Cold plunge is the most powerful mind altering activity that i know of. I have access to cold plunge im near where i live in l a. It's about nine degrees celsius, nine to ten degrees celsius. When temperature goes down, their blood flow suddenly blocked,. because the vascula systemcloses when it gets colder. The affects you had, because it's all veins, it like 70 thousand miles inside. And all those muscles will contract. By just putting your hands inside a a bucket of icy water, wend or the feet, and it's great.