Composición corporal, dermatoglifia y resistencia aeróbica en futbolistas bogotanos categoría sub 20 / Body Composition, Dermatoglyphics and Aerobic Resistance in Sub-20 Category Footballers from Bogota, Colombia

Resumen El fútbol como disciplina ha sido objeto de numerosas investigaciones que han permitido la potenciación de las cualidades de las personas deportistas para alcanzar el máximo rendimiento deportivo. El uso de nuevas herramientas ha permitido mejorar los procesos de selección de talentos y el desarrollo de las capacidades físicas, como es el caso de la dermatoglifia, que brinda información del genotipo de un individuo. El presente estudio pretende relacionar la composición corporal, la dermatoglifia y el consumo máximo de oxígeno en jugadores de fútbol categoría sub 20. La investigación fue cuantitativa, diseño no experimental, de tipo transversal. La muestra estuvo conformada por 22 futbolistas (edad 18 ± 1.1) de un club deportivo de Bogotá, a ellos se les realizó una valoración de composición corporal, se les calculó el somatotipo, se analizaron las huellas de las manos y se midió el consumo máximo de oxígeno con el Test Course Navette. Los resultados muestran predominio del somatotipo mesomorfo balanceado (53%), alta presencia de presillas "L" (66.36%), baja presencia de arcos "A" (1.82%) y un consumo máximo de oxígeno de 53.76 ± 3.73 ml/kg/min. Además, se encontraron relaciones significativas entre componentes dermatoglíficos D10-SCTL y el somatotipo endomorfo (p < 0.05), y entre el VO₂ máximo con somatotipo endomorfo y ectomorfo (p < 0.05). Se concluye que los futbolistas se caracterizan por tener una predisposición hacia la coordinación, la resistencia y la agilidad.

Abstract Soccer has generated endless research that has enhanced athlete's qualities to achieve maximum sports performance. According to the above, the use of new tools has been implemented to improve talent selection processes and develop physical abilities, as is the case with dermatoglyphics that provides information on an individual's genotype. The present study aims to relate body composition, dermatoglyphics, and maximum oxygen consumption in soccer players' category sub-20. The research had a quantitative, non-experimental, cross-sectional design. The sample comprised 22 players (age 18±1.1) from Bogota Sports Club, Colombia. They were assessed for body composition, the somatotype was calculated, handprints were analyzed, and the maximum oxygen consumption was measured with the Test Course Navette. The results show a predominance of balanced mesomorph somatotype (53%), high presence of "L" ridges (66.36 %), low presence of "A" arches (1.82%), and maximum oxygen consumption of 53.76±3.73 ml/kg/min. Furthermore, significant relationships were found between D10-SCTL dermatoglyphic components and the endomorph somatotype (p <0.05), and between the maximum VO₂ with endomorph and ectomorph somatotype (p <0.05). It is concluded that soccer players are characterized by having a predisposition towards coordination, resistance, and agility.

Resumo O futebol como disciplina tem sido objeto de inúmeras investigações que permitiram melhorar as qualidades dos desportistas para alcançar o máximo desempenho desportivo. A utilização de novas ferramentas tornou possível melhorar os processos de seleção de talentos e o desenvolvimento de capacidades físicas, como a dermatoglifia, que fornece informações sobre o genótipo de um indivíduo. O presente estudo visa relacionar a composição corporal, dermatoglifos e o consumo máximo de oxigênio nos jogadores de futebol sub-20. A pesquisa foi quantitativa, não-experimental e transversal. A amostra consistiu em 22 jogadores de futebol (18 ± 1,1 anos) de um clube desportivo de Bogotá, que foram submetidos a uma avaliação da composição corporal, foi calculado o somatotipo, foram analisadas as impressões digitais das mãos e foi medido o consumo máximo de oxigénio através do teste Course Navette. Os resultados mostram uma predominância do somatotipo mesomorfo balanceado (53%), presença elevada de presilha em "L" (66,36%), baixa presença de arcos em "A" (1,82%) e um consumo máximo de oxigênio de 53,76 ± 3,73 ml/kg/min. Além disso, foram encontradas relações significativas entre os componentes dermatoglíficos D10-SCTL e o somatotipo endomorfo (p < 0,05), e entre VO₂ máximo com somatotipo endomorfo e ectomorfo (p < 0,05). Conclui-se que os jogadores de futebol são caracterizados por uma predisposição para a coordenação, resistência e agilidade.

Coding Body Language in Sports: The Nonverbal Behavior Coding System for Soccer Penalties.

Nonverbal behavior (NVB) plays an important role in sports. However, it has been difficult to measure, as no coding schemes exist to objectively measure NVB in sports. Therefore, the authors adapted the Body Action and Posture Coding System to the context of soccer penalties, validated it, and initially used this system (Nonverbal Behavior Coding System for Soccer Penalties [NBCSP]) to explore NVB in penalties. Study 1 demonstrated that the NBCSP had good to excellent intercoder reliability regarding the occurrence and temporal precision of NVBs. It also showed that the coding system could differentiate certain postures and behaviors as a function of emotional valence (i.e., positive vs. negative emotional states). Study 2 identified differences in NVB for successful and missed shots in a sample of penalties (time spent looking toward the goal, toward the ground, right arm movement, and how upright the body posture was). The authors discuss the utility of the coding system for different sport contexts.

Is impaired coordination related to match physical load in footballers with cerebral palsy of different sport classes?

Impaired coordination is a characteristic feature in cerebral palsy (CP) football players. This study aimed to determine the relationships of three coordination tests with match physical load during competition of para-footballers from different sport classes. Records from 259 para-footballers from 25 national teams were obtained in four international competitions held in 2018 and 2019. The three coordination tests were conducted prior to competition (i.e., rapid heel-toe, side-stepping, and split jumps), and physical match load was recorded by GPS devices during the real game: i.e., maximum/mean, total distance, distance covered at different speed zones, number of accelerations/decelerations at different intensities, and player load. FT1 and FT3 players have the lowest and highest performance in all the coordination tests, respectively, but inconclusive between-groups differences were obtained (p=0.022‒0.238). Split jumps and side-stepping tests are associated with the performance of moderate and high accelerations during competition (r = -0.20‒0.71; p<0.01). Significant correlations (r = 0.36‒0.71; p<0.01) were obtained between all the coordination measures. Coordination tests better discriminate those with more severe impairments and some evidence for the validity of the new CP football sport classes is provided. Further research is necessary to identify the portion of the variance in sports performance that coordination explains.

Expert opinion on classification for footballers with vision impairment: Towards evidence-based minimum impairment criteria.

In Para sport, the aim of classification is to minimize the impact of impairment on the outcome of competition. Despite requirements of the International Paralympic Committee Athlete Classification Code for classification to be evidence-based and sport-specific, sports for athletes with VI, including football, use the same generic classes across almost all sports. The aim of this study was to consult with experts to establish the needs and challenges for developing a code-compliant system of classification for VI football. A panel of 18 experts with international experience in VI football (16.8 ± 10.2 years) took part in a three-round Delphi study using online surveys. Results showed that the panel did not think that the current system completely fulfils the aim of classification. The panel identified measures of visual function they considered to be relevant but are not currently measured during classification including dynamic acuity, depth and motion perception, and contrast and light sensitivity. Moreover, they identified technical skills such as ball control, dribbling and passing, as well as perceptual-cognitive skills, as most likely to be affected by vision impairment. Findings outline the need for change and offer a framework for future research to develop an evidence-based classification for VI football.

A Fraction of Recommended Practices: Implementation of the FIFA 11+ in NCAA Soccer Programs.

Background and Objectives: National Collegiate Athletic Association (NCAA) soccer coaches implement numerous warm-up and flexibility strategies to prepare athletes for training and competition. The Fédération Internationale de Football Association (FIFA) developed the 11+ injury prevention program to reduce non-contact injuries. This study aimed to analyze the level of familiarity with and implementation of the evidence-based FIFA 11+ amongst NCAA Division I (DI) and Division III (DIII) men's and women's soccer coaches. Materials and Methods: NCAA soccer coaches in the United States received an Institutional Review Board-approved survey hyperlink. A total of 240 coaches completed the survey. The respondents represented 47.5% men's and 52.5% women's teams distributed within DI and DIII programs. Descriptive statistics are reported as frequency counts and mean ± standard deviation where applicable. Pearson's chi-square tests were performed to assess potential differences with a significance level set at α < 0.05. Results: The results indicated that approximately 62% of the respondents reported being familiar with the FIFA 11+ program. Of those coaches familiar with the program, 15.0% reported full implementation, 57.5% reported partial implementation, and 27.5% reported no implementation. Chi-square analyses revealed significant differences in FIFA 11+ implementation based upon division level (χ2 = 4.56, p = 0.033) and coaching certification levels (χ2 = 13.11, p = 0.011). Conclusions: This study indicates that there is a gap between FIFA 11+ knowledge and actual implementation. To reduce the risk of non-contact injury, there is a need to educate coaches and athletic trainers on the purpose of the FIFA 11+ program and how to perform the exercises correctly.

Talent identification and development in soccer since the millennium.

At the turn of the millennium, a review paper was published in this journal on talent identification and development in soccer (Williams & Reilly, 2000). In the current paper, we assess progress made in this field over the last twenty years relative to the areas for future research highlighted in the original review. We evaluate developments in light of the calls made by Williams and Reilly to: a) undertake more multidisciplinary rather than mono-disciplinary research; b) embrace longitudinal rather than cross-sectional research designs; c) expand the research base on female football; and, d) better identify the subjective criteria used by scouts when selecting one player over another for entry into a formalised training environment. The body of mono-disciplinary research on this topic continues to expand, and progress has been made in publishing multidisciplinary, prospective, longitudinal data sets, along with advanced statistical modelling procedures, as well as in identifying the experiential criteria used by scouts. We found some variables in these studies have predictive value from adolescence to adult performance level in soccer. We present suggestions for future research to enhance knowledge and understanding of the best practices underpinning the identification and development of future generations of professional players.

Effect of the Modification of the Number of Players, the Size of the Goal, and the Size of the Field in Competition on the Play Actions in U-12 Male Football.

A player's sports development involves a long process. The modification of rules for youth players seeks to adapt the sport to the child and his/her development. The manipulation of rules affects the technical and tactical skills demonstrated by players and, therefore, their development. The objective of this study was to analyse the effect of a reduction in the number of players (from 8 per team to 5 per team), the size of the goal (from 6 × 2 m to 3 × 2 m) and the playing space (from 58 × 38 m to 38 × 20 m), on the technical and tactical actions in youth football players. A quasi-experimental A-B-A design was implemented to assess the effect of the rule changes. The players (n = 40) played three tournaments using two competition formats (official rules, modified rules, and official rules). The results show that the use of the modified rules generated a greater number and variability in the technical-tactical actions, a greater number of actions with teammates in the pass line, a greater continuity in the game, a greater number of attack and defence actions in areas close to the goal, and favours team play. The experimental format fits the players' individual progression better (U-12) as well as the players' and teams' collective development, and it will allow players to evolve from the individual development of previous stages.

A bioecological perspective on talent identification in junior-elite soccer: A Pan-European perspective.

Elite soccer clubs across Europe spend ever-increasing sums of money on transfers and salaries for world-class players. Consequently, clubs' talent identification and development processes for junior players have become more professionalised. Based on a holistic ecological approach, this study presents an analysis of talent identification practices across some of the most productive soccer academies in Europe (N = 11). Data were collected via semi-structured interviews with 11 heads of academy recruitment from clubs in the "big five" European leagues. Clubs were purposively sampled based on their player productivity ranking. Interviews ranged from 52:26 minutes to 114:06 minutes in length (m = 87:53 ± 20.10 minutes). This study argues that holistic ecological approaches the environments were characterised through the interplay of factors that ranged from high-level internal to international level relationships. This resulted in the identification and recruitment of players from local and international environments. The purpose of recruitment was suggested to have a dual purpose: recruitment of players for the first team; recruitment of players for further development/monitoring and/or selling to another club.

Evaluation of soccer players under the Moneyball concept.

The recruitment of athletes with limited resources is a global problem in professional sports. In US Major League Baseball, the experience of the Oakland Athletics' general manager in the last decade turned his "Moneyball" model into a synonym of quantitative analysis in the transfer market of baseball players. His strategy focused on hiring players with outstanding technical skills but relatively low market value. This study adapted this model to the framework of a multiple criteria decision aid (MCDA), by selecting undervalued players who have complementary abilities. The novelty here refers to the joint use of four algorithms explored by the composition of probabilistic preferences (CPP) (i.e., ranking, classification, dynamic evaluation and regularity analysis) and their application to soccer player performance evaluation. The new model analysed the recent transfer of a left-back soccer player to Europe. The results indicated 12 opportunities for better investment, among 32 left and right-back players considered. Two years later, the value of the same player was considerably lower. He played only five matches in the 2018-2019 season, without scoring or providing any assists. On the other hand, the players better classified by the CPP-MB model presented higher performances and market values.

[Anthropometric differences per playing position in Chilean professional footballers]. / Diferencias antropométricas por posición de juego en futbolistas profesionales chilenos.

INTRODUCTION: Introduction: given the characteristics of soccer, the tendency in the selection of these athletes and their allocation in certain game positions has been conditioned by the morphological characteristics that they present, so that the knowledge of anthropometric particularities by playing position is a relevant antecedent for the technical bodies of professional football. The objective of the present investigation is to identify and compare the anthropometric characteristics by playing position of Chilean professional soccer players. Methods: a total of 390 professional male soccer players, from 15 Chilean professional clubs, were evaluated morphologically by means of the measurement of 25 anthropometric variables, with which the body composition, the somatotype and the Z-score of Phantom were estimated. A Chi-square test with significance level of p < 0.05 was used to compare the variables between groups using SPSS software others players (greater adipose and muscular mass). As for a sample of active subjects, soccer players have a significantly different body composition, similarly occurs when compared to Phantom, where height, weight and muscle mass are greater and fat mass is lower. Conclusion: professional footballers differ by game position compared to other non-sports players and Phantom.

INTRODUCCIÓN: Introducción: dadas las características del fútbol, la tendencia en la selección de estos deportistas y su asignación en determinadas posiciones de juego se han visto condicionadas por las características morfológicas que estos presenten, por lo que el conocimiento de las particularidades antropométricas por posición de juego es un antecedente relevante para los cuerpos técnicos del fútbol de élite. El objetivo de la presente investigación es identificar y comparar las características antropométricas por posición de juego de jugadores de fútbol profesional chileno. Métodos: un total de 390 futbolistas profesionales varones, pertenecientes a 15 clubes profesionales chilenos, fueron evaluados morfológicamente mediante la medición de 25 variables antropométricas, con las que se estimaron la composición corporal, el somatótipo y los Z-score de Phantom. Para la comparación de las variables entre los grupos se utilizó una prueba Chi-cuadrado con nivel de significancia de p < 0,05, utilizando el software SPSS versión 21. Resultados: se observan diferencias entre las posiciones de juego, especialmente entre los porteros y el resto de los jugadores (p < 0,001), quienes presentan más de 2 kg de masa muscular y más de 1,8 kg de masa adiposa, frente a las otras posiciones de juego. Respecto de una muestra se sujetos activos, los futbolistas presentan una composición corporal significativamente distinta; de igual manera ocurre al comparar con Phantom, donde la estatura, el peso y la masa muscular son mayores y la masa adiposa es menor. Conclusión: los futbolistas profesionales presentan diferencias por posición de juego y en comparación a otros sujetos no deportistas y a Phantom.

A Coding System to Quantify Powerful Actions in Soccer Match Play: A Pilot Study.

PURPOSE: The powerful activity profile of elite soccer match play has not been documented appropriately to inform specific maximal power assessment and development criteria. The aims of the current study were to develop a reliable  soccer-specific powerful action (SSPA) notational analysis coding system that could be used to compare frequency and durations of powerful actions during elite youth soccer match play. METHODS: Sixteen elite male English Premier League (EPL) Academy players (19 ± 1 yrs) were recorded by an individual camera during 16 competitive EPL U18 and U21 games. Video footage was analyzed using performance analysis software and SSPAs were coded according to the following categories: initial acceleration, leading acceleration, sprint, unilateral jump and bilateral jump. RESULTS: The SSPA coding system demonstrated very good inter- and intra-rater reliability (kappa coefficients ≥ 0.827). Elite youth EPL soccer players undertook significantly more initial (31 ± 9) and leading (37 ± 12) accelerations than sprints (8 ± 3; p = .014, d = 1.7, and p < .001, d = 1.7, respectively) and jumps (6 ± 5; p = .002, d = 1.7 and p < .001, d = 1.7, respectively). Players performed a significantly greater number of initial and leading accelerations with action durations below 1.5 s compared to above 1.5 s (p = .001, d = 1.6, and p = .002, d = 1.4), respectively. CONCLUSIONS: Our SSPA coding system provides a reliable observational instrument for quantifying the frequency and duration of powerful actions performed during elite soccer match play. In our sample of elite youth soccer players, horizontal accelerations of short duration (< 1.5 s) from different starting speeds appear the most dominant powerful action in elite youth soccer match play.

Classification of playing position in elite junior Australian football using technical skill indicators.

​In team sport, classifying playing position based on a players' expressed skill sets can provide a guide to talent identification by enabling the recognition of performance attributes relative to playing position. Here, elite junior Australian football players were a priori classified into 1 of 4 common playing positions; forward, midfield, defence, and ruck. Three analysis approaches were used to assess the extent to which 12 in-game skill performance indicators could classify playing position. These were a linear discriminant analysis (LDA), random forest, and a PART decision list. The LDA produced classification accuracy of 56.8%, with class errors ranging from 19.6% (midfielders) to 75.0% (ruck). The random forest model performed at a slightly worse level (51.62%), with class errors ranging from 27.8% (midfielders) to 100% (ruck). The decision list revealed 6 rules capable of classifying playing position at accuracy of 70.1%, with class errors ranging from 14.4% (midfielders) to 100% (ruck). Although the PART decision list produced the greatest relative classification accuracy, the technical skill indicators reported were generally unable to accurately classify players according to their position using the 3 analysis approaches. This player homogeneity may complicate recruitment by constraining talent recruiter's ability to objectively recognise distinctive positional attributes.

Comparison of body fat percentage of male soccer players of different competitive levels, playing positions and age groups: a meta-analysis.

BACKGROUND: The aim of the present meta-analysis was to compare the body fat percentage (%) between male soccer players of different competitive levels, playing positions and age groups. EVIDENCE ACQUISITION: The systematic search was conducted using different databases and according to the Population/Intervention or Exposure/Comparison/Outcome(s) [PICO] criteria. EVIDENCE SYNTHESIS: Higher percentage values of body fat in lower-level soccer players than higher-level counterparts (ES=0.18, 95% CI -0.86 to -0.14, P=0.006) were noted. Higher body fat % values in goalkeepers than defenders (ES=0.21, 95% CI -1.17 to -0.34, P<0.001), midfielders (ES=0.26, 95% CI -1.50 to -0.45, P<0.001) and forwards (ES=0.18, 95% CI -1.26 to -0.53, P<0.001) were observed. There was no significant association between % of body fat and age (P=0.86). CONCLUSIONS: In conclusion, body fat percentage clearly distinguished higher- from lower-level soccer players. These findings also imply that body fat percentage differ as a function of positional role in soccer and that sports scientists, coaches, and strength and conditioning professionals need to be aware of the specific positional requirements in soccer in terms of body fat. However, due to some limitations of the present meta-analysis (high statistically significant heterogeneity and evidence of publication bias), further studies are urgently needed in the field.

Vertical and Horizontal Jump Capacity in International Cerebral Palsy Football Players.

PURPOSE: To evaluate the reliability and validity of vertical and horizontal jump tests in football players with cerebral palsy (FPCP) and to analyze the jump performance differences between current International Federation for Cerebral Palsy Football functional classes (ie, FT5-FT8). METHODS: A total of 132 international parafootballers (25.8 [6.7] y; 70.0 [9.1] kg; 175.7 [7.3] cm; 22.8 [2.8] kg·m-2; and 10.7 [7.5] y training experience) participated in the study. The participants were classified according to the International Federation for Cerebral Palsy Football classification rules, and a group of 39 players without cerebral palsy was included in the study as a control group. Football players' vertical and horizontal jump performance was assessed. RESULTS: All the tests showed good to excellent relative intrasession reliability scores, both in FPCP and in the control group (intraclass correlation = .78-.97, SEM < 10.5%). Significant between-groups differences (P < .001) were obtained in the countermovement jump, standing broad jump, 4 bounds for distance, and triple hop for distance dominant leg and nondominant leg. The control group performed higher/farther jumps with regard to all the FPCP classes, obtaining significant differences and moderate to large effect sizes (ESs) (.85 < ES < 5.54, P < .01). Players in FT8 class (less severe impairments) had significantly higher scores in all the jump tests than players in the lower classes (ES = moderate to large, P < .01). CONCLUSIONS: The vertical and horizontal jump tests performed in this study could be applied to the classification procedures and protocols for FPCP.

Premier League academy soccer players' experiences of competing in a tournament bio-banded for biological maturation.

Individual differences in the growth and maturation have been shown to impact player performance and development in youth soccer. This study investigated Premier League academy players' experiences of participating in a tournament bio-banded for biological maturation. Players (N = 66) from four professional soccer clubs aged 11 and 14 years and between 85-90% of adult stature participated in a tournament. Players competed in three 11 vs 11 games on a full size pitch with 25-min halves. Sixteen players participated in four 15-min focus groups and were asked to describe their experiences of participating in the bio-banded tournament in comparison to age group competition. All players described their experience as positive and recommended the Premier League integrate bio-banding into the existing games programme. In comparison to age-group competitions, early maturing players described the bio-banded games more physically challenging, and found that they had to adapt their style of play placing a greater emphasis on technique and tactics. Late maturing players considered the games to be less physically challenging, yet appreciated the having more opportunity to use, develop and demonstrate their technical, physical, and psychological competencies. Bio-banding strategies appear to contribute positively towards the holistic development of young soccer players.

External Match Loads of Footballers With Cerebral Palsy: A Comparison Among Sport Classes.

PURPOSE: To determine and compare the external match load, according to sport class (FT), of footballers with cerebral palsy (CP) during the International Federation of CP Football World Championships Qualification Tournament. METHODS: Forty-two international male footballers with CP participated in the data collection. The footballers with CP were classified according to their FT into 3 groups (ie, FT5/6, FT7, and FT8). External match load (ie, total distance covered, distance covered at different speeds, accelerations, decelerations, player load, peak metabolic power, and changes of directions) was collected for both halves during official matches with global positioning system devices. RESULTS: Players with lower impairment (FT8) covered more distance (effect size = 0.30-0.60) at high-intensity running (13.0-18.0 km·h-1) and sprinting (>18.0 km·h-1) and performed more (effect size = 0.29-1.08) accelerations, decelerations, and changes of direction at high intensity in matches than did other players (ie, FT5/6 and FT7 groups). CONCLUSION: Because high-intensity actions are relevant to football performance and there are differences caused by players' impairments, the International Federation of CP Football classification protocols should include high-intensity actions during the technical assessment as part of the procedures for determining the sport class of football players with CP.

Relación de los estilos de liderazgo, cohesión grupal, potencia de equipo y rendimiento en jugadores de fútbol no profesionales / Relationship of Leadership Styles, Group Cohesion, Power Equipment and Performance in Non-Professional Soccer Players

Resumen El objetivo del presente trabajo fue analizar las relaciones entre tipos de liderazgo (tarea y social), cohesión, potencia de equipo y rendimiento en 334 futbolistas federados de las categorías Alevín, Cadete, Juvenil y Absoluta, con una edad media de 15.97 (DE = 3.31). Los cuestionarios utilizados fueron de Liderazgo auténtico (ALQ), tarea (LSS), Cohesión grupal (CG), Potencia de equipo (CPEA) y rendimiento, que mostraron índices de ajuste óptimos (χ2/DF = 1.313 p = 0; CFI = 0.997; TLI = 0.994; RMSEA = 0.032; SRMS = 0.0343). Los resultados indican que el estilo de liderazgo, especialmente liderazgo tarea (p = 0.37) influye indirectamente en el rendimiento a través de la CG (p = 0.17) y CPE (p = 0.21). Como conclusión, se propone la mejora del rendimiento grupal a partir de la optimización de modelos de conducta individuales.

Abstract The objective was to analyze the relationships between types of leadership (task and social), cohesion, team potency and performance in 334 federated players of the categories Alevín, Cadet, Juvenile and Absolute, with a mean age of 15.97 (SD = 3.31). The questionnaires used were Authentic Leadership (ALQ), Task (LSS), Group Cohesion (CG), Team Power (CPEA), and Performance that showed optimal adjustment indexes (χ2 / DF = 1.313 p = 0; CFI = 0.997; TLI = 0.994; RMSEA = 0.032; SRMS = 0.0343). The results indicate that leadership style, especially leadership task (p = 0.37) indirectly influences performance through CG (p = 0.17) and CPE (p = 0.21). In conclusion, it is proposed to improve group performance by optimizing individual behavior models.

Longitudinal development of match-running performance in elite male youth soccer players.

This study longitudinally examined age-related changes in the match-running performance of retained and released elite youth soccer players aged 8-18 years. The effect of playing position on age-related changes was also considered. Across three seasons, 263 elite youth soccer players were assessed in 1-29 competitive matches (988 player-matches). For each player-match, total distance and distances covered at age group-specific speed zones (low-speed, high-speed, sprinting) were calculated using 1 Hz or 5 Hz GPS. Mixed modeling predicted that match-running performance developed nonlinearly, with age-related changes best described with quadratic age terms. Modeling predicted that playing position significantly modified age-related changes (P < 0.05) and retained players covered significantly more low-speed distance compared with released players (P < 0.05), by 75 ± 71 m/h (mean ± 95% CI; effect size ± 95% CI: 0.35 ± 0.34). Model intercepts randomly varied, indicating differences between players in match-running performance unexplained by age, playing position or status. These findings may assist experts in developing training programs specific to the match play demands of players of different ages and playing positions. Although retained players covered more low-speed distance than released players, further study of the actions comprising low-speed distance during match play is warranted to better understand factors differentiating retained and released players.

Characterization of the Sprint and Repeated-Sprint Sequences Performed by Professional Futsal Players, According to Playing Position, During Official Matches.

The purposes of this study were to investigate sprints and to characterize repeated-sprint sequences (RS) performed by athletes during professional futsal matches. We analyzed 97 players during 5 official matches using the DVideo automatic tracking system. The sprints were analyzed during the first and second halves according to playing position, and RS were categorized according to the number of sprints and the time between them. The results showed an increase (F[1, 2520] = 3.96; P = .046) in the sprint duration from the first (mean = 3.1 ± 1.3) to the second half (mean = 3.2 ± 1.2). However, no differences were found for other variables (distance covered, peak velocity, initial velocity, recovery time between sprints, and sprints performed per minute) or among playing positions. In addition, when considering RS, the results showed that RS comprising two sprints interspersed with a maximum of 15 seconds of recovery were significantly more frequent than other RS. The findings of this study characterizing the sprinting features of futsal players can help coaches to plan physical training and assessments according to the requirements of the sport.

Effect of team rank and player classification on activity profiles of elite wheelchair rugby players.

The aim of the current study was to establish which indicators of mobility are associated with successful wheelchair rugby performance and determine whether these indicators differed across classification. Data were collected from 11 international teams during 30 matches (353 match observations) using a radio-frequency-based, indoor tracking system across two tournaments. Players (n = 111) were first grouped by team rank as determined by their International Wheelchair Rugby Federation (IWRF) world ranking (LOW, MID, HIGH) and then into one of four groups based on their IWRF classification: Group I (0.5), Group II (1.0-1.5), Group III (2.0-2.5) and Group IV (3.0-3.5). The volume of activity (relative distance and mean speed), peak speed and time spent within classification-specific arbitrary speed zones were calculated for each individual. Although no differences were identified in the volume of activity, playing time was significantly reduced in LOW (34:51 ± 8:35) compared to MID (48:54 ± 0:51) and HIGH (45:38 ± 9:53), which was further supported by the greater number of substitutions performed by LOW. HIGH achieved greater peak speeds (3.55 ± 0.40 m · s-(1)) than LOW (3.27 ± 0.42 m · s(-1)) and MID (3.45 ± 0.41 m · s(-1)). Peak speed was further shown to be classification-dependent (P ≤ 0.005), whereby HIGH Groups III and IV players achieved greater peak speeds than LOW and MID. The time spent performing high-intensity activities was also greater in HIGH compared to LOW and MID, whilst further influenced by classification (P ≤ 0.0005). To conclude, peak speed and the ability to perform a greater number of high-intensity activities were associated with successful performance in wheelchair rugby.