"It's like being punched in the face," "Not hard, just a little bit. But you do it again, and again, and again. Eventually you start to flinch when you see the punch coming."
Think you can run 4.16666 miles in an hour? Probably.
Could you do it again the following hour? Quite possibly.
How about the hour after that? The legs might be feeling it by now.
What if you had to do it every hour for the next two or three days?
It's hard to say exactly how long you'll be running for - because this race only finishes when there's one person left standing.
The trouble is, some runners can keep going for quite a long time. The current record - held by a Belgian dentist - is 75 hours, or 312 miles.
Welcome to Big Dog's Backyard Ultra, the toughest - and weirdest - race you've never heard of.
First, the name.
Big Dog is race organiser Gary Cantrell's pet bulldog, who spends most of his time snoozing under a table at the start-finish line, barely lifting a droopy eyelid as dozens of sleep-deprived runners shuffle past him day and night.
The backyard is Cantrell and wife Sandra's sprawling farm in Bell Buckle, rural Tennessee, where runners complete a loop of the woods every hour during the day, before switching to an out-and-back route on the road at night for safety reasons.
And 'ultra' is surely the most apt title for a race in which someone can run for 300 miles yet still be classed as a Did Not Finish. "It's like being punched in the face," chuckles Cantrell from his kitchen via Zoom. "Not hard, just a little bit. But you do it again, and again, and again. Eventually you start to flinch when you see the punch coming."
Guillaume Calmettes, a French software engineer who ran 245 miles - 59 hours - to win in 2017, says: "It's painful, but it's painful in a good way."
"I enjoy some level of suffering," says American Maggie Guterl, who became the first woman to win when she breezed her way through 250 miles in 2019. "Most ultra-runners don't want to go to a spa for a relaxing break."
The event is endearingly low-key: makeshift tents double as runners' homes for days on end, food is whatever you can rustle up on a camping stove, and the closest that competitors get to comfort is slumping in a fold-up chair with their feet perched on a cool box.
"It's totally underground - way off the grid," says Canadian Dave Proctor, who clocked up 216 miles to 'finish' third in 2019. "We were running in the middle of the night and a police car came up with the siren on wondering what we were doing."
The hourly routine is the stuff of T-shirt slogans: run, eat, sleep, repeat. The reality is less straight forward - have you ever tried scoffing your dinner, going to the toilet, having a nap and changing your socks in less than 15 minutes?
The lucky ones will have persuaded a friend to be their support crew, although by the time the race is down to the final few runners there is no shortage of help from those who have dropped out.
Proctor, a 40-year-old massage therapist, says: "Later on you need somebody to tell you what to do - eat this, drink this, go to the bathroom and don't forget to wipe your bum. It sounds stupid but certain parts of your brain stop functioning."
There are other problems inherent in a race that has no set finish line: Guterl almost missed her flight home the year she won because she ran for 60 hours; runners go without sleep for so long that they start hallucinating; and just how do you convince yourself to keep moving when you're a physical and mental wreck and the easiest thing in the world is to stop?
Source: BBC Sport