Beast: Blood, Struggle, and Dreams at the Heart of Mixed Martial Arts

Mixed martial arts is America's fastest-growing sport--around the country, new gyms open their doors and enthusiastic viewers tune in to UFC matches. Although some dismiss it as brutal combat, its fighters are among the most dedicated athletes in any arena. But MMA also takes a heavy toll on the body, and it's a rare fighter who can earn a living in the sport's top ranks.

Beast follows four high-level fighters at one of the sport's elite gyms, Florida's American Top Team. Doug Merlino had ...