Shoulder Biomechanics, Part 2: The Infraspinatus and Teres Minor Muscles
Welcome to the second of our series on the shoulder joint in yoga. The first article in the series discussed the subscapularis muscle, the main shoulder internal rotator. Now we’re on to the antagonist muscles of the subscapularis, the infraspinatus and teres minor.
The infraspinatus arises in a trough below the scapular spine, hence its name (“infra” means below). The teres minor arises in the back part (dorsum) of the scapula along its outer (lateral) border. The infraspinatus and teres minor insert onto the back part of the greater tuberosity of the humerus, as shown in Figure 1.
These muscles externally rotate the humerus, with the infraspinatus being the strongest external rotator of the joint. The infraspinatus and teres minor also function to stabilize the humeral head in the socket (glenoid).
|
Figure 1: The infraspinatus and teres minor muscles of the rotator cuff (the supraspinatus is the faded muscle on top). |
The Force Couple
These muscles combine with the subscapularis at the front of the joint to form a “force couple.” In this manner, antagonist muscles (for rotation) become synergists (for stability). Therapy—and surgery—for rotator cuff pathology is directed toward restoring this force couple.
Figure 2 illustrates this biomechanical process. This view is looking down on the shoulder with the front of the joint towards the bottom of the page.
|
Figure 2: The force couple between the infraspinatus and subscapularis muscles. This view is looking down on the shoulder with the front of the joint towards the bottom of the page. |
Yoga poses with the arms in Reverse Namaste (Reverse Prayer Pose) stretch the infraspinatus and teres minor, as does the traditional arm position in Gomukhasana (Cow Face Pose). Those of you who are more flexible may gently press the knife edge of the hand into the back to “load” the external rotators. Folks who are tighter may simply grasp the elbows or hands behind the back.
|
Figure 3: Stretching the infraspinatus and teres minor by internally rotating the shoulders in Parsvottanasana. |
Externally rotating the shoulders in poses such as Trikonasana (Triangle Pose) can be used to activate the infraspinatus and teres minor. Figure 4 below illustrates this, as well as the myofascial connection between these muscles and the muscles that retract the scapula, the trapezius, and rhomboids.
Figure 4: Externally rotating the shoulders in Trikonasana or Triangle Pose
Stay tuned for the next post when I’ll go over the last muscle of the rotator cuff, the supraspinatus.
Would you like more shoulder asana tips from Dr. Ray Long? Online Yoga Teacher Ed: Dr. Ray Long on Stabilizing the Shoulder in Downward-Facing Dog.
Study Shoulder Health with Julie Gudmestad and YogaUOnline – Yoga Anatomy: Keeping Your Rotator Cuff Healthy in Yoga.
Reprinted with permission from Daily Bandha.
Author, Ray Long MD, FRCSC is a board-certified orthopedic surgeon and the founder of Bandha Yoga. Ray graduated from The University of Michigan Medical School with postgraduate training at Cornell University, McGill University, The University of Montreal and Florida Orthopedic Institute. He has studied hatha yoga for over twenty years, training extensively with B.K.S. Iyengar and other leading yoga masters.
3d Graphic Designer / Illustrator Chris Macivor has been involved in the field of digital content creation for well over ten years. He is a graduate of Etobicoke School of the Arts, Sheridan College and Seneca College. Chris considers himself to be equally artistic and technical in nature. As such his work has spanned many genres from film and television to video games and underwater imagery.
Also, read...
Related courses
Recent articles
Categories
Upcoming courses
FREE DOWNLOAD!
Recent articles
Almost there...
Sorry, we couldn't find anything...
Yoga Practice Tips
Dhanurasana (Bow Pose) with a Yoga Strap Bowstring
Years ago, I heard Judith Hanson Lasater pose this question: “Who should practice backbends?”…
Apr 19 –
Yoga and Healthy Aging
Empowered Aging: An Interview with Yoga Teacher Ellen Saltonstall
YogaUOnline: We are delighted today to be here with Ellen Saltonstall to discuss her…
Apr 17 – Sarah Bell ERYT-500, YACEP
Anatomy
4 Yoga Poses to Strengthen the 4 Muscles of the Rotator Cuff
The shoulder’s rotator cuff is a group of four separate muscles that work together…
Apr 15 – Leah Sugerman, E-RYT 500, YACEP
