Think you’re tough because you ran a marathon? Meet the death-defying competitors of the Yukon Artic Ultra, the toughest race on Earth.

By Darren Reidy

Many races claim the title of toughest in the world, but the Yukon Arctic Ultra actually deserves it. The biennial 430-mile ultramarathon is so physically and mentally grueling that its last incarnation had to be stopped with about 100 miles to go, when the leaders were caught in temperatures just south of 76 below — cold enough to freeze a man’s blood, and only a few degrees shy of the coldest mark ever recorded in North America. Beginning February 15 in Whitehorse, Yukon Territory, and ending in gold rush capital Dawson City, the roughly two-week race takes about 15 runners and skiers up a combined elevation gain of 20,000 feet, over King Solomon’s Dome, across the frozen tributaries of the Takhini River, and through hundreds of miles of wind-lashed tundra, almost all of it without another human being in sight. The participants, who each pay $1,850 to enter (and there’s no prize for winning), carry minimal gear and shelter — which they drag, themselves, by sled — and catch just enough sleep to get by. If something goes wrong, it can take up to 48 hours for help to arrive. “You can’t spend a lot of time thinking about that,” says Steve Reifenstuhl, this year’s favorite. You can follow their brutal progress online at arcticultra.de.

Quick video from last year’s starting line: