Modeling growth and maturation changes in peak oxygen uptake in 11-13 yr olds

Children's Health and Exercise Research Centre, University of Exeter, Exeter EX1 2LU, United Kingdom The influence of gender, growth, and maturation on peak O 2 consumption ( O 2 peak ) in 11-13 yr olds were examined by using multilevel regression modeling. Subjects were 119 boys and 115 girls, aged 11.2 ± 0.4 (SD) yr at the onset of the study. Sexual maturation was classified according to Tanner's indexes of pubic hair. O 2 peak was determined annually for 3 yr. The initial model identified body mass and stature as significant explanatory variables, with an additional positive effect for age and incremental effects for stage of maturation. A significant gender difference was apparent with lower values for girls, and an age-by-gender interaction indicated a progressive divergence in boys' and girls' O 2 peak . Subsequent incorporation of the sum of two skinfold thicknesses into the model negated stature effects, reduced the gender term, and explained much of the observed maturity effects. The body mass exponent almost doubled, but the age-by-gender interaction term was consistent with the initial model. aerobic fitness; growth; maturation; multilevel modeling; gender