The more runners I evaluate and treat the more interested I get in the serratus anterior muscle. How can a tight serratus anterior muscle affect running?
As we all know the serratus anterior muscle originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula (Platzer, 2004). The long thoracic nerve, nerve of Bell, a branch of the brachial plexus, innervates the serratus anterior muscle. Damage to this nerve can lead to a winged scapula.
The function of the serratus anterior muscle is to pull the scapula forward around the thorax, which is essential for anterversion of the arm. Thus, serratus anterior is largely responsible for the protraction of the scapula, which occurs when someone for example throws a punch. When the inferior and superior parts act together, they keep the scapula pressed against the thorax together with the rhomboids. The inferior portion of scapula can also pull the inferior part, medial border to inferior angle, of the scapula laterally and forward. This creates upward rotation that makes elevation of the arm possible. This upward rotation is created in sync with the upper and lower fibers of the trapezius (Levangie & Norkin, 2011). Additionally, all three parts can lift the ribs when the shoulder girdle is fixed, and thus assist in respiration (Platzer, 2004).
I have found that it is very common that this muscle is tight, especially in people with a lot of stress that has shallow breathing. If they on top of that do a lot of heavy overhead presses, or bench press, it is even more common.
Now we come back to the question, how can a tight serratus anterior muscle affect running?
When the scapula is tight and is in a protracted position the runner will have decreased shoulder extension when bringing the arm back and the arm /elbow will move more laterally. Furthermore, it will affect same side thoracic rotation. Can that affect the lower extremity? What I have seen is that after stretching a tight serratus anterior muscle the runner is able to bring the arm further back and help to load the same side hip and making it easier for the runner to re-supinate the same side foot for a more effective push off. By stretching the serratus anterior muscle I have been able to help many people with lower extremity pain from the feet, knees and hips.
This was another example of how integrated and linked the human body is. Also keep in mind that this is written from clinical experience and not research based, but a functional and pain free runner is always a good thing.
Jessica, Ali and Ola
Levangie, P. K., & Norkin, C. C. (2011). Joint Structure and function a comprehensive analysis, 5th Ed. Philadelphia, PA: F. A. Davis Company.
Platzer, W. (2004). Color Atlas of Human Anatomy, Vol 1: Locomotor System (5th ed.): Thieme.