"Weight–bearing" exercises strengthen the bones. Pilates is only mildly weight bearing but it is excellent for strengthening the muscles of the "core" the total body and for flexibility. Weight-bearing exercises are usually done standing. They force you to support your weight against the force of gravity. Walking, dancing and climbing stairs are weight-bearing exercises but, even better, are running and jumping, because the bone is "loaded" to exert pressure against the force. But note: exercises done on the hands and knees force the body to bear the weight of the trunk and that strengthens the wrists, a vulnerable spot for fractures when bones are thin.