1-30. doi: 10.2519/jospt.2018.7990. [Epub ahead of print]
Authors: Langhout R, Tak I, van Beijsterveldt AM, Ricken M, Weir A, Barendrecht M, Kerkhoffs G, Stubbe J
Summary: Groin injury and symptoms are common in soccer players. Their relationship with reduced hip range of motion (ROM) and previous injury is unclear. The purpose was to conduct a retrospective assessment of associations between previous injury and pre-season hip ROM and pre-season prevalence of severe groin symptoms; and prospective identification of risk factors for within-season groin injury. During 2015-2016, 190 players from 9 Dutch professional soccer clubs participated. Univariate and multivariate logistic regression were used to predict pre-season severe groin symptoms, identified using the Copenhagen Hip And Groin Outcome Score, from a history of previous groin injury, general injury (minimum 1 week duration) in previous season, and hip ROM. Cox regression was used to predict within-season groin injury. Point-prevalence of severe groin symptoms was 24% and within-season incidence of groin injury 11%. Total/training/match groin injury incidence was 0.5/0.2/2.6 injuries/1000 playing hours. A history of more than 1 previous groin injury was associated with current severe groin symptoms (Odds Ratio=3.0; 95% CI=1.0, 8.3; P=.038). General injury sustained in the previous season (ankle, knee, thigh, shoulder; median 9 weeks time-loss) was a risk factor for groin injury (Hazard Ratio=5.1; 95% CI=1.1, 14.6; P=.003). Severe injuries in the previous season to locations other than the groin increase the risk of groin injury the next season. A history of groin injury is associated with current severe groin symptoms. Pre-season hip ROM does not identify players at risk for groin injury.


#2 Talent identification for soccer: Physiological aspects
Reference: J Sci Med Sport. 2018 Jan 31. pii: S1440-2440(18)30027-6. doi: 10.1016/j.jsams.2018.01.009. [Epub ahead of print]
Authors: Dodd KD, Newans TJ
Summary: Soccer coaches are always looking to discover the next star player, without investing the necessary resources, time, and effort into a player's development. In the modern era, talent identification in soccer seems to be a comparative process rather than a developmental process. This article will look at the physiological profiles of soccer players in the modern era and how testing and talent identification processes should coincide with this data. An extensive literature search identifying the physiological attributes of soccer players that are required to compete at an elite level was conducted. An examination of the methods to test these attributes was also conducted. Studies were assigned into three areas to understand the physiological aspect of soccer: physiological testing methods, benchmark values, and correlations between different tests. A testing battery was established to test the key physiological attributes of prospective youth soccer players. Benchmark levels were also identified to allow coaches to understand areas of improvement. Using a physiological testing battery will allow teams to track their players' progress throughout their developmental years. This allows coaches to consistently identify a player's strengths and weaknesses, as well as allow players who may experience late maturation to still be identified.


#3 Influence of Team's Rank on Soccer Referees' External and Internal Match Loads During Official Matches
Reference: J Strength Cond Res. 2018 Jun;32(6):1715-1722. doi: 10.1519/JSC.0000000000002040.
Authors: Castillo D, Castagna C, Camara J, Iturricastillo A, Yanci J
Summary: The aim was to examine the external and the internal match loads (ML) of field referees (FRs) attending teams of different ranking during championship matches. Twenty FR who officiated in 30 official soccer matches (30 observations) participated in our study. The criteria for allocating the soccer referees' ML results were based on the teams' final league positions as follows: matches performed by Top 10 teams (TOP10), matches performed by bottom 10 teams (BOT10), and matches played among TOP10 and BOT10 teams (MIXED). External (match activities, accelerations [Acc], and decelerations [Dec]) and internal MLs (Edwards' heart rate [HR]-derived training impulse [TRIMPEDW], HRmean expressed as a percentage of HRpeak [%HRpeak], and differentiated rating of perceived exertion [dRPE]) were recorded. The main results showed that FR, who officiated TOP10 matches, covered more distance at a low walking speed (<3.6 km·h) and performed a higher percentage of high-intensity accelerations and decelerations than those FR who officiated lower ranked teams' matches. Moreover, FR who officiated MIXED matches registered lower values of TRIMPEDW MLs and %HRpeak and declared higher respiratory (sRPEres ML) and muscular (sRPEmus ML) perceived MLs during the second half. Considering those FR who officiate matches between teams of a higher competitive level will need to produce higher match responses, especially regarding the percentage of distance covered at high intensity, accelerations, and decelerations; physical trainers of soccer referees at a high competitive level should implement these high-intensity short-term actions in specific training regimes.


#4 Association of Physical and Technical Activities With Partial Match Status in a Soccer Professional Team
Reference: J Strength Cond Res. 2018 Jun;32(6):1708-1714. doi: 10.1519/JSC.0000000000002033.
Authors: Moalla W, Fessi MS, Makni E, Dellal A, Filetti C, Di Salvo V, Chamari K
Summary: The purpose of this study was to examine the association between physical and technical activities and partial match status (winning, drawing, or losing) in a professional soccer team over 2 seasons. Physical and technical activities of 52 official matches were collected and analyzed at each 15-minute interval, for each half (45 minutes), and full match (90 minutes) using a multiple-camera computerized tracking system. The results indicated that according to full match outcome: winning status was characterized by players covering more total distance (p ≤ 0.05) and low-intensity running (<14.4 km·h) (p ≤ 0.05), whereas, losing status induced more sprinting (≥25.2 km·h) (p < 0.01) and high-intensity running (≥19.8 km·h) (p ≤ 0.05). However, according to partial match status (i.e., 15 minutes and half time), players covered more distance for all running intensities while winning (p < 0.01). Technical match performance scores were not influenced by match status. In conclusion, the present study showed that the physical activities including high-intensity running and total distance covered were related to the match status, whereas technical activities were not. The overall outcome shows that higher physical activity was associated with winning partial match periods. This approach highlights the importance of physical fitness in soccer and may help coaches to better modulate players' roles and team tactical organization throughout the match.


#5 Observation of Women Soccer Players' Physiology During a Single Season
Reference: J Strength Cond Res. 2018 Jun;32(6):1702-1707. doi: 10.1519/JSC.0000000000002025.
Authors: Paulsen KM, Butts CL, McDermott BP
Summary: The purpose of this study was to observe heart rate (HR) responses in match settings over the course of a conference season in National Collegiate Athletic Association Division I women's soccer. Twenty-one female collegiate soccer players were provided a HR monitor and instructed to wear it for the duration of match play. Player positions included 6 defenders (DEF), 6 midfielders (MID), and 9 forwards (FWD). Defenders were further identified as either center defenders (CD) or outside defenders (OD). A 1-way analysis of variance was used to determine if mean HR varied between FWD, MID, and DEF. An independent t-test was used to determine if there was a difference between CD and OD HRs. The FWD, MID, and DEF did have significantly different mean HR (p ≤ 0.05), but post-hoc analysis revealed no significant differences (p ≥ 0.05). However, CD demonstrated significantly lower HRs than OD (p = 0.009). Player position, specifically in the CD and OD role, impact the intensity of exercise in match settings and may be used to specify training and conditioning sessions.


#6 Alpha-Actinin-3 R577X Polymorphism Influences Muscle Damage and Hormonal Responses After a Soccer Game
Reference: J Strength Cond Res. 2018 May 17. doi: 10.1519/JSC.0000000000002575. [Epub ahead of print]
Authors: Coelho DB, Pimenta EM, Rosse IC, Veneroso C, Pussieldi GA, Becker LK, Oliveira EC, Carvalho MRS, Silami-Garcia E
Summary: Alpha-actinin-3 R577X polymorphism influences muscle damage and hormonal responses after a soccer game. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to evaluate indicators of muscle damage and hormonal responses after soccer matches and its relation to alpha-actinin-3 (ACTN3) gene expression (XX vs. RR/RX), considering that the R allele produces alpha-actinin-3 and provides greater muscle strength and power. Thirty players (10 XX and 20 RR/RX) younger than 16 years were evaluated in this study. Blood samples were collected immediately before, after, 2, and 4 hours after the games to assess muscle damage (creatine kinase [CK] and alpha-actin) and hormonal responses (interleukin-6 [IL-6], cortisol, and testosterone). Postgame CK was higher as compared to the pregame values in both groups and it was also higher in the RR/RX (p < 0.05) than in the XX. The concentrations of alpha-actin and IL-6 were similar for both groups and did not change over time. Testosterone was increased after the game only in the RR/RX group (p < 0.05). Cortisol concentrations in group RR/RX were higher immediately after the game than before the game, and 2 and 4 hours after the game the concentration decreased (p < 0.05). The RR and RX individuals presented higher markers of muscle microtrauma and hormonal stress, probably because they performed more speed and power actions during the game, which is a self-regulated activity. From the different responses presented by RR/RX and XX genotypes, we conclude that the genotypic profile should be taken into account when planning training workloads and recovery of athletes.


#7 Psychosocial predictors and psychological prevention of soccer injuries: A systematic review and meta-analysis of the literature
Reference: Phys Ther Sport. 2018 May 15. pii: S1466-853X(17)30491-1. doi: 10.1016/j.ptsp.2018.05.006. [Epub ahead of print]
Authors: Slimani M, Bragazzi NL, Znazen H, Paravlic A, Azaiez F, Tod D
Summary: The purpose was To examine (a) the relationships between the psychosocial risk factors and injury rates and (b) the effects of psychological-based prevention interventions on the injury risk of soccer players. Scholarly electronic databases (PubMed/MEDLINE, Google Scholar, Scopus) were searched on 1 January 2017, complemented by manual searches of bibliographies. We identified 13 eligible studies, including a total of 1149 injured soccer players aged between 14 and 36 years. Psychosocial risk factors, psychological-based prevention interventions and injury risk in soccer players were set as main outcome measures. Personality traits, such as trait anxiety and perceived mastery climate, along with a history of stressors, like negative-life-event stress or high level of life stress, daily hassle, and previous injury, are the main predictors of injury rates among soccer players. Also, from injury prevention studies, it has been shown that psychological-based interventions reduce injury rates (effect size = 0.96; 95% CI 0.34-1.58; p = 0.002) in senior soccer players. Practitioners need to ensure injured soccer players are psychologically and socially ready to play. They should also employ psychological-based interventions (i.e., mindfulness, imagery, self-talk, stress management, relaxation, goal setting) when designing injury prevention programs.


#8 A review advocating caution with Major League Soccer expansion and investment in more rehabilitation professionals
Reference: Phys Ther Sport. 2018 May 9. pii: S1466-853X(18)30010-5. doi: 10.1016/j.ptsp.2018.05.008. [Epub ahead of print]
Authors: Mansfield CJ, Ferkovic-Mack C, Eibensteiner J, Zwolski C
Summary: Major League Soccer (MLS) has aggressively expanded from 10 teams to 23 teams. With the addition of more teams, the league will have to dictate a schedule that maximizes the league's popularity, while also maintaining the health of the players. A longer season and congested game schedule could increase the risk of injury for players. The purpose of this commentary is to make recommendations for the prevention of injuries among MLS players with respect to proposed league expansion. MLS has lengthened the regular season with each expansion in teams. An increase in season length was seen in conjunction with the MLS expansion from 14 to 19 teams during the 2008 through 2013 seasons. Data from the inaugural MLS season found injury rates were higher in games compared to practices and more injuries occurred later in the season. With the expansion of MLS, anterior cruciate ligament tears appeared to have increased each year. Current evidence suggests the implementation of a proper preseason in addition to the once-per-week game frequency would best promote player health and well-being. Players may benefit from in-season injury prevention training and weekly load monitoring.


#9 Strength recovery after anterior cruciate ligament reconstruction with quadriceps tendon versus hamstring tendon autografts in soccer players: A randomized controlled trial
Reference: Knee. 2018 May 15. pii: S0968-0160(18)30123-6. doi: 10.1016/j.knee.2018.03.011. [Epub ahead of print]
Authors: Martin-Alguacil JL, Arroyo-Morales M, Martin-Gomez JL, Monje-Cabrera IM, Abellan-Guillen JF, Esparza-Ros F, Lozano ML, Cantarero-Villanueva I
Summary: The comparison between HT and QT grafts in strength recovery and function after an ACLR is scarce in the literature. A total of 56 participants were enrolled in this randomized controlled trial and placed into two groups: HT or QT. The hamstring/quadriceps (H/Q) ratio was the primary end-point measured with a Genu-3 dynamometer. Peak torque, functional assessment (Lysholm knee scoring scale and Cincinnati Knee Rating System), and anteroposterior laxity (KT-2000™ arthrometer) were also assessed. An intention-to-treat analysis was performed. The results of the H/Q ratio analysis of the participants over time revealed significant differences at 60, 180, and 300°/s at three, six, and 12months of follow-up (60°/s: F=5.3, p=0.005; 180°/s: F=5.5, p=0.004; 300°/s: F=5.1, p=0.005). Furthermore, they revealed significant differences at 60°/s, 180°/s, and 300°/s in the participants over time for peak torque in the extensor muscle strength at three and six months of follow-up, with higher values in the hamstring tendon group but not at 12months of follow-up. There were no significant differences in functional endpoints or arthrometer assessments at 24months of follow-up. An ACLR with a QT graft showed similar functional results with a better isokinetic H/Q ratio compared to an ACLR with the HT at 12months of follow-up in soccer players. This higher H/Q ratio observed with the QT could be an advantage of this graft over the HT for an ACLR.


#10 No association between rate of torque development and onset of muscle activity with increased risk of hamstring injury in elite football
Reference: Scand J Med Sci Sports. 2018 May 23. doi: 10.1111/sms.13224. [Epub ahead of print]
Authors: van Dyk N, Bahr R, Burnett AF, Verhagen E, von Tiggelen D, Witvrouw E
Summary: Hamstring injuries remain a significant burden in sports that involve high speed running. In elite male football, hamstring injury has repeatedly been identified as the most common noncontact injury, representing 12% of all injuries. As the incidence remains high, investigations are aimed at better understanding how to improve prevention efforts. Intrinsic risk factors such as strength have been investigated extensively in a cohort of professional football players; however, other intrinsic measures of neuromuscular function have not been studied in this cohort. This study aims to investigate the association between timing of hamstring muscle activity onset and the rate of torque development during the early phase of isokinetic strength testing with risk of hamstring injury in professional football players in a prospective cohort study. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included rate of torque development and timing of muscle activity onset. A total of 367 unique players (60.6% of all QSL players) competed for 514 player seasons (103 players competed both seasons) and sustained 65 hamstring injuries. There was no difference in the onset of muscle activity between the biceps femoris and medial hamstrings comparing the injured to uninjured players. For both onset of muscle activity and rate of torque development, there were no significant differences between any of the variables (p>0.05), with small effect sizes detected across all the different variables (d<0.3). Rate of torque development and onset of muscle activity were not associated with a risk of future hamstring injury. The use of these measures as part of a periodic health evaluation to identify risk of hamstring injury is unsupported.


#11 A History of Anterior Cruciate Ligament Reconstruction at the National Football League Combine Results in Inferior Early National Football League Career Participation
Reference: Arthroscopy. 2018 May 19. pii: S0749-8063(18)30238-X. doi: 10.1016/j.arthro.2018.03.018. [Epub ahead of print]
Authors: Provencher MT, Bradley JP, Chahla J, Sanchez A, Beaulieu-Jones BR, Arner JW, Kennedy NI, Sanchez G, Kennedy MI, Moatshe G, Cinque ME, LaPrade RF
Summary: The purpose was to evaluate whether players with a history of an anterior cruciate ligament reconstruction (ACLR) before the National Football League (NFL) Combine played or started fewer games and/or participated in fewer eligible snaps compared with NFL Combine participants without a history of knee injury or surgery. We performed a retrospective review of all players who participated in the NFL Combine between 2009 and 2015 and who had a history of an ACLR. NFL Combine participants were included if they had a previous ACLR or combined anterior cruciate ligament (ACL) injury and nonoperatively managed medial collateral ligament injury. The number of games started, number of games played, draft number, overall draft pick, and snap percentage for each position were determined. The mean value of each outcome metric was compared between case and control players. We identified 110 players who had an ACL injury (n = 76) or a combined ACL and medial collateral ligament injury (n = 34). Players in the ACLR group had a significantly worse mean draft pick number (difference of 30.2, P = .002) and mean draft round (difference of 0.8, P = .019) versus controls. Compared with control players, players in the ACLR group started and played significantly fewer games in both season 1 (difference of 2.7 games started, P < .001; difference of 2.7 games played, P < .001) and season 2 (difference of 7.4 games started, P < .001; difference of 3.0 games played, P = .003) and had a significantly lower snap percentage in both season 1 (difference of 23.1%, P < .001) and season 2 (difference of 24.0%, P < .001). Athletes at the NFL Combine who previously underwent an ACLR had significantly lower early-career NFL player metrics, including fewer games started, fewer games played, and a lower snap percentage, than uninjured controls. Defensive linemen, defensive backs, and linebackers were the 3 most affected positions. Players with a prior ACLR and combined meniscal-chondral pathology had significantly lower numbers of games started and games played in seasons 1 and 2 and a significantly lower season 2 snap percentage.


#12 Strategies to improve impact efficiency in football kicking
Reference: Sports Biomech. 2018 May 22:1-14. doi: 10.1080/14763141.2018.1452970. [Epub ahead of print]
Authors: Peacock JCA, Ball K
Summary: In football, kicking with high ball velocity can increase scoring opportunities and reduce the likelihood of interception. Efficient energy transfer from foot to ball during impact is important to attain a high ball velocity. It is considered impact efficiency can be increased by reducing the change in ankle plantarflexion during foot-ball impact. However, conflicting evidence exists, questioning its effectiveness as a coaching cue. The aim of the present study was to systematically analyse joint stiffness, foot velocity and impact location with a mechanical kicking machine to determine if change in ankle plantarflexion during foot-ball impact and ball velocity are influenced. Sagittal plane data of the shank, foot and ball were measured using high-speed video (4,000 Hz). Increasing joint stiffness reduced change in ankle plantarflexion and increased ball velocity from a greater effective mass. Increasing foot velocity increased change in ankle plantarflexion and increased ball velocity. Distal impact locations increased change in ankle plantarflexion and reduced ball velocity as coefficient of restitution decreased. These results identify that change in ankle plantarflexion is a dependent variable during foot-ball impact and does not directly influence ball velocity. Coaches can assess ankle motion during impact to provide feedback to athletes on their impact efficiency.

Sat

30

Jun

2018

Latest research in football - week 19 - 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 geometry in young male and female football players: a peripheral quantitative computed tomography (pQCT) study
Reference: Arch Osteoporos. 2018 May 8;13(1):57. doi: 10.1007/s11657-018-0472-2.
Authors: Lozano-Berges G, Matute-Llorente ÁA, Gomez-Bruton A, Gonzalez-Aguero A, Vicente-Rodriguez G, Casajus JA
Summary: The present study shows that football practice during growth may improve bone geometry in male and female football players. However, only females had better bone strength in comparison with controls. The aim of this study was to compare bone geometry in adolescent football players and controls. A total of 107 football players (71 males/36 females; mean age 12.7 ± 0.6/12.7 ± 0.6 years) and 42 controls (20 males/22 females; mean age 13.1 ± 1.4/12.7 ± 1.3 years) participated in this study. Total and trabecular volumetric bone mineral content (Tt.BMC/Tb.BMC), cross-sectional area (Tt.Ar/Tb.Ar), and bone strength index (BSI) were measured at 4% site of the non-dominant tibia by peripheral quantitative computed tomography (pQCT). Moreover, Tt.BMC, cortical BMC (Ct.BMC), Tt.Ar, cortical Ar (Ct.Ar), cortical thickness (Ct.Th), periosteal circumference (PC), endosteal circumference (EC), fracture load in X-axis, and polar strength strain index (SSIp) were measured at 38% site of the tibia. Multivariate analyses of covariance were used to compare bone pQCT variables between football players and controls using the tibia length and maturity offset as covariates. Female football players demonstrated 13.8-16.4% higher BSI, Ct.Th, fracture load in X-axis, and SSIp than controls (p < .0036). Males showed no significant differences in bone strength when compared to controls (p > .0036). In relation to bone mineral content and area, male football players showed 8.8% higher Tt.Ar and Tb.Ar at the 4% site of the tibia when compared to controls; whereas 13.8-15.8% higher Tt.BMC, Ct.BMC, and Ct.Ar at the 38% site of the tibia were found in female football players than controls (p < .0036). In this study, female adolescent football players presented better bone geometry and strength values than controls. In contrast, only bone geometry was higher in male football players than controls.


#2 Physical preparation of the football player with an intramuscular hamstring tendon tear: clinical perspective with video demonstrations
Reference: Br J Sports Med. 2018 May 3. pii: bjsports-2017-098817. doi: 10.1136/bjsports-2017-098817. [Epub ahead of print]
Authors: Taberner M, Cohen DD
Download link: http://bjsm.bmj.com/content/bjsports/early/2018/05/02/bjsports-2017-098817.full.pdf



#3 "What is the score?" A review of football-based public mental health interventions
Reference: J Public Ment Health. 2017;16(4):144-158. doi: 10.1108/JPMH-03-2017-0011. Epub 2017 Dec 18.
Authors: Friedrich B, Mason OJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5868541/pdf/jpublicmenthealth-16-0144.pdf
Summary: Football exercise as an intervention for people with severe mental health problems has seen an increasing interest in the past years. To date, there is, however, no comprehensive review of the empirical evidence regarding the effectiveness of these interventions. In this review, the authors have comprised the research findings from the peer-review literature as well as the theoretical approaches to football exercise as an adjunct treatment. This overview will be informative to everybody who is planning to develop a football intervention for this population as well as to the people who are preparing evaluation studies that measure the effectiveness of such interventions. The paper aims to discuss these issues. The authors identified research papers in the peer-review literature that feature empirical findings on "football interventions" that aim at improving mental and/or physical well-being in participants with mental health problems. The authors are using the term "football intervention" here in the sense that the participants actively took part in football exercise, so the authors excluded studies in which the participants only watched football or used football as a metaphor to discuss mental health problems. In a table, the authors indicate the definition of the target group, targeted outcomes, measured outcomes, form and frequency of the intervention as well as the research method(s). The authors identified 16 studies on 15 projects. The majority of studies were qualitative and had positive findings in which the participants reported increased well-being and connectedness, elevation of symptoms and improved physical well-being. The outcomes of the quantitative studies, however, were mixed with some results suggesting that not all intended goals were achieved. There seems to be a need for more quantitative studies to triangulate the qualitative findings. Interestingly, most interventions take place in the UK. Many studies fail to give detailed methodological information and often the aims of the interventions are vague or not stated at all. Due to the heterogeneity of the studies and relative scarcity of evaluation projects on football interventions for people with mental health problems, the authors could not conduct an in-depth systematic review. Furthermore, the information on methods was often unsatisfying and despite efforts to get more detailed input from the authors of cited papers, those gaps could not always be filled. Instead of coming up with a crystal-clear summary of whether and how football interventions work for everybody, topics were identified that need to be addressed in the planning of interventions, in evaluation studies, in implementation efforts and in the theoretical discourse. This paper constitutes a helpful overview for everybody who is interested in the theoretical background of football interventions for people with mental health problems, for people who are planning to develop respective interventions, for researchers who engage in evaluation projects that look into the effectiveness of football interventions (or similar exercise interventions) as well as for the people who are interested in how football interventions can be implemented. This paper is likely to make a contribution to the advancement of alternative exercise interventions that aim at improving mental, physical and social health in people with mental health problems. This paper will help putting the topic of football interventions (and similar, alternative exercise interventions) further up on the public health agenda by providing an overview of the empirical evidence at hand and by specifying advantages of the approach as well as pointing out actions that need to be taken to make football a recognised, evidence based and viable option for adjunct mental health treatment that is attractive to potential participants as well as funders as well as to the potential participants. There is no comprehensive summary to date that provides a (reasonably) systematic overview of empirical findings for football interventions for people with MH problems. Furthermore, the literature on the theoretical background of these interventions has been somewhat patchy and heterogonous. This paper aims at filling both these gaps and identifies the issues that need to be covered in the planning of respective interventions and evaluations. This paper will be useful to everybody who is developing football interventions (or similar alternative adjunct exercise interventions), who is conducting evaluation research in this area and who is interested in the implementation of football interventions.


#4 The effects of short term detraining and retraining on physical fitness in elite soccer players
Reference: PLoS One. 2018 May 10;13(5):e0196212. doi: 10.1371/journal.pone.0196212. eCollection 2018.
Authors: Joo CH
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196212&type=printable
Summary: The aim of this study was to examine the effects of aerobic high-intensity training with reduced volume and training cessation on body composition and physical fitness after the end of season and the time required to recapture physical fitness with intensified retraining following two weeks of detraining in elite soccer players. Twenty male semi-professional soccer players participated in this study. The soccer players were assigned to either a group that completed high-intensity aerobic training (HAT, n = 10) or to a detraining and retraining group (DHAT, n = 10) for a 5-week period immediately after the end of the season. The first 2 weeks of the period, members of the HAT group performed high-intensity aerobic exercise (80-90% of HRmax, 12 min × 3, three times per week), whereas members of the DHAT group abstained from any physical activity. During the subsequent 3 weeks, members of both the HAT and DHAT groups completed high-intensity aerobic exercise. Exercise performance testing and body composition analysis were performed before; after 2 weeks of detraining; and at 1, 2 and 3 weeks of retraining. Intensified high-intensity training for 5 weeks maintained the performance in the Yo-Yo Intermittent Recovery level 2 test (Yo-Yo IR2) and repeated sprints at any time point (P > 0.05). However 2 weeks of detraining resulted in significant decreases in the performance on the Yo-Yo IR2 (P < 0.01) and repeated sprints test (P < 0.05). Performance on the Yo-Yo IR2 enhanced after 2 weeks of retraining and was maintained up to 3 weeks after retraining, with no significant differences between conditions (P > 0.05). In addition, repeated sprint performance markedly decreased after the detraining period (P < 0.05) and was continuously lower compared to the baseline at 2 weeks after retraining (P < 0.05). Furthermore, this value reached baseline level at the end of the experimental period (P > 0.05). There were no significant differences between conditions in body composition, performance of agility, or sprint ability throughout the 5-week experimental period (P > 0.05). The present data suggest that short-term detraining after the competitive season can markedly decrease performances in the Yo-Yo IR2 test and repeated sprints. To return to a previous level of ability on the Yo-Yo IR2 and/or sprint test with retraining through high-intensity aerobic training after a period of detraining, a similar or longer period of retraining is required. However, the high-intensity training with reduced amount of training after competitive season can prevent reductions in physical fitness.


#5 Angle-Specific Isokinetic Metrics Highlight Strength Training Needs of Elite Youth Soccer Players
Reference: J Strength Cond Res. 2018 May 2. doi: 10.1519/JSC.0000000000002612. [Epub ahead of print]
Authors: Eustace SJ, Page RM, Greig M
Summary: The purpose of this study was to assess traditional and angle-specific isokinetic strength of eccentric knee flexors (eccKFs) and concentric knee extensors (conKEs) between senior professional and youth soccer players. Thirty-four male soccer players (17 senior and 17 youth) were recruited for bilateral assessments at 180, 270, and 60°·s. Peak torque (PT), dynamic control ratio (DCR), angle of peak torque (APT), functional range (FR), angle-specific torque (AST), and angle-specific DCR (DCRAST) were compared. The eccentric knee flexor (eccKF) and conKE PT (p = 0.782) and DCR (p = 0.508) were not different between groups across all angular velocities. Significant differences were identified for eccKF APT (p = 0.018) and FR (p = 0.006), DCRAST at 270°·s (p = 0.031), and in AST data recorded across angular velocities for eccKF and conKE (p = 0.003). Traditional strength measures were not sensitive to playing age, with implications for misinterpretation in training prescription. By contrast, AST data did differentiate between ages. Strength deficits that highlight the muscle contraction type, angular velocity, and joint angle can be manipulated within an individualized training intervention. Given the relevance to injury etiology, this study highlights potential implications for improved assessment strategies to inform training prescription for performance and injury prevention. Given the high number of injuries in adolescent soccer players, and in line with previous recommendations, practitioners should consider using more informed and specific strength and conditioning practices at younger ages.


#6 Dose-Response Relationship between Training Load and Changes in Aerobic Fitness in Professional Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2018 May 10:1-22. doi: 10.1123/ijspp.2017-0843. [Epub ahead of print]
Authors: Fitzpatrick JF, Hicks KM, Hayes PR
Summary: The aim of this study was to compare the dose-response relationship between, traditional arbitrary speed thresholds versus an individualised approach, with changes in aerobic fitness in professional youth soccer players. Fourteen youth soccer players, completed a 1500 metre time trial to estimate maximal aerobic speed (km.h-1, (MAS)) at the start and the end of a six week period. Training load was monitored on a daily basis during this study. External load measures were; total distance covered (TD), total acceleration and deceleration distance > 2m.s-2 (A/D Load). Arbitrary high speed running measures were; metres covered and time spent > 17 km.h-1 (m>HSD, t>HSD) and 21 km.h-1 (m>VHSD, t>VHSD). Individualised high speed running measures were; metres covered and time spent > MAS km.h-1 (m>MAS, t>MAS) and 30% anaerobic speed reserve (m>30ASR, t>30ASR). In addition, internal load measures were also collected; heart rate exertion (HRE) and rating of perceived exertion (RPE). Linear regression analysis was used to establish the dose-response relationship between mean weekly training load and changes in aerobic fitness. Substantial very large associations were found between t>MAS and changes in aerobic fitness (R2 = 0.59). Substantial large associations were found for t>30ASR (R2 = 0.38) and m>MAS (R2 = 0.25). Unsubstantial associations were found for all other variables. An individualised approach to monitoring training load, in particular t>MAS, may be a more appropriate method than using traditional arbitrary speed thresholds when monitoring the dose-response relationship between training load and changes in aerobic fitness.


#7 Monitoring of Post-match Fatigue in Professional Soccer: Welcome to the Real World
Reference: Sports Med. 2018 May 8. doi: 10.1007/s40279-018-0935-z. [Epub ahead of print]
Authors: Carling C, Lacome M, McCall A, Dupont G, Le Gall F, Simpson B, Buchheit M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0935-z.pdf
Summary: Participation in soccer match-play leads to acute and transient subjective, biochemical, metabolic and physical disturbances in players over subsequent hours and days. Inadequate time for rest and regeneration between matches can expose players to the risk of training and competing whilst not entirely recovered. In professional soccer, contemporary competitive schedules can require teams to compete in excess of 60 matches over the course of the season with periods of fixture congestion occurring, prompting much attention from researchers and practitioners to the monitoring of fatigue and readiness to play. A comprehensive body of research has investigated post-match acute and residual fatigue responses. Yet the relevance of the research for professional soccer contexts is debatable, notably in relation to the study populations and designs employed. Monitoring can indeed be invasive, expensive, time inefficient, and difficult to perform routinely and simultaneously in a large squad of regularly competing players. Uncertainty also exists regarding the meaningfulness and interpretation of changes in fatigue response values and their functional relevance, and practical applicability in the field. The real-world need and cost-benefit of monitoring must be carefully weighed up. In relation to professional soccer contexts, this opinion paper intends to (1) debate the need for post-match fatigue monitoring; (2) critique the real-world relevance of the current research literature; (3) discuss the practical burden relating to measurement tools and protocols, and the collection, interpretation and application of data in the field; and (4) propose future research perspectives.


#8 Comparison of technical and physical activities between 8 vs. 8 and 11 vs. 11 games in young Korean soccer players
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):253-258. doi: 10.12965/jer.1836034.017. eCollection 2018 Apr.
Authors: Oh SH, Joo CH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931162/pdf/jer-14-2-253.pdf
Summary: The aims of this study were to examine the differences in technical aspects and physical demands between small-size games (SSG; 8 vs. 8) and regular-size games (RSG; 11 vs. 11) in young Korean soccer players. Seventy-nine young soccer players from 6 teams (U-12) volunteered to participate in the study. The players completed 4 games (2 SSG, 62×51 m, and 2 RSG, 80×54 m) in 2 days. Each game was filmed to evaluate technical actions. Physical demand variables were measured using global positioning system technology. SSG showed significantly greater numbers of technical plays among 17 variables when compared to RSG (P<0.05). The players covered significantly greater total distance during low-, moderate-, and high-speed running and sprinting in SSG than in RSG (P<0.05). Higher numbers of high-intensity activities (repeated high-intensity efforts, explosive efforts, decelera-tions, accelerations, and sprinting) were observed in SSG compared to RSG (P<0.05). Mean heart rate was also higher in SSG than in RSG (P<0.05). Despite the greater physical demands during SSG, the exercise intensity was similar to that reported in previous studies. Therefore, the SSG format applied in the present study can be a suitable official game format for Korean young soccer players, resulting in significantly greater exposure to technical plays without excessive physical demands.


#9 Hamstring and Ankle Flexibility Deficits Are Weak Risk Factors for Hamstring Injury in Professional Soccer Players: A Prospective Cohort Study of 438 Players Including 78 Injuries
Reference: Am J Sports Med. 2018 May 1:363546518773057. doi: 10.1177/0363546518773057. [Epub ahead of print]
Authors: van Dyk N, Farooq A, Bahr R, Witvrouw E
Summary: Hamstring injuries remain a significant injury burden in sports such as soccer that involve high-speed running. It has repeatedly been identified as the most common noncontact injury in elite male soccer, representing 12% of all injuries. As the incidence of hamstring injuries remains high, investigations are aimed at better understanding how to prevent hamstring injuries. Stretching to improve flexibility is commonly used in elite-level sports, but risk factor studies have reported contradicting results, leading to unclear conclusions regarding flexibility as a risk factor for hamstring injuries. The purpose was to investigate the association of lower limb flexibility with the risk of hamstring injuries in professional soccer players. All teams (n = 18) eligible to compete in the premier soccer league in Qatar (Qatar Stars League [QSL]) underwent a comprehensive musculoskeletal assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included passive knee extension and ankle dorsiflexion range of motion. A clustered multivariate Cox regression analysis was used to identify associations with the risk of hamstring injuries. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. A total of 438 unique players (72.4% of all QSL players) competed for 601 player-seasons (148 players competed both seasons) and sustained 78 hamstring injuries. Passive knee extension range of motion (hazard ratio [HR], 0.97 [95% CI, 0.95-0.99]; P = .008) and ankle dorsiflexion range of motion (HR, 0.93 [95% CI, 0.88-0.99]; P = .02) were independently associated with the injury risk. The absolute differences between the injured and uninjured players were 1.8° and 1.4 cm, respectively, with small effect sizes ( d < 0.2). The ROC curve analyses showed an area under the curve of 0.52 for passive knee extension and 0.61 for ankle dorsiflexion, indicating failed to poor combined sensitivity and specificity of the 2 strength variables identified in the multivariate Cox regression analysis. This study identified deficits in passive hamstring and ankle dorsiflexion range of motion as weak risk factors for a hamstring injury. These findings have little clinical value in predicting the risk of future hamstring injuries, and test results must therefore be interpreted cautiously in athletic screening.


#10 Maturity Status Strongly Influences the Relative Age Effect in International Elite Under-9 Soccer
Reference: J Sports Sci Med. 2018 May 14;17(2):216-222. eCollection 2018 Jun.
Authors: Muller L, Gehmaier J, Gonaus C, Raschner C, Muller E
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5950738/pdf/jssm-17-216.pdf
Summary: The aim of the study was to assess the role of the relative age effect (RAE) and to investigate the influence of the biological maturity status on the RAE in international under-9 soccer. The birth dates of 222 male participants of the U9 Eurochampionship Soccer Tournament in Vienna in 2016 were analyzed and divided into four relative age quarters (Q1-Q4) and the biological maturity status was assessed with the age at peak height velocity (APHV) method. Based on the mean±standard deviation of the APHV, the athletes were divided into three groups of maturity: early, normal and late maturing. Chi-Square-tests were used to assess the difference between the observed and the expected even relative age quarter distribution and to evaluate the difference between the observed distribution of early, normal and late maturing athletes and the expected normal distribution. A univariate analysis of variance was performed to assess differences in the APHV between the relative age quarters. A RAE was present (χ2 = 23.87; p < 0.001; ω = 0.33). A significant difference was found in APHV between the four relative age quarters (F = 9.906; p < 0.001); relatively older athletes were significantly less mature. A significant difference was found between the distribution of early, normal and late maturing athletes and the expected normal distribution for athletes of Q1 (high percentage of late maturing athletes: 27%; χ2 = 17.69; p < 0.001; ω = 0.46) and of Q4 (high percentage of early maturing soccer players: 31%; χ2 = 12.08; p = 0.002; ω = 0.58). These findings demonstrated that the selection process in international soccer, with athletes younger than 9 years, seems to be associated with the biological maturity status and the relative age. Relatively younger soccer players seem to have a better chance for selection for international tournaments, if they enter puberty at an earlier age, whereas relatively older athletes seem to have an increased likelihood for selection independent of their biological maturity status.


#11 Relation Between Iliopsoas Cross-sectional Area and Kicked Ball Speed in Soccer Players
Reference: Int J Sports Med. 2018 May 14. doi: 10.1055/a-0592-7370. [Epub ahead of print]
Authors: Wakahara T, Chiba M
Summary: This study aimed to investigate the relationship between the maximal anatomical cross-sectional area (ACSA) of the iliopsoas muscle and ball speed in side-foot and instep kicks. The ACSA of the psoas major and iliacus was measured in 29 male collegiate soccer players by using magnetic resonance imaging. They performed maximal side-foot and instep kicks to a stationary ball. The kicked ball speed was measured with a high-speed camera. Ball speed in the side-foot and instep kicks was significantly correlated with body height (side-foot kick: r=0.650, P<0.001; instep kick: r=0.583, P<0.001). After adjustment for body height, the maximal ACSA of the psoas major was significantly correlated with ball speed in the side-foot kick (r=0.441, P=0.017), but not in the instep kick. The maximal ACSA of the iliacus was not correlated with ball speed in side-foot or instep kicks, even after adjustment for body height. Our results suggest that: 1) body height is a significant determinant of the ball speed in side-foot and instep kicks, and 2) for a given body height, the maximal ACSA of the dominant psoas major is a factor that affects the ball speed in side-foot kick.

Wed

20

Jun

2018

Latest research in football - week 18 - 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 Effects of a lighter, smaller football on acute match injuries in adolescent female football: a pilot cluster-randomized controlled trial
Reference: J Sports Med Phys Fitness. 2018 May;58(5):644-650. doi: 10.23736/S0022-4707.17.07903-8.
Authors: Zebis MK, Thorborg K, Andersen LL, Moller M, Christensen KB, Clausen MB, Holmich P, Wedderkopp N, Andersen TB, Krustrup P
Summary: The high injury incidence during match-play in female adolescent football is a major concern. In football, males and females play matches with the same football size. No studies have investigated the effect of football size on injury incidence in female adolescent football. Thus, the aim of the present study was to investigate the effects of introducing a lighter, smaller football on the injury pattern in female adolescent football. We conducted a pilot cluster randomized controlled trial including 26 football teams representing 346 adolescent female football players (age 15-18 years). The teams were randomized to a new lighter, smaller football (INT, N.=12 teams) or a traditional FIFA size 5 football (CON, N.=14 teams) during a full match-season. Acute time-loss injuries and football-exposure during match-play were reported weekly by text-message questions and verified subsequently by telephone interview. In total, 46 acute time-loss injuries were registered (5 severe injuries), yielding an incidence rate of 15.2 injuries per 1000 hours of match-play (95% CI: 8.5-27.2) in INT and 18.6 injuries per 1000 hours of match-play (95% CI: 14.0-24.8) in CON. The estimated 22% greater injury incidence rate risk (IRR: 1.22 [95% CI: 0.64-2.35]) in the CON group was not significant. With an IRR of 1.22, a future RCT main study would need to observe 793 acute time-loss injuries during match-play, in order to have a power of 80%. A large-scaled RCT is required to definitively test for beneficial or harmful effects of a lighter, smaller football in adolescent female football.


#2 Football training improves metabolic and cardiovascular health status in 55- to 70-year-old women and men with prediabetes
Reference: Scand J Med Sci Sports. 2018 May 2. doi: 10.1111/sms.13081. [Epub ahead of print]
Authors: Skoradal MB, Weihe P, Patursson P, Mortensen J, Connolly L, Krustrup P, Mohr M
Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.13081
Summary: We examined the effects of 16 weeks of football training and dietary advice on blood glucose control and health status in 55- to 70-year-old women and men with prediabetes. Fifty participants with prediabetes (age; 61 ± 6 years, BMI; 29.6 ± 4.7; VO2max 22.3 ± 5.7 mL·min-1 ·kg-1 ) were randomized into a football and dietary advice group (F+D; n = 27) and a dietary advice group (D; n = 23). F+D performed football training (twice weekly 30- to 60-minutes sessions) and received dietary advice, while D only received dietary advice. An oral glucose tolerance test (OGTT) was completed pre and post the 16-week period. Body composition, blood pressure, and maximal oxygen uptake (VO2max ) were additionally measured. Both groups demonstrated a decrement (P < .05) in fasting blood glucose (-0.4 ± 0.5 mmol·L-1 ) and lowered blood glucose throughout OGTT. F+D displayed lower values than D (P < .05) after 60 minutes (9.0 ± 2.7 vs 10.6 ± 2.9 mmol·L-1 ) and 120 minutes (5.7 ± 1.6 vs 7.5 ± 2.4 mmol·L-1 ). VO2max increased by 14% in F+D, with a higher (P < .05) change score than in D (2%). Mean arterial pressure declined more (P < .05) in F+D than in D (-8 ± 9 vs -4 ± 11 mm Hg). Fat loss was greater (P < .05) in F+D than in D (-3.4 ± 2.8 vs -1.2 ± 2.0 kg), and the increase in lean body mass was also greater (P < .05) in F+D than in D (0.7 ± 1.5 vs -0.3 ± 1.6 kg). In conclusion, football training combined with dietary advice has broad-spectrum effects on metabolic and cardiovascular health profile with greater overall effects than professional dietary advice per se for 55- to 70-year-old women and men with prediabetes.


#3 Longitudinal motor performance development in early adolescence and its relationship to adult success: An 8-year prospective study of highly talented soccer players
Reference: PLoS One. 2018 May 3;13(5):e0196324. doi: 10.1371/journal.pone.0196324. eCollection 2018.
Authors: Leyhr D, Kelava A, Raabe J, Honer O
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196324&type=printable
Summary: Several talent identification and development (TID) programs in soccer have implemented diagnostics to measure players' motor performance. Yet, there is a lack of research investigating the relationship between motor development in adolescence and future, adult performance. This longitudinal study analyzed the three-year development of highly talented young soccer players' speed abilities and technical skills and examined the relevance of this development to their adult success. The current research sample consisted of N = 1,134 players born between 1993 and 1995 who were selected for the German Soccer Association's TID program and participated in nationwide motor diagnostics (sprinting, agility, dribbling, ball control, shooting) four times between the Under 12 (U12) and Under 15 (U15) age class. Relative age (RA) was assessed for all players, and a total motor score was calculated based on performances in the individual tests. In order to investigate players' future success, participants were divided into two groups according to their adult performance level (APL) in the 2014/2015 season: Elite (1st-5th German division; N = 145, 12.8%) and non-elite players (lower divisions; N = 989, 87.2%). Using multilevel regression analyses each motor performance was predicted by Time, Time2 (level-1 predictors), APL, and RA (level-2 covariates) with simultaneous consideration for interaction effects between the respective variables. Time and Time2 were significant predictors for each test performance. A predictive value for RA was confirmed for sprinting and the total motor score. A significant relationship between APL and the motor score as well as between APL and agility, dribbling, ball control, and shooting emerged. Interaction effects distinctly failed to reach significance. The study found a non-linear improvement in players' performance for all considered motor performance factors over a three-year period from early to middle adolescence. While their predictive value for future success was confirmed by a significant relationship between APL and most of the considered factors, there was no significant interaction between APL and Time. These findings indicate that future elite players had already been better at the beginning of the TID program and maintained this high level throughout their promotion from U12 to U15.


#4 Heading Frequency Is More Strongly Related to Cognitive Performance Than Unintentional Head Impacts in Amateur Soccer Players
Reference: Front Neurol. 2018 Apr 24;9:240. doi: 10.3389/fneur.2018.00240. eCollection 2018.
Authors: Stewart WF, Kim N, Ifrah C, Sliwinski M, Zimmerman ME, Kim M, Lipton RB, Lipton ML
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5928847/pdf/fneur-09-00240.pdf
Summary: Compared to heading, unintentional head impacts (e.g., elbow to head, head to head, head to goalpost) in soccer are more strongly related to risk of moderate to very severe Central Nervous System (CNS) symptoms. But, most head impacts associated with CNS symptoms that occur in soccer are mild and are more strongly related to heading. We tested for a differential relation of heading and unintentional head impacts with neuropsychological (NP) test performance. Active adult amateur soccer players were recruited in New York City and the surrounding areas for this repeated measures longitudinal study of individuals who were enrolled if they had 5+ years of soccer play and were active playing soccer 6+ months/year. All participants completed a baseline validated questionnaire ("HeadCount-2w"), reporting 2-week recall of soccer activity, heading and unintentional head impacts. In addition, participants also completed NP tests of verbal learning, verbal memory, psychomotor speed, attention, and working memory. Most participants also completed one or more identical follow-up protocols (i.e., HeadCount-2w and NP tests) at 3- to 6-month intervals over a 2-year period. Repeated measures General Estimating Equations (GEE) linear models were used to determine if variation in NP tests at each visit was related to variation in either heading or unintentional head impacts in the 2-week period before testing. 308 players (78% male) completed 741 HeadCount-2w. Mean (median) heading/2-weeks was 50 (17) for men and 26 (7) for women. Heading was significantly associated with poorer performance on psychomotor speed (p < 0.001) and attention (p = 0.02) tasks and was borderline significant with poorer performance on the working memory (p  = 0.06) task. Unintentional head impacts were not significantly associated with any NP test. Results did not differ after excluding 22 HeadCount-2w with reported concussive or borderline concussive symptoms. Poorer NP test performance was consistently related to frequent heading during soccer practice and competition in the 2 weeks before testing. In contrast, unintentional head impacts incurred during soccer were not related to cognitive performance.


#5 Soccer Injury Movement Screen (SIMS) Composite Score Is Not Associated With Injury Among Semi-Professional Soccer Players
Reference: J Orthop Sports Phys Ther. 2018 May 8:1-29. doi: 10.2519/jospt.2018.8037. [Epub ahead of print]
Authors: McCunn R, Funten KA, Whalan M, Sampson JA, Meyer T
Summary: The association between movement quality and injury is equivocal. No soccer-specific movement assessment has been prospectively investigated in relation to injury risk. The aim was to investigate the association between a soccer-specific movement quality assessment and injury risk among semi-professional soccer players. Semi-professional soccer players (n=306) from 12 clubs completed the Soccer Injury Movement Screen (SIMS) during the pre-season period. Individual training/match exposure and non-contact time loss injuries were recorded prospectively for the entirety of the 2016 season. Relative risks (RR) were calculated, and presented with 90% confidence intervals (CI), for the SIMS composite and individual sub-test scores from generalized linear models with Poisson distribution offset for exposure. When considering non-contact time loss lower extremity injuries (primary level of analysis), there was a most likely trivial association with the SIMS composite score. Similarly, SIMS composite score demonstrated most likely to likely trivial associations to all injury categories included in the secondary level of analysis (non-contact time loss hip/groin, thigh, knee and ankle injuries). When considering hamstring strains and ankle sprains specifically (tertiary level of analysis) the SIMS composite score, again, demonstrated very likely trivial associations. A total of 262 non-contact time loss injuries were recorded. The overall (training and match exposure combined) incidence of non-contact time loss injury was 12/1000 hours. The SIMS composite score demonstrated no association to any of the investigated categories of soccer-related injury. The SIMS composite score should not be used to group players into 'high' or 'low' risk groups.


#6 Accuracy of Anthropometric Equations for Estimating Body Fat in Professional Male Soccer Players Compared with DXA
Reference: J Sports Med (Hindawi Publ Corp). 2018 Mar 14;2018:6843792. doi: 10.1155/2018/6843792. eCollection 2018.
Authors: Lopez-Taylor JR1, Gonzalez-Mendoza RG1, Gaytan-Gonzalez A, Jimenez-Alvarado JA, Villegas-Balcazar M, Jauregui-Ulloa EE, Torres-Naranjo F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872598/pdf/JSM2018-6843792.pdf
Summary: There are several published anthropometric equations to estimate body fat percentage (BF%), and this may prompt uncertainty about their application. The purpose was to analyze the accuracy of several anthropometric equations (developed in athletic [AT] and nonathletic [NAT] populations) that estimate BF% comparing them with DXA. We evaluated 131 professional male soccer players (body mass: 73.2 ± 8.0 kg; height: 177.5 ± 5.8 cm; DXA BF% [median, 25th-75th percentile]: 14.0, 11.9-16.4%) aged 18 to 37 years. All subjects were evaluated with anthropometric measurements and a whole body DXA scan. BF% was estimated through 14 AT and 17 NAT anthropometric equations and compared with the measured DXA BF%. Mean differences and 95% limits of agreement were calculated for those anthropometric equations without significant differences with DXA. Five AT and seven NAT anthropometric equations did not differ significantly with DXA. From these, Oliver's and Civar's (AT) and Ball's and Wilmore's (NAT) equations showed the highest agreement with DXA. Their 95% limits of agreement ranged from -3.9 to 2.3%, -4.8 to 1.8%, -3.4 to 3.1%, and -3.9 to 3.0%, respectively.Oliver's, Ball's, Civar's, and Wilmore's equations were the best to estimate BF% accurately compared with DXA in professional male soccer players.


#7 Planning Training Workload in Football Using Small-Sided Games' Density
Reference: J Strength Cond Res. 2018 May 8. doi: 10.1519/JSC.0000000000002598. [Epub ahead of print]
Authors: Sangnier S, Cotte T, Brachet O, Coquart J, Tourny C
Summary: To develop the physical qualities, the small-sided games' (SSGs) density may be essential in soccer. Small-sided games are games in which the pitch size, players' number, and rules are different to those for traditional soccer matches. The purpose was to assess the relation between training workload and SSGs' density. The 33 densities data (41 practice games and 3 full games) were analyzed through global positioning system (GPS) data collected from 25 professional soccer players (80.7 ± 7.0 kg; 1.83 ± 0.05 m; 26.4 ± 4.9 years). From total distance, distance metabolic power, sprint distance, and acceleration distance, the data GPS were divided into 4 categories: endurance, power, speed, and strength. Statistical analysis compared the relation between GPS values and SSGs' densities, and 3 methods were applied to assess models (R-squared, root-mean-square error, and Akaike information criterion). The results suggest that all the GPS data match the player's essential athletic skills. They were all correlated with the game's density. Acceleration distance, deceleration distance, metabolic power, and total distance followed a logarithmic regression model, whereas distance and number of sprints follow a linear regression model. The research reveals options to monitor the training workload. Coaches could anticipate the load resulting from the SSGs and adjust the field size to the players' number. Taking into account the field size during SSGs enables coaches to target the most favorable density for developing expected physical qualities. Calibrating intensity during SSGs would allow coaches to assess each athletic skill in the same conditions of intensity as in the competition.


#8 Physical performance tests - a relationship of risk factors for muscle injuries in elite level male football players
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):282-288. doi: 10.12965/jer.1836028.014. eCollection 2018 Apr.
Authors: Svensson K, Alricsson M, Olausson M, Werner S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931166/pdf/jer-14-2-282.pdf
Summary: The purpose of the present study was to investigate whether there is a relationship between the outcome of preseason physical performance tests and the risk of sustaining lower extremity muscle injuries within the same season, in male football players at elite level. This is a cohort study of a male football team (63 players) from the first league in Sweden. The football players are prospectively followed, in terms of muscle injuries of the lower extremity during five seasons between 2010 and 2014. All muscle injuries were evaluated and diagnosed with ultraso-nography. The following physical performance tests were included: squats, chin-ups, YoYo intermittent recovery level 2, counter movement jump, squat jump, standing long jump, sprint, one leg squat test, and a functional movement screen. A total of 86 muscle injuries occurred during the study period. No significant correlation was found between the results of the physical performance tests and muscle injuries of the lower extremity. None of the evaluated tests predicted the risk of sus-taining muscle injuries of the lower extremity. We conclude that muscle injury risk factors are more complex than solely related to the results of the preseason physical performance tests.


#9 Perceived motivational factors for female football players during rehabilitation after sports injury - a qualitative interview study
Reference: J Exerc Rehabil. 2018 Apr 26;14(2):199-206. doi: 10.12965/jer.1836030.015. eCollection 2018 Apr.
Authors: Hildingsson M, Fitzgerald UT, Alricsson M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931154/pdf/jer-14-2-199.pdf
Summary: Compliance with a rehabilitation program is significant among athletes following a sports injury. It is also one of the main factors that influence the rehabilitation process; moreover, the outcome is also influenced by the athlete's motivation. It is primarily an autonomous motivation, resulting in rehabilitation adherence. The aim of this study was to investigate the perceived motivation of female football players during rehabilitation after a sports injury and the extent to which these motivating factors were autonomous. Qualitative interviews, based on a semistructured interview guide with injured female football players undergoing rehabilitation, were analyzed using content analysis. The motivational factors that were described were their set goals, social support as well as external and internal pressures during rehabilitation. The perceived autonomy varied somewhat but overall, they experienced external motivation; therefore, the behavior was not entirely self-determined. Results are expected to provide a better understanding of women football players' motivation in relation to their rehabilitation; hence, physiotherapists and coaches who are part of the rehabilitation process can contribute by increasing the autonomous motivation, thus, improving the compliance and outcome of the rehabilitation.


#10 Sub-Elite Football Players With Hip-Related Groin Pain and Positive Flexion Adduction Internal Rotation Test Exhibit Distinct Biomechanical Differences Compared With the Asymptomatic Side
Reference: J Orthop Sports Phys Ther. 2018 May 8:1-26. doi: 10.2519/jospt.2018.7910. [Epub ahead of print]
Authors: King MG, Semciw AI, Hart HF, Schache AG, Middleton KJ, Heerey JJ, Agricola R, Crossley KM
Summary: Study Design Observational cross-sectional study. Background Hip-related groin pain is common in sub-elite football players and may be associated with altered hip biomechanics. Objectives To compare the hip biomechanics, bony hip morphology associated with femoroacetabular impingement (FAI) syndrome, and hip strength and range of motion between the symptomatic and asymptomatic limb of sub-elite football players with unilateral hip-related groin pain and a positive flexion adduction internal rotation test. Methods Fifteen sub-elite football (soccer) players with unilateral hip-related groin pain and a positive flexion adduction internal rotation test were recruited. Three-dimensional motion analysis and ground reaction force data were recorded for walking and a single leg drop jump (SLDJ) task. Participants also underwent a standard anterior-posterior hip radiograph and hip strength and range of movement assessment. Between-limb differences were assessed using paired t-tests or Wilcoxon sign-rank tests. Results The symptomatic limb displayed a smaller peak hip extension angle (P=.01) and a lower peak hip adduction moment (P=.03) compared with the asymptomatic limb during the stance phase of walking. Additionally, during the SLDJ, the symptomatic limb demonstrated less total sagittal plane range of motion (P=.04). The symptomatic limb also demonstrated less external rotation range of motion (P=.03) however, no differences were found between limbs for bony hip morphology associated with FAI syndrome or hip strength. Conclusion This study found between limb asymmetries in low- and high-impact functional tasks such as walking and a SLDJ in football players with unilateral hip-related groin pain. Despite unilateral pain, bony morphology associated with FAI syndrome did not differ between limbs

Tue

29

May

2018

Football is...(#62)

The role of anthropometry for certain positions - debatable?

Mon

28

May

2018

Latest research in football - week 17 - 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 Assessing Repeated-Sprint Ability in Division I Collegiate Women Soccer Players
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002527. [Epub ahead of print]
Authors: Lockie RG, Liu TM, Stage AA, Lazar A, Giuliano DV, Hurley JM, Torne IA, Beiley MD, Birmingham-Babauta SA, Stokes JJ, Risso FG, Davis DL, Moreno MR, Orjalo AJ
Summary: Repeated-sprint ability (RSA) is a key component of soccer, and is the capacity to repeatedly produce near-maximal to maximal sprints with short recovery periods. Repeated-sprint ability has received little analysis in collegiate women soccer players. The purpose of this study was to investigate relationships between RSA and tests of soccer-specific performance. Nineteen players from the same Division I collegiate women's soccer team were recruited. The RSA test consisted of six 20-m sprints completed on 15-second cycles. The measurements taken were total time (TT) and percent decrement (PD; percent change from first to last sprint). Subjects also completed tests of: lower-body strength (1 repetition maximum [1RM] back squat); jump performance (vertical and standing long jumps); linear (0-5, 0-10, and 0-30 m sprint intervals) and change-of-direction (505 from each leg) speed; and soccer-specific fitness (Yo-Yo intermittent recovery test level 1 [YYIRT1]). Pearson's correlations (p ≤ 0.05) were used to calculate relationships between RSA TT and PD with the performance tests. Total time exhibited significant relationships with the 0-10 (r = 0.50) and 0-30 m (r = 0.71) sprint intervals, and the left-leg 505 (r = 0.57). However, lower-body strength measured by the 1RM back squat and jump performance did not relate to TT. Percent decrement correlated only with the left-leg 505 (r = 0.53) and no other performance test. This included the YYIRT1, although both PD and YYIRT1 performance are limited by fatigue. The results from this study indicated that faster linear sprinting speed could positively influence RSA in Division I collegiate women soccer players.


#2 EEG alpha activity during imagining creative moves in soccer decision-making situations
Reference: Neuropsychologia. 2018 Apr 24. pii: S0028-3932(18)30166-0. doi: 10.1016/j.neuropsychologia.2018.04.025. [Epub ahead of print]
Authors: Fink A, Rominger C, Benedek M, Perchtold CM, Papousek I, Weiss EM, Seidel A, Memmert D
Summary: This study investigated task-related changes of EEG alpha power while participants were imagining creative moves in soccer decision-making situations. After presenting brief video clips of a soccer scene, participants had to imagine themselves as the acting player and to think either of a creative/original or an obvious/conventional move (control condition) that might lead to a goal. Performance of the soccer task generally elicited comparatively strong alpha power decreases at parietal and occipital sites, indicating high visuospatial processing demands. This power decrease was less pronounced in the creative vs. control condition, reflecting a more internally oriented state of information processing characterized by more imaginative mental simulation rather than stimulus-driven bottom-up processing. In addition, more creative task performance in the soccer task was associated with stronger alpha desynchronization at left cortical sites, most prominently over motor related areas. This finding suggests that individuals who generated more creative moves were more intensively engaged in processes related to movement imagery. Unlike the domain-specific creativity measure, individual's trait creative potential, as assessed by a psychometric creativity test, was globally positively associated with alpha power at all cortical sites. In investigating creative processes implicated in complex creative behavior involving more ecologically valid demands, this study showed that thinking creatively in soccer decision-making situations recruits specific brain networks supporting processes related to visuospatial attention and movement imagery, while the relative increase in alpha power in more creative conditions and in individuals with higher creative potential might reflect a pattern relevant across different creativity domains.


#3 Inter-season variability in isokinetic strength and poor correlation with nordic hamstring eccentric strength in football players
Reference: Scand J Med Sci Sports. 2018 Apr 25. doi: 10.1111/sms.13201. [Epub ahead of print]
Authors: van Dyk N, Witvrouw E, Bahr R
Summary: In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aims to investigate the variability of isokinetic muscle strength over time, e.g. between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with one/two seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25Nm, 15%), whether separated by one or two seasons. Considering hamstring injuries, the same pattern was observed among injured (n=60) and uninjured (n=228) players. A poor correlation (r=0.35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes were not correlated (r=0.037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by one or two seasons, irrespective of injury. Also, eccentric hamstring strength and limb-to-limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests. This article is protected by copyright. All rights reserved.


#4 Variability of activity profile during medium-sided games in professional soccer
Reference: J Sports Med Phys Fitness. 2018 Apr 24. doi: 10.23736/S0022-4707.18.08376-7. [Epub ahead of print]
Authors: Rago V, Silva JR, Mohr M, Barreira D, Krustrup P, Rebelo AN
Summary: In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason. Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers). Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3 %). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59). During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.


#5 Landing Kinematics in Elite Male Youth Soccer Players of Different Chronologic Age and Stage of Maturation
Reference: J Athl Train. 2018 Apr 25. doi: 10.4085/1062-6050-493-16. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players. The aim was to use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation. A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV) participated in the study. Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe). A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups. Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.


#6 Team Dynamics, Running, and Skill-Related Performances of Brazilian U11 to Professional Soccer Players During Official Matches
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002577. [Epub ahead of print]
Authors: Palucci Vieira LH, Aquino R, Moura FA, Barros RML, Arpini VM, Oliveira LP, Bedo BLS, Santiago PRP
Summary: Analyses of movements during soccer competition have been used previously to help develop conditioning programs. However, this has not been extensively studied in youth populations. Therefore, the purposes of this study were to examine (1) dynamics of collective tactical movements, (2) running, and (3) skill-related performances during soccer matches disputed by children to senior players. A total of 120 Brazilian players in the age groups U11, U13, U15, U17, U20, and professional (PRO) were monitored during official competition matches (N = 12). Using semiautomatic video-based tracking (30 Hz), match running variables including total distance traveled, average speed, maximum sprint speed, and high-intensity activities were evaluated. Tactical metrics were computed as team surface area, spread, and median frequency. Through notational analysis, technical skills such as involvements with the ball, passes, ball touches, duels, and goal attempts were also recorded. One-way analysis of variance and magnitude-based inferences were used to detect differences between ages. Although the average speed, team surface area, and spread tended to present stabilized increases from the U15 (e.g., U15 > U13 > U11), maximal sprinting speed (PRO > U17 > U15, U13, U11) and percentage at very high-intensity activities (U20 > PRO, U17 > U15 > U13 > U11) demonstrated continuous gains. Median frequencies were higher in the younger groups (U13, U15, U17 > U20, PRO), although the percentage of successful passes was higher in the older groups (PRO > U17, U15 > U13, U11). We concluded that Brazilian U11 to PRO players present different performance profiles for running, collective movement dynamics, and technical skills, and that the rate of development regarding these components varies. Coaches should be aware of these differences to select and adapt training content for each age group.


#7 New Tool to Control and Monitor Weighted Vest Training Load for Sprinting and Jumping in Soccer
Reference: J Strength Cond Res. 2018 Apr 26. doi: 10.1519/JSC.0000000000002580. [Epub ahead of print]
Authors: Carlos-Vivas J, Freitas TT, Cuesta M, Perez-Gomez J, De Hoyo M, Alcaraz PE
Summary: The purpose of this study was to develop 2 regression equations that accurately describe the relationship between weighted vest loads and performance indicators in sprinting (i.e., maximum velocity, Vmax) and jumping (i.e., maximum height, Hmax). Also, this study aimed to investigate the effects of increasing the load on spatio-temporal variables and power development in soccer players and to determine the "optimal load" for sprinting and jumping. Twenty-five semiprofessional soccer players performed the sprint test, whereas a total of 46 completed the vertical jump test. Two different regression equations were developed for calculating the load for each exercise. The following equations were obtained: % body mass (BM) = -2.0762·%Vmax + 207.99 for the sprint and % BM = -0.7156·%Hmax + 71.588 for the vertical jump. For both sprinting and jumping, when the load increased, Vmax and Hmax decreased. The "optimal load" for resisted training using weighted vest was unclear for sprinting and close to BM for vertical jump. This study presents a new tool to individualize the training load for resisted sprinting and jumping using weighted vest in soccer players and to develop the whole force-velocity spectrum according to the objectives of the different periods of the season.


#8 Injury prevention and return to play strategies in elite football: no consent between players and team coaches
Reference: Arch Orthop Trauma Surg. 2018 Apr 20. doi: 10.1007/s00402-018-2937-6. [Epub ahead of print]
Authors: Loose O, Achenbach L, Fellner B, Lehmann J, Jansen P, Nerlich M, Angele P, Krutsch W
Summary: Injuries are a common problem in football. To improve prevention strategies, the players' (p) and coaches' (c) views need to be disclosed as they have a strong impact on return to play decisions. The aim of this study is to reveal current opinions with regard to injury prevention and return to play strategies to introduce new strategies in elite football. In a retrospective data analysis of elite salaried football players (n = 486) and team coaches (n = 88), a detailed investigation by means of a standardized questionnaire was carried out. In a preseason period of the 2015/16 season and as part of a large interventional research project in elite salaried German football, a request about players' and team coaches' knowledge and opinions was performed. Topics such as injury prevention, return to play after injuries, the importance of screening tests, general problems of injuries in football, or the decision-making in terms of prevention and return to play in elite football were investigated. The study revealed a high interest in injury prevention and screening tests among players and coaches (p 82.5%; c 99.1%). The participants of the study reported warm-up exercises (p 76.4%; c 74.7%), regeneration training (p 54.1%; c 56.3%), and core stability (p 53.8; c 70.1%) as the most important prevention methods, but the additional investigation of the teams' current daily training routine showed that the transfer is incomplete. Coaches are more familiar with scientific published warm-up programs like FIFA 11 + than players (42.5 vs. 12.6; p < 0.001). Knee injuries (p 90.7%; c 93.1%) and ACL injuries in particular were reported as the most severe and common problem in elite football. Players and coaches expressed different attitudes concerning return to play decisions. While players want to decide themselves (81.4%), team coaches consult medical advice ahead of the decision of return to play after injuries (83.5%; p < 0.001). Decisions against the doctor's recommendation are often made by both groups (p 64.4% vs. c 87.1%; p < 0.001). The basic knowledge of prevention and injuries is sufficient in elite football, but the transfer from theoretical knowledge to practical routine is suboptimal. The study also shows possibilities to improve the prevention process and communication between players, coaches, doctors, and physiotherapists, while there is no consent between players and coaches regarding return to play decision.


#9 Dynamics of submaximal effort soccer instep kicking
Reference: J Sports Sci. 2018 May 1:1-8. doi: 10.1080/02640414.2018.1470216. [Epub ahead of print]
Authors: Nunome H, Inoue K, Watanabe K, Iga T, Akima H
Summary: During a soccer match, players are often required to control the ball velocity of a kick. However, little information is available for the fundamental qualities associated with kicking at various effort levels. We aimed to illustrate segmental dynamics of the kicking leg during soccer instep kicking at submaximal efforts. The instep kicking motion of eight experienced university soccer players (height: 172.4 ± 4.6 cm, mass: 63.3 ± 5.2 kg) at 50, 75 and 100% effort levels were recorded by a motion capture system (500 Hz), while resultant ball velocities were monitored using a pair of photocells. Between the three effort levels, kinetic adjustments were clearly identified in both proximal and distal segments with significantly different (large effect sizes) angular impulses due to resultant joint and interaction moments. Also, players tended to hit an off-centre point on the ball using a more medial contact point on the foot and with the foot in a less upright position in lower effort levels. These results suggested that players control their leg swing in a context of a proximal to distal segmental sequential system and add some fine-tuning of the resultant ball velocity by changing the manner of ball impact.


#10 Periodic Health Examination and Injury Prediction in Professional Football (Soccer): Theoretically, the Prognosis is Good
Reference: Sports Med. 2018 Apr 27. doi: 10.1007/s40279-018-0928-y. [Epub ahead of print]
Authors: Hughes T, Sergeant JC, van der Windt DA, Riley R, Callaghan
Download link: https://link.springer.com/content/pdf/10.1007%2Fs40279-018-0928-y.pdf
Summary: In professional soccer and other elite sports, medical and performance screening of athletes (also termed periodic health examination or PHE) is common practice. The purposes of this are: (1) to assist in identifying prevalent conditions that may be a threat to safe participation, (2) to assist in setting benchmark targets for rehabilitation or performance purposes and (3) to assist clinicians in determining which athletes may be at risk of future injury and selecting appropriate injury prevention strategies to reduce the perceived risk. However, when using PHE as an injury prevention tool, are clinicians seeking to identify potential causes of injury or to predict future injury? This Current Opinion aims to examine the conceptual differences between aetiology and prediction of injury while relating these areas to the capabilities of PHE in practice. We also introduce the concept of prognosis-a broader approach that is closely related to prediction-and why this may have greater applicability to PHE of professional athletes.

Thu

24

May

2018

Latest research in football - week 16 - 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 Association between Cumberland Ankle Instability Tool score and postural stability in collegiate soccer players with and without functional ankle instability
Reference: Phys Ther Sport. 2018 Mar 23;32:29-33. doi: 10.1016/j.ptsp.2018.03.002. [Epub ahead of print]
Authors: Kunugi S, Masunari A, Yoshida N, Miyakawa S
Summary: The purpose of this study was to investigate the association between Cumberland Ankle Instability Tool (CAIT) scores and postural stability during a diagonal landing, and to investigate whether postural stability is altered in collegiate soccer players with and without functional ankle instability (FAI). Ninety-one soccer players were classified into a FAI group (history of at least two ankle sprains and a CAIT-Japanese version score ≤25, n = 28), a copers group (history of one ankle sprain and a CAIT-Japanese version score ≥26, n = 32), or a control group (no history of ankle sprain, n = 31). Time to anteroposterior stabilisation (TTSAP) and mediolateral stabilisation (TTSML) were measured during the diagonal single-leg landing. The CAIT scores were correlated with TTSAP (P < 0.05, rs = -0.214) and TTSML (P < 0.01, rs = -0.566). TTSAP was longer in the FAI group than in the control group, and TTSML was longer in the FAI group than in the other groups. Our findings indicate the presence of an association between the CAIT-J score and TTSML, as well as postural stability deficits in collegiate soccer players with FAI during diagonal landings.


#2 Isolated Subscapularis Tendon Tear in a Skeletally Immature Soccer Player
Reference: Joints. 2017 Dec 11;6(1):68-70. doi: 10.1055/s-0037-1608952. eCollection 2018 Mar.
Authors: Avanzi P, Dei Giudici L, Giovarruscio R, Gigante A, Zorzi C
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5906114/pdf/10-1055-s-0037-1608952.pdf
Summary: Subscapularis injury in adolescents, usually associated to an avulsion fracture of the lesser humeral tuberosity, accounts for less than 2% of all fractures of the proximal humerus. Isolated tears of the subscapularis tendon without a history of dislocation and associated avulsion fractures are an even rarer occurrence, and treatment is controversial. This article describes a rare case of a 12-year-old suffering from an isolated subscapularis tear and discusses its management. The patient was evaluated at presentation, and at 1 to 2.5 months after he underwent a cuff tear arthroscopic repair with a single "all suture" anchor loaded with two wires, active/passive range of motion (A/PROM), Constant-Murley score, and American Shoulder and Elbow Surgeons (ASES) score were noted. Patient reported an excellent outcome, recovered the whole ROM, was pain free, and returned to the previous level of activity. Isolated avulsion of the subscapularis tendon requires a high index of suspicion for a proper diagnosis as early treatment is required for a good recovery. Arthroscopy reserves more advantages in proper hands, restoring the previous levels of function and activity. An increase in attention for this condition is mandatory in a society where many adolescents are getting more and more active in high levels of sport activities.


#3 The relative age effect is larger in Italian soccer top-level youth categories and smaller in Serie A
Reference: PLoS One. 2018 Apr 19;13(4):e0196253. doi: 10.1371/journal.pone.0196253. eCollection 2018.
Authors: Brustio PR, Lupo C, Ungureanu AN, Frati R, Rainoldi A, Boccia G
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0196253&type=printable
Summary: The relative age effect (RAE; i.e., an asymmetry in the birth distribution) is a bias observed in sport competitions that may favour relatively older athletes in talent identification. Therefore, the aim of this study was to investigate the presence of RAE in elite soccer players competing in the Italian championships, even considering the discriminations of younger and older Serie A players (in relation to the median age of the sample), and different positional roles (i.e., goalkeeper, defender, midfielder, forward) for each observed category. A total of 2051 players competing into the 2017-2018 Italian under-15 (n = 265), under-16 (n = 362), under-17 (n = 403), Primavera (n = 421) and Serie A (n = 600) championships were analysed. The birth-date distributions, grouped in four quartiles (i.e., January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4), were compared to a uniform distribution using Chi-squared analysis. The week of birth was analysed using Poisson regression. The results showed a large over-representation of players born in Q1 in all soccer player categories. However, the effect size of this trend resulted smaller as age increased. Individuals born in Q1 have about two-folds more chances to become a Serie A player compared to those born in Q4. The Poisson regression analysis showed that RAE was greater for defenders than for forwards among all categories. Therefore, a strongly biased selection emerged among elite soccer players competing in Italian championships, highlighting how young individuals born in the first three months have many more chances to become elite players compared to the others.


#4 Ratios of torques of antagonist muscle groups in female soccer players
Reference: Acta Bioeng Biomech. 2018;20(1):153-158.
Authors: Struzik A, Siemienski A, Bober T, Pietraszewski B
Summary: An increase in the value of the hamstring-to-quadriceps (H/Q) ratio with an increase in angular velocity may effectively prevent injuries of the back of the thigh. Previous studies have found that the conventional H/Q ratio was unaltered along with an increasing angular velocity in females. Therefore, this study aimed to investigate the relationships between the conventional H/Q ratio and angular velocity in a group of female soccer players. The study was carried out on a group of 16 female soccer players (age: 20.7 ± 3.9 years, body height: 166.1 ± 5.8 cm, body mass: 58.4 ± 6.2 kg, training experience: 8.8 ± 4.1 years). Measurements of peak torque of extensors and flexors of the knee joint under static conditions and under isokinetic conditions (at angular velocities of 30°/s, 60°/s, 90°/s and 120°/s) were carried out using a Biodex dynamometer. There was a statistically significant increase in the conventional H/Q ratio with an increase in angular velocity. These differences occurred between measurements at angular velocities of 0°/s and 30°/s, and 30°/s and 60°/s. As previously found for males, an increase in conventional H/Q ratio with increased angular velocity was also present in this group of female players. This phenomenon should reduce the number of injuries of the muscles of back of the thigh. Coaches should pay attention to increasing the level of strength in the group of knee joint flexor muscles so as to make the value of the H/Q ratio appropriately high and increasing with increasing angular velocity.


#5 Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football
Reference: Scand J Med Sci Sports. 2018 Apr 19. doi: 10.1111/sms.13197. [Epub ahead of print]
Authors: Raisanen AM, Arkkila H, Vasankari T, Steffen K, Parkkari J, Kannus P, Forsman H, Pasanen K
Summary: This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA) during the single-leg squat and sustaining an acute lower extremity injury or acute non-contact lower extremity injury. Secondly, side-to-side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex and leg dominance on the FPKPA. A total of 558 youth football players (U11 to U14), participated in the single-leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA. Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear but the oldest girls displayed the smallest mean FPKPA in the study (12.2°+ 8.3°). The FPKPA was greater on the dominant kicking leg compared to the non-dominant support leg (P<0.001 for boys, P=0.001 for girls). However, side-to-side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single-leg squat was not associated with lower extremity injuries among young football players. As the single-leg squat to 90° knee flexion was too demanding for many subjects, easier single-leg squat test procedure or a different movement control test, such as a double-legged squat, could be more suitable for the young football players.


#6 Is the message getting through? Awareness and use of the 11+ injury prevention programme in amateur level football clubs
Reference: PLoS One. 2018 Apr 19;13(4):e0195998. doi: 10.1371/journal.pone.0195998. eCollection 2018.
Authors: Wilke J, Niederer D, Vogt L, Banzer W
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0195998&type=printable
Summary: A large body of evidence suggests that the 11+ warm-up programme is effective in preventing football-related musculoskeletal injuries. However, despite considerable efforts to promote and disseminate the programme, it is unclear as to whether team head coaches are familiar with the 11+ and how they rate its feasibility. The present study aimed to gather information on awareness and usage among German amateur level football coaches. A questionnaire was administered to 7893 individuals who were in charge of youth and adult non-professional teams. Descriptive and inferential statistics were used to analyse the obtained data. A total of 1223 coaches (16%) returned the questionnaire. There was no risk of a non-response bias (p>.05). At the time of the survey, nearly half of the participants (42.6%) knew the 11+. Among the coaches who were familiar with the programme, three of four reported applying it regularly (at least once per week). Holding a license (φ = .28, p < .0001), high competitive level (Cramer-V = .13, p = .007), and coaching a youth team (φ = .1, p = .001) were associated with usage of 11+. Feasibility and suitability of the 11+ were rated similarly by aware and unaware coaches. Although a substantial share of German amateur level coaches is familiar with the 11+, more than half of the surveyed participants did not know the programme. As the non-usage does not appear to stem from a lack of rated feasibility and suitability, existing communication strategies might need to be revised.


#7 Muscle injuries in professional football : Treatment and rehabilitation
Reference: Unfallchirurg. 2018 Apr 17. doi: 10.1007/s00113-018-0501-z. [Epub ahead of print]  [Article in German]
Authors: Riepenhof H, Del Vescovo R, Droste JN, McAleer S, Pietsch A
Summary: Muscle injuries are common in professional sports, especially in football. Recent epidemiological studies showed that muscle injuries account for more than 30% of professional football injuries (1.8-2.2/1000 h exposure); however, even though there are significant differences within a European comparison, a single professional football team diagnosed on average 12 muscle injuries per season, corresponding to more than 300 availability days lost. The aim of this work is to present the diagnosis, general treatment and comprehensive management of muscle injuries in professional football. The present work is based on current scientific findings, experiences of the authors and examples from routine practice in the management of muscle injuries in a professional sports environment. The authors present a model of gradual progression for the treatment of muscular injuries and their rehabilitation. Due to the time-pressured nature of the professional sports environment, often promoted by coaches and media, this model could help lead players to recover as quickly as possible and return to competitive sports without relapse or sequel injury. This model integrates the player into the treatment plan. The progression sequences in the rehabilitation should be made clear to players and other parties involved, which are crucial for optimal healing. Even if absolute certainty cannot be achieved, i.e. the occurrence of re-injury or secondary injury, this model attempts to minimize the level of risk involved for the returning athlete. Since it is hardly possible to act strictly in line with more conservative guidelines due to the particular circumstances of the professional sport environment, the experiences of the authors are presented in the sense of best practice in order to support future decision-making processes.


#8 Post-Game High Protein Intake May Improve Recovery of Football-Specific Performance during a Congested Game Fixture: Results from the PRO-FOOTBALL Study
Reference: Nutrients. 2018 Apr 16;10(4). pii: E494. doi: 10.3390/nu10040494.
Authors: Poulios A, Fatouros IG, Mohr M, Draganidis DK, Deli C, Papanikolaou K, Sovatzidis A, Nakopoulou T, Ermidis G, Tzatzakis T, Laschou VC, Georgakouli K, Koulouris A, Tsimeas P, Chatzinikolaou A, Karagounis LG, Batsilas D, Krustrup P, Jamurtas AZ
Download link: www.mdpi.com/2072-6643/10/4/494/pdf
Summary: The effects of protein supplementation on performance recovery and inflammatory responses during a simulated one-week in-season microcycle with two games (G1, G2) performed three days apart were examined. Twenty football players participated in two trials, receiving either milk protein concentrate (1.15 and 0.26 g/kg on game and training days, respectively) (PRO) or an energy-matched placebo (1.37 and 0.31 g/kg of carbohydrate on game and training days, respectively) (PLA) according to a randomized, repeated-measures, crossover, double-blind design. Each trial included two games and four daily practices. Speed, jump height, isokinetic peak torque, and muscle soreness of knee flexors (KF) and extensors (KE) were measured before G1 and daily thereafter for six days. Blood was drawn before G1 and daily thereafter. Football-specific locomotor activity and heart rate were monitored using GPS technology during games and practices. The two games resulted in reduced speed (by 3-17%), strength of knee flexors (by 12-23%), and jumping performance (by 3-10%) throughout recovery, in both trials. Average heart rate and total distance covered during games remained unchanged in PRO but not in PLA. Moreover, PRO resulted in a change of smaller magnitude in high-intensity running at the end of G2 (75-90 min vs. 0-15 min) compared to PLA (P = 0.012). KE concentric strength demonstrated a more prolonged decline in PLA (days 1 and 2 after G1, P = 0.014-0.018; days 1, 2 and 3 after G2, P = 0.016-0.037) compared to PRO (days 1 after G1, P = 0.013; days 1 and 2 after G2, P = 0.014-0.033) following both games. KF eccentric strength decreased throughout recovery after G1 (PLA: P=0.001-0.047-PRO: P =0.004-0.22) in both trials, whereas after G2 it declined throughout recovery in PLA (P = 0.000-0.013) but only during the first two days (P = 0.000-0.014) in PRO. No treatment effect was observed for delayed onset of muscle soreness, leukocyte counts, and creatine kinase activity. PRO resulted in a faster recovery of protein and lipid peroxidation markers after both games. Reduced glutathione demonstrated a more short-lived reduction after G2 in PRO compared to PLA. In summary, these results provide evidence that protein feeding may more efficiently restore football-specific performance and strength and provide antioxidant protection during a congested game fixture.


#9 Hip and groin time-loss injuries decreased slightly but injury burden remained constant in men's professional football: the 15-year prospective UEFA Elite Club Injury Study
Reference: Br J Sports Med. 2018 Apr 24. pii: bjsports-2017-097796. doi: 10.1136/bjsports-2017-097796. [Epub ahead of print]
Authors: Werner J, Hagglund M, Ekstrand J, Walden M
Summary: Hip and groin injuries are common in men's professional football, but the time-trend of these injuries is not known. The aim of the study was to investigate hip and groin injury rates, especially time-trends, in men's professional football over 15 consecutive seasons. 47 European teams were followed prospectively for a varying number of seasons between 2001/2002 and 2015/2016, totalling 268 team seasons. Time-loss injuries and individual player exposure during training and matches were recorded. Injury rate was defined as the number of injuries/1000 hours and injury burden as the number of lay-off days/1000  hours. Time-trends for total hip and groin injuries and adductor-related injury rates were analysed using Poisson regression, and injury burden was analysed using a negative binomial regression model. Hip and groin injuries contributed 1812 out of 12 736 injuries (14%), with adductor-related injury as the most common of hip and groin injuries (n=1139, 63%). The rates of hip and groin injury and adductor-related injury were 1.0/1000 hours and 0.6/1000 hours, and these rates decreased significantly with on average 2% (Exp(b)=0.98, 95% CI 0.97 to 0.99, P=0.003) and 3% (Exp(b)=0.97, 95% CI 0.95 to 0.99, P<0.001) per season (year on year), respectively. The seasonal trend of hip and groin injury burden did not improve (Exp(b)=0.99, 95% CI 0.97 to 1.01, P=0.40). Hip and groin injuries constitute a considerable part of all time-loss injuries in men's professional football. Although there was a promising slight decreasing trend in the rates of hip and groin injury (as a category) and adductor-related injury (as a specific diagnosis), the injury burden remained at a consistent level over the study period.


#10 Body composition and somatotypes of male Zimbabwean Premier League football referees
Reference: J Sports Med Phys Fitness. 2018 Apr 20. doi: 10.23736/S0022-4707.18.08326-3. [Epub ahead of print]
Authors: Banda M, Grobbelaar HW, Terblanche E
Summary: Elite athletes need to optimise their body composition to deliver world class performances and this argument could be extended to elite referees as well. Unfortunately, there is a scarcity of body composition information among football referees. The aim of the study was to determine and compare the body composition and somatotypes of male football referees and assistant referees who officiated in the 2013 Zimbabwe Premier Football League. Forty-one participants (21 referees, 20 assistant referees; 8 FIFA, 33 ZIFA licenced referees) with a mean age of 34.89 ± 5.13 years took part. They had on average 10.85 ± 3.85 years of refereeing experience. The ISAK restricted anthropometric profile was used to measure body mass, height, skinfolds, girths and bone breadths, from which body mass index (BMI), waist-to-hip ratio (WHR), percentage body fat and somatotype were calculated. The referees were significantly taller than the assistant referees. The FIFA referees had moderately more desirable anthropometric profiles than the ZIFA referees. With a mean somatotype of 2.62-4.65-2.65, the total sample could be classified as balanced mesomorphs. They had lower BMI and body fat percentages than that observed among referees from other nationalities in the available literature. The results add to the paucity of information on the body composition of football officials. Referees aiming to excel at higher levels need to obtain and maintain an ideal body composition since elite level football is intense and requires high fitness levels.

Thu

17

May

2018

Latest research in football - week 14 - 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 Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players
Reference: Hum Mov Sci. 2018 Apr 3;59:81-87. doi: 10.1016/j.humov.2018.03.016. [Epub ahead of print]
Authors: Coratella G, Beato M, Schena F
Summary: The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.


#2 "Good, better, creative": the influence of creativity on goal scoring in elite soccer
Reference: J Sports Sci. 2018 Apr 6:1-5. doi: 10.1080/02640414.2018.1459153. [Epub ahead of print]
Authors: Kempe M, Memmert D
Summary: This study investigated the level of creativity of goals scored in football. Therefore, all goals in the Football FIFA World Cup 2010 and 2014, as well as the Football UEFA Euro 2016 were qualitatively examined. Three Football experts evaluated the last eight actions before each goal using a creativity scale ranging from 0 to 10 (0 = not creative, 10 = highly creative) of all goals scored via open play (311 goals in 153 matches). Level of creativity was revealed using an Analysis of Variance and the frquency of high highly creative goals using a Kruskall- Wallis Test. The results showed that the closer the actions to a goal, the more creative they were evaluated. Teams that advanced to the later rounds of the tournament demonstrated greater creativity than teams that failed to do so. High creativity in the last two actions before the actual shot on goal proved to be the best predictor for game success. In conclusion, this study is the first one to show that creativity seems to be a factor for success in high level football. Thereby it provides an empirical basis for the ongoing debate on the importance of creativity training in football.


#3 Mental Fatigue and Soccer: Current Knowledge and Future Directions
Reference: Sports Med. 2018 Apr 5. doi: 10.1007/s40279-018-0908-2. [Epub ahead of print]
Authors: Smith MR, Thompson C, Marcora SM, Skorski S, Meyer T, Coutts AJ
Summary: Fatigue is a complex state with multiple physiological and psychological origins. However, fatigue in soccer has traditionally been investigated from a physiological perspective, with little emphasis on the cognitive demands of competition. These cognitive demands may induce mental fatigue, which could contribute to the fatigue-related performance decrements observed during and after soccer matches. Recent research investigating the relationship between mental fatigue and soccer-specific performance supports this suggestion. This leading article provides an overview of the research in this emerging field, outlining the impact of mental fatigue on soccer-specific physical, technical, decision-making, and tactical performances. The second half of this review provides directions for future research in response to the limitations of the existing research. Emphasis is placed on translating the current body of knowledge into practical applications and developing a greater understanding of the mechanisms underpinning the negative impact of mental fatigue on soccer performance. A conceptual model is presented to help direct this future research.


#4 Specific Changes in Young Soccer Player's Fitness After Traditional Bilateral vs. Unilateral Combined Strength and Plyometric Training
Reference: Front Physiol. 2018 Mar 22;9:265. doi: 10.3389/fphys.2018.00265. eCollection 2018.
Authors: Ramirez-Campillo R, Sanchez-Sanchez J, Gonzalo-Skok O, Rodriguez-Fernandez A, Carretero M, Nakamura FY
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874317/pdf/fphys-09-00265.pdf
Summary: The aim of this study was to compare changes in young soccer player's fitness after traditional bilateral vs. unilateral combined plyometric and strength training. Male athletes were randomly divided in two groups; both received the same training, including strength training for knee extensors and flexors, in addition to horizontal plyometric training drills. The only difference between groups was the mode of drills technique: unilateral (UG; n = 9; age, 17.3 ± 1.1 years) vs. bilateral (TG; n = 9; age, 17.6 ± 0.5 years). One repetition maximum bilateral strength of knee muscle extensors (1RM_KE) and flexors (1RM_KF), change of direction ability (COD), horizontal and vertical jump ability with one (unilateral) and two (bilateral) legs, and limb symmetry index were measured before and after an 8-week in-season intervention period. Some regular soccer drills were replaced by combination of plyometric and strength training drills. Magnitude-based inference statistics were used for between-group and within-group comparisons. Beneficial effects (p < 0.05) in 1RM_KE, COD, and several test of jumping performance were found in both groups in comparison to pre-test values. The limb symmetry index was not affected in either group. The beneficial changes in 1RM_KE (8.1%; p = 0.074) and 1RM_KF (6.7%; p = 0.004), COD (3.1%; p = 0.149), and bilateral jump performance (from 2.7% [p = 0.535] to 10.5% [p = 0.002]) were possible to most likely beneficial in the TG than in the UG. However, unilateral jump performance measures achieved likely to most likely beneficial changes in the UG compared to the TG (from 4.5% [p = 0.090] to 8.6% [p = 0.018]). The improvements in jumping ability were specific to the type of jump performed, with greater improvements in unilateral jump performance in the UG and bilateral jump performance in the TG. Therefore, bilateral strength and plyometric training should be complemented with unilateral drills, in order to maximize adaptations.


#5 Switching between pitch surfaces: practical applications and future perspectives for soccer training
Reference: J Sports Med Phys Fitness. 2018 Apr 4. doi: 10.23736/S0022-4707.18.08278-6. [Epub ahead of print]
Authors: Rago V, Silva JR, Brito J, Barreira D, Mohr M, Krustrup P, Rebelo AN
Summary: Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training / competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising on different pitch surfaces in soccer. Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations or injury outcomes according to different pitch surfaces. A total of 224 studies were retrieved from a literature search. Twenty articles met the inclusion criteria: 9 for acute physical and physiological responses, 2 for training adaptations and 9 for injury assessment. The literature lacks consistent evidence regarding the effects of pitch surface on performance and health outcomes in soccer players. However, it seems that occasionally switching training surfaces seems a valuable strategy for focusing on specific musculoskeletal queries and enhancing players' fitness. For instance, sand training may be occasionally proposed as complementary training strategy, given the recruitment of additional musculature probably not involved on firmer surfaces, but the possible training-induced adaptations of non-conventional soccer surfaces (e.g., sand) might potentially result into a negative transfer on AT or NG. Since the specific physical demands of soccer can differ between surfaces, coaches should resort to the use of non-traditional surfaces with parsimony, emphasizing the specific surface-related motor tasks, normally observed on natural grass or artificial turf. Further studies are required to better understand the physiological effects induced by systematic surface-specific training, or switching between pitch surfaces.


#6 Shoulder and elbow injuries in soccer goalkeepers versus field players in the National Collegiate Athletic Association, 2009-2010 through 2013-2014
Reference: Phys Sportsmed. 2018 Apr 4. doi: 10.1080/00913847.2018.1462083. [Epub ahead of print]
Authors: Goodman AD, Etzel C, Raducha JE, Owens BD
Summary: Examination of the incidence of shoulder and elbow injuries in the collegiate soccer player population is limited, as is comparison between goalkeepers and field players. We hypothesized that goalkeepers would have a higher incidence of shoulder and elbow injuries than field players. Furthermore, we sought to determine the incidence of shoulder and elbow injuries among National Collegiate Athletic Association (NCAA) soccer players, and to determine injury risk factors. The NCAA Injury Surveillance Program database was analyzed for injuries to NCAA men's and women's soccer players during the 2009-2010 through 2013-2014 academic years. The incidence of injury was calculated per 10,000 athletic exposures (AE) for goalkeepers versus field players, activity, and injury characteristics, and compared using univariate analysis and risk-ratios to determine injury risk factors. While the overall incidence of shoulder and elbow injuries in soccer players was 2.7/10,000AE [95% CI 2.62-2.78], the incidence among goalkeepers was 4.6-fold higher (8.3 vs. 1.8/10,000AE, p<0.0001). Goalkeepers had significantly higher incidences of injury in practice (21.3-fold) and in the preseason (16.1-fold) than field players. Women goalkeepers were disproportionately affected, with injury incidences 7.7-fold higher than women field players, and 1.9-fold higher than male goalkeepers. Acromioclavicular joint injuries, rotator cuff tears/sprains, and elbow and shoulder instability constituted the majority of the goalkeeper injuries. Shoulder and elbow injuries in NCAA soccer players are significantly more common in goalkeepers than field players. Incidence varies widely by position and injury, with a number of associated risk factors. Soccer players sustaining these injuries, along with their coaches and medical providers, may benefit from this injury data to best manage expectations and outcomes. Soccer governing bodies may use this to track injury incidence and response to preventative measures.


#7 The effects of maturation on jumping ability and sprint adaptations to plyometric training in youth soccer players
Reference: J Sports Sci. 2018 Apr 3:1-7. doi: 10.1080/02640414.2018.1459151. [Epub ahead of print]
Authors: Asadi A, Ramirez-Campillo R, Arazi H, Saez de Villarreal E
Summary: The aim of this study was to investigate the effects of maturation on power and sprint performance adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity [PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤ 0.05) and small to moderate effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64; 0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = -0.58; -0.66), and 20-m sprint with ball (ES = -0.44; -0.8; -0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-PHV in vertical jump and sprint performance after training (P ≤ 0.05). Short-term plyometric training had positive effects on sprinting and jumping-power which are important determinants of match-winning actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems effective in improving power and sprint performance in youth soccer players.


#8 Passing Decisions in Football: Introducing an Empirical Approach to Estimating the Effects of Perceptual Information and Associative Knowledge
Reference: Front Psychol. 2018 Mar 22;9:361. doi: 10.3389/fpsyg.2018.00361. eCollection 2018.
Authors: Steiner S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874613/pdf/fpsyg-09-00361.pdf
Summary: The importance of various information sources in decision-making in interactive team sports is debated. While some highlight the role of the perceptual information provided by the current game context, others point to the role of knowledge-based information that athletes have regarding their team environment. Recently, an integrative perspective considering the simultaneous involvement of both of these information sources in decision-making in interactive team sports has been presented. In a theoretical example concerning passing decisions, the simultaneous involvement of perceptual and knowledge-based information has been illustrated. However, no precast method of determining the contribution of these two information sources empirically has been provided. The aim of this article is to bridge this gap and present a statistical approach to estimating the effects of perceptual information and associative knowledge on passing decisions. To this end, a sample dataset of scenario-based passing decisions is analyzed. This article shows how the effects of perceivable team positionings and athletes' knowledge about their fellow team members on passing decisions can be estimated. Ways of transfering this approach to real-world situations and implications for future research using more representative designs are presented.


#9 Concurrent validation of an inertial measurement system to quantify kicking biomechanics in four football codes
Reference: J Biomech. 2018 Mar 21. pii: S0021-9290(18)30212-4. doi: 10.1016/j.jbiomech.2018.03.031. [Epub ahead of print]
Authors: Blair S, Duthie G, Robertson S, Hopkins W, Ball K
Summary: Wearable inertial measurement systems (IMS) allow for three-dimensional analysis of human movements in a sport-specific setting. This study examined the concurrent validity of a IMS (Xsens MVN system) for measuring lower extremity and pelvis kinematics in comparison to a Vicon motion analysis system (MAS) during kicking. Thirty footballers from Australian football (n = 10), soccer (n = 10), rugby league and rugby union (n = 10) clubs completed 20 kicks across four conditions. Concurrent validity was assessed using a linear mixed-modelling approach, which allowed the partition of between and within-subject variance from the device measurement error. Results were expressed in raw and standardised units for assessments of differences in means and measurement error, and interpreted via non-clinical magnitude-based inferences. Trivial to small differences were found in linear velocities (foot and pelvis), angular velocities (knee, shank and thigh), sagittal joint (knee and hip) and segment angle (shank and pelvis) means (mean difference: 0.2-5.8%) between the IMS and MAS in Australian football, soccer and the rugby codes. Trivial to small measurement errors (from 0.1 to 5.8%) were found between the IMS and MAS in all kinematic parameters. The IMS demonstrated acceptable levels of concurrent validity compared to a MAS when measuring kicking biomechanics across the four football codes. Wearable IMS offers various benefits over MAS, such as, out-of-laboratory testing, larger measurement range and quick data output, to help improve the ecological validity of biomechanical testing and the timing of feedback. The results advocate the use of IMS to quantify biomechanics of high-velocity movements in sport-specific settings.

Wed

16

May

2018

Football is...(#61)

Long throw-ins might create goal scoring opportunities

Mon

14

May

2018

Latest research in football - week 12 - 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 Evaluation of Seasonal Changes in Fitness, Anthropometrics, and Body Composition in Collegiate Division Ii Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002578. [Epub ahead of print]
Authors: Peart AN, Nicks CR, Mangum M, Tyo BM
Summary: The purpose of this study was to investigate anthropometrics, body composition, aerobic and anaerobic fitness of collegiate Division II female soccer players throughout a calendar year. Eighteen (20 ± 0.9y) NCAA division II female soccer players from the same team participated in the study. Anthropometrics and body composition variables were assessed in addition to the Counter Movement Jump (CMJ), Wingate Anaerobic Test (WAT), and peak oxygen uptake (VO2peak). Data were collected over five time points: end of competitive seasons (ECS1 and ECS2), beginning of off-season (BOS), end of off-season (EOS), and pre-season (PS). Repeated-measures analysis of variance (ANOVA) were conducted to compare test scores among all five data collection points. Where appropriate, Bonferroni post-hoc tests were used to determine which points were significantly different. Hip circumference (HC) decreased significantly (p < 0.001) from EOS (98.47 ± 6.5 cm) to PS (94.46 ± 6.8 cm). Fat mass (FM) (12.73 ± 5.4 kg) was significantly different in ECS2 compared to BOS and EOS means (p ≤ 0.05) and percentage of body fat (%BF) (20.08 ± 5.44) significantly different in ECS2 compared to ECS1, BOS, and EOS means (p ≤ 0.05), while fat-free mass (FFM) was maintained from ECS1 to ECS2. CMJ, WAT, and VO2peak performance did not significantly change from ECS1 to ECS2. Anthropometrics and body composition results are similar to previous studies measuring Division II to professional female soccer players. CMJ results remained consistent and are comparable to results on Division I female soccer players. Coaches and researchers can use these data to help design and evaluate training programs throughout a calendar year.


#2 The Effect of Match-Factors on the Running Performance of Elite Female Soccer Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002584. [Epub ahead of print]
Authors: Trewin J, Meylan C, Varley MC, Cronin J, Ling D
Summary: The purpose of this study was to examine the effects of match-factors on the match-running of elite female soccer players. Players from the same women's national team (n = 45) were monitored during 47 international fixtures (files = 606) across four years (2012-2015) using 10-Hz global positioning system devices. A mixed model was used to analyse the effects of altitude, temperature, match-outcome, opposition ranking and congested schedules. At altitude (>500 m) a small increase in the number of accelerations (ES = 0.40) and a small decrease in total distance (ES = -0.54) was observed, whereas at higher temperatures there were decreases in all metrics (ES = -0.83 to -0.16). Playing a lower-ranked team in a draw resulted in a moderate increase in high-speed running (ES = 0.89), with small to moderate decreases in total distance and low-speed running noted in a loss or a win. Winning against higher-ranked opponents indicated moderately higher total distance and low-speed running (ES = 0.75), compared to a draw. Whilst the number of accelerations were higher in a draw against lower-ranked opponents, compared to a win and a loss (ES = 0.95 and 0.89 respectively). Practitioners should consider the effect of match-factors on match-running in elite female soccer.


#3 Sequencing Effects of Plyometric Training Applied Before or After Regular Soccer Training on Measures of Physical Fitness in Young Players
Reference: J Strength Cond Res. 2018 Mar 22. doi: 10.1519/JSC.0000000000002525. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Gentil P, Loturco I, Sanchez-Sanchez J, Izquierdo M, Moran J, Nakamura FY, Chaabene H, Granacher U
Summary: The objective was to compare the effects of short-term (i.e., 7 week) plyometric training applied before (PJT-B) or after (PJT-A) soccer practice on components of physical fitness in young soccer players, a single-blind randomized controlled trial was conducted. Post-pubertal boys aged 17.0±0.5 years were allocated to three groups: PJT-B (n=12), PJT-A (n=14), and control (CON; n=12). The outcome measures included tests to evaluate 20-m speed, standing long jump [SLJ], squat jump [SJ], countermovement jump [CMJ], and drop jump [DJ], 20-m multistage shuttle running speed [MSSRT], and Illinois change of direction speed [ICODT]. While the CON performed soccer-specific training, the PJT-A and PJT-B groups conducted the same soccer-specific sessions but replaced ∼11% of their time with plyometric training. The PJT-B group performed plyometric exercises after a warm-up program, and the PJT-A group conducted plyometric exercises ∼10 minutes after the completion of soccer training. Analyses of variance (ANOVAs) were used to detect differences between groups in all variables for pre- and post-training tests. Main effects of time (all p<.01; d=0.19-0.79) and group x time interactions (all p<.05; d=0.17-0.76) were observed for all examined variables. Post hoc analyses revealed significant increases in the PJT-B group (SLJ: 9.4%, d=1.7; CMJ: 11.2%, d=0.75; 20-m MSSRT: 9.0%, d=0.77) and the PJT-A group (SLJ: 3.1%, d=0.7; CMJ: 4.9%, d=0.27; 20-m MSSRT: 9.0%, d=0.76). Post hoc analyses also revealed significant increases in the PJT-B group (20-m speed: -7.4%, d=0.75; 20-cm DJ reactive strength index: 19.1%, d=1.4; SJ: 6.3%, d=0.44; ICODT results: -4.2%, d=1.1). In general, our study revealed that plyometric training is effective in improving measures of physical fitness in young male soccer players when combined with regular soccer training. More specifically, larger training induced effects on physical fitness were registered if plyometric training was conducted prior to soccer specific training.


#4 Postactivation Potentiation Following Acute Bouts of Plyometric versus Heavy-Resistance Exercise in Collegiate Soccer Players
Reference: Biomed Res Int. 2018 Feb 7;2018:3719039. doi: 10.1155/2018/3719039. eCollection 2018.
Authors: Sharma SK, Raza S, Moiz JA, Verma S, Naqvi IH, Anwer S, Alghadir AH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5820625/pdf/BMRI2018-3719039.pdf
Summary: Postactivation potentiation is referred to as an acute and temporary enhancement of muscle performance resulting from previous muscle contraction. The purpose of this study was to compare the acute effect of plyometric exercise (PLY) and heavy-resistance exercise (RES) on the blood lactate level (BLa) and physical performance. Fourteen male collegiate soccer players were randomized to perform either RES or PLY first and then crossed over to perform the opposite intervention. PLY consisted of 40 jumps, whereas RES comprised ten single repetitions at 90% of one repetition maximum. BLa and physical performance (countermovement jump height and 20-m sprint) were measured before and at 1 and 10 min following the exercise. No significant difference was observed in the BLa for both exercises (PLY and RES). Relative to baseline, countermovement jump (CMJ) height was significantly better for the PLY group after 1 min (P = 0.004) and after 10 min (P = 0.001) compared to that of the RES group. The 20-m sprint time was significantly better for PLY at 10 min (P = 0.003) compared to that of RES. The present study concluded that, compared to RES, PLY causes greater potentiation, which leads to improved physical performance.


#5 Aerobic fitness in professional soccer players after anterior cruciate ligament reconstruction
Reference: PLoS One. 2018 Mar 22;13(3):e0194432. doi: 10.1371/journal.pone.0194432. eCollection 2018.
Authors: Almeida AM, Santos Silva PR, Pedrinelli A, Hernandez AJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864031/pdf/pone.0194432.pdf
Summary: Although anterior cruciate ligament (ACL) reconstruction is considered a successful procedure in restoring knee stability, few studies have addressed the issue of aerobic capacity after ACL surgery. Soccer players need technical, tactical and physical skills to succeed, such as good knee function and aerobic capacity. Our purpose is to evaluate aerobic fitness in ACL injured professional football players and six months after ACL reconstruction compared to a control group. Twenty athletes with ACL injury were evaluated and underwent ACL reconstruction with hamstrings autograft, and were compared to twenty healthy professional soccer players. The methods used to evaluate aerobic fitness were maximum oxygen uptake (VO2max) and ventilatory thresholds with a treadmill protocol, before and six months after surgery, compared to a control group. Knee function questionnaires, isokinetic strength testing and body composition evaluation were also performed. Median ACL-injured patients age was 21 years old, and controls 20.5 years old. (n.s.). Preoperative VO2max in the ACL injured group was 45.2 ± 4.3 mL/kg/min, postoperative 48.9 ± 3.8 mL/kg/min and controls 56.9 ± 4.2 mL/kg/min. (p< .001 in all comparisons). Body composition evaluation was similar in all situations. Knee function questionnaires and quadriceps peak torque deficit improved after surgery but were significantly lower compared to controls. Aerobic fitness is significantly reduced in professional soccer players with ACL injury, and six months of rehabilitation was not enough to restore aerobic function after ACL reconstruction, compared to non-injured players of the same level.


#6 Validation of Field Methods to Assess Body Fat Percentage in Elite Youth Soccer Players
Reference: Int J Sports Med. 2018 Mar 21. doi: 10.1055/s-0044-101145. [Epub ahead of print]
Authors: Munguia-Izquierdo D, Suarez-Arrones L, Di Salvo V, Paredes-Hernandez V, Alcazar J, Ara I, Kreider R, Mendez-Villanueva A
Summary: This study determined the most effective field method for quantifying body fat percentage in male elite youth soccer players and developed prediction equations based on anthropometric variables. Forty-four male elite-standard youth soccer players aged 16.3-18.0 years underwent body fat percentage assessments, including bioelectrical impedance analysis and the calculation of various skinfold-based prediction equations. Dual X-ray absorptiometry provided a criterion measure of body fat percentage. Correlation coefficients, bias, limits of agreement, and differences were used as validity measures, and regression analyses were used to develop soccer-specific prediction equations. The equations from Sarria et al. (1998) and Durnin & Rahaman (1967) reached very large correlations and the lowest biases, and they reached neither the practically worthwhile difference nor the substantial difference between methods. The new youth soccer-specific skinfold equation included a combination of triceps and supraspinale skinfolds. None of the practical methods compared in this study are adequate for estimating body fat percentage in male elite youth soccer players, except for the equations from Sarria et al. (1998) and Durnin & Rahaman (1967). The new youth soccer-specific equation calculated in this investigation is the only field method specifically developed and validated in elite male players, and it shows potentially good predictive power.


#7 Cardiac deformation parameters and rotational mechanics by cardiac magnetic resonance feature tracking in pre-adolescent male soccer players
Reference: Cardiol Young. 2018 Mar 21:1-3. doi: 10.1017/S1047951118000343. [Epub ahead of print]
Authors: Malek LA, Barczuk-Falęcka M, Brzewski M
Summary: The purpose of the study was to analyse whether prolonged and regular physical training in children leads to changes in myocardial systolic deformation and rotational mechanics. For that purpose, cardiac MRI feature tracking was performed retrospectively in 35 pre-adolescent male soccer players and 20 matched controls. There were no changes in global strain, but left ventricular twist and apical rotation were greater in soccer players, which adds to the features of paediatric athlete's heart.


#8 Effect of Core Muscle Strengthening Exercises (Including Plank and Side Plank) on Injury Rate in Male Adult Soccer Players: A Systematic Review
Reference: Sportverletz Sportschaden. 2018 Mar;32(1):35-46. doi: 10.1055/a-0575-2324. Epub 2018 Mar 20. [Article in German; Abstract available in German from the publisher]
Authors: Blasimann A, Eberle S, Scuderi MM
Summary: Soccer is seen as highly intensive sport with an increased injury rate. Male adults are the players with the highest injury incidence. Accordingly, the importance of core muscle strengthening to prevent injury has increased in the past few years. Up to date, core muscle strengthening plays an important role in different prevention programs, such as the "FIFA 11 +". The aim of this systematic review was to investigate the effect of core muscle strengthening on injury rate in male adult soccer players, including at least the known and easy exercises "plank" and "side plank", on injury rate in male adult soccer players. The databases PubMed, PEDro, Cochrane Library, SPORTDiscus and Cinahl were searched systematically. Included studies had to comprise exercises for core muscles as an intervention (as a part of a prevention program) for adult male soccer players. The control group had to continue their usual exercise routine. The exercises "plank" and "side plank" were mandatory elements of the training program. The number of injuries and/or the injury rate (per 1000 hours) were defined as outcomes. The quality of the included studies was assessed with the PEDro scale and the Risk of Bias tool. Seven studies with 2491 participants in total could be included. Two studies found a significant decrease in the injury rate in the intervention group (p < 0.05, p < 0.001 respectively). In two studies, no significance level was reported, but the training showed preventive effects in the intervention group. In the other three studies, no significant changes in the injury rate were found (p > 0.05). The seven included studies differed greatly with respect to the applied methods, the chosen interventions and the obtained results. Furthermore, core muscles were never trained separately but were always part of a program containing other preventive elements. Therefore, it was difficult to compare the studies. However, prevention programs including strengthening exercises for core muscles tend to positively affect the injury rate. Based on the literature found, the research question cannot definitively be answered. In the future, further studies are needed which investigate the effect of isolated core muscle training on the injury rate of soccer players.


#9 In-season monitoring of hip and groin strength, health and function in elite youth soccer: Implementing an early detection and management strategy over two consecutive seasons
Reference: J Sci Med Sport. 2018 Mar 14. pii: S1440-2440(18)30071-9. doi: 10.1016/j.jsams.2018.03.004. [Epub ahead of print]
Authors: Wollin M, Thorborg K, Welvaert M, Pizzari T
Summary: The primary purpose of this study was to describe an early detection and management strategy when monitoring in-season hip and groin strength, health and function in soccer. Secondly to compare pre-season to in-season test results. Twenty-seven elite male youth soccer players (age: 15.07±0.73years) volunteered to participate in the study. Monitoring tests included: adductor strength, adductor/abductor strength ratio and hip and groin outcome scores (HAGOS). Data were recorded at pre-season and at 22 monthly intervals in-season. Thresholds for alerts to initiate further investigations were defined as any of the following: adductor strength reductions >15%, adductor/abductor strength ratio <0.90, and HAGOS subscale scores <75 out of 100 in any of the six subscales. Overall, 105 alerts were detected involving 70% of players. Strength related alerts comprised 40% and remaining 60% of alerts were related to HAGOS. Hip adductor strength and adductor/abductor strength ratio were lowest at pre-season testing and had increased significantly by month two (p<0.01, mean difference 0.26, CI95%: 0.12, 0.41N/kg and p<0.01, mean difference 0.09, CI95%: 0.04, 0.13 respectively). HAGOS subscale scores were lowest at baseline with all, except Physical Activity, showing significant improvements at time-point one (p<0.01). Most (87%) time-loss were classified minimal or mild. In-season monitoring aimed at early detection and management of hip and groin strength, health and function appears promising. Hip and groin strength, health and function improved quickly from pre-season to in-season in a high-risk population for ongoing hip and groin problems.


#10 Exploring the effects of mental and muscular fatigue in soccer players' performance
Reference: Hum Mov Sci. 2018 Apr;58:287-296. doi: 10.1016/j.humov.2018.03.004. Epub 2018 Mar 15.
Authors: Coutinho D, Goncalves B, Wong DP, Travassos B, Coutts AJ, Sampaio J
Summary: This study examined the effects of induced mental and muscular fatigue on soccer players' physical activity profile and collective behavior during small-sided games (SSG). Ten youth soccer players performed a 5vs5 SSG under three conditions: a) control, playing without any previous activity; b) muscular fatigue, playing after performing a repeated change-of-direction task; c) mental fatigue, playing after completing a 30 min Stroop color-word task. Players' positional data was used to compute time-motion and tactical-related variables. The muscular fatigue condition resulted in lower distances covered in high speeds (∼27%, 0.3; ±0.5) than the control condition. From the tactical perspective, the muscular fatigue condition resulted in lower distance between dyads and players spent ∼7% more time synchronized in longitudinal displacements than the control condition (0.3; ±0.3). Additionally, players spent ∼14% more time synchronized with muscular fatigue than with mental fatigue (0.7; ±0.3). The mental fatigue condition resulted in a very likely more predictable pattern in the distance between dyads than in muscular fatigue condition (0.4; ±0.2). Also, the mental fatigue possibly decreased the teams' stretch index when compared with control (0.2; ±0.3) and likely increased compared with muscular fatigue (0.5; ±0.5). The better levels of longitudinal synchronization after muscular fatigue, might suggest the usage of tactical-related tasks after intense exercise bouts. The lower physical performance and time spent longitudinally synchronized after mental fatigue, should alert to consider this variable before matches or training activities that aim to improve collective behavior.


#11 Is Bony Hip Morphology Associated With Range of Motion and Strength in Asymptomatic Male Soccer Players?
Reference: J Orthop Sports Phys Ther. 2018 Mar 16:1-29. doi: 10.2519/jospt.2018.7848. [Epub ahead of print]
Authors: Mosler AB, Agricola R, Thorborg K, Weir A, Whiteley RJ, Crossley KM, Holmich P
Summary: Study Design Cross-sectional cohort study. Background Athletes with femoroacetabular impingement (FAI) syndrome have cam and/or pincer morphology, pain on orthopaedic testing, and often have reduced hip range of motion (ROM) and strength. However, cam and pincer morphology are also common in asymptomatic hips. Therefore, it is currently unknown whether the ROM and strength deficits observed in athletes with FAI syndrome result from the variance in their bony hip morphology or hip condition. Objectives To investigate the relationship between musculoskeletal screening findings and bony hip morphology in asymptomatic male soccer players. Methods Male professional soccer players in Qatar were screened specifically for hip/groin pain in 2 consecutive seasons. The screening battery included: pain provocation, ROM and strength tests, and hip radiographs. Univariate and multivariate regression analyses using generalised estimating equations evaluated the relationship between musculoskeletal screening findings and each bony hip morphological variant (cam, large cam, pincer, and acetabular dysplasia). Results Asymptomatic hips with cam and large cam morphology were associated with lower ROM in internal rotation and bent knee fall out, and a higher likelihood of pain on provocation testing. Pincer morphology was associated with lower abduction ROM and higher abduction strength. Acetabular dysplasia was associated with higher abduction ROM. Each association was weak and demonstrated poor or failed discriminatory power. Conclusion Bony hip morphology is associated with hip joint ROM and abduction strength, but musculoskeletal screening tests have a poor ability to discriminate between the different morphologies.


#12 Higher compliance to a neuromuscular injury prevention program improves overall injury rate in male football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2018 Mar 19. doi: 10.1007/s00167-018-4895-5. [Epub ahead of print]
Authors: Silvers-Granelli HJ, Bizzini M, Arundale A, Mandelbaum BR, Snyder-Mackler L
Summary: The 11+ injury prevention program has been shown to decrease injury rate. However, few studies have investigated compliance and if it is correlated to time loss. The purpose of this study was to (1) analyze how differences in compliance may impact injury rate and (2) if compliance may impact time loss due to injury. This study was a Level 1 prospective cluster randomized controlled trial conducted in NCAA men's football (soccer) teams that examined the efficacy of the 11+ injury prevention program. The two outcome variables examined were number of injuries and number of days missed from competition. Twenty-seven teams (n = 675 players) used the 11+ program. Compliance, injuries and time loss were recorded. There were three compliance categories, low (LC, 1-19 doses/season), moderate (MC, 20-39 doses/season), and high (HC, > 40 doses/season). There was a significant difference among the groups for injuries, p = 0.04, pη2  = 0.23. The LC group [mean (M) = 13.25, 95% confidence interval (CI) 9.82-16.68, injury rate (IR) = 10.35 ± 2.21] had a significantly higher injury rate than the HC group (M = 8.33, 95%CI 6.05-10.62, IR = 10.35 ± 2.21), p = 0.02. The MC group (M = 11.21, 95%CI 9.38-13.05, IR = 8.55 ± 2.46) was not significantly different than the LC group, p = 0.29, but was significantly greater than the HC group, p = 0.05. When examined as a continuous variable, compliance was significantly negatively related to injury rate (p = 0.004). It was also significantly negatively related to number of days missed (p = 0.012). When compliance was high, there was a significant reduction in injury and time loss. This evidence reinforces the importance of consistent injury prevention program utilization. Clinically, these findings have important implications when discussing the importance of consistent utilization of an injury prevention protocol in sport.


#13 Training Effects of the FIFA 11+ Kids on Physical Performance in Youth Football Players: A Randomized Control Trial
Reference: Front Pediatr. 2018 Mar 5;6:40. doi: 10.3389/fped.2018.00040. eCollection 2018.
Authors: Pomares-Noguera C, Ayala F, Robles-Palazon FJ, Alomoto-Burneo JF, Lopez-Valenciano A, Elvira JLL, Hernandez-Sanchez S, De Ste Croix M
Summary: The objective was to analyze the training effects of the FIFA 11+ kids on several parameters of physical performance in male youth football players. Twenty-three youth players were randomized within each team into two groups (control vs. intervention). The intervention group performed the FIFA 11+ kids programme 2 times a week for 4 weeks; the control groups completed their normal warm-up routines. Thirteen physical performance measures {range of motion (hip, knee, and ankle joints), dynamic postural control (measured throughout the Y balance test), 20 m sprint time, slalom dribble with a ball, agility, vertical jumping height [counter movement jump (CMJ) and drop jump (DJ)], horizontal jump distance, accuracy when volleying a ball [measured throughout the Wall Volley test]} were assessed. All physical performance parameters were compared via magnitude-based inference analysis. Significant between-group differences in favor of the FIFA 11+ players were found for dynamic postural control {anterior [mean and 90% confidence intervals (CI) = 1 cm, from -1.6 to 3.5 cm] and posteromedial (mean and 90% CI = 5.1 cm, from -1.8 to 12 cm) and posterolateral (mean and 90% CI = 4.8 cm, from 0.6 to 9.0 cm) distances}, agility run (mean and 90% CI = 0.5 s, from -0.9 to 0 s), vertical jump height [CMJ (mean and 90% CI = 3.1 cm, from 0.2 to 6.1 cm) and DJ (mean and 90% CI = 1.7 cm, from -0.5 to 3.9 cm)], and horizontal jump distance (mean and 90% CI = 2.5 cm, from -8 to 15 cm). The control groups showed better performance in 20 m sprint time (mean and 90% CI = -0.05 s, from -0.11 to 0.07) and wall volley tests (mean and 90% CI = 0.2, from -0.2 to 0.6) compared to the intervention group. The main findings of this study suggest that just 4 weeks of implementation of the FIFA 11+ kids produces improved physical performance compared with traditional warm-up routines in youth soccer players.

Sun

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2018

Football is...(#60)

Off-season = detraining

Thu

10

May

2018

Latest research in football - week 11 - 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 reliability and validity of a video-based method for assessing hamstring strength in football players
Reference: J Exerc Sci Fit. 2017 Jun;15(1):18-21. doi: 10.1016/j.jesf.2017.04.001. Epub 2017 Apr 28.
Authors: Lee JWY, Li C, Yung PSH, Chan KM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812858/pdf/main.pdf
Summary: Evaluating hamstring strength by isokinetic dynamometry is limited by various practical issues such as time and cost. A video-based Nordic hamstring exercise is introduced as an alternative option. The aims of this study are to evaluate 1.) the between-session reliability and 2.) concurrent validity of the testing method compared to a standardized isokinetic dynamometry. Thirty male elite footballers were recruited for the study. From the Nordic hamstring exercise, the video-analysis-determined Nordic break-point angles where the participant could no longer withstand the force of the fall (eccentric mode) and the number of seconds that the player could hold at 30° forward flexion angle (isometric mode) were measured. Intra-class correlation coefficients for between-session reliability, Pearson r correlations between the current method and isokinetic dynamometry were calculated. The reliability of the eccentric mode was moderate (ICC (2,1) = 0.82) while that of isometric mode was poor (ICC (2,1) = 0.57). The Nordic break-point angle of the eccentric mode significantly correlated with the concentric and eccentric hamstring peak torque (r = 0.48 and 0.58, p < 0.001), while the isometric was not (r = 0.02 - 0.07, p > 0.05). The eccentric mode of the video-based hamstring strength test was a moderately reliable and valid method to measure the eccentric hamstring strength in elite football players.


#2 Activity profile and physiological responses of Korean amateur football referees during matches
Reference: J Phys Ther Sci. 2018 Feb;30(2):351-354. doi: 10.1589/jpts.30.351. Epub 2018 Feb 28.
Authors: Choi Y, Roh J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5851381/pdf/jpts-30-351.pdf
Summary: The present study aimed to analyze and compare the activity profile and physiological responses of amateur football referees during competitive matches of high school and college students. Thirty referees (high school, 15; college, 15) were included in this study. The total distance covered, movement speed, and heart rate were measured using a global positioning system-enabled wireless heart rate monitor. The blood lactate concentration was measured immediately after the first and second half. College football referees covered a higher total distance than did their high school counterparts (7,547 m vs. 6,719 m). The maximal heart rate of college football referees was low in the first half alone, and the percentage of the heart rate within the "maximum" range was low throughout the game.  Refereeing imposes a significantly high physical load on the body while tracking player and ball movement. The present study suggests the need for developing and distributing physical training programs tailored for refereeing.


#3 Influence of Football on Physiological Cardiac Indexes in Professional and Young Athletes
Reference: Front Physiol. 2018 Feb 28;9:153. doi: 10.3389/fphys.2018.00153. eCollection 2018.
Authors: Francavilla CV, Sessa F, Salerno M, Albano GD, Villano I, Messina G, Triolo F, Todaro L, Ruberto M, Marsala G, Cascio O, Mollica MP, Monda V, Cibelli G, Valenzano A, Zammit C, Monda M, Messina A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835836/pdf/fphys-09-00153.pdf
Summary: After long-term intensive training, considerable morphological and functional heart changes occur in professional athletes. Such changes arise progressively and regress upon interruption of the physical activity. Morphological and functional alterations on heart are known as "Athlete's heart" condition. This study aims to compare echocardiographic parameters in two different groups of professional athletes. Furthermore, a prospective study is performed analyzing the echocardiographic changes occurring in 12 professional players in 3 years of follow-up. 78 football players were examined from July 2011 to May 2016 (40 enrolled in Group A and 38 in Group B). Twelve players of GROUP A were followed for 3 consecutive seasons. The general clinical examination, the cardiopulmonary evaluation, the ECG, the ergometer stress test, the spirometric examination and the standard cardiac eco color doppler test were recorded. Left ventricle dimensions, left atrium dimensions, and interventricular septum dimensions were higher in A players than in B players. Moreover, following up 12 players for 3 years, a statistically significant increase of such values was observed. In A players, higher dimensions of the left chambers and the interventricular septum were observed, compared to B players. No statistically significant difference was found regarding the ejection fraction. The 3 years follow-up showed a statistically significant increase of both left chambers and interventricular septum dimensions, particularly in the second and third year. These findings demonstrated that A players have higher echocardiographic parameters respect to B players. The results of this study support the scientific theory that long-term intensive training influences heart function, inducing "athlete's heart" with morphological adaptations. No significant echocardiographic variation within the examined sample was observed for different roles (goalkeeper, defender, midfielder, or attacker) or skills of individual players.


#4 Age-Predicted Maximal Heart Rate Equations Are Inaccurate for Use in Youth Male Soccer Players
Reference: Pediatr Exerc Sci. 2018 Mar 15:1-5. doi: 10.1123/pes.2017-0281. [Epub ahead of print]
Authors: Cicone ZS, Sinelnikov OA, Esco MR
Summary: The purpose of this study was to compare the differences between measured (MHRobt) and predicted (MHRpred) maximal heart rate (MHR) in youth athletes. In total, 30 male soccer players [14.6 (0.6) y] volunteered to participate in this study. MHRobt was determined via maximal-effort graded exercise test. Age-predicted MHR (MHRpred) was calculated for each participant using equations by Fox, Tanaka, Shargal, and Nikolaidis. Mean differences were compared using Friedman's 2-way analysis of variance and post hoc pairwise comparisons. Agreement between MHRobt and MHRpred values was calculated using the Bland-Altman method. There were no significant differences between MHRobt and MHRpred from the Fox (P = .777) and Nikolaidis (P = .037) equations. The Tanaka and Shargal equations significantly underestimated MHRobt (P < .001). All 4 equations produced 95% limits of agreement of ±15.0 beats per minute around the constant error. The results show that the Fox and Nikolaidis equations produced the smallest mean difference in predicting MHRobt. However, the wide limits of agreement suggests that none of the equations adequately account for individual variability in MHRobt. Practitioners should avoid applying these equations in youth athletes and utilize a lab or field testing protocol to obtain MHR.


#5 Laterality-Specific Training Improves Mental Rotation Performance in Young Soccer Players
Reference: Front Psychol. 2018 Feb 27;9:220. doi: 10.3389/fpsyg.2018.00220. eCollection 2018.
Authors: Pietsch S, Jansen P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835319/pdf/fpsyg-09-00220.pdf
Summary: This study investigates the influence of specific soccer training with the non-dominant leg on mental rotation performance of 20 adolescent soccer players between 10 and 11 years of age. While the experimental group performed soccer specific tasks only with the non-dominant foot once a week for 10 weeks, the control group absolved the same exercises with the dominant foot for the same period of time. Both groups performed a mental rotation task and shot, dribbling and ball control tests before and after the 10 week intervention. The most relevant result was that the experimental group showed a significantly larger increase in mental rotation ability than the control group.


#6 The Influence of Task Conditions on Side Foot-Kick Accuracy among Swedish First League Women's Soccer Players
Reference: J Sports Sci Med. 2018 Mar 1;17(1):74-81. eCollection 2018 Mar.
Authors: Carlsson T, Isberg J, Nilsson J, Carlsson M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844211/pdf/jssm-17-74.pdf
Summary: The purpose of this study was to investigate the influence of the task conditions on 20-m side foot-kick accuracy among Swedish first league women's soccer players. Twenty-three players performed three side foot-kick tests under different task conditions: stationary ball using match-relevant ball speed (SBRS) and maximal ball speed (SBMS) and a 5-m run with the ball from different approach angles (0°, 30°, and 60°) to a predetermined position, where passing of the ball on the move was executed using match-relevant ball speed (RBRS). With each test, the players performed 30 side-foot kicks, alternating between kicking legs with the aim of hitting a target stick. The accuracy was determined using video analysis. The side foot-kick accuracy was significantly greater for SBRS, compared to RBRS and SBMS. For all three test variables, the preferred leg displayed greater accuracy. The preferred leg's accuracy was greater for the approach angle of 30° compared to both 0° and 60°. A significant deviation from the target stick was found for the straight-ahead approach, in which the right-foot and left-foot kicks deviated to respectively the left and right of the stick; in contrast, for the approach angle of 60°, the deviation from the target stick was on the opposite side of the approach side for both legs.


#7 Effect of 8 Weeks Soccer Training on Health and Physical Performance in Untrained Women
Reference: J Sports Sci Med. 2018 Mar 1;17(1):17-23. eCollection 2018 Mar.
Authors: Ortiz JG, da Silva JF, Carminatti LJ, Guglielmo LGA, Diefenthaeler F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844205/pdf/jssm-17-17.pdf
Summary: This study aims to analyze the physiological, neuromuscular, and biochemical responses in untrained women after eight weeks of regular participation in small-sided soccer games compared to aerobic training. Twenty-seven healthy untrained women were divided into two groups [soccer group (SG = 17) and running group (RG = 10)]. Both groups trained three times per week for eight weeks. The variables measured in this study were maximal oxygen uptake (VO2max), relative velocity at VO2max (vVO2max), peak velocity, relative intensity at lactate threshold (vLT), relative intensity at onset of blood lactate accumulation (vOBLA), peak force, total cholesterol, HDL, LDL, triglycerides, and cholesterol ratio (LDL/HDL). VO2max, vLT, and vOBLA increased significantly in both groups (12.8 and 16.7%, 11.1 and 15.3%, 11.6 and 19.8%, in SG and RG respectively). However, knee extensors peak isometric strength and triglyceride levels, total cholesterol, LDL, and HDL did not differ after eight weeks of training in both groups. On the other hand, the LDL/HDL ratio significantly reduced in both groups. In conclusion, eight weeks of regular participation in small-sided soccer games was sufficient to increase aerobic performance and promote health benefits related to similar aerobic training in untrained adult women.


#8 Muscle Strength Is a Poor Screening Test for Predicting Lower Extremity Injuries in Professional Male Soccer Players: A 2-Year Prospective Cohort Study
Reference: Am J Sports Med. 2018 Mar 1:363546518756028. doi: 10.1177/0363546518756028. [Epub ahead of print]
Authors: Bakken A, Targett S, Bere T, Eirale C, Farooq A, Mosler AB, Tol JL, Whiteley R, Khan KM, Bahr R
Summary: Lower extremity muscle strength tests are commonly used to screen for injury risk in professional soccer. However, there is limited evidence on the ability of such tests in predicting future injuries. The purpose of the study was to examine the association between hip and thigh muscle strength and the risk of lower extremity injuries in professional male soccer players. Professional male soccer players from 14 teams in Qatar underwent a comprehensive strength assessment at the beginning of the 2013/2014 and 2014/2015 seasons. Testing consisted of concentric and eccentric quadriceps and hamstring isokinetic peak torques, eccentric hip adduction and abduction forces, and bilateral isometric adductor force (squeeze test at 45°). Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff throughout each season. Univariate and multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% CIs. In total, 369 players completed all strength tests and had registered injury and exposure data. Of these, 206 players (55.8%) suffered 538 lower extremity injuries during the 2 seasons; acute muscle injuries were the most frequent. Of the 20 strength measures examined, greater quadriceps concentric peak torque at 300 deg/s (HR, 1.005 [95% CI, 1.00-1.01]; P = .037) was the only strength measure identified as significantly associated with a risk of lower extremity injuries in multivariate analysis. Greater quadriceps concentric peak torque at 60 deg/s (HR, 1.004 [95% CI, 1.00-1.01]; P = .026) was associated with the risk of overuse injuries, and greater bilateral adductor strength adjusted for body weight (HR, 0.75 [95% CI, 0.57-0.97; P = .032) was associated with a lower risk for any knee injury. Receiver operating characteristic curve analyses indicated poor predictive ability of the significant strength variables (area under the curve, 0.45-0.56). There was a weak association with the risk of lower extremity injuries for 2 strength variables: greater quadriceps concentric muscle strength at (1) high and (2) low speeds. These associations were too small to identify an "at-risk" player. Therefore, strength testing, as performed in the present study, cannot be recommended as a screening test to predict injuries in professional male soccer.


#9 Close Encounter With a Prickly Soccer Ball: An Injury from an Indian Crested Porcupine
Reference: Wilderness Environ Med. 2018 Mar 9. pii: S1080-6032(18)30003-6. doi: 10.1016/j.wem.2018.01.003. [Epub ahead of print]
Authors: Thalgaspitiya SPB, Wijerathne BTB, Thennakoon BDB
Summary: The Indian crested porcupine, Hystrix indica, is a large rodent with the unique feature of long quills. These quills are an integral part of its defense mechanism against predators. Injuries resulting from human contact with quills may cause pain, bleeding, and swelling. Quill-related injuries are common among animals such as dogs, cats, and some wild animals. The mechanism of injury, consequences, and management of injuries to humans from H indica quills are rarely described. In this report, we describe the injuries and management of a man who sustained injury from H indica quills.

#10 Inferior heel pain in soccer players: a retrospective study with a proposal for guidelines of treatment
Reference: BMJ Open Sport Exerc Med. 2018 Feb 7;4(1):e000085. doi: 10.1136/bmjsem-2015-000085. eCollection 2018.
Authors: Saggini R, Migliorini M, Carmignano SM, Ancona E, Russo C, Bellomo RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841518/pdf/bmjsem-2015-000085.pdf
Summary: The cause of heel pain among soccer players is multifactorial and is related to repetitive microtrauma due to impact forces involving technical moves, but also the playground, the exercise mode, the recovery time, the climatic conditions and the footwear used. The aim was to investigate the aetiology of plantar heel pain of soccer players with the objective of proposing an example of guidelines for treatment. We investigated the prevalence and characteristics of inferior heel pain of 1473 professional, semiprofessional and amateur players. All evaluated subjects were submitted to a specific rehabilitation protocol that involved advanced physical therapies and viscoelastic insoles depending on the aetiology of pain. Clinical and instrumental examinations revealed that 960 of 1473 athletes had inferior heel pain. These patients were divided into seven groups based on aetiology: sural nerve compression, abductor digiti minimi compression, atrophy and inflammation of the fat pad, plantar fasciitis, stress injury of the heel spur, stress fracture of the heel bone and heel spur. The proposed rehabilitation treatment aims for a reduction of pain and an early return to sports, with excellent results. According to what was observed in the present study, related also to the specific treatment of inferior heel pain, and considering the technological progress achieved in recent years, we can now propose an integrated therapeutic approach to treatment of heel pain, properly differentiated according to specific aetiology.

Fri

04

May

2018

Football is ...(#59)

Training utilizing repeated sprint can have multiple benefits.

Wed

02

May

2018

Latest research in football - week 10- 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 Kicking Performance in Young U9 to U20 Soccer Players: Assessment of Velocity and Accuracy Simultaneously
Reference: Res Q Exerc Sport. 2018 Mar 7:1-11. doi: 10.1080/02701367.2018.1439569. [Epub ahead of print]
Authors: Vieira LHP, Cunha SA, Moraes R, Barbieri FA, Aquino R, Oliveira LP, Navarro M, Bedo BLS, Santiago PRP
Summary: The purpose of this study was to compare the kicking performance of young soccer players in the U9 to U20 age groups. Three hundred and sixty-six Brazilian players were evaluated on an official pitch using three-dimensional kinematics to measure (300 Hz) ball velocity (Vball), foot velocity (Vfoot), Vball/Vfoot ratio, last stride length, and distance between the support foot and the ball. Simultaneously, a two-dimensional procedure was also conducted to compute (60 Hz) the mean radial error, bivariate variable error, and accuracy. Possible age-related differences were assessed through one-way analysis of variance and magnitude-based inferences. Ball velocity increased by 103% (p < .001, η2 = .39) from the U11 age group (48.54 ± 8.31 km/hr) to the U20 age group (98.74 ± 16.35 km/hr). Foot velocity presented a 59% increase (p < .001, η2 = .32) from the U11 age group (49.08 ± 5.16 km/hr) to U20 (78.24 ± 9.49 km/hr). This finding was due to improvement in the quality of foot-ball impact (Vball/Vfoot ratio) from U11 (0.99 ± 0.13 a.u.) to U20 (1.26 ± 0.11 a.u.; p < .001, η2 = .25). Parameters such as mean radial error and accuracy appeared to be impaired during the growth spurt (U13-U15). Last stride length was correlated, low to moderately high, with Vball in all age groups (r = .36-.79). In summary, we concluded that simple biomechanical parameters of kicking performance presented distinct development. These results suggest that different training strategies specific for each age group could be applied. We provide predictive equations to aid coaches in the long-term monitoring process to develop the kick in soccer or search for talented young players.


#2 The biomechanical characteristics of elite deaf and hearing female soccer players: comparative analysis
Reference: Acta Bioeng Biomech. 2017;19(4):127-133.
Authors: Szulc AM, Busko K, Sandurska E, Kolodziejczyk M
Summary: The aim of this study was to examine the differences in body composition, strength and power of lower limbs, height of jump measured for the akimbo counter movement jumps, counter movement jump and spike jumps between deaf and hearing elite female soccer players. Twenty deaf (age: 23.7±5.0 years, hearing loss: 96±13.9 dB) and 25 hearing (age: 20.3±3.8 years) participated in the study. Their WHR and BMI were calculated. Body fat was measured using the BIA method. The maximal power and height of jump were measured by force plate. Biodex dynamometer was used to evaluate isokinetic isometric strength of the hamstrings and quadriceps. Significant differences between hearing and deaf soccer players in anthropometric values were for the waist and calf circumferences and the WHR index ( p < 0.01, effect size 0.24-0.79). Statistically significant differences were observed for flexion of the lower limb in the knee joint for the relative joint torque and relative power obtained for the angular velocity of 300 degˑs-1 for both lower limbs (p < 0.01, effect size 0.19-0.48) and for 180 degˑs-1 during flexion of the left limb (p = 0.02, effect size 0.13). The hearing female football players developed significantly greater MVC in all the cases. Statistically significant differences between deaf and hearing athletes were found for spike jump for maximal power (1828.6 ± 509.4 W and 2215.2 ± 464.5 W, respectively; p = 0.02, effect size 0.14). Hearing impairment does not limit the opportunities for development of physical fitness in the population of deaf women.


#3 Effect of Muscular Strength, Asymmetries and Fatigue on Kicking Performance in Soccer Players
Reference: Int J Sports Med. 2018 Mar 5. doi: 10.1055/s-0043-123648. [Epub ahead of print]
Authors: Maly T, Sugimoto D, Izovska J, Zahalka F, Mala L
Summary: The aim of this study was to determine the effect of muscular strength, strength asymmetries, and fatigue on the speed and accuracy of an instep kick in soccer players. We measured ball velocity (BV) and kicking accuracy (KA) in the preferred (PL) and non-preferred leg (NPL) before (PRE) and after (POST) physical load in the PL. Maximum peak muscle torque of the knee extensors and flexors in the PL and NPL as well as ipsilateral knee flexors and knee extensors ratio (H:Q ratio) for both legs were assessed. BV was significantly decreased in POST physical load (5.82%, BVPRE=30.79±1.70 m·s-1, BVPOST=29.00±1.70 m·s-1, t19=3.67, p=0.00, d=1.05). Instep kick accuracy after the physical load worsened by an average of 10% in the most accurate trials. Results revealed a significant decrease in instep kick accuracy after physical loading (KAPRE=2.74±0.70 m, KAPOST=3.85±1.24 m, t19=-3.31, p=0.00, d=1.10). We found an insignificant correlation between H:Q ratio and KA in PRE test value, whereas a lower ipsilateral ratio (higher degree of strength asymmetry) in the POST physical load significantly correlated with KA in all angular velocities (r=-0.63 up to -0.67, p=0.00).


#4 The independent effects of match location, match result and the quality of opposition on subjective wellbeing in under 23 soccer players: a case study
Reference: Res Sports Med. 2018 Mar 4:1-14. doi: 10.1080/15438627.2018.1447476. [Epub ahead of print]
Authors: Abbott W, Brownlee TE, Harper LD, Naughton RJ, Clifford T
Summary: This study examined if subjective wellbeing in soccer players was affected by match location, match result and opposition quality before a match (PRE), 1 day after (POST-1), and 3 days after a match (POST-3). Eleven professional male soccer players from the under 23 squad playing in the Premier League 2 division completed a wellbeing questionnaire before and after 17 matches. Match training load (session-rating perceived exertion) was not different, regardless of the location, result, or quality of opposition faced (P > 0.05). Subjective wellbeing was not different at PRE (P > 0.05); however, at POST-1 and POST-3, stress and mood were ≥20% lower after playing away from home or losing (P < 0.05). Stress, mood and sleep were ≥12% worse after playing against a higher-level opposition at POST-1. Coaches need to be aware that match location, match result and the quality of the opposition can influence post-match wellbeing, irrespective of match load.


#5 Childhood football play and practice in relation to self-regulation and national team selection; a study of Norwegian elite youth players
Reference: J Sports Sci. 2018 Mar 9:1-7. doi: 10.1080/02640414.2018.1449563. [Epub ahead of print]
Authors: Erikstad MK, Hoigaard R1, Johansen BT, Kandala NB, Haugen T
Summary: Childhood sport participation is argued to be important to understand differences in self-regulation and performance level in adolescence. This study sought to investigate if football-specific activities in childhood (6-12 years of age) is related to self-regulatory skills and national under 14- and 15-team selection in Norwegian elite youth football. Data of practice histories and self-regulatory skills of 515 youth football players selected at Norwegian regional level were collected and further analysed using multilevel analyses. The results revealed that high self-regulated players were more likely to be selected for national initiatives, and increased their involvement in peer-led football practice and adult-led football practice during childhood, compared to players with lower levels of self-regulation. While national level players reported higher levels of peer-led football play in childhood, the interaction effect suggest that the regional level players increased their involvement in peer-led play during childhood compared to national level players. In conclusion, the findings indicate that childhood sport participation may contribute to later differences in self-regulation, and highlights the importance of childhood engagement in football-specific play and practice in the development of Norwegian youth football players.


#6 "The Early Specialised Bird Catches the Worm!" - A Specialised Sampling Model in the Development of Football Talents
Reference: Front Psychol. 2018 Feb 21;9:188. doi: 10.3389/fpsyg.2018.00188. eCollection 2018.
Authors: Sieghartsleitner R, Zuber C, Zibung M, Conzelmann A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5826374/pdf/fpsyg-09-00188.pdf
Summary: Characteristics of learning activities in early sport participation play a key role in the development of the sporting talent. Therefore, pathways of specialisation or diversification/sampling are as well debated as the implementation of practice- or play-oriented activities. The related issues are currently perceived as a two-dimensional construct of domain specificity and performance orientation. In this context, it has been shown that early specialisation, with experiences in practice and play, has led to Swiss junior national team football players reaching higher success levels as adults. This study aimed to examine whether a similar approach improves chances of even being selected for junior national teams from a broader sample. Hence, 294 youth players answered retrospective questionnaires on their early sport participation when entering the Swiss football talent development programme. Using the person-oriented Linking of Clusters after removal of a Residue (LICUR) method, volumes of in-club practice, free play and activities besides football until 12 years of age were analysed along with age at initial club participation. According to the results, clusters of Football enthusiasts (p = 0.01) with the most free play and above average in-club practice and Club players (p = 0.02) with the most in-club practice and average free play had a greater chance of reaching junior national team level. Thus, high levels of domain-specific activities seem to increase the chances of junior national team participation. Furthermore, the most successful constellation (Football enthusiasts) may illustrate the relevance of domain-specific diversity, induced by several types of practice and play. In line with previous studies, specialising in football and sampling different experiences within this specific domain seems to be the most promising pathway. Therefore, we argue that the optimal model for the development of football talents is a specialised sampling model.


#7 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.


#8 Neophyte experiences of football match analysis: a multiple case study approach
Reference: Res Sports Med. 2018 Mar 5:1-17. doi: 10.1080/15438627.2018.1447473. [Epub ahead of print]
Authors: McKenna M, Cowan D, Stevenson D, Baker J
Summary: Performance analysis is extensively used in sport, but its pedagogical application is little understood. Given its expanding role across football, this study explored the experiences of neophyte performance analysts. Experiences of six analysis interns, across three professional football clubs, were investigated as multiple cases of new match analysis. Each intern was interviewed after their first season, with archival data providing background information. Four themes emerged from qualitative analysis: (1) "building of relationships" was important, along with trust and role clarity; (2) "establishing an analysis system" was difficult due to tacit coach knowledge, but analysis was established; (3) the quality of the "feedback process" hinged on coaching styles, with balance of feedback and athlete engagement considered essential; (4) "establishing effect" was complex with no statistical effects reported; yet enhanced relationships, role clarity, and improved performances were reported. Other emic accounts are required to further understand occupational culture within performance analysis.


#9 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.

Tue

01

May

2018

Football is....(#58)

Dynamic stretching as part of the warm-up, starting slow and controlled.

Mon

30

Apr

2018

Latest research in football - week 9 - 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 Vertical and Horizontal Asymmetries are Related to Slower Sprinting and Jump Performance in Elite Youth Female Soccer Players
Reference: J Strength Cond Res. 2018 Feb 27. doi: 10.1519/JSC.0000000000002544. [Epub ahead of print]
Authors: Bishop C, Read P, McCubbine J, Turner A
Summary: Inter-limb asymmetries have been shown to be greater during vertical jumping compared to horizontal jumping. Notable inter-limb differences have also been established at an early age in male youth soccer players. Furthermore, given the multi-planar nature of soccer, establishing between-limb differences from multiple jump tests is warranted. At present, a paucity of data exists regarding asymmetries in youth female soccer players and their effects on physical performance. The aims of this study were to quantify inter-limb asymmetries from unilateral jump tests and examine their effects on speed and jump performance. Nineteen elite youth female soccer players performed a single leg countermovement jump (SLCMJ), single, triple, and crossover hops for distance and a 20 m sprint test. Test reliability was good to excellent (ICC = 0.81-0.99) and variability acceptable (CV = 1.74-5.42%). A one-way ANOVA highlighted larger asymmetries from the SLCMJ compared to all other jump tests (p < 0.05). Pearson's correlations portrayed significant relationships between vertical asymmetries from the SLCMJ and slower sprint times (r = 0.49-0.59). Significant negative relationships were also found between horizontal asymmetries during the triple hop test and horizontal jump performance (r = -0.47 to -0.58) and vertical asymmetries during the SLCMJ and vertical jump performance (r = -0.47 to -0.53). The results from this study highlight that the SLCMJ appears to be the most appropriate jump test for identifying between-limb differences with values ∼12% showing negative associations with sprint times. Furthermore, larger asymmetries are associated with reduced jump performance and would appear to be direction-specific. Practitioners can use this information as normative data to be mindful of when quantifying inter-limb asymmetries and assessing their potential impact on physical performance in youth female soccer players.


#2 Oxidative stress biomarkers after a single maximal test in blind and non-blind soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08030-1. [Epub ahead of print]
Authors: Viana Gomes D, Santos Vigario P, Lima Piazera BK, Pereira Costa F, Vaisman M, Salerno Pinto V
Summary: Compare oxidative stress biomarkers, antioxidant capacity, muscle damage and hormone response between vision impaired and non-vision impaired athletes after a single maximal exercise test. Eight vision impaired and fifteen non-vision impaired athletes performed a maximal aerobic test with blood collected before and after. Non-vision impaired athletes displayed greater aerobic capacity than blind individuals (p<0.05). Lactate increased by four-fold, while CK and GGT as well as the oxidative stress biomarkers and antioxidants were unchanged. Cortisol increased, but testosterone and their ratio were not altered. Differences were observed for ALT and AST, which were increased only in non-blind athletes. Our data suggest that blind soccer players, in comparison to those with vision, experienced less cellular damage.


#3 The effect of acute match play loading on hip adductor strength & flexibility in soccer players
Reference: J Sports Med Phys Fitness. 2018 Mar 1. doi: 10.23736/S0022-4707.18.08194-X. [Epub ahead of print]
Author: Light N
Summary: Deficits in adductor strength and flexibility are known risk factors for soccer hip/groin injury, yet little is known about the acute effects of soccer match play on these physical features. The aim of this study therefore was to examine the changes in adductor strength and flexibility before; during and immediately after soccer match play. Design: Twenty, male university soccer players (age = 22.35 ± 1.98 years) participated in this field-based, within subject, repeated measures study. Each participant performed three adductor squeeze tests at both 0° and 45° hip flexed test positions alongside a bent knee fall out test. Adductor squeeze scores were quantified using pressure sphygmomanometer and BKFO values recorded in centimetres. Each test was performed before (0 mins) half time (45 mins) and at full time (90 mins) of a competitive match. Adductor strength decreased by 17.7% in 0° test position and 19.1% in 45° test position at 90 minutes of soccer play, whilst BKFO scores increased by 15% indicating a reduction in adductor flexibility. Statistical analysis showed significant effects of time Vs adductor strength and squeeze test position (P=<0.005), Positive correlations between time played and BKFO scores, and BKFO scores vs adductor squeeze scores at 0 and 45 minutes (P=<0.005) were also observed. University soccer players exhibit decreased adductor squeeze test and BKFO values as soccer match duration increases. These findings may have implications hip/groin injury management and recovery strategies, post or during soccer matches.


#4 Subungual Exostosis in a Young Soccer Player
Reference: Open Access Maced J Med Sci. 2017 Dec 30;6(1):52-54. doi: 10.3889/oamjms.2018.002. eCollection 2018 Jan 25.
Authors: Tchernev G, Grigorov Y, Philipov S, Chokoeva A, Wollina U, Lotti T, Cardoso J, Yungareva I, Lozev I, Maximov GK
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5816314/pdf/OAMJMS-6-52.pdf
Summary: Subungual exostosis is a relatively uncommon, benign osteocartilaginous tumor of the distal phalanx of the toes or fingers in young adults, considered as a rare variant of osteochondroma. Differential diagnoses include subungual verruca (viral wart), pyogenic granuloma, osteochondroma, amelanotic subungual melanoma and glomus tumour. Misdiagnosis and total onychodystrophy frequently occur as a result of late treatment or inadequate treatment strategy. Dermoscopy could be a useful technique, involved in the diagnostic process, although X-ray examination and histopathology are mandatory for the diagnosis. We report a rare case of subungual exostosis of the great toe associated with repeated trauma of the nail bed. The lack of radiographic and histopathological examination could lead to misdiagnosis and inadequate treatment. Although completely benign, subungual exostosis should be considered in differential diagnosis of nail bed tumors in young adults, in order to avoid associated complications and unneeded aggressive surgical interventions. Complete excision of the lesion and delicate separation from the underlying nail bed structures results in total resolve of the problem, by providing the lowest risk of recurrences.



#5 Acute lateral ankle sprain prediction in collegiate women’s soccer players
Reference: Int J Sports Phys Ther. 2018 Feb;13(1):12-18.
Authors: McCann RS, Kosik KB, Terada M, Beard MQ, Buskirk GE, Gribble PA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5808007/pdf/ijspt-13-12.pdf
Summary: Women's soccer has among the highest injury rates in collegiate sports, and lateral ankle sprains (LAS) are among the most commonly occurring injuries in that athletic population. However, no established LAS prediction model exists for collegiate women's soccer players.The purpose of this study was to develop a prediction model for acute LAS injuries in collegiate women's soccer players utilizing previous ankle sprain history, height, mass, and BMI as potential predictors.The authors' hypothesized that collegiate women's soccer players with greater height, mass, and body mass index (BMI), as well as a previous history of ankle sprain would have greater odds of sustaining a LAS.  Forty-three NCAA Division I women's soccer players' (19.7 ± 1.1yrs, 166.8 ± 3.7cm, 60.8 ± 4.4kg) height, mass, and BMI were measured one week before beginning preseason practices. Additionally, participants reported whether or not they had sustained a previous ankle sprain. The team athletic trainer tracked LASs over the competitive season. Independent t-tests, binary logistic regression analyses, receiver operating characteristic (ROC) curves, and diagnostic statistics assessed the ability of the variables to differentiate between those that did and did not sustain a LAS. Participants that sustained a LAS (n = 8) were significantly taller than those that did not sustain a LAS (n = 35) (t41 = -2.87, p = 0.01, d = 0.83[0.03,1.60]). A logistic regression analysis (odds ratio=1.30[1.00,1.70]) and area under the ROC curve analysis (AUROC=0.73[0.58,0.89], p=0.04) further exhibited predictive value of height. A height cutoff score of 167.6cm demonstrated excellent sensitivity (0.88), moderate specificity (0.51), and a favorable diagnostic odds ratio (7.5). A logistic regression analysis (odds ratio=1.87[1.22,1.98]) exhibited predictive value of previous ankle sprain history. That variable was also associated with good sensitivity (0.75) and specificity (0.71) within the model, as well as a favorable DOR (7.37). Mass and BMI demonstrated no predictive value for LAS. Taller collegiate women's soccer players and those with previous ankle sprain history may have a greater predisposition to LAS.


#6 Characteristics of goalkeepers' injuries: retrospective, self-reported study among adolescence football players
Reference: J Sports Med Phys Fitness. 2018 Feb 26. doi: 10.23736/S0022-4707.18.07849-0. [Epub ahead of print]
Authors: Blazkiewicz A, Grygorowicz M, Bialostocki A, Czaprowski D
Summary: Characteristic types of actions and training/matches loads of football goalkeepers show that goalkeeper's performance differs from other football's formations. Such situation may predispose to the occurrence of other kinds of injuries in this position. The aim of this study was to analyse epidemiology of injuries in young football goalkeepers. 48 football goalkeepers (aged:15.2±1.9 years) were filled the questionnaire aimed at collecting information about all injuries sustained within 12 months before the data collection. The anthropometric data, football experience and information regarding the injury types and occurrence were analysed. The injury rate proportion for acute and overuse injuries and values of injuries including the burden of the match game and training were evaluated. The level of significance was set at p<0.05. 33(68.8%) questionnaires were given back. 24(72.7%) goalkeepers reported the history of football related injury within a year before the survey. 52 injuries were reported. Significantly higher number of acute (76.9%) vs. overuse (23.1%) injuries was described (p=0.0012). Acute injuries involved fractures/subluxations of the fingers and thigh muscle strain/tears. The group of overuse injuries was dominated by trauma of the knee and pelvic girdle muscles. Majority of injuries occurred during training (88,5% of all injuries), and there was significant higher number of injuries sustained on artificial vs. natural grass for all, acute and overuse types of injuries (p<0,0001). Young football goalkeepers suffer mostly acute injuries (within the fingers of hands and muscles of thighs). It might be associated with specific characteristic of performance related to goalkeeper`s position.


#7 The elite player performance plan: the impact of a new national youth development strategy on injury characteristics in a premier league football academy
Reference: J Sports Sci. 2018 Feb 24:1-8. doi: 10.1080/02640414.2018.1443746. [Epub ahead of print]
Authors: Tears C, Chesterton P, Wijnbergen M
Summary: The objective of this study was to investigate the injury incidence and patterns in elite youth football at a category 1 Premier League Academy before and after the introduction of a new development strategy, the Elite Player Performance Plan (EPPP). A prospective study was performed over six consecutive seasons encompassing three years before and after the introduction of the EPPP. The findings revealed a most likely moderate increase in total exposure per player per season when the post-EPPP football exposure (640.86 ± 83.25 hours per player per year) was compared with the pre-EPPP football exposure (539.08 ± 71.59). The total injury incidence pre-EPPP was 3.0/1000 hours compared to 2.1/1000 hours post-EPPP (rate ratio 1.43). 6% of all injuries were re-injuries (20.24 ± 33.43 days) but did not result in a substantially longer absence (16.56 ± 15.77 days). The injury burden decreased for the U12-U15 from pre- to post-EPPP, whereas the injury burden increased for the U16-U18 (respectively 125 and 47% higher). These findings suggest that following the introduction of the EPPP there has been a reduction in injuries in the younger age groups U12-U15 but in the older age groups U16-U18 there has been an increase in the severity of the injuries sustained at this club.


#8 The influence of joint rigidity on impact efficiency and ball velocity in football kicking
Reference: J Biomech. 2018 Feb 20. pii: S0021-9290(18)30112-X. doi: 10.1016/j.jbiomech.2018.02.015. [Epub ahead of print]
Authors: Peacock JCA, Ball K
Summary: Executing any skill with efficiency is important for performance. In football kicking, conflicting and non-significant results have existed between reducing ankle plantarflexion during foot-ball contact with impact efficiency, making it unclear as to its importance as a coaching instruction. The aims of this study were to first validate a mechanical kicking machine with a non-rigid ankle, and secondly compare a rigid to a non-rigid ankle during the impact phase of football kicking. Measures of foot-ball contact for ten trials per ankle configuration were calculated from data recorded at 4000 Hz and compared. The non-rigid ankle was characterised by initial dorsiflexion followed by plantarflexion for the remainder of impact, and based on similarities to punt and instep kicking, was considered valid. Impact efficiency (foot-to-ball speed ratio) was greater for the rigid ankle (rigid = 1.16 ± 0.02; non-rigid = 1.10 ± 0.01; p < 0.001). The rigid ankle was characterised by significantly greater effective mass and significantly less energy losses. Increasing rigidity allowed a greater portion of mass from the shank to be used during the collision. As the ankle remained in plantarflexion at impact end, stored elastic energy was not converted to ball velocity and was considered lost. Increasing rigidity is beneficial for increasing impact efficiency, and therefore ball velocity.


#9 Cardiac Magnetic Resonance Assessment of the Structural and Functional Cardiac Adaptations to Soccer Training in School-Aged Male Children
Reference: Pediatr Cardiol. 2018 Mar 8. doi: 10.1007/s00246-018-1844-5. [Epub ahead of print]
Authors: Barczuk-Falęcka M, Malek LA, Krysztofiak H, Roik D, Brzewski M
Download link: https://link.springer.com/content/pdf/10.1007%2Fs00246-018-1844-5.pdf
Summary: Physical training is associated with changes in cardiac morphology called the "athlete's heart", which has not been sufficiently studied in children. The aim of the study was to analyze cardiac adaptation to exercise in pre-adolescent soccer players. Thirty-six soccer players (mean age 10.1 ± 1.4 years) and 24 non-athlete male controls (10.4 ± 1.7 years) underwent cardiac magnetic resonance. Measurements of myocardial mass, end-diastolic and end-systolic volume, stroke volume and ejection fraction for left and right ventricle (LV, RV) were performed. Additionally, left and right atrial (LA, RA) areas and volumes were analysed. Relative wall thickness (RWT) was calculated to describe the pattern of cardiac remodeling. Interventricular wall thickness and LV mass were significantly higher in athletes, but remained within the reference (6.9 ± 0.8 vs. 6.2 ± 0.9 mm/√m2, p = 0.003 and 57.1 ± 7.4 vs. 50.0 ± 7.1 g/m2, p = 0.0006, respectively) with no changes in LV size and function between groups. The RWT tended to be higher among athletes (p = 0.09) indicating LV concentric remodeling geometry. Soccer players had significantly larger RV size (p < 0.04) with similar function and mass. Also, the LA volume (p = 0.01), LA area (p = 0.03) and LA diameter (p = 0.009) were significantly greater in players than in controls. Cardiac adaptations in pre-adolescent soccer players are characterized by an increased LV mass without any changes in LV size and systolic function, which is typical of resistance training with tendency to concentric remodeling. This is accompanied by increase of LA and RV size. It should be taken into account during annual pre-participation evaluation.


#11 No better moment to score a goal than just before half time? A soccer myth statistically tested
Reference: PLoS One. 2018 Mar 8;13(3):e0194255. doi: 10.1371/journal.pone.0194255. eCollection 2018.
Authors: Baert S, Amez S
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0194255&type=printable
Summary: We test the soccer myth suggesting that a particularly good moment to score a goal is just before half time. To this end, rich data on 1,179 games played in the UEFA Champions League and UEFA Europa League are analysed. In contrast to the myth, we find that, conditional on the goal difference and other game characteristics at half time, the final goal difference at the advantage of the home team is 0.520 goals lower in case of a goal just before half time by this team. We show that this finding relates to this team's lower probability of scoring a goal during the second half.

Wed

18

Apr

2018

Latest research in football - week 8,5 - 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 Normalized STEAM-based diffusion tensor imaging provides a robust assessment of muscle tears in football players: preliminary results of a new approach to evaluate muscle injuries
Reference: Eur Radiol. 2018 Feb 8. doi: 10.1007/s00330-017-5218-9. [Epub ahead of print]
Authors: Giraudo C, Motyka S, Weber M, Karner M, Resinger C, Feiweier T, Trattnig S, Bogner W
Summary: The purpose of the study was to assess acute muscle tears in professional football players by diffusion tensor imaging (DTI) and evaluate the impact of normalization of data. Eight football players with acute lower limb muscle tears were examined. DTI metrics of the injured muscle and corresponding healthy contralateral muscle and of ROIs drawn in muscle tears (ROItear) in the corresponding healthy contralateral muscle (ROIhc_t) in a healthy area ipsilateral to the injury (ROIhi) and in a corresponding contralateral area (ROIhc_i) were compared. The same comparison was performed for ratios of the injured (ROItear/ROIhi) and contralateral sides (ROIhc_t/ROIhc_i). ANOVA, Bonferroni-corrected post-hoc and Student's t-tests were used. Analyses of the entire muscle did not show any differences (p>0.05 each) except for axial diffusivity (AD; p=0.048). ROItear showed higher mean diffusivity (MD) and AD than ROIhc_t (p<0.05). Fractional anisotropy (FA) was lower in ROItear than in ROIhi and ROIhc_t (p<0.05). Radial diffusivity (RD) was higher in ROItear than in any other ROI (p<0.05). Ratios revealed higher MD and RD and lower FA and reduced number and length of fibre tracts on the injured side (p<0.05 each). DTI allowed a robust assessment of muscle tears in athletes especially after normalization to healthy muscle tissue.


#2 Sideline Concussion Assessment: The King-Devick Test in Canadian Professional Football
Reference: J Neurotrauma. 2018 Feb 8. doi: 10.1089/neu.2017.5490. [Epub ahead of print]
Authors: Naidu D, Mrazik M, Borza C, Kobitowich T
Summary: Reasons for Study: Sideline assessment tools are an important component of concussion evaluations. To date there has been little data evaluating the clinical utility of these tests in professional football. The purpose of this study was to evaluate the clinical utility of the King-Devick Test (KD) in evaluating concussions in professional football players. Baseline data was collected over 2 consecutive seasons in the Canadian Football League as part of a comprehensive medical baseline evaluation. A pilot study with the KD began in 2015 with 306 participants and the next year (2016) there were 917 participants. In addition, a sample of 64 participants completed testing after physical exertion (practice or game). Participants with concussion demonstrated significantly higher (slower) results compared with baseline and the exercise group (F[2,211] = 5.94, p = 0.003). The data revealed a specificity of 84% and sensitivity of 62% for our sample. Reliability from season to season was good (ICC2,1 = 0.88, 95% CI: 0.83, 0.91). On average participants improved performances by a mean of 1.9 seconds (range -26.6 to 23.8) in subsequent years. High reliability was attained in the exercise group. (ICC2,1 = 0.93, 95% CI: 0.89, 0.96). The K-D test presents as a reliable measure although sensitivity and specificity data from our sample indicate it should be used in conjunction with other measures for diagnosing concussion. Further research is required to identify stability of results over multiple usages.


#3 Multivariate analysis of factors related to radiographic knee osteoarthritis based on the comparison between football players and matched nonsportsmen
Reference: Int Orthop. 2018 Feb 6. doi: 10.1007/s00264-018-3797-y. [Epub ahead of print]
Authors: Lv H, Chen W, Yuwen P, Yang N, Yan X, Zhang Y
Summary: Knee osteoarthritis (KOA) is the most common joint pathology worldwide and a major cause of later disability. It is unknown if the bone mass density (BMD) is correlated with KOA. This study aimed to investigate the prevalence of radiographic KOA among retired professional football players by comparing with matched nonsportsmen, and assess the correlation between BMD and KOA. A cross-sectional, descriptive study was performed on a group of retired professional football players without history of knee injury. A control group of nonsporting volunteers was matched to the football player group in terms of age, height, weight, and body mass index (BMI). Uni- and multivariate analyses were performed to identify risk factors for KOA and predictors for knee function. Eighty-six retired male professional football players, with a mean age of 53 (51-58) years and an average period of professional career of 19.8 ± 6.3 years, were enrolled into the study group. Eighty-six subjects were included in the control group. Radiographic KOA was more common in the control group (45.3%) than in the study group (15.1%; χ 2  = 18.633, P < 0.001). While the HSS, IKS score, and BMD of spine, femoral neck, and trochanter were all higher among sportsmen than the nonsportsmen (z = 10.250, z = 10.450, z = 7.237, z = 8.826, z = 8.776, all P < 0.001). Independent risk factors for ROA were age (55-60 + years, aOR 9.159, P < 0.001) and BMD (decrease, aOR 16.226, P = 0.001; osteoporosis, aOR 8.176, P = 0.005). The mathematical model of multiple linear regression for the HSS and IKS score were Y = 127.217-3.334 age + 8.971 BMD + 4.752 occupation and Y = 57.784-3.022 age + 7.241 BMD + 4.730 occupation, respectively. This study reveals that low BMD and advanced age are independent risk factors for KOA. High BMD and regular exercise have a positive impact on knee function as evaluated with the use of HSS and IKS. Our findings guarantee further study to investigate the possibility that KOA may be caused by low BMD.


#4 Structural differences in the lower extremities in children aged 7-9 years, caused by playing football: A cross-sectional study
Reference: Foot (Edinb). 2017 Nov 17;34:78-82. doi: 10.1016/j.foot.2017.11.004. [Epub ahead of print]
Authors: Diaz-Miguel S, Lopezosa-Reca E, Benhamu-Benhamu S, Ortega-Avila AB, Garcia-De-La-Pena R, Gijon-Nogueron G
Summary: Physical activity during childhood can be beneficial in the long term. However, this practice can influence the child's physiological development. The aim of this study was to determine whether the practice of soccer, in moderation, could be a risk factor for the inadequate development of the lower limb. The study group was composed of 115 children, of whom 59 (mean age 8.03±0.89years) practised soccer 3 times a week and had a positive Physical Activity Questionnaire for Adolescents (PAQ-A) score, while a further 56 (mean age 7.96±0.87years) did not perform any additional physical activity and had a negative PAQ-A score. A foot posture analysis, based on the foot posture index (FPI), the valgus index, the orientation of the subtalar joint (STJ) and the Q angle of the knee, was carried out. For the group of soccer players, the following results were obtained: FPI 4.79±2.38 (R) and 3.95±2.31 (L); valgus index 13.56°±1.66° (R) and 13.42°±1.48° (L); STJ test 79% pronated; Q angle 13.13°±2.06° (R) and 13.18°±1.93° (L). For the non-players, the corresponding values were: FPI 3.62±2.82 (R) and 3.74±2.77 (L); valgus index 12.76°±1.71° (R) and 12.84°±1.72° (L); STJ test 50% pronated; Q angle 13.87°±3.01° (R) and 13.86°±2.94° (L). There is a degree of difference between the two groups, but the values do not vary greatly from those considered normal for this age group. Any alterations in this respect can be assumed to be caused at older ages than those analysed.


#5 Prevalence of dermatomycoses in professional football players : A study based on data of German Bundesliga fitness check-ups (2013-2015) compared to data of the general population.
[Article in German]
Reference: Hautarzt. 2018 Feb 7. doi: 10.1007/s00105-017-4120-3. [Epub ahead of print]
Authors: Buder V, Augustin M, Schafer I, Welsch G, Catala-Lehnen P, Herberger K
Summary: The prevention, early diagnosis and treatment of onychomycosis is of great importance for professional athletes to avoid physical limitations by complications. So far, there is only little data on the prevalence of dermatomycosis in professional athletes. The aim of the study was to detect the prevalence of dermatomycosis in professional football players compared to the general population. The prospective, non-interventional, controlled study on the prevalence of dermatomycosis in professional football players was carried out on football players of a German Bundesliga team compared with a previously studied, equivalently aged German working population. A questionnaire survey, a dermatological check-up and a microbiological detection of pathogens in cases of suspicion were performed. Data of 84 football players (n = 45 in 2013; n = 39 in 2015) were compared to data of n = 8186 male employees between 17 and 35 years of age. In the group of athletes, there were findings of 60.7% onychomycosis, 36.9% of tinea pedis and 17.8% of pityriasis versicolor. In the group of the age-equivalent general German working population the findings were: onychomycosis 3.3%, tinea pedis 3.2%, pityriasis versicolor 1.4%. Our study shows a clearly higher risk for fungal diseases of the skin especially on the feet of professional football players. The results show a necessity for elucidation within prevention and the establishment of an appropriate therapy of dermatomycosis for professional football players.


#6 Depression and anxiety symptoms in 17 teams of female football players including 10 German first league teams
Reference: Br J Sports Med. 2018 Feb 2. pii: bjsports-2017-098033. doi: 10.1136/bjsports-2017-098033. [Epub ahead of print]
Authors: Junge A, Prinz B
Summary: Information on the prevalence of mental health problems of elite athletes is inconclusive, most probably due to methodological limitations, such as low response rates, heterogeneous samples. The aim of the study was to evaluate the prevalence and risk factors of depression and anxiety symptoms in high-level female football players. Female football players of 10 German first league (Bundesliga) and 7 lower league teams were asked to answer a questionnaire on players' characteristics, the Center of Epidemiologic Studies Depression Scale (CES-D) and the Generalised Anxiety Disorder (GAD-7) scale. A total of 290 players (184 first and 106 lower league players) took part in the study. The CES-D score indicated mild to moderate symptoms of depression in 48 (16.6%) and severe symptoms in 41 (14.1%) players. The GAD-7 score indicated an at least moderate generalised anxiety disorder in 24 (8.3%) players. The prevalence of depression symptoms and generalised anxiety disorders was similar to the female general population of similar age. However, significantly more second league players reported symptoms of depression than first league players, and thus the prevalence of depression symptoms in second league players was higher than in the general population. Only a third of the 45 (15.7%) players who stated that they currently wanted or needed psychotherapeutic support received it. The prevalence of depression and generalised anxiety symptoms in elite football players is influenced by personal and sport-specific variables. It is important to raise awareness of athletes' mental health problems in coaches and team physicians, to reduce stigma and to provide low-threshold treatment.


#7 Using Cartilage MRI T2-Mapping to Analyze Early Cartilage Degeneration in the Knee Joint of Young Professional Soccer Players
Reference: Cartilage. 2018 Feb 1:1947603518756986. doi: 10.1177/1947603518756986. [Epub ahead of print]
Authors: Waldenmeier L, Evers C, Uder M, Janka R, Hennig FF, Pachowsky ML, Welsch GH
Summary: The objective was to evaluate and characterize the appearance of articular cartilage in the tibiofemoral joint of young professional soccer players using T2-relaxation time evaluation on magnetic resonance imaging (MRI). Design In this study, we included 57 male adolescents from the youth academy of a professional soccer team. The MRI scans were acquired of the knee joint of the supporting leg. An "early unloading" (minute 0) and "late unloading" (minute 28) T2-sequence was included in the set of images. Quantitative T2-analysis was performed in the femorotibial joint cartilage in 4 slices with each 10 regions of interest (ROIs). Statistical evaluation, using Wilcoxon signed-rank tests, was primarily performed to compare the T2 values of the "early unloading" and "late unloading." Results When comparing "early unloading" with "late unloading," our findings showed a significant increase of T2-relaxation times in the weightbearing femoral cartilage of the medial ( P < 0.001) and lateral ( P < 0.001) compartment of the knee and in the tibial cartilage of the medial compartment ( P < 0.001). Conclusion In this study, alterations of the cartilage were found with a maximum in the medial condyle where the biomechanical load of the knee joint is highest, as well as where most of the chronic cartilage lesions occur. To avoid chronic damage, special focus should be laid on this region.


#8 A Trunk Stabilization Exercise Warm-up May Reduce Ankle Injuries in Junior Soccer Players
Reference: Int J Sports Med. 2018 Feb 15. doi: 10.1055/s-0044-100923. [Epub ahead of print]
Authors: Imai A, Imai T, Iizuka S, Kaneoka K
Summary: The aim of this study was to investigate the efficacy of a trunk stabilization exercise warm-up program in reducing the incidence of lower extremity injuries among male junior soccer players. Two junior soccer teams participated in this study. The intervention (INT) team performed three trunk stabilization exercises before practice sessions and games, while a control (CON) team performed their usual warm-up without trunk exercises. Both teams engaged in regular soccer training and games, and were followed for the incidence of injury. As a result, overall injury incidence rates (IRs) were 2.65 injuries/1,000 h and 4.94 injuries/1,000 h in the INT and CON teams, respectively (incidence rate ratio [IRR]=0.54, 95% confidence interval [CI]=0.32-0.89, p=0.013). The IR of acute injuries was significantly lower in the INT team (1.91 injuries/1,000 h) than in the CON team (4.06 injuries/1,000 h) (IRR=0.47, 95%CI=0.26-0.84, p=0.009). Regarding injury sites, the IRs of ankle injuries in the INT team (0.32 injuries/1,000 h) were significantly lower than that in the CON team (2.28 injuries/1,000 h) (IRR=0.14, 95%CI=0.04-0.47, p<0.001). These results suggest that a warm-up program comprising trunk stabilization exercises alone can prevent acute injuries, especially ankle injuries.


#9 Effect of oxygen therapy on chest pain in patients with ST elevation myocardial infarction: results from the randomized SOCCER trial
Reference: Scand Cardiovasc J. 2018 Feb 13:1-5. doi: 10.1080/14017431.2018.1439183. [Epub ahead of print]
Authors: Khoshnood A, Akbarzadeh M, Carlsson M, Sparv D, Bhiladvala P, Mokhtari A, Erlinge D, Ekelund U
Summary: Oxygen (O2) have been a cornerstone in the treatment of acute myocardial infarction. Studies have been inconclusive regarding the cardiovascular and analgesic effects of oxygen in these patients. In the SOCCER trial, we compared the effects of oxygen treatment versus room air in patients with ST-elevation myocardial infarction (STEMI). There was no difference in myocardial salvage index or infarct size assessed with cardiac magnetic resonance imaging. In the present subanalysis, we wanted to evaluate the effect of O2 on chest pain in patients with STEMI. Normoxic patients with first time STEMI were randomized in the ambulance to standard care with 10 l/min O2 or room air until the end of the percutaneous coronary intervention (PCI). The ambulance personnel noted the patients´ chest pain on a visual analog scale (VAS; 1-10) before randomization and after the transport but before the start of the PCI, and also registered the amount of morphine given. 160 patients were randomized to O2 (n = 85) or room air (n = 75). The O2 group had a higher median VAS at randomization than the air group (7.0 ± 2.3 vs 6.0 ± 2.9; p = .02) and also received a higher median total dose of morphine (5.0 mg ± 4.4 vs 4.0 mg ± 3.7; p = .02). There was no difference between the O2 and air groups in VAS at the start of the PCI (4.0 ± 2.4 vs 3.0 ± 2.5; p = .05) or in the median VAS decrease from randomization to the start of the PCI (-2.0 ± 2.2 vs -1.0 ± 2.9; p = .18). Taken together with previously published data, these results do not support a significant analgesic effect of oxygen in patients with STEMI.


#10 The Trainability of Adolescent Soccer Players to Brief Periodized Complex Training
Reference: Int J Sports Physiol Perform. 2018 Feb 12:1-25. doi: 10.1123/ijspp.2017-0763. [Epub ahead of print]
Authors: Chatzinikolaou A, Michaloglou K, Avloniti A, Leontsini D, Deli CK, Vlachopoulos D, Gracia-Marco L, Arsenis S, Athanailidis I, Draganidis D, Jamurtas AZ, Williams CA, Fatouros IG
Summary:  The purpose was to investigate the effect of a complex, short-term strength/power training protocol on performance and body composition of elite early-adolescent soccer players. Twenty-two players (14-15 years) were randomly assigned to (a) an experimental (EG, n=12, participated in a 5-week training protocol with traditional multi-joint power resistance exercises, Olympic-style lifts, plyometric drills and speed work, four times/week) or (b) a control group (CG, n=10). Strength and power performance [jumping, speed, change of direction, repeated sprint ability, endurance, isokinetic strength of knee flexors and extensors, maximal strength in various lifts, speed-endurance) were evaluated pre- and post-training. Cessation of training for five weeks in the CG induced a marked performance deterioration (~5-20%). Training not only prevented strength performance deterioration but also increased it (~2-30%). Endurance and RSA declined to a smaller extent in EG compared to CG (15% vs. 7.5%). Isometric strength, and body composition remained unaltered in both groups. Results demonstrate that (i) young players exhibit a high level of trainability of their strength/power performance (but not endurance) in response a short-term complex training protocol during early adolescence, (ii) Olympic-style lifts are characterized by increased safety in this age group and appear to be highly effective, (iii) it appears that lifts incorporating a hip thrust result in increased strength of both knee extensors and flexors, (iv) cessation of training for only five weeks results in marked deterioration of strength/power and endurance performance and (v) improvement of strength/power performance may be related to neural-based adaptation since body composition remained unaffected.


#11 Osteochondral lesion of the distal tibial plafond in an adolescent soccer player: a case report
Reference: J Can Chiropr Assoc. 2017 Dec;61(3):261-268.
Authors: Corso M, DeGraauw C, Hsu W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799846/pdf/jcca-61-261.pdf
Summary: Osteochondral lesions of the tibial plafond account for approximately 2.6% of osteochondral lesions in the ankle. There are few cases describing this lesion in the literature, with little information on mechanism of injury, history/physical findings or recommendations for management. A 17-year-old male competitive soccer player presented with a 6-7 month history of medial ankle pain after an inversion sprain. He presented with locking and giving way of the ankle with weight-bearing and pushing off the foot to the contralateral side. Radiographs were negative for fracture or osteochondral involvement. Magnetic resonance imaging revealed an osteochondral lesion of the tibial plafond with no injury to the talar dome. This case discusses the clinical presentation, imaging findings, management and outcomes of this osteochondral lesion of the distal tibial plafond.


#12 Modelling the impact of players' workload on the injury-burden of English Premier League football clubs
Reference: Scand J Med Sci Sports. 2018 Feb 23. doi: 10.1111/sms.13078. [Epub ahead of print]
Authors: Fuller CW
Summary: The loss of players through injury is known to affect team performance in many sports; it is important therefore for professional teams to be able to quantify the likely injury-burden that will be encountered throughout a season. A kinetic model, based on the rates at which match and training injuries are sustained and resolved, a team's squad size and the 2017/18 season fixture schedule for teams competing in the English Premier League, is used to produce daily forecasts of injury-burden experienced by a typical team. The incidences and median severities of match (incidence: 26.9 injuries/1000 player-match-hours, 95% CI: 21.5 to 33.7; severity: 17.5 days, 95% CI: 13.0 to 28.0) and training (incidence: 4.3 injuries/1000 player-training-hours, 95% CI: 3.4 to 5.5; severity: 14.0 days, 95% CI: 11.0 to 22.0) injuries were determined using data collected from four English Premier League football clubs during the 2016/17 season. Time-to-recovery curves for the match and training injuries sustained in the Premier League closely matched the time-to-recovery curves predicted by the kinetic model used in this study. The kinetic model predicted higher match and lower training injury burdens and a higher overall injury burden for successful teams competing in both national and European club competitions compared to teams competing only in national competitions. The model also showed that, in terms of injury-burden, there were no benefits in adopting a 4-week mid-season break during the season: reducing the number of clubs competing in the Premier League would, however, reduce the overall injury burden during a season. This article is protected by copyright. All rights reserved.

Tue

17

Apr

2018

Latest research in football - week 8 - 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 Psychological Characteristics in Talented Soccer Players - Recommendations on How to Improve Coaches' Assessment
Reference: Front Psychol. 2018 Feb 5;9:41. doi: 10.3389/fpsyg.2018.00041. eCollection 2018.
Authors: Musculus L, Lobinger BH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5807374/pdf/fpsyg-09-00041.pdf
Summary: Psychological characteristics, including personality traits and psychological skills, have been shown to be relevant predictors of soccer performance. In research, general and sport specific standardized self-report questionnaires have been applied in psychological diagnostics of sports talent. However, with regard to the assessment of psychological characteristics of talented soccer players, a gap between research and practice is apparent. While soccer clubs often ask their coaches to assess their players on self-designed, unevaluated scouting sheets, research widely neglects expert coaches' and clubs' perspectives on relevant performance characteristics. As we believe that expert coaches' assessments could be a valid predictor of a player's current performance and future success, we provide recommendations on how to improve coaches' assessment of psychological characteristics. As the quality of the assessment of psychological characteristics is crucial, we provide recommendations on how to ensure the central diagnostic standards: objectivity, reliability, and validity in talent assessment. Further, we argue that assessing psychological characteristics should combine self ratings of players and external ratings of coaches in talent development. Sport psychologists should assist clubs and coaches in improving the diagnostics of psychological characteristics as well as in embedding psychological diagnostics and interventions in the talent development process.


#2 Influence of biological maturity on the match performance of 8 to 16 year old elite male youth soccer players
Reference: J Strength Cond Res. 2018 Feb 14. doi: 10.1519/JSC.0000000000002510. [Epub ahead of print]
Authors: Goto H, Morris JG, Nevill ME
Summary: The aim of this study was to examine the influence of biological maturity on match performance in elite youth male soccer players. The participants were 80 Premier League Academy outfield players (8-16 years old). Biological maturity was determined by calculating estimated chronological age at peak height velocity. The U9 and U10 squads played 6-a-side and the U11-U16 squads played 11-a-side inter-academy matches. All matches were analyzed using a 1 Hz Global Positioning System (SPI elite, GPSport, Australia) with squad specific speed zones which were calculated based on 5 m flying sprint speed in the last 5 m of 10 m sprint test. In the U9/U10s, earlier maturers were given a longer pitch time by coaches (∼4 min per match, p = 0.029) and covered a greater total distance (∼9%, ∼400 m, p = 0.037) and a greater distance by walking (∼13%, ∼100 m, p = 0.024) and jogging (∼12%, ∼200 m, p = 0.014) during a match compared to later maturers. In the U13/U14s, earlier maturers covered a greater distance per hour of a match by high speed running compared to later maturers (∼25%, ∼130 m, p = 0.028) and spent a longer percentage of time in high speed running during a match compared to later maturers (3.4% vs. 2.7%, p = 0.034). Thus, coaches should take care to provide all players with a similar pitch-time and should be aware in the talent identification and development process, particularly with the U13/U14 age group, that maturity can influence high speed match running performance.


#3 Detection of Spatiotemporal Asymmetry in Pro Level Soccer Players
Reference: J Strength Cond Res. 2018 Mar;32(3):798-804. doi: 10.1519/JSC.0000000000001811.
Authors: Knudsen NS, Andersen TB
Summary: Several papers have focused on change of direction (COD) asymmetry investigated through standardized tests, and used this information to provide some spatiotemporal insight during games. The aim of this study was to investigate asymmetry in the reachable areas of the players through actual position data from soccer games. Sixteen professional players from the Danish Superliga participated in this study, but 5 were excluded because of lack of participation throughout the investigated games. The reachable areas of the players were investigated at varying sprint velocities (1-7 m·s) and within varying time intervals (0.5-4 seconds). The analysis found 7 players having spatiotemporal asymmetries in their reachable areas (0.5-3%) and shift of center of reachable area (4-29 cm). Four players (LB, RB, DM, and CF) had spatiotemporal asymmetries that could be attributed to COD and thus physiological asymmetries, whereas 3 players (LCB, LW, and RW) had spatiotemporal asymmetries that might be caused by their position or by use of tactic. This type of asymmetry was named a tactical spatiotemporal asymmetry. Coaches with knowledge about spatiotemporal asymmetries can use these actively in their tactical approach using the players' asymmetries in synergy, using opponents' asymmetries or improving the existing postgame spatiotemporal analyzing tools.


#4 Capture of Time-Loss Overuse Soccer Injuries in the National Collegiate Athletic Association's Injury Surveillance System, 2005-2006 Through 2007-2008
Reference: J Athl Train. 2018 Feb 21. doi: 10.4085/1062-6050-191-16. [Epub ahead of print]
Authors: Roos K, Kucera K, Golightly Y, Myers JB, Rosamond W, Marshall SW
Summary:  Overuse injuries are reported to account for nearly 50% of sports injuries and, due to their progressive nature and the uncertainty regarding date of onset, are difficult to define and categorize. Comparing the capture rates of overuse injuries between injury-surveillance systems and medical records can clarify completeness and determinants of how overuse injuries are represented in injury-surveillance data. The objective was to estimate the capture rate of time-loss medical-attention overuse injuries in men's and women's soccer in the National Collegiate Athletic Association Injury Surveillance System (NCAA ISS) compared with medical records maintained by certified athletic trainers and assess the differences in completeness of capture and factors contributing to those differences. Fifteen NCAA institutions provided NCAA ISS and medical record data from men's and women's soccer programs from 2005-2006 through 2007-2008. National Collegiate Athletic Association men's and women's soccer players participated in this study.  Time-loss medical-attention overuse injuries were defined as injuries with an overuse mechanism of injury in the NCAA ISS or medical records. Capture rates were calculated as the proportion of total overuse injuries classified as having overuse mechanisms in the NCAA ISS and the NCAA ISS and medical records combined. The NCAA ISS captured 63.7% of the total estimated overuse mechanisms of injury in men's and women's soccer players. The estimated proportion of overuse injury mechanisms captured by both the NCAA ISS and medical records was 37.1%. The NCAA ISS captured more overuse injury mechanisms in men's soccer than in women's soccer (79.2% versus 45.0%, χ2 = 9.60; P = .002) athletes.  From 2005-2006 through 2007-2008, the NCAA ISS captured only two thirds of time-loss medical-attention overuse mechanisms of injury in men's and women's soccer players. Future researchers should consider supplementing injury-surveillance data with a clinical record review to capture the burden of these injuries.


#5 Is the technical performance of young soccer players influenced by hormonal status, sexual maturity, anthropometric profile, and physical performance?
Reference: Biol Sport. 2017 Dec;34(4):305-311. doi: 10.5114/biolsport.2017.69817. Epub 2017 Sep 20.
Authors: Moreira A, Massa M, Thiengo CR, Rodrigues Lopes RA, Lima MR, Vaeyens R, Barbosa WP, Aoki MS
Summary: The aim of this study was to examine the influence of hormonal status, anthropometric profile, sexual maturity level, and physical performance on the technical abilities of 40 young male soccer players during small-sided games (SSGs). Anthropometric profiling, saliva sampling, sexual maturity assessment (Tanner scale), and physical performance tests (Yo-Yo and vertical jumps) were conducted two weeks prior to the SSGs. Salivary testosterone was determined by the enzyme-linked immunosorbent assay method. Technical performance was determined by the frequency of actions during SSGs. Principal component analyses identified four technical actions of importance: total number of passes, effectiveness, goal attempts, and total tackles. A multivariate canonical correlation analysis was then employed to verify the prediction of a multiple dependent variables set (composed of four technical actions) from an independent set of variables, composed of testosterone concentration, stage of pubic hair and genitalia development, vertical jumps and Yo-Yo performance. A moderate-to-large relationship between the technical performance set and the independent set was observed. The canonical correlation was 0.75 with a canonical R2 of 0.45. The highest structure coefficient in the technical performance set was observed for tackles (0.77), while testosterone presented the highest structure coefficient (0.75) for the variables of the independent set. The current data suggest that the selected independent set of variables might be useful in predicting SSG performance in young soccer players. Coaches should be aware that physical development plays a key role in technical performance to avoid decision-making mistakes during the selection of young players.


#5 Expression analysis of selected classes of circulating exosomal miRNAs in soccer players as an indicator of adaptation to physical activity
Reference: Biol Sport. 2017 Dec;34(4):331-338. doi: 10.5114/biolsport.2017.69820. Epub 2017 Sep 1.
Authors: Domanska-Senderowska D, Jastrzębski Z, Kiszalkiewicz J, Brzezianski M, Pastuszak-Lewandoska D, Radziminki L, Brzezianska-Lasota E, Jegier A
Summary: Recently studies have shown that, depending on the type of training and its duration, the expression levels of selected circulating myomiRNAs (c-miR-27a,b, c-miR-29a,b,c, c-miR-133a) differ and correlate with the physiological indicators of adaptation to physical activity. To analyse the expression of selected classes of miRNAs in soccer players during different periods of their training cycle. The study involved 22 soccer players aged 17-18 years. The multi-stage 20-m shuttle run test was used to estimate VO2 max among the soccer players. Samples serum were collected at baseline (time point I), after one week (time point II), and after 2 months of training (time point III). The analysis of the relative quantification (RQ) level of three exosomal myomiRNAs, c-miRNA-27b, c-miR-29a, and c-miR-133, was performed by quantitative polymerase chain reaction (qPCR) at three time points - before the training, after 1 week of training and after the completion of two months of competition season training. The expression analysis showed low expression levels (according to references) of all evaluated myomiRNAs before the training cycle. Analysis performed after a week of the training cycle and after completion of the entire training cycle showed elevated expression of all tested myomiRNAs. Statistical analysis revealed significant differences between the first and the second time point in soccer players for c-miR-27b and c-miR-29a; between the first and the third time point for c-miR-27b and c-miR-29a; and between the second and the third time point for c-miR-27b. Statistical analysis showed a positive correlation between the levels of c-miR-29a and VO2 max. Two months of training affected the expression of c-miR-27b and miR-29a in soccer players. The increased expression of c-miR-27b and c-miR-29 with training could indicate their probable role in the adaptation process that takes place in the muscular system. Possibly, the expression of c-miR-29a will be found to be involved in cardiorespiratory fitness in future research.


#6 The Impact of Soccer Match Play on the Muscle Damage Response in Youth Female Athletes
Reference: Int J Sports Med. 2018 Feb 23. doi: 10.1055/s-0044-101147. [Epub ahead of print]
Authors: Hughes JD, Denton K, S Lloyd R, Oliver JL, De Ste Croix M
Summary: Post-match assessment of creatine kinase (CK) activity and delayed-onset muscle soreness (DOMS) are common markers of exercise-induced muscle damage and recovery status in soccer players. These responses have not been examined in youth female players. This study examined the effect of competitive match play on CK activity and DOMS in elite youth players. Thirty-four elite female players, divided into three chronological age groups (U13, n=11; U15, n=10; U17 n=12). Players completed baseline testing for CK and DOMS that was repeated immediately (for DOMS), 80, 128 and 168 h post-competitive match play for CK. Significant time effects were reported for CK (P=0.006) and DOMS (P<0.01). Significant differences between baseline and 168 h post-match were reported for CK (P<0.01), with significant group differences between the U13 and U17 groups for CK (P<0.01). All parameters returned to baseline in U17s at 168 h, but increased CK was evident for U13s and U15s at 168 h. In conclusion, seven days may be insufficient for biochemical recovery in youth female athletes. Therefore, monitoring strategies to assess muscle damage between training and match play should be considered to track recovery and potentially reduce muscular injury risk.


#7 Age-Related Differences in Functional Hamstring/Quadriceps Ratio Following Soccer Exercise in Female Youth Players: An Injury Risk Factor
Reference: Pediatr Exerc Sci. 2018 Feb 27:1-7. doi: 10.1123/pes.2017-0034. [Epub ahead of print]
Authors: De Ste Croix M, Priestley A, Lloyd R, Oliver J
Summary: Fatigue negatively alters dynamic knee control, and the functional hamstring/quadriceps ratio (H/QFUNC) plays an important role in stabilizing the joint. The aim of this study was to investigate the influence of soccer-specific exercise on H/QFUNC in under (U) 13-, U15-, and U17-year-old female soccer players. A total of 36 female players performed concentric and eccentric actions of the hamstrings at 60°, 120°, and 180°/s before and after an age group-specific field-based soccer protocol. H/QFUNC was determined in the first 30° of knee flexion. Significant angle × velocity (P = .001) and time × angle (P = .033) interaction effects were found indicating a lower H/QFUNC with increased movement velocity at 0°-10° as opposed to greater knee flexion angles. Fatigue-related effects were only evident near full knee extension. Probabilistic inferences indicated that changes in H/QFUNC were generally unclear in U13s, likely detrimental in U15s, and very likely beneficial in U17s. Altered muscular control following soccer-specific exercise is age dependent with players' 1-year post-peak height velocity at greatest risk of injury. Injury prevention and screening need to be age and maturation appropriate, should consider the effects of fatigue, and include movements near full extension.


#8 Discovery of a Sweet Spot on the Foot with a Smart Wearable Soccer Boot Sensor That Maximizes the Chances of Scoring a Curved Kick in Soccer
Reference: Front Physiol. 2018 Feb 13;9:63. doi: 10.3389/fphys.2018.00063. eCollection 2018.
Authors: Fuss FK, Duking P, Weizman Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5816831/pdf/fphys-09-00063.pdf
Summary: This paper provides the evidence of a sweet spot on the boot/foot as well as the method for detecting it with a wearable pressure sensitive device. This study confirmed the hypothesized existence of sweet and dead spots on a soccer boot or foot when kicking a ball. For a stationary curved kick, kicking the ball at the sweet spot maximized the probability of scoring a goal (58-86%), whereas having the impact point at the dead zone minimized the probability (11-22%). The sweet spot was found based on hypothesized favorable parameter ranges (center of pressure in x/y-directions and/or peak impact force) and the dead zone based on hypothesized unfavorable parameter ranges. The sweet spot was rather concentrated, independent of which parameter combination was used (two- or three-parameter combination), whereas the dead zone, located 21 mm from the sweet spot, was more widespread.


#9 Anterior cruciate ligament ruptures in German elite soccer players: Epidemiology, mechanisms, and return to play
Reference: Knee. 2018 Feb 22. pii: S0968-0160(18)30031-0. doi: 10.1016/j.knee.2018.01.010. [Epub ahead of print]
Authors: Schiffner E, Latz D, Grassmann JP, Schek A, Thelen S, Windolf J, Schneppendahl J, Jungbluth P
Summary: Anterior cruciate ligament ruptures (ACLRs) are severe sports-related injuries with significant consequences for affected players and teams. This study aims to identify the epidemiology and injury-related lay-off after ACLR in professional male soccer players from the first-division German Bundesliga. Exposure times and incidence of anterior cruciate ligament ruptures were collected during 7.5 consecutive seasons using two media-based registers. A total of 72 total ACLRs were registered in 66 different players with an incidence of 0.040 per 1000h of exposure (95% CI 0.009-0.12). On average there were 9.6 ACLRs per season and 0.53 per team and season. The mean age of players affected was 24 (standard deviation±3.6) years. The number of ACLRs recorded per season fluctuated during the period observed. Goalkeepers are significantly (P<0.05) less prone to suffer an ACLR compared to outfield players. Understanding ACLR loading mechanisms, knowing risk factors for the injury and mean off time after ACLR are essential information for the coach, the medical staff, the elite soccer players, the insurance and team managers. Our results are in accordance with reports based on information from medical team staff. Therefore, our analysis of ACLR based on media sources may serve as an alternative for injury reports in elite soccer. The information of this study may be helpful for the medical staff taking care of professional soccer players and for orthopedic surgeons performing ACL reconstructions in this patient population.

Tue

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Apr

2018

Football is...(#57)

High pace dribbling to penetrate lines

Mon

16

Apr

2018

Latest research in football - week 6 - 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 cluster set warm-up configurations on sprint performance in collegiate male soccer players
Reference: Appl Physiol Nutr Metab. 2018 Jan 24. doi: 10.1139/apnm-2017-0610. [Epub ahead of print]
Authors: Nickerson BS, Mangine GT, Williams TD, Martinez IA
Summary: The purpose of this study was to determine if back squat cluster sets (CS) with varying inter-repetition rest periods would potentiate greater sprint performance compared to a traditional set parallel back squat in collegiate soccer players. Twelve collegiate male soccer players (21.0 ± 2.0 years; 180.0 ± 9.0 cm; 79.0 ± 9.5 kg) performed a 20-meter sprint prior to (PRE) a potentiation complex and at 1-, 4-, 7-, and 10-minutes post-exercise on three separate, randomized occasions. On each occasion, the potentiation complex consisted of 1 set of 3 repetitions at 85% one-repetition maximum (1RM) for the traditional parallel back squat. However, on one occasion the 3-repetition set was performed in a traditional manner (i.e., continuously), whereas on the other two occasions, 30- (CS30) and 60-seconds (CS60) of rest were allotted between each repetition. Repeated measures analysis of variance revealed greater (p = 0.022) mean barbell velocity on CS60 compared to the traditional set. However, faster (p < 0.040) 20-meter sprint times were observed for CS30 (3.15±0.16 sec) compared to traditional (3.20±0.17 sec) only at 10-minutes post-exercise. No other differences were observed. These data suggest that a single cluster set of three repetitions with 30-second inter-repetition rest periods at 85% 1RM acutely improves 20-meter sprinting performance. Strength and conditioning professionals and their athletes might consider its inclusion during the specific warm-up to acutely improve athletic performance during the onset (≤ 10 minutes) of training or competition.


#2 The Effects of Cupping on Hamstring Flexibility in Collegiate Soccer Players
Reference: J Sport Rehabil. 2018 Jan 24:1-18. doi: 10.1123/jsr.2017-0199. [Epub ahead of print]
Authors: Williams JG, Gard HI, Gregory JM, Gibson A, Austin J
Summary: Collegiate soccer players suffer hamstring injuries due to inflexibility and repetitive motions involving intense hamstring lengthening and contraction during sport. Although a popular intervention for muscular injury, there exists limited evidence of the effects of therapeutic cupping on hamstring flexibility. The objective was to determine the effect of cupping therapy on hamstring flexibility in collegiate soccer players. Twenty-five, asymptomatic, NCAA Division III soccer players (10 males, 15 females) (age = 19.4 ± 1.30 years, height = 175.1 ± 8.2 cm, mass = 69.5 ± 6.6 kg) participated in this study.  A 7-minute therapeutic cupping treatment was delivered to the treatment group. Four 2-inch cups were fixed atop trigger point locations within the hamstring muscle bellies of participants' dominant legs. Control group participants received no intervention between pre- and post-test measurements. Pretest and posttest measurements of hamstring flexibility, using a Passive Straight Leg Raise (PSLR), were performed on both groups were used as outcome measures. PSLR measurements were conducted by blinded examiners using a digital inclinometer. An independent samples t-test was used to analyze changes in hamstring flexibility from pre- to post-treatment with p-values set a priori at 0.05. An independent samples t-test demonstrated no significant difference in change in hamstring flexibility between participants in the treatment group and those in the control group (t23 = -.961, p = .35). The findings of this study demonstrated no statistically significant changes in hamstring flexibility following a cupping treatment.


#3 Reliability of internal and external load parameters in recreational football (soccer) for health
Reference: Res Sports Med. 2018 Jan 24:1-7. doi: 10.1080/15438627.2018.1431532. [Epub ahead of print]
Authors: Beato M, Jamil M, Devereux G
Summary: There is limited research focussed around the analysis of internal and external load parameters during football health programmes. The aim of this study was to assess the reliability of internal and external load parameters in this activity. Thrity subjects were enrolled (mean ± SDs; age = 43 ± 3 years, weight = 84 ± 14 kg, height = 176 ± 7 cm, BMI = 27.1 ± 3, VO2max = 40.7 ± 3.4 ml.kg.min-1). The football matches (five a-side) took place on an artificial grass outdoor field (pitch size of 36 × 18.5 m). Participants completed the match (60 min) and replicated the same match a week later. The analysis took into account several parameters: heart rate (HR), total distance (TD), high speed running (HSR), number of accelerations (>2 m.s-2) and metabolic power (MP). We found a good score of reliability in several parameters: TD (ICC = 0.66), accelerations (ICC = 0.62), mean HR (ICC = 0.82), HSR (ICC = 0.77) and MP (ICC = 0.66). The results reported in this study revealed good scores of absolute reliability and small/trivial effect size.


#4 Activity monitoring in men's college soccer: a single season longitudinal study
Reference: Res Sports Med. 2018 Jan 23:1-13. doi: 10.1080/15438627.2018.1431535. [Epub ahead of print]
Authors: Slater LV, Baker R, Weltman AL, Hertel J, Saliba SA, Hart JM
Summary: Performance in soccer has been characterized previously using time-motion analyses; however, it is unclear if men's college soccer shares performance characteristics with women's college or men's professional soccer. The purpose of this study was to compare proportions of matches spent walking, jogging, running, and sprinting in men's college soccer. Twenty-two male college soccer players wore global positioning system units during matches. Proportions of walking, jogging, running, high-speed running, and sprinting were calculated for each player based on time period (first half, second half, extra time) and outcome (win, loss, tie). Multivariate analyses of variance were run for each time period to compare positions. Means, 95% confidence intervals, and effect sizes were calculated for each position based on time period and match outcome. There were differences in low-speed and high-speed activities based on position, with forwards and midfielders demonstrating increased high-speed activities. Positional differences may require different physiological profiles and should be a consideration during training.


#5 Noninvasive Ventilation in Hypoxemic Patients: an Ongoing Soccer Game or a Lost One?
Reference: Turk J Anaesthesiol Reanim. 2017 Dec;45(6):329-331. doi: 10.5152/TJAR.2017.241102. Epub 2017 Dec 1.
Authors: Gregoretti C, Cortegiani A, Raineri SM, Giarrjatano A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772410/pdf/tard-45-6-329.pdf


#6 Acute Effects of Ballistic vs Passive Static Stretching Involved in A Pre-Match Warm-Up Regarding Vertical Jump and Linear Sprint Performance in Soccer Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002477. [Epub ahead of print]
Authors: Mariscal SL, Garcia VS, Fernandez-Garcia JC, Saez de Villarreal E
Summary: The purpose of this study was to compare the effects of introducing passive static and ballistic stretching in a standard soccer match warm-up. The variables addressed were the Counter Movement Jump (CMJ), Abalakov jump and the 40 m linear sprint. The sample was composed of 33 male subjects, divided in two age groups. U16 and adult players formed the groups, in order to cross check if there were differences between them. Each group was further subdivided into two groups regarding the type of stretching carried out during the stretching phase. Prior to the warm-up, the tests previously described were assessed. In the experimental phase, standard stretching was carried out consisting of: an initial phase in which players had to execute continuous running; a general phase in which players had to make articulate moves; a technical phase, in which players had to execute exercises with the ball; a 5 vs. 5 small sided game was carried out during the tactical phase; and, in the final phase, activation exercises and sprints were carried out by the players. Eventually, the same variables were assessed again once the warm-up was finished. There were no statistically significant differences between the two types of stretching included in the pre-match warm-up. It can be concluded that ballistic and passive static stretching (<10s) did not cause, under these circumstances, any effect in the assessed variables related to soccer performance (linear sprint, CMJ and Abalakov). This has to be considered by coaches when devising soccer related warm-ups.


#7 Optimal Reactive Strength Index: Is it an Accurate Variable to Optimize Plyometric Training Effects on Measures of Physical Fitness in Young Soccer Players?
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002467. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Garcia-Pinillos F, Sanchez-Sanchez J, Yanci J, Castillo D, Loturco I, Chaabene H, Moran J, Izquierdo M
Summary: This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) versus an optimal drop-box height (i.e, 10-cm to 40-cm: generating an optimal [OPT] reactive strength index [RSI]) in youth soccer players' physical fitness. Athletes were randomly allocated to a control-group (CG: n=24; age=13.7 years), a fixed drop-box height group (FIXED, n=25; age=13.9 years) or an optimal drop-box height group (OPT, n=24; age=13.1 years). Before and after 7 weeks of training, tests for the assessment of jumping (countermovement jump [CMJ], five multiple bounds [MB]), speed (20-m sprint time), change of direction (Illinois change of direction test [CODT]), strength (RSI and 5 maximal squat repetition test [5RM]), endurance (2.4 km time trial), and kicking ability (maximal kicking distance) were undertaken. Analyses revealed main effects of time for all dependent variables (p<0.001, d=0.24-0.72), except for 20-m sprint time. Analyses also revealed group×time interactions for CMJ (p<0.001, d=0.51), DJ (p<0.001, d=0.30), 20-m sprint time (p<0.001, d=0.25), CODT (p<0.001, d=0.22), and 5RM (p<0.01, d=0.16). Post-hoc analyses revealed increases for the FIXED group (CMJ: 7.4%, d=0.36; DJ: 19.2%, d=0.49; CODA: -3.1%, d=-0.21; 5RM: 10.5%, d=0.32) and the OPT group (CMJ: 16.7%, d=0.76; DJ: 36.1%, d=0.79; CODA: -4.4%, d=-0.34; 5RM: 18.1%, d=0.47). Post-hoc analyses also revealed increases for the OPT group in 20-m sprint time (-3.7%, d=0.27). Therefore, to maximize the effects of plyometric training, an OPT approach is recommended. However, using adequate fixed drop-box heights may provide a rational and practical alternative.


#8 Accuracy, intra- and inter-unit reliability, and comparison between GPS and UWB-based position-tracking systems used for time-motion analyses in soccer
Reference: Eur J Sport Sci. 2018 Jan 31:1-8. doi: 10.1080/17461391.2018.1427796. [Epub ahead of print]
Authors: Bastida Castillo A, Gomez Carmona CD, De la Cruz Sanchez E, Pino Ortega J
Summary: There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20 ± 1.6 years, 1.76 ± 0.08 cm, and 69.5 ± 9.8 kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig-zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57-5.85%), test-retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69-6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03).


#9 Osteoarthritis of the hip and knee in former male professional soccer players
Reference: Br Med Bull. 2018 Jan 29. doi: 10.1093/bmb/ldy001. [Epub ahead of print]
Authors: Petrillo S, Papalia R, Maffulli N, Volpi P, Denaro V
Summary: Professional soccer (PS) players are at great risk of osteoarthritis (OA) of the knee and hip. Sources of data: Following the PRISMA guidelines, the key words 'osteoarthritis' and 'soccer' or 'football' were matched with 'players' or 'former' or 'retired' and with 'hip' or 'knee' on December 24, 2017 in the following databases: PubMed, Cochrane, Google scholar, Embase and Ovid. Only comparative studies reporting the prevalence rate of OA of both hip and knee joint in former PS athletes (fPSa) and age and sex matched controls were considered. In fPSa, the prevalence rate of OA of both hip and knee is significantly higher compared to age and sex matched controls. The pathological pathways responsible for the development of OA of the hip and knee in PS athletes (PSa) are still not clearly understood. The prevalence rate of clinical OA of the hip was 8.6% in fPSa and 5.6% in controls (odd ratio (OR) = 1.5; 95% CI: 1.06-2.31). The radiographic rate of OA was 21.2% in fPSa and 9.8% in controls (OR = 2.4; 95% CI: 1.66-3.69). A total of 14.6 and 53.7% of fPSa presented clinical and radiographic signs of OA of the knee, respectively, vs 12.9% (OR = 1.16; 95% CI: 0.86-1.55) and 31.9% (OR = 2.47; 95% CI: 2.03-3.00) of controls. Sonographic evidence of OA of the knee was found in 52% of fPSa and 33% of controls (OR = 2.2; 95% CI: 1.24-3.89). Preventive training programmes should be developed to reduce the number of fPSa presenting early OA.


#10 Key team physical and technical performance indicators indicative of team quality in the soccer Chinese super league
Reference: Res Sports Med. 2018 Jan 31:1-10. doi: 10.1080/15438627.2018.1431539. [Epub ahead of print]
Authors: Yang G, Leicht AS, Lago C, Gomez MA
Summary: The aim of this study was to identify the key physical and technical performance variables related to team quality in the Chinese Super League (CSL). Teams' performance variables were collected from 240 matches and analysed via analysis of variance between end-of-season-ranked groups and multinomial logistic regression. Significant physical performance differences between groups were identified for sprinting (top-ranked group vs. upper-middle-ranked group) and total distance covered without possession (upper and upper-middle-ranked groups and lower-ranked group). For technical performance, teams in the top-ranked group exhibited a significantly greater amount of possession in opponent's half, number of entry passes in the final 1/3 of the field and the Penalty Area, and 50-50 challenges than lower-ranked teams. Finally, time of possession increased the probability of a win compared with a draw. The current study identified key performance indicators that differentiated end-season team quality within the CSL.


#11 Influence of well-being variables and recovery state in physical enjoyment of professional soccer players during small-sided games
Reference: Res Sports Med. 2018 Jan 28:1-12. doi: 10.1080/15438627.2018.1431540. [Epub ahead of print]
Authors: Selmi O, Goncalves B, Ouergui I, Sampaio J, Bouassida A
Summary: This study aimed to assess the effects of the total quality of recovery and well-being indices (self-ratings of sleep during the preceding night, stress, fatigue and delayed onset muscle soreness) on rating of perceived exertion (RPE) and physical enjoyment (PE) during small-sided games. A total of 20 professional soccer players (25 ± 0.8 years) completed four 5-a-side game sessions of 25-min duration each (4 × 4 min work with 3-min passive recovery in-between). All variables were collected before each game session with the exception of RPE and Physical Activity Enjoyment Scale that were collected after. The results demonstrate that recovery state and pre-fatigue states were not contributing signals of affected internal intensity and enjoyment of players. The study established the objectivity and utility of RPE as a useful tool for determining internal intensity during soccer-specific training as well as PE for assessing emotional response during exercise or training session.


#12 Effects of Soccer Training on Anthropometry, Body Composition, and Physical Fitness during a Soccer Season in Female Elite Young Athletes: A Prospective Cohort Study
Reference: Front Physiol. 2017 Dec 22;8:1093. doi: 10.3389/fphys.2017.01093. eCollection 2017.
Authors: Lesinski M, Prieske O, Helm N, Granacher U
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5770736/pdf/fphys-08-01093.pdf
Summary: The objectives of this study were to (i) describe soccer training (e.g., volume, types), anthropometry, body composition, and physical fitness and (ii) compute associations between soccer training data and relative changes of anthropometry, body composition, and physical fitness during a soccer season in female elite young athletes. Seasonal training (i.e., day-to-day training volume/types) as well as variations in anthropometry (e.g., body height/mass), body composition (e.g., lean body/fat mass), and physical fitness (e.g., muscle strength/power, speed, balance) were collected from 17 female elite young soccer players (15.3 ± 0.5 years) over the training periods (i.e., preparation, competition, transition) of a soccer season that resulted in the German championship title in under-17 female soccer. Training volume/types, anthropometrics, body composition, and physical fitness significantly varied over a soccer season. During the two preparation periods, higher volumes in resistance and endurance training were performed (2.00 ≤ d ≤ 18.15; p < 0.05), while higher sprint and tactical training volumes were applied during the two competition periods (2.22 ≤ d ≤ 11.18; p < 0.05). Body height and lean body mass increased over the season (2.50 ≤ d ≤ 3.39; p < 0.01). In terms of physical fitness, significant performance improvements were found over the soccer season in measures of balance, endurance, and sport-specific performance (2.52 ≤ d ≤ 3.95; p < 0.05). In contrast, no statistically significant changes were observed for measures of muscle power/endurance, speed, and change-of-direction speed. Of note, variables of muscle strength (i.e., leg extensors) significantly decreased (d = 2.39; p < 0.01) over the entire season. Our period-specific sub-analyses revealed significant performance improvements during the first round of the season for measures of muscle power/endurance, and balance (0.89 ≤ d ≤ 4.01; p < 0.05). Moreover, change-of-direction speed significantly declined after the first round of the season, i.e., transition period (d = 2.83; p < 0.01). Additionally, significant medium-to-large associations were observed between training and anthropometrics/body composition/physical fitness (-0.541 ≤ r ≤ 0.505). Soccer training and/or growth/maturation contributed to significant variations in anthropometry, body composition, and physical fitness outcomes throughout the different training periods over the course of a soccer season in female elite young soccer players. However, changes in components of fitness were inconsistent (e.g., power, speed, strength). Thus, training volume and/or types should be carefully considered in order to develop power-, speed- or strength-related fitness measures more efficiently throughout the soccer season.


#13 Orthopaedics injuries in male professional football players in Brazil: a prospective comparison between two divisions
Reference: Muscles Ligaments Tendons J. 2018 Jan 10;7(3):524-531. doi: 10.11138/mltj/2017.7.3.524. eCollection 2017 Jul-Sep.
Authors: Arliani GG, Lara PHS, Astur DC, Pedrinelli A, Pagura JR, Cohen M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5774927/pdf/524-531.pdf
Summary: Football is a high-speed contact sport and the risk of injury is high. The objective of this study was to compare the two main divisions (A1 and A2) of the São Paulo Football Championship and to perform a correlation analysis of the variables studied. A prospective study was conducted using an electronic questionnaire previously developed by the Medical Committee of the São Paulo Football Federation. The questionnaire was sent to the doctors of the teams playing in the A1 and A2 divisions of the São Paulo Football Championship after each round. Setting: 2016 São Paulo Football Championship. The comparison of divisions A1 and A2 showed few significant differences among the various variables analysed in this study. The only significant differences were for right-side involvement in division A1 (p=0.044) and morning matches in division A2 (p<0.001). The correlation analysis of the variables studied showed expected associations, including sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains. Despite the differences between the two divisions regarding budgets and team characteristics, there was a little difference in the variables analysed and there were associations such as sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains.

 


American Football
#1 Incidence, Severity, and Time Loss Associated With Collegiate Football Fractures, 2004-2005 to 2013-2014
Reference: Am J Sports Med. 2018 Jan 1:363546517749914. doi: 10.1177/0363546517749914. [Epub ahead of print]
Authors: Cairns MA, Hasty EK, Herzog MM, Ostrum RF, Kerr ZY
Summary: The inherent risk of any time loss from physical injury in football has been extensively discussed, with many such injuries having a profound effect on the lives of National Collegiate Athletic Association (NCAA) football players. However, the incidence of fractures in collegiate football has not been well established. The purpose of the study was to examine the epidemiology of fractures in NCAA football. Fracture data reported in college football during the 2004-2005 to 2013-2014 academic years were analyzed from the NCAA Injury Surveillance Program (NCAA-ISP). Fracture rates per 1000 athlete-exposures, surgery and time loss distributions, injury rate ratios, injury proportion ratios (IPRs), and 95% CIs were reported. Overall, 986 fractures were reported. The rate of competition fractures was larger than the rate of practice fractures (1.80 vs 0.17 per 1000 athlete-exposures; injury rate ratio = 10.56; 95% CI, 9.32-11.96). Fractures of the hand/fingers represented 34.6% of all injuries, while fibula fractures (17.2%) were also common. A majority (62.5%) of all fractures resulted in time loss >21 days. Altogether, 34.4% of all fractures required surgery, and 6.3% were recurrent. The proportion of fractures resulting in time loss >21 days was higher for fractures requiring surgery than fractures not requiring surgery (85.0% vs 50.7%; IPR = 1.68; 95% CI, 1.53-1.83). The proportion of recurrent and nonrecurrent fractures requiring surgery did not differ (35.5% vs 34.3%; IPR = 1.03; 95% CI, 0.73-1.46); however, recurrent fractures were more likely to require surgery than nonrecurrent fractures when restricted to the hand/fingers (66.7% vs 27.2%; IPR = 2.45; 95% CI, 1.36-4.44). Fractures in collegiate football were sustained at a higher rate in competition than practice and frequently required extended time lost from participation, particularly among those requiring surgery. Prevention strategies are warranted to reduce incidence and severity of fractures.


#2 Association Between Playing American Football in the National Football League and Long-term Mortality
Reference: JAMA. 2018 Feb 1. doi: 10.1001/jama.2018.0140. [Epub ahead of print]
Authors: Venkataramani AS, Gandhavadi M, Jena AB
Summary: Studies of the longevity of professional American football players have demonstrated lower mortality relative to the general population but they may have been susceptible to selection bias. The objective was to examine the association between career participation in professional American football and mortality risk in retirement. Retrospective cohort study involving 3812 retired US National Football League (NFL) players who debuted in the NFL between 1982 and 1992, including regular NFL players (n = 2933) and NFL "replacement players" (n = 879) who were temporarily hired to play during a 3-game league-wide player strike in 1987. Follow-up ended on December 31, 2016. NFL participation as a career player or as a replacement player. The primary outcome was all-cause mortality by December 31, 2016. Cox proportional hazards models were estimated to compare the observed number of years from age 22 years until death (or censoring), adjusted for birth year, body mass index, height, and position played. Information on player death and cause of death was ascertained from a search of the National Death Index and web-based sources. Of the 3812 men included in this study (mean [SD] age at first NFL activity, 23.4 [1.5] years), there were 2933 career NFL players (median NFL tenure, 5 seasons [interquartile range {IQR}, 2-8]; median follow-up, 30 years [IQR, 27-33]) and 879 replacement players (median NFL tenure, 1 season [IQR, 1-1]; median follow-up, 31 years [IQR, 30-33]). At the end of follow-up, 144 NFL players (4.9%) and 37 replacement players (4.2%) were deceased (adjusted absolute risk difference, 1.0% [95% CI, -0.7% to 2.7%]; P = .25). The adjusted mortality hazard ratio for NFL players relative to replacements was 1.38 (95% CI, 0.95 to 1.99; P = .09). Among career NFL players, the most common causes of death were cardiometabolic disease (n = 51; 35.4%), transportation injuries (n = 20; 13.9%), unintentional injuries (n = 15; 10.4%), and neoplasms (n = 15; 10.4%). Among NFL replacement players, the leading causes of death were cardiometabolic diseases (n = 19; 51.4%), self-harm and interpersonal violence (n = 5; 13.5%), and neoplasms (n = 4; 10.8%). Among NFL football players who began their careers between 1982 and 1992, career participation in the NFL, compared with limited NFL exposure obtained primarily as an NFL replacement player during a league-wide strike, was not associated with a statistically significant difference in long-term all-cause mortality. Given the small number of events, analysis of longer periods of follow-up may be informative.


#3 Anthropometric and Athletic Performance Combine Test Results Among Positions within Grade Levels of High School-Aged American Football Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002481. [Epub ahead of print]
Authors: Leutzinger TJ, Gillen ZM, Miramonti AM, McKay BD, Mendez AI, Cramer JT
Summary: The purpose of the present study was to investigate differences among player positions at three grade levels in elite, collegiate-prospective American football players. Participants' data (n = 7,160) were analyzed for this study [mean height (Ht) ± standard deviation (SD) = 178 ± 7 cm, weight (Wt) = 86 ± 19 kg]. Data were obtained from 12 different high school American football recruiting combines hosted by Zybek Sports (Boulder, Colorado). Eight two-way (9x3) mixed factorial ANOVAs [position (defensive back (DB), defensive end (DE), defensive lineman (DL), linebacker (LB), offensive lineman (OL), quarterback (QB), running back (RB), tight end (TE), and wide receiver (WR) x grade (freshmen, sophomores, and juniors)] were used to test for differences among the mean test scores for each combine measure [Ht, Wt, 40-yard (40yd) dash, pro-agility drill (PA), L-cone drill (LC), vertical jump (VJ), and broad jump (BJ)]. There were position-related differences (p ≤ 0.05) for Ht, 40yd dash, and BJ, within each grade level and for Wt, PA, LC, and VJ independent of grade level. Generally, the results showed that OL were the tallest, weighed the most, and exhibited the lowest performance scores among positions. RBs were the shortest, while DBs and WRs weighed the least, and exhibited the highest performance scores among positions. These results demonstrate the value of classifying high school-aged American football players according to their specific position rather than categorical groupings such as 'line' vs. 'skill' vs. 'big skill' when evaluating anthropometric and athletic performance combine test results.


#4 Initial symptom presentation after high school football-related concussion varies by time point in a season: an initial investigation
Reference: Sports Med Open. 2018 Jan 31;4(1):8. doi: 10.1186/s40798-018-0121-8.
Authors: Brett BL, Kuhn AW, Yengo-Kahn AM, Kerr ZY, Bonfield CM, Solomon GS, Zuckerman SL
Download link: https://sportsmedicine-open.springeropen.com/track/pdf/10.1186/s40798-018-0121-8?site=sportsmedicine-open.springeropen.com
Summary: Schedule-based and in-season factors (e.g., competition type) have been shown to be associated with symptom reporting patterns and injury severity in sport-related concussion (SRC). To determine if acute neurocognitive and symptom presentation following SRC differ by time point within a high school football season. Multicenter ambispective cohort of high school football players who sustained a SRC (N = 2594). Timing (early, mid, and late season) of SRC was based on median dates for the start of the pre-season, regular season, and playoffs of each states' football schedules. Analysis of covariance (ANCOVA) investigated differences across season period groups for: (1) neurocognitive test scores, (2) total symptom scores (TSS), and (3) individual symptom increases from baseline within 1-week post-injury. Significant group differences were observed in TSS, F(2, 2589) = 15.40, p <  0.001, ηp2 = 0.01, and individual symptom increases from baseline, F(2, 2591) = 16.40, p <  0.001, ηp2 = 0.01. Significant increases were seen from baseline to both midseason and late season in both TSS, χ2 = 24.40, p <  0.001, Φ = 0.10 and individual symptoms, χ2  = 10.32, p = 0.006, Φ = 0.10. Post hoc tests indicated a linear trend, with late-season injured athletes reporting approximately twice the TSS (13.10 vs. 6.77) and new symptoms (5.70 vs. 2.68) as those with early-season injuries. In a cohort of American high school football student-athletes, those suffering SRC in the late-season time period had increased acute symptom burden. SRC sustained later in-season may require more conservative management.


Wed

28

Feb

2018

Latest research in football - week 5 - 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 Iron, Hematological Parameters and Blood Plasma Lipid Profile in Vitamin D Supplemented and Non-Supplemented Young Soccer Players Subjected to High-Intensity Interval Training
Reference: J Nutr Sci Vitaminol (Tokyo). 2017;63(6):357-364. doi: 10.3177/jnsv.63.357.
Authors: Jastrzebska M, Kaczmarczyk M, Suarez AD, Sanchez GFL, Jastrzebska J, Radziminski L, Jastrzebski Z
Download link: https://www.jstage.jst.go.jp/article/jnsv/63/6/63_357/_pdf/-char/en
Summary: Vitamin D deficiency has been associated with increased risk for cardiovascular disease and anemia. Vitamin D-related changes in lipid profile have been studied extensively but the relationship between vitamin D and lipid metabolism is not completely understood. As both vitamin D and intermittent training may potentially affect iron and lipid metabolism, the aim of the study was to evaluate whether a daily supplementation of vitamin D can modulate the response of hematological and lipid parameters to high-intensity interval training (HIIT) in soccer players. Thirty-six young elite junior soccer players were included in the placebo-controlled, double-blind study. Participants were non-randomly allocated into either a supplemented group (SG, n=20, HIIT and 5,000 IU of vitamin D daily) or placebo group (PG, n=16, HIIT and sunflower oil). Hematological parameters were ascertained before and after the 8-wk training. The change score (post- and pre-training difference) was calculated for each individual and the mean change score (MCS) was compared between SG and PG using the t test and analysis of covariance. There were no differences between SG and PG at baseline. The red and white cell count, hemoglobin, hematocrit, MCHC, ferritin, and HDL-cholesterol changed significantly over the 8-wk HIIT. However, no significant differences in MCS were observed between SG and PG for any variable. A daily vitamin D supplement did not have any impact on alteration in hematological or lipid parameters in young soccer players in the course of high-intensity interval training.


#2 Impact of the EURO-2016 football cup on emergency department visits related to alcohol and injury
Reference: Eur J Public Health. 2018 Jan 15. doi: 10.1093/eurpub/ckx233. [Epub ahead of print]
Authors: Noel GN, Roch AR, Michelet PM, Boiron LB, Gentile SG, Viudes GV
Summary: In Marseille, the 2016 EURO football cup days were independently associated with a 43% increase in alcohol-related visits in the Emergency Department (ED). Patients admitted for alcohol consumption were younger (41 vs. 46.6;P < 0.001), more often male (82.8% vs. 60.1%; P < 0.001) and more often admitted as inpatients (24.0% vs. 16.5%; P = 0.03) than those admitted for injury. Unlike reported in previous studies, injury-related visits did not increase. This could be explained by coding practice variability between EDs (alcohol or injury). To account for this variability, both diagnosis groups must be separately included when using ED data for preparing and monitoring major gatherings.


#3 Exploring the effects of playing formations on tactical behaviour and external workload during football small-sided games
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002445. [Epub ahead of print]
Authors: Baptista J, Travassos B, Goncalves B, Mourao P, Viana JL, Sampaio J
Summary: This study aimed to identify the effects of playing formations on tactical behaviour and external workload during football small-sided games. Twenty-three semi-professional footballers integrated three different playing formations in a 7-a-side small-sided game, according to their specific player positions: team 4:3:0 (4 defenders, 3 midfielders); team 4:1:2 (4 defenders, 1 midfielder, 2 forwards); and team 0:4:3 (4 midfielders, 3 forwards). Based on players' movement trajectories, the following individual and collective tactical variables were calculated: total distance covered and distance covered while walking, jogging, running and sprinting, distance from each player to both own and opponent's team centroid (Dist CG and Dist OPP CG, respectively), individual area, team length, team width and surface area. Approximate entropy (ApEn) was computed to identify the regularity of each variable. The team 4:3:0 promoted players' space exploration with moderate physical efforts. The team 4:1:2 promoted compactness and regularity of the team with increase in the physical efforts. The team 0:4:3 promoted team balance and adaptability on space coverage with increase in physical efforts. Concluding, different playing formations support different game dynamics, and variations on external load were directly linked with the variations on tactical behaviour. The analysis tactical behaviour through quantification of variability of patterns of play and quantification of distance covered at different velocities were the most useful information for the analysis of the effects of practice task manipulations. Therefore, in a practical sense, strength and conditioning coaches should plan and monitor these tasks in interaction with the head coaches.


#4 The Importance of Strength and Power on Key Performance Indicators in Elite Youth Soccer
Reference: J Strength Cond Res. 2018 Jan 24. doi: 10.1519/JSC.0000000000002446. [Epub ahead of print]
Authors: Wing CE, Turner AN, Bishop CJ
Summary: The purpose of this investigation was to examine the importance of strength and power in relation to key performance indicators (KPI's) within competitive soccer match play. This was achieved through using an experimental approach where fifteen subjects were recruited from a professional soccer club's scholarship squad during the 2013/14 season. Following anthropometric measures, power and strength were assessed across a range of tests which included the squat jump (SJ), countermovement jump (CMJ), 20 metre (m) sprint and arrowhead change of direction test. A predicted 1-repetition maximum (RM) was also obtained for strength by performing a 3RM test for both the back squat and bench press and a total score of athleticism (TSA) was provided by summing z-scores for all fitness tests together, providing one complete score for athleticism. Performance analysis data was collected during 16 matches for the following KPIs: passing, shooting, dribbling, tackling and heading. Alongside this, data concerning player ball involvements (touches) was recorded. Results showed that there was a significant correlation (p < 0.05) between CMJ (r = 0.80), SJ (r = 0.79) and TSA (r = 0.64) in relation to heading success. Similarly, a significant correlation (p < 0.05) between predicted 1RM squat strength and tackle success (r = 0.61). These data supports the notion that strength and power training are important to soccer performance, particularly when players are required to win duels of a physical nature. There were no other relationships found between the fitness data and the KPI's recorded during match play which may indicate that other aspects of player's development such as technical skill, cognitive function and sensory awareness are more important for soccer-specific performance.


#5 The Effect of Heat Stress on Measures of Running Performance and Heart Rate Responses During A Competitive Season in Male Soccer Players
Reference: J Strength Cond Res. 2018 Jan 24. doi: 10.1519/JSC.0000000000002441. [Epub ahead of print]
Authors: Coker NA, Wells AJ, Gepner Y
Summary: Measures of running performance (RP) and heart rate responses (HR) to matchplay during three different heat stress (HS) conditions were assessed in seven National Collegiate Athletic Association (NCAA) Division I male soccer players. Total distance (TD), as well as distance covered within distinct velocity zones [walking (WALK), jogging (JOG), low speed running (LSR), high-speed running (HSR), sprinting (SPRINT), low-intensity running (LIR), and high-intensity running (HIR)] were assessed using GPS units over 12 matches. HS was monitored during each match, and matches were defined as low (HSlow, n=4), moderate (HSmod, n=4), or high (HShigh, n=4) HS. Minutes played were significantly different across HS conditions (p=0.03). Therefore, distance covered within each movement velocity was assessed relative to minutes played, and as a percentage of total playing time. WALKrel was significantly greater during HShigh compared to HSlow (p=0.035). LIRrel was significantly greater during HSmod (p=0.015) compared to HSlow. A trend was observed for %WALK being higher during HShigh compared to HSlow (p=0.066). %LIR was significantly greater during HShigh compared to HSlow (p=0.048). HIR was not significantly different across HS conditions. Percent of time spent >85% HRmax was significantly greater during HShigh (p=0.002) and HSmod (p<0.001) compared to HSlow. Percent of time spent between 65-84% HRmax was significantly greater during HSlow compared to HShigh (p<0.001). Results indicate that HS resulted in increased LIR and %HR≥85, while HIR was maintained. HIR performance may be conserved through decreased playing time and/or the adoption of pacing strategies. This may assist coaches in altering player management strategies to optimize team performance.


#6 Combined Anterolateral, Anterior, and Anteromedial Ankle Impingement in an Adolescent Soccer Player-A Case Report and Review of the Literature
Reference: Clin J Sport Med. 2018 Jan 24. doi: 10.1097/JSM.0000000000000576. [Epub ahead of print]
Authors: Cosma DI, Vasilescu DE, Corbu A, Todor A, Valeanu M, Ulici A
Summary: A unique case of combined anterolateral, anterior, and anteromedial ankle impingement in an adolescent soccer player is presented in this article. To the best of our knowledge, this is the only report of circumferential, massive, anterior ankle impingement in children described in the literature. The importance of proper diagnosis and treatment of such a lesion is illustrated in this case report. We also emphasize that clinical examination combined with 3D computed tomography scan reconstruction is an excellent and cost-effective imaging modality that can help with the diagnosis of anterior ankle impingement. Finally, open surgical treatment showed excellent results in an elite athlete.


#7 Match Situations Leading to Head Injuries in Professional Male Football (Soccer)-A Video-based Analysis Over 12 Years
Reference: Clin J Sport Med. 2018 Jan 19. doi: 10.1097/JSM.0000000000000572. [Epub ahead of print]
Authors: Beaudouin F, Aus der Funten K, Troß T, Reinsberger C, Meyer T
Summary: The purpose was to identify risk situations promoting head injuries in professional male football (soccer) and to investigate the impact of a rule change in 2006 punishing elbow-head contacts. Professional football players of the first male German Bundesliga participated in this study.  Observational criteria of head impacts on video recordings (players' actions preceding head injuries, foul play-referee's decision and assessment of rater, ball possession, on-pitch medical treatment, and consequences of head impact). Three hundred thirty-four head injuries were reported in kicker Sportmagazin corresponding to an incidence rate of 2.25 (95% confidence interval 2.01-2.51) per 1000 player match hours. The injured player predominantly jumped (60%), headed the ball (36%), or ran forwards (20%); the noninjured players mainly jumped (64%), headed the ball (27%), or raised the elbow to the head (23%). Free ball situations (2 players challenge for the ball) caused most of the head injuries (81%). The players' action "raising the elbow" during a head injury seemed to be lower after the rule change. Jumping for the ball with the intention of heading is the predominant action associated with head injury risk. Head injuries occur most often when players challenge for the ball in a header duel. As head injuries bear the potential risk of long-term health sequelae, the identification of situational circumstances is essential to develop preventative means in the future.


#8 Linear Acceleration in Direct Head Contact Across Impact Type, Player Position, and Playing Scenario in Collegiate Women's Soccer
Reference: J Athl Train. 2018 Jan 26. doi: 10.4085/1062-6050-90-17. [Epub ahead of print]
Authors: Caccese JB, Lamond LC, Buckley TA, Glutting J, Kaminski TW
Summary: Heading, an integral component of soccer, exposes athletes to a large number of head impacts over a career. The literature has begun to indicate that cumulative exposure may lead to long-term functional and psychological deficits. Quantifying an athlete's exposure over a season is a first step in understanding cumulative exposure. The objective was to measure the frequency and magnitude of direct head impacts in collegiate women's soccer across impact type, player position, and game or practice scenario. Twenty-three collegiate women's soccer athletes participated in this study. Athletes wore Smart Impact Monitor accelerometers during all games and practices Impacts were classified during visual, on-field monitoring of athletic events. All direct head impacts that exceeded the 10 g threshold were included in the final data analysis. The dependent variable was linear acceleration, and the fixed effects were (1) type of impact: clear, pass, shot, unintentional deflection, or head-to-head contact; (2) field position: goalkeeper, defense, forward, or midfielder; (3) playing scenario: game or practice. Shots (32.94 g ± 12.91 g, n = 38, P = .02) and clears (31.09 g ± 13.43 g, n = 101, P = .008) resulted in higher mean linear accelerations than passes (26.11 g ± 15.48 g, n = 451). Head-to-head impacts (51.26 g ± 36.61 g, n = 13, P < .001) and unintentional deflections (37.40 g ± 34.41 g, n = 26, P = .002) resulted in higher mean linear accelerations than purposeful headers (ie, shots, clears, and passes). No differences were seen in linear acceleration across player position or playing scenario. Nonheader impacts, including head-to-head impacts and unintentional deflections, resulted in higher mean linear accelerations than purposeful headers, including shots, clears, and passes, but occurred infrequently on the field. Therefore, these unanticipated impacts may not add substantially to an athlete's cumulative exposure, which is a function of both frequency and magnitude of impact.


#9 Preseason Maximal Aerobic Power in Professional Soccer Players Among Different Divisions
Reference: J Strength Cond Res. 2018 Feb;32(2):356-363. doi: 10.1519/JSC.0000000000001810.
Authors: Marcos MA, Koulla PM, Anthos ZI
Summary: The purpose of this study was to examine and compare the anthropometric, maximal oxygen uptake (V[Combining Dot Above]O2max), and positional differences of first division (D1) professional football players from players of second (D2) and third (D3) divisions in Cyprus football leagues. Four hundred twenty-one professional male football players participated in this study. All subjects underwent anthropometric and body composition evaluation. In addition, they performed an incremental cardiopulmonary exercise testing (CPET) on a treadmill for V[Combining Dot Above]O2max evaluation. The results were analyzed using 1-way analysis of variance, between subjects design revealing significant effects among the divisions. Tukey's honest significant difference (HSD) tests demonstrated that players from D1 scored significantly higher on V[Combining Dot Above]O2max and lasted significantly longer on the treadmill than participants of D2 and D3 (p ≤ 0.05). Similar findings were demonstrated when D2 was contrasted against D3 players. Goalkeepers, defenders, and forwards demonstrated significantly higher anthropometric measurements, whereas wingers and midfielders demonstrated significantly higher V[Combining Dot Above]O2max (p ≤ 0.05) than goalkeepers and defenders. The findings of this study clearly demonstrated that cardiovascular fitness, as determined by CPET, is an important fitness parameter that differentiates professional football players who play at a more advanced level. This could be attributed to the different seasonal schedules that allow for longer transition time for lower division players and thus favoring greater detraining effects. Emphasis should be given by fitness professionals on transition period training to minimize the detraining effects especially in lower divisions.


#10 Performance Differences Among Skilled Soccer Players of Different Playing Positions During Vertical Jumping and Landing
Reference: J Strength Cond Res. 2018 Feb;32(2):304-312. doi: 10.1519/JSC.0000000000002343.
Authors: Harry JR, Barker LA, James R, Dufek JS
Summary: Both jumping and landing performance of skilled soccer players is diminished when task demands are increased. However, it is unclear if performance changes are specific to players of certain playing positions. Therefore, we assessed jumping and landing performance among skilled soccer players of different playing positions. Twenty-five National Collegiate Athletic Association (NCAA) Division 1 male soccer players (179.5 ± 7.8 cm, 75.5 ± 7.1 kg, 19.7 ± 1.2 years) performed maximum effort vertical jump landings (VJLs), whereas vertical ground reaction force (vGRF) data were obtained. Participants were stratified into goalkeeping (GK), defensive (DEF), midfield (MID), and attacking (ATT) group according to their primary playing position. One-way analyses of variance (α = 0.05) and effect sizes (ESs; large ≥ 0.80) were used to compare differences among groups. The jumping phase variables evaluated were jump height, unloading and amortization vGRF magnitudes, eccentric rate of force development, and the reactive strength index. Landing phase variables included the peak vGRF magnitude, vGRF loading rate, vGRF attenuation rate, and landing time. No statistically significant differences were detected for any jumping or landing variable (p ≥ 0.05). However, a number of large magnitude differences were detected during landing after ES calculations. Specifically, greater peak vGRF magnitudes were detected in DEF vs. both MID (ES = 1.08) and ATT (ES = 0.93), a greater vGRF loading rate occurred in DEF vs. MID (ES = 0.93), and a greater vGRF attenuation rate occurred in DEF vs. both MID (ES = 1.00) and AT (ES = 0.80). It is concluded that highly skilled soccer players possess position-specific abilities with respect to the landing phase of VJL. Skilled soccer players might experience enhanced training outcomes after VJL training regimens tailored to the specific demands of their primary playing position.


#11 Importance of Speed and Power in Elite Youth Soccer Depends on Maturation Status
Reference: J Strength Cond Res. 2018 Feb;32(2):297-303. doi: 10.1519/JSC.0000000000002367.
Authors: Murtagh CF, Brownlee TE, OʼBoyle A, Morgans R, Drust B, Erskine RM
Summary: Importance of speed and power in elite youth soccer depends on maturation status. J Strength Cond Res 32(2): 297-303, 2018-Maturation status is a confounding factor when identifying talent in elite youth soccer players (ESP). By comparing performance of ESP and control participants (CON) matched for maturation status, the aims of our study were to establish the importance of acceleration, sprint, horizontal-forward jump, and vertical jump capabilities for determining elite soccer playing status at different stages of maturation. Elite youth soccer players (n = 213; age, 14.0 ± 3.5 years) and CON (n = 113; age, 15.0 ± 4.4 years) were grouped using years from/to predicted peak height velocity (PHV) to determine maturation status (ESP: pre-PHV, n = 100; mid-PHV, n = 25; post-PHV, n = 88; CON: pre-PHV, n = 44; mid-PHV, n = 15; post-PHV, n = 54). Participants performed 3 reps of 10- and 20-m sprint, bilateral vertical countermovement jump (BV CMJ), and bilateral horizontal-forward CMJ (BH CMJ). Elite youth soccer players demonstrated faster 10-m (p < 0.001) and 20-m sprint (p < 0.001) performance than CON at all stages of maturation. Mid-PHV and post-PHV ESP achieved greater BV CMJ height (p < 0.001) and BH CMJ distance (ESP vs. CON; mid-PHV: 164.32 ± 12.75 vs. 136.53 ± 21.96 cm; post-PHV: 197.57 ± 17.05 vs. 168.06 ± 18.50 cm; p < 0.001) compared with CON, but there was no difference in BV or BH CMJ between pre-PHV ESP and CON. Although 10 and 20 m and sprint performance may be determinants of elite soccer playing status at all stages of maturation, horizontal-forward and vertical jumping capabilities only discriminate ESP from CON participants at mid- and post-PHV. Our data therefore suggest that soccer talent identification protocols should include sprint, but not jump assessments in pre-PHV players.


#12 Direct player observation is needed to accurately quantify heading frequency in youth soccer
Reference: Res Sports Med. 2018 Jan 24:1-8. doi: 10.1080/15438627.2018.1431534. [Epub ahead of print]
Authors: Harriss A, Walton DM, Dickey JP
Summary: In soccer, heading may be related to subsequent neurological impairment. Accurate measures of heading exposure are therefore important. This study evaluated whether 12 female youth players accurately recalled their average number of headers over an entire soccer season (20 games total). Their self-reported average number of headers per game was multiplied by the number of games that they participated in, and were compared to actual number of headers extracted from game video. All players overestimated the number of headers compared to game video. Linear regression analysis indicated that self-reported headers overestimated the number of headers by 51%. While self-reports are a convenient way to estimate heading behaviour, they do not accurately represent the number of headers that players perform. Self-reports of heading exposure should be interpreted with caution.


#13 Dietary habits and energy balance in an under 21 male international soccer team
Reference: Res Sports Med. 2018 Jan 25:1-10. doi: 10.1080/15438627.2018.1431537. [Epub ahead of print]
Authors: Caruana Bonnici D, Akubat I, Greig M, Sparks A, Mc Naughton LR
Summary: Soccer presents a metabolic challenge which is not necessarily matched by players' habitual dietary intake. To examine the effects of a bespoke diet, 22 players completed the Ball Sport Endurance and Sprint Test (BEAST90mod) protocol, followed by 4 days of regulated nutritional intake. The diet consisted of 10 g∙kg-1 body mass (BM) and 1.7 g∙kg-1 BM of carbohydrate and protein, respectively. On day 5, players followed a prematch nutritional strategy of 7 g∙kg-1 BM of carbohydrate and 1 g∙kg-1 BM of protein divided into three meals and then repeated the BEAST90mod. The players' pre-intervention intake consisted of 49 ± 7.1% or 3.5 g ± 1.0 g∙kg-1 BM for carbohydrate and 19 ± 3.8% of total daily energy intake or 1.3 g ± 0.5 g∙kg-1 BM for protein. Following the tailor-made dietary intervention, players ran an additional 887 ± 233 m (8.1%; d = 2.4). An acute dietary intervention provided a positive effect on a valid simulated soccer match play test.


American Football
#1 Fatal Exertional Heat Stroke and American Football Players: The Need for Regional Heat-Safety Guidelines
Reference: J Athl Train. 2018 Jan 13. doi: 10.4085/1062-6050-445-16. [Epub ahead of print]
Authors: Grundstein AJ, Hosokawa Y, Casa DJ
Summary: Weather-based activity modification in athletics is an important way to minimize heat illnesses. However, many commonly used heat-safety guidelines include a uniform set of heat-stress thresholds that do not account for geographic differences in acclimatization. The purpose was to determine if heat-related fatalities among American football players occurred on days with unusually stressful weather conditions based on the local climate and to assess the need for regional heat-safety guidelines. Incidents of fatal exertional heat stroke (EHS) in American football players were obtained from the National Center for Catastrophic Sport Injury Research 5 and the Korey Stringer Institute. Sixty-one American football players at all levels of competition with fatal EHSs from 1980 to 2014. We used the wet-bulb globe temperature (WBGT) and a z-score WBGT standardized to local climate conditions from 1991 to 2010 to assess the absolute and relative magnitudes of heat stress, respectively. We observed a poleward decrease in exposure WBGTs during fatal EHSs. In milder climates, 80% of cases occurred at above-average WBGTs, and 50% occurred at WBGTs greater than 1 standard deviation from the long-term mean; however, in hotter climates, half of the cases occurred at near-average or below-average WBGTs. The combination of lower exposure WBGTs and frequent extreme climatic values in milder climates during fatal EHSs indicates the need for regional activity-modification guidelines with lower, climatically appropriate weather-based thresholds. Established activity-modification guidelines, such as those from the American College of Sports Medicine, work well in the hotter climates, such as the southern United States, where hot and humid weather conditions are common.


#2 Balance Regularity Among Former High School Football Players With or Without a History of Concussion
Reference: J Athl Train. 2018 Jan 13. doi: 10.4085/1062-6050-326-16. [Epub ahead of print]
Authors: Schmidt JD, Terry DP, Ko J, Newell KM, Miller LS
Summary: Subclinical postural-control changes may persist beyond the point when athletes are considered clinically recovered postconcussion. The purpose was to compare postural-control performance between former high school football players with or without a history of concussion using linear and nonlinear metrics. A total of 11 former high school football players (age range, 45-60 years) with 2 or more concussions and 11 age- and height-matched former high school football players without a history of concussion. No participant had college or professional football experience. Participants completed the Sensory Organization Test. We compared postural control (linear: equilibrium scores; nonlinear: sample and multiscale entropy) between groups using a 2 × 3 analysis of variance across conditions 4 to 6 (4: eyes open, sway-referenced platform; 5: eyes closed, sway-referenced platform; 6: eyes open, sway-referenced surround and platform). We observed a group-by-condition interaction effect for medial-lateral sample entropy ( F2,40 = 3.26, P = .049, ηp2 = 0.140). Participants with a history of concussion presented with lower medial-lateral sample entropy values (0.90 ± 0.41) for condition 5 than participants without a history of concussion (1.30 ± 0.35; mean difference = -0.40; 95% confidence interval [CI] = -0.74, -0.06; t20 = -2.48, P = .02), but conditions 4 (mean difference = -0.11; 95% CI: -0.37, 0.15; t20 = -0.86, P = .40) and 6 (mean difference = -0.25; 95% CI: -0.55, 0.06; t20 = -1.66, P = .11) did not differ between groups. Postconcussion deficits, detected using nonlinear metrics, may persist long after injury resolution. Subclinical concussion deficits may persist for years beyond clinical concussion recovery.

 

Tue

27

Feb

2018

Football is...(#56)

Floaters in SSG...

Mon

26

Feb

2018

Latest research in football - week 4 - 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 Relative Age Effect on Soccer Players in Formative Stages with Different Sport Expertise Levels
Reference: J Hum Kinet. 2017 Dec 28;60:167-173. doi: 10.1515/hukin-2017-0100. eCollection 2017 Dec.
Authors: Praxedes A, Moreno A, Garcia-Gonzalez L, Pizarro D, Del Villar F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765797/pdf/hukin-60-167.pdf
Summary: The Relative Age Effect (RAE) in sport has been targeted by many research studies. The objective of this study was to analyze, in amateur clubs, the RAE of soccer players, according to the sport expertise level of the team (e.g., A, B, C and subsequent) that they belong to within the same game category. 1,098 soccer players in formative stages took part in the study, with ages varying between 6 and 18 years old (U8 to U19 categories). All of them were members of 4 Spanish federated clubs. The birth dates were classified into 4 quartiles (Q1 = Jan-Mar; Q2 = Apr-Jun; Q3 = Jul-Sept; Q4 = Oct-Dec)according to the team they belonged to. The results obtained in the chi-squared test and d value (effect size) revealed the existence of RAE in the teams with the highest expertise level, "A" (X2 = 15.342, p = .002, d = 0.4473) and "B" (X2 = 10.905, p = .012, d = 0.3657). However, in the lower level teams, "C and subsequent", this effect was not observed. Present findings show that players born during the first months of the year tend to be selected to play in teams with a higher sport expertise level of each category, due to their physical maturity. Consequently, this causes differences in terms of the experience they accumulate and the motivation that this creates in these players.


#2 Physical Performance and Anthropometric Characteristics of Male South African University Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:153-158. doi: 10.1515/hukin-2017-0098. eCollection 2017 Dec.
Authors: Kubayi A, Paul Y, Mahlangu P, Toriola A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765795/pdf/hukin-60-153.pdf
Summary: Soccer is the most popular sport worldwide. Despite its global acclaim, scientific studies of soccer have tended to focus on tactics and techniques, thereby neglecting the physical and physiological profile of the players. Therefore, the purpose of this study was to examine physical and anthropometric characteristics of male South African university soccer players. Twenty-seven male soccer players aged 19 to 24 (mean age: 22.1 years; s = 1.5 years) volunteered to participate in the study. The results showed that goalkeepers (77.5 ± 9.7 kg) and defenders (68.2 ± 6.5 kg) were the heaviest compared to players in other playing positions. The goalkeepers also had the highest percentage of body fat (11.3 ± 2.3%), in contrast to midfielders who had the lowest body fat content (9.1 ± 0.9%). With regard to flexibility, defenders (45.1 ± 4.9 cm) and midfielders (45.9 ± 5.4 cm) performed better than goalkeepers (37.1 ± 4.3 cm) and strikers (40.1 ± 3.4 cm). Midfielders (57.2 ± 3.1 ml1·kg-1·min1) and defenders (56.1 ± 5.1 ml1·kg-1·min1) had significantly higher values of maximal oxygen uptake (VO2max) than goalkeepers (47.9 ± 0.2 ml-1·kg-1·min-1) and strikers (49.8 ± 6.2 ml-1·kg-1·min-1). No significant (p > 0.05) differences were observed for all other variables, with the exception of body height, body mass, and VO2max. It was therefore concluded that sports scientists and coaches should tailor conditioning programmes in soccer according to players' positions in view of the implications for successful performance.


#3 Effects of Passive and Active Rest on Physiological Responses and Time Motion Characteristics in Different Small Sided Soccer Games
Reference: J Hum Kinet. 2017 Dec 28;60:123-132. doi: 10.1515/hukin-2017-0095. eCollection 2017 Dec.
Authors: Arslan E, Alemdaroglu U, Koklu Y, Hazir T, Muniroglu S, Karakoc B
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765792/pdf/hukin-60-123.pdf
Summary: The purpose of this study was to investigate the effects of resting regimes on physiological responses and time motion characteristics between bouts during small sided games (SSGs) in young soccer players. Sixteen players (average age 16.87 ± 0.34 years; body height 176.69 ± 3.21 cm; body mass 62.40 ± 2.59 kg; training experience 3.75 ± 0.44 years) performed four bouts 2-a-side, 3-a-side and 4-a-side games with three minutes active (SSGar: Running at 70% of HRmax) and passive (SSGpr) rest between bouts at two-day intervals. The heart rate (HR) along with total distance covered in different speed zones - walking (W, 0-6.9 km·h-1), low-intensity running (LIR, 7.0-12.9 km·h-1), moderate-intensity running (MIR, 13.0-17.9 km·h-1) and high-intensity running (HIR, >18km·h-1), were monitored during all SSGs, whereas the rating of perceived exertion (RPE, CR-20) and venous blood lactate (La-) were determined at the end of the last bout of each SSG. The results demonstrated that all SSGpr elicited significantly higher physiological responses compared to SSGar in terms of the RPE and La- (p < 0.05). In addition, 2-a-side SSGpr induced significantly lower %HRmax responses and total distance covered than 2-a-side SSGar (p < 0.05). Moreover, the distance covered at HIR was significantly higher in 4-a-side SSGar than 4-side SSGpr. The results of this study indicate that both SSGs with passive and active rest can be used for soccer specific aerobic endurance training. Furthermore, all SSGs with active recovery should be performed in order to increase players and teams' performance capacity for subsequent bouts.


#4 Multivariate Profiles of Selected versus Non-Selected Elite Youth Brazilian Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:113-121. doi: 10.1515/hukin-2017-0094. eCollection 2017 Dec.
Authors: Aquino R, Alves IS, Padilha MB, Casanova F, Puggina EF, Maia J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765791/pdf/hukin-60-113.pdf
Summary: This study determined whether a multivariate profile more effectively discriminated selected than non-selected elite youth Brazilian soccer players. This examination was carried out on 66 youth soccer players (selected, n = 28, mean age 16.3 ± 0.1; non-selected, n = 38, mean age 16.7 ± 0.4) using objective instruments. Multivariate profiles were assessed through anthropometric characteristics, biological maturation, tactical-technical skills, and motor performance. The Student's t-test identified that selected players exhibited significantly higher values for height (t = 2.331, p = 0.02), lean body mass (t = 2.441, p = 0.01), and maturity offset (t = 4.559, p < 0.001), as well as performed better in declarative tactical knowledge (t = 10.484, p < 0.001), shooting (t = 2.188, p = 0.03), dribbling (t = 5.914, p < 0.001), speed - 30 m (t = 8.304, p < 0.001), countermovement jump (t = 2.718, p = 0.008), and peak power tests (t = 2.454, p = 0.01). Forward stepwise discriminant function analysis showed that declarative tactical knowledge, running speed -30 m, maturity offset, dribbling, height, and peak power correctly classified 97% of the selected players. These findings may have implications for a highly efficient selection process with objective measures of youth players in soccer clubs.


#5 High-Intensity Small-Sided Games versus Repeated Sprint Training in Junior Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:101-111. doi: 10.1515/hukin-2017-0104. eCollection 2017 Dec.
Authors: Eniseler N, Şahan C, Ozcan I, Dinler K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765790/pdf/hukin-60-101.pdf
Summary: The aim of this study was to compare the effects of high-intensity small-sided games training (SSGT) versus repeated-sprint training (RST) on repeated-sprint ability (RSA), soccer specific endurance performance and short passing ability among junior soccer players. The junior soccer players were recruited from of a professional team (age 16.9 ± 1.1 years). The tests included the repeated-shuttle-sprint ability test (RSSAT), Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and Loughborough Soccer Passing Test (LSPT). Nineteen participants were randomly assigned to either the small-sided games training (SSGTG) (n = 10) or repeated-sprint training group (RSTG) (n = 9). Small-sided games or repeated-sprint training were added to the regular training sessions for two days of the regular practice week. The Wilcoxon signed-rank and Mann-Whitney U tests were used to examine differences in groups and training effects. A time x training group effect was found in the improvement of short-passing ability for the smallsided games training group which showed significantly better scores than the repeated-sprint training group (p ≤ 0.05). Both groups showed similar improvements in RSAdecrement (p < 0.05). Only the repeated-sprint training group improved in the Yo-Yo IR1 (p < 0.05). This study clearly shows that high-intensity small-sided games training can be used as an effective training mode to enhance both repeated sprint ability and short-passing ability.


#6 Association between Match Activity Variables, Measures of Fatigue and Neuromuscular Performance Capacity Following Elite Competitive Soccer Matches
Reference: J Hum Kinet. 2017 Dec 28;60:93-99. doi: 10.1515/hukin-2017-0093. eCollection 2017 Dec.
Authors: Varley I, Lewin R, Needham R, Thorpe RT, Burbeary R
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765789/pdf/hukin-60-093.pdf
Summary: The aim of the study was to assess the relationships between match activity variables, subsequent fatigue and neuromuscular performance capacity in elite soccer players. Subjects (n = 10) were professional soccer players participating in the English Championships. Match activity variables and markers of fatigue status were measured before and following two matches. Creatine kinase (CK) and muscle soreness were measured at baseline, immediately following, as well as 40 and 64 h post-match. Countermovement jump performance and perceived ratings of wellness were measured at baseline, then 40 and 64 h post-match. Relationships were shown between CK and the total number of accelerations and decelerations immediately (r = 0.63; large), 40 h (r = 0.45; moderate) and 64 h post-match (r = 0.35; moderate) (p < 0.05). Relationships between CK and total sprint distance (r = 0.39; moderate) and the number of sprints (r = 0.35; moderate) 40 h post-match (p < 0.05) were observed. Furthermore, relationships were shown between the perceived rating of wellness and number of accelerations 40 (r = 0.52; large) and 64 h (r = 0.40; moderate) post-match, sprint distance 40 h post-match (r = 0.40; moderate) and the total number of sprints 40 h post-match (r = 0.51; large) (p < 0.05). The quantification of match activity variables, particularly the total number of accelerations and decelerations and the number of sprints, provides insights into the fatigue status in elite soccer players 40 and 64 h post-match.


#7 Physiological Demands, Morphological Characteristics, Physical Abilities and Injuries of Female Soccer Players
Reference: J Hum Kinet. 2017 Dec 28;60:77-83. doi: 10.1515/hukin-2017-0091. eCollection 2017 Dec.
Authors: Milanovic Z, Sporis G, James N, Trajkovic N, Ignjatovic A, Sarmento H, Trecroci A, Mendes BMB
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765787/pdf/hukin-60-077.pdf
Summary: The popularity of female soccer is increasing as well as the number of females playing soccer. Similarly, over the last twenty or so years, research in soccer has increased significantly, but a large disparity exists in the volume of studies involving male and female players. As a consequence of this, female players remain less well understood compared to males. The purpose of the present narrative review was to describe morphological characteristics, physiological demands, physical abilities and injuries in female soccer players. Physiological demands are similar between men's and women's soccer, but competitive women's matches were characterized by nearly 33% less distance covered, although at higher intensity levels (maximum speeds greater than 15 km/h) than typically found in the men's game. Sub-elite female players also tended to run less at higher intensity levels at the end of both halves in comparison with elite female players. High intensity running is an important factor of success in soccer since many critical moments of the game occur under this condition. The ability to rapidly change direction also determined elite, sub-elite and amateur levels. The implementation of functional training, which focused on soccer-specific drills and plyometric exercises, to improve explosive power, may improve conditioning in female soccer players as well as decrease the risk of injuries which was 3-8 times higher in females compared to males. This review presents an in-depth overview of the most influential factors for determining success in female soccer.


#8 Effects of Plyometric and Resistance Training on Muscle Strength, Explosiveness and Neuromuscular Function in Young Adolescent Soccer Players
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002428. [Epub ahead of print]
Authors: McKinlay BJ, Wallace P, Dotan R, Long D, Tokuno C, Gabriel D, Falk B
Summary: This study examined the effect of 8-weeks of free-weight-resistance (RT) and plyometric (PLYO) training on maximal strength, explosiveness and jump performance compared with no added training (CON), in young male soccer players. Forty-one 11[FIGURE DASH]13-year-old soccer players were divided into three groups (RT, PLYO, CON). All participants completed isometric and dynamic (240°/s) knee extensions pre- and post-training. Peak torque (pT), peak rate of torque development (pRTD), electromechanical-delay (EMD), rate of muscle activation (Q50), m. vastus-lateralis thickness (VLT), and jump performance were examined. pT, pRTD and jump performance significantly improved in both training groups. Training resulted in significant (p<0.05) increases in isometric pT (23.4 vs. 15.8%) and pRTD (15.0 vs. 17.6%), in RT and PLYO, respectively. During dynamic contractions, training resulted in significant increases in pT (12.4 and 10.8% in RT and PLYO, respectively), but not pRTD. Jump performance increased in both training groups (RT=10.0%, PLYO=16.2%), with only PLYO significantly different from CON. Training resulted in significant increases in VLT (RT=6.7%. PLYO=8.1%). There were no significant EMD changes. In conclusion, 8-week free-weight resistance and plyometric training resulted in significant improvements in muscle strength and jump performance. Training resulted in similar muscle hypertrophy in the two training modes, with no clear differences in muscle performance. Plyometric training was more effective in improving jump performance, while free-weight resistance training was more advantageous in improving peak torque, where the stretch reflex was not involved.


#9 Comparison of step-by-step kinematics in repeated 30m sprints in female soccer players
Reference: J Strength Cond Res. 2018 Jan 4. doi: 10.1519/JSC.0000000000002429. [Epub ahead of print]
Authors: van den Tillaar R
Summary: The aim of this study was to compare kinematics in repeated 30m sprints in female soccer players. Seventeen subjects performed seven 30m sprints every 30s in one session. Kinematics were measured with an infrared contact mat and laser gun, and running times with an electronic timing device. The main findings were that sprint times increased in the repeated sprint ability test. The main changes in kinematics during the repeated sprint ability test were increased contact time and decreased step frequency, while no change in step length was observed. The step velocity increased in almost each step until the 14, which occurred around 22m. After this, the velocity was stable until the last step, when it decreased. This increase in step velocity was mainly caused by the increased step length and decreased contact times. It was concluded that the fatigue induced in repeated 30m sprints in female soccer players resulted in decreased step frequency and increased contact time. Employing this approach in combination with a laser gun and infrared mat for 30m makes it very easy to analyse running kinematics in repeated sprints in training. This extra information gives the athlete, coach and sports scientist the opportunity to give more detailed feedback and help to target these changes in kinematics better to enhance repeated sprint performance.


#10 Mild jugular compression collar ameliorated changes in brain activation of working memory after one soccer season in female high school athletes
Reference: J Neurotrauma. 2018 Jan 15. doi: 10.1089/neu.2017.5262. [Epub ahead of print]
Authors: Yuan W, Dudley J, Barber-Foss K, Ellis JD, Thomas S, Galloway RT, DiCesare C, Leach J, Adams J, Maloney T, Gadd B, Smith D, Epstein J, Grooms DR, Logan K, Howell DR, Altaye M, Myer GD
Summary: Recent neuroimaging studies have suggested that repetitive sub-concussive head impacts, even after only one sport season, may lead to pre- to post-season structural and functional alterations in male high school football athletes. However, data on female atheletes is limited. In the current investigation, we aimed to (1) assess the longitudinal pre- to post-season changes in fMRI of working memory and working memory performance, (2) quantify the association between the pre- to post-season change in fMRI of working memory and the exposure to head impact and working memory performance, and (3) assess whether wearing a neck collar designed to reduce intracranial slosh via mild compression of the jugular veins can ameliorate the changes in fMRI brain activation observed in the non-collar group after a full soccer season. A total of 48 female high school soccer athletes (age range: 14.00 - 17.97 years) were included in the study. These athletes were assigned to the non-collar group (n=21) or to the collar group (n=27). All athletes undewent MRI at both pre-season and post-season. In each session, a fMRI verbal N-Back task was used to engage working memory. A significant pre- to post-season increase in fMRI BOLD signal was demonstrated when performing the N-back working memory task in the non-collar group but not in the collar group, despite the comparable exposure of head impacts during the season between the two groups. The collar group demonstrated significantly smaller pre- to post-season change in fMRI BOLD signal than the non-collar group, suggesting a potential protective effect from the collar device. Significant correlations were also found between the pre- to post-season increase in fMRI brain activation and the decrease in task accuracy in the non-collar group, indicating an association between the compensatory mechanism in underlying neurophysiology and the alteration in the behavioral outcomes.


#11 Effects of resisted sprint training on sprinting ability and change of direction speed in professional soccer players
Reference: J Sports Sci. 2018 Jan 15:1-7. doi: 10.1080/02640414.2018.1426346. [Epub ahead of print]
Authors: Gil S, Barroso R, Crivoi do Carmo E, Loturco I, Kobal R, Tricoli V, Ugrinowitsch C, Roschel H
Summary: Resisted sprint training consists of performing overloaded sprints, which may produce greater effects than traditional sprint training. We compared a resisted sprint training with overload control versus an unresisted sprint training program on performance in soccer players. Eighteen elite athletes were randomly assigned to resisted (RST) or unresisted sprint training protocol (UR). Before and after a 6-week training period, sprinting ability, change of direction speed (COD), vertical jumps (SJ and CMJ), mean power (MP) and mean propulsive power (MPP) at distinct loads were assessed. Both groups improved sprinting ability at all distances evaluated (5m: UR = 8%, RST = 7%; 10m: UR = 5%, RST = 5%; 15m: UR = 4%, RST = 4%; 20m: UR = 3%, RST = 3%; 25m: UR = 2%, RST = 3%;), COD (UR = 6%; RST = 6%), SJ (UR = 15%; RST = 13%) and CMJ (UR = 15%; RST = 15%). Additionally, both groups increased MP and MPP at all loads evaluated. The between-group magnitude-based inference analysis demonstrated comparable improvement ("trivial" effect) in all variables tested. Finally, our findings support the effectiveness of a short-term training program involving squat jump exercise plus sprinting exercises to improve the performance of soccer players.


#12 Does inside passing contribute to the high incidence of groin injuries in soccer? A biomechanical analysis
Reference: J Sports Sci. 2018 Jan 15:1-9. doi: 10.1080/02640414.2017.1423193. [Epub ahead of print]
Authors: Dupre T, Funken J, Muller R, Mortensen KRL, Lysdal FG, Braun M, Krahl H, Potthast W
Summary: Groin injuries are common in soccer and often cause time-loss from training. While groin injuries have been linked to full effort kicking, the role of inside passing is unclear. Therefore, the purpose of this study was to investigate hip joint kinematics and muscle force, stress and contraction velocity for adductor longus and gracilis during inside passing. 3D kinematics of ten soccer players (23.4 yrs; 77.5 kg; 1.81 m) were captured with a motion capture system inside a Footbonaut. Muscle force and contraction velocity were determined with AnyBody Modelling System. Gracilis muscle forces were 9% lower compared to adductor longus (p = 0.005), but muscle stress was 183% higher in gracilis (p = 0.005). Contraction velocity reveals eccentric contraction of gracilis in the last quarter of the swing phase. Considering the combination of eccentric contraction, high muscle stress and the repetitive nature of inside passing, gracilis accumulates high loads in matches and training. These results indicate that the high incidence of groin injuries in soccer could be linked to isolated pass training. Practitioners need to be aware of the risk and refrain from sudden increases in the amount of pass training. This gives the musculoskeletal system time to adapt and might avoid career threatening injuries.

 



American Football
#1 Making Football Safer: Assessing the current NFL policy on the type of helmets allowed on the playing field
Reference: J Neurotrauma. 2018 Feb 8. doi: 10.1089/neu.2017.5446. [Epub ahead of print]
Authors: Colello R D.Phil., Colello IA, AbdelHameid D, Cresswell KG, Merchant R, Beckett E
Summary: In an effort to reduce concussions in football, a helmet safety-rating system was developed in 2011 that rated helmets based on their ability to reduce g-forces experienced by the head across a range of impact forces measured on the playing field. Although this was considered a major step in making the game safer, the NFL continues to allow players the right to choose what helmet to wear during play. This prompted us to ask: what helmets do NFL players wear and does this helmet policy make the game safer? Accordingly, we identified the helmets worn by nearly 1000 players on Weeks 13 and 1 of the 2015-2016 and 2016-2017 seasons, respectively. Using stop-motion footage, we found that players wore a wide range of helmets with varying safety ratings influenced, in part, by the player's position and age. Moreover, players wearing lower safety-rated helmets were more likely to receive a concussion than those wearing higher safety-rated helmets. Interestingly, many players suffering a concussion in 2015 did not switch to a higher safety-rated helmet in 2016. Using a helmet-to-helmet impactor, we found that the g-forces experienced in the highest safety-rated helmets were roughly 30% less than that for the lowest safety-rated helmets. These results suggest that the current NFL helmet policy puts players at increased risk of receiving a concussion as many players are wearing low safety-rated helmets, which transmits more energy to the brain than higher-safety-rated helmets, following collision. Thus, the NFL should mandate that players only wear helmets that receive the highest safety rating. This policy change would likely represent the simplest and most straightforward way to reduce concussions in football.

 



Gaelic Football
#1 An Acceleration Profile of Elite Gaelic Football with Special Reference to Position of Play
Reference: J Strength Cond Res. 2018 Feb 1. doi: 10.1519/JSC.0000000000002479. [Epub ahead of print]
Authors: Ryan M, Malone S, Donnellan A, Collins K
Summary: The current study aimed to characterize the positional match-play demands of elite Gaelic football players with special reference to acceleration utilizing predetermined 5- min periods (epochs). Thirty-five male Gaelic players (Mean ± SD, age: 24 ± 6 years; height: 180 ± 7 cm; mass: 81 ± 7 kg) across five playing positions (full-back, half-back, midfield, half-forward, full-forward) were monitored during the investigation. Player movement was recorded during nineteen matches using 4-Hz global positioning system technology (GPS; VXSport, New Zealand) resulting in 154 player observations. GPS was used to record total distance (m), high-speed running (HSR; m; ≥17 kmh), very high-speed running distance, (VHSR; m; ≥22 kmh), the number of accelerations (n), duration of accelerations (s), peak acceleration (m), and distance of accelerations (m). Acceleration profiles were position dependent with midfielders found to have a high accumulation of acceleration movements when compared to all other positions (p < 0.05). Declines of -2% to -32% for acceleration distance (m) depending on positional line of play were observed during match-play. Less HSR and VHSR, was performed by the full-back line (HSR; -39%, VHSR; -36%) and full-forward line (-35%; -29%) when compared to half-back, midfielders and half-forwards (p=0.01, d = 1.35 to 1.77). Similar trends were reported for peak acceleration distance (p=0.01, d = 1.15 to 1.93). The current investigation provides a greater understanding of temporal differences in acceleration profiles of playing position. We show that half-back, midfield and half-forwards have the highest acceleration movements these data can assist coaches in appropriately preparing players for the required acceleration distances required during match-play.


#2 The Pre-Competition Macronutrient Intake of Elite Gaelic Football Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Feb 6:1-20. doi: 10.1123/ijsnem.2017-0292. [Epub ahead of print]
Authors: Cassidy C, Collins K, Shortall M
Summary: Competition related dietary intake has not yet been investigated in Gaelic football. The present study examined the pre-competition macronutrient intake of elite male Gaelic football players. Forty players from two teams completed a food diary on the two days preceding competition (DAY-1 & DAY-2) and on match date pre-match (MATCH-DAY). Carbohydrate intake was significantly greater on DAY-2 compared to DAY-1, for both absolute [295 ± 98 vs. 318 ± 77 g] (p = 0.048; -23.6 g [-47.3 to 0.2]; Cohen's d = 0.27) and relative intake [3.4 ± 1.1 vs. 3.7 ± 1.0 g.kg-1] (p = 0.027; -0.3 g.kg-1 [-0.6 to -0.03]; Cohen's d = 0.32). The number of players in accordance with and not in accordance with the guidelines for carbohydrate intake on DAY-2 was significantly different to an expected frequency distribution [χ2 (1) = 32.400; p = <0.001; ϕ = 0.9] with a greater number of players not meeting the guidelines [observed N = 2 vs. 38]. The number of players in accordance with and not in accordance with the recommendations for carbohydrate intake on MATCH-DAY was significantly different to an expected frequency distribution [χ2 (1) = 8.100; p = 0.004; ϕ = 0.45] with a greater number of players meeting the guidelines [observed N = 29 vs. 11]. The major finding from the current investigation was that a significantly greater number of players did not meet carbohydrate intake guidelines on the day before competition. Individualised nutritional interventions are required in order to modify current pre-match dietary intake.

Fri

23

Feb

2018

Football is...(#55)

Cognition in football - some thoughts

Wed

07

Feb

2018

Latest research in football - week 3 - 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 Mixed Training Methods: Effects of Combining Resisted Sprints or Plyometrics with Optimum Power Loads on Sprint and Agility Performance in Professional Soccer Players
Reference: Front Physiol. 2017 Dec 12;8:1034. doi: 10.3389/fphys.2017.01034. eCollection 2017.
Authors: Loturco I, Kobal R, Kitamura K, Cal Abad CC, Faust B, Almeida L, Pereira LA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5732948/pdf/fphys-08-01034.pdf
Summary: The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.


#2 Time course of oxidative stress, inflammation and muscle damage markers for five days after a soccer match: effects of sex and playing position
Reference: J Strength Cond Res. 2018 Jan 3. doi: 10.1519/JSC.0000000000002436. [Epub ahead of print]
Authors: Souglis A, Bogdanis GC, Chryssanthopoulos C, Apostolidis N, Geladas ND
Summary: This study examined the influence of sex and playing position on the time-course of selected oxidative stress, inflammation and muscle damage markers following an official soccer match. Sixty professional soccer players (30 male and 30 female) were divided into three groups, according to their playing position: defenders, midfielders and attackers. Each group consisted of 10 male and 10 female players. Sixty healthy volunteers (30 males and 30 females) served as control. Blood samples were taken before and after the match and daily for five days after the match. Analysis of variance revealed different responses over time between sex and playing positions, as shown by the 3-way interaction, for creatine kinase (CK), protein carbonyls (PC), catalase, fibrinogen (FIB), uric acid (UA), lactate dehydrogenase (LDH), reduced glutathione, C-reactive protein and interleukin-6 (IL-6) (p < 0.01).Male players had higher values compared with females of the same playing position, for all oxidative, inflammatory and muscle damage indices (p<0.01). Also, in both sexes, midfielders had higher peaks in all indices compared with defenders (p < 0.05). Five days after the game CK and UA concentrations had not returned to pre-game levels in any exercise group, whereas PC were still elevated in male midfielders and attackers (p < 0.05).These results show that sex and playing position influence the time-course of selected oxidative stress, inflammation and muscle damage markers following an official soccer game. This information should be taken into account by practitioners for the design of training programs following match play.


#3 Comparison between traditional strength training and complex contrast training on soccer players
Reference: J Sports Med Phys Fitness. 2018 Jan 4. doi: 10.23736/S0022-4707.18.07934-3. [Epub ahead of print]
Authors: Spineti J, Figueiredo T, Willardson JM, Bastos de Oliveira V, Assis M, Fernandes DE Oliveira L, Miranda H, Machado de Ribeiro Reis V, Simao R
Summary: The purpose of this study was to compare traditional strength training (TST) versus and contrast training (CCT) on sprint, change of direction speed (COD) and squat jump (SJ) in young male soccer players. Twenty-two soccer players (age: 18.4 ± 0.4 years, body mass: 70.2 ± 9.1 kg, height: 179.9 ± 7.5 cm), were randomly assigned to one of two groups: TST (n=12) and CCT (n = 10). The study was conducted using a randomized experimental design over an eight- week period. The participants assigned to the CCT group performed high-power exercises paired with high-velocity exercises. The participants assigned to the TST group performed resistance exercises in a straight-set forma. During the study period, sprint tests for 5, 10, 20 and 30 m split times, COD and SJ were applied. A two-way ANOVA was applied, and the alpha level was p <0.05. The results demonstrated that the CCT regimen elicited significant within-group differences in 5 m sprint time (1.032 s to 0.997 s, pre- and post-intervention, respectively, effect size (ES) = -0.5, medium; p = 0.04), COD (5.963 s to 5.639 s, pre- and post-intervention, respectively, ES = -2.7, large; p<0.001) and SJ (30.9 cm to 34.4 cm, pre- and post-intervention, respectively, ES = 0.8, large; p<0.001). Conversely, the TST did not elicit significant within-group differences for any of the dependent variables. No differences were found between post-test time point. In conclusion, the CCT protocol could be used to improve sprint, in male soccer players.


#4 Differential Learning as a Key Training Approach to Improve Creative and Tactical Behavior in Soccer
Reference: Res Q Exerc Sport. 2018 Jan 19:1-14. doi: 10.1080/02701367.2017.1412063. [Epub ahead of print]
Authors: Santos S, Coutinho D, Goncalves B, Schollhorn W, Sampaio J, Leite N
Summary: The aim of this study was to identify the effects of a differential-learning program, embedded in small-sided games, on the creative and tactical behavior of youth soccer players. Forty players from under-13 (U13) and under-15 (U15) were allocated into control and experimental groups and were tested using a randomized pretest to posttest design using small-sided games situations. The experimental group participated in a 5-month differential-learning program embodied in small-sided games situations, while the control group participated in a typical small-sided games training program. In-game creativity was assessed through notational analyses of the creative components, and the players' positional data were used to compute tactical-derived variables. The findings suggested that differential learning facilitated the development of creative components, mainly concerning attempts (U13, small; U15, small), versatility (U13, moderate; U15, small), and originality (U13, unclear; U15, small) of players' actions. Likewise, the differential-learning approach provided a decrease in fails during the game in both experimental groups (moderate). Moreover, differential learning seemed to favor regularity in pitch-positioning behavior for the distance between players' dyads (U13, small; U15, small), the distance to the team target (U13, moderate; U15, small), and the distance to the opponent target (U13, moderate; U15, small). The differential-learning program stressed creative and positional behavior in both age groups with a distinct magnitude of effects, with the U13 players demonstrating higher improvements over the U15 players. Overall, these findings confirmed that the technical variability promoted by differential learning nurtures regularity of positioning behavior.


#5 The neuromuscular, biochemical, endocrine and mood responses to small-sided games training in professional soccer
Reference: J Strength Cond Res. 2018 Jan 17. doi: 10.1519/JSC.0000000000002424. [Epub ahead of print]
Authors: W S, An T, M W, M R, Mj J, Lp K
Summary: The 24h responses to small-sided games (SSG) soccer training were characterized. Professional soccer players (n=16) performed SSG's (4vs4 + goalkeepers; 6x7-min, 2-min inter-set recovery) with performance (peak-power output, PPO; jump height, JH), physiological (blood creatine kinase: CK, lactate; salivary testosterone, cortisol), and mood measures collected before (baseline), and after (immediately; 0h, +2h, +24h). For PPO and JH, possibly small-moderate reductions occurred at 0h (-1.1W·kg; ±0.9W·kg, -3.2cm; ±1.9cm, respectively), before returning to baseline at +2h (trivial) and declining thereafter (small-moderate effect) at +24h (-0.9W·kg; ±0.8W·kg, -2.5cm; ±1.2cm, respectively). Lactate increased at 0h (likely-large; +1.3mmol·L; ±0.5mmol·L), reduced at +2h (likely-small; -0.5mmol·L; ±0.2mmol·L), and returned to baseline at 24h (trivial). A very-likely small increase in CK occurred at 0h (+97u·L; ±28u·L), persisting for +24h (very-likely small; +94u·L; ±49u·L). Possibly-small increases in testosterone (+20pg·ml; ±29pg·ml) occurred at 0h, before likely-moderate declines at +2h (-61pg·ml; ±21pg·ml) returning to baseline at +24h (trivial). For cortisol, possibly-small decreases occurred at 0h (-0.09ug·dl; -±0.16ug·dl), before likely-large decreases at +2h (-0.39ug·dl; ±0.12ug·dl), which persisted for 24h (likely-small; -0.12ug·dl; ±0.11ug·dl). Mood was disturbed by SSG's at 0h (likely-moderate; +13.6AU, ±5.6AU) and +2h (likely-small; +7.9AU; ±5.0AU), before returning to baseline at +24h (trivial). The movement demands of SSG's result in a bimodal recovery pattern of neuromuscular function and perturbations in physiological responses and mood for up to 24h. Accordingly, when programming soccer training, SSG's should be periodized throughout the competitive week with submaximal technical/tactical activities.


#6 Effects of Contrast Strength vs. Plyometric Training on Lower Limb Explosive Performance, Ability to Change Direction and Neuromuscular Adaptation in Soccer Players
Reference: J Strength Cond Res. 2018 Jan 17. doi: 10.1519/JSC.0000000000002425. [Epub ahead of print]
Authors: Hammami M, Gaamouri N, Shephard RJ, Chelly MS
Summary: The aim was to compare the effects of two differing 8-week in-season strength training programs (contrast strength training [CST] vs. plyometric training [PT]) on selected performance tests (5 and 40m sprints, S 4 X 5 m change of direction test, squat (SJ) and countermovement (CMJ) jumps , leg peak power on a cycle ergometer force-velocity test, 1-repetition maximal (1-RM) half squat, and electromyographic [EMG] activity of the vastus lateralis, vastus medialis and rectus femoris muscles during vertical jump tests). Forty male soccer players (age = 15.8 ± 0.4 years; body mass = 58.8 ± 6.3 kg; body height = 1.74 ± 0.06 m; body fat = 10.5 ± 1.9 %) were divided between a contrast strength (CSG, n = 14), plyometric (PG, n = 14) and control groups (CG, n = 12). Both training programs enhanced sprint performance (p<0.001 in 5m; p≤0.05 in 40m) and change of direction test scores (p<0.001) relative to controls. PG and CSG increased SJ height relative to the CG, with a slightly greater response in CSG compared to PG (p≤0.05). The majority of CMJ scores increased significantly in both CSG and PG relative to the CG, with no inter-group differences in training response. The majority of force-velocity scores increased significantly in the CSG relative to PG and CG. The EMG parameters also increased in the CSG relative to both PG and CG. In summary, most measures of athletic performance in male soccer players were enhanced after CST and PT. However, the improvement of physical performance was better with eight weeks of CST than with PT. Thus, coaches should be encouraged to include CST as an element of in-season conditioning.


#7 Preseason Adductor Squeeze Strength in 303 Spanish Male Soccer Athletes: A Cross-sectional Study
Reference: Orthop J Sports Med. 2018 Jan 11;6(1):2325967117747275. doi: 10.1177/2325967117747275. eCollection 2018 Jan.
Authors: Esteve E, Rathleff MS, Vicens-Bordas J, Clausen MB, Holmich P, Sala L, Thorborg K
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5768277/pdf/10.1177_2325967117747275.pdf
Summary: Hip adductor muscle weakness and a history of groin injury both have been identified as strong risk factors for sustaining a new groin injury. Current groin pain and age have been associated with hip adductor strength. These factors could be related, but this has never been investigated. The purpose was to investigate whether soccer athletes with past-season groin pain and with different durations of past-season groin pain had lower preseason hip adductor squeeze strength compared with those without past-season groin pain. We also investigated whether differences in preseason hip adductor squeeze strength in relation to past-season groin pain and duration were influenced by current groin pain and age. In total, 303 male soccer athletes (mean age, 23 ± 4 years; mean weight, 74.0 ± 7.9 kg; mean height, 178.1 ± 6.3 cm) were included in this study. Self-reported data regarding current groin pain, past-season groin pain, and duration were collected. Hip adductor squeeze strength was obtained using 2 different reliable testing procedures: (1) the short-lever (resistance placed between the knees, feet at the examination bed, and 45° of hip flexion) and (2) the long-lever (resistance placed between the ankles and 0° of hip flexion) squeeze tests. There was no difference between those with (n = 123) and without (n = 180) past-season groin pain for hip adductor squeeze strength when adjusting for current groin pain and age. However, athletes with past-season groin pain lasting longer than 6 weeks (n = 27) showed 11.5% and 15.3% lower values on the short-lever (P = .006) and long-lever (P < .001) hip adductor squeeze strength tests, respectively, compared with those without past-season groin pain. Male soccer athletes with past-season groin pain lasting longer than 6 weeks are likely to begin the next season with a high-risk groin injury profile, including a history of groin pain and hip adduction weakness.


#8 Are Current Physical Match Performance Metrics in Elite Soccer Fit for Purpose or is the Adoption of an Integrated Approach Needed?
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-23. doi: 10.1123/ijspp.2017-0433. [Epub ahead of print]
Authors: Bradley PS, Ade JD
Summary: Time-motion analysis is a valuable data-collection technique used to quantify the physical match performance of elite soccer players. For over 40 years researchers have adopted a 'traditional' approach when evaluating match demands by simply reporting the distance covered or time spent along a motion continuum of walking through to sprinting. This methodology quantifies physical metrics in isolation without integrating other factors and this ultimately leads to a one-dimensional insight into match performance. Thus, this commentary proposes a novel 'integrated' approach that focuses on a sensitive physical metric such as high-intensity running but contextualizes this in relation to key tactical activities for each position and collectively for the team. In the example presented, the 'integrated' model clearly unveils the unique high-intensity profile that exists due to distinct tactical roles, rather than one-dimensional 'blind' distances produced by 'traditional' models. Intuitively this innovative concept may aid the coaches understanding of the physical performance in relation to the tactical roles and instructions given to the players. Additionally, it will enable practitioners to more effectively translate match metrics into training and testing protocols. This innovative model may well aid advances in other team sports that incorporate similar intermittent movements with tactical purpose. Evidence of the merits and application of this new concept are needed before the scientific community accepts this model as it may well add complexity to an area that conceivably needs simplicity.


#9 Effects of Late-Night Training on "Slow-Wave Sleep Episode" and Hour-by-Hour Derived Nocturnal Cardiac Autonomic Activity in Female Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-26. doi: 10.1123/ijspp.2017-0681. [Epub ahead of print]
Authors: Costa JA, Brito J, Nakamura FY, Oliveira EM, Rebelo AN
Summary: The purpose was to assess the sensitivity of nocturnal heart rate variability (HRV) monitoring methods to the effects of late-night soccer training sessions in female athletes. Eleven female soccer players competing in the 1st division of the Portuguese soccer league wore HR monitors during night-sleep throughout a one-week competitive in-season microcycle, after late-night training sessions (n = 3) and rest days (n = 3). HRV was analyzed through "slow-wave sleep episode" (SWSE; 10 min duration) and "hour-by-hour" (all the RR intervals recorded throughout the hours of sleep). Training load was quantified by session rating of perceived exertion (sRPE: 281.8 ± 117.9 to 369.0 ± 111.7 a.u.) and training impulse (TRIMP: 77.5 ± 36.5 to 110.8 ± 31.6 a.u.), added to subjective well-being ratings (Hopper index: 11.6 ± 4.4 to 12.8 ± 3.2 a.u.). These variables were compared between training and rest days using repeated measures ANOVA. The ln-transformed SWSE cardiac autonomic activity (lnRMSSD varying between 3.92 ± 0.57 and 4.20 ± 0.60 ms; ηp2 = 0.16 [0.01-0.26]), lnHF, lnLF, lnSD1 and lnSD2 and the non-transformed LF/HF were not different among night-training session days and resting days (P > 0.05). Considering the hour-by-hour method (lnRMSSD varying between 4.05 ± 0.35 and 4.33 ± 0.32 ms; ηp2 = 0.46 [0.26-0.52]), lnHF, lnLF, lnSD1 and lnSD2 and the non-transformed LF/HF were not different among night-training session days and resting days (P > 0.05). Late-night soccer training does not seem to affect nocturnal SWSE and "hour-by-hour" HRV indices in highly-trained athletes.


#10 Post-match Perceived Exertion, Feeling and Wellness in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2018 Jan 18:1-22. doi: 10.1123/ijspp.2017-0725. [Epub ahead of print]
Authors: Fessi MS, Moalla W
Summary: The aim of this study was to assess post-match perceived exertion, feeling and wellness according to the match outcome (winning, drawing or losing) in professional soccer players. Twelve outfield players were followed during 52 official matches where the outcomes (win, draw or lose) were noted. Following each match players completed both a 10-point scale rating of perceived exertion (RPE) and an 11-point scale rating of perceived feeling. Rating of perceived sleep quality, stress, fatigue and muscle soreness were collected separately on a 7-point scale the day following each match. Player RPE was higher by a very largely magnitude following a loss compared to a draw or a win and higher by a small magnitude after a draw compared to a win. Players felt more pleasure after a win compared to a draw or loss and more displeasure after a loss compared to draw. The players reported a largely and moderately better-perceived sleep quality, less stress and fatigue following a win compared to draw or a loss, and a moderately bad-perceived sleep quality, higher stress and fatigue following a draw compared to a loss. In contrast, only a trivial-small change was observed in perceived muscle soreness between all outcomes. Matches outcomes moderately to largely affect RPE, perceived feeling, sleep quality, stress and fatigue whereas perceived muscle soreness remains high regardless of the match outcome. However, winning a match decreases the strain and improves both pleasure and wellness in professional soccer players.

Wed

31

Jan

2018

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 The Demands of Amputee Soccer Impair Muscular Endurance and Power Indices But Not Match Physical Performance
Reference: Adapt Phys Activ Q. 2018 Jan 5:1-17. doi: 10.1123/apaq.2016-0147. [Epub ahead of print]
Authors: Simim MAM, da Mota GR, Marocolo M, da Silva BVC, de Mello MT, Bradley PS
Summary: We investigated the match demands (distances covered and acute physiological responses) of amputee soccer and its impact on muscular endurance and power. Measures such as heart rate, blood lactate concentration, subjective rating of perceived exertion, and time-motion characteristics were recorded in 16 Brazilian amputee soccer players during matches. Before and after matches, players completed a battery of tests: push-ups, countermovement vertical jump performance, and medicine ball throwing. Small differences were found between the first and second half for the distance covered in total and across various speed categories. Heart rate responses, blood lactate concentrations, and peak speed did not differ between halves, and all neuromuscular performance measures decreased after the match particularly after push-ups, although the rating of perceived exertion increased markedly compared with prematches. Although match physical performances were consistent across halves, the overall demands impaired test performance, especially for upper limb and closed kinetic chain exercise.


#2 Carbohydrates for Soccer: A Focus on Skilled Actions and Half-Time Practices
Reference: Nutrients. 2017 Dec 25;10(1). pii: E22. doi: 10.3390/nu10010022.
Authors: Hills SP, Russell M
Download link: www.mdpi.com/2072-6643/10/1/22/pdf
Summary: Carbohydrate consumption is synonymous with soccer performance due to the established effects on endogenous energy store preservation, and physical capacity maintenance. For performance-enhancement purposes, exogenous energy consumption (in the form of drinks, bars, gels and snacks) is recommended on match-day; specifically, before and during match-play. Akin to the demands of soccer, limited opportunities exist to consume carbohydrates outside of scheduled breaks in competition, such as at half-time. The link between cognitive function and blood glucose availability suggests that carbohydrates may influence decision-making and technical proficiency (e.g., soccer skills). However, relatively few reviews have focused on technical, as opposed to physical, performance while also addressing the practicalities associated with carbohydrate consumption when limited in-play feeding opportunities exist. Transient physiological responses associated with reductions in activity prevalent in scheduled intra-match breaks (e.g., half-time) likely have important consequences for practitioners aiming to optimize match-day performance. Accordingly, this review evaluated novel developments in soccer literature regarding (1) the ergogenic properties of carbohydrates for skill performance; and (2) novel considerations concerning exogenous energy provision during half-time. Recommendations are made to modify half-time practices in an aim to enhance subsequent performance. Viable future research opportunities exist regarding a deeper insight into carbohydrate provision on match-day.


#3 Talent Identification and Development in Male Football: A Systematic Review
Reference: Sports Med. 2018 Jan 3. doi: 10.1007/s40279-017-0851-7. [Epub ahead of print]
Authors: Sarmento H, Anguera MT, Pereira A, Araujo D
Summary: Expertise has been extensively studied in several sports over recent years. The specificities of how excellence is achieved in Association Football, a sport practiced worldwide, are being repeatedly investigated by many researchers through a variety of approaches and scientific disciplines. The aim of this review was to identify and synthesise the most significant literature addressing talent identification and development in football. We identified the most frequently researched topics and characterised their methodologies. A systematic review of Web of Science™ Core Collection and Scopus databases was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The following keywords were used: "football" and "soccer". Each word was associated with the terms "talent", "expert*", "elite", "elite athlete", "identification", "career transition" or "career progression". The selection was for the original articles in English containing relevant data about talent development/identification on male footballers. The search returned 2944 records. After screening against set criteria, a total of 70 manuscripts were fully reviewed. The quality of the evidence reviewed was generally excellent. The most common topics of analysis were (1) task constraints: (a) specificity and volume of practice; (2) performers' constraints: (a) psychological factors; (b) technical and tactical skills; (c) anthropometric and physiological factors; (3) environmental constraints: (a) relative age effect; (b) socio-cultural influences; and (4) multidimensional analysis. Results indicate that the most successful players present technical, tactical, anthropometric, physiological and psychological advantages that change non-linearly with age, maturational status and playing positions. These findings should be carefully considered by those involved in the identification and development of football players. This review highlights the need for coaches and scouts to consider the players' technical and tactical skills combined with their anthropometric and physiological characteristics scaled to age. Moreover, research addressing the psychological and environmental aspects that influence talent identification and development in football is currently lacking. The limitations detected in the reviewed studies suggest that future research should include the best performers and adopt a longitudinal and multidimensional perspective.


#4 Monitoring loads and non-contact injury during the transition from club to National team prior to an international football tournament: A case study of the 2014 FIFA World Cup and 2015 Asia Cup
Reference: J Sci Med Sport. 2017 Dec 20. pii: S1440-2440(17)31825-X. doi: 10.1016/j.jsams.2017.12.002. [Epub ahead of print]
Authors: McCall A, Jones M, Gelis L, Duncan C, Ehrmann F, Dupont G, Duffield R
Summary: Injured and non-injured national team footballers were compared for external and internal loads during transition from club to National team training camp. Load and injury data were collected from the same National team prior to and during training camps of 2 tournaments; World (n=17) and Asian Cups (n=16). External (number sessions) and internal (s-RPE) loads were collected 4-weeks prior to and during camps. The acute:chronic load ratio was calculated for the first week of camp based on the mean of previous 4-weeks. Respective loads and ratios were compared between injured and non-injured players for non-contact injuries occurring during camp. Seven non-contact injuries occurred during World Cup camp and 1 during Asian Cup (preventing statistical analyses). Small-to-moderate effect sizes were found for lower chronic internal loads (ES=0.57; 90% CI: 0.39-1.08) and higher acute:chronic ratio (ES=0.45; 90% CI: 0.31-0.87) for injured compared to non-injured players. Moderate-large effects (ES=0.83; 90% CI: 0.56-1.60) were evident for increased acute:chronic ratio for number of sessions in injured compared to non-injured players. However, small-moderate effect sizes were present for lower chronic training and match loads (ES=0.55; 90% CI: 0.38-1.06) in injured players prior to the World Cup camp, alongside an increased number of sessions in week 1 of camp (ES=0.47; 90% CI: 0.33-0.91). Players incurring non-contact injury during training camp prior to an international tournament performed less prior chronic external and internal load and a concomitant higher relative increase in camp, thus representing a practical marker to monitor in national teams.


#5 Ecological validity and reliability of an age-adapted endurance field test in young male soccer players
Reference: J Strength Cond Res. 2018 Jan 11. doi: 10.1519/JSC.0000000000002255. [Epub ahead of print]
Authors: Castagna C, Krustrup P, D'Ottavio S, Pollastro C, Bernardini A, Araujo Povoas SC
Summary: The purpose of this study was to examine the reliability and the association with relevant match activities (ecological validity) of an age-adapted field test for intermittent high-intensity endurance known as Yo-Yo intermittent recovery level 1 children test (YYIR1C) in young male soccer players. Twenty-eight young male outfield soccer players (age 11.1±0.9 years, height 142±4.4 cm, body mass 37.0±5.9 kg) with at least 2 years of experience in soccer competitions were tested twice using YYIR1C and an age-adapted competitive small-sided game (i.e., 9v9), 7 days apart in a random order. The YYIR1C performance showed an excellent relative (ICC=0.94) and a good absolute reliability (TEM as %CV=5.1%). Very large and significant associations were found between YYIR1C performance and match high-intensity activity (r=0.53). Large correlations were found between YYIR1C and match sprinting (r=0.42) and high-intensity metabolic power (r=0.46) distances. Match total distance was largely associated with YYIR1C (r=0.30). The results of this study showed that YYIR1C may be considered a valid and reliable field test for assessing intermittent high-intensity endurance in young male soccer players. Due to the relevance of aerobic fitness in youth soccer, future studies testing the sensitiveness of YYIR1C are necessary.


#6 A previous hamstring injury affects kicking mechanics in soccer players
Reference: J Sports Med Phys Fitness. 2018 Jan 10. doi: 10.23736/S0022-4707.18.07852-0. [Epub ahead of print]
Authors: Navandar A, Veiga S, Torres G, Chorro D, Navarro E
Summary: Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury. 45 professional players (males: n=19, previously injured players=4, age=21.16 ± 2.00 years; females: n=19, previously injured players=10, age=22.15 ± 4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases. A shorter backswing (20.20 ± 3.49% vs 25.64 ± 4.57%), and differences in knee flexion angle (58 ± 10o vs 72 ± 14o) and hip flexion velocity (8 ± 0rad/s vs 10 ± 2rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50 ± 0.84m/s vs 4.10 ± 0.45m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern. Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.


#7 Physical Fitness Performance of Young Professional Soccer Players Does not Change During Several Training Seasons in A Spanish Elite Reserve Team: A Club Study, 1996-2013
Reference: J Strength Cond Res. 2018 Jan 5. doi: 10.1519/JSC.0000000000002426. [Epub ahead of print]
Authors: Los Arcos A, Martins J
Summary: The purpose of the study was to assess the changes in physical fitness performance in young professional soccer players during several training seasons in a Spanish elite reserve team. Physical test values (i.e. vertical jump test, straight line sprint test, and discontinuous and progressive submaximal running test) of 97 young professional soccer players that belonged for at least two consecutive seasons to the reserve team of a Spanish professional team from 1996 to 2013 were analyzed. A distinction was made between the soccer players that were promoted to the Spanish 1/2 Divisions (n = 38) (PFL) and those that were not (n = 59) (non-PFL) (until the end of the 2016/2017 season). Players were also classified according to their playing positions. Independently of the competitive level reached and the playing position, the variability of the fitness performance was limited (coefficient of variation <6%) and the players did not improve their fitness values [ZERO WIDTH SPACE][ZERO WIDTH SPACE](ES ≤ small) from the first to the last season in which they were enrolled in the team (after 2-4 seasons). During the last stage of training in an elite soccer academy, young professional soccer players achieve a very similar physical fitness performance when their soccer competence is evaluated, and other soccer performance factors are those which make them stand out for selection.


#8 Investigating Effects of Sex Differences and Prior Concussions on Symptom Reporting and Cognition Among Adolescent Soccer Players
Reference: Am J Sports Med. 2018 Jan 1:363546517749588. doi: 10.1177/0363546517749588. [Epub ahead of print]
Authors: Brooks BL, Silverberg N, Maxwell B, Mannix R, Zafonte R, Berkner PD, Iverson GL
Summary: There has been increasing concern regarding the possible effect of multiple concussions on the developing brain, especially for adolescent females. Hypothesis/Purpose: The objectives were to determine if there are differences in cognitive functioning, symptom reporting, and/or sex effects from prior concussions. In a very large sample of youth soccer players, it was hypothesized that (1) there would be no differences in cognitive test performance between those with and without prior concussions, (2) baseline preseason symptoms would be better predicted by noninjury factors than concussion history, and (3) males and females with prior concussions would not have differences in cognition or symptoms. Participants included 9314 youth soccer players (mean = 14.8 years, SD = 1.2) who completed preseason baseline cognitive testing, symptom reporting, and a health/injury history questionnaire from the ImPACT battery (Immediate Post-concussion Assessment and Cognitive Testing). On the basis of injury history, athletes were grouped by number of prior concussions: 0 (boys, n = 4012; girls, n = 3963), 1 (boys, n = 527; girls, n = 457), 2 (boys, n = 130; girls, n = 97), or ≥3 (boys, n = 73; girls, n = 55). The primary measures were the 4 primary cognitive scores and the total symptom ratings from ImPACT. Primary outcomes were assessed across injury groups, controlling for age, sex, learning disability, attention-deficit/hyperactivity disorder (ADHD), treatment for headaches/migraines, substance abuse, and mental health problems. Cognitive test performance was not associated with concussion history but was associated with sex, age, learning disability, ADHD, and prior mental health problems. Greater symptom reporting was more strongly associated with psychiatric problems, older age, learning disability, substance abuse, headaches, being female, and ADHD than with a history of multiple concussions. Boys and girls did not differ on cognitive scores or symptom reporting based on a history of concussion. In this very large sample of youth soccer players with prior concussion, there was no evidence of negative effects on cognition, very weak evidence of negative effects on symptom reporting, and no evidence of sex × concussion differences in cognition or symptom reporting.


#9 Breast Injuries in Female Collegiate Basketball, Soccer, Softball and Volleyball Athletes: Prevalence, Type and Impact on Sports Participation
Reference: Eur J Breast Health. 2018 Jan 1;14(1):46-50. doi: 10.5152/ejbh.2017.3748. eCollection 2018 Jan.
Authors: Smith LJ, Eichelberger TD, Kane EJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5758063/pdf/ejbh-14-1-46.pdf
Summary: In 2015-2016, over 214,000 female athletes competed at the collegiate level in the United States (U.S.). The National Collegiate Athletic Association (NCAA) collects injury data; however, breast-related injuries do not have a specific reporting category. The exact sequelae of breast injury are unknown; however, a relationship between breast injury and fat necrosis, which mimics breast carcinoma, is documented outside of sports participation. Breast injuries related to motor vehicle collisions, seatbelt trauma, and blunt trauma have been reported. For these reasons, it is important to investigate female breast injuries in collegiate sports. The objectives of this study are to report the prevalence of self-reported breast injuries in female collegiate athletes, explore injury types and treatments, and investigate breast injury reporting and impact on sports participation. A cross-sectional study of female collegiate athletes at four U.S. universities participating in basketball, soccer, softball, or volleyball. Main outcome measure was a questionnaire regarding breast injuries during sports participation. Almost half of the 194 participants (47.9%) reported a breast injury during their collegiate career, less than 10% reported their injury to health personnel with 2.1% receiving treatment. Breast injuries reported by breast injuries reported by sport include softball (59.5%), basketball (48.8%), soccer (46.7%), and volleyball (34.6%). The long-term effects and sequelae of breast injuries reported by female collegiate athletes during sport play are unknown. Nearly 50% of participants had a breast injury during sports activities. Although 18.2% indicated that breast injury affected sports participation, only 9.6% of the injuries were reported to medical personnel with 2.1% receiving treatment.



American Football
#1 Can Functional Movement Assessment Predict Football Head Impact Biomechanics?
Reference: Med Sci Sports Exerc. 2017 Dec 30. doi: 10.1249/MSS.0000000000001538. [Epub ahead of print]
Authors: Ford JM, Campbell KR, Ford CB, Boyd KE, Padua DA, Mihalik JP.
Summary: The purpose was to determine functional movement assessments' ability to predict head impact biomechanics in college football players, and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance. Participants (N = 44, mass = 109.0 ± 20.8 kg, age = 20.0 ± 1.3 years) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test, and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75); moderate (50 to 75); and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors); moderate (6-7 errors); and poor (> 7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We employed random intercepts general linear mixed models to analyze our data. There were no effects of preseason movement assessment group on the two HIT System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R=0.006) or the LESS (F1,36 < 0.01 p = 0.988, R<0.001) assessments. Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.


#2 "But He's a Star Football Player!": How Social Status Influences Mock Jurors' Perceptions in a Sexual Assault Case
Reference: J Interpers Violence. 2017 Jun 1:886260517713715. doi: 10.1177/0886260517713715. [Epub ahead of print]
Authors: Pica E, Sheahan C, Pozzulo J
Summary: There have been several recent, high-profile cases in the media that have shed light on the perceived leniency in sentencing defendants in sexual assault cases. In a number of these cases, the defendant was well known within their community (e.g., Brock Turner; People v. Turner) or nationally (e.g., Ghomeshi; R v. Ghomeshi). The purpose of this study was to examine how the social status of the defendant (low vs. high), victim social status (low vs. high), victim gender (male vs. female), and the reason the victim was unconscious during the assault (consuming alcohol vs. consuming cold medicine) influenced mock jurors' decisions in a sexual assault case. Mock jurors ( N = 489) read a mock trial transcript depicting an alleged sexual assault. Mock jurors were asked to render a dichotomous verdict, continuous guilt rating, and rate their perceptions of the victim and defendant. There was no influence of the variables on mock jurors' dichotomous verdicts; however, social status influenced guilt ratings. There also was a combined influence of the defendant's social status and the reason the victim was unconscious such that when the defendant was described as low status, and the victim was unconscious due to alcohol consumption, the defendant received higher guilt ratings compared with when the victim was unconscious due to cold medicine. Moreover, the victim was perceived as having more control over the situation when the defendant was the star quarterback (i.e., high status), the victim was female, and she was unconscious due to alcohol consumption compared with cold medicine. These results suggest that victims may be blamed based on their perceived social status and other factors that may have influenced their control over the sexual assault, such as alcohol consumption.


#3 The Evolving Treatment Patterns of NCAA Division I Football Players by Orthopaedic Team Physicians Over the Past Decade, 2008-2016
Reference: Sports Health. 2018 Jan 1:1941738117745488. doi: 10.1177/1941738117745488. [Epub ahead of print]
Authors: Carver TJ, Schrock JB, Kraeutler MJ, McCarty EC
Summary: Previous studies have analyzed the treatment patterns used to manage injuries in National Collegiate Athletic Association (NCAA) Division I football players. The hypothesis is that Treatment patterns used to manage injuries in NCAA Division I football players will have changed over the study period.  The head orthopaedic team physicians for all 128 NCAA Division I football teams were asked to complete a survey containing questions regarding experience as team physician, medical coverage of the team, reimbursement issues, and treatment preferences for some of the most common injuries occurring in football players. Responses from the current survey were compared with responses from the same survey sent to NCAA Division I team physicians in 2008. Responses were received from 111 (111/119, 93%) NCAA Division I orthopaedic team physicians in 2008 and 115 (115/128, 90%) orthopaedic team physicians between April 2016 and April 2017. The proportion of team physicians who prefer a patellar tendon autograft for primary anterior cruciate ligament reconstruction (ACLR) increased from 67% in 2008 to 83% in 2016 ( P < 0.001). The proportion of team physicians who perform anterior shoulder stabilization arthroscopically increased from 69% in 2008 to 93% in 2016 ( P < 0.0001). Of team physicians who perform surgery for grade III posterior cruciate ligament (PCL) injuries, the proportion who use the arthroscopic single-bundle technique increased from 49% in 2008 to 83% in 2016 ( P < 0.0001). The proportion of team physicians who use Toradol injections prior to a game to help with nagging injuries decreased from 62% in 2008 to 26% in 2016 ( P < 0.0001). Orthopaedic physicians changed their injury treatment preferences for NCAA Division I football players over the study period. In particular, physicians have changed their preferred techniques for ACLR, anterior shoulder stabilization, and PCL reconstruction. Physicians have also become more conservative with pregame Toradol injections.

Tue

16

Jan

2018

Latest research in football - week 1 - 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 Physiological and Physical Responses According to the Game Surface in a Soccer Simulation Protocol
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-22. doi: 10.1123/ijspp.2017-0570. [Epub ahead of print]
Authors: Lopez-Fernandez J, Sanchez-Sanchez J, Garcia-Unanue J, Felipe JL, Colino-Acevedo E, Gallardo L
Summary: Recent studies have shown that soccer player's responses are similar on natural grass (NG) and artificial turf (AT), but they did not control the mechanical properties of these surfaces. This work aimed to analyse the influence of the game surface on amateur soccer player's physical and physiological responses using a soccer simulation protocol (SSP). Sixteen amateur players performed three bouts of the SSP on AT and NG. The mechanical properties of both surfaces were recorded. The order of surfaces was randomly established for each participant. Physiological responses of players were assessed before and after the six-repeated sprints test existing at the midpoint of each bout. Fatigue (% Best; % Diff) and general variables (total time; best time, mean time; maximum speed) for both the repeated sprint test and the agility tests (nonlinear actions at maximum speed) incorporated into the SSP were also analysed. The two surfaces displayed different mechanical properties. Physical responses were found similar for both surfaces (p>0.05) before and after the repeated sprint test. There were no surface differences in sprint times or fatigue variables for the repeated sprint test (p>0.05). The agility test was faster on AT than on NG in bout 1 (average speed [+1.17 Km/h; p=0.037]; agility test cut time [-0.31 s; p=0.027] and best time [-0.52 s; p=0.042]). The differences in the mechanical properties of the two surfaces are not sufficient to cause differences in the physiological and physical responses of soccer players, although they may affect turns and cuts.


#2 Investigating the influence of intra-individual changes in perceived stress symptoms on injury risk in soccer
Reference: Scand J Med Sci Sports. 2017 Dec 28. doi: 10.1111/sms.13048. [Epub ahead of print]
Authors: Clement D, Ivarsson A, Tranaeus U, Johnson U, Stenling A
Summary: Research has shown that high levels of stress and stress responsivity can increase the risk of injuries. However, most of the research that has supported this notion has focused on between-person relationships, ignoring the relationships at the within-person level. As a result, the objective of this study was to investigate if within-person changes in perceived stress symptoms over a one-month time period could predict injury rates during the subsequent three months. A prospective design with two measurement points (Time 1 - at the beginning of the season and Time 2 - one month into the season) was utilized. A total of 121 competitive soccer players (85 males and 36 females; Mage = 18.39, SD = 3.08) from Sweden and the United States completed the Kessler Psychological Distress Scale (KPDS) and a demographic sheet at Time 1. The KPDS was also completed at Time 2 and all acute injuries that occurred during the subsequent three-month period were recorded. A Bayesian latent change scores model was used to determine if within-person changes in stress symptoms could predict the risk of injury. Results revealed that there was a credible positive effect of changes in stress symptoms on injury rates, indicating that an increase in reported stress symptoms was related to an increased risk for injury. This finding highlights the importance of creating caring and supportive sporting environments and relationships and teaching stress management techniques, especially during the earlier portion of competitive seasons, to possibly reduce the occurrence of injuries.


#3 Soccer helps build strong bones during growth: a systematic review and meta-analysis
Reference: Eur J Pediatr. 2017 Dec 28. doi: 10.1007/s00431-017-3060-3. [Epub ahead of print]
Authors: Lozano-Berges G, Matute-Llorente A, Gonzalez-Aguero A, Gomez-Bruton A, Gomez-Cabello A, Vicente-Rodriguez G, Casajus JA
Summary: The aim of this study was to analyze the effects of soccer practice on bone in male and female children and adolescents. MEDLINE, PubMed, SPORTDiscus and Web of Science databases were searched for scientific articles published up to and including October 2016. Twenty-seven studies were included in this systematic review (13 in the meta-analysis). The meta-analysis was performed by using OpenMeta[Analyst] software. It is well documented that soccer practice during childhood provides positive effects on bone mineral content (BMC) and density (BMD) compared to sedentary behaviors and other sports, such as tennis, weightlifting, or swimming. Furthermore, soccer players present higher BMC and BMD in most weight-bearing sites such as the whole body, lumbar spine, hip, and legs. Moreover, bone differences were minimized between groups during prepuberty. Therefore, the maturity status should be considered when evaluating bone. According to meta-analysis results, soccer practice was positively associated with whole-body BMD either in males (mean difference 0.061; 95%CI, 0.042-0.079) or in females (mean difference 0.063; 95%CI, 0.026-0.099). Soccer may be considered a sport that positively affects bone mass during growth. Pubertal soccer players presented increased bone mass compared to controls or other athletes; however, these bone differences are minimized during the prepubertal stage. What is known: • It has been described that childhood and adolescence are important periods for bone mass and structure. • Previous studies have demonstrated that soccer participation improves bone mass in male and female children and adolescents. What is new: • The differences between soccer players and controls are more marked during puberty than prepuberty. • Weight-bearing sites such as lumbar spine, hip, femoral neck, trochanter, intertrochanteric region and both legs are particularly sensitive to soccer actions.


#4 Assessing Differences in Cardiorespiratory Fitness With Respect to Maturity Status in Highly Trained Youth Soccer Players
Reference: Pediatr Exerc Sci. 2017 Dec 23:1-13. doi: 10.1123/pes.2017-0185. [Epub ahead of print]
Authors: Doncaster G, Iga J, Unnithan V
Summary: The purpose of the study was to examine differences in measures of cardiorespiratory fitness and determinants of running economy with respect to maturity status in a group of highly trained youth soccer players. A total of 21 highly trained youth soccer players participated in this study. On separate visits, players' peak oxygen uptake (VO2peak), running economy at 3 different speeds [8 km·h-1, 80% gaseous exchange threshold (GET), and 95% GET], and pulmonary oxygen uptake (VO2) kinetics were determined. Players also performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Players were categorized as either "pre-PHV" (peak height velocity) or "mid-PHV" group using the measure of maturity offset. Independent t tests and Cohen's d effect sizes were then used to assess differences between groups. The mid-PHV group was significantly taller, heavier, and advanced in maturity status. Absolute measures of VO2peak were greater in the mid-PHV group; however, when expressed relative to body mass, fat-free mass, and theoretically derived exponents, VO2peak values were similar between groups. Pre-PHV group presented a significantly reduced VO2 response, during relative submaximal running speeds, when theoretically derived exponents were used, or expressed as %VO2peak. VO2 kinetics (tau) were faster during a low (standing) to moderate (95% GET) transition in the pre-PHV group. Yo-Yo IR1 performance was similar between groups. Although measures of VO2peak and Yo-Yo IR1 performance are shown to be similar between groups, those categorized as pre-PHV group display a superior running economy at relative submaximal running speeds and faster taus during a low to moderate exercise transition than their more mature counterparts.


#5 Reliability, Validity and Sensitivity of a Novel Smartphone-Based Eccentric Hamstring Strength Test in Professional Football Players
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-19. doi: 10.1123/ijspp.2017-0336. [Epub ahead of print]
Authors: Lee JWY, Cai MJ, Yung PSH, Chan KM
Summary: This study aims to evaluate the test-retest reliability, sensitivity and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players. Twenty-five healthy male professional football players have performed CUHK Nordic break-point test, hamstring fatigue protocol and isokinetic hamstring strength test. CUHK Nordic break-point test is based on a Nordic hamstring exercise. The Nordic break-point angle was defined as the maximum point where the participants could no longer support the weight of their body against gravity. The criterion for the sensitivity test was the pre-sprinting and post-sprinting difference of the Nordic break-point angle with a hamstring fatigue protocol. The hamstring fatigue protocol consists of 12 repetitions of the 30m sprint with 30 seconds recovery between each sprint. Hamstring peak torque of the isokinetic hamstring strength test was used as the criterion for validity. A high test-retest reliability (ICC = 0.94, 95% CI = 0.82 - 0.98) was found in the Nordic break-point angle measurements. The Nordic break-point angle significantly correlated with isokinetic hamstring peak torques at eccentric action of 30 °/s (r = 0.88, r2 = 0.77, p < 0.001). The minimal detectable difference was 8.03 °. The sensitivity of the measure was good enough that a significance difference (ES = 0.70, p < 0.001) was found between pre-sprinting and post-sprinting value. The CUHK Nordic break-point test is a simple, portable, quick smartphone based method to provide reliable and accurate eccentric hamstring strength measures among male professional football players.


#6 Electrocardiographic patterns and long-term training-induced time changes in 2484 elite football players
Reference: Arch Cardiovasc Dis. 2017 Dec 21. pii: S1875-2136(17)30233-4. doi: 10.1016/j.acvd.2017.10.005. [Epub ahead of print]
Authors: Huttin O, Selton-Suty C, Venner C, Vilain JB, Rochecongar P, Aliot E
Summary: High-level physical training induces cardiac structural and functional changes, including 12-lead electrocardiogram modifications. The purpose of this cross-sectional longitudinal study was to establish a quantitative electrocardiographic profile in highly trained football players. Initial and serial annual electrocardiogram monitoring over subsequent years allowed us to investigate the long-term effects of exercise on cardiac conduction and electrophysiological remodelling. Between 2005 and 2015, serial evaluations, including 12-lead electrocardiograms, were performed in 2484 elite male football players from the French Professional Football League. A total of 6247 electrocardiograms were performed (mean 2.5±1.8 electrocardiograms/player). Heart rate (beats/min), atrioventricular delay (PR, ms), intraventricular conduction delay (QRS, ms), corrected QT delay (QTc) and electrical left ventricular hypertrophy (LVH) (Sokolow-Lyon index, mm) were measured, and the fixed effect of time was evaluated using panel data analysis (β [95% confidence interval] change between two visits). According to European Society of Cardiology and Seattle criteria, 15% of the electrocardiogram intervals were considered abnormal. We observed 17% sinus bradycardia<50 beats/min (mean heart rate 60±11 beats/min), 8% first-degree atrioventricular block>200ms (mean PR 170±27ms), 1.5% QRS>120ms (mean QRS 87±19ms) and 3% prolonged QT interval (mean QTc using Bazett's formula [QTcB] 395±42ms). Electrical LVH (mean Sokolow-Lyon index 34±10mm) was noted in 37% of players. Over time, electrocardiogram changes were noted, with a significant remodelling trend in terms of decreased heart rate (-0.41 [-0.55 to -0.26] beats/min), QRS duration (-2.4 [-2.7 to -2.1] ms) and QTcB delay (-1.2 [-1.9 to -0.5] ms) (all P<0.001). This study describes usual electrocardiographic training-induced changes in a large series of football players over the follow-up timeframe. The most frequent outliers were electrical LVH and sinus bradycardia. These results have important implications for optimizing electrocardiogram interval measurements in initial screening and during follow-up of football players, with potential cost-effective implications.


#7 A Multinational Cluster Randomised Controlled Trial to Assess the Efficacy of '11+ Kids': A Warm-Up Programme to Prevent Injuries in Children's Football
Reference: Sports Med. 2017 Dec 22. doi: 10.1007/s40279-017-0834-8. [Epub ahead of print]
Authors: Rossler R, Junge A, Bizzini M, Verhagen E, Chomiak J, Aus der Funten K, Meyer T, Dvorak J, Lichtenstein E, Beaudouin F, Faude O
Summary: The objective of this study was to assess the efficacy of a newly developed warm-up programme ('11+ Kids') regarding its potential to reduce injuries in children's football. Children's football teams (under 9 years, under 11 years, and under 13 years age groups) from Switzerland, Germany, the Czech Republic and the Netherlands were invited. Clubs were randomised to an intervention group and a control group, and followed for one season. The intervention group replaced their usual warm-up by '11+ Kids', while the control group warmed up as usual. The primary outcome was the overall risk of football-related injuries. Secondary outcomes were the risks of severe and lower extremity injuries. We calculated hazard ratios using extended Cox models, and performed a compliance analysis. In total, 292,749 h of football exposure of 3895 players were recorded. The mean age of players was 10.8 (standard deviation 1.4) years. During the study period, 374 (intervention group = 139; control group = 235) injuries occurred. The overall injury rate in the intervention group was reduced by 48% compared with the control group (hazard ratio 0.52; 95% confidence interval 0.32-0.86). Severe (74% reduction, hazard ratio 0.26; 95% confidence interval 0.10-0.64) and lower extremity injuries (55% reduction, hazard ratio 0.45; 95% confidence interval 0.24-0.84) were also reduced. Injury incidence decreased with increasing compliance. '11+ Kids' is efficacious in reducing injuries in children's football. We observed considerable effects for overall, severe and lower extremity injuries. The programme should be performed at least once per week to profit from an injury preventive effect. However, two sessions per week can be recommended to further increase the protective benefit.


#8 Crowd medical services in the English Football League: remodelling the team for the 21st century using a realist approach
Reference: BMJ Open. 2017 Dec 21;7(12):e018619. doi: 10.1136/bmjopen-2017-018619.
Authors: Leary A, Kemp A, Greenwood P, Hart N, Agnew J, Barrett J, Punshon G
Summary: The objective was to evaluate the new model of providing care based on demand. This included reconfiguration of the workforce to manage workforce supply challenges and meet demand without compromising the quality of care. Currently the Sports Ground Safety Authority recommends the provision of crowd medical cover at English Football League stadia. The guidance on provision of services has focused on extreme circumstances such as the Hillsborough disaster in 1989, while the majority of demand on present-day services is from patients with minor injuries, exacerbations of injuries and pre-existing conditions. A new model of care was introduced in the 2009/2010 season to better meet demand. A realist approach was taken. Data on each episode of care were collected over 14 consecutive football league seasons at Millwall FC divided into two periods, preimplementation of changes and postimplementation of changes. Data on workforce retention and volunteer satisfaction were also collected. The data were obtained from one professional football league team (Millwall FC) located in London, UK. The primary outcome was to examine the demand for crowd medical services. The secondary outcome was to remodel the service to meet these demands. In total, 981 episodes of care were recorded over the evaluation period of 14 years. The groups presenting, demographic and type of presentation did not change over the evaluation. First aiders were involved in 87.7% of episodes of care, nurses in 44.4% and doctors 17.8%. There was a downward trend in referrals to hospital. Workforce feedback was positive. The new workforce model has met increased service demands while reducing the number of referrals to acute care. It involves the first aid workforce in more complex care and key decision-making and provides a flexible registered healthcare professional team to optimise the skill mix of the team.



Australian Football
#1 The Quantification of Within Week Session Intensity, Duration and Intensity Distribution Across a Season in Australian Football Using the Session RPE Method
Reference: Int J Sports Physiol Perform. 2017 Dec 28:1-21. doi: 10.1123/ijspp.2017-0626. [Epub ahead of print]
Authors: Juhari F, Ritchie DM, O'Connor F, Pitchford N, Weston M, Thornton HR, Bartlett JDB
Summary: Team-sports training requires the daily manipulation of intensity, duration and frequency with pre-season focusing on meeting the demands of in-season competition and in-season on maintaining fitness. To provide information about daily training in Australian Football (AF), this study aimed to quantify session intensity, duration, and intensity distribution across different stages of an entire season. Intensity (session Ratings of Perceived Exertion [s-RPE]; CR-10 scale) and duration were collected from forty-five professional male AF for every training session and game. Each s-RPE was categorized into the corresponding intensity zone; Low (<4.0 AU), Moderate (≥4.0 and <7.0), and High (≥7.0) to categorize session intensity. Linear mixed models were constructed to estimate session duration, intensity and distribution between the 3 pre-season and 4 in-season periods. Effects were assessed using linear mixed models, and magnitude-based inferences. The distribution of the mean session intensity across the season was 29% low-, 57% moderate- and 14% high-intensity. While 96% of games were high-intensity, 44% and 49% of skills training sessions were low- and moderate-intensity, respectively. Running had the highest proportion of high-intensity training sessions (27%). Pre-season displayed higher training session intensity (ES = 0.29-0.91) and duration (ES = 0.33-1.44), while in-season game intensity (ES = 0.31-0.51) and duration (ES = 0.51-0.82) were higher. By using a cost-effective monitoring tool, this study provides information about the intensity, duration and intensity distribution of all training types across different phases of a season, thus allowing a greater understanding of the training and competition demands of Australian Footballers.



American Football
#1 Catastrophic Eye Injury in