Olympics
Through most of the 20th century the Olympics nominally only allowed amateur athletes to participate and this amateur code was strictly enforced - Jim Thorpe was stripped of track and field medals for having taken expense money for playing baseball in 1912.
Later on, however, successful Olympians from Western countries often accepted endorsement contracts from sponsors. Complex rules, involving the payment of the athlete's earnings into trust funds rather than directly to the athletes themselves, were developed in an attempt to work around this issue, but the intellectual evasion involved was considered embarrassing to the Olympic movement and the key Olympic sports by some. In the same era, the nations of the Communist bloc entered teams of Olympians who were all nominally students, soldiers, or working in a profession, but many of whom were in reality paid by the state to train on a full-time basis. (Cuba, North Korea, and to some extent China still do this; although China allows professionalism in popular team sports, it can be assumed that athletes in disciplines such as gymnastics from these countries are trained in state academies and have state-given stipends.)
After the 1972 retirement of IOC President Avery Brundage, the Olympic amateurism rules were steadily relaxed and in many areas amount only to technicalities and lip service. In the United States, the Amateur Sports Act of 1978 prohibits national governing bodies from having more stringent standards of amateur status than required by international governing bodies of respective sports.
Olympic regulations regarding amateur status of athletes were eventually abandoned in the 1990s with the exception of boxing and wrestling, where the rules for participation still require amateur status rather than professional status for the safety of the participants.
Read more about this topic: Amateur Sports