Pectoralis Major

The pectoralis major is a large muscle in the upper chest, fanning across the chest from the shoulder to the breastbone. It is divided into two sections, the upper head (clavicular head) and the lower head (sternal head). Both heads converge towards the upper arm (humerus).

The main functions of the pectoralis major muscle are rotation, adduction, and flexion of the humerus, as seen when you perform actions such as swinging a bat or throwing a ball. The muscle also aids in deep inspiration (breathing in), and when developed, it can contribute to the overall aesthetics of the chest.

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man muscle model
model chest muscle

Pectoralis Major

Anatomy

[Origin]

  • Clavicular head: anterior surface of medial half of clavicle
  • Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique

[Insertion]

  • Lateral lip of intertubercular sulcus of humerus

[Action]

  • Adducts and medially rotates humerus; draws scapula anteriorly and inferiorly
  • Acting alone, clavicular head flexes humerus and sternocostal head extends it from the flexed position

Clinical Relevance

Absence of Pectoral Muscles

Absence of part of the pectoralis major, usually its sternocostal part, is uncommon, but when it occurs, no disability usually results. However, the anterior axillary fold, formed by the skin and fascia overlying the inferior border of the pectoralis major, is absent on the affected side, and the nipple is more inferior than usual.

In Poland Syndrome, both the pectoralis major and minor are absent; breast hypoplasia and absence of two to four rib segments are also seen.

~ Evidence-Based Exercises ~

According to an EMG study, the exercises that demonstrated significant muscle contractions of Pectoralis Major are;

  • Upper Pec: Press Exercise with 30 degrees Inclination
  • Lower Pec: Decline Dumbbell Press, Seated Cable Fly

Incline Press

man bench press

Decline Press

Bench Press Figure

Cable Fly

Man cable chest

< Reference >

  • Keith L. Moore, Anne M. R. Agur, Arthur F. Dalley. Moore Clinically Oriented Anatomy 7th Edition, Lippincott Williams & Wilkins, 2013
  • Rodríguez-Ridao D, Antequera-Vique JA, Martín-Fuentes I, Muyor JM. Effect of Five Bench Inclinations on the Electromyographic Activity of the Pectoralis Major, Anterior Deltoid, and Triceps Brachii during the Bench Press Exercise. Int J Environ Res Public Health. 2020;17(19):7339.
  • The Best Chest Exercises: A $12,000 Machine Reveals What They Are by Jeremy Ethier, November 11, 2022: https://builtwithscience.com/workouts/the-best-chest-exercises

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