Once the athlete begins to dread going to practice, it’s as good as over. Of course there are tough days, but a regular does of 600’s will make the typical sprinter/hurdler hate track. I say this from my personal experience and from speaking to former teammates. At the time none of us said a word. It was the 70’s and you simply didn’t speak up.
Look at programs with poor athlete retention and that is often the answer.