Right now we all go to the gym...once...ever.
It might be nice to change this a little in one of two ways:
1) Your pockets very slowly diminish back to 40kg over time so you have to go workout to get them back to 70kg.
2) You initially expand to 70kg, but can then do extra workouts that raise your pockets to some higher value that only lasts for a very short period of time. Example: I'm about to go make armor so I go to the gym and get pumped up and increase my pockets to 90kg, but only