Are sex differences in child motor activity level a function of sex differences in maturational status?

By virtue of being farther along a developmental path for motor activity level, girls may appear to be the less active sex when compared to less physically mature but same-aged boys. If so, observed sex differences in activity level may be an epiphenomenon of sex differences in maturity related declines in AL. To test this hypothesis and the associated premise that females would be more mature and less active than males, the customary activity levels and relative physical maturities of 83 5-8-year-olds were assessed. Relative maturity (percentage of estimated adult height attained) was negatively related to activity level, and girls were both less motorically active and more mature than boys. Though reduced in magnitude, the sex effect remained significant after maturity was added as a predictor of AL. Thus, sex differences are not due only to maturity differences but may be partially mediated by them.