Sauna and Cold Plunge: What Does the Science Actually Say?

There was a time when a sauna session was something you did at the end of a gym workout or on a Scandinavian holiday, and a cold plunge belonged to elite athletes, open-water swimmers and the particularly committed.

Now, heat and cold exposure have become part of the mainstream wellness conversation. Sauna and plunge studios are appearing across cities, cold-water immersion’s all over social media, and alternating between sauna sessions and cold plunging, and repeating the cycle has become a wellness ritual in its own right.

So what actually happens inside the body when you expose yourself to extreme heat and cold? What does the research tell us about the potential benefits? And is there any evidence that combining the two is better than using either alone?

What happens when you cold plunge?

1. Physiological response

Cold-water immersion creates an immediate physiological response. Within seconds, cold receptors in the skin detect the sudden temperature drop and send signals to the brain, instantly activating the sympathetic nervous system - often associated with your “fight or flight” response.^1,2

Common initial effects of the cold-shock response can include a gasp reflex, rapid breathing or hyperventilation, an increased heart rate and higher blood pressure.³ Sympathetic activation also releases adrenaline and noradrenaline, which can increase alertness and make some people feel more awake.³

(Photo by iStock of a man taking a cold plunge bath) 

This is why the first 30–90 seconds can feel the most uncomfortable. Your body’s reacting as though it’s under threat, and that’s why it’s important to focus on steady, controlled breathing, avoid sudden full submersion, and build up gradually as your tolerance to cold improves.

Cold water exposure also causes peripheral vasoconstriction, meaning the blood vessels near the skin narrow. This reduces blood flow to the skin, limiting heat loss and helping maintain core body temperature.

It’s also why your skin may look slightly pale or feel numb: narrowed blood vessels send less warm blood to the surface.

2. Changes in circulation

Your circulation also changes temporarily because the peripheral blood vessels narrow, blood pressure may rise and the heart may work slightly harder..

For healthy individuals, this short-lived response is usually tolerated. However, for susceptible people with cardiovascular or respiratory conditions, uncontrolled high blood pressure, arrhythmias, or other risk factors, cold plunges can be risky and seeking medical guidance before trying cold exposure is necessary.^3,4

3. Hormonal responses and mood changes

Cold exposure also increases the release of stress hormones like noradrenaline. One foundational research study found cold-water immersion at 14°C sharply increased noradrenaline, dopamine, and metabolic rates while decreasing cortisol.²

Cold plunging may also provide a short-term mood boost. In one study, participants reported feeling more active, alert and inspired, with fewer feelings of distress and nervousness afterwards.⁵

This wellness practice may leave some people feeling more alert or refreshed in the short term, although individual results vary. It’s worth noting, cold plunging should not be viewed as a treatment for anxiety or depression, and research into its long-term effects on mental wellbeing remains preliminary.

4. Supports post-exercise recovery

Cold exposure can also temporarily slow sensory nerve signals and reduce blood flow in the exposed muscles, which may alter how post-exercise muscle soreness is felt and help some people feel recovered sooner.⁶

(Photo from iStock of a man in an ice bath) 

This is why cold-water immersion and ice baths are often included in recovery because the cooling sensation may temporarily ease feelings of muscle soreness and leave the body feeling refreshed. However, there’s some nuance: after strength training, immediate cold immersion may blunt some muscle-building adaptations, because your body needs post-workout inflammation to trigger the muscle repair and growth process.

5. Metabolism and heat production responses

Metabolism and heat production has also been found to increase, as the body works to maintain core temperature.² It does this through shivering thermogenesis - involuntary muscle contractions - and non-shivering thermogenesis, which involves the activation of brown adipose tissue, or brown fat.

Brown fat burns energy to produce heat, and some research suggests that regular cold exposure may increase brown fat activity.⁷ However, responses vary between individuals, and cold plunging should not be viewed as a weight-loss tool but rather as part of a broader wellness routine.

In short, cold plunging works by exposing the body to a controlled stressor. The sudden cold activates the sympathetic nervous system, temporarily alters peripheral circulation, releases stress hormones, and forces the body to work harder to maintain core temperature.

With repeated exposure, some people may become more accustomed to the sensation of cold and report feeling alert or refreshed afterwards.

Read More: Can Saunaing Help You Lose Calories?

What happens when you combine cold plunge with a sauna session?

Alternating between saunas and cold plunges is often called contrast therapy, because the body is exposed to heat stress followed by cold stress.

In a sauna, your body works to cool itself down. Blood vessels near the skin widen, heart rate increases, peripheral circulation rises and sweating begins, and this helps move heat toward the surface of the body so it can be released.

(Photo from iStock of a man getting into a cold plunge bath after using the sauna) 

When you are exposed to cold water, the opposite happens. Blood vessels near the skin narrow, breathing changes, heart rate and blood pressure can rise, and the body works to preserve core temperature.

This shift from heat to cold creates a strong physical response. The sauna encourages blood flow toward the skin, while the cold plunge pulls blood away from the surface and toward the core.

This is one reason contrast therapy is often described as a “vascular workout” as your blood vessels are repeatedly widening and narrowing in response to temperature changes, although this routine is not a replacement for exercise.

Therefore these practices engage your body in distinct ways, triggering completely different stress signals. Heat exposure can promote relaxation, while cold exposure activates the sympathetic nervous system,² your fight or flight response. Both practices can be complementary when applied appropriately.

Moving between the two creates a controlled physiological challenge and offers an opportunity to practise steady breathing and composure.

Many people describe feeling clear, refreshed and energised after alternating heat and cold. While individual experiences vary, the contrast can offer an invigorating reset followed by a welcome sense of calm.

The combination may also support post-activity comfort. Heat offers soothing warmth that can help ease feelings of muscle tension, while cold provides a cooling sensation that many people find refreshing after exercise for recovery purposes.

Together, they may support perceived recovery, although the evidence varies depending on timing, temperature, duration and the type of exercise.

It’s important to note that more intense is not always better. Moving from very hot to very cold places extra demand on the cardiovascular system, so sessions should be gradual, controlled and suited to the individual.

In short, combining sauna and cold plunge exposes the body to two opposite forms of temperature conditions and bodily responses; heat exposure widens blood vessels and increases sweating, while cold exposure narrows blood vessels and activates the stress response. Alternating between the two in the right way may support overall wellness and recovery and provide that clear, refreshed feeling many people experience afterwards.

However, alternating heat and cold may not be suitable for everyone. If you are pregnant, have a cardiovascular or respiratory condition, blood-pressure or heart-rhythm concerns, a history of fainting, or difficulty tolerating heat or cold, consult a qualified healthcare professional before starting. Always follow the relevant product instructions.

Read More: Should Men Wear Ice Packs During Sauna?

Next Level Commitment: The Søberg Principle

Drawing on her work in cold exposure and thermoregulation, BON CHARGE Scientific Advisor, Dr Susanna Søberg developed the Søberg Principle:⁸ finish with cold and allow the body to rewarm naturally rather than immediately returning to a sauna or hot shower. During this natural rewarming phase, the body generates heat through thermogenic processes that may include brown-fat activity.⁸

The principle is intended to allow the body’s natural heat-producing responses to continue as it returns to a comfortable temperature.

Dr Søberg led a study involving experienced male winter swimmers suggesting that habitual winter swimming, often combined with sauna use, may be associated with altered brown-fat thermoregulation and greater cold-induced thermogenesis.⁹

How to “sauna and plunge” at home using the BON CHARGE Infrared PEMF Sauna Dome and a cold shower

A simple heat-and-cold ritual to support relaxation, a healthy sweat, post-activity comfort and a refreshed, reset feeling - all from home.

The BON CHARGE Infrared PEMF Sauna Dome combines FAR infrared heat, PEMF, red light and near-infrared light, and is designed for a spa-like full-body wellness experience at home.⁠

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Before you begin

• https://link.boncharge.com/mAtHxv
• Read the Infrared PEMF Sauna Dome instructions before your first session.
• Start on a low temperature and build gradually according to your comfort.
• Keep drinking water in a sealed bottle nearby to hydrate.
• Avoid use if you feel unwell, overheated, lightheaded or uncomfortable.
• Do not stare directly into the LEDs.
• Do not operate the Infrared PEMF Sauna Dome while sleeping, smoking or under the influence of alcohol or drugs. The device is not waterproof: never submerge it, and keep the controller, cables and other electrical components away from water and damp areas.
• The Sauna Dome is not suitable for children or anyone who is pregnant, may be pregnant, is planning to become pregnant or is breastfeeding. Read all warnings and contraindications in the user manual, and consult a qualified healthcare professional before beginning if you are under medical care, have a pre-existing condition or implanted medical device, take medication that may increase light sensitivity, or have concerns about heat or cold exposure.

(Photo of the BON CHARGE Infrared PEMF Sauna Dome) 

Step-by-step routine

1. Set the space

Lay the Sauna Dome mat on a stable surface in a comfortable, well-ventilated area. Place the towel insert over the mat and connect the device according to the user manual.The Sauna Dome is not waterproof and should never be submerged or used near water.⁠⁠

2. Choose your heat setting

For your first few sessions, start with a lower temperature and increase gradually over time. The manual advises starting low, building up slowly, and avoiding the highest heat setting for more than 10 minutes.⁠

3. Begin your sauna session

Lay down in your Infrared PEMF Sauna Dome with your head outside the domes. Use the towel insert and wear clothing during the session. The user manual recommends a 20–30 minute session depending on the settings you’re using and your personal wellness goals, and says not to exceed 30 minutes per session.⁠

Beginner recommendation: Start with around 10–15 minutes at a comfortable heat, then gradually increase the duration only if you feel comfortable.

4. Transition slowly

When the heat session ends, sit up slowly and give yourself a minute before standing. Drink water if needed. This is not a race, the goal is a calm contrast ritual, not pushing intensity.

5. Take a cool or cold shower

Step into the shower and begin with cool water rather than immediately cold. Let the water run over your arms, legs and torso first, then progress to colder water as comfortable.

• Beginner recommendation: 30–60 seconds of cool water.

• Intermediate: 1-2 minutes of cold water. 
  

• Experienced: Up to 2–3 minutes, only if it feels manageable.

Listen to your body and stop if you feel dizzy, faint, short of breath or unwell. If you have any health concerns or are unsure whether cold exposure is right for you, check with a qualified healthcare professional before adding it to your wellness routine

6. Warm back up naturally

If you are invested in contrast therapy, you might want to follow the Søberg Principle:⁸

After the cold shower, let your body return to a comfortable temperature naturally. This encourages the body to generate its own heat, supporting cold-induced thermogenesis and brown-fat activity.

7. Clean and store the Sauna Dome

After use, turn the device off, unplug it, and allow it to cool down. Wipe down with a damp cloth if needed, wash the towel insert, and allow the components to air before packing away.⁠

Frequency

The Sauna Dome user manual recommends using it consistently, at least three times per week.⁠ For contrast routines (sauna and cold shower), two to three times per week is a sensible starting point, increasing only if your body responds well.

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References

1. Tipton, M. J. The initial responses to cold-water immersion in man. Clin. Sci. (Lond.) 77, 581–588 (1989).

2. Šrámek, P., Šimečková, M., Janský, L., Šavlíková, J. & Vybíral, S. Human physiological responses to immersion into water of different temperatures. Eur. J. Appl. Physiol. 81, 436–442 (2000).

3. Ossowska, W. et al. Health benefits and physiological effects of cold water immersion: a review of current research. J. Educ. Health Sport 83, 61851 (2025).

4. Tipton, M. J., Collier, N., Massey, H., Corbett, J. & Harper, M. Cold water immersion: kill or cure? Exp. Physiol. 102, 1335–1355 (2017).

5. Yankouskaya, A., Williamson, R., Stacey, C., Totman, J. J. & Massey, H. Short-term head-out whole-body cold-water immersion facilitates positive affect and increases interaction between large-scale brain networks. Biology 12, 211 (2023).

6. White, G. E. & Wells, G. D. Cold-water immersion and other forms of cryotherapy: physiological changes potentially affecting recovery from high-intensity exercise. Extrem. Physiol. Med. 2, 26 (2013).

7. Huo, C. et al. Effect of acute cold exposure on energy metabolism and activity of brown adipose tissue in humans: a systematic review and meta-analysis. Front. Physiol. 13, 917084 (2022).

8. Søberg Institute. The Søberg Principle: cold plunge to burn calories. https://soeberginstitute.com/pages/the-soeberg-principle-cold-plunge-aligned-with-metabolism

9. Søberg, S. et al. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Rep. Med. 2, 100408 (2021).

BON CHARGE: This content is for general education and is not medical advice. Our products are not intended to diagnose, treat, cure, or prevent any disease. Always follow product instructions and consult a qualified healthcare professional for guidance tailored to you. Individual results may vary.