I see a lot of gymcels who dont even know wich muscle does what and just go off wathever exercise their 30sec titkok video told them to do, so i tought id make my first post here a guide on that so that you can recognize wich exercises actually work a muscle, you gotta not be an iqlet and know what angles and planes are to read this post tho.

UPPER BODY: shoulder joint actions

First of all, the pecs: its composed of three parts, one actually separate (upper chest) and two regions : mid and lower pec, all of these perform horizontal adduction, wich is bringing your upper arm into your body on the transverse plane, so a chest press or chest fly for example, they both perform the same movement for chest, a horizontal adduction exercise will cover all your chest, and is enough to see gains.

HOWEVER, you dont wanna be mediocre right? So to put in the extra effort you can add exercies to bias the upper and lower pec.

The upper pec performs shoulder flexion too, so any exercise where your upper arm is going from the side to front of your body will be good, like a tucked arm path incline press (not too tucked tho, i think adding some horizontal adduction will be better).

For the lower chest, the fiber orientation makes it able to perform shoulder extension, so any exercise where your upper arm is going from 180° to 90° in the saggital plane will have a good deal of lower chest involvement, this is something like a full range pullover or a high to low fly to involve horizontal adduction, its also theorized that once your arm is far enough behind your body the lower pec could become a shoulder flexor so something like a dip could work it, not sure abt that tho.

Now lets move onto the back, specifically the muscles that do shoulder joint actions: the lats and rear dealts.

For the lats, it can perform shoulder extension and adduction on the frontal plane, for the first one its best on the 90° to 0° range of motion, so anything like a pullover, close grip pulldown or close grip row in wich your arm is going directly from the front to side of the body, this will bias more of your upper lats according to some, its not fully agreed on tho.

For adduction, its simple, just do anything that has your upper arm moving like in a pull up, this means: a wide grip pulldown, keenan flap, or pull ups itself, this is supposed to bias the lower lats more, try to keep your arm path on the frontal plane to not turn it onto a upper back row.

The rear delts are involved in both shoulder extension and shoulder abduction, so while any of the shoulder extension lat exercises will work it, i recomend incorporating some sort of shoulder abduction exercise, like a wide grip upper back row, or rear delt fly.

Moving onto the front and side delts: the front delts perform shoulder flexion, frontal plane abduction and also some internal adduction, so most pec exercises will train them, however i recomend having a front delts bias one, wich is one where you are doing either shoulder abduction (in frontal plane) or flexion, both in the 90° to 180° degrees range, so basically a shoulder press.

For the side delts, the main function is shoulder abduction on the frontal plane with the best leverage at 0-90° degrees, this means a lateral raise.

ill make another post on scapula and lower body.