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Breathing Wim Hof - Science explained

There are several variants of breathingWim Hof.

The breathing technique remains similar in the different variants but the protocol changes (apneas, rhythm and intention). 

In this article, I will focus on the basic breathing technique to explain its physiology.

Executive Summary

  1. BreathingWim Hof: the technique

  2. BreathingWim Hof : the science and effects on the body

  3. To summarize on physiology and science

  4. The beneficial effects of breathing Wim Hof 

  5. Points of attention for good breathing practice Wim Hof 

  6. Conclusions and conclusions 

1) The Breathing Technique Wim Hof

In this video, find the explanation in French of breathing Wim Hof and the mistakes to avoid.


The basic respiratory protocol includes about 30 full breaths, preferably with the nose, each followed by passive breathing. Complete breathing begins with ventral breathing with the diaphragm and goes through intercostal breathing, ending with breathing in the chest (some also do a last clavicular part).

The inhalation is therefore ascending and the exhalation is "in the atmosphere", i.e. relaxed and effortless (we also say 2/3 or 70% of a total exhalation). 

After the 30 breaths, on the last exhalation, one ends with an apnea with empty lungs (almost empty because the exhalation is at 2/3) to hold as long as possible but without forcing (until the first sign of body spasms of the involuntary contraction of the diaphragm type). We breathe in at the end of the apnea fully and by keeping the air we do a full lung retention phase for 15 seconds. Once these steps, which form a complete cycle of breathing, are completed, 2 or even 3 more cycles are repeated.

Figure 1: Complete Breathing Cycle Wim Hof

2) Breathing Wim Hof - the science and effects on the body

In this paragraph we will go into more detail about the science of breathingWim Hof.

During the 30 breaths (deep and complete) one gets oxygen and reaches an oxygen saturation in the blood of 99% (the breathing phase resembles a controlled hyperventilation, also called hypocapnia).

To measure the oxygen saturation of the blood, the ratio of oxyhemoglobin to hemoglobin in the blood is determined. The normal saturation of a healthy and resting person is more than 95%. The role of this active breathing phase is also to significantly reduce the concentration of CO2 in the blood. During the apnea phase the oxygen concentration drops (even up to 50% saturation, see Wim's explanations in the online courses Fundamentals or try it for yourself with an oximeter at home).

When the CO2 concentration begins to increase until it reaches the body's maximum CO2 tolerance level, the amount of CO2 in the blood activates the need to breathe. This is achieved by chemoreceptors that trigger breathing if the CO2 pressure has reached a maximum threshold (depending on how well everyone is trained to tolerate CO2).

You can see this threshold in the following Figure 2 with a horizontal blue dotted line. 


With a typical Wim Hofbreath, we decrease the need to breathe (long apnea) because we reduce the concentration of CO2 during breathing, which makes it possible to hold longer in apnea and drastically reduce the oxygen saturation during apnea (with apneas that can easily last 2-3 minutes). Normally with daily breathing during apnea the maximum CO2 tolerance threshold is reached before reaching the physiologically tolerable minimum threshold of oxygen concentration (shown in Figure 2 with the horizontal red dashed line).

After a breathWim Hof, the initial CO2 to apnea is very low and therefore the increase in CO2 concentration takes longer than the decrease in O2 concentration. This, for novice practitioners, can cause a loss of consciousness followed by automatic breathing (initiated by the central nervous system) to rebalance the O2 and CO2 concentration. This is still safe, but breathing Wim Hof should not be practiced for diving or freediving in the water.

It is also necessary to practice lying or sitting breathing. 

Figure 2: Variation of O2 and CO2 concentration in the blood during the whole breathing process: left is normal breathing and right is breathingWim Hof.

Breathing is also accompanied by tingling and tingling in the extremities (and lips, face etc.). This is due to the fact that breathing considerably reduces CO2 in the blood during the 30 breaths. A low concentration of CO2 leads to an increase in the pH in the blood (a significant part of the CO2 is converted into bicarbonate ions which will dissolve in the blood and regulate the blood pH. The pH may change slightly on the base and increase from 7.4 to 7.7 as shown in Figure 3).

Figure 3: PH variation measured during breathing Wim Hof

An alkaline pH inhibits pain receptors (also linked to temperature receptors).

I will talk about this phenomenon in another article: analgesic effect of cold (see in the Blog)

The increase in pH also has an impact on the Bohr effect and the link between hemoglobin in the blood and available oxygen (hemoglobin affinity to O2).

When the CO2 concentration is low and the pH is alkaline the bond between hemoglobin and O2 is strong and the O2 is not released to the tissues quickly, but remains available in the blood. Nevertheless, at the beginning of the respiration a large amount of oxygen starts to be stored in the tissues (which explains, for example, the apnea pump exercise proposed by Wim Hof and the fact that you can do much more than usual even when you are in apnea without breathing).

And also because the oxygen in the blood is then gradually released to the tissues throughout the apnea (or apnea pumps), and the oxygen saturation in the blood drops, CO2 increases and tissues and muscles feel a kind of tetanization and tingling.*

Excess oxygen due to hyperventilation can cause muscle stiffness at a tissue level that can be seen in the extremities (the "T-Rex" or "midwife" type hands that are often seen with the deep breathing led by Wim in Poland).  

In the nervous and endocrine system: happy hormones such as serotonin, dopamine, oxytocin, noradrenaline are produced in hypoxia (lack of oxygen towards the end of apnea) to activate a state of relaxation that activates the vagus nerve to stimulate breathing. 

In addition, CO2 is a vasodilator and therefore its low concentration determines vasoconstriction (e. g. hands and feet can become cold). 

The physiological result of breathing is therefore to promote the production of hormones of happiness and a state of stress with adrenaline production that activates the metabolism and stimulates the body to react and then reach a state of balance (hormesis by apnea).

During this breathing phase, the autonomous nervous system (SNA)* is activated, which goes into lotta-fuga mode and therefore into the orthosympathetic side (the accelerator). These short-term effects are inconsequential and are totally balanced and reversed by the following empty and full lung apnea (without forcing on the apneas) and which cause us to switch to the parasympathetic autonomic nervous system (the brake). This 3/4 cycle switch between the sympathetic and parasympathetic autonomic nervous system results in a significant balance of the autonomic nervous system (which regulates a majority of vital functions in daily life). 

Figure 4: Variation in body physiology during 2.5 hours of WHM breathing and then in the following hours without WHM breathing.
Extract from the scientific study of endotoxin by Wim and his students

To go further: breathing also Wim Hof impacts cardiac coherence and its variability. For this fascinating subject I will write another article soon. 


3) To summarize on physiology

The different phases during the breathing cycles: 

  1. Oxygenation and CO2 reduction phase, the orthosympathetic autonomic nervous system is activated (activation phase). The inhalation and exhalation phase 30 times...

  2. Apnea phase, the tendency of CO2 and O2 gases in the blood is reversed, the hormones of happiness are produced and the body is relaxed with apnea to the empty lungs, which can be compared to a long exhalation, which relaxes and increases the vagal tone and leads to a state of parasympathetic autonomous nervous system (rest, digestion, relaxation). 

  3. Short-term full lung apnea (15 seconds) to establish calm and rebalance the autonomic nervous system (which is now at the centre in superposition between sympathetic and orthosympathetic) and physiology (we emerge more alkaline, therefore with an increased pH and well oxygenated)

*Small physiological reminders:

- Oxygen is carried by the red blood cells. These cells are composed of about 1/3 of a protein called hemoglobin. When hemoglobin is oxygen loaded, it is called oxyhemoglobin.

- The Bohr effect: is the increase in hemoglobin affinity for oxygen (O2) when the partial pressure of carbon dioxide (CO2) is reduced or the pH is increased. The partial pressure of carbon dioxide is high in the tissues. The Bohr effect then implies an optimal release of the oxygen (O2) carried by the hemoglobin, in the muscles during physical efforts in particular.

- In Figure 4 graph D we observe that during breathing there is a reduction in bicarbonate (decrease in CO2 which is vasodilating, therefore vasoconstriction which explains the cold extremities but also can explain tissue tetany, cramps or muscle contractions linked to a decrease in intracellular calcium). It should also be added that the tetany that can be observed during the active breathing phase (especially in new practitioners), can be caused otherwise by neuromuscular hyperexcitability due to nervous excitation by the sympathetic system, or spasmophilia, sometimes called hyperventilation syndrome (considered benign because not pathological). 

- Thanks to a high concentration of O2 in the muscles, a higher amount of ATP can be produced in the tissues and therefore the available energy (cellular metabolism) 

- The autonomic nervous system together with the somatic nervous system constitute the two components of the peripheral nervous system. The autonomic (or vegetative) nervous system is responsible for the body's automatic functions (digestion, heart rate, sweating...). It includes two systems: the sympathetic and parasympathetic nervous systems. 

These two systems control the activity of the internal organs by opposing actions as shown in Figure 5. Their fibers communicate with cells in smooth muscles (found in the walls of many organs), heart muscle, glands and immune system cells.

The sympathetic system responds to stress by preparing for action, while the parasympathetic system causes a general slowdown in the body's functions. The latter's activity is promoted by relaxation.

Figure 5: Sympathetic system and parasympathetic system

4) The beneficial effects of breathing Wim Hof

  • Rebalance the autonomic nervous system and reduce stress, anxiety and/or beat depression: thanks to the switch between the sympathetic and parasympathetic autonomic nervous system, we make our ANS able to adapt, respond flexibly to external (and internal) stresses and return to the centre in an area of balance and health. This zone is the healthy superposition between the sympathetic and parasympathetic nervous system, where the two are balanced and work together as needed (for more information on polyvagal theory). 

  • Increasing CO2 tolerance through apnea in empty lungs: the body is taught to tolerate a gradually higher CO2 concentration and therefore to be able to function with an upper threshold. This will help us in our daily physical efforts and in endurance and sports performance. 

  • Reducing inflammation with the anti-inflammatory protocol (this will be explained in another article): by changing the basic protocol (but with the same breathingWim Hof) we can reduce inflammation in the body later.

  • Facilitate the immune system to be attentive and effective because the autonomic nervous system that regulates it is balanced and ready to act.

  • Regulate hormone production (including the right happiness hormones), metabolism and circadian rhythm (always through the balance of the autonomic nervous system and regulated by the hypothalamus) 


5) Attention points for good breathing practice Wim Hof

In this video, you will find our tips for good breathing Wim Hofpractice.

  • Never force (neither during breathing nor during apnea)

  • Practice breathing lying down or sitting down (and never in the water)

  • Do not use WHM breathing for subsequent underwater diving

  • Do not breathe superficially or too quickly 

  • Breathe through the nose unless otherwise advised by an instructor (certain types of spot breathing) 

  • Do not improvise a breathing Wim Hof session without knowing the technique. 

  • SAFETY RULES: Breathing Wim Hof is not recommended for pregnant women, people with epilepsy and people with serious heart problems.  


6) Conclusion

With my scientific background (I am an engineer and not a doctor) I have tried to explain to you (in some detail) the basic physiology of WHM breathing, thanks to the research I have done during my years of practice and the different resources available to instructors. Breathing physiology Wim Hof remains complex and requires further scientific study. My deep conviction is that to fully understand this breathing one must practice assiduously and consistently for at least a year (even if Wim Hof it can change people's lives in 5 days with its method). A purely scientific explanation (out of the books) uncorrelated to the experiences lived during this breathing can only remain incomplete.


If you have something to contribute to enrich this short article, I can only thank you for helping others to better understand this famous and "still investigating" breathing. 


See you soon for more on breathingWim Hof,


Matthijs Kox, et al (2014) Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans


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