Ultra Marathon Man: Dean Karnazes
For most long-distance runners, the 26-mile-long marathon is the crown jewel, the pinnacle of human endurance. But for Dean Karnazes, aged 46, that's just a warm-up run. Dean regularly competes in races that are over 100 miles long. He's one of a growing breed of ultra marathoners pushing at the limits of human endurance. Among the places these marathoners compete is the Badwater Ultra Marathon. Considered the toughest race in the world, it's a grueling 135-mile trek through Death Valley in the middle of summer.










