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The Dose Transcript for June 7, 2023

Host: Dr. Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. When I was a kid, I remember seeing footage of people taking a New Year's Day plunge into icy waters. Well, these days they post videos on Tik Tok or YouTube touting the benefits of cold water immersion. And while there may be benefits, there are also some dangers. So this week, we're getting past the hype to ask what do we actually know about the health benefits and the risks of cold water immersion? Hi, Steven. Welcome to The Dose.

STEPHEN CHEUNG: Hi there, Brian.

BRIAN GOLDMAN: Have you ever tried cold water immersion?

STEPHEN CHEUNG: I always say that this is my job and I don't need to add it to my pleasure list. So no, I let my wife do the new year dip and everything, and I stayed. Try to stay dry and. And warm and comfortable instead.

BRIAN GOLDMAN: Your wife does the New Year's Day?

STEPHEN CHEUNG: Yeah. She and a German exchange student we had once when we were living in Halifax and did our big Heron Cove polar bear jump. And I was just sitting there cheering them on and. And wrapped up in a parka.

BRIAN GOLDMAN: Wow. Okay. Is there any reason why you didn't want to join in?

STEPHEN CHEUNG: I don't mind being out in the cold. I love outdoor activities in the cold as long as I'm dressed appropriately. But I've also been silly enough in my lab to do a 24 hour shivering study where we had people continuously shivering for 24 hours. And that definitely cured me of any desire to ever be really cold, more than I need to ever again.

BRIAN GOLDMAN: But you study it, and we are certainly grateful for that. But before I start asking you some questions about this, can you give us a Hi, my name is tell us what you do and where you do it. Just ad lib.

STEPHEN CHEUNG: Sure. I'm Dr. Stephen Cheug and I'm a professor and senior research fellow in the Department of Kinesiology at Brock University in St Catharines, Ontario. And I directed the Environmental Ergonomics Lab, where we study extreme environments and how it impacts human physiology and performance. So both extreme cold that we'll talk about today and also heat and a bit of altitude.

BRIAN GOLDMAN: Here we go. First off, let's define what exactly we're talking about here. Cold showers swimming in cold water, all of the above. What are we talking about?

STEPHEN CHEUNG: Yeah, pretty much all of the above. There is definitely the easiest way to get into cold plunges or code therapy is simply take a cold shower. And so that's the easiest do it yourself method. And then there's also obviously swimming in a cold lake or a cold body of water. And then there's also sitting in a cold tub. And probably the most extreme and kind of definitely not a do it yourself method is there are some specific cryotherapy chambers where you're in dry air, but it's down at -110 degrees Celsius and you're there for about 3 minutes. So it can go from the very, very easy do it yourself at home to very complex specialized equipment.

BRIAN GOLDMAN: And one of the themes of our discussion, Steven, if I've got this right, is that there aren't a lot of hard and fast rules about how long what the temperature is. There's a few guidelines and I want to unpack some of those. So let's start with how long are most people staying in the water?

STEPHEN CHEUNG: Sure. I would say for most people it's probably around the three day, maybe at most five minute range of, again, whether you're in a cold bath or a cold shower or if you're taking a cold dip, it's usually not much more than that because then it actually does get seriously uncomfortable. Then you can start shivering quite a bit and most people find that uncomfortable. So they'll go in for about 3 minutes or so and then get out and get warm again.

[00:04:00] BRIAN GOLDMAN: I've read from a number of sources that the temperature in the water is 10 to 15 degrees Celsius. Have I got it right?

[00:04:09] STEPHEN CHEUNG: Yeah, in the shower. I guess it depends on how cold your your water is coming out of the shower. So yeah, probably about 10 to 15 degrees. Anything above 15 degrees. I wouldn't really call being kind of really cold therapy or cold plunges. Probably the lower the better. And certainly we'll be talking about its use for athletes. Athletes are getting into near ice water, so it'll probably be closer to five degrees, four degrees or so for them. But basically about as cold as you can make your shower. So I would say, yeah, probably about ten degrees Celsius, maybe a little bit lower.

BRIAN GOLDMAN: Okay. What's happening inside our bodies when we immerse ourselves in cold water?

STEPHEN CHEUNG: The main thing that's happening is that our skin temperature is going to drop very rapidly. So arresting skin temperature, if we're just out on a nice room environment or in a in a summer day, is probably about 30 degrees. So if we go jump into cold water, let's say it's four degrees, then our skin temperature is going to within about 5 minutes or last drop down to. Not necessarily to four or five degrees, but maybe to about ten degrees, eight degrees Celsius. So it's that sudden drop in skin temperature that sets off a chain reaction of responses in your body. And the main thing that happens is that drop in skin temperature sets off the sympathetic nervous system, which we often know as our fight or flight response. So it gets us ready for action. And one of the things that it does is that it gets our heart rate pumping really high. It gets us hyperventilating or breathing more rapidly and shallowly so that we can get more oxygen into our lungs. And also the blood vessels in our skin becomes very rapidly constricted as a result of the cold and also the sympathetic drive. And that gets more blood back to the heart so that it can pump it out to the muscles. So that's what we really feel when we go take a cold bath or a cold shower. We feel that hyperventilation. We're breathing really rapidly and it can be hard to control or breathing. Our heart rate goes up and also our body is flooded with adrenaline. So that's the arousal. That's kind of the high that we get after coming out of the cold shower.

BRIAN GOLDMAN: And why? In what way is that supposed to be good for us.

STEPHEN CHEUNG: In terms of why people think that is a good thing from the cold therapy angle? It's that it gets us aroused. You know, it gets us really alert. You know, and you definitely are not going to fall asleep, you know, after coming out of a cold shower kind of right away. And so that's one of the main kind of benefits. There is also a number of other ideas about why kind of cold therapy may be beneficial. And a lot of it comes from not necessarily your typical healthy, everyday individual doing it, but it comes from athletes using it as a form of recovery or in some clinical conditions. So, for example, we know that individuals with multiple sclerosis, they can't handle the heat. And it's in studies that I've done. For example, we've cooled down multiple sclerosis individuals before. They had to do a number of series of kind of typical everyday tasks of walking, of getting up and moving around. And we find that when they are cooled down, they can actually perform these activities daily, living a lot better in similar ways. We also know that when you are cooled down, you have less inflammatory stress and that's certainly one of the big kind of catch phrases for proponents of of ice therapy or cold therapy is that it's going to reduce inflammation. And that's a good thing for health overall. And we do know that occurs. And that's certainly, again, the reason why athletes use it after exercise when there is a lot of muscle damage and lots of inflammatory stress. And one of the ideas with sitting in an ice bath afterwards is that it's going to reduce it. And again, there's also been work done on people who have depression, who have kind of some cognitive issues. And it does seem that having this cold therapy does improve a little bit of their cognitive functioning, their mental capacity, their working memory, for example, and things like that, and also reduces some of the symptoms of depression. So again, those have all been done on either athletes or on kind of clinical conditions. And proponents of cold therapy are really saying, well, maybe if it works for those specific clinical conditions, maybe it's also a good thing from preventative standpoint for everyday individuals.

BRIAN GOLDMAN: We've been talking in general about cold water immersion and some of the potential benefits. You started by talking about the immediate effects of of going into the cold, of being immersed in the cold or taking a cold shower as a one off kind of effect on the body. It increases arousal by increasing the flight or flight response. Is there a training effect? If somebody does this regularly, will they notice more longstanding improvements or changes?

STEPHEN CHEUNG: There's a couple of responses to that one. The big thing that's going to happen is that your brain is going to become sensitized or desensitized to the cold shock. So your skin, for example, is still getting just as cold. The temperature sensors, the cold receptors in your skin are still firing at the same rate. But essentially, the brain is tuning it down and saying, okay, I'm used to this. I know what this feels like. And so after a number of days, your physiologically, your response may be the same, but it won't feel as uncomfortable. So that kind of goes back to what we were saying about, you know, whether you want to gradually ease into it or whether you just want to, you know, to use the pine, go cold turkey and just go and really have the shower as cold as possible. So that's one thing that happens physiologically. The other question is whether we actually adapt the cold long term. And there have been some studies looking at kind of long term cold exposure and whether that changes your physiology. We know there can be a little bit of an increase in your metabolism overall if you are long term exposed. The cold and by the way, that's another kind of often cited kind of benefit. The cold therapy is like, oh yeah, it'll increase your metabolism. Well, in this case, were you really only in the cold for about 3 to 5 minutes? I really don't think that's going to be the case. You may marginally increase your your metabolism, but it's really only going to be for about that 3 to 5 minutes. So it's not as if you have done a lot of exercise, a lot of weight training where the muscle is still. Going to have a really high metabolism throughout the day. So it's not really the same thing. So again, that increase in metabolism is also often cited as a benefit from cold therapy, but I don't think it is really enough to really have any significant factors. So it's if you are using it as a cure for obesity, it really isn't going to happen.

BRIAN GOLDMAN: And you've started to talk about about some of the science. There have been studies of patients with MS, studies of athletes. Are there any other groups that have been studied where we can say there's there's science behind this?

STEPHEN CHEUNG: Yeah, I would say the main group is athletes. And again, why do athletes use it? They use for probably two main reasons. One is for that inflammatory damage that they have after hard exercise. So, you know, think about rugby players who've just been running and getting hit and tackled and it's really popular for them to be using cold baths afterwards. And again, it's to reduce the inflammatory response and the damage that comes from it and also it reduces your muscle soreness. So the main thing that we see with cold therapy in those individuals is that the next day they seem to recover more and that their muscles don't seem to be as sore. And part of it is because there is less inflammatory stress on the body. The challenge with using ice therapy or cold therapy long term is that again, I use the example of a rugby player. They've just been tackled, they've been hit in training and they need to recover so that they can perform in another match, maybe in two or three days time or in a case of rugby sevens within within hours. And that's quite different from taking it to a case of let's say I know you're a runner, Brian, and you you do an ice bath after every run. Well, is that going to be the same benefit? And it may actually be a negative thing for you in terms of using it as a regular training tool because a lot of research is starting to show that. The reason we adapt to exercise, the reason we get stronger is because of that inflammatory damage and that our body responds to that inflammation. And that is the main stimulus that we're getting from the training belt. Right. So so athletes also need to be careful about when they use to use cold therapy. I wouldn't use it after just everyday training because we want that long term inflammatory, low grade inflammatory stress to adapt. But I would certainly use it after, you know, again, if you're a rugby player and you need to perform again the next day or again within hours in those tournament type of situations, they're very effective because in those case, you're not worried about long term training benefits, you're worried about being able to go back out in the field again in a couple of hours.

BRIAN GOLDMAN: Or, you know, if that runner, you know, if I haven't done a marathon or a half marathon for a few years now. But if I did, then I cold baths might be something that I would entertain doing after that, after a marathon or half marathon just to get me back on my feet a little faster.

STEPHEN CHEUNG: Yeah, absolutely. Because in the case of those, it's not, you know, you're not doing a marathon for training. It is your peak event. And you know, you really are doing so much damage to yourself that you want to be able to accelerate recovery as much as possible. And that's the other reason why athletes will use cold therapy is especially if it's a long race or if it's a hot day, it's to get their body temperature cooled again. We also know that if your body is hot, there's a whole bunch of systemic kind of responses in your body. And, you know, you don't want your body temperature to be really, really high for a really long time. So you want to use an ice bath really to drop your body temperature quite quickly. And that's the other reason for using cold therapy for athletes is, again, for the inflammatory response to reduce that and also for cooling your body down.

BRIAN GOLDMAN: You mentioned depression, mental health. I think a lot of people listening to us might be surprised about that. You know, suppose somebody came to you at a cocktail party and said, you know, I've tried a whole bunch of anti-depressants. None of them seem to work. I hear that that cold water immersion might be helpful for my mood. What would you say to them?

STEPHEN CHEUNG: I would say it's a relatively kind of harmless method of kind of trying to treat your your symptoms. And yeah, it's not going to have as many side effects as most pharmaceuticals have. And again, why do we kind of think that it helps with mental health or with depression is because of that flood of adrenaline through our body. It gets us really aroused, gets us really alert. And so that is going to kind of counteract any kind of negative aspects of mental health or depression. So, again, it may not necessarily cure depression, but it can certainly reduce the symptoms. So I would see it as a relatively kind of harmless intervention and experiment with it and see if it does help you. And I would certainly advocate, you know, cold therapy. I would advocate exercise both as great kind of ways to improve your mental health potentially.

BRIAN GOLDMAN: So for people listening to our conversation now, how would you recommend that they get started if they're interested?

STEPHEN CHEUNG: Well, first off, I don't think you need to spend thousands of dollars. I know I've also seen on social media that there are these specialized cooling tubs that you can buy. And of course, they cost hundreds, if not thousands of dollars. When you don't need that, you can just do it with a cold shower. I would say that is the simplest, cheapest way. We all have access to showers, so that would be the easiest way. And then again, you can either ease into it by gradually lowering the temperature of the shower each time you go in. Or you can just again go in and turn the cold all the way right away and see what works better for you. And then the other thing we should probably talk about is who should not be trying it. And there are two kind of situations where I would absolutely not be recommending you even to try it. And the first group, there are people with heart conditions or with hypertension or with known cardiovascular diseases. And that goes because one of the things we talked about is that the first thing that happens is that your heart rate goes up very, very high and also your blood pressure goes up very high. So if you already are predisposed to heart issues or cardiovascular issues, that's the last thing that we need, especially if you are relatively sedentary and you're not used to your heart rate going up really high, you know, in a normal everyday life. And the second group I would not recommend is that you go to your cottage and just go by yourself and jump off into the lake without anyone knowing. I would always use a buddy system because you never know how you're going to respond. And so you always want to have someone there with you in case of any issues. So those are the two big counter indications of people or situations where I would absolutely not advocate for trying cold therapy.

BRIAN GOLDMAN: And the conditions that I'm about to talk about are rare, but they're also worth keeping in mind. If you've got Reynolds disease where your extremities turn purple on exposure to the cold, or if you have one of those rare conditions where you develop hives or urticaria in response to too cold, you should not be engaging in cold immersion therapy.

STEPHEN CHEUNG: Yeah, absolutely. If you are sensitive to cold or have these reactions to cold, then absolutely should avoid it.

BRIAN GOLDMAN: And I think what you're also saying is, you know, if you're older or if you're in doubt, if you're on medications for cardiovascular diseases, you should definitely talk to your doctor first or your other. Your health care provider could be a nurse practitioner.

STEPHEN CHEUNG: Yeah, absolutely. Treat it as if you're starting an exercise program. And just like we always advocate getting a good physical, getting good check up before starting an exercise for the first time if you're not an exerciser. The same thing applies with this because it's going to be a big stress to your cardiovascular system. You really want to make sure that you're able to handle it.

BRIAN GOLDMAN: Last question I wanted to ask you. You briefly mentioned shivering and shivering is an unpleasant thing. You know, it's an involuntary reaction to the cold. But is that is that something that we can control? Is that something that we can avoid? Is it an end point where if you're shivering a lot, then you're probably doing this too much?

STEPHEN CHEUNG: Yeah, I think that's such a really important point to raise with the with the three minute kind of cold shower or cold baths or jumping in the lake, you're going to start shivering. And that's because shivering is really strongly driven by skin temperature, which explains why when we go into the freezer aisle of a supermarket on a summer day, we already, you know, start kind of having goosebumps and starting to shiver just slightly. And that's not because our core temperature has dropped, just because our skin temperature has dropped. And that's also one of the side effects of our skin temperature dropping is that we start having an increase in shivering. However, if you're not really going to get hypothermic from 3 minutes of exposure in the cold is just simply really not possible because your body is has too much heat to be lost that quickly. No, the real danger comes from the fact that you may not be able to control your muscles as well because your skin is cold and your muscles are starting to cool in those first minutes. And that's really where the danger is.

BRIAN GOLDMAN: Well, Dr. Stephen Cheug, you are a fountain of of knowledge on cold water immersion. Even if you don't do it yourself, I might just take a cold shower, though. Based on what you've had to say, A brief one.

STEPHEN CHEUNG: Well, and some of these are really hot days. After coming back home from a bike ride, I got to say, that's when I break my rule. That's. That's when a cold shower is really, really it feels amazing.

BRIAN GOLDMAN: Okay. Well, an endorsement. Thank you much for speaking with us on The Dose.

STEPHEN CHEUNG: You're very welcome, Brian.

BRIAN GOLDMAN: Dr. Steven Cheng is a professor in the Department of Kinesiology at Brock University in St Catherine's, Ontario, where he directs the Environmental Ergonomics Lab. Here's your dose of smart advice. Cold water immersion involves immersing yourself in cold water up to your neck. A lot of people use social media to tout the benefits, but the popularity has outstripped actual scientific evidence. A number of studies have shown that immersion in cold water reduces muscle soreness following exercise. Cold water also reduces the general inflammatory response that accompanies exercise that might be beneficial to athletes following highly strenuous and debilitating exercise like competitive sports and running marathons. But that inflammatory response may be helpful to weekend athletes in training. There are suggestions that cold immersion may improve immune function and may also boost mood and cognition in people who are depressed. But the evidence is not solid. Recent studies suggest that cold immersion may enable people with ALS and multiple sclerosis to carry out activities of daily living more effectively. Cold water immersion also carries risks. They include frostbite, hypothermia, heart rhythm disturbances and even heart attacks. Researchers haven't determined an ideal amount of time to submerge or even a preferred water temperature. What we can say is that you need to achieve a temperature of less than 15 degrees Celsius for a maximum of 3 minutes. If you want to try it. Check with your health care provider first to make certain it's safe for you. That's especially true if you have heart disease or high blood pressure. You should not immerse in cold water if you have open wounds or broken skin or if you have a medical condition that makes your body hypersensitive to cold, such as Raynaud's disease or Cold urticaria. Have someone nearby in case you feel chest pain or palpitations or feel like you're going to pass out. Other safe suggestions include trying cold immersion indoors where you can control the temperature. Trying cold showers allows for very brief exposure and a relatively safe way to start slow and build up. If you have topics you'd like discussed or questions answered, our email address is The Dose at cbc.ca. If you like this episode, please give us a rating and review wherever you listen. This edition of The Dose was produced by Isabelle Gallant. Our senior producer is Colleen Ross. The Dose I want you to be better informed about your health. If you're looking for medical advice, see your health care provider. I'm Dr. Brian Goldman. I'll tell you your next dose.

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What do we know about the health benefits and risks of cold-water immersion? - Transcript

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