Articles

Belgian Ultrarunner Karel Sabbe's Record-Breaking Pacific Crest Trail Run Showcased in New YouTube Documentary

Explore Karel Sabbe's record-breaking Pacific Crest Trail run in a riveting documentary. Jour..

Trail Running: How it Can Help Reduce Stress and Anxiety

Trail running is an effective way to reduce stress, anxiety, and improve physical and mental he..

Trail Running vs. Road Running: Which One Is Right For You?

When it comes to running, there are two primary options to choose from: trail running and road..

Les 40 Bosses

Name: Les 40 Bosses
Start: 2025-12-06
End: 2025-12-07
Location: Saint-Leu-la-Forêt

Saint-Leu-la-Forêt, France • 6-7 Dec 2025

The Les 40 Bosses will take place in Saint-Leu-la-Forêt from Saturday 6 December 2025 to Sunday 7 December 2025. You can run between 20 and 120 kilometers. Visit the organization's website for the most recent information.

France Val-d'Oise Île-de-France Saint-Leu-la-Forêt

Race information

Website

UTMB 20K UTMB 50K UTMB 100K UTMB 100M

120 km

5500 m+

Les 40 Bosses - 120 Km

75 km

3300 m+

Les 40 Bosses - 75 Km

45 km

2100 m+

Les 40 Bosses - 45km

20 km

900 m+

Les 40 Bosses - 20 Km Nocturne

20 km

900 m+

Les 40 Bosses - 20km

Visit the organization's website for the most recent information.

Trail runs nearby

Saturday Jun 28

Trail du Bois des Côtes

Bailleval - 40 km from Saint-Leu-la-Forêt

The Trail du Bois des Côtes will take place in Bailleval on Saturday 28 June 2025. You can run between 10 and 43 kilometers.

UTMB Index

Sunday Jun 29

Urban Trail Senlisien

Senlis - 32 km from Saint-Leu-la-Forêt

5 km

10 km

The Urban Trail Senlisien is a unique running event that combines sport, history, and exploration in the charming city of Senlis. Participants can enjoy a scenic route through cobblestone streets, passing by the stunning Notre-Dame Cathedral, a gothic masterpiece. The event features both a 10 km rac..

Sunday Jun 29