UTMB 2026 kicks off in Chamonix without several of its great champions

On August 24th next, the clock will start running again in Chamonix. But this time, when the 846 elite runners from 54 countries step up to the starting line of the 23rd edition of UTMB Mont-Blanc, there will be missing faces that defined the last decade of this sport: Kilian Jornet, Jim Walmsley, Tom Evans, and record holder Katie Schide will not be on the line. For anyone who follows trail running, this is no minor detail — it is proof that the most important race on the calendar is already bigger than its own legends.

The context

The UTMB (Ultra-Trail du Mont-Blanc) is, for trail running, what the Tour de France is to cycling: the flagship race, the thermometer that measures who's in charge in the mountains. It's 171 kilometers and nearly 10,000 meters of positive elevation gain skirting Mont Blanc, crossing France, Italy, and Switzerland, with a brutal time limit of 46.5 hours that demands endurance, nutritional strategy, and a clear head to manage fatigue for nearly two days of nearly uninterrupted effort.

The absence of figures like Jornet (six-time champion) or Walmsley (2023 winner) is no coincidence: it reflects an increasingly saturated calendar, where elite athletes selectively prioritize their seasons, manage injuries, or pursue other objectives (Jornet, for example, has been focused on mountaineering projects and other races). Far from weakening the event, this opens the door to a new generation hungry for prominence, and confirms that the UTMB — as a brand, as an experience, and as a community — transcends any individual.

The other major headline of this edition is organizational: the UTMB World Series has doubled its anti-doping controls, a signal that trail running, as it grows in prestige and money, also grows in scrutiny. And for the first time, runners will be required to carry headlamps with red light mode in a protected section of the course — likely a sensitive wildlife area or high nighttime traffic zone — a gesture that shows how mountain sports are beginning to engage more seriously with environmental sustainability.

What the science says

Running 171 km with that much elevation gain is, above all, an exercise in management: of energy, of temperature, and of decisions under extreme fatigue. The review by Cao et al. (2025) on carbohydrate strategies in elite endurance exercise reminds us that in ultra-long efforts, the ability to sustain energy input — not just VO2max or raw strength — is usually the factor that separates those who finish on the podium from those who drop out at an aid station.

Add to this the thermal component: UTMB runners face temperatures that swing from valley heat to the cutting cold of high passes, often within the same hour. The classic research by Lorenzo and Halliwill (2010) on heat acclimatization shows that progressive exposure to extreme thermal conditions directly improves performance, something that elite teams are already integrating into their specific preparation blocks for Mont Blanc.

And then there's mental and neuromuscular fatigue. The work by Azevedo et al. (2021) on the development of fatigue in self-regulated exercise explains why, after 20-25 hours of racing, the perception of effort becomes as decisive as pure physiology: the brain starts to negotiate with the body, and whoever manages that internal conversation better wins real time on the clock.

What it means for you

You don't need to run 171 km to apply these lessons:

• Train your "durability," not just your speed. Recent evidence on strength training (Zanini et al., 2025) shows that strength work improves running economy even in a state of fatigue — exactly what you need in the second half of any long race, trail or road.
• Practice your nutrition on long training runs. Don't wait until race day to test gels or carbohydrate strategies: your intestinal tolerance window can be trained, just like your legs.
• If you run in changeable climates, expose your body to them first. A few weeks of acclimatization — even with layered clothing or training during hotter hours — makes a real difference in mountain or summer races.
• Train your head like you train your legs. Perceived fatigue is manageable with strategy: break long goals into small targets, the way ultramarathoners do between aid stations.

UTMB 2026 will remind us, once again, that in mountain races the winner is not necessarily the fastest on paper, but the one who best manages his body and mind for the duration of the challenge. That lesson applies to Chamonix and to your next 10K race.

References

• Cao W, He Y, Fu R. "A Review of Carbohydrate Supplementation Approaches and Strategies for Optimizing Performance in Elite Long-Distance Endurance." Nutrients, 2025. https://pubmed.ncbi.nlm.nih.gov/40077786/
• Lorenzo S, Halliwill JR, Sawka MN. "Heat acclimation improves exercise performance." J Appl Physiol, 2010. https://pubmed.ncbi.nlm.nih.gov/20724560/
• Azevedo RA, Silva-Cavalcante MD,