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Diaphragm
The domed sheet between chest and abdomen that produces most of every quiet breath you take.
Latin name: Diaphragma. In plain English, the dome of muscle that does your breathing. It is filed here under core, breathing and pelvic floor.
Reference information, not a diagnosis. Where a symptom is described below, it is there so you can describe your own more precisely to a clinician — not so you can name what you have.
Where it is
The diaphragm is a double dome of muscle and tendon separating the chest from the abdomen. Muscle fibres arise all around its rim — from the breastbone in front, the lower ribs at the sides, and the lumbar vertebrae behind through two tendinous pillars called the crura — and run inward to converge on a central sheet of tendon rather than onto a bone. When the muscle shortens, the domes descend and flatten.
Three structures pass through it at different levels: the inferior vena cava at about the eighth thoracic vertebra, through the central tendon; the oesophagus at about the tenth, through the muscular part of the right crus; and the aorta at about the twelfth, passing behind the diaphragm under the median arcuate ligament. The old mnemonic — the vena cava has eight letters, oesophagus ten, aortic hiatus twelve — is how generations of students have remembered it.
| Feature | Detail |
|---|---|
| Origin | Sternal part from the back of the xiphoid process; costal part from the inner surfaces of the lower six ribs and their cartilages; lumbar part from the crura on the upper lumbar vertebrae and the arcuate ligaments |
| Insertion | The central tendon |
| Nerve | Phrenic nerve (C3-C5) |
| Main actions | Contracts and flattens to draw air into the lungs; contributes to raising intra-abdominal pressure |
What it does
At rest it does the great majority of the work of breathing. As the domes descend, the volume of the chest increases, pressure falls, and air flows in; the belly moves outward because the abdominal contents are being displaced downward. Breathing out at rest is mostly passive, as the diaphragm relaxes and elastic recoil of the lungs does the rest.
It also has a mechanical role away from breathing. Holding a breath against a closed airway while the abdominal muscles contract produces the pressure that stiffens the trunk during a heavy lift. The same system produces a cough, a sneeze and the strain used in childbirth or defaecation.
Its nerve supply is high — the third to fifth cervical nerve roots — because the muscle develops in the neck region and migrates downward during embryonic life. This is why a spinal cord injury above the fifth cervical level threatens breathing, and why diaphragm irritation is felt at the tip of the shoulder rather than in the chest.
Exercises that load it
| Exercise | Category | Muscles the exercise library lists |
|---|---|---|
| Easy running (8 km/h) | Cardio | Legs, heart, lungs |
| Tempo running (12 km/h) | Cardio | Legs, heart, lungs |
| Swimming, freestyle | Cardio | Whole body, heart, lungs |
| Yoga (hatha) | Mobility | Whole body, balance, breath |
| Rowing machine | Cardio | Legs, back, arms, heart |
Endurance exercise loads it in the most direct way there is: hard aerobic work raises breathing rate and depth for a sustained period, and the muscle fatigues like any other. Inspiratory muscle training with a resistance device is a real intervention with a real evidence base in some clinical groups. For most people, running, swimming and rowing already load it plenty.
How it is lengthened
You cannot stretch the diaphragm the way you stretch a hamstring, but you can free the structures around it. Positions that open the rib cage and the thoracic spine — a supported backbend over a roller, a side-lying open book — make it easier for the lower ribs to expand. Slow breathing with a long exhale is often more useful than any stretch, and it also acts on the nervous system.
When it goes wrong
| Problem | What it typically feels like | Usual setting |
|---|---|---|
| Hiatus hernia | Heartburn, regurgitation and discomfort behind the breastbone, worse lying down or after meals | Part of the stomach passing up through the oesophageal opening; common with age |
| Phrenic nerve palsy | Breathlessness lying flat, with one side of the diaphragm sitting high | Injury to the phrenic nerve in the neck or chest, sometimes after surgery or a viral illness |
| Referred shoulder tip pain | Pain at the very top of the shoulder that has nothing to do with the shoulder | Irritation of the underside of the diaphragm, for example by blood or infection in the abdomen |
New breathlessness, breathlessness lying flat, or pain at the tip of the shoulder with abdominal pain needs medical assessment promptly. None of these is a training problem.
Nothing on this page is a treatment plan. If a problem is limiting what you do, is not improving, or is getting worse, the right next step is an assessment by a doctor or a physiotherapist who can examine you.
Sources: descriptive anatomy from Gray's Anatomy of the Human Body, 20th US edition (1918), which is in the public domain; Latin names follow Terminologia Anatomica, published by the Federative International Programme for Anatomical Terminology. Nerve root levels are the conventional ranges taught from those sources and vary between individuals and between textbooks. Exercise cross-links use the TempoLife exercise library. Checked 2026-09-06.
Frequently asked questions
What is a stitch?
The honest answer is that it is not settled. Exercise-related transient abdominal pain has been attributed to diaphragm ischaemia, to irritation of the parietal peritoneum lining the abdominal wall, and to strain on the ligaments supporting the abdominal organs. The peritoneal explanation currently has the most support.
Is belly breathing better than chest breathing?
At rest, most people already breathe diaphragmatically, and outward belly movement is simply what happens when the diaphragm descends. Slow breathing with a longer exhale has measurable calming effects; the label matters less than the pace.
Why does C3, 4, 5 keep the diaphragm alive?
Because the phrenic nerve arises from those cervical roots. A spinal cord injury above that level removes the drive to the muscle, which is why the level of a neck injury determines whether someone can breathe unaided.
Nearby in this reference
Rectus abdominis
The straight abdominal muscle, the six-pack
Abdominal obliques
The side abdominal muscles that twist the trunk
Transversus abdominis
The deepest abdominal layer, a corset around the waist
Pelvic floor
The sling of muscle at the base of the pelvis
Deltoid
The cap of the shoulder
Rotator cuff
The four small muscles that hold the shoulder in its socket
All 34 body parts · Exercise library · Body map
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