Quote from peilthetraveler:
Prior to 1952, there was only one kind of athlete allowed in the Olympic Games-- Winter and Summer. Then the Soviet Union and its 14 Communist allies entered the games. All their athletes were fully supported by their governments. None ever held a job. They trained 8 hours a day, 365 days a year. They won most of the gold, silver and bronze during the 1970s and 1980s. None of these athletes were amateur, and yet they were allowed to compete in the Olympics (which made athletes sign pledges that they were amateurs) because the communist athletes were not definable, they were not "pros" like Michael Jordan. It was unfair. So in 1986, the IOC (International Olympic Committee) changed its rule book (Olympic Charter) to allow "all the world's great male and female athletes to participate."