Regular exercise has effects on bone density, size, and shape, resulting in substantial improvements in mechanical strength. The positive association between exercise and bone mass has prompted many physicians and public health officials to recommend that people engage in daily exercise, with the goal of reducing the incidence of osteoporotic fracture and the morbidity/mortality that ensues. However, there is no clear consensus on exactly how one should exercise in order to reap the greatest returns in terms of bone health. What exercises are best? How often should one exercise? Is it sometimes better not to exercise?

A LITTLE BONE GOES A LONG WAY

Proper exercise can add new bone and/or reduce bone loss to ultimately affect bone mass, but bone mass (or areal bone mineral density) is merely a surrogate measure for bone strength. The real issue at hand is whether or not a person will fracture their hip, spine, or wrist. Bone mineral content and bone mineral density are related to bone strength, but sometimes inferring strength from bone mineral measurements can be misleading. With exercise, small gains in bone mineral can result in large improvements in bone strength,¹ because new bone formation is often localised to …