Breathing practices: what has been measured in the Wim Hof method, hyperventilation, box breathing, and slow rhythm techniques

The term "breathing practices" usually refers to four different things: slow rhythm, equal phases of inhalation and exhalation, conscious hyperventilation, and the Wim Hof protocol, where breathing is combined with cold exposure and meditation. Because of this, discussions about the "benefits of breathing" quickly become confusing: studies measure different indicators in different people under different conditions.

One sign, four different interventions

Slow breathing at a rate of about six cycles per minute changes heart rate variability, the baroreflex, and sometimes blood pressure. "Box breathing" usually means equal duration for the inhale, hold, exhale, and another hold. Controlled hyperventilation does something else: it rapidly lowers the level of carbon dioxide in the blood and therefore shifts the point at which a strong urge to inhale occurs. The Wim Hof method combines cycles of hyperventilation, breath-holding, focus, and cold exposure.

If you put these schemes into one basket, the conclusion will be too general. This is exactly the case discussed in the article what is biohacking: one word combines interventions with different physiology and varying levels of evidence.

The Wim Hof method: there is an effect, but it is a package deal

The most famous work on the Wim Hof method is a randomized study on 24 healthy volunteers, where 12 people were trained in meditation, breathing techniques, and cold exposure for ten days, while 12 served as a control group. Afterward, everyone was injected with endotoxin in an experimental inflammation model. In the training group, adrenaline increased during practice, IL-10 rose faster, and levels of TNF-α, IL-6, and IL-8 were lower; subjective "flu-like" symptoms were also weaker. Source: PubMed.

But this is not a study of "breathing only." The protocol consisted of three parts at once, and the number of participants was small, with all being healthy adults. A later pilot study by the same group attempted to break down the contribution of cold and breathing separately, but the samples there were also small and male-only: 40 participants in the training phase and 48 in the component comparison. Source: PubMed.

Therefore, the accurate formulation is: the "breathing plus cold plus concentration" package has measurable acute effects on physiology, but there is little basis to extrapolate them to long-term health, let alone attribute them to breathing alone. This overlaps directly with the topic of cold, because part of the method's brand is built specifically on it — more details in the article about cold and brown fat.

Controlled hyperventilation: more time without inhaling, less oxygen reserve

Hyperventilation before breath-holding does not significantly increase oxygen reserves, but it does noticeably lower carbon dioxide. For the subjective sensation, this is important: it is carbon dioxide that strongly influences the urge to inhale. In an experiment with 18 volunteers, fifteen seconds of hyperventilation before a series of static apneas extended breath-holding from 111 to 133 seconds, but simultaneously lowered final oxygen values: minimum saturation after apnea was 90.6% versus 93.6% after normal breathing. Source: PubMed.

This is an important detail because, in marketing, hyperventilation is often presented as a way to "train oxygen." In fact, such studies show something else: a person endures longer but reaches deeper hypoxia. Outside the laboratory, this is not proof of benefit, but a description of a risk mechanism.

"Box breathing": data is mainly about acute stress

The evidence base for "box breathing" is narrower and simpler. Researchers usually look not at diseases or mortality, but at short-term changes in heart rate, subjective anxiety, and salivary stress markers. In a 2026 randomized laboratory study, 66 participants were assigned to normal breathing, extended exhalation, and "box breathing." Both breathing schemes attenuated the increase in heart rate, anxiety scores, and alpha-amylase after a stress test; there were no differences in cortisol or HRV. Source: PubMed.

There is also a larger remote study from 2023, where three breathing protocols and meditation were compared over a month. "Box breathing" was one of the branches, but the best result for mood was not shown by it, but by a variant with an emphasis on long exhalation. This is a good example of how the word "breathing" hides schemes with different effects. Source: PubMed.

Slow breathing: the most common and most studied branch

Of all the practices, slow breathing at about 0.1 Hz, which is approximately six cycles per minute, is closest to standard physiology. In a small randomized study of 36 healthy adults, a month of daily practice was associated with a decrease in spontaneous respiratory rate, a slight decrease in mean blood pressure, and shifts in some HRV indicators. Source: PubMed.

When more such studies accumulated, researchers attempted to aggregate the effect on blood pressure into a meta-analysis. In a review of 17 studies, slow breathing was associated with a decrease in systolic pressure by approximately 5.6 mm Hg and diastolic by 3 mm Hg, but heterogeneity between studies was high. Source: PubMed.

A later mini-review showed the same picture: acute shifts in the baroreflex and autonomic indicators are reproduced more often than long-term effects. That is, slow breathing does provide a signal, but the size and stability of the effect depend on exactly who was measured: healthy people, patients with hypertension, or small clinical groups. Source: PubMed.

The main safety boundary: hyperventilation plus water

The most serious part of the topic is not about well-being, but about fatalities. Hyperventilation before breath-holding in water is described in the literature as a mechanism for hypoxic blackout, or shallow water blackout. The logic is simple: carbon dioxide decreases, the urge to inhale comes later, and oxygen meanwhile drops to the point of loss of consciousness. If this happens underwater, the person loses consciousness before they can surface.

A review of cases in New York State from 1988–2011 described 16 fatal and non-fatal drownings related to dangerous underwater breath-holding; the investigation was prompted by the death of two healthy young men after intentional hyperventilation before diving in a pool. Source: PubMed. A separate review on this topic in StatPearls directly links prior hyperventilation to loss of consciousness underwater at any depth, not just "shallow" ones. Source: PubMed.

This is not a rare theoretical disclaimer at the end of an article, but a central fact regarding safety. Therefore, breathing protocols involving hyperventilation cannot be discussed as a harmless "anti-stress practice" outside the context of gas exchange and real accidents.

What is supported by data in the end

The most consistent evidence base is for slow breathing: there are small randomized studies, meta-analyses, and understandable physiological mechanisms. For "box breathing," the data is mainly short-term and concerns stress markers. The Wim Hof method has measurable effects, but they are difficult to separate from cold and concentration. Controlled hyperventilation changes blood gases the most and therefore relates more to the risk of hypoxia than to a promise of benefit.

It is useful to keep this in mind in a broader sense as well. The more impressive a protocol sounds, the more often it is backed by either surrogate markers, mixed interventions, or small sample sizes. A significant part of the "self-experimentation" market is built on this gap — see the article about self-experimentation.

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Frequently asked questions

Are the Wim Hof method and breathing exercises the same thing?

No. In research, the Wim Hof method typically includes not only breathing but also cold exposure and focused attention. Therefore, the observed effects cannot be automatically attributed to the breathing component alone.

What does controlled hyperventilation show in a laboratory setting?

It reduces carbon dioxide levels, delays the urge to breathe, and allows for longer breath-holding. At the same time, by the end of the hold, oxygen levels drop more significantly than after normal breathing.

Is there data on box breathing regarding diseases and mortality?

There is almost no such data. The main studies look at acute changes in heart rate, anxiety, and stress biomarkers following short-term practice.

Why is a rate of six breaths per minute discussed more often than others?

Because this specific rhythm has been used most frequently in physiological studies. There are small randomized trials, meta-analyses on blood pressure, and reviews on the baroreflex and HRV for this rate.

Why is the combination of hyperventilation and water considered particularly dangerous?

Due to the mechanism of hypoxic blackout. After hyperventilation, the signal to breathe is delayed while oxygen levels continue to drop. The literature describes drownings and loss of consciousness in pools and while diving following this exact scenario.

Read next

• Biohacking: separating what has been tested from what is being sold — There is no definition of biohacking that two people would both sign.
• Cold exposure and brown fat: how many calories an ice bath actually costs — Brown fat is one of the rare cases where the elegant mechanism turns out to be real: the tissue genuinely converts fat into heat, bypassing the usual route.
• Testing it on yourself: telling an effect apart from noise — Trying something on yourself is the only available way to find out whether it works for you specifically.

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