A study conducted at Duke University and published in the journal Chest compared the effects of three different exercise regimens on fitness improvements in overweight men and women who were at risk for heart disease.

Broken into four groups, the volunteers either did not exercise, walked briskly for 12 miles a week at a moderate intensity, walked briskly or jogged slowly 12 miles a week at a vigorous intensity, or jogged 20 miles a week at a vigorous intensity.

Two measurements of fitness – time to exhaustion and oxygen consumption – were measured before and after 7 to 9 months of training.

All exercise groups saw fitness improvements compared to baseline. Results indicated that two to three hours of mild exercise a week at a moderate intensity is sufficient to increase aerobic fitness and cut the risk of cardiovascular disease. Increasing either the intensity or the amount of exercise provided additional improvements in fitness.

Although more vigorous exercise should still be encouraged for maximum benefit, this study demonstrates that it is appropriate to recommend mild exercise to improve fitness levels and reduce cardiovascular disease risk, especially in those who are overweight and sedentary.

Chest. 2005;128:2788-2793.