Exercise and the preservation of bone health.

Exercise is generally accepted as having favorable effects on bone health and, subsequently, a reduction in fracture risk. In the absence of large randomized controlled trials of the potential benefits of exercise on fracture risk, support for this belief comes from cross-sectional studies and interventional studies using surrogate endpoints such as bone mineral density and falls. In this review, we discuss the characteristics of exercise programs that provide an osteogenic stimulus. The goals and benefits of exercise on bone across the age spectrum are discussed. Where there is a paucity of human data, animal studies examining the roles of variables such as exercise intensity, frequency, duration, and mode in shaping the response of bone to exercise are discussed. The effects of disuse and the limited response of bone to remobilization are described. The rapid and dramatic decrease in bone mineral density observed in the early period after heart or lung transplantation is discussed, as are the available data on the benefits of exercise on bone in this population. For cardiopulmonary rehabilitation programs to improve bone health, they should include not just weight-supported activities (eg, cycling) but also weight-bearing activities (eg, walking, resistance exercise). Although the optimal exercise routine for bone health is unknown, components of an osteogenic program are discussed.