For one race morning, EDF pauses production at the Grand'Maison hydroelectric plant so athletes can swim in Lac du Verney, a reservoir where swimming is otherwise forbidden. The Triathlon de l'Alpe d'Huez is a five-day mountain triathlon series based around Allemont, Alpe d'Huez, and the Oisans Valley in the French Alps. The program includes four races: a short duathlon, a middle-distance triathlon, a long-distance triathlon, and youth-friendly options. The long race is the main event: a 2.2 km swim, 118 km bike ride, and 19.2 km run.
The long-course swim is one loop in Lac du Verney, where the water has averaged about 17C in recent editions and athletes have a 1 hour 30 minute cutoff from the last start. The bike leg carries the real weight of the day, with 3,200 m of climbing, the Alpe du Grand-Serre, and the famous 21 hairpins up to Alpe d'Huez. The race draws triathletes who want a hard Alpine course rather than a flat time trial, plus families and juniors through the wider week of racing. After racing, people usually stay close by: a walk around Lac du Verney, a trip up to Alpe d'Huez, or a break in Bourg-d'Oisans all fit naturally into the weekend.