What Happens in the Brain during a 15-Minute Ice Bath?

Popularized by Wim “The Iceman” Hof, cold exposure and particularly ice baths have become increasingly fashionable – and rightly so. Ice baths have scientifically proven benefits to the human body, mind, and spirit.

Anyone who has done an ice bath knows that it can induce an altered (often blissful) state of consciousness. However, I was curious – what exactly happens in the brain during an ice bath? How do the brain waves behave?

To find out, I strapped on my trusty Muse2 Brain Sensing Headband paired with specialized brain wave monitoring software and submerged myself in an ice bath for 15 minutes.

Ice Bath Benefits

I’m a huge fan of the Wim Hof Method, where cold exposure is key. But it wasn’t always that way for me. When I started, I loved the breathing technique but despised cold showers.

However, after researching the health benefits of ice baths and with friends pushing me to try it, I took the plunge – and haven’t looked back since.


Rustic, outdoor cold shower in the French countryside

Surprisingly, I discovered that cold showers actually relax my body more than warm ones (even though our egos adore the latter). Hot showers can help you feel relaxed, but cold showers help you to truly be relaxed. Let that sink in.

Hot showers can help you feel relaxed, but cold showers help you to truly be relaxed.

Hot showers causing one to feel relaxed versus cold showers making one be relaxed is a subtle but important distinction. It’s comparable to watching Netflix vs meditating.

Netflix n’ Chill can definitely make you feel relaxed. Indeed, the ego finds solace in Netflix just like it does in a hot shower. However, we all know that watching Netflix every night does not promote long-lasting feelings of contentment. The positive feelings experienced while watching a movie do not transfer into everyday (non-Netflix) life. 

Meditation, however, can change your life. Fascinatingly, it has been scientifically proven that regular meditation can actually alter the structure of the nerve cells in your brain, leading to lasting feelings of contentment, reduced stress, and higher levels of focus. That means with regular practice, meditation can enable you to be relaxed (literally, on a cellular level!)

Analogously, although hot showers are easy, enjoyable, and relaxing (like Netflix), they do not teach you how to experience those same positive feelings when the hot shower is over. Cold showers on the other hand, though much harder on the ego and initially less relaxing, teach your mind and body a new way to be and can act as a catalyst for lasting personal evolution (like meditation).

Some proven ice bath benefits are:

  • Reduces inflammation
  • Decreases recovery time after physical exercise 
  • Helps regulate the central nervous system
  • Trains the vagus nerve
  • Improves sleep
  • Reduces stress
  • Boosts immune system

But don’t take it from me. One of the things I really appreciate about Wim Hof is his enthusiasm for science – read all about the scientifically proven benefits of cold therapy from the man himself here.

The health benefits of cold therapy are well known, but what I wanted to know was – what exactly happens in the brain? How do the brain waves change during an ice bath? What clues could this provide about the nature of the ego?

What Happens in the Brain during an Ice Bath?

To find out, I used the Muse2 Brain Sensing Headband device and sat in an ice bath for a bit over 15 minutes.

This was my first ice bath so I was excited to collect virgin brain data (yes, you read that right). Since I had never experienced an ice bath (no previous conditioning except occasional cold showers lasting max 2 minutes), I assumed my brain readings would be very honest and was excited about the results. 

ice bath brain waves
Sitting in ice and measuring brain waves

What are Brain Waves?

One of my scientist friends made a valid point one night at chess club when I told him about this experiment. He rightfully asserted:

“if you knew in advance that you would stay in the ice bath for 15 minutes, then probably your brain waves are going to behave differently as you approach the 15-minute mark. You would know that your time is almost up and that alone is going to affect the reliability of your data”.

This is absolutely true. The brain is the only organ that studies itself, therefore paradoxes like this often arise when doing experimental neuroscience.

Luckily, I actually did not intend to stay in the ice bath for 15 minutes. I was planning for 3 minutes, but I fell into such a state of bliss that I lost track of time (more on that later). So thankfully, this actually allowed me to collect better and more realistic data (otherwise my friend’s comment would have been certainly valid).

The brain is the only organ that studies itself

Pairing the hardware with MindMonitor, I was able to capture the full spectrum of brain waves ranging from low-frequency delta waves to high-frequency gamma waves and everything in between.

brain wave spectrum
Human brain waves

For a deeper understanding of brain waves, check out this short video:

Ice Bath Effect on Brain Waves

After collecting, cleaning, and analyzing the raw data collected using Muse2 and Mindmonitor, we have an answer to what happens in the brain during a 15-minute ice bath:

ice bath brain waves
Brain wave behaviour during 15-min ice bath

Time, measured in minutes, is on the x-axis and PSD (Power Spectral Density) of the brain wave is on the y-axis. 

For our purposes, you can think of PSD as the “loudness” or amplitude of the wave. Although the relationship between brain waves, PSD, and mental state is much more nuanced than this, for our purposes we could rightly interpret lower PSD to mean a mind that is much calmer, still, and tranquil. The story my brain waves above tell during the 15-minute ice bath is quite compelling:

subjective and objective experience during 15-min ice bath
Objective & subjective experience during 15-min ice bath

Upon entering the ice bath, during the initial minute, I experience a complete freak-out. My body and mind are shocked, desperately craving warmth and wanting to escape the cold.

In that first minute, I distinctly recall thinking:

Oh, shit…maybe this wasn’t such a good idea. Perhaps I’m just not cut out for this because it feels extremely uncomfortable right now.”

You’ll notice that the PSD (or “loudness”) of each brain wave type actually increases during this initial minute. This aligns well with my intense state of discomfort. My monkey mind (ego) is screaming at the top of its lungs: GET THE FUCK OUT OF THIS ICE BATH!

stepping into ice bath
Oh FUCK, maybe this wasn't a good idea

After the initial minute of freaking out, I recalled the importance of my breathing. Instead of dwelling on the unbearable nature of the ice bath, I focused on deep belly breaths and prolonged exhalation to activate my parasympathetic nervous system and induce relaxation. You can clearly observe this shift occurring between the 1st and 4th minute on the brain wave chart, as my mind started to become much calmer.

From minutes 4 to 14, it can only be described as absolute bliss. I no longer felt the cold, and at times, I even experienced warmth. Time seemed to slip away, and I was surprised when my friend informed me that I had already been in the bath for 15 minutes, highlighting the importance of having a companion for safety. I was immersed in pure joy and serenity. At one point, a muscle in my pelvic area spasmed and then released, dissolving tension I hadn’t even been aware of. This sensation opened up more space in my body and intensified the feeling of ecstasy. It seemed like I could comfortably remain in the ice bath for an even longer duration.

Throughout this blissful period, the Power Spectral Density (PSD) of all my brain waves remained low, indicating a state of calmness in my mind. This aligns perfectly with the euphoric emotions I experienced during that time.

Here’s the remarkable part—observe that the PSD of all my brain waves during this period is actually lower than before I entered the ice bath. This suggests that my brain became quieter and more meditative while in the ice bath compared to my normal, non-icy life.

It’s mind-boggling and unexpected. Who would have guessed that my mind could become more relaxed while sitting in an ice bath? Even if I could endure it for 15 minutes, I would have assumed it required sheer willpower and pushing through the discomfort.

However, in reality, it wasn’t about pushing through; I had to let go and surrender to the bliss, and my brain waves reflect that. It’s absolutely fascinating! This is why I conduct experiments. While I am genuinely curious about the brain’s response during an ice bath, my true interest lies in the human experience, the nature of the ego, and consciousness itself.


I had to let go and surrender to the bliss, and my brain waves reflect that

Ice Bath Effect on Brain Hemispheric Coherence

Brain coherence is considered important in the realm of consciousness neuroscience by influential researchers like Joe Dispenza. I measured my brain coherence during the ice bath by calculating the correlation between brain wave activity originating from the left hemisphere and that from the right hemisphere.

Below is how my brain coherence behaved during the 15-minute ice bath:

brain hemispheric correlation during 15-min ice bath
Brain hemispheric correlation during 15-min ice bath

The chart provided above is rather inconclusive. There seems to be a decrease in hemispheric coherence during the blissful period (minutes 3-10), which is somewhat noteworthy since I would have anticipated the opposite—heightened coherence during such a profound state of bliss. However, this unexpected finding is one of the intriguing aspects of experimental neuroscience, where surprises and inconclusive results can occur.

Therefore, the question arises: Is brain coherence entirely unrelated to cold exposure, or do we simply need to gather more data? My inclination is towards the latter, and I intend to delve deeper into this subject through future case studies.

Ice Bath Insights: Nature of the Ego

My ultimate passion lies in exploring the human condition and the essence of consciousness. It can be argued that the human experience is essentially the light of pure consciousness refracted through the prism of the ego.

Regardless of how we perceive this experience, the ego assumes a crucial position within it. Therefore, every time we gain a deeper understanding of the ego, we come closer to unraveling the mysteries of our own consciousness. After all, the ego and consciousness are intricately intertwined partners, at least during our existence in this physical form.

Human experience is simply the light of pure consciousness refracted through the prism of the ego

The ice bath provided me with two significant lessons regarding the ego:

1. It’s not always about persevering; there is strength in letting go.

In Western society, we tend to embrace the mentality of fighting through challenges with slogans like “No pain, no gain,” “Just Do it,” and “Push through it.” While there is value in this culture of assertive energy (yang), my experience with the ice bath taught me that it doesn’t encompass the entirety of human potential. Relaxation and receptive energy (yin) are often undervalued because we believe they lead to decreased productivity and power. However, reality lies in finding balance, as true strength arises from the harmonious integration of yin and yang. In our society, we idolize the yang (representing the sympathetic nervous system) and undermine the yin (representing the parasympathetic nervous system). The brain wave measurements from the ice bath reveal the untapped potential in the yin aspect that the yang lacks. The data clearly demonstrates that my mind and body become calmer and more relaxed during the ice bath compared to before entering it. I couldn’t have forced my way through a 15-minute ice bath; I had to surrender to it. This act of letting go enabled me to achieve something I believed was impossible (considering it was my first ice bath, and I initially expected to last barely three minutes).

2. The same ego that often deceives you can also speak the truth.

The ego serves the crucial role of self-preservation. In the first minute, my ego was in a panic, bombarding me with thoughts like, “This is dangerous, you’re going to die, get out now!” Clearly, this was a false narrative. I didn’t perish, and I felt great afterward. It’s not surprising that the ego frequently fabricates stories. However, what fascinated me was that around the 14-minute mark, the same ego calmly suggested, “Hey, buddy, it might be a good time to consider getting out, no rush, just putting it out there.” Wow, ego, you had an entirely different demeanor 14 minutes ago when you were in full-blown panic mode! Yet, it’s the same ego, but this time it was fulfilling its genuine purpose of self-preservation. That’s the lesson to be learned. The same ego that tells you false narratives about yourself and the world also acts as your protector. Recognizing when to heed the ego’s warnings and when to disregard its fallacies is a crucial aspect of personal growth and development.

Hardware & Software

I used the same hardware/software stack as I have for previous case studies, such as the Ayahuasca Experiment.

The hardware used was the Muse2 Brain-sensing headband – a portable 4-node EEG technology that adheres to the 10-20 international node placement system

While the device itself is wonderfully reliable, the company software associated with it was designed for the retail meditation market and not scientific inquiry. Therefore, I paired the Muse2 with a more robust 3rd party software called MindMonitor (also used in previous cases studies, read about it here)


I am acutely aware that this study is limited to a single participant, which is not ideal in scientific experiments where a larger sample size is preferred.

However, the answers to the inquiries I seek are often not easily attainable. It would be impractical to gather ten individuals and have them consume ayahuasca in the jungle for an extended period of 30 days while measuring their brain waves. Hence, I took it upon myself to undergo this experience.

Likewise, in the case of the ice bath, it would be exceedingly challenging to find ten volunteers willing to immerse themselves in freezing water for a duration of 15 minutes while having their brain waves measured.

On that particular day, I did encounter two other courageous enthusiasts of brain data who were willing to partake in the ice bath and have their brain waves monitored. However, their time spent in the ice bath was under 3 minutes each, making it scientifically unsound to compare their results to mine, considering my extended duration of 15 minutes.

That being said, upon examining their data, it does appear that their brain waves exhibit similar patterns to mine during the initial entry into the ice bath. The power spectral density (PSD) of their brain waves also initially spikes (signifying an ego-induced reaction) before rapidly declining as the participants begin to relax. This observation is quite intriguing and bolsters my confidence in formulating the following hypotheses:

  1. The PSD of all brain waves experiences an initial spike upon entering the ice bath, followed by a decrease as the mind becomes calmer during the duration of the immersion.
  2. The PSD of all brain waves starts to exhibit increased electrical activity shortly before the participant must exit the ice bath. This could be interpreted as a natural and healthy survival instinct.

Raw Data

The data collected during this case study is freely available here. If you have any questions, send me a message

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