The serratus anterior is divided up in to three parts. All three parts pull the shoulder blade forward and on to the rib cage. The muscle is an antagonist to the rhomboids which are found between the shoulder blades. When the inferior and superior parts act together, they keep the scapula pressed against the rib age together with the rhomboids and therefore these parts also act as synergists to the rhomboids.
The inferior part can pull the lower end of the scapula laterally and forward and thus rotates the scapula to make elevation of the arm possible. Additionally, all three parts can lift the ribs when the shoulder girdle is fixed, and thus assist in respiration.
The serratus anterior is largely responsible for the protraction of the scapula — that is, the pulling of the scapula forward and around the rib cage that occurs when someone performs a press up or chest press.
The serratus anterior also plays an important role in the upward rotation of the scapula, such as when lifting a weight overhead. It performs this in sync with the upper and lower fibers of the trapezius.
Commonly in those with shoulder pain you will see the scapular wing or there is an anterior tilted scapula. This is related to having an over active pec minor which causes the change in shoulder position. In this case the serrated anterior is not strong enough to maintain the position of the scapula flat against the thorax.
Having a healthy functioning serratus anterior is vital for the shoulder joint. Without sufficient strength in this muscle poor scapula position will lead to shoulder pain specifically from shoulder impingement. This is where tendons are pinched as they don’t have enough space to sit in the shoulder joint. In an exercise programme this is usually caused by excessive amounts of pushing work such as shoulder press and bench press. In the next post I will upload some videos of drills we use to wake the serratus anterior up in our personal training sessions.