A couple will take part in every Olympic sport over the 17 days of the Tokyo Games to raise money for charity.
Charlotte Nichols and Stuart Bates believe they are the first to attempt the feat that will see them run, throw and jump their way through almost 100 sports.
Their challenge will include a 50km speed walk, a 10km swim, a 240km road cycle and a marathon.
It is in memory of Mr Bates’ brother, Spencer Bates, known as Spenny, a father of two who died aged 49 from motor neurone disease in 2011.
The couple aim to raise £10,000 for the Motor Neurone Disease Association with their challenge, which they have dubbed the Spennylympics.
Miss Nichols, 21, who is studying to become a doctor at the University of Bristol, said: “We’re terrified and excited at the same time.
“It’s been a real journey already – we’ve had to learn loads of new sports and we’ve met some amazing people along the way.
“The training has been tough, particularly fitting it around studying medicine. But there have been some incredible moments too, like sailing in Weymouth as the sun was setting.
“It has been a chance for us both to think about Spenny a lot too. When you’re feeling achy and tired and you don’t want to go out and train, having him in your mind really helps.”
Miss Nichols and Mr Bates, 51, who works as a window cleaner in Oxford, will begin their challenge on July 23 – completing 96 sports in 17 days.
They will visit Reading to cycle on the velodrome, Bath for some of their track and field and Bristol to surf at The Wave inland surfing venue.
The couple, who live in Oxford, will go sailing and windsurfing in Weymouth – the home town of Mr Bates’ brother – and play a football match with his friends and family.
On the final day of their challenge, they will take on the marathon.
Mr Bates said his brother, who died leaving wife Nicky and sons Samuel and Isaac, was “a truly one-off character”.
“There is not a day goes by that his presence isn’t missed and we will continue to do everything that we can to raise money so that a cure can be found for this brutal and 100% fatal disease,” he added.
Since his death, the family have raised more than £100,000 for the Motor Neurone Disease Association.
The couple have recruited more than 55 former and current Olympians to be ambassadors for their challenge, including rower Ollie Cook, pole vaulter Holly Bradshaw and runner Sally Gunnell.
Others have offered lessons in sports from canoeing to rhythmic gymnastics, while the University of Bristol has given the pair free run of its sporting facilities.
Miss Nichols said she would find the 10-metre dive “daunting” but would get through it.
Mr Bates added: “There are so many events where there is a real danger of injury, so we will need a huge slice of luck along the way.
“Staying on the horse whilst showjumping is something giving me sleepless nights.”
The couple’s JustGiving page can be found here https://www.justgiving.com/fundraising/spennylympics