David Sinclair is one of the top American trail runners, yet he spends a large part of his winter training on skis, not in running shoes. Sinclair, a collegiate cross country skier while attending Dartmouth University, has won and set records at the country’s most iconic races including Broken Arrow, Speedgoat 50K, JKF 50 Mile and The Rut. He’s also represented Team USA several times at the World Championships in Trail and Mountain Running in 2018, 2019, 2022 and 2025. But while many know Sinclair from his extensive trail running achievements, he has also made a name for himself in the past five years as a pioneer for the US Ski Mountaineering Team. Featured photo courtesy: Andy Wacker.
Ski mountaineering (a.k.a. skimo), a discipline of skiing that combines uphill climbing and downhill skiing on technical, snowy terrain, will be introduced into the Olympics for the first time in 2026 Milano Cortina Winter Olympics. Sinclair has been an integral part of the US Ski Mountaineering and spent the majority of his 2025 winter/spring competing in Europe at World Cup events to aid the US in earning a spot in the Olympics. While the fate of Team USA will not be decided until December 2025 at the final qualifying race in Solitude, Utah, Sinclair has given all he can to the team.
In the following article, Sinclair shares his thoughts on merging his skiing and running passions and how each has made him a strong well-balanced athlete. He also shares his insider knowledge on the US Ski Mountaineering Team and Olympics.
Seasons of training
To say Sinclair is drawn to snow would be an understatement. For five years, Sinclair lived on the infamous Donner Pass—routinely the snowiest place in the US, which reached 800 inches of snow in one season during Sinclair’s time there. “There are inevitably days where it would dump five feet of fresh snow and I couldn’t even run on the road. But I actually like this mental break from running. Skiing has made me super strong and helps me build my aerobic base. It’s been a great way to set me up for long summers of running.”
Similar to many runners living in wintery places, being a multisport athlete (trail runner by summer and skier by winter) is not just essential because of the weather, but aids in balancing oneself mentally and physically. The trouble for many multisport athletes, however, is that it can be difficult to switch between two very different athletic disciplines. Sinclair speaks of his experience switching between winter ski mountaineering/cross country skiing and summer trail running, “The hardest thing is returning to running after skiing. Even though the first runs can be pretty tough, the muscle memory in the legs starts to come back quickly. But what you need to be wary of most is that even if these muscles adapt quickly, the tendons and bones might not adjust at the same rate. I’ve had tendon struggles coming back too quickly to running after spending most of my winter skiing.”
Sinclair on the podium at Broken Arrow. Photo: Andy Wacker
A season of unexpected results
After a successful World Cup Ski Mountaineering season, Sinclair’s 2025 trail running season had a rocky start. In his first race of the season, Sinclair received a did not finish (DNF) at one of Europe’s toughest ultramarathons, Transvulcania. “I felt knee pain in the race that turned out to be a full blown case of patellar tendonitis.”
While Sinclair had planned to swap his ski training for more running, his injury forced him to instead turn to cycling. “I took my road bike on the rural, hilly roads around the green mountains in Vermont where I am living now. It turned out to be some amazing base training on the bike. Cycling set me up great for the end of the summer trail running season.”
Though not one hundred percent healthy, Sinclair placed second at the 2025 Broken Arrow Skyrace in June, earning a spot on the World Mountain and Trail Running Team. “I hung on for the first loop of the race and managed to stay strong. My knee flared up and I could barely walk after the race.” Fortunately for Sinclair, his knee recovered quickly in the following weeks and continued training for his next big summer competition: the UTMB CCC 100K in Chamonix, France (read another story on CCC and adaptive athlete Julien Veysseyre here).
Sinclair trained intensely for CCC. He tested his fitness with workouts on his local ski hill in Vermont, routinely accumulating over 10,000 feet of vertical gain in twenty-five mile runs. In spite of his injuries and inability to run as much as he had in previous summers, his result at CCC was better than he ever could have imagined. Sinclair placed second in a time of ten hours thirteen minutes and fourteen seconds. “I’m incredibly proud of my result at CCC. It’s not only how I ran on the day, but how I was able to adjust my plan because of injuries and setbacks. It’s hard to be confident and trust in your training when you’re not totally healthy, but I’m super grateful for how everything came together for this huge result.”
Sinclair’s podium position at CCC also earned him automatic entry into the historic Western States 100 Mile Endurance Run (read Kilian Jornet’s Western States 100 Training Tips here). The race will be held June 26 to 27, 2026. “I’ve earned a golden ticket into this race before, but I never felt ready. This will be the longest race that I’ve run by far, but I’m finally feeling ready. I’m going to plan my season around this race and be as prepared as I can.”
Catching up with Sinclair on the trails.
Complimentary sports
While transitioning between SkiMo and trail running may be difficult for many athletes (Sinclair included), practicing both sports can offer many benefits,“They are very complementary sports, especially when it comes to the longer mountainous races. For runners who live in cold, wintery places who can’t access running trails, it’s a perfect way to build strength that translates well into summer running training.”
Jim Walmsley, Katie Schide, Kilian Jornet, Lara Hamilton, Max King, Kelly Wolf, Cam Smith, Remi Bonnet and Emelie Forsberg are several of many more top trail runners in the world who use ski mountaineering as an integral part of their winter trail running training.
Curious about other complimentary cross training methods for trail runners? Read Better Together: Cross Training.
David Sinclair during the 2024 Speedgoat Mountain Race. Photo by: Kris Braunberger.
Winter Olympics for trail runners?
Trail runners have found success in ski mountaineering competitions, largely due to their abilities in climbing and aerobic endurance. That said, ski mountaineering has many specific skillsets that make it difficult for full-time trail runners to make it to the Olympics or earn medals, “Especially with the chosen Olympic disciplines for SkiMo, the races are very short, incredibly technical, with emphasis on transitions and downhill technique around gates. The best athletes spend time doing explosive gym training. In some ways, the top SkiMo athletes train much more closely to Olympic cross country ski athletes.”
While the shorter “sprint” ski mountaineering distances (typically between three to five minutes) have taken the center stage at the Olympics, many athletes have expressed their concerns about the sport gravitating towards these increasingly shorter races. “It’s a huge issue in the sport right now,” said Sinclair, “There’s certainly tension amongst more experienced European athletes who have been racing longer, more traditional ski mountaineering races for decades. The Olympics has put emphasis on shorter events and relays on prepared snow, but not on the more classic back country races that involve crampons and roping up to partners. It’s really become two totally different sports.”
Sinclair reflects on the state of ski mountaineering and its entry into the Olympics for the first time in 2026, “In the long run, this could be really great for the sport to be in the Olympics and have more exposure. That said, I’m definitely more passionate about the traditional, longer races which won’t be a part of next year’s winter Games.”
Curious to learn more about the Olympics and trail running? Read Why Isn’t Trail Running in the Olympics here.
Sinclair with USA teammates in Argentina.
Olympic Hopefuls
As of October 2025, the United States ranks in thirteenth place in the Ski Mountaineering relay discipline. Only one point behind Canada, the US must finish ahead of their maple-leaf border nation in order to send a team to the 2026 Winter Olympic Games. Only one male and one female from the US can participate in this relay team. While Sinclair is focusing most of his energy on trail running in coming months, he shares his thoughts on the efforts he’s put towards supporting the US Ski Mountaineering team the best that he can, “I’m incredibly proud to have been a part of pushing the US team forward and my teammates to be even better versions of themselves. I’m hoping everything works out this winter for us to send a team to the games.”
Follow Sinclair on his Instagram here.
