Is cold water swimming actually good for you?

Does immersion in cold water have special therapeutic qualities or it just an exercise trend with great PR? Photo / 123RF

Phoebe Luckhurst asks the alfresco evangelists - and the scientists.

Here’s a riddle. How do you know if someone is a cold water swimmer? The answer is, of course, they’ll tell you. In recent years the activity has attracted a vocal lobby of devotees in Dryrobes — hale, hearty and evangelical.

“Cold water” is generally agreed to be 20C and below — open water in the UK rarely gets any warmer than that. Nor do unheated lidos, except perhaps during the hottest heatwaves, although most cold water swimmers prefer the sea, lakes and rivers. According to Sport England, an estimated 3.6 million people in England swam in open water in 2022. You may feel like you’ve met every single one of them.

Of course getting your body moving is generally a good idea. But does immersion in cold water have special therapeutic qualities or is it just an exercise trend with great PR?

“Exposing yourself to cold water is a good thing,” insists Dr Mark Harper, a consultant anaesthetist at Brighton and Sussex University Hospitals and the author of Chill: The Cold Water Swimming Cure. Harper, 56, started swimming in the sea when his local pool was closed for two weeks. Twenty years later he’s still at it. Over that time he has conducted research into the physiological and mental health benefits of a regular outdoor dunk.

So what happens when you immerse yourself in cold water? Immediately the body goes into shock. “Your body puts up levels of stress hormones — cortisol and adrenaline,” Harper says, “and all the blood vessels in the skin close.” This is to insulate the body and protect our vital organs from the cold. Your blood pressure and heart rate go up. You may also start to hyperventilate.

These all sound like bad things. “When you get in the first time it has a really powerful effect that is not good for you as such,” Harper concedes. But after “four or five times” your body adapts to the stress of exposure to the cold. Stress is an evolutionary response, but the body needs to find an equilibrium between the push-pull of the sympathetic nervous system — the “fight or flight” response that elevates the heart rate and blood pressure — and the parasympathetic nervous system, which resets the body during rest, slowing the heart rate and blood pressure again. Regular exposure to cold water can help to find that balance.

The activity also has so-called “soft” benefits, Harper says. “Being out in nature, views of the sea, the community The vast majority of cold water swimming happens as part of a group. Reduced social isolation is an important factor in mental and physical health, which are closely bound up together.” And the “extreme” nature of plunging into the chill can be a great bonding experience.

After years of taking part in triathlons and ultramarathons, Sian Richardson, 58, was looking for an activity that was easier on the joints and found cold water swimming to be “the whole package”. In 2014 she founded the Bluetits Chill Swimmers, which is now a network of 100,000 cold water “dippers” around the world. There are local Bluetit groups all over the UK: from Tooting, southwest London, to Pembrokeshire, where Richardson is based. Beginners are very welcome. “Somebody will always swear,” Richardson says. “And then, suddenly, you’ve done it. And the Bluetit next to you will say, ‘You’re amazing.’ "

It’s cheap and efficient exercise — “just 20 minutes out of your day and then you can live off that buzz”. It is inclusive too. “A lot of people in their fifties think they aren’t athletes, but dipping is one thing they can do,” Richardson says. And all you need is a swimsuit (she usually has a spare for newbie Bluetits). For all these reasons people tend to keep it up, unlike other exercises such as running that can risk injury.

Convinced to take the plunge? The good news is that you don’t have to be in there very long. “After 20 years I still get the ‘shock’ when I get in,” Harper says, “but it passes very quickly, and once you’re at ease you’ve been in there long enough to get the vast majority of the effect. Straight in, straight out.” Harper also advises starting in the summer, doing it in a group (and never alone) and to “make sure you know how you’ll get out of the water afterwards”.

Be careful where you swim: Britain’s sewage scandal is well documented. Surfers Against Sewage has produced the Safer Seas & Rivers Service app, which logs the water quality in real time at 370 beaches across the UK. And be wary of some rivers and lakes: Weil’s disease is rare but can be a risk.

Is there anyone who shouldn’t attempt it? “If you are fit enough to walk down a beach, you are fit enough to get into cold water,” Harper says. “If you have a serious medical condition — a cold-induced heart arrhythmia, for example — then no. But everyone else, go for it.”

Just know that once you start you risk becoming a cold water cliché. “The endorphins are a drug,” Richardson says. “The best free drug on the market.”

Written by: Phoebe Luckhurst

© The Times of London