Joshua Mullins had endured a lot already: Trudging through mud, swimming through ice water, dragging a large rock on a rope.

Now, he was alternating hauling sandbags and five gallon buckets of rocks up a steep hill, "a giant mountain of a hill, for Texas at least." And he was doing it in the cold, driving rain.

He kept thinking to himself, "I've carried heavier things," recalling the massive drum cases he'd carry for his musician wife in and out of her gigs. The Bag of Doom, he called them.

Still, this was different. He'd signed a death waiver to do this.

Mullins, a 29-year-old recruiter in the Texas oil and gas industry, wasn't being punished. He wasn't in military training. He actually paid to haul those sandbags and buckets, part of an extreme adventure course called Super Spartan. It's just one of many extreme adventure courses in a booming industry that just doesn't seem to know the meaning of "enough is enough."

The Ironman Triathlon might be insanely long, but hey, no one's getting electrocuted during that 2.4-mile swim, 112-mile bike ride and full marathon run. There's the Tough Mudder, Warrior Dash, Spartan Sprint, Spartan Beast, GORUCK, Mud on the Mountain, Survivor Mud Run, Obstacle Apocalypse, Hero Rush, Urban Dare and yes, the Spartan Death Race.

Many require signing a death waiver, and mud is the common denominator, along with a disdain toward the buttoned-up, vanilla marathon (or half-marathon, or any other traditional race). Discomfort, rather than time, is of the essence. Who wants to run on the concrete for two hours only to be greeted by a banana and an ugly T-shirt when you could crawl through barbed wire, get electrocuted, chop wood and finish it all off with a cold beer and live music?

For Mullins, conquering his first Spartan Sprint, and then the Super Spartan, was a way to get back in shape after a back injury.

"I'm the kind of guy that likes the extreme type of stuff that tries to punish the body while testing your mental fortitude," he says. "Movies and TV have made extreme sports and reality challenges seem so easy, it's nice to be able to sign up for one of these things and know you will be challenged. It breaks up the monotony of work and working out just to stay fit."

***

Ask anyone who works in the growing adventure race industry, and they'll tell you that breaking up the monotony of our lives is exactly what they're trying to do.

"The vast majority of people will say, 'Why would you want to pay $100 to put yourself through electric shock, ice water, jumping off platforms into cold lakes?' But we see this as an emerging industry. People are attracted to it because it's different," says Alex Patterson, chief marketing officer for Tough Mudder, one of the leading obstacle courses.

Patterson says the event aims to shake up the lives of people with a 9-to-5 "Office Space" lifestyle who spend their weekends raking leaves and watching TV. It's one thing to stand at the water cooler and boast about your 5k, but tell a story about being electrocuted after swimming in ice water and maybe your colleagues will look at you a little differently.

"We are innovating our way out of having to do anything difficult," Patterson says. "We have roller bags so we don't have to carry our luggage. Dishwashers, elevators, Segways…Tough Mudder is the anti-Segway."

***

The market for these events wasn't always so crowded. In 1981, a man named Bob Babbitt hit a rather muddy trail for a 28 mile relay of sorts. He would ride a horse for a few miles, tie the horse to a tree and break into a run. Meanwhile, his partner would be finishing up his own run, jump on the horse and ride until the next stop, when they'd switch it up again.

It's a creative idea in theory, but horses aren't for everyone. Even if horses are your thing, you may not have regular access to one for training. Enter the Columbia Muddy Buddy, where four hooves have been replaced with two wheels. The partner concept still holds, so "muddy buddies" take turns running and riding mountain bikes. Now there are eight events held around the country and almost 150,000 buddies have conquered the trail.

Fast forward, and there are dozens of adventure races and obstacle competing in an almost Darwinian fashion, all hoping you'll choose them when you want to be the badass envy of your nosy Facebook friends and starched colleagues.

"These mud events really are their own genre," says Babbitt, founder of Muddy Buddy and editor of Competitor Magazine. "Now there's what I like to call an endurance buffet," Babbitt says. "In the early days, you had to pigeonhole yourself. You were a runner or you were a person who worked out at the gym or a cyclist. Now, the same person can do a 5k one weekend, a triathlon one month, a Muddy Buddy in a few months without labeling yourself. You’re just an endurance athlete."

Babbitt explains that as the new events like Tough Mudder and Warrior Dash began to launch, they all advertised in Competitor to reach the right market. While his event doesn't focus on extreme discomfort (unless you think running and cycling in, say, a Central Texas summer is extremely uncomfortable) he’s happy that the market has expanded.

"Some people dig getting electrocuted, jumping in freezing water. Some people really get off on that," says Babbitt. "I look at our events as challenging, but there's a family atmosphere where you can make lifelong friends."

Of course, each event is competing for participants and sponsors. But mostly, they seem to think of themselves as fighting one collective battle.

"I like to think we aren't competing with each other,” says Tough Mudder’s Patterson, “but competing with people sitting on the couch."

***

But really, what’s with the mud? Mud seems to be the glue holding these events and their diehard fans together.

Babbitt says the mud factor is about being a kid again.

“Playing in the mud is fun, but we were told at a young age not to do it. Now, there’s a way to connect with that part of yourself,” he says.

Rob Dickens, COO of Rugged Races LLC, says his company’s Rugged Maniac race offers a return to childhood.

“People no longer have the ability to satisfy their primal need to get outdoors and be active,” Dickens says. “Sure, people can workout at a gym, but it’s not the same without fresh air in your face, grass stains on your knees and mud on your hands.”

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The mud gives these adventure races a rough and tumble image that says, “We eat your triathlon for lunch.” But Mudders and Spartans and Buddies will say it goes a lot deeper.

Spartan Races combine spear-throwing, jumping over flaming bales of hay, climbing greased walls and constantly dodging Spartan Warriors. Tough Mudder will have you crawling through barbed wire. And did I mention you actually get electrocuted in the Tough Mudder? If you're hoping to score a date with the cute girl in marketing, and your only competition is Steve from accounting and his 10k , this might not be a bad idea.

Mullins describes his first Super Spartan as “exhilarating” despite the nasty weather and excruciating obstacles. The camaraderie aspect is huge in these races. Although friends and family stand on the sidelines of marathons cheering you on, usually the run is kind of a solo thing. In the Muddy Buddy, you obviously have a designated partner, and in events like Tough Mudder and Spartan, everyone is looking out for each other. Mullins says he'll never forget one woman who was tirelessly chipper during the mountain exercise.

"One of the things I like most is the fact that Spartan Race does not give you a map with the obstacles before the race. You are literally running into the unknown,” he says. "You'd hear people crying out and cussing, and I had to remind myself that I paid to do this to myself."

Still, the Super Spartan isn't the toughest race on the Spartan menu. Enter the Spartan Death Race. Unless you belong to the certain breed of adrenaline junkie that would be excited to crawl through barbed wire, it's hard to not shake your head and think, "How completely ridiculous" when visiting the Spartan Death Race website, which lives on the URL www.youmaydie.com. The New York Times even produced a 10 minute documentary on the race, likening it to "Survivor" meets "Jackass."

In one image, a man has blood running down the side of his face. The caption reads "This competitor should feel lucky that he just got a small scrape." The rest of the page is full of gems like "Please only consider this adventure style race if you have lived a full life to date," "Death sounds cool until you're dead" and "The adventure starts when everything goes wrong, which God will be on your side." Only about 10 percent of the poor souls who start the race finish it.

Mullins is still trying to convince his wife to let him do the Spartan Death Race.

"She says I need a better life insurance policy because she knows that I’ll go through whatever obstacle, challenge or insanity to finish something like that."

Not every adventure race aims for the testosterone-overloaded "We are Sparta" image.

"Most extreme race companies market themselves as brutal, punishing events that only the manliest of men should attempt,” says Dickens with Rugged Maniac. “Not surprisingly, we’ve found that most people don’t like to be electrocuted, beaten with sticks or submerged in ice water.”

Rugged Maniac was designed with the assistance of Navy SEALS, but their image is definitely playful. Dickens says registration is often full of people who tried other races and wanted something less, well, abrasive. They claim to have the highest percentage of female runners of any co-ed adventure race.

Tough Mudder’s website says they strongly encourage women to take the challenge, and that women make up 25 percent of participants.

Obstacle course races tailored for women are popping up, too. There’s the SHAPE Diva Dash (pink T-shirts, cowgirl hats and fluffy tutus encouraged) and the Go Dirty Girl (“It’s like a day at the spa, but way more therapeutic!").

***

With so many races competing to beat the couch potato out of America, can the entrepreneurs behind them all end up in the black? It’s too early to say, and most of the companies keep tight lids on their financials.

But, Tough Mudder seems to be succeeding. Their 2011 revenue was around $22 million, up from $2.2 million in 2010. Patterson sees the industry as a trend that’s here to stay.

Brad Scudder, a former litigation attorney in Springfield, Missouri, launched Rugged Races in June 2010. Dickens, a former Wall Street attorney, won’t reveal their numbers, but says they barely made enough in their first year to survive.

“And that was before the extreme race industry became overcrowded with small, local companies popping up all over the country,” says Dickens. “If we had to start out today with all of the competition that exists now, we’d need hundreds of thousands of dollars in private funding just to get our feet on the ground.”

The event companies make money through registration tickets and sponsorships. Most events also partner with charities, which perhaps is the only way they resemble traditional races. Many of the partnerships are with military organizations. Tough Mudder partners with the Wounded Warrior Project, and has raised more than $2.5 million for the cause. Rugged Maniac supports The Fisher House Foundation, which provides “comfort homes” on military bases for families of injured or sick servicemen and women. It all adds up to a few hours of feeling really bad that participants can feel good about.

***

Back in Texas, Joshua Mullins has no plans to stop adventure racing. He says the thrill of the races, combined with having a training goal, makes it easier to get up in the morning. He was so inspired by how the events helped him overcome his back injury pain that he’s working on his personal training certification to help others with injuries enjoy exercise again.

He's even made an unlikely friend.

"After finishing the Super Spartan, one of the first things I told my wife was that I was going to hug 'The Bag of Doom' for being such an awesome training buddy," he says.

The Bag of Doom has become an integral part of Mullins' workouts. After all, if he ever plans to take on the Death Race, The Bag of Doom could truly be his best friend.

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