Exercise Doesn't Increase Bone Strength

It's a commonly-held belief that weight-bearing exercise is a good way to increase bone density and strength. But it isn't true. The notion comes from the fact that you do lose bone mass if you are bed-ridden for a long time (or if you are an astronaut in space). But the inverse idea; that you gain bone mass when you exercise, doesn't seem to be true, according to an article in The New York Times that summarizes recent research. The available research shows that exercise only increases bone mass about 1% - not enough to have much effect on overall bone strength. Apparently, just the effects of gravity on your normal types of activity are enough to keep your bones healthy.

However, exercise does reduce the risk of bone fractures, especially in older people. Apparently that's not due to stronger bones, but to better balance and/or stronger muscles, both of which reduce the risk of falling.