A MAN is about to take on a gruelling mountain bike challenge - despite only being able to pedal with one leg.

Robert Tyas, 58, of Skelmanthorpe, will be undertaking the Holme Valley Mountain Bike Challenge on Sunday, using a specially-adapted bike.

Mr Tyas contracted osteomyelitis, a disease which attacks bones and joints, when he was just 12.

The disease damaged his left hip joint and, as hip replacements had not been invented, he had to have the joint fused to his pelvis.

This meant he had no moveable joint - making walking difficult and cycling impossible.

But three years ago, Mr Tyas retired from his technology teaching job at Honley High School and decided he wanted to take up cycling.

So he adapted a mountain bike to meet his needs.

Special clips have been fitted to the right pedal to allow his foot to stay firmly on the pedal during its full rotation.

A rest has been added to the back of the bike for his left leg.

He said: "It's hard work to pedal with just one foot. But after doing 1,000 miles in my first year of retirement I got used to it.

"However, I've only ever done about 20 miles in one go before, so the 28-mile Holme Valley event will be a challenge."

The route, which starts and ends at Hade Edge, will take in tough off-road terrain, plus lanes.

Mr Tyas will be collecting sponsorship for the challenge.

All the cash he raises will be split between Macmillan Cancer Relief and the 1st Holme Valley Scout group.

He chose the two charities because they are linked to the Huddersfield Falcon Motorcycle Club, of which he is secretary and his wife, Elaine, is treasurer.

Mr Tyas said: "Motorbikes are something I have always been able to ride, despite my disability.

"My club has done fundraising events every year and we usually support Macmillan.

"But this year, the Scouts asked if we would help them to send two of their members to Africa next year."

One of the Scouts heading for Africa in 2006 is Mr Tyas's 14-year-old granddaughter, Natalie Smith.

She will be accompanied by fellow Scout Damien Armitage, also 14.

They will spend three weeks working on marine conservation and animal management projects, as well as helping at orphanages.

Natalie will be tackling the mountain bike challenge with Mr Tyas and her mother, Louise Smith.

Mr Tyas said: "We've been training together on the route. Hopefully some more members of the Huddersfield Falcons will take up the challenge and help raise more money."

Anyone who wants to sponsor Mr Tyas and his family should phone him on 01484 863144.