The evidence that exercise during growth or adulthood reduces the risk of fragility fractures is weak

There has never been, and will never be, a randomized double-blind placebo- controlled trial demonstrating that exercise in youth, adulthood or old age reduces fragility or osteoporosis-related fractures in old age. The next l evel of evidence, a randomized, controlled but unblinded study with fractur es as an end-point is feasible but has never been done. The basis for the b elief that exercise reduces fractures is derived from lower levels of 'evid ence', namely, retrospective and prospective observation cohort studies and case-control studies. These studies are at best hypothesis generating, nev er hypothesis testing. They are all subject to many systematic biases and s hould be interpreted with extreme scepticism. Surrogate measures of anti-fr acture efficacy are the next level of evidence, such as the demonstration o f a reduction in risk factors for falls, a reduction in falls, a reduction in fractures due to falls, an increase in peak bone size and mass, preventi on of bone loss in midlife and restoration of bone mass and structure in ol d age.