Hof once immersed himself in ice for 1 hour and 44 minutes. Image Credit: CC BY-SA 2.0 Aad Villerius
The 58-year-old's extreme resistance to freezing temperatures has seen him break multiple world records.
Over the years his remarkable feats of endurance have included running a marathon in the snow while wearing nothing but a pair of shorts and being immersed up to his neck in ice for almost two hours
The Dutch athlete attributes his unique talent to breathing techniques based on Tibetan Tummo meditation and has been working with scientists to prove that his methods work.
In a recent study, researchers from Wayne State University School of Medicine conducted an experiment which involved Hof wearing a special suit infused with temperature-controlled water.
He underwent a functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scan to see what happened to his body when exposed to extreme cold.
The team discovered that his breathing techniques really were able to regulate his skin temperature.
"The willful regulation of skin temperature - and, by implication, core body temperature, even when the body is being stressed with cold - is an unusual occurrence and may explain his resistance to frostbite," said study author Professor Otto Muzik.
The scans also revealed some unusual activity in Hof's upper brain stem.
"This area is associated with brain mechanisms for the control of sensory pain and is thought to implement this control through the release of opioids and cannabinoids," said Prof Muzikof.