Exercise and Musculoskeletal Health in Men With Low Bone Mineral Density: A Systematic Review.

The 13 reports come from only 6 trials, so the same men are counted in several of them and the studies are not independent. The review could not assess whether exercise prevents fractures, because it states that none of the included studies examined that outcome. Eight of the 13 studies did not monitor what the control group was doing, so controls may have been exercising on their own. Some studies were not fully randomised, and in one trial participants chose whether to be a control, so the improvements cannot be credited to exercise alone. In the largest trial both groups took protein, vitamin D and calcium supplements, so the bone and muscle results cannot be separated from the supplements. Exercise programmes and outcome measures varied too much to pool or compare directly. Numbers were small, 320 men in total, and participants were mostly men with few other illnesses, so the findings may not apply to frailer patients. The review protocol was not registered in advance.

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Do not read this as evidence that exercise prevents fractures. The review states that none of the included studies assessed fracture prevention, so it cannot say whether any of these programmes stops someone breaking a bone.