We have a lot of changes in the Gym!
Let's start at the beginning, to enter the Gym we will need a pass, you can buy it at the counter store, there you will find a one-use pass and a 7-use pass. You can buy the pass you want and enter with it, once inside you will have a lot of npcs to talk to and up to 4 activities to use.
Every day you can do a training of 2 activities without being able to do the same 2 times, the activities are: Boxing, weights, running on a treadmill and stationary bicycle.
Doing these things will increase your character's entertainment.