Section 01 of 20
Introduction
Pectoralis major is a thick, fan-shaped muscle that covers the upper front of the chest. It has a clavicular head from the collarbone and a larger sternocostal head from the breastbone and upper ribs. Its fibers converge into a flat tendon that twists as it reaches the upper arm bone.
It forms the front fold of the armpit, lies over pectoralis minor, and is the main muscle used in pushing and hugging movements. The breast tissue lies on top of it in the front, so respectful draping and consent matter in this area.
Section 02 of 20
Origin
| Origin | Clavicular head: medial half of the clavicle. Sternocostal head: the front of the sternum (manubrium and body), the costal cartilages of the upper six ribs, and the aponeurosis of external oblique. |
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Section 03 of 20
Insertion
| Insertion | Lateral lip of the intertubercular (bicipital) groove of the humerus, by a flat, two-layered tendon. |
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Section 04 of 20
Actions
No dedicated action video is currently available. This movement is explained below and video will be added when verified source media becomes available.
| Primary action | Adduction and medial rotation of the arm. |
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| Secondary actions | Flexion by the clavicular head, extension from a flexed position by the sternocostal head, and chest wall support. |
| Movement at the joint | Glenohumeral (shoulder) joint. |
| Heads / fiber groups | Two heads: clavicular and sternocostal (with an abdominal slip in some people). |
| Functional examples | Push-ups and bench press; throwing; swimming strokes; hugging; pushing a door. |
Shoulder adduction
Pulls the arm across the body toward the midline.
Medial (internal) rotation
Turns the arm inward, as in placing a hand on the opposite shoulder.
Shoulder flexion and extension
The clavicular head flexes the raised arm forward; the sternocostal head extends the flexed arm back down.
Chest wall support
With the arm fixed, it helps lift the chest, as in pull-ups, and assists forced inhalation.
Section 05 of 20
Nerve Innervation
| Nerve | Lateral pectoral nerve (C5–C7) mainly to the clavicular head and medial pectoral nerve (C8–T1) mainly to the sternocostal head, from the brachial plexus. |
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The pectoral nerves come from the brachial plexus near the collarbone. Weakness of the chest muscle with arm symptoms may reflect nerve problems, not only muscle tightness.
Section 06 of 20
Blood Supply
| Blood | Pectoral branch of the thoracoacromial artery, with contributions from the lateral thoracic artery and perforating branches of the internal thoracic artery. |
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Section 07 of 20
Pictures and Visual Anatomy
Section 08 of 20
Functional Movement
Pectoralis major powers pushing, throwing, and hugging movements, such as push-ups, bench presses, swimming strokes, and pushing a door. It also helps carry loads close to the body.
Section 09 of 20
Synergists and Antagonists
Synergists: anterior deltoid, coracobrachialis, and subscapularis (flexion and medial rotation), and latissimus dorsi and teres major (adduction and medial rotation). Antagonists: posterior deltoid, the rhomboids, the middle and lower trapezius, and infraspinatus and teres minor (extension, retraction, and lateral rotation).
Section 10 of 20
Palpation and Location
Client position and technique
Position the client supine with the arm supported. Locate the collarbone, the breastbone, and the front fold of the armpit. Ask the client to press the palm of the hand into the other hand or to adduct the arm against light resistance to feel the muscle tighten. Follow the fibers from the sternum and clavicle toward the arm.
Protect nearby structures
Obtain explicit consent, use secure draping, and follow the scope of practice and local rules for work near breast tissue. Avoid deep pressure in the armpit, where the brachial plexus, axillary vessels, and lymph nodes are close, and stop if the client reports tingling, numbness, or sharp pain.
Section 11 of 20
Massage Therapy Relevance
Pectoralis major is commonly shortened with rounded-shoulder posture, desk work, and heavy pressing exercise. Tightness in the chest may be associated with restricted overhead reach and upper back strain, but many other structures can produce similar symptoms.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce pushing and adduction strength and may be associated with more work by the anterior deltoid and triceps.
When it is tight or shortened
Tightness may be associated with forward, rounded shoulders, limited overhead reach and external rotation, and upper back tension.
When it is overused
Heavy pressing and repeated push movements may overload the muscle and its tendon and may contribute to chest and front-shoulder pain.
When it is strained
A strain may cause chest or front-shoulder pain with resisted adduction and a bruised look; a tear needs assessment.
When it is inhibited or others compensate
Reduced activation may be associated with poor pressing control and more work by the shoulder and arm muscles.
When it does not coordinate well with synergists and antagonists
Poor coordination with pectoralis minor, the serratus anterior, and the upper back muscles may alter scapular position and may be associated with shoulder symptoms.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Pectoralis strain or tear
Heavy bench pressing, sudden force on the arm, and contact sports can strain or tear the muscle or its tendon, causing bruising, pain, and weakness. A tear needs medical assessment.
Chest tightness and rounded shoulders
A shortened muscle may be associated with forward shoulders, limited shoulder external rotation, and upper back tension.
Trigger point referral
Trigger points in the muscle may refer pain to the front of the chest and inner arm, but heart and lung problems can look the same and must be considered.
Differential considerations
Costochondritis, rib problems, thoracic outlet syndrome, cervical radiculopathy, rotator cuff conditions, and heart disease can all cause chest and shoulder pain.
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Example Clinical Relationship
A client who lifts weights reports a tight chest, rounded shoulders, and pain in the front of the shoulder when bench pressing. Pectoralis major may be involved, and the pattern may be associated with tightness or overuse, but rotator cuff, rib, and nerve problems can look similar. Gentle, draped work along the fibers may support comfort, while chest pressure, a sudden pop with bruising, or a new lump needs referral.
Section 15 of 20
Massage and Treatment Approaches
For healthy, non-acute tissue, position the client supine with the arm supported. Begin with broad effleurage over the upper chest, then use kneading and gentle longitudinal strokes along the fibers, with gentle arm movement when appropriate. Always maintain secure draping.
| Movement | Use gentle shoulder horizontal abduction and external rotation within comfort to lengthen the muscle; do not force range. |
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| Regional work | Consider pectoralis minor, anterior deltoid, subscapularis, latissimus dorsi, and the upper back when assessment supports it. |
| Avoid | Deep pressure in the axilla, over an acute strain or tear, over the breast tissue, or at any point that reproduces arm tingling. |
Section 16 of 20
Precautions and Contraindications
Precautions and contraindications
- Acute strain or suspected tear, recent trauma, or recent chest, breast, or shoulder surgery.
- Use caution with a pacemaker or implant near the chest wall, breast implants, or radiation treatment fields.
- Use caution with anticoagulant use or easy bruising.
- Stop if pressure causes sharp pain, arm numbness, or tingling.
Section 17 of 20
Red Flags and When to Refer
Red flags and referral
- Chest pain or pressure, shortness of breath, sweating, or pain that spreads to the jaw or arm.
- A sudden pop with a bulge, bruising, and weakness after a heavy lift (possible tendon rupture).
- A new lump in the breast, chest wall, or armpit, or skin changes over the chest.
- Arm weakness, numbness, or swelling of the arm.
Section 18 of 20
Study Summary
Attachments
Origin: medial clavicle, sternum, upper costal cartilages. Insertion: lateral lip of the intertubercular groove.
Actions
Adduction and medial rotation of the arm; flexion (clavicular head) and extension (sternocostal head).
Supply
Lateral and medial pectoral nerves (C5–T1); thoracoacromial artery.
Section 19 of 20
Instructor Narration
Open narration transcript
Pectoralis major is the large fan-shaped muscle of the upper chest, with a clavicular head and a sternocostal head.
It arises from the medial clavicle, the sternum, and the upper costal cartilages, and inserts on the lateral lip of the intertubercular groove of the humerus.
It adducts and medially rotates the arm, the clavicular head flexes it, and the sternocostal head extends it from a flexed position. The anterior deltoid and latissimus dorsi help it, and the posterior deltoid and rhomboids oppose it.
The lateral and medial pectoral nerves supply it, from C5 to T1, and the thoracoacromial artery provides its blood.
Palpate with the client supine, follow the fibers from the sternum and collarbone toward the arm, and ask for gentle arm adduction. Obtain consent, drape securely, and avoid deep pressure in the armpit.
Strain, tightness with rounded shoulders, and trigger points are common, and heart, lung, rib, and nerve problems can overlap. Refer chest pain or pressure, a sudden pop with bruising after lifting, a new lump, or arm weakness or swelling.
Remember: clavicle, sternum, and costal cartilages to the intertubercular groove; adduction and medial rotation; pectoral nerves.
Section 20 of 20