Last September, I met Joe De Sena at his in-laws’ house in suburban Massachusetts. Earlier that day, De Sena had driven south from Vermont for a meeting in Boston, and we had arranged to get together for dinner. Sitting at a kitchen island in front of his computer, De Sena turned to his mother-in-law, Laurel, and said that he had a new project: a truck driver from Chicago named Danny.

De Sena is an entrepreneur and longtime endurance and adventure racer. A decade ago, he sold his Wall Street trading firm and moved to a farm in the small central Vermont town of Pittsfield, in the Green Mountains, where he lives with his family. Soon he started hosting his own races, including the Death Race, a multi-day event that is a cross between an adventure race and a military survival course. In 2010, he launched Spartan Race Inc., which is now a $60 million business and one of the most popular obstacle-race series in the world. For years, De Sena has kept an open-door policy at his home, but since Spartan has taken off the farm has become a boardinghouse for a mix of elite Spartan racers, wannabes, and people like Danny—men and women looking for something more out of life.

When Danny showed up at an event last summer, he was severely overweight and burned out from driving the truck. After his father died, when he was 17, eating became his coping mechanism. By his mid-twenties, Danny was close to 400 pounds. Danny said, “Joe, I’m overweight, I was hoping—” and De Sena said, “Yes, you can come.”

Last year more than two million people entered obstacle events, four times the number who ran marathons. By some measures, obstacle racing is the fastest-growing sport in American history.

Last year more than two million people entered obstacle events, four times the number who ran marathons. By some measures, obstacle racing is the fastest-growing sport in American history.

Danny arrived in Pittsfield in late July, and De Sena laid down the ground rules. In keeping with the ideals of both ancient Sparta—only have what you need—and Spartan Race, Danny agreed to give up his wallet and do whatever De Sena said. It’s hard to imagine that Danny could’ve understood exactly what this would mean, but he agreed.

A few minutes later, De Sena gave Danny a bag of apples and a gallon of water and told him to hike to a small stone cabin on top of his mountain, one mile and more than 1,000 vertical feet above his idyllic 700-acre farm. Over the next week, De Sena put Danny to work doing manual labor, 12 to 14 hours at a stretch. Some days, Danny walked and hiked more than 15 miles. For the first ten days, Danny was only allowed to eat apples.

“Only apples?” I asked.

“Only apples,” De Sena said. “Ten days, only apples. And I cleaned him out. Because he’d been on, like, Chicago deep-dish pizza for twenty years.”

“How many apples is that?”

“I don’t know—twenty, thirty apples a day?” De Sena said. “He said he never wanted to see another apple.” De Sena paused to eat a grape, and I noticed that Laurel and her husband, Bob, who had been making baked salmon and a salad with strawberries, were listening closely. De Sena was on the verge of revealing himself as a sadist, and they looked a little concerned.

“How are his spirits?” Laurel asked.

“At this point,” De Sena said, meaning after spending a few months in Vermont and losing more than 100 pounds, “he’s pretty broken.”

“At this point,” Laurel scoffed.

“Oh, this is great,” De Sena continued, grinning. “Yesterday morning we heard that somebody flipped him a protein shake, which is a no-no because I only want him on raw fruits and vegetables. Andy and I”—Andy is Andy Weinberg, who started the Death Race with De Sena—“we wake him up at 4 a.m. It’s pitch black. Andy’s carrying a chainsaw because he wants to cut a couple of fallen trees.

“Danny doesn’t even notice that Andy’s got the chainsaw, because Danny is out of it, you know, 14-hour days and all that, and we’re berating him on this protein-shake thing. So now we go into the woods where it’s even darker, you can’t see anything, and Andy finds the tree and starts the chainsaw up, right? But after we cut through the tree, which takes ten minutes, we can’t find Danny.”

Eventually, De Sena and Weinberg returned to the house. Danny was inside, terrified and shivering.

“He thinks because of the protein-shake discussion we just had, we’re going to chop him up—”

“Oh no!” Laurel gasped.

“—with the chainsaw,” De Sena said, laughing.

“Alright,” Laurel said, looking at me. “Don’t put that in, that’s really scary.”

A few months later, in January, I visited De Sena in Pittsfield, just before dawn. In winter he often works out in the two-story red barn attached to his farmhouse. As I stepped inside, De Sena’s dog, a black and white pit bull mutt named Noodle, greeted me at the door. I could make out the sound of hard, rhythmic expulsions of air and the distinctive thump-and-tumble of someone doing burpees. Upstairs, De Sena was in the middle of a set, wearing flannel pajama pants and a black hoodie. He is 45 years old and has a large forehead, short hair, and a thick, muscular torso. His first business was cleaning and building pools in Queens, New York, and he retains the callused look of men who do manual labor. He stopped briefly to quiet Noodle and say hello, then dove into another round.

In the corner, Weinberg, who lives nearby, was doing lunges and pull-ups in a red tee and olive hiking pants. An earnest and energetic 43-year-old race organizer, teacher, and former swim coach, he begins many sentences by saying “Check this out!” and tapping you lightly on the shoulder. In October he completed a quintuple Ironman—a 12-mile swim, followed by a 560-mile bike ride, followed by a 131-mile run, one of the first triathlons of that length in history. One night in Pittsfield, I bumped into Weinberg as he was preparing to head out for a run and noticed he was wearing a 50-pound weight vest.

In 2004, De Sena and Weinberg held the first edition of the Death Race, during which one participant almost drowned after getting trapped in a narrow, belowground culvert. “When we started laying out the Death Race, we had to reel Joe in a little bit,” said Shaun Bain, a former adventure-race teammate of De Sena’s. “We were like, ‘You can’t do that, people are gonna die!’ ” Today the race is marginally safer, though it’s still a deranged sufferfest that might involve everything from wheelbarrowing manure to diving for submerged sacks of pennies, and there are now team, winter, and international versions. At last year’s main event, which is held annually at the farm, the field of 300 participants spent the entire first day building a stone staircase a mile up the mountain. Only 40 made it to the finish.

By 2009, the Death Race had begun attracting national media attention, though not many participants. Hoping to create a more accessible event, De Sena and Weinberg launched the significantly less punishing Spartan Race series the following year and set about recruiting elite runners, triathletes, and CrossFitters. Tough Mudder, Spartan’s main rival, and other OCR (obstacle-course race) events, as they’re known, had just launched. From the start, De Sena was adamant that Spartan be an actual race. Unlike Tough Mudder, which De Sena disdains because it’s not as competitive, all Spartan events are timed, and the results are published online. Participants can choose from races that are three, six, or thirteen miles in length; anyone who fails to complete an obstacle must perform sets of burpees.

Back in the barn, Weinberg told me cheerfully that at 5 a.m., he and De Sena had gone for a short run before getting De Sena’s kids out of bed. “He fuckin’ wakes me up in the morning,” De Sena told me at one point. “Or I wake him up. He’s definitely a lunatic, and it’s inspiring to be around. Plus, if I’m ever in a jam or whatever, or need some help, he makes shit happen.”

As Weinberg and I chatted about his daughter, who was traveling in Europe with the U.S. junior luge team, De Sena finished his set of 300 burpees, which he does every morning, and began hefting himself up a thick, braided climbing rope, similar to the ones racers scale at Spartan events, suspended from the barn’s timbers.

A few feet away, three of De Sena’s four kids—eight-year-old Jack, six-year-old Charlie, and four-year-old Catherine—were doing a series of stretches and high kicks in their pajamas. (De Sena’s youngest, Alexandra, is 18 months old.) A kung-fu teacher from China who goes by Sunny, a mixed-martial-arts fighter named Jose, and a third man were giving instructions.

Jose asked Charlie to count to 30 in Chinese, and then each of the kids lined up and braced themselves against a beam for one-legged pistol squats, with one ankle wedged above the opposite knee. Sunny called out “chi” for down and “qilai” for up. When Charlie didn’t get up after rep three, Sunny scolded him gently in Mandarin and then grabbed him by the scruff of his shirt and pulled him back into position.

Soon the kids were absorbed in a lighthearted game of Red Rover. Jack, the eldest, pulled off his pajama top. “It’s good that he’s taking his shirt off,” De Sena said when he walked over to me. “It means he’s getting into it. You know that Tiger Mom book that came out a couple years ago? You push them and they hate it, but then they get good. He fought us on this stuff for two years, but who knows what happened. Maybe some kid at school said, ‘Wow, you’ve got a good six pack.’ ” Jack made it safely from one side of the barn to the other, then ran to the bathroom. De Sena excused himself to jump rope.

After his workout, De Sena took a quick shower and we drove a mile north to the town’s General Store, which De Sena bought in 2004. “I was on my computer for ten and a half hours yesterday,” he told me in the car. “I fucking hate that. I moved up here so I wouldn’t do that.” Besides the store, De Sena also owns a hotel, a wedding business, a Spartan-themed retreat for corporate types, and half a dozen residential properties around town. Most of the Spartan Race staff—about 50 people—now work at the company’s headquarters in Boston, but De Sena bounces between the store and his kitchen counter in Pittsfield, where he mans a MacBook Air, a cell phone, and a landline, often at the same time.

De Sena has invited tens of thousands of people to Vermont. Of the hundreds who have shown up, he estimates that about 95 percent leave within a few days and that, at most, 150 people have stayed for a meaningful duration.

Last year more than two million people entered obstacle events in the U.S., four times the number who ran marathons. By some measures, obstacle racing is the fastest-growing sport in American history, with dozens of spin-offs ranging from women’s-only Dirty Girl races to Zombie Obstacle Runs to Superhero Scrambles. In the early days, De Sena and Tough Mudder’s crafty CEO, Will Dean, waged a fierce marketing battle. At one point, Tough Mudder began recruiting racers with a clever hack of Spartan’s Facebook page: when someone liked Spartan, they received a taunting instant message from Tough Mudder offering a discount on an upcoming event with the code “Spartan.” De Sena once told a reporter for this magazine that there’s nobody on the planet he despises more than Dean, though he’s since toned down his rhetoric. Now he’s focused on defining the differences between the two races. “I don’t want it to be beer and partying,” he told me. “I want it to be a serious sport. Mudder is more like a biker rally.”

In mid-2012, Spartan received funding from a major private-equity firm, and in June 2013, Reebok signed on as a title sponsor in a deal worth at least $10 million. Last year, Spartan attracted more than 650,000 competitors at 35 domestic and 20 international events and generated more than $60 million in revenue. Still, the company has yet to turn a profit. “The game for me is just to stay alive long enough to watch the little guys die,” De Sena said. “Hopefully, TV catapults us.” In November, NBC aired a 90-minute edited version of last September’s Spartan Race World Championships and, this spring, agreed to a five-year deal to broadcast at least 12 races. De Sena is currently involved in an effort to organize a governing body for the sport. His ultimate goal is to see obstacle racing included in the summer Olympics.

As Spartan grows, the other businesses have become distractions, and this spring De Sena set up a plan to transfer equity in the store to a couple from New York City. “Spartan is so big now and so awesome, I just want to get rid of the other businesses,” he said.

In the store’s back office, De Sena checked in with his wife, Courtney, who manages the wedding business. “Joe builds things, but then he has to find people to run them,” she said. After the discussion, De Sena ordered some eggs and hash browns and sat at one of the store’s big picnic tables. He pointed to a fit-looking, squared-away man wearing a military-style backpack with an ax handle protruding from the top. His name was Mark Jones, and although he had been in town for only a week, De Sena was clearly excited by his presence. “Right away, I like Mark,” he said later. “He’s just all business, you know?”

I introduced myself, and Mark joined us at the table. He was 31 and had served two tours in Iraq. A medical issue had recently prevented him from gaining a Special Forces appointment, and five days earlier he had driven to Pittsfield from Virginia after getting a mass e-mail from Weinberg and De Sena. The pair had offered to train and house anyone willing to complete the Death Race Challenge: finishing four events—the winter, summer, team, and Mexican versions—in a single year. Mark’s wife had recently left him, and he had nowhere else to go. “Their e-mail saved my life, and I’ll leave it at that,” he said.

After breakfast, Mark left with Miguel Medina, a professional Spartan racer who was living on the farm. In September, Medina had been invited to move to Vermont on the condition that he build a cabin and live in it all winter. During my first visit, in November, De Sena had shown me Medina’s building site. We met at the General Store, where De Sena told me he had spent the morning carrying rocks. “I love carrying rocks,” he said. A few minutes later, we drove from the store to the farm, and De Sena hopped out of my car and began jogging uphill, first along an ATV path, then on a singletrack mountain-bike trail, then just straight through the woods.

We picked up another bike trail, which led to a steep hillside. Suddenly, the rocks made sense. I had assumed Medina was building a wood cabin, but De Sena had decided it would be constructed from stone. Medina and a small crew of men had dug a foundation into the hill and were busy stacking rocks into walls three feet deep and six feet high. The afternoon was cold and drizzly, and Medina, clothed in battered ski pants and sporting a wild black beard and long hair, looked more like a miserable hobo than an elite athlete.

Medina had left a job as a medical interpreter in Los Angeles, sold most of his possessions, and had no cold-weather gear. During the first, unusually frigid weeks of fall, he slept in a borrowed children’s sleeping bag in an unheated barn on the farm. The cabin project was sapping his energy to train, and I thought there was a real chance he wouldn’t last through the winter.

I had thought of Medina often in the ensuing months, and an hour after breakfast, I hiked into the woods to see how he was doing. When I reached the still-unfinished cabin this time, Medina was all smiles. After months of suffering, he’d figured out a routine: he would run or lift weights at 5 a.m. and again at 5 p.m., working for De Sena on construction and maintenance projects in between. “It’s not every day that somebody says, ‘Come train in Vermont,’ ” he said. “It’s easy to quit. It’s hard to keep going with anything.”

As things go on the farm, Medina’s story is fairly typical. A lot of the people who come to Pittsfield are extremely fit—soldiers and professional or semiprofessional endurance athletes. But there are also people like Danny, the apples guy who needed to lose weight, or Matt, who turned up four years ago in search of a place to live and now maintains De Sena’s trail network.

Among those who persevere on the farm, the common trait is tenacity, not physical strength. “It’s really missing a huge part of it to say it’s just an ex-military physical test,” Marion Abrams, a Pittsfield local who does videography for De Sena, told me. “For these people, it… I don’t know what it is exactly, but it’s a magical thing, and it’s life changing.”

Over the years, De Sena has invited tens of thousands of people to Vermont. Of the hundreds who have shown up, he estimates that about 95 percent leave within a few days and that, at most, 150 people have stayed for a meaningful duration. In one of my first interviews with De Sena, in Massachusetts last fall, I asked how many people were staying with him. He looked puzzled and then started listing names. “Eight?” he said. “Maybe 12?” Later, in Vermont, I tried to do a quick census of my own, but the boundaries between Spartan employees and Spartan disciples never seemed that clear. I gave up after I counted 14.

Danny flew back to Chicago in late September, before I got a chance to meet him. When we spoke by phone, he said that the chainsaw incident and the apples were both really hard but that his worst experience had come during the first week. One evening he got lost in the woods while hiking from the farm to the cabin. He spent six hours alone in the forest, then found a back road that led to town, where he spent the night in an unlocked restaurant. “I was like, I’m going to get my stuff and get the first ticket home,” he said. “But a lot of people rallied around me.” He ended up staying for another two months and left after completing a 13-mile Spartan Race at Killington.

Back in Chicago, Danny gained back about half the 100 pounds he lost. He was still trying to make healthy choices, but he found it difficult to stick to the Pittsfield lifestyle. “I can’t just head over to the organic market when I want,” he said. Still, Danny views his time in Vermont as overwhelmingly positive. “I have a better quality of life than I had,” he said. “I ended up learning a lot of things about myself in general, besides the health thing. How to be a little more self-reliant.”

One of the oddest things about De Sena is that most people eventually disappoint him, yet because he is so positive and enthusiastic, few ever realize it. In September, De Sena had raved about Danny. “This kid is unbelievable,” he said. But as much as De Sena liked him, by January it was clear that he thought Danny was capable of more. On occasion De Sena comes across someone like Weinberg, but mostly he seems resigned to watching people achieve less than he thinks they can.

De Sena’s father, Ralph, a serial entrepreneur and real estate investor in Queens, was a workaholic. He demanded the same from his son. One Saturday when De Sena was in middle school, his father tasked him with moving a pile of bricks. De Sena stayed up all night, hoping to get Sunday off. “I moved—I don’t know—a truckload of bricks by myself, just so I could sleep in on Sunday,” he told me. On Sunday morning, his father’s response was, “I see you’ve got the bricks done. Let’s go”—on to the next project. “It was never enough,” De Sena told me. “And I’ve got that gene.”

Most people eventually disappoint De Sena, yet because he is so positive, few ever realize it. On occasion he comes across someone who impresses him, but mostly he seems resigned to watching people achieve less than he thinks they can.

In the early eighties, De Sena’s parents divorced and he and his sister moved to Ithaca with their mother. In Queens, De Sena’s father had connections to the Italian mafia, and a precocious De Sena started negotiating black-market-fireworks deals with one of the contacts, sneaking out to use a pay phone near his house. For a short time, he sold smoke bombs and Black Cats at his new school. When the administrators shut down his operation, he started selling T-shirts. Then he became obsessed with BMX racing. When he was 15, he rode his bike 35 miles to an event in upstate New York, won three races, and then tried to ride back. (A friend’s mom drove him home after finding him sleeping by the road, exhausted.)

During summers in college, at Cornell University, he started a pool-cleaning business back in Queens. The only way to make money was to out-hustle the competition, and in 1994, looking to make a change, he took the advice of a friend on Wall Street, sold the business, and moved to Manhattan to begin investing the proceeds.

Trading was a thrill, but there was too much down time. “I didn’t know what to do on the weekends, when the markets were closed,” he said. He would wake up early and pace around Manhattan, fidgeting. In the late nineties, De Sena founded a small investment-management firm called Burlington Capital Markets. The company had a few early stumbles but then went on what De Sena describes as a “very successful ten-year run.”

Sitting at a desk all day, De Sena put on 30 pounds. Not one for gyms, he started running up and down the 32 flights of stairs in his apartment building to lose weight. Then he discovered endurance racing. Within months he was hooked. At the height of his racing career, he completed a 100-mile trail-running race, an Ironman triathlon, and the 168-mile Badwater Ultramarathon in a single week.

In 2000, De Sena entered a 350-mile winter adventure race in northern Quebec. On day three, while waiting for race officials to repair a broken line on their next obstacle—a 1,500-foot rappel down a bluff—De Sena and his teammates were forced to burrow under the snow to stay warm. Temperatures dropped to minus 30, and De Sena began hallucinating about hamburgers. The race left him with a new tolerance for suffering and an appreciation for the distinction between a difficult experience and a desperate one. “It changed my frame of reference,” he said.

A few years later, at a triathlon on Nantucket, in Massachusetts, De Sena met Courtney Lawson, a talented athlete who captained Penn State’s soccer team to the NCAA final four in 1997. Their first date was an eight-hour sea-kayak tour, during which De Sena told her his life story. “I said to him, ‘Man, you must just burn through people,’ ” she said. “And he does. You meet him and then get so excited that you literally burn yourself. He either burns through you, or you get burned out.”

In 2004, De Sena and Courtney purchased the farm and moved to Vermont. The first years were not easy. The town has a population of about 500, and not everybody was thrilled that a wealthy New Yorker suddenly started buying up property. Nor were local officials enamored with his build-first, apply-for-permits-later approach to development. Signs began appearing around town that read Joe, go home.

But as Spartan Race and the other businesses have grown, the town’s residents have either embraced the De Senas or made a grudging peace with them. The economic activity generated by Spartan has helped, as did De Sena’s response to 2011’s Hurricane Irene, which devastated central Vermont and left Pittsfield isolated for more than two weeks. Piloting a backhoe for 20 hours a day during and after the storm, De Sena built berms against the floodwaters, cleared debris, and patched washed-out sections of roads and driveways for his neighbors.

Increasingly, De Sena sees himself as an evangelist for a physically active, fully committed lifestyle. Whereas the idea behind the Death Race was to identify exceptional people, the idea behind Spartan is to encourage normal people to live more exceptional lives. “The majority of OCR racers are not coming from the traditional running world’s ‘been there, done that’ types,” said Running USA spokesman Ryan Lamppa, “but are new runners and new to the sport.”

At one point, De Sena admitted that he wasn't sure if he was building character or deforming it. This seemed like a fair concern. Over the previous months, he had told me several slightly worrying stories about raising his kids.

Pittsfield is the nucleus for Spartan culture, but De Sena regularly hears from Spartan workout groups across the country. There is a special designation for people who complete all three Spartan distances—the Sprint, Super Spartan, and Spartan Beast—in a single season and another for racers who complete the trifecta in a single weekend. Challenge people, De Sena believes, and often they will respond in ways they never expected.

As the company expands, De Sena has had to learn to be more diplomatic. There are now people who might object, for example, if he decides on the spot to hire one of his Pittsfield refugees. Still, as far as I can tell, it is mostly the organization and the obstacle-racing world that is adapting to De Sena. “He’s one of the hardest guys to work with, business-wise,” says Mike Reilly, VP of endurance events at Active.com, the world’s largest site for participatory sports. “But not in a bad way. I’ve got so much respect for him it’s crazy. He’s building a company to make sure that nothing gets in his way. Which is fine, you’ve just got to battle him on that front.”

Out in the woods one day, carrying rocks up to Medina’s cabin site, I asked De Sena if he was worried that some people view him as a wild man who needs to be reined in. “I think even my investors have that issue,” he said, hefting a 50-pound bucket of fist-size stones in each hand. “And actually, I don’t think I’m a wild man. I think this could be perceived as wild,” he continued, referring to the rocks, “because it’s not normal. But I think if you look at it, it’s actually very logical. Everything I do is thought out.”

A few loads later, De Sena mentioned that he wasn’t sure if his boys would grow into the kind of men who take guns away from bad guys or if they’ll be the bad guys with guns—in other words, he wasn’t sure if he was building character or deforming it. This seemed like a fair concern. Over the previous months, De Sena had told me several slightly worrying stories about raising his kids: The time he convinced the boys to run a half-marathon, at ages five and seven. Or the time he made Jack boot-pack up nearby Killington Resort instead of taking the chairlift. Last summer, he strapped Charlie into a life vest and took him swimming across a nearby lake.

“We were three-quarters of the way across the lake,” De Sena said. “He starts screaming. He’s freezing, right? And I said, ‘Charlie, greatness is a quarter-mile away. We gotta make it. A quarter-mile.’ And at the dock, there’s a woman’s house. She hears Charlie, and she comes out on a paddleboard and starts screaming at me. We’re in a fight now. She’s screaming, ‘You gotta get him on shore!’ I said, ‘On shore? We’re a quarter-mile from greatness! He’s five years old, he’s gonna do a mile!’ We’re fighting over my kid!”

De Sena paused, signaling that he was done with the story.

“How’d that end?” I asked.

“He got it done,” De Sena said.

For all his energy, De Sena is relatively mild mannered—more lighthearted than his lifestyle might suggest—and I never heard him or Courtney raise their voices, around their children or otherwise. One evening, as I sat drinking tea with them in the kitchen, I asked what they would say to people who think their parenting is extreme.

“The way I look at it,” Courtney said, “this is what Joe likes to do, and I agree with it. I admire it. We’re not golfers, we don’t own a sailboat. Whatever your family does, I think, is what you do.” She turned to Joe. “I think you would say the same. Do you care if Jack or Charlie are ever in the Olympics?” De Sena shrugged. “Or do you want them to be waking up and working hard?”

On my way out of town the next morning, I got up late and stopped by the General Store for a cup of coffee. It was cold and sunny outside, and I was feeling sheepish about bailing on the morning workout with De Sena and Weinberg. Inside, I bumped into Mark Jones, who was about to give Medina a ride to a nearby train station.

“Did you work out together this morning?” I asked.

“Miguel didn’t, because he’s got a race coming up,” Jones said. I nodded, then drifted toward the coffee thermoses. Jones hesitated.

“I got up at midnight and did a six-hour hike,” he said. “I wanted to practice navigating while sleep deprived. And, you know, everything looks different when it’s dark.”

I paid for my coffee, wished Jones and Medina luck, and drove home.

The print version of this story incorrectly referred to Matt, a young man who manages the Green Mountain Trails network, as autistic. We regret the error.