Builds strong bones

Robert Recker, an endocrinologist and current president of the National Osteoporosis Foundation in Washington, D.C., says research indicates that moderate exercise increases and maintains bone mass and reduces the risk of osteoporosis. “The most compelling evidence,” he says, “is that if you don’t do anything, your is much greater.”

Like muscles, bones become stronger when forced to bear more weight than normal. “The skeleton is a smart structural organ and knows how much load [force] is being put on it,” Recker says. “Pick up a pail of water, and you’re loading your arm, your shoulder, your spine, your legs and your hips.” That means muscles are contracting, exerting forces on the bones supporting those body parts. This force stimulates the bone to maintain or even build new tissue. But scientists have yet to figure out why. “That’s a focus,” he says, “of incredibly aggressive research.”

Recker says that researchers speculate, however, that it has to do with exercise triggering osteocytes (the most mature bone cells) to instruct bone-building cells called osteoblasts to increase bone formation.