After arriving back in Australia eight days ago, Comboyne mountain bike champion Luke Meier-Smith has created his own fun overlooking Sydney's central business district.

Within walking distance is the The Australian Golf Club while in the distance sits Royal Randwick Racecourse.

A little further afield is the Sydney Cricket Ground and Fox Studios, but the 18-year-old can only appreciate these landmarks from afar.

Instead of lying on the couch watching countless hours of Netflix, he set himself the challenge of running 100 kilometres in seven days.

He successfully achieved it just after 4pm on November 17.

"I was trying to kill time and raise money for the Westpac Rescue Helicopter as well," he said.

"I broke my femur three years ago and was flown by the Westpac so I thought it would be good to raise money for them."

A small portion of the funds raised will also go towards a follow-up operation in two weeks where doctors are expected to take some "hardware" out of Meier-Smith's leg.

It will then be six weeks out of action before a return to training for the national Down Hill and Pump Track junior champion ahead of the 2021 season.

Meier-Smith's two-bedroom location at the Meriton Suites was little more than 15 metres in area, meaning it required a lot of running back and forth to achieve the 100-kilometre goal.

"I don't know of too many people who have run 100 kilometres in a hotel room before so it's probably a world first," he said.

"A lot of people thought I wouldn't be able to do it, but it's been a good challenge and I've probably done a few thousand laps."

In total, Meier-Smith had to run 13 to 15 kilometres each day, taking an hour and a half to two hours to complete.

"After the first day I thought 'what have I done' because I had a few problems with my FitBit watch and connecting it so it took me nearly three hours to run 13 kilometres," he said.

"It's been a bit hard the last few days because I've gotten a bit bored and sore because running is pretty hard on your feet and knees."

Meier-Smith will return to elite racing next year, with his 2021 campaign set to start with the national championships in March.

The World Cup events begin in April.

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