Mechanical load which comes mainly from muscle force as well as gravitational force associated with body weight plays an important role in increasing bone mass and bone strength. The greater is mechanical load to the bone, the larger are the increases in bone mass and bone strength. In particular, jumping exercise produces a large amount of mechanical forces loaded to the bone through muscle force. Jumping exercise together with calcium supplementation during the pre- and peri-pubertal periods is reported to be effective in stimulating bone growth and thereby increasing bone mineral content. In girls, interventions must be initiated during the pre-menarcheal period to effectively maximize peak bone mass.