Answers lead to more questions

We should all be well aware by now that physical activity is important for preventing diseases, including coronary heart disease (CHD), the leading cause of mortality for women. However, many unanswered questions remain. How much exercise? What kind? How vigorous? Harvard University researchers attempted to answer some of these questions and then published their findings in a recent issue of the Journal of the American Medical Association

Researchers looked at the exercise habits of about 39,000 female health professionals who were part of the larger Women's Health Study. The volunteers were asked the amount of time (if any) they spent each week on a variety of activities, including walking, jogging, bicycling, playing tennis, and stretching exercises like yoga. By estimating the amount of energy expended in each activity, the researchers categorized the participants according to the number of calories burned weekly from exercise.

Because walking is such a common form of exercise among women, it was evaluated more carefully. The women were asked to estimate their usual walking pace. The researchers also assessed other CHD risk factors like smoking history, dietary patterns, blood pressure, and body fat. The women were followed for 3 years and any development of heart disease was recorded.

Study results

The study showed that the women who burned 600-1500 calories per week and those women who walked just one hour each week were half as likely to develop CHD than less active women. Surprisingly, higher levels of exercise did not offer any additional protection. The amount of time spent walking seemed to be more important than walking pace for reducing risk.

Fitness Advice

Current guidelines recommend moderate physical activity for 30 minutes a day most days of the week. If you assume that "most days" is equal to five, then the guidelines seem to recommend that you do some form of moderate activity for two and a half hours a week. But this study suggests that as little as an hour of walking per week is protective against CHD. So what should you strive for?

This study is one of just a few to find that such a small amount of exercise is beneficial. But when you put these results alongside those from other studies, it's still clear that physical activity does play an important role in heart health. The amount of exercise you need depends at least partially on how much you're currently doing.

• If you aren't doing any physical activity right now, then an hour of walking per week would be a good goal to start with. Don't worry about how fast you're going, just get out there and do it!
• If you are meeting or exceeding the current guidelines recommending moderate physical activity for 30 minutes a day most days of the week, continue the good work! These findings don't give you a reason to cut back. Try to gradually increase the amount of activity you do.
• Even if you have risk factors such as excess weight, smoking, or elevated cholesterol, walking can help you reduce your risk.