When doing the Sims 4: Body Builder aspiration, eventually you’ll get to the push the limits while energized milestone and this is one that has stumped even the best sims players out there.
There are two important aspects to completing this milestone, being able to get energized, and having the ability to push the limits.
To get your sim to have the option to push the limits, you just need to finish an entire workout (on equipment, or going for a jog) and once your first workout is done you should have the option to push the limits when clicking on equipment.
To get your sim to feel energized, they can take a brisk shower which I’ve always found to be the easiest option. You can also use the Bracing Breezes lot trait which will give your sim a random energized moodlet. You also have the option to use plumbob mood lamps in the room where you sim will workout to ensure that your sim will be energized!
Once your sim is feeling energized, click on a piece of workout equipment or click to go jogging on your sim. When you finish an hour of pushing the limits while energized you should see the milestone completed!