The effect of physical activity on the skeleton.

Immobilization of the whole body or a part of it will lead to a self-limited osteoporosis in the parts of the skeleton involved. This may be prevented by physical training, especially if the anti-gravity muscles are employed. It is uncertain whether physical activity can increase the maximal bone mass or limit the loss of bone due to ageing, although individual reports suggest that both are possible. It would be of considerable significance to have this point clarified, since fractures in osteoporotic patients pose a significant medical and health economics problem.