in: Health, Health & Fitness, Podcast

• Last updated: May 13, 2022

Podcast #801: The Cold Water Swim Cure

Have you ever driven along the coastline, or walked by a local pond or lake and thought about taking a dip, but felt hesitant about swimming in what you know is cold water? My guest today, who argues that cold water swimming is one of the very best things you can do for your mental and physical health, will inspire you to finally take the plunge.

His name is Dr. Mark Harper and he’s an anesthesiologist and the author of Chill: The Cold Water Swim Cure. We begin our conversation with how Mark’s research into the prevention of hypothermia during surgery led him to investigate the benefits of cold water exposure in managing the body’s overall stress response. We discuss the effect cold water has on the body, and the potential mental and physical benefits this effect can have, from reducing inflammation, to reducing depression caused by inflammation, to improving conditions from diabetes to migraines. We get into how long you need to be in the water to get these benefits, and the temperature the water needs to be, which may not be as cold as you think, and potentially makes, depending on where you live, cold water swimming viable as a year-round practice. Mark also explains how to get started with cold water swimming, and do it safely and effectively, including why you should start in the summer, and how best to prepare your body before you get in the water and recover after you get out of it. We end our conversation with whether or not you can get the same benefits of cold water swimming from taking an ice bath or cold shower.

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Read the Transcript

Brett McKay: Brett McKay here and welcome to another edition of The Art of Manliness podcast. Have you ever driven along the coastline or walked by a local pond or a lake and thought about taking a dip, but felt hesitant about swimming in what you know is cold water? My guest today who argues that cold water swimming is one of the very best things you can do for your mental and physical health will inspire you to finally take the plunge. His name is Dr. Mark Harper. He’s an anesthesiologist and the author of “Chill: The Cold Water Swim Cure.” We begin our conversation with how Mark’s research into the prevention of hypothermia during surgery led him to investigate the benefits of cold water exposure in managing the body’s overall stress response.

We discuss the effect cold water has on the body, and the potential mental and physical benefits this effect can have, from reducing inflammation to reducing depression caused by inflammation, to improving conditions from diabetes to migraines. We get into how long you need to be in the water to get these benefits, the temperature the water needs to be which may not be as cold as you think, and potentially makes, depending on where you live, cold water swimming viable as a year-round practice. Mark also explains how to get started with cold water swimming, and do it safely and effectively, including why you should start out in the summer, and how to best prepare your body before you get in the water, and how to recover after you get out. We end our conversation with whether or not you can get the same benefits of cold water swimming from taking an ice bath or cold shower. After show’s over, check out our shownotes at

Mark Harper, welcome to the show.

Mark Harper: Thank you very much. Thank you for having me. It’s a great privilege to be here. Yeah, I have followed The Art of Manliness since I came across your Roadmap To Manhood in 2014, and it’s been a great inspiration for me.

Brett McKay: Oh, yeah, that’s a big blast from the past. That was a really long article that we wrote. So thanks for reading that and also, thanks for listening to the podcast all these years. I really appreciate that. I’m excited to have you on the podcast today. You are an anesthesiologist, but you’ve written a book called, “Chill: The Cold Water Swim Cure.” How did you get started with cold water swimming?

Mark Harper: Really, it was by accident. I’ve always swum in a swimming pool. Thanks to my mum who used to drag me along as a reluctant teenager, but ever since then, I’ve swum maybe three, four times a week in the swimming pool, training with a club. But one summer I moved back to Brighton in my mid-thirties and the pool closed for two weeks. So I was complaining about this to a friend that I’d known since those teenage days, and he said, “Oh, go and join the sea swimming section.” I didn’t even know the club had a sea swimming section and so I thought I’ll just go and have a quick swim around the pier, and do that for two weeks. And I went around the pier. I had a nice time, and nearly 20 years later, I’m still swimming around the pier in Brighton, and wherever I can get my cold water fix.

Brett McKay: So you started off doing this just as recreation, something to do, ’cause you enjoyed it, it’s good for your health, you enjoyed the people, but then you started making these connections that maybe there were some real health benefits to swimming outside in cold water. When did you start making those connections?

Mark Harper: Well, in a way, it was that first swim that gave me an inkling, but I was only kinda to know that later because I remember getting out of the water, having just gone for a swim, and walking up the beach thinking, “God, yeah, I feel really good.” Yeah, it’s something I just didn’t expect and that was what kept me going back for more, and that’s why I continue to do it to this day, but the other thing that got me into it was my research at the time. So my PhD is in something called the prevention of perioperative hypothermia. Basically, what this means is when you have an operation, if you get cold, it’s bad for you. And in fact, this is a really important point because hypothermia is bad for you at any time. Exposing yourself to cold, what I’m gonna talk about today, is potentially very good for you, but if you stay in the water too long and you become cold, that’s actually bad for you.

So I was researching this and the thing is when you have an operation, you have a real stress response. You may not feel it because you have an anesthesiologist like myself stopping you from feeling that pain, but it generates a stress response in the body. And if you get cold, it increases that stress response. So around this time, I started reading articles about the effect of cold water on the body. And these effects, this was a stress response as well, and this stress response was exactly the same as the stress response you get to surgery. And then more than that, I started reading about how you can adapt to cold, and if you adapt to cold, it reduces that stress response, and that reduction in stress response would potentially reduce the complications following surgery.

Brett McKay: Okay, so this is a connection to your work. You thought, okay, as an anesthesiologist, one of our jobs is to keep people warm during surgery, ’cause their body temperature goes down. So that’s why you have a warm blanket put over you. You had a hunch that maybe if we can help the body adapt to cold, it will improve surgery outcomes after general anesthesia. Is that correct?

Mark Harper: Yeah, that’s correct. And as a more general thing, not just in your response to cold, but in your response to the whole stress of surgery.

Brett McKay: Gotcha. Okay, so this is basically you thought that cold water exposure through cold water swimming could help develop the overall stress response of the body, not only the stress of being under anesthesiology, but also the stresses of just everyday life as well.

Mark Harper: Yeah. Well, that’s how things progressed, yeah. I began to think… Well, it was when I read an article a few years later. I’d done quite a lot of work on operation, preventing hypothermia during operations, and a few years later, I came across an article which. In the newspaper, this wasn’t a medical article by any means. About how inflammation had been linked to depression. Now, one of the main things, we need inflammation. It’s the body’s response to infection, to injury. It’s really important, but like everything, you can have too much of a good thing. And if you have an overactive stress response, you have an overactive inflammatory response, and it becomes bad stress or bad inflammation rather than good or physiological inflammation. And linking it to depression, and I thought, well, I know that if you adapt to cold water, your levels of inflammation go down. That’s one of the reasons it’s good for you and potentially good for patients having surgery.

And I also knew how good I felt when I came out of the water without having depression. So I began to wonder, well, maybe then we could use cold water swimming to treat depression.

Brett McKay: We’re gonna talk about that today, how it could possibly treat depression, but let’s talk about what do you think is going on about being exposed to cold water that has these… Again, as you said, being cold usually isn’t good. That’s something we think of as a stressor to the body, but you’re saying that, okay, in small doses, it can actually help you become more resilient to different types of stressors. So what is going on? When you expose yourself to cold, what’s going on in your body that allows you to overcome or be resilient to acute or chronic stress?

Mark Harper: So what goes on, as I said, you get a stress response when you get into water, but if you go in regularly… And by the way, cold water isn’t actually that cold. It’s anything less than 20 degrees centigrade has a significant physiological effect on the body. So when you get into cold water, you have this stress response. Now, if you do that regularly, and most cold… Or studies of cold water swimming, they use a regime of about six immersions at probably around 15 degrees centigrade. And if you go into this cold six times, you develop an adaptation to cold. And what this means is… So the stress response is generated by the autonomic nervous system, so that’s your sympathetic, which is your fight flight, and a parasympathetic, which is your rest and digest.

And what getting into cold water several times does is it reduces that sympathetic response to stress. So this means if you’re running a high level of stress and, consequently usually a high level of inflammation, your baseline goes down, and also those peaks of stress go down. So what you’re doing is you’re keeping that stress and that inflammation in the good physiological zone rather than the bad pathological zone. Interestingly, on top of this, if you put your face in cold water, you get stimulation of the parasympathetic nervous system. So this is the other side of the autonomic nervous system, which is good, and this actually directly reduces levels of inflammation in the body. And so you’re having a kind of double effect from swimming in cold water in reducing inflammation.

Brett McKay: So it sounds like what’s happening is when you get into cold water, you’re giving your nervous system… It’s like a workout for your nervous system in a way.

Mark Harper: Yeah, completely. You just think about if you go to the gym, you work out hard. You can work out too hard and you injure yourself. But if you work out just right, and you can work out pretty hard without injuring yourself, you become stronger. It’s exactly the same principle.

Brett McKay: And so you mentioned, you threw out some numbers there for how cold the water needs to be. It’s 15 degrees Celsius. That’s what? Like 59 degrees Fahrenheit. And I think 20 is about like 68 degrees Fahrenheit, correct?

Mark Harper: Yeah, exactly, yeah, yeah. That’s about right. So under about 68, you get a really good effect, and they reckon the maximum effect is probably somewhere between 10 and 15 degrees centigrade. So what’s that? 48, 58 degrees Fahrenheit, something like that.

Brett McKay: And what you’ve done in this book too is you’ve made this connection to cold exposure to your work as an anesthesiologist about the benefits of it, but there’s a whole history of doctors or thinkers or writers, you can even say religious people, touting the benefits of cold water exposure. How far back of the record we have that shows that getting in the cold water outdoors can have benefits?

Mark Harper: Well, I think it goes back as far as medicine goes back. Hippocrates, the father of medicine as he’s known, he wrote a treatise called, “On Airs, Waters, and Places.” And in that, he invoked the power of water. I think, for me, the most significant figure is Richard Russell, who was a doctor in my hometown of Brighton on the South Coast of England, who in the early 18th century started bringing people to the cold waters of Brighton and taking them in and using that. And he is credited with starting a craze for sea bathing, which, in fact, the Prince Regent came to stay in his house after he had died and became an… Really started to enjoy this cold water thing, and that’s why Brighton built up from this small fishing village into a kind of sea-bathing metropolis. And he, Richard Russell, wrote a treatise on treating the diseases of the glands, including the king’s evil, leprosy, scurvy, all kinds of things that I wouldn’t say it does help. And he also advocated drinking the seawater, which I also wouldn’t advocate. But for many years, this was probably one of the few effective treatments we had, but come the era of antibiotics and drugs and pharma, it kind of got forgotten.

Brett McKay: Okay, so these doctors, they knew that… They put people in cold water. They saw that it had benefits. They probably didn’t understand why, what was going on in the body. They probably had theories about humors and whatnot, but recent research has really explained what is going on in our bodies when we expose ourselves to the cold, and you highlight that, and so we talked about these different nervous systems. But I wanna talk about what, besides the response that we have in our nervous system, what else goes on in our bodies once we jump into that cold water? What’s the first thing that happens? Why is it that we have that… We wanna gasp for breath, our joints ache. Sometimes when I get into cold water, I wanna pee. What’s going on in our body?

Mark Harper: Well, I think the basis for this is the fact that all the blood vessels to the skin immediately shut down. So your circulation to your skin, which is what we call the peripheral compartment, that closes down and goes straight into… And it’s just used, it’s kept inside the body, so you have kind of more blood going round the main part of the body. This expands the heart, and expanding the heart releases a hormone called atrial natriuretic peptide, which makes you want to pee. It puts more fluid through the kidneys, but the effect of just a direct effect on the nervous system causes you to want to hyperventilate. You take a big gasp when you get into the water, you hyperventilate. It’s very much like a panic attack, which can be a bit of a problem, but the thing is it’s… And this is actually the most dangerous part of it. So if your head goes straight under, you cannot control this, but after a few times doing it, you can absolutely control it, and that really helps you.

Brett McKay: Okay. So we jump in, our blood vessels constrict. So this is also a workout for our cardiovascular system in a way.

Mark Harper: Yeah, it is. It’s absolutely a workout. In a way, it’s an exercise free workout for the whole cardiovascular system because your blood pressure goes up, your heart rate goes up, but all these responses are still there when you adapt to cold water, but they’re not as powerful.

Brett McKay: You mentioned when you got out of the water that first time you went, did the swim around the pier, you said you just felt great, kind of almost euphoric. Is there something going on with our brain chemistry that gives us that euphoric feeling?

Mark Harper: There’s certainly something going on in the brain, but as to quite what it is, I don’t think we really know and we might never know. The brain is phenomenally complex. Yeah, it does something like a billion, billion calculations every second. So, for me… And there are two ways of thinking about it. First is you get all these adrenaline and no adrenaline going around the body, and that is kind of what cocaine does to you, and yeah, if you’re wondering, guys, I’ve done this with a doctor I mentioned in the book, Chris Van Tulleken. One of the things he said to me after I had started him on the cold water swimming, was he said, “If this was a drug, they’d make it illegal.”

And the other thing is that I think it’s something in how it resets the brain. Yeah, this is… I can’t explain it, but there’s this amazing woman, Jill Bolte Taylor, who has a 25 million times seen TED Talk. And she had a stroke and she had a stroke… She’s a neuroscientist, and she had a stroke where she had a bleed into the left side of the brain, and she was aware of this. And she found while she couldn’t do everyday tasks like ring up someone and tell them, “I’m having a stroke,” she didn’t care. She just felt at one with the world. And this, her theory is that the left-hand side of our brain gives us our sense of self, our sense of fear, sense of time. Whereas the right-hand side of the brain, that is about empathy and feeling at one with the world. And this is the reset I get when I go into the water. So I can’t give you a scientific explanation, but that’s absolutely how it feels to me.

Brett McKay: Okay. You mentioned some hormones that are released. There’s that peptide hormone from our heart that causes us to wanna go pee, there’s adrenaline. Any other hormones that are released when we jump in cold water?

Mark Harper: Yeah, it’s a kind of complex reaction, but you get all the stress hormones come in, things like cortisol, and it also affects insulin. Insulin is the main sugar-regulating hormone in the body and really important for many metabolic processes. So when you initially go in, it kind of has a bad effect on insulin, but again, when you’ve adapted to cold water, that effect on insulin becomes better. And actually your body becomes more sensitive to the effects of insulin, which is a really good thing. And this is why it may be possible to help treat type two diabetes, for example.

Brett McKay: Okay, so when you jump into cold water, a lot’s going on physiologically. Blood vessels constrict to keep the heat in our body inside that’s gonna help your cardiovascular system. There’s this nervous response that can help us respond better to stress. There’s hormones that are released. Is there anything that happens… What is it about cold water that can help reduce inflammation? Is there something going on there? Is it just quieting down the inflammatory response?

Mark Harper: Yeah, so it’s kind of a two-pronged attack. The first is the… Yeah. Actually, getting into the cold water will lead to some kind of inflammation, but it will keep it in the good zone. So if you do it regularly, it will keep that baseline of inflammation down, so you have sort of a long-term effect. And you also have an immediate effect, and that immediate effect is what you get, it’s the diving reflex that when you put your face in the water, it directly stimulates the vagal nerve and that directly reduces inflammation. So the long-term effect lasts a while. So yeah, you go in six times, yeah, you have 60% of your response left 14 months later. But you can always boost it by going in, and getting your face in the water, and that gives you an immediate effect.

Brett McKay: Alright. So you want the water to be about 68 degrees Fahrenheit to maybe 50 degrees Fahrenheit to get the benefits. There’s some famous doctor or philosopher who said that the dose makes the poison. How cold is too cold and how long is too long in the water when it starts causing problems?

Mark Harper: Well, in my experience, there is… If you’re properly prepared, I think there’s no too cold. What it is is too long. And as you said, the dose is the thing that… The dose is in the timing really. And I’ve been in water, actually, I measured it at minus 0.2 in the sea just as I was getting in once. And it’s fine because I go in warm, I go in prepared. So the thing is not to become hypothermic. So if it’s really cold, you’re just in for a minute, two minutes, something like that. If it’s warmer, you can stay in for a long time.

Brett McKay: Well, how do you know if you’re becoming hypothermic? What are the tell-tale signs?

Mark Harper: Well, for me, I think that the best sign is what’s called clawing of the hands, and this means when you… Yeah, to do a stroke, you bring your fingers together to do a swimming stroke. After a while, when you begin to get cold, you can’t really bring your fingers together anymore, and it becomes difficult. And that’s quite a good sign that you’re getting too cold, but it’s an early sign, so that gives you time to get back to shore and get back in and start getting warm.

Brett McKay: Any other things? I guess, one, you mentioned is you start… You can’t think straight. Like you have a hard time talking and keeping your thoughts together.

Mark Harper: Yeah, that’s when you’re kinda going a bit too far. And I think that the thing is the fumbles, the mumbles, the tumbles. Basically your hands, your coordination goes, your mental coordination goes, and at that point, yeah, someone needs to look after you.

Brett McKay: Alright. So as soon as you experience those hypothermic symptoms, that’s the time to get out of the water. We’re gonna take a quick break for a word from our sponsors. And now back to the show. So you’ve done a study surveying cold water swimmers in the UK about the benefits they’ve gotten from their polar plunges, and this is, you’re basically asking people, “Tell us about your experience.” And you’ve got all sorts of great responses. In one area where you saw there was a lot of benefit was helping people with mental health issues like anxiety and depression. Tell us about that story. Like how has cold water swimming helped people with their mental health issues and what do you think is going on there?

Mark Harper: Well, that came about… Yeah, well, I read this article talking about the connection between inflammation and depression. And yeah, maybe if we reduced inflammation, therefore we could treat depression. And so I took this theory to a guy called Mike Tipton. He’s a professor of extreme physiology in Portsmouth and he was the guy who’d been writing all these papers I’ve been reading on the effects of cold water on the body’s physiology. And he said, “Oh, that’s a really interesting idea.” There was no particular way forward at the time, but then a few weeks later, he was contacted by Chris Van Tulleken, TV doctor, who said, “Look, I’m doing this program called, “The Doctor Who Gave Up Drugs”. Is there anything we can use cold water swimming for?” And he said, “Well, coincidentally, I’ve just met someone who thinks they can use it for this.” So basically, the BBC found us this wonderful, young woman, Sarah, 24 at the time, who was depressed and had been on anti-depressants for eight years, and just wanted to come off them because she didn’t want her baby daughter growing up seeing her mom take tablets. So we took her down to Mike’s lab, we put her through a cold water adaptation program. It was four dips in about 15 degree centigrade in this special tank. And then the next day, we went out for a swim in the lake.

She kept up with it afterwards, and within a few months, she’d stopped taking her medication, and when I spoke to her just a few months ago, and this is, we’re talking about five years later, she’s still free from medication. Still doesn’t need the medication, still swimming occasionally, and it really helps. So next, we had to do this in real life. So what we did was I met this guy, Mike, who is with the coast guard and you know, a general outdoors person down in Devon, in the Southwest corner of England, and he said, “I’d really like to run these courses for you and we can do some research.” So we gathered together, in the end, about 60 people, all with clinical depression and anxiety, and put them through a basic course. It’s eight sessions, eight 30, 45 minute sessions, and that includes warming up, having a cup of tea, things like that. And eight sessions in the water in summer. Started summer, went into winter. So it was temperatures probably between 58 and 48 degrees Fahrenheit say. And saw what happened and the results were utterly remarkable. Yeah, we were getting cure rates, you know, and this is total recovery rates of about 70% for anxiety and the same for depression. If it was a pill, no one will believe that kind of results.

Brett McKay: No, this inflammation-depression connection is really interesting. We’ve had Charles Raison, I think is his name on the podcast.

Mark Harper: Yeah.

Brett McKay: He wrote a book about…

Mark Harper: I’ve heard that one. It was really useful. That really helped me with my research, if you see what I mean.

Brett McKay: Yeah. And I think his takeaways there, so when you have chronic inflammation, it basically disrupts how the brain responds and you start acting like a depressive. And so his idea is that if you can reduce inflammation, you can reduce depressive symptoms. And he found that’s the case, but his way was interesting. He used heat, so he used sauna treatments to reduce inflammation. What you’re doing is using cold, which is another way to reduce inflammation.

Mark Harper: Yeah, and it’s really interesting because, well, I heard that podcast and then I went to a conference, which was on thermoregulation. So it was, you know, both hot and cold. And a lot of the work from people using saunas and using heat stress, so rather than cold stress, does seem to have very similar effects. I think the advantage of the cold is certainly that it’s… Certainly for us in the UK and probably parts of the US, it’s just more easily accessible. You don’t need special equipment for it. You just need some cold water.

Brett McKay: And one thing you point out in the book and then Charles pointed out in his work as well is that the inflammation-depression connection, it’s only in some people. Like some people have depression that is caused by inflammation. It’s like half and half basically. So I think the takeaway that he had, and I think the take away you have too in your book, is if you have depression or anxiety and you tried treating it with medications or talk therapy and that hasn’t really done much for you, you might have depression caused by inflammation, so maybe you just focus on reducing inflammation.

Mark Harper: Yeah, I think that’s a really valid point. I think the thing about… A thing to remember about cold water swimming is that it’s not just… The effect of the cold on the inflammation is one part of it, but there’s so much more to it. You know, if you’re going outside, being outside in nature, we know that’s good for you. We know views of water are good for you. We know being with other people… One of the important things is to do this with other people. And certainly, yeah, when we’ve been running studies, one of the things people valued most is that having that group dynamic. So there’s more to it. And of course, you’re getting exercise. So there is more to it than just the cold and the effect of the cold on the inflammation.

Brett McKay: But continuing on this thread of it’s the cold effect on inflammation, you also found that people who had inflammatory problems, like chronic pain, arthritis, Crohn’s disease, these are all problems that are often associated with inflammation, they saw a reduction in symptoms as well. Can you highlight some of those things that you found?

Mark Harper: Yeah, yeah. You’ve summed it up really. So a theory was that, you know, if it has an effect on inflammation, depression is inflammation, so we’ve been through that, but maybe it’ll work on other illnesses. And so we sent out a survey to see were people using it, were people using it against these kinda conditions, and the responses came back mapping exactly what we had thought. That type two diabetes is lifestyle illnesses… It’s the modern lifestyle illnesses is what we’re looking at here, and it was type two diabetes. And there’s a guy I’ve been swimming with for years in the sea, Rob, who had bad Crohn’s disease, and he’d kinda find out by accident. Yeah, he’d started doing a thing for charity and you had to swim in the sea, and he noticed that his Crohn’s disease had become better. And then also on the course, we had one guy with chronic pain who came along because he was getting really depressed and he just came for the depression part of it, but noticed his pain was getting better. And another guy had fibromyalgia, and similarly, he came across it. He was more anxious, but he found that his fibromyalgia symptoms got a whole lot better as a consequence.

Brett McKay: Well, and so the theories, they’re okay. There could be an inflammatory reduction going on with some of the stuff, but also the other theory… Again, this is very speculative. This is kind of we’re on the cutting edge of research, but another theory that’s out there is that idea that cold exposure can somehow reset our nervous system. I think a lot of times with one of the theories of fibromyalgia or chronic pain is that the brain’s pain wiring has gone haywire, so you’re feeling pain even though there isn’t anything wrong with you, but you just think it’s there, and the idea is that somehow the cold helps reset that.

Mark Harper: Yeah, and I think that’s it. As you say, this is very speculative, but what you get with these conditions are these abnormal circuits and these circuits, and they reinforce. The brain tends to reinforce the circuits and what the cold does in some way is it reset these circuits. Maybe it just overwhelms the whole thing, overwhelms the whole system, and it brings you right into the present moment. Those loops just are broken up and you can start to produce new and less unhealthy circuits.

Brett McKay: Well, and another area where you saw benefits of cold water swimming was reduction in migraines. What do you think is going on there?

Mark Harper: Again, it’s a really complicated thing. Migraine is a terrible affliction. And we came across a girl, Beth, who is… She was young, in her 20s, doing her PhD, but had to give up her PhD ’cause she was having 28 migraines a month. Yeah, I think that’s virtually every day. And the WHO suggests that a day with a migraine is like a day being paraplegic and if… And she wanted to do something in nature, and again, found by coincidence that it helped the symptoms of her migraines. And I think, again, we’re being speculative, but I think again, it’s these things that resets the mind, it resets those electronic circuits, and it just takes you out of things and reduces inflammation. So it’s a complex thing. And a lot of this, you could argue that we should be doing research starting from the bottom up saying, “Why does cold water swimming work?” But for me, I think I prefer to start at the top and say, “Well, does it work? Let’s see who it works for, and then we’ll get their stories and we can start beginning to work out why it works afterwards.”

Brett McKay: Okay, so it looks like there are benefits to cold water swimming. So if someone’s listening to this and they think, “Well, I wanna get started with this. I wanna give this a try,” how do you find a place to swim in the first place? Are there… You found there… Are there only certain times of the year that you can get the benefits of cold water swimming? Is it like just winter time?

Mark Harper: No, well, it depends where you live. If you live in Tahiti, you probably don’t get much cold water at all, but for most of us in temperate climates, really you can get the benefit all year round. And in fact, what I recommend doing is you start in the summer. Start when it’s at its warmest. That’s what I did and then you carry on for as long as you feel good about it and you feel safe. So yeah, it’s finding a place. There are lots of… There are more and more wild swim maps and things like this, but essentially, the golden rule is find a place, find some cold water, whether it’s a lake, a stream, a bit of the ocean, but before you go in, make sure you know how you get out because there’s this book, the official rules, which were popular in the ’80s. And one of my favorites from that is Agnes Allen’s rule, which is almost anything is easier to get into than out of and that applies to all of life, in my opinion, and it’s particularly true for cold water swimming.

And then the other thing is take a friend along. Always do it with someone else because they can… Having someone else out there, even if they’re not swimming with you, that increases the safety and it will help you get out of any trouble.

Brett McKay: I’m sure they can probably tell if you’re becoming hypothermic as well.

Mark Harper: Yeah, absolutely, yeah. And that’s a really important part of it is that they can recognize that kind of thing.

Brett McKay: Okay. So look for oceans. It can be done all year. I think in the United States, there’s lots of little swim holes where the water stays really cold. If you live in mountain areas, the rivers are freezing, ’cause it’s just the water’s coming from snow melt. So this can be an all year thing if you want. Let’s talk about you wanna do it in a group for safety, but you also think there’s a benefit just from being around people. That’s one of the benefits you think. What’s going on, it’s sort of social medicine.

Mark Harper: Yeah, totally. One of the biggest issues with the pandemic, for example, has been the way the increase in social isolation and going and doing this with a group. For a start you’re meeting with a group, you’re reducing social isolation, but also it’s just so much fun. [chuckle] When you go do it with a group, you have a laugh and that shared euphoria was really one of the things that came out of our studies. When people get to comment on how it benefited them, it was that shared laughter, and then going and having a cup of hot chocolate or hot tea or hot coffee up together afterwards. So I think there’s a lot more to it, that community rather than just the safety aspect.

Brett McKay: So you found your place. Do you just jump in or do you recommend doing a warm-up before you get in the water?

Mark Harper: I think it’s really important to be warm before you get in. So essentially, our body is very good at protecting our core organs, our core and so the outside bit of it, the skin, the muscles, the fat layer which is also known as biopreen in a cold swimming community, that is there is kind of a heat sink and it’s like a storage heater. And so if you think… If you go into water when you’re cold, you’ve got nothing in your storage heater, so your cold core will cool down and your vital organs, which you really need to preserve, will cool down really quickly. But if you go into the water warm and you’ve got that storage heater totally full, you will be able to stave off that hypothermia a whole lot longer.

And the other thing, I think, about going into water, so one, go in warm. The other thing that is important is certainly before you are used to it is that you go in, you just put your body in first because you don’t want the signals, the conflicting signals from the body, which is that sympathetic fight-flight response, going along with the signals from your face, which is the parasympathetic drive. And also, when you’re not used to it, you’ll get that gasp, you’ll get that hyperventilation, which you cannot control. And so the biggest danger for new swimmers or people who are just pulled out of the water in these crazy things is that the head goes under and they breathe in a whole lung falls of water.

Brett McKay: Okay, so don’t jump right in the first time. So the warm-up is that just… You’re recommending people exercise. You wanna raise your internal temperature. You’re trying to treat your body like a water bottle, basically. Get the inside to warm up.

Mark Harper: Yeah, and the most effective way of doing it is actually to warm yourself from the inside out, so by exercise is a great way of doing it. If you’re just sort of warm on the surface and cold in the next bit and then warm in the middle, you know, that’s actually worse than being cold. But if you do something like, for example, as they have in the Nordic countries for many years, if you go into a sauna and you warm yourself completely through, that’s fine, that’s good. And yeah, the Finns particularly have been showing us that for many years.

Brett McKay: All right. So you warm yourself up, you get in the first time. You’re gonna get in slowly, just your body, get your body acclimated before you stick your face into the water, ’cause you don’t want those two nervous systems criss crossing each other and you inhaling a bunch of water. How long should a swim be? You said earlier it just depends on how cold it is, correct?

Mark Harper: A swim, it’s difficult to judge. A swim should be… It depends on the temperature. So to get the benefits, I think, the most important thing is to know. To get the benefits, you do not have to be in very long. You need to be in as long as it takes for you to get your breath back. You know, you have that initial gasp and hyperventilation and you feel, “Oh my god, this is awful.” And then after a minute or so, that passes and that is long enough. So in the middle of winter, what I suggest is maybe three minutes, put your face in three times. That’s it. And yeah, when it’s super cold, you may not even need three minutes. Beyond that, it’s how good you feel and the things we discussed about clawing of the hands, feeling cold, get out. There’s no virtue beyond a bit of extra exercise from staying in for a long time.

Brett McKay: Gotcha. What about warming up? Are there any protocols you recommend for warming yourself up after you’re cold water swim?

Mark Harper: Well, again, warming up afterwards best done from the inside out, so do some exercise, go for a run, get on your bike. After my swim, I get on my bike and go to a cafe and have coffee.

Brett McKay: Okay, so you warm yourself up. Is going into a sauna directly after a cold water swim okay, ’cause I’ve heard different things?

Mark Harper: Right. A sauna, I think, is a good thing. Again, you know, we’ve got so much evidence that it’s perfectly safe because so many people have been doing it in Finland and Sweden and Norway for so many years. The thing is hot air… Air just doesn’t hold that much heat. It feels warm, but it doesn’t hold that much heat. So it’s a very safe way of warming people. And this is why we use it in the operating theater, because it’s so safe and that… I think you’ve gotta be more careful about a hot shower. If you start with a lukewarm shower. This is how I tend to do. I haven’t got the luxury of a sauna most of the time. But if you start lukewarm with a shower, that’s fine. But if you start with a hot shower, you can damage your skin and things like this because the body isn’t moving the blood away from the skin and you can damage it.

Brett McKay: You could scald to yourself, basically.

Mark Harper: Yeah, exactly.

Brett McKay: Yeah. Well, here’s a question I forgot to ask. Are there people who should maybe be careful with the cold water swims because of heart issues? I’ve heard that you jump in, you have that reaction, and it could cause a heart attack. Is there anything to that idea?

Mark Harper: So yes, of course, there’s some people whose hearts are so bad that you just don’t want to get them into cold water, but really, if you can walk down to the beach or get yourself into the swimming place and get yourself out again, you are probably fit enough to go into the water. You do… Yeah, be careful if you have a heart condition, but it’s a bit of a myth that it’s the heart attack that kills people. It’s these hyperventilation. It’s getting the face under the water and not being able to hold your breath under the water. That’s what kills most people rather than the stress on the heart. That stress on the heart is probably no greater than walking up two, three flights of stairs.

Brett McKay: Okay. So what if you don’t have access to outdoor cold water? Can you get these same benefits by taking cold showers or ice baths?

Mark Harper: You can get the benefits, but not the same benefits. There was one study of cold showers which showed that people who took a cold shower in the morning had less sick days. The thing is the effect from the cold comes from two main sources, is it… Well, there’re two main determinants of it, and that is the actual temperature of the water and the rate it’s cooling. And in a shower, it’s probably not gonna be as cold. It might be… Yeah, it’s gonna be room temperature or whatever, and you’re not immediately immersing yourself in cold water, so you don’t become cold quite so quickly. An ice bath? Well, yes, that will give you those benefits, but for me, it’s just not as much fun unless you have a really big ice bath with lots of people jumping in and out. It’s not as much fun as being with lots of people jumping in and out of the sea, but yes, you would see benefits.

Brett McKay: I think another point too, besides the social benefit of swimming outdoors, there’s something about being outside that amplifies these benefits as well. There’s been lots of studies done about the benefits of being outside in nature for depression and other sicknesses.

Mark Harper: Yeah, without a doubt. Yeah, I like to think of cold water swimming or outdoor swimming as a total package. It’s not just about the cold. I think the cold brings you some unique benefits, but it’s the community, it’s being out in nature. We do know that’s good. Just the view of water brings mental health benefits plus the exercise and everything else that you get from it. So it’s really not just about the cold.

Brett McKay: Okay. But yeah, if you can’t have access to cold water for… You live in Tahiti, for example, an ice bath, you can get benefits for the cold.

Mark Harper: Yeah, you would get the benefits of the cold, and then maybe if you did it in Tahiti, you could be looking out over the ocean in your ice bath and you get in and get out, and you’re warm the whole time. So, fantastic.

Brett McKay: [chuckle] You’re living the dream. You’ve won life if you’re doing that. Well, Mark…

Mark Harper: Yeah, I think so.

Brett McKay: Mark, this has been a great conversation. Where can people go to learn more about the book and your work?

Mark Harper: Well, with the book, go to your favorite local bookshop and order it. That’s the thing with that. I send out occasional tweets from the worldswimdoctor about swimming, but I think what I’d like people most to do is look at some of the work that’s being done by organizations to get people out and help people find the benefits of cold water swimming. And so this is or and are three organizations I work with who do amazing stuff. You know, really bringing access to this fantastic therapy.

Brett McKay: Well, Dr. Mark Harper, thanks for your time. It’s been a pleasure.

Mark Harper: Absolute pleasure for me, too. Thanks for having me.

Brett McKay: My guest here is Dr. Mark Harper. He’s the author of the book “Chill: The Cold Water Swim Cure.” It’s available on Make sure to check out our short notes at where you can find links to resources where we delve deeper into this topic. Well, that wraps up another edition of The AOM podcast. Make sure to check out our website at where you find our podcast archives as well as thousands of articles that we’ve written over years about pretty much anything you could think of. And if you’d like to enjoy ad-free episodes of the AOM Podcast, you can do so on Stitcher Premium. Head over to, sign up, use code MANLINESS to check out for a free month trial. Once you’re signed up, download the Stitcher app on Android or iOS so you can start enjoying ad-free episodes of the AOM podcast. And if you haven’t done so already, I’d appreciate if you take one minute to give us a review on Apple Podcasts or Spotify. Helps out a lot. If you’ve done that already, thank you. Please consider sharing the show with a friend or a family member who you think would get something out of it. As always, thank you for your continued support. Until next time, it’s Brett McKay. Remember, it’s not only listening to a podcast, but put what you’ve heard into action.

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