The contribution of biological maturation to the strength and motor fitness of children.

The interrelationships among skeletal maturity, body size, strength and motor fitness were examined in American children 7-12 years of chronological age (CA). A total of 391 Black (184 boys, 207 girls) and 349 White (193 boys, 156 girls) children participated in the study. Biological maturity was assessed by the Tanner-Whitehouse II method, 20 bone skeletal ages (SA). Strength items included right and left grip strength, and pushing and pulling strength of the shoulders. Motor fitness items included a 35-yard dash, the standing long jump, and softball throw for distance. The standardized residuals of SA on CA (AG) were used to represent the effects of SA, independent of CA. Interaction terms were also computed by multiplying standardized values of stature (ST), body mass (MA), and AG together in all combinations. Regression analyses showed that the strongest predictor of strength was MA, while AG was the best predictor of motor performance. The interaction terms were also significant predictors of performance, explaining between 2% and 9% of the variance in 19 of the 41 significant regressions. The results highlight the complexity of the interrelationships among body size, biological maturation, strength and motor fitness. The effects of SA in children 7-12 years of age are expressed mainly through body size, but SA apparently influences motor fitness more so than muscular strength.