It is impressive but doesn't surprise me. My elder son was born with only one hand and one short arm and there is very little he can't do. When he was little we went to a couple of hospitals where there were a group of young people who were affected by the thalidomide drug. Seeing one young man in a wheel chair who had no legs at all and only hands which came out of his shoulders, who was propelling his chair by means of crutches, and who was just off for a game of football (ok crutch ball in his case) made me realise that we had nothing to worry about with Richard. Sometimes I wish it did hold him back, especially when he does things like abseiling, bungy jumping, scuba diving (he has all his certificates) and, his latest venture, mountain biking 3000 miles round Asia with his then fiancee (now wife).
With enough determination and family support, people are amazingly adaptable and resilient.
Still wouldn't fancy holding the tyre in my mouth though.