“. . . according to the Yoga Sutra (3.1), the term [Bandha] refers to the ‘binding’ of consciousness to a particular object or locus (desha), which is the very essence of concentration.”
Georg Feuerstein



Sunday, March 6, 2016

Shoulder Biomechanics, Part I: The Subscapularis Muscle

Hello Friends,

This is the first of a four-part series on the shoulder joint, focusing specifically on the rotator cuff and its biomechanical relationship with the deltoid muscle. Let's begin by looking at the muscles that comprise the rotator cuff, starting with the subscapularis. As figure 1 illustrates, the subscapularis occupies the space, or fossa, at the front of the scapula. From there it attaches to the lesser tuberosity, a knob-like structure on the humerus bone at the front of the shoulder. Concentrically contracting the subscapularis muscle (shortening the muscle on contraction) internally rotates the shoulder. The subscap also acts, in conjunction with the infraspinatus muscle, as a stabilizer of the humeral head in the socket (glenoid). We test strength and function of this muscle with the "belly press" test or the "bear hug" test. Tightness in the subscapularis can limit external rotation of the shoulder.


Figure 1: The subscapularis muscle, illustrating the origin on the inside of the scapula and the insertion on the lesser tuberosity of the humerus.


Figure 2 illustrates one of the poses that stretch the subscapularis muscle, namely, Gomukhasana. The upper side humerus externally rotates in this pose, thus stretching the muscle as shown.

Figure 2: This illustrates the effect on the subscapularis muscle of the upper arm in Gomukhasana. External rotation of the humerus stretches the muscle.


Figure 3 illustrates engaging the subscapularis muscle in Ardha Baddha Padma paschimottanasana. Advanced practitioners can attempt to lift the hand off the back to engage the muscle in this pose. This also replicates the "lift off" test, which is used in orthopedics to test the function of the subscap muscle.

Figure 3: This image illustrates contraction of the subscapularis muscle to internally rotate the humerus.



Finally, we have the subscapularis as a stabilizer during a static position in a pose. In Warrior II, attempt to internally rotate the shoulders by imagining pressing the mound at the base of the index fingers down against an object. Resist this by externally rotating the shoulders at the same time. Co-contracting opposing muscles--like the subscap and infraspinatus--stabilizes the head of the humerus in the socket while the deltoid contracts to abduct the humerus. Click here to go into a bit more depth on the subject of stabilizing your shoulders in your Downward dog pose. 


Figure 4: Co-contracting the subscapularis and the infraspinatus stabilizes the humeral head in the socket while the deltoid muscle abducts the humerus.



Click here to take the rotator cuff quiz and test your knowledge!

Thanks for stopping by. Stay tuned for the next post when I'll go over the antagonist muscle for the subscapularis. By the end of this four-post series, you'll have a good understanding of the functional anatomy and biomechanics of the shoulder joint as applied to yoga. Click here to browse through the Bandha Yoga book series on anatomy, biomechanics and physiology for yoga.

All the Best!

Ray Long, MD

21 comments:

  1. Your books have been a tremendous asset to my Personal Training and Yoga teaching career. Thank you so much!

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    1. You're welcome, Terri. Thanks for your appreciation of our work! Ray

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  2. Replies
    1. Glad you enjoyed it, Virginia--Ray

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  3. these folks are always giving all of us great information with great links. and after watching and reading I always come away with how much more there is to all of this therapeutic work that we all are capable of contributing. Stay open to all modalities and all information and then see what it triggers in your own inner therapist. You, we, will all see more and as we study and apply What we learn, we become the new innovators of an ancient and modern methods .

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    1. Thanks for your comment, Anthony--delighted that you appreciate our work! Ray

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  4. Always an inspiration to further my yoga practice seeing from inside what benefits it gives. Many thanks

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    Replies
    1. You're welcome, Leigh. Very happy to hear that this inspires your practice! Ray

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  5. Thank you so much!!

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  6. Fantastic every time.

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  7. Very clear illustrations and explainations. Thank you.

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    1. Glad to hear you enjoy this, Vibha--thanks for your feedback! Ray

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  8. The images are so helpful. Additionally, I appreciate the simplicity within the thorough explanations. Thank you.

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    1. Thanks Yvette,

      I'm glad that you appreciate the simplicity and directness. That's a big compliment to me. Someone once said that if you can't explain something simply, you don't understand it (I think it was Einstein). I agree with that! Best~Ray

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