Two people walking into the sea. Life Solved logo and title overlaid

Is cold water swimming really great for your health and wellbeing?

  • 15 February 2022
  • 23 min listen

In recent years, new outdoor swimming enthusiasts have flocked to lidos, lakes and the sea to enjoy health and wellbeing benefits. But there are plenty of us who might still be wary of our icy British waters.

So how safe is cold water swimming? How might it improve your mental health? And is it really as good for your body as the anecdotes suggest?

In the latest episode of the Life Solved podcast, Dr Heather Massey takes us through her research into physiology under extreme conditions. An outdoor swimming enthusiast herself, Heather has spent years exploring the processes and behaviour of our bodies in hot or cold environments or at altitudes.

She says that a deeper public understanding of our physiology can help keep us safer and help us enjoy outdoor swimming even more.

What are the benefits people are reporting?

In response to the recent spike in outdoors swimmers since the pandemic, Heather and her team are now turning their research towards understanding some of the other benefits reported by swimmers.

These vary from people suggesting that they have fewer symptoms of pain if they have chronic pain. Women who have menopausal symptoms. Some people have also suggested that they have fewer migraines because of the cold water immersion.

Dr Heather Massey, Senior Lecturer

But it’s not just the reported physiological perks that have caught her attention. Heather’s also looking at reports that anxiety, depression and mental health have all improved for people taking the dive. She’s hoping to study this in a clinical trial with outdoor swimming groups.

Top tips before taking a dip

Heather advised that anyone thinking of trying out cold water swimming should first consult with their GP to make sure no underlying conditions might be triggered by the extreme cold. After that, her safety tips are to swim with a group to familiarise yourself with common hazards, plan your exit from the water before you get in and swim for less time than you think you can handle.

When you've got out of the water, get yourself dry and dressed as quickly as you possibly can.

Dr Heather Massey, Senior Lecturer

In the podcast, Heather takes you through the four stages of cold response to look out for in your swimming pals.

Helping people regulate their physiology

She’s also been turning her experience in extreme temperature body physiology to helping sufferers of Ectodermal dysplasias – a group of disorders that can impact sweat gland function. For people unable to sweat normally, research can help them find ways of staying comfortable and safe in changeable conditions:


Our role is to try to find ways of keeping people active but also to keep them cool. So it's looking at ways we can remove a lot of that heat from the body and allow them to carry out a fairly normal life.

Dr Heather Massey, Senior Lecturer

To listen to the full podcast and hear more about Heather’s research, search for “Life Solved” from on your podcast app of choice, and why not share this story with a friend who might be interested.

Episode transcript:

John Worsey: Thanks for downloading this episode of Life Solved. In this podcast we find out how researchers across the University of Portsmouth are combining their skills and insights to change our world for the better. This time…. can cold water swimming really improve your mental health? How can you try it out safely? And how could the study of physiology help change lives for people with a genetic skin disorder?

Heather Massey: There's a range of different potential mechanisms some physiological, some psychological and some social as well and really trying to tease those out, which is going to be the challenge.

John Worsey: Let’s dive in. Dr Heather Massey’s work and her passion go hand in hand.

Heather Massey: I'm a cold water swimmer, so I'm one of these crazy people that go swimming in the sea all year round. I just thoroughly enjoy it. One of my university tutors got me into a study group looking at extreme environments and what happens to the body. So right from an undergraduate degree sort of pathway, I was really interested in what happened to the body when you got hot or cold.

John Worsey: Today, she’s a researcher in the Extreme Environments Laboratory in the School of Sport, Health and Exercise Medicine here at the University of Portsmouth.

Heather Massey: My research background is looking at what happens to the body when we are in hot environments or cold environments or at altitude.

John Worsey: In cold water studies, much of her work has focussed on how to keep the body safe in such environments and manage physiological changes. Now, as more and more people embrace the great outdoors (and our chilly British waters) she’s also looking at another side to this past time.

Heather Massey: We're moving more into looking at the potential for benefits from being in cold water. There's quite a large amount of qualitative research and quantitative evidence to indicate that people are finding there may be benefit from being in cold water. Over the last 15 years, there's been a small rise in the number of people wanting to swim outdoors. And really, in the last two years when we've had the COVID lockdowns and swimming facilities and gymnasiums have been shot, open water swimming has really sort of expanded to fill a void. And lots of people have taken up outdoor swimming and found that they've had some benefit from doing so. So our research is really building on the qualitative evidence that we have there and trying to add some quantity to that. So how much benefit is occurring? What are the mechanisms that these benefits occur and who benefits to?

John Worsey: There’s already a lot of curiosity about the qualitative benefits cold water enthusiasts are reporting. Could this be some sort of cure-all for common ailments? There are plenty of avenues to explore, and plenty more questions to ask.

Heather Massey: These vary from people suggesting that they have fewer symptoms of pain if they have chronic pain. Women who have a menopausal symptom have suggested that they have fewer menopausal symptoms as a consequence. Some people that have experience of migraines also suggesting that they have fewer migraines because of the cold-water immersion or showering. I mean, there's one study that was done in the Netherlands that had that had several groups of people that cold water showered for 30 seconds at the start of the day in comparison to a control group. And they found that those people that cold water showed for 30 seconds a day had about had about 29 percent reduction in the sickness absence from work. So it has some big knock-on effects, potentially. There's also some research underway at the moment looking at and cold-water immersion being supportive of a reduction in neurodegeneration. Now, neurodegeneration can lead to dementia. And so if we can reduce the rate at which neurodegeneration occurs, we might sort of stave off that, that progression into dementia. So these are some of the things that are being looked at actively in the field in this area at the moment is incredible.

John Worsey: But there is one particular area that Heather has homed in on in her latest research: the question of cold water and mental health. It’s down to researchers to untangle a spiderweb of influences that might hold a clue to easing one of our society’s biggest challenges.

Heather Massey: We're also very interested in looking at the potential impact on depression and anxiety or reduction of symptoms of depression and anxiety. In terms of the mechanisms of the causes of these potential beneficial effects, we don't know, and it may be that it's multiple effects. So we think there may be some physiological changes that occur. So as you say, it may be related to that blood being redistributed around the body when you're getting cold, so it redistributes from the skin to the centre of the body, which is a perfectly normal thing to happen if you're going to cold water or cold shower. We think it may be related to the fact that it's an extreme stressor. And actually, if you can undertake that sort of extreme stress that might have some impact on you being better able to cope with other stressors in your life. And it may be related to distraction. It may be related to some psychological components. So if you're swimming outdoors, you may be more connected with nature. It has a transformative effect. It may be the group that you go with if your shower. If you're if you're swimming in cold water in a group, so often it might be considered a group therapy or if you prefer to swim alone. We're not suggesting that that's particularly safe. But if you like the idea of being in an a in a nature-based environment which is quite isolating and you find that quite calming, then some people are suggesting that it might be those sort of calming impacts as well. The next area of research that we're really starting to focus on is looking at the use of outdoor swimming to promote improvement in symptoms of depression. And this is something that we're looking to move towards a clinical trial with the hope that we can recruit not only people with lived experience of depression to an outdoor swimming group, but also look at a control group as well, so that we can start to see the real impacts of outdoor swimming and not just have one single group where we may see some improvements because of the group, because of other reasons other than the outdoor swimming. So we need to start to improve the level of science that we're producing, not just using a single group studies, but using things called randomised controlled trials.

John Worsey: Heather’s previous work means she’s well-versed in the physiological effects of cold water on the body. If you’re thinking about taking up cold water swimming, or if you’re just passionate about spending time outdoors, then it’s essential you’re aware of the four stages of cold response. Here’s Heather’s guide on what to expect, and how to respond to make sure your outdoor experience is safe.

Heather Massey: As we get into the cold water, we cool the skin and that stimulates the cold receptors, which are right underneath the surface of the skin, and that causes the cold shock response. Now, that cold shock response is a big inspiratory gasp where you take a big, deep breath in and then rapidly breathe after that: hyperventilatory response. It also causes an increase in blood pressure and also your heart rate as well. Now this response is something that we can dull that response down. We can habituate that response with repeated immersions in cold water. And so often you'll see that the people have been swimming for long periods of time. They won't necessarily have such a pronounced cold shock response. But for those that are new to the activity, we may find that they have quite a large cold shock response. And the cold shock response is one of those things that can be quite hazardous. It's because you're taking a large, uncontrolled breath and carrying on breathing in an uncontrolled manner. If your head and airway and not above the water, you're going to start to take in and breathe in water, aspirate water, and that can start the processes in drowning. In addition, the changes in blood pressure and heart rate are quite it can be quite problematic, especially if you have an underlying heart condition. And so if you are going to go into cold water for the first time, it's always worth having a quick chat with your GP just to check that there's no underlying problems that will cause you problems when going into the cold water.

John Worsey: According to Heather, the cold shock response lasts between 90 seconds to 3 minutes. After that, the superficial nerves and muscles of the body begin to cool. Given the normal temperature of your nerves and muscles is between 30 and 35 degrees, as your body temperature decreases, you’ll start to notice the effects.

Heather Massey: Once they get down to about 27 degrees, we're going to start to notice that they won't work as well. So our nerves won't be able to conduct the nervous impulses as well, and our muscles will become less... they don't work as well. And so what will end up doing is we'll have a less coordinated swim stroke. When it when we're swimming, we may find that we become a little bit stiff and that can lead to something called swim failure, whereby if we're not able to get to a point of safety, it might mean that we go from swimming in quite a horizontal fashion to our legs, starting to drop a little bit and leading to us being in a quite a vertical position, making no forward progress and ultimately will start to fatigue so much that unfortunately our airway will go under the water and we'll start that drowning process again. So it's really important if is swimmers are swimming in cold water and start to experience that slight coordination in the stroke or the fingers are starting to get stiffer that they exit the water there and then so that they don't develop that swim failure.

John Worsey: So, check with a GP, keep an eye out for hyperventilation and be on the lookout for any reduction in your muscle response or coordination. Wise advice so far, but there are two further stages of cold response that any outdoor swimmer should know about, and they can take you by surprise if you don’t know what to look for.

Heather Massey: Once you cool the skin, once you've called the superficial nerves and muscles, we then start to cool the deep body. And we normally operate on deep body temperature around thirty seven degrees, thirty six and a half, something like that. And once we once we get past that initial short term responses, we're going to be cooling that deep body. And now that is going to mean that we're moving towards becoming hypothermic and we clinically call hypothermia a deep body temperature of 35 degrees. Now, without without actually measuring that, we have no formal way of knowing how cold somebody is. But there are some very obvious differences in our behaviour when we get when we start to cool and medics often term these the umbles. So people start to stumble, fumble, grumble and mumble, so they become less coordinated when they're when they're walking around. They start to stumble, fumble. They're not able to coordinate their hands to dress themselves. They're grumbling, so they have quite a low mood. So whereas somebody that may have been in for a few minutes may be quite euphoric, somebody who's hypothermic will be quite low in their mood. And the final one is mumble some mumbling where your speech becomes quite incoherent, as if you've had a few to drink. And these four changes in behaviour really quite key. So if you are swimming in a group of people that you that you know quite well, if people start to develop these symptoms or have some quite clear changes in their behaviour, there's a good probability that they're starting to get quite cold. You really need to get them out of the water dry and dressed as quickly as possible so that they can start that rewarming process.

John Worsey: That’s good advice for any swimming group. But how do you make sure someone in this state is able to get their body back up to a safe temperature?

Heather Massey: People often think as soon as they get out of the water, they're instantly going to heat back up. That's not really the case. We're going to continue to cool for about a further 30 minutes or so after we've got out of the water. And that's purely because we're still the whole of our body. The tissues of our body are still very cold. So even though we stopped applying the cool stimulus of the water, we still got those cold tissues and it takes a long time for the body to reverse that cooling. So we have to heat up from the outside in. So it takes quite a while for us to reverse that cooling. And one of the main ways that we heat up is by shivering and shivering is quite a cost inefficient way of rewarming, but it is absolutely the thing we need to do. So lots of people say, Oh, people are shivering. That's a bad sign actually is someone's cold and they're shivering. That's a good sign. It shows that they're defending their body temperature and they're going to start to warm up. The problems occur when somebody stops shivering and they're cold.

John Worsey: Cold shock, short-term immersion, deep body cooling and rewarming: now you understand the 4 stages of cold water immersion, hopefully you’re better clued up on how to enjoy yourself safely out there in the water. But here’s a quick checklist for taking care of a friend who’s struggling.

Heather Massey: If people are wanting to rewarm either themselves or they find that one of their swimming buddies is a bit cold and they need to be warm, the best things to do or to get people into a sheltered environment out of the wind, also remove any wet clothes because that's going to continue to cool people. Having water next to the skin will mean that that water will evaporate from the surface of the skin. Making sure that they're in waterproof clothing or in shelter. That's absolutely key. Keep talking to them. Find out a little bit about their thought processes. Use that those “umbles”. So that’s fumble stumbles, mumbles to just assess the mood and behaviour, and as they start to rewarm, you'll start to see that that mood will lift. The speech will become more coherent and that they're able to function better, so they may be able to hold on to things. So it's really important that if you do have a cold water swimmer that is experiencing hypothermia, that you stay with them, you support them in their rewarming, and it can take some considerable time for them to get to the point where they are starting to operate at a more normal level in terms of their cognition.

So for someone wanting to dip their toe into the (sometimes chilly) water, what would Heather recommend for anyone embarking on a new outdoors swimming hobby?

Heather Massey: Contact local groups. They will have an awareness of the hazards and also be aware of what happens to your body when you go into cold water so they can be great allies in supporting you for your first swim sessions, and they strongly promote going into cold water with groups. It's safer to be in cold water if there are any problems, as always, somebody to help. Also, things like before you go swimming, make sure you know how you're going to get out of the water. When you're getting out of the water, you're going to be colder, you're going to be much weaker because you've had you set your strengths sapped from being in the cold water. So you need to make sure that that exit from the cold water is easy for you to get out before you've got in. So that's a really key point, and I would suggest always and always swim for shorter than you think you're going to need that you're going to want to. Swimming in a swimming pool, for instance, is very different to swimming outdoors. So even if you're able to do quite a long distance in swimming pools, you'll notice that you'll be able to do much less in open water than you do in a swimming pool. And then finally, it's really about when you're getting out of the water and not hanging around, enjoying the view and the vista. When you've got out of the water, get yourself dry and dressed as quickly as you possibly can.

John Worsey: And when you’re dressed and warmed up, don’t forget to enjoy a cuppa, some great company, and the mental health benefits of being outdoors! We’re looking forward to learning more about those in the next phases of Heather’s research. Before we go though, one more story from this exciting and developing area of study. You may be thinking about how to manage your body to stay comfortable when we talk about staying warm in extreme cold. But what if your body didn’t work like everyone else’s? Ectodermal dysplasias are a group of inherited disorders that can affect your hair, nails, sweat glands and teeth. For those patients who are unable to sweat normally, regulating body temperature can be a matter of life and death. Heather explained more.

Heather Massey: Part of their condition means that they have either few or non-functioning sweat glands and they have a range of other problems associated with the condition as well. The problem we focus on is the poor functioning sweat glands or lack of sweat glands, and that can really impact how you regulate your deep body temperature. So it particularly in hot environments, if you're not able to sweat, then you're obviously going to start getting hotter and hotter and hotter. And it can get to the point where people become very unwell because of that and they develop a heat illness. And there have been deaths, unfortunately, from heat illness. So our role here is really to try to find ways of keeping people active who have this, who have this condition, but also to keep them cool. So it's looking at ways we can remove a lot of that heat from the body that is being produced and allow them to carry out a fairly normal life. So that's what we've been trying to do with that population.

John Worsey: Even here in our relatively mild UK climate, hot summer days, warm heated rooms and changes in our environments can make daily life a challenge for people experiencing the condition.

Heather Massey: Ectodermal dysplasia is a rare genetic disorder, and we don't actually know how many patients there are in the UK, but the estimate is around 400 to a thousand patients in the UK. And so, as I say, it's quite a rare condition, but the problems they have are quite large and even down to being able to wear the right uniform at school, particularly in the summer months they struggle, particularly especially if they have to wear thick blazers in a warm classroom. It's really going to impact their behaviour and also their ability to learn and so impacts children more than it does adults purely because of the constraints children have on their on their schooling environment. Whereas adults can generally choose and have developed coping mechanisms to help them to cope with their activities of daily living.

John Worsey: Research in Heather’s team here at the University of Portsmouth is looking closely at the physiology of heat response in order to find solutions that make everyday life safer and more achievable for patients.

Heather Massey: We're looking at individual cases at the moment. This work is really in its early days and we have a number of patients that have come in with very specific problems about their ability to thermoregulate. So we get them into one of our warm chambers and we'll do some moderate exercise with them while they're wearing various instruments. So will measure the deep body temperature by sticking an hour semester into the air. We'll look at their skin temperatures by looking at Infra-red thermal imaging cameras, and that not only tells us about their skin temperature, but it also pinpoints where they're sweating and if they're sweating. Because if you'll be able to sweat, then your skin will start to cool down because of the water that is on the skin, the sweat that's on the skin. Whereas if you don't have much sweating or patchy sweating, then the dry skin will become very, very hot. We also look at the amount of sweating that is produced. And so from these basic measures, we can start to see how much of a problem it is for an individual. We can then start to look at the impact of that by trying to suggest ways that we can cool people down, whether that is by immersing their hands and feet in cold water. Now we do that because the hands and feet are amazing radiators of heat. And so we can lose a lot of our excess heat by just putting our hands and feet in cold water. You'll know yourself if you've ever been hot and you've gone to wash your hands after you've been to the toilet. Actually, it's a really comfortable thing to do is to put your hands under the cold tap. So a lot of ectodermal dysplasia patients do that now. They put their hands and feet in cold water, or they spray themselves with a water bottle and stunned in the wind with wet clothing because again, they feel comfortable because they're losing heat, because that sprays acting like sweat on the skin. I'm being evacuated as a consequence. Our goal here is to try to help promote the patients to develop coping strategies that will mean that they can they can keep themselves cool and also undertake a normal life so they can work. They can be physically active. You know, they may have to alter their timetable a little bit. So exercising first thing in the morning when it's cooler, for instance, may be staying out of the sun in the summer when it's warm. And those sorts of things may, may have to be, you know, things that they do. But ultimately, it's about keeping them, keeping them cooler so that they can carry out their work, their schooling so that they can keep developing and progressing. So that's the goal for this research. But ultimately, the field in the field of research with ectodermal dysplasia is actually developing to look for gene therapies that may be able to reduce the likelihood of the genes which are code for this condition to prevent that that condition from actually occurring. So there are now a gene therapy trials going on at the moment to see if those babies that would likely be born with ectoderm dysplasia either develop fewer symptoms or no symptoms.

John Worsey: Sharing insights into environmental and physical management, alongside the hope to break new ground in gene therapy: it looks like the Extreme Environments Laboratory here at Portsmouth has more than a few avenues to make an impact that changes lives for the better. Hopefully this episode has not only debunked a few myths around cold water swimming, but has also empowered you with the knowledge to dive into your new hobby safely, and with maximum benefits! You can find more tips from Dr Heather Massey and the team by looking them up on our website And if you’ve enjoyed this episode, share it with a friend or on social media using the hashtag lifesolved. Next time, we’ll be looking at another of our national pastimes: football. How is the beautiful game changing lives and making new opportunities? And where are there still issues of corruption and inequality to be addressed? We look at economics, rights and mental health in football. See you next time.

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