Sean Van Horn has been putting in a lot of work at Buttermilk.

He’s just logged three hours skinning 8,500 feet on the Tiehack side, up and down. It’s not because he has any particular affinity for the little hill; it’s because he’s training to break the North American vertical record for skiing. In 24 hours, Van Horn will attempt to skin 63,000 feet — that’s 40 laps — up Tiehack. So, he’s getting pretty comfy in the skin track.

Van Horn, 32, doesn’t mind retracing his steps in the snow. The Carbondale local is an endurance athlete with ultrarunning, cycling and ski mountaineering accolades. He recently placed third in Aspen’s Power of Four and he prides himself on a discipline that borders on obsession.

Many endurance athletes, including ski mountaineers like Van Horn, are fueled by a similar desire to go to extremes and push their limits. It’s a niche in the sports world where training metrics are logged in terms of hours spent on foot, thousands of vertical feet climbed. Athletes routinely brag about their capacity for suffering.

This ultra-masculine reverence for the ability to withstand pain and discipline in training has allowed eating disorders to fester.

“The world of endurance sports is very different from the rest of the world,” Van Horn said. “There’s a lot of pressure to look a certain way.”

According to the National Eating Disorders Association, one-third of people who have a clinically diagnosed eating disorder are men.

For Van Horn, it was a mix of anorexia and exercise bulimia. He monitored what he ate compulsively, severely restricting his calories. He would set out on long runs — upwards of 20 miles, day after day, grinding out the painful distance. Eventually, he’d become so hungry that when he did eat, he’d binge, locking himself in his room for days at a time.

“I was on the verge of starvation and completely out of control,” Van Horn said.

Athletes, particularly those that participate in sports that emphasize speed and a svelte physique, like the spandex-intensive SkiMo and ultrarunning where Van Horn competes, are especially susceptible to eating disorders.

In a study by the National Eating Disorders Association, male athletes were 38 percent more likely than the average male to develop bulimia and 10 percent more likely to be anorexic. It’s estimated that eating disorders in men are underreported. These numbers likely don’t represent the full reality that men in endurance sports confront: the pressure to have an idealized physical body and a steely-hard mentality.

Sports that celebrate the ability to shave a couple of grams off a race ski or bicycle also laud weight loss as part of the program. Size and speed are intertwined, to a point.

That message gets internalized. Van Horn noticed the veins popping out of his competitor’s lean limbs and worried that he didn’t look the part.

Social media can intensify the problem. Bright images might broadcast an athlete’s sculpted muscles or recent epic training mission, but they don’t show private moments of pain and dissatisfaction with one’s body.

There’s a deep-seated stigma against expressing insecurity in endurance sports. Mental anguish about appearance and performance can get buried under a tough-guy facade. Eating disorders are historically underdiagnosed in men, who may struggle to ask for help in a culture that praises independence. Eating disorders are often seen as a female problem, and men might be hesitant to identify with that.

“You’re supposed to be tough, you’re supposed to be hard,” said Van Horn. “You’re supposed to put yourself through hell and suck it up, no complaints.”

Van Horn knew he was in trouble. The cycles of deprivation, over-training and then bingeing were wearing on him. The loss of control scared him. He felt isolated and ashamed.

He decided to get help. He started seeing a therapist. He started training more seriously for running, channeling some compulsive tendencies into a more regimented schedule that mandated days off and a well-rounded diet.

“It’s amazing,” said Van Horn. “You can take something that’s really ugly and it can be shifted to something that’s really positive.”

For Van Horn, recovery has been a process. He admits that he’ll probably never be “cured.” But fully committing himself to healing and training helped.

“I started viewing my body and exercise as a tool. I started wanting to get the most out of it. I wanted to be strong again,” said Van Horn.

Now, he’s trying to share his story so that others can see eating disorders for what they are — a mental illness, not a character defect.

He hopes that his record-breaking attempt will be a platform for others to see that they’re not alone if they’re battling an eating disorder or other mental illness. He hopes his honesty will strip away some of the stigma and start conversations. It’s also a fundraiser for Aspen Strong, an organization that connects valley residents to mental health resources. Van Horn has a GoFundMe page set up for donations.

“Everyone has their struggles and their battles. When you hear others have some kind of demon, it lets you know that you’re not alone, it allows you to take your own journey and get help,” Van Horn said.

Casey Weaver, one of Van Horn’s training partners, said that Van Horn “is one of the most passionate people I know.”

“When he sets a goal, he pours himself into it fully. It’s been cool seeing him pour himself into this goal in particular,” Weaver said.

On Sunday, Van Horn will channel those struggles to push himself harder than he ever has. Breaking the North American record will be hard. It was set by SkiMo legend Mike Foote one year ago in Whitefish, Mont., at an elevation almost 4,000 feet lower than Buttermilk. The record is the vertical equivalent of skiing up Everest from sea level to summit just over two times.

Van Horn knows it will be an uphill battle in every sense of the phrase.

“If I can beat the record, that’s great,” said Van Horn. “But that’s only one part of it. I’m more interested in pushing myself and changing some of the dialogue around mental illness.”

Van Horn loves surrendering to the motion of ski-mountaineering. He loves the churn of skinning up and skiing down over and over again.

Friends and family will be at the base to support him with snacks and high-fives. And for Van Horn, that’s what it’s all about. Knowing that even at your lowest point, you can get help on your way back to the summit.

Zoë Rom is a reporter at Aspen Public Radio and has contributed articles covering endurance sports to Outside, Trail Runner and the REI Co-op Journal.