I often read that resistance training is good for your bones. I'm wondering if that means it's good for the limbs that you exercise, or if in a more general way it's somehow good for the whole body. If you work the muscles of your arms, for example, do bones elsewhere in your body benefit?
Buena Vista, Colo.
To be sure, simple resistance or strength training is good for the bones, says Dr. Gregory A. Schmale, an orthopedic surgeon and sports medicine specialist at Children's Hospital in Seattle.
Numerous studies have found that participating in such training programs two to three times per week builds bone mineral density, he writes in an e-mail.
"Bone is constantly remodeling -- that is, old bone is chewed up by a group of bone-eating cells that are followed along by a group of bone-making cells," he says. "This process of breaking down and building up of bone is encouraged by loading of the bone, or pushes and pulls on the bone."
Gravity creates just such a push or pull, and adding additional weights by weightlifting or resistance training increases the amount of push or pull on the bones. Thus, "greater loading leads to greater activity of the bone-chewing and reforming cells, with a net gain in bone over time," Schmale says. "When this process is slowed by decreased forces on the bone -- for instance, for astronauts in a weightless environment, -- there is a net overall loss of bone."
Now, to your question. Resistance training will result in increased bone density in other areas as well, Schmale says, particularly areas close to the area being exercised. That's because when you exercise one particular area of the body, you're calling into action a number of muscles surrounding the affected joint, thus creating a push or pull on surrounding bones.
Resistance or strength training that involves the upper arm, for example, also involves the many muscles that cross the shoulder, including ones that start on the back. Working these muscles places increased force on the bones of the arm and spine, thus building bone mineral density in those areas.
There are also many muscles that cross the hip, connecting the pelvis to the thigh. As a result, resistance or strength training of the legs will typically also work muscles that cross the hip. Working these muscles places increased force on the bones of the pelvis and thigh, helping to boost bone mineral density in those areas as well.
And here's another idea: "Performing arm exercises while standing would result in increased forces on the legs and pelvis as well," he says, "resulting in an increased bone density at all of these sites."
-- Janet Cromley