ChestSource-checked

Intercostal muscles

Musculi intercostales (externi & interni)

Pronunciation: in-ter-KOS-tul

For beginners

The little muscles between your ribs. One set helps lift the ribs to breathe in; another set helps pull them down to breathe out hard.

Show the advanced explanation

The external intercostals are more active in inspiration; the internal (and innermost) intercostals assist active expiration. They also provide chest-wall rigidity that aids trunk stability.

Structure & function

Location: Short muscles filling the spaces between the ribs.
Origin: Lower border of each rib.
Insertion: Upper border of the rib below.
Main action(s): External intercostals help raise the ribs for inhalation; internal intercostals help lower them for forced exhalation. Together they stiffen the chest wall.
Joint(s) crossed: Costovertebral / sternocostal joints
Movement plane: —
Innervation: Intercostal nerves (T1–T11)
In daily movement: Assist breathing, especially deeper or faster breathing.
In exercise: Support forceful breathing during hard effort and stabilize the trunk.
Commonly confused with: Confused with the serratus anterior, which lies more to the side and moves the scapula.
Common misconceptions: They are not major 'movement' muscles for exercises; their main role is breathing and chest-wall support.

⚠ Safety note

Sharp rib or breathing pain (e.g. after a fall) needs medical assessment, not exercise.

Sources

“External intercostals aid inspiration and internal intercostals aid forced expiration by moving the ribs.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.4 Axial Muscles of the Abdominal Wall and Thorax

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