Track and field athletes from the United States and abroad are unionizing, they said Friday, in part to fight a rule against promoting private sponsors, achieve collective bargaining and seek prize money in the Olympics.

Some of the biggest names in the sport, including Americans Sanya Richards-Ross and Bernard Lagat and Jamaican stars Usain Bolt and Yohan Blake, are part of a movement that gained momentum during the London Games. At the heart of the matter is Rule 40, an International Olympic Committee bylaw that prohibits Olympic participants from advertising for non-Olympic sponsors just before and during the Games.