Peak height velocity in young athletes: A longitudinal meta-analysis.

The present longitudinal meta-analysis aimed to estimate the growth curves and age at peak height velocity (PHV) in young male athletes, considering anthropometric data from available longitudinal studies. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, studies with repeated measurements in young male athletes were identified from searches across four databases (MEDLINE, SPORTDiscus, Web of Science, and SCOPUS). Estimations were based on multilevel polynomial models using a fully Bayesian framework. After a full-text screening of 317 studies meeting the eligibility criteria, 31 studies were considered. Studies were excluded mainly due to study design, repeated reporting, and incomplete reporting of the outcomes. Of the 31 studies analysed, 26 (84%) focused on young European athletes. The average age at PHV for the total sample of studies with young athletes was 13.1 years (90% credible interval: 12.9; 13.4). When considering data by sport, there was substantial variation in the age at PHV estimates (range: 12.4 to 13.5 years). As most studies in the meta-analysis focused on young European football players (52%), predictions for young athletes from other sports may be limited. The age at PHV in the available data occurred earlier than in general paediatric populations.

Performance, motivation, and enjoyment in young female basketball players: An interdisciplinary approach.

The purpose of this study was to examine the variation in accumulated basketball training experience, body size, functional performance, deliberate practice motivation, achievement and competitiveness motivation and sources of enjoyment among young female basketball players, partitioning the potential variation by individuals´ biological characteristics (menarche status) and contextual characteristics (competitive age group and competitive level). We considered 114 adolescent female basketball players aged 14.3 (1.8) years. We used multilevel regression and poststratification estimations. The adolescent female basketball players selected for state-level had more accumulated experience, were taller and with better functional performance. Conditional on the data, youth female coaches tend to value (probably overvalue) size and function when selecting/promoting players, even at early age groups, likely contributing to an overrepresentation of early maturing girls in at early age groups. Players from club- and state-level were similarly highly motivated for deliberate practice and to achievement. Only for competitiveness, state-level players had higher values than club level players. The sources of enjoyment were influenced by context (competitive levels) for self-referenced competencies and others-referenced competencies. Structured programs of training and competition in youth female basketball provide a nurturing environment for the development of players´ engagement and commitment to training and excellence attainment.

Determinants of drop-out in youth basketball: an interdisciplinary approach.

Using an interdisciplinary approach, we examined the baseline variation in biological maturity status, training experience, body size, functional capacities (Line Drill test and Yo-Yo Intermittent Recovery level 1 test) and motivation for achievement, competitiveness and deliberate practice of youth basketball players according to their participation status in the sport two years after assessment. Fifty-seven players were considered (10.5 to 15.5 years). Two years later we ascertained whether players discontinued participation (dropout), or remained playing engaged within a structured basketball training program. Taller adolescent players were more likely to be selected/promoted in youth basketball regardless of their lower functional capacity. Achievement and competitiveness motivation (will to excel and competitiveness) were related to dropping out or persisting in this sample of youth basketball players. Overall, there is a need to consider the interaction between physical growth, biological maturation, functional capacities and behavioural characteristics, specifically among players on the path to sport expertise.

Growth, functional capacities and motivation for achievement and competitiveness in youth basketball: an interdisciplinary approach.

The interaction of multiple influences on the path to sport success is not yet fully understood by sport scientists. In this study, we examined variation in body size, functional capacities and motivation for achievement, competitiveness and deliberate practice of youth basketball players associated with differences in biological maturity status, chronological age and years of training experience. Reflecting the importance of interactive effects, we examined the relationships between the psychological variables and functional capacities. Fifty-eight male basketball players aged 9.5 to 15.5 years were considered. Variables included chronological age, estimated age at peak height velocity, stature, body mass and sitting height by anthropometry; the Work and Family Orientation and Deliberate Practice Motivation Questionnaires were also used. Finally, the Line Drill test and Yo-Yo Intermittent Recovery level 1 (Yo-Yo IR1) tests were used as functional capacities indicators for basketball. Variance components models derived from series of multilevel linear regression models revealed a substantial variation by maturity status for body size, functional capacities indicators, mastery and will to excel. The influence of estimated maturity status on mastery and will to excel was independent of age and years of experience. In contrast, no relationships were observed between psychological variables and functional capacities indicators. We conclude that growth-related changes are relevant to understanding players´ motivations for achievement, competitiveness and deliberate practice. This should be of interest to those involved in the selection and development of youth basketball players.

Acute Hematological and Inflammatory Responses to High-intensity Exercise Tests: Impact of Duration and Mode of Exercise.

The purpose of this study was to investigate the hematological and inflammatory responses to 4 maximal high-intensity protocols, considering energy expenditure in each test. 9 healthy volunteers performed 4 high-intensity exercise tests of short [Wingate (WANT); Repeated-sprints (RSA)] and long durations [Continuous VO2 test (VCONT); intermittent VO2 test (VINT)] in a cycle-ergometer, until exhaustion. Hematological parameters and IL-6, IL-10 and creatine kinase (CK) levels were determined before (PRE), POST, 30 min, 1, 2, 12 and 24 h after the end of the protocols. Additionally, energy expenditure was determined. Leucocytes, erythrocytes and lymphocytes increased at POST and returned to PRE values at 30 min for all protocols. Lymphocytes had a second decreased at 2 h and granulocytes increased at 2 h when compared to PRE. Both variables returned to PRE values between 12-24 h into recovery. The magnitude of response for IL-6 was greater in VINT and for IL-10 in VCONT. There was no association of energy expenditure within each exercise protocol with the pattern of IL-6, IL-10 and CK responses to the exercise protocols. The present finding support that similar responses after continuous or intermittent acute protocols are observed when exercises are performed to volitional failure, regardless of the duration and mode of exercise.

Validity and usefulness of the Line Drill test for adolescent basketball players: a Bayesian multilevel analysis.

The study examined the validity of the Line Drill test (LD) in male adolescent basketball players (10-15 years). Sensitiveness of the LD to changes in performance across a training and competition season (4 months) was also considered. Age, maturation, body size and LD were measured (n = 57). Sensitiveness of the LD was examined pre- and post-competitive season in a sub-sample (n = 44). The time at each of the four shuttle sprints of the LD (i.e. four stages) was modelled with Bayesian multilevel models. We observed very large correlation of performance at stage 4 (full LD protocol) with stage 3, but lower correlations with the early LD stages. Players' performance by somatic maturity differed substantially only when considering full LD protocol performance. Substantial improvements in all stages of the protocol were observed across the 4-month competitive season. The LD protocol should be shortened by the last full court shuttle sprint, remaining sensitive to training exposure, and independent of maturity status and body size.

Mesenchymal stem cells from different murine tissues have differential capacity to metabolize extracellular nucleotides.

Mesenchymal stem cells (MSCs) have shown a great potential for cell-based therapy and many different therapeutic purposes. Despite the recent advances in the knowledge of MSCs biology, their biochemical and molecular properties are still poorly defined. Ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) and ecto-5'-nucleotidase (eNT/CD73) are widely expressed enzymes that hydrolyze extracellular nucleotides, generating an important cellular signaling cascade. Currently, studies have evidenced the relationship between the purinergic system and the development, maintenance, and differentiation of stem cells. The objective of this study is to identify the NTPDases and eNT/CD73 and compare the levels of nucleotide hydrolysis on MSCs isolated from different murine tissues (bone marrow, lung, vena cava, kidney, pancreas, spleen, skin, and adipose tissue). MSCs from all tissues investigated expressed the ectoenzymes at different levels. In MSCs from pancreas and adipose tissue, the hydrolysis of triphosphonucleosides was significantly higher when compared to the other cells. The diphosphonucleosides were hydrolyzed at a higher rate by MSC from pancreas when compared to MSC from other tissues. The differential nucleotide hydrolysis activity and enzyme expression in these cells suggests that MSCs play different roles in regulating the purinergic system in these tissues. Overall MSCs are an attractive adult-derived cell population for therapies, however, the fact that ecto-nucleotide metabolism can affect the microenvironment, modulating important events, such as immune response, makes the assessment of this metabolism an important part of the characterization of MSCs to be applied therapeutically.

Semaphorins and the bone marrow microenvironment: New candidates that influence the hematopoietic system.

The bone marrow is a haven for hematopoietic and non-hematopoietic cells, creating complex micro-anatomical regions called niches. These distinct niches all participate in an intricate orchestra of cellular interactions that regulates the hematopoietic stem cell and its progenies. In this review, we provide a detailed description of the three most well-known bone marrow niches and their participation in hematopoiesis. We use pre-clinical data, including different in vitro and in vivo studies to discuss how a group of proteins called Semaphorins could potentially modulate both hematopoietic and non-hematopoietic cells, establishing links between the niches, semaphorins, and hematopoietic regulation. Thus, here we provide a deep dive into the inner functioning of the bone marrow and discuss the overarching implications that semaphorins might have on blood formation.

Longitudinal Meta-Analysis of Peak Height Velocity in Young Female Athletes.

Growth patterns and biological milestones in youth sports are key to interpreting the development of young athletes. However, there is no analysis of longitudinal meta-analysis describing the growth of young female athletes. This longitudinal meta-analysis estimated growth curves and age at peak height velocity (PHV) in young female athletes based on anthropometric data from longitudinal studies found in the literature. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, studies with repeated measurements in young female athletes were identified from searches of four databases (MEDLINE, Web of Science, SCOPUS, and SPORTDiscus) without date restrictions through August 2023. We adapted our bias assessment criteria using the Cochrane risk of bias tool for randomized controlled trials as a reference. Bayesian multilevel modeling was used to perform a longitudinal meta-analysis to extract stature growth curves and age at PHV. Fourteen studies met our eligibility criteria. Twenty-one independent samples could be included in the analysis. Conditional on the data and models, the predicted mean age at PHV for female athletes was 11.18 years (90% CI: 8.62; 12.94). When studies were aggregated by sport in the models, the models could not capture sport-specific growth curves for stature and estimate a corresponding age at PHV. We provide the first longitudinal meta-analytic summary of pubertal growth and derive age at PHV in young female athletes. The meta-analysis predicted that age at PHV occurs at similar ages to those in the general pediatric population. The data pool was limited in sports and geographic distribution, emphasizing the need to promote longitudinal research in females across different youth sports contexts.

Student-Athlete Identity Variation Across the Undergraduate Period: A Mixed-Methods Study.

We examined the influence of individual and contextual characteristics on student-athlete identities and then explored identity variations across the undergraduate college years. Our main analysis relied on a quantitative study of a large sample of cross-sectional data (n = 862: females = 490, males = 372) with follow-up data for 102 participants. We also used qualitative semi-structured interviews within a small sub-sample (n = 4) who participated in international competitions to provide deeper insight into their identities across time. We used the Portuguese version of the Baller Identity Measurement Scale (BIMS) to explore student-athlete identities, and we examined the influence of sex, student-athlete status (based on institution documents), the participant's competitive level in the sport, and the student athlete's university type. We modelled response probability on BIMS items with multilevel ordinal regression in a cumulative model based on the Bayesian framework. For the follow-up in-depth qualitative interviews of four participants competing at the international level, we used thematic analysis, with two independent researchers generating thematic codes. We found a non-significant trend toward a decreased student-athlete identity across the undergraduate years. Participants' statements reflected their difficulty combining both aspects of the student-athlete identity, such that they tried to shift their identities, depending on the circumstances, while their athletic identity seemed to be privileged. Hence, participants had difficulty combining a dual academic-sport career within a context oriented toward academic achievement and transition to professional life. The higher education context was unprepared to support student-athletes toward a dual academic-sport career.

Does early specialization provide an advantage in physical fitness development in youth basketball?

The present study examined the influence of the specialization onset on the magnitude and patterns of changes in basketball-specific physical fitness within a competitive season and developmental fitness trends between 11 and 17 years in young basketball players. Repeated measures of 181 young basketball players (female, n = 40; male, n = 141) were examined. Anthropometry, age, estimated maturity status, and basketball-specific physical fitness (assessed with the countermovement jump, line drill, and yo-yo intermittent recovery level-1 and fitness score) were considered. Players were grouped by the onset of specialization as related to biological maturation milestones (pre-puberty, mid-puberty, and late-puberty specialization). The within-season and developmental changes in physical fitness were fitted using multilevel modeling in a fully Bayesian framework. The fitness outcomes were similar between-player and within-player changes when grouped by specialization across a season. Fitness improvements across a season were apparent for female players, while male players maintained their performance levels. There was no variation in the patterns of physical fitness development between 11 and 17 years associated with the onset of specialization. Conditional on our data and models, the assumption that early sport specialization provides a physical fitness advantage for future athletic success does not hold.

Predictors of maximal short-term power outputs in basketball players 14-16 years.

Relationships between growth, maturation and maximal short-term power outputs were investigated in 94 youth basketball players aged 14-16 years. Data included chronological age (CA), skeletal age (SA), years of training; body dimensions, estimated thigh volume, a running based short-term exercise assessed by the line drill test (LDT), the Bangsbo sprint test (BST) and short-term muscle power outputs with the Wingate anaerobic test (WAnT). Multiple linear regression analyses were used to estimate the effects of CA, skeletal maturity (SA/CA), years of training experience, body size and lower-limb volume on short-term performance in the LDT, BST and WAnT, respectively. Explained variances differed between cycle-ergometry outputs (52-54%) and running test performances (23-46%). The independent effects of predictors were small in the fatigue scores of the WAnT (4%) and the BST (11%). Skeletal maturity, body mass and leg length were primary predictors for all maximal short-term power output measures. Leg length was more relevant as a predictor than stature in the WAnT outputs, while stature and body mass appeared in the model with the running tests as dependent variable. Maximal short-term running abilities were also sensitive to years of training. In summary, skeletal maturation, body size and thigh muscle mass explained moderate to large proportions of the variance on maximal short-term performances of adolescent basketball players. The results highlight the importance of considering maturity status in evaluating the maximal short-term power outputs of adolescent athletes.

Age-related variation of anaerobic power after controlling for size and maturation in adolescent basketball players.

BACKGROUND: Adolescence is characterized by increments in body size and physical performance. Short bursts of maximal intensity, requiring anaerobic metabolism, are important in many team sports including basketball. AIM: Variation of anaerobic power of adolescent basketball players (n = 93, 14-16 years) in relation to years before and after estimated age at peak height velocity (PHV) and variation in body size was considered. METHODS: The cross-sectional study included chronological age, estimated age at PHV, training experience; stature, body mass (BM), free-fat mass (FFM) and estimated lower-limb volume (LLV) by anthropometry; and short-term power outputs derived from the Wingate Anaerobic Test (WAnT). Based on proportional allometric modeling, power outputs were partitioned for biological maturity status and size variables. Pearson correlations were used to estimate the associations between distance to PHV (maturity offset) and training experience with absolute and scaled estimates of short-term power. RESULTS: Absolute WAnT increased linearly (PP, r = 0.72; MP, r = 0.74) through the interval of rapid growth of the adolescent spurt. Increments were related mainly to BM and muscle mass. Nevertheless, a residual significant positive influence of chronological age per se on maximal short-term power outputs remained independent of body size. CONCLUSION: Allometric modelling to partition size may reveal other potentially meaningful factors in the development of short-term performance in adolescent athletes.

Cross-validation and reliability of the line-drill test of anaerobic performance in basketball players 14-16 years.

This study evaluates the validity and reliability of the line-drill (LD) test of anaerobic performance in 76 male basketball players 14.0-16.0 years of age. The Wingate Anaerobic Test (WAnT) was used as the reference for anaerobic performance. Wingate Anaerobic Test and LD test were moderately correlated (0.39 and 0.43, p < 0.01). Estimated age at peak height velocity (APHV) was moderately, negatively, and significantly (p < 0.01) correlated with WAnT peak (r = -0.69) and mean power (r = -0.71); earlier-maturing players had greater anaerobic power. Training experience was not associated with anaerobic performance, but chronological age (CA) and estimated APHV were significant covariates of the LD test (p < 0.05). National players were better than local players on the LD test (p < 0.01) after controlling for CA and body size. Short-term reliability of the LD test (n = 12, 1-week interval) was good: technical error of measurement = 0.44 seconds (95% confidence interval [CI] 0.31-0.75 seconds), intraclass correlation coefficient = 0.91 (95% CI 0.68-0.97), and coefficient of variation = 1.4% (95% CI 1.0-2.3%). Although the relationship between the LD test and WAnT was moderate, the LD test effectively distinguished local- and national-level adolescent basketball players. In contrast to WAnT, the LD test was not influenced by estimated biological maturity status. Thus, the LD test may be suitable for field assessment of anaerobic performance of youth basketball players.

Why do they engage in such hard programs? The search for excellence in youth basketball.

Excellent performance in sport has a strong positive relationship with the accumulated hours of practice. The specialization years are seen as a decisive moment to lift the skill level, athletic readiness and commitment but the selection and orientation of talent has been strongly dependent of biological and motor variables. The purpose of this study is to describe the achievement and motivation variables that can explain the belonging to an elite competitive level of young basketball players. Eighty-two basketball players under 16 years fulfilled the WOFO Questionnaire (Spence and Helmreich, 1983), and an adapted version of the DPMQ (De Bruin, Rikers and Schmidt, 2007). Forty players (mean age 15. 8 ± 0.96) were engaged in high performance centres and forty-two (mean age 15.6 ± 1.01) played in national level clubs. A decision tree and a random forest analysis between elite and national level players were performed. The most discriminant variable was Will to Excel, with 85,2% true positives in elite or national level. Mastery and competitiveness did not enter the final model. The will to reach excellence in performance can be considered as a condition to engage in more specialized and demanding practice. The assessment of the path to expertise only through motor variables or through the accumulated hours of deliberate practice is limited and can lead to mistaken identification or orientation of young sport talents. The use of a more comprehensive model is needed. Key pointsExcellent performance in sport has a strong positive relationship with the accumulated hours of practice.It seems reasonable that if the young athletes are better selected, have better training conditions and practice and compete more time with better teammates and opponents, the chance of becoming competent adult athletes is greater.A self orientation to excellence may play a crucial role in persistence in practice, in order to achieve higher standards in competition.The specific motivation that underpins participation at different levels and help the coaches to be sensitive to non-biological or non-functional variables, leading to a better knowledge and caring of the adolescents they teach.The assessment of the path to expertise only through motor variables or through the accumulated hours of deliberate practice is limited and can lead to mistaken identification or orientation of young sport talents.

Validity and usefulness of the student-athletes' motivation toward sport and academics questionnaire: a Bayesian multilevel approach.

BACKGROUND: Reliable assessment and understanding of student-athletes' motivation for dual careers are crucial to support their career development and transitions. The purpose of this research was to examine the validity and usefulness of the student-athletes' motivation toward sport and academics questionnaire (SAMSAQ-PT) in the Brazilian higher education context. Four studies were performed. METHODS: In study one, conceptually and semantic translation of the questionnaire and Bayesian exploratory factor analysis were conducted. In study two, a Bayesian confirmatory factor analysis with an independent sample was performed. In study three, Bayesian multilevel modeling was applied to examine the construct validity of the questionnaire in a cross-sectional sample. In study four, the SAMSAQ-PT sensitiveness was examined in a longitudinal sample, and the results were interpreted based on multilevel regression and poststratification. RESULTS: Altogether the results provided evidence validity and usefulness of the SAMSAQ-PT in Brazilian student-athletes. The Brazilian student-athletes' motivation scores were sensitive to the influence of sex, sport level, and type of university on career and sport motivation. SAMSAQ-PT estimate scores across an academic year showed a trend of stability in the scores, adjusting for sex, sport level, type of university, and student-athlete status. CONCLUSION: The SAMSAQ-PT proved to be a robust and valuable questionnaire, which could be used in Portuguese-speaking countries. The findings of the cross-sectional and longitudinal surveys urge to consider individual and contextual characteristics when investigating motivation of dual-career of athletes, also concerning the sex-related opportunities in university sports. Furthermore, there is a need for a call for action to promote and nurture the student-athletes motivation to remain engaged in both sports and educational commitments.

Multidimensional characteristics of young Brazilian volleyball players: A Bayesian multilevel analysis.

Brazil has been the benchmark for volleyball performance for at least two decades, providing a unique context to examine expertise development. This study examined the variation in body size, functional capacities, motivation for achievement, competitiveness, and deliberate practice of youth volleyball players associated with differences in biological maturity status, chronological age, and accumulated deliberate volleyball practice, adopting a Bayesian multilevel modeling approach. We considered 68 female and 94 male adolescent players (14.2 years, 90% confidence interval: 12.7 to 16.0). Players were grouped by the onset of deliberate volleyball practice as related to biologic maturation milestones [pre-puberty deliberate practice onset (12% of the sample), mid-puberty deliberate practice onset (51% of the sample), and late-puberty deliberate practice onset (37% of the sample). There was substantial variation in body dimensions and functional performance by gender. There was no variation by gender for motivation for deliberate practice and motivation for achievement and competitiveness. The young volleyball players appeared to be highly motivated and committed to deliberate practice, achievement, and competitiveness. Alignment of chronological age, biological maturation, and accumulated training experience allow more in-depth insights into young volleyball players' development, providing sounder support for coaches´ decisions.

Student-Athletes' Motivation and Identity: Variation Among Brazilian and Portuguese University Student-Athletes.

This study examined the variation of student-athletes' identity and motivation across Portuguese and Brazilian universities, accounting for variation in gender, student-athletes' training hours per week, sports level, student-athletes status within each university, and university type. We initially established the validity of the Baller Identity Measurement Scale questionnaire and the Student-Athletes' Motivation toward Sports and Academics Questionnaire-based observations among 441 Brazilian and Portuguese student-athletes. Then, the validated version of the questionnaires was applied to a total sample of 765 student-athletes from Brazil (n= 568) and Portugal (n = 197). We further considered individual (hours of training and student-athlete status) and contextual characteristics (university type and country). Multilevel regression and poststratification were used to estimate each student-athlete identity and motivation as a function of his or her individual and contextual characteristics. Overall, the predictions showed that cultural (country), academic (type of university), and athletic (training hours) context likely have a substantial influence on student-athletes' identity and motivation.

Deliberate Practice, Functional Performance and Psychological Characteristics in Young Basketball Players: A Bayesian Multilevel Analysis.

BACKGROUND: Early sport specialization has increased its popularity mostly based on the deliberate practice theory premises. In this study, we examined the influence of the age of onset of deliberate basketball practice on body size, functional performance (countermovement jump, line drill and yo-yo intermittent recovery level 1), motivation for achievement and competitiveness, motivation for deliberate practice and sources of enjoyment among young Brazilian basketball players. In addition, we adjusted for the influence of gender, age group, maturity status and state basketball federation on the outcomes. METHODS: The sample included 120 female and 201 male adolescent basketball players aged 14.0 (1.7) years, on average. We grouped players by the age of onset of deliberate basketball practice as related to biologic maturation milestones (pre-puberty deliberate practice onset, mid-puberty deliberate practice onset and late-puberty deliberate practice onset). RESULTS: There was no substantial variation among contrasting players by the onset of deliberate practice in all of the outcomes. Adjusting for gender, male players with late-puberty deliberate practice onset had better functional performance than players with pre- and mid-puberty onset of practice. Females players with late-puberty deliberate practice onset had slightly worst functional performance than players with pre- and mid-puberty onset of practice. CONCLUSIONS: Early deliberate basketball practice does not appear to provide an advantage for the development of physiological functions. Likewise, enjoyment, motivation for deliberate practice and motivation for achievement and competition do not appear to be negatively influenced by early deliberate basketball practice. The debate about the relationship between time spent in deliberate practice and performance development in young athletes will need to emphasize the coaching pedagogical quality and the training environment and account for informal practice and deliberate play.

Youth soccer players, 11-14 years: maturity, size, function, skill and goal orientation.

BACKGROUND: Participants in many youth sports are commonly combined into age groups spanning 2 years. AIM: The study compared variation in size, function, sport-specific skill and goal orientation associated with differences in biological maturity status of youth soccer players within two competitive age groups. METHODS: The sample included 159 male soccer players in two competitive age groups, 11-12 years (n=87) and 13-14 years (n=72). Weight, height, sitting height and four skinfolds, four functional capacities, four soccer skills and goal orientation were measured. Skeletal maturity was assessed using the Fels method. Each player was classified as late, on time or early maturing based on the difference between skeletal and chronological ages. ANOVA was used to compare characteristics of players across maturity groups. RESULTS: Late, on time and early maturing boys are represented among 11-12-year-olds, but late maturing boys are under-represented among 13-14-year-olds. Players in each age group advanced in maturity are taller and heavier than those on time and late in skeletal maturity, but players of contrasting maturity status do not differ, with few exceptions, in functional capacities, soccer-specific skills and goal orientation. CONCLUSION: Variation in body size associated with maturity status in youth soccer players is similar to that for adolescent males in general, but soccer players who vary in maturity status do not differ in functional capacities, soccer-specific skills and goal orientation.