It's pretty costly to use the gyms at WDW but if you really enjoy working out then it's worth it. I believe you can buy length of stay passes. I'm sure someone has more info on that.
I thought it was around $15 a day to use the gym.
I'd like some detailed info on the gym at AKL, as well.
I know I will be scheduling a massage for my DH when we are there in October-it wasn't a problem at WL-just called the concierge desk and they called the gym and I had a massage scheduled for him in about 5 minutes for that very same evening.