The science behind the Wim Hof Method
The start of scientific research
What "The Iceman" Wim Hof is capable of was long viewed as scientifically impossible. It wasn't until the first Radboud University study in 2011 that things really kicked off. The study showed that by using his method, Wim was able to voluntarily influence his autonomic nervous system - something which until then was thought impossible. This ground-breaking finding, published in PNAS, established credibility, quite literally rewrote biology textbooks and piqued scientists' curiosity.
Since then, many researchers have taken an interest in the potential benefits of the Wim Hof Method. Today, Wim and his team continue to work with research institutions and various promising studies are currently underway.
Key scientific studies
The Netherlands 
Aimed to test if the results from the first study on Wim could be reproduced with a larger group
Injected 12 Wim Hof Method practitioners with an endotoxin
Results showed that, like Wim, they were able to control their sympathetic nervous system and immune response
Anti-inflammatory mediators were —200% higher, while pro-inflammatory mediators were —50% lower
Potentially important implications for "conditions associated with excessive or persistent inflammation, especially autoimmune diseases." [2014, Knox et. al.)
Wayne State University
The Netherlands 
Also known as the 'Brain Over Body' study
Aimed to understand the brain function that allows Wim to withstand extreme cold exposure
Wim was put in a special temperature controlled suit and placed in both an fMRI and a PET scanner
Results showed activation of areas in the brain associated with pain suppression, self-reflection and well-being, in particular the periaqueductal gray area (PAG)
This may have implications for "lifestyle interventions that might ameliorate multiple clinical syndromes." (2018, Muzik et. al.)
Ongoing worldwide scientific interest
University California San Fransisco is measuring the WHM on mental health and stress resilience.
Reade is following up a promising pilot study with an RCT investigating the effects of WHM practice on health-related quality of life in people with spinal cord injury.
Authors: Otto Muzik, Timothy Mann, John Kopchick, Asadur Chowdury, Mario Yacou, Jamie Vadgama, Daniel Bonello, Vaibhav A. Diwadkar.
In this study, researchers investigated the neurobiological changes in novice volunteers who underwent a 6-week Wim Hof Method (WHM) training regimen. The study involved PET and fMRI imaging sessions to explore changes in CB1 receptor binding and interoceptive brain regions during sympathetic responses.
The results showed significant increases in CB1 receptor binding across the brain, especially in regions associated with the interoceptive network. These increases were linked to improvements in sub-threshold depressive symptoms. Additionally, the WHM training enhanced the engagement of the brain's interoceptive network during sympathetic responses, indicating a priming of interoceptive function.
The study suggests that the WHM may drive changes in brain biology and mood by balancing autonomic responses to stress and associated psychological processes.
This was a small study with just 4 participants and no control group, but the striking findings form an excellent springboard for follow-up research into the specific components and mechanisms of the WHM, and its potential for mood and stress management.
Authors: Sonja de Groot, Frank W. L. Ettema, Christel M. C. van Leeuwen, Wendy J. Achterberg, Thomas W. J. Janssen and Sven P. Hoekstra
A small pilot study investigated the efficacy of Wim Hof Method breathing and mindset exercises for people with spinal cord injury.
Participants experienced multiple positive physical and mental changes, with overall improvements in sleep, stress, energy and pain for the test group versus the control group.
With the great potential for improvements in physical and mental health outcomes for spinal cord injury patients, a full-fledged follow-up RCT trial is already in the works.
Authors: J. Zwaag, H. Timmerman, P. Pickkers, M. Kox.
This study builds upon previous research conducted in 2016 and 2013, which demonstrated that healthy individuals who practiced the Wim Hof Method (WHM) could consciously activate their sympathetic nervous system and decrease the inflammatory response to endotoxemia.
This new study specifically focused on whether the WHM breathing exercises and cold exposure could affect pain perception.
The results showed that the WHM breathing exercises effectively reduced pain perception (induced by electrical stimulus), lasting for at least four hours. Additionally, cold exposure training may also reduce pain perception caused by immersion of the hand in ice water.
These findings suggest again that the WHM has the potential as a novel treatment method for individuals with inflammatory conditions.
Authors: Cristopher Siegfried Kopplin & Louisa Rosenthal
A couple of researchers from the University of Bayreuth happen to also be avid Wim Hof Method enthusiasts. They decided to use their assets and expertise to try to find out just how effective WHM practice is at bringing down perceived stress.
Test subjects were divided into groups that did either the breathing exercises, cold exposure, or both. All groups showed markedly lower stress levels after the 2-week intervention, however results were most pronounced for the group that practiced both the breathing and cold exposure, attesting to the synergistic effect of the full method.
Authors: J. Zwaag, R. Naaktgeboren, AE. van Herwaarden, P. Pickkers, M. Kox
This research further elaborates and addresses the raised questions in the previous study from 2014, where those who practiced the WHM could activate their sympathetic nervous system by will and reduce the inflammatory response to endotoxemia. The current research attempts to determine the following: (1) which combination of the WHM elements is most effective in bringing down the inflammatory response, (2) whether the presence of Wim himself would affect the symptomatology and (3) whether a short WHM explanation is comparable to a more intensive training (e.g. climbing up a mountain in freezing temperatures). The results of the research showed that: (1) the combination of practicing the breathing exercise and cold exposure is the most effective one in decreasing the inflammatory response of the body and alleviating symptoms (rather than only practicing cold exposure and/or breathing exercise), (2) the mentioned immunological response is present regardless of who teaches the method (Wim or an independent Instructor), (3) no difference in the physiological effects can be attributed to the length of the training; thus the techniques are acquired within a short time frame. Importantly, this research shows that elements of the WHM (combination of cold exposure and breathing exercises) can potentially be used to treat various autoimmune diseases due to its anti-inflammatory effect.
Authors: J. Zwaag, R. Ter Horst, I. Blaženović, D. Stoessel, J. Ratter, JM. Worseck, N. Schauer, R. Stienstra, MG. Netea, D. Jahn, P. Pickkers, M. Kox. This research extends the study published in 2014 of the effect of the WHM on our sympathetic nervous system and the innate immune response. It was demonstrated that the sympathetic nervous system can be voluntarily activated following the WHM. This study assessed whether the WHM affects the plasma metabolome and if these changes are linked to the observed immunomodulatory effects. The present study demonstrated that practitioners in the WHM had higher plasma concentrations of lactate and pyruvate (among others). This points towards increased activation of the Cori cycle. The study believes that within the trained group, lactate and pyruvate in part contributed to the increase in anti-inflammatory IL-10 and lower pro-inflammatory IL-1beta, IL-6 and TNF alpha. Lactate and pyruvate in high enough amounts have been shown to cause an anti-inflammatory response from our immune system. As it turns out, our metabolism does affect the immune system. The method causes a shift in metabolism which partly contributes to an anti-inflammatory response.
Authors: G. Buijze, M. de Jong, M. Kox, M. van de Sande, D. van Schaardenburg, R. van Vugt, C. Popa, P. Pickkers, D. Baeten - Amsterdam Medical Centre Summary: The main goal of this paper is to assess whether the WHM could modulate innate immune responses in patients with axial spondyloarthritis, which is a chronic rheumatic inflammation of the spine. This proof of concept study was based on previous research, showing how healthy individuals were able to voluntarily influence the physiological stress response to induce inflammation, after WHM training. The study primarily investigates the safety of practicing the method for this group of patients, yet also looked at changes in inflammatory markers and patient-reported disease activity and quality of life. The results showed that the WHM can safely be applied in patients with axial spondyloarthritis, which is a prototypical chronic inflammatory condition. Furthermore, a significant decline in the inflammatory markers of ESR and CRP levels was found, which are validated disease activity biomarkers. Lastly, various measures of disease activity and quality of life were found to improve following the intervention. Thus, the results suggest that the WHM does not only enable healthy individuals to voluntarily initiate the immune response in acute inflammation but also in chronic inflammation related to immune-mediated inflammatory conditions.
Authors: O. Muzik, K. Reilly, V. Diwadkar - Wayne State University School of Medicine Summary: In this paper, a brain imaging study was conducted to measure the relative contributions of the brain and the periphery that endow the Iceman to withstand the cold using his Wim Hof Method techniques. The results provide compelling evidence for the primacy of the brain (CNS) rather than the body (peripheral mechanisms) in mediating the Iceman's responses to cold exposure. They also suggest the compelling possibility that the WHM might allow practitioners to develop higher level of control over key components of the autonomous system, with implications for lifestyle interventions that might ameliorate multiple clinical syndromes.
Authors: H. van Middendorp, M. Kox, P. Pickkers, A.W.M. Evers - Radboud University Medical Centre Summary: This paper adds to a previous study, published in 2014, on the ability to voluntarily influence the physiological stress response in healthy men to experimentally induced inflammation, after WHM training. It is a proof-of-principle study that investigated how one’s expectancies might play a role in treatment outcome. Indications were found that generalized outcome expectancy optimism is a potential determinant of the autonomic and immune response to induced inflammation after training.
Authors: M. Kox, P. Pickkers et al. - Radboud University Medical Center (published in PNAS) Summary: In this paper, the effects of the Wim Hof Method on the autonomic nervous system and innate immune response are evaluated. A group of twelve people was trained with the Wim Hof Method before undergoing an experiment to induce inflammation, normally resulting in flu-like symptoms. Compared to a control group who were not trained in the Wim Hof Method, the trained participants showed fewer flu-like symptoms, lower levels of proinflammatory mediators, and increased plasma epinephrine levels. In conclusion, the trained group was able to voluntarily activate their sympathetic nervous system.
Authors: G. Buijze, M.T. Hopman Summary: This report deals with the effects of the Wim Hof Method on acute mountain sickness (AMS). During an expedition to Mt. Kilimanjaro, a group of 26 trekkers who were trained in the Wim Hof Method used the breathing techniques to largely prevent and, if needed, reverse symptoms of AMS.
Authors: J. Vosselman, W.D. van Marken-Lichtenbeld - Maastricht University Medical Center Summary: This study tested the effects of a lifestyle with frequent exposure to extreme cold on brown adipose tissue (BAT) and cold-induced thermogenesis (CIT). The experiment compared Wim Hof, who is used to extreme cold exposure, to his monozygotic twin brother who isn’t. Both used a g-Tummo like breathing technique. The results showed no significant difference in BAT or CIT between the two subjects. However, Wim’s core temperature dropped less compared to his brother and his subjective response to the cold temperature was more positive. Furthermore, the body heat generated of both brothers was considerably higher than the average person. Thus, it seems that g-Tummo like breathing during cold exposure might cause additional heat production.
Authors: M. Kox, M. Hopman, P. Pickkers. et al. - Radboud University Medical Center Summary: This case-study research was conducted after Wim Hof claimed he could influence his autonomic nervous system and thereby his innate immune response. His inflammatory response was measured during an 80-minute full body ice immersion and practicing the Wim Hof Method concentration technique. In addition, an endotoxemia experiment was conducted to study Wim’s in vivo innate immune response. The results showed how the techniques of the Wim Hof Method seemed to evoke a controlled stress response. This response is characterized by sympathetic nervous system activation, which seems to attenuate the innate immune system. Here, Wim Hof proved he was able to influence his autonomic nervous system.
Summary: During Wim’s world record attempt of full ice immersion wearing only shorts, he swallowed a vital sense monitor capsule to measure his core temperature. His core temperature started at 98.6 °F and dropped to 88 °F after 75 minutes of cold immersion. Remarkably, his temperature rose again to 94 °F within the next 20 minutes. Standard medical dogma states that once your core temperature falls below 90 °F, your body is not able to warm itself again. Thus, if no external source of heat is provided, your temperature will continue to spiral downward and you will eventually die of hypothermia. However, Wim proved he was able to raise his core temperature from 88 °F to 94 °F by using the Wim Hof Method techniques.
Led by Dr. K. Tracey
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