The ultimate endurance athlete, Marshall Ulrich has run more than 120 ultramarathons averaging over 125 miles each, completed 12 expedition-length adventure races, and climbed the Seven Summits all on his first attempts.

He finished the first-ever circumnavigation on foot of Death Valley National Park, about 425 miles in one of the hottest, driest places on earth, during the most blistering month in U.S. history (July 2012). He's ranked this expedition as tougher than ascending Mount Everest, but not as challenging as his record-setting transcontinental run of more than 3,000 miles from San Francisco to New York City, which was the subject of his memoir, Running on Empty.

In his 60s, Marshall inspires adventurers, active and armchair athletes, and a growing general audience by sharing his experiences and defying the ideas of "too far," "too old," and "not possible."