I have been reading lots of posts everywhere that the Gym moodlet is broken in the game. It actually makes skilling Athletic SLOWER in the gym. I tested it, having one sim skill at home and one sim skill at the gym, and lo and behold, they were right!
So I was wondering if someone knew where a fix was. I don't want to mess with tuning it myself unless I absolutely have to. And considering how well known the bug is, I would be surprised there isn't a fix out there I can just download as a package.