Dean Karnazes

American athlete, setting records for long distance running. Karnazes is the author of "Ultra Marathon Man: Confessions of an All-Night Runner" (2005).

He says his life as he knew changed on his 30th birthday, when he ran for the first time since high school and ran all night (30 miles). Since then he has achieved many records for speed and endurance, in various athletic endeavors, such as swimming, surfing, cycling and especially running. Some of his awe-inspiring accomplishments are: running 10 marathons non-stop (262 miles), swimming across the San Francisco Bay, running a marathon to the South Pole, mountain-biking for 24-hours straight, and running 146 miles across Death Valley in the middle of summer.

Karnazes is also owner and president of EnergyWell Natural Foods in San Francisco. He is slight but muscular, standing 5'9" and weighing 155 pounds. When asked why he does what he does, he responds, "It's just the supreme challenge of seeing how far the human body can be pushed."