ULTRA ENDURANCE AND THE ULTRA-FIT: THE RISKS AND REWARDS Exercise is one of the best-supported ways to improve health and extend life. It lowers the risk of cardiovascular disease, diabetes, several cancers, and premature death. That fact is not in dispute. Less certain is whether the benefits keep increasing when exercise becomes extreme: ultramarathons, Ironman-distance triathlons, multi-day cycling races, and years of high-volume endurance training. The popular claim that ultra-fit athletes “often die young” is not supported by the strongest available evidence. In fact, elite endurance athletes generally live longer than the wider population. Former Tour de France competitors have shown substantially lower mortality, while research following Olympic athletes has found gains in life expectancy, including fewer years of life lost to cardiovascular disease and cancer ( Parry-Williams and Sharma, 2020 ; Antero-Jacquemin et al., 2018 ). That does not mean extreme exercise is harmle...