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The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status., Competing Interests: The authors have declared that no competing interests exist.

Background: Sport has high social valence and is a primary context for physical activity for the majority of youth. The aim of this study was to estimate the contribution of participation in organized sport to the total daily energy expenditure and also to its moderate-to-vigorous portion in male adolescents., Methods: The sample comprised 165 Portuguese male youth, aged 13 to 16 years. Physical activity was assessed with a multi-method approach (Actigraph GT1M accelerometer plus 3-day diary record). Differences in the intensities of physical activity and sedentary behavior of male sport participants and nonsport participants were compared using independent sample t-test., Results: Male participants in organized sports spent significantly more time in moderate-to-vigorous activities than nonparticipants, although the P-value for the 15 to 16 years age-group was marginal (P = .08) on the weekend days. In addition, male adolescents spent 11% to 13% of total daily energy expenditure in organized sports which corresponded to 35% to 42% of the moderate-to-vigorous portion of daily energy expenditure., Conclusion: Organized sport appears to be a relevant component of daily activity energy expenditure to promote healthy lifestyles among male adolescents.

The purpose of the study was to compare the anthropometric, functional and sport-specific skill characteristics and goal orientations of male youth soccer players at the extremes of height and skeletal maturity in two competitive age groups, 11-12 and 13-14 years. The shortest and tallest players, and least and most skeletally mature players (n = 8 per group) within each age group were compared on chronological age; skeletal age (Fels method); pubertal status (pubic hair); size, proportions and adiposity; four functional capacities; four soccer-specific skills; and task and ego orientation. The tallest players were older chronologically, advanced in maturity (skeletal, pubertal) and heavier, and had relatively longer legs than the shortest players in each age group. At 11-12 years, the most mature players were chronologically younger but advanced in pubertal status, taller and heavier with more adiposity. At 13-14 years, the most mature players were taller, heavier and advanced in pubertal status but did not differ in chronological age compared with the least mature players. Players at the extremes of height and skeletal maturity differed in speed and power (tallest > shortest; most mature > least mature), but did not differ consistently in aerobic endurance and in soccer-specific skills. Results suggested that size and strength discrepancies among youth players were not a major advantage or disadvantage to performance. By inference, coaches and sport administrators may need to provide opportunities for or perhaps protect smaller, skilled players during the adolescent years.

Sex differences in physical activity (PA) through pubertal maturation and the growth spurt are often attributed to changing interests. The contribution of sex differences in biological maturation to the adolescent decline has received limited attention. This study examined the contribution of somatic maturation to sex differences in objective assessments of sedentary behavior and PA in Portuguese adolescents (N = 302, aged 13-16 years). Maturation was estimated from the percentage of predicted mature stature and physically active and inactive behaviors assessed with Actigraph GT1M accelerometers. The influence of age, sex and their interaction on body size, maturation and physical behaviors were examined using factorial ANOVA and, subsequently, ANCOVA (controlling for maturation) tested the effect of sex. Males spent more time in MVPA and less time in sedentary behavior than females. However, sex differences were attenuated when maturation was controlled; thus suggesting that maturity may play an important role in adolescent behaviors.