Part of the Mont-Blanc Marathon program since 2011, the Chamonix KV is one of the longest and most technical vertical kilometers in the world. Over 3.8 kilometers between Chamonix and Plan de l'Aiguille, the average gradient sits around 26%, more moderate than Fully or Grand Serre.
Don't be fooled though: the profile alternates rolling sections and technical singletrack passages with roots, rocks, occasional scree. That diversity has made it a classic of the Skyrunning circuit and a true test for versatile trail runners.
François Gonon set the men's record at 34:07 in 2015, taking 11 seconds off Kilian Jornet's previous mark. On the women's side, American Hillary Gerardi has held the time of 42:54 since 2018.
The race is run at sunset, in the heart of the massif. The technical terrain demands solid footwork and constant placement: running fast here requires reading the ground as much as raw aerobic capacity. The finish at Plan de l'Aiguille, at 2,317 meters altitude, offers a sweeping view over the valley and the Bossons glacier.
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