Exercise During Growth: Compelling Evidence for the Primary Prevention of Osteoporosis?

Exercise during growth is widely recommended as a key strategy in the primary prevention of osteoporosis. This theory seems reasonable if exercise is pursued into adulthood, but perhaps not if exercise is ceased; in the latter case, the mechanostat theory predicts a decrease in bone strength due to a decrease in the largest forces applied to the skeleton. However, recent findings suggesting maintenance of bone strength after exercise cessation contradict the mechanostat theory. Former elite athletes display greater bone mass and bone strength than age-matched controls despite several years of retirement (i.e., several years of reduced loading). Recent animal studies that investigated the effects of detraining on bone strength also support this view. As many confounders can modulate bone strength during the period of detraining, these observations need further support before they can be validated. There is still not enough evidence to ascertain confidently that the skeletal benefits obtained during growth can be maintained into old age, and that these benefits are large enough to reduce the risk of fracture at a population level. BoneKEy. 2007 June;4(6):171-180. ©2007 International Bone and Mineral Society