Exercise Won’t Help Your Bones
First, we should emphasize that exercise is good for you. A body in motion tends to be much healthier than one that is sedentary.
But exercise doesn’t cure everything.
There are logical reasons for people to think that exercise will lead to stronger bones. Bedridden people lose bone mass. So do astronauts who spend time weightless in space. But osteoporosis researchers know that this logic is not backed up by the results of rigorous studies.
About a decade ago scientists wondered if weight bearing exercise increased bone density in adults. To find out, they used DEXA machines, which measure bone density by hitting bones with X-rays. Those studies failed to find anything more than a minuscule exercise effect – something like 1% increased density.
More recently, as tests for bone density grow more sensitive, machines can scan bone and are able to show its structure at a microscopic scale. Even so, just a very small effect from exercise is seen in one part of the bone’s architecture known as the trabecula -- little branches inside bone that link to each other.
Also, the cortical shell (the outer layer of bone) may become slightly thicker with weight bearing exercise. But these are minute changes. There is no evidence that they make bone stronger or protect it from osteoporosis.
So do continue to get your exercise, and do continue to appreciate the good it does you (even if you need to look for other ways to help strengthen you bones).