Serratus anterior
Serratus anterior
Pronunciation: ser-AY-tus an-TEER-ee-or
For beginners
Nicknamed the 'boxer's muscle' because it powers a forward punch. It pulls the shoulder blade forward and helps rotate it upward so you can lift your arm overhead safely.
Show the advanced explanation
It forms a force couple with the trapezius to upwardly rotate the scapula during arm elevation. Weakness causes 'scapular winging' (the inner edge of the blade lifting off the rib cage).
Structure & function
- Location
- A fan-shaped muscle along the side of the rib cage, under the arm.
- Origin
- Outer surfaces of ribs 1–8/9.
- Insertion
- Medial (inner) border of the scapula, on its rib-cage side.
- Main action(s)
- Protracts the scapula (pulls it forward) and, crucially, upwardly rotates it so the arm can reach overhead; holds the scapula flat against the rib cage.
- Joint(s) crossed
- Scapulothoracic articulation
- Movement plane
- multiple
- Innervation
- Long thoracic nerve (C5–C7)
- In daily movement
- Reaching and pushing forward; keeping the shoulder blade stable when you carry or press.
- In exercise
- Key stabilizer in push-ups and pressing; prime mover in scapular protraction ('push-up plus').
- Commonly confused with
- Confused with the intercostals because of its serrated look along the ribs — but the serratus moves the scapula.
- Common misconceptions
- It is not just an aesthetic muscle; it is essential for healthy overhead motion.
Exercises that use this muscle
As a primary mover
As a secondary / stabilizer
- Barbell Bench Press (stabilizer)
⚠ Safety note
Winging of the shoulder blade or loss of overhead motion should be professionally assessed.
Sources
“The serratus anterior protracts and upwardly rotates the scapula and holds it against the thoracic wall.”
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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