Guide

What is a backyard ultra?

A backyard ultra is a last-runner-standing race. Everyone sets off on the same loop at the top of every hour and has to be back inside that hour to start the next one. There is no finish line and no set distance. It ends when one runner is left.

The rules, in full

The format is unusually short to state, which is part of its appeal:

• The loop is 6.706 km — 4.167 miles. Twenty-four of them is 100 miles exactly, which is the whole reason for the number.
• A new loop starts on the hour, every hour. Not an hour after you finished the last one.
• You must be in the starting pen when the hour begins. Finish in 45 minutes and you get 15 minutes; finish in 59 and you get one.
• Fail to complete a loop inside the hour, or fail to start the next one, and you are out.
• It continues until one runner is left — and that runner has to complete one more loop, alone, to be declared the winner.

The last point is the one that surprises people. If two runners are left and both quit at the same time, there is no winner at all. Everyone who is not the last runner standing records a DNF, however far they went. A backyard ultra with 200 entrants has 199 DNFs and one finisher.

Where it came from

The format was created by Gary Cantrell — better known as Lazarus Lake, the man behind the Barkley Marathons — and first run as Big's Backyard Ultra in Bell Buckle, Tennessee. It is named after his dog, Big.

Satellite races now run all over the world, most using the same 6.706 km loop so that results are comparable. Many run a trail loop in daylight and switch to a road loop overnight, so the distance holds while the footing stops being a lottery in the dark.

The vocabulary

What people are saying at the start line

Word	Means
Yard	One loop, and by extension one hour of the race. “I got 32 yards” means 32 hours and a little over 133 miles.
Corral	The pen everyone gathers in before each start — and, loosely, the hour itself.
Cut-off	The deadline the loop has to be finished inside. The plainer word for the same thing, and what this app uses.
Buffer	The gap between finishing a loop and the next hour starting. Your rest.
Assist	The runner who lasts second-longest, credited for forcing the winner to run one more yard.

Why it is harder than it sounds

A 47-minute loop is an easy run. The difficulty is not the loop, it is that you have to do it again in thirteen minutes, and again after that, through a night, and possibly through a second one. Sleep deprivation and the accumulating cost of eating, changing and treating your feet inside a shrinking window is what ends most races — not pace.

This is also why the number that matters is the buffer rather than the split. Work out what a lap time actually buys you with the lap and rest calculator, or read why the loop is 6.706 km.