A sedentary, overweight, middle-aged woman rolls her eyes when you encourage her to become more physically active. "I don't have time to exercise more than once or twice a week, so what good will it do?" she asks. How would you respond?

Inadequate physical activity is a well-recognized independent risk factor for coronary artery disease (CAD), the leading cause of death in the United States.1,2 More than 60% of American adults are not regularly active, and 25% are not active at all.3 Although it is common knowledge that exercise is healthful, what is less clear is the level of exercise needed to benefit cardiovascular health.

Moderate-intensity activity produces reductions in diastolic blood pressure similar to those achieved with vigorous exercise—and it may produce even greater reductions in systolic blood pressure.4 Moreover, moderate exercise together with modification of diet has been shown to lower the risk of type 2 diabetes.5-7 However, these data still do not establish that moderate physical activity has a cardioprotective effect. Nor do they answer the question: what amount or intensity of exercise is needed to help prevent stroke, myocardial infarction (MI), and cardiovascular mortality?

In this article, we examine the available evidence on the cardioprotective benefits associated with various intensity levels, types, and amounts of physical activity. We also offer tips on how to help your patients initiate—and maintain—a beneficial yet realistic exercise program.

WHAT THE GUIDELINES SAY

Revised guidelines from the American Heart Association (AHA), the CDC, and the American College of Sports Medicine (ACSM) recommend moderate to vigorous aerobic activity (at 50% to 75% of maximum heart rate) for at least 30 minutes on most days of the week, either in a single session or in several 10- to 15-minute sessions.4,8 Examples of moderate- and vigorous-intensity activities are listed in Table 1.

Earlier recommendations were updated to include moderate activities on the assumption that more inclusive recommendations would be easier for the general population to follow. In the past 10 years, however, data have become available that also show potential health benefits of regular moderate-intensity exercise. A few caveats in interpreting the results of studies of exercise are listed in the Box.

Table 1 — Definitions and examples of moderate- and vigorous-intensity exercise
    Moderate-intensity exercise   Vigorous-intensity exercise
VO2max   40% - 60%   > 60%
METs   3 - 6   > 6
Calories burned   3.5 - 7 kcal/min   > 7 kcal/min
Examples   Walking at a moderate pace (3 - 4.5 mph); bicycling at 5 - 9 mph on level terrain; yoga; ballroom dancing; shooting baskets; doubles tennis   Race-walking, jogging, or running; bicycling at > 10 mph or on uphill terrain; professional ballroom dancing, performed energetically; playing in a basketball game; singles tennis
VO2max, maximum oxygen consumption; MET, metabolic equivalent.
Data from Thompson PD et al. Circulation. 2003.21

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