Latest research in football - week 10 - 2016

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 Multivariate analyses of individual variation in soccer skill as a tool for talent identification and development: utilising evolutionary theory in sports science
Reference: J Sports Sci. 2016 Feb 26:1-13. [Epub ahead of print]
Authors: Wilson RS, James RS, David G, Hermann E, Morgan OJ, Niehaus AC, Hunter A, Thake D, Smith MD
Summary: The development of a comprehensive protocol for quantifying soccer-specific skill could markedly improve both talent identification and development. Surprisingly, most protocols for talent identification in soccer still focus on the more generic athletic attributes of team sports, such as speed, strength, agility and endurance, rather than on a player's technical skills. We used a multivariate methodology borrowed from evolutionary analyses of adaptation to develop our quantitative assessment of individual soccer-specific skill. We tested the performance of 40 individual academy-level players in eight different soccer-specific tasks across an age range of 13-18 years old. We first quantified the repeatability of each skill performance then explored the effects of age on soccer-specific skill, correlations between each of the pairs of skill tasks independent of age, and finally developed an individual metric of overall skill performance that could be easily used by coaches. All of our measured traits were highly repeatable when assessed over a short period and we found that an individual's overall skill - as well as their performance in their best task - was strongly positively correlated with age. Most importantly, our study established a simple but comprehensive methodology for assessing skill performance in soccer players, thus allowing coaches to rapidly assess the relative abilities of their players, identify promising youths and work on eliminating skill deficits in players.

#2 Is workload associated with injuries and performance in elite football? A call for action
Reference: Br J Sports Med. 2016 Mar 3. pii: bjsports-2016-095988. doi: 10.1136/bjsports-2016-095988. [Epub ahead of print]
Authors: Nassis GP, Gabbett TJ

#3 Injury prediction in veteran football players using the Functional Movement Screen™
Reference: J Sports Sci. 2016 Mar 3:1-9. [Epub ahead of print]
Authors: Hammes D, Aus der Fünten K, Bizzini M, Meyer T
Summary: The Functional Movement Screen™ (FMS™) is aimed at assessing fundamental movements and is often used to identify players' injury risk. The purpose of this study was to determine whether the FMS™ can be used to predict injuries in veteran footballers (aged > 32 years). Eighteen veteran football teams (n = 238) were recruited and prospectively followed for 9 months. The players (44 ± 7 years; 178 ± 7 cm, 84 ± 11 kg) performed the FMS™ at the start of the study period. Players' exposure hours and injuries were recorded. The difference of FMS™ overall score between injured and uninjured players was not significant (11.7 ± 2.9 vs 12.2 ± 2.8 points; Mann-Whitney U-test P = 0.17). Players scoring <10 (score < 1 standard deviation [SD]) below the mean) had a significantly higher injury incidence (z-statistics P < 0.05) compared to an intermediate reference group (mean ± 1 SD; scores of 10-14). No lower injury incidence for players with scores of >14 (score > 1 SD above the mean) was found. Further analyses of potential risk factors suggest higher age, lower body mass and a longer football career to be risk factors for injuries. The findings of this study suggest that the suitability of the FMS™ for injury prediction in veteran footballers is limited.

#4 Risk Factors for Injuries in Professional Football Players
Reference: Folia Med (Plovdiv). 2015 Apr-Jun;57(2):138-43. doi: 10.1515/folmed-2015-0033.
Authors: Haxhiu B, Murtezani A, Zahiti B, Shalaj I, Sllamniku S
Summary: The aim of this study was to identify risk factors related to the occurrence of injuries in football players. The study included 216 football players from 12 teams in the elite football league. Football-related injury data were collected prospectively during the 2012/2013 competitive season. At baseline the following information was collected for the players: anthropometric measurements (weight, height, BMI, subcutaneous skinfolds), playing experience, injury history, physical fitness performance test (agility run), peak oxygen uptake. The incidence, type and severity of injuries and training and game exposure times were prospectively documented for each player. Most of the players (n = 155, 71.7%) sustained the injures during the study period. The overall injury incidence during the regular season was 6.3 injuries per 1000 athlete-exposures (95% confidence interval, 4.31-9.67). Multivariate logistic regression analysis showed that playing experience (odds ratio [OR] = 0.44; 95% CI = 0.32-0.61, p < 0.01), age (OR = 2.05; 95% CI = 1.49-2.81, p < 0.01) and a previous injury (OR = 4.4; 95% CI = 2.14-9.07, p < 0.01) were significantly correlated to increased risk of injuries. Body mass index was not associated with risk of injury. Strains (34.19%) and sprains (25.81%) were the major injury types. Twenty-seven percent of injured players were absent from football for more than 1 month, with knee injuries (25.42%) being the most severe type. The risk factors that increase injury rates in football players were previous injury, higher age and years of playing. Future research should include adequate rehabilitation program to reduce the risk of injuries.

#5 Influence of football match time-motion parameters on recovery time course of muscle damage and jump ability
Reference: J Sports Sci. 2016 Mar 1:1-8. [Epub ahead of print]
Authors: de Hoyo M, Cohen DD, Sañudo B, Carrasco L, Álvarez-Mesa A, Del Ojo JJ, Domínguez-Cobo S, Mañas V, Otero-Esquina C
Summary: We analyzed the time course of recovery of creatine kinase (CK) and countermovement jump (CMJ) parameters after a football match, and correlations between changes in these variables and match time-motion parameters (GPS-accelerometry) in 15 U-19 elite male players. Plasma CK and CMJ height (CMJH), average concentric force (CMJCON) and average eccentric force (CMJECC) were assessed 2 h before and 30 min, 24 h and 48 h post-match. There were substantially higher CK levels 30 min, 24 h and 48 h (ES: 0.43, 0.62, 0.40, respectively), post-match. CMJECC (ES: -0.38), CMJH (ES: -0.35) decreased 30 min post, CMJCON (ES: -0.35), CMJECC (ES: -0.35) and CMJH (ES: -1.35) decreased 24 h post, and CMJCON (ES: -0.41) and CMJH (ES: -0.53) decreased 48 h post. We found correlations between distance covered at velocities ≤21 km · h-1 and changes in CK at 24 h (r = 0.56) and at 48 h (r = 0.54) and correlations between CK and distance covered >14 km · h-1 (r = 0.50), accelerations (r = 0.48), and decelerations (r = 0.58) at 48 h. Changes in CMJCON 30 min and 24 h post (both r = -0.68) correlated with impacts >7.1·G. Decelerations >2 m · s-2 correlated with changes CMJCON (r = -0.49) at 48 h and CMJECC (r = -0.47) at 30 min. Our results suggest that match GPS-accelerometry parameters may predict muscle damage and changes in components of neuromuscular performance immediately and 24-48 h post-match.

#6 Effects of emphasising opposition and cooperation on collective movement behaviour during football small-sided games
Reference: J Sports Sci. 2016 Feb 29:1-9. [Epub ahead of print]
Authors: Gonçalves B, Marcelino R, Torres-Ronda L, Torrents C, Sampaio J
Summary: Optimizing collective behaviour helps to increase performance in mutual tasks. In team sports settings, the small-sided games (SSG) have been used as key context tools to stress out the players' awareness about their in-game required behaviours. Research has mostly described these behaviours when confronting teams have the same number of players, disregarding the frequent situations of low and high inequality. This study compared the players' positioning dynamics when manipulating the number of opponents and teammates during professional and amateur football SSG. The participants played 4v3, 4v5 and 4v7 games, where one team was confronted with low-superiority, low- and high-inferiority situations, and their opponents with low-, medium- and high-cooperation situations. Positional data were used to calculate effective playing space and distances from each player to team centroid, opponent team centroid and nearest opponent. Outcomes suggested that increasing the number of opponents in professional teams resulted in moderate/large decrease in approximate entropy (ApEn) values to both distance to team and opponent team centroid (i.e., the variables present higher regularity/predictability pattern). In low-cooperation game scenarios, the ApEn in amateurs' tactical variables presented a moderate/large increase. The professional teams presented an increase in the distance to nearest opponent with the increase of the cooperation level. Increasing the number of opponents was effective to overemphasise the need to use local information in the positioning decision-making process from professionals. Conversely, amateur still rely on external informational feedback. Increasing the cooperation promoted more regularity in spatial organisation in amateurs and emphasise their players' local perceptions.

#7 The acute effect of match play on hamstring strength and lower limb flexibility in elite youth football players
Reference: Scand J Med Sci Sports. 2016 Mar 1. doi: 10.1111/sms.12655. [Epub ahead of print]
Authors: Wollin M, Thorborg K, Pizzari T
Summary: The aim of this study was to investigate the effect of competitive football match play on hamstring strength and lower limb flexibility. Fifteen male international youth football players were included. Hamstring strength and associated pain ratings, ankle dorsiflexion, hip extension, knee extension and flexion range of motion were evaluated immediately post-match and at intervals of 24, 48, and 72 h post-match. Strength significantly reduced post-match (P < 0.01), mean difference -0.43 (CI95 : -0.56, -0.30) and 24 h post (P < 0.05) mean difference -0.12 Nm/kg (CI95 : -0.20, -0.04). The associated pain scores significantly increased at the post-match (P < 0.01, ES = 0.61) and 24 h (P < 0.01, ES = 0.55) time intervals. At the 48 and 72 h post-match tests no significant difference was found for strength or pain ratings. No significant differences were detected for any of the range of motion measures. Competitive football match play has a significant acute and transient effect on isometric hamstring strength and associated pain levels during resisted knee flexion in male international youth players. Range of motion measures appear to remain relatively unaffected by match play. Isometric hamstring strength testing and associated pain levels might be considered for inclusion in-season to monitor player's post-match hamstring recovery characteristics.

#8 Talent identification and selection in elite youth football: An Australian context
Reference: Eur J Sport Sci. 2016 Feb 29:1-8. [Epub ahead of print]
Authors: O'Connor D, Larkin P, Mark Williams A
Summary: We identified the perceptual-cognitive skills and player history variables that differentiate players selected or not selected into an elite youth football (i.e. soccer) programme in Australia. A sample of elite youth male football players (n = 127) completed an adapted participation history questionnaire and video-based assessments of perceptual-cognitive skills. Following data collection, 22 of these players were offered a full-time scholarship for enrolment at an elite player residential programme. Participants selected for the scholarship programme recorded superior performance on the combined perceptual-cognitive skills tests compared to the non-selected group. There were no significant between group differences on the player history variables. Stepwise discriminant function analysis identified four predictor variables that resulted in the best categorization of selected and non-selected players (i.e. recent match-play performance, region, number of other sports participated, combined perceptual-cognitive performance). The effectiveness of the discriminant function is reflected by 93.7% of players being correctly classified, with the four variables accounting for 57.6% of the variance. Our discriminating model for selection may provide a greater understanding of the factors that influence elite youth talent selection and identification.

#9 Assessing performance, stability, and cleat comfort/support in collegiate club soccer players using prophylactic ankle taping and bracing
Reference: Res Sports Med. 2016 Mar 11:1-15. [Epub ahead of print]
Authors: Stryker SM, Di Trani AM, Swanik CB, Glutting JJ, Kaminski TW
Summary: Soccer athletes at all levels of play are keenly aware of their equipment needs including cleat wear, and want to be protected from injury but without impeding on-field performance. Ankle injury is a common disorder that is prevalent in the sport of soccer and recent improvements in ankle prophylaxis interventions have proven effective. The aim of this study was to determine if the use of elastic taping or a neoprene sleeve alters performance, stability, and cleat comfort/support in soccer players compared to wearing a soccer cleat without any external support. Twenty male collegiate club soccer players were recruited and randomly assigned to the three conditions (untaped control, taped, neoprene sleeve). Performance testing and comfort/support assessment for each condition took place in one on-field test session, while stability testing was completed during a separate laboratory session. The only significant finding was improved inversion/eversion stability in both the tape and sleeve conditions as compared to the cleated condition. The addition of tape or a sleeve did not have an adverse effect on performance or comfort during functional and stability testing, and should therefore be considered as a method to decrease ankle injuries in soccer athletes as external supports provide increased stability in inversion/eversion range of motion.

#10 The quantification of game-induced muscle fatigue in amputee soccer players
Reference: J Sports Med Phys Fitness. 2016 Mar 10. [Epub ahead of print]
Authors: Simin MA, Bradley PS, DA Silva BV, Mendes EL, DE Mello MT, Marocolo M Jr, DA Mota GR.
Summary: This study quantified the degree of game-induced muscular fatigue in amputee soccer players. Thirty-three male amputee soccer players performed muscular tests (push up test [PUT], countermovement jump test [CMJ] and medicine-ball throw [MBT]) before and after a competitive match. Five players served as a control group. The rating of perceived exertion was recorded after each battery. Control group demonstrated no differences between the two testing batteries (p > 0.05, effect size [ES]: 0.1-0.4). However, match group illustrated markedly lower performances for PUT (-17%, p <0.01, ES: 0.9) with less pronounced declines in MBT (-8%, p <0.01, ES: 0.7) and CMJ (-5%, p <0.01, ES: 0.3) compared to pre-match values. The rating of perceived exertion were higher after the match compared to baseline values (+60%, p <0.01, ES: 2.4).  The data demonstrate that the fatigue experienced after amputee soccer matches causes impairments in muscular performance and this could be different to able-bodied players.

#11 Rate of physical development in boys aged 10-11 years and the effects of training loads during a 12-month soccer program
Reference: Dev Period Med. 2015 Jul-Sep;19(3 Pt 2):367-74. [Article in Polish]
Authors: Boraczyński M, Sozański H.
Summary: The aim of the study was to evaluate the rate of physical development in prepubertal boys in response to training at different loads. The study involved two groups of soccer players, experimental groups E1 (n = 26, age 10.4 ± 0.6 years) and E2 (n = 27, age 10.3 ± 0.8 years) who were involved in a 12-month soccer training program, and a control group (C) of age-matched untrained boys (n = 22). The training protocol of E1 involved a greater share of coordination-based exercises, in E2 more focus was placed on conditioning fitness and strength. Body height, mass, fat percentage, and body mass index were measured pre-, peri-, and post-training. Chronological and developmental age were used to calculate a Biological State Maturity Index (BSMI). Between-group differences were observed in body fat percentage, which was higher in the control group by 6.8% at post-training compared with E1 (p < 0.05). E1 showed the most congruence between chronological and developmental age. Developmental age was most retarded in E2 by an average of 4.3 months. Greatest between-group differences were observed in E1 and the control group for the BSMI of body height (49.9%) at pre-training. BSMI of height and mass in the control group were different (p < 0.01) from both experimental groups at pre-, peri-, and post-training. 1. The experimental soccer training programs were conducive to the physical development of boys aged 10-11 years as evidenced by the absence of disturbances in the range of observed variables characterizing the body built and biological development. 2. Body mass index did not accurately reflect changes in body composition. A more detailed analysis of body composition is required in the recruitment and selection of young soccer players in order to better control the effects of training and diet. 3. The adopted BSMI measure indicated a delay in growth according to developmental age norms in the entire sample. However, the accelerated physical development in E1 during the study duration may be indicative of the stimulative effect of this group's training program and the adopted training load on physical development.

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