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Shoulder Anatomy: Pectoralis Major

Jul 27, 2020


MUSCLE OF THE DAY: “Pectoralis Major”

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The pectoralis major is one muscle with three parts located on the anterior surface of the thoracic cage. If you're a gym lover, you'll hear these muscles also being referred to as the pecs, #chesticles, and every bro in the world hits the pecs on, “International Chest Day”! The pectoralis major has a broad origin and is divided into three parts: clavicular (upper), sternal (middle) and costal region (lower) aka block region.


Origin (proximal attachment): Clavicular part: anterior surface of medial half of clavicle. Sternocostal part: anterior surface of sternum and costal cartilages of ribs 1-6. Abdominal part: anterior layer of rectus sheath.

Insertion (distal attachment): Crest of greater tubercle of humerus.

Actions: As a whole, humeral horizontal adduction, adduction, and internal rotation. Acting independently, the clavicular part helps to flex shoulder up to 90 degrees and the sternocostal part helps with shoulder extension. Draws scapula anteriorinferiorly (forward and down).

The pectoralis Major is a large anterior thoracic muscle. It adducts, internally rotates, flexes, extends, and horizontally adducts. Learn all this and more during Show Up Fitness 2-month Personal training Internship in Los Angeles, Santa Monica, an&

Common Injuries to the Pec Major

The pectoralis major tendon is most commonly injured during an eccentric contraction, when the external force on the muscle is greater than the force that the muscle can generate and when the arm is extended and externally rotated, like when performing a bench press. Bench pressing is the most common cause of injury (specifically incline due to the greater stress on the AC-joint). Pectoralis major injuries typically occur in men aged 20 to 40. The injury can result in pain in the chest and upper arm and weakness/deformity of the chest and upper arm. Read more on how to help fix your chest injuries from our partners at The Prehab Guys HERE.


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