When you finally get off the couch and experience your first runner’s high, you may want to run forever, but is it possible to get too much exercise? The answer is yes, according to a recent review of research by a team led by cardiologist Dr. James O’Keefe. In some ways, exercise is like a medication that can be used to prevent and treat many chronic diseases. As with prescription drugs, though, it’s possible to “overdose” on exercise. The researchers, who published their work in the Mayo Clinic Proceedings, looked at studies of people who competed in marathons, iron man triathlons, ultramarathons, and long distance bicycle races.