Taking Your Shoulders Up and Back is a Terrible Instruction
The universal instruction to “take your shoulders back” is one of great disservice to mankind on a long list of disservices. The instruction is most connected to what is known as military posture but I don’t 
think it serves military preparedness so I’d love to know where the concept began.
Unfortunately the instruction to “stand up straight” is equally troubling because most people lean backwards when they think they are standing up straight. But at least the image of standing up straight is a good one to offer—“take the shoulders back”, is not.
Everyone leans backwards through life. This is my constant refrain here on the blog and in all of the classes and workshops that I teach. We lean back because our lumbar curve allows for it and because well-meaning parents and teachers have constantly told us to take our shoulders back and stand up straight even though taking your shoulders back makes you lean backwards and compresses your lower vertebrae.
In terms of the shoulders—the arms are a hanging structure meant to fall loosely out of the shoulder socket. The head of the arm bone would like to fall within an imaginary perpendicular line that runs through the center of the ear, shoulder, hip, knee and ankle. Taking the shoulders back automatically pulls the shoulders behind this plumb line.
If you stand up and slump forward a little, even though this isn’t good posture, you should feel what I mean about the arm hanging from the shoulder socket. If and when you find that hanging sensation (which you shouldn’t have to round too far forward to feel) then try to stand back up straight but stop if you lose that hanging feeling.
Good posture means that all the disparate pieces of the puzzle must fit together. The head wants to sit on top of the spine and the shoulders want to hang from the shoulder socket. While the head, shoulder girdle, rib cage and arm are actually all separate structures that should move on their own, we often find these elements glued together so to speak.
This makes accomplishing all of the aspects of good posture very difficult when first starting to change one’s body. But you have to start somewhere and allowing your arms to hang from their sockets is as good a place as any.
I often refer to the very specific design of the body, and arms that hang are a key part of that design so stop taking your shoulders back no matter what anyone tells you.
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