Users of the Dam Strong outdoor gym at Shrewsbury Town FC's ground are planning a 24-hour event where one of them uses a training machine while another person has to hold up a beer barrel.
Dam Strong Team fundraiser Carol Camfield said: "The idea is to use the skiing machine, which is a kind of stand up rowing machine, but make it harder by needing the beer barrel to be held off the ground to use it."
Two of the group, Tom Davies and Sian Wood, have a friend and father of four who has had a tough time after being diagnosed with acute myeloid leukaemia in April.
They have been joined by fellow crossfitters and gym-goers Carol Camfield, Steve Burnside and Nathan Simon, who are in training for their madcap marathon fundraising effort on Friday, December 2.
"We will be raising awareness of stem cell donation and money for the Anthony Nolan charity," said Carol.
"We are hoping to raise money, educate and also encourage people to sign up to become stem cell and bone marrow donors, if they are able to."
On their JustGiving page they say: "Simon is in the middle of some really tough treatment. The aim is to prepare him for his stem cell transplant that will save his life and mean that, with time, he can start living again. Please help us to support our friend, by supporting this cause."
Carol and the other hardcore 24-hour fundraisers will be joined by about 20 others, including friends and family, for the marathon effort.
They have already raised £1,160 of a £2,000 target on the Just Giving website.
Timings for the marathon have been planned so they can end at 2pm on December 3 and allow Town fans to give their support and cash before the game against Lincoln City that is due to have an earlier than usual 12.30pm kick-off due to the World Cup.
To donate visit justgiving.com/fundraising/damstrong