Glenohumeral Joint (Shoulder Socket)

The intricacies of the shoulder are crazy.  Everything fits just right, in the tiniest of divots and crevasses and seams.  The body is brilliant in its precise perfection.
Just look at this thing:
photo credit:

And then you add the layers of muscle:

It’s a web of a masterpiece, and yet we wreck it so easily.
Dozens of delicate layers and fixtures hold the upper arm into it’s socket.  The hip and glenohumeral joint are mirrors of each other, with the hip being more padded and the shoulder having more protrusions.  The arms are much more mobile than the legs.  With greater mobility comes the greater chance for injury.  (Again, we have the responsibility of CONTROLLING that large range of motion).  
The body is built to be balanced, but we rarely work or train with balanced movements in mind.  We like to push a lot, because it’s studly to see how much we can bench in twenty different ways.   But chin ups are HARD.  So we get better at what we can do and ignore what we can’t.  
We also have a tendency to drive movement from the hands instead of the torso.  This ‘outside-in’ chain wreaks havoc on the shoulder capsule.  It’s designed to be an extension of the trunk, not the fulcrum on which the weighted hinges turn.
Let’s take a look at properly training the four main Glenohumeral movements:
1.  OVERHEAD FLEXION – rotating ball in socket to get hands overhead

You should drive this movement from the lats, just below the armpit.
More from the incredibly knowledgeable Eric Cressey:
Supine Alternating Shoulder Flexion 
This can be done with or without the tennis balls/roller.  
These increases thoracic extension and elevates the body, making for a further overhead reach. 
(If you are lying on the ground your hand will hit sooner)
SQUISH that lower back hole.
Standing Back to Wall Shoulder Flexion

Standing version.  Must be more aware of posture as you work against gravity in ‘normal’, upright position.  Gravity HELPS when you’re lying down.  The floor acts as a spine stabilizer.
2.  ABDUCTION – pulling your hands apart

You should feel this just inside the armpit towards the spine.
Just listen to Eric on this one.  
3.  EXTERNAL ROTATION – Elbow at Sides

This should be the easier version as the arm just ‘sits’.  Make sure not to shrug (keep shoulders away from ears.  You should feel this right above your armpit on your back.

Chin tuck and squish lower back hole against the wall. 
Palms up and thumbs to wall.

This can also be done laying down flat, lying vertically on on a roller, or holding a band to add resistance.  
4.  EXTERNAL ROTATION – Elbow at Shoulder Height

You should drive this movement from the BICEP.  Think of your upper arm as a rotisserie chicken that the bicep turns.  You should feel very little around your shoulder blade.  

Supine External Rotation
A half roller or helps hold the elbow up and out.  Note that the elbow is slightly ABOVE the shoulder line.

Hand stays stiff.  Gravity helps.

Prone External Rotation

Much more difficult version as the scapula and shoulder musculature must hold the arm ‘straight’ within the socket.  
Hand drives END RANGE motion.

This prone, chest down position makes you acutely aware of what’s working.  Gravity attempts to work against your back, turning it on and taking pressure off the front of the shoulder.
Tuck that chin.

Standing External Rotation to Wall

It’s easy to cheat with this upright positioning, 
so attempt to nail the prone version first to learn the patterning.   
Control the movement, don’t rush, and add very little weight, if any. 

  • The glenohumeral joint is a ball and socket.
  • The shoulder is relatively fragile.  It’s got a lot of connections in very tight spaces.  Any one of them gets inflamed (overused or out of balance), you’ve got pain.
  • Tuck chin and squish lower back hole to minimize neck and mid-back involvement in what’s meant to be a shoulder movement
  • If you can’t get the arms overhead, don’t try rotation.
  • If you can’t get something lying down, don’t try it standing up.
  • Movement should come from the back areas around the armpit, except for external rotation at shoulder height, which should stem from the bicep.
  • Driving through the front to the shoulder (collar bone extended to the AC joint) will only make things worse. 
Super Perfectionist Tip: If you just can’t get enough of the marvelous Mr. Cressey and his shoulder knowledge, give this superb seven and a half minuter a try:

8 Ways You’re Messing Up Your Rows

These also work for prone or ‘bent over’ rows.

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