He runs and runs and runs. Ultramarathon runner Dean Karnazes, who was named one of TIME Magazine's 100 most influential people in the world in 2006, pushes his body and mind to incredible limits: he runs hundreds of miles or 80 hours straight without sleeping, swims across the San Francisco Bay, or rides a mountain bike for 24 hours. In 2004, he won the toughest race in the world: a 217-kilometer race through Death Valley at temperatures around 50 °C. In 2007, he took on an even greater challenge: 50 marathons in 50 consecutive days across all 50 states of the USA. Karnazes recounts this impressive feat in his book "50/50." The captivating account of his experiences, along with the many practical tips, insider advice, and training plans offered in the book, inspire every athlete, whether amateur or professional.