It seems that the rotator cuff muscles (SITS – suprapinatus, infraspinatus, teres minor and subscapularis) are receiving a lot of press these days, yet one of its members is often obscured from the spotlight: the subscapularis.
The largest of the four members, the subscapularis is challenging to visualize due to its location on the anterior (front) side of the scapula. Furthermore, its deep position between the shoulder blade and the ribcage makes it tricky to palpate. And although a key function of the subscapularis is to internally rotate the shoulder, there are larger neighboring muscles that also contribute to this action, making it even more elusive to actually feel for isolating it upon contraction.
With all of this obscurity, why not just skip over it and instead focus on the larger, more easily accessible neighboring internal rotators? To begin to answer that question, let’s take a closer look at the subscapularis and its function in rotator cuff muscle anatomy.
This triangularly shaped muscle originates from the medial anterior surface of the scapula and is the only rotator cuff muscle that inserts on the lesser tuberosity of the humeral head (the front portion of the upper arm bone). It fills the subscapular fossa and is sandwiched between the scapula and serratus anterior. As previously mentioned, the subscapularis internally rotates the shoulder. Also involved in creating internal rotation are the anterior fibers of the deltoid, latissimus dorsi, pectoralis major, and teres major (antagonists for internal rotation are the posterior fibers of the deltoid, infraspinatus and teres minor).
So just what makes the subscapularis so important? Why should we give this member of the rotator cuff more press, respect and even celebration?
For one, we might consider that overly tight internal rotators (including of course, the subscapularis) can inhibit our ability to externally rotate our shoulders. More importantly, however, we can find great cause for celebration of this muscle in the significant role it plays (along with the other RC muscles) in the dynamic stabilization of the shoulder. That’s an elaborate way of saying that it prevents the shoulder from dislocating. Consider that the glenohumeral joint has a greater degree of range of motion than any other joint in the body when it is fully functional and healthy. The subscapularis is essential for keeping the humerus centered in the glenoid cavity (the socket) and prevents anterior dislocation due to its insertion at the anterior lesser tuberosity. If we find our shoulders to be unstable or prone to dislocation, it’s definitely worth taking a closer look at the subscapularis. In addition to this important role of stabilization, the subscapularis makes a valuable contribution to everyday activities – such as opening a tightly sealed jar, reaching around to scratch your back, clutching a book to your chest, lifting things, throwing a fast ball, swimming the overhead stroke, and even giving a hug.
So now that we’ve come to a greater awareness of the function and importance of the subscapularis, how can we awaken, lengthen and strengthen it within our own bodies? Stay tuned for some suggestions in Friday’s post!
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