For the first time, researchers are looking at the incredibly grueling competition called the Ultraman, and what it does to your body. The Ultraman is a three-day competition designed to test an athlete’s physical and mental endurance. The first day is a 6.2-mile open swim, followed by a 90-mile bike ride. The second day is a 172-mile bike ride. And the third day is a double marathon — a 52.4-mile run.