MOBILITY + STABILITY ... FINDING YOUR RHYTHM

The shoulder complex houses the most mobile joint in the human body allowing us the freedom to move and use our arms in a multitude of ways.

The shoulder complex is comprised of three joints:

sternoclavicular joint (where the sternum (breastbone) and clavicle (collarbone) meet)

·      Connects arm & shoulder to the rest of the skeleton

·      Saddle type joint that allows for movement of the clavicle

·      Supported by a strong network of ligaments

acromian clavicular joint (where the clavicle (collarbone) and scapula (shoulder blade) meet)

·      Allows us the ability to raise our arms overhead

·      Stabilized by a small network of ligaments

glenohumeral joint (where the head of the humerus (upper arm bone) meets with the glenoid fossa of the scapula (shoulder blade))

·      Most mobile joint in the body

·      Shallow ball & socket joint

·      Rotator cuff muscles help to hold the head of the humerus in the glenoid fossa (supraspinatus, infraspinatus, subscapularis, teres minor & major).

  

 ROTATOR CUFF MUSCLES:

In addition to these three joints, there is also a scapulothoracic articulation.  Although not a true joint, the articulation between the posterior thoracic cage and the anterior surface of the scapula is very important for the stability of the glenohumeral joint.

The coordinated movement of the glenohumeral joint and the movement of the scapula on the posterior thoracic cage are called scapulohumeral rhythm.

To understand how all the muscles involved in scapulohumeral rhythm work, let’s first look at the different ways in which the scapula can move:

http://www.pt.ntu.edu.tw/hmchai/Kinesiology/KINupper/Shoulder.files/ShoulderStructure.htm

The muscles that support the scapula throughout this range of motion include: serratus anterior, trapezius, rhomboids & levator scapulae

Action	Muscle(s)
Elevation	upper trapezius, rhomboids & levator scapulae
Depression	lower trapezius, lower serratus anterior
Protraction (abduction)	serratus anterior
Retraction (adduction)	mid trapezius and rhomboids
Upward rotation	serratus anterior, upper & lower trapezius
Downward rotation	rhomboids & levator scapulae

SCAPULAR STABILIZERS

credit: www.bandhayoga.com (Dr. Ray Long & Chris McIvor)

When all of the scapular stabilizers are working together in a synchronous way, the scapula and the arm bone will move together in a way that will keep the humerus securely seated in the glenoid fossa and will keep the scapula in even contact with the posterior thoracic cage.

When the scapular stabilizers are not working properly the scapula and the humerus move in a dysrhythmic way.  This scapular dysrhythmia can lead to pain, weakness and impairment of shoulder mobility.  The rotator cuff muscles often wind up overworked or injured as a result.

A physical sign that helps to indicate a problem with scapulohumeral rhythm is scapular winging.  True scapular winging is due to complete loss of function of the serratus anterior muscle and is very rare.  However, more subtle muscular imbalances, weaknesses or pain can also cause subtle scapular winging or scapula dyskinesis.  Noticing this sign early and learning to retrain your scapular stabilizers to work together in a synchronous way can help to increase stability & mobility of the shoulder complex and prevent injuries down the line.

Here is what scapular winging looks like and some suggestions for strengthening the scapular stabilizers to restore scapulothoracic rhythm.

Looking at the big picture:  The shoulder is a very complex joint.  Alignment of the thoracic spine, rib cage alignment, head carriage and neck alignment will all effect the position of the scapula and therefore the mobility of the joint and the ability of the scapular stabilizers to work in a synchronous way.  Understand your starting point before you begin any exercise routine.
 

• Do you tend to slouch or hunch your shoulders forward?
• Do you tend to jut your chin forward and carry your head forward of your chest?
• If you pull your shoulders down and in and open your chest does your ribcage thrust forward? 

If you answered yes to any of these questions you may need to begin by working on your thoracic spine alignment and mobility before being able to properly improve your shoulder strength and mobility (more on that in future posts!)

Improving strength & flexibility:  remember that you want to achieve a balance between mobility and stability in the shoulder complex.  Exercises that strengthen the scapular stabilizers such as the “push up plus” must be coupled with exercises to stretch the chest muscles and anterior shoulder. 

Improving motor control:  exercises that use resistance to lengthen muscles as they contract (eccentric contraction) can help to improve motor control.  Slowing the pace of exercises like push ups or lat pulls and using internal resistance throughout the full range of motion will help to make sure all the scapular stabilizers are working together throughout the full range of motion.

Here is a great simple article about cueing scapular motion during different exercises.  I particularly appreciate the mention of ribcage and neck alignment:  http://www.acefitness.org/certifiednewsarticle/2384/correct-cues-for-scapular-motion/

There is so much to think about when it comes to proper shoulder alignment.  Remembering to focus on alignment & stability first coupled by a balance between strength and flexibility will help you find your rhythm and keep you injury free for years to come!

References:

http://www.shoulderdoc.co.uk/article.asp?section=492

http://www.jaaos.org/content/11/2/142/F1.expansion

http://www.pt.ntu.edu.tw/hmchai/Kinesiology/KINupper/Shoulder.files/ShoulderStructure.htm