Thousands of youngsters will be packing a punch as part of a fund-raising appeal to help a boy with a rare muscle and nerve-wasting illness.

Members of the Sama organisation, which runs martial arts clubs throughout the South, will hold a sponsored punch at classes from Monday.

The aim is to buy a special paraplegic sports wheelchair for 11-year-old Luis Coward, who has red and yellow belts in karate despite losing full use of his legs.

His mother Marie, 30, of Sparshott Road, Selsey, near Chichester, also plans to conquer her fear of heights by making a parachute jump in May to raise money towards research into the rare hereditary condition.

It was mistakenly thought to be cerebral palsy and took five years to diagnose.

She said: "I have a real terror of heights but I would do anything for my little boy."

Mrs Coward said going to Sama sessions had been a real tonic for Luis, who is being treated at the Great Ormond Street Hospital for children in London.

She said: "Sama has been brilliant and all the kids are so nice and cannot do enough for him. He was over the moon when he won his yellow belt a week ago and cannot wait for the certificate to arrive."

The organisation trains an estimated 5,000 youngsters a week in an area stretching from Eastbourne to Hampshire.

Club members have been asked to find sponsors for the event in which the number of punches they can throw in a minute will be counted.

Luis's father Tony, 30, is a fruit and vegetable wholesaler and the couple have two other sons Mitchell, seven, and Sam, six, who are unaffected.

Luis is a pupil at St Anthony's Special School in Chichester and needs a light-framed wheelchair for sport because his is too bulky to manoeuvre.

Mrs Coward said: "Research is badly needed because it could take between five and ten years to identify the gene which is causing the disease."

Luis's Sama instructor, Andy Drain, from Worthing, said: "He is an inspiration to all the kids and to myself. It puts everything into perspective.

"Any money above the amount needed for the wheelchair will go towards research."