From Rob Groves' excellent hand cycling site: http://www.hand-cycling.co.uk/
"Hand-cycling is becoming one of the world’s fastest growing disability sport, the speed and adrenalin in this new sport is very addictive and its recent inclusion into the Paralympic program only highlights its popularity. Classifications of both paraplegic and tetraplegic compete in time trials and road races of differing distances using cycles propelled by arm cranks. Hand cycling began in the 1980s as a recreational sport. Early equipment was hard to find, clunky, and expensive. The leap from “leg only” powered to “arm powered” was made by cyclists from within the ranks of the human powered vehicle movement. Ironically, the original hand cycle was not intended for someone with a disability. Nonetheless, the development made it possible for individuals of all abilities to experience the joy of cycling. Today, hand cyclists reap the benefits of both the modern cycling industry and cutting-edge wheelchair technology, including light weight components, high pressure tires, wide-range gearing systems, hi-tech. seating systems, hydration systems, and ingenious steering systems for optimal handling."