About 300 runners will hit the track as the Tumbarumba to Rosewood marathon launches its first ever race on Saturday.

"Some time ago I started what's called a Run Streak," John said.

"At the time I was struggling to find time to do exercise with the kids around," he said.

"And when I would go running, I'd try and do 10 kilometres and get injured because it was so intermittent.

"So my wife Clare put me onto a Run Streak, where you try and do at least a kilometre each day.

"I thought was a great idea because that takes as little as five or ten minutes out of each day, so there's no excuses."

As of April 18, John was on his 990th consecutive day and said the running has been great.

"By taking the girls with me out on runs, I would give my wife a bit of a break," he said.

"It's also been great for my physical health and mental wellbeing.

"But I think it's about time to close this chapter and get into some other exercise like cycling or swimming, because it is quite demanding.

"I think if I don't finish it at 1,000 days, the next round number could be 1,500.

"I think running a marathon is a great way to finish off the milestone, because when I first began, I'd hardly ever run five or ten kilometres before.

"Even now I'm not sure how I will go come Saturday, but I'm just trying to challenge myself and go out with a bit of a bang."

John's wife and their two children will also be taking part in the event.

"Clare will do the 10km race and run with Abby in the pram and Amy will run with her," he said.

The marathon will be held on the new Tumbarumba to Rosewood Rail Trail, which opened at the height of COVID in 2020.

The 42km race will start the day off departing from Tumbarumba at 7am and running a loop to Rosewood and back.

A half marathon will then depart from Rosewood at 9:15am, followed by a 10km run and 10km walk leaving Tumbarumba at 10am and 11am respectively.

Of key interest to athletes, the course has been officially certified through AIMS (Association of International Marathons and Distance Races) and will serve as a qualifier for international events including the Boston Marathon.

"It is the first marathon race to be officially metred in NSW," organiser Peter Fitzpatrick said.

"It is also the first one in the state to be run on a rail trail," he said.

The course is also unique in several ways.

"It's a very fast track and only has a climb of 85 metres from Rosewood to Tumbarumba," he said.

"It also features some of the old railway sites including Glenroy Siding, and Woolsley Park and is really worth the trip."

Participants have until Wednesday night to register online at: http://humehovellultra.com/trrt-entry-fees-and-entry/

Alternatively, people can register on the day.