After a decade-long addiction to crack cocaine and alcohol, Charlie Engle hit bottom with a near-fatal six-day binge that ended in a hail of bullets. As Engle got sober, he turned to running, which became his lifeline, his pastime, and his salvation. He began with marathons, and when marathons weren't far enough he began to take on ultramarathons, races that went for 35, 50, and sometimes hundreds of miles, traveling to some of the most unforgiving places on earth to race.

Scott Jurek is one of the world's best known and most beloved ultrarunners. Renowned for his remarkable endurance and speed, accomplished on a vegan diet, he's finished first in nearly all of ultrarunning's elite events over the course of his career. But after two decades of racing, training, speaking, and touring, Jurek felt an urgent need to discover something new about himself. He embarked on a wholly unique challenge, one that would force him to grow as a person and as an athlete: breaking the speed record for the Appalachian Trail.

Writing from both the cutting edge of scientific discovery and the front-lines of elite athletic performance, National Magazine Award-winning science journalist Alex Hutchinson presents a revolutionary account of the dynamic and controversial new science of endurance.

Why does it make sense to Ethiopian runners to get up at three a.m. to run up and down a hill? Who would choose to train on almost impossibly steep and rocky terrain, in hyena territory? And how come Ethiopian men hold six of the top 10 fastest marathon times ever? Michael Crawley spent 15 months in Ethiopia training alongside (and sometimes a fair way behind) runners at all levels of the sport, from night watchmen hoping to change their lives to world-class marathon runners, in order to answer these questions.

David Clark is a formerly obese alcoholic and fast food junkie who found a new life in running. Now, 13 years after his transformation, he shares his inspiring story of taking running to the extreme edge of his physical and spiritual breaking points. Having run more than a hundred races, including the Leadville 100-Mile Trail Run and the Hardrock 100, David has achieved unimaginable success in the ultramarathon world, considering his humble start.