Using Deliberate Cold Exposure for Health and Performance

This section of the episode develops the topic through the following source points: Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today we are going to discuss the use of deliberate cold exposure for health and performance. Temperature is a powerful stimulus on our nervous system and, indeed, on every organ and system of our body. And cold in particular can be leveraged to improve mental health, physical health and performance, meaning for endurance exercise, for recovering from various forms of exercise, for actually improving strength and power, and for enhancing mental capacity. In order to properly leverage deliberate cold exposure for sake of mental health, physical health and performance, you have to understand how cold impacts the brain and body. So today we are going to discuss that. We're going to talk about some of the neural circuits and pathways, some of the hormones involved. I promise to make it all clear and accessible, regardless of whether or not you have a scientific background or not. We are also going to discuss very specific protocols that you can apply which leverage variables like temperature: how cold, how to deliver the cold — for instance, whether or not use a cold shower, cold immersion, ice bath, circulating water, or still water, whether or not you're going for walks outside in a T-shirt when it's cold, or whether or not you're purposefully using things like cryo if you have access to that or not. One thing I can promise you is that by the end of today's episode, you will know a lot about the biology of thermoregulation. That is how your brain and body regulates its temperature. You will also have a lot of tools in your arsenal that you can use and leverage toward improving mental health, physical health, reducing inflammation in the body, improving athletic performance, improving mental performance. I promise to spell out all those protocols in detail as I go along and to summarize them again at the end. I'd like to make a point now that I'm going to make several additional times during today's episode, and that is that temperature is a very potent stimulus for the brain and body. That also means that it carries certain hazards if it's not done correctly.

This section of the episode develops the topic through the following source points: Now, as you go from your temperature minimum to the time in which you're going to awake, your temperature is rising slightly. And then at the point where you wake up, your temperature starts to go up more sharply and will continue to go up into the early and sometimes even into the late afternoon. And then sometime in the late afternoon and evening, your temperature will start to decline. And indeed, as you approach sleep, your body temperature will drop by anywhere from one to three degrees. And in fact, that decrease in core body temperature is important, if not essential for getting into and staying in deep sleep. Okay, so temperature rises with waking. That's easy to remember. It tends to continue to rise throughout the day. And in the late afternoon and evening, your temperature will start to go down and the drop in temperature actually helps you access sleep. That background or what we call baseline circadian rhythm in core body temperature is important to remember because it helps us frame both the effects of deliberate cold exposure and helps us frame when you might want to use deliberate cold exposure in order to access specific states. It also points to times within the 24-hour cycle when you might want to avoid using deliberate cold exposure if your primary goal is to get to sleep. Okay, so that's the circadian rhythm in temperature. Now, I just briefly want to touch on thermoregulation at the level of the body and the brain. And this will be very surprising to many of you. Let's do what's called a Gedankin experiment, which is a thought experiment. Let's say I send you out into the desert heat for a jog or a run, and it's very hot outside, 102 degrees or 103 degrees, and you start to move, you start to sweat, and of course your core body temperature goes up. Now then I offer you a cold towel, maybe a really, really cold towel, and this towel is saturated with water, so you could actually squeeze the water out of that and cool your body off. And our Gedankin experiment is for me to say, "Okay, where are you going to place the towel? How are you going to cool yourself off?" And I'm guessing that most of you would think that the best way to cool yourself off would be to drape that towel over your head, maybe your, neck over your torso, that it would feel really, really good, and they would cool you off. Well, that's exactly the wrong approach if you want to cool off, and in fact, if you were to use that approach, your body temperature would continue to increase even more, yes, even more than had you not placed that cold towel on your head or your torso. And here is why. Thermoregulation, meaning your brain and body's ability to regulate your internal core temperature is somewhat like a thermostat, and that thermostat resides in your brain. So if you think about the thermostat in your home or apartment, if it's too warm in your home or apartment and you were to take a bag of ice and to put it on that thermostat, what would the thermostat do? It would register the environment as artificially cool; it would think that the environment was actually much colder than it is. And so as a consequence, it would trigger a mechanism to further increase the temperature in the room. And you have such a thermostat as well. It's called the medial preoptic area of the hypothalamus. The hypothalamus is a small region of brain tissue about over the roof of your mouth and a little bit in front of that. So it's basically right behind your nose and over the roof of your mouth, and it's a collection of neurons. Those neurons have a lot of different functions that include things like the control of aggression, the control of sex behavior, the control of temperature regulation, and so on.