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Pectoralis major

Pectoralis major

Pronunciation: pek-tor-AL-iss MAY-jor

Simplified front view of the chest showing the sternum in the middle, ribs curving to each side, and the fan-shaped pectoralis major over the upper chest.
Chest region — rib cage, sternum, and pectoralis major (simplified). A beginner-level schematic of the chest's bony frame (sternum and ribs) and the location of the pectoralis major.
Illustration: Anatomy Learning Platform (original) · CC0-1.0 (public domain dedication)

For beginners

The main chest muscle. It powers pushing movements and pulls the arm toward and across the body. Even though we call it a 'chest' muscle, it actually acts on the arm at the shoulder.

Show the advanced explanation

Its clavicular and sternocostal heads have different lines of pull, so incline vs. flat pressing emphasizes them differently. It is a strong internal rotator and horizontal adductor of the humerus.

Structure & function

Location
The large fan-shaped muscle across the front of the chest.
Origin
Clavicle, sternum, and cartilage of the upper ribs.
Insertion
Greater tubercle / intertubercular groove of the humerus.
Main action(s)
Flexes, adducts, and internally rotates the arm at the shoulder; a strong horizontal adductor (drawing the arm across the body).
Joint(s) crossed
Glenohumeral joint
Movement plane
multiple
Innervation
Medial and lateral pectoral nerves (C5–T1)
In daily movement
Pushing movements and drawing the arm across the body — pushing a door or a shopping cart, hugging.
In exercise
Prime mover in push-ups, bench press, chest press, and chest fly; assists in dips.
Commonly confused with
Confused with the deeper pectoralis minor, which moves the shoulder blade rather than the arm.
Common misconceptions
Pushing exercises are compound: the chest works with the deltoids and triceps, not alone.

Exercises that use this muscle

As a primary mover

As a secondary / stabilizer

⚠ Safety note

Very heavy pressing with a fully stretched shoulder can strain the pec tendon; control range and load.

Sources

“The pectoralis major flexes, adducts, and medially rotates the humerus and is a primary mover of arm flexion/horizontal adduction.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.5 Muscles of the Pectoral Girdle and Upper Limbs

Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19

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