The commander is under no obligation to allow you to go to the gym. The commander can direct you to conduct PT at the unit location within the limits of your profile. They may even assign you a supervisor responsible for developing a routine for you during this time. The only limit is that you cannot be directed to do something in violation of your profile. The command could improvise and put together a series of sandbags of varying weights is they desire and allow you to lift those or they could eliminate the requirement to lift and require you to do a series of exercises as outlined in FM 7-22 that do not violate your profile.