A New Approach for Training-load Quantification in Elite-level Soccer: Contextual Factors.

The aims of this study were to analyse the physical responses of professional soccer players during training considering the contextual factors of match location, season period, and quality of the opposition; and to establish prediction models of physical responses during training sessions. Training data was obtained from 30 professional soccer players from Spanish La Liga using global positioning technology (N=1365 performances). A decreased workload was showed during training weeks prior to home matches, showing large effects in power events, equivalent distance, total distance, walk distance and low-speed running distance. Also, the quality of the opposition also affected the training workload (p<0.05). All regression-models showed moderate effects, with an adjusted R2 of 0.37 for metabolic-work, 0.34 for total distance covered, 0.25 for high-speed running distance (18-21 km·h-1), 0.29 for very high-speed running distance (21-24 km·h-1), 0.22 for sprint running distance (>24 km·h-1) and 0.34 for equivalent distance. The main finding of this study was the great association of match location, season period and quality of opposition on the workload performed by players in the training week before the match; and the development of workload prediction-models considering these contextual factors, thus proposing a new and innovative approach to quantify the workload in soccer.

Head impact exposure in youth football-Are current interventions hitting the target?

Restrictions on heading in youth football have been implemented in some countries to limit head impact exposure. However, current interventions remain poorly guided by evidence. Our objective was to quantify heading exposure in youth football, assessing the effects of sex and age. Football matches played during an international youth football tournament with no heading restrictions were directly observed, including players from both sexes (11-19 years). The elite senior level was included for comparison, using video analysis. All heading events were registered, classified, and assigned to individual players. Heading rates were calculated for each sex and age group. We observed a total of 267 matches, corresponding to 4011 player hours (1927 player hours for females, 2083 player hours for males). Males headed more frequently than females (2.7 vs 1.8 headers/player hour; P < .001). Heading rates increased with age (ANOVA, P < .001), approaching the elite senior level for players 16 years and older. There was substantial variation within teams for all age and sex groups, with the widest range (1-18 headers) observed for girls aged 19. Girls younger than 12 years had the lowest exposure, with an average of <2 players per team heading the ball, each with 1-2 headers. In conclusion, age and sex influence head impact exposure in youth football, and warrants careful consideration when introducing injury prevention measures. Males are more frequently exposed than females, heading rates increase with age, and there is substantial variation between players. Heading is a rare event in the youngest age groups, especially among females.

Nutrition for Female Soccer Players-Recommendations.

Soccer is one of the most popular sports in the world. As its number of players is increasing, the number of female players is also on the rise. However, there are limited data about how the diets of female soccer players should be designed. Thus, the aim of our work is to deliver concise nutritional recommendations for women practicing this sport. Based on a literature review, we emphasize that individual adjustment of the energy value of the diet is the key factor for the physical performance of female soccer players. Appropriate macronutrient intake makes it possible to achieve the proper energy value of the diet (5-10 g/kg body mass/day carbohydrates; 1.2-1.7 g/kg body mass/day proteins; <30% fats from energy). The micronutrients should be consumed in amounts corresponding to individual values recommended in national standards. Soccer players should pay special attention to the proper consumption of such micronutrients, as well as vitamins such as iron, calcium, and vitamin D. The right amount of fluid intake, consistent with the player's needs, is crucial in maximizing exercise performance. The diet of a female practicing soccer is usually characterized with low energy values, which increases the risk of various health consequences related to low energy availability. Monitoring the diets of female soccer players is, therefore, necessary.

Lower extremity kinematic analysis in male athletes with unilateral anterior cruciate reconstruction in a jump-landing task and its association with return to sport criteria.

BACKGROUND: Return to sport (RTS) criteria are widely being used to identify anterior cruciate ligament reconstructed (ACLR) athletes ready to return to sportive activity and reduce risk of ACL re-injury. However, studies show a high rate of ACL re-injury in athletes who passed RTS criteria. This indicates that the current RTS criteria might not be sufficient to determine return to sport time in ACLR athletes. Previous studies have reported a close association between altered lower limb kinematics and ACL re-injury. However, it is not clear how lower extremity kinematics differs between ACLR athletes who passed the RTS-criteria and who failed. This study compared lower extremity kinematics in a jump-landing task between ACLR athletes who passed the RTS criteria (Limb symmetry in hop tests, quadriceps strength and questionnaires) to those who failed and to the healthy individuals. METHODS: Participants were 27 male football players with unilateral ACLR including 14 who passed -RTS criteria and 13 failed, and 15 healthy football players. A 3D motion capture system recorded participants' lower extremity motion while performing 10 trials of a bilateral jump-landing task. Hip, knee and ankle angular motion were examined at initial contact. Two-way mixed analysis of variances (2 limbs × 3 groups) and Bonferroni post-hoc tests were performed to compare the joint angles between the limbs and groups. RESULTS: lower hip abduction angle was found in the failed (involved limb 4.1 ° ± 4.2) and passed RTS (involved limb 6.8° ± 3.3) groups compared to the healthy group (non-dominant limb 10.7° ± 3.7). Ankle inversion in the failed RTS (0.4° ± 4.9) group was significantly lower than both passed RTS (4.8° ± 4.8, p = 0.05) and healthy (8.2° ± 8.1, p < 0.001) groups. There were no significant differences between the groups in knee kinematics. CONCLUSIONS: Our findings indicate reduced hip abduction during initial contact phase of landing in athletes returned to sport. Reduced hip abduction during the complex multiplanar movement of jump-landing is a risk factor for ACL re-injury. Current RTS criteria may not be sufficient to identify ACLR athletes at high risk of re-injury. The kinematic analysis in conjunction with current RTS criteria can provide additional insight into the return to sport decision making.

The dribbling agility test as a potential tool for evaluating the dribbling skill in young soccer players.

The present study examined the construct validity and reliability of a new dribbling agility test (DAT) that incorporates reactive agility and multiple change of direction. To check its' validity, (a) DAT was performed by four groups (under 10, under 12, under 14 and under 16 yrs) of young soccer players (n = 125 in each group) and (b) a regression analysis was conducted to define the best DAT predictors. The reliability of DAT was assessed with repeated measurements. This test can differentiate the dribbling skill between groups (p < 0.01). Furthermore, 68% of the observed variance in DAT was explained by zigzag dribbling test, Illinois agility test, reaction time and running speed. The test-retest reliability was high in all groups (ICC = 0.77 - 0.90, p < 0.01). It was concluded that DAT can be a potential tool to evaluate the dribbling performance in young soccer players.

Validation of the Loughborough Soccer Passing Test in young soccer players.

The aim of this study was to examine the validity and reliability of the Loughborough Soccer Passing Test (LSPT) in adolescent soccer players. Eighty-seven players, aged 14-17 years, were recruited according to their playing level: elite (n = 44), sub-elite (n = 22), and non-elite (n = 21). Two attempts of the LSPT were performed at baseline. Players then completed 10 attempts over 3 weeks to familiarize themselves with the test. Subsequently, 2 main trials, separated by 1 week, were performed; the mean of the 2 attempts was recorded as the performance score. After familiarization, the performance scores showed significant differences (p < 0.01) between elite (40.3 ± 8.3 seconds), sub-elite (58.1 ± 10.2 seconds), and non-elite players (66.6 ± 11.7 seconds). There was low-to-moderate reliability between trials with sub-elite (r = 0.35, p < 0.05) and non-elite players (r = 0.47, p < 0.05), but very good for elite players (r = 0.96, p < 0.05). Scores at baseline were better (p < 0.05) for elite players (51.0 ± 9.3 seconds) compared with sub-elite (60.8 ± 8.2 seconds) and non-elite players (69.0 ± 11.1 seconds). The LSPT seems to be a valid and reliable protocol to assess differences in soccer skill performance in adolescent players and can distinguish players according to their playing level. The LSPT was able to distinguish different abilities without players undergoing any familiarization with the test, thus enabling it to be used for talent identification purposes.

Is it better to be an English little pea than a Mexican little pea?: The role of the categorization process on the evaluation of football players.

Two studies investigated the effects of manipulating team membership on the evaluation of a football player. We hypothesized that the evaluations of the same football player, Javier "Chicharito" Hernandez, would vary as a function of the categorization process. For study 1, participants were randomly assigned to one of three conditions: Manchester United, Mexican National team or control. Results showed that "Chicharito" obtained better evaluations when his membership to Manchester United was made salient. In study 2, participants were randomly assigned to one of two conditions: Manchester United and Mexican National team condition. We found support for the mediating role of team evaluation on the relationship between team membership and the evaluations of Chicharito. The theoretical and applied implications were discussed.

Factors influencing the implementation of anterior cruciate ligament injury prevention strategies by girls soccer coaches.

Women are 3 times more likely to injure their anterior cruciate ligament (ACL) while playing soccer than men. ACL injury prevention programs (IPPs) involving stretching and strengthening drills can reduce the incidence of ACL injury when incorporated into routine training. The rate of implementation among coaches is largely unknown. The purpose of this study was to determine the rate of implementation of ACL IPP, to identify factors that influence implementation, and to acquire information to assist in design dissemination and implementation strategies. Study subjects were coaches of woman soccer players aged 11-22 years in Utah (n = 756). Data were gathered using a Web-based survey followed by a qualitative study in which "best practice coaches"-coaches who met criteria for successful implementation of ACL IPP-were interviewed via telephone. A minority of survey respondents, 19.8% (27/136), have implemented ACL IPP. Factors associated with successful implementation include length of coaching experience and presence of additional support staff such as a strength and conditioning coach or athletic trainer. Best practice coaches (14/136) unanimously agreed on the following: (a) there are performance-enhancing benefits of ACL IPP, (b) education on ACL injury prevention should be required for licensure, and (c) dissemination and implementation will require soccer associations to enact policies that require IPPs. In conclusion, a minority of girls soccer coaches have implemented ACL IPP and those that have do so because they believe that prevention improves performance and that soccer organizations should enact policies requiring ACL injury prevention education and implementation. Efforts to implement ACL IPP should be driven by soccer organizations, emphasize performance-enhancing benefits, and engage additional coaching staff.

Global positioning system data analysis: velocity ranges and a new definition of sprinting for field sport athletes.

Global positioning system (GPS) technology has improved the speed, accuracy, and ease of time-motion analyses of field sport athletes. The large volume of numerical data generated by GPS technology is usually summarized by reporting the distance traveled and time spent in various locomotor categories (e.g., walking, jogging, and running). There are a variety of definitions used in the literature to represent these categories, which makes it nearly impossible to compare findings among studies. The purpose of this work was to propose standard definitions (velocity ranges) that were determined by an objective analysis of time-motion data. In addition, we discuss the limitations of the existing definition of a sprint and present a new definition of sprinting for field sport athletes. Twenty-five GPS data files collected from 5 different sports (men's and women's field hockey, men's and women's soccer, and Australian Rules Football) were analyzed to identify the average velocity distribution. A curve fitting process was then used to determine the optimal placement of 4 Gaussian curves representing the typical locomotor categories. Based on the findings of these analyses, we make recommendations about sport-specific velocity ranges to be used in future time-motion studies of field sport athletes. We also suggest that a sprint be defined as any movement that reaches or exceeds the sprint threshold velocity for at least 1 second and any movement with an acceleration that occurs within the highest 5% of accelerations found in the corresponding velocity range. From a practical perspective, these analyses provide conditioning coaches with information on the high-intensity sprinting demands of field sport athletes, while also providing a novel method of capturing maximal effort, short-duration sprints.

Sport-related concussion return-to-play practices of medical team staff in elite football in the United Kingdom.

INTRODUCTION: This study explored sport-related concussion (SRC) return-to-play (RTP) behaviours and attitudes of medical team staff working in elite football in the United Kingdom. Usage and awareness of The Football Association (FA) guidelines, concussion education rates of players and coaching staff, and collection of baseline concussion assessments. Additionally, confidence in managing RTP post-SRC, perceived player under-reporting of symptoms, use of enhanced RTP pathways, and coaching pressure on RTP were investigated. METHODS: A cross-sectional questionnaire study was distributed online by organisations including or representing medical staff working in elite football in the United Kingdom. RESULTS: A total of 112 responses were gathered. High awareness rates of the FA guidelines were found (96%) with variable rates of player and coaching staff concussion education. Baseline concussion assessments were collected by 80% of respondents with 93% feeling very confident or confident in managing the RTP of a player with a SRC. 60% rarely or never experienced coaching pressure around player RTP, and 24% felt players always or very often under-reported symptoms to expedite their return. 90% had a moderate to high confidence in the Sport Concussion Assessment Tool-5 (SCAT-5) as a RTP decision tool, and 66% always or very often used an enhanced RTP pathway. CONCLUSION: Confidence in managing player RTP post SRC and use of enhanced RTP pathways were high, as was confidence in the SCAT-5 as a RTP decision tool. Respondents raised concerns around player under-reporting of symptoms to accelerate RTP post-SRC, and perceived coaching pressure around decision making.

Reliability and factorial validity of agility tests for soccer players.

The purpose of this study was to evaluate the reliability and factorial validity of agility tests used in soccer. One hundred fifty (n = 150), elite, male, junior soccer players, members of the First Junior League Team, volunteered to participate in the study. The slalom test (ST) sprint 4 x 5 m (S4 x 5) and sprint 9-3-6-3-6-9 m with 180 degree turns (S180 degrees) tests had a greater reliability coefficient (alpha = 0.992, 0.979, and 0.976), whereas the within-subject variation ranged between 2.9 and 5.6%. The mentioned 6 agility tests resulted in the extraction of 2 significant components. The S4 x 5 test had the lowest correlation coefficient with the first component (r = 0.38), whereas the correlation coefficients of the other 5 agility tests were higher than 0.63. The T-test (TT) showed statistically significant differences between the defenders and midfielders (p < 0.05) and between the defenders and attackers (p < 0.05). Statistical significant differences were determined between the attackers and defenders in the sprint 9-3-6-3-9 m with backward and forward running (SBF) and p < 0.05. It can be concluded that of the 6 agility tests used in this study, the SBF, TT, and S180 degrees are the most reliable and valid tests for estimating the agility of soccer players. According to the results of the study, the TT proved to be the most appropriate for estimating the agility of defenders, the SBF, and S180 degrees for estimating the agility of midfielders, whereas the S4 x 5 test can be used for estimating the agility of attackers.

Low-cost match analysis of Italian sixth and seventh division soccer refereeing.

At every level, soccer referees and their assistants perform a significant amount of physical activity while refereeing; therefore, they must evaluate and keep an adequate physical condition. The author described the outcome of a functional evaluation protocol on adult healthy sportsmen refereeing in the Italian sixth and seventh division. Results have been compared with others published in the literature and gathered by means of different protocols. Referees and assistant referees have been monitored during official matches by means of wrist global positioning system receivers-instead of commonly used imaging techniques-and heart rate monitors. Total match distances covered, distances covered at different clustered speeds, match average heart rate, and its proportion over significant values have been measured. To detect differences over the match, first and second half total distance, distances covered at speeds over significant values, heart rate, and its proportion over significant values have been measured separately. Both whole-match and between-halves results were similar to highest literature data. Italian sixth and seventh division soccer referees show adequate physical capabilities and can use inexpensive wrist global positioning system receivers and heart rate monitors to evaluate them.

Preventing knee injuries in adolescent female football players - design of a cluster randomized controlled trial [NCT00894595].

BACKGROUND: Knee injuries in football are common regardless of age, gender or playing level, but adolescent females seem to have the highest risk. The consequences after severe knee injury, for example anterior cruciate ligament (ACL) injury, are well-known, but less is known about knee injury prevention. We have designed a cluster randomized controlled trial (RCT) to evaluate the effect of a warm-up program aimed at preventing acute knee injury in adolescent female football. METHODS: In this cluster randomized trial 516 teams (309 clusters) in eight regional football districts in Sweden with female players aged 13-17 years were randomized into an intervention group (260 teams) or a control group (256 teams). The teams in the intervention group were instructed to do a structured warm-up program at two training sessions per week throughout the 2009 competitive season (April to October) and those in the control group were informed to train and play as usual. Sixty-eight sports physical therapists are assigned to the clubs to assist both groups in data collection and to examine the players' acute knee injuries during the study period. Three different forms are used in the trial: (1) baseline player data form collected at the start of the trial, (2) computer-based registration form collected every month, on which one of the coaches/team leaders documents individual player exposure, and (3) injury report form on which the study therapists report acute knee injuries resulting in time loss from training or match play. The primary outcome is the incidence of ACL injury and the secondary outcomes are the incidence of any acute knee injury (except contusion) and incidence of severe knee injury (defined as injury resulting in absence of more than 4 weeks). Outcome measures are assessed after the end of the 2009 season. DISCUSSION: Prevention of knee injury is beneficial for players, clubs, insurance companies, and society. If the warm-up program is proven to be effective in reducing the incidence of knee injury, it can have a major impact by reducing the future knee injury burden in female football as well as the negative long-term disabilities associated with knee injury. TRIAL REGISTRATION: NCT00894595.

Some factors in sanctions for unsportsmanlike behavior of players and coaches in youth soccer.

Reasons and motives for sanctions imposed on players and coaches in youth soccer were examined to evaluate frequency and type of infraction by competition category (Under 12, 13-14, 15-16, and 17-18 years). Analysis of the first 30% of competitions yielded 1,202 sanctions of 340 teams with 6,120 players and 340 coaches. For older groups, the number of sanctions for aggressive conduct by the players was significantly higher; frequency of sanctions imposed on the coaches for disrespect also was significantly higher, and those for aggression were higher although not significantly so; the number of sanctions for disrespect by players was not different. Transgressions of the game rules recorded by officials are a valid representation of a pedagogical factor important for coaches and players. Implementing informative programs for knowledge and conduct of rules is suggested.

The influence of the "big five" factors on the demands-abilities fit in soccer academies.

The influence of the Big Five factors on the fit between demands and abilities in soccer was examined for school and boarding home domains for newcomer trainees of soccer academies. 81 male trainees from 4 academies participated in the survey (M age = 16.3 yr., SD = 1.1). The fit between demands and abilities was measured three times during the academic year. In each domain, three repeated measures were aggregated into a single composite measure to define the fit index in the soccer, school, and boarding home domains. Results from the NEO Personality Inventory-Revised revealed that Neuroticism and Conscientiousness were, respectively, negatively and positively correlated with the school and boarding home fit index, Extraversion was negatively related to the boarding home fit index, and no personality factors were related to the soccer fit index. Stepwise regression analyses showed that Conscientiousness was the strongest predictor of the school and boarding home fit indexes. The individual differences approach to predict the success of newcomer trainees of soccer academies is discussed.

Selection and promotion processes are not associated by the relative age effect in an elite Spanish soccer academy.

The aim of this study was to analyze the influence of the relative age effect (RAE) on the selection and promotion processes in an elite soccer academy. One hundred and eleven elite youth players who belonged to an elite soccer club from the Spanish "La Liga" participated in this study. Players were classified into three age-categories: under 14 years (U14), under 16 years (U16) and under 18 years (U18); and they were also classified in quartiles based on their date of birth (i.e., January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4). In addition, two further classification criteria were established based on the selection (i.e., selected and non-selected players) and promotion (i.e., promoted and non-promoted players) processes. The main results showed that in U14 and U16 age-categories, players born early in the year were over-represented compared to players born late in the year, although birth-distribution was not associated with the likelihood of a player to be selected or promoted. In addition, less fat in sum skinfolds, less percentage of fat, higher percentage of muscle and lower endomorphy and mesomorphy components were showed in U14 selected players, in comparison with non-selected players. Likewise, better sprint performance was found in U16 selected players versus non-selected ones. However, no significant differences on anthropometry, body composition, somatotype and physical performance were found between promoted and non-promoted players. Therefore, our results suggest there is need for coaches to reorient their talent identification programs in order to make sure that players selected to continue playing in the club have the potential to promote to the excellence in soccer.

Alcohol management practices in community sporting clubs: Validation of an online self-report tool.

INTRODUCTION AND AIMS: Those involved in organised sport have a high risk of excessive alcohol consumption and alcohol-related harm, the implementation of alcohol management practices have been proven to reduce these risks. Measuring alcohol management practice implementation by sporting clubs is impeded by a lack of valid tools. The aim of this study was to determine the validity of online self-report of alcohol-management practices by community football clubs via comparison with observational methods. DESIGN AND METHODS: A cross-sectional study was undertaken with a sample of community football clubs within Australia. The implementation of 12 alcohol management practices was collected via: (i) an online survey; and (ii) observational audit at a clubs home ground. The prevalence of implementation of alcohol management practices for both data collection methods was calculated as was percent agreement and Kappa/Prevalence Adjusted and Bias Adjusted Kappa (PABAK) statistics. RESULTS: Data were collected from 58 football clubs. For both assessment methods, implementation prevalence was greater than 80% for 6 of the 12 alcohol management practices. A total of 75% (n = 9) of practices had at least 70% agreement between the online and observation methods of assessment. Kappa/PABAK scores ranged from -0.08 (poor agreement) to 0.97 (almost perfect agreement). DISCUSSION AND CONCLUSION: The online survey provided valid measure of assessing some but not all alcohol management practices in community sporting clubs. The validity of the measure may be improved by enhancements to the manner in which the self-report data are collected.