DOCTOR'S VIEW ARCHIVE
Exercise has been shown in a number of studies to provide some protection against heart disease and stroke. Regular exercise such as swimming, cycling and many other aerobic fitness methods can have benefits beyond the cardiovascular system. Routine exercise strengthens and tones muscles, increases the flexibility of joints, and clearly reduces bone thinning (osteoporosis). This enhanced fitness reduces the risk of falling and breaking bones. Regular exercise can also promote socialization and a general sense of well being.
Controversy over Walking
However, the effectiveness of walking as compared with more vigorous exercise in preventing coronary heart disease has remained controversial. In a study published in the August 26, 1999 issue of the New England Journal of Medicine, a team of investigators compared brisk walking with more vigorous exercise in the prevention of heart disease. Their results would appear to settle the issue.
The research team led by JoAnn Manson of the Channing Laboratory at Harvard Medical School based their findings on the Nurses' Health Study. This is an extraordinarily large, prospective (forward- looking) study. It was started in 1976 when 121,700 female registered nurses 30 to 55 years old completed a mailed questionnaire on their medical history and lifestyle. Every two years, follow-up questionnaires were sent to these nurses to obtain updated information on potential risk factors and to identify newly diagnosed cases of coronary heart disease or other illnesses.
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Research on Walking
To study the effectiveness of brisk walking versus vigorous exercise, base-line data were gathered in 1986. The population sample for analysis was made up of 72,488 women in the Nurses' Health Study who were then 40 to 65 years old. All of the women were free of diagnosed cardiovascular disease and cancer when the present study began in 1986.
The women were divided into 2 groups: those who walked briskly for at least three (3) hours a week and those who exercised vigorously for one and a half (1 1/2) hours a week. Vigorous exercise was jogging, running, bicycling (including the use of a stationary bike), swimming laps, tennis, squash, or participating in calisthenics, aerobics or aerobic dance.
These women were studied for eight years from 1986 to 1994. The end points for study were coronary "events." These were defined as a nonfatal heart attack or death due to coronary disease that occurred after the return of the 1986 questionnaire and before the end of the study in 1994. During that 8-year period, 645 "incident coronary events" (nonfatal heart attacks or deaths from coronary disease) were documented.
The risk of a "coronary event" (a heart attack or coronary death) was found to be significantly reduced -- by 30 to 40 percent -- for both groups of women!
Why was this substantial reduction in heart risk similar for both groups? This can be explained by the fact that the total metabolic equivalent score for the walkers and the vigorous exercisers was similar because the walkers worked out longer each week. Therefore, walking can get the same results as vigorous exercise. It just takes a bit longer.
Conclusions for Heart Health
Dr. Manson and her co-authors conclude that both walking and vigorous exercise reduce the risk of a heart event in women. The strengths of their study include: its prospective design, the large number of women in the study, the long-term follow-up, the repeated measures of physical activity, and the uniform and strict criteria for coronary events. Although this study was exclusively for women, there is every reason to believe that the implications of the study also apply to men.
This study confirms what has been known for a long time -- that routine exercise is an excellent, accessible preventative health measure. What is new is the finding that regular moderate-intensity exercise such as brisk walking is every bit as good as more vigorous exercise for the heart.
Source: Manson JE, Hu FB, Rich-Edwards JW, Colditz GA, Stampfer MJ, Willett WC, Speizer FE, Hennekens CH: A Prospective Study of Walking as Compared with Vigorous Exercise in the Prevention of Coronary Heart Disease in Women. New Engl J Med 341: 650-658, 1999.
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