John Joseph swims, bikes and runs by day and stage dives by night.

John Joseph swims, bikes and runs by day and stage dives by night. The hard-living frontman of the ’80s seminal punk rock band The Cro-Mags, Joseph may seem like an unlikely triathlete. But beneath the tattooed surface, there’s a fierce competitor answering the universal appeal of a life-changing challenge: Ironman.

Underneath the spires of two traffic-choked bridges, the grimy chop of the East River laps at the rocks along the waterline of Brooklyn Bridge Park. You’d definitely need a dose of antibiotics if you swam across to Manhattan. And if this were the old New York—the New York that made John Joseph who he is today—you might have seen a body or two wash up on those rocks.

Clad in vegan Nikes and a black T-shirt with the words “Plant Strong” printed across the chest, Joseph makes his way to a patch of sun-drenched lawn for a few sprints. Orion Mims, his mentor and a nine-time Ironman competitor, is tethered to him by the four cords of the Power Sprinter, a device usually used to develop explosiveness but which Mims has redeployed to fine-tune Joseph’s running form. Joseph furiously pumps his tattooed arms and freshly shaven legs, blowing percussive breaths and meeting the machine’s intransigence with his own.

Exactly three months from that day, Joseph faced resistance of a much higher magnitude at the 2012 U.S. Ironman Championship, the first-ever Ironman held in New York City—and Joseph’s first competitive triathlon. A New Yorker best known as the frontman for the influential punk rock band The Cro-Mags, Joseph survived abuse, drugs, violence and the lawless 1970s and ’80s, when Times Square was best known for peep shows and the Lower East Side was a bombed-out haven for all order of criminals. A hardwired refusal to quit carried him through those trying times. But would his will close the experience gap and carry him to the finish line of an Ironman?

With just a few gray hairs in the copper mop on his head, Joseph looks at least a decade younger than his 49 years. Faded tattoos cover his arms, back and legs with figures and scenes from the Bhagavad Gita, the book of Vedic scripture that he says saved his life. Joseph has an Irish face, taut and hard-angled, with steely blue eyes that radiate intensity even when he cracks a joke. He speaks with bravado—he plays the hero in most of the stories he tells—but he is just as kindhearted. Colleen Armour, who works for Team Cindy—the Brain Aneurysm Foundation fundraising group that Joseph represented in the race—says Joseph’s true nature shines through his gruff visage. “Tattoos are just tattoos,” she says.

Born John Joseph McGowan in October 1962, he was one of three brothers who grew up under an abusive, alcoholic father, passing through orphanages and nightmarish foster homes before landing on the streets. For refusing to rat out the guy for whom he was selling angel dust, he did a stint in Spofford Juvenile Center in the Bronx and, later on, a group home in upstate New York. After a year in the Navy, a passion for punk rock led him to go AWOL for a decade and a half and head to the Lower East Side when drugs and prostitutes were on every corner. That atmosphere bred The Cro-Mags, a band whose raw riffs and streetwise lyrics propelled them to punk rock royalty in the mid-1980s with Joseph as the frontman. Joseph continues to play with the band today, summoning the energy of his 20-something self to sprint across the stage, shout into the mic, and punctuate songs with stage dives.

Paradoxes are at the core of Joseph’s biography. He stuck with a vegetarian diet even while in the throes of addiction. “I’d be smoking crack and still go get a wheat grass juice,” he says with a laugh. He squatted in abandoned buildings, pulled scams to get by, and pummeled his enemies. He also found spiritual fulfillment in the Hare Krishna movement and organized benefit concerts to feed the homeless. Joseph’s stories could fill a book, and they have: He authored his memoir, The Evolution of a Cro-Magnon, in 2007.

Through the ups and downs, sports were Joseph’s solace. He learned to box in youth correctional facilities. While touring with the seminal punk band Bad Brains, he would go for daily runs with the lead singer. At the end of long days working as a bike messenger, he would join other cyclists for the pack ride through Central Park. And after getting sober in 1989, he says exercise and diet have helped him stay clean ever since.

He’s evangelical about what his dedication to fitness and a vegan diet has helped him achieve in his life’s second act. In 2010, he authored a tongue-in-cheek guide to nutrition and exercise, and he’s in the midst of writing another book that outlines an in-depth meal and exercise plan based on the same principles. At its core is a diet he terms “organic, whole foods, plant-based.” The word “veganism” holds a lot of baggage he doesn’t want to carry, but the dietary tenets are similar: no meat, no animal products, no genetically modified foods, no processed garbage. It’s a diet he says is born of both empathy for animals and pragmatism.

Joseph first fell in love with triathlon while watching Ironman recaps on TV in the 1980s, marveling at the rivalry between Dave Scott and Mark Allen. He put an Ironman on his bucket list, but those dreams were deferred until last year, when Joseph found an Ironman event in his backyard and Orion Mims procured him the fifth spot on Team Cindy. (The team is named for Cindy Sherwin, a friend of Mims and a triathlete who died of a brain aneurysm during training five years ago at age 33.)

Mims towers over Joseph. “He’s the only person I let call me ‘son,’” Joseph says, laughing. Like Joseph, the 40-year-old Mims grew up in the city’s bad old days (he’s from Harlem). And like Joseph, he’s been an athlete all his life, boxing and shooting hoops before becoming a personal trainer. After bluffing his way into getting a client ready for his first triathlon, Mims found himself genuinely in love with competing in the sport. Now his chest bears a ring of nine tattooed flags—one for each of the countries in which he’s completed an Ironman.

The pair became fast friends last year after a mutual acquaintance at Sid’s Bike Shop on 19th Street introduced them. Joseph mentioned his Ironman aspirations, and Mims invited Joseph out for a 20-mile run to see if he was serious. “By the end,” Mims says, “he was looking like he needed an ambulance.”

Years of high-impact training and high-impact music have left Joseph with a litany of lingering injuries and imbalances: a pulled groin, a pulled hamstring, compressed discs in his neck, stiff hip flexors, and tight lats and pectorals. That’s why he meets twice a week with Aaron Drogoszewski, a trainer at Crunch Fitness on Lafayette Street. Drogoszewski grew up listening to the Cro-Mags in his native Syracuse and struck up a friendship with Joseph early last year. Now he puts Joseph through foam rolling, stability work, and all manner of corrective exercise as well as CrossFit-style conditioning workouts. “I beat the hell out of him, and he doesn’t bat a lash,” Drogoszewski says.

That was on top of a regimen geared toward the race ahead. At the peak of his training, Mims’ protocols had Joseph swimming 12,000 meters, running 50 miles and biking 400 miles in a week. They were miles ridden on the same brutal hills that he’d encounter on race day. They were meters swum in the chop off of Rockaway Beach or with Mims swimming too close for comfort in the pool. With the help of his nutritional gurus, Dr. Fred Bisci and vegan nutritionist/former pro triathlete Brendan Brazier, he honed his nutrition for the race.

But for all of Joseph’s affinity for triathlons, before this past August he’d never competed in one. Aside from a 4:20:41 finish at the Marine Corps Marathon in 2007, all of Joseph’s training had been an end unto itself. But Mims had no doubt in Joseph’s ability to finish an Ironman, and neither did Joseph—the fact that The Cro-Mags were booked to play a show in Philadelphia the night before the race speaks volumes about his confidence.

To Joseph, finishing an Ironman was to prove that a drug-free lifestyle and plant-based diet provide a path to surmounting something that appears impossible. Mims has a different take. “He thinks it’s very, very amazing that people do this,” says Mims. He thinks it’s going to exalt him. But I think the exaltation that he’s going to get just from being involved and understanding the reality of the event is going to bring him down to earth. It’s going to make him a better person. It’s going to make him feel like he can do anything. And it’s also redemption—the kid’s been through tons of self-destructive behavior, and this is the last nail in the coffin of self-destruction.”

Some obstacles cannot be overcome by sheer determination. One such obstacle reared its head two days before the U.S. Ironman Championship in New York: A sewer break spilled millions of gallons of sewage into the Hudson River—the same river incorporated into the Ironman course. If the water quality didn’t improve by Friday afternoon, the swim would be off. Without a true Ironman swim, Joseph says he would have walked away.

After an uncertain 24 hours, word arrived that the race would proceed as planned. Joseph’s Friday afternoon became a whirlwind of trips between the transition areas and his Manhattan apartment, while the show at the Electric Factory in Philadelphia was a whirlwind of stage dives. He was back at his apartment at 2:30 a.m. and he was on his way to the course by 4 a.m. Up until they slid into their wetsuits at the mass start, Mims kept watching Joseph’s sleepless eyes for traces of nervousness or anxiety. He found none.

On the second loop of the run course and on Mims’ way to an 11:55:30 finish, he spotted his charge—glossy with sweat, moving at a steady cadence. Mims yelled to him to come catch him. Joseph smiled, clapped his hands, and picked up his pace. “It just all fell into place for him,” Mims says. “It was natural for him to be in an environment where he was struggling.”

Thirteen hours, 33 minutes and two seconds after he started, John Joseph McGowan finished his first Ironman.

Forget about congratulating Joseph on finishing. He says he could have done better: He held back on the swim to stay within his pace, he needed extra time in transition to ice an aggravated injury in his foot, and the effects of sleep debt hit him around the 20-mile mark on the run. But he takes heart in having completed what Mims calls the hardest and hilliest of the 10 courses he’s experienced without swallowing any of the gastrointestinal-system-wrecking water from the Hudson. (“It tasted like hot sauce,” Mims says.) Watching the camaraderie between athletes on the course made the race a beautiful, inspirational experience. “I crossed the finish line and I was like, ‘When’s the next Ironman? Let’s go,’” Joseph says.

A few days after the race, Mims and Joseph booked tattoo appointments—Mims for an American flag to add to the ring on his chest, Joseph for a design commemorating his first Ironman finish.

Qualifying for Kona by 2014 is the next goal: Mims is two Ironmans away from an automatic entry through WTC’s legacy program, while Joseph has to winnow down his time to qualify. To reach Kona, Joseph knows he’ll have to work even harder, stick to the plan even more diligently, and endure even greater suffering. To hear him tell it, he wouldn’t have it any other way. “There’s no glory in surrender, man. You know what I’m sayin’?”

To learn more about celebrities who compete in triathlon, check out our “I’m A Triathlete” archives.