Longitudinal analysis of scaling VO2 for differences in body size during puberty : the Muscatine study

The purpose of this study was to determine an appropriate method to "normalize" oxygen uptake (VO2) for body size in children and adolescents. We examined allometric scaling factors for a cohort of 126 children (mean age at baseline = 10.3 yr) participating in a 5-yr follow-up study. Each year for 5 yr we measured peak VO2, submaximal VO2, body mass, height, body composition, and sexual maturation. We sorted the 5-yr data set by sexual maturation and gender and then used the generalized estimating equation method to estimate regression parameters that described the influence of log transformed body mass on log transformed VO2. All analyses were repeated using log transformed fat-free body mass (FFM) in lieu of log transformed body mass. Models using FFM appeared better at eliminating the effect of body size on VO2. In boys a univariate model with a FFM exponent of 0.91 and in girls a univariate model with a FFM exponent of 0.87 satisfactorily normalized peak VO2. However, we could not identify a common body size exponent for both boys and girls. Results support the use of allometric scaling of VO2 as a function of FFM for maturing boys and girls but indicate that the effects of maturation on the relationship between VO2 and body size differ between boys and girls.