Backyard Ultra: What It Is and How the Format Works

A backyard ultra is an ultramarathon format in which runners must complete a fixed loop of 4.1667 miles (6.7056 km) in under one hour, then start the next identical loop exactly on the hour, repeating indefinitely. There's no set finish line or distance. A runner who fails to complete a lap in time, or isn't ready to start the next one, is eliminated. The winner is the last person still running; if the final two runners both stop at the same time, there's officially no winner at all.

It was created by Gary "Lazarus Lake" Cantrell, the same race director behind the notoriously brutal Barkley Marathons. Unlike Barkley, the backyard ultra was designed to be simple and cheap to organize, needing no mountains, technical trails or heavy permits, just a flat loop and a clock, which is a big part of why the format has spread to hundreds of races worldwide since its debut at Big's Backyard Ultra in Tennessee.

Each loop is exactly 4.1667 miles (6.7056 km), a distance chosen so that running 24 loops in 24 hours adds up to precisely 100 miles. Runners get whatever time is left in the hour after finishing a loop to eat, rest, treat injuries or sleep, before the bell sends everyone out again.

You're eliminated. Missing the 60-minute cutoff for a loop, or not being in the starting corral when the next hour's bell rings, ends your race immediately, no partial credit, no second chances. This is what makes the format brutal mentally as much as physically: the clock never stops, even to sleep.

The race continues until only one runner completes a loop that no one else finishes. That runner must then complete one final "victory lap" alone to be declared the winner. If the last two competitors both drop out or fail to finish the same lap, the event officially has no winner at all, a rule that has occasionally produced controversial, winner-less finishes at major events.

It's the fourth edition of the global team format, scheduled for October 17, 2026, with the flagship Last Man Standing race hosted at Big's Backyard Ultra in Bell Buckle, Tennessee. More than 1,000 runners from over 70 countries compete simultaneously at satellite venues worldwide (Australia hosts its team at Red's Backyard Ultra in Kembla Grange, NSW), with each country fielding up to 15 athletes. A nation's score is the combined loop total of its team; the highest total wins the World Team title. Sources: bigsbackyardultra.com, autra.asn.au.

Records in this format are unusually contested because outside assistance disqualifies a result. American Harvey Lewis has held some of the sport's most recognized marks at Big's Backyard Ultra. A widely reported 123-lap performance by a Russian runner in mid-2026 was voided by race organizer Lazarus Lake after video evidence showed non-competitors on the course, which counts as outside aid under the format's rules. Given how often marks get disputed, treat any single record claim with caution until it's confirmed by the race's official body.

A standard ultramarathon has a fixed distance (50K, 100 miles, etc.) and everyone races to finish it as fast as possible. A backyard ultra has no fixed distance at all, it's pure elimination and endurance, structured entirely around the clock rather than the course. That structure is also what makes it accessible to organize: no need for mountains or a huge crew, just a 4.1667-mile loop and a bell.