Three-year follow-up of changes in aerobic fitness during puberty: the Muscatine Study.

To assess the tracking of aerobic fitness during puberty and its relationship to changes in body composition and indexes of growth, the authors of this study measured body fat, echocardiographic left ventricular mass (LVM), fat-free mass (FFM), height, physical activity, resting blood pressure, sexual maturation, and maximal aerobic fitness (VO2peak) in 123 children (ages 7-12 years). Measures were repeated 3 years later. Tracking was assessed by Spearman rank correlation coefficients between baseline and follow-up data. Predictors of changing aerobic fitness were examined using stepwise regression. Significant tracking of aerobic fitness was observed with correlations ranging from .70-.75. Increased FFM and increased LVM explained 51% of the variability in improved aerobic fitness (ml.min-1) in boys. Increased FFM and increased height explained 26% of the variability in improved aerobic fitness (ml.min-1) in girls. During puberty, children who gain the greatest amount of lean tissue (including cardiac) experience the greatest improvements in aerobic fitness (ml.min-1). Measures of aerobic fitness prior to and during early puberty tend to predict aerobic fitness during puberty.