There are gyms at several resorts. We stayed at CBR and my daughter went to CSR a few times to use the facilities. I think it's $15 a day if you are not staying there. We had a rental car which made it that much easier. Otherwise you have to bus to a park, or Downtown, and transfer to a bus to CSR, as there are no resort to resort buses. Taxi would be another option.
then gym is $25.00 for length of stay i use boardwalk all the time and i stay at pop or allstars,,i do it all the time ,,you can use any gym on disney property..they have cybex and free weights and all cardio equip you need