Wheelchair basketball, from its inception in the USA during World War II, had developed by the mid-1960s into the most physically and technically demanding of wheelchair sports. In 1961, athletes affected by poliomyelitis entered the games at Stoke Mandeville for the first time and this increased the great differences in physical ability among players. Until 1966 two forms of competition existed in wheelchair basketball, one for teams of players with complete lesions (mostly spinal cord injured) and another for teams of players with incomplete lesions (mostly polio cases).