Imagine running a race that even if you ran 300 miles for three days straight, you could be classed as 'not finishing'.
'Big Dog's Backyard Ultra' is an annual event which takes place in rural Tennessee in the back garden of a man called Lazarus Lake. The premise is simple, every hour you run 4.16667 miles and then you do it again, and again every hour until you're the last person standing.
It doesn't matter if you're the quickest runner, the slowest runner or if you crawl, as long as you cross the finish line within the hour and you're ready to go again, you stay in the race.
It's a battle of the mind, versus the body, and hoping against hope that your competitors fall before you do.
Lazarus has some experience in the world of weird, and wonderful, races. He's also the man behind The Barkley Marathons, often regarded as one of the hardest races in the ultramarathon world. Since it's inception in 1986, only 15 people have completed it.
Speaking to Dermot and Dave, Lazarus explained where the ideas came from, why people decide to take part in massive numbers every year and how often, women do better than men!
You can catch the chat by clicking play below:
