WARTBURG, Tenn. (WATE) – Each year the conch is sounded, and a select few runners lace up for the ultimate challenge, a near impossible 100-mile race that only 15 people have ever finished in the event’s 35 year history.

The 2021 Barkley Marathons got underway at Frozen Head State Park this week. A group of brave runners set off on the ‘not so secret’ ultramarathon that has become known around the globe.

The Barkley Marathons is considered one of the toughest 100-mile races in the world. It consists of five unmarked 20-mile loops that must be completed in under 12-hours a-piece, or 60 hours total.

There are no aid stations on the course except for water at two points along the route.

For runners to prove they’ve completed each loop, they must find books at various points along the course and return a page from each.

Elevation change, difficult terrain, and bad weather only adds to the degree of difficulty.

The race was first run in 1986. The idea for the race came when course creator Gary Cantrell read about Martin Luther King Jr. assassin James Earl Ray’s escape from nearby Brushy Mountain State Penitentiary in which he ran 8 miles in 55 hours in the mountainous region before his capture.

At last check, 10 runners are still in the race. Those who are left must finish the Barkley Marathons by 3:04 p.m. Saturday or they are disqualified.