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How Much Exercise Is Best for Women's Hearts?

The CDC recommends that people exercise at moderate intensity for 30 minutes on most days to achieve important health benefits, and suggests that additional exercise might enhance this benefit. Previous recommendations had endorsed vigorous endurance exercise at least three times per week to achieve cardiovascular fitness. So how much is the best to recommend?

This study of 1837 women from the National Runners' Health Study focused on serum HDL cholesterol levels. The longer the weekly running distance, the higher the mean HDL: levels increased from 59 mg/dl among women running less than 16 km (about 10 miles) to 69 mg/dl in those running over 64 km (about 40 miles). This significant difference could not be explained by age, diet, hormone use, menstrual status, or other coronary risk factors. HDL levels rose with increasing mileage even beyond 64 km/week. Women who ran more were also more likely to have lower blood pressure, body-mass index, and total cholesterol.

Comment: This study supports the belief that exercise exceeding the current CDC recommendation further raises HDL levels and maximizes cardiovascular health. However, as an editorial points out, the risks of very high levels of exercise -- including amenorrhea, possible bone loss associated with hormonal changes and weight loss, and musculoskeletal injury -- may offset the cardiac benefits of long-distance running. The optimal exercise prescription for women has yet to be written.

— W Levinson

Published in Journal Watch Women's Health July 1, 1996

Citation(s):

William PT. High-density lipoprotein cholesterol and other risk factors for coronary heart disease in female runners. N Engl J Med 1996 May 16 334 1298-1303.

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Manson JE; Lee IM. Exercise for women -- how much pain for optimal gain? N Engl J Med 1996 May 16 334 1325-1326.

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• Medline abstract (Free)