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 find
the minimum threshold of stimulus
that will allow you to derive 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
and 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 mediating 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 age students,
and they had two groups.
One group did 15 minutes of jogging at moderate intensity.
So when 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 minutes 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.
And 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 the 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
So 1, 2, 3, 4, 5, 6, 7, 8, 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 a 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 feeling, 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 this would be writing, arithmetic,
basically cognitive work of any kind,
15 minutes of moderate exercise done prior to that work bout
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 bout,
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’ve 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 can 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 bout.
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 bout,
engage in the cognitive work or learning bout,
and then mindfulness meditation, NSDR and so forth
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 attentional control and perceptual speed,
testing the mediating role of feelings 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.
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.
Athletic Greens is an all-in-one
vitamin mineral probiotic drink.
I’ve been taking Athletic Greens since 2012.
So I’m delighted that they’re sponsoring the podcast.
The reason I started taking Athletic Greens
and the reason I still take Athletic Greens
once or twice a day is that it helps me cover
all of my basic nutritional needs.
It makes up for any deficiencies that I might have.
In addition, it has probiotics,
which are vital for microbiome health.
I’ve done a couple of episodes now
on the so-called gut microbiome
and the ways in which the microbiome interacts
with your immune system, with your brain to regulate mood,
and essentially with every biological system
relevant to health throughout your brain and body.
With Athletic Greens, I get the vitamins I need,
the minerals I need, and the probiotics
to support my microbiome.
If you’d like to try Athletic Greens,
you can go to athleticgreens.com slash Huberman
and claim a special offer.
They’ll give you five free travel packs
plus a year supply of vitamin D3 K2.
There are a ton of data now showing that vitamin D3
is essential for various aspects
of our brain and body health.
Even if we’re getting a lot of sunshine,
many of us are still deficient in vitamin D3.
And K2 is also important because it regulates things
like cardiovascular function, calcium in the body,
and so on.
Again, go to athleticgreens.com slash Huberman
to claim the special offer of the five free travel packs
and the year supply of vitamin D3 K2.
Today’s episode is also brought to us by Element.
Element is an electrolyte drink that has everything
you need and nothing you don’t.
That means the exact ratios of electrolytes are an element,
and those are sodium, magnesium, and potassium,
but it has no sugar.
I’ve talked many times before on this podcast
about the key role of hydration and electrolytes
for nerve cell function, neuron function,
as well as the function of all the cells
and all the tissues and organ systems of the body.
If we have sodium, magnesium, and potassium
present in the proper ratios,
all of those cells function properly,
and all our bodily systems can be optimized.
If the electrolytes are not present and if hydration is low,
we simply can’t think as well as we would otherwise,
our mood is off, hormone systems go off,
our ability to get into physical action,
to engage in endurance and strength,
and all sorts of other things is diminished.
So with Element, you can make sure that you’re staying
on top of your hydration and that you’re getting
the proper ratios of electrolytes.
If you’d like to try Element, you can go to drinkelement,
that’s element.com slash Huberman,
and you’ll get a free Element sample pack
with your purchase.
They’re all delicious.
So again, if you want to try Element,
you can go to elementlmnt.com slash Huberman.
Today’s episode is also brought to us by Thesis.
Thesis makes what are called nootropics,
which means smart drugs.
Now, to be honest, I am not a fan of the term nootropics.
I don’t believe in smart drugs in the sense that
I don’t believe that there’s any one substance
or collection of substances that can make us smarter.
I do believe based on science, however,
that there are particular neural circuits
and brain functions that allow us to be more focused,
more alert, access creativity, be more motivated, et cetera.
That’s just the way that the brain works,
different neural circuits for different brain states.
Thesis understands this.
And as far as I know, they’re the first nootropics company
to create targeted nootropics for specific outcomes.
I’ve been using Thesis for more than six months now,
and I can confidently say that their nootropics
have been a total game changer.
My go-to formula is the clarity formula,
or sometimes I’ll use their energy formula before training.
To get your own personalized nootropic starter kit,
go online to takethesis.com slash Huberman,
take a three-minute quiz,
and Thesis will send you four different formulas
to try in your first month.
That’s takethesis.com slash Huberman,
and use the code Huberman at checkout
for 10% off your first order.
I’m pleased to announce that the Huberman Lab Podcast
is now partnered with Momentus Supplements.
We partnered with Momentus for several important reasons.
First of all, they ship internationally
because we know that many of you are located
outside of the United States.
Second of all, and perhaps most important,
the quality of their supplements is second to none,
both in terms of purity and precision
of the amounts of the ingredients.
Third, we’ve really emphasized supplements
that are single ingredient supplements,
and that are supplied in dosages
that allow you to build a supplementation protocol
that’s optimized for cost,
that’s optimized for effectiveness,
and that you can add things and remove things
from your protocol in a way
that’s really systematic and scientific.
If you’d like to see the supplements
that we partner with Momentus on,
you can go to livemomentus.com slash Huberman.
There you’ll see those supplements,
and just keep in mind that we are constantly expanding
the library of supplements available through Momentus
on a regular basis.
Again, that’s livemomentus.com slash Huberman.
Okay, 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 on 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 superimposed 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.
Okay, so if you normally wake up around 6 a.m.,
your temperature minimum is probably about 4 a.m.
If you normally wake up at about 7 a.m.,
your temperature minimum is probably about 5 a.m.
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 are going to awake,
your temperature is rising slightly.
And then at the point where you wake up,
your temperature starts to go up more sharply
and will continue to go up into the early
and sometimes even into the late afternoon.
And then sometime in the late afternoon and evening,
your temperature will start to decline.
And indeed, as you approach sleep,
your body temperature will drop
by anywhere from one to three degrees.
And in fact, that decrease in core body temperature
is important, if not essential,
for getting into and staying in deep sleep.
Okay, so temperature rises with waking,
that’s easy to remember.
It tends to continue to rise throughout the day.
And in the late afternoon and evening,
your temperature will start to go down
and the drop in temperature actually helps you access sleep.
That background, or what we call baseline,
circadian rhythm in core body temperature
is important to remember because it helps us frame
both the effects of deliberate cold exposure
and it helps us frame when you might want to use
deliberate cold exposure in order to access specific states.
It also points to times within the 24-hour cycle
when you might want to avoid using deliberate cold exposure
if your primary goal is to get to sleep.
Okay, so that’s the circadian rhythm in temperature.
Now, I just briefly want to touch on thermal regulation
at the level of the body and the brain.
And this will be very surprising to many of you.
Let’s do what’s called a 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,
you know, 102 degrees or 103 degrees.
And you start to move, you start to sweat,
and of course your core body temperature goes up.
Now, then I offer you a cold towel,
maybe a really, really cold towel.
And this towel is saturated with water
so you could actually squeeze the water out of that
and cool your body off.
And our 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,
and that it would feel really, really good
and they would cool you off.
Well, that’s exactly the wrong approach
if you want to cool off.
And in fact, if you were to use that approach,
your body temperature would continue to increase even more.
Yes, even more than had you not placed that cold towel
on your head or your torso.
And here is why.
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.
It 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,
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 and the upper half of the face,
you have what are called arteriovenous asthmosis.
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 cool mitt
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.
And you’ll get multiple scientists
naming the same molecule different things.
Norepinephrine 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 will 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, so 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
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,
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 as 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
in 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 do
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 Crum some weeks ago.
If you haven’t seen that episode, I highly recommend it.
And the science of 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 the distinction,
please see the episode with Ali Crum.
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
because 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.
Okay, 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 were confident that you could stay in
without risking your health, right?
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 will 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 the 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.
Okay, 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 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 that 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 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 realized there’s a fourth category
of cold exposure out there.
People who 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 glabber 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.
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.
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 attention 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
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, excuse me,
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 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, right?
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 greater mental toughness,
but it’s a reductionist way of explaining it
that is very closely tied to the biology
and to 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, okay?
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 interoceptive awareness, as we call it,
of when that next surge in 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 will 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 like 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 bottom 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 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.
Okay, 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.
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 breathing
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 of 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 neuroscientists,
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 with stress.
So in the boxing chess example,
the replacement for the cold water
is actually the boxing, right?
It’s the thing that’s supposed to induce the stress
because 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 here discussed,
but is vitally important
is whether or not you move around or not.
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 are 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 experienced 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 glab or skin cooling.
So keep those submerged,
move your body, pedal,
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
or 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 or 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 a cold immersion, et cetera.
Okay, 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 and 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 of 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,
if 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, excuse me,
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 degrees Celsius, 20 degrees Celsius,
or 14 degrees 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 nor epinephrine
or these other catecholamines.
The group that was in 20 degrees 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
is not a, you know, 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, okay?
And they did, 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 Lemke 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 it’s 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 lasts 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 accompany
moderate intensity zone to 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 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 use stress,
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 use stress.
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 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 the study,
Dr. Susanna Soberg,
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 oneself 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 Soberg 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 at 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 was 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 thermogenically 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 candle,
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 thermogenically 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 PPAR gamma
and cofactor 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 thermogenically 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 mechanisms,
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 UCP-1, PPAR-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 UCP-1,
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’re 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 haven’t 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
D2, D3 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 and action
and also suppressing planning and 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 pathways 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 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 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,
because 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, maybe 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 Soberg 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’re 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 Soberg principle.
At least I call it the Soberg principle.
The Soberg principle named after first author
of this study I referred to earlier, Dr. Susanna Soberg.
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 Soberg principle,
but I did that to give it appropriate credit
to Dr. Susanna Soberg, 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.
I do 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 Soberg 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 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 the Soberg 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,
then 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 cold 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 will 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,
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
in 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
or, 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
that was 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 Bout 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 interesting dose response relationships
for things like endurance training,
meaning the longer the cold exposure,
the more improvement in endurance performance,
reductions in circulating creatine kinases
and things that relate to muscle damage
under certain conditions.
Some point in the future, by the way,
we’ll do an entire episode
on creatine and creatine kinases,
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, okay?
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, 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,
may be 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
in cold water or 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 hold 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-6.
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 on 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.
What this study involved was having subjects
walk on a treadmill at a pretty significant incline,
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 the 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 is hyperthermic,
one way to cool them down quickly
is to cool these palmar 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 arteriovenous asthmoses,
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 will 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 at a temperature
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 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 that 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 at 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 askance,
and they think, well, that’s not possible, right?
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 pull-ups 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 has seen,
and that are documented 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 that 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 discussed 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 bout 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 can eliminate it entirely.
And that’s very interesting
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 bi-directional and people stop.
They quit, right?
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 realized 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, right?
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,
the 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 an 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, right?
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 bottoms 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
some 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 on the 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 it in the comment section on YouTube
or even just email me.
We have a email that you can find at 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
and particularly 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
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 testes 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 too 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 p.m., 7 p.m., 9 p.m. 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 my 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, 5 or 6 p.m.
and have no trouble sleeping.
I have done deliberate cold exposure very late at night,
10 p.m., 11 p.m. 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 even 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 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
We do not share your email with anybody else.
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 goals simultaneously.
If you’re learning from and or enjoying this podcast,
please subscribe to our YouTube channel.
That’s a terrific zero cost way to support us.
In addition, please subscribe to the podcast
on Spotify and or Apple.
And on Apple, you have the opportunity
to leave us up to a five-star review.
You can also now leave reviews on Spotify.
So we’d appreciate if you would do so.
If you have suggestions for future guests
or topics that you would like us to cover
or feedback generally for the Huberman Lab podcast,
please put that in the comment section on YouTube.
Please also check out the sponsors mentioned
at the beginning of today’s episode.
That is the best way to support this podcast.
And as mentioned at the beginning of today’s episode,
we are now partnered with Momentous Supplements
because they make single ingredient formulations
that are of the absolute highest quality
and they ship international.
If you go to livemomentous.com slash Huberman,
you will find many of the supplements
that have been discussed on various episodes
of the Huberman Lab podcast,
and you will find various protocols
related to those supplements.
If you’re not already subscribed to Huberman Lab
on Instagram and Twitter,
please do so.
There I cover science and science-related tools
that sometimes overlap with the content of the podcast,
but oftentimes is distinct from the information
covered on this podcast.
So thank you once again for joining me in the discussion
about the use of deliberate cold exposure
for health and performance.
And last, but certainly not least,
thank you for your interest in science.