Good news, couch potatoes: you're healthier than you think. Two new studies—presented at a recent medical conference—suggest that in older, high-endurance athletes, the benefits of running are nearly canceled out by the cardiac risk they present. In a study that followed 52,600 people, both runners and nonrunners, for three decades, researchers found that the runners in the group had a 19 percent lower death rate, but that number disappeared in the group who went on high-endurance runs (more than 20–25 miles per week). A second study found no mortality benefit for those who ran faster than eight miles per hour. While not everyone in the health world is behind the data, sports cardiologists are beginning to take note of the wear-and-tear that chronic exercise imparts on the body over time.