Low-impact exercise may boost women's bone mass

By Amy Norton

NEW YORK, Oct 29 (Reuters Health) - Aerobic exercise can increase women's bone density, and it need not be a high-impact regimen to work, new research shows.

In fact, experts' recommendations for general health--walking for about 30 minutes a day, a few days a week--is enough to lend the bones a hand, George A. Kelley, of the MGH Institute of Health Professions in Boston, an academic affiliate of Massachusetts General Hospital.

In a review of 24 studies on aerobic exercise and bone mineral density in women, Kelley's team found that, on average, regular exercisers saw about a 2% bone mass gain over non-exercisers.

Whether the modest gain translates into a lower risk of the bone-thinning disease osteoporosis and its associated fractures is unclear, Kelley told Reuters Health. However, he added, because exercise improves balance and coordination, it could lower older women's odds of falling, which would provide benefits beyond any boosts in bone mass.

Kelley presented the study findings last week in Atlanta, Georgia, at the annual meeting of the American Public Health Association.

Kelley's team analyzed studies that followed women aged 18 and older, the majority of whom were sedentary. In each study, some women were assigned to an aerobic exercise regimen that lasted at least 16 weeks.

Walking was the most common form of exercise used in the studies, Kelley said. On average, women walked about a half-hour, 3 days a week.

Overall, women who exercised gained close to 0.4% in bone mineral density in the lower spine, while non-exercisers saw a decrease of nearly 2%. Exercisers also saw a 1.4% gain in the thighbone, while non-exercisers recorded a loss of about 0.6%.

The benefits were similar among premenopausal and postmenopausal women, Kelley noted.

Exercise helps strengthen bones because it forces them to bear weight. Accordingly, some research shows that exercise that requires more weight-bearing--such as high-impact activities like running--provides the greatest benefits to bone.

"But then there's the practical part of getting people to stick with it," Kelley pointed out.

"Our adherence to physical activity programs is abominable," he added.

So the good news from this study is that the most popular form of exercise in the US--walking--can give a lift to bone mass, according to Kelley.

Since strength training with weights also helps bone density, he added, the ideal exercise plan includes aerobics and weights.

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