that his "concentration/meditation during ice immersion" greatly reduced his "ex vivo proinflammatory and anti-inflammatory cytokine response":"The concentration/meditation technique used by this particular individual seems to evoke a controlled stress response. This response is characterized by sympathetic nervous system activation and subsequent catecholamine/cortisol release, which seems to attenuate the innate immune response." In 2014 an assessment compared Wim Hof and his identical twin brother Andre. The scientists had them practice Wim's breathing exercises, then exposed them to the lowest temperature that would not induce shivering. They concluded that, "No significant differences were found between the two subjects, indicating that a lifestyle with frequent exposures to extreme cold does not seem to affect BAT activity and CIT (cold-induced thermogenesis)." The researchers stated that the "results must be interpreted with caution given the low subject number and the fact that both participants practised the g-Tummo-like breathing technique." In 2018, a study published in the journal NeuroImage titled Brain over body–A study on the willful regulation of autonomic function during cold exposure, used a combination of fMRI and PET/CT imaging, and found, "forceful respiration results in increased sympathetic innervation and glucose consumption in intercostal muscle, generating heat that dissipates to lung tissue and warms circulating blood in the pulmonary capillaries. Our results provide compelling evidence for the primacy of the brain (CNS) rather than the body (peripheral mechanisms) in mediating the Iceman's [Wim Hof's] responses to cold exposure." Studies on Wim Hof Method In 2014, a paper published in PNAS titled Voluntary Activation of The Sympathetic Nervous System and Attenuation of the Innate Immune Response In Humans, extended the 2012 case study of Wim Hof with a randomized group of twenty-four healthy volunteers, twelve of whom were trained with the Wim Hof Method:"In conclusion, we demonstrate that voluntary activation of the sympathetic nervous system results in epinephrine release and subsequent suppression of the innate immune response in humans in vivo. These results could have important implications for the treatment of conditions associated with excessive or persistent inflammation, such as autoimmune diseases."In 2014, a report written by Geert A. Buijze, MD, PhD and Maria T. Hopman, MD, PhD titled Controlled Hyperventilation After Training May Accelerate Altitude Acclimatization, dealt 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