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Transversus abdominis
The deepest abdominal muscle, running horizontally like a belt and raising the pressure inside the abdomen.
Latin name: Musculus transversus abdominis. In plain English, the deepest abdominal layer, a corset around the waist. 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
This is the innermost of the three flat abdominal muscles, and its fibres run horizontally around the waist — hence the name. It arises from the inside of the lower ribs, from the thoracolumbar fascia at the back, and from the pelvis, then wraps forward to end in an aponeurosis that joins the midline. Functionally it is a belt: when it shortens, the waist narrows and the pressure inside the abdomen rises.
Its connection to the thoracolumbar fascia at the back is what gives it a role in the lower back. Tensioning that fascial sheet stiffens the region in a way that does not depend on any single muscle pulling on a bone.
| Feature | Detail |
|---|---|
| Origin | Inner surfaces of the costal cartilages of ribs seven to twelve, the thoracolumbar fascia, the iliac crest and the lateral third of the inguinal ligament |
| Insertion | Linea alba, pubic crest and pecten pubis, partly through the conjoint tendon |
| Nerve | Thoracoabdominal nerves T7-T12 and L1 |
| Main actions | Compression of the abdominal contents, raising intra-abdominal pressure, and tensioning the thoracolumbar fascia |
What it does
It works with the diaphragm above and the pelvic floor below to manage pressure. Before a heavy lift, all three activate together; the same system operates in coughing, sneezing, straining and forced breathing out. It also flattens the abdominal wall and supports the viscera.
The claim that has not held up is the stronger one. For about two decades, isolated "draw in your belly button" training was taught as the cure for low back pain, on the theory that this muscle is selectively delayed in people who have it. Later trials comparing specific deep-abdominal training against general exercise have not shown it to be superior. The muscle is real and it does real work; the specific training protocol built around it turned out not to be special. General strengthening and graded activity remain the better-supported approach.
Exercises that load it
| Exercise | Category | Muscles the exercise library lists |
|---|---|---|
| Plank | Core | Deep core, shoulders, glutes |
| Farmer's carry | Strength | Grip, core, upper back, legs |
| Barbell back squat | Strength | Quads, glutes, core, back |
| Overhead press | Strength | Shoulders, triceps, core |
| Deadlift | Strength | Hamstrings, glutes, back, grip |
It is loaded any time abdominal pressure has to rise, which means every heavy lift, every loaded carry and every hard brace. Deliberate isolation is possible but of limited value for most people. The practical version is to breathe out against a braced abdomen during heavy effort and to train positions where the trunk resists being bent or twisted.
How it is lengthened
It is not a muscle you stretch in any meaningful sense — its fibres run around the trunk rather than along it, and there is no joint it crosses to open up. If the abdominal wall feels tight after heavy training, general trunk extension and rotation movements are more useful than trying to target this layer.
When it goes wrong
| Problem | What it typically feels like | Usual setting |
|---|---|---|
| Abdominal wall weakness after surgery | A feeling of instability or bulging in the abdominal wall, sometimes with a visible swelling on straining | After abdominal surgery, particularly where the muscle or its nerves were cut |
| Athletic groin pain | Deep groin or lower abdominal pain on sprinting, twisting or kicking, hard to localise | Common in football and hockey; involves several structures around the pubic bone and needs proper assessment |
| Pressure-management problems | Leaking urine, a bulging abdominal wall or a held breath during heavy lifting | Coordination between diaphragm, abdominal wall and pelvic floor rather than weakness of any one part |
Leaking urine during exercise, a heaviness or bulge in the vagina, or a bulge in the abdominal wall are all reasons to see a clinician or a pelvic health physiotherapist. They are common, they are not something to train through, and they are treatable.
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
Does hollowing my stomach protect my back?
The evidence does not support making it a specific rule. Trials comparing deep-abdominal isolation training with general exercise for back pain have not found it superior. A general brace during heavy effort is enough for most people.
What is the difference between bracing and hollowing?
Hollowing means drawing the abdominal wall inward, aiming at this muscle specifically. Bracing means stiffening the whole abdominal wall as if preparing to be pushed. Bracing is what people naturally do under load.
Can I feel it working?
Only indirectly. It lies beneath the obliques, so what you feel when you tense your waist is the whole abdominal wall rather than one layer.
Nearby in this reference
Rectus abdominis
The straight abdominal muscle, the six-pack
Abdominal obliques
The side abdominal muscles that twist the trunk
Diaphragm
The dome of muscle that does your breathing
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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