The wait is over. I'm backstage, listening to the crowd cheer an invisible fight, and I'm next. My hands are taped and strapped into tiny fingerless gloves, just enough protection so that I won't shatter my knuckles on somebody's head. I'm warmed up and ready, but my lower left rib is twinging slightly. I don't know it yet – I won't find out till after my fight – but I actually broke a rib during one of my training sessions. I'm going to be fighting another man in a cage, and somehow all of this seems perfectly ordinary,

I hear my name over the loudspeakers, and an ugly rush of adrenaline floods my system. My opponent is announced, "Jason Kenneman, at 205 pounds...," but I don't hear the rest. Two hundred and five? This can't be my fight. I've been cutting weight for almost two weeks to make 185. The promoter said 185. But now, entering the hall, I see there's no mistake. I have been starving and dehydrating myself to make weight, but instead of gaining an advantage I have dug myself into a deep 20-pound hole.

The promoter is in front of me as I'm about to go into the cage, trying to make excuses for the weight mix-up, but I just brush past. I'll fight anybody right now. This is what we do.

I'm not a tough guy, but like everybody, I've always wanted to be one. In high school I was a nerd who idolized Bruce Lee. I fell in love with the physical when I started boxing at Harvard, and a few years after graduation I went to Thailand to study muay Thai kickboxing.

After Thailand I tried other things – I worked as a sailor and did construction and was a wilderness firefighter – but somewhere in the back of my mind I was still curious about fighting. I wanted to feel that extreme passion again, the excitement of desperate struggle. In my secret heart I knew I wasn't a real fighter. I still wondered if I could take a big punch. I was still afraid; so I wasn't quite through with fighting yet.

I always thought the scariest professional fighters in the world were the Ultimate Fighters, who compete in what is known as MMA, or mixed martial arts. You've seen them on pay-per-view: those indestructible, muscle-bound monsters with shaved heads, tattoos, and eyes popping with fury. Could I find that rage, and what would happen if I did?There are few rules in Ultimate Fighting. Once a fighter gets knocked down the fight just continues on the ground, and that's what gives MMA its extra kick, the terror and claustrophobia and desperation of being pinned underneath a man trying to hurt you.

I wanted to learn how to fight in the MMA style, so I asked around and learned about Pat Miletich. A former MMA champion, he now runs Champions Fitness Center in Bettendorf, Iowa, and his stable of fighters is one of the strongest MMA teams in the country. I got Pat's number and called him up; he said, "Sure, c'mon down and train with us and we'll get you a fight."

Wednesday nights are infamous at Pat Miletich's gym. Wednesdays mean full-contact kickboxing with headgear and shin guards and no screwing around – it's hard sparring, and you'd better be ready. There are knockouts on Wednesday nights, not to mention bloody noses and cut lips. Somebody is always dashing to the paper towels, blood spattering the mats in heavy drops. I saw experienced pro fighters go down like sacks of potatoes from head kicks: boom, lights out. I broke my nose at least once and fractured a rib while training at Pat's, both on Wednesday nights.

On my first Wednesday night I could feel everyone's eyes on me, coolly assessing the new kid in school. I sparred with a few people, and felt as if I was doing okay for a beginner; my time in Thailand had given me a foundation in "stand-up" fighting. But toward the end of the night Pat grabbed me and said, "Hey, Sam, c'mere, spar the heavyweight champion of the world." Sure. No problem.

I found myself staring up at Tim Sylvia, the former Ultimate Fighting Heavyweight Champ. He's about 6' 8" and 250 pounds, and much, much quicker than he looks. Every time I threw a rear-leg kick he trapped it and dumped me. He was so tall his head was miles away from my jab, and hitting his body was like hitting a tree. His hands were like sledgehammers; if he had landed a hard body shot I would have died.

I found myself sparring with him again and again over those first few weeks. I would get hit hard, stagger, and then get blasted again, desperate for the round to end, nose running blood. People would laugh, yelling, "Clean up your mess!" and Tim would crow, "Sam can't hold his mud!"

A few days after my first Wednesday night session I was having coffee at the local Denny's with Pat and some other guys when he looked at me and said, "You broke your nose. You know that, don't you? It's crooked."

"It is?"

"Yeah," he said, and everyone started to laugh.

Ultimate Fighting was invented to answer the question that had persisted since the karate boom of the '60s: Which fighting style is most effective? Is my Tiger Crane kung fu deadlier than your karate? Who wins when a good boxer meets a good kickboxer? Can a wrestler beat a kung fu expert? The first Ultimate Fighting Championship was held in 1993. It was conducted in an octagonal cage, with no rules and no holds barred. Since then it has evolved into something more refined, with a few basic ground rules (no head-butts or eye-gouging) and a referee. The combatants still fight in a cage, but mainly as a safety issue, because fighters grappling on the ground can roll right out of a ring. The UFC has inspired a passionate grassroots fan base that doesn't just watch, but also trains and fights. I was shocked to discover that there are hundreds of amateur cage-fighting events a year in the U.S. "Fight Club" is alive and well.

The first three UFC events were dominated by a slender Brazilian named Royce Gracie, who won by taking the fight to the ground and using his family's Brazilian jujitsu to control his opponents.

The Gracie victories stood the American martial arts world on its head. All these guys who had been doing karate for 20 years and who had their own schools suddenly realized that they had an Achilles heel: the ground game. If the fight went to the ground (and it nearly always does), their crisp kicks and punches were useless.

So everyone scrambled to learn Brazilian jujitsu, and what has emerged is a new style, mixed martial arts. The first American to effectively blend boxing, kickboxing, and muay Thai with free-style wrestling and jujitsu was Pat Miletich, and he changed the sport forever.

Pat "the Croatian Sensation" Miletich was born and bred in Iowa, the wrestling capital of the U.S. After college he boxed and kickboxed professionally for five years, then got interested in the early UFC world and sought out the best trainers in the country. "I wanted to win a championship to give my mom something to smile about," he told me.

Before Pat, UFC fighters would stick to their one discipline and use it for everything, or maybe they were able to do two styles well. But Pat had it all: He could box and wrestle, he had submissions, he had takedowns and good kicks, and he understood how to put them all together – especially the transitions between styles, which is perhaps the most important part of professional MMA. He could find the weak spot in any fighter, then match his style to his opponent's weakness with brutal efficiency. Pat is also tougher than anyone I've ever met: He has never been put down by a punch to the head in his entire career. At 35, he is semiretired as a fighter, but is now widely regarded as the best MMA trainer in the world.

Pat is also friendly, charismatic, and fun to be with. He has two false front teeth he likes to pull out so he can give you a big gap-toothed, hayseed "I'm a country idiot" grin. His secret ambition is to climb Mount Everest, because the first book he ever read was an account of Edmund Hillary's first ascent.

My dirty little rental apartment is across the alley from the gym, and every morning I wake up in pain. I coined the term car wreck-itis: that feeling of having been in a car accident the night before, where everything is strained and black-and-blue, and little muscles you didn't know existed are ripped to shreds. Getting out of bed takes half an hour. At the gym someone asks me how I'm doing and I say, "Oh, not bad, a little car wreck-itis this morning..."

Tuesdays and Thursdays are for grappling, called "rolling," two classes during the day and an open session at night. There is nothing worse than being on the ground with a good ground-fighter; it's like being in the water with a shark. You're struggling, desperate to escape, and suddenly you can't breathe, you're smothered, you can't see, and your arms are getting twisted off, so you "tap," and it's all over. Tapping is how you let your opponent know you concede the fight, that he's caught you in a "submission." A submission is when you get your opponent in an arm-bar, or a knee-bar, or a choke; essentially threatening him with a broken limb or being choked unconscious. So he taps out, and you win.

As a novice, I get yanked, cranked, and thrashed by everyone who can get his hands on me. My biceps hurt so bad I cornered Pat about it, and he looked thoughtful and massaged my arm a bit and asked, "Are you sure it isn't a case of wuss-itis?" I laughed. What else could I do? Pat is so tough, I think it's a little hard for him to understand the difficulties the rest of us might have.

As the home of team Miletich, Champions Fitness Center has a roster that reads like a who's who of mixed martial arts. Jens "Little Evil" Pulver is a five-time world champion, and at 155 pounds hits harder than guys twice his size. Matt Hughes, Jason Black, and "Ruthless" Robbie Lawler, a crowd favorite for his explosiveness, are three of the top 10 welterweights in the world. Tony Fryklund is the badly underrated 185-pounder (he should rank in the top 10). Jeremy Horn is a legend at 28, with a record of 112-6, and Tim Sylvia is the dominant heavyweight in America.

Besides these guys, there are a dozen or so pro fighters who are up-and-coming, men like Spencer Fisher, Rory Markham, and Sam Hoger. They all have other jobs. Sam, a 22-year-old heavyweight, works as an environmental lobbyist and is getting his MBA. He's also dead set on Harvard Law.

They are all different, but they each love to fight. I end up talking a lot with Tony "the Freak" Fryklund, partly because we discovered that we went to the same junior high – my mom was even one of his teachers.

At 33, Tony is one of the older guys, and he's been down a long road to get here. He was a coast guard rescue diver and EMT, a safety officer on the Big Dig in Boston, and a movie stuntman before his constant training in martial arts eventually took over his life. Being on Team Miletich is an integral part of his identity, a tremendous source of pride. "A lot of these fighters are from broken homes," said Tim Sylvia, who lives with Tony in the apartment above the gym. "Team Miletich is their family."

Tony will play the philosopher if given the chance. "The martial arts are about respect and discipline and knowledge," he says. "Fighting is different. Fighting is about ego. When we're fighting, it's 'I'm going to fuck you up. Prove me wrong. Prove to me that you're tougher than me.'" He doesn't mean ego in the negative sense – the "Oh, look at me" ego. He means self-knowledge and dedication, testing and pushing oneself as far as possible. There is a famous image of Tony where he is covered in blood, raging. He took an elbow to the forehead, and it bled so badly the ref stopped the fight. Tony went temporarily insane from the emotional dam-burst. He blacked out, and doesn't remember rampaging around the ring until Pat and Matt Hughes dragged him down into his corner and covered his face with a towel, like an animal. "I could fight fine; if I had trouble seeing, that was my problem, you know? It was cosmetic, a scratch on the hood. You don't throw away the car just because a windshield wiper is busted." Tony had also been running a fever of 103. "Now I can understand a temporary insanity plea," he says. Fighting, for him, is a way to know himself.

Whoever wins an MMA cage fight, the unspoken significance of victory is: I could have killed you. If we were alone, in some back alley or on some desert island, and we fought without all these people and this cage and its rules, then I would have killed you. That's the appeal of Fight Club: It's the siren song of violence, the ancient urge to dominate, and in my heart I want to understand that emotion.

One day Tony asks me rhetorically, "How can you know anything about yourself if you've never been in a fistfight?" I didn't want to tell him that even though I'd fought in the ring, I'd never been in a real street fight.

I've got to learn to move my head, to make it less of a target. I can still feel the stinging impact that jars my world, the rushing in my ears as if I'm underwater, and then the gushing from my nostrils, the droplets spattering my gloves and shirt. I rush outside to the paper towels, and the gym rats, lifting weights, stare with pity. I joke with Pat that I'm going to bleed all over my opponents to scare them, but then I mop up the blood, put my headgear back on, and try to get back in there, until I get popped again and repeat the whole process. Sam can't hold his mud.

I don't talk to Jens Pulver much, but he is one of the fighters I most admire. One day I'm on the sidelines holding paper towels to my nose and he leans over and says, "You got to find a way to survive in here. We all did."

So the following Wednesday night I stay away from the heavyweights and decide instead to spar with the "little" guys. Because I'm tall I always stood with the heavyweights, but they outweigh me by 20 or 40 pounds, and punch quality is changed drastically by even a slight difference in weight.

I tower over the lighter guys, but when I spar with them I survive and my nose doesn't bleed. I start keeping people on the end of my jab, where Pat wants me to, too far away to hit me back.

After eight three-minute rounds we all jump rope together, and for the first time I feel a little bit as if I belong here, as if I could stay and train forever. It's a warm wash of contentment, of virtuous exhaustion, and of true camaraderie.

After weeks of nonstop training, including weight-lifting, circuit-training, roadwork, and sprints, Pat got me the fight he promised, in Ohio, not far from Cincinnati. I spoke to Monte Cox, the promoter, and everything was set to go. I would be fighting at 185 pounds, the perfect weight to give me a reach advantage. I am 6' 3", and most 185 pound guys are well under six feet.

Pat started working with me personally, and my stand-up fighting began to feel really strong. I still got car wreck-itis, but at least I was staying away from the heavyweights. Then, on a Wednesday night about two weeks before the fight, I was sparring with some kid (never seen before or since). We were just boxing because he couldn't kick, and I had him bleeding into his mouth guard when he landed a hard body shot and knocked the wind out of me. We stopped for a second so I could catch my breath. I signaled I was okay and we started sparring again, but a secret part of me was saying, "Oh, shit."

I have a recurring injury to my costal cartilage, the stuff in between my ribs; I keep separating and straining it. I knew I'd done it again. It first happened working construction at the South Pole Station, in Antarctica, when a wall fell on me. When you injure your ribs you're screwed for four to six weeks, maybe longer. Almost every motion involves flexing the rib cage in some way, and it hurts just to breathe. (I didn't get it X-rayed until months later, so I didn't realize it was actually broken.)

I took a few days off to rest and think. Fighting hurt was part of the deal; it's what the pros did. I would just have to stay off the ground at all costs.

I still had to make weight, and I was stuck at 193. Because of the rib injury I stopped training, as even shadowboxing seemed to make it worse. I went to the sauna with Tony, who was cutting weight for the biggest fight of his career, against the number one guy in the world, Matt Lindland. Tony dyed his hair blond and started calling everybody he sparred with "Lindland" while verbally abusing them. He was moving into the final stages of fight psychosis, preparing himself for the coming ordeal. With the approach of scheduled violence one's normal contract with society becomes slightly tenuous.

I started eating one meal a day and bought a "sauna suit," one of those garbage bag outfits you wear under your clothes to make you sweat, like a high school wrestler making weight. I worked out in my sauna suit every day, even the day of the fight. I was dehydrated, and was eating almost nothing, but at the weigh-in, two hours before the fight, I came in at 183.

Brandon Addamson, a 23-year-old with two kids who was turning pro, would be my corner at the Ohio fight. It was a struggle for Brandon to keep training, even with his wife working, but he loved it, and it defined him. I once asked him why he fights, a question I asked a lot of guys there. It's something that most fighters don't really talk about.

"It's about clout," Brandon said, and he kept hold of that word, repeating it as if there were some deeper significance that I was missing. I think he meant the respect of others and self-respect. I think that's why most of these fighters fight. It's not for the money, because only a few of the very top pros make enough to live on. They fight for themselves, for the visceral thrill of the action, and for clout. I was fighting more out of curiosity. And my final test was going to be inside a cage in Ohio with a total stranger.

Tori's Station in Fairfield, Ohio, is a typical small-town venue, a nondescript hall usually rented out for concerts and private parties. I think the last thing there was a wedding, since I found bowls of potpourri in the bathroom.

Walking through the hollering crowd in my borrowed shorts, I got my first look at my opponent. He was shorter than me and not bulging with muscles, which was something. I was in better shape than he was. But he still had that extra 20 pounds on me.

Once I was in the cage the ref asked me if I had a cup on, and without any more fanfare it was time to go. I came out and offered my opponent an outstretched glove. He blinked, we touched gloves, and it was on.

The first exchange was clear: We traded hard jabs, and I think I hit him a little harder than he hit me. I ate a lot of shots to the head, but they didn't hurt at all. It was exhilarating.

I hit him again, then we went into a clinch a couple of times and I landed a few knees. He landed a few too, but I barely felt them. When my knees went into his soft stomach, I thought, Go down, go down!

He was tough. I rocked him with a hook and blasted a kick into his side and he actually went down, but when I stepped forward to try to finish, he was back up. I realized two things then: He was tougher than I wanted him to be, and I was running out of gas already, in the first round. In just three minutes.

As the round ended I was bleeding from the nose. I walked over to the corner; Brandon was talking to me, but it didn't really matter. I was breathing too hard – I was already "gassed" (meaning no gasoline in the tank). He offered me some water, but I couldn't take it. He was telling me to punch my way in.

The fight started back up, and I went after my opponent again. He caught me with a few good shots and staggered me. I moved backward and managed to get him in a clinch, but I lost my mouth guard. He was rocking me, but I didn't feel as if I was in danger. I was still trying to get through to him, and I could hear my own grunts as I threw knees in the clinch. But they sounded as though they were coming from someone else.

Then the ref stopped the fight to look at me, the EMT came out, and I could hear them talking right in front of me as if I weren't there. I felt nothing. If they let the fight go on I'd keep fighting. If they stopped it I'd stop. After a brief discussion, they waved it over.

I walked into the bathroom and looked at myself and laughed; it was some serious horror-movie shit, blood everywhere. Brandon was wide-eyed and pale, as if he wanted to beat somebody up himself.

While I was getting dressed one of the promoters came by and offered me a pro fight. It turned out I was something of a crowd favorite, basically for bleeding all over the place and standing in there and taking my licks. People kept telling me it was the fight of the night. As my eye started to swell shut I thought, Yeah, well, great. I still lost. I had brought my Team Miletich T-shirt to wear after the fight (Brandon and Ryan, my other corner, had theirs on), but instead I put on a regular T-shirt. I didn't want to associate the team with losing. I was too embarrassed.

I drank beer out of a plastic bottle, balanced ice on my eye, and chatted with my opponent, Jason, while we watched the rest of the fights. He was a nice guy. He had been fighting muay Thai and kickboxing for four years, with a record of 9-1, and this had been his first MMA fight, too. He hadn't wanted to go to the ground at all, and neither had I, because of my rib. My one muay Thai fight was four years ago. I had trained only about two months, and I gave up 20 pounds and still fought a decent fight. That's what training with Pat's guys can do for you; it can make up for a lot. But I had fought stupidly and not dodged or slipped a single punch as I had been trained to. Instead, I'd come straight at him. Those little gloves aren't like boxing gloves; they cut you quickly and easily, and though there was no pain at all, I was bleeding enough for the ref to get nervous and call it.

Watching the crowd react to the later matches I realized that these weren't just fights; they were celebrations of courage. The crowd lives vicariously through the fighters and even loves the losers as "honorable warriors." The fighters revel in both the ordeal and the crowd's attention. Brandon had told me to pause on my way out, to "soak up" the crowd's attention, but I didn't care about the crowd.

What surprised me was how much fun it had been. Being in there, bouncing around, pasting him, getting blasted, whatever – I had enjoyed it. I didn't feel any pain at all during the fight; adrenaline takes care of that. Sure, you know things are bad – like, "Oops, that shot was bad" – but it doesn't hurt.

The crappy part would be coming back to Pat's with a loss and looking as if I'd gotten my ass kicked. I looked terrible, my face was all swollen up like a Halloween monster mask; driving back we'd stop at gas stations and people would fastidiously avoid looking at me, as if I were a burn victim.

No matter what people said about how it was a good fight and how I gave nearly as good as I got, I dreaded walking into the gym. I had let Pat down, and he was going to take one look at my face and know I'd fought a stupid fight.

On the way back to Iowa, I thought about how I could make excuses – the extra 20 pounds, for example. But that stuff just happens, especially at the amateur level in MMA. Pat and Tony had both given up 20 pounds or more in fights, and they still won. And the injured rib hadn't really bugged me at all, except mentally.

Instead, I avoided the gym altogether. I just packed up my stuff and got out of town as quickly as possible. I was embarrassed. I had some good new friends there, but I didn't want to face them. I had let Pat down.

Driving home to Massachusetts, I got a call from Tony Fryklund. He'd lost a decision to Lindland in Hawaii that same night (but had gone the distance and fought well) and we commiserated.

"It just sucks to lose," I said.

"Yeah," he said, "but there's a lot more to it, to doing what we do, than just the fight. If the fight was all there was to it then it wouldn't be worth it."

I thought about what Brandon and I had talked about, the meaning of clout. It's not really about the admiration or respect of others; it's about self-respect. We all have an innate hatred of fear, and some of us climb into the cage to prove to ourselves that we aren't afraid. I've heard Pat compare his boys to soldiers – how they don't fight for an ideal, they fight for one another – and it's true. I made some lifelong friends, guys I would invite to my wedding – although I might have to keep an eye on some of them.

After I got home Pat sent me an e-mail. He said, "I just wanted to let you know you can fly our colors anytime you want. You showed a lot of heart and 90 percent of the fighters who come here do not last as long as you did." He closed by saying, "You are without a doubt a fighter."

Pat Miletich said that about me.