The 42 km is the flagship race of the Chamonix weekend, with 2,540 metres of climbing and a 10-hour limit. Quick, rolling trails come first, then steep technical slopes up the Aiguillette des Posettes, the main difficulty, before a finish facing the Mont Blanc range. It is semi-self-sufficient, with three full aid stations, and mandatory kit includes a waterproof jacket and at least one litre of water. An 88 km ultra, a 23 km and a 10 km run the same weekend.
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