What is a backyard ultra? The endurance race with no finish line that can last for days and hundreds of miles

It’s one of the simplest race formats — and one of the most brutal.A “backyard ultramarathon” may conjure images of runners looping on a compact lawn with a picket fence, but the reality is actually much more extreme.The latest endurance trend taking over the running world, the backyard ultra is a race in which the fastest runner doesn’t always win, there’s no finish line and there’s no predetermined distance.While many ultramarathons — races that exceed 26.2 miles — take place in scenic locations across the globe, the backyard ultramarathon pops up in parking lots and on mixed-use trails around the US and the world.The rules are simple: Run one 4.167-mile loop (referred to as a “yard”) in an hour, then do it again every hour, on the hour, until the last person is standing.Races can last more than 100 miles and, in extreme cases, may go on for days, with the record set last year in Australia at nearly 500 miles and sixteen straight days.If runners complete the yard before the hour’s up, they can rest for the remainder of the time.If they fail to finish the lap within the hour, though, they’re eliminated and marked “DNF” (Did Not Finish.)But where “DNF” is a mark of shame in typical races, it’s considered a badge of honor for the backyard ultra.Despite the intense setup, people are racing to sign up, with hundreds on the calendar in the US alone.The race was created by Gary Cantrell, who also came up with the infamous Barkley Marathons, a 100-plus-mile race only 20 runners have finished since its start in 1995.Rather than make another complicated race, Cantrell invented the backyard ultra as a way to use his 150-acre farmland, as required by Tennessee’s Greenbelt tax program, and fulfill his wish to make a race with no finish line.It worked and quickly grew in popularity because it doesn’t require permits or much in the way of logistics as many mountain-central ultra races do.“You just shake your head in amazement,” he tol...