According to Wolf's Law, the body responds to stress by laying down more bone, making weight-bearing exercise important for building bone density, particularly before age 30.

“the body reacts to this there's I think it's called Wolf's law where the body reacts to stress so the more stress that's put on it the more bone that's laid down for in so that's why we emphasize weight-bearing exercise for patients their thirties in particular before they start losing bone so that they can build up their bone density”