- 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 you 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 thermal regulation, 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. Now, everyone shows up to the table, meaning to protocols, with a different
background of health status and there's simply no way that I can know what your health status is. So anytime you are going
to take on a new protocol, that means a behavioral protocol
or a nutritional protocol or a supplementation protocol, you should absolutely consult
a board certified physician before initiating that protocol. I don't just say this to protect us, I also say this to protect you. If you'd like to see
our medical disclaimer, you can go to our show
notes, it's described there. In fact, I encourage
you to please do that. And in general, when embarking on new
protocols in particular, if they involve strong stimuli
like changing temperature or placing yourself into
unusual temperatures, I would encourage you
to progress gradually. I would also encourage you to not look at gradual progression as
the kind of weak version of a protocol. In fact, today I'm going to discuss a really beautiful peer reviewed study that involved having people
do deliberate cold exposure so they were immersing
themselves into water up to about their neck and the water was actually not that cold. It was only about 60 degrees Fahrenheit, which for most people is pretty tolerable. So nowhere near the kinds
of extreme temperatures that one could use in other protocols. And the interesting thing is despite that fairly modest cold temperature, by simply extending the duration of time that people were in that water, they experienced enormous
increases in neurochemicals that ought to translate to
improvements in focus and mood. And indeed, that's what's been observed in subsequent studies. So again, please see
our medical disclaimer in our show notes, please
proceed with caution always, please also understand that
the most potent stimulus isn't always the one that you experience as the most intense in the moment. In fact, I would encourage you to you find the minimum threshold of stimulus that will allow you to
drive the maximum benefit from each protocol and indeed, I will point out what those
thresholds ought to be today. I'll give you some simple formulas, gauges or guides that you
can use in order to navigate this extremely interesting and potent tool that we call deliberate cold exposure. Before we talk about
deliberate cold exposure and its many powerful applications, I'd like to highlight a study that I find particularly interesting, that I think you will find particularly interesting and useful. The title of this study
is brief aerobic exercise immediately enhances
visual attentional control and perceptual speed, testing the mediated role
of feelings of energy. Now, the reason I like
this study is first of all, it's a fairly large size sample group. They looked at 101 students. These were college-aged students
and they had two groups. One group did 15 minutes of
jogging at moderate intensity. So they did measure percent
heart rates, et cetera, but this would be analogous
to zone two cardio, which I've discussed
on this podcast before. Zone two cardio is cardiovascular exercise that places you at a level where
you can hold a conversation with a little bit of strain, meaning that you can get the words out, but every once in a while
you have to catch your breath whereas if you were to push
any harder by any mechanism going faster or on a
steeper incline, et cetera, that you would have a hard time
carrying out a conversation. So zone two cardio is a
common form of describing that level of intensity that
they call moderate intensity. So one group did 15 minute of
jogging at moderate intensity, which I'm translating to
roughly zone two cardio. The other group did 15 minutes
of relaxation concentration that is somewhat akin to
mindfulness meditation. And then they were analyzed
for perceptual speed, visual attentional control,
something called working memory, which is your ability to keep certain batches
of information online. Just imagine someone telling
you their phone number, and you have to remember
that sequence of numbers in your head for some period
of time, that's working memory. And it depends very
heavily on the so-called prefrontal cortical networks, which are involved in planning and action. And they also looked at
people's feelings of energy and they measured that subjectively, how energetic people felt. Now the major takeaways from this study that I'd like to emphasize are that the 15 minutes of jogging group experienced elevated levels of energy for some period of time after
they ceased the exercise whereas the group that
did mindfulness meditation actually reported feeling more calm and having less overall energy. Now that's very subjective
and indeed they used subjective measures to analyze energy, but what gets interesting is
when they looked at performance on these various cognitive
tasks and the two tasks that they use were called
the trail making tests, they have different versions of this, version A, version B, I don't want to go into too much detail, but version A essentially
involves having a page of numbers that are distributed somewhat randomly. So one, two, three, four, five,
six, seven, eight and so on, but distributed randomly across the page and people have to use visual search to circle those numbers in sequence. So this involves visual attention, it involves some motor skills, involves a number of things that certainly require energy and focus. The second test was the
trail making test part B, as I mentioned earlier, and this involved also
circling numbers in sequence, but interspersed between
those numbers were letters. So rather than just having to circle off numbers in sequence, they actually had to connect one, then the letter A, then two,
then the letter B, et cetera and remember these are randomly
distributed across the page. The major takeaway from the
study is that the group that did the 15 minutes of moderate
exercise prior to these two tests showed significant decreases
in the amount of time required to complete these tests accurately. That is interesting and indeed
surprising at least to me, because there have been many
studies looking at the effects of mindfulness meditation
on the ability to focus. The key variable in the study
turned out to be energy. This subjectively measured
feeling I should say of having more energy and
thereby the ability to focus, especially in these high
cognitive demand tasks. Now the takeaway from
this study for all of us I think is pretty straightforward. If you are going to sit
down to do some work that requires focus and working memory and cognitive attention and especially if it's some
visual spatial control, meaning you have to search
for things on a page, you have to organize things on a page, so some writing, arithmetic, basically cognitive work of any kind, 15 minutes of moderate exercise done prior to that work about could
be very beneficial for you. This does not mean that
mindfulness meditation would not be a benefit to you. I wouldn't want you to conclude that, but if you had to choose between doing 15 minutes of mindfulness meditation and doing 15 minutes of moderate exercise prior to a cognitive work about, I would say the 15 minutes
of moderate exercise would be more valuable at least based
on the data in this paper. In many previous podcasts, I have talked about the
powerful effects of doing things like mindfulness meditation,
and other forms of NSDR, non-sleep deep rest. So these could be 20 minute
naps or just lying there quietly with your eyes closed or yoga nidra or NSDR scripts are available on YouTube and various other places
free of cost of any kind. You just go to YouTube, put in NSDR, non-sleep deep rest. Those protocols have been
shown to be very beneficial for enhancing neuroplasticity, the changes in the brain
and body that encode or shift the neural circuits that allow for memory to change, that allow for learning to
occur after a learning about. What I'm referring to today
in this particular study is the use of moderate exercise in order to increase
one's focus and attention in order to trigger that neuroplasticity. So the simple sequence here
is get energetic and alert, do that prior to the learning about, engage in the cognitive
work or learning about, and then mindfulness meditation, NSDR and so forth should follow. And if you would like to access this paper and like to look more at
the details in the paper, we'll be sure to put a
link in the show notes. The first author is Legrand. And again, the title of this
paper is brief aerobic exercise immediately enhances
visual potential control and perceptual speed, testing the mediating
role of feeling of energy. And I also just want to
emphasize immediately. I think most people out
there are interested in tools and protocols that work the first time and that work every time and indeed, I think this
protocol fits that bill. I'm pleased to announce that I'm hosting two live events this May. The first live event will be hosted in Seattle, Washington on May 17th. The second live event will be hosted in Portland,
Oregon on May 18th, both are part of a lecture series entitled the Brain Body Contract during
which I will discuss science and science-based tools for mental health, physical health and performance. And I should point out that
while some of the material I'll cover will overlap with
information covered here on the Huberman Lab Podcast and on various social media posts, most of the information I will
cover is going to be distinct from information covered on
the podcast or elsewhere. So once again, it's Seattle on May 17th, Portland on May 18th. You can access tickets by
going to hubermanlab.com/tour and I hope to see you there. Before we begin, I'd like to emphasize that
this podcast is separate from my teaching and
research roles at Stanford. It is however part of my desire and effort to bring zero cost to consumer
information about science and science-related tools
to the general public. In keeping with that theme, I'd like to thank the
sponsors of today's podcast. Our first sponsor is Athletic
Greens, also called AG One. I started taking AG One way back in 2012 so I'm delighted that they're
sponsoring the podcast. The reason I started taking AG One and the reason I still take AG One once or twice a day is that it covers my foundational vitamin
mineral and probiotic needs. It also has adaptogens
and things like zinc for immune system function, but the probiotics are one
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for our immune system, brain function and so on. One way to enhance our gut microbiome to ensure that it's
healthy is to make sure that we get the correct
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order and two free pillows. Let's talk about the use of
cold for health and performance. I confess I love this topic because it takes me back
to my undergraduate years when I worked in a laboratory
studying cold physiology, its effects on the brain
and its effects the body. And over the years, I've always kept track of
the literature in this area and indeed there have been
some tremendous discoveries, both in animal models, so in
rodents like mice and rats, but also in humans and today we're going to
talk about both categories of studies and I'll be careful
to point out when discoveries were made in animal models and when they were made in humans. A key point when thinking about
the use of cold as a tool, and the key point is that
you have a baseline level of temperature that is varying, changing across the 24 hour cycle. So any use of deliberate cold exposure is going to be super
imposed on that rhythm, that circadian rhythm,
meaning that 24 hour rhythm. The basic contour of your
circadian rhythm in temperature is that approximately two hours
before the time you wake up is your so-called temperature minimum. So your temperature minimum is a time within the 24 hour cycle when your body temperature
is at its lowest. So if you normally wake up around 6:00 AM, your temperature minimum
is probably about 4:00 AM. If you normally wake up at about 7:00 AM, your temperature minimum
is probably about 5:00 AM. It's not exactly two hours
before your wake up time, it's approximately two hours
before your wake up time. 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. 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. So that's the circadian
rhythm in temperature. Now I just briefly want to touch on thermal regulation at the
level of body and the brain. And this will be very
surprising to many of you. Let's do what's called
a Gedanken 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 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 Gedanken 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 it 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. Thermal regulation 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. The medial preoptic area
has connections with the rest of the brain or areas within the brain, I should say and with many areas within the body, it receives input from
receptors in our skin and inside our body that
register temperature and it acts as a thermostat. So if the surface of
your body is made cool, your medial preoptic
area will send signals by way of hormones and by way of chemicals that will serve to heat your body up. So what this means is that
if you want to cool down, the last thing you want to
do is to bring a cold surface of any kind, towel or splashing water, to the majority of your body surface. It might be very, very surprising to you. And you might say, wait,
if I want to cool down, I should jump into a cold lake
or something of that sort. That's a different thing altogether. What I'll tell you, and we'll get into this
in more depth later, is that if you really want to cool down quickly and efficiently, you should leverage particular portals, meaning particular sites on your body where heat can leave
your body more readily and where cooling can have
a dramatic and fast impact on your core body temperature, can even save your life if
you're going hyperthermic. We're going to talk more about
the specific protocols to reduce core body temperature
for sake of performance and avoiding hyperthermia
later in the episode. Hyperthermia of course is a
very, very dangerous situation because while your body can
drop in core temperature somewhat and still be safe, you can't really increase your
body temperature that much before your brain starts to cook and other organs start
to cook and by cook, I mean the cells actually start to die. So you have to be very, very
careful with the use of heat. Heat stroke is no joke. People die from heat stroke all the time. You really want to avoid that. One way to avoid that is to
cool the appropriate surfaces of your body and the appropriate
surfaces in this case are the upper cheeks or I would say the upper half of the face, the palms of your hands and
the bottoms of your feet. I've talked about this
on the podcast before and in the guest episode
with Dr. Craig Heller, my colleague in the biology
department at Stanford, but just very briefly, these surfaces, the upper half of the face, the palms of the hands and
the bottoms of the feet are what we call glabrous skin surfaces,
G-L-A-B-R-O-U-S, glabrous. And those surfaces are unique
in that just below them, the vasculature is different
than elsewhere in the body. Normally the passage of blood goes from arteries to capillaries to veins, but just beneath the
glabrous skin on the bottoms of the feet, the hands in
the upper half of the face, you have what are called
arterio-venous anastomoses. These are portals of
blood that go directly from arteries to veins and in doing so, allow the body to dump heat
more readily, more quickly. So as it turns out that if
you are to cool the palms of the hands, the bottoms of the feet and the upper half of the face, you can more efficiently
reduce core body temperature for sake of offsetting hyperthermia and for improving athletic performance and maybe even cognitive performance. So we will return to
the specific protocols for doing that later in the episode, I'll give you a lot of
details about how to do that, how to do that without the use of any fancy or expensive technology. There are some technologies that are now commercially
available, for instance, the so-called CoolMitt that will allow you to do
that with maximum efficiency, but I'll also give you some
at home methods to do this either in the gym or on runs
or for sake of cognitive work. So the two key themes again are understand that
baseline circadian rhythm in temperature, and understand
that the best way to cool the body is going to be by making sure that
something cold contacts the bottoms of your feet, the palms of your hands and
the upper half of the face. Ideally all three if your goal is to lower core
body temperature quickly, and again, just cooling
off the back of your neck or the top of your head
or your torso with a towel is going to be the least efficient way to lower core body temperature
and might even increase body temperature under certain conditions. With those two points in mind, we can start to think
about directed deliberate cold exposure protocols, and there are a number
of different reasons to use deliberate cold exposure. And I want to separate those out for you. There are cold protocols
that have been tested in peer reviewed studies that are designed to improve mental performance. They are designed to improve
things like resilience or your grittiness, or your ability to move through challenge or to regulate your mind
and your internal state under conditions of stress and we can define stress
very specifically as times when adrenaline also called epinephrine and or norepinephrine
also called noradrenaline, are elevated in your body. Forgive me for the noradrenaline, norepinephrine, adrenaline,
epinephrine nomenclature, I didn't make that up. It turns out that every once in a while, scientists disagree, imagine that, and you'll get multiple scientists naming the same molecule different things. So epinephrine and adrenaline
are the same thing. I will use them interchangeably. Norepinephrine and noradrenaline
are the same thing. I will use those terms interchangeably. Noradrenaline and adrenaline are often co-released
in the brain and body. So they work as kind of a pair to increase our level of agitation, our level of focus and our
desire and our ability to move. They are often co-released
from different sites in the brain and body with dopamine, a molecule that is commonly misunderstood as the molecule of pleasure, but is actually the
molecule of motivation, reward and pursuit. So dopamine, norepinephrine
and noradrenaline tend to be released together
under certain conditions and today you'll learn how
deliberate cold exposure can be used to cause increases
in the release of several, if not, all of these in ways that can improve your levels
of attention and your mood. But the key point is that
your mental state is shifted when you are exposed to
certain forms of cold, and many people use
deliberate cold exposure specifically to shift
their body state as a way to train their mental state
so that they can better cope with stress in real life and by real life, I mean when life presents
stressful events, and I will give you specific protocols as to how you can do that, in other words, how you can become more resilient through the use of
deliberate cold exposure. Now, because of the ways in
which deliberate cold exposure can increase this category of chemicals called the catecholamines, that includes dopamine,
norepinephrine and epinephrine, it can also be used to elevate mood for long periods of time. And I'm going to discuss
a specific protocol that has been shown to
increase these chemicals anywhere from 2.5X to
250%, to as high as 500%, five times over baseline. Now you might be asking whether
or not it is a good thing to raise chemicals like
norepinephrine and dopamine to such a great degree, whether or not that's healthy for us, whether or not they can harm us. But it turns out that these
elevations in norepinephrine and dopamine are very long lasting in ways that people report
feeling vast improvements in mood and vast improvements in levels of cognitive
attention and energy. So by my read of the literature, these seem to be healthy
increases in our baseline levels of these chemicals in ways
that can really support us so I'll give you a protocol for that. Now, those are some of the mental effects of deliberate cold exposure, but deliberate cold exposure
has also been studied in animal models and in humans in the context of increasing metabolism, even in converting certain fat cells that we call white fat cells, which are the ones where energy is stored, they're the ones that
we typically think of as kind of blubbery fat,
to beige or brown fat, which is thermogenic fat, meaning that it can increase
core body temperature and serves kind of the furnace by which we increase our core metabolism. So with a very broad stroke, I can say that white fat is
generally the kind of fat that people want less of
and beige fat and brown fat is generally the kind of fat that if you're going to have fat cells and you certainly need fat
cells that you want more of. They are thermogenic,
they help you stay lean. They actually serve as a
reservoir for heating your body up if you're ever confronted
with a cold challenge. So we're going to talk
about how to use cold for metabolism as well. And of course, people are using deliberate cold exposure to reduce inflammation post exercise, to reduce inflammation generally. And people are also using
cold to enhance performance in the context of strength training, in the context of endurance training and we'll talk about those data as well, but where I'd like to start
is with mental performance and I'd like to detail what happens when we deliberately
expose ourselves to cold. It's key to point out the word deliberate. If I don't say otherwise,
then throughout this episode, if I say cold exposure, I
mean deliberate cold exposure. And the reason I point that
out is that as my colleague, David Spiegel, and the
department of psychiatry at Stanford says, it's not just about the
state that we are in, it's about the state that
we are in and whether or not we had anything to with placing
ourselves into that state and whether or not we did
that on purpose or not. And what he really means
by that statement is that there are important effects
of what we call mindset. Mindset was a topic discussed
in the guest episode with Ali Crumb some weeks ago. If you haven't seen that
episode, I highly recommend it. And the science of my mindset
tells us that if we are doing something deliberately and we believe that it's going to be good for us, it actually can lead to a different set of physiological effects than if something is happening to us against our
will or without our control. Now, this is different
than placebo effects. Placebo effects are distinct
from mindset effects. If you want to learn more
about that distinction, please see the episode with Ali Crumb. But again, when I talk about
cold exposure in this episode, I'm talking about
deliberate cold exposure, meaning that you are
placing yourself into a cold environment on
purpose in order to extract a particular set of benefits. When we talk about deliberate
cold exposure, almost always, that means getting uncomfortable. And one of the most common questions I get when discussing the use
of cold for sake of mental or physical performance,
metabolism, et cetera, is how cold should it be? How cold should the water be? How cold should the environment be? And I just will tell you now and I'm going to say this again and again throughout the episode, cause it will continue to be
true throughout the episode and long after the episode is over, how cold depends on your cold tolerance, your core metabolism, and a number of other features
that there is simply no way I could know or have access to. So I would like you to
use this rule of thumb. If you are using deliberate cold exposure, the environment that
you place yourself into should place your mind
into a state of whoa, I would really like to get
out of this environment, but I can stay in safely. Now that might seem a
little bit arbitrary, but let's say you were
to get into a warm shower and it would feel really, really nice and you were to start
turning down the warm and turning up the cold. There would be some threshold at which it would feel uncomfortable to you. And if you were to continue
to make a little bit colder than that, you would really
want to get out of the shower, but you are confident
that you could stay in without risking your health,
without risking a heart attack. Now that's very different
than jumping into a very, very cold lake or I've seen these images of
people that will cut holes into frozen over lakes and they'll
get into that cold water. If you are trained to do that and you have the right
conditions, et cetera, that can be done reasonably safely, but that's certainly not
what I would start with. And for many people,
that would be too cold and indeed some people
can go into cold shock and can die as a consequence of getting to that extremely cold water very quickly. Now that's not to scare you away from deliberate cold exposure. It's just to say that there's
no simple prescriptive of how cold to make environment in order to extract maximum benefit for mental or physical performance. So the simple rule of thumb is going to be place yourself into an environment that is uncomfortably cold, but that you can stay in safely. And you'll have to experiment
a bit and that number, meaning that temperature,
will vary from day to day. It will vary across the 24 hour cycle because of that endogenous, meaning that internal rhythm, in temperature that I
talked about earlier. Low early in the day, rises into the afternoon, drops at night. You can actually do this
experiment if you like. Try getting into a cold
shower at 11 o'clock at night if you want versus try doing it in the middle of the afternoon. It's quite a different experience and by quite a different experience, I mean it requires quite a
different degree of resilience and leaning into the practice. Your willpower will have
to be higher I suspect late in the day as it
compared to early in the day, but that will vary of course
between individuals as well. So the most common question I get about deliberate cold exposure is how cold should the water be? And we've answered that with
uncomfortably cold to the point where you want to get out, but you can safely stay in. The second most common question I get about deliberate cold
exposure is whether or not cold showers are as good, better or worse than cold water immersion up to the neck, for instance. I also get a lot of questions
about whether or not cryo chambers are better
than all the others, et cetera, et cetera. I'm going to make all of that very simple for you by
saying cold water immersion up to the neck with your
feet and hands submerged also is going to be the most effective. Second best would be cold shower. Third best would be to go outside with a minimum amount of
clothing, but of course, clothing that is culturally appropriate and that would allow you to
experience cold to the point where you would almost want
to shiver or start shivering. Now there are a number of different, important constraints
that are going to dictate whether or not you use
one form of cold exposure or the other. For instance, some
people don't have access to cold water immersion. They don't have access to ice
baths or cold water tanks, cold ocean or cold lakes, et cetera. In that case, showers would
be the next best solution. I do want to emphasize that
there have been very few, if any, studies of cold showers, and you can imagine why
this would be the case. In a laboratory, you want to control for as
many variables as possible. So placing people into a cold
water immersion or an ice bath up to the neck and insisting
they keep their hands and feet under is very easy to control. It means that everyone can
do essentially the same thing whereas with cold showers, people are different sized bodies. Some people are going
to put their head under. Some people are going to lean forward. Measuring the amount of cold
water exposure on the body is very hard to do and so there aren't a lot
of studies of cold showers, but of course, a lot of people don't have
access to cold water immersion so they have to use cold showers. And if you don't have
access to both, of course, then going outside on a cold
day can be of a benefit. But I will point out
that the heat transfer from your body into water is much higher, four times greater, if not even greater, depending on the temperature of the water, in water as opposed to in air. So it's going to be much more efficient to do cold water immersion
than anything else, cold showers after that
and put yourself into a cold environment would
be the third best thing. I'm not going to get into cryo chambers because they carry quite
a high degree of cost. And again, there aren't
many studies of them. So if you have access to cryo chambers, I'm sure that the cryo chamber facility has told you about all
these incredible benefits and I don't doubt that some
of those benefits truly exist, but most people just
don't have the resources or the access to those so we're going to leave cryo chambers out of today's discussion. And of course I realize
there's a fourth category of cold exposure out there. People are wearing ice vests. Believe it or not, those
exist, ice underwear. Yes, those exist. You can look for them
on Amazon if you like. They are putting cold
packs in their armpits or in their groin or elsewhere in order to stimulate some of the effects of cold on mental and physical performance. I'm not going to address those
in too much detail today. They can be efficient in certain ways, but as you'll learn about
later in the episode, cooling the palms, the upper face and the bottoms of the feet is going to be far more efficient and unfortunately I think most
of the people that are using ice packs to increase
their core metabolism are not aware of the glabrous skin cooling and how it can be a very,
very potent stimulus so we'll return to that later. Unless I say otherwise, I'm mainly going to be focusing
on cold water immersion and cold showers. So let's talk about protocols
for enhancing mental health and performance using
deliberate cold exposure. What happens when we get into
cold is that we experience an increase in norepinephrine, in noradrenaline release
and in adrenaline release. The fact that cold
exposure, deliberate or no, increases norepinephrine and epinephrine in our brain and body means that it is a very reliable stimulus for increasing norepinephrine and epinephrine. That's sort of an obvious statement, but that obvious
statement can be leveraged to systematically build up
what we call resilience. Now, when we experience
a stressor in life, whether or not it's something bad happens in our relationship or something
bad happens in the world and we feel stress, that stress is the
consequence of increases in norepinephrine and epinephrine
in our brain and body. Very similar, if not identical, to the kinds of increases that come from deliberate cold exposure. So deliberate cold
exposure is an opportunity to deliberately stress our body and yet, because it's deliberate and because we can take certain steps, which I'll describe in a moment, we can learn to maintain mental clarity, we can learn to maintain
calm while our body is in a state of stress. And that can be immensely useful when encountering stressors
in other parts of life. And that's what we call
resilience or grit, our ability or mental toughness, our ability to lean into
challenge or to tolerate challenge while keeping our heads
straight, so to speak. So one simple protocol
for increasing resilience is to pick a temperature
that's uncomfortable of shower or cold immersion, and then to get in for a
certain duration of time and then to get out. Now, it's important to understand that people will
experience different levels of norepinephrine and adrenaline release when getting into cold water. Some people, because they
dread the cold so much, will actually experience norepinephrine and epinephrine increases even before they get into the cold water or under the cold shower. Now you may have experienced this. I've certainly experienced this. I'm dreading it, I don't want to do it and I have to force myself to do it. And indeed epinephrine and
norepinephrine and its surges can be thought of as sort of
walls that we have to confront and go over. And I'd like you to
conceptualize them that way, because it allows us to build protocols that can be very
objective and can allow us to monitor our progress in
terms of building resilience. So one option is to simply say, okay, I'm going to force myself to get into the cold
shower for one minute. How cold, again, uncomfortably cold, but you can stay in safely or I'm going to get into
the ice bath for one minute. Ice baths are very cold inevitably. And what is also inevitable is that when you get into the cold, you will experience a surge in epinephrine and norepinephrine. That's non-negotiable
because it's mediated by cold receptors on
the surface of your body and your skin and the way
that they trigger the release of norepinephrine and epinephrine, not just from the adrenals, from the adrenal glands
above your kidneys, but also from regions of your brain, like the locus coeruleus, which cause increases in
the tension and alertness, and from other locations in
your body where epinephrine and norepinephrine are released. In other words, cold is
a non-negotiable stimulus for increasing epinephrine
and norepinephrine. Even if you are the
toughest person in the world and you love the cold, that increase in epinephrine
and norepinephrine is going to happen. So the way to think about
norepinephrine and epinephrine in this context of
building mental resilience is that you have two options. You can either try to
extend the duration of time that you are in the
deliberate cold exposure. So going from one minute to
75 seconds to two minutes and so on over a period of days or one way to approach this and the way that I particularly favor is to take the context of the day and the moment into account, meaning we have different
levels of grit and resilience on different days and
depending on the landscape of our life at the time, even the time of day that
we're doing these protocols and start to be able to sense
the release of epinephrine, and norepinephrine in our
brain and body and see those as walls that we want to climb over in order to build resilience
and to start counting the number of walls that we traverse and the distance between those walls as we do deliberate cold exposure. Let me give you an example
of the timed protocol because that one is very straightforward, although I do not think it is as powerful for building mental resilience. The time protocol would be Monday, I do one minute of
deliberate cold exposure at a given temperature. Wednesday, I extend
that by 50% and Friday, I do deliberate cold
exposure for twice as long as I did it on Monday. And if I were to continue that every week, Monday, Wednesday, Friday, I would continue to either
increase the duration or I would lower the temperature
and reduce the duration, this kind of thing, very much
like sets and reps in the gym. Now that option is very objective. You could even log it in a book and as you develop the ability
to stay in cold temperatures, even progressively colder
and colder temperatures for longer and longer periods of time, you will become more resilient. What do I mean by that? Well, my operational
definition of resilience is that you are able to resist
escape from the stressor, the cold, by virtue of your willpower, which is really your prefrontal cortex causing top down control on your reflexes and your limbic system
and your hypothalamus, which are basically telling you to get out of that cold water, get out of that cold
environment and in doing so, you are basically getting better at controlling your behavior
when your brain and body are flooded with
norepinephrine and epinephrine. That's a very reductionist
way to explain resilience or grit or mental toughness, but it's a reductionist
way of explaining it that is very closely
tied to the biology end of the psychology. And it is a fact that
norepinephrine and epinephrine release in the brain and body are the generic universal
code for stressor. There is no unique chemical signature for different forms of
stressors, that is the only one, although of course there are other chemicals involved as well. So you could go for time and you could try and reduce the temperature
and increase the time over a period of days or weeks. Now that's an attractive
way to approach things, but the problem is that you
don't have an infinite amount of room with which to lower temperature, because eventually you
will get into temperatures that are either so cold
that they are dangerous or you have to stay in cold temperatures for such long periods that
it becomes impractical because presumably you also have to take care of other aspects of your life, you can't just sit all
day in the ice bath. Now for that reason, I favor a protocol in which
you build mental resilience and mental toughness through two different types of protocols. The first one involves counting walls. Now, what do I mean by walls? I mean the sensation of, no, I don't want to do this and
the idea or the sensation in your brain and body that
you actually want to leave that environment and go warm up. Now again, for some people, that will be even before
getting into the ice bath or cold shower. So if you are feeling very resistant to getting into the ice bath or cold shower and you manage to do that, that's going over what
I would call one wall. Then for some period of time, you might actually feel
comfortable in the ice bath, cold water or cold shower. And you feel like you could stay there for some period of time, that you could stay there
for a minute or two minutes, but inevitably, the next wall will arrive. And I would encourage
you to pay attention to when that next wall arrives and actually having an awareness, that so-called interceptive
awareness as we call it, of when that next surge
adrenaline epinephrine comes or whether or not it
reaches a certain threshold in your brain and body that
you feel you want to get out and you're able to stay in for
even just 10 seconds longer, that means you've
traversed yet another wall. And if you continue to stay
in that cold environment, you'll find that the next wall will come and the next wall will come. Now eventually of course,
you will get very, very numb depending on how cold it is and you could also place
yourself into danger. So you have to maintain cognitive control, counting these walls,
traversing these walls, but getting out at some point, of course. So my favorite protocol for
building mental toughness AKA grit, AKA resilience, is to take into account that some days, just getting into the ice bath or cold shower represents a
wall, some days it doesn't. Some days you get in and you
feel you could go 10 minutes, other days you get in and you feel like you could only go a minute and
setting a designated number of walls before you start the protocol is going to be very beneficial here. So you say, as long as I can do it safely, I'm going to do three walls today. The first wall is getting in. The second wall will
arrive when it arrives and the third wall will
arrive when it arrives and I'll get over that
wall and then I'll get out. The next day, you might do five walls. The next day, you might
do three walls again, but you might lower the temperature. This gives you tremendous flexibility and indeed it gives you much more latitude to be able to use the same
temperatures in different ways, or to reduce the temperature
only a little bit and still get a lot of stimulus, meaning a lot of results
out of a given protocol. Whereas people who are just
going for temperature and time eventually become cold adapted. They get very, very good
at doing three minutes or six minutes or even 10
minutes at a given temperature and so then they feel like they have to lower the temperature
even more and even more and eventually they just bought them out. There's nowhere else to go. There's no way to get
improvements out of the protocol. At least not in terms
of mental resilience. Of course, there's still
the positive effects on inflammation and metabolism, et cetera, that we'll talk about in a little bit. But the key thing here
is to design protocols that are going to work for you over time and for you very, very hardy, very, very tough guys and gals out there that can get right into an ice bath or a very, very cold immersion and you can just grind it
out for six or 10 minutes, or you can even do that
by remaining peaceful, well more points to you, but guess what? That's the equivalent of
already having loaded up the barbell with 600 pounds
and done your 10 reps. There's not a whole
lot more variable space with which to get benefits
from that stimulus. And in the weight room, people understand that you
can adjust, for instance, the speed of the movement, or you can start combining that movement with pre-exhaustion, et cetera. With cold exposure, you don't have as much
variable space to play with. So if your goal is to build resilience, either go for time as a
function of temperature, or what I suggest is to
start recognizing these walls as an experience of resistance in you and going over those walls,
set a certain number of walls that you're going to go over
on a given day and do that at a given temperature,
and then to mix it up. And ideally you might even
throw in one more wall at the end, if you're really feeling bold and brave because that's going to
build out further resilience. But if you want cold
exposure to work for you for sake of building up resilience and mental toughness over time, you're going to want to
vary this parameter space in some sort of way. And you don't have to be
super systematic about it. That's the beauty of this kind of approach because you're relying on the fact that those walls really represent times in which you are forcing
your top down control, your prefrontal cortex to
clamp down on your reflex and you're learning behavioral
control in the context of your body having elevated levels of these catecholamines,
norepinephrine and epinephrine. And that translates to real life in a much more realistic way I
believe because in real life, you're not really engaging in stressors for a given amount of time that you know how long it's going to last and you know the context, no. Most stressors arrive
in the form of surprises we don't like, text messages
that deliver bad news, information about the
outside world or real world and online interactions
that send our system into a state of increased
norepinephrine and epinephrine. And if you start to
think of those as walls that you can tolerate and climb over while staying and calm and clear of mind, then you can really
imagine how the ice bath and other forms of cold
exposure are really serving to train you up for real life stressors. The next question that I always get is what should my mental state be while I'm exposing myself
to this uncomfortable, yet safe condition of cold? Well, you have two options and there are probably
other options as well. One is to try and calm yourself to remain as mentally still as possible. The other is to lean into that challenge and so to grind it out and here, I have to say that this is
a lot like teaching someone to drive on a gravel road. For any of you that have
driven on a gravel road, you know that there is no optimal speed for all gravel roads. It depends on the density
of the gravel, et cetera, and the vehicle, et cetera. So for instance, on some gravel roads, when you start to drive and
the dust starts to kick up, your best option is to drive fast and put that dust cloud behind you. On other gravel roads,
if you try and do that, the dust actually kicks
up around the vehicle and it makes it hard to see and sometimes you have to slow down. The same thing is true for getting through deliberate cold exposure. Sometimes it's easier to calm yourself. One way to do that is
through double inhales through the nose and extended
exhales through the mouth, or simply by trying to
control your breathing and reduce the pace of
your breath and increase the volume of your breathing. I have to say that everyone
experiences a shortening of breath when they get into
uncomfortably cold water, that is a universal
physiological response. Everyone also experiences
a 30 to 80% decrease in cognitive function, in
particular, the frontal cortex. The metabolism of your
frontal cortex goes down, the metabolism meaning the
activity of brain areas associated with stress
and panic goes way up. And so anchoring your mind
in cognitive activities as you get into the cold can be very, very helpful for
maintaining clarity of mind. In fact, one thing that
I sometimes recommend is that people try and engage in some sort of cognitive
exercise while in the cold, not as a form of distraction, but as a way to maintain
clarity of thinking and to learn how to do that
when the body is flooded with all these chemicals
that make us stressed. So for instance, you could do math problems and
not two plus two equals four, not three times three equals nine, but things that require
a little bit more focus and attention working memory and so forth. You could also start to have thoughts that you deliberately impose
a full sentence structure on. That's actually quite tough. You could try and recall
specific bouts of information that are challenging. This is teaching your
mind how to stay online, or rather I should say, this is you teaching
your prefrontal cortex, how to stay engaged while you
have high levels of stress in your body. Years ago, I had a friend who works in the neuroscience world,
research neuroscientist, who was obsessed with
this very bizarre sport that I don't necessarily recommend at all, which is the combination
of boxing and chess. You may have seen this on YouTube where people will box around, legitimate boxing around,
they're sparring all out often. And then at the end of the round, instead of resting in the corner, they actually sit down and play chess, and then they go back to
boxing and back to chess. Again, not a sport that I recommend, but the reason he was
obsessed with this is because he studies the impact of stress
on cognitive performance. And what that particular
very bizarre sport was doing was toggling back and forth between different states of mind. Now it's used both to
increase cognitive clarity for the fighter when they box, because staying calm and clear thinking is very important to
winning boxing matches. Believe it or not, it's
not an all outrage. It's a very calculated
game of mental chess and physical chess
that's quite high stakes as you can imagine. It's also used in some circles
as a way to teach people how to engage in cognitive performance when their body is simply
filled to a stress. So in the boxing chess example, the replacement for the cold
water is actually the boxing, it's the thing that's
supposed to induce the stress cause getting hit is
stressful and the risk of getting hit is
stressful for most people. So again, if you think about
deliberate cold exposure as a way of just
systematically and reliably inducing epinephrine and
norepinephrine release and delivering stress, well then this idea of
maintaining cognitive clarity and actually engaging in cognitive tasks while in the ice bath or cold shower can actually be very beneficial. Even though it might
sound a little bit silly, you are really training up your ability to keep your brain working when the reflex is to shut
down the parts of your brain that are involved in deliberate
planning and thinking. Now another important aspect
of deliberate cold exposure that I rarely if ever hear discussed, but is vitally important is whether or not you move around or not. And here's the reason. When you get into cold
water and you remain there for some period of time, your body is generating
heat and that heat generates what's called a thermal layer that surrounds your entire body. So if you stay still, you are actually warmer
than if you move around, you can try this the next time you're doing your
deliberate cold exposure. If you're submerged up to the neck, sit there for about 10, 30 seconds and be very, very still of body. In fact, this is the way
that most people start to do deliberate cold exposure. They give this very stoic look. They don't blink, they look very peaceful. Some of them even look tough or they make a very even A, emotional face and so it looks like they're really tough, but they are so still
that believe it or not, they're not providing
the most potent stimulus. If they or you were to
move around in that water, what would happen is you'd
break up the thermal layer and that you actually
experience that as much colder. So if you really want to
push the resilience aspect, or for instance, if you want
to use a given temperature that you're comfortable in, but that you want to increase the stimulus and you want to get some more benefit for mental resilience training, well then get into the cold water, move your body around continuously, but try and keep your mind still, or even do some sort of cognitive task. So as you're starting to realize, there are a bunch of different variables that you can play with while maintaining the same temperature of
water and in doing so, really keep you in the zone of what should and absolutely has to be safe for you without having to just
continually drop the temperature from say 60 degrees to 55 to 40 to 33 because as I mentioned before, eventually you're going to bottom out. So if you're one of those
people that likes to look tough or really relaxed while
you're in the ice bath or cold water immersion, just realize that you're
actually cheating yourself out of part of the stimulus. Keep those limbs moving and of course, limbs under the water, feet and hands is going to be a more potent stimulus than hands and feet out for reasons that should be obvious based
on what we talked about in terms of glabrous skin cooling. Keep those submerged, move your body, maybe move your knees up
and down, pedal your feet and trust me, it's going
to feel a lot colder than were you to remain stone still. Another very common question is how often to do
deliberate cold exposure. It's tough to make a
recommendation on that based on any peer reviewed study although there are a few in
humans that point to a threshold of 11 minutes total per week. So that's total throughout the week divided into two or four sessions of two or three minutes or so. Now that 11 minute cutoff
is not a strict threshold and is actually geared more
towards increases in metabolism, we'll get into this a little
bit later in the episode, but I think the 11 minute threshold, meaning 11 minutes total
of deliberate cold exposure per week is a pretty good number to use if you need a number in
order to keep you consistent. But as we talked about earlier, some of you are going
to be in the ice bath or cold immersion or cold
shower for one minute, others of you will be
in there for 10 minutes, depending on how frequent
and how high, if you will, those walls of adrenaline are coming. So for some of you, getting into a cold shower
for three minutes total for the whole week will
represent a tremendous achievement in terms of
willpower and overcoming the resistance to doing
that, overcoming those walls. For others of you, three
minutes is nothing. So what do I recommend, I recommend that you get at
least 11 minutes total per week, but at the point where
11 minutes total per week is very easy for you, where is no longer representing a significant mental challenge, meaning you're not experiencing
many of these walls, you're excited to get into
the cold shower immersion, you're going through it easily,
you're cruising basically. Then I would say either
lower the temperature safely, of course, extend the
duration safely, of course, or increase the frequency
so that you're doing this perhaps every day or
maybe five days a week or three days a week. I personally get tremendous benefit from doing deliberate cold
exposure three times a week and using the walls method
that I described earlier as my gauge for how long to stay in and typically that means that
I'm staying in for anywhere from two minutes to
six minutes per session and that averages out to about 11 to 15 minutes total per week. So again, I do not think that
you need to be super strict about these guidelines. It's most important when
embracing a protocol A, that you do it safely, but secondarily that
you do it consistently. So find what you can do consistently and then vary the parameters that will allow you to continue to do deliberate cold exposure consistently, regardless of whether or not
you have access to a shower or cold immersion, et cetera. So we've been talking about mental effects and the use of deliberate cold exposure for sake of building resilience, which I do believe can
be tremendously powerful. Look, it's no coincidence
that the screening and the training for Navy Seals involves a lot of exposure to cold water. One could argue that it is deliberate because they elect to go to buds, but when they get into
the cold water at buds is dictated by the
instructors and the reason they use cold water
exposure as the stressor is that it does offer considerable leeway in terms of duration and temperature, in terms of how you can
use it as a stressor whereas things like heat don't
offer much variable space as we say. There isn't a lot of room
beyond which you start injuring or even killing people by using heat. So there are a lot of forms
of stressors out there, but cold is one that we can titrate, that we can adjust in
ways that can allow us to continually build up and
or maintain mental toughness. Now, deliberate cold exposure
also has many effects on chemicals other than
norepinephrine and epinephrine, most notably the neuromodulator dopamine, which is involved in elevating our mood, making us feel energized and
enhancing our ability to focus. And that has a lot to do
with how dopamine engages us in motivated states, tends to narrow our
thinking in our behavior into a particular trench
of goal-directed behavior. If you want to learn more about dopamine, you can learn a lot about dopamine in our episode about dopamine,
it's at hubermanlab.com. You can find it, it's a
two and a half hour plus kind of deep dive into
all things dopamine, focus, motivation, et cetera. Deliberate cold exposure
has a very powerful effect on the release of dopamine
in our brain and body. And this is one of the main
reasons why people continue to do deliberate cold exposure. Basically it makes us feel good and it continues to make us feel good even after we get out
of the cold environment. In fact, some people would say they don't feel good in
the cold environment, it's all stress for them, but afterwards they feel great. One of our previous
guests, Dr. Anna Lembke, who's a medical doctor
at Stanford University School of Medicine, she's
a close colleague of mine, described the use dopamine
in her book, Dopamine Nation, an incredible book about
addiction and dopamine I should mention. And the use of dopamine
elicited by cold water exposure by one of her patients. What I'm referring to is the
fact that one of her patients helped themselves get
and stay sober off drugs by using deliberate cold
exposure to increase dopamine. So a healthier form of dopamine release than they were engaged in
prior to getting sober. Now, the basis for dopamine release in response to cold exposure is that the catecholamines,
norepinephrine, epinephrine and dopamine
tend to be co-released by the same sorts of stimuli, but most stressors and
in particular things that evoke stress or our
feelings of stress internally that we don't like do
not increase dopamine. They only increase
norepinephrine and epinephrine, but deliberate cold exposure seems to cause a dramatic
increase in dopamine. And this has actually been substantiated in a really beautiful study entitled human physiological responses to immersion into water
of different temperatures. The first author is Sramek. I'm almost certainly
pronouncing that poorly and if not incorrectly, S-R-A-M-E-K. This was published in the European Journal of Applied Physiology in the year 2000, really a beautiful
study, I love this study. They took people and they
had them sit in chairs underwater but their head was
out and so they were immersed up to the neck in either of
three different temperatures. 32 degrees Celsius, which
is 89 degrees Fahrenheit, 20 degrees Celsius, which
is 68 degrees Fahrenheit, or 14 degrees Celsius, which
is 57.2 degrees Fahrenheit. So not super cold, but then what they did is they measured people's core
body temperature throughout. They measured their metabolism and they looked at serum levels of things like norepinephrine,
epinephrine, dopamine, and cortisol, serum
meaning within the blood. So a really nice and quite thorough study. There were not a huge number
of subjects in the study, but nonetheless, it was
a very thorough study in terms of the number of
variables that they explored. So I just want to briefly highlight some of what they saw or what
they observed in this study. First of all, all the
groups were in the water of a given temperature for one hour, which is much longer than most of the deliberate cold exposure protocols that anyone is using at home. I mean, maybe you're taking
one hour long cold showers, maybe you're getting into
the ice bath for an hour although I don't recommend that. I think you'd probably get
badly hypothermic or maybe you're getting into a cold water immersion for some period of time, but I have a hard time imagining
that it would be an hour and I don't suggest
that if it's very cold. So this study focused on actually somewhat moderately cool temperatures, not what I think most
people would consider very, very cold temperatures, but extended the duration
for quite a while. So again, 32 degree Celsius, 20 degree Celsius or 14 degree Celsius. Here's what they observed. The group that was immersed up to the neck in 32 degrees Celsius, that
is 89 degrees Fahrenheit, water did not experience
a shift in metabolism nor a significant increase in dopamine, norepinephrine or these
other catecholamines. The group that was in 20 degree Celsius, meaning 68 degree Fahrenheit, water for an hour
experienced a 93% increase in metabolic rate, which is remarkable given that the water wasn't that cold and yet an hour is a pretty
long time to be in there. And again, it speaks
to the dramatic effect of heat transfer that water
has, which I mentioned earlier, as opposed to being out
in the air at 68 degrees, it would certainly not cause that increase in metabolic rate. The group that was at 14 degrees Celsius, meaning 57.2 degrees Fahrenheit, water for an hour experienced
a 350% increase in metabolism. So huge increases in metabolism. Now the most interesting data to me, at least in terms of mental effects of deliberate cold exposure, were that the plasma or serum
levels of norepinephrine in the blood increased 530%. These are huge increases in norepinephrine so it suggests that this
is a stressful stimulus at least neurochemically
speaking, stressful, despite the fact that
it's not super super cold, although 57.2 degrees Fahrenheit, 14 degrees Celsius it's
not a warm environment, but it's not a ultra,
ultra cold environment, but an hour is a very
long time to be in there. The subjects also
experienced a 250% increase in dopamine concentrations, which while not 530% as
it was with norepinephrine is still a very large increase in baseline levels of dopamine. And what was interesting is
that those increases in dopamine persisted for a very long
period of time afterwards, even out to two hours. And they stopped the
study after 120 minutes of getting out of the
cold, but nonetheless, these increases in norepinephrine
are huge and long lasting and these increases in dopamine are very large and long lasting. And I do believe that these
documented effects in humans explain much of the enhancement
of attention and of feelings of wellbeing and mood that
people typically experience after doing deliberate cold exposure. And the reason I say that is that if you were to go back to the episode that I did on dopamine, or you were to go back to the episode that I did with Dr. Anna Lembke
on addiction and dopamine, what you would find is
that increases in dopamine of the sort evoked by
deliberate cold exposure are actually very similar
to the kinds of increases in dopamine that are elicited
by things like nicotine or from other behaviors that are known to be
addictive and bad for us because they lead to
other effects on the brain and body that we simply don't want. And yet deliberate cold
exposure provided is done safely can create similar if not
greater increases in dopamine that are not just fleeting,
that don't just occur during, say the consumption of some
deleterious drug or activity, but that are very long lasting
and that can be leveraged toward activities other than
deliberate cold exposure. So I want to emphasize this. I'm not suggesting that people do deliberate cold
exposure for an hour a day. And unfortunately there
are not many studies yet exploring how shorter colder temperature environment exposure, say
one minute or three minutes or six minutes at 55
degrees or at 50 degrees, whether or not that leads to similar, greater or reduced levels of
dopamine in the brain and body. And yet almost everybody who
does deliberate cold exposure will say yeah, it was stressful. I didn't enjoy it, or I
eventually grew to like it, but that I always feel better afterwards and then that feeling last
a very long period of time. And I think it's almost certain that those experiences that people report relate to these increases in dopamine and in concert with the
increases in norepinephrine also explain the other effect
that's commonly reported, which is an enhancement in mental acuity and the ability to focus. Now, here we can extrapolate to the study that I discussed at the
early part of the episode, where I was talking about the use of short 15 minute exercise, kind of moderate intensity exercise and how that was shown to
increase levels of energy and mental acuity in these working memory,
visual attention tasks. And there, again, we
have to assume somewhat because they weren't doing
neurochemical measurements, but we can reasonably assume
that those improvements in cognitive performance were due at least in part to the
increase in catecholamines known to a company, moderate
intensity zone two cardio. So what you're starting
to see here is a theme. The theme is that virtually any stimulus that delivers more norepinephrine, epinephrine and dopamine to our system will sharpen our mental
acuity and elevate our mood and will do so for some period of time. Deliberate cold exposure, it turns out, is a very potent way to
increase these catecholamines, this category of chemicals
and thereby to improve mood, mental acuity and levels of alertness. And as we'll next see, it
not only has that effect, which can be very
beneficial for many people in a bunch of different circumstances, but it also has the positive
effects that many people seek in terms of metabolism, in
lowering inflammation in the body and other physiological effects as well. And forgive me, I was almost ready to move on to effects of deliberate cold exposure on metabolism and inflammation and so forth, but I neglected to point
out one of the other very interesting aspects of the study showing deliberate cold exposure can increase in
norepinephrine and dopamine, which is that they observed
no significant increases in the stress hormone cortisol and that is both surprising,
interesting, and important because what it means is
that the quality of stress that deliberate cold exposure
is creating in the body is likely to be one of
what we call use stress. Hans Selye, the great physiologist, won a Nobel Prize for
distinguishing between distress, which is stress in the brain and body that causes the release
of things like cortisol along with the other catecholamines, and that we experience as
negative happening to us and can lead to negative health outcomes. And he distinguished that from eustress, which was stress that we now understand is associated with increases
in things like norepinephrine and dopamine, but no
increases or minimal increases in cortisol, and that can lead
to positive health outcomes. So it appears that deliberate
cold exposure can create what we call or what Hans
Selye called eustress. In other words, it can create
a condition in the brain and body in which we
are stressing ourselves, we are training up resilience, and yet we are creating
a neurochemical milieu that actually has many health benefits. Now I'd like to shift our attention to the effects of deliberate
cold exposure on metabolism. And I'd like to start by detailing a study that was performed on humans and published just at
the end of last year. The title of the study is altered brown fat thermoregulation, and enhanced cold induced thermogenesis in young, healthy winter swimming men. And I should point out
that while the study was only performed on male subjects, there's no reason to
think that the effects that they discovered
would only pertain to men. I would hope that they would
also do a study on women at some point in the future, but the effects that they describe are very basic core
physiological processes. What they did is they looked
at at deliberate cold exposure in this group of young men, and they used that 11
minute threshold per week. So in other words, they had
them get into cold water for approximately 11 minutes per week. And again, that's 11
minutes total per week. They divided that into two sessions although in speaking with the
first author of this study, Dr. Susanna Søberg, I learned that it
probably is not important that it be two sessions, it could be three or even four sessions, as long as it reaches
that 11 minute threshold. What they discovered was that by going into
these cold environments, in this case cold water
immersion up to the neck, for 11 minutes total per week, that these men experienced increases in so-called brown fat thermogenesis, I'll talk more about
what that is in a moment, and increases in core body temperature that translate to increases
in core body metabolism. Now, the overall increases
in core body metabolism that they experienced
were not extremely large. They were statistically significant, but they weren't extremely large. However, the changes in brown fat stores are perhaps what's most
interesting about this study and I'll tell you why. The metabolic increases of
deliberate cold exposure are both acute meaning
happening in the short term. When you get into the cold
and immediately after, one does experience an
increase in core metabolism, you burn some calories, in other words, and while those might not be
very significant increases, or I should say they can be
statistically significant, but they are not enormously large numbers of calories burned, the longer lasting effects
of deliberate cold exposure on metabolism seem to take
place by changes that occur in the types of fat that
we store in our body and the way that that fat
impacts our metabolism at other times throughout
the 24 hour cycle. This actually has a
somewhat anecdotal basis, in particular in Scandinavia. I don't speak Swedish nor I speak Danish, nor do I speak Norwegian, but I do have Danish relatives and they were able to help me decipher a common Swedish saying, which essentially
translates to the fact that in preparation for the summer, they say, one should expose themselves
to warm environments so that one is comfortable
in warm environments in the summer. That's one half of this
traditional Swedish and also Danish saying. The other half of this
traditional Danish-Swedish saying is that in preparation for winter, in order to not feel too
cold in cold environments, one should prepare for those in the fall by not wearing a jacket
and exposing one's self to cold environments. Now, of course, this is just
anecdotal cultural lore, but it actually has a physiological basis, which is by exposing
oneself to cold environments on a repeated basis in
anticipation of exposure to more extreme cold environments, one can feel more comfortable in those extreme cold environments. And that's exactly what they observed in this study by Søberg et al. The men felt more
comfortable in extreme cold if they had trained through
deliberate cold exposure, which might not seem surprising at all, but based on what we talked about earlier, whereby deliberate cold
exposure evokes this discomfort and this experience of
norepinephrine release, at least in the short term,
then you would say, well, shouldn't that deliberate
cold exposure also make them feel uncomfortable like they really want to get out? Well, that is true in the beginning of a deliberate
cold exposure protocol, meaning in the first week
or in the second week or the third week, but what one finds and what you will find if you do deliberate cold exposure
consistently is that you will then become more comfortable
at cold temperatures away from the deliberate cold exposure. So whereas you might have
previously been the person who is always cold in the
room with air conditioning, or always seeking a sweater,
always wanting to bundle up, you will be more comfortable
in those cold environments. And the reason for that
is well substantiated from this study and from animal studies whereby deliberate cold exposure converts one particular kind of fat cell, the white fat cell, which is a very low metabolic output cell. It's basically a storage site for energy in the body fat cells to a
different type of fat cell, which is the beige fat cell called beige because it's actually
beige or slightly brown under the microscope, or
even to brown fat cells, which are very dark under
the microscope and dark because they contain mitochondria and are very metabolically
and thermogenetically active. In other words, white fat
doesn't burn many calories. It's basically a storage site. It's a bank account for energy. It's filled with lipids, and those lipids can be used
if the body needs energy and if it goes into a caloric deficit. Beige fat and brown fat
acts as sort of a furnace or the sort of fat that
you would find in a kindle, a fuel that can increase
core body temperature. So beige fat and brown fat is very good at raising our metabolism
and helps burn white fat. Now of course, it does that only in the
context of a caloric deficit, but it can actually help
create that caloric deficit. Having more beige fat and brown fat can increase your overall core
metabolism, in other words, the number of calories
that you burn per day, and therefore the number of calories that you need to either
maintain or to lose weight. The simple translation of
this is that getting into cold water for a total of
11 minutes, perhaps more, but at least 11 minutes per week divided into two or four sessions can increase your core metabolism in part by increasing your beige
and brown fat stores. And we know how that works
at least in animal models and there's now reason to suspect that the exact same mechanisms
are occurring in humans. The primary way in which
deliberate cold exposure converts white fat cells into
these more metabolically thermogenetically active
metabolism increasing beige and brown fat cells
is because norepinephrine released when we get into
the cold binds to receptors on the surface of white
fat cells and activates downstream pathways such as UCP1, so this is an uncoupling protein one, that acts on the mitochondrial
metabolism of cells and increases the mitochondrial
output of those cells and the mitochondrial
density of those cells. In other words, it takes a cell that has
a kind of a weak engine or no engine for generating energy. Although every cell has some mitochondria, it takes cells that have
very few mitochondria and increases the engine size. It kind of stokes the furnace
of those particular cells and actually can change gene
expression in those cells. So that's what's really interesting. Deliberate cold exposure causes
increases in norepinephrine. which bind to receptors on the
surfaces of white fat cells, which triggers the release
of things like UCP1. It also causes the release
of things like P-part gamma, and co-factor PGC1. I'm going to refer you to a review if you want to learn more about these. For those of you that
don't want to learn more, all you need to know is that
the downstream of all that are increases in
mitochondria and metabolism and actual genetic changes
in the white fat cells that convert them into
beige and brown fat cells. This is especially important for adults because babies and young
children actually don't have the ability to shiver or they have a less
robust capacity to shiver. Very small babies really can't shiver so they have a lot of brown
fat in order to keep them warm. Young children eventually
develop the ability to shiver and maintain these brown fat stores, mainly around the clavicles,
the heart, the upper spine, and in the upper back. And it's no coincidence that
kids can often run around with a minimal of clothing
and be comfortable in environments that
adults would be cold in. As life goes on, we tend to
lose beige and brown fat, but this mechanism that I'm referring to points to the plasticity of white fat, meaning the ability for
white fat to actually convert its identity into this
metabolically thermogenetically enhancing form of beige and brown fat. So deliberate cold
exposure is a terrific way to increase your core metabolism and oftentimes critics will say, well, the increase in metabolism
isn't that significant although I do want to point out again, the 93% and 350% increases in metabolism from that previous study. But critics then will say, well, that doesn't really translate
to that big of a caloric burn during the deliberate cold exposure. But to that, you should say, ah, but that's only limiting your optics to just a portion of the effects of deliberate cold exposure
because deliberate cold exposure can also convert white fat
to beige fat and brown fat and lead to these more lasting
increases in metabolism. So for any of you interested
in increasing your metabolism and or being comfortable
in cold environments and or being comfortable in terms of being able to combat stress mentally, deliberate cold exposure, I
do believe is a powerful tool. And there is simply no reason
why you couldn't and shouldn't use the same protocols
that I described earlier for building resilience
to increase metabolism. Provided you're hitting that
11 minute per week threshold, you ought to be stimulating
both mechanism increases in resilience and increases
in core metabolism. As I mentioned earlier, most of the detailed studies
on the conversion of white fat to beige fat and brown fat
through the use of cold have been done in animal models, but the human data are starting to emerge. And if you'd like to do the
deep dive into these mechanisms, things like UCP1, P-part gamma, et cetera, there's a beautiful review
that was published recently in the journal cell, which is one of the three apex journals, nature, science, cell. And the title of that paper
is adipose tissue plasticity in health and disease. I love this review. It has beautiful diagrams
detailing all of the pathways from cold to norepinephrine through UCP1 downstream of things like cyclic AMP. If none of those names
mean anything to you, don't worry about it. You certainly don't need
to know these mechanisms to benefit from deliberate
cold exposure protocols. If those names do mean something to you, or you are interested in
exploring the downstream effects of deliberate cold
exposure and something else that's really nice that's
covered in this paper is how deliberate cold exposure interacts with fasted states and fed states. I think you'll also find
this review very interesting. I don't want to go too
deeply into fasted states and fed states right now, suffice to say that when we are fasted, meaning when we have an eaten
for some period of time, our baseline levels of norepinephrine and epinephrine are already elevated. And so cold exposure at those times ought to have an even
greater effect on metabolism and resilience and so on. So for you fasters or your
intermittent fasters out there, if you really want to get fancy, you can do your deliberate cold exposure when you are fasted. I certainly wouldn't recommend doing it with a very full stomach in any case. And as I mentioned before on this podcast, intermittent fasting is, but one way, and certainly there are other ways to limit total caloric intake
for sake of maintaining or losing weight if that's your goal. I know many people are using and benefit from intermittent fasting, however, and so it certainly can be combined with deliberate cold exposures in order to get even greater increases in norepinephrine and epinephrine. So for those of you that
are primarily interested in using deliberate cold exposure to increase dopamine levels
in your brain and body, you can also do a combined protocol whereby you ingest
caffeine 60 to 120 minutes before the deliberate cold exposure. This is based on a study
that I've talked about before entitled caffeine increases
striatal dopamine D-2, D-3 receptor availability
in the human brain. And as the title suggests,
this study was done on humans, looking at the density and or efficacy of these dopamine receptors in an area of the brain
called the striatum, which is involved in planning in action and also suppressing planning in action. It's involved very closely
with whether or not we can engage in behavior
and withhold behavior, the so-called go and no
go ways in the brain. Dopamine plays a critical role in that and many other things
as well as you now know. So why would you want to ingest
caffeine 60 to 120 minutes before deliberate cold exposure? Well, as I talked about earlier, dopamine can increase quite substantially in response to deliberate cold exposure, but dopamine on its own
doesn't do anything, it has to bind to receptors and this paper shows quite definitively that ingesting caffeine in this case, it was 300 milligram dose of caffeine, which is about the dose of caffeine in two or three cups of coffee, it depends on the strength
of the coffee, of course, but it's not an outrageous
amount of caffeine, that increases the density and or efficacy of these receptors, which you would allow that dopamine to have its greatest effect. And for those of you that want
to get really, really fancy, I suppose you could do this fasted so you get the further
increase in norepinephrine, then you get the dopamine
increase from the cold exposure, the binding of the dopamine. Although I do want to point
out that at some point, you start layering
together enough protocols that you would to be
spending your entire day trying to get this dopamine pulse and I would hope that you
would have other activities that you would engage in, but if you're getting up in
the morning and you're fasted because you haven't eaten all night and you have a cup of coffee,
and then 60 minutes later, you take your cold shower
or two hours later, you do your cold immersion
or your cold shower, you would be layering together these different mechanisms
of dopamine receptors, epinephrine and so forth in
a way that at least to me, doesn't seem incompatible
with having some other life like going to school and having
relationships, et cetera. And this increase in dopamine, particularly in the striatum
is not a trivial one. I do want to point out as the authors do that preclinical studies have shown that increases in striatal dopamine induced by things like modafinil, which is used to treat
ADHD and treat narcolepsy, is necessary for their
wake promoting actions. What this really says is that
just having elevated levels of dopamine from a drug
or from an ice bath, or what have you is not sufficient to get the effects of dopamine, you really need the
receptors to be available and you need those
receptors to be available in the appropriate density and you need those
receptors to be available in the appropriate density in
the striatum in particular. So I think there are a
number of reasons why if it's compatible with the
other aspects of your health, cause of course always
you have to consider this on a background of cardiovascular health and blood pressure, et cetera, that ingesting a cup or two of coffee an hour before your ice
bath may be fasted as well could be quite beneficial
for increasing dopamine over quite extended periods of time. A couple of key points that
you'll want to pay attention to in thinking about deliberate
cold exposure and metabolism. In the Søberg study, they also explored the use of
sauna and how to use sauna, meaning deliberate heat
in conjunction with cold. We are going to do an entire
episode about the use of heat for health and performance. So that is not the focus now, however, it does raise an important point that we do need to address at this moment, which is if you are using sauna or if you are taking warm showers or if you are simply using
deliberate cold exposure of any kind, should you get into the heat afterward or before or not at all? And this is where we can
point to the so-called Søberg principle, at least I
call it the Søberg principle, the Søberg principle named after
first author of this study, I referred to earlier, Dr. Susanna Søberg. In science, it is appropriate
to take a key piece of data and call it a principle if in fact it translates
to something larger, which I believe it does. It is generally not appropriate for people to name a principle after themselves although there are a few
scientists that have done that. So I have named it the Søberg principle, but I did that to give
it appropriate credit to Dr. Susanna Søberg, who discovered that and pointed
out quite appropriately, that to achieve the greatest
increases in metabolism through deliberate cold exposure, you want to force yourself
to reheat on your own after the deliberate cold exposure, meaning you wouldn't want
to go from the cold shower to a hot shower or from
the cold shower to a sauna. Rather if you were going
to start with a hot shower or you're going to start with a sauna that you would end with the cold, and then you would reheat naturally. Now I personally take a cold
shower a few times a week or do cold immersion and because I'm not specifically focused on increasing metabolism,
although I probably should be, that's not what I'm using it for now, I will take a hot shower
afterwards and in doing so, I'm short circuiting some of the further metabolic
increases that I would achieve were I to just end with the cold. So the Søberg principle is if you want to increase your
metabolism, end with cold, and we can take this
a step further and say that if you want to use
deliberate cold exposure to increase metabolism,
that you should make sure that you get to the
point where you shiver. And the reason in for
this is that there are a series of studies, but in particular, one study published in the journal Nature, excellent journal in the year 2018, showing that deliberate cold
exposure that evokes shivering from the muscles causes
the release of a molecule called succinate from the muscles and that succinate plays a key role in activating
brown fat thermogenesis, which you now have heard
about and understand as critical to the increases in metabolism caused by deliberate cold exposure. So what this means is if you want to increase your metabolism, end on cold, that's a Søberg principle
and as best you can, try and get to the point
where you are shivering either when you are in the cold exposure or immediately afterwards. Now one efficient way to do
this is to, for instance, you could get into the
cold shower for a minute or two minutes or three
minutes, uncomfortably cold, but safe to stay in. Remember that's our general rule of thumb. Then turn off the water and stand there, make sure that you're not holding yourself close to your body, you're not hugging yourself
to try and keep yourself warm, but rather your limbs are
extended at your sides. And then if that fails to induce shiver than to turn on the cold water again, and then turn it off again, so alternating perhaps a
minute to three minutes of cold exposure followed
by a minute to three minutes of drying out in air and going back into the
cold exposure, et cetera. I can tell you this from experience, this is a pretty brutal protocol. If you have never tried
getting into an ice bath or cold water immersion
or shower for one minute and then getting out and
trying to stand there with your arms extended in cool
or cold air for one minute, and then getting back into the cold shower or water immersion, you are
in for an experience because even for those of you that
are pretty shiver resistant, you'll find that it is much, much harder to get out of that cold water
and stand there arms extended and drying off by evaporation, which further draws heat from the body than it is to wrap yourself in a towel, get in a warm shower or a sauna. So there's certainly no
requirement to end on cold. There's certainly no
requirement to induce shiver, but if your primary goal is to induce increases in metabolism, both in the short term
and in the long term, following the cold exposure, well then you'll want to end on cold and you'll want to find a way to shiver provided that the level of cold that you're exposing yourself to is still safe for you overall. So up until now, I've been talking about
deliberate cold exposure as a potent stimulus for the
release of norepinephrine in the brain and body and indeed it is, but the way I've been describing
it has been in the context of circulating plasma
levels of norepinephrine, meaning circulating within the blood. What I haven't mentioned, but is absolutely true is
that the fat cells themselves actually receive input from neurons. So there are neurons that
release norepinephrine in response to cold,
directly into the fat. So I want to give you this
picture of how the architecture of all this works, because I think it can help you navigate and indeed build better deliberate
cold exposure protocols. Your adrenal glands release
norepinephrine and epinephrine. Your brain has sites within
it like the locus coeruleus that release norepinephrine
and epinephrine, but there are also neurons
within your skin that sense cold and other neurons that can
directly release norepinephrine into the fat stores and
cause those white fat cells to convert to beige and brown fat. And I think this particular
aspect of our physiology is often overlooked in studies. And when people say, oh, well the increases in
metabolism aren't that great, the circulating levels of norepinephrine, those are very large, but
they're very transient and so on, that fails to understand that neurons that actually sense cold are
in a position to communicate via other neurons
directly to the fat cells and release norepinephrine
into those fat cells, which as I pointed out earlier, set off a huge set of immediate and long term cascades of
even gene expression changes. So the picture that I'd like
you to have in your mind is that when you get into the cold, yes, of course you experience
that as a experience of I don't want to do this,
I'm going to overcome this, I'm going to climb over these mental walls that represent adrenaline
release in my brain and body, but also that your fat
cells are receiving signals, norepinephrine signals that
are changing those fat cells and the way that they metabolize energy. Now I'd like to shift
our attention to the use of deliberate cold exposure for sake of physical performance. And there are a lot of opinions out there about the use of deliberate cold, whether or not it should
be done for instance, before or after exercise, whether or not if done immediately
after strength training or hypertrophy training, meaning training designed to grow muscles or make them stronger, whether or not it can inhibit that process and so on and so forth. I think today in looking
over the literature and trying to bring forward the simplest and most straightforward, and yet scientifically grounded protocols, we can set up some general
guidelines that will allow most, if not, all of you to
still extract the benefits of deliberate cold exposure
on physical performance without getting too neurotic
about the exact timing, but for sake of discussion and because it's a prominent theme in many online communities, let's just start with
the big one out there, meaning the question of whether
or not doing an ice bath or doing deliberate cold
exposure or taking a cold shower after strength slash hypertrophy training, meaning training designed
to increase strength and or I should say the size of muscles will somehow short circuit
or diminish that process, whether or not it will reduce or eliminate those strength gains
and hypertrophy gains. And the short answer that
I was able to arrive at on the basis of a review
article that I'll talk about in a moment and some
other studies as well, is that if your main goal
is hypertrophy and strength, it is probably best to
avoid cold water immersion and ice bath immersion in the four hours immediately following that strength and or hypertrophy training. Again, if your main goal
is to achieve hypertrophy or strength or some combination of those, probably best to avoid cold
water immersion up to the neck or ice bath immersion up to the neck immediately after strength
and hypertrophy training and extending out to about
four hours after that training. If you're really neurotic about this, then perhaps you'd want to
move the cold water exposure to a different day entirely, but it all depends on how
neurotically attached you are to getting every last bit
of strength and hypertrophy. And if that's your goal, terrific, well then probably moving
the cold exposure four hours or more away from that training is going to be necessary for you. Now you'll notice I did
not talk about cold showers and the reason I did not
talk about cold showers is that there simply are
not very many studies of deliberate cold exposure
through cold showers for the reasons I talked about at the beginning of the episode. It's hard for me to imagine
that taking a brief cold shower after a strength or
hypertrophy training session would completely reverse or
short circuit the effects of that strength and hypertrophy training. But again, if you're neurotically attached to getting every last bit
of strength and hypertrophy out of your training
sessions, then by all means, err on the side of caution
and wait four hours or more to do your cold shower just
as you would wait four hours or more to do your cold water immersion. Now there are nice data
pointing to the fact that doing cold water
immersion after a hard run, so endurance training, or even sprint and interval training or after a weight workout
where your main focus is on performance of those movements or after a skill training workout where your main focus on
performance of those movements, that there's no reason to think that that cold water immersion or
ice bath or cold shower would inhibit the progress or the stimulus that would lead to progress that occurred during
that training session. In other words, I don't see any reason based on the literature to
avoid deliberate cold exposure immediately after training, again unless your goal is
hypertrophy and strength. And in fact, there's a very nice
review recently published on deliberate cold exposure and how it can impact
physical performance, whether or not it's done before or after, different types of training and so forth. The paper is entitled impact
of cold water immersion compared with passive recovery, following a single about
of strenuous exercise on athletic performance in
physically active participants, a systematic review with
meta-analysis and meta regression. So this is a meta-analysis of 52 studies that looked at a tremendous
number of variables and contexts, as you would
expect in a meta-analysis of 52 studies. I'm going to read you the
conclusions of the study and I will provide a link. We certainly don't have
the time to go through all the details of the study. I will highlight a few specific outcomes that I found particularly interesting, but here I am paraphrasing
their conclusions, that cold water immersion, I
want to emphasize immersion, not cold showers, but cold water immersion they say was an effective recovery tool after high intensity exercise. They observed positive outcomes, meaning improvements in certain variables, for muscular power, muscular soreness, meaning reduced muscular soreness, increased muscular power, perceived recovery after
24 hours of exercise. However, there were
certain forms of exercise that were not benefited
by cold water immersion, such as eccentric exercise, exercise focusing only
on the lowering component or the so-called eccentric
component of resistance exercise. They saw some very entry
dose response relationships for things like endurance
training, meaning the longer the cold exposure post-endurance training, the more improvement in
endurance performance, reductions in circulating creatine kinases and things that relate to muscle damage under certain conditions. At some point in the future, by the way, we'll do an entire episode on
creatine and creatine kinase, which are important not
just for muscular function, but also for brain function. But the basic takeaway was
that cold water immersion performed after high intensity exercise was beneficial from a number
of different standpoints and indicated that shorter duration, cold exposure and lower temperatures can improve the efficacy
of cold water exposure if used after high intensity exercise. There I'm directly pulling
from their conclusions. So what this says is
that it's not just those longer duration, 30, 45
minute and 60 minute protocols of cold water immersion
that we discussed earlier, but also shorter duration
of one minute, three minute, five minute exposures
to lower temperatures. Temperatures that would
make you psychologically want to get out as soon
as you possibly can, but again that you can safely stay in done after training
really have been shown to improve outcomes in terms
of reducing soreness and improving training efficacy, meaning your ability to get
back into training more quickly and thereby deliver more training stimuli to a given muscle or in your
endurance training protocol. Translate to English, what this means is that taking
a cold shower or getting into an ice bath or some other
form of cold water immersion within the immediate minutes
or even the immediate hours following your training has
been shown to be beneficial. I'm sure a number of you
have questions for instance, how long should you be
in that cold exposure? Is it the same as the 11 minute
threshold described earlier? To be honest with you, there are not enough
studies to really point to the critical threshold for eliminating or reducing delayed onset muscle soreness or for getting maximal results from power and endurance training, but this study does make
a couple of key points and here I will just paraphrase. For instance, that cold water immersion is more likely to positively influence muscular power performance, to reduce muscle soreness, to
reduce serum creatine kinase, and to improve perceived recovery after high intensity exercise, as compared with passive recovery. This can be translated to cold
water exposure after training is beneficial and probably better than passive recovery from
a number of standpoints. In addition, they say that
dose response relationships meaning the amount and the degree of cold that people were exposed to
and how often they did that in particular in lower
temperature cold immersion. So these would be the sorts
of cold immersion protocols that are one minute or two
minutes, three minutes, maybe five minutes, but that one couldn't stay in there longer because it feels stressful and one wants to get out. Maybe more effective after
high intensity exercise for removal of serum creatine kinase as well that these shorter duration cold water immersion approaches
may be more effective after high intensity
endurance performance as well. So all of this can be
translated to say that unless your main goal is
hypertrophy and strength, that cold exposure, ideally cold immersion and cold water ice bath, but if you don't have access to that, then cold showers is likely
going to be beneficial if done immediately
after or in the minutes or hours after your training, especially high intensity training. One particularly nice thing
about this meta-analysis is that it included some studies that involve the use of cooling packs. So again, vests that can
essentially ice packs and indeed even cryotherapy
chambers and so on. There's a nice table in the study if you want to get really detailed and go and look specifically at those studies, I invite you to do that. We'll put a link to this
study in the caption for this episode, but all in all, what this study shows is
that deliberate cold exposure can be very useful for recovery
likely through reductions in inflammation, in muscle
and connective tissue. And while this study did
not look specifically at the mechanisms of reduced inflammation caused by deliberate cold exposure, those mechanisms are somewhat known. There are a number of studies
that have pointed to the fact that deliberate cold and cold generally can reduce inflammatory cytokines, such as IL-6, interleukin six. It can increase
anti-inflammatory cytokines such as interleukin 10 and so on. Without getting into all those details, I think it's sufficient to say that if you are somebody who experiences a lot of delayed onset muscle soreness, taking a cold shower after your training or getting into a cold
immersion after your training, even if it's a few hours
later ought to help. And if you are doing
particularly intense training, then you probably want
to ratchet up the number of cold exposure sessions
that you're doing even if those have to
be done on separate days from your training, because a lot of the
inflammatory effects of training, endurance and strength
training are actually occurring some hours away from
the training stimulus. So it's not just that inflammation goes up radically during training,
which it often can, but that it can occur even in the days and even weeks afterwards, depending how intense
and how long duration that training is. So deliberate cold
exposure is very powerful as an anti-inflammatory tool. Now I'd like to emphasize
the topic that we touched on at the beginning of the episode, which are those glabrous skin surfaces, the hands, the upper face, and the bottoms of the
feet through which heat is especially good at leaving the body. And another way of putting
that is that one can cool the body much more efficiently through the glabrous skin surfaces. Now, if you want to
understand all of the science behind this and all of
the various applications, I invite you to please
listen to the episode that I did with Dr. Craig Heller, again, in the biology department at Stanford. For sake of this episode, I'm just going to detail
a couple of findings from his laboratory. The first one, dealing with
exercise induced hyperthermia, because I think this is very interesting and it can even save lives if you understand the way this works. There's a particular paper
that focuses on this, and we will put a link to this as well. The title of this paper
is novel application of chemical cold packs for treatment of exercise induced hyperthermia, a randomized control trial. This is a pretty brutal study, brutal for the subjects that is. This study involved was having
subjects walk on a treadmill at a pretty significant
incline and anywhere from nine to 17% wearing a
substantial amount of clothing that was not well ventilated and the room was kept
to 40 degrees Celsius, which is 104 degrees Fahrenheit. This is definitely not
something to do at home. This study was designed
to induce hyperthermia, which as I mentioned earlier,
can be quite dangerous. And they compared two types of cooling. In the first form of cooling that they call traditional cooling, they had ice packs on their neck, in their armpits and in their groin. And in the other group, there was the so-called
glabrous skin cooling. So the palms, the soles of the feet, which were actually so they
were cooling inside the boots or inside of gloves and on
the upper portion of the face. And the basic takeaway of this study is that by cooling the glabrous skin, the subjects were able
to sustain this walking on these inclined
treadmills for much longer than were the people who
received traditional cooling. And also the return to
baseline temperature was much faster in the
glabrous skin cooling group. So how this translates to the real world is that if ever you are hyperthermic or someone else's hyperthermic, one way to cool them
down quickly is to cool these palmer glabrous,
soles of the feet glabrous and upper portion of the face
glabrous portions of the body using cool rags, using ice
packs or using any number of different cold objects or temperatures. One key thing, if you're going
to use glabrous skin cooling, is that whatever you use
to cool those surfaces cannot be so cold that it
causes vasoconstriction. Because as I mentioned earlier, the arterio-venous anastomoses these portals of arteries
directly to veins that exist only in these
glabrous skin surfaces, the way that they're able to cool the body and essentially pass cool into the body although that's not
really what they're doing, they're actually extracting
heat from the body to be technical, they're
extracting heat from the body, the only way they can do
that is if those veins don't collapse and veins will collapse if they are made very, very cold. So if you want to use
glabrous skin cooling to offset hyperthermia or for the other forms of performance, which we'll talk about in a moment, you need to use a cool object or surface that is not so cold that
it causes vasoconstriction. And this can be a little
bit tough to dial in, meaning it can be tough to
identify such an object. And for that reason, Dr. Heller and some of his
colleagues have developed a commercial product called the CoolMitt. You can actually go to
their website, coolmitt.com. I don't have any financial or
other relationship to them. I know they've been
developing this technology for some period of time. It involves a glove that
you put your hand into, it circulates water of a given
temperature and it does so, and does so at a tempera
or that is sure to not cause vasoconstriction of the palm. And you may be asking, how can you just put
your hand into one glove and have this work? Well, that's how powerful these
glabrous skin surfaces are. Even just by cooling one palm, the core body temperature drops radically. Now that's their commercial technology. I know that some people out
there have started to experiment with a home version of this, which would be taking
a package for instance of frozen blueberries
or some other cold drink or cold metal object, and
actually bringing it into the gym or out on a run. There are even people
who are now developing cooled psych bicycle
handles for long rides. This might seem a little
kooky or crazy to you, but as you'll soon hear in the study I'm about to describe,
the increases in endurance and in the volume of strength training that people can conduct
if they appropriately cool their body through these
glabrous skin portals is actually quite significant. So again, as it relates to hyperthermia, if someone is overheating by all means, try and get them out of that heat, get them to stop exercising,
you can die from hyperthermia, try and cool the bottoms of the feet, the palms of their hands and the upper portion of their face. That does not mean it would be a bad idea to put cold water on
the top of their head. That probably would also help
and perhaps on their neck. What is probably not going
to be a good idea is to do the more standard thing of
draping someone in cold towels on the surface of their
body because as I mentioned, the beginning of the episode, that thermostat in the hypothalamus, the medial preoptic area
will typically react to that by increasing core body
temperature further. The effects of glabrous skin
cooling on physical performance are truly remarkable provided the glabrous skin
cooling is done correctly. And I want to point out that
the main degree of effect is on volume or the
ability to do more work. And I want to point this out
because I think that many people, certainly in the exercise
science community, but even in the general public, when they hear about some of these effects that are measured in the laboratory, they sort of look at those
effects a bit of scans and they think, well, that's not possible. Effects for instance,
that have been documented showing doubling or tripling
of the number of dips that one can do in a
relatively short amount of time or doubling of the number
of pullups one can do or 14% increases in strength
or even comparable degrees in increase in weight training output to people who are on
performance enhancing drugs, et cetera, et cetera. Part of the confusion is that the effects of proper palmer cooling, because it almost always
is done by palmer cooling and less often in these experiments by cooling of the bottoms of the feet and the upper portion of the face, but those effects tend to be
the ability to do more work over time and just to illustrate
some of the major effects that the Heller lab is seen and they are document
entered in this manuscript that I'll share with you in a moment. The typical protocol is
to have people come in and do some endurance training so running on a treadmill
and to have a condition where one group is actually doing palmer cooling while they are on a bike or on a treadmill and inevitably the outcome is
that they can do more work. They can pedal further at a given speed, or they can run longer at
a given speed than people who are not doing palmer cooling or who are receiving cooling by way of cold compress to the back
of the neck or ice pack to the armpits, et cetera. So the effects of palmer
cooling are very clear and very robust. And in the context of endurance exercise almost always allow
people to do more work, to go longer with less perceived
effort and to quit later so to speak. In terms of strength training, they've looked at the capacity
to perform sets of dips. So one of the more famous examples of this that Dr. Heller shares in the
episode that we did earlier, and that you can find at
hubermanlab.com involves someone coming in and doing
sets of dips, maybe 40 dips. This person actually could do
40 dips on their first set, then resting for a period
of two to three minutes and then doing 35 and then resting for a period
of two or three minutes, and then doing progressively
fewer and fewer and fewer to the point where over a period of time, they add up the total number
of dips that they can do and then they have them come back after a period of recovery,
so not immediately after, but take a couple of days, come back and do effectively
the same protocol, but during their rest periods, they're doing two minutes
of palmer cooling, which essentially allows
heat to move out of the body, lowering core body
temperature in other words. And what they find is that
they see enormous increases in the total number of
dips that people can do, but that doesn't mean that the person goes from being able to do 40 dips, to being able to do 50 dips
or 60 dips on that first set, what it means is they are able
to do 40 on the first set, then 40 on the second, then 38 on the third
and so on and so forth so that the total duration
of the workout is extended and yet they're doing much more work, even though it takes more time. So that's an important point and I think a point that
perhaps wasn't as clear or as clearly made by me
in the previous episodes that discuss this topic. For those of you that are interested in exploring palmer cooling, first of all, I recommend taking a brief
glance or even a deep dive into this study, which is entitled work volume and strength training
responses to resistive exercise improve with periodic heat
extraction from the palm. In this study, they describe
big increases in anaerobic, meaning strength training output, things like improvement in dips, improvement in bench press, improvement in pull-ups, et
cetera, in human subjects. And it's a really nice study and points to some of the protocols
that you might be able to adapt in your own setup. For instance, over six
weeks of pull up training, palm cooling in between sets
improved volume by 144%, and this was in experienced subjects. So that's interesting
because a lot of studies of strength training and
improvements in hypertrophy and strength are done in
inexperienced untrained athletes, which changes the picture somewhat compared to experienced athletes. They found that strength, meaning the one repetition maximum, increased 22% over 10 weeks
in bench press training. And they point to the
particularly strong effects of using palmer cooling
when people reach plateaus in endurance and strength training. And there, I think it's
an important point. I think that if you're going
to explore palmer cooling, it's probably not the sort of
thing that you're going to do in every run or in every about of cycling or in every strength training session, but that it might be used to
vastly increase your volume or vastly increase your endurance in a given session or a set of sessions in order to push through plateaus. A particularly interesting
point in light of that is Dr. Heller has observed again and again that palmer cooling reduces
delayed onset muscle soreness, or it can eliminate it entirely. And that's very interest because
it also points to the fact that reducing core body
temperature may somehow be involved in short circuiting the normal mechanisms of
delayed onset muscle soreness. And you might say, well, how would temperature be involved in delayed onset muscle soreness? Well, I want to refer you
back to the meta-analysis that we talked about earlier,
where the short duration, very cold temperature exposure
after training did indeed reduce delayed onset muscle soreness in part through reduction,
excuse me, in creatine kinase. So it's not inconceivable that temperature and delayed onset muscle
soreness are related. And that raises perhaps
the most important point, which is the way that palmer
cooling can improve performance by way of reducing core
body temperature is known and that is because when
one engages in exercise or muscular output of any kind, strength or endurance exercise, the range of temperatures under
which a muscle can perform is actually very narrow. There's an enzyme called pyruvate kinase, which is critical to muscle contractions and pyruvate kinase can only function in a very narrow range of temperatures. If that temperature gets too hot, meaning if the muscle heats up locally, whether or not by running or cycling or swimming or weightlifting, the ability for that muscle to continue to contract is reduced and eventually is short circuited completely. And I think this is a much underexplored or at least a much under discussed aspect of so-called muscular
failure or the failure of one to continue to endure in running. So for instance, when you run as compared to
a bench press or something, you don't stop running because you can't actually
contract the muscles further, but somehow signals about the heating up of muscular tissue are
conveyed to the brain. There's a crosstalk there, it's probably bidirectional
and people stop, they quit. This is the quitting reflex. In strength training, one can
no longer perform a repetition or set of repetitions in part because of heating up
of the muscle locally. There are other mechanisms
as well, of course, and I realize that, but what's very clear from the
palmer cooling work is that by simply holding onto a cool object, remember not an object so cold that it constricts the
vessels of the palms or constricts the vessels
on the bottoms of the feet, but by holding onto a
relatively cool object in one or both hands in between
sets for two minutes or so, you can very efficiently reduce
your core body temperature and in doing so, reduce the
temperature of the muscles that are doing the work, increase the capacity for pyruvate kinase to continue to allow
your muscles to contract and thereby allow you to
do more volume of endurance and strength training. So a simple protocol that
Dr. Heller passed to me is find a relatively cool object. So you could, for instance, fill two bottles with cold water, maybe put a few ice cubes in there. This is not exact because
we're not talking about the commercial CoolMitt product here, we're talking about an at home version or use a pack of frozen
blueberries or broccoli sort of pack of those
as what he described. And then in between sets to put your hands and ideally you'd put
the bottoms of your feet, but that's not always
feasible in most gyms where they won't let you take
off your shoes and so forth, but to put the palms of your
hands on that cool surface for a minute or two minutes between sets and then returning to your sets of work. Now, if you are heating up
through other mechanisms like you're wearing a stocking cap and you're in a very warm environment, this might not have as potent effect as if you were to do this cooling in a more moderate environment, wearing lighter clothing, et cetera. So by all means warm
up to do your exercise, lubricate your joints, and get into a place where you're
not going to injure yourself, doing whatever form of exercise you do. But then if you'd like to
explore palmer cooling, I know a number of people
who've written to me saying they heard about palmer cooling on the episode with Dr. Heller. They've tried this and they
see quite excellent results. It does take some discipline. It's one thing to just
kind of hang out in the gym and play on your phone in between sets. It's another to do deliberate
cooling with your palms or the bottom of your feet or the upper portion of your face. You might get some weird looks, but of course you'll be the one doing significantly more volume, not experiencing delayed onset
muscle soreness and achieving better endurance and strength gains were you to do this properly. Now as a final topic related to the use of deliberate cold exposure
for improving health and performance, I'd like
to touch on this theme that exists online, on social media, on YouTube and in various
fitness communities of using deliberate cold
exposure to the groin, in particular to the testicles, in order to try and increase testosterone. And while this might sound really kooky, indeed this practice exists. Indeed if you were to go onto Amazon, there are actually ice pack underwear that are being marketed for
sake of increasing testosterone. Now, I am not aware of any
specific well-controlled studies that show that this indeed works. I can imagine based on what I
know about the nervous system, testosterone and cold, et cetera, that there are a couple of mechanisms by which one might experience
increases in testosterone as a consequence of
deliberate cold exposure. First off, let me say
there is no reason why you would have to apply these ice packs in the way that I just described. One could of course take a cold shower. One could of course use cold
immersion of various kinds, and you're still going
to get that exposure of the groin and the testicles to cold. Now I should point out
that people do report at least anecdotally
increases in testosterone as a consequence of this practice and I have to imagine that they are measuring
their serum testosterone, that they're not just guessing that their testosterone went up. If you know of a study
exploring this directly, please let me know, put in the
comment section on YouTube, or even just email me. We have a email that you can
find it, hubermanlab.com. Please email me the reference. I wasn't able to find a reference, but I can imagine two
reasonably plausible mechanisms by which deliberate cold
exposure to the groin, in particular the testicles,
would increase testosterone. The first is somewhat direct, which is that anytime
you cool a body surface, that if it's cold enough, you're going to get vasoconstriction. And then subsequently you're going to get a rebound increase in vasodilation, meaning you're going to constrict the blood vessels in that area. And then after the cold is removed, there's going to be more
blood flow to that area. And of course, blood flow relates to organ health and tissue health generally. So perfusion of that region
and the gonads to be specific with additional blood, you could imagine in some
ways increasing testosterone, that's reasonably plausible. The other probably more likely mechanism relates to the dopamine
increases caused by cold exposure that we talked about earlier. Again, anytime you have a
somewhat stressful stimulus, but in particular with cold exposure, it seems that the catecholamines, norepinephrine, epinephrine
and dopamine all increase and dopamine is known to be in the pathway that can stimulate testosterone. And so while there isn't
a direct relationship between dopamine stimulating testosterone, there is an interesting
pathway way whereby dopamine increases can trigger increases in things like luteinizing hormone, which can trigger
increases in testosterone as well as estrogen for that matter. So I know that there are
a lot of people out there that are interested in
the use of cold exposure for increasing testosterone. And some of those people
in communities are indeed using cold exposure
directly on the gonads, on the testees in order to do this. I'm not certain that that
direct contact is necessary. And in some cases it might
actually be quite dangerous or you at least should be
careful in terms of tissues there and avoiding damage. But nonetheless, I think
that a dopamine impact on testosterone is very likely
given the 250% increases in dopamine that have been observed with cold water immersion and
all of that points to the fact that cold water immersion very likely increases testosterone, but as a downstream consequence of the cold water immersion
effects on dopamine and luteinizing hormone, and again there's no reason
to think that the increases in luteinizing hormone would
also increase estrogen. Probably not to dangerous or levels that one would want to avoid, but I don't think that there's anything particularly specific about cold for inducing testosterone
and not other hormones. I think it's very likely to increases a number of different hormones. I do hope that there will be
a systematic study on this in the not too distant future. I also hope to not be a subject in the cooling of the gonads experiment. Now I promise you the last
topic was the last topic, but there's one other
really important point that I think everyone should be aware of if you're going to use
deliberate cold exposure. And that brings us back
to the very first thing that we discussed today, along the lines of
deliberate cold exposure, which is that your baseline temperature is going to be lowest about
two hours before you wake up, it's going to increase in the morning and as you wake up and increase throughout
the day and afternoon, and then start to drop in the
evening and come down at night as you head to sleep. I also want you to remember
that if you are to cool the external portion of your
body, in particular your torso, the net effect of that is
going to be an increase in body temperature. So for many people, not
all, but for many people, if you are going to do
deliberate cold exposure, you are going to increase
your core body temperature and that makes sense if you think about how
deliberate cold exposure can increase metabolism by
increasing thermogenesis. What that all means is
that if you are doing your deliberate cold
exposure early in the day, you are going to get
yet a further increase in core body temperature that would be associated with wakefulness, your ability to be alert that morning or throughout the day and so on. It also means that if you do
your deliberate cold exposure very late in the evening, or at night, so 6:00 PM, 7:00 PM, 9:00 PM and so on, you are going to increase
your core body temperature and if you recall, a decrease in core body temperature of one to three degrees
is not just beneficial, but is necessary in order
to get into deep sleep and remain in deep sleep. So the takeaway from this
is deliberate cold exposure done properly will increase
your core body temperature and make you feel more alert. So if you're doing it early in the day, that's probably terrific given that most of us want
to be alert during the day. However, if you do it too late
in the day, evening or night, it can disrupt sleep by way of disrupting your core body temperature. Now, the caveat to that is I myself tend to do deliberate cold
exposure early in the day. Maybe not first thing in the
morning, but mid morning, maybe as late as three
or four in the afternoon in some cases. In the longer days of summer,
I might do it even later, five or 6:00 PM and have
no trouble sleeping. I have done deliberate cold
exposure very late at night, 10:00 PM, 11:00 PM and so on as part of a 30 day challenge of doing deliberate cold
exposure every day for 30 days and I got sloppy with my timing and then in order to not miss a day, I would do it at 11 o'clock at night. And I must say I found that I could still
fall asleep very easily, even doing deliberate cold
exposure very late at night. However, on those particular
days, I was particularly busy and so I was particularly
exhausted when I arrived at the deliberate cold exposure and I had no trouble falling asleep after doing deliberate cold exposure, and then taking a nice warm
shower and then going to sleep. But I could imagine that
because of the increases in core body temperature caused
by deliberate cold exposure, that were one to do that
too late in the day, evening or night that it could
indeed disrupt your sleep. So my recommendation would be for most people only do
deliberate cold exposure if you are prepared to be
fairly alert for the next one to four or maybe had been six hours following that deliberate cold exposure. So for today's episode, as is the case with most episodes of the Huberman Lab Podcast,
I covered a lot of material. We talked about mechanisms
of catecholamines and stress and pulsatile release of
epinephrine, metabolism, mental effects, performance,
glabrous skin cooling and on and on and on. And while the goal of course
is to make sure that everyone arrives at specific, very clear mechanistic
and actionable protocols, I do realize that it is an
immense amount of information. And for that reason, I've created a list of deliberate
cold exposure protocols aimed at improving mental
toughness and resilience, mood, performance, metabolism,
reducing inflammation, and so on and so forth. All of those have been
condensed into succinct form and can be found at the Huberman Lab Neural Network Newsletter. This is a monthly or
semi-monthly newsletter that we release that includes takeaways from
the podcast and protocols. You can access those
as protocols zero cost by simply going to hubermanlab.com, signing up for the neural
network newsletter. It's very easy to do, you
just supply your email and you will receive the newsletter. We do not share your
email with anybody else. In fact, we have our
privacy policy laid out on the hubermanlab.com website so you can find that
there and the protocols that I've designed should
make it very straightforward for you to create a set of protocols that you could use with cold
showers, with cold immersion, with or without ice in
combination with exercise specifically for one goal or another, or to accomplish multiple
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