How does strength training slow bone loss?


I was recently diagnosed with osteopenia. My doctor advised strength training because it can help slow bone loss. How does it do that?


Osteopenia is a thinning of the bones. It is often a precursor to osteoporosis, a more severe thinning of the bones. Osteoporosis puts you at risk for disabling, and sometimes debilitating, fractures.

Bones are filled with cells. Some cells build up new bone; other cells tear down old bone. In most people, those two processes are in good balance. But in some people, particularly as they grow older, more bone gets torn down than built up.

To reverse that imbalance, and the osteopenia that comes from it, you need to stimulate the bone-building process. Bone, like muscle, follows the “use it or lose it” rule. One way to “use it” is to exercise. When you exercise, particularly in strength training, it stimulates the formation of new bone. The tug of the muscles on the bone, and the weight that the bone is being asked to support, signal the bone-building cells to work harder.

Strength-training exercises build muscle by harnessing resistance — that is, an opposing force that muscles must strain against. Resistance can be supplied by your body weight, free weights, elasticized bands or specialized machines. No matter what kind of resistance you use, putting more than the usual amount of load on your muscles makes the bones stronger.

Strength training should target bones of the hips, spine and wrists, as these are the bones that are most likely to fracture.

People with osteopenia, like you, or with osteoporosis have to exercise carefully. A person should not do exercises that could cause thin bones to fracture. For example, I tell my patients to protect their spine. This means avoiding activities and exercises that require you to bend your spine, especially to lift a weight. Bowling is a common example.

I also advise my patients to avoid free-weight exercises and machines that put added stress on the spine. These include some leg-press machines, leg raises performed lying down, and squats done with weight bars resting on the shoulders. A person with thinning spine bones needs to do strength-training exercises that build strong core muscles.

I don’t know your age, but it’s possible that you’re thinking as you read this: “I’m too old to do strength training, to work out with machines and weights and such.” That’s wrong. Supervised weight training in older people builds muscle and bone.

Finally, don’t stop with strength training. Add a few balance exercises to your routine to reduce your risk of falls.

(This column ran originally in October 2014.)