TV presenter Paddy McGuinness has said Sir Chris Hoy pushed him to his "absolute limits" when they trained together ahead of his ultra-endurance cycling challenge for BBC Children in Need.
McGuinness, 51, is set to ride nearly 300 miles (483km) when he sets off from Wrexham in Wales later, before aiming to arrive at the finish line on Friday in Glasgow, Scotland.
"Chris Hoy has been absolutely, as you can imagine with someone like him, outstanding, first class, brilliant with his advice," McGuinness said.
"When I go on a bike ride with Chris, I really know about it, because he pushes me to my absolute limits," he added.
McGuinness, who hosts a Sunday morning show on BBC Radio 2, will cycle through three nations and eight counties on a modified Raleigh Chopper bike.
The Bolton-native said he was motivated to take on the challenge by the people he had met who benefitted from projects funded by BBC Children in Need.
"When you meet these people... that's what spurs you on, and when you see the work that's being done in and around it, and again, when you're out and about, just people stopping me," he said.
Sir Chris, 48, announced last month he had been diagnosed with terminal prostate cancer.
The Olympic gold medallist told BBC Breakfast the news of his diagnosis came "completely out the blue", adding it had been the "toughest year of our lives so far by some stretch".
He said chemotherapy had been "one of the biggest challenges I've ever faced and gone through".
But Sir Chris added he had tried to focus on the positives and see it as "a good thing, we're here to try and to start punching back".
This year's televised Children in Need appeal will take place on Friday, the day McGuinness hopes to complete his cycling challenge, at 19:00 GMT on BBC One.