They're crowding up to the starting line now – 500 or 600 of them, raring to go. They have just scaled an eight-foot wall, dropping into the type of cramped holding pen you might see at a factory-farm slaughterhouse – a not altogether inapt comparison. A loudspeaker is blaring the Foo Fighters' "My Hero"; shirtless Marines are punching one another to get pumped up. It smells like energy bars, sweat, and fear. For a moment, there is calm, as the "Star-Spangled Banner" plays and everyone bows their head. Then an amped-up MC gets on the mic. "We're gonna hurt you today, folks," he promises. "If you're ready, give me a hoo-rah!"

"Hoo-rah!"

Now everyone's raising their right hand and reciting a pledge. I understand that Tough Mudder is not a race but a challenge. I put teamwork and camaraderie before my course time. I do not whine – kids whine. Then, before anyone can change his or her mind, the gates open, an air horn blares, and they're off, charging up a hill with the kind of screams rarely heard since, say, Antietam. Out on the course, the obstacles begin. On a slicked-up quarter-pipe, nicknamed Everest, runner after runner sprints to the 15-foot wall at full speed, leaps grasping for the top, and smashes face-first into the side, sliding back down to try again. Elsewhere, at the obstacle called Electroshock Therapy, a team is crawling through a field of dangling live electrical wires, one guy screaming "Fuck! Fuck! Fuck!" at every 10,000-volt jolt. As thousands of spectators cheer them on, one angelic-looking little girl in the crowd overhears a couple of dudes discussing the release forms everyone has signed. "Mommy," she says, tugging at her mom's hand. "Did Daddy sign a death waiver?"

It's 8 am on a Saturday, and on this normally sleepy golf course in the Poconos, 10,000 people are going for one hell of a morning jog. It's called a Tough Mudder, and its founders boast that it is "Probably the Toughest Event on the Planet." In basic terms, it's a 10- to 12-mile cross-country trail run, dotted with 20 or so military-style obstacles. But describing it that way is like getting into a ring with a bull and calling it a petting zoo: The reality is far more insane.

Today, participants will have to dive into the Kiss of Mud, a belly crawl under barbed wire. They will also confront something called Arctic Enema – a bone-chilling jump into a Dumpster full of ice water – and the Cliff Hanger, a climb up a slope so steep and muddy that a human chain is often necessary to reach the top. Don't forget the Death March and the Fire Walker, which are both pretty much just what they sound like. By the end of the day, they'll have risked broken bones, hypothermia, fire, and electric shocks – all for nothing more than a cold beer, an orange headband and T-shirt, and the opportunity to call themselves tough.

In the past couple of years, obstacle-style endurance runs like Tough Mudder have proliferated as the newest fitness trend. Last year, an estimated million-plus people did at least one – most of them in big-name events like Spartan Race, Warrior Dash, and Muddy Buddy. The whole thing goes hand in hand with the "functional fitness" movement currently in vogue – things like CrossFit, Insanity, P90X.

The largest, most popular of them all is the three-year-old Tough Mudder. If you haven't run one yourself, you probably know someone who has – or you've seen ads for it on Facebook or posters in your gym. A projected half-million people will enter one of nearly three-dozen events spread across four different countries this year alone. How many of those will finish is another story.

Here in Pennsylvania, Jonathan Geller is running his ninth Tough Mudder. A 31-year-old personal trainer from New Jersey, he heard about TM on Facebook three years ago and was at the starting line for the very first one. Since then, he's done Mudders at ski resorts in Pennsylvania and Vermont and a motocross park in New Jersey. Last December, he also ran in the World's Toughest Mudder, a sort of unofficial Mudder championship where entrants fight to see how many loops they can do in 24 hours. "It's probably the hardest thing I've done in my life," says Geller. "I dislocated my shoulder three times on the first lap."

Like most Mudder participants, Geller runs as part of a team, usually him and his brothers-in-law. (Their name: "Same Mud, Different Day.") He appreciates that unlike other races, Tough Mudder doesn't track its runners with timing chips or even record results. "I don't like comparing myself to other people on a scoreboard," he says. "It's more about helping each other through." He's probably a Mudder for life, having been ruined for anything calmer, less obstacle-driven. Recently he signed up for a traditional 10-K, but when race day rolled around, he couldn't even be bothered to show up. "If I wasn't going to get to climb anything or run through crap, what was the point?"

"We like to say Tough Mudder is a switch in your head that flips yes or flips no," says Alex Patterson, Tough Mudder's chief creative officer. "You hear about it, and you either say, 'That's what I've been waiting for,' or 'Why would anyone pay $125 to put themselves through that?'" According to Patterson, the event fills a very modern need. "We don't really know if we're tough anymore," he says. "We don't have fistfights. We don't chop wood. Life has become convenient and easy. At Tough Mudder, we get a lot of what we call the 'Fight Club' male – the 25- to 40-year-old guy in a white-collar job who hasn't been scared, hasn't been wet and muddy, and wants to test himself to see what he's made of – to prove that even though he's 38 and has a rollerbag and a door on his minivan that closes by itself, he still has this inner badass. It's this visceral sense of accomplishment that handing in the Q2 report doesn't give you."

It's hard to argue with success. What started three years ago as a business-school project marketed with $20 Facebook ads has swiftly become a $70 million corporation and is still growing. It's been praised in 'The New York Times' and credited by 'Forbes' with "creat[ing] a new business model for sports."

At the Pennsylvania event, it's easy to see what people find so fun about it. There's a pull-up contest, a keg toss, and other feats of strength. A party near the finish line features a local band doing serviceable Rolling Stones covers, and the smell of roasted corn and funnel cakes fills the air. Mother's Day is tomorrow, and families are out in full force, with more than a few people wearing shirts that say happy mudder's day. And one should never underestimate the draw of a free beer.

Even Tough Mudder's rivals admit to a sort of grudging respect. "You have to hand it to them – they've got an incredible business," says Joseph Desena, a former Wall Street trader and the founder of Spartan Race. "They've really gotten their name out there and promoted themselves. I just wonder how long it will last."Tough mudder's headquarters are located in an old brick warehouse in downtown Brooklyn, not far from the Manhattan Bridge. Most of the building's other lofts are populated by young creative types – art gallerists, design firms, Etsy.com. If you want to find the Mudder people, just look for anyone with a tanned build and workout socks. Even the company's warren of offices, spread pell-mell throughout the third floor, stand testament to their somewhat astonishing success: They're growing so fast, their real estate agent can't keep up.

One afternoon in July, a group of new hires is in a conference room watching a PowerPoint training slideshow. On a dry-erase board nearby, someone is brainstorming a list of "Badasses in History." (First two entries: Ernest Shackleton and Gandhi.) In one bullpen-style office, a few dozen young people are hard at work on their computers, scouting course locations and assembling spreadsheets. And high on one wall, like a ticker at a PBS pledge drive, a big plasma screen displays the latest registration stats: 674 people so far today; 4,310 for the event that weekend; 411,194 for the year.

Down the hall, in a sunny conference room that smells of fresh paint, the company's co-founder, a toweringly self-confident 31-year-old Englishman named Will Dean, sits sipping a bottle of water. Dean is dressed in CEO-casual – Birkenstocks, cargo shorts, a Tough Mudder T-shirt – and his boyish face looks like it hasn't seen a razor in a couple of days. Soft-spoken and unflaggingly polite, he could be Chris Martin's slightly plumper cousin – a low-key presence for such a high-intensity company.

Dean grew up near Nottingham, literally down the road from Sherwood Forest. His parents were lawyers, and he figured he would be one, too, but when he was 16, he and a boarding-school friend, Guy Livingstone, participated in a school project where they were basically given government money to start a company. They acquired the rights to distribute color-changing nail polish in the U.K. and traveled to trade shows around the country, using their own nails as models. "We probably made £10,000," Dean says. Just like that, he'd caught the business bug.

After graduation, he went to work for the Foreign and Commonwealth Office – the British equivalent of the U.S. State Department – and was stationed in the Middle East, coordinating with Arab governments to freeze terrorist assets. Dean found counterterrorism work in the post-9/11 years exciting. "You could be 24 and be the de facto expert on something," he says. "You'd come up with some idea and say, 'It costs £10 million,' and they'd be like, 'Here's 12.'"

A few years later, Dean enrolled at Harvard Business School, where, according to an official company biography, "he finished in the top 10 percent of his class despite sadly finding much of his time there very boring indeed." "Most people there did not blow my mind," Dean says. A summer working at Bain, Mitt Romney's old firm, sealed the deal: "I was, like, 'This is as good as it gets post-MBA – I'm going to be partially lobotomized if I stay here for six months.'"

In the meantime, he was getting back into exercising. He'd grown up playing rugby and rowing, and at Harvard, he started thinking about how he might be able to turn fitness into a business. He'd already seen the potential for a Tough Mudder-style event: One semester, he conducted a field study of a race in Germany called the Strongman Run, which sold out its 8,000 spots in a matter of minutes. "I started thinking I could do this in the States," Dean says, "that Americans would really enjoy this sort of thing." (A cynical mind might wonder if he was doing more than just research; in 2010, a long-running, and very similar, event in the U.K. called the Tough Guy filed suit against Tough Mudder in the U.S., alleging the company had stolen its idea. The case was later settled out of court.)

Dean's second year at Harvard, he captained a team in the school's prestigious Business Plan Contest. The pitch? A seven-mile, military-style obstacle race. Dean's team made it to the semifinals but lost in the final round because none of the judges believed the company could be profitable. "No one is going to come to this," their professors told them. It's a story Dean loves telling because it highlights Tough Mudder's underdog roots – but also because it shows he's smarter than his professors.

After graduation, Dean recruited his old boarding-school friend Livingstone, who'd recently left his job as a corporate attorney and was drifting around Syria trying to learn Arabic. They moved to New York, because that's where Dean's girlfriend was, and put up $10,000 each in seed capital. They spent a few months sketching out obstacles, basically ripping off what Dean had picked up from the special-forces guys he used to run with overseas, and driving around the East Coast in their beat-up Jetta, scouting racetracks and ski resorts as possible locations. They were working 20 hours a day, and Livingstone was sleeping on a mattress in Dean's Brooklyn living room. They ate a lot of bagels, a lot of noodles, didn't shave. "I look at how we looked in October 2009 and in the spring of 2010," Dean says, "and it looks like we took up heroin."

One of the things Dean had learned was that it's good to have what's called a "positive cash inversion cycle": You tell people what you're going to sell them, take their money up front, and use that money to make the thing you're selling. You're not spending your own money at all. When it came to Tough Mudder, Dean says, "I thought, 'This is the same. I can get all the money in before I actually have to do anything.'"

They set up a $300 website, which, after expenses and the pittance they paid themselves, left them with an $8,200 marketing budget, which they spent entirely on Facebook ads. For their first race, at a ski resort in Pennsylvania, Dean thought they'd be lucky if 500 people signed up. ("I remember the day we got 10. We all went for beers.") Instead, they sold all 4,500 spots in about a month. At $85 per person, their costs were covered weeks in advance of the race. Even before they'd started, they'd turned a profit.

"I had, like, $100,000 in student loans," Dean says. "Six weeks after the website went live, I wrote a check for the whole amount."The first Tough Mudder was held on Sunday, May 2, 2010. It did not go well. At midnight on the morning of the race, Dean and Livingstone were still out on the course, wearing headlamps and frantically banging rebar into the ground. Once the race began, there were massive lines at some of the obstacles, with some people waiting nearly an hour just to climb a wall. The day turned out to be hot, and they'd severely underestimated how much water they'd need – they ran out in about an hour. (Dean: "People seemed to be pretty angry about that.") In hindsight, he rates the whole thing a C-minus. "If there'd been any other competitors in the market," he says, "we could have become an also-ran."

One reason Tough Mudder didn't is that it found the sweet spot between tough and accessible. As Patterson puts it, "You don't have to quit your job or dump your girlfriend to train full-time." The biggest draw, of course, is the obstacles: a rotating arsenal of 60 or so, about half of which will appear in any given race. Some are your garden-variety basic-training staples, like the so-called Berlin Walls (12-foot climbing walls). Sometimes the elements come into play as well: At one sleety event near Big Bear last year, Dean remembers climbing out of the Arctic Enema and running straight into a snowstorm, the coldest he's ever been. Afterward, he says, his ass "felt like a frozen steak." He still has a scar on his knee from a mild case of frostbite.

According to Patterson, the next frontier in obstacles is probably psychological. "One we're thinking of is called Dark Lightning – it's like the Electric Eel but in a completely black space, so you can't see where the wires are. Or we'll have mileage markers, but we'll put them every nine-tenths of a mile – so when you think you're done, you still have another mile to go." They're currently looking to hire someone with the enviable title of Director of Obstacle Innovation, who will have a big work space in Brooklyn in which to experiment. "It definitely needs to be near a Home Depot," Patterson says. "Actually...they would be a good sponsor."

From a business standpoint, there are two things Tough Mudder has done better than anyone else. The first is branding. It's perfectly positioned itself as a bro-ish, dude-ish good time, employing gimmicks like intentionally sophomoric obstacle names (Hold Your Wood, the Ball Shrinker), free mullets and tattoos (more than a thousand people have taken advantage of the latter), and a free cup of beer for everyone who finishes (courtesy of Dos Equis, a sponsor). Dean says he took his inspiration from rugby culture: "It's not about trying to create some giant frat party or trying to be Jackass. It's just guys being guys, playing hard and going for beers after."

Tough Mudder's organizers also constantly point out that it's "not a race but a challenge." The event stresses cooperation, not competition, and it doesn't time participants or even have clocks. To hear Dean tell it, this is no accident. "This is where I start sounding like a Marxist-Leninist," he says. "But I genuinely believe that marathons and triathlons are kind of a continuation of the values of our corporate rat race, where it's about getting ahead, doing it on your own, putting in the hours, not getting help." Tough Mudder, on the other hand, is a little more like socialism, where teams go only as fast as their slowest member and pledge to "Leave No Mudder Behind." "I don't pretend to be some sociologist," Dean says, "but I did see this as all part of it."

The second thing they've done well is sell themselves. The company has grown in organic fashion, with three-fourths of new business coming by word of mouth. Almost all their marketing is done via social media – YouTube videos, Twitter posts. When someone likes Tough Mudder on Facebook, their friends start seeing ads. The customers do the selling for them. Even the notion that Tough Mudder is best done as a team is a stroke of commercial genius – once one person signs up, he's dragging three or four friends along with him.

As a result, the company has grown exponentially. In 2010, Tough Mudder staged three events and earned around $2 million. This year, it's 35 events and an estimated revenue of more than $70 million. Pretty soon Dean and Livingstone will move into another building in Brooklyn like the one they started in three years ago Рthe difference is, last time they had two desks, this time they'll have 250.

Meanwhile, that initial $20,000 that Dean and Livingstone invested is all the seed money the company has ever had. They've never tried to raise outside money; they've never even needed to. As a result, all profits are theirs, 50-50. And with $70 million in revenue this year – and overhead that basically consists of plywood, straw, and nails – they must be making just absurd amounts of cash.

At this point, the company is probably starting to reach its peak in the U.S. "We clearly can't keep doubling in size," Dean says. "It's unsustainable." He sees it topping out at around 50 events here, with maybe a million participants. "But, as you can see," he says, pointing to a large, orange world map with black dots stuck everywhere there's an event, "there are still a lot of countries that don't have dots." They expect people will eat it up in countries like Germany and Sweden – "cold places, places with Viking blood" – as well as more Westernized Asian countries like South Korea and Japan. They're also looking at everything from Tough Mudder-branded fitness gear to boot camps to a TV show – even to their own hotel-booking company. "Most of the Tough Mudder spending is not captured by Tough Mudder," says Dean. "We're looking into that."

Run for Your Lives, founded in Baltimore, is a "zombie-infested" 5-K obstacle course where participants try to get to the finish line before being "eaten." It started last year and has already spread to a dozen cities and towns. "Twelve thousand people at their first event," marvels Dean. "Amazing. And just to be chased by zombies. We think we don't have any costs – we still have to build obstacles. They're just like, 'Hey! Who wants to play tag?'"Of course, the only way to really know what a Tough Mudder is like is to do one. Which is why, one Saturday morning in July, I found myself at the foot of a ski slope in California wearing Dri-Fit and trail shoes, and prepared to get muddy.

A few weeks earlier, I'd emailed some college friends to say, "Hey, no pressure, but I'm thinking of doing this, and does anyone want to join?" (Actually, what I said was, "Come on, don't be a pussy.") We graduated eight years ago, but we're still close, and we're all in the same fantasy-football league. But everyone has moved away, some have started families, and we don't see each other that much anymore. The excuses ran the gamut:

"Part of me is really intrigued, but I don't think my body can handle it."

"My friend just told me he did one of these last year, and they were pulling people out for fear of hypothermia...yikes."

"I need to start doing some push-ups ASAP."

"We have baptism classes that weekend."

Five said yes, though, and over the next month, we planned our strategy in an email chain that eventually hit more than 300 messages and included discussions about chest hair, compression shorts, tree-climbing skills, proper push-up techniques, 8 Minute Abs, 7 Minute Power Abs, the 1992 Dream Team, Game of Thrones, the Wikipedia definition of hypothermia, and what it feels like to be electrically shocked. (Of the last one, my friend Joe, who worked as an electrician in college, said: "It's not so bad. Feels like hitting a baseball on the wrong part of a bat.")

On the afternoon before the event, we all drove from Los Angeles to the Snow Valley Mountain Resort near Big Bear, where we scoped out the course. It was the same one where Will Dean had gotten frostbite the year before – but today was so hot and dry that there wasn't even mud, just rocks and dust. My friends are all in reasonably good, but not exceptional, shape: Three of us have run marathons; one rowed crew in college; and another plays soccer and works out several times a week. Still, standing there at 7,000 feet, having not really trained, the 1,000-foot ski slope looked like it would be hard to climb once, much less five times.

From a marketing standpoint, it's a pretty smart move to tell people over and over again how hard your event is, because by the time they finish, they've been conditioned to believe they've really done something special. Meanwhile, the company claims that only 75 to 80 percent of entrants actually finish, but since there are no timing chips or official records, this is based on the number of headbands handed out at the end, which seems like an imprecise measure.

So how tough is it, really? Well, Arctic Enema was definitely take-your-breath-away cold; I can't imagine doing it on a less-hot day. No one on our team could climb the 45-degree-incline Cliff Hanger without stopping to walk, and Nick, the ex-rower, was the only one to make it across the rings without falling. But Everest, the quarter-pipe, was pretty easy, and even the electric shocks weren't that bad. (Joe, the electrician, figured they must have been on a pulse timer – otherwise, given how wet everyone was, it would basically mean mass death.) Sure, you might get a little banged-up or wet. But strictly from a fitness standpoint, if you can do a triathlon, or a marathon, or even a 10-K, you can definitely finish a Tough Mudder.

A few days after the event, I asked my friends what they thought: None were overly impressed. Nick said he was sore for three days, but he was expecting worse. "I definitely built up in my mind that it was going to be crazy hard," he said. "But the obstacles were a little underwhelming. I was expecting to barely be able to cross the finish line, but I felt like I could have kept going."

Joe agreed. "It wasn't as hard as I thought it'd be. Going into it, I was intimidated, but I shouldn't have been. I did have some (minor) injuries, which I guess says something about its toughness. Ultimately, I think it's just a fun afternoon for reasonably fit people."

Reid was disappointed in the field. "I'm sure there were some ex-Marines and ultramarathoners who smoked us, but I was surprised by the number of people who struggled to make it up the hills. I wanted to be in awe of the other participants, but I wasn't."

And Ted, finally, put it most succinctly: "I wish I had gotten more bruises."

All of which prompts the question: Can you really bill yourself as "Probably the Toughest Event on the Planet" when half a million people do it in any one year, and a lot of them are smiling at the finish? Dean thinks so: "It's kind of like calling the Ford Mustang the Best Sports Car on the Planet," he says. "People have definitely heard of Porsches and Ferraris, but I think what we're trying to say is we're tough in our own way." Also, to be fair, you get out what you put in: Our team, while not exactly pushing itself, still passed more people than passed us – but if we'd gone all out, we probably would have collapsed.

On the other hand, as an excuse to spend some fun, quality time together, Tough Mudder accomplished exactly what we'd hoped. "I definitely felt a strong sense of camaraderie among the five of us," my friend Nick said. Reid said his favorite parts were obstacles like Berlin Walls and Everest, where we had to work together to push and pull each other up: "I felt like that's where we bonded the most." Driving back to our rental cabin that afternoon, we stopped at a bar for some burgers and beers, and talked about girls, football, the guys who weren't there. Except for some talk about who was having babies, it almost felt like we were back in school.

Back at the cabin, we all showered and packed up our things, including our brand-new Tough Mudder headbands and T-shirts. The shirts were nice to have, Reid said – a silhouette of a soldier running through orange flames on a field of black, with the Tough Mudder pledge on the back. "But I doubt I'll wear it very often," he added. "The toughest people I know don't need to tell anyone they're tough."

 

Related links:

Best Obstacle Courses