Do you have to be crazy to swim outside in winter?

Winter swimming in Belgium appears to be reserved for the few dedicated human ‘polar bears’ and those having access to a heated outdoor swimming pool. Outdoor swimming in our region is often considered a summer-only activity, but scientists seem to disagree. Winter swimming might hold the key to a better physical and mental health. If you look up ‘cold water swimming’ on google, you’ll be bombarded with its positive health claims. Some of them remain unsupported by scientific research, while others have been backed.



Cold water swimming increases your libido.

Don’t dip your scrotum in cold water yet (if you're a guy ...) as this claim has not been supported. Many sources refer to a publication by Dr. Vijay Vir Kakkar, a professor who ran the Thrombosis Research Institute of Chelsea, in the European in 1990. But this was simply his opinion and since then no scientific publication has backed this claim. Therefore it remains a myth.



Cold water swimming improves the blood circulation.

This does appear to be the case. Dr Kakkar was able to provide evidence that training patients with high LDL-cholesterol (considered the ‘bad cholesterol’) to take cold water baths decreased their cholesterol levels (1). So this would indeed improve your blood circulation.



Cold water swimming increases brown fat.

This one is tricky! Brown fat is what many of us know as ‘baby fat’. It’s stored in the neck, shoulders and around the spine, and is considered to help dispose of white fat (the one we don’t really like) because they convert calories into heat. So it could actually make you lose weight. Brown fat is difficult to study, but attempts have been made. It appears to get activated in lean men when exposed to cold temperatures, but less in overweight or obese men (2), and might help reduce the risk to obesity-related diabetes (3,4).  



Cold water swimming influences the immune system.

This might be one of the more spectacular findings surrounding cold water swimming. When a man who climbed several mountains in his shorts and set several ice-water records, started collaborating with scientists at Radboud University in Nijmegen (5), things got interesting. Wim Hof appears to be able to generate adrenaline levels equal and above those experienced on a rollercoaster ride. Moreover, he claimed that he’s able to do this through cold water swimming, breathing techniques and meditation, and is able to train others to show the same physiological response. Over a 10-day period he trained 12 participants while under scientific supervision. Hof and the research team were able to demonstrate that humans can voluntarily manipulate their immune system over a relatively short period of time without any medication by setting off an adrenaline rush, which subsequently lead to an increase in anti-inflammatory responses. This allowed the participants to resist an intravenously administered bacterial infection. Although these results should be treated with caution, they do provide an interesting explanation for a claim made by several cold water swimmers (6) that they get sick less and recover faster from illness.



Cold water swimming increases your metabolism.

Upon impact, cold water initially opens all of the blood vessels below the skin (7), and subsequently constricts them, leading to an increase in blood pressure in an effort to preserve core heat in the body. When this is done repeatedly, the human body appears to adapt to colder surroundings, rather than just becoming used to it (8).



Cold water swimming reduces inflammation.

This one shouldn’t come as a surprise. Ice is regularly used to reduce swelling, and this also occurs in water below 15°C. There does appear to be some discussion as to whether it prevents additional muscle damage after exercising (9,10).



Cold water swimming improves the quality of sleep.

There appears to be no impact of cold water swimming on the quality of sleep (11).



Cold water swimming as a treatment for depression.

Several online articles make this claim. Although this might be theoretically possible, currently no evidence has been provided for this (12).


Even though cold water swimming can’t be considered an alternative to Prozac or Viagra, it does hold several health benefits making it a valid reason to unpack your swimsuit in the dead of winter.

Now all you need is a place to enjoy it in Brussels!



Picture from, the website of the winter swimming club Deurnese Ijsberen in Antwerp. 

(1) De Lorenzo, F., Mukherjee, M., Kadziola, Z., Sherwood, R., & Kakkar, V. V. (1998). Central cooling effects in patients with hypercholesterolaemia. Clinical Science, 95(2), 213-217.
(2) van Marken Lichtenbelt, W. D., Vanhommerig, J. W., Smulders, N. M., Drossaerts, J. M., Kemerink, G. J., Bouvy, N. D., ... & Teule, G. J. (2009). Cold-activated brown adipose tissue in healthy men. New England Journal of Medicine, 360(15), 1500-1508
(3) Hanssen, M. J., van der Lans, A. A., Brans, B., Hoeks, J., Jardon, K. M., Schaart, G., ... & van Marken Lichtenbelt, W. D. (2016). Short-term cold acclimation recruits brown adipose tissue in obese humans. Diabetes, 65(5), 1179-1189.
(4) Hanssen, M. J., Broeders, E., Samms, R. J., Vosselman, M. J., van der Lans, A. A., Cheng, C. C., ... & Schrauwen, P. (2015). Serum FGF21 levels are associated with brown adipose tissue activity in humans. Scientific reports, 5, 10275.
(5) Kox, M., van Eijk, L. T., Zwaag, J., van den Wildenberg, J., Sweep, F. C., van der Hoeven, J. G., & Pickkers, P. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. Proceedings of the National Academy of Sciences, 111(20), 7379-7384.
(8) Young, A. J., Muza, S. R., Sawka, M. N., Gonzalez, R. R., & Pandolf, K. B. (1986). Human thermoregulatory responses to cold air are altered by repeated cold water immersion. Journal of Applied Physiology, 60(5), 1542-1548.
(9) Bailey, D. M., Erith, S. J., Griffin, P. J., Dowson, A., Brewer, D. S., Gant, N., & Williams, C. (2007). Influence of cold-water immersion on indices of muscle damage following prolonged intermittent shuttle running. Journal of sports sciences, 25(11), 1163-1170.
(10) White, G. E., & Wells, G. D. (2013). Cold-water immersion and other forms of cryotherapy: physiological changes potentially affecting recovery from high-intensity exercise. Extreme physiology & medicine, 2(1), 26.
(11) Robey, E., Dawson, B., Halson, S., Gregson, W., King, S., Goodman, C., & Eastwood, P. (2013). Effect of evening postexercise cold water immersion on subsequent sleep. Med Sci Sports Exerc, 45(7), 1394-402.
(12) Shevchuk, N. A. (2008). Adapted cold shower as a potential treatment for depression. Medical hypotheses, 70(5), 995-1001.