It’s very unlikely that a member could do much if they felt that their gym was too full. The main problem is how you define ‘too full’.
- the overall number of members
- the number of members in the gym at any one time
- a waiting time of over X minutes to use a machine
- or which machines are available. It’s fair to say that you will usually find a machine available but it might not be the one you want.
There may however be other ways of ending a gym membership if your contract isn’t ‘rolling’ where you can give one month’s notice.