So, what is wrong with what the person is doing above?  She’s smiling and exercising…all good, right?  Uh, no!  I’ll cut to the chase.  That woman is looking at significant shoulder damage coming her way due to the movement she is performing.

Many people go the gym and try to isolate, or train, their shoulders.  There is plenty of debate about isolation movements vs. more regional training, but we’ll leave that for another day.  There are many machines the people use to work on their shoulders and there are plenty of exercises with dumbbells.

This discussion is about one particular exercise that rates high on my list of ‘Don’t Be a Meathead.’

Let’s first start with anatomy.  The supraspinatus muscle is one of the 4 rotator cuff muscles and its function is shoulder abduction in the SCAPULAR plane along with a bit of external rotation.  The problem with this muscle is that it travels under a bone that comes off the scapula, called the acromion.

As far as kinesiology goes, the supraspinatus helps to bring the arm out to the side about 30 degrees.  Although it continues to work for a longer period of time, the middle deltoid takes over and brings it up from there.

The acromion is an odd kind of bone as it has 4 potential shapes.  First, Type 1 is straight.  Second, type 2 curves downward.  Third, type 3 ‘hooks’ down and around. Finally, Type 4 is found in very few people and that shape is convex.  It’s important to note that type 2, which we can consider as being the type that creates most of our injuries, accounts for about 44% of all acromion processes.  Type 1 and 3 are found in equal percentages (about 28% for type 1 and 23% for type 3), and type 4 is actually quite rare.

Being types 2 and 3 are the culprits for impingement syndrome and otherwise supraspinatus tears, and they account for about 67% of the shape of the acromion in the population, it makes a lot of sense to work on moving the shoulder properly so as to not further increase the risk for injury. I’m not going to say that you cannot develop a tear with a type 1 or type 4 acromion, but it’s much harder as the bone is not pushing on the muscle.

Now back to what too many people do in the gym.

Being the supraspinatus runs under acromion, it’s easy to see why if the bone is type 2 or 3 it might end up rubbing, pinching, and ultimately tearing the supraspinatus muscle.  This occurs mostly if you bring your arm straight out to the side, called the ‘CORONAL’ plane.  

Now let’s consider what most people do in the gym.  They sit on a machine or grab a weight or band or whatever and bring their arm out to the side.  They think they are training their shoulder(s) properly.  But what is really happening for the 67% of people who are working out?  Yes, you guessed right.  They are putting the shoulder in a position that dramatically increases the risk for shoulder impingement injury.  In addition to the muscle damage, we must also consider that there will be a high probability of bursa damage in the region as well.  The sub-acromial bursa gets irritated.

It amazes me just how many people working out, and even trainers working with clients, perform this movement improperly.  This is a big NO NO!!!

We can avoid impingement and other damage to the shoulder if we move the shoulder in the scapular plane vs. the coronal plane. How do we do this?  Simply bring your shoulder out to the side and about 30-45 degrees in front of the body and you will significantly reduce the likelihood of injury. By moving in the scapular plane, you will effectively move the muscle in front of the acromion and avoid the bone from bearing down on the muscle.

A neat example to demonstrate impingement is to simply bring your arm up from the side as high as it will go.  You will notice that it cannot go all the way up.  To do so, you’d need to externally rotate your shoulder (this helps get the muscles out of the way). 

Now, do the same movement starting at you side but at about 30 degrees in front of the body.  What happens?   You can now bring your arm up about 180 degrees.  Why is this?  As mentioned above, when you abduct in the scapular plane (30 degrees in front of the body abduction), you move the supraspinatus out from under the acromion, and by doing so, you can move the shoulder without fear of impingement.

So, don’t move your shoulder out to the side in the coronal plane as you’re likely to impinge it.  If you do, you are going to tear the supraspinatus and maybe even worse.  Stick to movements in the scapular plane and save your shoulder!

Don’t Be a Meathead!
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