How cold is the water??? Benefits of cold water swimming

Alex Reis
Science of Cold
Published in
6 min readApr 27, 2018

When German philosopher, Friedrich Nietzsche said, “what doesn’t kill you makes you stronger,” he wasn’t talking about open water swimming, but he could well have been as it fits like a glove.

Credit: Sunart Media (Simon Willis)

Most people don’t really understand the point of spending an afternoon trying to get friendly with the cold and I counted myself as one of them until recently. But, as I watch crazy friends jump into freezing waters and come out grinning their heads off, I have to concede maybe there’s something in it after all, a little something extra that a warm swimming pool cannot offer. This is certainly not for the faint-hearted (no, really, medically it isn’t — not without a doctor’s ok), but it turns out open water swimming has a multitude of health benefits that I was blissfully unaware.

Cold water is stressful at first, but it gets easier

As warm-blooded animals, our body is definitely not designed to cope with freezing cold water. If you’ve never done it before, expect your body to go into full shock mode the first time you go for a swim in cold water. Your skin feels so cold it hurts. Your heart is pounding and it feels like your lungs are about to give up. Your blood pressure keeps getting higher and you find it hard to breathe.

This is your brain shouting “GET ME OUT OF HERE NOW”, but don’t panic just yet. As experienced swimmers will tell you, it gets easier with practice. This may be hard to believe at this stage, but there is actually scientific evidence to support their claim: repeated swims — some studies suggest as few as four — will dampen this response. As you get used to cold water, your body relaxes and stress levels go down. Heart rate and blood pressure don’t go up as much and you may find it easier to control your breathing. Congratulations, you are now acclimatised to swimming in cold water.

For researchers, the fascination with this gradual adaptation to cold water started in the 50s, when crossing the Channel was getting popular and yet victims of shipwrecks succumbed to the cold water and hypothermia in very a short period. The accepted theory back then was that trained swimmers were somehow able to switch off their thermoregulatory system and still feel comfortable despite their lower body temperature.

Over the years, this idea developed into the concept of insulative acclimatisation to cold. For experienced swimmers, this means cold hands and cold feet, but crucially their body can keep core temperature and metabolic rate stable. In other words, the body enhances mechanisms to conserve body heat by diverting circulation away from extremities. The idea is to protect the body’s core and vital internal organs with a layer of insulation.

This is good news for swimmers, but the story doesn’t end here. It turns out our body seems able to ‘learn’ to cope and apply it in other stressful situations. There is actually a name for this: hormetic stress, or in other words, stress that is good for our body (as long as it is in small doses).

Our bodies are very good at maintaining everything in balance. If something changes — say, you decide to take up cold water swimming — your body fights this stress by becoming stronger in order to keep the status quo. In most cases, however, your body tends to overcompensate and you become stronger/faster/more resistant to stress than you were before. For example, researchers found experienced swimmers not only were better at exercise under low oxygen conditions compared to a control group but also registered a lower increase in stress hormones.

For those of you out there who already embraced this sport, this is the perfect win-win scenario: not only you benefit from exercise during swimming, but you’ll be cool as a cucumber next time your broadband is off or the bus is late!

No more colds!

Most cold water swimmers I know also brag about how they (almost) never get sick. As annoying as this may be for non-swimmers, these claims are actually supported by hard evidence and several studies confirm cold water swimmers have a lower incidence of colds, and when they get one, infections are shorter and less severe.

If you think hormetic stress again (remember Nietzsche?), jumping into cold water shocks your body at first, but then it triggers your immune system into overdrive with an increased production of white blood cells. This challenge keeps your immune system on standby and ready to react at the first signs of infection. Next winter, when everybody around you is sniffing and sneezing, you’ll be thankful for your time in the water.

Credit: Sunart Media (Simon Willis)

Alfresco weight watchers — Burn more calories

This is where open water swimming takes the benefits of conventional swimming to the next level. Everybody knows that swimming is an excellent way to get fit, but exercising in the cold means more calories gone — after all, your body is not only trying to move fast but it’s also using up your energy (read: fat reserves) to keep warm.

Interestingly, recent research has shown these calories don’t come from your normal fat tissues. You know, the stubborn deposits around your stomach and hips. These calories come instead from a type of fat called brown fat. Babies are born with large reserves, but as we grow up, these tend to disappear in detriment of the white variety. It turns out that cold water activates left-over brown fat which is great for swimmers as its main purpose is to produce heat without shivering. Think of it as your own built-in personal heater that may also help you lose a few pounds!

Other Benefits

One further aspect that inspires swimmers to brave the cold and pain is the resulting mix of endorphins, serotonin, and dopamine. The ‘post-swim high’ as some may call it is actually backed up by hard evidence! Some studies go even further and suggest this release of ‘happy’ chemicals could potentially be used as part of a treatment for depression. Researchers are still cautious about these claims, but if you ask cold water swimmers whether open water has helped them mentally, I would say you would get a nod from most of them.

Other conditions helped by open water swimming may include psoriasis and eczema. The theory — which still needs further proof — is that sea water, in particular, can rejuvenate the skin and promote healing. The many reports defending that cold water somehow magically removes toxins from the body may be slightly exaggerated, but there is some anecdotal evidence to suggest that cold water does promote circulation.

Finally, for the romantics out there, you may be interested in knowing that cold water increases testosterone and sperm count, as well as improve libido and fertility. So, if you’re looking for a perfect date experience, why not include a dip in the ocean?

Me and my wee man — New year’s day 2017

It’s more than just swimming…

Open water swimming may not be a magic treatment to ensure weight loss and low stress by itself but, as part of a balanced lifestyle, it boasts too many health benefits to ignore. The evidence is somewhat sketchy in some areas — after all this is a recent trend — but it certainly worth further investigations. And, even researchers find out that all these benefits are just wishful thinking, a dip in the cold water is still a great way to clear your head!

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