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Educating the Student Body
Sex-related differences in muscular development contribute to differ-
ences in physical performance. Muscle strength develops in proportion to 
the cross-sectional area of muscle, and growth curves for strength are essen-
tially the same as those for muscle (Malina and Roche, 1983). Thus the sex 
difference in muscle strength is explained largely by differences in skeletal 
muscle mass rather than muscle quality or composition. Aerobic (endur-
ance) exercise has little effect on enhancing muscle mass but does result 
in significant improvement in oxygen extraction and aerobic metabolism 
(Fournier et al., 1982). In contrast, numerous studies have shown that high-
intensity resistance exercise induces muscle hypertrophy, with associated 
increases in muscle strength. In children and adolescents, strength training 
can increase muscle strength, power, and endurance. Multiple types of resis-
tance training modalities have proven effective and safe (Bernhardt et al., 
2001), and resistance exercise is now recommended for enhancing physical 
health and function (Behringer et al., 2010). These adaptations are due to 
muscle fiber hypertrophy and neural adaptations, with muscle hypertrophy 
playing a more important role in adolescents, especially in males. Prior to 
puberty, before the increase in anabolic sex steroid concentrations, neural 
adaptations explain much of the improvement in muscle function with 
exercise in both boys and girls.