How do you stimulate the vagus nerve?
The vagus nerve is the heart's brake: with each breath out, it slows it down a little. Breathing slowly, about 6 times a minute, is the best-proven way to strengthen this brake (review of 223 studies, Laborde 2022).
Choose a way of breathing: the nerve tightens or loosens, and the counter follows the pulse beat by beat.
Simplified diagram: starting pulse set at 68 beats per minute, changes estimated from the studies cited.
What is the vagus nerve?
It is a long nerve that starts in the brainstem and runs down to the heart, lungs and gut. It is part of the parasympathetic system, the rest-and-digest system. On the heart, it acts as a constant brake: when this brake is blocked with a medicine, the resting heart of a young adult rises to about 100 beats per minute or more (Jose 1969).
What does the vagus nerve do throughout the body?
The vagus nerve slows the heart, narrows the airways a little, starts digestion (acid, enzymes, bile, gut movements) and calms inflammation. It does not directly control adrenaline or cortisol. And most of its fibers run up from the organs to the brain: about 4 in 5, according to a count done in cats (Foley and DuBois, 1937). Choose a situation, then tap an organ.
Green dots: orders going down to the organs. Blue dots: messages going up to the brain. Branch thickness: illustration, not a measurement.
Which methods really work?
| Method | What is observed | Level of evidence |
|---|---|---|
| Slow breathing (about 6 per minute) | The pulse gap between breathing in and out grows during the exercise | ● Shown in humans |
| Breathing out longer than you breathe in | The brake acts mainly during the breath out | ● Mixed results: out of 9 studies, 4 see a benefit, 3 no effect (Meehan 2024) |
| Cold water on the face, breath held | The pulse drops within seconds: this is the diving reflex | ● Shown in humans |
| Regular endurance sport | Lower resting pulse over the months | ● Shown in humans |
| Electrical ear stimulator | No clear effect on pulse in a 2021 review | ● Uncertain results |
| Singing, humming, gargling | Very little studied; singing often slows breathing | ● Hypothesis |
How long should you breathe slowly?
Studies often use sessions of 5 to 20 minutes. The clearest effect is seen during the session; the effect that remains afterward, over several weeks, is smaller and less certain (Laborde 2022).
Frequently asked questions
How should you breathe to activate the vagus nerve?
Breathe in through the nose for about 4 seconds, breathe out gently for about 6 seconds, without forcing. That makes 6 breaths a minute. If you feel dizzy, go back to normal breathing.
Why does the heart speed up when you breathe in?
When you breathe in, the brain eases the vagus nerve brake a little; when you breathe out, it tightens it again. This is respiratory sinus arrhythmia: it is normal, and stronger in young and fit people.
Is cold water on the face safe?
For most people, yes. But cold also switches on the heart's accelerator at the same time, and this mix can upset the rhythm in someone with a heart problem. In that case, talk to a doctor first.
Does stimulating the vagus nerve lower cortisol?
Not directly: the vagus nerve does not control the adrenal glands. Breathing slowly calms the stress system. In a small study of 40 healthy adults, those who practiced 8 weeks of slow belly breathing then had lower cortisol (Ma 2017): this is encouraging, but still little studied. The best-proven effect remains the one on the heart.
What is heart rate variability?
It is the small differences in time between two heartbeats. When the vagal brake works well, these gaps are larger at rest. Smartwatches measure it, but their numbers vary a lot from one day to the next.
See also
Breath-holding The stress of an oral exam The adrenal glands Coffee
Sources
- Laborde S et al. Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis. Neurosci Biobehav Rev. 2022;138:104711. doi:10.1016/j.neubiorev.2022.104711
- Jose AD, Taylor RR. Autonomic blockade by propranolol and atropine to study intrinsic myocardial function in man. J Clin Invest. 1969;48(11):2019-31. doi:10.1172/JCI106167
- Wolf V et al. Does transcutaneous auricular vagus nerve stimulation affect vagally mediated heart rate variability? A living and interactive Bayesian meta-analysis. Psychophysiology. 2021;58(11):e13933. doi:10.1111/psyp.13933
- Koopman FA et al. Vagus nerve stimulation inhibits cytokine production and attenuates disease severity in rheumatoid arthritis. Proc Natl Acad Sci U S A. 2016;113(29):8284-9. doi:10.1073/pnas.1605635113
- Taylor IL, Feldman M. Effect of cephalic-vagal stimulation on insulin, gastric inhibitory polypeptide, and pancreatic polypeptide release in humans. J Clin Endocrinol Metab. 1982;55(6):1114-7. doi:10.1210/jcem-55-6-1114
- Garg P et al. Effect of breathing exercises on blood pressure and heart rate: A systematic review and meta-analysis. Int J Cardiol Cardiovasc Risk Prev. 2024;20:200232. doi:10.1016/j.ijcrp.2023.200232
- Meehan ZM, Shaffer F. Do longer exhalations increase HRV during slow-paced breathing?. Appl Psychophysiol Biofeedback. 2024;49(3):407-417. doi:10.1007/s10484-024-09637-2
- Ma X et al. The effect of diaphragmatic breathing on attention, negative affect and stress in healthy adults. Front Psychol. 2017;8:874. doi:10.3389/fpsyg.2017.00874
- Caspers C et al. Diving reflex: can the time course of heart rate reduction be quantified?. Scand J Med Sci Sports. 2011;21(1):18-31. doi:10.1111/j.1600-0838.2010.01246.x
- Foley JO, DuBois FS. Quantitative studies of the vagus nerve in the cat. I. The ratio of sensory to motor fibers. J Comp Neurol. 1937;67(1):49-67. doi:10.1002/cne.900670104