On that spring day across America, the CrossFit faithful gathered--and toiled. There were hundreds of thousands of them, certainly. Maybe a million, maybe two. In an old industrial facility in New Orleans, they hoisted themselves on gymnastic rings and did dips up there. In a strip mall in Santa Cruz, California, they threw 20-pound medicine balls against a wall over and over again. In a business park near the Dulles airport in Virginia, they pushed weighted barbells above their heads, first once a minute, and then as fast as they could for three minutes straight--or until they couldn't lift their arms.

Meanwhile, in a bar called El Borracho, the king of CrossFit finished his tacos and ordered a second margarita.

He was in Seattle on business. The calendar that morning said Thursday, but Glassman's gut said the mall, and the day had meandered from there. He had bought himself and his pilot new blaze-orange parkas at Mountain Hardwear, and taken his girlfriend to Tiffany's to buy her a diamond pendant for her birthday. At first, the Tiffany's staff had eyed him suspiciously: With his faded jeans, his parka, and the backward red baseball cap over his scraggly wisps of gray hair, the 56-year-old looked as if he had wandered in from a tailgate party somewhere or might whip out a hammer for a smash-and-grab. But then, it turned out the saleswoman was one of them. Her sinewy body should have been a giveaway. "Greg Glassman!" she said, looking at his credit card. "My husband was with you last night!"

Glassman is getting used to this kind of surprised recognition. The man who invented the WOD, the world's most beautifully addictive workout, doesn't look like a paragon of clean living. He doesn't look like a paragon of anything. But then, Glassman enjoys defying conventional notions of good sense and good taste and good practice. And yet the business succeeds. So far, phenomenally.

The night before, he had rolled up with his entourage about 20 minutes late to a packed lecture hall of 500 CrossFitters at the University of Washington campus. He had been invited to speak there by the Freedom Foundation, a local libertarian group. Libertarians love CrossFit. It's neither a wholly owned chain of gyms nor a franchise, but the nucleus of a sprawling worldwide network of entrepreneurs. A local CrossFit gym is referred to as a box, because it can be anywhere and any style, and the culture of any box may be nothing like that of Glassman's company, or of any other CrossFit box. Boxes may even have different business models. And yet, there in the audience was the order spawned from the chaos: rows and rows of passionate CrossFitters, united in their love of the WOD, their muscled physiques rippling beneath T-shirts and hoodies.

In his gruff way, Glassman recounted his story for the faithful: how a novel, exquisitely punishing system of exercise he had designed, centered on the WOD (workout of the day; it's pronounced "wad"), had started in his backwater Santa Cruz gym, then turned into an online phenomenon, then paved the way for 6,775 CrossFit locations (soon to be 10,000), and now was fast becoming its own sport. (This month, the finals of the CrossFit Games will be broadcast live on ESPN2.) He explained the contrarian way he thinks about the CrossFit business (he shuns most new sources of revenue) and how he goes about protecting its brand (viciously).

But the truth is--and this is apparent to anyone watching Glassman wile away an afternoon at El Borracho--that CrossFit's success doesn't derive from any conventional business strategy. Glassman doesn't behave the way he's supposed to. Sometimes he rebels out of cunning, other times for the sheer petulant fun of it. Often, it's hard to tell which. As a result, CrossFit is a workout and a company no conventional trainer or M.B.A. would ever have built. Glassman is sitting atop a firecracker of a company. And the relevant question is, as always, What's he going to do now?

Glassman grew up in Woodland Hills, a suburb of Los Angeles in the San Fernando Valley. In the Glassman household, education trumped everything. Glassman's father was a rocket scientist at Hughes Aircraft and an all-around hard-ass who lorded math and the scientific method over Glassman, his younger sister, and their stay-at-home mom. Arguments with the old man inevitably required data sets, says Glassman--"Any point you made had to be measurable, repeatable"--and Glassman clashed with his dad frequently.

Glassman escaped into athletics and fell in love with gymnastics (the source, he says, of his pronounced limp), weightlifting, and cycling. After dropping out of several colleges and junior colleges, Glassman began working in fitness full time, as a personal trainer at local gyms.

He developed wacky routines: He had clients race their way through repetitions on a weight machine, and at one facility, he had them scramble up a 30-foot column in the middle of the room. Eventually, the owner of that gym welded disks to the pole to make him stop. "They added a hazard 15 feet up," Glassman cracked to clients, before signaling them to go up anyway. He got kicked out of that gym. He got kicked out of several gyms. "I've never wanted to be told what to do," Glassman says. "I think it's genetic."

In 1995, as Glassman was burning the last of his bridges at local gyms, he got a call from a friend who worked at the sheriff's department in Santa Cruz. The department had heard about him and wanted him to train officers. Glassman, who was in the middle of a breakup with a longtime girlfriend, decided to go. He set up shop in a health center called Spa Fitness and taught his own brand of fitness training, which he had begun calling CrossFit, to officers and anyone else looking to buy 60 minutes of sweat.

The Santa Cruz mornings and evenings became packed with fitness clients. The stretch of day in between grew into a time of study and reflection. He had a friend bring in printouts of fitness articles the friend had found using his newfangled Internet connection. "I went through thousands of pages like that," says Glassman. "When I finally got a computer, there was nothing on the Web on fitness I hadn't already seen."

Glassman began refining his approach. He favored gymnastic and powerlifting moves he knew from growing up, and functional calisthenics (squatting, pull-ups) that forced the body to use large muscle groups together, like in real life. He liked the idea of throwing exercises at clients seemingly randomly, believing it resembled the way early humans had to overcome daily physical obstacles. To goose participants' natural competitiveness, he mandated that the workouts be for time, or for as many rounds or reps as possible in a set time period, so that no one slacked off.

Glassman attracted a little flock. "I was looking for a trainer, and a friend of my wife's went to Spa Fitness," says Ben Elizer, who today is CrossFit's chief information officer. He went to Spa Fitness and was told he had his pick of two: "one guy who is really nice and not that good, and another guy who is really good but super-opinionated and arrogant"--Glassman, of course. Glassman's crew was tight-knit. He even ended up marrying one of his clients, a hairdresser named Lauren Jenai. When the Spa Fitness owner inevitably showed the CrossFitters the door, and they leased a corner of a jujitsu studio, Lauren would manage the books and teach CrossFit classes herself. Soon they outgrew that space, and the Glassmans took their motley little group of cops, jujitsu fighters, and tech-company commuters to a 1,250-square-foot truck garage on a remote road three miles out in Soquel. In 2000, a number of clients asked if Glassman could put the WODs online so they could do them when they traveled, so he put up CrossFit.com.

It seems unlikely, from today's perspective, that a rudimentary site featuring a daily workout, a daily link to other fitness sites, and occasionally a photo of an athlete could generate a passionate viral following.But then you probably haven't tried a WOD. To a skeptical initiate, the commitment to the WOD seems odd: It might be just 10 minutes of alternating five reps of deadlifts with 100-yard sprints. Simple enough, you think, as you picture yourself running around like a beheaded, powerlifting chicken. (In conventional gyms, CrossFit workouts draw stares.) But when you actually do that workout, halfway through you hit the baptismal version of what early CrossFitters fondly called the mess-you-up moment--the recognition that there's devilish magic in this offbeat combination. In a few minutes, you're the sorest you've been in years. You're not sure you will survive. It's an adrenaline rush. For anyone bored with standard weights routines or the elliptical, it's addictive.

So, although Glassman keeps the CrossFit business model radically loose and open, he protects the brand name with an iron fist.

An early client of Glassman's described the CrossFit experience as "agony coupled with laughter." Glassman liked that. It was as if his increasingly fit posse had a subversive secret: combinations of exercises that seemed strange and reckless and maybe dangerous to the ignorant. When Elizer, who volunteered to build the website, asked Glassman if he had a logo in mind, Glassman thought about the idea of agony mixed with laughter, then thought about thumbing his nose at all the ho-hum personal trainers he had ever endured. He came up with a vomiting clown. He called it Uncle Pukie.

All around the country and the world, people tried CrossFit workouts, got hooked, and told their friends. When CrossFit.com added a comment board, it started filling up with people's posting their times and records and asking for help. Then, at the little truck garage in Soquel, pilgrims began to arrive.

Soon, Glassman started advertising seminars. For $4,500 plus airfare and accommodations, he would come to you. Or, for $1,000 a head, people could come to Soquel. He would lecture on everything he had concluded about fitness and run participants through workouts. Meanwhile, CrossFit.com devotees were attracting followers of their own. Robb Wolf, a biochemist and former powerlifter from Seattle, visited the Glassmans in early 2002. He and some friends were starting a little gym--could they call it CrossFit?

In 2004, Glassman started teaching his seminars regularly and formalized the affiliation process. The Glassmans incorporated the business and hired their first employee. In two years, the number of CrossFit boxes grew from three to more than 50. CrossFit was becoming a real company.

In December 2005, The New York Times ran a story about the budding CrossFit craze. The reporter interviewed some of the original CrossFitters and chronicled their fitness accomplishments, which were considerable. But the part of the article that grabbed the most attention was the opening anecdote: A first-time CrossFitter named Brian Anderson had experienced a true mess-you-up moment--he had ended up in the emergency room after his baptismal WOD. Repeated kettlebell swings had torn up his lower back to the point that he could barely stand. In intensive care, he was told he had rhabdomyolysis, a condition wherein muscle tissue breaks down to the point that it starts poisoning the kidneys. Rhabdomyolysis is rare as a result of athletics; ultramarathoners sometimes get it, but ER doctors are much more accustomed to finding it in cases of crushed limbs or massive third-degree burns. Anderson didn't need dialysis, but he spent six days on an IV drip in intensive care, followed by two months of physical therapy for his back.

Glassman was already familiar with the Anderson case. In May 2005, the owner of the garage gym where the incident took place wrote about it in the CrossFit Journal, the company's online publication. In October, Glassman wrote an article himself, "CrossFit-Induced Rhabdo," in which he soberly explained the circumstances of the six CrossFit-related cases he knew about, outlined ways affiliates could lower the likelihood of injury, and announced he would add a rhabdomyolysis discussion to his weekend seminars and to the website.

But in the Times article--headlined "Getting Fit, Even If It Kills You"--Glassman used the kind of tough-guy talk he used to shout at CrossFitters during their WODs. "It can kill you...I've always been completely honest about that," he said. "If you find the notion of falling off the rings and breaking your neck so foreign to you, then we don't want you in our ranks." Punctuating his blunt attitude, he had led his October journal article with a cartoon of a new clown, Uncle Rhabdo, who stands exhausted before a dialysis machine, his kidneys splattered in a pool of blood. The Times mentioned that, too.

It was within this context that Glassman began ramping up his affiliation program. This was growth without a safety net: Anyone who passed his two-day seminar could apply to open a box, call it CrossFit, and then rush paying customers through squats and snatches or whatever crazy WOD they dreamed up. To Glassman, himself a passionate libertarian, this was the right thing to do: He wants his affiliates to be free to open up a box in a garage or a warehouse or wherever else, and train how they want, and charge what they want. They should have the opportunity he had. He detests supposed experts who say their certification or education makes them better than him or his people. At the end of the day, he believes, the free market will provide all the necessary quality control.

To the outside world, though, as Glassman's company has exploded from a cult fitness website to a gym concept primed to have more locations than Curves by the end of 2013, CrossFit can appear risky, unhinged: Here is a fitness routine that has sent people to the hospital, overseen by people who may have had no more than two days of instruction. (Although every real trainer I met had considerable experience and was genuinely excellent, I attended the seminar and passed the test on my fourth day reporting this story. I am, believe me, no fitness savant.) And it's all led by a man who, in a 2006 CrossFit.com comment, wrote, "We have a therapy for injuries at CrossFit called STFU." As in, Shut the f-k up. That's enough to make even the most devoted laissez faire-ists get a little, well, Uncle Pukie.

Glassman reigns over this rampantly growing horde like a tribal chieftain. He now owns 100 percent of CrossFit and answers to no board of directors. Cash tends to race through the company. Until recently, the Glassmans each drew a salary of $750,000 a year; the travel and entertainment budget is in the tens of millions of dollars, and Glassman also spends money on what he calls "brand statements," including a set of $15,000 single-speed Swiss bikes and a $350,000, 1,500-horsepower fully customized 2011 Camaro convertible. (Before our visit to El Borracho, I followed him to a meeting to see about another "brand statement": custom luggage for his senior team, emblazoned with Uncle Pukie.)

He also makes a concerted effort to avoid new streams of revenue. (See "CrossFit Doesn't Want Your Money.") CrossFit makes most of its money from training seminars: Every weekend, it certifies hundreds of people as trainers, at $1,000 a pop. It also collects registration fees for the CrossFit Games, royalties from Reebok for CrossFit apparel, and annual affiliate fees. The affiliate fees, which top out at $3,000 a year, are locked in at their original rates. Joshua Newman, who runs a big, successful box called CrossFit NYC, told me he pays just $500 a year.

To Glassman, this is a philosophical choice. Selling CrossFit-branded equipment, nutritional supplements, or anything else would encroach on his box owners' freedom. "They're their own tribes," he says. "I'm not going into spaces that aren't our own."

As a result, his company's revenue (set to double this year, to $100 million) is fueled almost completely by CrossFit's rampant proliferation. Meanwhile, a burgeoning ecosystem of other businesses has risen up to cater to these squatting, thrusting fiefdoms. There are multiple apparel companies; food and beverage companies (serious CrossFitters are often serious about the Paleo Diet); businesses that cater specifically to box owners, with iPad apps that track workouts and manage membership rolls; business consultants who show box owners how to increase their revenue. A Web design firm specializes in CrossFit box sites. There are even two print magazines, The Box and WOD Talk.

Glassman is proud of his role in all this, but the system puts him and CrossFit at a very real risk. As the world of CrossFit grows, as more businesses enter and profit, and his share of it becomes smaller, CrossFit's greatest success--gaining mainstream acceptance as exercise and a sport--could turn it generic, like baseball or skiing. "One of our greatest fears is becoming escalator," says Dale Saran, CrossFit's general counsel, referring to what was once a trademarked name brand of Otis Elevator. So, although Glassman keeps the CrossFit business model radically loose and open, he protects the brand name with an iron fist.

Glassman has always been a fighter, an us-versus-them kind of guy, and as his company has grown, so has his arsenal: CrossFit now has seven lawyers on staff and at any given time is engaging 12 to 20 outside legal firms to pursue trademark-infringement cases. CrossFit has a database of more than 5,000 possible infringements and is litigating a dozen lawsuits in the U.S. and several more internationally.

This traditional legal effort is paired with an aggressive social-media operation run by two men, Russ Greene and Russell Berger. At CrossFit headquarters in Santa Cruz, they are known as the Russes.The Russes assist the company's conventional corporate social-media efforts (running the Twitter handle, promoting company news on the CrossFit Facebook page) while also closely monitoring what they call "the wide world of Internet assholes": chronic complainers, trolls, Wikipedia page editors, cynical bloggers, even the American College of Sports Medicine, which the Russes and Glassman believe has it in for CrossFit. When the Russes feel any of these parties go over the line, their approach is simple: They obliterate them. (See "Social Media, CrossFit Style.")

After the Internet fitness community began talking about an Ohio State University study that described relatively high injury rates among CrossFitters, the Russes mobilized. They had Glassman's father, Jeffrey Glassman (now "chief scientist" at CrossFit), write a comprehensive rebuttal to the study for the CrossFit website. Berger called each and every research subject who had been reported as injured, to conclude that none actually were hurt, and then added an entire stammering Q&A with one of the paper's authors, kinesiology professor Steven Devor. Here's the kicker: The actual subject of the study was the great improvements in fitness the researchers found in CrossFit athletes. Aside from a handful of sentences, it was all positive.

It was in Glassman's own divorce case, though, that the CrossFit defense arsenal launched its full firepower. Lauren and Greg's marriage hit the rocks in 2009. Lauren became pregnant with twins and could no longer travel to the seminars.Greg, wrapped up with CrossFit, became more and more distant. Rumors of infidelity swirled. Soon the two were living in separate houses. In March 2010, Lauren officially filed for divorce. But the case didn't come to a head until July 2012, when Lauren filed a motion to sell her 50 percent stake in the company to Anthos Capital, a Menlo Park, California-based venture capital firm, for $20 million. Glassman, and in short order CrossFit, hit the ceiling.

In court, Greg moved to block the sale. Lauren made a strong case. The $17.5 million, five-year payment plan he was offering was too risky, she said. In documents filed in court, she showed how much the company spent on what seemed to her like frivolous expenses, including an $11,000 a month lease on a house in San Diego and a $763,000 four-seater plane. The Anthos deal was cash, and she still says she honestly believes Anthos had CrossFit's best interests in mind. At one point, according to court filings, Anthos proposed that affiliates get 1 percent equity to cast a deciding vote where Anthos and Glassman disagreed.

Outside of court, Glassman launched World War III against his wife and Anthos Capital. Glassman focused on one point: Anthos would kill CrossFit's spirit, transforming it into a franchise as regimented and conservative as McDonald's. Berger wrote a rallying cry that was originally posted on an internal CrossFit Facebook page and then went wider: "If Anthos gets ownership and forces Greg out, the affiliates can tell Anthos to go f-- off and all de-affiliate in mass....If every single one of you can get 5 people to care about this enough to write Anthos a 'f-- you' email, they will get the picture very quickly."Employees called affiliates around the clock to ask if they had questions and educate them about Anthos's true intentions as CrossFit saw them. When Anthos partner Bryan Kelly offered to field affiliate questions on Lauren's Facebook page, the Russes assaulted him with pointed questions.

"He's always had this tendency toward incredible kindness,"says a former affiliate," but he also has this rattlesnake intensity and cruelty."

Brian Mulvaney, an adviser to Glassman, did his part. He sent Kelly a text message: "Bryan, I understand that you are 'in it for the fight.' This is my notice to you that I will make it my highest purpose to see that you lose. Lose the deal, lose your job, lose your reputation. Ah, I forgot something. Lose your dignity."

That fall, the judge took a hard line with Greg, giving him a November deadline to come up with a cash counteroffer. Glassman came through with last-minute financing, in the form of a $16 million loan at what he characterized to me as "credit card rates." He has five years to pay it off.

As CrossFit gets bigger and bigger, Glassman is no longer the underdog. Well-known employees and boxes have been tossed out after clashing with Glassman or voicing disagreements with the CrossFit approach to fitness or nutrition--or, in particular, criticizing other CrossFitters close to Glassman. In 2009, Robb Wolf, one of the first affiliates, was exiled. "You have to kowtow and not let your star shine too brightly," Wolf says. "He's always had this tendency toward incredible kindness, but he also has this rattlesnake intensity and cruelty."

CrossFit headquarters' aggression can be enough to stunt interest in the WOD--almost. In April 2012, two avid CrossFitters, Jason and Shannon Janke, opened up the PR Cave, a sporting goods store in Yorba Linda, California, designed to cater to boxgoers all around Orange County. In November, they added a sign, "Where CrossFitters Shop," and had the slogan printed on mixer bottles for protein shakes. On January 16, they received a cease-and-desist from CrossFit, objecting to the use of CrossFitter. A month later, CrossFit filed suit.

"We settled, because I don't want to spent 50 to 75 grand getting sued," says Jason Janke. "I covered up the sign." Saran, CrossFit's general counsel, says it's all part of the fight against "the road to genericization." If people can sell "CrossFit equipment" the way they sell "baseball equipment," says Saran, then it becomes crossfit. Soon anyone will be able to coach crossfit or promote a crossfit tournament--effectively killing the value of being an official affiliate, or being CrossFit, for that matter.