The serratus anterior (SA) muscle is critical in healthy shoulder function. It is a prime mover and stabilizer of the scapula, contributing to normal scapulohumeral rhythm.
The humerus sits within the glenoid fossa of the scapula, forming the glenohumeral joint. The scapula attaches then to the back of the rib cage forming the scapulothoracic joint. These two joints are designed to work together when performing movement of the shoulder. For example, when lifting overhead, the scapula must rotate upward and laterally and, when lowering the arm, the scapula should downward and medially.
When there are muscular imbalances and/myofascial restrictions which alter muscle activation patterns, diminished scapular control and poor GH/scapular association can result and contribute to GH joint injuries.
The Serratus Anterior (SA)
The (SA) is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax and inserts along the superior angle, medial border, and inferior angle of the scapula.
The SA in provides a link between the shoulder girdle and the trunk. When it is not functioning properly or at capacity, it can contribute to shoulder pathologies.
The SA assists in stabilizing the shoulder and moving the arm forward and overhead. The SA plays a major role in upward rotation and protraction of the scapula. Poor recruitment of the SA, both in contraction and timing, can result in limited scapular rotation and protraction, producing a relative anterior-superior translation of the humeral head in the glenoid fossa. This translation of the humeral head can result in subacromial impingement and/or rotator cuff pathologies.
The SA primarily functions to:
- Rotate the scapula upward during active shoulder abduction from 30 degrees to end range.
- Protract and stabilize the scapula with active shoulder flexion and overhead activity.
- Posteriorly tilt the scapula
- Stabilize the scapula on the thorax with pushing motions.
- Stabilize the medial border of the scapula in upper extremity weight bearing such as a push up.
Sport examples requiring optimal function of the SA:
- Boxing: The SA is commonly known as the “boxer’s muscle”.
- Significant muscle in throwing a punch and achieving maximum reach of the upper extremity.
- The SA also bracing the scapula for impact of a punch. This allows transfer of force and improve power.
- The SA facilitates protraction during the follow through of the pitch or during the throw.
- The SA functions as a “brake” during the deceleration of an overhead throw
- Swimming: The SA contributes to full scapular upward rotation for reaching upon hand entry into the water.
- Tennis: The SA provides full scapular upward rotation while serving.
- : The SA assists in protraction on the long side during the catch phase of the stroke.
The serratus anterior plays a significant role in shoulder health, optimal sports performance, and injury prevention. Including exercises designed to improve strength, endurance, proprioception, and stability of the SA is crucial to the patient/athletes, training, rehabilitation, and injury prevention programs.
Example SA Exercises
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