When Wang Chen immigrated to the United States in 2000 after retiring from China’s national table tennis team, she never imagined she would keep playing in her adopted country. But at 26, when most professional Chinese players have stopped competing, she began a second act that led to the Beijing Olympics, where she reached the quarterfinals, the furthest any American has reached since table tennis became an Olympic sport in 1988.

Wang was not alone on that path. A look at national table tennis teams over the last few decades shows hundreds of Chinese players who took their superior game abroad. More often than not, they became the best players wherever they landed.

But now, Wang represents an endangered breed of player. After the Beijing Games, the International Table Tennis Federation, the sport’s governing body, established waiting periods and other restrictions to make it harder for players to represent new countries after relocating. The I.T.T.F. said it did so because the widespread presence of Chinese players on national teams around the world hindered the development of local talent.

For decades, China has been the sport’s powerhouse. When the I.T.T.F. recognized China over Taiwan in 1953, that was enough for Chairman Mao Zedong to put together a system for churning out an army of superplayers who could dominate the sport. And they did: China has won a vast majority of world titles in the last 50 years and 20 of 24 Olympic gold medals. In Rotterdam, where the world championships started Sunday, the Chinese team featured four of the top five ranked men and all of the top five women in singles competition. (Germany, with Timo Boll at No. 2, has the only other top-ranked player.)