Walking as little as one hour a week can cut a women's risk of heart disease in half compared to women who don't exercise, according to new research.

The study, published in the March 21/01 issue of the Journal of the American Medical Association, suggests that the time spent walking may be more important than the pace, and some form of physical activity is better than none at all for women at all levels of risk.

"It's encouraging that our study shows even if you do modest levels of activity, you will get benefits," says study author I-Min Lee, ScD, associate professor of epidemiology at Brigham and Women's Hospital and Harvard Medical School in Boston.

Lee says it's clear that physical activity is associated with a lower heart disease risk in men and women. But, until now, little research has been done or known about what kind and intensity of activities are needed to provide heart healthy benefits.
Physical activity recommendations have also changed over time. In the 1970's and 1980's, Lee says the philosophy was "no pain, no gain" and vigorous activity like running and jogging was recommended for at least 20 minutes a day, at least three days a week. Then in 1995, new physical activity recommendations advised adults to accumulate 30 minutes of moderate activity, such as brisk walking, on most, preferably all days of the week.

Lee says the new recommendations were not meant to replace the previous ones, but to give people a choice, as both expend the same amount of energy, about 1,000 kcal a week for women. In this study, researchers found women who followed either recommendation had a 25-45% reduction in heart disease risk compared to sedentary women.

When they looked at specific activities that the women participated in, researchers found women who engaged in vigorous activities endorsed by the older guidelines such as running, tennis and swimming laps had about a 37% reduction in risk compared to those who didn't exercise at all.

"That's fine and good, but we know that most women in the US don't exercise vigorously," says Lee. "It may be hard to persuade people to exercise vigorously." In fact, 60% of the women in the study were not involved in any vigorous activity, but among that 60% the most popular activity was walking.

Researchers followed 39,372 healthy women aged 45 and older enrolled in the Women's Health Study from September 1992 to May 1995, with a follow-up in 1999. The women reported the time they spent each week on recreational activities.

Lee stresses that people who are already exercise more than an hour a week should not reduce their level of physical activity, or they may risk losing cardiovascular and other benefits. She says more research is also needed to verify the findings of this study.

For most healthy people, the American Heart Association currently recommends vigorous activity for at least 30 minutes, 3-4 days each week at 50-75% of maximum heart rate for health benefits to the heart, lungs and circulation.

Activities that are especially beneficial when performed regularly include:

• Brisk walking, hiking, stair-climbing, aerobic exercise.
• Jogging, running, bicycling, rowing and swimming.
• Activities such as soccer and basketball that include continuous running.

By Jennifer Warner

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