Osteoporosis and Strength Training

Osteoporosis is a major public health problem. Mechanical strain, imparted by muscle action and ground reaction forces, regulates bone size, shape, mineral mass, and density and subsequently bone strength. Thus, physical activity is critical for bone development, bone health, and fracture risk reduction. Animal studies, in which strain can be manipulated and measured directly, consistently show bone responds to high-strain magnitudes and rates, and only a few repetitions are needed to elicit a response. Extrapolation to humans suggests resistance exercise may be effective for osteoporosis prevention. Indeed, strength-trained athletes have significantly higher bone mass and density than athletes and nonathletes who do not engage in similar training. Prospective studies also support the benefits of resistance exercise demonstrating slowed bone loss and often an increase of 1% to 3% in regional bone mineral density, especially in women. Although more work is needed to define the optimal dose and the effects of nonmechanical factors (eg, nutritional, endocrine, body composition) on the response, the effects of resistance exercise on muscle mass and strength, balance, and agility, in addition to direct skeletal benefits, underscore its importance for osteoporosis, falls, and fracture prevention.