These days I'm doing contrast baths. The reason: to train the feeble autonomic nervous system of a modern desk worker.
This post describes the method and the effects of contrast bathing.
Method
Why do high performers love the sauna? I'm going off what I remember reading in a book.
The core of it is repeating heat stimulus → cold stimulus → rest.
- Heat stimulus Sit in the sauna. Take your pulse and stay until your heart rate climbs a bit. Roughly 3 minutes, then get out.
- Cold stimulus Get into a cold bath below 18°C for about 30 seconds, then get out. This part hurts the most. So at first, even holding out for just 5 seconds is fine. For what it's worth, most ordinary bathhouses don't have a cold bath that gets down to around 18°C.
- Rest Just lie on a bed and let your heart rate settle. About 4 minutes.
Do only one set at first, and add sets as you get used to it. I'm currently doing three.
Effects
- As mentioned above, it trains the autonomic nervous system. You're forcibly alternating tension and relaxation, so it trains the switching between the sympathetic and parasympathetic systems. There's no solid evidence for this.
- It feels like your mind gets reset. That may just be the well-known effect of a cold shower. Or maybe your body simply jolts awake from the shock of the cold water.
- You get used to cold water. That feeling is better than you'd expect. Once you're used to cold water, you don't necessarily need a hot shower. A feeling of getting stronger. The effect shows up pretty quickly.