Latest research in football - week 24 - 2014

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 World Cup 2014: festival of football or alcohol?
Reference: BMJ. 2014 Jun 10;348:g3772. doi: 10.1136/bmj.g3772.
Author: Gornall J.
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#2 The development of a method for identifying penalty kick strategies in association football
Reference: J Sports Sci. 2014 Jun 10:1-10. [Epub ahead of print]
Authors: Noël B, Furley P, van der Kamp J, Dicks M, Memmert D.
Summary: Penalty takers in association football adopt either a keeper-independent or a keeper-dependent strategy, with the benefits of the keeper-independent strategy presumed to be greater. Yet, despite its relevance for research and practitioners, thus far no method for identifying penalty kick strategies has been available. To develop a validated and reliable method, Experiment 1 assessed characteristics that observers should use to distinguish the two strategies. We asked participants to rate 12 characteristics of pre-recorded clips of kicks of penalty takers that used either a keeper-independent or keeper-dependent strategy. A logistic regression model identified three variables (attention to the goalkeeper, run-up fluency and kicking technique) that in combination predicted kick strategy in 92% of the penalties. We used the model in Experiment 2 to analyse prevalence and efficacy of both the strategies for penalty kicks in penalty shoot-outs during FIFA World Cups (1986-2010) and UEFA Football Championships (1984-2012). The keeper-independent strategy was used much more frequently (i.e., 78-86%) than the keeper-dependent strategy, but successes did not differ. Penalty takers should use both the strategies to be less predictable. Goalkeepers can use the developed model to improve their chances to succeed by adjusting their behaviour to penalty takers' preferred penalty kick strategy.

#3 Influence of Weather, Rank, and Home Advantage on Football Outcomes in the Gulf Region
Reference: Med Sci Sports Exerc. 2014 Jun 9. [Epub ahead of print]
Authors:  Brocherie F, Girard O, Farooq A, Millet GP.
Summary: The objective of this study was to investigate the effects of weather, rank and home advantage on international football match results and scores in the Gulf Cooperation Council (GCC) region. Football matches (n = 2008) in six GCC countries was analysed. To determine the weather influence on the likelihood of favourable outcome and goals difference, generalised linear model with a logit link function, and multiple regression analysis were performed. In GCC region, home teams tend to have greater likelihood of a favourable outcome (P < 0.001) and higher goals difference (P < 0.001). Temperature difference was identified as a significant explanatory variable when used independently (P < 0.001) or after adjustment for home advantage and team ranking (P < 0.001). The likelihood of favourable outcome for GCC teams increases by 3% for every 1 unit increase in temperature difference. After inclusion of interaction with opposition, this advantage remains significant only when playing against non GCC (nGCC) opponents. While home advantage increased the odds of favourable outcome (P < 0.001) and goals difference (P < 0.001) after inclusion of interaction term, the likelihood of favourable outcome for a GCC team decreased (P < 0.001) when playing against a stronger opponent. Finally, the temperature and wet bulb globe temperature approximation were found as better indicators of the impact environmental conditions than absolute and relative humidity or heat index on match outcomes. In GCC region, higher temperature increased the likelihood of a favourable outcome when playing against nGCC teams. However, international ranking should be considered since an opponent with a higher rank reduced, but did not eliminate, the likelihood of a favourable outcome.

#4 Age estimation in U-20 football players using 3.0 tesla MRI of the clavicle
Reference: Forensic Sci Int. 2014 May 21;241C:118-122. doi: 10.1016/j.forsciint.2014.05.008. [Epub ahead of print]
Authors: Vieth V, Schulz R, Brinkmeier P, Dvorak J, Schmeling A.
Summary: To guarantee equal chances for participants in U-20 football tournaments, it seems desirable to verify the ages given by players with questionable dates of birth. To study the potential use of 3.0 tesla MRI of the clavicle in estimating the ages of U-20 football players. The ossification stage of the medial clavicular epiphyses was evaluated prospectively in 152 male footballers in the age group from 18 to 22 years using 3.0 tesla MRI. Average age increased with any higher degree of fusion. The only footballer with full ossification of the medial clavicular epiphyseal plate was 21.2 years old. The presence of a fully ossified clavicular epiphyseal plate appears to provide evidence of completion of the 20th year of life. The results of the pilot study need to be verified in a larger number of cases.

#5 Allometric Multilevel Modelling of Agility and Dribbling Speed by Skeletal Age and Playing Position in Youth Soccer Players
Reference: Int J Sports Med. 2014 Apr 15. [Epub ahead of print]
Authors: Valente-Dos-Santos J, Coelho-E-Silva MJ, Duarte J, Pereira J, Rebelo-Gonçalves R, Figueiredo A, Mazzuco MA, Sherar LB, Elferink-Gemser MT4 Malina RM
Summary: This study evaluates the contributions of age, skeletal maturation, body size and composition, training and playing position to the development of agility and dribbling speed in young male soccer players (10-18 years) followed longitudinally. 83 players [defenders (n=35), midfielders (n=27), forwards (n=21)] were followed annually over 5 years (average: 4.4 observations per player). Skeletal age (SA), stature, body mass, triceps and subscapular skinfolds, agility and dribbling speed were measured annually. Body composition was estimated from the 2 skinfolds. Annual training volume was estimated from weekly participation forms completed by coaches. The multiplicative allometric models with the best statistical fit showed that statural growth of 1 cm predicts 1.334 s and 1.927 s of improvement in agility and dribbling speed, respectively. Significant independent effects of fat-free mass and annual volume training were found for agility and dribbling speed, respectively (P<0.05). Predicted agility (from 12 to 18 years of SA) and dribbling speed (from 13 to 18 years of SA) differed significantly among players by playing positions (midfielders>forwards>defenders). The present results provide developmental models for the interpretation of intra- and inter-individual variability in agility and dribbling speed among youth soccer players across adolescence, and may provide a framework for trainers and coaches to develop and evaluate individualized training protocols.

#6 'There are a lot of new people in town: but they are here for soccer, not for business' a qualitative inquiry into the impact of the 2010 soccer world cup on sex work in South Africa.
Reference: Global Health. 2014 Jun 10;10(1):45. [Epub ahead of print]
Authors: Richter ML, Scorgie F, Chersich MF, Luchters S.
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Summary: Sports mega-events have expanded in size, popularity and cost. Fuelled by media speculation and moral panics, myths proliferate about the increase in trafficking into forced prostitution as well as sex work in the run-up to such events. This qualitative enquiry explores the perceptions of male, female and transgender sex workers of the 2010 Soccer World Cup held in South Africa, and the impact it had on their work and private lives. A multi-method study design was employed. Data consisted of 14 Focus Group Discussions, 53 sex worker diaries, and responses to two questions in surveys with 1059 male, female and transgender sex workers in three cities. Overall, a minority of participants noted changes to the sex sector due to the World Cup and nothing emerged on the feared increases in trafficking into forced prostitution. Participants who observed changes in their work mainly described differences, both positive and negative, in working conditions, income and client relations, as well as police harassment. The accounts of changes were heterogeneous - often conflicting in the same research site and across sites. No major shifts occurred in sex work during the World Cup, and only a few inconsequential changes were noted. Sports mega-events provide strategic opportunities to expand health and human rights programmes to sex workers. The 2010 World Cup missed that opportunity.

#7 The influence of pitch dimensions on performance during small-sided and conditioned soccer games
Reference: J Sports Sci. 2014 Jun 10:1-9. [Epub ahead of print]
Authors: Vilar L, Duarte R, Silva P, Chow JY, Davids K.
Summary: This study examined the influence of pitch dimensions in small-sided soccer games in shaping opportunities for performers to maintain ball possession, pass to teammates and shoot at goal. Fifteen amateur standard male participants (M = 21.87, σ = 1.96 years) played 5 v 5 small-sided soccer games in three varying pitch conditions (28 m × 14 m, 40 m × 20 m and 52 m × 26 m). Thirty sequences of play in each condition were selected for digitisation using TACTO software, allowing the capture of bi-dimensional displacement coordinate data of all players and the ball. The values of interpersonal distance between all attackers and immediate defenders and the relative distances of defenders to intercept a shot and a pass were computed as dependent variables. Results showed existence of fewer opportunities to maintain ball possession on smaller pitches, compared to medium and larger pitches. Conversely, the different dimensions set to the pitch did not influence opportunities for players to shoot at goal, or to perform passes to other teammates. By examining the specific spatial-temporal relationships of players and key-task constraints, the data from this study explain how effects of manipulating pitch dimensions of small-sided games might enhance opportunities for acquiring specific movement and decision-making skills.

#8 Repeated Sprint Ability in Young Soccer Players at Different Game Stages
Reference: J Strength Cond Res. 2014 Jun 6. [Epub ahead of print]
Authors: Meckel Y, Einy A, Gottlieb R, Eliakim A.
Summary: The purpose of this study was to determine young (16.9±0.5 yr) soccer players' repeated sprint ability (RSA) at different game stages. Players performed repeated sprint test (RST) (12X20 m) after warm-up prior to a game, at half-time and after a full soccer game, each on a different day, in random order. Ideal (fastest) sprint time (IS) and total (accumulative) sprint time (TS) were significantly slower at the end of the game compared to after the warm-up prior to the game (p<0.01 for each). Differences between IS and TS after the warm-up prior to the game and at half-time, and between half-time and end of the game, were not statistically significant. There was no significant difference in the performance decrement (PD) during the RST after warm-up prior to the game, at half-time, or the end of the game. Significant negative correlation was found between predicted VO2 and the difference between TS after the warm-up prior to the game and the end of the game (r=-0.52), but not between predicted VO2 and the difference in any of the RST performance indices between warm-up prior to the game and half-time, or between half-time and the end of the game. The findings indicate a significant RSA reduction only at the end but not at the half time of a soccer game. The results also suggest that the contribution of the aerobic system to soccer intensity maintenance is crucial, mainly during the final stages of the game.

# 9 Effects of a 10-week In-Season Eccentric Overload Training Program on Muscle Injury Prevention and Performance in Junior Elite Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Jun 6. [Epub ahead of print]
Authors: de Hoyo M, Pozzo M, Sañudo B, Carrasco L, Gonzalo-Skok O, Domínguez-Cobo S, Morán-Camacho E.
Summary: The aim of the current study was to analyse the effect of an eccentric overload training program (i.e., half squat and leg curl exercises using flywheel ergometers) with individualized load, on muscle injury incidence and severity, and performance in junior elite soccer players. Thirty-six young players (U-17 to U-19) were recruited and assigned to either experimental (EXP) or control group (CON). Training program consisted of 1-2 session/week (3-6 sets with 6 repetitions) during 10 weeks. The outcome measured included muscle injury (incidence per 1000 h of exposure and injury severity) and performance tests (counter movement jump; [CMJ], 10-m and 20-m sprint test). Between-group results showed a likely (ES: 0.94) lower number of days of absence per injury and a possibly decrement of incidence per 1000 h of match in EXP in comparison to CON. Regarding muscle performance, a substantial better improvement (likely to very likely) was found in 20-m sprint time (ES: 0.37), 10-m flying sprint time (ES: 0.77) and CMJ (ES: 0.79) for EXP compared to CON. Within-group analysis showed an unclear effect in each variable in CON. Conversely, substantial improvements were obtained in CMJ (ES: 0.58), 20-m sprint time (ES: 0.32), 10-m flying sprint time (ES: 0.95) and injury severity (ES: 0.59) in EXP. Furthermore, a possibly decrement in total injury incidence was also reported in EXP. The eccentric-based program led to a reduction in muscle injury incidence and severity, and showed improvements in common soccer tasks, such as jumping ability and linear sprinting speed.

#10 High frequency performance analysis of professional soccer goalkeepers: a pilot study
Reference: J Sports Med Phys Fitness. 2014 Jun 11. [Epub ahead of print]
Authors: Padulo J, Haddad M, Ardigò LP, Chamari K, Pizzolato F.
Summary: Hi speed video analysis was performed during ten official-matches, to assess the performance of ten goalkeepers (GK) from Italian third/fourth divisions (C-D). The variables studied were: number (n) of frontal and lateral actions with distance covered (speed during firstlast meter) and total distance covered during match. Match analysis showed that n of lateral (right/left)changes of direction in GK-C was 48% (p<0.005) lower and forward changes of action 53% greater (p<0.001) compared to GK-D. n of forward and lateral actions in GK-C was 49% and 67% (p<0.001 and p<0.0001) greater than GK-D, respectively. Particularly, in GK-C average distance, frontal and lateral, covered was 27% and 58% (p<0.005 and p<0.001) greater than in GK-D, respectively. Velocity of first meter of forward and lateral actions for GK-C were 9% and 27% lower (p>0.05 and p>0.05) than GK-D, respectively. Last meter of forward and lateral actions for GK-C was 57% greater and 43% lower (p<0.001 and p<0.005) than GK-D, respectively. Finally, total covered distance, considering all actions was 60% greater for GK-C compared to GKD (p<0.001). The work presented in this paper identifies the relevant aspects of the goalkeeper game that are valuable for a coach in terms of team and individual performance analysis.


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