• Dean Karnazes holds the world record for the longest distance a human has ever run nonstop.
• His advice for going farther than you think you can: redefine success before the race begins.
• When the pain hits, Karnazes says there’s one rule: keep moving — even if you have to walk.

For decades, scientists have tried to understand what separates people capable of extraordinary endurance from everyone else. Is it genetics? VO₂ max? Pain tolerance? Mental toughness?

Dean Karnazes has spent more than 30 years giving them a remarkable case study.

He's run 50 marathons in 50 states in 50 consecutive days, crossed Death Valley in the middle of summer, and in 2005 set the record for the longest nonstop run — covering 350 miles in 80 hours and 44 minutes.

Even that wasn't enough.

"I actually made it 350 miles, which was somewhat of a letdown because I thought maybe I could run 500 miles," Karnazes told me. "That was kind of the ultimate goal." His world record still stands today, 21 years later.

After decades of ultrarunning, Karnazes says he's learned that doing hard things comes down to a handful of simple habits that anyone can practice.

Don't make winning the goal

Karnazes has finished on the podium plenty of times, but he says that's never been what pulled him to the starting line.

"I do it for the adventure," he said. "Both the inner and the outer adventure. I've never really said I want to win a race. I just thought, be the best Dean that Dean can be on race day."

He says approaching races that way has changed how he defines success. The podium, if it comes, is just the cherry on top.

That mindset, he says, has kept him motivated through hundreds of marathons and ultramarathons, long after chasing trophies stopped being interesting.

Redefine what success looks like

When Karnazes gives advice to new ultrarunners, he doesn't start with mileage or pace.

"Just set your goal on finishing," he said. "Don't say I want to do it in sub five hours or sub six hours. Just say, 'For me, success is reaching the finish line before the cutoff.'"

Karnazes says that approach has a way of changing how you see your own limits.

"You'll prove to yourself that you're better than you think you are. And you can go further than you think you could."

Keep moving, even if you have to slow down

The advice sounds simple, but following it is another story.

At some point during his 350-mile run, Karnazes stopped trusting what he was seeing.

After nearly three days without sleep, he said he started hallucinating. He felt as though he had left his own body and was watching himself from above.

"When you're in these altered states, it's as though you don't have conscious control of your mind," he said. "You're fighting your mind to stay present, but your mind gets away from you."

Despite that, he kept running.

I asked Karnazes for his advice to aspiring ultrarunners who worry they'll hit a point where the pain becomes too much.

"You walk if you have to," he said. "You slow down, you push through the pain, and you come out the other side, and you're rejuvenated."

In 2022, Aleksandr Sorokin ran 198.6 miles in 24 hours, nearly eight marathons in a single day — a new world record.

How does anyone run that far, that fast, for that long? It turns out six factors have to be perfectly dialed in to break a distance-running world record: VO₂ max, form, footwear, fuel, environment, and the mind.

To understand each one, Business Insider met with athletes and scientists who are pushing the limits of human endurance. We tracked down Kristian Blummenfelt, the Olympic and Ironman champion whose team recorded a VO₂ max of 101.1.

We visited Stanford's biomechanics lab, where researchers built a digital model of Dean Karnazes, who holds the record for the longest distance ever run nonstop.

We tried on supershoes and looked at how much energy their foam gives back. We explored what an ultrarunner's gut can handle, and what a hot room does to the body's core temperature.

Then there's the mind. We went to Queens, New York, for the Sri Chinmoy 3100, a race where runners circle the same block for 52 days, and asked the front-runner what keeps him going.

Watch the full video to find out what it takes.

Running with Rachel Entrekin must be pretty wild—she encourages competitors and stops mid-race to pet dogs. But her personality is even bigger off the course. Tough and empathetic, her running success has come after 13 years of hard work and a battle to transform an addictive, perfectionist past into a healthier relationship with food, rest, and herself. And even as success came and ultramarathons were won, she watched opportunities go to her male competitors. Gloria Liu honors the incredible achievement of “smashing records while battling impostor syndrome and the fragility of your own self-worth in a world enamored with men, and their accomplishments.”

The key word, however, is average. As any female runner who’s ever passed a dude working himself into a froth to stay ahead of her on the trail knows, women beat men on an individual basis daily. And as athletes like Entrekin and Dauwalter have shown, they do so, occasionally and spectacularly, even at the elite level. We have an understandable reflex to point to categorical advantages that might explain why women can do this, Malcolm says: “It’s inherently feel good, the David and Goliath aspect of a woman winning outright.”

But in searching for the advantages we hope all women have, we may be missing a simpler truth: Most men are faster than most women, but some women still beat most men. The point is not that we have any advantage. The point is that they have almost every advantage—and we still win.

I have a vague eighth-grade memory of trying to run 400 meters in under a minute. The operative word here, of course, is “trying.” But what eluded me then is nothing for the middle- and high-school kids of today, who are shattering track records on a weekly basis. Some of that is sneaker technology, some of it is training, some of it seems to be an intense competitive drive fueled by social media. Whatever it is, Brendan I. Koerner has seen it in his own kids—and now he throws himself into the world of scholastic speedsters for his latest Wired feature.

The results make track old-timers shake their heads with wonder. In April, for example, an eighth-grade boy shattered the national middle-school record for the mile (he ran it sub-4:18). Just two weeks later, an eighth-grade girl ran the 400 meters faster than any US high schooler had at that point in the year (she clocked 51.58).

It’s not just the superstars who are getting faster. The runners in the pack behind them are picking up the pace, too, and they’re transforming what’s considered a decent time. “I think I have 10 middle-school girls who run between a 4:56 and a 5:16 mile,” says Peterson. “Ten years ago, you’d be like, ‘That’s insane.’ Now it’s nothing.” When these kids head to high school, they have the strength and experience to flourish right away. But given the sky-high expectations they face, the intensity can come at a cost.