Serratus Anterior and Forward Shoulder Posture

Forward Shoulder Posture – Copyright

Forward Shoulder Posture is very common these days.  You see it everywhere; especially those people who work at computers for a living. It has become very prevalent in younger people too as more and more time is spent hunched over smartphones. I don’t want to sound like an old person here yelling at those whippersnappers to “sit up straight and pull up your pants” but I can’t help it sometimes. The truth is, while many people have poor posture for a multitude of reasons, smartphone usage truly is a big culprit in an increased amount of people walking around (and sitting) with their chin at the same level as their chest and their shoulders almost touching in the front (okay a minor exaggeration).

At the root of this problem is not a single muscle or easy fix that will miraculously turn Mr./Ms. slouch into a perfectly sculpted posture poster child.   No, the root cause is much more complex than this. However, what we as manual therapists can do, in order to understand this condition better, is to take the involved structures and look at them individually in order to better understand the contributing factors which keep our clients in their poor state of posture.

For this first of many in this series, I would like to dive into the Serratus Anterior Muscle. This muscle is commonly overlooked when treating forward shoulder posture and, in my opinion, should be given a bit more attention. Let us proceed…!

Photo Credit: Osteomyoamare

The Serratus Anterior is a strong muscle which has action on the scapula. It originates from the upper 8 or 9 ribs and inserts into the anterior medial border of the scapula.  Its primary action is to protract the scapula which pulls the scapula anteriorly around the ribs toward the front of the body. This action is usually described best when using the motion of throwing a punch. As the arm and shoulder travel forward, the serratus anterior contracts, moving the scapula anteriorly and laterally around the ribs.

The serratus anterior also as the ability to stabilize the scapula against the rib cage (along with the rhomboid muscles) as well as upwardly rotate the scapula. These actions are all done with the separate muscle fiber orientations within the serratus anterior. This is a key point to understand about serratus anterior. It has a fan shape which gives the muscle many degrees of orientation and action. In other words, the differently oriented fibers have the ability to do different actions. With all these details in mind, let us talk about how this muscle affects posture.

The more work we do on computers, smartphones, or any sort of task in front of us, the more our shoulders are prone to move and stay in a forward position.  This is simply our bodies adapting to everyday habits and needs. Our bodies have the great ability to adapt to different environments and needs as stresses are put on them. Whether it is gaining strength or flexibility or more stability, our bodies adapt to what is habitual and frequent in our lives. This is true for athletes who train for strength and speed by continually reminding their body to have peak physical performance. This is also true for a person who works at a desk and types for many hours in a day. Their body, like an athlete, is conditioned to do what they ask of it.

This principle can be applied to posture as well. If the posture which we use on a daily basis is poor, it is because we have trained (or enabled) our body to be in this position. The opposite is true for those who have good posture. They have trained their body (whether on purpose or not) to have good posture. Their body has simply adapted to the conditions which it is being used for.

Serratus Anterior

So, how does this apply to the serratus anterior? As the body adapts to the positioning of computer work, chronic smartphone usage, or any activity which allows for poor posture,  the serratus anterior begins to become shortened down. This occurs because the arms and shoulders are being used in an anterior position drawing the scapulas into protraction and the shoulders into a forward position.  (This is also seen in weightlifters who over train the serratus anterior or pectoral muscles)

Once the Serratus Anterior has become chronically shortened, it locks the scapula in a semi-protracted position. If you remember back to the point I made about the different orientation of the muscle fibers of serratus anterior, one of the most important aspects of this muscle is the middle and inferior fibers. These fibers not only draw the serratus anterior laterally around the ribs (protract) but they also depress the scapula (and really the whole shoulder girdle) inferiorly. This is what locks the shoulders into a forward posture. 

Once the serratus anterior is chronically shortened, it loses its ability to lengthen easily, and thus the shoulder loses the ability to retract. This keeps the shoulder stuck in a forward, inferior posture. This forward, inferior position limits the overall mobility of the shoulder which can lead to a host of other issues, which we will not get in to here, the most important of which is immobility of the scapula.  Once the scapula has lost its ability to move freely, the likelihood of regaining the ability to retract and thus release the shoulder from being stuck in a forward posture is slim without some sort of intervention; whether it be stretching, manual therapy, or both. The lesson is clear, release the serratus anterior, and shoulder positioning and function will be restored.

Of course, many other muscles are involved once the shoulder is chronically positioned this way. However, the serratus anterior is a key component of a forward shoulder posture and should always be considered when treating this condition.

*As a side note, working at a computer also encourages forward head and neck posture which also contributes to poor posture. As the head and neck travel anteriorly, the thoracic spine develops a greater kyphosis. Once this occurs, the scapulas are even more prone to move laterally away from the spine, adding to the forward (or protracted) positioning of the shoulders.

Additional resources:

Serratus Anterior Stretching Guide


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