How is it known to be the breathing and not the cold?
I’ve been studying the “Science of Breath” for many years. The difference between this method and most other methods is the period of holding the exhale. This is very beneficial to the body, but it is especially beneficial spiritually.
When I’m presenting on this topic, I do a demonstration with couples having them hug each other first by holding an inhale, and then by hugging while holding the exhale. The difference in a person’s ability to connect with their partner is very profound.
I have also found this to be true in prayer. Prayer has more profound results when you hold the exhale. If you really want to feel the difference, pray while holding the exhale while you are standing in the shower.
When a person holds the inhale, it’s as though they are full of themselves and have no room for other people or God. It’s as though holding the inhale inflates the ego.
To further enhance the influence of prayer, fasting changes the body chemistry in several ways that increases effectiveness. Ketosis causes a decrease in CO2 accumulation in the body that extends the ability to hold the exhale.
Scientific studies have shown that long inhales with short exhales energies the body, while long exhales with short inhales relaxes the body. I first discovered this many years ago when I was very thin and a daily runner. The breathing change helped me on the long hills. Articles on this were published more recently by a holistic psychiatrist at Columbia University School of Medicine, Dr. Brown.
I think it is both... I joined a family in their daily hot sauna and then jumping into the cold lake water in Northern Finland. It was a bit odd as everyone was totally nude, from grandmother to grandchildren. And, as you looked around the lake, so was everyone else. The people were very healthy into old age.