Developmental aspects of physiological function relating to aerobic exercise in children.

The many physiological determinants of exercise performance mature throughout the childhood years. Current research suggests that the improvements in maximal aerobic power which occur as the child ages are an expression of both increased body size and improved function. Absolute VO2max increases during the childhood years in both girls and boys. Average VO2max related to bodyweight, however, remains stable in boys of all ages, while values in girls decline progressively as they grow. VO2 at a given treadmill speed or slope falls during the growing years. This improvement in running economy may explain parallel advances in endurance exercise performance. The explanation for greater running economy with growth is uncertain, but lower step rate, improved running mechanics, and changes in body mass: surface area ratio may play a role.