The shoulder is a confusing area. If you asked most people where their shoulders were located, they would gesture vaguely to the area at the top of the arm. This wouldn’t be wrong; this is definitely one aspect of the shoulder. What supports much of this movement is the connection between the upper arm to the scapula, or shoulder blade, a bone we can’t see and many struggle with moving when first asked. It’s not an area we spend a lot of brain space on, unless we have spent time studying (or thinking) about it.
A cue frequently used in athletic settings is “bring your shoulders down and back.” This achieves a certain aesthetic from the front. It likely comes from the military posture of attention, a position that involves “chin up, chest up, shoulders back, stomach in.”* This position closely resembles the beginning of the startle response, a reflexive response mammals do when there is a potential threat. There is nothing relaxed about this posture. Coupled with the disconnect many have from the shoulder blades, it leads to rigidity and often ends up with people leaning back to accomplish the position.
I am working with a woman right now that has low back pain and balance issues. She leans back in her heels when she stands, and the first time I asked her to reach her arm, there was no movement in her shoulder blade. She wasn’t sure how that area worked, or how it supported her. I played with a few things and managed to get her moving her shoulders blades independently of the rest of herself. “This feels incredible,” she said. “I’ve always been taught to have my shoulders down and back, but it feels so much better to let them move.” (Coincidentally, she told me excitedly at the end of her session her back no longer hurt). Letting go of a sense of “perfect” posture or holding ourselves a certain way can lead to more fluid, less uncomfortable movement.
*Different versions of attention: https://en.wikipedia.org/wiki/At_attention