The exercise you SHOULD be doing

If you have been going to the gym for any length of time you will inevitably have your favorite exercises for each body part.

I do, we all do.

That's absolutely fine. It's actually a good thing because it shows you have realized which exercises "work" with your body, biomechanically and neurologically.

BUT, if you have a lagging body part, you are executing your favored exercises correctly, with the right tempo, using a variety of rep ranges and you are still struggling then I suggest trying something new.

There are multiple exercises out there for every body part and then on top of that, there are also many variations of each exercise. Minor tweaks can make a massive difference to the transfer of stress and load on the target muscle.

This isn't about "shocking" the muscle, it's about discovering a plane of movement which helps you stimulate the fibers within that muscle to a degree where you haven't been able to before now.