Bone mass and exercise.

The overall role of exercise as an integral part of osteoporosis prevention and treatment remains unclear and controversial. Comparatively well accepted are the facts that disuse results in bone mass loss, that sedentary individuals in general have less bone mass than exercising individuals (from cross-sectional study data), that exercise may produce a modest increase in bone mass (from longitudinal study data), and that exercise cannot compensate for estrogen loss. However, numerous questions regarding exercise and the skeleton remain to be answered, such as how the apparent osteogenic effect of exercise is mediated, what is the relationship of exercise in reducing fractures, how to reconcile the discrepancy between exercise-induced bone mass gain (lesser) and disuse bone loss (greater). At present, it seems reasonable to recommend avoidance of a sedentary existence, and participation in a moderate exercise program, for individuals seeking to prevent or treat osteoporosis, recognizing that much of the benefit may be in the resultant increase in muscle strength, in coordination, and in flexibility associated with such a program.