From the Olympic Programme Commission, 2002:
"In 1995, the IOC recognised the international bodies of the ‘games’ of bridge (WBF) and chess (FIDE) as IOC-recognised organisations. Following this, an increasing number of NOCs began officially affiliating the national federations of these bodies, and the IOC therefore reviewed the status of the International Federations within the Olympic Movement. The status of the two Federations changed in 1999, when the IOC acknowledged that bridge and chess should be considered as sports, and therefore the status of the respective IFs changed from recognised organisations to Recognised Federations.
However, in reviewing the requests of these sports for entry to the Olympic Programme in January 2002, the Programme Commission believed that the IOC should clarify the position of mind sports in relation to the Olympic Programme, and expressed the opinion that they should not be eligible for admission.
In this regard, while making reference extensively to ‘sports’, the Olympic Charter does not provide a definition of a sport. Therefore, the Olympic Programme Commission could present a broad definition of ‘mind sports’ to allow the position of the Commission and the IOC Executive Board to be applied in current and future cases.
While there is no global definition of what constitutes a sport, and what the difference between a sport and a game is, the most commonly accepted element of a sport is physical exertion in the conduct of competition. In this regard, ‘mind sports’ could be considered as sports where the physical elements are not necessarily performed by the player in the conduct of the competition."
Source:
http://www.olympic.org/Documents/Reports/EN/en_report_527.pdf