The Measure of a Mountain: Jim Walmsley’s Evolving Limits

Just after 10 a.m. on August 28, more than a thousand runners surged from Orsières, Switzerland, toward Chamonix, France, to compete in the prestigious Orsières-Champex-Chamonix (OCC) ultramarathon. 

The course comprised nearly 38 miles of alpine trail with 3,400 meters (11,155 feet) of elevation gain, including a punishing climb toward the Col de Balme high mountain pass in the second half of the race. Running at this elevation requires the body to operate efficiently with less oxygen, which makes preparation at altitude, or simulating it, a critical part of an elite athlete’s training plan.

Although the race started in Switzerland and was estimated to be longer than previous editions, Chamonix (normally a sleepy summer town) buzzed. Other UTMB races were still underway, and thousands of runners and spectators filled the streets, the energy building long before the OCC athletes would arrive. Cowbells jingled, horns blared, and cheers erupted from every corner, so loud it became almost white noise. Bibs flashed names from across the globe, headlamps bobbed in the drizzle, and cameras documented each step, every stumble, every surge.

No casual runners here. Each person had their own reason for being on the trail: divorce, loss, personal redemption, or, in Jim Walmsley’s case, to push his own preconceptions of limitation. He had originally planned to run the Ultra-Trail du Mont-Blanc (UTMB), a 171-kilometre (106-mile) race with approximately 10,040 metres (32,940 ft) of elevation gain, often referred to as the Super Bowl of ultramarathons. But knee issues and his goal of peaking for the World Mountain & Trail Running Championships, a race he went on to win just a few weeks later, led him to the OCC instead. This wasn’t his first rodeo, either. He’s won the Western States 100 four times and took home gold at UTMB in 2023.

For Walmsley, there’s a profound calm in the chaos. The nerves that flutter before a race fade within 30 seconds, replaced by a deep focus.

“That's generally when I feel a big rush of relief, calmness, and everything will be fine,” he says. “Now we're just trying to execute on the race plan and take care of what we can control.”

But at a race this challenging, even the most experienced runners encounter chaos. At OCC, Walmsley’s carefully mapped nutrition plan went sideways when water stations were limited, a critical detail when every ounce of fluid and carbohydrate matters.

“So, OCC, I had six pre-filled bottles of powder. I started with one liter and was planning to refill one more bottle, but we didn’t see the water at all,” he said. “I think I didn’t get enough fluids in. My nutrition kind of was a bit of a disaster.” On a course like this, with steep climbs and the thin air, every misstep in hydration can amplify the challenge, testing how efficiently the body uses oxygen. Despite this, he adapted, managing gels, sugar, and caffeine while navigating one of the most challenging alpine trail races in the world. 

The race itself was a chess match at altitude. At this elevation, every climb becomes a strategic decision, demanding both careful pacing and adaptation to low-oxygen conditions. 

Walmsley was part of an early break alongside Sweden’s Petter Engdahl and Canada’s Sam Hendry, taking the lead after strong climbing on the Col de Balme. Despite his months of training, the hiccup at the water station allowed rival Cristian Minoggio to pull ahead. With about 6 km left, Walmsley shifted gears, hunting Minoggio down on the flats. A mile from the finish, he overtook him and crossed the line just 20 seconds ahead, in 5:00:35.

Related: I Asked UTMB Athletes How They Prepare for the World’s Toughest Races—Here’s Their Advice

Watching races like this makes it easy to understand why runners do what they do. For Walmsley, it’s simple: the mountains, the rhythm of his own body, and the collective breath of those around him create a space where the world falls away.

“In a race context and in a professional sport, I think the suffering is much more on the enjoyable spectrum of pushing yourself and finding how far you can, or how much effort you can really get out of yourself,” he says. “You can do more. You can go farther, really push your own preconceptions of limitations.”

The way he describes how he runs is somewhat like a cheetah, fast, instinctual, precise, something you wouldn’t expect from Walmsley’s otherwise composed demeanor. Sitting across from him in the press room in Chamonix, or on the other side of a screen halfway across the world, he seems unshakable. So when he told me he doesn’t run with any music, podcasts, or other distractions (even during a 19-hour-plus run at UTMB in 2023), my mouth couldn’t have hung open any wider.

“There's not much stimulus out there besides you going through the mountains,” he explains. “You can hear each other's breathing. You can feel like if you make an acceleration, you can feel how people react to that, whether it's slow or fast or immediate, if they're rushing, if they're letting you gain a couple steps…it’s a lot of reactions, and a bit of a play or a dance with someone else to feel their own rhythms.”

Later in the season, at the World Mountain & Trail Running Championships, the run was smoother compared to OCC. While it was longer in both distance and time (just over eight hours, much of it neck and neck with competitors Benjamin Roubiol and Louison Coiffet), he felt ready. 

He had spent months preparing, running long vertical routes and climbs designed to mimic the thin-air conditions he’d face, building both endurance and oxygen efficiency. One standout session was a 40-mile run with over 16,000 feet of up and down. Despite the soreness that followed, he felt more prepared than ever to tackle this challenging new terrain.

“So the course had over 18,000 feet of up and down within 50 miles,” he recalls. “In the U.S., there's no course that comes close to that. It's not like we don't have the terrain, but we don't have trails with the opportunity to host races like they do in Europe. So this goes through more extreme mountains and very vertical up and down. On race day, I saw about four feet in front of me and all the rocks coming at me. Basically, my attention had to be very, very much on the trail and a hundred percent focus on the technicality of it.”

Even with the breathtaking Pyrenees around him, Walmsley’s attention stayed glued to the ground, picking his way through every rock and root. “For the last three to six thousand feet, your legs are out of running, and you're forced to hike the last couple of climbs,” he says. “I felt like I just had more confidence in the pace I was setting through power hiking and using trail running poles…and I was still able to put time in between me and a second and third place.”

It’s here, after these races, that Walmsley reflects on the strategies that keep him healthy and competitive. “Even when I have injuries, I don’t typically take too many days off. Usually, I’ll slow down or manipulate the terrain for what I can do,” he explains. “Sometimes I get stuck doing flat road running—that’s fine, depending on what’s going on. You have to really listen and avoid what causes pain.”

But according to Walmsley, who’s been running professionally since 2016, true ultras like UTMB go far beyond what anyone can fully prepare for. “It’s getting into a slog, into grittiness, whether it’s a pain cave or suffering…that’s a bit beyond you, you’ve stretched a little further that day,” he says. “And we take away a lot of growth when we’re put in those uncomfortable situations. That’s a really special part of what I would define as true ultra running.”

Whether it was picking his way over rocks on the OCC course or navigating the technical Pyrenees at Worlds, Walmsley moved with focus and precision. Every step was measured, every climb calculated, every descent read in real time. The mountains demanded attention, and he gave it fully.

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