Scott Carney looks at Wim Hof his method which involves a specific breathing technique combined with cold exposure and is reputed to have huge health benefits.
It was an interesting read, not really my thing but came highly recommended. For me, it read like most diet/health movement books that make connections between a particular diet/activity and better health. There appears to be science in it, but some of the connections made seemed tenuous and the concept itself has no appeal to me, so I am not prepared to investigate further.