Five minutes of strenuous activity such as running, jumping rope or pedaling flat out on a stationary bike might add years to your life. A large-scale study of exercise and mortality says only five minutes of intense activity each day could significantly lower your risk of dying prematurely. Research suggests that even short periods of vigorous exercise may yield benefits much great than experts had thought.

Runners in the study lived about three more years than those who never ran. It didn’t matter how much or how little people ran. Those who ran the least, including people who ran daily only five or 10 minutes at 10 minutes a mile or slower, did not live significantly shorter lives than those who ran far and fast. The fast participants ran six minutes per mile, and the long distance runners ran at least two and a half hours.

Researchers say there is nothing magical about running, but rather that the intensity of exercise is the cause of increasing longevity. Running probably is the most convenient intense exercise for most people, they say. The study did not address who and why running reduced the risk of dying prematurely, and it did not focus on whether the benefits of increased longevity are limited to runners. They did find that runners enjoyed longer life than those who took part in more moderate exercise such as walking.

Most exercise recommendations in recent years have focused on moderate activities such as brisk walking. In 2008, the government issued formal exercise guidelines recommending about 30 minutes of moderate exercise on most days of the week. Ramping up to vigorous exercise for 15 minutes, or about half the time, should provide the same benefits, according to the guidelines.

The study published in The Journal of the American College of Cardiology used a huge database maintained at the Cooper Clinic and Cooper Institute in Dallas. Researchers looked at 55,137 healthy men and women ages 18 to 100 who had been to the clinic at least 15 years before the study began. Among the participants, 24 percent said they ran. Their speeds and distances varied greatly. Over the 15 years of the study, almost 3,500 of the group had died. Heart disease was the culprit in many cases.

In examining the death records, researchers found the runners’ risk of dying from heart disease was 45 percent lower than the risk for non-runners. That finding held up even when scientists took into account the runners who were overweight or who smoked. However, not many of the runners smoked. Overweight runners who smoked were less likely to die prematurely than people who did not run.

The study found runners had a 30 percent lower risk of dying from any cause compared to non-runners.

Researchers warn that those who have never exercised or who have health problems should consult a doctor before taking up running or any other intense activity.