Nauli in yoga: what happens inside your abdomen?
Nauli, a yoga exercise, makes the rectus muscles stand out while the rest of the abdomen stays drawn in, and pressure in the colon was measured in 1924 at 30 to 47 mmHg below air pressure. No controlled trial has shown an effect on digestion.
Also called Nauli kriya, this exercise comes from hatha yoga. It builds on Uddiyana Bandha, the belly hollowed with empty lungs.
The contraction moves from one side to the other: right, center, left, center. People once thought this movement reversed the flow in the gut; in 1924, Kuvalayananda showed a drop in pressure in the colon instead.
For people in good health, on an empty stomach, to be learned with a teacher. It does not replace any treatment.
Schematic drawing, based on descriptions. Pressures: Kuvalayananda, 1924 (colon); Nespor, 1981 (stomach).
What has been measured during Nauli?
Pressure lower than that of the air, in the colon as well as in the stomach. These measurements are old and involve very few people, and the number is not always given.
| Where | Value | How | Source |
|---|---|---|---|
| Colon, during Nauli | 30 to 47 mmHg below air pressure, depending on how clean the colon was (40 mm in the first test) | Mercury barometer connected to the colon by a tube passed through the rectum | Kuvalayananda, 1924 |
| Stomach, during Uddiyana | -18 mmHg (slender female student) to -44 mmHg (professional dancer), on average | Experiment published in a Czech medical journal, summarized by its author | Nespor, 1981 |
| Abdomen, during Nauli | Pressure drops further than in Uddiyana, no figure given | The author's description | Nespor, 1981 |
Does Nauli draw water upward and move the colon?
Yes, that is what the 1924 experiments describe, in one subject. A young man who had practiced for six months received an opaque liquid under X-rays: the liquid stopped at the left bend of the colon, then reached the cecum, at the other end, as soon as he did Nauli. The author rejects the idea of reversed gut movement, because water also rises through a tube placed in the rectum, where this movement does not exist.
How do you practice Nauli?
These steps come from yoga schools, not from studies. They are done in a single exhale.
- In the morning, on an empty stomach, after using the toilet.
- Standing, legs slightly bent, hands on the thighs, torso leaning forward.
- Breathe out fully, close the throat, open the ribs: the belly hollows. This is Uddiyana Bandha.
- Without breathing in, press the hands on the thighs and contract the lower abdomen: the rectus muscles stand out in the center.
- Press harder with one hand to isolate one side, then move from one side to the other.
- Release the belly, and only then breathe in.
What do we really know about its effects?
- Measured: low pressure in the colon and stomach, and the contents of the colon moving under X-rays.
- Hypothesis: massage of the organs and help with bowel movements. Nespor claimed this in 1981 without presenting a measurement.
- Tradition: cleansing and “digestive fire,” ideas that cannot be measured.
Who should avoid Nauli?
People with heart disease: the 1924 article advises against Uddiyana for them and repeats the same warning for Nauli. It also limits beginners to three attempts a day, on an empty stomach. Yoga schools add pregnancy, menstruation, recent abdominal surgery, hernia and gallstones. This advice does not come from clinical studies. With high blood pressure or an ulcer, ask a doctor before trying it.
Frequently asked questions
What is the difference between Nauli and Uddiyana in yoga?
Uddiyana hollows the whole belly, with empty lungs. Nauli starts from this hollow belly and makes the rectus muscles stand out, together or one at a time.
Does Nauli help you lose belly fat?
We found no study on Nauli and waist size. It is done in short bursts, on a single held exhale: nothing suggests it is enough to melt belly fat.
How long does it take to learn?
No study has measured this. The young man in the 1924 X-rays had practiced for six months. You first need to hold Uddiyana without straining.
Does Nauli cure constipation?
This has not been shown: we found no controlled trial on the subject. Constipation that lasts or changes is worth discussing with a doctor.
Is Nauli dangerous?
No study has measured its safety. Caution comes from what it does to the body: pressure that changes quickly in the abdomen and chest, and held breath. Stop if you feel dizzy or have pain.
See also
Uddiyana Bandha The muscles of breathing The vagus nerve
Sources
- Kuvalayananda S. The Discovery of a Partial Vacuum in the Colon in Nauli. Yoga-Mimansa. 1924;1(1):27-28. Full issue (PDF)
- Kuvalayananda S. What is Uddiyana? and X-ray experiments on Uddiyana. Yoga-Mimansa. 1924;1(1):9-24. Full issue (PDF)
- Nespor K. Uddiyana Bandha. Yoga (Bihar School of Yoga). June 1981. Article text
- Tummee. Nauli Kriya: variations and precautions taught by yoga schools. Page
True or false?
Nauli reverses the direction of gut movement.
False. The 1924 article rejects this idea: water also rises through a tube placed in the rectum, where this movement does not exist. It points instead to the effect of low pressure (Kuvalayananda, 1924).
During Nauli, pressure in the colon falls below air pressure.
True. A barometer connected to the colon showed 30 to 47 mmHg less than the air, depending on how clean the colon was (Kuvalayananda, 1924).
A controlled trial has proven that Nauli cures constipation.
False. We found no controlled trial on this. The effect remains a hypothesis.
Cite this page
To cite this page in a paper, an article or a presentation:
Metabolive. "Nauli in yoga: what happens inside your abdomen?" Updated October 31, 2026. https://metabolive.com/en/effort-stress/nauli.