You unfortunately can’t just work on your competition movements to get better at them. A lot of secondary muscles have to be considered if you want to improve your performance on the squat, bench press or deadlift and such.
The question is what muscles work in priority?
Certainty it’s important to work a minimum of every muscle, they are useful and help keep a good balance, and several injuries are due to an imbalance of antagonist muscles, such as weak lower back and weak abs, and all of this will increase the risk of injuries.
Many beginners also make the error of thinking that to be stronger on the bench, they have to do only pecs exercises, or quads for a bigger squat, but that’s all false. A strong bench, squat, deadlift or clean and press involves your whole body. The more muscles involved in the execution of a given movement, the more weight can be lifted. I hope this enlightens you on some bs you probably heard in your typical gym.
Now let’s put that to practice.
When you squat or deadlift, the range of muscles that you work is pretty similar: the posterior chain which involves hamstrings, glutes and lower back. Some other important muscles as the quads are also involved, but here we’re talking about the posterior chain. When it comes to bench press, strong triceps, deltoids, lats and even biceps brachialis are really important, because all those muscles are involved in an explosive and well-lifted bench press. So, on the bench, it’s important to keep a good balance between the antagonist muscles (dorsal/pectoral, deltoid posterior and anterior) to avoid bad injuries again, such as the rotator cuffs.
Here is a chart of the principal exercises to do in addition to the basic exercises and the muscles they target.
These exercises are vital for the development of good muscle chains that are required for most athletes, and a lot for powerlifters. It's obvious that other exercises should not be overlooked, such as hammer curls, lateral raises, rows, adductor work, etc. All these exercises help to strengthen muscles and a general balance. I also recommend using as much or free weights as possible, because not only do they work the targeted muscles, but they work the stabilizers as well. You can perform any movement that a machine can provide, with a barbell, squat rack, bench and pull-up bar and get away better results because your body works harder. The more exercises you switch out from machines to free weights, the more muscles you pack on.
-Will, Hybreed Athletics