Théo Detienne

From triathlon to the ridges of Font-Romeu 🏊

It all starts with athletics and triathlon. In 2016, he joins the sports science (STAPS) degree program in Font-Romeu, a haven for endurance sports perched in the Pyrenees ⛰️.

The turning point comes in 2017. The day after the French triathlon championships, he competes in his first French mountain running championships and takes 12th place, according to Sud Radio. Trail running has just recruited a new member.

Before making a living from his passion, he went through the gendarmerie and a course linked to mountain rescue. He then settled near Chambéry, in Savoie 🏔️.

The 90 km du Mont-Blanc, his springboard 🚀

In 2024, he takes 4th place in the "epic race" of the Marathon du Mont-Blanc over 90 km, in 11h14'. The following year, he returns to the same 90 km and wins it 🥇.

Right after, he discovers the UTMB in 2025, his first 100 miler. He leads until around the 95th km. Two falls at night reawaken a pain in his hip, and he drops out at Trient, around the 144th km 🩹.

2026, between podiums and lessons in humility 📈

The season starts strong. He takes 9th place at Transvulcania in the Canary Islands, then 2nd place at the Maxi-Race around Lake Annecy, in 9h56'48" on the 100K.

Back in Chamonix in late August, with a UTMB index of 903 and a more cautious start. Sick and vomiting, he watches the head of the race pull away 🤢. Yet he refuses to quit and finishes 71st in 24h00'41" over 173.6 km and 9,700 m D+. A guard of honor awaits him at the finish.

On November 7, 2026, he wins "Les 25 heures qui courent", the charity backyard ultra organized by Clemquicourt: he beats Mathieu Delpeuch and Victor Guerdin after the 25th and final loop, extended for the occasion 🔁.

The green suit, from joke to controversy 🟢

In spring 2026, a mysterious runner in a fluorescent green bodysuit, like a movie green screen, slips onto the start line of the Trail du Printemps. This 25 km race takes place in Saint-Pierre-d'Albigny. Under the disguise, Théo Detienne drops the pack, wins and leaves without waiting for the podium 🏃.

The video goes around social media and divides opinion. Some see humor in it, others a lack of respect for the volunteers and amateur runners. The trail runner ends up reaffirming his attachment to local races. This taste for green brings him closer to another trail-running troublemaker, Casquette Verte😏. As for gear, he now runs for Brooks, his official sponsor.

Want to follow in his footsteps? 🎯

No need to aim for the UTMB right away 😉. Start with a local trail race, which requires neither a costume nor giant sunglasses, then gradually increase the distance. Go through the trail race calendar, compare races on MyTrails and book your bib 🏁.