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Vagus Nerve Modulation Through Breathing Exercises

Original Editor - Apoorva Top Contributors - Apoorva and Vidya Acharya

Introduction

The vagus nerve (cranial nerve X) is the primary nerve of the parasympathetic nervous system, regulating cardiovascular, respiratory, gastrointestinal, and immune function, including heart rate, respiratory control, stress responses, and homeostasis.[1][2]

Breathing exercises are widely used in rehabilitation to improve breathing efficiency, reduce excessive accessory muscle activity, and promote relaxation. Slow, controlled breathing does not directly stimulate the vagus nerve, but it may enhance vagally-mediated autonomic regulation, including increases in heart rate variability (HRV).[3][4][5]

The Physiology of Breathing and Vagal Activity

Breathing and autonomic function are linked through respiratory sinus arrhythmia (RSA): heart rate speeds up on the in breath and slows on the out breath, because the vagus nerve's braking effect on the heart eases during inhalation and strengthens during exhalation.[4] This pattern is a main driver of HRV, a non invasive marker of autonomic function; higher HRV generally reflects greater parasympathetic influence.[6]

Slow, controlled breathing at around 5 to 6 breaths per minute may support autonomic regulation by:[3][4][5]

  • Amplifying respiratory sinus arrhythmia
  • Increasing vagally mediated HRV
  • Improving baroreflex sensitivity (the body's automatic ability to adjust heart rate in response to blood pressure changes)
  • Improving autonomic flexibility and reducing sympathetic predominance

A 2022 meta-analysis of 223 studies (from 1,842 screened abstracts) found that voluntary slow breathing reliably increases vagally-mediated HRV during practice (small-to-moderate effect), and to a smaller degree after single and repeated training sessions (Hedges' g approximately 0.14 to 0.32).

Breathing Techniques for Autonomic and Vagally Mediated Regulation

Diaphragmatic Breathing

Diaphragmatic breathing emphasises activation of the diaphragm during inspiration while minimising upper chest movement.

Technique

  1. Position the individual comfortably in sitting or lying.
  2. Place one hand on the abdomen and the other on the upper chest.
  3. Inhale slowly through the nose while allowing the abdomen to expand.
  4. Exhale slowly while allowing the abdomen to relax.
  5. Maintain a comfortable, relaxed rhythm.

Potential Effects: may improve breathing efficiency, reduce accessory muscle activity, promote relaxation, and support parasympathetic modulation.[3]

[7]

Slow Paced Breathing

Slow paced breathing intentionally reduces the respiratory rate to approximately 5 to 6 breaths per minute.[3][4] It has the strongest evidence base of the three techniques and is commonly used in cardiovascular rehabilitation, relaxation training, and stress management.[3][4] A 2024 study found that the specific breathing frequency used meaningfully affects the size of the resulting HRV increase, supporting individualised pacing over a single fixed rate.[8]

Potential Effects: may increase respiratory sinus arrhythmia, improve HRV, and increase baroreflex sensitivity.[3] [4]

[9]

Extended Exhalation Breathing

Extended exhalation breathing makes the out-breath deliberately longer than the in-breath, for example inhaling for 4 seconds and exhaling for 6 to 8 seconds.[4] A longer exhalation is thought to enhance parasympathetic influence by extending the phase of strongest vagal activity.[4] Evidence is mixed, however: a 2024 controlled study found that, at a fixed rate of 6 breaths per minute, a 1:2 inhale to exhale ratio did not produce significantly different HRV outcomes than a 1:1 ratio.[10] This suggests overall breathing rate may matter more than the exact ratio, and the technique is best offered as a useful variation rather than one with guaranteed extra benefit over evenly paced breathing.

Potential Effects: may support parasympathetic modulation during the lengthened out breath, and may suit patients who find evenly-paced breathing hard to sustain, though added benefit over evenly paced breathing alone is inconsistent.[4]

[11]

Clinical Applications

Breathing exercises may be used as an adjunct alongside standard evidence-based care in the following areas: [3]

  • Breathing Pattern Disorder: retraining inefficient breathing strategies and excessive accessory muscle recruitment.
  • Cardiovascular rehabilitation: supporting autonomic regulation and recovery.
  • Pain rehabilitation: supporting relaxation, self regulation, and coping.
  • Stress-related conditions: regulating physiological stress responses via autonomic balance.

Clinical Considerations

Individualise the technique to the patient's goals, tolerance, and response rather than a single fixed protocol, for example adjusting the target rate based on individual HRV response rather than defaulting to 6 breaths per minute for everyone.[8]

  • Encourage relaxed breathing rather than excessive voluntary control.
  • Progress gradually based on the patient's response.
  • Monitor for dizziness, discomfort, or increased anxiety.
  • Assess patients with significant cardiopulmonary conditions before initiating new breathing interventions.[3][12]

Evidence for Vagally-Mediated Effects of Slow Breathing

Slow breathing techniques can influence autonomic markers including HRV and RSA, and systematic reviews suggest benefits for cardiovascular and psychological outcomes, though differences in protocols, populations, and outcome measures limit conclusions on optimal frequency, duration, and long term effects.[3][4][5]

Recent evidence has begun to address these gaps. The 2022 meta analysis found consistent, small to moderate HRV increases across more than 200 studies.[5] A 2025 case control study of 126 health care workers (58 with Long COVID, 53 never infected, and 14 fully recovered) found that slow paced breathing significantly improved baroreflex sensitivity and vascular modulation in the Long COVID group, although longer follow up is needed to determine whether these benefits are sustained.[13] A 2025 scoping review of six studies on slow breathing and HRV biofeedback likewise concluded the techniques are promising, but that protocol standardisation and long term evaluation remain priorities.[14] HRV biofeedback, which commonly incorporates paced breathing, has also shown potential benefits for autonomic regulation and stress related outcomes.[12]

Breathing exercises should be considered a complementary strategy, used alongside evidence based interventions such as exercise therapy, education, and functional training.

Summary

Diaphragmatic breathing, slow-paced breathing, and extended exhalation techniques may support autonomic regulation by enhancing vagally mediated physiological responses. Evidence for slow-paced breathing has strengthened in recent years, including in applied populations such as Long COVID and cardiovascular rehabilitation, though protocol standardisation and long-term outcome data remain limited.[5][13] [14] These interventions are simple, low cost, and can be incorporated into rehabilitation as an adjunct to evidence based care.

References

  1. ↑ Standring S, ed. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2020.
  2. ↑ Ottaviani MM, Macefield VG. Structure and Functions of the Vagus Nerve in Mammals. Compr Physiol. 2022;12(4):3989-4037.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Zaccaro A, Piarulli A, Laurino M, et al. How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing. Front Hum Neurosci. 2018;12:353.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 Russo MA, Santarelli DM, O'Rourke D. The Physiological Effects of Slow Breathing in the Healthy Human. Breathe (Sheff). 2017;13(4):298-309.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Laborde S, Allen MS, Borges U, 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.
  6. ↑ Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Front Public Health. 2017;5:258.
  7. ↑ Rehab My Patient. How to do Diaphragmatic breathing lying down. Available from: https://www.youtube.com/watch?v=6YB0pv3iv0g [last accessed 7/22/2026]
  8. ↑ 8.0 8.1 You M, Laborde S, Ackermann S, Borges U, Dosseville F, Mosley E. Influence of Respiratory Frequency of Slow-Paced Breathing on Vagally-Mediated Heart Rate Variability. Appl Psychophysiol Biofeedback. 2024;49(1):133-143.
  9. ↑ Fullscript. Slow-paced breathing 101. Available from: https://www.youtube.com/watch?v=Bf1dtO5eC0s [last accessed 7/22/2026]
  10. ↑ Meehan ZM, Shaffer F. Do Longer Exhalations Increase HRV During Slow-Paced Breathing? Appl Psychophysiol Biofeedback. 2024.
  11. ↑ Benilda Therapy. Extended Exhale | Breathing Practice • Vagus Nerve Exercise. Available from: https://www.youtube.com/watch?v=bJI7-jLmFdo [last accessed 7/22/2026]
  12. ↑ 12.0 12.1 Lehrer PM, Gevirtz R. Heart Rate Variability Biofeedback: How and Why Does It Work? Front Psychol. 2014;5:756.
  13. ↑ 13.0 13.1 Mauro M, Cegolon L, Bestiaco N, Zulian E, Larese Filon F. Heart Rate Variability Modulation Through Slow-Paced Breathing in Health Care Workers with Long COVID: A Case-Control Study. Am J Med. 2025;138(5):870-883.e5.
  14. ↑ 14.0 14.1 Giorgi F, Tedeschi R. Breathe Better, Live Better: The Science of Slow Breathing and Heart Rate Variability. Acta Neurol Belg. 2025;125(6):1497-1505.
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