If you have spent any time around breathwork or cold-exposure communities, you have heard some version of the pitch: a pattern of fast, deep breathing followed by breath-holding, paired with cold showers or ice baths, can calm inflammation, lift mood, and let ordinary people do things that look physically implausible, like standing in ice water for long stretches or running half-dressed through snow. The method is named for Wim Hof, a Dutch extreme athlete who built his reputation, and later a media career and training business, on feats like those. What sets it apart from most wellness trends is that it did not stay anecdotal. Hof actively sought out researchers willing to test him and his method in a lab, and one of those tests, published in a major scientific journal in 2014, produced a genuinely startling result. In the years since, a slow trickle of small trials has tried to work out how much of that finding holds up, and for what, exactly.
The Study That Made Everyone Pay Attention
The method itself has three parts: a breathing exercise (cycles of controlled hyperventilation followed by a breath-hold at low lung volume), cold exposure (showers, ice baths, or snow), and a meditation or visualization practice. In 2014, a team at Radboud University in the Netherlands put all three together in a tightly controlled experiment (Kox et al., 2014). Twelve healthy volunteers trained for ten days in the full method; twelve more did no training at all. Afterward, everyone received an intravenous dose of bacterial endotoxin, a standard way to trigger a short, controlled inflammatory response in a lab without any real infection.
The results were striking. During the breathing and cold exercises, the trained group showed sharp spikes in adrenaline, driven by intermittent respiratory alkalosis and mild oxygen deprivation from the breath-holds. When the endotoxin hit, that group produced more of the anti-inflammatory signal interleukin-10, and less of the pro-inflammatory signals TNF-alpha, interleukin-6, and interleukin-8, than the untrained group. They also reported fewer flu-like symptoms afterward. The paper's own framing was bold: the autonomic nervous system and the innate immune response, two systems long assumed to sit outside voluntary control, could apparently be influenced on purpose.
It is worth sitting with how small and artificial this study was before anything else. Twelve people per group is a tiny sample. The "infection" was a single controlled endotoxin dose in healthy young adults, not an illness caught in the real world. And because meditation, breathing, and cold exposure were trained together, there was no way to tell from this study alone which piece, or which combination, was doing the work. None of that makes the finding meaningless. It is a real, published, peer-reviewed result from a serious academic group, and it is the reason this method has been taken seriously enough by scientists to generate a decade of follow-up research. It just was not, on its own, proof that the method works as advertised.
Ten Years and Eight More Trials Later
A 2024 systematic review in PLOS ONE set out to add up everything tested since (Almahayni & Hammond, 2024). The authors registered their protocol in advance, searched two databases for studies published through mid-2022, and found nine papers covering eight separate trials, five of them full randomized controlled trials, three crossover designs, and one observational cohort.
Two things stand out from how the review scored that evidence. First, nearly every trial was judged to carry a high risk of bias, mostly for an unavoidable reason: there is no realistic way to blind someone to whether they are doing cyclic hyperventilation and ice baths or sitting in a waiting room. Second, when the reviewers broke the inflammation findings apart by component, a pattern emerged. Cold exposure by itself looked to do little to epinephrine or cytokine levels. The breathing technique alone, without the breath-hold, lowered pro-inflammatory markers but did not reliably raise interleukin-10. It was the combination, breathing techniques together with cold exposure, that most consistently moved both sides of the inflammatory response in the trials reviewed. Outside of inflammation, the review described effects on exercise performance and breathing mechanics as mixed, not consistently positive or negative.
The review raised one more point worth taking seriously rather than brushing past: Wim Hof has personally participated in, or otherwise been involved with, several of the studies that make up this evidence base, and he now runs a media career and a commercial training company built on the method. The reviewers themselves flagged this as a real conflict-of-interest concern, not a reason to dismiss the research, but a reason to weigh it with the same caution applied to any health claim with a commercial interest attached to the evidence behind it.
Does the Breathing Alone Make You a Better Athlete? Two Trials Say Not Much
Separate from inflammation, a natural question is whether the breathing technique itself, the hyperventilation-and-breath-hold cycles, does anything for exercise performance. Two controlled studies tested this directly, and both came back largely negative.
A four-week trial in nineteen adolescent middle- and long-distance runners had about half the group practice the Wim Hof breathing technique daily, while the rest trained normally (Marko et al., 2022). Before and after, both groups ran incremental treadmill tests measuring breathing frequency, tidal volume, and minute ventilation, the technical markers of how efficiently someone breathes under exertion. The technique produced no measurable improvement in any of them.
A pilot study in fifteen amateur runners tested something more immediate: a single session of the breathing method performed right before a repeated-sprint test, compared with plain voluntary hyperventilation and with normal breathing (Citherlet et al., 2021). The physiological swings during that single session were dramatic. Blood oxygen saturation, normally pinned near 100 percent, dropped to an average of 60 percent by the end of the breath-holds, and blood chemistry showed a clear respiratory alkalosis. None of that translated into better sprint performance. Peak power, average power, and fatigue over the repeated sprints came out statistically the same across all three conditions.
That oxygen-saturation figure is worth pausing on for a different reason than performance. Hyperventilating before a breath-hold does not add extra oxygen to the body; it mainly lowers carbon dioxide, which is what delays the body's urge to breathe, not the point at which oxygen actually runs low. This session's research did not turn up a dedicated study tracking drowning or blackout incidents tied specifically to this breathing method, so that connection should not be overstated. But the basic physiology, confirmed directly by the oxygen drop measured in the sprint study above, is the same mechanism behind documented blackouts in breath-hold diving: a person can lose consciousness from low oxygen before their body ever signals that something is wrong. That is a reasonable basis for a plain safety note, not a dramatic one: these breathing patterns should not be practiced in or near water, alone, or without knowing how your own body responds.
Cardiovascular and Mood Trials Mostly Come Back Null, With One Interesting Wrinkle
Two more recent trials looked past inflammation and performance toward cardiovascular health and mental well-being, and largely came up empty on the method's own terms.
A fifteen-day trial of forty-two adults measured heart rate, heart rate variability, blood pressure, and arterial stiffness, both at rest and during a cold-pressor stress test (Ketelhut et al., 2023). None of it changed significantly compared with a control group, and neither did measures of perceived stress, mood, or vitality. The authors' own reading was straightforward: performing the method daily for two weeks did not produce the cardiovascular or psychological benefits often claimed for it.
A more pointed test came from a 2024 trial of eighty-four midlife women with high stress and high depressive symptoms (Blades et al., 2024). Half practiced the full method, including cold showers; the other half did a slow-paced breathing exercise with warm showers instead, as an active comparison rather than a do-nothing control. Both groups improved by similar amounts on depression, anxiety, and perceived stress, improvements that held up three months later. Cortisol reactivity to a lab stress test dropped about the same in both groups too. The one place the Wim Hof group pulled ahead was in how much they ruminated after a stressful day, a smaller and more specific effect than the mental-health transformation often advertised. Worth noting also: every dropout in the study, six people, came from the Wim Hof group, not the slow-breathing comparison group.
Read together, these two trials suggest something a little different from "the method doesn't work." They suggest that a meaningful share of what people feel from it may come from practicing any structured, calming breathing routine consistently for a few weeks, not from something unique to the hyperventilation-and-cold-shower combination specifically.
A 2026 Trial in Spinal Cord Injury Found a More Specific, More Useful Signal
The most recent and most rigorously designed trial in this body of research tested the method in a real clinical population: sixty-two adults with chronic spinal cord injury, randomized into the full method with cold exposure, the breathing and mindset portion without cold exposure, or usual care, over seven supervised weeks (de Groot et al., 2026).
The primary outcome, a standard mental health index, did not differ significantly across any of the three groups. But the group doing breathing exercises together with cold exposure showed real improvements in two specific, physical measures compared with usual care: inspiratory muscle strength went up by about 27 percent on one measure and 23 percent on another, and fasting glucose dropped by about 6 percent. That same group also reported less pain interfering with daily life, even though reported pain intensity itself did not change. No serious adverse events occurred. A handful of participants reported tingling, headaches, lightheadedness, or spasms, expected enough from deep breathing and cold exposure in people with spinal cord injury that three chose to drop part of the program rather than stop entirely. The more striking adherence finding ran the other direction: eight people dropped out of the group doing breathing exercises without any cold exposure, compared with just one dropout in each of the other two arms, a disproportionate share of the roughly twenty people in that arm.
This is a smaller, more specific kind of finding than "cures inflammation" or "fixes your mood," and that is exactly what makes it useful. A measurable gain in how forcefully someone can inhale is a concrete, clinically relevant result for a population at real risk of respiratory complications, verified with objective lung-function testing rather than a questionnaire.
Takeaway
One small, legitimate, peer-reviewed study in 2014 is the reason the Wim Hof Method has been taken seriously enough by scientists to generate a decade of further testing, and that original inflammation finding has broadly held its direction across the handful of trials that followed it, though every serious review of that evidence base flags small sample sizes, a near-total inability to blind participants, and a genuine conflict of interest tied to Wim Hof's own commercial and media involvement in parts of the research. Move away from inflammation and the picture thins out fast. Two controlled trials found no real benefit to the breathing technique for athletic performance, two more found no cardiovascular or broad mental-health benefit beyond what a simple slow-breathing comparison group achieved on its own, and the most rigorous recent trial, in people with spinal cord injury, found its clearest benefit in a narrow, physical measure, respiratory muscle strength, rather than the sweeping claims the method is often sold on. None of this makes the practice dangerous for most healthy adults in ordinary settings. It does mean the version of this story that travels on social media runs well ahead of what a decade of actual trials has shown, and the one place real caution belongs, combining hard hyperventilation with breath-holding in or near water, is grounded in measured physiology, not speculation.
Sources
- 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. Proceedings of the National Academy of Sciences, 111(20), 7379-7384. https://doi.org/10.1073/pnas.1322174111
- Almahayni, O., & Hammond, L. (2024). Does the Wim Hof Method have a beneficial impact on physiological and psychological outcomes in healthy and non-healthy participants? A systematic review. PLOS ONE, 19(3), e0286933. https://doi.org/10.1371/journal.pone.0286933
- Marko, D., Bahenský, P., Bunc, V., Grosicki, G. J., & Vondrasek, J. D. (2022). Does Wim Hof Method improve breathing economy during exercise? Journal of Clinical Medicine, 11(8), 2218. https://doi.org/10.3390/jcm11082218
- Citherlet, T., Crettaz von Roten, F., Kayser, B., & Guex, K. (2021). Acute effects of the Wim Hof breathing method on repeated sprint ability: a pilot study. Frontiers in Sports and Active Living, 3, 700757. https://doi.org/10.3389/fspor.2021.700757
- Ketelhut, S., Querciagrossa, D., Bisang, X., Metry, X., Borter, E., & Nigg, C. R. (2023). The effectiveness of the Wim Hof method on cardiac autonomic function, blood pressure, arterial compliance, and different psychological parameters. Scientific Reports, 13, 17517. https://doi.org/10.1038/s41598-023-44902-0
- Blades, R., Mendes, W. B., Don, B. P., Mayer, S. E., Dileo, R., O'Bryan, J., Fromer, E., Guan, J. Y., Cheng, S. S., Mason, A. E., Prather, A. A., & Epel, E. S. (2024). A randomized controlled clinical trial of a Wim Hof Method intervention in women with high depressive symptoms. Comprehensive Psychoneuroendocrinology, 20, 100272. https://doi.org/10.1016/j.cpnec.2024.100272
- de Groot, S., Ettema, F. W. L., van der Bijll, M., Janssen, T. W. J., Achterberg-Warmer, W. J., & Hoekstra, S. P. (2026). The effect of breathing exercises and mindset with or without cold exposure on mental and physical health in persons with a spinal cord injury: Results of a randomized controlled trial. Clinical Rehabilitation, 40(8), 1016-1034. https://doi.org/10.1177/02692155261428705