This sounds akin to sitting in a sauna during the winter then hopping into ice cold water and back into the sauna. I've always heard that could be bad for your

This sounds akin to sitting in a sauna during the winter then hopping into ice cold water and back into the sauna. I've always heard that could be bad for your heart but I have no proof beyond what people say. Rapid changes in temperature must be a well researched area though?