Marathoners are the thoroughbreds of high-performance runners, but even the draft horses of the running world — slow and steady joggers — improve their health. A study out this week in the Journal of the American College of Cardiology finds that even five to 10 minutes a day of low-intensity running is enough to extend life by several years, compared with not running at all. It shows that the minimal healthy “dose” of exercise is smaller than many people might assume. But if your favorite activity is a brisk walk in the park or a quick game of tennis, the research has implications for you, too. If you don’t currently exercise and make the decision to start — whether it’s walking, jogging, cycling, or an elliptical machine — you are going to improve your health.