Latest research in footbal - week 43 - 2013

Latest research in football

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

Following studies were retrieved for this week:


#1 Differences in the number of accelerations between small-sided games and friendly matches in soccer
Authors:  Castellano J, Casamichana D.
Reference: J Sports Sci Med. 2013 Mar 1;12(1):209-10.
Summary: There was no summary available, however please see the link below to get free access to the article.
Download link:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761762/pdf/jssm-12-209.pdf

#2 Analysis of balance, rapidity, force and reaction times of soccer players at different levels of competition
Authors: Ricotti L, Rigosa J, Niosi A, Menciassi A.
Reference: PLoS One. 2013 Oct 10;8(10):e77264. doi: 10.1371/journal.pone.0077264.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3795057/
Summary: In the present study we analyzed 12 physical parameters, namely force, static and dynamic balance (both quantified by means of 4 parameters each), rapidity, visual reaction times and acoustic reaction times, over 185 subjects. 170 of them played soccer in teams enrolled in all the ten different Italian soccer leagues. Results show that 6 parameters (out of the 12 analyzed) permit to identify and discriminate top-level players, among those showing the same training frequency. The other parameters are strictly related to training frequency or do not discriminate among players or control subjects (non-athletes), such as visual and acoustic reaction times. Principal component analysis permits to identify 4 clusters of subjects with similar performances, thus representing a useful instrument to characterize the overall ability of players in terms of athletic characteristics, on the basis of their location on the principal component parameters plane.

#3 The impact of playing in matches while injured on injury surveillance findings in professional football
Authors: Hammond LE, Lilley JM, Pope GD, Ribbans WJ.
Reference: Scand J Med Sci Sports. 2013 Oct 10. doi: 10.1111/sms.12134. [Epub ahead of print]
Summary: This study aimed to analyze the frequency, nature, and consequences of footballers playing matches while injured, and to examine the impact on injury surveillance findings. High levels of inter-rater reliability and content validity were established for a tool designed to document players who were already injured at the start of a match. The tool was implemented in three English football teams (a Championship, League 1, and League 2 team) for one season, using a "time loss" definition of injury. One hundred forty-three matches were surveyed, revealing 102 match appearances by players who were already injured. Almost half of all games featured at least one injured player, with episodes of playing with injury occurring more frequently and lasting longer in League 2 players compared with higher level players. No association was observed between the number of injured players starting matches and match outcome [χ2 (4, N = 143) = 3.27, P = 0.514]. Fifteen percent of all injury episodes captured were only through prospective documentation of playing while injured. The findings show that both traumatic and overuse injuries are managed by footballers through competitive matches, and have important implications for aiding understanding of the epidemiology of injury in professional football.

#4  Injuries Among Spanish Male Amateur Soccer Players: A Retrospective Population Study
Authors: Herrero H, Salinero JJ, Del Coso J.
Reference: Am J Sports Med. 2013 Oct 17. [Epub ahead of print]
Summary: Soccer is the most popular sport worldwide, with about 265 million players, both professionals and amateurs. Most research investigating soccer injuries has focused on professional players because they have greater exposure time, but most soccer players are at the recreational level. The purpose of the study was to perform a retrospective epidemiological study of the injuries sustained in Spanish amateur soccer during the 2010-2011 season. Any injuries incurred by the 134,570 recreational soccer players (aged 18-55 years) registered with the Spanish Football Federation were reported to the federation's medical staff. A standardized medical questionnaire, based on the Fédération International de Football Association (FIFA) Medical and Research Centre (F-MARC) consensus for collection procedures in studies of soccer injuries, was used to classify the injury according to type, severity, location, and treatment. A total of 15,243 injuries were reported, with an average of 0.11 injuries per player and per year. From the total number of injuries, 67.2% were classified as injuries that resulted in time loss, while the remaining 32.7% were injuries that required medical attention. Most injuries led to a minimum of 1 competitive match being missed (87%), and only 2.5% were recurrent injuries. The rate of injuries per 1000 hours of play was double during games (1.15/1000 hours) compared with during training (0.49/1000 hours). From the total number of injuries reported, 7.7% corresponded to goalkeepers, 24.2% to forwards, 33.8% to defenders, and 34.3% to midfielders. The knee (29.9%) and ankle joints (12.4%) were the most common body locations injured, while ligament sprains and ruptures accounted for 32.1% of the total injuries attended. Older amateur players (age ≥30 years) had a greater number of injuries per year and per 1000 hours of play than their younger counterparts. The authors concluded that the risk of injury in amateur soccer is lower than that previously reported in professional players. The most common complaints in amateur players are knee ligament injuries. Further research is needed to investigate ways of reducing the incidence of injuries in amateur soccer.

#5 Movement analysis of Australian National League Soccer players using global positioning system technology
Authors: Wehbe, GM.,  Hartwig, TB., Duncan, CS
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e3182a35dd1
Summary: Player activity profiles of match play provide valuable information for optimal athlete training prescriptions, competition strategies and managing load and recovery and are currently lacking in elite Australian-league (A-League) soccer. The aims of the study were therefore, to (a) determine match activity profiles for elite A-League soccer players and make match-half and positional comparisons, and (b) examine the effect of situational factors including evolving match status (drawing, winning, or losing) and goals being scored and conceded on selected match activity profile variables. Global positioning system tracking devices were used to determine activity profiles of 19 elite male adult soccer players during eight pre-season matches (n = 95 files). Total distance, average speed, high-intensity-running (HIR) distance, and very high-intensity running (VHIR) distance decreased from the first to the second half by 7.92%, 9.47%, 10.10%, and 10.99%, respectively. Midfielders covered 11.69% more total distance, 28.08% more HIR distance, and had a 10.93% higher average speed than defenders (p < 0.05; d = 1.90, 1.03, and 1.83, respectively). Attackers performed 27.50% and 30.24% less medium accelerations than defenders and midfielders, respectively (p < 0.01; d = 1.54, and 1.73). Whilst the team was winning, average speed was 4.17% lower than when the team was drawing (p < 0.05, d = 0.32). Scoring or conceding goals did not appear to affect HIR. This study adds to limited knowledge of match demands in elite A-League soccer. The match activity profiles provide descriptive benchmarks that could be used to make comparisons with other elite level soccer populations while also providing a framework for game-specific training prescription, competition strategy and load management. The generalization that defenders experience a relatively lower match load may be questionable given their relatively high acceleration and deceleration demands.

#6 Technical demands of soccer match play in the english championship
Authors: Russell, M., Rees, G., and Kingsley, MI.
Reference: J. Strength. Cond. Res. 27: 2869-2873, 2013.
Summary: The aim of this study was to investigate the effect of match play on the performance of technical actions in professional soccer players. Using computerized notational analysis, technical performance was quantified for the outfield players of one team during the 2010/2011 English Championship season. This retrospective study evaluated temporal patterns in the performance of players who completed more than 10 games (n = 10). Total possessions and number of ball distributions were lower in the second versus the first half of match play (10 +/- 7%, p = 0.010 and 11 +/- 8% p = 0.009, respectively). Analysis across 15-minute intervals revealed reductions during the last 15-minutes of match play in the total number of possessions (0:00-14:59 minutes: 11.8 +/- 1.9 vs. 75:00-89:59 minutes: 9.5 +/- 1.7, p < 0.05) and distributions (0:00-14:59 minutes: 10.9 +/- 2.3 vs. 75:00-89:59 minutes: 8.7 +/- 2.1, p < 0.05). The number of touches taken per possession, number of challenges, percentage of challenges won, length of forward distributions and percentage success of distributions were all similar between halves and across 15-minute intervals. These results demonstrate that match-specific factors reduced total possessions and number of passes in the second half of match play. Coaching staff could use this information to inform team tactics and technical training sessions.

#7 The Effect of Combined Resisted Agility and Repeated Sprint Training Vs. Strength Training on Female Elite Soccer Players'
Authors: Shalfawi, SA, Haugen, T, Jakobsen, TA, Enoksen, E, Tonnessen, E.
Reference: J. Strength. Cond. Res., 2013.
Summary:  The aim of the present study was to compare the effects of in-season combined resisted agility and repeated sprint training against strength training on soccer players` agility, linear single sprint speed, vertical jump, repeated sprint ability, and aerobic capacity. Twenty well-trained elite female soccer players aged (+/- SD) (19.4 +/- 4.4 years) volunteered to participate in the present study. Participants were randomly assigned to either agility & repeated sprint training group or strength training group. All participants were tested before and after a 10-week specific conditioning program. The pre- and post-tests were conducted on three separate days with one day of low intensity training in between. Test day one consisted of squat jump (SJ), counter movement jump (CMJ) and repeated sprint ability (RSA). Test day two consisted of 40 m maximal linear sprint and an agility test, while a Beep-test was conducted on test day three to assess aerobic capacity. The agility and repeated sprint training implemented in this study did not have a significant effect on agility, although there was a tendency for moderate improvements from 8.23 +/-0.32 s to 8.06 +/-0.21 s (d = 0.8). There was a significant (p<0.01) and moderate-positive effect on Beep-test performance from level 9.6 +/-1.4 to level 10.8 +/-1.0, and only a trivial - small effect on all other physical variables measured in this study. The strength training group had a positive, moderate, and significant (p<0.01) effect on Beep-test performance from level 9.7 +/-1.3 to level 10.9 +/-1.2 (d = 1.0) and a significant (p<0.05) but small effect (d = 0.5) on SJ performance (25.9 +/-2.7 cm to 27.5 +/-4.1 cm). Furthermore, the strength training implemented in this study had a trivial and negative effect on agility performance (d = -0.1). No between groups differences were observed. The outcome of the present study indicate the importance of a well planned program of conditioning that do not result in a decreased performance of the players, the great importance of strength and conditioning specialist in implementing the training program and the importance of choosing the time of the year to implement such conditioning training programs. However, the fact that the present training program did not cause any decline in performance indicate that it is useful in maintaining the soccer players' physical performance during the competition period.

#8 Effects of stabilization training on trunk muscularity and physical performances in youth soccer players
Authors: Hoshikawa, Y, Iida, T, Muramatsu, M, Ii, N, Nakajima, Y, Chumank, K, and Kanehisa, H.
Reference: J. Strength. Cond. Res., 2013.
Summary:  The purpose of the present study was to examine the effects of stabilization training on trunk muscularity and physical performances in youth male soccer players aged 12 - 13 yrs (n = 28). The subjects allocated to training (TG, n = 16) performed a stabilization exercise program consisting of 5 exercises (elbow-toe, elbow-heel, side-bridge, modified one-legged squat, and bent-knee push-up) 4 times per week anda training program specific to soccer 6 times per week, whilethe others (CON, n = 12) conducted the soccer training only for 6 months. Before and after the intervention, the cross-sectional areas (CSAs) of five muscles (rectus abdominus, oblique, psoas major, quadratus lumborum, and erector spinae) were determined using magnetic resonance imaging. Furthermore, peak torques during hip extension and flexion at 1.05 rad/s, heights of squatand countermovement jumps, and time taken to sprint 15 m were also measured. After 6 months, both groups significantly increased the CSAs of the five muscle groups (TG: 4.4 - 13.4%, CON: 5.5 - 10.9%) and improved sprint time (TG: -1.4%, CON: -1.6%), without significant effect of group, but only TG significantly increased the heights of squat(5.0%) and countermovement (6.8%) jumps. In addition, a greater increase in hip extension torque was found in TG (40.8%) than in CON (17.4%). The current results indicate that, at least in early adolescent soccer players, adding stabilization exercise to soccer training cannot increase the trunk muscularity but it will improve hip extensor strength and vertical jump performance.

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