fMRI analyses indicated that the WHM activates primary control centers for descending pain/cold stimuli modulation in the periaqueductal gray (PAG), possibly initiating a stress-induced analgesic response. This acquisition allowed us to determine changes in sympathetic innervation (HED) and glucose consumption (FDG) in muscle and fat tissues in the absence of the WHM. In addition, the Iceman also underwent a whole body PET/CT imaging session using the tracers C11-hydroxyephedrine (HED) and 18F-fluorodeoxyglucose (FDG) during both thermoneutral and prolonged mild cold conditions. fMRI was acquired in two separate sessions: in a typical (passive) state and following the practice of WHM. Thermoregulatory defense was evoked by subjecting the Iceman (and a cohort of typical controls) to a fMRI paradigm designed to generate periods of mild hypothermia interspersed by periods of return to basal core body temperature. To investigate this, we conducted multi-modal imaging assessments of the brain and the periphery using a combination of fMRI and PET/CT imaging. The relative contributions of the brain and the periphery that endow the Iceman with these capabilities is unknown. Here we present a case study of a 57-year old Dutch national, Wim Hof, the so-called 'Iceman', with the ability to withstand frequent prolonged periods of extreme cold exposure based on the practice of a self-developed technique involving a combination of forced breathing, cold exposure and meditation (collectively referred to as the Wim Hof Method, henceforth 'WHM'). There is however, anecdotal evidence of a unique set of individuals known for extreme cold tolerance. Autonomous mechanisms of thermoregulation are only weakly affected by top-down modulation, allowing only transient tolerance for extreme cold. The defense of body temperature against environmental thermal challenges is a core objective of homeostatic regulation governed by the autonomic nervous system.

Wim hof method results