6. Ultrarunning

For the past few years, ultrarunning’s biggest prize purse—the $10,00 first place reward at The North Face Endurance Challenge’s 50-mile race—has been split between Matt Carpetner and Uli Steidl. Steidl, 36, took the 10 G’s back in 2007—but last year, the 44-year-old Carpenter beat him out by more than five minutes. So who reigns supreme at the 50-mile distance? Well, as Steidl says of his rival, that might depend on where the race takes place: “Whenever we race,” Steidl says, “I know it’s going to be a good competition—unless it’s at high altitude, and then I don’t stand a chance.” Check out this New York Times video of Carpenter’s training.