This video features superhuman athletes. For most runners, winning a marathon is the pinnacle of their sport. Running more than 26 miles is no small feat. But an elite few can’t seem to stop there.

The Badwater Ultramarathon is considered the world’s toughest race. It’s 135 miles long. That’s more than five marathons run back to back. It starts in one of the hottest places on earth – Death Valley. And it ends with a grueling climb 8,000 feet up a mountain. Its participants race non-stop for more than 24 hours.

It’s hard to imagine what kind of person tackles such a race.