I too am not quite sure how this would work with my business. I currently only take on clients that can work within my schedule. If they would like additional sessions and I don’t currently have the availability, I let them know that they will get the first option when it becomes available.
Personal training, is very personal. You develop a bond with the client. They share and give you additional insight into what is or is not working. They may not have that same bond or develop that if they’re being shuttled between different trainers.
That being said, with proper feedback between the trainers and a documentation system that supports it, it may be beneficial to the client to have a different pair of eyes and skill set work on them. For instance, I have a client who meets with me twice a week and a personal pilates instructor once a week. We often share notes and observations with the client’s ok.