Sauna Basics 02: How ”totonoi” Works

In Sanokuni, we recommend the best way to experience a sauna based on medical evidence supervised by an active physician who serves as the president of the Japan Sauna Society.

What is "totonoi"?

Simply put, "totonoi" is a phenomenon unique to saunas where deep relaxation and a clear, refreshed mind occur simultaneously.

The key factors here are the autonomic nervous system and hormones in the blood.

Entering saunas and cold baths is an emergency situation for the body. The sympathetic nervous system is what works at such times. The autonomic nervous system is divided into the sympathetic nervous system, which works when you are tense, and the parasympathetic nervous system, which works when you are relaxed.

After entering the sauna and cold bath to activate the sympathetic nervous system, taking a rest makes the body feel that it has escaped the crisis, which in turn activates the parasympathetic nervous system much more than usual. In other words, you experience a deeper level of relaxation than normal.

At this moment, a unique state is occurring within the body. The autonomic nervous system operates on electrical activity, so it reacts quickly, keeping up without delay even during rapid temperature changes such as the transition from sauna to cold bath to rest.

However, hormones in the blood circulate through the bloodstream and lose their effect mainly by being metabolized in the liver, so their response is slightly delayed. Although hormone metabolism is usually quick enough that it wouldn't be delayed unless artificially switched, in the case of a sauna, it lags a bit.

Immediately after exiting the cold bath, the parasympathetic nervous system quickly activates to relax you. However, it takes up to two minutes for the effects of stimulant substances like adrenaline, which were released during the sauna and cold bath, to be cut in half.

In other words, immediately after getting out of the cold bath, you enter a unique state where your nerves are ultra-relaxed, yet stimulant substances still remain in your bloodstream.

This is what it means "totonoi".

How to experience "totonoi"?

Try using your heart rate as a guide.
Heart rate serves as an indicator that sensitively reflects the autonomic nervous system (especially the sympathetic nervous system).

It is said that taking a sauna puts a load on the body equivalent to light exercise.
As a guideline, we use the heart rate during light exercise as a target. Since the intensity of light exercise varies greatly from person to person, please adjust it to a level where you do not feel strained.

Then, once you enter the sauna and your body warms up, measure your heart rate and leave the sauna room when it reaches the target.

How to monitor your heart rate

Two tendons are visible on the palmar side of the wrist. On the thumb side of the thumb-side tendon, there is a blood vessel called the radial artery.

Lightly touch that spot using three fingers—your index, middle, and ring fingers—to take your pulse.

In a sauna, clocks often lack a second hand, which can make it difficult to measure your heart rate. In such cases, let's utilize the rhythm of music.

Find out the BPM of your favorite music in advance and memorize songs that are close to your target heart rate. Then, inside the sauna, play that music in your head while taking your pulse, and step out when your pulse matches the rhythm. This not only helps you understand the state of your autonomic nervous system but also provides a meditative effect, killing two birds with one stone.

By doing so, you can enjoy your sauna session without putting excessive strain on your body.

The above is the ultimate way to "totonoi" proposed by "Sanokuni".

Please use this as a reference for your sauna session and experience "totonoi"!

---