Pectoralis Major

Clinical Notes

• Dual innervation from the medial pectoral nerve (C8–T1, medial cord) and lateral pectoral nerve (C5–C7, lateral cord). The sternal head is primarily medial pectoral nerve; the clavicular head is primarily lateral pectoral nerve. Selective nerve injury can produce partial pectoralis major weakness.

• One of Janda's "tight" muscles in conditions/upper-crossed-syndrome. Shortened pectoralis major bilaterally protracts and internally rotates the shoulders, increasing thoracic kyphosis. This shortening reciprocally inhibits the scapular retractors (middle trapezius, rhomboids) and lateral rotators (infraspinatus, teres minor).
• Contributes to conditions/subacromial-impingement — the internally rotated, protracted shoulder narrows the subacromial space during abduction and flexion.
• Sternal head TrPs contribute to anterior chest wall pain — relevant in the differential diagnosis of conditions/costochondritis and non-cardiac chest pain.
• Pectoralis major strain occurs in overhead pressing and bench press — the musculotendinous junction at the bicipital groove is the common failure site.

• Shortened bilaterally in virtually every client with rounded-shoulder posture. The client's shoulders are internally rotated, the anterior chest is concave, and the posterior scapulae are protracted. When the client lies supine, the shoulders do not rest flat on the table — they hover above it due to pectoral shortening.
• TrPs in the sternal head are very common in desk workers, particularly those who type with shoulders protracted and arms forward.
• The anterior axillary fold is often tender and thickened. Grasping the fold reveals taut bands in the lateral fibers.

• Responds well to longitudinal stripping along each head — follow the fiber direction from origin to insertion.
• Pin-and-stretch: compress a TrP and passively abduct and laterally rotate the arm to stretch the muscle under the compression. This is highly effective for the sternal head.
• Cross-fiber friction at the sternal attachment can address sternal head TrPs.
• Post-treatment, the client's shoulders will visibly rest lower and further back. Supine shoulder height above the table should decrease measurably.

• In female clients, obtain informed consent before working on the pectoralis major. Proper draping and communication are essential. Work through the drape if appropriate, or undrape with clear explanation and consent.
• The cephalic vein runs in the deltopectoral groove — avoid sustained deep pressure in this groove.
• The thoracoacromial artery branches exit deep to the clavicular head — avoid aggressive deep work near the clavicle.
• The brachial plexus and axillary vessels are deep to the pectoralis major in the axillary region — do not compress deeply into the axilla.

• Pectoralis major shortening is one of the primary drivers of upper crossed syndrome. It internally rotates and protracts the shoulders, increases thoracic kyphosis, and reciprocally inhibits the middle trapezius, lower trapezius, and infraspinatus. Stretching pectoralis major (doorway stretch, corner stretch) and strengthening its antagonists are foundational interventions for this postural pattern.

• The supine "shoulder hover" test is the simplest screen for pectoral shortening. With the client supine and arms at the side, observe the distance between the posterior shoulder and the table. A gap of more than 2–3 cm bilaterally indicates significant pectoralis major shortening. After treatment, repeat the measurement — it is a clear, visible outcome marker.