António J. Figueiredo

Characteristics of youth soccer players who drop out, persist or move up

Abstract In this study, we compared the growth, maturity status, functional capacity, sport-specific skill, and goal orientation of 159 male soccer players, aged 11–12 (n = 87) and 13–14 years (n = 72) years, who at follow-up 2 years later discontinued participation (dropout), continued at the same standard (club) or moved to a higher level (elite). Age group-specific multivariate analysis of variance was used for comparisons. Among 11- to 12-year-old players at baseline, a gradient of elite > club > dropout was suggested for size and function, although differences were not consistently significant. Elite players performed significantly better in only two of the four skills, dribbling and ball control. A gradient of elite > club > dropout was more clearly defined among 13- to 14-year-old players at baseline. Elite players were older chronologically and skeletally, larger in body size and performed better in functional capacities and three skill tests than club players and dropouts. Baseline task and ego orientation did not differ among dropouts and club and elite players at follow-up in either age group. The results suggest an important role for growth and maturity status, functional capacities, and sport-specific skills as factors in attrition, persistence, and moving up in youth soccer.

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.

Discrimination of U-14 Soccer Players by Level and Position

Adolescence is often viewed as a critical period for selection in youth soccer. The present study compared the characteristics of regionally selected and non-selected under-14 players (U-14) as a group and by position. Players were classified as local (n=69) and regional (n=45). Weight, height, skinfolds, functional capacities, soccer skills and goal orientation were measured and skeletal age was assessed with the Fels method. Factorial ANOVA was used to test the effect of selection, position and respective interaction terms, while discriminant analysis was used to identify the variables that contributed to selection. Selected players had an advanced maturity status (F=24.97, p<0.01), were heavier (F=30.67, p<0.01) and taller (F=35.07, p<0.01); performed better in explosive power (F=21.25, p<0.01), repeated sprints (F=20.04, p<0.01) and ball control (F=3.69, p<0.05); and were more ego oriented (F=13.29, p<0.01). The 2 competitive groups did not differ in agility, aerobic endurance, dribbling, shooting, passing, and task orientation. Position-related variation was negligible. The percentage of players who were correctly classified in the original groups was slightly lower when the analysis was performed for the total sample (86%) than by position (86-90%). Future research on talent identification and selection should adopt a multidimensional approach including variables related to the physiological, perceptual, cognitive and tactical demands.

Interrelationships among invasive and non-invasive indicators of biological maturation in adolescent male soccer players

Abstract The relationships among indicators of biological maturation were evaluated and concordance between classifications of maturity status in two age groups of youth soccer players examined (11–12 years, n = 87; 13–14 years, n = 93). Data included chronological age (CA), skeletal age (SA, Fels method), stage of pubic hair, predicted age at peak height velocity, and percent of predicted adult height. Players were classified as on time, late or early in maturation using the SA-CA difference, predicted age at peak height velocity, and percent of predicted mature height. Factor analyses indicated two factors in players aged 11–12 years (maturity status: percent of predicted mature height, stage of pubic hair, 59% of variance; maturity timing: SA/CA ratio, predicted age at peak height velocity, 26% of variance), and one factor in players aged 13–14 years (68% of variance). Kappa coefficients were low (0.02–0.23) and indicated poor agreement between maturity classifications. Spearman rank-order correlations between categories were low to moderate (0.16–0.50). Although the indicators were related, concordance of maturity classifications between skeletal age and predicted age at peak height velocity and percent predicted mature height was poor. Talent development programmes call for the classification of youth as early, average, and late maturing for the purpose of designing training and competition programmes. Non-invasive indicators of maturity status have limitations for this purpose.

Predictors of functional capacity and skill in youth soccer players

Predictors of functional capacities and skills in 143 soccer players aged 11–14 years from five clubs in Portugal were investigated. Data for players aged 11–12 (n=75) and 13–14 (n=68) years included chronological age, skeletal age, stage of pubic hair (PH), anthropometry, four functional capacities, four soccer skills and experience; composite functional and skill scores were derived. Multiple linear regression analysis was used to examine the independent effects of age, maturity, body size and proportions, adiposity and experience on individual functional capacities and skills and composite scores. Explained variances differed among functional capacities (22–48%) and skills (<25%), and were greater for composite functional (younger 37%, older 58%) than skill (younger 26%, older 18%) scores. Skeletal maturity was a predictor of the counter‐movement jump in both groups and of composite functional and skill scores in older players. Age and adiposity were primary predictors in players aged 11–12 years, while experience and a proportionally longer trunk (conversely, relatively shorter lower extremities) appeared among predictors in players aged 13–14 years. PH was not among predictors. Except for the counter‐movement jump, predictors of functional capacities and soccer skills differed between age groups.

Anthropometric Characteristics, Physical Fitness and Technical Performance of Under-19 Soccer Players by Competitive Level and Field Position

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n=95; non-elite, n=85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players (d>1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders (d>0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control (d>1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests (d>1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles (d>0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions.

Biological maturation of youth athletes: assessment and implications

The search for talent is pervasive in youth sports. Selection/exclusion in many sports follows a maturity-related gradient largely during the interval of puberty and growth spurt. As such, there is emphasis on methods for assessing maturation. Commonly used methods for assessing status (skeletal age, secondary sex characteristics) and estimating timing (ages at peak height velocity (PHV) and menarche) in youth athletes and two relatively recent anthropometric (non-invasive) methods (status—percentage of predicted near adult height attained at observation, timing—predicted maturity offset/age at PHV) are described and evaluated. The latter methods need further validation with athletes. Currently available data on the maturity status and timing of youth athletes are subsequently summarised. Selection for sport and potential maturity-related correlates are then discussed in the context of talent development and associated models. Talent development from novice to elite is superimposed on a constantly changing base—the processes of physical growth, biological maturation and behavioural development, which occur simultaneously and interact with each other. The processes which are highly individualised also interact with the demands of a sport per se and with involved adults (coaches, trainers, administrators, parents/guardians).

Functional capacities and sport-specific skills of 14- to 15-year-old male basketball players: Size and maturity effects

Abstract The aim of the study was to estimate the influence of body size and pubertal status on variation in functional capacities and sport-specific skills of 59 youth basketball players aged 14.0–15.9 years. Height and mass were measured and stage of pubic hair was assessed at clinical examination. Six tests of functional capacity were evaluated: squat jump, countermovement jump, 60-s sit-ups, 2-kg standing medicine ball throw, hand grip strength, and 20-m multi-stage shuttle run. Four basketball skills were tested (shooting, passing, dribbling, and defensive movements). Comparisons between basketball players of different sexual maturity status were performed using analysis of covariance (controlling for chronological age). Functional capacities and basketball skills appeared to be largely independent of pubertal status especially after controlling for variation in body size. Results of multiple linear regressions indicated chronological age as a significant predictor for four items, while maturity status was a significant predictor for only one item. The influence of body mass was negative for two functional indicators (jumping, multi-stage shuttle run) and two basketball skills (dribbling, defensive movements), but positive for two functional tests of upper body strength (hand grip, ball throw). Height was positively correlated with two specific skills (passing, defensive movements), while a combination of tallness and heaviness was associated with a disadvantage on three functional capacities and two sport-specific skills.

The European Integrated Tokamak Modelling (ITM) effort: achievements and first physics results

A selection of achievements and first physics results are presented of the European Integrated Tokamak Modelling Task Force (EFDA ITM-TF) simulation framework, which aims to provide a standardized platform and an integrated modelling suite of validated numerical codes for the simulation and prediction of a complete plasma discharge of an arbitrary tokamak. The framework developed by the ITM-TF, based on a generic data structure including both simulated and experimental data, allows for the development of sophisticated integrated simulations (workflows) for physics application.The equilibrium reconstruction and linear magnetohydrodynamic (MHD) stability simulation chain was applied, in particular, to the analysis of the edgeMHDstability of ASDEX Upgrade type-I ELMy H-mode discharges and ITER hybrid scenario, demonstrating the stabilizing effect of an increased Shafranov shift on edge modes. Interpretive simulations of a JET hybrid discharge were performed with two electromagnetic turbulence codes within ITM infrastructure showing the signature of trapped-electron assisted ITG turbulence. A successful benchmark among five EC beam/ray-tracing codes was performed in the ITM framework for an ITER inductive scenario for different launching conditions from the equatorial and upper launcher, showing good agreement of the computed absorbed power and driven current. Selected achievements and scientific workflow applications targeting key modelling topics and physics problems are also presented, showing the current status of the ITM-TF modelling suite.

Skeletal Age in Youth Soccer Players: Implication for Age Verification

Objective:To evaluate variation in skeletal age (SA) within single-year chronological age (CA) groups of soccer players aged 11 to 17 years in the context of using SA for age verification in age-group competitions. Design:Cross sectional. Setting:Regional and elite youth soccer programs. Participants:Five hundred ninety-two male players from Portugal and Spain. Independent Variables:Skeletal age assessed with the Fels method. Main Outcome Measures:Skeletal age and maturity status (late, average, early, or mature). Results:Chronological age and SA overlapped in players aged 11 to 12 years, but SA was advanced relative to CA in players aged 14 to 16 years. The majority of players between 11 and 12 years of age were on time in skeletal maturity and percentages of late and early maturers did not differ. The majority of players between 13 and 14 years of age were also on time, but early maturers were 4 times more frequent than late maturers. Percentages of late maturers were low among players aged 14 to 16 years. Among 200 players aged 15 to 16 years, 80 (40%) were advanced in SA by >1 year and 27 (14%) were skeletally mature, whereas among 23 players aged 17 years, 9 (39%) were skeletally mature. Conclusions:Among adolescent soccer player, boys advanced in SA for CA are overrepresented and those later in SA for CA are underrepresented with increasing CA. If Fels SA was used to verify CA in this sample of youth for under-17 competition, 36 skeletally mature players aged 15 to 17 years (16%) would be disqualified. The results for this sample of male soccer players question the utility of SA or magnetic resonance imaging as a valid estimate of CA in youth sport competitions.