A reasonable amount is the amount of time it takes you to feel well prepared for your client’s session (or program) or group exercise class. For each of my clients, I probably spend about 15 minutes as well reviewing the previous sessions and looking for any modifications or progressions to the workout. Many times I have a plan in place, but I also always have Plan B depending on how the client feels that day. Always expect the unexpected.
For my group exercise classes, on average I probably spend 15 minutes as well to prepare–many times it’s less than this. I’ve been teaching for many years and can put together a well prepared class in little time. However, if there are new moves or sequence of moves to incorporate it may take me a little longer. Sometimes I can get caught up in searching new resources.
So, wow, all said and done it looks like a few hours per week outside of training and teaching.
It may get easier for you the more you train and teach! I hope things are going well for you.