Marty Dent has raced around the world on some of the toughest marathon courses, but even after decades on the road the Olympian admits he doesn't know what to expect in his six-hour slog at Mount Stromlo on Saturday night.
Six months after running past some of London's landmarks at the Olympic Games, Dent is preparing for a new challenge at the Stromlo Running Festival.
Instead of doing his usual 42 kilometres and smashing himself in a marathon, Dent will push his body to the limit in a 100km grind for the first time in his career.
The plan is to start on pace with the Australian record of six hours and 29 minutes and then see what's left in the tank when he gets to the 70km mark.
''I ran my first marathon over 10 years ago now but I was just looking for another challenge,'' Dent said.
''I didn't feel like focusing on another major marathon and I thought this was pretty convenient.''
The Stromlo Running Festival, in its fifth year, started on Friday night with primary and high school challenges. The action heats up on Saturday with the cross-country event, a corporate challenge, a 50km race, a six-hour race, a 12-hour race and the 100km event. Record numbers have entered the 30km Lightning Strike race on Sunday.
Darwin's Emma Cameron - part of the Indigenous Marathon Program - will run in the 30km event as a selection test event for the Boston Marathon.
Dent spent Friday trying to get enough fuel into his body to get him through the entire race.
The 34-year-old will race 100 laps of a 1km circuit from 7pm and is estimating he will finish between 1am and 2am.
''One of the reasons I chose to do this race is because it's at home and I'll have family and friends there, quite a few people are interested to see how I go and if I crash and burn,'' Dent said.
''The intensity is a lot lower than the marathon and hopefully I don't get wobbly like you do at the end of a marathon when the pace is still pretty quick. Hopefully the suffering isn't too bad.''
There will be no rest for Dent - he'll return to his job at the Department of Industry, Innovation, Science, Research and Tertiary Education.
His London marathon time has qualified him for the world championships this year, but he will wait to see if Athletics Australia selects him before preparing.
He ran 6756km last year on his way to the biggest stage of his career at the London Olympics.
Dent still wants to compete at the Commonwealth Games next year. But for now he's focused on the 100km and the impending birth of his fourth child in April.