Oh yeah. I think my back muscles begin to fatigue when trying to sit in proper posture. I always want to lean to one side and use my arm as a crutch. I think this is what really did it for me. Having a weak core and lower back caused me to lean to one side on an arm rest. That side became weak. Then I spent way too much time on the computer in that position. Then I went into a job where I had to stand and use my hands in front of me all day. Muscles hot fatigued, burned out and eventually my shoulder just sort of collapsed down. My right shoulder does not like to retract. If I hold my arm out at 90 degrees and bend my elbow up at 90 degrees and try to rotate from elbow to hand down Infront of me that is where I am limited in motion. To make the full rotation my shoulder rolls forward. It's like my joint is really limited in that specific movement as well as my shoulder doesn't want to stay elevated and keep that space open. It's like my back muscles that keep the shoulders pull back and down gave up or something. My main goal is to try and make my back stronger and keep stretching out my chest. Strengthen my neck muscles so that they can also bare the weight of my shoulder as well. For instance.. the SCM connects to your collarbone and sternum. You need to have a strong SCM to keep these lifted as well as have healthy scalenes that can allow your ribs to move up and down normally. So strengthen back, romboids, upper, mid, lower traps, strengthen neck (chin tucks, neck curls) stretch chest, pec minor, lay on towels rolled up length wise, doorway/corner stretch, and many others. Soft tissue release with a lacrosse ball is great too. Dry needling for pec minor is nice.. idk I'm just sharing ideas. Not saying it's wrong or right but this is kind of where I am at right now. Trying not to overdo it and be conscious about how I sit at work.