Dumbbells and barbells in Grand Theft Auto San Andreas Gym can exercise muscles. Treadmill can exercise endurance, running and swimming can also exercise endurance and increase muscles (this is too slow).

It is useful to click the left mouse button with the space bar.

Besides, I usually eat more. Generally, three points of obesity can be converted into a little muscle and a little endurance.

There are restrictions in the gym, so you can't exercise to a certain extent, and you must wait until the next day (24 hours apart, not enough).