How do I get my reserve and U18's match preperation to stop changing?

[Fraz100]

I'm trying to change the match preparation so I can put players on heavy personal workloads, but whenever I change it my u18 and reserve managers keep on reverting it back so the players with the heavy workloads now have 'very heavy' workloads. Is there any way to stop this happening?

EDIT - By match preparation I mean the 'scheduling' slider.