The coracobrachialis is a long, thin muscle that lies deep on the medial arm between the biceps and triceps brachii. It originates on the coracoid process, along with the pectoralis minor and the short head of the biceps brachii. Its parallel muscle fibers run deep to the pectoralis major and anterior deltoid, extending about halfway down the humerus before inserting on the medial shaft. This landmark mirrors the insertion of the deltoid, located on the lateral shaft of the humerus at the deltoid tuberosity. 

The coracobrachialis works strongly with the anterior deltoid, upper fibers of the pectoralis major, and biceps brachii to flex the shoulder. Shoulder flexion occurs during daily activities like lifting, pushing, and reaching. This motion is opposed or controlled by the posterior deltoid, latissimus dorsi, teres major, and lower fibers of the pectoralis major.

The coracobrachialis, latissimus dorsi, teres major, pectoralis major, and long head of the triceps brachii all work together to adduct the shoulder. Movements that involve pulling down and in toward the body, weight-bearing activities on the arms, and activities such as climbing, gymnastics rings, parallel bars, and pull-ups involve powerful shoulder adduction. The coracobrachialis is also utilized when bringing the arm in and across the body as with a golf swing or a pitching motion in fast-pitch softball.

Repetitive or prolonged activities that require moving or maintaining the upper extremity up and forward may create hypertonicity in the coracobrachialis and associated muscles. This position is commonly used when doing computer work, driving, texting, typing, video gaming, and writing. Sleeping with arms overhead, or performing repetitive tasks like painting or scrubbing, also creates tension and decreases tissue mobility in this area. This tension or decreased mobility may be observed as an inability to lay the shoulder and arm flat on the table and next to the body when the client is supine. 

Coracobrachialis

Attachments

•
Origin: Coracoid process of the scapula

•
Insertion: Medial shaft, middle third of the humerus

Actions

•
Flexes and adducts the shoulder

Innervation

• Musculocutaneous nerve

• C5–7

Palpating Coracobrachialis

Positioning: client supine with arm resting at the side.

1. Locate the anterior border of the axilla.

2.
Palpate posteriorly and laterally along the medial surface of the humerus.  

3.
Locate the muscle belly deep and medial to the biceps brachii, following toward its insertion on the medial shaft of the humerus.

4.
As the client performs shoulder adduction, resist to ensure proper location.

Christy Cael is a licensed massage therapist and certified strength and conditioning specialist. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.

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