"This feels better than sex!" the guy running next to me howled. We'd just started to descend after a steep, slippery slog up a ribbon of single track at Killington Peak, Vermont, and he was letting everybody know how relieved he was to be going downhill.
I can't say I felt quite that good. For three and a half hours, roughly 5,000 of us competing in a race and endurance test known as the Spartan Beast, had run 10 miles of trails, while negotiating 30 obstacles, scaling walls, carrying sandbags, and crab walking under barbed wire through a shallow brook. We'd climbed the 4,241-foot-high peak at least four times, waded through giant mud puddles, and swam across ponds.
During the past two years, this extreme and unusual niche of trail running has exploded in popularity, thanks in large part to its ability to draw armchair athletes off the couch and into the mud. Two of the most popular obstacle course series,Spartan (which also offers 3-, 8-and 12-mile-long races in Canada and the United Kingdom) and Tough Mudder (a 10-to 12-mile event that takes place worldwide),kicked off operations in 2010 with about 30,000 and 50,000 participants, respectively, joining the 65-stop sprint series Warrior Dash and the team-oriented Muddy Buddy.
Last year, entries grew to 150,000 for Tough Mudder and 110,000 for Spartan. In 2012, the two series alone are expected to draw a combined 620,000 runners,many of them first-timers.
The events have grabbed national media attention too. In June, The Wall Street Journal profiled Hobie Call, 35, a Utah father of five who installs HVAC units for a living, and who won 13 of the 14 Spartan races he entered in 2011. That story came on the heels of a 2010 New York Times article introducing the world to Tough Mudder.
Lower-tier celebrities like former NFL wide receiver David Tyree, Jack Osbourne (son of Ozzy), the Denver Nuggets' Al Harrington, and several contestants from The Biggest Loser have all taken on the challenge, and not only as a media stunt to draw more attention to their dimly lit stars.
What's driving the craze, in the opinion of Joe DeSena, one of Spartan's founders, is an innate human attraction to the kinds of challenges involved in the races. "Jumping, crawling, and climbing are all things we're naturally born to do," he says. "We're wired to do them, but we don't anymore; we just type." To get in ultimate shape for your next mud run, try these Workout Challenges From Other Sports.