Using Deliberate Cold Exposure for Health and Performance | Huberman Lab Podcast #66

- Welcome to the Huberman Lab Podcast,

where we discuss science

and science based tools for everyday life.

I'm Andrew Huberman,

and I'm a professor of neurobiology

and ophthalmology at Stanford School of Medicine.

Today, we are going to discuss the use

of deliberate cold exposure

for health and performance.

Temperature is a powerful stimulus on our nervous system

and indeed on every organ and system of our body

and cold in particular can be leveraged

to improve mental health, physical health, and performance,

meaning for endurance exercise, for recovering

from various forms of exercise,

for actually improving strength and power

and for enhancing mental capacity.

In order to properly leverage deliberate cold exposure

for sake of mental health, physical health and performance,

you have to understand how cold impacts the brain and body.

So today we are going to discuss that.

We're going to talk about some of the neural circuits

and pathways, some of the hormones involved.

I promise to make it all clear and accessible

regardless of whether or not

you have a scientific background or not.

We are also going to discuss very specific protocols

that you can apply,

which leverage variables like temperature,

how cold, how to deliver the cold, for instance,

whether or not you use a cold shower,

cold immersion, ice bath, circulating water, or still water,

whether or not you're going for walks outside in a t-shirt

when it's cold or whether or not

you're purposefully using things like cryo,

if you have access to that or not.

One thing I can promise you

is that by the end of today's episode,

you will know a lot about the biology of thermal regulation,

that is how your brain and body regulates its temperature.

You will also have a lot of tools in your arsenal

that you can use and leverage

toward improving mental health,

physical health, reducing inflammation in the body,

improving athletic performance,

improving mental performance.

I promise to spell out all those protocols in detail

as I go along and to summarize them again at the end.

I'd like to make a point now that I'm going to make

several additional times during today's episode

and that is that temperature is a very potent stimulus

for the brain and body.

That also means that it carries certain hazards

if it's not done correctly.

Now, everyone shows up to the table,

meaning to protocols,

with a different background of health status

and there's simply no way that I can know

what your health status is.

So anytime you are going to take on a new protocol,

that means a behavioral protocol or a nutritional protocol

or a supplementation protocol,

you should absolutely consult a board certified physician

before initiating that protocol.

I don't just say this to protect us,

I also say this to protect you.

If you'd like to see our medical disclaimer,

you can go to our show notes, it's described there.

In fact, I encourage you to please do that.

And in general,

when embarking on new protocols in particular,

if they involve strong stimuli like changing temperature

or placing yourself into unusual temperatures,

I would encourage you to progress gradually.

I would also encourage you to not look at

gradual progression as the kind of weak version

of a protocol.

In fact, today I'm going to discuss

a really beautiful peer reviewed study

that involved having people do deliberate cold exposure

so they were immersing themselves into water

up to about their neck

and the water was actually not that cold.

It was only about 60 degrees Fahrenheit,

which for most people is pretty tolerable.

So nowhere near the kinds of extreme temperatures

that one could use in other protocols.

And the interesting thing is despite

that fairly modest cold temperature,

by simply extending the duration of time

that people were in that water,

they experienced enormous increases in neurochemicals

that ought to translate to improvements in focus and mood.

And indeed, that's what's been observed

in subsequent studies.

So again, please see our medical disclaimer

in our show notes, please proceed with caution always,

please also understand that the most potent stimulus

isn't always the one that you experience

as the most intense in the moment.

In fact, I would encourage you to you find

the minimum threshold of stimulus

that will allow you to drive the maximum benefit

from each protocol and indeed,

I will point out what those thresholds ought to be today.

I'll give you some simple formulas,

gauges or guides that you can use in order to navigate

this extremely interesting and potent tool

that we call deliberate cold exposure.

Before we talk about deliberate cold exposure

and its many powerful applications,

I'd like to highlight a study

that I find particularly interesting,

that I think you will find

particularly interesting and useful.

The title of this study is brief aerobic exercise

immediately enhances visual attentional control

and perceptual speed,

testing the mediated role of feelings of energy.

Now, the reason I like this study is first of all,

it's a fairly large size sample group.

They looked at 101 students.

These were college-aged students and they had two groups.

One group did 15 minutes of jogging at moderate intensity.

So they did measure percent heart rates, et cetera,

but this would be analogous to zone two cardio,

which I've discussed on this podcast before.

Zone two cardio is cardiovascular exercise

that places you at a level where you can hold a conversation

with a little bit of strain,

meaning that you can get the words out,

but every once in a while you have to catch your breath

whereas if you were to push any harder by any mechanism

going faster or on a steeper incline, et cetera,

that you would have a hard time carrying out a conversation.

So zone two cardio is a common form of describing

that level of intensity that they call moderate intensity.

So one group did 15 minute of jogging at moderate intensity,

which I'm translating to roughly zone two cardio.

The other group did 15 minutes of relaxation concentration

that is somewhat akin to mindfulness meditation.

And then they were analyzed for perceptual speed,

visual attentional control, something called working memory,

which is your ability

to keep certain batches of information online.

Just imagine someone telling you their phone number,

and you have to remember that sequence of numbers

in your head for some period of time, that's working memory.

And it depends very heavily on the so-called

prefrontal cortical networks,

which are involved in planning and action.

And they also looked at people's feelings of energy

and they measured that subjectively,

how energetic people felt.

Now the major takeaways from this study

that I'd like to emphasize are that

the 15 minutes of jogging group

experienced elevated levels of energy

for some period of time after they ceased the exercise

whereas the group that did mindfulness meditation

actually reported feeling more calm

and having less overall energy.

Now that's very subjective and indeed they used

subjective measures to analyze energy,

but what gets interesting is when they looked at performance

on these various cognitive tasks and the two tasks

that they use were called the trail making tests,

they have different versions of this,

version A, version B,

I don't want to go into too much detail,

but version A essentially involves having a page of numbers

that are distributed somewhat randomly.

So one, two, three, four, five, six, seven, eight and so on,

but distributed randomly across the page

and people have to use visual search

to circle those numbers in sequence.

So this involves visual attention,

it involves some motor skills,

involves a number of things

that certainly require energy and focus.

The second test was the trail making test part B,

as I mentioned earlier,

and this involved also circling numbers in sequence,

but interspersed between those numbers were letters.

So rather than just having

to circle off numbers in sequence,

they actually had to connect one,

then the letter A, then two, then the letter B, et cetera

and remember these are randomly distributed across the page.

The major takeaway from the study is that the group that did

the 15 minutes of moderate exercise prior to these two tests

showed significant decreases in the amount of time required

to complete these tests accurately.

That is interesting and indeed surprising at least to me,

because there have been many studies looking at the effects

of mindfulness meditation on the ability to focus.

The key variable in the study turned out to be energy.

This subjectively measured feeling I should say

of having more energy and thereby the ability to focus,

especially in these high cognitive demand tasks.

Now the takeaway from this study for all of us

I think is pretty straightforward.

If you are going to sit down to do some work

that requires focus and working memory

and cognitive attention

and especially if it's some visual spatial control,

meaning you have to search for things on a page,

you have to organize things on a page,

so some writing, arithmetic,

basically cognitive work of any kind,

15 minutes of moderate exercise done prior

to that work about could be very beneficial for you.

This does not mean that mindfulness meditation

would not be a benefit to you.

I wouldn't want you to conclude that,

but if you had to choose between doing

15 minutes of mindfulness meditation

and doing 15 minutes of moderate exercise

prior to a cognitive work about,

I would say the 15 minutes of moderate exercise would be

more valuable at least based on the data in this paper.

In many previous podcasts,

I have talked about the powerful effects of doing things

like mindfulness meditation, and other forms of NSDR,

non-sleep deep rest.

So these could be 20 minute naps or just lying there quietly

with your eyes closed or yoga nidra

or NSDR scripts are available on YouTube

and various other places free of cost of any kind.

You just go to YouTube, put in NSDR,

non-sleep deep rest.

Those protocols have been shown to be very beneficial

for enhancing neuroplasticity,

the changes in the brain and body that encode

or shift the neural circuits that allow

for memory to change,

that allow for learning to occur after a learning about.

What I'm referring to today in this particular study

is the use of moderate exercise

in order to increase one's focus and attention

in order to trigger that neuroplasticity.

So the simple sequence here is get energetic and alert,

do that prior to the learning about,

engage in the cognitive work or learning about,

and then mindfulness meditation,

NSDR and so forth should follow.

And if you would like to access this paper

and like to look more at the details in the paper,

we'll be sure to put a link in the show notes.

The first author is Legrand.

And again, the title of this paper is brief aerobic exercise

immediately enhances visual potential control

and perceptual speed,

testing the mediating role of feeling of energy.

And I also just want to emphasize immediately.

I think most people out there are interested in tools

and protocols that work the first time

and that work every time

and indeed, I think this protocol fits that bill.

I'm pleased to announce

that I'm hosting two live events this May.

The first live event will be hosted

in Seattle, Washington on May 17th.

The second live event

will be hosted in Portland, Oregon on May 18th,

both are part of a lecture series entitled

the Brain Body Contract during which I will discuss science

and science-based tools for mental health,

physical health and performance.

And I should point out that while some of the material

I'll cover will overlap with information covered here

on the Huberman Lab Podcast

and on various social media posts,

most of the information I will cover is going to be distinct

from information covered on the podcast or elsewhere.

So once again, it's Seattle on May 17th,

Portland on May 18th.

You can access tickets by going to hubermanlab.com/tour

and I hope to see you there.

Before we begin,

I'd like to emphasize that this podcast is separate

from my teaching and research roles at Stanford.

It is however part of my desire and effort

to bring zero cost to consumer information about science

and science-related tools to the general public.

In keeping with that theme,

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Let's talk about the use of cold for health and performance.

I confess I love this topic

because it takes me back to my undergraduate years

when I worked in a laboratory studying cold physiology,

its effects on the brain and its effects the body.

And over the years,

I've always kept track of the literature in this area

and indeed there have been some tremendous discoveries,

both in animal models, so in rodents like mice and rats,

but also in humans

and today we're going to talk about both categories

of studies and I'll be careful to point out when discoveries

were made in animal models

and when they were made in humans.

A key point when thinking about the use of cold as a tool,

and the key point is that you have a baseline level

of temperature that is varying,

changing across the 24 hour cycle.

So any use of deliberate cold exposure

is going to be super imposed on that rhythm,

that circadian rhythm, meaning that 24 hour rhythm.

The basic contour of your circadian rhythm in temperature

is that approximately two hours before the time you wake up

is your so-called temperature minimum.

So your temperature minimum is a time

within the 24 hour cycle

when your body temperature is at its lowest.

So if you normally wake up around 6:00 AM,

your temperature minimum is probably about 4:00 AM.

If you normally wake up at about 7:00 AM,

your temperature minimum is probably about 5:00 AM.

It's not exactly two hours before your wake up time,

it's approximately two hours before your wake up time.

Now, as you go from your temperature minimum

to the time in which you're going to awake,

your temperature is rising slightly.

And then at the point where you wake up,

your temperature starts to go up more sharply

and will continue to go up into the early

and sometimes even into the late afternoon.

And then sometime in the late afternoon and evening,

your temperature will start to decline.

And indeed, as you approach sleep,

your body temperature will drop

by anywhere from one to three degrees.

And in fact that decrease in core body temperature

is important if not essential for getting into

and staying in deep sleep.

So temperature rises with waking, that's easy to remember.

It tends to continue to rise throughout the day

and in the late afternoon and evening,

your temperature WILL start to go down and the drop

in temperature actually helps you access sleep.

That background or what we call baseline circadian rhythm

in core body temperature is important to remember

because it helps us frame both the effects

of deliberate cold exposure and helps us frame

when you might want to use deliberate cold exposure

in order to access specific states.

It also points to times within the 24 hour cycle

when you might want to avoid using deliberate cold exposure,

if your primary goal is to get to sleep.

So that's the circadian rhythm in temperature.

Now I just briefly want to touch on

thermal regulation at the level of body and the brain.

And this will be very surprising to many of you.

Let's do what's called a Gedanken experiment,

which is a thought experiment.

Let's say I send you out into the desert heat

for a jog or a run and it's very hot outside,

102 or 103 degrees, and you start to move,

you start to sweat

and of course your core body temperature goes up.

Now, then I offer you a cold towel,

maybe a really, really cold towel

and this towel is saturated with water

so you could actually squeeze the water out of that

and cool your body off.

And our Gedanken experiment is for me to say okay,

where are you going to place the towel?

How are you going to cool yourself off?

And I'm guessing that most of you would think

that the best way to cool yourself off

would be to drape that towel over your head,

maybe your neck, over your torso,

that it would feel really, really good,

and it would cool you off.

Well, that's exactly the wrong approach

if you want to cool off.

And in fact, if you were to use that approach,

your body temperature would continue to increase even more.

Yes, even more than had you not placed

that cold towel on your head or your torso.

And here is why.

Thermal regulation meaning your brain and body's ability

to regulate your internal core temperature

is somewhat like a thermostat and that thermostat

resides in your brain.

So if you think about the thermostat

in your home or apartment,

if it's too warm in your home or apartment

and you were to take a bag of ice

and to put it on that thermostat,

what would the thermostat do?

It would register the environment as artificially cool.

It would think that the environment

was actually much colder than it is.

And so as a consequence,

it would trigger a mechanism

to further increase the temperature in the room.

And you have such a thermostat as well.

It's called the medial preoptic area of the hypothalamus.

The hypothalamus is a small region of brain tissue

about over the roof of your mouth

and a little bit in front of that.

So it's basically right behind your nose and over the roof

of your mouth and it's a collection of neurons.

Those neurons have a lot of different functions

that include things like the control of aggression,

the control of sex behavior,

the control of temperature regulation and so on.

The medial preoptic area has connections with

the rest of the brain

or areas within the brain, I should say

and with many areas within the body,

it receives input from receptors in our skin

and inside our body that register temperature

and it acts as a thermostat.

So if the surface of your body is made cool,

your medial preoptic area will send signals

by way of hormones

and by way of chemicals that will serve

to heat your body up.

So what this means is that if you want to cool down,

the last thing you want to do is to bring a cold surface

of any kind, towel or splashing water,

to the majority of your body surface.

It might be very, very surprising to you.

And you might say, wait, if I want to cool down,

I should jump into a cold lake or something of that sort.

That's a different thing altogether.

What I'll tell you,

and we'll get into this in more depth later,

is that if you really

want to cool down quickly and efficiently,

you should leverage particular portals,

meaning particular sites on your body

where heat can leave your body more readily

and where cooling can have a dramatic and fast impact

on your core body temperature,

can even save your life if you're going hyperthermic.

We're going to talk more about the specific protocols to reduce

core body temperature for sake of performance

and avoiding hyperthermia later in the episode.

Hyperthermia of course is a very, very dangerous situation

because while your body can drop in core temperature

somewhat and still be safe,

you can't really increase your body temperature that much

before your brain starts to cook

and other organs start to cook and by cook,

I mean the cells actually start to die.

So you have to be very, very careful with the use of heat.

Heat stroke is no joke.

People die from heat stroke all the time.

You really want to avoid that.

One way to avoid that is to cool the appropriate surfaces

of your body and the appropriate surfaces in this case

are the upper cheeks

or I would say the upper half of the face,

the palms of your hands and the bottoms of your feet.

I've talked about this on the podcast before

and in the guest episode with Dr. Craig Heller,

my colleague in the biology department at Stanford,

but just very briefly, these surfaces,

the upper half of the face,

the palms of the hands and the bottoms of the feet

are what we call

glabrous skin surfaces, G-L-A-B-R-O-U-S, glabrous.

And those surfaces are unique in that just below them,

the vasculature is different than elsewhere in the body.

Normally the passage of blood goes from

arteries to capillaries to veins,

but just beneath the glabrous skin on the bottoms

of the feet, the hands in the upper half of the face,

you have what are called arterio-venous anastomoses.

These are portals of blood that go directly

from arteries to veins and in doing so,

allow the body to dump heat more readily, more quickly.

So as it turns out that if you are to cool the palms

of the hands, the bottoms of the feet

and the upper half of the face,

you can more efficiently reduce core body temperature

for sake of offsetting hyperthermia

and for improving athletic performance

and maybe even cognitive performance.

So we will return to the specific protocols

for doing that later in the episode,

I'll give you a lot of details about how to do that,

how to do that without the use of

any fancy or expensive technology.

There are some technologies

that are now commercially available, for instance,

the so-called CoolMitt

that will allow you to do that with maximum efficiency,

but I'll also give you some at home methods to do this

either in the gym or on runs or for sake of cognitive work.

So the two key themes again

are understand that baseline circadian rhythm

in temperature, and understand that the best way to cool

the body is going to be

by making sure that something cold contacts

the bottoms of your feet,

the palms of your hands and the upper half of the face.

Ideally all three

if your goal is to lower core body temperature quickly,

and again, just cooling off the back of your neck

or the top of your head or your torso with a towel

is going to be the least efficient way

to lower core body temperature and might even increase

body temperature under certain conditions.

With those two points in mind,

we can start to think about directed deliberate

cold exposure protocols,

and there are a number of different reasons

to use deliberate cold exposure.

And I want to separate those out for you.

There are cold protocols that have been tested

in peer reviewed studies that are designed

to improve mental performance.

They are designed to improve things like resilience

or your grittiness,

or your ability to move through challenge

or to regulate your mind and your internal state

under conditions of stress

and we can define stress very specifically as times

when adrenaline also called epinephrine

and or norepinephrine also called noradrenaline,

are elevated in your body.

Forgive me for the noradrenaline,

norepinephrine, adrenaline, epinephrine nomenclature,

I didn't make that up.

It turns out that every once in a while,

scientists disagree, imagine that,

and you'll get multiple scientists

naming the same molecule different things.

So epinephrine and adrenaline are the same thing.

I will use them interchangeably.

Norepinephrine and noradrenaline are the same thing.

I will use those terms interchangeably.

Noradrenaline and adrenaline

are often co-released in the brain and body.

So they work as kind of a pair to increase

our level of agitation,

our level of focus and our desire and our ability to move.

They are often co-released from different sites

in the brain and body with dopamine,

a molecule that is commonly misunderstood

as the molecule of pleasure,

but is actually the molecule of motivation,

reward and pursuit.

So dopamine, norepinephrine and noradrenaline

tend to be released together under certain conditions

and today you'll learn how deliberate cold exposure

can be used to cause increases in the release of several,

if not, all of these in ways

that can improve your levels of attention and your mood.

But the key point is that your mental state is shifted

when you are exposed to certain forms of cold,

and many people use deliberate cold exposure

specifically to shift their body state as a way

to train their mental state so that they can better cope

with stress in real life and by real life,

I mean when life presents stressful events,

and I will give you specific protocols

as to how you can do that, in other words,

how you can become more resilient

through the use of deliberate cold exposure.

Now, because of the ways in which deliberate cold exposure

can increase this category of chemicals

called the catecholamines,

that includes dopamine, norepinephrine and epinephrine,

it can also be used to elevate mood

for long periods of time.

And I'm going to discuss a specific protocol

that has been shown to increase these chemicals

anywhere from 2.5X to 250%, to as high as 500%,

five times over baseline.

Now you might be asking whether or not it is a good thing

to raise chemicals like norepinephrine and dopamine

to such a great degree,

whether or not that's healthy for us,

whether or not they can harm us.

But it turns out that these elevations in norepinephrine

and dopamine are very long lasting in ways

that people report feeling vast improvements

in mood and vast improvements

in levels of cognitive attention and energy.

So by my read of the literature,

these seem to be healthy increases in our baseline levels

of these chemicals in ways that can really support us

so I'll give you a protocol for that.

Now, those are some of the mental effects

of deliberate cold exposure,

but deliberate cold exposure has also been studied

in animal models and in humans

in the context of increasing metabolism,

even in converting certain fat cells

that we call white fat cells,

which are the ones where energy is stored,

they're the ones that we typically think of

as kind of blubbery fat, to beige or brown fat,

which is thermogenic fat,

meaning that it can increase core body temperature

and serves kind of the furnace

by which we increase our core metabolism.

So with a very broad stroke,

I can say that white fat is generally the kind of fat

that people want less of and beige fat and brown fat

is generally the kind of fat that

if you're going to have fat cells and

you certainly need fat cells that you want more of.

They are thermogenic, they help you stay lean.

They actually serve as a reservoir for heating your body up

if you're ever confronted with a cold challenge.

So we're going to talk about how to use cold

for metabolism as well.

And of course,

people are using deliberate cold exposure

to reduce inflammation post exercise,

to reduce inflammation generally.

And people are also using cold to enhance performance

in the context of strength training,

in the context of endurance training

and we'll talk about those data as well,

but where I'd like to start is with mental performance

and I'd like to detail what happens

when we deliberately expose ourselves to cold.

It's key to point out the word deliberate.

If I don't say otherwise, then throughout this episode,

if I say cold exposure, I mean deliberate cold exposure.

And the reason I point that out is that as my colleague,

David Spiegel, and the department of psychiatry

at Stanford says,

it's not just about the state that we are in,

it's about the state that we are in and whether or not

we had anything to with placing ourselves into that state

and whether or not we did that on purpose or not.

And what he really means by that statement is that

there are important effects of what we call mindset.

Mindset was a topic discussed in the guest episode

with Ali Crumb some weeks ago.

If you haven't seen that episode, I highly recommend it.

And the science of my mindset tells us that if we are doing

something deliberately and we believe

that it's going to be good for us,

it actually can lead to a different set

of physiological effects than if something

is happening to us against our will or without our control.

Now, this is different than placebo effects.

Placebo effects are distinct from mindset effects.

If you want to learn more about that distinction,

please see the episode with Ali Crumb.

But again, when I talk about cold exposure in this episode,

I'm talking about deliberate cold exposure,

meaning that you are placing yourself into a

cold environment on purpose in order to extract

a particular set of benefits.

When we talk about deliberate cold exposure, almost always,

that means getting uncomfortable.

And one of the most common questions I get

when discussing the use of cold for sake of mental

or physical performance, metabolism, et cetera,

is how cold should it be?

How cold should the water be?

How cold should the environment be?

And I just will tell you now

and I'm going to say this again and again

throughout the episode,

cause it will continue to be true throughout the episode

and long after the episode is over,

how cold depends on your cold tolerance,

your core metabolism,

and a number of other features that there is simply no way

I could know or have access to.

So I would like you to use this rule of thumb.

If you are using deliberate cold exposure,

the environment that you place yourself into

should place your mind into a state of whoa,

I would really like to get out of this environment,

but I can stay in safely.

Now that might seem a little bit arbitrary,

but let's say you were to get into a warm shower

and it would feel really, really nice

and you were to start turning down the warm

and turning up the cold.

There would be some threshold at which

it would feel uncomfortable to you.

And if you were to continue to make a little bit colder

than that, you would really want to get out of the shower,

but you are confident that you could stay in

without risking your health, without risking a heart attack.

Now that's very different than jumping into

a very, very cold lake or

I've seen these images of people that will cut holes into

frozen over lakes and they'll get into that cold water.

If you are trained to do that

and you have the right conditions, et cetera,

that can be done reasonably safely,

but that's certainly not what I would start with.

And for many people, that would be too cold

and indeed some people can go into cold shock

and can die as a consequence of getting

to that extremely cold water very quickly.

Now that's not to scare you away

from deliberate cold exposure.

It's just to say that there's no simple prescriptive

of how cold to make environment

in order to extract maximum benefit

for mental or physical performance.

So the simple rule of thumb is going to be

place yourself into an environment

that is uncomfortably cold,

but that you can stay in safely.

And you'll have to experiment a bit and that number,

meaning that temperature, will vary from day to day.

It will vary across the 24 hour cycle

because of that endogenous,

meaning that internal rhythm,

in temperature that I talked about earlier.

Low early in the day,

rises into the afternoon, drops at night.

You can actually do this experiment if you like.

Try getting into a cold shower at 11 o'clock at night

if you want versus try doing it

in the middle of the afternoon.

It's quite a different experience

and by quite a different experience,

I mean it requires quite a different degree of resilience

and leaning into the practice.

Your willpower will have to be higher I suspect

late in the day as it compared to early in the day,

but that will vary of course between individuals as well.

So the most common question I get

about deliberate cold exposure

is how cold should the water be?

And we've answered that with uncomfortably cold to the point

where you want to get out,

but you can safely stay in.

The second most common question I get

about deliberate cold exposure is whether or not

cold showers are as good,

better or worse than cold water immersion

up to the neck, for instance.

I also get a lot of questions about whether or not

cryo chambers are better than all the others,

et cetera, et cetera.

I'm going to make all of that

very simple for you by saying cold water immersion

up to the neck with your feet and hands submerged also

is going to be the most effective.

Second best would be cold shower.

Third best would be to go outside

with a minimum amount of clothing, but of course,

clothing that is culturally appropriate

and that would allow you to experience cold to the point

where you would almost want to shiver or start shivering.

Now there are a number of different,

important constraints that are going to dictate

whether or not you use one form of cold exposure

or the other.

For instance, some people don't have access

to cold water immersion.

They don't have access to ice baths or cold water tanks,

cold ocean or cold lakes, et cetera.

In that case, showers would be the next best solution.

I do want to emphasize that there have been very few,

if any, studies of cold showers,

and you can imagine why this would be the case.

In a laboratory,

you want to control for as many variables as possible.

So placing people into a cold water immersion or an ice bath

up to the neck and insisting they keep their hands

and feet under is very easy to control.

It means that everyone can do essentially the same thing

whereas with cold showers,

people are different sized bodies.

Some people are going to put their head under.

Some people are going to lean forward.

Measuring the amount of cold water exposure on the body

is very hard to do

and so there aren't a lot of studies of cold showers,

but of course,

a lot of people don't have access to cold water immersion

so they have to use cold showers.

And if you don't have access to both, of course,

then going outside on a cold day can be of a benefit.

But I will point out that the heat transfer

from your body into water is much higher,

four times greater, if not even greater,

depending on the temperature of the water,

in water as opposed to in air.

So it's going to be much more efficient

to do cold water immersion than anything else,

cold showers after that and put yourself into

a cold environment would be the third best thing.

I'm not going to get into cryo chambers

because they carry quite a high degree of cost.

And again, there aren't many studies of them.

So if you have access to cryo chambers,

I'm sure that the cryo chamber facility

has told you about all these incredible benefits

and I don't doubt that some of those benefits truly exist,

but most people just don't have the resources

or the access to those

so we're going to leave cryo chambers

out of today's discussion.

And of course I realize there's a fourth category

of cold exposure out there.

People are wearing ice vests.

Believe it or not, those exist, ice underwear.

Yes, those exist.

You can look for them on Amazon if you like.

They are putting cold packs in their armpits

or in their groin or elsewhere in order to

stimulate some of the effects of cold

on mental and physical performance.

I'm not going to address those in too much detail today.

They can be efficient in certain ways,

but as you'll learn about later in the episode,

cooling the palms, the upper face

and the bottoms of the feet

is going to be far more efficient

and unfortunately I think most of the people that are using

ice packs to increase their core metabolism

are not aware of the glabrous skin cooling

and how it can be a very, very potent stimulus

so we'll return to that later.

Unless I say otherwise,

I'm mainly going to be focusing on cold water immersion

and cold showers.

So let's talk about protocols for enhancing mental health

and performance using deliberate cold exposure.

What happens when we get into cold is that we experience

an increase in norepinephrine,

in noradrenaline release and in adrenaline release.

The fact that cold exposure, deliberate or no,

increases norepinephrine and epinephrine

in our brain and body means that it is

a very reliable stimulus for increasing

norepinephrine and epinephrine.

That's sort of an obvious statement,

but that obvious statement can be leveraged

to systematically build up what we call resilience.

Now, when we experience a stressor in life,

whether or not it's something bad happens

in our relationship or something bad happens in the world

and we feel stress,

that stress is the consequence of increases

in norepinephrine and epinephrine in our brain and body.

Very similar, if not identical,

to the kinds of increases

that come from deliberate cold exposure.

So deliberate cold exposure is an opportunity

to deliberately stress our body and yet,

because it's deliberate

and because we can take certain steps,

which I'll describe in a moment,

we can learn to maintain mental clarity,

we can learn to maintain calm while our body

is in a state of stress.

And that can be immensely useful

when encountering stressors in other parts of life.

And that's what we call resilience or grit,

our ability or mental toughness,

our ability to lean into challenge or to tolerate challenge

while keeping our heads straight, so to speak.

So one simple protocol for increasing resilience

is to pick a temperature that's uncomfortable

of shower or cold immersion,

and then to get in for a certain duration of time

and then to get out.

Now, it's important to understand

that people will experience different levels

of norepinephrine and adrenaline release

when getting into cold water.

Some people, because they dread the cold so much,

will actually experience norepinephrine

and epinephrine increases

even before they get into the cold water

or under the cold shower.

Now you may have experienced this.

I've certainly experienced this.

I'm dreading it, I don't want to do it

and I have to force myself to do it.

And indeed epinephrine and norepinephrine and its surges

can be thought of as sort of walls that we have to confront

and go over.

And I'd like you to conceptualize them that way,

because it allows us to build protocols

that can be very objective and can allow us

to monitor our progress in terms of building resilience.

So one option is to simply say, okay,

I'm going to force myself

to get into the cold shower for one minute.

How cold, again, uncomfortably cold,

but you can stay in safely

or I'm going to get into the ice bath for one minute.

Ice baths are very cold inevitably.

And what is also inevitable is that

when you get into the cold,

you will experience a surge

in epinephrine and norepinephrine.

That's non-negotiable because it's mediated

by cold receptors on the surface of your body

and your skin and the way that they trigger the release

of norepinephrine and epinephrine,

not just from the adrenals,

from the adrenal glands above your kidneys,

but also from regions of your brain,

like the locus coeruleus,

which cause increases in the tension and alertness,

and from other locations in your body where epinephrine

and norepinephrine are released.

In other words, cold is a non-negotiable stimulus

for increasing epinephrine and norepinephrine.

Even if you are the toughest person in the world

and you love the cold,

that increase in epinephrine and norepinephrine

is going to happen.

So the way to think about norepinephrine and epinephrine

in this context of building mental resilience

is that you have two options.

You can either try to extend the duration of time

that you are in the deliberate cold exposure.

So going from one minute to 75 seconds to two minutes

and so on over a period of days

or one way to approach this

and the way that I particularly favor

is to take the context of the day

and the moment into account,

meaning we have different levels of grit and resilience

on different days and depending on the landscape

of our life at the time,

even the time of day that we're doing these protocols

and start to be able to sense the release of epinephrine,

and norepinephrine in our brain and body and see those

as walls that we want to climb over

in order to build resilience and to start counting

the number of walls that we traverse

and the distance between those walls

as we do deliberate cold exposure.

Let me give you an example of the timed protocol

because that one is very straightforward,

although I do not think it is as powerful

for building mental resilience.

The time protocol would be Monday,

I do one minute of deliberate cold exposure

at a given temperature.

Wednesday, I extend that by 50% and Friday,

I do deliberate cold exposure for twice as long

as I did it on Monday.

And if I were to continue that every week,

Monday, Wednesday, Friday,

I would continue to either increase the duration

or I would lower the temperature and reduce the duration,

this kind of thing, very much like sets and reps in the gym.

Now that option is very objective.

You could even log it in a book

and as you develop the ability to stay in cold temperatures,

even progressively colder and colder temperatures

for longer and longer periods of time,

you will become more resilient.

What do I mean by that?

Well, my operational definition of resilience

is that you are able to resist escape from the stressor,

the cold, by virtue of your willpower,

which is really your prefrontal cortex

causing top down control on your reflexes

and your limbic system and your hypothalamus,

which are basically telling you

to get out of that cold water,

get out of that cold environment and in doing so,

you are basically getting better

at controlling your behavior when your brain and body

are flooded with norepinephrine and epinephrine.

That's a very reductionist way to explain resilience

or grit or mental toughness,

but it's a reductionist way of explaining it

that is very closely tied to the biology end

of the psychology.

And it is a fact that norepinephrine and epinephrine

release in the brain and body

are the generic universal code for stressor.

There is no unique chemical signature

for different forms of stressors, that is the only one,

although of course there are

other chemicals involved as well.

So you could go for time and you could try

and reduce the temperature and increase the time

over a period of days or weeks.

Now that's an attractive way to approach things,

but the problem is that you don't have an infinite amount

of room with which to lower temperature,

because eventually you will get into temperatures

that are either so cold that they are dangerous

or you have to stay in cold temperatures

for such long periods that it becomes impractical

because presumably you also have to

take care of other aspects of your life,

you can't just sit all day in the ice bath.

Now for that reason,

I favor a protocol in which you build mental resilience

and mental toughness through

two different types of protocols.

The first one involves counting walls.

Now, what do I mean by walls?

I mean the sensation of, no,

I don't want to do this and the idea or the sensation

in your brain and body that you actually want to leave

that environment and go warm up.

Now again, for some people,

that will be even before getting into the ice bath

or cold shower.

So if you are feeling very resistant

to getting into the ice bath

or cold shower and you manage to do that,

that's going over what I would call one wall.

Then for some period of time,

you might actually feel comfortable in the ice bath,

cold water or cold shower.

And you feel like you could stay there

for some period of time,

that you could stay there for a minute or two minutes,

but inevitably, the next wall will arrive.

And I would encourage you to pay attention to

when that next wall arrives

and actually having an awareness,

that so-called interceptive awareness as we call it,

of when that next surge adrenaline epinephrine comes

or whether or not it reaches a certain threshold

in your brain and body that you feel you want to get out

and you're able to stay in for even just 10 seconds longer,

that means you've traversed yet another wall.

And if you continue to stay in that cold environment,

you'll find that the next wall will come

and the next wall will come.

Now eventually of course, you will get very, very numb

depending on how cold it is

and you could also place yourself into danger.

So you have to maintain cognitive control,

counting these walls, traversing these walls,

but getting out at some point, of course.

So my favorite protocol for building mental toughness

AKA grit, AKA resilience,

is to take into account that some days,

just getting into the ice bath

or cold shower represents a wall, some days it doesn't.

Some days you get in and you feel you could go 10 minutes,

other days you get in and you feel like

you could only go a minute and setting a designated number

of walls before you start the protocol

is going to be very beneficial here.

So you say, as long as I can do it safely,

I'm going to do three walls today.

The first wall is getting in.

The second wall will arrive when it arrives

and the third wall will arrive when it arrives

and I'll get over that wall and then I'll get out.

The next day, you might do five walls.

The next day, you might do three walls again,

but you might lower the temperature.

This gives you tremendous flexibility

and indeed it gives you much more latitude

to be able to use the same temperatures in different ways,

or to reduce the temperature only a little bit

and still get a lot of stimulus,

meaning a lot of results out of a given protocol.

Whereas people who are just going for temperature and time

eventually become cold adapted.

They get very, very good at doing three minutes

or six minutes or even 10 minutes at a given temperature

and so then they feel like they have

to lower the temperature even more and even more

and eventually they just bought them out.

There's nowhere else to go.

There's no way to get improvements out of the protocol.

At least not in terms of mental resilience.

Of course, there's still the positive effects

on inflammation and metabolism, et cetera,

that we'll talk about in a little bit.

But the key thing here is to design protocols

that are going to work for you over time

and for you very, very hardy,

very, very tough guys and gals out there

that can get right into

an ice bath or a very, very cold immersion

and you can just grind it out for six or 10 minutes,

or you can even do that by remaining peaceful,

well more points to you, but guess what?

That's the equivalent of already having loaded up

the barbell with 600 pounds and done your 10 reps.

There's not a whole lot more variable space

with which to get benefits from that stimulus.

And in the weight room,

people understand that you can adjust, for instance,

the speed of the movement,

or you can start combining that movement

with pre-exhaustion, et cetera.

With cold exposure,

you don't have as much variable space to play with.

So if your goal is to build resilience,

either go for time as a function of temperature,

or what I suggest is to start recognizing these walls

as an experience of resistance in you

and going over those walls, set a certain number of walls

that you're going to go over on a given day and do that

at a given temperature, and then to mix it up.

And ideally you might even throw in one more wall

at the end,

if you're really feeling bold and brave

because that's going to build out further resilience.

But if you want cold exposure to work for you

for sake of building up resilience

and mental toughness over time,

you're going to want to vary this parameter space

in some sort of way.

And you don't have to be super systematic about it.

That's the beauty of this kind of approach

because you're relying on the fact

that those walls really represent times

in which you are forcing your top down control,

your prefrontal cortex to clamp down on your reflex

and you're learning behavioral control in the context

of your body having elevated levels

of these catecholamines, norepinephrine and epinephrine.

And that translates to real life

in a much more realistic way I believe because in real life,

you're not really engaging in stressors

for a given amount of time

that you know how long it's going to last

and you know the context, no.

Most stressors arrive in the form of surprises

we don't like, text messages that deliver bad news,

information about the outside world or real world

and online interactions that send our system

into a state of increased norepinephrine and epinephrine.

And if you start to think of those as walls

that you can tolerate and climb over

while staying and calm and clear of mind,

then you can really imagine how the ice bath

and other forms of cold exposure are really serving

to train you up for real life stressors.

The next question that I always get is

what should my mental state be

while I'm exposing myself to this uncomfortable,

yet safe condition of cold?

Well, you have two options

and there are probably other options as well.

One is to try and calm yourself

to remain as mentally still as possible.

The other is to lean into that challenge

and so to grind it out and here,

I have to say that this is a lot like teaching someone

to drive on a gravel road.

For any of you that have driven on a gravel road,

you know that there is no optimal speed

for all gravel roads.

It depends on the density of the gravel, et cetera,

and the vehicle, et cetera.

So for instance, on some gravel roads,

when you start to drive and the dust starts to kick up,

your best option is to drive fast

and put that dust cloud behind you.

On other gravel roads, if you try and do that,

the dust actually kicks up around the vehicle

and it makes it hard to see

and sometimes you have to slow down.

The same thing is true for getting through

deliberate cold exposure.

Sometimes it's easier to calm yourself.

One way to do that is through double inhales

through the nose and extended exhales through the mouth,

or simply by trying to control your breathing

and reduce the pace of your breath and increase

the volume of your breathing.

I have to say that everyone experiences a shortening

of breath when they get into uncomfortably cold water,

that is a universal physiological response.

Everyone also experiences a 30 to 80% decrease

in cognitive function, in particular, the frontal cortex.

The metabolism of your frontal cortex goes down,

the metabolism meaning the activity of brain areas

associated with stress and panic goes way up.

And so anchoring your mind in cognitive activities

as you get into the cold can be very,

very helpful for maintaining clarity of mind.

In fact, one thing that I sometimes recommend

is that people try and engage

in some sort of cognitive exercise while in the cold,

not as a form of distraction,

but as a way to maintain clarity of thinking

and to learn how to do that when the body is flooded

with all these chemicals that make us stressed.

So for instance,

you could do math problems and not two plus two equals four,

not three times three equals nine,

but things that require a little bit more focus

and attention working memory and so forth.

You could also start to have thoughts

that you deliberately impose a full sentence structure on.

That's actually quite tough.

You could try and recall specific bouts of information

that are challenging.

This is teaching your mind how to stay online,

or rather I should say,

this is you teaching your prefrontal cortex,

how to stay engaged while you have high levels of stress

in your body.

Years ago, I had a friend who works

in the neuroscience world, research neuroscientist,

who was obsessed with this very bizarre sport

that I don't necessarily recommend at all,

which is the combination of boxing and chess.

You may have seen this on YouTube

where people will box around,

legitimate boxing around, they're sparring all out often.

And then at the end of the round,

instead of resting in the corner,

they actually sit down and play chess,

and then they go back to boxing and back to chess.

Again, not a sport that I recommend,

but the reason he was obsessed with this is because

he studies the impact of stress on cognitive performance.

And what that particular very bizarre sport was doing

was toggling back and forth

between different states of mind.

Now it's used both to increase cognitive clarity

for the fighter when they box,

because staying calm and clear thinking

is very important to winning boxing matches.

Believe it or not, it's not an all outrage.

It's a very calculated game of mental chess

and physical chess that's quite high stakes

as you can imagine.

It's also used in some circles as a way to teach people

how to engage in cognitive performance

when their body is simply filled to a stress.

So in the boxing chess example,

the replacement for the cold water is actually the boxing,

it's the thing that's supposed to induce the stress

cause getting hit is stressful and the risk

of getting hit is stressful for most people.

So again, if you think about deliberate cold exposure

as a way of just systematically and reliably

inducing epinephrine and norepinephrine release

and delivering stress,

well then this idea of maintaining cognitive clarity

and actually engaging in cognitive tasks

while in the ice bath or cold shower

can actually be very beneficial.

Even though it might sound a little bit silly,

you are really training up your ability

to keep your brain working

when the reflex is to shut down the parts of your brain

that are involved in deliberate planning and thinking.

Now another important aspect of deliberate cold exposure

that I rarely if ever hear discussed,

but is vitally important is whether or not

you move around or not.

And here's the reason.

When you get into cold water and you remain there

for some period of time,

your body is generating heat and that heat generates

what's called a thermal layer

that surrounds your entire body.

So if you stay still,

you are actually warmer than if you move around,

you can try this the next time

you're doing your deliberate cold exposure.

If you're submerged up to the neck,

sit there for about 10, 30 seconds

and be very, very still of body.

In fact, this is the way that most people start

to do deliberate cold exposure.

They give this very stoic look.

They don't blink, they look very peaceful.

Some of them even look tough

or they make a very even A, emotional face

and so it looks like they're really tough,

but they are so still that believe it or not,

they're not providing the most potent stimulus.

If they or you were to move around in that water,

what would happen is you'd break up the thermal layer

and that you actually experience that as much colder.

So if you really want to push the resilience aspect,

or for instance, if you want to use a given temperature

that you're comfortable in,

but that you want to increase the stimulus

and you want to get some more benefit

for mental resilience training,

well then get into the cold water,

move your body around continuously,

but try and keep your mind still,

or even do some sort of cognitive task.

So as you're starting to realize,

there are a bunch of different variables

that you can play with while maintaining

the same temperature of water and in doing so,

really keep you in the zone of what should

and absolutely has to be safe for you

without having to just continually drop the temperature

from say 60 degrees to 55 to 40 to 33

because as I mentioned before,

eventually you're going to bottom out.

So if you're one of those people that likes to look tough

or really relaxed while you're in the ice bath

or cold water immersion,

just realize that you're actually cheating yourself out

of part of the stimulus.

Keep those limbs moving and of course,

limbs under the water, feet and hands

is going to be a more potent stimulus

than hands and feet out for reasons

that should be obvious based on what we talked about

in terms of glabrous skin cooling.

Keep those submerged, move your body,

maybe move your knees up and down, pedal your feet

and trust me, it's going to feel a lot colder

than were you to remain stone still.

Another very common question

is how often to do deliberate cold exposure.

It's tough to make a recommendation on that

based on any peer reviewed study

although there are a few in humans that point to a threshold

of 11 minutes total per week.

So that's total throughout the week

divided into two or four sessions

of two or three minutes or so.

Now that 11 minute cutoff is not a strict threshold

and is actually geared more towards increases in metabolism,

we'll get into this a little bit later in the episode,

but I think the 11 minute threshold,

meaning 11 minutes total of deliberate cold exposure

per week is a pretty good number to use

if you need a number in order to keep you consistent.

But as we talked about earlier,

some of you are going to be in the ice bath

or cold immersion or cold shower for one minute,

others of you will be in there for 10 minutes,

depending on how frequent and how high, if you will,

those walls of adrenaline are coming.

So for some of you,

getting into a cold shower for three minutes total

for the whole week will represent a tremendous

achievement in terms of willpower and overcoming

the resistance to doing that, overcoming those walls.

For others of you, three minutes is nothing.

So what do I recommend,

I recommend that you get at least 11 minutes total per week,

but at the point where 11 minutes total per week

is very easy for you,

where is no longer representing

a significant mental challenge,

meaning you're not experiencing many of these walls,

you're excited to get into the cold shower immersion,

you're going through it easily, you're cruising basically.

Then I would say either lower the temperature safely,

of course, extend the duration safely, of course,

or increase the frequency so that you're doing this

perhaps every day or maybe five days a week

or three days a week.

I personally get tremendous benefit

from doing deliberate cold exposure three times a week

and using the walls method that I described earlier

as my gauge for how long to stay in

and typically that means that I'm staying in for anywhere

from two minutes to six minutes per session

and that averages out to about

11 to 15 minutes total per week.

So again, I do not think that you need to be super strict

about these guidelines.

It's most important when embracing a protocol A,

that you do it safely,

but secondarily that you do it consistently.

So find what you can do consistently

and then vary the parameters

that will allow you to continue to do

deliberate cold exposure consistently,

regardless of whether or not you have access to a shower

or cold immersion, et cetera.

So we've been talking about mental effects

and the use of deliberate cold exposure

for sake of building resilience,

which I do believe can be tremendously powerful.

Look, it's no coincidence that the screening

and the training for Navy Seals

involves a lot of exposure to cold water.

One could argue that it is deliberate

because they elect to go to buds,

but when they get into the cold water at buds

is dictated by the instructors and the reason

they use cold water exposure as the stressor

is that it does offer considerable leeway

in terms of duration and temperature,

in terms of how you can use it as a stressor

whereas things like heat don't offer much variable space

as we say.

There isn't a lot of room beyond which you start injuring

or even killing people by using heat.

So there are a lot of forms of stressors out there,

but cold is one that we can titrate,

that we can adjust in ways that can allow us

to continually build up and or maintain mental toughness.

Now, deliberate cold exposure also has many effects

on chemicals other than norepinephrine and epinephrine,

most notably the neuromodulator dopamine,

which is involved in elevating our mood,

making us feel energized and enhancing our ability to focus.

And that has a lot to do with how dopamine engages us

in motivated states,

tends to narrow our thinking in our behavior

into a particular trench of goal-directed behavior.

If you want to learn more about dopamine,

you can learn a lot about dopamine

in our episode about dopamine, it's at hubermanlab.com.

You can find it, it's a two and a half hour plus

kind of deep dive into all things dopamine,

focus, motivation, et cetera.

Deliberate cold exposure has a very powerful effect

on the release of dopamine in our brain and body.

And this is one of the main reasons why people continue

to do deliberate cold exposure.

Basically it makes us feel good

and it continues to make us feel good

even after we get out of the cold environment.

In fact, some people would say

they don't feel good in the cold environment,

it's all stress for them,

but afterwards they feel great.

One of our previous guests, Dr. Anna Lembke,

who's a medical doctor at Stanford University

School of Medicine, she's a close colleague of mine,

described the use dopamine in her book, Dopamine Nation,

an incredible book about addiction and dopamine

I should mention.

And the use of dopamine elicited by cold water exposure

by one of her patients.

What I'm referring to is the fact that one of her patients

helped themselves get and stay sober off drugs

by using deliberate cold exposure to increase dopamine.

So a healthier form of dopamine release

than they were engaged in prior to getting sober.

Now, the basis for dopamine release

in response to cold exposure

is that the catecholamines, norepinephrine,

epinephrine and dopamine tend to be co-released

by the same sorts of stimuli,

but most stressors and in particular things

that evoke stress or our feelings of stress internally

that we don't like do not increase dopamine.

They only increase norepinephrine and epinephrine,

but deliberate cold exposure

seems to cause a dramatic increase in dopamine.

And this has actually been substantiated

in a really beautiful study entitled

human physiological responses

to immersion into water of different temperatures.

The first author is Sramek.

I'm almost certainly pronouncing that poorly

and if not incorrectly, S-R-A-M-E-K.

This was published in the European Journal

of Applied Physiology in the year 2000,

really a beautiful study, I love this study.

They took people and they had them sit in chairs

underwater but their head was out and so they were immersed

up to the neck in either of three different temperatures.

32 degrees Celsius, which is 89 degrees Fahrenheit,

20 degrees Celsius, which is 68 degrees Fahrenheit,

or 14 degrees Celsius, which is 57.2 degrees Fahrenheit.

So not super cold, but then what they did

is they measured people's core body temperature throughout.

They measured their metabolism

and they looked at serum levels

of things like norepinephrine, epinephrine, dopamine,

and cortisol, serum meaning within the blood.

So a really nice and quite thorough study.

There were not a huge number of subjects in the study,

but nonetheless, it was a very thorough study

in terms of the number of variables that they explored.

So I just want to briefly highlight

some of what they saw or what they observed in this study.

First of all, all the groups were in the water

of a given temperature for one hour,

which is much longer than most

of the deliberate cold exposure protocols

that anyone is using at home.

I mean, maybe you're taking one hour long cold showers,

maybe you're getting into the ice bath for an hour

although I don't recommend that.

I think you'd probably get badly hypothermic or maybe

you're getting into a cold water immersion

for some period of time,

but I have a hard time imagining that it would be an hour

and I don't suggest that if it's very cold.

So this study focused on actually somewhat

moderately cool temperatures,

not what I think most people would consider

very, very cold temperatures,

but extended the duration for quite a while.

So again, 32 degree Celsius,

20 degree Celsius or 14 degree Celsius.

Here's what they observed.

The group that was immersed up to the neck

in 32 degrees Celsius, that is 89 degrees Fahrenheit,

water did not experience a shift in metabolism

nor a significant increase in dopamine,

norepinephrine or these other catecholamines.

The group that was in 20 degree Celsius,

meaning 68 degree Fahrenheit,

water for an hour experienced a 93% increase

in metabolic rate, which is remarkable

given that the water wasn't that cold

and yet an hour is a pretty long time to be in there.

And again, it speaks to the dramatic effect

of heat transfer that water has, which I mentioned earlier,

as opposed to being out in the air at 68 degrees,

it would certainly not cause that increase

in metabolic rate.

The group that was at 14 degrees Celsius,

meaning 57.2 degrees Fahrenheit,

water for an hour experienced a 350% increase in metabolism.

So huge increases in metabolism.

Now the most interesting data to me,

at least in terms of mental effects

of deliberate cold exposure,

were that the plasma or serum levels of norepinephrine

in the blood increased 530%.

These are huge increases in norepinephrine

so it suggests that this is a stressful stimulus

at least neurochemically speaking, stressful,

despite the fact that it's not super super cold,

although 57.2 degrees Fahrenheit,

14 degrees Celsius it's not a warm environment,

but it's not a ultra, ultra cold environment,

but an hour is a very long time to be in there.

The subjects also experienced a 250% increase

in dopamine concentrations,

which while not 530% as it was with norepinephrine

is still a very large increase

in baseline levels of dopamine.

And what was interesting is that those increases in dopamine

persisted for a very long period of time afterwards,

even out to two hours.

And they stopped the study after 120 minutes

of getting out of the cold, but nonetheless,

these increases in norepinephrine are huge and long lasting

and these increases in dopamine

are very large and long lasting.

And I do believe that these documented effects in humans

explain much of the enhancement of attention and of feelings

of wellbeing and mood that people typically experience

after doing deliberate cold exposure.

And the reason I say that is that

if you were to go back to the episode

that I did on dopamine,

or you were to go back to the episode

that I did with Dr. Anna Lembke on addiction and dopamine,

what you would find is that increases in dopamine

of the sort evoked by deliberate cold exposure

are actually very similar to the kinds of increases

in dopamine that are elicited by things like nicotine

or from other behaviors

that are known to be addictive and bad for us

because they lead to other effects on the brain

and body that we simply don't want.

And yet deliberate cold exposure provided is done safely

can create similar if not greater increases in dopamine

that are not just fleeting, that don't just occur during,

say the consumption of some deleterious drug or activity,

but that are very long lasting and that can be leveraged

toward activities other than deliberate cold exposure.

So I want to emphasize this.

I'm not suggesting

that people do deliberate cold exposure for an hour a day.

And unfortunately there are not many studies yet

exploring how shorter colder temperature

environment exposure, say one minute or three minutes

or six minutes at 55 degrees or at 50 degrees,

whether or not that leads to similar,

greater or reduced levels of dopamine in the brain and body.

And yet almost everybody who does deliberate cold exposure

will say yeah, it was stressful.

I didn't enjoy it, or I eventually grew to like it,

but that I always feel better afterwards

and then that feeling last a very long period of time.

And I think it's almost certain

that those experiences that people report

relate to these increases in dopamine

and in concert with the increases in norepinephrine

also explain the other effect that's commonly reported,

which is an enhancement in mental acuity

and the ability to focus.

Now, here we can extrapolate to the study

that I discussed at the early part of the episode,

where I was talking about the use of

short 15 minute exercise,

kind of moderate intensity exercise

and how that was shown to increase levels of energy

and mental acuity

in these working memory, visual attention tasks.

And there, again, we have to assume somewhat

because they weren't doing neurochemical measurements,

but we can reasonably assume that those improvements

in cognitive performance were due

at least in part to the increase in catecholamines

known to a company, moderate intensity zone two cardio.

So what you're starting to see here is a theme.

The theme is that virtually any stimulus

that delivers more norepinephrine,

epinephrine and dopamine to our system

will sharpen our mental acuity and elevate our mood

and will do so for some period of time.

Deliberate cold exposure, it turns out,

is a very potent way to increase these catecholamines,

this category of chemicals and thereby to improve mood,

mental acuity and levels of alertness.

And as we'll next see, it not only has that effect,

which can be very beneficial for many people

in a bunch of different circumstances,

but it also has the positive effects that many people seek

in terms of metabolism, in lowering inflammation in the body

and other physiological effects as well.

And forgive me,

I was almost ready to move on to effects

of deliberate cold exposure on metabolism

and inflammation and so forth,

but I neglected to point out one of the other

very interesting aspects of the study

showing deliberate cold exposure

can increase in norepinephrine and dopamine,

which is that they observed no significant increases

in the stress hormone cortisol

and that is both surprising, interesting, and important

because what it means is that the quality of stress

that deliberate cold exposure is creating in the body

is likely to be one of what we call use stress.

Hans Selye, the great physiologist,

won a Nobel Prize for distinguishing between distress,

which is stress in the brain and body

that causes the release of things like cortisol

along with the other catecholamines,

and that we experience as negative happening to us

and can lead to negative health outcomes.

And he distinguished that from eustress,

which was stress that we now understand

is associated with increases in things like norepinephrine

and dopamine, but no increases or minimal increases

in cortisol, and that can lead to positive health outcomes.

So it appears that deliberate cold exposure can create

what we call or what Hans Selye called eustress.

In other words, it can create a condition in the brain

and body in which we are stressing ourselves,

we are training up resilience,

and yet we are creating a neurochemical milieu

that actually has many health benefits.

Now I'd like to shift our attention

to the effects of deliberate cold exposure on metabolism.

And I'd like to start by detailing a study

that was performed on humans

and published just at the end of last year.

The title of the study is altered

brown fat thermoregulation,

and enhanced cold induced thermogenesis

in young, healthy winter swimming men.

And I should point out that while the study

was only performed on male subjects,

there's no reason to think that the effects

that they discovered would only pertain to men.

I would hope that they would also do a study on women

at some point in the future,

but the effects that they describe

are very basic core physiological processes.

What they did is they looked at at deliberate cold exposure

in this group of young men,

and they used that 11 minute threshold per week.

So in other words, they had them get into cold water

for approximately 11 minutes per week.

And again, that's 11 minutes total per week.

They divided that into two sessions

although in speaking with the first author of this study,

Dr. Susanna Søberg,

I learned that it probably is not important

that it be two sessions,

it could be three or even four sessions,

as long as it reaches that 11 minute threshold.

What they discovered was

that by going into these cold environments,

in this case cold water immersion up to the neck,

for 11 minutes total per week,

that these men experienced increases

in so-called brown fat thermogenesis,

I'll talk more about what that is in a moment,

and increases in core body temperature

that translate to increases in core body metabolism.

Now, the overall increases in core body metabolism

that they experienced were not extremely large.

They were statistically significant,

but they weren't extremely large.

However, the changes in brown fat stores

are perhaps what's most interesting about this study

and I'll tell you why.

The metabolic increases of deliberate cold exposure

are both acute meaning happening in the short term.

When you get into the cold and immediately after,

one does experience an increase in core metabolism,

you burn some calories, in other words,

and while those might not be very significant increases,

or I should say they can be statistically significant,

but they are not enormously large numbers

of calories burned,

the longer lasting effects of deliberate cold exposure

on metabolism seem to take place by changes that occur

in the types of fat that we store in our body

and the way that that fat impacts our metabolism

at other times throughout the 24 hour cycle.

This actually has a somewhat anecdotal basis,

in particular in Scandinavia.

I don't speak Swedish nor I speak Danish,

nor do I speak Norwegian,

but I do have Danish relatives

and they were able to help me decipher

a common Swedish saying,

which essentially translates to the fact that

in preparation for the summer, they say,

one should expose themselves to warm environments

so that one is comfortable in warm environments

in the summer.

That's one half of this traditional Swedish

and also Danish saying.

The other half of this traditional Danish-Swedish saying

is that in preparation for winter,

in order to not feel too cold in cold environments,

one should prepare for those in the fall

by not wearing a jacket and exposing one's self

to cold environments.

Now, of course, this is just anecdotal cultural lore,

but it actually has a physiological basis,

which is by exposing oneself to cold environments

on a repeated basis in anticipation of exposure

to more extreme cold environments,

one can feel more comfortable

in those extreme cold environments.

And that's exactly what they observed

in this study by Søberg et al.

The men felt more comfortable in extreme cold

if they had trained through deliberate cold exposure,

which might not seem surprising at all,

but based on what we talked about earlier,

whereby deliberate cold exposure evokes this discomfort

and this experience of norepinephrine release,

at least in the short term, then you would say, well,

shouldn't that deliberate cold exposure also

make them feel uncomfortable

like they really want to get out?

Well, that is true

in the beginning of a deliberate cold exposure protocol,

meaning in the first week or in the second week

or the third week, but what one finds

and what you will find if you do

deliberate cold exposure consistently is that you will then

become more comfortable at cold temperatures

away from the deliberate cold exposure.

So whereas you might have previously been the person

who is always cold in the room with air conditioning,

or always seeking a sweater, always wanting to bundle up,

you will be more comfortable in those cold environments.

And the reason for that is well substantiated

from this study and from animal studies

whereby deliberate cold exposure

converts one particular kind of fat cell,

the white fat cell,

which is a very low metabolic output cell.

It's basically a storage site for energy

in the body fat cells to a different type of fat cell,

which is the beige fat cell called beige

because it's actually beige or slightly brown

under the microscope, or even to brown fat cells,

which are very dark under the microscope and dark

because they contain mitochondria

and are very metabolically and thermogenetically active.

In other words, white fat doesn't burn many calories.

It's basically a storage site.

It's a bank account for energy.

It's filled with lipids,

and those lipids can be used if the body needs energy

and if it goes into a caloric deficit.

Beige fat and brown fat acts as sort of a furnace

or the sort of fat that you would find in a kindle,

a fuel that can increase core body temperature.

So beige fat and brown fat is very good

at raising our metabolism and helps burn white fat.

Now of course,

it does that only in the context of a caloric deficit,

but it can actually help create that caloric deficit.

Having more beige fat and brown fat

can increase your overall core metabolism, in other words,

the number of calories that you burn per day,

and therefore the number of calories

that you need to either maintain or to lose weight.

The simple translation of this is that getting into

cold water for a total of 11 minutes, perhaps more,

but at least 11 minutes per week

divided into two or four sessions

can increase your core metabolism in part

by increasing your beige and brown fat stores.

And we know how that works at least in animal models

and there's now reason to suspect

that the exact same mechanisms are occurring in humans.

The primary way in which deliberate cold exposure converts

white fat cells into these more metabolically

thermogenetically active metabolism increasing

beige and brown fat cells is because norepinephrine

released when we get into the cold binds to receptors

on the surface of white fat cells and activates

downstream pathways such as UCP1,

so this is an uncoupling protein one,

that acts on the mitochondrial metabolism of cells

and increases the mitochondrial output of those cells

and the mitochondrial density of those cells.

In other words,

it takes a cell that has a kind of a weak engine

or no engine for generating energy.

Although every cell has some mitochondria,

it takes cells that have very few mitochondria

and increases the engine size.

It kind of stokes the furnace of those particular cells

and actually can change gene expression in those cells.

So that's what's really interesting.

Deliberate cold exposure causes increases in norepinephrine.

which bind to receptors on the surfaces of white fat cells,

which triggers the release of things like UCP1.

It also causes the release of things like P-part gamma,

and co-factor PGC1.

I'm going to refer you to a review

if you want to learn more about these.

For those of you that don't want to learn more,

all you need to know is that the downstream of all that

are increases in mitochondria and metabolism

and actual genetic changes in the white fat cells

that convert them into beige and brown fat cells.

This is especially important for adults

because babies and young children actually don't have

the ability to shiver

or they have a less robust capacity to shiver.

Very small babies really can't shiver

so they have a lot of brown fat in order to keep them warm.

Young children eventually develop the ability to shiver

and maintain these brown fat stores,

mainly around the clavicles, the heart, the upper spine,

and in the upper back.

And it's no coincidence that kids can often run around

with a minimal of clothing and be comfortable

in environments that adults would be cold in.

As life goes on, we tend to lose beige and brown fat,

but this mechanism that I'm referring to

points to the plasticity of white fat,

meaning the ability for white fat to actually convert

its identity into this metabolically thermogenetically

enhancing form of beige and brown fat.

So deliberate cold exposure is a terrific way

to increase your core metabolism

and oftentimes critics will say, well,

the increase in metabolism isn't that significant

although I do want to point out again,

the 93% and 350% increases in metabolism

from that previous study.

But critics then will say, well,

that doesn't really translate to that big of a caloric burn

during the deliberate cold exposure.

But to that, you should say, ah,

but that's only limiting your optics

to just a portion of the effects

of deliberate cold exposure because deliberate cold exposure

can also convert white fat to beige fat and brown fat

and lead to these more lasting increases in metabolism.

So for any of you interested in increasing your metabolism

and or being comfortable in cold environments

and or being comfortable in terms of

being able to combat stress mentally,

deliberate cold exposure, I do believe is a powerful tool.

And there is simply no reason why you couldn't and shouldn't

use the same protocols that I described earlier

for building resilience to increase metabolism.

Provided you're hitting that 11 minute per week threshold,

you ought to be stimulating both mechanism increases

in resilience and increases in core metabolism.

As I mentioned earlier,

most of the detailed studies on the conversion of white fat

to beige fat and brown fat through the use of cold

have been done in animal models,

but the human data are starting to emerge.

And if you'd like to do the deep dive into these mechanisms,

things like UCP1, P-part gamma, et cetera,

there's a beautiful review that was published recently

in the journal cell,

which is one of the three apex journals,

nature, science, cell.

And the title of that paper is adipose tissue plasticity

in health and disease.

I love this review.

It has beautiful diagrams detailing all of the pathways

from cold to norepinephrine through UCP1

downstream of things like cyclic AMP.

If none of those names mean anything to you,

don't worry about it.

You certainly don't need to know these mechanisms

to benefit from deliberate cold exposure protocols.

If those names do mean something to you,

or you are interested in exploring the downstream effects

of deliberate cold exposure and something else

that's really nice that's covered in this paper

is how deliberate cold exposure interacts

with fasted states and fed states.

I think you'll also find this review very interesting.

I don't want to go too deeply into fasted states

and fed states right now,

suffice to say that when we are fasted,

meaning when we have an eaten for some period of time,

our baseline levels of norepinephrine

and epinephrine are already elevated.

And so cold exposure at those times

ought to have an even greater effect on metabolism

and resilience and so on.

So for you fasters or your intermittent fasters out there,

if you really want to get fancy,

you can do your deliberate cold exposure

when you are fasted.

I certainly wouldn't recommend doing it

with a very full stomach in any case.

And as I mentioned before on this podcast,

intermittent fasting is, but one way,

and certainly there are other ways

to limit total caloric intake for sake of maintaining

or losing weight if that's your goal.

I know many people are using and benefit

from intermittent fasting, however,

and so it certainly can be combined

with deliberate cold exposures in order

to get even greater increases

in norepinephrine and epinephrine.

So for those of you that are primarily interested

in using deliberate cold exposure

to increase dopamine levels in your brain and body,

you can also do a combined protocol

whereby you ingest caffeine 60 to 120 minutes

before the deliberate cold exposure.

This is based on a study that I've talked about before

entitled caffeine increases striatal dopamine D-2,

D-3 receptor availability in the human brain.

And as the title suggests, this study was done on humans,

looking at the density and or efficacy

of these dopamine receptors

in an area of the brain called the striatum,

which is involved in planning in action

and also suppressing planning in action.

It's involved very closely with whether or not

we can engage in behavior and withhold behavior,

the so-called go and no go ways in the brain.

Dopamine plays a critical role in that

and many other things as well as you now know.

So why would you want to ingest caffeine 60 to 120 minutes

before deliberate cold exposure?

Well, as I talked about earlier,

dopamine can increase quite substantially

in response to deliberate cold exposure,

but dopamine on its own doesn't do anything,

it has to bind to receptors

and this paper shows quite definitively

that ingesting caffeine in this case,

it was 300 milligram dose of caffeine,

which is about the dose of caffeine

in two or three cups of coffee,

it depends on the strength of the coffee, of course,

but it's not an outrageous amount of caffeine,

that increases the density and or efficacy

of these receptors,

which you would allow that dopamine

to have its greatest effect.

And for those of you that want to get really, really fancy,

I suppose you could do this fasted

so you get the further increase in norepinephrine,

then you get the dopamine increase from the cold exposure,

the binding of the dopamine.

Although I do want to point out that at some point,

you start layering together enough protocols

that you would to be spending your entire day

trying to get this dopamine pulse

and I would hope that you would have other activities

that you would engage in,

but if you're getting up in the morning and you're fasted

because you haven't eaten all night

and you have a cup of coffee, and then 60 minutes later,

you take your cold shower or two hours later,

you do your cold immersion or your cold shower,

you would be layering together

these different mechanisms of dopamine receptors,

epinephrine and so forth in a way that at least to me,

doesn't seem incompatible with having some other life

like going to school and having relationships, et cetera.

And this increase in dopamine,

particularly in the striatum is not a trivial one.

I do want to point out as the authors do

that preclinical studies have shown

that increases in striatal dopamine

induced by things like modafinil,

which is used to treat ADHD and treat narcolepsy,

is necessary for their wake promoting actions.

What this really says is that just having elevated levels

of dopamine from a drug or from an ice bath,

or what have you is not sufficient

to get the effects of dopamine,

you really need the receptors to be available

and you need those receptors to be available

in the appropriate density

and you need those receptors to be available

in the appropriate density in the striatum in particular.

So I think there are a number of reasons why

if it's compatible with the other aspects of your health,

cause of course always you have to consider this

on a background of cardiovascular health

and blood pressure, et cetera,

that ingesting a cup or two of coffee

an hour before your ice bath may be fasted as well

could be quite beneficial for increasing dopamine

over quite extended periods of time.

A couple of key points that you'll want to pay attention to

in thinking about deliberate cold exposure and metabolism.

In the Søberg study,

they also explored the use of sauna and how to use sauna,

meaning deliberate heat in conjunction with cold.

We are going to do an entire episode about the use of heat

for health and performance.

So that is not the focus now, however,

it does raise an important point

that we do need to address at this moment,

which is if you are using sauna

or if you are taking warm showers

or if you are simply using deliberate cold exposure

of any kind,

should you get into the heat afterward

or before or not at all?

And this is where we can point to the so-called

Søberg principle, at least I call it the Søberg principle,

the Søberg principle named after first author of this study,

I referred to earlier, Dr. Susanna Søberg.

In science, it is appropriate to take a key piece of data

and call it a principle

if in fact it translates to something larger,

which I believe it does.

It is generally not appropriate for people

to name a principle after themselves

although there are a few scientists that have done that.

So I have named it the Søberg principle,

but I did that to give it appropriate credit

to Dr. Susanna Søberg,

who discovered that and pointed out quite appropriately,

that to achieve the greatest increases in metabolism

through deliberate cold exposure,

you want to force yourself to reheat on your own

after the deliberate cold exposure,

meaning you wouldn't want to go from the cold shower

to a hot shower or from the cold shower to a sauna.

Rather if you were going to start with a hot shower

or you're going to start with a sauna

that you would end with the cold,

and then you would reheat naturally.

Now I personally take a cold shower a few times a week

or do cold immersion

and because I'm not specifically focused

on increasing metabolism, although I probably should be,

that's not what I'm using it for now,

I will take a hot shower afterwards and in doing so,

I'm short circuiting

some of the further metabolic increases that I would achieve

were I to just end with the cold.

So the Søberg principle is

if you want to increase your metabolism, end with cold,

and we can take this a step further and say

that if you want to use deliberate cold exposure

to increase metabolism, that you should make sure

that you get to the point where you shiver.

And the reason in for this is that there are

a series of studies, but in particular,

one study published in the journal Nature,

excellent journal in the year 2018,

showing that deliberate cold exposure that evokes shivering

from the muscles causes the release of a molecule

called succinate from the muscles

and that succinate plays

a key role in activating brown fat thermogenesis,

which you now have heard about and understand

as critical to the increases in metabolism

caused by deliberate cold exposure.

So what this means is if you want to

increase your metabolism, end on cold,

that's a Søberg principle and as best you can,

try and get to the point where you are shivering

either when you are in the cold exposure

or immediately afterwards.

Now one efficient way to do this is to, for instance,

you could get into the cold shower for a minute

or two minutes or three minutes, uncomfortably cold,

but safe to stay in.

Remember that's our general rule of thumb.

Then turn off the water and stand there,

make sure that you're not holding yourself

close to your body,

you're not hugging yourself to try and keep yourself warm,

but rather your limbs are extended at your sides.

And then if that fails to induce shiver

than to turn on the cold water again,

and then turn it off again,

so alternating perhaps a minute to three minutes

of cold exposure followed by a minute to three minutes

of drying out in air

and going back into the cold exposure, et cetera.

I can tell you this from experience,

this is a pretty brutal protocol.

If you have never tried getting into an ice bath

or cold water immersion or shower for one minute

and then getting out and trying to stand there

with your arms extended in cool or cold air for one minute,

and then getting back into the cold shower

or water immersion, you are in for an experience because

even for those of you that are pretty shiver resistant,

you'll find that it is much, much harder

to get out of that cold water and stand there arms extended

and drying off by evaporation,

which further draws heat from the body

than it is to wrap yourself in a towel,

get in a warm shower or a sauna.

So there's certainly no requirement to end on cold.

There's certainly no requirement to induce shiver,

but if your primary goal

is to induce increases in metabolism,

both in the short term and in the long term,

following the cold exposure,

well then you'll want to end on cold

and you'll want to find a way to shiver

provided that the level of cold

that you're exposing yourself to

is still safe for you overall.

So up until now,

I've been talking about deliberate cold exposure

as a potent stimulus for the release of norepinephrine

in the brain and body and indeed it is,

but the way I've been describing it has been in the context

of circulating plasma levels of norepinephrine,

meaning circulating within the blood.

What I haven't mentioned,

but is absolutely true is that the fat cells themselves

actually receive input from neurons.

So there are neurons that release norepinephrine

in response to cold, directly into the fat.

So I want to give you this picture of how the architecture

of all this works,

because I think it can help you navigate

and indeed build better deliberate cold exposure protocols.

Your adrenal glands release norepinephrine and epinephrine.

Your brain has sites within it like the locus coeruleus

that release norepinephrine and epinephrine,

but there are also neurons within your skin that sense cold

and other neurons that can directly release norepinephrine

into the fat stores and cause those white fat cells

to convert to beige and brown fat.

And I think this particular aspect of our physiology

is often overlooked in studies.

And when people say, oh,

well the increases in metabolism aren't that great,

the circulating levels of norepinephrine,

those are very large, but they're very transient and so on,

that fails to understand that neurons

that actually sense cold are in a position to communicate

via other neurons directly to the fat cells

and release norepinephrine into those fat cells,

which as I pointed out earlier,

set off a huge set of immediate

and long term cascades of even gene expression changes.

So the picture that I'd like you to have in your mind

is that when you get into the cold, yes,

of course you experience that as a experience of

I don't want to do this, I'm going to overcome this,

I'm going to climb over these mental walls

that represent adrenaline release in my brain and body,

but also that your fat cells are receiving signals,

norepinephrine signals that are changing those fat cells

and the way that they metabolize energy.

Now I'd like to shift our attention to the use

of deliberate cold exposure

for sake of physical performance.

And there are a lot of opinions out there

about the use of deliberate cold,

whether or not it should be done for instance,

before or after exercise,

whether or not if done immediately after strength training

or hypertrophy training,

meaning training designed to grow muscles

or make them stronger,

whether or not it can inhibit that process

and so on and so forth.

I think today in looking over the literature

and trying to bring forward the simplest

and most straightforward,

and yet scientifically grounded protocols,

we can set up some general guidelines that will allow most,

if not, all of you to still extract the benefits

of deliberate cold exposure on physical performance

without getting too neurotic about the exact timing,

but for sake of discussion

and because it's a prominent theme

in many online communities,

let's just start with the big one out there,

meaning the question of whether or not doing an ice bath

or doing deliberate cold exposure or taking a cold shower

after strength slash hypertrophy training,

meaning training designed to increase strength

and or I should say the size of muscles

will somehow short circuit or diminish that process,

whether or not it will reduce or eliminate

those strength gains and hypertrophy gains.

And the short answer that I was able to arrive at

on the basis of a review article that I'll talk about

in a moment and some other studies as well,

is that if your main goal is hypertrophy and strength,

it is probably best to avoid cold water immersion

and ice bath immersion in the four hours

immediately following that strength

and or hypertrophy training.

Again, if your main goal is to achieve hypertrophy

or strength or some combination of those,

probably best to avoid cold water immersion up to the neck

or ice bath immersion up to the neck

immediately after strength and hypertrophy training

and extending out to about four hours after that training.

If you're really neurotic about this,

then perhaps you'd want to move the cold water exposure

to a different day entirely,

but it all depends on how neurotically attached you are

to getting every last bit of strength and hypertrophy.

And if that's your goal, terrific,

well then probably moving the cold exposure four hours

or more away from that training

is going to be necessary for you.

Now you'll notice I did not talk about cold showers

and the reason I did not talk about cold showers

is that there simply are not very many studies

of deliberate cold exposure through cold showers

for the reasons I talked about

at the beginning of the episode.

It's hard for me to imagine that taking a brief cold shower

after a strength or hypertrophy training session

would completely reverse or short circuit the effects

of that strength and hypertrophy training.

But again, if you're neurotically attached

to getting every last bit of strength and hypertrophy

out of your training sessions, then by all means,

err on the side of caution and wait four hours or more

to do your cold shower just as you would wait four hours

or more to do your cold water immersion.

Now there are nice data pointing to the fact

that doing cold water immersion after a hard run,

so endurance training,

or even sprint and interval training

or after a weight workout where your main focus

is on performance of those movements

or after a skill training workout

where your main focus on performance of those movements,

that there's no reason to think that that

cold water immersion or ice bath or cold shower

would inhibit the progress or the stimulus

that would lead to progress

that occurred during that training session.

In other words, I don't see any reason

based on the literature to avoid deliberate cold exposure

immediately after training,

again unless your goal is hypertrophy and strength.

And in fact,

there's a very nice review recently published

on deliberate cold exposure

and how it can impact physical performance,

whether or not it's done before or after,

different types of training and so forth.

The paper is entitled impact of cold water immersion

compared with passive recovery,

following a single about of strenuous exercise

on athletic performance in physically active participants,

a systematic review with meta-analysis and meta regression.

So this is a meta-analysis of 52 studies

that looked at a tremendous number of variables

and contexts, as you would expect in a meta-analysis

of 52 studies.

I'm going to read you the conclusions of the study

and I will provide a link.

We certainly don't have the time to go through

all the details of the study.

I will highlight a few specific outcomes

that I found particularly interesting,

but here I am paraphrasing their conclusions,

that cold water immersion, I want to emphasize immersion,

not cold showers, but cold water immersion

they say was an effective recovery tool

after high intensity exercise.

They observed positive outcomes,

meaning improvements in certain variables,

for muscular power, muscular soreness,

meaning reduced muscular soreness,

increased muscular power,

perceived recovery after 24 hours of exercise.

However, there were certain forms of exercise

that were not benefited by cold water immersion,

such as eccentric exercise,

exercise focusing only on the lowering component

or the so-called eccentric component of resistance exercise.

They saw some very entry dose response relationships

for things like endurance training, meaning the longer

the cold exposure post-endurance training,

the more improvement in endurance performance,

reductions in circulating creatine kinases

and things that relate to muscle damage

under certain conditions.

At some point in the future, by the way,

we'll do an entire episode on creatine and creatine kinase,

which are important not just for muscular function,

but also for brain function.

But the basic takeaway was that cold water immersion

performed after high intensity exercise

was beneficial from a number of different standpoints

and indicated that shorter duration,

cold exposure and lower temperatures

can improve the efficacy of cold water exposure

if used after high intensity exercise.

There I'm directly pulling from their conclusions.

So what this says is that it's not just those

longer duration, 30, 45 minute and 60 minute protocols

of cold water immersion that we discussed earlier,

but also shorter duration of one minute, three minute,

five minute exposures to lower temperatures.

Temperatures that would make you psychologically

want to get out as soon as you possibly can,

but again that you can safely stay in

done after training really have been shown to

improve outcomes in terms of reducing soreness

and improving training efficacy,

meaning your ability to get back into training more quickly

and thereby deliver more training stimuli

to a given muscle or in your endurance training protocol.

Translate to English,

what this means is that taking a cold shower or getting into

an ice bath or some other form of cold water immersion

within the immediate minutes or even the immediate hours

following your training has been shown to be beneficial.

I'm sure a number of you have questions for instance,

how long should you be in that cold exposure?

Is it the same as the 11 minute threshold described earlier?

To be honest with you,

there are not enough studies to really point

to the critical threshold for eliminating

or reducing delayed onset muscle soreness

or for getting maximal results from power

and endurance training,

but this study does make a couple of key points

and here I will just paraphrase.

For instance, that cold water immersion

is more likely to positively influence

muscular power performance,

to reduce muscle soreness, to reduce serum creatine kinase,

and to improve perceived recovery

after high intensity exercise,

as compared with passive recovery.

This can be translated to cold water exposure after training

is beneficial and probably better

than passive recovery from a number of standpoints.

In addition, they say that dose response relationships

meaning the amount and the degree of cold

that people were exposed to and how often they did that

in particular in lower temperature cold immersion.

So these would be the sorts of cold immersion protocols

that are one minute or two minutes, three minutes,

maybe five minutes,

but that one couldn't stay in there longer

because it feels stressful

and one wants to get out.

Maybe more effective after high intensity exercise

for removal of serum creatine kinase

as well that these shorter duration

cold water immersion approaches may be more effective

after high intensity endurance performance as well.

So all of this can be translated to say that

unless your main goal is hypertrophy and strength,

that cold exposure, ideally cold immersion

and cold water ice bath,

but if you don't have access to that,

then cold showers is likely going to be beneficial

if done immediately after or in the minutes

or hours after your training,

especially high intensity training.

One particularly nice thing about this meta-analysis

is that it included some studies that

involve the use of cooling packs.

So again, vests that can essentially ice packs

and indeed even cryotherapy chambers and so on.

There's a nice table in the study

if you want to get really detailed and go

and look specifically at those studies,

I invite you to do that.

We'll put a link to this study in the caption

for this episode, but all in all,

what this study shows is that deliberate cold exposure

can be very useful for recovery likely through reductions

in inflammation, in muscle and connective tissue.

And while this study did not look specifically

at the mechanisms of reduced inflammation

caused by deliberate cold exposure,

those mechanisms are somewhat known.

There are a number of studies that have pointed to the fact

that deliberate cold and cold generally

can reduce inflammatory cytokines,

such as IL-6, interleukin six.

It can increase anti-inflammatory cytokines

such as interleukin 10 and so on.

Without getting into all those details,

I think it's sufficient to say that

if you are somebody who experiences

a lot of delayed onset muscle soreness,

taking a cold shower after your training

or getting into a cold immersion after your training,

even if it's a few hours later ought to help.

And if you are doing particularly intense training,

then you probably want to ratchet up the number

of cold exposure sessions that you're doing

even if those have to be done on separate days

from your training,

because a lot of the inflammatory effects of training,

endurance and strength training are actually occurring

some hours away from the training stimulus.

So it's not just that inflammation goes up

radically during training, which it often can,

but that it can occur even in the days

and even weeks afterwards,

depending how intense and how long duration

that training is.

So deliberate cold exposure is very powerful

as an anti-inflammatory tool.

Now I'd like to emphasize the topic that we touched on

at the beginning of the episode,

which are those glabrous skin surfaces,

the hands, the upper face,

and the bottoms of the feet through which heat

is especially good at leaving the body.

And another way of putting that is that one can cool

the body much more efficiently

through the glabrous skin surfaces.

Now, if you want to understand all of the science

behind this and all of the various applications,

I invite you to please listen to the episode

that I did with Dr. Craig Heller, again,

in the biology department at Stanford.

For sake of this episode,

I'm just going to detail a couple of findings

from his laboratory.

The first one, dealing with exercise induced hyperthermia,

because I think this is very interesting

and it can even save lives

if you understand the way this works.

There's a particular paper that focuses on this,

and we will put a link to this as well.

The title of this paper is novel application

of chemical cold packs for treatment

of exercise induced hyperthermia,

a randomized control trial.

This is a pretty brutal study,

brutal for the subjects that is.

This study involved was having subjects walk on a treadmill

at a pretty significant incline and anywhere

from nine to 17% wearing a substantial amount of clothing

that was not well ventilated

and the room was kept to 40 degrees Celsius,

which is 104 degrees Fahrenheit.

This is definitely not something to do at home.

This study was designed to induce hyperthermia,

which as I mentioned earlier, can be quite dangerous.

And they compared two types of cooling.

In the first form of cooling

that they call traditional cooling,

they had ice packs on their neck,

in their armpits and in their groin.

And in the other group,

there was the so-called glabrous skin cooling.

So the palms, the soles of the feet,

which were actually so they were cooling inside the boots

or inside of gloves and on the upper portion of the face.

And the basic takeaway of this study

is that by cooling the glabrous skin,

the subjects were able to sustain this walking

on these inclined treadmills for much longer

than were the people who received traditional cooling.

And also the return to baseline temperature

was much faster in the glabrous skin cooling group.

So how this translates to the real world

is that if ever you are hyperthermic

or someone else's hyperthermic,

one way to cool them down quickly is to cool

these palmer glabrous, soles of the feet glabrous

and upper portion of the face glabrous portions of the body

using cool rags, using ice packs or using any number

of different cold objects or temperatures.

One key thing, if you're going to use glabrous skin cooling,

is that whatever you use to cool those surfaces

cannot be so cold that it causes vasoconstriction.

Because as I mentioned earlier,

the arterio-venous anastomoses

these portals of arteries directly to veins

that exist only in these glabrous skin surfaces,

the way that they're able to cool the body

and essentially pass cool into the body

although that's not really what they're doing,

they're actually extracting heat from the body

to be technical, they're extracting heat from the body,

the only way they can do that is if those veins

don't collapse and veins will collapse

if they are made very, very cold.

So if you want to use glabrous skin cooling

to offset hyperthermia

or for the other forms of performance,

which we'll talk about in a moment,

you need to use a cool object or surface

that is not so cold that it causes vasoconstriction.

And this can be a little bit tough to dial in,

meaning it can be tough to identify such an object.

And for that reason,

Dr. Heller and some of his colleagues have developed

a commercial product called the CoolMitt.

You can actually go to their website, coolmitt.com.

I don't have any financial or other relationship to them.

I know they've been developing this technology

for some period of time.

It involves a glove that you put your hand into,

it circulates water of a given temperature and it does so,

and does so at a tempera or that is sure to not

cause vasoconstriction of the palm.

And you may be asking,

how can you just put your hand into one glove

and have this work?

Well, that's how powerful these glabrous skin surfaces are.

Even just by cooling one palm,

the core body temperature drops radically.

Now that's their commercial technology.

I know that some people out there have started to experiment

with a home version of this,

which would be taking a package for instance

of frozen blueberries or some other cold drink

or cold metal object, and actually bringing it into the gym

or out on a run.

There are even people who are now developing

cooled psych bicycle handles for long rides.