Two of the world's most elite mountain runners are about to attempt what most would call impossible: a full-speed race up and down the southern face of Mount Everest. When the mountain's brief, roughly two-week climbing season opens later this month, these super athletes will aim to dash from base camp to summit and back in record time—all while navigating what could be the most dangerously crowded season in Everest's history.

Karl Egloff and Tyler Andrews couldn't come from more different worlds, yet they share the same audacious goal. Egloff, 45, is an Ecuadorian-born climber now living in Switzerland. The son of a mountain guide, he was scaling Ecuador's towering peaks before kindergarten and later became a world-class mountain bike racer. He approaches the mountain with a meditative, almost metaphysical mindset.

Andrews, 35, grew up in the Boston suburbs. A self-described high school band geek, he discovered his talent for distance running in college and now holds a 2:15 marathon time. He lives in Quito, Ecuador, training on the same jagged Andes that forged Egloff. Andrews only committed to big mountain running when the pandemic shut down road racing—but he committed hard. In 2021, he got a massive chest tattoo of Rucu Pichincha, the Ecuadorian volcano where he trains daily.

Neither Egloff nor Andrews is among the roughly 7,500 people who've stood atop Everest since Sir Edmund Hillary first conquered it in 1956. This time, both will climb with fixed ropes but without supplemental oxygen, aiming for a round-trip speed record on the mountain's most popular route. They'll start at Everest's Nepali Base Camp, elevation 17,598 feet, then navigate the dangerously shifting Khumbu Icefall. From there, they'll push through the gentle glacial valley of the Western Cwm and ascend the steep, icy Lhotse Face toward the mountain's two most congested bottlenecks: the Cornice Traverse, which narrows to just two feet wide in places with thousand-foot drops on both sides, and the Hillary Step, a near-vertical ice slope just 200 feet below the summit.