Breathwork: the fastest access to your nervous system

Your heartbeat, your digestion, your hormones and your immune function all run without your input. Breathing is the exception. It works automatically and can be taken over consciously at any moment. That makes it your direct route into a system that otherwise decides everything on its own.

Why breathing holds a special position

You can barely influence your blood pressure by will. Your heart rate just as little. Through your breath you reach both.

The mechanism is called respiratory sinus arrhythmia. Your heart rate rises slightly as you inhale and falls as you exhale. The braking effect of the vagus nerve on the heart is stronger during the exhale. Extend your exhale and you extend the window in which your parasympathetic branch is working.

Six breaths a minute: the resonance frequency

There is one breathing rate at which the fluctuation in your heart rate reaches its maximum. It sits at about 0.1 hertz, or roughly six breaths a minute.

The reason is mechanical. The baroreflex, which regulates your blood pressure, works with a natural delay of about five seconds. Breathe in exactly that rhythm and the control loop swings with you. Heart rate fluctuation peaks and baroreflex sensitivity rises sharply in the moment. After several months of regular practice it stays elevated at rest too (Lehrer & Gevirtz, Frontiers in Psychology, 2014).

In practice: around five seconds in, around five seconds out. For the beginning, that is all the technique you need.

What breathwork does for you

Your heartbeat becomes more flexible

Heart rate variability, or HRV, describes how much the gaps between your heartbeats fluctuate. A healthy heart beats flexibly and adapts continuously. The greater the fluctuation, the more easily your body switches between tension and recovery.

Slow breathing raises this value reliably: during the practice, immediately afterwards and lastingly after several weeks of regular practice. That is the conclusion of a meta-analysis covering more than 200 studies (Laborde et al., Neuroscience & Biobehavioral Reviews, 2022).

Why this should interest you: high HRV goes hand in hand with better self-regulation, meaning concentration, impulse control and the ability to stay calm under demand. Of all the effects of breathwork, this one is the best documented.

It lowers stress, anxiety and low mood

A meta-analysis of randomised controlled trials found consistent effects across all three areas: stress with a standardised effect size of 0.35 across 12 studies with 785 participants, anxiety 0.32 across 20 studies, depressive symptoms 0.40 across 18 studies (Fincham et al., Scientific Reports, 2023).

Those effects count as small, and in relation they are remarkable: five minutes a day, free, possible anywhere, with no side effects. There are few comparisons for that ratio of effort to result.

Guided practice works harder

With heart rate variability biofeedback, meaning slow breathing with direct feedback, the numbers come out considerably higher. A meta-analysis of 24 studies with 484 participants found an effect size of 0.83 in group comparison (Goessl, Curtiss & Hofmann, Psychological Medicine, 2017).

That is a finding that goes beyond technique. Guidance and feedback make a difference. Which is exactly why breathwork with us is guided and built into the session.

Placed in scientific context: the authors of the 2023 meta-analysis note that the included studies have room to improve methodologically. The direction of the results is consistent across many investigations, and the precision of the numbers will keep improving with future studies. One further finding from the same analysis is particularly useful in practice: the effects appeared with slow breathing techniques. Those happen to be both the simplest and the safest.

The physiological sigh: the technique for the moment

The most popular single technique right now is the double inhale with a long exhale. Two inhales in a row, then a slow exhale through the mouth.

A Stanford University study compared four conditions over 28 days at five minutes of daily practice: mindfulness meditation, cyclic sighing, box breathing and cyclic hyperventilation with breath holds. Of 108 randomised people, 100 entered the analysis. The breathing techniques improved positive mood more than meditation, and cyclic sighing was the only method to achieve a significant lead. Resting breathing rate also fell most in that group, and the effect grew across the four weeks (Balban et al., Cell Reports Medicine, 2023).

Two notes for completeness: heart rate variability stayed stable in all four groups, and state anxiety fell equally in breathwork and meditation. The widespread explanation involving a connection from the breathing centre to the locus coeruleus comes from work in mice (Yackle et al., Science, 2017). It is an elegant hypothesis, and researchers are currently testing how far it transfers to humans.

What remains for you is the practical finding: five minutes a day over four weeks measurably lifted mood. That is a result you can work with.

What fast breathing techniques deliver

Hyperventilation based methods, known above all through the Wim Hof method, have their own and surprisingly precise body of evidence.

A much cited study with 24 healthy men showed that after ten days of training the trained group responded far more mildly to an experimentally triggered inflammatory reaction. The pro-inflammatory messengers TNF alpha, interleukin 6 and interleukin 8 were roughly halved, while the anti-inflammatory interleukin 10 was strongly elevated (Kox et al., PNAS, 2014).

A follow up study with four separate groups identified which component does the work: the breathing. The rise in adrenaline appeared only in the groups doing the breathing exercise (Zwaag et al., Psychosomatic Medicine, 2022). A remarkable finding, because it shows how deeply breathing reaches into immune regulation.

For mood and perceived stress, the strength lies with the slow techniques. In a blinded study with 200 participants and an active placebo control, both groups improved equally (Fincham et al., Scientific Reports, 2024). So if you want to unwind, six breaths a minute will take you further.

How to breathe safely

Slow breathing has practically no prerequisites. With fast techniques a little knowledge pays off, and this section is missing from almost every article on the topic.

Hyperventilation lowers the CO₂ level in your blood. Two things follow. Your pH rises, which can cause tingling, muscle cramps in hands and feet and dizziness. And your drive to breathe drops away, because it is governed by rising CO₂. Lack of oxygen alone stays silent. Hold your breath after hyperventilating and you lose the signal that would otherwise make you breathe (Fincham et al., Neuroscience & Biobehavioral Reviews, 2023).

In water that is dangerous. There are documented cases of loss of consciousness with seizures after prior hyperventilation while diving (Kumar & Ng, Medical Journal of Australia, 2010), and the American Red Cross has published its own safety advisory on it.

That is why CYRCL has one clear rule: at the water, breathing stays calm and slow. Which is exactly the technique with the best evidence behind it anyway.

For hyperventilation based techniques there is more. With epilepsy, only slow methods are suitable, since hyperventilation is used deliberately in neurology to provoke seizures. With psychotic disorders, panic disorder, cardiovascular and lung conditions and during pregnancy, the decision belongs with a specialist. And as a rule: stay on dry land and away from heights.

Just five minutes

Two methods with the most solid evidence behind them:

• Resonance breathing: five seconds in, five seconds out, through the nose. Five to ten minutes. Ideal in the morning or before a demanding situation. This is the frequency at which your heart rate variability peaks.
• Extended exhale: four seconds in, six to eight seconds out. Five minutes. For the evening, after exertion, or whenever you want to wind down on purpose.

Consistency counts for most. Five minutes daily beats an hour once a month. On that point the evidence in this field agrees.

What this means for you

Breathwork shifts your autonomic balance towards the parasympathetic branch within minutes. It therefore complements sleep, training and recovery at exactly the point where you would otherwise have to wait.

At CYRCL it is built in. In the Contrast formats it guides you through the alternating stimuli, and in the Ground Room it forms part of the de-stress sessions.

You will feel it.

Frequently asked questions

How do you breathe to calm your nervous system?

Slowly, with an extended exhale. Around six breaths a minute, meaning roughly five seconds in and five seconds out, produce the maximum heart rate fluctuation, because that frequency coincides with the natural delay of the baroreflex. To wind down deliberately, four seconds in and six to eight seconds out works well.

Why do six breaths a minute work so well?

The baroreflex, which regulates blood pressure, works with a delay of about five seconds. At around six breaths a minute this control loop swings in resonance with your breathing. Heart rate variability reaches its maximum and baroreflex sensitivity rises sharply in the moment.

How quickly does breathwork work?

The shift in heart rate variability begins during the practice itself and continues immediately afterwards. For effects on stress and mood, studies show a build up across weeks. In a Stanford study, the improvement in positive mood grew steadily over 28 days at five minutes of daily practice.

How strongly does breathwork work against stress?

A meta-analysis of randomised controlled trials found consistent effects with standardised effect sizes of 0.35 for stress, 0.32 for anxiety and 0.40 for depressive symptoms. The effects appeared with slow breathing techniques. With guided slow breathing plus feedback the numbers were considerably higher, at an effect size of 0.83 across 24 studies.

Does the physiological sigh work?

In a Stanford study with 100 analysed participants, cyclic sighing over 28 days at five minutes of daily practice improved positive mood more than mindfulness meditation and lowered resting breathing rate more clearly. Heart rate variability stayed stable in all groups, and state anxiety fell equally in breathwork and meditation.

What does Wim Hof breathing deliver?

Its strength lies in the immune domain and has been replicated. Trained participants showed a markedly milder inflammatory response, and a follow up study identified the breathing as the active component. For mood and perceived stress, a blinded study with 200 participants found both groups improving equally. If you want to unwind, slow breathing takes you further.

Which breathing exercises suit the ice bath?

Calm, slow breathing. It helps you take control of the breathing reflex in the first seconds and is entirely safe in the water. Hyperventilation and breath holds belong on dry land, because hyperventilation lowers CO₂ and switches off your drive to breathe. Oxygen levels can then fall to the point of unconsciousness, and there are documented cases involving seizures.

What is CO₂ tolerance training?

A term from breathing coaching practice. As a method for building stress resilience it is still waiting for controlled human studies, and the widely used BOLT score has not been validated as a measure of it. Clinical research on breathing related disorders pursues the opposite approach, namely normalising CO₂ levels.

Sources

• Laborde, S., Allen, M. S., Borges, U., Dosseville, F., Hosang, T. J., Iskra, M., Mosley, E., Salvotti, C., Spolverato, L., Zammit, N. & Javelle, F. (2022). Effects of voluntary slow breathing on heart rate and heart rate variability. Neuroscience & Biobehavioral Reviews, 138, 104711.
• Lehrer, P. M. & Gevirtz, R. (2014). Heart rate variability biofeedback: how and why does it work? Frontiers in Psychology, 5, 756.
• Goessl, V. C., Curtiss, J. E. & Hofmann, S. G. (2017). The effect of heart rate variability biofeedback training on stress and anxiety: a meta-analysis. Psychological Medicine, 47(15), 2578–2586.
• Fincham, G. W., Strauss, C., Montero-Marin, J. & Cavanagh, K. (2023). Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials. Scientific Reports, 13(1), 432.
• Fincham, G. W., Epel, E., Colasanti, A., Strauss, C. & Cavanagh, K. (2024). Effects of brief remote high ventilation breathwork with retention on mental health and wellbeing: a randomised placebo-controlled trial. Scientific Reports, 14, 16893.
• Fincham, G. W., Kartar, A., Uthaug, M. V., Anderson, B., Hall, L., Nagai, Y., Critchley, H. & Colasanti, A. (2023). High ventilation breathwork practices. Neuroscience & Biobehavioral Reviews, 155, 105453.
• Balban, M. Y., Neri, E., Kogon, M. M., Weed, L., Nouriani, B., Jo, B., Holl, G., Zeitzer, J. M., Spiegel, D. & Huberman, A. D. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), 100895.
• Zaccaro, A., Piarulli, A., Laurino, M., Garbella, E., Menicucci, D., Neri, B. & Gemignani, A. (2018). How Breath-Control Can Change Your Life. Frontiers in Human Neuroscience, 12, 353.
• Kox, M., van Eijk, L. T., Zwaag, J., van den Wildenberg, J., Sweep, F. C. G. J., van der Hoeven, J. G. & Pickkers, P. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS, 111(20), 7379–7384.
• Zwaag, J., Naaktgeboren, R., van Herwaarden, A. E., Pickkers, P. & Kox, M. (2022). The Effects of Cold Exposure Training and a Breathing Exercise on the Inflammatory Response in Humans. Psychosomatic Medicine, 84(4), 457–467.
• Yackle, K., Schwarz, L. A., Kam, K., Sorokin, J. M., Huguenard, J. R., Feldman, J. L., Luo, L. & Krasnow, M. A. (2017). Breathing control center neurons that promote arousal in mice. Science, 355(6332), 1411–1415.
• Kumar, K. R. & Ng, K. (2010). Don't hold your breath: anoxic convulsions from coupled hyperventilation and underwater breath-holding. Medical Journal of Australia, 192(11), 663–664.
• Immink, R. V., Pott, F. C., Secher, N. H. & van Lieshout, J. J. (2014). Hyperventilation, cerebral perfusion, and syncope. Journal of Applied Physiology, 116(7), 844–851.
• American Red Cross Scientific Advisory Council (2021). Voluntary Hyperventilation Preceding Underwater Swimming: Scientific Review and Advisory.