The effects of exercise on growth.

The way in which exercise influences statural, hypertrophic and reparative growth is examined from the perspective of the human lifespan. Statural growth depends on a neuroendocrine programme which channels nutrient energy towards increments in lean body mass. Exercise can facilitate statural growth and is a necessary stimulus for reparative growth through its stimulatory effects on secretion of growth hormone (GH) and other anabolic hormones. An exercise-associated increase in GH secretion is a response to acute or prolonged exercise-induced fuel shortage that directs metabolism towards utilisation of lipids and promotes growth. Exercise can transiently block the expression of statural growth by competitively removing the necessary nutritional support for growth. Statural growth retardation can be corrected by catch-up growth, but stunting may also be permanent (depending on the timing and magnitude of the energy drain). Hypertrophic growth is less dependent on hormonal and nutritional support than statural growth, and exercise provides the necessary mechanical stress for growth and remodelling of the musculoskeletal system. Excessive mechanical strain may suppress hypertrophic growth. The intermittent nature of exercise provides temporal organisation that is necessary for the normal operation of cellular growth process. Exercise by pregnant women does not appear to influence fetal growth. Evaluation of the effect of exercise on growth of children and adolescents is complicated by nonrandom selection of individuals for participation in organised sports, and by lack of information on the magnitude of exercise-induced energy drain. Exercise is essential for regulation of body composition in adulthood. It provides mechanical and metabolic stimuli that are necessary for hypertrophy of the musculoskeletal system and increased GH secretion for reparative growth.