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Robert M. Malina

The growth status and rate of a mixed-longitudinal sample (N = 19) of female volleyball players 9–13 years of age were compared to reference data for the general population. The athletes were measured at the beginning and end of the school year. Growth rates in stature and weight adjusted to 6-month intervals were calculated. The results indicate mean statures that are above U.S. reference medians and mean weights that are near the medians (i.e., tall girls with average body weights). Estimated half-year growth rates in stature and weight from 10.0–13.0 years closely match the respective medians of the Fels longitudinal study. The data thus suggest that the larger body size of young volleyball players is not a function of accelerated growth rate during these early adolescent ages and, thus, not due to earlier maturation; body size is likely genotypic and probably reflects selection at relatively young ages for the size demands of the sport.

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Robert M. Malina and Tadeusz Bielicki

Based on information provided at a follow-up interview at age 27 of male participants in the Wroclaw Growth Study, 16 of 176 males (9.1 %) were identified as regularly active in sport during childhood, adolescence, and young adulthood. The Wroclaw Growth Study followed a large cohort of boys and girls from ages 8 through 18. Complete growth and maturation records from ages 8 through 18 were available for 13 of the 16 active boys. Mean ages at attaining several indicators of somatic, skeletal, and sexual maturity were generally earlier in the active boys. This would suggest that the sample of boys who were active in sport were advanced in biological maturation. The advanced maturity status of the active boys was also apparent in greater stature, weight, and biacromial breadth, especially during the pubertal years, while bicristal breadth and skinfolds did not differ from the longitudinal series.

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Robert M. Malina

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Peter T. Katzmarzyk and Robert M. Malina

The contribution of organized sport participation to the total daily energy expenditure (TDEE) of youth was estimated in a sample of 90 males and 93 females, 12-14 years of age. TDEE and moderate-to-vigorous energy expenditure (MVEE) were estimated using a 3-day activity record. Males expended 20.4% of TDEE in youth sports; the corresponding estimate for females was 16.3%. Males and females expended 55% and 64.6%, respectively, of MVEE in youth sports. Youth who participated in organized sports had greater TDEE and MVEE, and spent less time watching television than those who did not participate. Thus, organized sport participation appears to be a significant component of daily energy expenditure among youth.

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André F. Seabra, Denisa M. Mendonça, Martine A. Thomis, Robert M. Malina and José A. Maia

Background:

The present study considered age- and sex-associated variation in sports participation (SP) in Portuguese youth.

Method:

A national survey of 12,568 students, ages 10 to 18 y, was conducted. Two items of the Baecke et al. (1982) questionnaire that deal with SP were considered. Logistic regression and factorial ANOVA were used.

Results:

The prevalence of SP is greater in males than females. Mean sport scores increased in both sexes from ages 10 to 18 y. Soccer was the most practiced sport among males, while swimming and soccer were the most practiced sports among females. Males participated in SP >5 hours per week compared to 1 to 2 hours per week in females. High-intensity sports were more prevalent among males, while sports of mid-level intensity were more prevalent among females. The majority of youth participate in sport more than 9 months of the year.

Conclusion:

SP is an important component of physical activity among Portuguese youth and has a relatively stable prevalence between ages 10 to 18 y.

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Humberto M. Carvalho, Manuel J. Coelho-e-Silva, Joey C. Eisenmann and Robert M. Malina

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.

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Joey C. Eisenmann, Robert M. Malina and Roy J. Shephard

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Gillian K. Myburgh, Sean P. Cumming, Manuel Coelho E. Silva, Karl Cooke and Robert M. Malina

Purpose:

To evaluate relationships among skeletal maturity, body size, and functional capacities of elite junior tennis players.

Methods:

Participants were 88 elite British Junior tennis players (44 male; 44 female), 8–16 years of age (12.4 } 1.9 years). Skeletal age estimated maturty. Anthropometry, grip strength, countermovement jump, squat jump, forehand agility, backhand agility, Yo-Yo, 5-m, 10-m and 20-m sprints were measured. Comparative analysis for each sex was performed, relating advanced maturers (Male: 15; Female: 29) to a combination of on-time and late maturers (Male: 29; Female: 31). ANCOVAs were used to determine absolute differences between male and female players and between the 2 maturity subgroups, with chronological age as the covariate.

Results:

Advanced maturity afforded male players advantages in absolute measures of grip strength, speed, upper and lower body power but not in acceleration, agility or aerobic endurance. Male players were significantly taller than females in the U13-U16 age group. Advanced maturity in female players afforded advantages in absolute measures of grip strength, agility and overhead power, but not in backhand agility, aerobic endurance or squat jump power.

Conclusion:

It is important that talent identification protocols consider the maturity of youth athletes to more satisfactorily address athletic potential rather than transient physical capabilities.

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Robert M. Malina, Audrey C. Choh, Stefan A. Czerwinski and Wm. Cameron Chumlea

Sex-specific equations for predicting maturity offset, time before or after peak height velocity (PHV), were evaluated in 63 girls and 74 boys from the Fels Longitudinal Study. Serially measured heights (0.1 cm), sitting heights (0.1 cm), weights (0.1 kg), and estimated leg lengths (0.1 cm) from 8 to 18 years were used. Predicted age at PHV (years) was calculated as the difference between chronological age (CA) and maturity offset. Actual age at PHV for each child was derived with a triple logistic model (Bock-Thissen-du Toit). Mean predicted maturity offset was negative and lowest at 8 years and increased linearly with increasing CA. Predicted ages at PHV increased linearly with CA from 8 to 18 years in girls and from 8 to 13 years in boys; predictions varied within relatively narrow limits from 12 to 15 years and then increased to 18 years in boys. Differences between predicted and actual ages at PHV among youth of contrasting maturity status were significant across the age range in both sexes. Dependence of predicted age at PHV upon CA at prediction and on actual age at PHV limits its utility as an indicator of maturity timing and in sport talent programs.

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Robert M. Malina, Sean P. Cumming and Manuel J. Coelho e Silva

“Gaps in Our Knowledge” are discussed in the context of the need to integrate biological and behavioral factors in a biocultural approach to physical activity and movement proficiency. Specific issues considered include outdoor play, organized and informal activity, biological maturation, tracking of activity, development of movement proficiency, and individual differences. Studies considered are largely based on youth in economically better-off, developed countries in the western culture context. There is a need to extend studies of physical activity and movement proficiency to different cultural contexts.