Fans of the Barkley Marathons are familiar with Lazarus Lake. One of his other events is Big's Backyard Ultra where participants run a 4.166667 mile loop at 40 minutes after the hour. During the day, it's a trail loop starting in Laz's back yard. At night, it's an out-and-back on the country road Laz lives on. This is not a random distance; it works out to 100 miles in 24 hours.
Runners must return within 60 minutes and they must start their next loop at exactly 40 minutes after the hour. All food, water, sleep, first aid and other breaks need to be squeezed into the minutes or seconds between loops. The winner is the Last Man Standing, which is also the generic name for this race format.
This year the Last Man Standing might be a Woman - the incredible Courtney Dauwalter who won Western States this year. After 57 hours and 237.5 miles, just 3 runners remain of 70+ who started. Defending champion Guillaume Calmettes was hobbled by tendinitis on Loop 55 and had to drop out. Greg Salveson was a finalist but did not finish his 57th loop in time to continue. Johan Steene of Sweden and Gavin Woody of Washington are the two other contenders.
Live results are available here, updated realtime - most interesting if you check at about 35 minutes past each hour. The record for this race format is 245.8 miles and it looks like they're going to pass it soon.