Shoulder biomechanics in back bending - Part 2 Glenohumeral joint

Get the most out of back bends knowing what to do with your shoulders.
Ashleigh Flanagan
May 19, 2022

Being aware of your shoulder positioning when back bending is essential because;

Many backbends require a lot of shoulder flexion to complete and need shoulders to be stable and bear weight (e.g. bridge/wheel pose).
The muscles that orientate the shoulder attach to the spine, influencing its movement.
Shoulder movements can be used as cues to engage muscles and establish movement patterns that facilitate spine extension.
Shoulder alignment will influence the form and function of back bending poses. Being aware of the variable means you can manipulate these as needed. 

Joints of the shoulder 

The shoulder complex is three synovial joints and a pseudo joint.

These are: 

-Sternoclavicular (SC)- collar bone articulated with the breast bone

-Acromioclavicular (AC)- collar bone articulates with the shoulder blade

-Glenohumeral (GH)- Arm articulates with the shoulder blade

-Scapulothoracic- Describing the movement of the shoulder blade over the rib cage

While all of these joints are important for good shoulder movement, this series will focus on the glenohumeral and scapulothoracic joints, as these have the most significant impact on backbends.

The last post looked at the role of the scapulothoracic joint. Take a look here. This post focuses on the Glenohumeral (GH) joint.

The Glenohumeral joint

The Glenohumeral joint is the main synovial joint of the shoulder and is where the majority of the freedom of movement comes from. Limited bony concurrency and a relatively loose joint capsule make it one of the most mobile joints in the body. The stability of this joint is supported by a blanket like group of muscles called the rotator cuff that wrap around the humeral head (ball of the ball and socket joint) and work together to maintain the connection between the articular surfaces. The rotator cuff muscles are attached to the scapular (shoulder blade). 


As discussed in the last post, the scapulothoracic and the glenohumeral joints work together to allow the shoulder to have incredible range without becoming too unstable. Think of the scapulothoracic joint as the movable launch pad of the shoulder—approximately ⅓ of shoulder flexion and abduction comes from scapular movement.


Internal and external rotation

Identifying internal and external rotation in different shoulder positions can get confusing. I find the easiest way to work it out is to hold your arm straight out in front of you at chest height and extend your wrist (fingers point up). Rotating your thumb to the floor is internal rotation and turning your thumb up and away from your body is external rotation. By keeping the rotation the same and moving your arm you will learn to identify if your shoulder is internally or externally rotated in any position.

When considering back bending, we are most often interested in the glenohumeral joint rotation when hands are overhead.

Overhead rotation can make a big difference to the range and the stability of the shoulder joint. Generally, handstands benefit from the external rotation of the glenohumeral joint because this provides more stability. Overhead external rotation tightens the joint capsule, puts lat dorsi on stretch and moves the humeral head towards bony limits. Overhead internal rotation allows for more shoulder flexion as it avoids relative bony impingement and allows the capsule to slack. 

To feel how internal rotation allows more range and external rotation tightens the shoulder in overhead positions, try this exercise in internal and external rotation. 

Note that thumbs close together is internal rotation and thumbs apart is external rotation. Which variation has more range available, and which is more stable?

If we consider the whole shoulder, including the scapulothoracic joint, the combination that allows the most range is scapular upwards rotation and glenohumeral joint internal rotation with a touch of adduction (enables the humerus to get around the AC joint).

This doesn't mean that all back bend positions that require shoulder flexion need to have a lot of glenohumeral joint internal rotation. Internal rotation will really help those who have shoulders on the tighter side, but it is a more unstable position. If you already have more than enough shoulder flexion, unstable shoulders, or a history of subluxations/dislocations, this combination may not be for you. Similarly, relative external rotation may benefit those working on Mexican handstands as this will provide more stability. Generally, the balance between stability and range will help you decide the best shoulder alignment for you, though asthetic, traditions and transition between skills may factor in.

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