Subscapularis: A New Perspective

October 13, 2010 at 6:16 AM | Posted in Health and Fitness, Psychological Wellness | 2 Comments
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I’m going to try something new with my blog posts and try to cite as much of my information as I can.  I’ll follow up with a references section at the end.

I’ve been browsing around the interwebz using all of my trusted websites to gather information concerning my ongoing shoulder pain. For those of you who may or may not know, I have suffered with impingement syndrome in my left shoulder for about 5 years now. This blog is the result of everything I have researched in an effort to end my own pain.

Subscapularis Definition/Function

I recently came upon some functional anatomy information that made a lot of things much clearer to me. First off, let’s explain what the subscapularis muscle even is. The subscapularis is part of the rotator cuff. It is the only muscle in the rotator cuff that has a large advantage in internal rotation.

 

The muscle highlighted in red is the subscapularis muscle. As you can see, it is pretty well-nestled in there with the latissimus dorsi and serratus anterior.

 

The above picture shows the location of subscapularis. It is the muscle in dark red. The following picture shows it from the front. As you can see, the muscle is actually on the “underside” of the shoulder blade, and it attaches to the FRONT of the humerus (upper arm bone).

 

The subscapularis from the front. It is behind the ribcage, and it comes from the "underside" of the shoulder blade. It attaches to the front of the humerus.

 

If you think about the basic physics of it, the subscapularis is an internal rotator. That is, when it contracts, it tends to rotate your palm so it faces backwards. Therefore, it tends to get a bad reputation because most people have internally rotated humeri. Of course, this is bad. You’ve heard of it being called “protracted shoulders,” “kyphosis,” or rounded shoulders. Other internal rotators are the pecs and lats. But there’s more to the story. Note that the lats are generally considered antagonist to the pecs. This means that the lats can’t only perform internal rotation – they have to be able to do something else. Indeed, the pecs and lats can both do other things. So can the subscapularis.

What else does the subscapularis do, then? Well, being part of the rotator cuff, it is responsible for dynamic stabilization. [1]  That’s fancy for keeping your arm in the socket. But its most critical function is when your arms are above your head. Take a look at the following force diagram:

 

Force Diagram for the Rotator Cuff During Abduction

 

This figure really gets at the heart of the matter. Notice that the supraspinatus (SS) and deltoid drive the humerus up. If you only have those two forces acting on the bone, then the top of the humerus is going to be driven up. This wouldn’t be a problem except that the surpraspinatus and the bursa next to it are trying to operate in that space between the two bones (called the subacromial space). If the arm bone is driven up into the shoulderblade, you’re going to get impingement. This is where your pain comes from. But, this is also why your subscapularis (SSc) is far more than an internal rotator. The dynamic stabilization provided by the subscapularis is CRITICAL for preventing impingement because it directly opposes the pull of both muscles. In order to do this, the subscapularis needs to have fibers that can pull in any direction, because the arm can go through such a huge range of motion. Indeed, as verified in the next picture, the subscapularis has lower, mid-lower, mid-upper and upper fibers that act at different degrees of abduction (raising your arm).

 

Note that the fibers of the subscapularis have different orientations. This enables the muscle to pull on the inside of the humerus head at all of the angles the shoulder moves through.

 

As you can probably guess, any sort of dysfunction with this muscle leads to impingement syndrome. Depending on the problem in the subscapularis muscle, the problem will manifest itself in different ways. Sometimes, people only have pain at a certain part of their shoulder abduction. You can use this as a way to tell what part of your subscapularis is affected. Generally, there are three trigger points. However, if you let the problem progress for too long, your entire muscle will become affected. The subscapularis can simply fail to function and you can get impingement that way. It can also become too tight, causing every one of your external rotators and the supraspinatus to become fatigued from the constant pull.

Why It’s Important

For most people, the ability to raise the arm above the head is pretty important, wouldn’t you say? So in terms of general range of motion, you should care about the subscapularis.

However, if you’re any kind of athlete or weightlifter, bodybuilder, etc., then you probably care a lot. Let’s talk about what the subscapularis does for you when you lift weights.

The subscapularis is an enormously powerful muscle given its size. This is due to the fact that it usually has a surprisingly large cross-sectional area and its tendon is positioned to give it a good mechanical advantage. During any kind of exercise where the arm is at or above shoulder level (benchpress, chins, etc.), the subscapularis generally opposes the upward translation of the humerus. This prevents impingement. When you think about it, the subscapularis needs to be able to resist the pull of the supraspinatus (a relatively small and weak muscle but with a decent mechanical advantage) and the deltoid combined (a massive, powerful muscle with a strong multi-pennate structure). It’s not hard to see how this muscle can become overworked.

In the cult-like world of powerlifting, studies have been done that directly correlate strength on upper body lifts to cross-sectional area of the subscapularis. [2]  2This would suggest that overhead movements are limited mainly by the strength and conditioning of the subscapularis muscle in most people. If you think about it, that shouldn’t be too surprising. Generally, people recommend against using the “behind-the-neck press.” The basis for avoiding this move is that it leads to RC damage/impingement.

 

This guy is dominating you on a lift you aren't even supposed to be doing. What gives? His shoulders are enormous.

 

Yet, some people do this move and have massive shoulders and no problems from it. What gives? Well, what’s happening when you do a behind-the-neck press? Your shoulder is in what’s called hyperextension. It’s really not hyperextension, it’s just range of motion that normal people don’t have. At the bottom of the movement, your subscapularis is operating at the end of its range of motion. When you consider that people generally don’t have strength at the end of the ROM for even the biggest, strongest muscles in the body, it’s no wonder most people get an injury from this lift. However, a “properly conditioned” RC can handle this move with respectable weight and attention to form (and perhaps special attention to the subscapularis). I always wondered what that meant, and now I see. Properly conditioned refers to full ROM strength for the subscapularis.

The Rest of the Problem

There are a few things that complicate things with this seemingly simple issue.

1. Trigger Points

Yes, you’ve heard me rant and rave about trigger points. Here are the big ones in the subscapularis:

 

Note that the referred pain is in the back of the shoulder.

 

If you have trigger points in your subscapularis, any number of things could be going wrong and causing you pain. A tight subscapularis usually manifests itself in pain in the back of the shoulder and a general feeling of tightness in the armpit. [3]

2. Faulty Strengthening Moves

If you’re any kind of bodybuilder or powerlifter with hair on your balls, you’ve probably already Googled some strengthening moves for the subscapularis. Here’s what you found:

 

Yes, that's right. This is internal rotation cable work with a naked chick.

 

You can thank me later for making it interesting with a naked chick. You biomechanics nerds have noticed that this is pure internal rotation of the humerus. Well, big woop. This does nothing for the dynamic stabilization function of the subscapularis. It does get blood to the muscle and work one specific part of the muscle (making it ok for recovery). But the upshot is if you only do this (or the bench side-lying internal rotation move with a dumbbell), you’re not really training the muscle to do what you want it do.

For contrast, take a look at this page: http://www.muscleactivation.com/cds/U08.pdf

It shows how to activate the different regions of the subscapularis. You’ll notice that they’re not really anything like that cable move.

I’ll follow up with some dynamic stabilization moves when I find them. The internet is lacking badly in giving me this info.

3. Worthless stretches

If you Google subscapularis stretches, you’ll come up with this:

 

The 'broomstick' stretch.

 

This one stretches one particular plane of motion that the subscapularis can operate in, and it will probably feel really good when you do it. But it doesn’t stretch the whole thing. What else can you do?

Well, your creativity is the limit on this one. However, I’ve devised my own stretch that seems to work particularly well for all of the planes of motion for the subscapularis. I’ll describe the setup in words, then give a picture.

  • Lay on the floor on your stomach, but support yourself with one arm.  With the other arm, make an “L.”
  • Place the “L” arm on the ground, palm down.  You should be facing sideways, and a little down, with the support of your other hand.
  • Now if you turn your trunk upwards, away from the palm down, you should begin to feel a stretch in your armpit.
  • If you are new to this stretch, or if it feels exceptionally tight, stay here and statically stretch it for a minute or so.  Be patient.
  • Once you have loosened up, you can vary the angle of the stretch.  Keep your elbow bent at a 90 degree angle, and move your body.  You’re going to be moving the shoulder joint (not the elbow).  You can put the arm above your head and you can go all the way down, as though you were doing a pullup.

Since this is pretty hard to describe, here’s a picture. Thanks to an army of douchebags, I no longer own a digital camera and this will have to do:

 

Just be sure to turn your palm so that it's facing the floor. The rest of this is right.

 

This stretch is greatly intensified and much more useful if you attempt to “pull” your arm from the socket. Remember that the primary purpose of the RC is to keep the humeral head in the socket, so trying to pull your arm out of the socket is a good way to stretch. However, if you’re prone to shoulder dislocations, be careful (though if you’re prone to shoulder dislocations you probably aren’t having issues with tight muscles here). Play around with the stretch to see what works and what doesn’t – everyone is different.

Summary

The subscapularis performs far more than internal rotation of the humerus. Its most vital role is in dynamically stabilizing the head of the humerus during shoulder abduction. Any time the arm is at or above shoulder level, the subscapularis is critical to preventing impingement. Overall upper body strength has been directly linked to the strength and conditioning of the subscapularis. Moreover, people with a strong, healthy subscapularis can generally perform shoulder exercises at a greater range of motion than others and still be safe about it. And they generally have the most well-developed shoulders and the highest lifts. Although a bold statement, I believe it reasonable to suggest that most shoulder pain has the subscapularis involved to some degree.

Dysfunction in the subscapularis can be caused by any of several problems. Weakness, tightness, trigger points and nerve entrapment (rarely) are the main problems. It can be injured through unbalanced shoulder training and generally shortens if you have bad posture. Clicking in the glenero-humeral joint (what most people consider to be the shoulder joint) indicates tightness in one or more of the RC muscles, generally beginning with the subscapularis and the supraspinatus.

Imbalances in strength or tone can also lead to chronically tight external rotators. If you frequently suffer from pain in the infraspinatus, supraspinatus, and/or rear deltoid, check the subscapularis. Because the deltoid is a strong, powerful muscle, trigger points and overuse in the deltoid are almost always the result of other muscles being in trouble.

Traditional subscapularis stretches and exercises don’t really get to the heart of the problem. They focus too much on the internal rotation ability of the muscle and ignore the dynamic stabilization strength. Since most people need the latter, many people are frustrated when their strengthening and stretching efforts do not produce results. Likewise, people who are educated enough to attempt to ward of RC injury using these stretches and lifts will be disappointed to learn that this particular mode of shoulder failure is not at all prevented using the traditional treatment.

References

1.  http://en.wikipedia.org/wiki/Subscapularis_muscle

2.  http://ericcressey.com/random-friday-thoughts-103009

3.  http://www.triggerpoints.net/

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