Diaphragm
Diaphragm
Pronunciation: DY-uh-fram
For beginners
Your main breathing muscle. When it tightens it drops down like a piston, pulling air into your lungs; when it relaxes, air flows out.
Show the advanced explanation
The diaphragm co-contracts with the abdominal wall and pelvic floor to generate intra-abdominal pressure, contributing to spinal stability during loaded tasks (the basis of the 'brace and breathe' cue).
Structure & function
- Location
- A dome-shaped sheet of muscle at the bottom of the rib cage, separating the chest from the abdomen.
- Origin
- Lower ribs, sternum (xiphoid process), and lumbar vertebrae.
- Insertion
- Central tendon of the diaphragm.
- Main action(s)
- The main muscle of breathing: it flattens and descends to draw air into the lungs (inhalation).
- Joint(s) crossed
- —
- Movement plane
- —
- Innervation
- Phrenic nerve (C3–C5)
- In daily movement
- Every breath. Also contributes to core pressure (bracing) and stability.
- In exercise
- Breathing and intra-abdominal pressure during lifting; 'breathe out on effort' cues relate to it.
- Commonly confused with
- Confused with the abdominal muscles; the diaphragm is deeper and is primarily a breathing muscle.
- Common misconceptions
- You cannot 'train the diaphragm' like a biceps curl, but breathing mechanics can be practiced.
⚠ Safety note
Holding the breath under heavy load (Valsalva) raises blood pressure; general exercisers should usually exhale on effort. People with cardiovascular conditions should follow professional guidance.
Sources
“The diaphragm is the primary muscle of inspiration; contracting it increases the volume of the thoracic cavity.”
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
Sign in to bookmark this and save notes.