Train All Night
Credit: Astrid Riecken For The Washington Post / Getty Images

GoRuck Challenge

Distance: 15 to 20 miles
Intensity: Extreme. It's not a race, but an all-night military-style training course designed by a former Green Beret. "You see what our troops go through every day," says Kit Klein, a manager at Goruck.
Training: 5 to 6 times a week of endurance cardio, plus functional strength
Obstacles: Copious push-ups, bear crawls, crab walks, and tasks like carrying a 100-pound railroad tie across town. [goruck.com/events]

Spartan Beast

Distance: 12-plus miles
Intensity: Extreme
Training: 5 to 6 workouts a week for at least 3 months, including weekend runs of up to 12 miles. "If you are not ready, you're going to be hating life," says Joe Decker, two-time winner of the Spartan Death Race.
Obstacles: 20 to 25, similar to those of the Super Spartan, including the burpee penalty. [spartanrace.com]