Funky Monkey. Sweati Yeti. Ball Shrinker. Death March. The only thing more impressive than the names of the obstacles in the Tough Mudder racing series are the number of athletes willing to subject themselves to their torture: 180,000 this year alone. “We bill ourselves as Ironman meets Burning Man,” says Tough Mudder founder Will Dean, a former counterterrorism officer in the UK. “Endurance sports don’t have to be boring.” Indeed, in the past five years, adventure races and their old-school endurance cousins, marathons and triathlons, have morphed into amenity-laced parties. There are pre-race meals at Tavern on the Green (New York City Marathon), in-race live music (Austin Triathlon), and post-race parties with barbecue feasts and knife-throwing contests (Warrior Dash). And the best reason to sign up? They’ll break you out of your fitness rut in a way that Crossfit, P90X, and Zumba never will. Just take our crash course in each discipline, then select an event from our list of favorites. Suffering shouldn’t be this much fun.