Some small studies have suggested that too much vigorous exercise might harm your heart, perhaps by triggering heart rhythm changes or other problems. New evidence allays this concern. In fact, the more fit you are, the longer you may live. For the study, researchers reviewed data from more than 122,000 people who underwent exercise treadmill testing from 1991 to 2014. Based on the findings, they divided the subjects into five performance groups: elite, high, above average, below average, and low. Elite performers — who had fitness levels comparable to endurance athletes — had the lowest risk of dying of any cause during the follow-up period, which averaged just over eight years. The survival benefit was most notable among people ages 70 or older and those with high blood pressure. According to the study authors, there does not appear to be an upper limit of fitness above which a survival benefit is no longer seen. They published their findings online Oct. 19, 2018, in JAMA Network Open.