"most" no. Define what "fixed" means first. Do they push a horse to its fullest week after week, no. Most horses would not be able to race week to week if they pushed 100% every week. They would be like the Tbreds and need 3 to 6 weeks off after every race. That being said, If they feel the horse has little chance to compete against a given field they might not pust it as hard, but that does not mean they wont try to win if there is a chance to win without sacrificing the horse and what is left in the tank next week. Are many class conscience, and afraid to win, where they have to move up, Yeah. But I have seen that theory back fire.