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Understand Hormones Relevant to Contrast Therapy

If you’ve been to PLUNJ, you have probably experienced for yourself the bliss of contrast therapy. One customer described it as, “a wake-up call to all my cells,” and said, “it made my entire body feel so refreshed!” Others say it helps them feel happier, sleep better, reset their body and mind, relax, and feel invigorated.

What’s going on beneath the surface when we switch back and forth between icy cold water and high heat/humidity (besides the bubbly feeling underneath your skin from the cold water)?

Hormones and neurotransmitters

Turns out, when we are exposed to either extreme cold or extreme heat, our bodies and brains release chemicals as a response to stress. In other words, our body reacts like it does in fight-or-flight (or freeze). These chemicals are hormones and neurotransmitters that work together to help our body adapt to specific circumstances.

Notes about neurotransmitters: they are noticeably different by the thoughts, feelings, and behaviors with which they are most often associated. Second, they can be classified according to their chemical structure. Lastly, most neurotransmitters usually have either an excitatory (activating) or inhibitory (deactivating) effect on affected cells. Stress Response Hormones:

  • Epinephrine (adrenaline): a combat hormone that makes you aware and alert. When exposed to cold, epinephrine signals to your cells to release glucose into the bloodstream so the muscles can access it for energy.

  • Norepinephrine (noradrenaline): a neurotransmitter and combat hormone secreted from the adrenal gland in response to perceived or real danger. It’s what raises heart rate and blood pressure, as well as what activates brown fat. Brown fat warms you up and boosts your metabolism by burning sugar and fat from the bloodstream as energy.

    • Studies show that the cold-shock response can increase norepinephrine by four times within only a couple of minutes. These findings suggest that health benefits of cold water immersion can come even just with a change in skin temperature, so very long bouts in cold water are not necessary.

    • If you allow your body to reheat itself naturally, your norepinephrine will remain active long after your plunge, keeping that brown fat working hard for you! Plus, it will keep you energized throughout the day.

  • Cortisol: the third combat hormone. It is released from the adrenal gland during stressful situations, breaks down the body’s energy stores, and wakes up the body. A buildup of cortisol over time indicates that the body is chronically stressed. Regular winter swimmers have higher levels of cortisol during swimming or after a swimming season. But their cortisol levels are lower at rest. In addition, studies show that sauna bathing can also decrease cortisol levels.

As a reaction to the release of these hormones, several other hormones are secreted. These ones help you feel GOOD:

  • Dopamine: a feel-good hormone and neurotransmitter that is part of the brain’s reward system. Believe it or not, cold water immersion at about 57°F or lower can increase plasma dopamine levels by 250%! This could explain the euphoria you feel when you get out of the cold tub. Getting warm again (like when you use a sauna) increases dopamine as well, causing a pleasant, joyful intoxication afterward.

  • Serotonin: like dopamine, this hormone belongs to the brain’s reward system and is released during cold-water immersion. Its effects include good sleep, relaxation, happiness, and mental balance. Serotonin contributes to regulating appetite and memory as well. During the cold shock response, serotonin plays an essential role in keeping us calm and relaxed.

Aren’t our brains and bodies are incredible? Even simple activities like deliberate cold exposure and sauna bathing can release chemicals in our brains that help us feel and perform better in our daily lives. Who’s in?


[Andrew Huberman]. (2023, May 15). “Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health | Huberman Lab Podcast.” YouTube.

Chara, P. J., Jr. (2023). Neurotransmitters. Salem Press Encyclopedia of Health.

[Dhru Purohit]. (2023, March 16). The INSANE BENEFITS Of Heat & Cold Therapy After 30 Days (TRY THIS & SEE RESULTS)|Dr. Susanna Søberg [Video]. YouTube.

[Rangan Chatterjee]. (2023, Jan 4,). What Happens After 30 Days of COLD SHOWERS? - This Will SHOCK YOU! | Dr. Susanna Søberg. YouTube.

Ruiz, J. R., Martinez-Tellez, B., Sanchez-Delgado, G., Osuna-Prieto, F. J., Rensen, P. C. N., & Boon, M. R. (2018). Role of Human Brown Fat in Obesity, Metabolism and Cardiovascular Disease: Strategies to Turn Up the Heat. Progress in Cardiovascular Diseases, 61(2), 232–245.

Søberg, S. 2022. Winter Swimming (E. DeNoma, Trans., 1st ed.). MacLehose Press. (Original work published 2019).

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