Kosci100

Race strategy

Run easy on the first mountain, then go all out on the second.

• 435m descent. Go easy, save your quads.
• Final 644m descent. Save your legs to go all out on it.
• Long race. Control your HR and effort. Early mistakes cost the most.
• Ease into the early runnable section, save your quads on the descents until 72.1km, then run your race pace, and go all out on the final descent from 101km.
• Start · 0.0km–1.5km · Race-day nerves push your heart rate up: don't follow the crowd, find your own rhythm.
• Settle in · 1.5km–27.0km · Climb of 492m, high point 2223m. Ease in: hold back more than feels necessary. The race is still ahead. Climb by heart rate or breathing, not pace. Running pays off here: run wherever you can.
• Work · 27.0km–63.6km · Descent of 435m averaging 9%. This is where the race is built: steady, solid effort. This descent is hard on the legs: short steps, stay in control, poles if you have them. Running pays off here: run wherever you can.
• Fade · 63.6km–101km · Descent of 716m averaging 8%, climb of 607m. Your energy fades, and that's normal: hold a steady effort and stop counting the miles. Climb by heart rate or breathing, not pace. This descent is hard on the legs: short steps, stay in control, poles if you have them. Running pays off here: run wherever you can. Your heart rate drifts down on its own: don't chase your early-race numbers, go by feel.
• Home · 101km–106km · Descent of 644m averaging 13%. No heroics: settle back into your own effort and hold it to the line. Long descent: keep it even and let go only near the end.

Course

By gradient, 36% of the distance is uphill, 34% downhill and 30% flat. The longest climb runs 10.7km at an average 4.6% grade (492m of vertical). The longest descent runs 8.5km at an average 8.4% grade (716m of vertical). The steepest climb averages 18.0% over 0.8km. The steepest descent drops at 27.5% over 0.3km. Surface: 72% trail, 17% smooth, and 10% road. Flat-equivalent effort: 127.5 FlatKM.

Poles

Poles bring little benefit here: only about 3.5km of pole-friendly terrain.

Quad damage

Quad damage risk is moderate (index 41 of 100), with 49% of the load in the first half: 2 descents deserve a plan and a couple of downhill sessions before race day.

• Ease into the early runnable section, save your quads on the descents until 72.1km, then run your race pace, and go all out on the final descent from 101km.
• #1 · 33.8–38.8 km · 435 m D−, -8.8% · 67.0 km ahead → control
• #2 · 63.6–72.1 km · 716 m D−, -8.4% · 33.7 km ahead → control
• 100.9–105.8 km · 644 m D−, -13.1% · 0.0 km ahead → even, let go at the end

Weather

On race day, start temperatures have historically ranged from 5°C to 16°C, with around 11°C at the highest point; the chance of precipitation is about 43%.

Results

893 finishers completed the 2025 edition. Men's winner: Loris Lassere (France) in 9:53:20. Women's winner: Sophie Broome (Great Britain) in 11:58:10.