James Carr, from Workington, will today begin a 4-day challenge in a bid to raise £10,000 for charity.
He's hoping to raise money for 2-year-old Emily Shutt, who's being treated for leukaemia both at home and at the Royal Victoria Infirmary in Newcastle.
Mr Carr, 37, has lost 4 stones in weight since September last year and the training and gym sessions have encouraged him to take on the challenge.
The event takes place over 4 days, beginning with a marathon from Workington to Whitehaven today.
The following two days will feature rowing and swimming challenges before finishing with a coast to coast cycle event in Newcastle on Tuesday 11th September.
More top news
Firefighters at the Sellafield nuclear site will go on strike tomorrow, as part of a long running dispute over pay.
More harsh weather is expected in Cumbria, Dumfries and Galloway and the Scottish Borders, with possible delays to journey times.
Peter Morrison sent a string of WhatsApp messages, before hitting two highways officers on the M6, killing one and paralysing the other.