never heard of it but from above it sounds like "tempering". like getting out the sauna (when the body is trying to release heat fast so a lot of blood is in the outer extremities) and jumping in a plunge pool. all the blood rushes to the core and creates a sort of temporary fever, very good for illnesses as long as you dont have heart problems. in fact i believe it was widely used to treat bad colds and the flu, the patient was dropped in to a freezing cold bath three times daily.
also tempering is very good after a strenuous work out or walk, jump under a cold shower for about a minute and allow the body to heat up again slowly afterwards and i guarantee your aches and pains will be much less the next day.
cheers dan