Sorry to ask but I wanted to ask the requirements for working out with the characters and Veronica
The only girl you can workout with is Sophia on weekday afternoons. You would need to buy the workout clothing from the mall first.
Now, having said that, you can work for Amy at the health club. There is only one girl that you would need to focus on and that's fitness babe. You would need to get her up to level 3 and receive an alternate form of "payment" from her (General #10 - more specifically, "Personal trainer" and General #11 - more specifically, "Personal trainer: protein shake").
You can also help Claire with her yoga every weekday morning on the rooftop, and eventually join Claire, Veronica and Ashley for group yoga Saturday mornings. But you would need to progress Ashley's and Veronica's storylines first.