How many times have you been in an exercise class and heard the phrase ‘lower your shoulders from your ears.’ It’s quite common. People put their hands above their heads and end up with their shoulders up around their ears.
I was approached in my yoga class the other month by someone whose other yoga instructor was telling her that her arm position in downward facing dog was wrong and try as she might, this person could not correct her pose.
‘Show me how you are getting there.’ I said, and there in lay the problem. Depending upon how you take your arms above your head, your shoulder position will differ. One way your shoulders will end up around your ears and it will then be difficult to bring them down or to move your shoulder blades around on your back, as needed for many yoga asana. The other way of getting your arms above your head will result in your shoulders being lower and more mobile.
So, what’s going on?
The bone in your arm, your humerus, has two large ridges towards the top of it, your greater 
and lesser tubercules. These are the sites for a lot of muscle attachments, in fact the whole of your rotator cuff inserts around these as does your chest muscles and your back muscles (pecs and lats).
Just above the top of your humerus you can see we have the tip of the acromium process of your scapula and the end of your clavicle.
The acromium is the continuation of the spine of your scapula, the bony part you can feel on most peoples shoulder blades.
If you lift your arm straight out to the side you will reach a point, just above horizontal, where the tubercules of your humerus meet your acromium process and then the two things (your arm and your shoulder blade) move as one.
If you’ve been to a yoga class then your instructor might have told you that as you take your arms up above your head you should rotate your arms outwards so that your palms end up facing upwards. They might have told you that this is something to do with spiral anatomy or to do with spirals that are established in the development of the foetus. They aren’t entirely wrong.
Why is this a better way to get your arms above your head? As you rotate your arm outwards you move the tubercles of your humerus so that the arm can lift higher before the bone meets the acromium process. Your shoulders stay down.
There is nothing magic about it – you just need to understand the shape of your bones.
anatomyfundamentals.com 