An ultra-marathon runner who only started in the sport three years ago says his 231km desert triumph was "an eating competition, with some running thrown in".

Scottish-born Nick Bamford was smiling, standing and coherent on Sunday after running for almost two days straight with no sleep.

"The main limit on your speed is how well you can eat," the 36-year-old said. 

Mr Bamford completed the Sonder Monster in Central Australia in 46 hours, 57 minutes and two seconds. 

He was sustained by water, energy gels and McDonald's meals brought to him by his crew during two cold nights where the temperature dropped below 5 degrees Celsius and long days under the harsh desert sun.

The race began with a steep, rocky climb to the top of Mount Sonder and continued along the entire length Larapinta Trail west of Alice Springs - a journey which most people took at least a fortnight to hike. 

"Every other step I felt like I was kicking a rock," Mr Bamford said. 

He said he loved being on the trail and hanging out with the people and volunteers.

"It is really just a fun thing, I don't really have a deeper story than that," he said.

Mr Bamford said he would recover from his win and then launch into training for his next challenge: the ultra trail du Mont-Blanc in France, in August. 

The Sonder Monster record is still held by 2019 winner Shane Johnstone, who completed the race in 40 hours, 55 minutes and 18 seconds.

Returning 2021 champion Elizabeth Woodgate, 58, finished in 58 hours, 20 minutes and 57 seconds.

The West Macs Monster annual running festival in Central Australia includes five events of various lengths along the Larapinta Trail. 

The second longest event, the 128km Ellery Monster, was won by Daniel James in a course record of 19 hours, 31 minutes and five seconds. 

Reesha Lewis, 35, was the first woman to cross the finish line in 22 hours, 31 minutes and 37 seconds. 

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She said she started running ultra-marathons after succeeding at an elite level in mountain running and boxing. 

"I've found my passion, my calling - I just love it," she said. 

Ms Lewis said she took a couple of tumbles early on in the race and badly injured her knee 17km from the start line, but it never occurred to her to pull out.  

"I'm here to complete a race," she said. 

The Ellery Monster is the longest race Ms Lewis has completed.

She said she had dreams days before the race about sitting on a rock in the dark, crying. 

"That didn't happen - it was actually beautiful," she said. 

"There's like nothing out there - it's pitch black. It's just you and your headlamp.

"You just get in your zone and enjoy it."