Cath Muir and Ruth Thompson will take part in the North Yorkshire Half Iron Man which starts at Ellerton Lakes.
The event on Sunday, August 3, includes a 1.5-mile swim, a 56-mile cycle, and ends with a half marathon.
Ms Muir was diagnosed with motor neurone disease (MND) 10 years ago and uses a wheelchair.
She said: “We take these crazy challenges on because we want to raise awareness and funds to help people with MND and their families.
“I am so happy after 11 years that I am still able to partake in these challenges and hope it shows other people with MND that there are still things they can enjoy out there.
“Ruth has always enjoyed pushing herself through the limit and is a machine when it comes to doing things a normal person would never dream of doing, so together we can take on this challenge for MND – I think we make a brilliant team.”
The sisters will complete the Iron Man using three modes of transport.
Ms Thompson will pull Ms Muir in a kayak during the swim, before taking on the cycle route from Ellerton to Eppleby via Catterick Village and Northallerton.
The challenge will end with Ms Thompson pushing her sister in a wheelchair during a half marathon around Eppleby.
The pair are raising money for the MND Association’s Hambleton and Richmondshire Group, which supports people living with MND across the region.
Ms Thompson said: “I’m doing these challenges because when I was nine, I got my first pair of boxing gloves, something which coincided with Ian asking Cath out and coming to pick her up at our house.
“Every time he came, I would have my boxing gloves on, ready to fight with him and because he was new to our family he wouldn’t say no.
“Now the tables have turned and Cath and Ian are putting me through my paces with their challenges – payback time for the annoying little sister.
“In the words of Kevin Sinfield, ‘I’m doing it for a mate!”
MND is a terminal neurological disease that affects more than 5,000 people in the UK. It can leave people unable to speak, eat, or breathe.
There are currently no effective treatments or a cure. To donate visit
