Longitudinal changes of maximal short-term peak power in girls and boys during growth

The aims of this study are twofold: first, to analyze the influence of age, body mass, and lean leg volume (LLV) on short-term leg peak power (Pmax) of young females and males during growth using multilevel regression analysis and, second, to compare the regression results of boys and girls.

The individuals were 100 girls and 109 boys aged 7.5-17.5 yr old. Pmax, LLV, and mass were determined on two occasions using the cycling force-velocity test. The optimal force (Fopt) and pedaling frequency (Vopt) corresponded to the force and pedaling frequency at Pmax.

It was observed that the increase of Pmax doesn't depend on gender until the age of 14. From that age, Pmax values are significantly lower in girls than in boys. In girls, LLV is the main predictor of Pmax variance (68%; P < 0.001), whereas in boys it is age (57%; P < 0.001). Results of ANCOVA were that for the same leg length (LL), Vopt is significantly (P < 0.001) higher in boys than in girls. It also indicated that for the same LLV, there are no significant (P > 0.05) gender differences of Fopt.

These results illustrated that during the growth period, the increase of Pmax is significantly higher in boys than in girls. Qualitative muscular factors (Type II fiber, glycolytic ability, motor coordination, and motor unit activation) may account for the significantly higher Pmax production in boys than in girls. Precisely, the gender differences might be explained by neuromuscular determinants of contraction velocity. In conclusion, children should develop their neuromuscular determinants of contraction velocity rather than their lean leg volume.