A better way to position the shoulders
Here's my thought process, as simply as possible...
1) There is no one "best" position that the shoulder blades (scapulae) must stay for optimal posture or function
2) Constantly pulling your scapulae back and down could cause just as many problems as having them hunched forward or up
3) Your scapulae float. The only skeletal structure holding your whole shoulder and arm complex to you torso is your clavicle
4) Because of this, your scapulae are designed to move. If they weren't meant to move, they would be fixed secularly to your torso
5) The reason your scapulae NEED TO MOVE is to maintain optimal articulation between the head of the humerus and the glenoid cavity of the scapula. All this means is that the ball stays in the the socket, no matter what position your shoulder is in
When I think about how the shoulder joint and the scapula (scapulothoracic joint) are functioning I think about these two principles (because principles > technique)
1) Which ever direction the arm goes, the scapula will follow
- If your arm goes above your head, your scapula will go up as well e.g. When you hang the washing out
- If your arm moves forward of your body, your scapula will move forward e.g. Pushing forward when vacuuming
- If your arm moves behind your body, your scapula will move backwards e.g. Pulling the cord back when starting a lawn mower
- If your arms are down by your side, your scapulae will move downwards e.g. Pushing yourself out of a chair
2) Optimal shoulder position is relative to the direction force is being applied to it
The next principle builds on the scapula movements from above, however the way in which you consciously exert effort to maintain a shoulder position that is stable and effective is relative to the way you are orientated with the force acting upon it.
In English - There could be two different scenarios where your arms and shoulders are in the same position e.g. Above your head, yet you apply effort in different directions to maintain a strong shoulder position.
Example 1 - If you are hanging from a pullup bar, gravity is pulling your torso downward (your shoulders are now shrugged up in your ears). Therefore you would pull your scapulae downward into a depressed position to support the shoulders.
Example 2 - If you are in a handstand (the same position as hanging from a bar, except inverted) gravity is compressing your body, so you would push your scapulae upward (pushing your hands into the floor), putting them in a upwardly rotated, somewhat elevated position.
In simple terms, you are applying force and movement in the opposite direction to the force that is acting on your body. This buffers the external force and maintains shoulder position. I also talk about the difference between compressive and tension loads in my post about the overhead position - https://movementandmobility.wordpress.com/2015/06/29/big-5-overhead/
How constantly pulling your shoulders back and down creates issues
Having your shoulders back and down in every situation is not advantageous as I talked about above, but it can also create serious issues. Your brachial plexus is the bundle of nerves exiting from your cervical spine that then split into individual nerves to provide innovation to the muscles of your shoulders, arms, and hands.
As you can see in the images below, the pathway of the brachial plexus arises from the cervical spine, runs posterior to the clavicle and deep to pectoralis minor where it reaches the Axilla. It then splits into the indivuidual nerves that run down the arm.
Image credit to blique.deviantart.com and differentialdiagnosisoftos.weebly.com
Nerves have very little give compared to muscle and connective tissue. If you're continuously pulling your shoulder blades down (especially when your arms are above your head) you're forcefully increasing the distance between the start and finish of a structure that doesn't have the capacity to change in length. Restricting the normal mechanics of the nervous system could produce pain, numbness, or injury to nervous tissue.
Yes this is technical, and no not every one needs to know this, so why does it matter?
If you are training people in the gym or in sport, then having a decent understanding around anatomy, physiology, and biomechanics is probably necessary. If you're someone that doesn't work in a movement field then you probably don't understand much of the above nor care about it, and that's cool too.
If you're the latter then, a) It's always good to challenge your mind and learn new information, but more so b) This post is less about shoulder mechanics and more about awareness and practicing the art of critical thinking. Just like every other topic, modality, area of life, piece of advice, or whatever else... context matters. It's important to understand context with an open mind when giving advice but more importantly when receiving it.
If you're the former, a cue e.g. shoulders back and down is something specific, used for a certain person in a certain context. It's not a universal one size fits all umbrella statement that should be dropped on all of humanity.
There is never one be-all end-all.