Gabe Mirkin, M.D.
A study from Wolverhampton University in England shows that exercising to strengthen muscles strengthens the bones on which these same muscles attach.
Bones in the arm that holds the racquet of a professional tennis player are much larger and stronger than the bones in the other arm. The arm bones are bigger, denser and stronger in athletes who whose activities involve upper body strength, such as rugby, rock climbing, kayaking, and weight lifting, while runners were observed to have the lowest arm bone mineral density, even lower than that of the controls.
Leg bone mineral density was highest in rugby players, whose activities included both running and strength training, but when bone density was corrected for body fat, runners had the strongest leg bones. So training is specific. When you strengthen your muscles, you also strenghen the bones on which muscles attach.