In the Barkley Marathons' thirty years, only 14 people have ever completed it. But it’s not for lack of trying. Some 1000 runners have attempted to complete Barkley’s five loop course of agony through Frozen Head State Park in Tennessee. The route is supposed to be 100 miles, but Barkley veterans guess that it’s more like a very hilly 130. With no GPS, no course markers, and not an aid station to speak of, sleep deprived runners are challenged more than just physically. For the vast majority of runners, this race isn’t about finishing. It’s about pushing themselves to their absolute limits. This episode of Human Race is brought to you by Brooks. Sign up for the Brooks Big Endorsement and become a sponsored athlete at www.BrooksAthlete.com/rw. Further reading: The 2016 Barkley Marathons: One Person Finishes! by Brian Dalek Notorious by Charlie Engle Episode Credits: Host: Rachel Swaby  Producers: Brian Dalek, Rachel Swaby  Editor: Audrey Quinn with help from Christine Fennessy  Production help: Mervyn Degaños  Thanks to Pam Bede from Swim, Bike, Run, Eat! and Bryce Mander from UC Berkeley’s Sleep and Neuroimaging Laboratory for their help on this story  Theme music: Danny Cocke  Human Race editor-in-chief: David Willey  Learn more about your ad choices. Visit podcastchoices.com/adchoices