Exercise and osteoporosis.

Bone formation and resorption are ongoing phenomena. When bone resorption equals bone formation, bone mass remains stable. When resorption exceeds formation, bone mass is reduced--a process that leads to osteopenia or osteoporosis. Osteopenia is reduced bone mass and osteoporosis is reduced bone mass with resultant fractures. Reduced bone mass may be postmenopausal or related to ovarian failure (type I osteoporosis), it may be age-related (type II osteoporosis), or it may result from several other etiologic factors (secondary osteoporosis). Disuse and inactivity can cause bone loss, whereas weight-bearing exercises may maintain or improve bone mineral density. There is a significant correlation between muscle strength and bone mineral density. There is evidence that strengthening exercises may lead to an increase in the mineral density of the bones to which the muscles are attached. Currently, drug regimens are available to decrease or halt bone loss in osteoporotic patients. Properly designed exercise programs may prove to be effective for retarding age-related bone loss. In patients with osteoporosis, the cause should be investigated before treatment is commenced.