Does This Advice Make Sense?

Image courtesy of womenshealthmag.com

One piece of advice that seems to be haphazardly thrown around by personal trainers and strength coaches is to keep your shoulder blades pinched together or pulled back (retracted) while horizontally pressing.  Looking at this advice from a structural perspective of the shoulder complex, I cannot say this makes sense or should be a general rule.

The Shoulder Complex--posterior view. Image courtesy of The Skeletal System Pro III

First, look at the size of the area of the contact surfaces between the glenoid and the head of the humerus.  The head of the humerus is significantly bigger than the face of the glenoid.  Combine that with the overall lack of structural support of the gleno-humeral (GH) joint, and you can see that this joint has great potential, from a structural perspective, for movement.  Which makes sense.  For many of us, our shoulders move through greater ranges of motion than any other joint in our body.

Second, the structure of the glenoid itself is not ideal for keeping the head of the humerus articulating with it, especially anteriorly and posteriorly (to the front and to the back).  It would be like if you took a golf tee and chopped off the sides of it.  On the superior and inferior edges of the glenoid there is a bit of a ridge, but not anteriorly or posteriorly.

Golf Tee vs. Glenoid--Professional Depiction

Combine this with the difference in ligamentous support between the anterior and posterior aspects of the shoulder complex.

Ligamentous Support--anterior view. Image courtesy of The Skeletal System Pro III

Ligamentous Support--posterior view. Image courtesy of The Skeletal System Pro III

So, now we have a situation where there is better bony structural support on the superior and inferior aspects and better ligamentous support on the anterior aspect of the glenoid.  Posteriorly there isn't nearly the number of ligaments back there to support this structure.  Additionally, there are muscles attaching around the head of the humerus to try to control how this is sitting in the glenoid.

Okay, cool, so what's the point of presenting all this?

Well, imagine a situation where you are lying flat on your back on a bench and pressing dumbbells up towards the ceiling.  If you do not allow your shoulders blades to protract (come forward), i.e. you try to keep them pulled back or pinched together, you are potentially loading this joint such that at the top of the rep you have a zero moment to the shoulder, but there is still the potential to be creating large shearing forces within the GH if the scapulas (shoulder blades) stay retracted.

However, if you allow the scapulas to protract as you press through the range, there will be more structural support from the glenoid, minimizing the potential shearing forces within the GH.

See the image below for a visual depiction of what I just said.

Horizontal Press with and without Protraction--Professional Depiction

Does it make sense to always protract as you move throughout the range of a horizontal press.  I'm not sure saying that would be any different than saying you never should protract because there may or may not be situations where what that offers you is desirable, but I would suggest that the heavier the load is, the more sense it may make to allow the scapulas to protract if you are concerned with minimizing the shearing forces within the GH at the top of that range of motion.

Question:  Do you try to monitor what is happening to your scapulas when you horizontally press?  What about when your clients do?  Why or why not?

Your body.  Your training.

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