She didn't seem stressed on Friday, though. After all, it was a mere prologue for a 1000km bike race through the Monaro next month.

While most people opt for a sleep-in on Sundays, the Canberra school teacher doesn't shy away from discomfort.

Ms Marshall is the only Australian woman to have ever completed the Enduroman Arch to Arc. The triathlon involves a 140km run from London to Dover, a 35km swim across the English Channel and a 300km cycle from Calais to Paris.

That's 28 bridge-to-bridge runs, 700 laps of the big pool at the Australian Institute of Sport and about 11 laps of Lake Burley Griffin by bike.

Fellow ultra runner Martin Fryer made his way to the mountains this weekend, too, helping put on a multisport race combining swimming, mountain biking, paddling and running on and around Lake Jindabyne.

While currently recovering from injury, the Weston doctor was somewhat of a legend in the world of ultra running.

Dr Fryer had competed in - and won - many of what were considered the world's toughest events.

Over the years, both Ms Marshall and Dr Fryer had acquired an artillery of mental methods to conquer the doubt and pain that creeps in after days and weeks of pushing their bodies to the limit.

They said breaking up long distances with the promise of a food reward or a walk at the next goal post could be enough to push through the next 10, 20 and then 50km.

Sometimes those tricks helped the kilometres sail past unnoticed, but sometimes the rewards talk wasn't enough.

Dr Fryer said during a New York event where competitors tried to clock up the most laps around a one-mile loop in 10 days, he fell into a "deep, dark despair" on day two.

"I actually said to my crew, 'That's it I'm packing up and going back to Australia'," Dr Fryer said.

Despite being in the lead, the crew had to convince their mentally spent runner after two days of hardly closing his eyes, a little sleep was probably all that was required.

Dr Fryer went on to win the event, clocking up more than 1100km over the 10 days.

They said while positive self talk could allow them to transcend beyond the physical discomfort, avoiding the "sleep monsters" in the night was important.

Strangely, Ms Marshall was prone to avocado tree hallucinations, while Dr Fryer once got the wobbles at the 800km mark after seeing gremlins and goblins at night during one of his six-day races.

Ms Marshall said having the right support person was crucial, crediting her partner Erin Foley as her "logistics guru".

"The biggest thing for me is my nutrition and making sure I'm eating and drinking right," Ms Marshall said.

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"She can pick up when I'm mentally sort of going into a trough and she knows what to say to pep me up or when to just give me an egg and bacon roll."

Depending on COVID, Ms Marshall planned to run, ride and swim the length of New Zealand later this year.

The race involved riding the South Island, swimming the Cook Strait and then running the Te Araroa Trail; in total around 2400km.

Dr Fryer's ultimate goal was an event which involved running around an 800m block in the middle of New York in summer, trying to out lap opponents.

To stay in the running, competitors had to complete 100km a day for 50 days in a row.

"I'm not sure if I'm too old to get there now, though," Dr Fryer said.

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