Wim Hof (born 20 April 1959), also known as The Iceman, is a Dutch extreme athlete noted for his ability to withstand freezing temperatures. He has set Guinness world records for swimming under ice and prolonged full-body contact with ice, and still holds the record for a barefoot half-marathon on ice and snow.
He attributes these feats to his Wim Hof Method (WHM), a combination of frequent cold exposure, breathing techniques and meditation. However, skeptics question whether or not his identical twin brother's similar brown fat composition shows that Wim's tolerance of cold is mostly a result of his genetics. Preliminary and proof-of-principle studies of Hof's method, as well as similar breathing practices, have shown that hyperventilating can temporarily suppress the innate immune response as well as temporarily increase heart rate and adrenaline levels. Hof is the subject of The New York Times bestselling book What Doesn't Kill Us, which tells the story of how the investigative journalist Scott Carney took an assignment supposedly to debunk the WHM but ended up learning Hof's techniques. He is also the subject of the Vice documentary Iceman in which journalist Matt Shea learned the WHM. Hof was born in Sittard, Limburg, Netherlands as one of nine children, one of whom (Andre) is an identical twin brother.