Moderate- or Vigorous-Intensity Exercise: What Should We Prescribe?

T he U.S. Surgeon General recommended in 1996 that adults obtain at least 30 minutes of moderate-intensity physical activity on most days of the week (1). This physical activity will reduce one’s risk for coronary heart disease (CHD), as well as other health problems such as type 2 diabetes, obesity, and certain forms of cancer (1). The U.S. Surgeon General’s Report went on to state that exercise of longer duration or ‘‘of more vigorous intensity’’ would provide more benefit (1). Despite this endorsement by the Surgeon General, acting in concert with the U.S. Centers for Disease Control and Prevention, little emphasis has been placed on vigorous-intensity exercise in public health promotion. Several recent scientific articles suggest that vigorous aerobic exercise may result in substantially more benefits than moderate-intensity exercise, including greater improvements in aerobic fitness and greater reductions in CHD risk. This is true even when the duration of the moderate effort is prolonged so that the same total amount of work is performed. For example, if one person walks an hour a day at 4 mph, he or she would cover 28 miles per week and expend about 1,400 Kcal above rest (based on a net energy expenditure of 50 Kcal per mile for a 136-lb person; a heavier person would expend proportionally more). Running burns twice as many calories per mile as walking, so a runner would only need to cover 14 miles to burn the same 1,400 Kcal, for example, by jogging at 7 mph for only 30 minutes, 4 days per week. Although the walker and runner would burn the same number of calories, by doing so at a vigorous intensity, the runner could expect a greater increase in aerobic fitness and greater benefits regarding cardiovascular health.