[Exercise increases muscle strength and probably prevents hip fractures].

No hypothesis-testing studies (blinded, randomized, controlled, prospective) with fracture as endpoint have been published so far. Instead we have to rely on observational cohort and case-control studies, from which available data imply that physical activity reduces the risk of hip fracture in women and perhaps also in men. This could be the case, but repeated sampling bias could present the same outcome. Whether or not exercise reduces the number of vertebral fractures and other fragility fractures is less often evaluated. Fracture rate seems not to be reduced with cessation of exercise. The evidence that exercise modifies the risk of falling is compelling. Exercise is associated with improved muscle strength, coordination and balance. Exercise increases muscle strength even in octogenarians by 20-200 per cent, but these benefits are lost if activity is reduced. Exercise reduces the risk of falling and perhaps also the number of falls. Whether or not the number of injurious falls is reduced by exercise is even more hotly debated.