Keep seeing that in multiple threads. Why?
If you try this go easy at first, that means start with a warm shower and finish with a moderately cold shower, it supposedly boost metabolism and Testosterone, but I personally don't think it's worth it lol :-\
See BS About Cold Showers You've Been Told So Far - The Broscientist (http://www.thebroscientist.com/BS-cold-showers-youve-told-far/)
Paul (paolo) :)
Wim Hof made it popular.