New Insight Into Physical Activity and Heart Health
Numerous studies have shown that physical activity can reduce the risk of coronary heart disease (CHD), but until now we had no idea about the optimal type, duration, or intensity of exercise needed for this benefit. New findings in the October 23, 2002 Journal of the American Medical Association suggest that men who consistently run, walk, or weight train have a reduced risk of CHD compared to men who do not do these activities. Past research has suggested that physical activity might increase the efficiency of the heart muscle, improve cholesterol levels, lower blood pressure, thin the blood, and increase insulin sensitivity.
About the Study
Researchers from the Harvard School of Public Health, Brigham and Women’s Hospital, and Harvard Medical School studied 44,452 US health professionals between the ages of 40 and 75 who participated in the Health Professionals’ Follow-up Study. The original study was designed to evaluate the effects of nutritional factors on the incidence of serious illnesses like heart disease. This reanalysis of the data looked at the amount, types, and intensity of exercise in relation to the risk of CHD in men. Men from the original study group were excluded from this analysis if they had difficulty climbing stairs or walking, or were diagnosed with cardiovascular disease or cancer other than nonmelanoma skin cancer prior to the start of the study. Men were also excluded if they drastically changed their activity levels from one questionnaire to the next.
Participants were asked to fill out a detailed questionnaire about medical history, diet, and lifestyle, including leisure-time physical activity. These questionnaires were sent every two years over a 12-year period (1986-1998). The self-reported time spent at each physical activity (in hours per week) was multiplied by the amount of energy it took to do that activity. The researchers specifically looked at running, jogging, rowing, cycling, swimming, racquet sports, walking, and weight training.
The researchers then collected information on the number of deaths from CHD and the number of non-fatal heart attacks. They compared the CHD deaths and heart attacks among men who did different types and levels of exercise.
Men with the highest levels of total physical activity had a 12% to 40% lower risk of CHD compared to those with the lowest activity levels. The breakdown of benefit for various exercises was as follows:
- Running for an hour or more per week - 23% to 56% risk reduction
- Training with weights for 30 minutes or more per week - 2% to 39% reduction in risk
- Walking briskly (independent of the number of hours of walking) - 19% to 55% reduction in risk
In addition, exercise intensity was associated with additional risk reduction.
The researchers made adjustments for alcohol consumption, smoking, family history of heart attack before age 50, other types of physical activity, and nutrient intake (vitamin E supplements, fiber, folic acid, polyunsaturated fat, trans fatty acids). They additionally adjusted for baseline presence of high blood pressure, high cholesterol, and diabetes. Adjustments made for current body mass index (measure of risk for weight related health outcome) did not significantly change the results.
Although these results suggest that certain types of physical activity may be more beneficial than others, there are limitations to this study. First, the researchers studied only male health professionals, who may not adequately represent the general US male population, and certainly don’t represent the female population. Second, self-reported physical activity could very well differ from actual activity, though a validity study did find pretty good agreement between actual and self-reported physical activity. Third, the researchers did not adjust for a variety of other factors like medication or marital status, which some researchers have found can influence cardiovascular health. Finally, the researchers only measured baseline diabetes, high cholesterol, and hypertension, so there could have been men that developed these health conditions later on in the study, which could influence the final results.
How Does This Affect You?
So does this mean that you should switch from swimming to running in order to get more heart health benefits? Not necessarily—unless you like both. Though this study only found that running, brisk walking, and weight lifting had a significant effect on the risk of CHD, other research in this area suggests that any type of activity can be beneficial. Regardless of its effects on the heart, exercising is still a part of a balanced lifestyle, and you’re far more likely to make an activity a part of your lifestyle if you enjoy doing it. It is also important to note that although moderate exercise (like brisk walking) seems to reduce your chances of developing CHD, intense exercising may yield even greater protection. It is still safe to say that a reasonable goal for cardiovascular fitness is to do at least 30 minutes of moderate activity on most days of the week.
American Heart Association
The National Heart, Lung and Blood Institute
Tanasescu M, Leitzmann M, Rimm E, et al. Exercise type and intensity in relation to coronary heart disease in men. JAMA. 2002;288:1994-2000.
Last reviewed Oct 23, 2002 by ]]>Richard Glickman-Simon, MD]]>
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