The serratus anterior (SA) muscle is vitally important for shoulder function. The muscle is best known for it's role in scapular upward rotation and posterior tilting of the scapula during shoulder movements. Additionally, it works in conjunction with the upper trapezius as a force couple to achieve full shoulder elevation. The SA is often weak in many of my patients with shoulder dysfunction. The reason for this is multi-fold. Two common reasons for SA weakness include: 1. anterior tilting of the scapula secondary tightness pec muscles & 2. over-dominant downward rotators. Both of these causes can be attributed in part to chronic postural positioning. With anterior tilting of the scapula, the shoulder is placed in an anterior and internally rotated position, lengthening the SA and inhibiting its function. With over-dominant downward rotators, the forward head posture stresses the upper cervical spine creating tension in the levator scapulae and rhomboids. Again, this posture facilitates the downward rotators, making full upward rotation difficult to achieve.
Testing the Strength of the Serratus Anterior
Supporting the arm on your shoulder, passively flex the arm to 110 degrees and protract the scapula. Monitor inferior scapular angle. Ask the patient to maintain this position as you release the arm If not, apply a downward force proximal to the elbow. If the scapula jogs underneath your fingers, the test is graded <3-/5.
Strengthening the SA Muscle
A 2006 JOSPT article entitled, "A Comparison of Serratus Anterior Activation During a Wall Slide Exercise and Other Traditional Exercises" found that the wall slide exercise was an effective exercises for SA strengthening. The article also found that the push-up plus exercise had good activation at 90 degrees of shoulder flexion. Clinically, I prefer to have my patients perform wall slides over the push-up plus. As I mentioned earlier, the SA helps the shoulder reach full upward rotation. The wall slides exercise allows for SA activation through the entire range of motion. Below is a video of several exercises by our author Chris Fox for strengthening the SA.