"Exercise does a lot of good things — it burns calories, helps keep your weight in check and lowers your risk of heart disease, stroke and diabetes. Now add one more thing to the list: physical activity can change your DNA. Unlike the aberrations and genetic mutations caused by carcinogens and toxins, exercise-induced alterations to DNA are more like tune-ups, helping muscles to work better and more efficiently ... these changes occur even after a single 20-minute workout." (Quoted from article)