What does the science say?
- The first part was about appreciating all the seasons for what they are
- The second part was about how I started and even more important – why I continued
- In the third part I gave some of my advice about how you can start if you want to
- In the forth and final part (this one) I’m gonna look at what the science have to say about it
Before we jump into this we first need to cover the presumptions.
A: There are probably a lot of other people who is way more experienced of reading research articles than me. Although I think it’s interesting and I want to learn more, so what better way than to actually do it?
B: When I was searching I realized that there aren’t that much research done in the field, especially not for all the claims that are made about it.
C: The results can vary because the scientists used different methods (showers, baths, cryotherapy), different temperatures (5-20 degree Celsius – Come on, 20?! That’s like summer), different times (30 seconds to like one hour) and they ask different questions.
And I think we can all agree on that it’s a bit different to swim in 5 degree water for one hour than to stand in a 20 degree shower for 30 seconds., right?
D: Finally it’s hard to make double-blinded randomized controlled trials, which is a very valid method, since it’s quite hard to placebo a cold bath – You kinda know if you take one.
So with that said, let’s dig in!
To get some structure in this and divide the different questions I have tried to categorized it by: Recovery & Performance, Immune system & Health, Mental health and finally Relaxation.
Recovery & Performance
Cold exposure for recovery and performance have been around for quite some time and this is where most of the research in the field have been done, at least what I could find. Because athletes who are already doing a lot of things to perform, every little advantage they can find can be the difference between winning or loosing. So the question is how relevant these results are for just ”normal” people who are cold bathing just because the nice feeling they get out of it?
A meta analysis from 2016 came to the conclusion that Cold Water Immersion (CWI) can be slightly more effective than passive recovery in management of muscle soreness and means that 10-15 minutes in a temperature between 10-15 degree Celsius gives the best results (1).
Another meta analysis from 2017 wanted to investigate about team sports and made a difference between CWI and Contrast Water Therapy (CWT) which means that the temperatures are changing. They came to the conclusion that both CWI and CWT could be beneficial for neuromuscular recovery and perceived fatigue but not for muscle soreness (2).
Although there might be some good effects of CWI among young football players who could increase the aerobic capacity with one cold session (Standing to the hip in 11-12 degree water for 10 minutes) per week for 8 weeks (3) it doesn’t seem to be any recovery effects after resistance training (4).
The researchers of a study from 2018 that wanted to compare the recovery after running with 5- and 14 degree water also came to the conclusion that CWI is not to recommend for acute recovery and based on their data the time should instead be put on more effective methods (5).
One of the most interesting studies was from 2014 (6). They wanted to see if the effects of the cold water was placebo. To do this they had three groups who first did High Intensity Sprints for 4×30 sec, followed by either:
- Cold water (10,3 degree Celsius)
- Thermoneutral water Placebo (34,7 degree Celsius)
- Thermoneutral water Control (34,7 degree Celsius)
The placebo group was falsely told that they were given a new, special recovery oil. The results showed that both the CWI group and the Placebo group recovered better both physically and mentally. The authors conclude
”This can likely be attributed to improved subjective ratings of pain and readiness for exercise, suggesting that the hypothesized physiological benefits surrounding CWI may be at least partly placebo related”.
So what propose is that since placebo has similar effects as CWI, the effects of Cold water could be to some degree a placebo effect. Although I think they are on to something very important here. Us humans are very easily tricked. We want to believe that when we feel something intense, like a cold bath, foam rolling, copping or acupuncture something good is happening to us. And maybe it does, the Placebo effect is a real and powerful thing. Just know that there is a difference between a Placebo effect and an effect of the actual treatment.
The title of the article is ”Postexercise Cold Water Immersion Benefits
Are Not Greater than the Placebo Effect”. So before we get to sure about this maybe a better title would be ”Placebo is as good as Cold water”.
Immune system & Health
Something that is very common among Cold bathers that are not looking for the performance enhancing effects of Cold exposure is the positive effects on the immune system.
When we expose ourselves to the cold indeed things start to happen inside of us and there is an increase of proteins involved in the immune system. The question is although how big the practical relevance of this is (7).
There is although also some evidence that there might be positive effects even in practice. The study from 2014 which Wim Hof refers to a lot, where 12 people were trained in his method and then exposed for a virus showed that they could resist it better than the control group. The authors says that this shows that we can voluntarily activate sympathetic nervous system but they also say that it was probably more due to the breathing exercises than the cold water (8). Although as I mentioned in my previous articles, the cold can be a great teacher when it comes to breathing.
Another study from 2016 had their participants do Hot-to-Cold showers for 30, 60 or 90 seconds. The results showed 29 % less sick days compared to the control group and a self experienced increase energy level. This effect was also larger with physical activity, so another conclusion is that a active and healthy lifestyle is good in general. Although as many as 91 % of the participants said that they would continue with the cold showers since they enjoyed them (9).
A large review article from 2020 wrote that cold swim have an effect on the immune system and people who do it on regular basis could have 40 % less risk of infections of the upper respiratory tract. They also point out that there is a big difference of being still and swimming in the cold water and by getting the most health benefits out of it you should slowly acclimatize yourself (10).
I couldn’t really find so many studies in this area. Although the review article mentioned before stated that cold swimming can have some positive mental effects and work as anti-depressive, which was mostly based on case reports. They also say that these are effects that also can be seen by physical activity in warmer temperatures as well (10).
A study from 2008 wanted to see if depression can be treated with cold bath. Even though they used showers with 20 degree Celsius, which I would say is not very cold, they came to the conclusion that it can be an effective treatment, with the addition the we need more research to say for sure (11).
Many people say that they experience a feeling of relaxation after a cold bath. I could only find one study on this subject, from 2019. Using CWI of 10 degree Celsius and CWT of 10-38 degree Celsius they came to the conclusion that both conditions had the potential effect to increase the acute sensation of relaxation, which can have a positive roll in an athletes performance and general well-being (12).
Even though the science is not yet clear I would say it points in a direction where there might be some benefits of cold exposure. Also remember that there is also some risks with it, which I didn’t really bring up here. As usual it’s probably a question of dosage and not go into the extremes. So always make sure to do it in a safe way and listen to your body.
So if You feel that you get in a good mode and feels awesome after your cold baths, by all means continue. I’m happy for you. The science can’t say if you specifically gets in a good mode or not. Although be careful by making up explanations of your own, because there is a big difference what makes you feel good and what makes everyone feel good. And if you don’t like it, don’t worry, you don’t have to do it. Find your own thing that makes you feel good.
With those words I wish you a happy bath and may you have an abundance of coldness in your life. Thanks for reading!