Fifty-two hours and three minutes after Brett Maune left the starting line of the 2012 Barkley Marathons, he returned to that same spot and placed his hand on the finish line: a yellow State Park gate. Briars had shredded his legs. He was dirty and disheveled, his hydration pack hanging off one shoulder, an empty sport-spout Gatorade bottle clutched in his right hand, glasses still somehow resting on his nose. He’d slept for just one hour during the entire race. But he had done it: broken the 55-hour, 42-minute Barkley course record by more than three hours. He was the first person to finish the race twice, a win immortalized in the documentary The Barkley Marathons: The Race That Eats Its Young.

Some people call the Barkley the hardest race in the world. To finish, participants must complete five loops (some clockwise, some counter-) on an approximately 20-mile unmarked, off-trail course through the dense Tennessee mountains. The race director and course-maker, Gary Cantrell, had been smoking Camels and smiling under a shade tent while awaiting Maune’s arrival. Cantrell stood at the yellow gate to congratulate the new record-holder, who was one of just three people to finish that year.

But afterward, Maune—who doesn’t really compete in other organized events—simply went back to his job at HRL Laboratories, where he worked on quantum electronics. He’s a physicist by training (he did his PhD at Caltech, finishing a thesis titled “Fluidic and polymeric integration and functionalization of optical microresonators.”) Then he worked on Wall Street for a couple years, played pro poker briefly, and rejoined the physics world at HRL.

Many physicists and astronomers—and STEM professionals in general—compete in long, hard, miserable athletic endeavors like this one. Marathons, ultramarathons, triathlons, cycling centuries, Ironpeoples: You name it, they suffer through it. Or so it seemed to me as a sometime-participant in such races, whose Facebook timeline is filled with triumphant science-types crossing finish lines and climbing mountains. So I talked to Maune and 15 other running, biking, climbing, masochistic scientists who participated in an open-answer survey about endurance sports.

Nearly all of them agreed that scientists in general (and 10 out of 16 agreed that astro/physical scientists specifically) show up more often than they statistically “should” at endurance races. They were quick to point out things scientists would: They live in an echo chamber; correlation doesn’t mean causation; the variables aren’t isolated; and socioeconomics are at play. But they tended to agree that the personality types that lend themselves to a physical-science career also lend themselves to physical feats.

Maune sees a connection between academic degree and the degree of athletic difficulty someone is willing to endure. “It takes a lot of effort, a lot of focus, and there’s a lot of pain and suffering that goes on in a PhD,” he says. “If you make it through the process, for better or worse, it's a signal that you can have a long-term focus on a problem and see it through to the end.”

All the way back to that yellow park gate.

Just Keep Moving

Physicists and astronomers, although they get paid to dissect the grandness of the cosmos, actually spend most of their time in front of computers—coding, analyzing data, zooming in on a hyperspecific problem for long periods of time. The day-to-day of understanding the universe is tedious. That’s something science has in common with pounding trail for hours, and something that predisposes scientists for success in endurance sports—especially since you don’t have to be the world’s fastest runner to do well. You just have to be willing to put one foot in front of the other, or push that pedal around again, for a long time.

Suzie Sheehy, a physicist and distance runner at the University of Oxford, calls it resilience. “The ability to push myself out the door to train even when I don't always want to is the same as my willpower to re-do a calculation or simulation or even edit a paper for what feels like the thousandth time,” she says.

All that writing, computer-sitting, and universe-decoding is mentally exhausting. After a day of that, it makes sense that scientists would want to exhaust their bodies and give their brains a break. Running, biking, hiking, climbing, swimming, or parkouring for hours shushes the inner voices. “When you are doing something that physically difficult your brain can't really do anything except quiet down,” says Sarah Hörst, a planetary scientist, runner, and triathlete from Johns Hopkins University.

And, importantly, a quiet mind fills itself with ideas—solving problems in the background, drawing filamentary connections between disparate idea-clouds. “It is also on long runs or rides that I come up with some of my best ideas or solve problems I've been working on,” says Hörst.

Doing a physical thing repeatedly for many hours is, while not easy, at least straightforward—more straightforward than dark energy and digital signal processing, or becoming a better scientist. “The way to get better at running is to run more,” says Katie Keating, a physicist and runner from Rincon Research Corporation. “It's nice to have a simple brute-force kind of thing to work at.” These scientists are working even when they’re not.

The Limit Does Not Exist

In their work-work and in their play-work, scientists don’t know that they will succeed. And that’s kind of the point. “What I enjoy about astronomy is trying to solve a problem that might not have an answer,” says Adele Plunkett, an Ironperson from the European Southern Observatory. “What I enjoy about endurance sports is setting goals that might not be possible. These are probably rooted in the same intrinsic desire to test limits and break barriers.”

And then there’s that other intrinsic desire that scientists—at least in today’s funding environment, where successfully getting grants and faculty jobs is the exception rather than the norm—have: to battle it out. “You can't really have success in astronomy or endurance sports, in my opinion, if you do not like fast-paced, competitive things with little immediate tangible reward,” says Maura McLaughlin, a pulsar astronomer and runner from West Virginia University.

In a long athletic event, you could crash and burn, literally or figuratively, no matter how well you train. “In races and in [telescope] observing, you arrive to the big day and you have prepared everything the best you can, but there are a million unknowns that determine the outcome, and you have to know how to deal with those factors,” says Plunkett. She likes the glandular rush of all those variables, and the attempt to vanquish them. And then there’s the reward: Not just the finish line but, along the way, the secret waterfall or the moonscape above treeline, the first dribble of data—discovering something new, about a distant galaxy or the home planet.

Fear of Failure

Maune, who has again left physics for finance (this time, for a start-up hedge fund), agrees. “The [Barkley] race director says this all the time,” he says. “There has to be a risk of failure in order for anything to have value.” Cantrell—a retired accountant who spent his younger years ultrarunning around—actually changes the course every year that someone manages to finish, because that signals the course was possible. And so it needs to push people harder.

Maune recently failed at a challenge he set for himself: climbing the 58 of Colorado’s mountains that peak higher than 14,000 feet. He made three attempts between 2014 and 2015, and he just…couldn’t. On the third day of every try, he started wheezing. It was exercise-induced asthma: dangerous, potentially deadly, and definitely a slowdown (other humans have to stop and suck wind every 15 steps at 14,000 feet in the best conditions). He hopes to find a medical solution and get back to bagging peaks (Colorado local Andrew Hamilton set a new record—9 days, 21 hours and 51 minutes—in 2015). At the moment, though, Maune’s brand-new hedge-fund job keeps him so busy it’s hard to stay in shape.

This point—free time—is also key to physical scientists’ prevalence in endurance sports, which require months of training and often time off to travel to races. Yes, academics, you are very, very busy. But work hours are usually flexible, with built-in breaks. That socioeconomic self-selection is real: 47.3 percent of trail runners and 72.9 percent of Running USA members make more than $75,000 a year. The median household income of UltraRunning subscribers is $122,000; 55 percent of triathletes make more than $100,000. Almost 90 percent of triathletes have attended college or more, compared to 30 percent of the general population. Endurance sports are sports of privilege. And scientists—while not usually rich—do fit the general profile.

The barriers to entry and biases in ultra-sports, then, are some of the same that plague academia itself. And that is perhaps a harder problem to solve than either “What is dark energy?” or “How do I get better at running?”

The Barkley director does what he can, though: The application fee is just $1.60, compared to a marathon’s typical $100.