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.

This podcast is separate from my teaching

and research roles at Stanford.

It is, however, part of my desire and effort

to bring you zero cost to consumer information

about science and science-related tools

to the general public.

In keeping with that theme,

I’d like to thank the sponsors of today’s podcast.

Our first sponsor is Athletic Greens.

Athletic Greens is an all-in-one

vitamin mineral probiotic drink.

I’ve been taking Athletic Greens since 2012,

so I’m delighted that they’re sponsoring the podcast.

The reason I started taking Athletic Greens

and the reason I still take Athletic Greens

once or twice a day

is that it helps me cover

all of my basic nutritional needs.

It makes up for any deficiencies that I might have.

In addition, it has probiotics,

which are vital for microbiome health.

I’ve done a couple of episodes now

on the so-called gut microbiome

and the ways in which the microbiome interacts

with your immune system, with your brain to regulate mood,

and essentially with every biological system

relevant to health throughout your brain and body.

With Athletic Greens, I get the vitamins I need,

the minerals I need,

and the probiotics to support my microbiome.

If you’d like to try Athletic Greens,

you can go to athleticgreens.com slash Huberman

and claim a special offer.

They’ll give you five free travel packs

plus a year’s supply of vitamin D3 K2.

There are a ton of data now

showing that vitamin D3 is essential

for various aspects of our brain and body health.

Even if we’re getting a lot of sunshine,

many of us are still deficient in vitamin D3.

And K2 is also important

because it regulates things like cardiovascular function,

calcium in the body, and so on.

Again, go to athleticgreens.com slash Huberman

to claim the special offer of the five free travel packs

and the year’s supply of vitamin D3 K2.

Today’s episode is also brought to us by Element.

Element is an electrolyte drink

that has everything you need and nothing you don’t.

That means the exact ratios of electrolytes are an element,

and those are sodium, magnesium, and potassium,

but it has no sugar.

I’ve talked many times before on this podcast

about the key role of hydration and electrolytes

for nerve cell function, neuron function,

as well as the function of all the cells

and all the tissues and organ systems of the body.

If we have sodium, magnesium, and potassium

present in the proper ratios,

all of those cells function properly,

and all our bodily systems can be optimized.

If the electrolytes are not present,

and if hydration is low,

we simply can’t think as well as we would otherwise,

our mood is off, hormone systems go off,

our ability to get into physical action,

to engage in endurance and strength,

and all sorts of other things is diminished.

So with Element, you can make sure

that you’re staying on top of your hydration

and that you’re getting the proper ratios of electrolytes.

If you’d like to try Element, you can go to drinkelement,

that’s lmnt.com slash Huberman,

and you’ll get a free Element sample pack

with your purchase.

They’re all delicious.

So again, if you want to try Element,

you can go to elementlmnt.com slash Huberman.

Today’s episode is also brought to us by Thesis.

Thesis makes what are called nootropics,

which means smart drugs.

Now, to be honest, I am not a fan of the term nootropics.

I don’t believe in smart drugs in the sense that

I don’t believe that there’s any one substance

or collection of substances that can make us smarter.

I do believe based on science, however,

that there are particular neural circuits

and brain functions that allow us to be more focused,

more alert, access creativity, be more motivated, et cetera.

That’s just the way that the brain works,

different neural circuits for different brain states.

Thesis understands this.

And as far as I know, they’re the first nootropics company

to create targeted nootropics for specific outcomes.

I’ve been using Thesis for more than six months now,

and I can confidently say that their nootropics

have been a total game changer.

My go-to formula is the clarity formula,

or sometimes I’ll use their energy formula before training.

To get your own personalized nootropic starter kit,

go online to takethesis.com slash Huberman,

take a three-minute quiz,

and Thesis will send you four different formulas

to try in your first month.

That’s takethesis.com slash Huberman,

and use the code Huberman at checkout

for 10% off your first order.

I’m pleased to announce that the Huberman Lab Podcast

is now partnered with Momentus Supplements.

We partnered with Momentus for several important reasons.

First of all, they ship internationally

because we know that many of you are located

outside of the United States.

Second of all, and perhaps most important,

the quality of their supplements is second to none,

both in terms of purity and precision

of the amounts of the ingredients.

Third, we’ve really emphasized supplements

that are single ingredient supplements,

and that are supplied in dosages

that allow you to build a supplementation protocol

that’s optimized for cost,

that’s optimized for effectiveness,

and that you can add things and remove things

from your protocol in a way

that’s really systematic and scientific.

If you’d like to see the supplements

that we partner with Momentus on,

you can go to livemomentus.com slash Huberman.

There you’ll see those supplements,

and just keep in mind that we are constantly expanding

the library of supplements available through Momentus

on a regular basis.

Again, that’s livemomentus.com slash Huberman.

This episode marks the beginning of a new topic

for the Huberman Lab Podcast.

As many of you already know,

we go deep into a particular topic over four,

sometimes even five episodes.

We just closed out the episodes on hormones.

Now we are going to talk about

how to optimize physical performance and skill learning.

We’re going to look deep at the science behind this,

as well as specific practices.

In fact, today, you’re going to hear about specific tools

that you can use to improve endurance and strength

by up to, I’m not making this up,

three or four times your current capacity.

This is based on studies that were done at Stanford

and are currently in use

by collegiate and professional teams.

If you’re not a professional athlete or a serious athlete,

that’s okay.

The topics this month

and all the information we are going to cover

are going to make you a better recreational exerciser

as well.

If you’re not an exerciser

and you’re thinking about getting into that,

or if you live in the Northern Hemisphere

and you’re just thinking about the beach this summer,

fat loss, muscle building, that sort of thing,

this month, we’re going to cover all of that as well.

There’s so much confusion out there

about how to optimize fat loss, muscle building,

improvements in flexibility, for instance,

or skill learning.

I know many of you aren’t so focused

on the cosmetic aspects of physical exercise,

but are interested in actual skill learning.

We’re going to talk about that too.

I want to just take a moment

to reflect on something that came up last episode.

If you didn’t see that episode, that’s quite all right.

But last episode,

we were talking about the hormones adrenaline and cortisol

and how to leverage those towards attention and learning.

And there was a little bit of confusion

that I want to clarify.

I mentioned an optimal protocol for learning

that involved leveraging adrenaline,

also called epinephrine, and it involved four steps.

The four steps that I spelled out

were to be calm and focused

while one is trying to acquire or learn the new skill,

cognitive skill or motor skill,

then to have a spike in adrenaline.

I mentioned ways to do that,

using cold or breathing or other tools.

Immediately after the learning episode,

then to incorporate what I call non-sleep deep rest,

a 20 minute episode of a shallow nap

or some other protocol like NSDR,

non-sleep deep rest protocol,

of which we always provide links in the captions.

And then to try and optimize sleep later that night

and the subsequent night.

Some of you heard this and it sunk in right away

and it was straightforward.

Others said, wait,

I thought from a previous episode, even before that,

you said you’re supposed to do non-sleep deep rest

immediately after learning.

No, we added another step.

The logic still follows

that you want to be calm and focused during learning.

Then you want to spike adrenaline at the end.

Most people get that backward.

They’re drinking too much coffee

or even taking nootropics and things,

trying to be really focused while learning.

Some people are taking Adderall recreationally,

something I don’t recommend.

That’s actually getting the whole process backwards

if you look at the data and the physiology.

You want to spike adrenaline at the end

or immediately after a learning episode

and then non-sleep deep rest and then sleep itself.

Okay, four steps.

Hope that clarifies things for you.

If you have any additional questions,

please put them in the comment section below.

Okay, so let’s talk about physical performance.

There are so many variables to physical performance

and we can manage physical performance and skill learning

from a variety of contexts.

I made just a short list of some of the things

that come to mind that can powerfully impact

physical performance and skill learning.

Some of them are what I would consider foundational.

They allow you to show up with your current ability.

And if you were to disrupt those,

you would perform less well.

So things like getting a good night’s sleep,

things like being properly hydrated,

things like being well-nourished,

whatever that means to you.

I know some of you like to exercise fasted.

Some of you prefer to have food in your stomach

or have eaten a couple hours before.

There are supplements, there are drugs,

there are different ways to breathe.

There are so many tools related to mindset,

visualization, there are machines and devices.

It’s just a vast space, but it’s not infinite.

And there are a few things in the list of things

that can impact and even optimize physical performance

and skill learning that have an outsized effect

that any of you can use.

Many of them, most of them are low to zero cost.

So today we are going to focus on what I believe

to be one of the most powerful tools

to improve physical performance and skill learning

and recovery.

And we’ll talk about why that’s important.

And that’s temperature.

Many of you might think, oh, well, that’s kind of boring.

I want to know about the magic pill that I can take

that’s going to allow me a dunk of basketball

if I currently can’t,

or I want to know about the thing

that’s going to let me run further and faster

is going to shed fat.

Believe it or not, temperature is the most powerful variable

for improving physical performance and for recovery.

I would argue it’s even more important than sleep

because temperature itself is going to dictate how well

and when you sleep and the depth of your total recovery.

There are two aspects to temperature, of course.

There’s heat and there’s cold.

We are mainly going to focus on cold

as a way to buffer heat.

In a previous podcast episode,

I talked all about growth hormone.

You can find that episode about thyroid and growth hormone

and how heat can be a powerful stimulus

for increasing growth hormone,

which is involved in tissue repair and et cetera,

can burn fat and improve metabolism in various ways.

However, cold, I would argue,

is even more powerful than heat as a tool.

And I’m not just talking about putting ice packs

on sore muscles or slightly sprained limbs and ankles

and things of that sort.

We’re going to talk about cold

from the standpoint of thermal physiology.

This is a literature that’s rich in scientific information

that goes back very deep into the last century

where physiologists and neuroscientists figured out

that there are different compartments in your body

that heat and cool you differently

and that you can leverage those

in order to double, and as I mentioned before,

even triple or quadruple your work output,

both strength, repetitions, and endurance.

So this is not weak sauce, as they say.

This is the stuff that can really shift the needle

quite a bit.

And it’s not just about performing well once,

it’s about being able to perform well

and recover from that performance

so that you do even better

when you’re not incorporating these tools.

On days where, for instance, you can’t access cold

or an ice pack or an ice bath or things of that sort.

Okay, so we’re going to cover cold.

We’re going to talk a little bit about

the physiology of cold and heat and how they work

because, as you’ve probably heard me say before,

if you can understand some mechanism,

if you can just push yourself

through a little bit of new knowledge

into understanding a little bit of mechanism

about how you work,

you will be in a far better position

to implement the tools in the best

and most flexible ways for your needs.

This is why at the Huberman Lab Podcast,

I never ever do a just list of the things

that you should do.

I don’t believe in the just tell me what to do.

First, I tell you why you should do something.

What’s the logical framework that it’s grounded in?

And then we distill that down to specific protocols.

For those of you that are too impatient for that,

there are millions, if not billions,

of other resources out there

that will take you into the cul-de-sac

of one protocol that will work and then stop working

or might work for you indefinitely.

That’s not how we work here.

This is about really understanding the mechanism

so that you can tweak things and modify things,

adjust the timing and the dosage of things,

and really get the most out of these tools and protocols.

Everything I’m going to talk about

pertains to both endurance exercise

and strength and speed type exercise.

So sprints, weightlifting, endurance work,

and to some extent flexibility,

but we are going to cover flexibility in depth,

as well as another feature that’s not often talked about,

which is suppleness or smoothness of movement

over different ranges of movement in a subsequent episode.

Let’s start by talking about temperature.

What is temperature?

How does temperature impact the body

and its ability to perform, including learn new skills?

So everyone probably remembers,

or has at least heard of the word homeostasis, right?

That the body wants to remain

in a particular range of temperatures,

that it doesn’t like to be too hot or too cold.

And I want to emphasize from the outset

that there are many mechanisms that are installed into us

by way of our evolutionary design and our genome,

meaning we were just born with this stuff ready

to keep our body temperature in a particular narrow range.

Heating up too much is just plain bad.

It’s not just bad for physical performance,

it’s bad for all tissue health.

If your brain heats up too much, neurons start dying,

and those neurons don’t come back, okay?

You may have heard about neurogenesis,

the ability for the brain to regenerate itself

or generate new neurons in adulthood.

There’s very little neurogenesis, excuse me, in adulthood,

even anytime after puberty, really.

And you don’t want to lose neurons

in the central nervous system.

If you get too hot, that’ll happen.

It’s called hyperthermia.

You want to avoid hyperthermia.

And you have many mechanisms that are built into you

to avoid becoming hyperthermic.

The other thing that happens when we get too warm

is that we have in all of our cells what are called enzymes.

You generally know if something’s an enzyme

because it ends in the letters A-S-E, right?

So lipase is an enzyme that exists to digest fats.

You have proteases that are there to digest proteins, right?

So anytime you see A-S-E, chances are it’s an enzyme.

Enzymes are proteins,

and they have a particular structure,

and their structure becomes modified when heat increases,

and that’s not good.

You want their structure to be of a particular type.

Imagine a car with four wheels.

Let’s just say the car is the enzyme.

If it gets too hot, it’s like two of the wheels fall off,

and that thing can’t function.

So one of the reasons why the body and nature

goes through so much effort to build in mechanisms

to make sure that we don’t become too warm

is because when we get too warm,

these enzymes don’t function.

Cells stop functioning.

They stop being able to generate energy.

They stop being able to digest things.

You stop being able to think,

and eventually those cells start dying off entirely.

So keeping temperature in a particular range is really good.

You don’t want to get too hot.

We have much more flexibility in terms of getting cold.

Now, you don’t want to become hypothermic either.

You can die from hypothermia

just like you can die from hyperthermia.

However, that you have a lot more range to be cold

than you do to be too warm, okay?

And in general, the idea is to keep the body

and brain in a particular range,

but anytime we do anything,

our body temperature can shift.

So for instance, if you were to stand next to a campfire

or you were outside on a hot day,

various things would happen to dump heat from your body.

If you were outside on a cold day

or you were to get into a cold shower or a cold lake,

various things would happen

to insulate heat within your body.

This is all pretty straightforward and obvious, I realize.

Now, what are those things?

Well, there are a huge category of them.

When you get into cold water, you secrete adrenaline.

On a hot day, if it’s really hot or in a very hot sauna

or in the hot desert,

you will generate what are called heat shock proteins,

which will set off other sets of cascades,

metabolic cascades, biological cascades.

But the simplest way to think about this process

is that when we get cold, we tend to vasoconstrict.

Our blood vessels tend to constrict

and we tend to push energy toward the core of our body

to preserve our core organs, okay?

So our periphery, our hands and our feet and our toes

and our legs become colder

and our core therefore can maintain blood to that area

and we are insulating our core.

Conversely, when we heat up, our blood vessels vasodilate.

They expand a bit and more blood flows to our periphery

and more blood can move throughout the body generally

and we will perspire, we will sweat.

Water will actually get pulled out of the blood

to some extent, moved up through sweat glands

and will be brought to the skin surface

so that it can be dumped.

We are dumping heat.

Animals, as you know, vary in their capacity to sweat.

Some animals like camels won’t start sweating at first

if they heat up.

What they’ll do is they’ll spit.

They’ll dump heat by spitting, okay?

Dogs pant.

Costello’s off to my left here.

He pants when he gets too warm.

He can’t sweat or dogs can maybe sweat a little bit

but we can sweat and you’ve probably noticed

that on a humid hot day, you’ll feel much warmer

just walking or running than you would

with the equivalent exercise or movement

that you would on a cold day

and some of you probably know this but if you don’t,

the reason is you sweat on a cold day

but because the air is dry typically,

you will bring that sweat to the surface

and provided you’re wearing clothes

that allow some air to get out away from the body

so you’re not wearing really tight spandex type clothing

or something like that

or seal type, saran wrap type clothing,

that sweat will evaporate off into the dry atmosphere

whereas on a humid day,

the reason you see people in New York and Florida

on a humid summer day

and they’re like moving their shirts off themselves

and you see people with big sweat stains

and back sweat stains and all this kind of stuff

is because they’re sweating as they normally would

but it’s humid and so the humidity of the air

doesn’t allow transfer of that sweat

into the atmosphere as readily and so you’re hot, okay?

So without the evaporation, you’re going to be warmer.

So we evaporate off sweat, we sweat

and we vasodilate when we want to dump heat.

When we want to maintain heat, we vasoconstrict

and we tend to not sweat.

The other thing that happens is you’ll get goose bumps,

so-called goose pimples they’re sometimes called.

Those are a throwback to the time where we had fur

over most not all of our body.

All mammals in the cold have a process

whereby adrenaline is released at low levels

typically into the body.

That adrenaline activates what are called

sympathetic fibers, they have nothing to do with sympathy.

Those little fibers which are neurons,

those fibers that what I’m saying are fibers are neurons

not clothing fibers, reach up into the skin

so your whole body is covered with these little tiny neurons

that reach up into the skin and when we are cold,

they actually mechanically take the hair follicle

and bend it up.

It’s a process called piloerection, P-I-L-O erection, okay?

So on a hot day, you want to dump heat, okay?

So on a hot day, what would happen is

you’d actually not see those goose pimples

because you want the hairs lying down

which actually you would think that might insulate you more

but would actually let more heat dissipate

out through the skin.

On a cold day, you get these goose pimples or goose bumps

which are really just an ancient carryover

from the body’s attempt to make hair stand up on end

and when hair stand up on end

and they’re very close together,

that traps air in between them

and actually creates a sort of insulated blanket of warm air.

If you’ve ever seen an animal like a malamute or a husky,

you might think, oh, that poor thing on a hot day,

what does it do with all that hair?

Well, it can be warm so the animal will typically pant

and its hair will lay down

which you might think would act as more of a blanket

but on a cold day, what’ll happen is

they’ll become very puffy,

their hair will stand up on end

and that’s actually trapping heat between the hairs

and they’re actually quite well insulated.

So it’s very important that if you want to understand

how you can leverage temperature for physical performance,

you have to understand that you have vasoconstriction

to conserve heat, vasodilation to dump heat,

that you have sweating to dump heat

and you have conservation of fluids

in order to preserve heat.

That’s the most important thing

in terms of understanding the mechanisms

of maintaining and dumping heat.

And now the most important thing to understand

is that if you get too hot,

not only do those enzymes stop working

but your ability to contract your muscles stops, okay?

I’m going to repeat this because it’s vitally important.

ATP is involved in the process

of generating muscle contractions,

doesn’t matter if you’re running a marathon,

doesn’t matter if you’re doing a yoga class,

doesn’t matter if you’re going for a 700 pound squat.

The range of temperatures within which ATP can function

and muscles can contract is very narrow.

Somewhere around 39 or 40 degrees Celsius,

it drops off and you will not be able

to generate more contractions.

Now it’s pretty hot,

but that temperature can be generated locally really fast.

Now, if you’re too cold, it’s true,

it’s hard to generate muscle contractions.

I got into doing some cold water swimming a little while ago

and we would joke that, you know, you come out of the water,

we do no wetsuits.

I’m not recommending people do this necessarily

unless you’re certainly with somebody else

who’s skilled at doing it, which I was.

And you come out and you feel like you have claws for hands.

You can, you know, you could never text on a phone

for the first few minutes.

I mean, the water was very, very cold

and you can’t even move your face.

And so muscles will become rigid,

but heating up muscles causes them to fail

to be able to generate more contractions.

Put simply, if you get too hot, you stop exercising.

You may not even realize it,

but your will to exercise further,

your ability to push harder is entirely dependent

on the heat of the muscle, both locally

and your whole system.

So let’s talk about your whole system

because I just described heat dumping and heat maintaining.

I told you that increasing heat makes it hard

for muscles to contract.

It will stop you from being able to run further and faster.

It will stop you from being able to lift more weights,

more sets, more repetitions.

If you can keep temperature in range, however,

in a proper range, you will be able to do more work.

You will be able to create greater output.

You’ll be able to lift more weight, more sets, more reps,

and you’ll be able to run further.

Now, there are data that I’m going to talk about

in a little bit that are absolutely striking

that underscore that statement.

There are data from my colleague, Craig Heller’s lab

in the Department of Biology at Stanford.

And there are data that are now being implemented.

They were first implemented in a grant funded by DARPA,

but now in professional sports teams.

Many, if not all the NFL teams are now using this technology

as well as military uses it.

And not just for sports performance,

but also firefighters, construction workers,

other professions where elevated heat

becomes a barrier to performance.

And you can leverage this to really improve your workouts.

And when I say really improve, it is striking.

I’m going to give away a little hint of this now,

and then I’m going to tell you a little bit more

of the data later after I tell you the protocols.

Proper cooling of the body,

which has to be done in a very specific way,

has allowed recreational athletes or college students

and typical adults, as well as professional athletes

to go from doing their usual output,

in this case, that what comes to mind best

would be a particular professional athlete

who’s a member of the 49ers at the time,

was able to do 40 dips on his first set, 30, 20, 20,

basically did 10 sets of dips unassisted with anything else.

That’s an impressive, impressive,

especially since he’s a really large guy.

40 dips is a respectable.

These are strict full range dips.

And then by the 10th set, there’s a steep drop-off.

Using proper cooling of particular body compartments,

he was able to triple that within less than a week

and maintain that performance

even without the cooling approach.

So it was actually a conditioning effect, all right?

I’ll get back to this in a little bit,

but there are other fantastic leaps of effort

and leaps of performance that were demonstrated,

including endurance running.

Before I continue any further,

I just want to underscore again

that overheating is terrible.

There’s a famous example of this.

This was about 10, 15 years ago

when a number of dietary supplements

that included things like epinephrine,

which is a stimulant.

It’s a beta adrenergic stimulant.

Drugs like clenbuterol,

which were then banned from the Olympics,

which are still out there a bit in recreational use,

which were beta adrenergic agonists.

So these are drugs that sort of mimic

epinephrine adrenaline to some extent.

I know I’m oversimplifying this here.

They improve fat loss because of the effects on metabolism,

but they heat up the body.

And what happened was, this hit the press very widely,

is high school football players

and various professional athletes were dropping dead

because they were overheating

during practice or in competition.

So much so that clenbuterol was banned,

although every once in a while

somebody gets in trouble for using this.

There was an instance of this recently

in professional boxing,

which was attributed to a bad meat

that contained the clenbuterol.

I don’t know what the source was.

I don’t have any commentary about that,

but it still is in use,

but these drugs increase body temperature,

increase fat loss, but carry a severe danger.

And that’s the danger of hyperthermia.

In fact, I would argue,

and I think in talking to some folks

at various professional fighting organizations,

it’s very clear that a lot of the deaths

that one sees in professional combat sports

may have to do as much with dehydration and overheating

as it does with getting hit in the head,

which is also bad, but that things can compound,

they can have a synergistic effect.

And just a note about that and hyperthermia

and its dangers as well.

My first project ever in science

was to evaluate the thermogenic effects of MDMA, of ecstasy.

That was my senior thesis in college actually.

And so what we found was that indeed drugs

that remove your understanding of how warm you are

cause you to not take on the appropriate behaviors

to cool yourself, right?

So your vasoconstriction and your sweating,

those are autonomic.

Those are going to happen no matter what,

unless you happen to take something

that blocks that effect.

However, there are a lot of things that we as humans do

to prevent ourselves from overheating.

And the main one is stop.

When we are running in the desert

or when we’re running very hard and suddenly we stop,

oftentimes that’s because the muscles are overheating.

It’s a subconscious thing.

We won’t often think, oh, I’m really much too warm.

It’s just that we stop

and it’s a self-preservation mechanism.

Sometimes it kicks in too early.

Sometimes it kicks in too late.

Kicks in too late, you can die.

There’s an instance in the 1984 Olympics

where that was the first year I believe

that there was a women’s marathon.

I think that’s correct.

And one of the front runners or top picks for winning

was heading into the stadium.

And all of a sudden it seemed as if she was lost.

She was kind of wandering around

not knowing where she should go.

And in fact, she was in a position to win

or at least take second place, at least take silver,

got totally disoriented and did miserably in the race.

And she was hyperthermic.

She was running against that reflex to stop.

So dumping heat is key.

So how do you dump heat

in order to perform longer safely?

Well, in order to understand that,

you have to understand that the body

has three main compartments for regulating temperature.

We don’t just have a center and a periphery.

We have three main compartments.

And there’s one compartment in particular

that all of you or most all of you, I have to assume have.

And if you can understand how that works,

you can do tremendous things for your performance

and for your recovery.

So what I’m about to tell you will allow you

to perform better in all forms of exercise.

And it is not commonly known, unfortunately.

I’m here to try and change that.

You have three compartments

for increasing or dumping heat in your body.

One is your core.

We already talked about that.

Your core organs, your heart, your lungs,

your pancreas, your liver, the core of your body.

The other is your periphery,

which are obviously your arms and your legs

and your feet and your hands.

But then there’s a third component,

which is there are three locations on your body

that are far better at passing heat out of the body

and bringing cool into the body,

such that you can heat up

or cool your body everywhere very quickly.

Those three areas are your face,

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

Now, the skin on your hands

and on the bottoms of your feet,

and to some extent on your face,

are called glabrous skin.

That’s G-L-A-B-O-R-O-U-S, glabrous skin.

And what’s special about those areas of your body

and the glabrous skin

is that the arrangement of vasculature,

of blood vessels, capillaries,

and arteries that serve those regions,

is very different than it is elsewhere in your body.

Now, this has ancient roots.

Typically, if you were another mammal,

like a bear or some sort of ape,

you would have hair all over your body.

Now, we all know some pretty hairy people,

or presumably you’ve heard that there are these hairy people.

I know a few excessively hairy people,

and Costello is excessively hairy,

but he’s not a person, obviously.

But all mammals have hair on their bodies.

Just some people have very light hair or very fine hair.

We don’t have hair on these glabrous skin regions.

Now, of course, you can have beard or facial hair growth,

but there are still regions like the cheeks

and other areas that maintain this special vasculature, okay?

So technically, the hands and feet are real glabrous skin,

and the face is not always quite classified as glabrous,

but these three locations,

face, palms of hands, not tops, and bottoms of feet,

are very good at dumping heat and bringing in cool.

And the reason is there’s a rule in vascular biology

that blood moves from arteries to capillaries

and then to veins and then back to the heart, okay?

So arteries, which are the big ones, obviously,

capillaries, which are the little fine ones

where oxygen and carbon dioxide are exchanged,

and veins, which then bring blood back to the heart

and other tissues, of course.

In these three regions of your hands, your face,

and the bottoms of your feet,

we have what are called AVAs.

AVAs are a very special pattern of vasculature.

AVAs are described in the medical textbooks.

You can find them in Grey’s Anatomy,

not the television show,

but the actual Grey’s Anatomy textbook,

which is a real thing that exists,

and in all medical textbooks, okay?

So let’s talk about AVAs and what they are

and why they allow these three regions of the body

to heat or cool ourselves more readily.

So what are AVAs?

AVAs are arteriovenous asthmoses.

So if you want to look that up,

you can just look up AVAs, veins,

capillaries, arteries, if you like,

but I’ll spell it for you.

A-R-T-E-R-I-O, arteriovenous, V-E-N-O-U-S,

arteriovenous anastomosis, A-N-A-S-T-O-M-O-S-E-S.

Arteriovenous asthmoses, okay?

You want to know about arteriovenous asthmoses, trust me.

And you want to remember that they are in your hands,

the bottoms of your feet, and on your face,

and in particular, on the palms of your hands,

not the tops of your hands.

Now, before I said blood flows typically

from arteries to capillaries to veins,

and then back to the heart,

but AVAs are direct connections

between the small arteries and the small veins.

They bypass the capillaries to some extent.

They are little short vessel segments.

They have a big, large inner diameter,

and they have this very thick muscular wall,

and they get input from what are called adrenergic neurons.

They get input from neurons

that release norepinephrine and epinephrine,

which allows them to contract or dilate.

Now, there’s some rules of physics

that talk about how the radius of a pipe

and small changes in the radius of a pipe

leads to massive increases in the rate

and amount of stuff that can flow through that pipe, okay?

That’s a rule of physics that says essentially

that the radius is proportional

to the amount of stuff that can flow

through something to the fourth power.

We’re not going to make this a physics class,

but if you want to look that up, you can.

You can just look up how does the radius of a tube or pipe

relate to how quickly or how much stuff can flow through it.

What you need to know,

even if you don’t want to know any of the underlying physics,

is that these AVAs allow more heat

to leave the body more quickly

and more cool to enter the body more quickly

than other venous arterial capillary beds

throughout the body.

In other words, you can heat up best at the face,

the palms, and the bottoms of the feet,

and you can cool down best at the face,

the palms, and the bottoms of the feet

than you can anywhere else on your body.

And when I say heat up or cool down,

I mean actually heat or cool the core and your brain, okay?

So this is vitally important.

I realize we’re getting down

into the mechanistic weeds here,

but you need to know that these three compartments

of your body, palms, bottoms of feet, and face

are your best leverage points for manipulating temperature

to vastly improve physical performance, okay?

I also want to point out

that the work that I’m going to tell you about

is not work from my laboratory.

It’s the work of, as I mentioned,

my colleague Craig Heller’s laboratory at Stanford.

And we’re going to have Craig on as a guest

to talk more about these discoveries.

They are his and his colleagues’ discoveries

and how you can leverage them.

They’re building out some amazing technology.

I had a conversation with Craig yesterday

as a prelude to this episode

and to the future conversation with him.

So you’re getting the very latest on this topic.

So what Craig and his colleagues did

really illustrates perfectly

what these body surfaces can do and why.

They were studying overheating in athletes

and in military and in construction workers

and trying to prevent it.

And they did a bunch of experiments.

I won’t go into all of them now,

but what they essentially found

was that cooling the palms, Palmer cooling,

allowed people, athletes, and recreational athletes

to run much further, to lift more weight,

and to do more sets and reps

to a absolutely staggering degree.

Let’s talk for a second a bit more about why we stop,

why we shut off effort when we get too hot.

Because in doing so, you’ll really understand

how and why the best protocols exist

for being able to do more work,

to be able to exercise longer

and actually to feel good doing it.

You actually can make a doubling of your dips

or believe it or not, a tripling or quadrupling

or more of your pull-ups fairly straightforward.

I mentioned before that when muscle heats up,

enzymes start getting disrupted

and ATP and muscles can’t work so well

and those muscles can’t contract.

Let’s get a little more specific about that.

The enzyme that’s involved here

is something called pyruvate kinase.

You don’t need to know about pyruvate kinase,

but what you do need to know is that it ends A-S-E,

which means it’s an enzyme.

And pyruvate kinase is essentially a rate-limiting step.

It’s a critical step that you can’t bypass

if you want muscles to contract

and it’s very temperature sensitive.

Therefore, if you can keep temperature lower,

you can do more work per unit time.

You can do more pull-ups.

And that actually was done by Craig and his colleagues.

The pull-ups weren’t actually done by Craig.

I don’t know how many pull-ups Craig can do.

I’ll ask him next time, both cooled and uncooled,

how many pull-ups he can do.

But what they essentially did

is they brought someone into their laboratory

who could do 10 pull-ups on the first set

and they were able to get 10, rest two or three minutes,

get another 10, rest two or three minutes.

And if you’ve ever tried this,

what you find is that you start dropping

to eight, seven, six, et cetera.

Now, the person might not necessarily feel

like they’re overheating,

but the muscle is heating up.

Then with their knowledge that these AVAs,

that these portals in the palms are a great way

to both heat the body,

but also to dump heat from the body,

they used a device.

And I’ll talk about what you can do at home,

but a device where they had people hold on

to what was essentially a cold tube.

Now, this is crucial.

The tube can’t be so cold

that it causes vasoconstriction

because then the cold won’t pass from the tube

to the hand and to the core.

But if it’s the right temperature,

it’s neither too hot nor too cold,

that cool from the cold tube passes into the hand,

these so-called palmar regions,

and then cools the core.

And in theory, by lowering body temperature

would allow the person or the athlete to do more work.

And indeed, that’s what they saw.

The actual data, the specific data showed

that subjects could do,

at least the subjects they worked with,

on their first day with no cooling,

about a hundred pull-ups

across the timeframe that they had, okay?

So it might’ve taken anywhere from 10 to 15

or maybe more sets,

depending on how skilled that person was,

but in a fixed amount of time.

Then they came back and did the cooling.

They did it the very next day,

which if you’ve ever trained a muscle the very next day,

typically you wouldn’t do as well in its training

if it took any damage from the previous session,

or you at least do as well,

but you probably wouldn’t do what they then observed,

which was they started cooling after every other set.

The person would just hold the cold tube,

cool down the body after every other set rest,

everything else was kept the same.

And they found that they went to 180 pull-ups,

which is incredible, it’s a near doubling.

And by doing this repeatedly over several sessions,

over several weeks,

they quickly went in the cooling group

from a maximum of somewhere between 180 and 200,

as I recall, I’m sort of estimating now,

to 600 pull-ups in the equivalent amount of time,

which is absolutely incredible.

They then repeated this in a study on the bench press.

And actually the bench press study was pretty interesting

because they actually had a control group

that was admittedly taking specific amounts

of anabolic steroids,

the anabolic steroid was testosterone cypionate,

which is essentially testosterone.

And indeed the testosterone cypionate,

the steroid group improved at a rate of about 1% per week.

In other words, there were differences.

And the cooling group basically left all other groups

in the dust, it was just remarkable.

So cooling the core,

I want to be very clear that it’s not cooling the muscle,

it wasn’t about cooling the chest alone

or just cooling the palms.

It was about allowing cold to pass through the palms

because of the unique vasculature that’s there,

these AVAs, allowed the subjects

to do far more work per unit time.

And the important thing is that if they were to come back

after doing 600 pull-ups or 500 pull-ups,

you might say, well, wow,

that’s going to create a situation

where recovery is going to be absolutely impossible.

They could come back, not use the cooling,

and they still saw a highly significant increase

in the amount or the number of pull-ups or dips

or bench press weight that they could do, okay?

So what that meant is that it was both

an excellent performance

and an excellent training stimulus

that they were able to recover from, okay?

I don’t know if all of you are following this,

but these are the sorts of increases in exercise output

that are absolutely staggering.

And that’s why professional teams and the military

and others capitalized on them very quickly

and use these, okay?

Now, you may be asking, what about endurance, right?

Not everyone wants to be able to bench press a lot

for multiple reps and sets.

And I should just mention for the bench pressing,

it was, I believe they found people

that could bench press 225,

so that’s two 45-pound plates

on the 45-pound standard Olympic bar

for repetitions of anywhere from six to 10.

And then they had them do the same thing.

They did a set, they’d rest two or three minutes,

sometimes up to four minutes,

then do another set, repeat, repeat, repeat.

And with cooling, they were able to increase

the amount of work, the number of reps with the same weight.

Sometimes they did have to increase sets

to approximately double, so it was pretty fantastic.

So with endurance, similar increases have been shown.

And the way that they would do those tests

are a little bit different.

And they also point to a really important mechanism

of why we stop doing work at all

when we perceive that we are putting in too much effort.

And so it gets right to the heart

of the relationship between temperature and muscle

and your willpower.

Those are directly related.

Your body heat and your willpower

are linked in a physiological way.

So I’m not talking about the kind of stuff

that you see as kind of like clickbait on the internet

or like increase willpower now or become resilient now

or never do this again if you want to be mentally strong.

I’m talking about a physiological mechanism

that exists in the body and brain

that causes you to stop or that will allow you

to continue to go harder and further

than you normally would.

Okay, so let’s talk about willpower and heat

and how heat shuts you down.

In other words, if you are cool,

if your body temperature is in a particular range,

not only can you go further,

but you will go further if you want to.

Said differently, if you heat up too much,

you will stop or you will die.

Typically people stop.

There are individuals who will push to the point

where they black out and die in the same way that,

and please don’t do this experiment.

There are people who can sit down face-to-face

and say, let’s hold our breath

and whoever breathes first loses.

Some people will just go until it’s painful

and then they’ll gasp and take a big breath.

There are always those individuals

who can override that reflex

and they will go until they pass out, okay?

And if you do that in water, you can very easily die.

So please don’t do that experiment.

But there’s a reflex that relates the body to the brain

and the brain to the body

that shuts off our effort when we get too hot.

So what Craig and his colleagues and now others have done

is to do a test in the laboratory

where rather than ask people to run outside

until they absolutely don’t want to run anymore,

you put them on a treadmill and you set the speed, okay?

So they have to keep up with the treadmill

and at some point they quit.

And you take groups and you do those

in different temperature environments.

So some people are running in a nice chilly laboratory,

they get their heart rate up.

So maybe their heart rate goes from, you know,

40 or 50 baseline heart rate,

maybe it gets up to 80 or 100.

And then they keep the rate of the treadmill going the same

and they will just plateau.

So they’re getting to a steady state cadence or rhythm

and their heart is beating at more or less a steady state.

Eventually they’ll probably stop

because they have something else to do,

but people will continue at that temperature

and at that heart rate,

unless you start turning up the temperature in the room.

And at some point they will stop

and they’ll stop much earlier when it gets hot

because of something called cardiac drift, okay?

So let’s say I’m running

and I’m running at a steady cadence on this treadmill

and my heart rate is 85 beats per minute

or 100 beats per minute, doesn’t matter.

Let’s say 100, just for sake of example.

Well, just making the room hotter

is going to increase my heart rate further,

even though I’m at the same output.

And the brain does a computation.

It somehow figures out that there’s a heat component

that’s increasing heart rate.

And there’s an effort component from running

that’s driving heart rate.

And if the heat component

and the heart rate output from the effort

get to hit a certain threshold, I stop, okay?

And some of you may think,

well, there are people who just run and run and run

and never stop.

Eventually everyone stops.

Maybe it’s because the race ended.

Maybe it’s because everyone else quit.

I actually saw some stuff online.

There are these races where people

just will continuously do the same loop

until everyone else drops out.

And then one guy or gal keeps going past everybody.

But typically it stops because the race is over

or because people quit.

Increasing temperature increases the rate of quitting

in part, not entirely, but in part

because of this thing called cardiac drift,

which you’ve probably experienced

if you’ve been out on a hot day and you’re walking uphill,

you might stop to take a breath.

If you sit in a sauna, your heart rate will increase.

Heat increases heart rate.

Effort increases heart rate.

At a steady effort, you’ll have a steady heart rate.

If you increase the heat in the environment

that you’re engaging in that steady heart rate,

your heart rate will now go up due to cardiac drift

and you will quit, okay?

So Heller and colleagues have done experiments

where they do Palmer cooling under these environments.

And that’s wonderful because not only does it enable people

to go further and faster for much longer,

that’s been shown statistically significant every time,

but it also protects the brain and body

against hyperthermia, overheating, coma, nerve injury,

nerve death, and actual death, okay?

So you can see why this is such a valuable tool.

So what are they doing?

Well, in this case too,

they’re having them cool their hands

and they’re cooling the palms.

Cooling the palms of the feet is a little trickier,

but cooling the face could actually work as well.

And we’re going to talk about cooling the face

and how to incorporate this.

So at this point,

I’ve just really wanted to impress upon you,

not impress you, but impress upon you,

the fact that you have these three surfaces of your body

that are very good at passing cold into the body

such that it cools the core body temperature.

And that’s a good thing for health and safety.

And in order to maintain work output

over longer periods of time,

or actually just do more work.

I mean, to me, the result is just so staggering

is the 100 to 180 pull-ups in the controls

and then 600 pull-ups in the cooled individuals, right?

They actually also feel mentally

as if they can do more work.

It’s not just that they can,

their willpower is adjusted somehow

by these shifts in temperature.

Now, before we continue and get to the exact ways

that any number of us can start to use this information,

I want to talk about the opposite thing, which is heating.

And you have to remember that these surfaces,

the palms and the bottoms of the feet and the face,

were not just arranged with these AVAs,

these special ways to pass blood from arteries to veins

in order to cool us for better athletic performance

or to heat us on cold days, but for both of those things.

Now, Heller and colleagues and others have also explored

how these can be used to heat up the core.

There are times when we want to heat up our core.

Typically, we hear that most of the heat escapes

through our head, so we’ll put on a hat when we go outside.

That’s actually not true.

Most of your heat escapes through your face,

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

Now you should know why that’s the case.

What this means is that for post-surgery patients

or for people that are hypothermic,

indeed, you want to heat the core, right?

But actually, I was on a swim recently

where a friend became hypothermic.

He was kind of slurring his words

and kind of staggering around

when we got him back on the beach.

We brought him over to the lifeguard station.

He turned out to be fine.

Again, this is why cold water swims

are something that you really need to do in groups,

not alone, and you really have to know what you’re doing.

There were reasons for why this happened that day.

But we were, basically, people thought

we were a little strange

until they realized what was happening.

We were walking down the beach,

basically sandwiching him at our chest

because we were still warmer than the ambient environment,

the environment around us,

and we were pushing our chest against him

to try and warm him up, to warm up his core.

In retrospect, that was the wrong thing to do.

In talking with Craig and talking to other colleagues

that work on thermogenesis,

what we should have done was warm the palms of his hands,

the bottoms of his feet, and his face

because that would insulate the heat loss.

Now, he was very cold,

so presumably there was vasoconstriction of the veins

at these locations,

and so it’s not clear

that that would have been the only strategy to use.

But they have explored how to heat up post-surgery patients,

and one of the best ways to do that

is to get warm socks on the bottoms of the feet,

get gloves on the hands,

and if it can be done safely, to warm the face.

Now, of course, you don’t want to obstruct respiration

and things of that sort.

But again, the ability to pass heat into the body

or to remove heat to the body

is best done through these three surfaces.

I can’t emphasize that enough.

So I mentioned before that you want to cool the palms

or the bottoms of the feet,

although that’s a little harder to do, or the face,

but not so much that the blood vessels constrict

because then you won’t be able to pass cool into the body

because those pipes got smaller,

and therefore you can’t pass cool into the body.

So how can you start to incorporate this?

Well, Craig and colleagues have a company

that they’ve spun out through Stanford.

We’ll talk about that when we sit down with Craig,

that has made engineered devices that are optimal for this,

that are going to keep those passages open,

keep the size of those veins correct

to pass cool into the body quickly

for sake of elite sports performance

and even recreational sports performance.

But you can actually start to incorporate this.

First of all, I always get asked,

how cold should the water be?

Should it be ice water?

Should it be very cold water?

The answer is no.

If you want to experience some of this effect

without a device, one thing you could do

would be for instance, to do, I don’t know,

I’ll use the gym or the treadmill as an example.

You could do your maximum number of pull-ups, stop,

and then you could actually put your hands into

or on the surface of a sink that is presumably stopped up

with cool water.

So not ice water, not freezing cold, but cool water.

Slightly cooler than body temperature

before you started training would be a good place to start.

You do that for 10 to 30 seconds,

then you could go back and do your next set.

You would repeat the cooling.

You would want to extend the amount of cooling somewhat.

So you might want to do that for 30 seconds to a minute.

This is not going to be perfect.

You’re going to have to play with how cold to make it

in order to get the optimal effect.

But you ought to see an effect nonetheless.

The same is true if you’re running and you’re fatiguing,

obviously you don’t want to become hyperthermic,

cooling the hands or the bottoms of your feet or the face

would be the ideal way to dump heat

in order to be able to generate more output.

Now, the face is something

that we haven’t talked a lot about.

Everything I’ve told you up until now also says

that if you are somebody who tends to get cold

when you are outside, say in the winter or even in the fall,

you tend to run cold,

warming your face is going to be the most important thing

that you can do.

Now, it’s kind of hard to do that without looking strange,

like wearing a ski mask or something like that,

but that is going to be more effective

than covering and warming any other part of your body.

Although it would be quite strange

if you only had a ski mask on

and you weren’t wearing clothes anywhere else on your body.

I don’t recommend doing that outside.

That will get you into all sorts of other kinds of trouble.

It wouldn’t be good for anybody.

But now you understand the principle and the locations

at which to deliver heat and cold.

So let’s say that you are out for a run

and you want to incorporate this cooling mechanism.

I talked to Craig about this.

I said, what would be the kind of poor person’s approach

to this before this device is commercially available?

And he said, well, you could take a frozen juice can,

if you have one of those, or a very cold can of soda,

and you would want to pass it back and forth

between your two hands.

The reason the passing back and forth is really important

is because, again, you don’t want to be so cold

that you constrict those venous portals

that will allow cold to go into the body.

Now, there are certainly people

that are working on bike handles

and that can actually cool the hands.

You can expect with the Olympics coming up,

people are aware of these data

and are starting to incorporate it into a number of things.

Here’s what you don’t want to do.

And there are sports teams

that I won’t mention by name or brand

that have made this mistake and it costs them dearly.

You don’t want to cool the core

if you want to cool the body, right?

If it’s a very hot day and you’re going to train,

getting into an ice bath first,

sure, it will cool you down,

but that’s not going to be as effective

as cooling the palms, the bottoms of the feet, and the face.

I have a friend who does some important work in this space

with people in various, let’s just say,

cultures where heat is generated quite a lot

and they need to dump heat.

Ice packs delivered to the face

are something that they actually use

in order to dump heat quickly.

Now, again, you don’t want to keep the ice pack

on your face.

These are people that are very high work output, right?

Firefighters and similar, at very high work output.

And then they’ll put this,

essentially it’s like a cool face mask on their face.

It’ll allow their core body temperature to come down

and then they remove it.

They’re not keeping it on there so long

that they’re getting the vasoconstriction.

Okay, so there are a number of ways that you could do this.

And again, I’m not giving specific temperatures

because it depends on how hot that day

and how hot your body temperature is.

So you can see why there’s a need

to create more devices for this,

but you can see a considerable improvement

in endurance, in strength, and in all kinds of explosive

and sort of explosive power type output in athletics

by using these surfaces of the hands

and bottoms of the feet and face.

The one that I’ve tried

because in anticipation of this episode

was the dips where then I would cool my hands.

I actually decided to cool the bottoms of my feet as well

because it just feels good

and it’s particularly hot out lately.

So no shoes or socks on, put my feet into,

the bottoms of my feet just kind of hovering

about a centimeter or two below the surface

of a bucket of water that was just slightly,

it felt cool, slightly cooler than body temperature or so.

It just basically what came out of the spigot

after I let it run for a little bit.

And indeed I saw a 60% increase in the number of dips

that I can do in a single session.

So it’s actually a quite significant effect

and you don’t have to be perfectly precise

in order to do it.

And of course, if you want to heat up for whatever reason,

like you’re camping or you’re lost in the environment,

remember these three surfaces are going to be the best way

to heat your core as well.

So up until now, we’ve been talking about

how to use cold during a workout

in order to improve performance.

And indeed cold applied to the appropriate parts

of the body, the appropriate times,

can vastly improve our performance

in endurance and strength.

Now I want to talk about the use of temperature,

in particular cold, to improve the speed

and the depth of recovery.

Recovery is obviously vital, right?

During a weight training session

or during an endurance session,

that’s just the stimulus for getting better the next time.

And if you don’t recover,

you not only won’t get better, but you’ll get worse.

There’s a lot of interest in the use of cold

in order to improve recovery in the short term.

We see this and probably the best example of this

would be fighters in combat sports between rounds

or athletes in between quarters or halftime.

That’s one form of recovery.

The ability to go back into the sport very soon

on an order of minutes, anywhere from like one minute

in between rounds in typical combat sports

or several minutes at a halftime, et cetera.

Typically what we see is people cooling their core,

cooling the back of their neck,

cooling the top of their head.

So it might be a sponge with cold water

over the top of the head

or an ice pack on the back of the neck,

or in some cases even wearing cold ice vests.

This has actually been done.

That’s going to be a very inefficient way

to improve recovery of that kind.

Far better would be to cool the face,

the palms of the hands or the bottoms of the feet

for the reasons that I described up until now.

Submerging the body in an ice bath or taking a cold shower,

say up to the neck or up to the chest

or getting under cold water or jumping in a cold lake

or something of that sort,

or in the locker room getting under the cold shower

also would be a terrible way to cool off the body quickly

compared to the ways that I described

through the palms of the hands,

the bottoms of the feet or the face

for the following reason.

First of all, it’s not optimizing those portals

of the face, palms, the hands and the feet.

And in addition, if it’s very cold and you submerge

or you cover a lot of the body with that cold,

you’re going to cause constriction

of the very vessels and pathways

that allow the body to efficiently dump heat.

So again, the key thing is to cool these one or two

or three of these surfaces,

but not so cold that you cause the vasoconstriction.

So what does this mean for you?

It means that getting in an ice bath or a cold shower

or putting an ice pack on the back of your neck

in most cases is not going to be as good

as splashing cold water on your face

or even just holding your face with a damp, cool cloth

or something of that sort.

It seems kind of counterintuitive.

You would think, oh, if I just jump into an ice bath,

I’m going to cool down much faster

than if I just cooled these one or two or three

of these select regions of the body,

but that’s actually not the case.

And then of course, there’s recovery that occurs

from session to session.

So outside of the game or the match

or the exercise session.

And many people are now relying on things like cryotherapy,

which requires a lot of expensive equipment,

big liquid nitrogen driven machine.

Those aren’t so common for most people

or accessible for most people.

But a lot of people are using cold baths

or ice baths or cold showers.

And again, that’s not going to optimize recovery.

In fact, it’s going to have an additional effect

that is going to potentially block the training stimulus.

When you get into an ice bath,

indeed there are, provided it’s not very, very cold.

If you get into a cold shower,

provided it’s not very, very cold,

you are indeed blocking some of the inflammation

that occurs because of the training session.

But in doing so, you also are blocking pathways

such as mTOR, mammalian targeted rapamycin,

which are involved in the adaptation

for a muscle to become stronger or bigger.

Put simply, covering the body in cold

or immersing the body in cold after training

can short circuit or prevent the hypertrophy

or muscle growth response.

It has other effects that can be positive, right?

It can induce thermogenesis, et cetera.

It can reduce inflammation,

but it can prevent some of the positive effects of exercise.

Now, it hasn’t been examined so much for endurance work,

but let’s say you come back from a round of endurance work,

a run or a bike or a swim,

getting into a cool bath or cooling the palms,

the bottoms of the feet or the face,

in my opinion, based on the science,

would be better than completely immersing the body

in the ice bath or the cold shower.

There is a time and a place for the use of the ice bath

or the cold shower or the cold plunge.

Those tend to be when you want to deliberately increase

brown fat thermogenesis,

or when you want to deliberately work on mental resilience.

And in a subsequent episode on fat loss,

I’m going to talk about how to optimize the use of cold

specifically for increasing metabolism and fat loss.

But for now, since we’re talking about the use of cold

for improving performance and recovery,

the suggestion that I’m going to provide

is based on the work of Craig Heller and colleagues

that I’ve been talking about, as well as a excellent book.

I mainly rely on textbooks and special volume books,

which are collections of papers from experts

in a particular area that go beyond

standard kind of college level textbooks.

The one that I’ve been relying on

is called Thermal Regulation in Human Performance,

Physiological and Biological Aspects by F.E. Marino.

I don’t know the publisher.

I don’t know the author.

I do recognize some of the names

of the particular papers there,

but I just want to be clear,

there’s no sort of business relationship or deal with them,

but it’s an excellent text.

It’s called Thermal Regulation in Human Performance.

You can find it online

if you want to go really deep into this.

But basically what they show is that

if you can cool the body back to its resting temperature,

by resting temperature, I mean,

within the range that you would see

at any time of waking day, but not in exercise.

So just bringing the body temperature down to baseline.

If you can do that,

the sooner you can do that after a workout,

the sooner that the muscle will recover,

that the tendons will recover,

and that the person, you,

can get back into more endurance training,

more weight training, et cetera.

So cold actually can be a very powerful tool for recovery,

but to maximize return to baseline levels of temperature,

it’s my belief based on the studies

that are published in this book,

as well as my discussions with my colleague, Craig Heller,

and in reviewing the literature overall,

that just simply cooling the entire body

by jumping into an ice bath or a cold shower

is not the best way to go.

You really want to rely

on one of these three glabrous skin portals

of the palms, the bottoms of the feet, or the face.

So now you probably know more than you ever wanted to know

about how we regulate body temperature

and how it can be applied to exercise,

both during the exercise session

and afterward to optimize recovery.

Many of us, all of us presumably,

are also eating and drinking things

and taking things at various times

that can impact this process.

And so because of that,

we should ask whether or not those things

are impacting body temperature.

And when we do that,

we find that there are certain things

that many of us are doing

that are actually impairing our performance.

So for instance, if you are taking a pre-workout drink

or you’re ingesting a lot of caffeine or other substance

to bring your body temperature up before exercise,

you are limiting the amount of exercise that you can do.

I can recall a time in college

when I would drink a lot of espresso.

Back then, ephedrine was sold over the counter.

I remember taking it.

It will really energize you for workouts.

You can generate a lot of energy

and get extremely focused taking those things.

They do increase heart rate.

They can be quite dangerous.

I don’t recommend people take them.

In fact, I think ephedrine is now off the shelves

as a non-prescription compound

because various people died from taking it

who were sensitive to it or exercised in heat.

But looking back at that,

I realized it was a foolish approach.

It was increasing core thermogenesis.

Sure, I might’ve burned a few more calories,

but actually when I look at the data

that are coming from specific cooling

and how that can so increase in performance

if done properly,

and then I compare that to the effects

of taking some sort of thermogenic compound,

whatever it is, some pre-workout or some pill

or high levels of caffeine,

it’s very clear that increasing body temperature

prior to working out is the exact wrong thing

that one would want to do.

You don’t want to stay so cold

that you can’t generate good muscle contractions.

You don’t want to be like I am coming out of the cold ocean

with claws for hands,

but one wants to have your body temperature

in a range that still allows you to work hard

and perform well.

Now, in terms of recovery,

things like alcohol, we know are vasodilators.

So those are going to cause people

to drop body temperature.

So you might think, oh, well,

that sounds great for recovery.

And I don’t think people should be drinking

who have problems with alcohol intake,

alcoholics or they’re not of drinking age, et cetera.

I’m not a drinker,

but I do have a good friend

who’s a quite accomplished athlete

who basically drinks a beer or two after his long runs

or cycling and his argument is,

well, I’m dumping body heat and I like a beer.

And he’s probably right.

It’s probably a really good tool

provided you don’t have issues with alcohol

that would preclude that as a tool

or you’re not of drinking age.

But anything that you ingest after exercise

that would increase body temperature

is going to impede recovery.

Anything that you do that lowers body temperature

provided it’s in safe ranges

is going to accelerate recovery.

And that brings us to the whole host of compounds

that people take that can increase body temperature.

And many people are taking these things

in order to increase fat burning and increase metabolism.

But in my opinion,

it’s impeding their ability to perform well.

And especially if the performance

is something that you’re focused on

aside from body recomposition, losing fat, building muscle.

But even if you’re focused on losing fat, building muscle,

you have to ask yourself,

is the body temperature increase

that I’m getting from these compounds really worth it

given that it can block or prevent my performance

from being as good as it could?

In other words, is it worth taking something

that makes you feel very energized to go work out,

but then you now know that you are stopping earlier

and you’re performing less well,

fewer reps, fewer steps overall.

Is it worth it?

If you had not taken that thing,

then you could perform much longer

and at much higher capacity.

Some of you are probably saying, well, that’s ridiculous

because when I drink a quadruple espresso

and I pop a whatever pre-workout or drink a pre-workout,

then I know I can go much further.

Ah, that might be true,

but the increase in temperature

is also costing you on the recovery side.

And unless you’re doing other things

to improve your recovery,

and I know many people that are, I don’t judge,

but many people who are doing those things

are also augmenting their recovery

through hormone augmentation

and other performance enhancing tools.

Then for the typical person who’s not doing that,

it’s probably shooting yourself in the foot.

So let’s take a look at what some of those compounds are

and what they do, and just briefly review

whether or not they would be a good or a bad idea

to include if your main goals are performance

or your main goals are body recomposition or both.

So let’s just briefly discuss stimulants.

This could be caffeine,

this could be any other kind of stimulant

that are typically in a pre-workout drink

or anything that might get you revved up before exercising.

This could even be very strong tea.

I’ve mentioned I’m a big consumer of mate.

I like yerba mate, I love that stuff.

And I also drink caffeine.

I love coffee of various kinds, mushroom coffee,

black coffee, espresso, et cetera.

I’m a chronic caffeine user.

I don’t think I’m an addict,

but I’m a chronic caffeine user,

meaning when I drink caffeine,

my heart rate doesn’t increase so much

that it feels like a shock to my system.

Some people are not caffeine adapted

or they’re very caffeine sensitive.

Here’s the straightforward rule.

Caffeine for somebody who doesn’t drink caffeine very much

will constrict the blood vessels

and will increase retention of body heat

and is probably a bad idea before exercise.

For somebody who’s caffeine adapted

and is used to drinking caffeine,

it won’t have that vasoconstriction effect.

That’s what the data point to because I’m adapted to it,

but it will cause vasodilation

and will allow me to dump body heat.

So for me, I use it before I train

or do any kind of exercise

because I tend to do that early in the day.

It won’t prevent me from sleeping

and it causes vasodilation.

And then afterwards, I’m aware that it causes

vasoconstriction after the caffeine wears off.

So for somebody who drinks two or three or more

cups of coffee a day or mate a day,

so we’re talking intake of anywhere from 100

to 400 milligrams of caffeine,

what you want to do is you want to make sure

that you would do that before exercise

and probably not after exercise.

That just makes logical sense

given what we know about thermal regulation.

And if you’re somebody who doesn’t drink caffeine,

drinking caffeine before a workout

is going to be about the worst thing

that you could possibly do

because it’s going to increase core body temperature

through its thermogenic effects

and it’s going to constrict your blood vessels

and make it even harder to dump heat.

So I don’t suggest that people drink caffeine or not.

I just suggest that you think about

whether or not you’re caffeine adapted or not

and decide whether or not you want to drink caffeine.

In general, you’re going to be better

not drinking any caffeine than you are drinking caffeine

unless you’re a heavy caffeine user or abuser,

in which case not drinking caffeine

is going to give you vicious headaches

and it’s going to make it very hard to get motivated

because you’re just not used to it.

It takes about three weeks to get used to no caffeine.

It’s brutal.

I’ve done it before.

I’ve done caffeine fast.

I don’t know that I ever want to do it again.

That’s how painful it was.

But you get headaches

because of the effects on vasodilation and constriction.

If you like caffeine, use in moderate amounts

and use it before your workouts, not after.

If you don’t like caffeine or you don’t use it very often,

stay away from it anywhere close to exercise

before or after for that matter.

One of the more commonly used compounds

that’s sold over the counter

are non-steroid anti-inflammatories.

So things like Tylenol and Advil and other trade names

and naproxen sodium, things of that sort.

Almost all of those drop body temperature to some extent.

And that’s why it’s often recommended

that people take them when they have a fever.

Although the whole business

of dropping body temperature artificially

when you have a fever is itself an interesting discussion,

whether or not that’s the most adaptive

or best thing to do.

Certainly you don’t want fever to go too high.

It can be very dangerous, can kill you.

But artificially dropping body temperature

with these compounds can be tricky.

Now, a number of athletes, especially endurance athletes,

will rely on these non-steroid anti-inflammatory drugs

specifically to keep body temperature lower

during long bouts of exertion.

This is a little bit of a pharmacologic version

of dumping heat instead of using Palmer cooling

or face ice pack cooling.

They’re relying on pharmacology

to drop their core body temperature.

That has certain obvious advantages.

Those advantages should be obvious

and the reasons for them should be obvious

based on everything we’ve talked about up until now.

Lower temperature allows you to go further harder

with more intensity.

However, they do have effects on the liver

and they can also have effects on the kidneys.

And during long bouts of exercise

or even short bouts of exercise,

water balance and salt balance are also going to be vital

to maintain in order to perform well,

generate the best muscle contraction,

stay mentally alert, and also to stay alive.

We will do an episode on salt electrolytes

and water and water balance,

but you probably want to think carefully

about whether or not you want to use

non-steroid anti-inflammatories before any training session

just for the performance augmentation effect,

unless you’re working carefully with a coach,

whether or not you’ve done that in practices.

And of course, whether or not you are in a situation

where monitoring your body temperature carefully

is going to be important.

You might ask, well, when would that be?

Well, desert races, summer training and races, winter rides.

You certainly don’t want to get too cool either.

So alcohol, caffeine,

and non-steroid anti-inflammatory drugs,

because of their effects on temperature,

will impact performance and recovery,

but you want to be cautious about how you approach them.

I personally am more a fan of using caffeine

in moderate doses for the reasons I described before,

as well to use the cooling of the palms,

cooling of the bottoms of my feet, right,

by placing them into a bucket

or into a cool bath after training,

or cooling the face after training,

or sometimes even during training.

It just seems like there’s more of a margin

to play with the variables,

to heat up the water, cool it down a little bit,

to include one palm or the other palm.

There’s just all sorts of good parameter space,

as we call it in science,

that you can play with and work with

to find what works for you.

Whereas when you pop a pill,

sure, you can adjust the dose

and you can adjust it next time,

but once it’s in you, it’s in you,

and there’s going to be some period of time

before you can modulate it.

What I’ve offered today are ways

in which you can use temperature

to powerfully improve performance.

And if you think about it,

you can vary that from set to set.

You could do your pull-ups or your sprints

and then cool your palms,

and then try and go with colder water the next round,

or warmer water the next round,

or do both feet and palms and face.

I mean, you can do all sorts of things moment to moment

and see what works for you.

Again, essentially zero cost or no cost.

Whereas when you pop something,

you take a pill,

you’re basically in that regimen

for the next hour or two or more.

You can always take more,

but you can’t really take less.

You can’t really extract it from your body in real time.

So it doesn’t give you a lot of opportunity

to play scientist,

which is what I like to do,

because what I’m always trying to do

is trying to dial in the best protocols possible

based on the mechanisms and data.

And if you can do that moment to moment,

that places you in a position of power.

Once again, we’ve covered a lot of material.

By now, after seeing this episode

or listening to this episode,

you should understand a lot

about how your body heats and cools itself

and the value of that for physical performance.

I hope you’ll also appreciate

that you have tools at your disposal

to vastly improve your physical performance.

And should you try those,

please let us know how it goes.

If you decide to do Palmer cooling during your runs

or after your runs,

during your weight workouts,

during your yoga sessions,

whatever it is, let us know.

Please place that in the comments.

I’ve given you specific protocols and some direction,

but I’ve also left it slightly vague

because as I mentioned earlier,

I don’t know all the environmental conditions.

I don’t know how hot your yoga studio is

or how cool your gym happens to be

or your body temperature or time of day.

Remember, your temperature will vary

according to the time of day.

We did a whole episode about that related to sleep.

Typically, your body temperature is rising early in the day

and is coming down as you approach the late evening

and late night hours for sleep.

In the middle of the night,

your temperature is very low,

at its absolute lowest,

something we call the temperature minimum.

So we don’t know exactly where you’re at.

You need to take the information that you received today

and should you try and incorporate it,

try and do it intelligently.

Don’t cool yourself off so much

that you become cryogenic

and please don’t warm yourself up.

In fact, we didn’t talk at all about warming yourself up

because warming yourself up too much

can be quite dangerous.

You never, ever, ever want to be hypothermic.

That’s what your body and your brain are trying to avoid.

We talked a little bit about supplements,

but not the standard sorts of supplements

I usually list off on these episodes.

Rather, we talked about caffeine,

non-steroid anti-inflammatories

and how those can impact temperature,

how alcohol can impact temperature.

And I should just mention in closing

that every time we eat, we also increase temperature.

There’s a eating-induced thermogenic effect,

but that’s a minor one.

That’s a small one.

So you wouldn’t worry about eating before training

because of its effects on temperature

because it tends to be really minor.

Going forward, we’re going to talk more about temperature

and other ways to improve physical performance

and skill learning.

We’re going to talk about specific ways

to accelerate fat loss, to improve muscle growth,

to improve suppleness and flexibility.

These approaches and mechanisms are anchored deeply

in neuroscience and physiology

and the relationship between our peripheral organs,

which include our skin and our brain

and all the organs in between.

So it’s really a pleasure for me

because I’m able to look to the textbook literature

that exists and really came out

over the last 50 to 100 years.

And unlike a lot of areas of neuroscience,

which are still sort of mystical,

like consciousness and dreaming,

of which we understand a little bit about,

these core mechanisms of temperature and physiology,

which are so powerful, involve very concrete studies

that, as you learned today, are very actionable.

If you’re enjoying this podcast

and you like the information that you’re receiving,

if you’re incorporating it into your life in useful ways,

please recommend the podcast to other people

if you think they could benefit from it as well.

Please subscribe to the podcast on YouTube.

So you want to hit the subscribe button

as well hit the notifications button.

We come out with new episodes every Monday,

but from time to time, we also release shorter content

and we will be releasing additional content

in between episodes from time to time.

If you don’t already subscribe on Apple and or Spotify,

please do so.

Also on Apple, you have the opportunity to leave us

up to a five-star review,

if you think that we deserve a five-star review,

and to leave us feedback.

They have a comment section there.

It’s really a feedback section where you can rate

and describe the podcast as you experience it.

If you’d like to support the podcast in other ways,

please check out our sponsors.

That’s a terrific way to support us.

And as mentioned at the beginning of today’s episode,

we are now partnered with Momentous Supplements

because they make single ingredient formulations

that are of the absolute highest quality

and they ship international.

If you go to livemomentous.com slash Huberman,

you will find many of the supplements

that have been discussed on various episodes

of the Huberman Lab Podcast,

and you will find various protocols related

to those supplements.

And last but not least,

I want to thank you for your time and attention.

I realize this is a lot of information.

I hope you’ll find some of it to be actionable

and useful for you and for people that you know.

And as always, thank you for your interest in science.