IT's enough to make you weak the knees just thinking about but competitors are already signing up in their droves to complete what could be the world's toughest triathlon.

TriathlonX will see 200 hardy souls travel in total more than 140 miles and scale 5,100 metres of ascent in a challenge that will test mind, body and soul.

In a new partnership with the Youth Hostel Association, organiser Mark Blackburn has designed the 2016 route to start from the YHA Ambleside, at the head of Windermere.

"We are thrilled with the new arrangement with YHA which will mean that our race will be much more accessible to competitors from all over the world," he said. "It will be another great sporting event for Windermere, Ambleside and the Lake District.”

On June 25 competitors will swim twice round Seamew Crag island in Windermere and then cycle all the Lake District passes - Honister; Newlands; Whinlatter; Hardknott; Wrynose - on the route of the famed 112 mile Fred Whitton challenge, which takes in a huge 3,700m elevation gain.

The marathon run of 26 miles will take the athletes out and back to the top of the 978m Scafell Pike, England's highest mountain, via Elterwater and Great Langdale.

Andy Barnett, YHA operations manager, said: “YHA Ambleside is the perfect setting for Triathlon X and I’m delighted that it will be starting and finishing here. Being a Lake District youth hostel, we’re geared up for outdoor events and have the facilities for competitors - whether that’s bike storage, a drying room for clothes, a bed for the night or simply a hot meal and drink."

He added: “We’re delighted that Triathlon X and its participants have chosen to support YHA’s bursary fund for disadvantaged young people, Breaks for Kids."

Richard Greenwood, Cumbria Tourism’s head of operations, said: "As the UK's Adventure Capital the Lake District, Cumbria has an adrenaline fuelled calendar of outdoor challenge events every year and this event is no exception. There are plenty of events for the first time competitor, and others for more experienced athletes that require total endurance and dedication.

"Hosting TriathlonX on Windermere will allow even more people to access this high level event and allow them to come and embrace their adventurous side here in the Lake District."

Visit www.wasdalex.co.uk/index.php/enter-2016 for more details and to enter.