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This study examined the within- and between-day variability of time-segmented sedentary behavior (SB), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA) in adolescents. The sample comprised 154 adolescents (11–16 years old) from two public schools in Florianópolis, Brazil. The proportion of time spent in SB, LPA, and MVPA was measured using Actigraph GT3X+ accelerometers for the following weekday time segments: before school (07:00–07:59), school time (08:00–11:59), after school (12:00–12:59), afternoons (13:00–17:59), and evenings (18:00–23:00). Participants were more active during commuting-related time segments. Females showed lower MVPA than males during school time, afternoons, and evenings, but not before school and after school. Higher age was associated with higher SB and lower LPA during school time, afternoons, and evenings, and slightly lower MVPA during afternoons. The variability of SB, LPA, and MVPA for all time segments was mainly explained by within-participant day-to-day variations rather than between-participant differences of daily-averaged estimates. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Relationships among chronological age (CA), maturation, training experience, and body dimensions with peak oxygen uptake (VO2max) were considered in male basketball players 14-16 y of age. Data for all players included maturity status estimated as percentage of predicted adult height attained at the time of the study (Khamis-Roche protocol), years of training, body dimensions, and VO2max (incremental maximal test on a treadmill). Proportional allometric models derived from stepwise regressions were used to incorporate either CA or maturity status and to incorporate years of formal training in basketball. Estimates for size exponents (95% CI) from the separate allometric models for VO2max were height 2.16 (1.23-3.09), body mass 0.65 (0.37-0.93), and fat-free mass 0.73 (0.46-1.02). Body dimensions explained 39% to 44% of variance. The independent variables in the proportional allometric models explained 47% to 60% of variance in VO2max. Estimated maturity status (11-16% of explained variance) and training experience (7-11% of explained variance) were significant predictors with either body mass or estimated fat-free mass {P < .01) but not with height. Biological maturity status and training experience in basketball had a significant contribution to VO2max via body mass and fat-free fat mass and also had an independent positive relation with aerobic performance. The results highlight the importance of considering variation associated with biological maturation in aerobic performance of late-adolescent boys. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

The present 4-year longitudinal study examined physical growth and development of intermittent endurance run performance in young Basque soccer players aged 10–15 years applying multilevel regression modeling. Anthropometry, predicted adult stature and Yo-Yo Intermittent Recovery level 1 test (Yo-Yo IR1) of players from the under-11 teams from the Athletic Club of Bilbao were measured at pre- and end-season (two measurements per year of study, n = 33 considered for analysis). A non-linear effect of age on intermittent endurance run was observed, with significantly higher increases in Yo-Yo IR1 between 10–11 year-old and 14–15 year-old players. The development of Yo-Yo IR1 performance in all the years of the study was influenced positively by training exposure during the seasons (P < 0.01) and independent of maturity status and body size (P > 0.05). The steady development of intermittent endurance run performance during pubertal years in adolescent Basque soccer players is partially influenced by training exposure. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the agreement of lower-limb volume estimates based on anthropometry and dual-energy X-ray absorptiometry (DXA) as a reference method in male rugby athletes. Predictive models using body mass and skinfolds were tested to improve the relative agreement between protocols (anthropometry, DXA). Rugby players ( n = 41; 19.9 ± 2.2 years) volunteered for the study. Lower-limb total and fat-free volumes were estimated by anthropometry and also derived using DXA. Cross-validation between the anthropometry technique and DXA was then performed. Lower-limb volume estimates by anthropometry overestimated reference values and tended to be further from the reference values with the increase of scale. For the total sample, standard errors of measurement for volume estimates by anthropometry were 1.99 L and 1.34 L for total and fat-free volumes, respectively. Correlations with reference values were 0.81 for lower-limb volume and 0.90 for lower-limb fat-free volume. Correlations between estimated prediction equations and reference values showed higher correlations ( r = 0.96 for lower-limb volume and r = 0.93 for lower-limb fat-free volume) compared with anthropometric estimates. Overall, the agreement of anthropometry method to quantify lower-limb volumes with DXA as a reference in young adult rugby players is acceptable and is a practical method when more expensive and complex techniques are not available. The consideration of body mass and lower-limb skinfolds increases the precision of lower-limb volume estimates using anthropometry in the young adult rugby players. [ABSTRACT FROM AUTHOR]