The study found that the 20% of the men who regularly participated in heavy exercise were 62% less likely to die early from heart disease -- even though they only expended an average of about 54 calories a day. That energy expenditure translates to about nine minutes of jogging or seven minutes of climbing stairs.
Researchers say the intensity of the exercise rather than the calories burned seemed to be the critical factor in reducing the risk of heart-related death. Men in the light-to-moderate exercise group burned an average of 343 calories per day (equivalent to a 90 minutes of walking or an hour of ballroom dancing), but they did not experience any reduction in the risk of early death due to heart disease.
Cardiologist Richard A. Stein say this study suggests that there is a threshold to how low you can go when it comes to reaping the benefits of exercise and physical activity.
"This is an interesting study that suggests that very slow walking or strolling does not afford much cardioprotective value," says Stein, who is chief of cardiology at the Brooklyn Hospital Center and a spokesman for the American Heart Association (AHA).
He says the light level of physical activity examined in this study falls well below the moderate-intensity exercise recommended to reduce the risk of heart disease. A brisk walk, for example, equates to about a mile per 15 minutes and burns about 100 calories per mile, which is about twice as fast as the rate mentioned in the study.
"Some exercise is better than none, but more is better than less. And more intensity is better than less intensity," Stein tells WebMD. "Many of the heart health gains can be achieved with moderate physical activity for 30 minutes five to seven days a week or moderately vigorous activity for 40 minutes three times per week."
Stein says people can determine their own level of moderate activity by asking themselves what their perceived level of exertion is while exercising on a scale from one to 10, with one being sitting in front of the TV and 10 being finishing a race. He says a self-reported rate of about 7 or 8 is a good level of exercise.