Latest research in football - week 21 - 2019

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

Following studies were retrieved for this week:

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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