Why do ski mountaineers remove skins before skiing downhill?

Ski mountaineers remove skins before skiing downhill because the skins are designed specifically to provide traction for ascending slopes. These high-friction coverings, which have evolved from animal pelts to modern synthetic materials, are essential for gripping the snow while climbing.12

If left on during a descent, the skins would create significant drag and prevent the skis from gliding effectively, making it impossible to perform the fluid, high-speed maneuvers characteristic of downhill skiing. Consequently, athletes must remove and properly stow their skins at the top of a climb before transitioning to the descent phase of their route or race.2