So long, Soul Cycle: "Adventure Racing" will be 2013's most popular, painful, obsessive-crazy workout

A participant in a recent Tough Mudder race crawls in the mud under live wires. (Getty images)

Warning: Before you attempt this year's trendiest workout, you may have to sign a death waiver.

The world's most bizarre races

No, seriously. Adventure racing--a workout event that combines hardcore endurance training (cross-country running, climbing) with reality-TV-like, into-the-wild challenges (obstacle courses, mapping)--is  quickly becoming one of the nation's fastest growing outdoor sports, according to everyone from Outdoor Magazine to Forbes. It's also one of the most painful. Barbed wire, freezing dipping pools, and even 100-miles of rugged terrain with little more than a compass for navigation serve as obstacles in the growing number of team races being offered around the country for both triathletes and amateur goofballs alike. 

Though it was originally designed for super-athletes (your 'Iron Man' types, Navy Seals), in the past two years, courses have been modified for amateur daredevils who want in on the action. Instead of 100-mile courses, many adventure races have now shrunk to 10 miles. And instead of real (steep!) mountain climbing, today's climbing portions include a wall with a mud pit at its base. Additionally, while many teams still take the sport seriously, others fool around a bit, dressing in wacky colorful costumes (imagine Smurfs on acid) and adding mental challenges to the day's lineup, like reciting the names of every U.S. president after hauling a giant sack full of rocks.

Another reason for the growth in popularity: co-ed teams. "There's a social scene with it," Troy Farrar, president of the USARA, the governing body of adventure racing, explains. "[Couples] train together, they go and race and afterward they camp out and party together." Farrar tells Shine he's seen "tremendous growth" in couples' participation in the sport since 2010. Adventure racing teams have spawned relationships, and in some cases even marriages. "I produced an urban adventure race in Houston," recalls Farrar. "One of the guys on the field proposed right before they took off racing. "

Even with this romance/couples/co-ed aspect, the sport is still largely male-dominated ("alpha-male" dominated, if you ask the New York Times). Farrar estimates 75 percent of teams are made up of guys--but don't count the women out.

"The girls of adventure racing are hammers," says Farrar, pointing to Robyn Benicasa, one of the top ranked racers, who doubles as a San Diego firefighter in her free time. "I think women are much better sufferers," says Farrar. "In general I think men complain when things aren't going so well. "

The race that pushes runners to extremes

And in adventure racing, things often don't go well. In fact, in the past few years, courses have gotten downright dangerous.

At Spartan Races, one of the most popular new racing events, participants crawl under barb wire, launch spears into the air, haul sacks of stones and traverse greased-up inclines at their own risk. The Tough Mudder races, which involve 10 to 12 mile courses packed with mud pools, high-voltage electric wires and freezing cold ice baths, require that aforementioned death waiver, absolving the organizers should the worst come to pass.

At a 2011 Tough Mudder event in Wisconsin, twenty-one participants finished the race at the hospital.

"We had people with orthopedic issues such as fractures to their arms or legs. Some suffered from dehydration. We had one person with a cardiac complaint," Kari Hall, director of emergency room services and urgent care at Sauk Prairie Memorial Hospital told a local reporter after the event. "That was just Saturday, but on Sunday we took five more Tough Mudder patients with some of the same type of injuries - fractures, dislocations and dehydration."

In the past, event organizers have come under fire for lack of safety measures. Spartan, Tough Mudder and similar "torture" races provide on-site medical assistance, and the USARA has been instrumental applying more stringent safety measures in outdoor courses. (For example, if you're scaling a mountain, you've got to wear the proper helmet now. This wasn't always the case, according to Farrar.)

"In most races someone's going to get a little scrape here or there," says Farrar. "But serious injuries are not really very common. "

Anyway, pain is part of the game.

Tami Collingwood, 40, a veteran half-marathon runner, twisted her ankle while climbing over an 8 foot wall during a race called The Ruckus in Pittsburgh. She still finished the course, ankle be damned.

"You get kind of addicted," she told the Pittsburgh-Post Gazette. "It's like an adrenaline rush."

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