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Fire & Ice - The Practice of Sauna & Cold Water Immersion (Netty Sopata & Norma MacLeod)

Immersion in cold water is something that many of you reading this will be acquainted with. If you are, then you know how it makes you feel and you may also have an awareness of the science behind those feelings. But, have you ever combined the hot with the cold? The fire with the ice?

Gilly McArthur plunging into an ice hole. Image Credit: Scott Salt

We’re not just talking about the warming up, and cake eating process post dip here, we're talking about repeated alternation between cold water and extreme heat (or if you're in Iceland hot water and extreme cold). The holistic immersion of the whole

body in either extreme heat, or extreme cold is not new.

From the ancient sweat lodges of the Native Americans, the banyas of Russia, the more modern Japanese Waon Therapy and recent recognition of the cultural significance of Sauna in the Estonian based film - Smoke Sauna Sisterhood , Sauna has, and continues to play an integral part in the health and well being of many Europeans, and, is becoming increasingly popular in the UK. In a recent article in the Economist it was reported that the number of Saunas across Britain has doubled every year since 2018 and if you explore the British Sauna Society the magnitude of what that means and the

sub-culture developing from it is extensive.

‘Sauna’( pronounced ‘sow-nah’) is a Finnish term that refers to a spruce or pine panelled room within which a source of heat is used to create a temperature ranging from 70 – 110 degrees and people ‘bathe’. If you already ‘Sauna’ you will know that it makes you feel fantastic, but do you know why it makes you feel this way?

In Japan the state of well-being that comes from enjoying hot sauna and cold water is known as the ‘totonou’ state - to be ‘prepared’ or in the context of sauna, “the well being state in which the body and mind are automatically conditioned by entering the

sauna, and the original ability of the person is restored.” (Chang et al 2023). To reach this state of being, the body needs to be repeatedly heated and cooled at least three times inclusive of the following stages - Cold - Hot - Outdoor Rest. When

doing this activity, your body is having to work to maintain its core temperature through a process of thermoregulation. As your body heats up, Vasodilation’ occurs - your blood vessels widen to increase the flow of blood to the skins surface where it is cooler. As your body cools down ‘Vasoconstriction’ occurs - your blood vessels

become narrower to decrease the blood flow to the skin, this enables the body to keep your vital organs warm by retaining the heat in the inner body. It is believed that it is at the ‘Rest’ stage that the state of ‘Totonou’ is achieved.

A recent study by Chang et al (2023) set out to determine what occurs in the brain during this state of ‘Totonou’. The anecdotal accounts of sauna users repeatedly confirm post-sauna feelings of well being and happiness, and research has been conducted to determine that sauna use can lower blood pressure, reduce the risk of heart disease, ease muscular and joint pain and release hormones that make your

brain more receptive to endorphins, which in turn creates an increased sense of wellbeing (Soberg, 2022). At the same time, studies have revealed that frequent sauna use is associated with reduced risk of developing age-related neurodegenerative conditions such as dementia and Alzheimer's disease. But, Chang et al (2023) identified that there had been no research into what actually

happens to the brain during the process of repeated thermoregulation, specifically the point of ‘Totonou’.

After an extensive study they concluded that the use of sauna in this manner, significantly increases “neural alpha and theta powers, improving attention and brain efficiency…..Theta activity is associated with efficiency in cognitive and emotional processing, while alpha activity indicates increased relaxation.’ Francisco de Souza (2023). In essence, going through the process to reach the stage of ‘Totonou’ does indeed restore (or maybe even improve) the original ability of the individual, whilst also increasing a sense of ‘physical and mental relaxation, clarity of mind and happiness.’ Chan et al (2023) which can be seen in the faces of many who use the sauna.

If you have read this far it would be safe to hazard a guess that you have already enjoyed the experience of sauna or are thinking of exploring it. Saltbox Sauna, the first mobile sauna in the Outer Hebrides can offer you that experience in a different location each week framing the natural beauty of the coastlines of the Outer Hebrides with it’s half-moon panoramic window. The Isle of Lewis, with its Viking Heritage, seems a fitting place to introduce the Scandinavian practice of hot and old therapy, and now it’s here, we wonder why it never reached us before:

A little caution to outdoor swimmers and sauna practice

In the UK in recent years wild swimming social groups have grown exponentially, but so has the placement of outdoor saunas near wild swimming spots. Both relatively new practices to many in the UK but there have been increasing reports of collapses inside saunas after a swim in cold water (anything below 15 degrees celsius) or cases of violent shivers inside the sauna causing alarm amongst users. Our basic survival instinct tells us to get warm if we’re cold, with many jumping into a sauna or hot shower immediately after a swim or dip. It seems natural, right? But there should be some caution applied to the length of time immersing in cold and the time in the sauna afterwards as it takes time to cool your body down in cold water, therefore it takes time to warm it up again. Your body may not respond as you would expect it to jumping inside a warm sauna after a swim.

If you have stayed in cold water too long and you enter a hot sauna, your blood vessels can dilate quickly causing a drop in blood pressure which may lead to collapse. The same applies when we stay too long in the sauna and we start to feel light-headed often feeling the desire to exit. There are limits to what our bodies can handle and going from extremes to hot and cold could trigger some unwanted responses.

So how long is too long for a swim or dip and sauna? Here is our advice on the best practice of cold immersion and sauna therapy:

1. Ensure you are properly hydrated before cold water immersion or sauna therapy. Dehydration leads to low blood pressure so make sure you are drinking plenty of water before, during and after your practice. Alcohol should be avoided. Entering a sauna hungover may also be unpleasant as you will be dehydrated.

2. Existing Health Conditions - Speak to your doctor about any health conditions you have and whether it is safe for you to practice cold water and sauna therapy. Cautionary conditions would be high/low blood pressure, thyroid issues, lung

conditions, epilepsy and cardiovascular disease.

3. If you are new to the practice, start low and build slow. Don’t overdo it, and listen to

your body.

4. If you have booked an hour in the sauna, arrive 5-10 minutes beforehand. Take a short dip in cold water or plunge pool for no more than 2 minutes or less for some. We believe a cold dip first prepares you for the heat if it's your first time experiencing extreme heat.

5. Start with 5 minutes in the sauna or less for some, then repeat the cold plunge. You can do this ritual repeatedly within the hour and you may find that you can tolerate longer in the sauna by the end. It’s not advised to stay in the sauna anymore than 15 minutes, in fact there are studies to suggest that this may cause harm beyond 19 minutes (Soberg, 2022).

5. Practising this 3-4 times per week is comparable to moderate intensity exercise and

is proven to improve cardiovascular outcomes. It's also a great practice for those who are less mobile.

6. If you want to improve metabolic function and activate brown fat (high energy consumer), evidence suggests that you end your sauna session on cold. (Soberg et al., 2021)

7. Self-Awareness. Only you know how you feel and how you respond to heat and cold. Listen to your body and follow the health and safety guidance advertised at any of the saunas you use.

8. Lastly, whilst in the sauna use the scented water to humidify the sauna, breathe deeply and enjoy the detox from work, life commitments, mobile phones and daily stresses.

Regular sauna users Netty, Lindy & Julie enjoying each other's company after a sauna on a cold day


Hussain, J. N., Greaves, R. F., & Cohen, M. M. (2019 ). A hot topic for health: Results of the Global Sauna Survey. Complementary Therapies in Medicine, 223-234 .

Kenkt, P., Jarvinen, R., Rissanen, H., Heliovaara, M., & Aromaa, A. (2020). Does sauna

bathing protect against dementia ? Preventive Medicine Reports.

Laukkanen, T., Kunutsor, S., Kauhanen, J., & Laukkanen, J. A. (2017). Sauna bathing is

inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men.

Rhonda P. Patrick, T. L. (2021). Sauna use as a lifestyle practice to extend healthspan .

Experiential Gerontology .

Soberg et al. (2021) Altered brown fat thermoregulation and enhanced cold-induced

thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine

Soberg, S. (2022). Winter Swimming. The Nordic Way Towards a Healthier and Happier Life

(First ed.). London : MacLehose Press.

"Britons warm up to saunas." The Economist, 18 Mar. 2023, p. NA. Gale OneFile: News,

Jan. 2024.

Tipton M Prof et al., (2017) Cold water immersion kill or cure?

The "totonou" effect: physiological and subjective benefits of sauna relaxation By Hugo Francisco

de Souza Dec 1 2023 Reviewed by Lily Ramsey, LLM

News Medical Life Sciences


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