Shorter exercise periods also benefit heart health, studies show

CAMBRIDGE, Massachusetts (CNN) -- Exercising for as little as 15 minutes several times a day can do as much to decrease the risk of heart disease as one longer session, two new studies indicate.

"If you want to exercise 45 minutes in a day, you don't necessarily have to do 45 minutes all at once," said Howard Sesso, a researcher with the Harvard School of Public Health, where the studies were conducted. "You could do 15 minutes in the morning (and) perhaps a half hour in the evening."

The key appears to be intensity rather than duration, Sesso and colleagues report in this week's issue of Circulation, the journal of the American Heart Association.

"Physical activity does not have to arduously long to be beneficial," Sesso said.

Brisk walking, yard work, gardening and golf were shown to have an equally positive effect on heart health as more vigorous sports and activities such as swimming, tennis, jogging and cycling, Sesso found.

"The important thing, apparently, is just to do it," the researcher said. "If you are unable to set aside 30 minutes all at once for exercise, try two 15-minute sessions."

Results were based on analysis of questionnaires returned as part of the Harvard Alumni Study, a database of thousands of men who were graduated between 1916 and 1950. The long-term study began in 1962.

Subjects reported on their health habits, medical history and levels of physical activity each week. Those who accumulated at least 30 minutes of exercise five or six days weekly had a 20 percent reduction in heart disease, one study found.

A related study seems to confirm the findings, indicating that light or moderate activity appears to provide a lower level of benefit. Again, intensity is the crucial factor.

"For those who reported walking three miles or more per week, which is a moderate level of exercise, we found a 10 percent reduction in risk," Sesso said. "You don't have to become an Olympic athlete to reap these benefits. Just push yourself a little and get your heart rate up."

These studies could help to diminish the barriers of time and boredom that people throw up against beginning an exercise program, observed Gregory Heath of the Centers for Disease Control and Prevention in Atlanta.

"You can even do two activities," Heath said. "You might, for example, walk in the morning and then, in the afternoon, bicycle or go to the pool."

CNN Correspondent Elizabeth Cohen contributed to this report.

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Harvard School of Public Health
Centers for Disease Control and Prevention
American Heart Association

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