Evidence for a new model of the complex interrelationship of ball possession, physical intensity and performance in elite soccer.

BACKGROUND: How the physical metrics, especially physical intensity, and possession interact with each other, and subsequently combine to influence performance remains opaque. Therefore, we investigated the interrelationship of possession, physical metrics, and team performance in elite soccer. METHODS: Four seasons of a top European league were used to derive 80 team league performances (points), together with possession and physical data. Physical metrics were absolute distances (m) during the whole match and ball-in-play, and rates of distance covered (m⋅min-1 ) as the index of physical intensity, notably when in-possession/out-of-possession, in total and within five speed categories. Interrelationships of possession, physical metrics, possession, and performance were assessed with Pearson's correlations and mediation analysis. RESULTS: Overall possession (r = 0.794) and time out-of-possession within the defensive third (r = -0.797) were most strongly correlated with performance. The strong relationships between in-possession distances and performance appeared coincidental due to greater time in-possession. Physical intensity had a complex relationship with possession and performance, with opposite relationships according to possession status: lower physical intensity when in-possession and higher physical intensity when out-of-possession were associated with possession and performance. Mediation analysis revealed the direct, independent importance of possession for team performance; however, the association of physical intensity with performance was largely (>79%) mediated by possession. CONCLUSION: Based on these findings, we propose a novel model of the interrelationships between possession, physical intensity, and performance, whereby higher possession is the largest, direct contributor toward enhanced team performance, with lower physical intensity in-possession a consequence of higher possession, but greater physical intensity when out-of-possession a cause of increased possession.

Análisis descriptivo y comparativo de los goles conseguidos tras saques de esquina en la liga española 1ª división: temporadas 2015 y 2019 / Descriptive and comparative analysis of the goals achieved after corner kicks in the Spanish league 1st division: 2015 and 2019 seasons / Análise descritiva e comparativa dos gols marcados após escanteios na 1ª divisão do liga espanhola: temporadas de 2015 e 2019

El objetivo del estudio fue describir de manera exhaustiva la manera de obtener goles tras saque de esquina para analizar la existencia de diferencias, entre las temporadas 2014/15 y 2018/19 en la Liga de Primera División española. El estudio pretendió analizar la incidencia real de esta acción del juego e identificar qué variables están asociadas a la eficacia de la acción al analizar todos los saques de esquina que acaban en gol en dichas temporadas. Para ello se construyó una herramienta de registro en la que se incluyeron criterios contextuales y criterios relacionados con el desarrollo de la acción de gol. Como conclusión, los resultados evidencian una estimación de la tendencia hacia un predominio de los saques de esquina directos o de primera acción (2014/15) hacia saques de esquina de segundas acciones (2018/19). Se observó un incremento del número de jugadores que actúan y una pérdida del predominio del remate de cabeza como acción finalizadora. (AU)

The objectives of the study were to exhaustively describe the way of scoring goals after corner kicks in order to analyze the existence of differences, between the 2014/15 (n = 112) and 2018/19 (n = 90) seasons, in the Liga de Spanish First Division. The study aimed to analyze the real incidence of this game action and identify which variables are associated with the effectiveness of the action by analyzing all the SDE actions thatend in a goal in those seasons. As a main conclusion, the results could show a certain evolution of the predominance of direct or first-action corner kicks (2014/15) towards second or third-action corner kicks (2018/19). Increased the number of players involved in the action and a loss of the dominance of the header as a finishing action, probably related to the change in trend from direct corner kicks (2014/15) towardssecond-action corner kicks or rebounds (2018/19). (AU)

Os objetivos do estudo foram descrever exaustivamente a forma de marcar golos após pontapés de canto, de forma a analisar a existência de diferenças, entre as épocas 2014/15 (n=112) e 2018/19 (n=90), na primeira Liga Espanhola. O estudo teve como objetivo analisar a real incidência dessa ação no jogo e identificar quais variáveis que estão associadas à efetividade da ação analisando todas as ações da SDE que terminam em golos nessas temporadas. Como principal conclusão, os resultados puderam evidenciar uma certa evolução da predominância dos pontapés de canto diretos ou de primeira ação (2014/15) para os pontapés de canto de segunda ação (2018/19). Verificou-se ainda um aumento do número de jogadores envolvidos na ação e perdado domínio do cabeceamento como ação de finalização, provavelmente relacionado à mudança na tendência do canto direto (2014/15) para cantos ou ressaltos de segunda ação (2018/19). (AU)

Is there a relationship between executive functions and resilience in youth elite soccer players?

BACKGROUND: While the relationship between cognitive performance and sport performance in youth elite soccer players has proponents as well as opponents, many aspects of this relationship remain unclear. Therefore, this quasi-experimental study wants to contribute to this relationship including the psychological aspect of resilience when investigating youth elite soccer players during an assessment selection for a representative team. METHODS: Questionnaires as well as computer-based tests were conducted. RESULTS: Results of this study showed no relationship between resilience and executive function in youth elite soccer players. Furthermore, no differences in executive functions or in resilience were found between those players who are selected for a representative team and those who were not selected. CONCLUSION: The results indicate that further research needs to be conducted to clarify possible relationships in more detail.

The Effect of a Single Dose of Citrulline on the Physical Performance of Soccer-Specific Exercise in Adult Elite Soccer Players (A Pilot Randomized Double-Blind Trial).

PURPOSE: The purpose of this study was to evaluate the effect of a single intake of citrulline at 3 g and 6 g doses in adult elite soccer players performing sport-specific exercise. MATERIALS AND METHODS: This randomized double-blind placebo-controlled study analyzed 18 soccer players from the top divisions of three European countries. Participants were randomized into three groups of six each and performed a field-based soccer-specific test for 18 min. Comparative analysis of heart rate, fatigue and post-exercise recovery was conducted. RESULTS: There were no statistically significant differences in most of the analyzed parameters, nor at any of the time points for lactate concentration. Players' RPE exercise test score did not reveal any differences. CONCLUSIONS: Neither a single intake of 3 g nor of 6 g of citrulline malate affected physical performance, subjective feelings of fatigue or post-exercise recovery in adult elite soccer players who performed a soccer-specific test.

Influence of the COVID-19 lockdown on Spanish professional soccer teams' external demands according to their on-field ranking.

The main objective of this study was to analyse the changes in external demand parameters (e.g., total distance, high-speed running distance, accelerations/decelerations) in Spanish professional soccer teams after the COVID-19 lockdown considering their on-field ranking (i.e., teams whose ranking worsened after the COVID-19 lockdown [WRS] vs. teams that improved their ranking after the COVID-19 lockdown [IMP]). A total of 23,527 individual match observations were collected on players competing during the 2019/20 season in the First Spanish Professional soccer League (LaLiga). Goalkeepers and players who participated for less than 10 minutes in each match were excluded. Relative total distance (TD/min), distance covered at 21-24 km · h-1 (HIRD/min) and > 24 km · h-1 per minute (VHIRD/min), high metabolic load distance (HMLD), and the number of accelerations (3 m/s2) and decelerations (< 3 m/s2) performed were analysed by the ChryonHego video-tracking system. These variables were analysed during two differentiated periods, before the COVID-19 lockdown (i.e., 27 matches) and after the COVID-19 lockdown (i.e., 11 matches), and teams were classified into two groups according to their ranking (i.e., WRS vs. IMP). R-Studio was employed for data analysis and a mixed linear model was conducted. A decrease in external demands in all teams after the COVID-19 lockdown was observed, and this decrease was greater in WRS. These results suggest that, after an inactive period (i.e., the COVID-19 lockdown), teams that return with better physical performance, mainly related to high-intensity actions, have more possibilities of improving their final qualifying position.

High metabolic load distance in professional soccer according to competitive level and playing positions.

Background: High metabolic load distance provides global information about the soccer players' total high-intensity activities. Thus, this study aimed to examine the Spanish professional soccer players' high metabolic load distance profile, comparing competitive level and playing positions. Methods: A total of 18,131 individual match observations were collected from outfield players competing during the 2018/2019 and 2019/20 seasons in the First and Second Spanish Professional Soccer Leagues (LaLiga™). High Metabolic Load Distance (HMLD; distance covered with a power consumption above 25.5 W·kg-1 and accelerations or decelerations (e.g., accelerating from 2 to 4 m·s-2 for 1 s) were included), and HMLD per minute (HMLDmin) were analyzed by the ChryonHego® video-tracking system. Players were classified according to their playing position as follows: Central Backs (CB), Full Backs (FB), Center Midfields (CM), Wide Midfields (WM), and Forwards (FW). Results: No differences between competitive levels were found in any variable when all players were analyzed conjointly except for HMLDmin overall and during the second half. However, when playing positions were considered, differences between competitive levels were observed in all positions, mainly in HMLD and HMLD during the first-half variables. In addition, several differences between playing positions were observed, with CB presenting the lowest values in all variables compared to their counterparts in both competitive levels, whereas CM in First Division and WM in Second Division showed the highest values in the HMLD variables. Discussion: The findings are of interest to analyze the HMLD in professional soccer players, enabling the adaptation and individualization of training in this population according to the competitive level and specific playing position of each player.

The effect of ball possession on physical and technical performance in UEFA Champions league matches.

This study aimed to examine the effects of low-percentage ball possession teams (LPBPT) and high-percentage ball possession teams (HPBPT) on the physical and technical performance of UEFA Champions League (UCL) players. All data were obtained from group stage matches of UCL during the 2020/21 season using a semi-automatic optical tracking system. Linear mixed model was fitted with contextual variables as covariates. Wide midfielders and forwards in LPBPT covered more total distance, low-intensity running, and achieved greater average speed than in HPBPT (all large effect sizes [ES]). Central defenders and fullbacks covered more high-intensity running (small ES), while CMs covered more sprinting (medium ES) in HPBPT than in LPBPT. Players on all playing positions produced greater number of passes and successful passes in HPBPT than in LPBPT (large ES), except forwards who produced more passes in LPBPT than in HPBPT (small ES). Both physical and technical performance were highly dependent on ball possession percentages, with evident position-specific changes, indicating that the effect of ball possession is highly position-dependent. These findings provide information for soccer coaches on physical and technical demands across teams with varying percentage ball possession, which could be used to individualise training programs based on playing style and position.

Identification of Neuromuscular Performance Parameters as Risk Factors of Non-contact Injuries in Male Elite Youth Soccer Players: A Preliminary Study on 62 Players With 25 Non-contact Injuries.

Introduction: Elite youth soccer players suffer increasing numbers of injuries owing to constantly increasing physical demands. Deficits in neuromuscular performance may increase the risk of injury. Injury risk factors need to be identified and practical cut-off scores defined. Therefore, the purpose of the study was to assess neuromuscular performance parameters within a laboratory-based injury risk screening, to investigate their association with the risk of non-contact lower extremity injuries in elite youth soccer players, and to provide practice-relevant cut-off scores. Methods: Sixty-two elite youth soccer players (age: 17.2 ± 1.1 years) performed unilateral postural control exercises in different conditions, isokinetic tests of concentric and eccentric knee extension and knee flexion (60°/s), isometric tests of hip adduction and abduction, and isometric tests of trunk flexion, extension, lateral flexion and transversal rotation during the preseason period. Non-contact lower extremities injuries were documented throughout 10 months. Risk profiling was assessed using a multivariate approach utilizing a Decision Tree model [Classification and Regression Tree (CART) method]. Results: Twenty-five non-contact injuries were registered. The Decision Tree model selected the COP sway, the peak torque for knee flexion concentric, the functional knee ratio and the path of the platform in that hierarchical order as important neuromuscular performance parameters to discriminate between injured and non-injured players. The classification showed a sensitivity of 0.73 and a specificity of 0.91. The relative risk was calculated at 4.2, meaning that the risk of suffering an injury is four times greater for a player, who has been classified as injured by the Decision Tree model. Conclusion: Measuring static postural control, postural control under unstable condition and the strength of the thigh seem to enable a good indication of injury risk in elite youth soccer players. However, this finding has to be taken with caution due to a small number of injury cases. Nonetheless, these preliminary results may have practical implications for future directions in injury risk screening and in planning and developing customized training programs to counteract intrinsic injury risk factors in elite youth soccer players.

Comparative Analysis of Soccer Performance Intensity of the Pre-Post-Lockdown COVID-19 in LaLiga™.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) forced a stoppage in the 2019/2020 season of LaLiga™, possibly influencing performance indicators in the return to competition. Therefore, here, we evaluated whether the stoppage due to the coronavirus 2019 disease (COVID-19) lockdown influenced physical performance compared to the start of LaLigaTM in terms of high-intensity efforts. Using a semi-automatic, multiple-camera system, running activities during 22 matches were analyzed. We compared the first 11 matches of the season (pre-lockdown) with the 11 matches just after the restart of LaLiga™ (post-lockdown). The results showed higher (p < 0.05) performance in the pre-lockdown period compared with the post-lockdown period, including in medium-speed running (14.1-21 km/h), high-speed running (21.1-24 km/h), and sprinting speed running distances (>24 km/h). However, the number of accelerations/min and decelerations/min were significantly higher during the post-lockdown period. Therefore, we conclude that the stoppage due to the COVID-19 lockdown generated lower physical performance in the post-lockdown period compared with the pre-lockdown period, most likely due to the accumulation of matches (congested schedules).

Game Insight Skills as a Predictor of Talent for Youth Soccer Players.

Perceptual-cognitive skills are found to be important factors for soccer players. The aim of this study was, therefore, to find within-group differences for game insight in an elite group of youth soccer players by means of a Game Insight inDicator (GID). In addition, the prospective value of perceptual-cognitive skills was examined by following the trajectory of the participants. The GID consisted of film clips that show game situations. The task of the players was to predict the trajectory and destination of the ball and move toward the correct position to receive the pass of a teammate. The film clips stopped 80 ms before, at, and 80 ms after the football contact of a teammate. We also sought to validate the GID against game performance. Participants were talented soccer players 11-13 years old and playing at the elite level for their age. Based on eight independent elite-coach judgments, two groups were created: highly talented players (HT) and less talented players (LT). The coach ratings were supported by a significant difference between the two groups based on the objective notational analysis of their game performance in 4 vs. 4 and 11 vs. 11 matches. With respect to the GID, a significant interaction effect for the groups (HT vs. LT) by occlusion time (-80, 0, and +80 ms) was found, showing that the HT performs better than the LT in 0 and +80 ms condition. In addition, GID scores were compared with soccer levels at the mean age of 19 years. Longitudinal data did not show significant differences between elite and sub-elite. Overall, the GID was found to be a valid and useful indicator for players anticipating the ball's trajectory and destination at age 11-13 years but failed to predict the players' level at age 19 years. The latter indicates how difficult it is to predict talent development.

Comparison of Selected CD45+ Cell Subsets' Response and Cytokine Levels on Exhaustive Effort Among Soccer Players.

BACKGROUND: Immunological alterations may led to the reduction in capacity and endurance levels in elite athletes by e.g. increased susceptibility to infections. There is a need to explain the impact of intensive physical effort on the CD4+ memory T cell subsets. METHODS: Fourteen participants median aged 19 years old (range 17-21 years) were recruited form Pogon Szczecin S.A., soccer club. They performed progressive efficiency test on mechanical treadmill until exhaustion twice: during preparatory phases to spring and autumn competition rounds. We examined the influence of exhaustive effort on the selected CD45+, especially CD4+ memory T cell subsets and inflammation markers determined before, just after the test and during recovery time. RESULTS: Significant changes in total CD45+ cells and decrease in T lymphocytes percentage after the run was observed. Significant fluctuations in T cells' distribution were related not only to the changes in Th or Tc subsets but also to increase in naïve T cell percentage during recovery. Increase in TNF-α and IL-8 post-exercise, IL-6 and IL-10 plasma levels in recovery was also found. CONCLUSIONS: The novel finding of our study is that the run performed on mechanical treadmill caused a significant release of CD4+ T naïve cells into circulation. Post-exercise increase in circulating NK cells is related with fast biological response to maximal effort. However, at the same time an alternative mechanism enhancing inflammation is involved.

Patellar and Achilles Tendon Stiffness in Elite Soccer Players Assessed Using Myotonometric Measurements.

BACKGROUND:: Tendon overuse injuries are an issue in elite footballers (soccer players) and may affect tendon function. Achilles and patellar tendinopathy are the most frequent pathologies. Tendon stiffness, the relationship between the force applied to a tendon and the displacement exerted, may help represent tendon function. Stiffness is affected by training and pathology. Nevertheless, information regarding this mechanical property is lacking for elite soccer athletes. HYPOTHESIS:: Achilles and patellar tendon stiffness assessed using myotonometric measurements will be greater in elite soccer athletes than in control participants. STUDY DESIGN:: Cross-sectional study. LEVEL OF EVIDENCE:: Level 4. METHODS:: Forty-nine elite soccer athletes and 49 control participants were evaluated during the 2017 preseason. A handheld device was used to measure Achilles and patellar tendon stiffness. Dominant and nondominant limbs were assessed for both groups. RESULTS:: A significantly stiffer patellar tendon was found for both the dominant and the nondominant limb in the elite soccer athletes compared with the control group. Nevertheless, no differences were found in Achilles tendon stiffness between groups. When comparing between playing positions in soccer athletes, no significant differences were found for both tendons. CONCLUSION:: Greater patellar tendon stiffness may be related to an improvement in force transmission during muscle contraction. On the other hand, it seems that after years of professional training, Achilles tendon stiffness does not change, conserving the storing-releasing function of elastic energy. The nonsignificant differences between positions may be attributable to the years of homogeneous training that the players underwent. CLINICAL RELEVANCE:: The present study shows another technique for measuring mechanical properties of tendons in soccer athletes that could be used in clinical settings. In the future, this technique may help clinicians choose the best exercise protocol to address impairments in tendon stiffness.

Tactical Variables Related to Gaining the Ball in Advanced Zones of the Soccer Pitch: Analysis of Differences Among Elite Teams and the Effect of Contextual Variables.

Attacking tactical variables have been commonly studied in soccer to analyze teams' performance. However, few studies investigated defensive tactical variables during match-play and the influence of contextual variables on them. The aims of the present study were (1) to examine the defensive behaviors of soccer teams when gaining the ball in advanced zones of the pitch and (2) to evaluate the effect of contextual variables on these defensive behaviors. A sample of 1,095 defensive pieces of play initiated in the opposing half of the pitch obtained from 10 matches of the season 2010/11 of La Liga and involving 13 teams was collected using the semiautomated tracking system Amisco Pro. Five defensive tactical variables, the outcome of defensive pieces of play, and contextual variables (i.e., match status, venue, quality of opposition, and match period) were recorded for every defensive piece initiated in the opposing half of the pitch. Results showed that there were significant differences among teams in the outcome of defensive pieces of play originating from the opposing half (χ2 = 111.87, p < 0.01, φc = 0.22), and in the outcome of offensive pieces of play following ball gains (χ2 = 49.92, p < 0.001, φc = 0.22). Cluster analysis revealed four groups describing different defensive behaviors from high-pressure to a defense close to their own goal. Match status (χ2 = 25.87, p < 0.05, φc = 0.11) and quality of opposition (χ2 = 21.19, p < 0.05, φc = 0.10) were the contextual variables that showed a significant effect on defensive pieces of play initiated in the opposite half of the pitch. Teams winning gained more balls in the zone close to their own goal, and losing teams gained more balls in advanced zones of the pitch. Moreover, the greater the quality of the opponent the lesser the chance of gaining the ball in advanced zones of the pitch. Neither venue or match period influenced the defensive pieces of play analyzed. Soccer teams could employ a similar analysis to improve their performance and prepare for opposition teams in competition.

The lack of standardized outcome measures following lower extremity injury in elite soccer: a systematic review.

PURPOSE: Sport-specific, performance-based outcomes are increasingly used to improve evaluation of treatment efficacy in elite athletes; however, its usage in elite soccer may be limited. The purpose of this investigation is to (1) assess current outcome reporting in elite soccer; (2) identify any variability in reporting of outcomes; and (3) determine how sport-specific performance-based outcomes are utilized to assess treatment efficacy in elite soccer. METHODS: A systematic review of the Pubmed, MEDLINE, and Embase, Scopus, SportDiscus, CINAHL and HealthSource: Nursing databases was performed without limitation on publication year. Inclusion criteria were (1) reporting of outcomes after a (2) lower extremity injury in (3) elite soccer players. The study's population, type of injury, return to play, as well as functional, objective, and sport-specific performance-based outcomes were extracted from each article. The methodological index for nonrandomized studies was used for quality assessment. RESULTS: Twenty-one studies were selected after application of the inclusion and exclusion criteria. Objective outcomes were reported by 6 (29%) studies, and 6 (29%) employed patient-reported outcomes. The visual analog scale, Lysholm, and Tegner scores were the most common patient-reported outcomes (PROs). Return to play was reported by 18 (86%) studies, and only 2 (10%) utilized sport-specific performance-based outcomes. Despite the majority of studies reporting return to play, variation was seen in the definitions, and 15 (71%) studies reported the activity level of the players at final follow-up. CONCLUSION: Assessment of treatment efficacy is limited in elite athletes, and PROs lack the sensitivity to identify residual performance deficits after an injury. Although performance-based measures are available at the elite level, these outcomes were seldom used for evaluation of treatment efficacy. CLINICAL RELEVANCE: When treating elite soccer players, patient-reported outcome measures lack the sensitivity to detect changes in patient function, thus performance-based metrics may be more efficacious in assessing return from injury in these patients. LEVEL OF EVIDENCE: IV.

Effects of match situational variables on possession: the case of England Premier League season 2015/16

Aim: The main aim of this study was to identify the effects of match location, quality of opponents and match status on possession during the 2015/16 Season of England Premier League. Methods: Three hundred and eighty matches played by 20 teams were analysed. For each match, two values were recorded, resulting in 760 observations. Results Teams who played at home (51.77 ± 10.22%) presented higher possession values (EF=moderate) than those who played away (48.21 ± 10.30%). Quality of opponents also had a significant difference, as possession was higher (EF=large) when teams played against weak (52.30 ± 9.77%) than strong opponents (46.48 ± 10.38%). The multivariate analysis revealed no interaction between situational variables and possession (p = 0.76). Despite the teams classified as "best-ranking" (1st to 8th position: 50.60 ± 10.35%) presented greater possession (EF=moderate) than "worst-ranking" (9st to 20th position: 47.59 ± 9.74%), no significant differences were found in the comparisons of match status (winner [50.34 ± 10.48%] x drawer [49.95 ± 10.25%] x loser [49.68 ± 10.48%]). Conclusion: General interpretations should be viewed with caution, since this possession can represent an indicator of success for a team but not for others.(AU)

Identification of Defensive Performance Factors in the 2010 FIFA World Cup South Africa.

The aim of this study was to determine the efficacy of defensive play in elite football, to identify variables associated with the direct recovery of ball possession, and to propose a model for predicting the success of defensive transitions. We analyzed 804 transitions in the final stages of the Fedération Internationale Football Association (FIFA) World Cup 2010, and investigated the following variables using univariate, bivariate, and multivariate analyses: duration of defensive transition, possession loss zone, position of players at the start and end of the defensive transitions, defensive organization, general defensive approach, time of the match, position of defense, zone in which the offensive transition ends, match status, and outcome of the defensive transition. We found that the defensive transitions started most frequently in the middle offensive zone (48.9%), with an organized defense set-up (98.8%), and were unsuccessful on 57.2% of occasions. The bivariate analysis showed that the variable most strongly associated with direct recovery of the possession of the ball (p = 0.018) is the area in which the ball is lost, and the multivariate analysis showed that the duration of the defensive transition can be used as a performance indicator, with transitions lasting between 0 and 15 s associated with a higher likelihood of directly recovering the ball. This work has allowed us to identify a pattern of tactical-strategic behavior with major probabilities of success in the defensive transitions. These results will be able to be used by coaches to improve the performance of their teams in this type of situation in the game.

Salivary hormones and IgA in relation to physical performance in football.

Salivary biomarkers have shown to be useful to assess physiological stress in football, but their relationship with physical performance is unknown. The aims of this study were to investigate the effect of a football match on salivary cortisol, testosterone and immunoglobulin A (IgA) concentrations in elite footballers, and to examine the relationship of physical performance during the match to these biomarkers. Nine elite football players were assessed before, during and after a friendly international match. Physical performance during the match was measured by time-motion analysis, whilst salivary cortisol, testosterone and IgA were measured before and 10 min post-match. The results showed that players covered an average of 9463 ± 458 m during the match. Salivary cortisol did not change post-match. Testosterone and IgA concentrations decreased by 30.6% and 74.5%, respectively. The testosterone/cortisol (T/C) ratio decreased by 64.2% after the match. Changes in testosterone concentrations correlated (r = 0.85) with distance covered. Pre- and post-match testosterone levels correlated with post-match IgA concentrations (r = 0.8 and 0.89, respectively). These results suggest that a football match induces catabolic stress as indicated by the decreased T/C ratio. It seems that footballers with smaller decreases in testosterone levels covered more distance and decreased their immune function less.

The biological age of 14-year-old boys and success in adult soccer: do early maturers predominate in the top-level game?

Talent identification and development in soccer is often biased by maturation-related differences of young athletes. However, there is no information available about success rates for youth maturing at different tempos to achieve success in elite adult soccer. The purposes of this study were to determine the prevalence of different maturational groups among boys playing soccer, and to track them for competence in adult performance. A prospective cohort study design was used to follow 55, 14-year-old boys playing in Serbian youth soccer Division I over eight years. At the age of 14, biological age using skeletal age rates was determined, and participants were categorized as early maturers (EaM), normal maturers (NoM), and late maturers (LaM). Game competence for adult soccer at age 22 was described as elite if an individual played for clubs competing in top-five international soccer leagues (La Liga, Premier League, Bundesliga, Serie A, and Ligue 1), and/or has become a member of an adult National team. Among boys in our study group, 43.8% were categorized as EaM, 35.4% as NoM, and 20.8% as LaM (P = 0.11). A significant difference in biological age was found among maturational groups at age 14, with EaM > NoM > LaM (P > 0.0001). When assessed for adult soccer competence, 33.3% of participants (16 out of 48 players) succeed in achieving elite level. Elite soccer competence acquired 60.1% players from the group of LaM, 38.1% from NoM, and 11.8% from EaM (P > 0.0001). Our comparative analysis suggests that soccer excludes early maturing boys and favors late maturing boys as level of performance increases.

The influence of situational variables on ball possession in the English Premier League.

Abstract The aims of this study were twofold: (1) to examine the influence of situational variables on ball possession in elite soccer and (2) to quantify the variables that discriminate between high or low percentage ball possession teams (HPBPT and LPBPT) across different playing positions. Match performance data were collected from English Premier League matches using a multiple-camera system. Data were examined using linear regression, a 2 × 5 factorial analysis of variance and discriminant analysis. Playing against weak opposition was associated with an increase (P < 0.01) in time spent in possession while playing away decreased (P < 0.01) the time spent in possession by ~3%. Possession was increased (P < 0.01) when losing than winning or drawing. Finally, the better the ranking of a team, the higher (P < 0.01) the time spent in possession. The playing position effect was significant for all variables (P < 0.05); however, there were only interactions with team ball possession in some cases. The discriminant analysis identified functions for all five playing positions (P < 0.01). The variables that discriminated performance between HPBPT and LPBPT were different for various playing positions, although the number of successful passes was the most common discriminating variable. The results demonstrate that HPBPT and LPBPT developed different possession strategies during matches and that selected variables such as successful passes were identified to explain these data trends across various playing positions. Combinations of variables could be used to develop a probabilistic model for predicting time spent in possession by teams.