Initially Guttmann was adamant the Games would only be open to those with spinal cord injuries and for 16 years (1960 -1976) this remained the case.
In 1976, though this changed with the addition of two new athlete classes; athletes with a visual impairment and athletes who were amputees.
In 1980 athletes with cerebral palsy were added and in 1984 a fifth category, called 'les autres' which covers athletes who do not fit into the other categories already outlined.
In 1996 the sixth, and to date, final impairment group was added for the first time, athletes with an intellectual disability (ID), known in the UK as learning disability.
Although athletes with an intellectual disability were admitted in 1996 not long after Sydney 2000 was over, the very next Games, they were out again.
A Spanish journalist, Carlos Ribagorda, became part of the Spanish Basketball team with intellectual disabilities even though he had no impairment. At the Sydney Games he helped Spain take gold in an emphatic 87 to 63 point win over Russia. Barely had the medal been placed round his neck when he told his story claiming many of the team, not just himself, had not been checked for an impairment.
After an investigation found his story to be true, the Spanish team were ordered to return their medals and athletes with learning disability were banned from participation in future Games until a more robust, accurate way could be found to verify an athlete's disability within a particular sport.
In 2009 the IPC were satisfied of new testing methods ensuring athletes with learning disability could compete in three of the 20 sports at London - Athletics, Swimming and Table Tennis. The decision meant that for London 2012 the number of disability groups returned to six for the first time in more than a decade.