Voluntary Activation of the Sympathetic Nervous System and Attenuation of the Innate Immune Response in Humans

A 2014 controlled physiology study led by Matthijs Kox and Peter Pickkers at Radboud University Medical Center in the Netherlands, published in the Proceedings of the National Academy of Sciences. Twelve men trained for ten days in a combination of breathing exercises, cold exposure and meditation, the technique associated with Wim Hof, were injected with bacterial endotoxin alongside untrained controls; the trained group showed markedly higher plasma epinephrine, milder flu-like symptoms and lower plasma levels of inflammatory mediators than controls, evidence that the technique can influence the autonomic nervous system and innate immune response, a physiological effect previously thought to be involuntary. The study is small, twelve trained subjects, and tests the combined technique rather than isolating which of breathing, cold or mindset produced the effect, limits the authors themselves note.