They have to run a staggering 5649 laps of an 883 metre course on a concrete footpath in the summer heat, with the winner taking just over 47 days last year.
Weaving around New Yorkers going about their lives from 6am to midnight, runners take a break to sleep then return the next morning to head in the opposite direction.
There is no prizemoney. Just a modest trophy or a T-shirt.
As the new documentary 3100: Run and Become shows, the Self-Transcendence 3100 Mile Race is more than a test of physical endurance. Runners have to go deep into their emotional resilience to finish before the 52-day cut-off, which means averaging almost 100 kilometres a day.
The film follows a Finnish newspaper delivery man, Ashprihanal Aalto, and an Austrian concert cellist, Shamita Achenbach-Konig, as they take on the race in extreme temperatures.
Director Sanjay Rawal, a filmmaker and marathon runner who lives a few blocks away from the course, watched the first race in 1997 and thought it looked like a shocking way to spend the summer.
“But as I observed the race for 20 years and made friends with some of the runners, I saw that they were getting a lot more out of running than I ever did,” he said from New York. “My curiosity stemmed from observing that after one or two or three weeks, the faces of the runners literally went from being clenched and focused to being serene.”
The 3100 was started by Indian spiritual leader Sri Chinmoy, who had a meditation centre nearby in Queens, to encourage runners to push their limits.
“For most first-timers, the experience looks and feels like utter agony until the last quarter of the race,” Mr Rawal said. “There’s a point in each race – sometimes not until the fourth or fifth week – where the happiness finally exceeds the pain and it just becomes fun in a weird, non-masochistic way.”
He believes ordinary runners can learn from these racers, just as he has done to clock an impressive 2 hours and 37 minutes marathon at the age of 45 recently.
“I’ve seen there is a way to find happiness in running,” Mr Rawal said. “I’ve learned that comes from disconnecting from my playlist and from not worrying about how many miles I’m doing and how fast I’m going.
“It’s disconnecting from expectations and trying to be in the moment.”
Australian runner Grahak Cunningham has raced the 3100 five times – winning in 2012 – and plans to do it again. The 42-year-old became interested after learning meditation from Sri Chinmoy when he was 19 and, after following an Australian who ran it one year, was inspired to enter.
Mr Cunningham has become very familiar with the rectangular course around a high school and playground.
“I know every crack in the pavement,” he said. “If you get to 111 laps each day, you’ve [virtually] done 100 kilometres or 60 miles and that’s what you need to finish. You know you’re having a good day when you get to 111 laps and you’ve still got a few hours to go.”
While recognising the 3100 seems crazy, Mr Cunningham said he reaches a point every race where he feels “happy and really peaceful”.
“You’re running round and round a block for 18 hours a day but there’s really nothing like it in terms of a way to grow as a person,” he said. You have to have resilience and inner strength. You’ve got to keep your focus and your concentration. You’ve got to stay happy and positive so it’s a really good metaphor for life.
“After doing it I realised, gee, if you put your mind to something, you can really do anything.”
The documentary screens with a Skype Q&A with director Sanjay Rawal at the National Film and Sound Archive in Canberra on Thursday , Randwick Ritz on Friday Fairmont Resort & Spa in the Blue Mountains on Saturday , Cinema Nova in Melbourne on March 27 then streams on Amazon Prime and iTunes from March 30.
Garry Maddox is a Senior Writer for The Sydney Morning Herald.