Unmasking the painful, tearful, stirring obsession of endurance athletes

A sailor stitches his gashed tongue during a solo sailing race where no assistance is allowed. An adventurer loses seven toenails while crossing 1,600km of the Gobi desert. A climber on the wall of the Eiger sleeps on a foot-wide ledge and claws up rock the next day with bleeding fingers.

Out in the “untamed world” of nature, as the mountaineer Reinhold Messner described it, exists a tribe of humans who examine themselves. The geography that their expeditions explore includes not just areas of the planet but the unknown spaces within themselves.