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Using Deliberate Cold Exposure for Health and Performance | Huberman Lab — Transcript

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0:00- Welcome to the Huberman Lab Podcast,
0:01where we discuss science
0:03and science based tools for everyday life.
0:09I'm Andrew Huberman,
0:10and I'm a professor of neurobiology
0:11and ophthalmology at Stanford School of Medicine.
0:15Today, we are going to discuss the use
0:16of deliberate cold exposure
0:18for health and performance.
0:20Temperature is a powerful stimulus on our nervous system
0:23and indeed on every organ and system of our body
0:26and cold in particular can be leveraged
0:29to improve mental health, physical health, and performance,
0:33meaning for endurance exercise, for recovering
0:36from various forms of exercise,
0:38for actually improving strength and power
0:41and for enhancing mental capacity.
0:43In order to properly leverage deliberate cold exposure
0:46for sake of mental health, physical health and performance,
0:50you have to understand how cold impacts the brain and body.
0:53So today we are going to discuss that.
0:55We're going to talk about some of the neural circuits
0:57and pathways, some of the hormones involved.
0:59I promise to make it all clear and accessible
1:02regardless of whether or not
1:03you have a scientific background or not.
1:05We are also going to discuss very specific protocols
1:08that you can apply,
1:09which leverage variables like temperature,
1:11how cold, how to deliver the cold, for instance,
1:14whether or not you use a cold shower,
1:16cold immersion, ice bath, circulating water, or still water,
1:20whether or not you're going for walks outside in a t-shirt
1:23when it's cold or whether or not
1:25you're purposefully using things like cryo,
1:28if you have access to that or not.
1:30One thing I can promise you
1:31is that by the end of today's episode,
1:33you will know a lot about the biology of thermal regulation,
1:36that is how your brain and body regulates its temperature.
1:40You will also have a lot of tools in your arsenal
1:42that you can use and leverage
1:44toward improving mental health,
1:45physical health, reducing inflammation in the body,
1:48improving athletic performance,
1:50improving mental performance.
1:51I promise to spell out all those protocols in detail
1:54as I go along and to summarize them again at the end.
1:57I'd like to make a point now that I'm going to make
1:59several additional times during today's episode
2:02and that is that temperature is a very potent stimulus
2:06for the brain and body.
2:07That also means that it carries certain hazards
2:10if it's not done correctly.
2:12Now, everyone shows up to the table,
2:14meaning to protocols,
2:15with a different background of health status
2:17and there's simply no way that I can know
2:19what your health status is.
2:20So anytime you are going to take on a new protocol,
2:23that means a behavioral protocol or a nutritional protocol
2:26or a supplementation protocol,
2:28you should absolutely consult a board certified physician
2:31before initiating that protocol.
2:34I don't just say this to protect us,
2:35I also say this to protect you.
2:37If you'd like to see our medical disclaimer,
2:39you can go to our show notes, it's described there.
2:41In fact, I encourage you to please do that.
2:43And in general,
2:45when embarking on new protocols in particular,
2:48if they involve strong stimuli like changing temperature
2:51or placing yourself into unusual temperatures,
2:54I would encourage you to progress gradually.
2:56I would also encourage you to not look at
2:59gradual progression as the kind of weak version
3:02of a protocol.
3:03In fact, today I'm going to discuss
3:04a really beautiful peer reviewed study
3:06that involved having people do deliberate cold exposure
3:10so they were immersing themselves into water
3:12up to about their neck
3:13and the water was actually not that cold.
3:15It was only about 60 degrees Fahrenheit,
3:17which for most people is pretty tolerable.
3:19So nowhere near the kinds of extreme temperatures
3:22that one could use in other protocols.
3:25And the interesting thing is despite
3:27that fairly modest cold temperature,
3:30by simply extending the duration of time
3:31that people were in that water,
3:33they experienced enormous increases in neurochemicals
3:36that ought to translate to improvements in focus and mood.
3:40And indeed, that's what's been observed
3:42in subsequent studies.
3:44So again, please see our medical disclaimer
3:46in our show notes, please proceed with caution always,
3:50please also understand that the most potent stimulus
3:54isn't always the one that you experience
3:56as the most intense in the moment.
3:58In fact, I would encourage you to you find
3:59the minimum threshold of stimulus
4:02that will allow you to drive the maximum benefit
4:05from each protocol and indeed,
4:07I will point out what those thresholds ought to be today.
4:10I'll give you some simple formulas,
4:12gauges or guides that you can use in order to navigate
4:15this extremely interesting and potent tool
4:18that we call deliberate cold exposure.
4:20Before we talk about deliberate cold exposure
4:22and its many powerful applications,
4:24I'd like to highlight a study
4:26that I find particularly interesting,
4:27that I think you will find
4:29particularly interesting and useful.
4:31The title of this study is brief aerobic exercise
4:35immediately enhances visual attentional control
4:37and perceptual speed,
4:39testing the mediated role of feelings of energy.
4:43Now, the reason I like this study is first of all,
4:46it's a fairly large size sample group.
4:48They looked at 101 students.
4:52These were college-aged students and they had two groups.
4:55One group did 15 minutes of jogging at moderate intensity.
5:01So they did measure percent heart rates, et cetera,
5:04but this would be analogous to zone two cardio,
5:08which I've discussed on this podcast before.
5:10Zone two cardio is cardiovascular exercise
5:14that places you at a level where you can hold a conversation
5:18with a little bit of strain,
5:20meaning that you can get the words out,
5:21but every once in a while you have to catch your breath
5:23whereas if you were to push any harder by any mechanism
5:27going faster or on a steeper incline, et cetera,
5:30that you would have a hard time carrying out a conversation.
5:32So zone two cardio is a common form of describing
5:37that level of intensity that they call moderate intensity.
5:40So one group did 15 minute of jogging at moderate intensity,
5:44which I'm translating to roughly zone two cardio.
5:47The other group did 15 minutes of relaxation concentration
5:52that is somewhat akin to mindfulness meditation.
5:55And then they were analyzed for perceptual speed,
5:59visual attentional control, something called working memory,
6:01which is your ability
6:02to keep certain batches of information online.
6:06Just imagine someone telling you their phone number,
6:08and you have to remember that sequence of numbers
6:10in your head for some period of time, that's working memory.
6:13And it depends very heavily on the so-called
6:15prefrontal cortical networks,
6:18which are involved in planning and action.
6:20And they also looked at people's feelings of energy
6:23and they measured that subjectively,
6:24how energetic people felt.
6:26Now the major takeaways from this study
6:28that I'd like to emphasize are that
6:30the 15 minutes of jogging group
6:32experienced elevated levels of energy
6:35for some period of time after they ceased the exercise
6:38whereas the group that did mindfulness meditation
6:41actually reported feeling more calm
6:44and having less overall energy.
6:46Now that's very subjective and indeed they used
6:48subjective measures to analyze energy,
6:52but what gets interesting is when they looked at performance
6:55on these various cognitive tasks and the two tasks
6:58that they use were called the trail making tests,
7:01they have different versions of this,
7:02version A, version B,
7:03I don't want to go into too much detail,
7:05but version A essentially involves having a page of numbers
7:09that are distributed somewhat randomly.
7:11So one, two, three, four, five, six, seven, eight and so on,
7:14but distributed randomly across the page
7:15and people have to use visual search
7:17to circle those numbers in sequence.
7:19So this involves visual attention,
7:21it involves some motor skills,
7:23involves a number of things
7:24that certainly require energy and focus.
7:27The second test was the trail making test part B,
7:30as I mentioned earlier,
7:31and this involved also circling numbers in sequence,
7:34but interspersed between those numbers were letters.
7:36So rather than just having
7:37to circle off numbers in sequence,
7:39they actually had to connect one,
7:41then the letter A, then two, then the letter B, et cetera
7:44and remember these are randomly distributed across the page.
7:47The major takeaway from the study is that the group that did
7:50the 15 minutes of moderate exercise prior to these two tests
7:55showed significant decreases in the amount of time required
7:58to complete these tests accurately.
8:01That is interesting and indeed surprising at least to me,
8:05because there have been many studies looking at the effects
8:08of mindfulness meditation on the ability to focus.
8:11The key variable in the study turned out to be energy.
8:14This subjectively measured feeling I should say
8:17of having more energy and thereby the ability to focus,
8:20especially in these high cognitive demand tasks.
8:23Now the takeaway from this study for all of us
8:25I think is pretty straightforward.
8:27If you are going to sit down to do some work
8:30that requires focus and working memory
8:32and cognitive attention
8:33and especially if it's some visual spatial control,
8:36meaning you have to search for things on a page,
8:38you have to organize things on a page,
8:39so some writing, arithmetic,
8:41basically cognitive work of any kind,
8:4415 minutes of moderate exercise done prior
8:48to that work about could be very beneficial for you.
8:51This does not mean that mindfulness meditation
8:53would not be a benefit to you.
8:55I wouldn't want you to conclude that,
8:57but if you had to choose between doing
8:5815 minutes of mindfulness meditation
9:00and doing 15 minutes of moderate exercise
9:02prior to a cognitive work about,
9:05I would say the 15 minutes of moderate exercise would be
9:09more valuable at least based on the data in this paper.
9:12In many previous podcasts,
9:14I have talked about the powerful effects of doing things
9:17like mindfulness meditation, and other forms of NSDR,
9:21non-sleep deep rest.
9:23So these could be 20 minute naps or just lying there quietly
9:25with your eyes closed or yoga nidra
9:28or NSDR scripts are available on YouTube
9:31and various other places free of cost of any kind.
9:34You just go to YouTube, put in NSDR,
9:36non-sleep deep rest.
9:38Those protocols have been shown to be very beneficial
9:41for enhancing neuroplasticity,
9:43the changes in the brain and body that encode
9:47or shift the neural circuits that allow
9:49for memory to change,
9:51that allow for learning to occur after a learning about.
9:55What I'm referring to today in this particular study
9:58is the use of moderate exercise
10:00in order to increase one's focus and attention
10:03in order to trigger that neuroplasticity.
10:06So the simple sequence here is get energetic and alert,
10:12do that prior to the learning about,
10:14engage in the cognitive work or learning about,
10:16and then mindfulness meditation,
10:18NSDR and so forth should follow.
10:20And if you would like to access this paper
10:23and like to look more at the details in the paper,
10:25we'll be sure to put a link in the show notes.
10:27The first author is Legrand.
10:29And again, the title of this paper is brief aerobic exercise
10:31immediately enhances visual potential control
10:33and perceptual speed,
10:34testing the mediating role of feeling of energy.
10:37And I also just want to emphasize immediately.
10:40I think most people out there are interested in tools
10:42and protocols that work the first time
10:43and that work every time
10:45and indeed, I think this protocol fits that bill.
10:47I'm pleased to announce
10:48that I'm hosting two live events this May.
10:51The first live event will be hosted
10:52in Seattle, Washington on May 17th.
10:55The second live event
10:56will be hosted in Portland, Oregon on May 18th,
10:59both are part of a lecture series entitled
11:01the Brain Body Contract during which I will discuss science
11:04and science-based tools for mental health,
11:07physical health and performance.
11:08And I should point out that while some of the material
11:11I'll cover will overlap with information covered here
11:14on the Huberman Lab Podcast
11:15and on various social media posts,
11:17most of the information I will cover is going to be distinct
11:20from information covered on the podcast or elsewhere.
11:23So once again, it's Seattle on May 17th,
11:26Portland on May 18th.
11:27You can access tickets by going to hubermanlab.com/tour
11:31and I hope to see you there.
11:32Before we begin,
11:33I'd like to emphasize that this podcast is separate
11:36from my teaching and research roles at Stanford.
11:38It is however part of my desire and effort
11:40to bring zero cost to consumer information about science
11:43and science-related tools to the general public.
11:45In keeping with that theme,
11:46I'd like to thank the sponsors of today's podcast.
11:49Our first sponsor is Athletic Greens, also called AG One.
11:53I started taking AG One way back in 2012
11:56so I'm delighted that they're sponsoring the podcast.
11:59The reason I started taking AG One
12:00and the reason I still take AG One
12:02once or twice a day is that it covers my
12:04foundational vitamin mineral and probiotic needs.
12:07It also has adaptogens and things like zinc
12:10for immune system function,
12:12but the probiotics are one of the key features in there.
12:14I've done several podcasts on the gut microbiome,
12:17which are these trillions of microbiota
12:18that live in our digestive tract,
12:20and that are crucial for our immune system,
12:22brain function and so on.
12:24One way to enhance our gut microbiome
12:26to ensure that it's healthy is to make sure
12:28that we get the correct probiotics and Athletic Greens
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12:35a healthy gut microbiome.
12:36If you'd like to try Athletic Greens,
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12:46So in the car and on the plane.
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13:06many of us, even if we do get sunlight,
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13:10So the year supply of vitamin D three also has K two,
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13:24Today's episode is also brought to us by ROKA.
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13:38Now the glasses were initially designed
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15:37Let's talk about the use of cold for health and performance.
15:40I confess I love this topic
15:42because it takes me back to my undergraduate years
15:45when I worked in a laboratory studying cold physiology,
15:49its effects on the brain and its effects the body.
15:52And over the years,
15:54I've always kept track of the literature in this area
15:56and indeed there have been some tremendous discoveries,
15:59both in animal models, so in rodents like mice and rats,
16:02but also in humans
16:04and today we're going to talk about both categories
16:07of studies and I'll be careful to point out when discoveries
16:10were made in animal models
16:11and when they were made in humans.
16:15A key point when thinking about the use of cold as a tool,
16:19and the key point is that you have a baseline level
16:23of temperature that is varying,
16:26changing across the 24 hour cycle.
16:29So any use of deliberate cold exposure
16:32is going to be super imposed on that rhythm,
16:36that circadian rhythm, meaning that 24 hour rhythm.
16:40The basic contour of your circadian rhythm in temperature
16:44is that approximately two hours before the time you wake up
16:49is your so-called temperature minimum.
16:51So your temperature minimum is a time
16:54within the 24 hour cycle
16:56when your body temperature is at its lowest.
16:59So if you normally wake up around 6:00 AM,
17:03your temperature minimum is probably about 4:00 AM.
17:07If you normally wake up at about 7:00 AM,
17:10your temperature minimum is probably about 5:00 AM.
17:13It's not exactly two hours before your wake up time,
17:16it's approximately two hours before your wake up time.
17:19Now, as you go from your temperature minimum
17:22to the time in which you're going to awake,
17:25your temperature is rising slightly.
17:27And then at the point where you wake up,
17:30your temperature starts to go up more sharply
17:33and will continue to go up into the early
17:36and sometimes even into the late afternoon.
17:38And then sometime in the late afternoon and evening,
17:41your temperature will start to decline.
17:44And indeed, as you approach sleep,
17:46your body temperature will drop
17:48by anywhere from one to three degrees.
17:50And in fact that decrease in core body temperature
17:53is important if not essential for getting into
17:56and staying in deep sleep.
17:59So temperature rises with waking, that's easy to remember.
18:02It tends to continue to rise throughout the day
18:05and in the late afternoon and evening,
18:07your temperature WILL start to go down and the drop
18:10in temperature actually helps you access sleep.
18:13That background or what we call baseline circadian rhythm
18:18in core body temperature is important to remember
18:21because it helps us frame both the effects
18:24of deliberate cold exposure and helps us frame
18:28when you might want to use deliberate cold exposure
18:31in order to access specific states.
18:33It also points to times within the 24 hour cycle
18:36when you might want to avoid using deliberate cold exposure,
18:39if your primary goal is to get to sleep.
18:42So that's the circadian rhythm in temperature.
18:45Now I just briefly want to touch on
18:47thermal regulation at the level of body and the brain.
18:51And this will be very surprising to many of you.
18:55Let's do what's called a Gedanken experiment,
18:57which is a thought experiment.
18:58Let's say I send you out into the desert heat
19:01for a jog or a run and it's very hot outside,
19:05102 or 103 degrees, and you start to move,
19:11you start to sweat
19:12and of course your core body temperature goes up.
19:14Now, then I offer you a cold towel,
19:18maybe a really, really cold towel
19:21and this towel is saturated with water
19:22so you could actually squeeze the water out of that
19:24and cool your body off.
19:26And our Gedanken experiment is for me to say okay,
19:29where are you going to place the towel?
19:31How are you going to cool yourself off?
19:33And I'm guessing that most of you would think
19:35that the best way to cool yourself off
19:37would be to drape that towel over your head,
19:39maybe your neck, over your torso,
19:42that it would feel really, really good,
19:43and it would cool you off.
19:45Well, that's exactly the wrong approach
19:48if you want to cool off.
19:49And in fact, if you were to use that approach,
19:52your body temperature would continue to increase even more.
19:56Yes, even more than had you not placed
19:59that cold towel on your head or your torso.
20:02And here is why.
20:04Thermal regulation meaning your brain and body's ability
20:07to regulate your internal core temperature
20:10is somewhat like a thermostat and that thermostat
20:13resides in your brain.
20:15So if you think about the thermostat
20:16in your home or apartment,
20:18if it's too warm in your home or apartment
20:22and you were to take a bag of ice
20:24and to put it on that thermostat,
20:27what would the thermostat do?
20:29It would register the environment as artificially cool.
20:32It would think that the environment
20:34was actually much colder than it is.
20:37And so as a consequence,
20:39it would trigger a mechanism
20:41to further increase the temperature in the room.
20:43And you have such a thermostat as well.
20:45It's called the medial preoptic area of the hypothalamus.
20:48The hypothalamus is a small region of brain tissue
20:52about over the roof of your mouth
20:54and a little bit in front of that.
20:56So it's basically right behind your nose and over the roof
21:00of your mouth and it's a collection of neurons.
21:02Those neurons have a lot of different functions
21:04that include things like the control of aggression,
21:07the control of sex behavior,
21:09the control of temperature regulation and so on.
21:11The medial preoptic area has connections with
21:15the rest of the brain
21:17or areas within the brain, I should say
21:19and with many areas within the body,
21:21it receives input from receptors in our skin
21:26and inside our body that register temperature
21:29and it acts as a thermostat.
21:31So if the surface of your body is made cool,
21:34your medial preoptic area will send signals
21:38by way of hormones
21:40and by way of chemicals that will serve
21:42to heat your body up.
21:44So what this means is that if you want to cool down,
21:47the last thing you want to do is to bring a cold surface
21:52of any kind, towel or splashing water,
21:54to the majority of your body surface.
21:56It might be very, very surprising to you.
21:59And you might say, wait, if I want to cool down,
22:00I should jump into a cold lake or something of that sort.
22:02That's a different thing altogether.
22:05What I'll tell you,
22:06and we'll get into this in more depth later,
22:08is that if you really
22:09want to cool down quickly and efficiently,
22:11you should leverage particular portals,
22:14meaning particular sites on your body
22:18where heat can leave your body more readily
22:21and where cooling can have a dramatic and fast impact
22:26on your core body temperature,
22:27can even save your life if you're going hyperthermic.
22:29We're going to talk more about the specific protocols to reduce
22:32core body temperature for sake of performance
22:34and avoiding hyperthermia later in the episode.
22:37Hyperthermia of course is a very, very dangerous situation
22:40because while your body can drop in core temperature
22:44somewhat and still be safe,
22:45you can't really increase your body temperature that much
22:48before your brain starts to cook
22:50and other organs start to cook and by cook,
22:52I mean the cells actually start to die.
22:54So you have to be very, very careful with the use of heat.
22:56Heat stroke is no joke.
22:58People die from heat stroke all the time.
23:00You really want to avoid that.
23:02One way to avoid that is to cool the appropriate surfaces
23:06of your body and the appropriate surfaces in this case
23:10are the upper cheeks
23:11or I would say the upper half of the face,
23:14the palms of your hands and the bottoms of your feet.
23:16I've talked about this on the podcast before
23:18and in the guest episode with Dr. Craig Heller,
23:20my colleague in the biology department at Stanford,
23:23but just very briefly, these surfaces,
23:26the upper half of the face,
23:28the palms of the hands and the bottoms of the feet
23:31are what we call
23:32glabrous skin surfaces, G-L-A-B-R-O-U-S, glabrous.
23:38And those surfaces are unique in that just below them,
23:42the vasculature is different than elsewhere in the body.
23:46Normally the passage of blood goes from
23:48arteries to capillaries to veins,
23:50but just beneath the glabrous skin on the bottoms
23:54of the feet, the hands in the upper half of the face,
23:56you have what are called arterio-venous anastomoses.
23:59These are portals of blood that go directly
24:03from arteries to veins and in doing so,
24:05allow the body to dump heat more readily, more quickly.
24:11So as it turns out that if you are to cool the palms
24:15of the hands, the bottoms of the feet
24:16and the upper half of the face,
24:17you can more efficiently reduce core body temperature
24:20for sake of offsetting hyperthermia
24:23and for improving athletic performance
24:25and maybe even cognitive performance.
24:27So we will return to the specific protocols
24:29for doing that later in the episode,
24:31I'll give you a lot of details about how to do that,
24:34how to do that without the use of
24:35any fancy or expensive technology.
24:38There are some technologies
24:39that are now commercially available, for instance,
24:41the so-called CoolMitt
24:43that will allow you to do that with maximum efficiency,
24:45but I'll also give you some at home methods to do this
24:48either in the gym or on runs or for sake of cognitive work.
24:52So the two key themes again
24:54are understand that baseline circadian rhythm
24:57in temperature, and understand that the best way to cool
25:01the body is going to be
25:02by making sure that something cold contacts
25:07the bottoms of your feet,
25:08the palms of your hands and the upper half of the face.
25:10Ideally all three
25:11if your goal is to lower core body temperature quickly,
25:13and again, just cooling off the back of your neck
25:17or the top of your head or your torso with a towel
25:19is going to be the least efficient way
25:21to lower core body temperature and might even increase
25:24body temperature under certain conditions.
25:27With those two points in mind,
25:28we can start to think about directed deliberate
25:31cold exposure protocols,
25:32and there are a number of different reasons
25:34to use deliberate cold exposure.
25:36And I want to separate those out for you.
25:40There are cold protocols that have been tested
25:42in peer reviewed studies that are designed
25:45to improve mental performance.
25:47They are designed to improve things like resilience
25:49or your grittiness,
25:50or your ability to move through challenge
25:52or to regulate your mind and your internal state
25:56under conditions of stress
25:57and we can define stress very specifically as times
26:01when adrenaline also called epinephrine
26:04and or norepinephrine also called noradrenaline,
26:09are elevated in your body.
26:10Forgive me for the noradrenaline,
26:12norepinephrine, adrenaline, epinephrine nomenclature,
26:15I didn't make that up.
26:16It turns out that every once in a while,
26:17scientists disagree, imagine that,
26:20and you'll get multiple scientists
26:21naming the same molecule different things.
26:23So epinephrine and adrenaline are the same thing.
26:26I will use them interchangeably.
26:28Norepinephrine and noradrenaline are the same thing.
26:31I will use those terms interchangeably.
26:34Noradrenaline and adrenaline
26:36are often co-released in the brain and body.
26:38So they work as kind of a pair to increase
26:41our level of agitation,
26:42our level of focus and our desire and our ability to move.
26:47They are often co-released from different sites
26:50in the brain and body with dopamine,
26:52a molecule that is commonly misunderstood
26:56as the molecule of pleasure,
26:58but is actually the molecule of motivation,
27:00reward and pursuit.
27:02So dopamine, norepinephrine and noradrenaline
27:04tend to be released together under certain conditions
27:08and today you'll learn how deliberate cold exposure
27:11can be used to cause increases in the release of several,
27:15if not, all of these in ways
27:16that can improve your levels of attention and your mood.
27:21But the key point is that your mental state is shifted
27:26when you are exposed to certain forms of cold,
27:29and many people use deliberate cold exposure
27:32specifically to shift their body state as a way
27:35to train their mental state so that they can better cope
27:38with stress in real life and by real life,
27:41I mean when life presents stressful events,
27:43and I will give you specific protocols
27:45as to how you can do that, in other words,
27:47how you can become more resilient
27:49through the use of deliberate cold exposure.
27:52Now, because of the ways in which deliberate cold exposure
27:55can increase this category of chemicals
27:57called the catecholamines,
27:58that includes dopamine, norepinephrine and epinephrine,
28:02it can also be used to elevate mood
28:05for long periods of time.
28:07And I'm going to discuss a specific protocol
28:10that has been shown to increase these chemicals
28:13anywhere from 2.5X to 250%, to as high as 500%,
28:21five times over baseline.
28:23Now you might be asking whether or not it is a good thing
28:26to raise chemicals like norepinephrine and dopamine
28:29to such a great degree,
28:31whether or not that's healthy for us,
28:32whether or not they can harm us.
28:34But it turns out that these elevations in norepinephrine
28:36and dopamine are very long lasting in ways
28:39that people report feeling vast improvements
28:43in mood and vast improvements
28:45in levels of cognitive attention and energy.
28:48So by my read of the literature,
28:50these seem to be healthy increases in our baseline levels
28:55of these chemicals in ways that can really support us
28:57so I'll give you a protocol for that.
28:59Now, those are some of the mental effects
29:01of deliberate cold exposure,
29:03but deliberate cold exposure has also been studied
29:05in animal models and in humans
29:07in the context of increasing metabolism,
29:09even in converting certain fat cells
29:12that we call white fat cells,
29:14which are the ones where energy is stored,
29:16they're the ones that we typically think of
29:17as kind of blubbery fat, to beige or brown fat,
29:21which is thermogenic fat,
29:23meaning that it can increase core body temperature
29:25and serves kind of the furnace
29:27by which we increase our core metabolism.
29:31So with a very broad stroke,
29:33I can say that white fat is generally the kind of fat
29:35that people want less of and beige fat and brown fat
29:38is generally the kind of fat that
29:40if you're going to have fat cells and
29:42you certainly need fat cells that you want more of.
29:45They are thermogenic, they help you stay lean.
29:47They actually serve as a reservoir for heating your body up
29:50if you're ever confronted with a cold challenge.
29:52So we're going to talk about how to use cold
29:53for metabolism as well.
29:55And of course,
29:56people are using deliberate cold exposure
29:57to reduce inflammation post exercise,
30:00to reduce inflammation generally.
30:02And people are also using cold to enhance performance
30:06in the context of strength training,
30:08in the context of endurance training
30:10and we'll talk about those data as well,
30:12but where I'd like to start is with mental performance
30:14and I'd like to detail what happens
30:18when we deliberately expose ourselves to cold.
30:21It's key to point out the word deliberate.
30:24If I don't say otherwise, then throughout this episode,
30:27if I say cold exposure, I mean deliberate cold exposure.
30:30And the reason I point that out is that as my colleague,
30:33David Spiegel, and the department of psychiatry
30:34at Stanford says,
30:36it's not just about the state that we are in,
30:38it's about the state that we are in and whether or not
30:40we had anything to with placing ourselves into that state
30:43and whether or not we did that on purpose or not.
30:45And what he really means by that statement is that
30:50there are important effects of what we call mindset.
30:53Mindset was a topic discussed in the guest episode
30:56with Ali Crumb some weeks ago.
30:58If you haven't seen that episode, I highly recommend it.
31:01And the science of my mindset tells us that if we are doing
31:04something deliberately and we believe
31:06that it's going to be good for us,
31:08it actually can lead to a different set
31:11of physiological effects than if something
31:15is happening to us against our will or without our control.
31:18Now, this is different than placebo effects.
31:20Placebo effects are distinct from mindset effects.
31:23If you want to learn more about that distinction,
31:25please see the episode with Ali Crumb.
31:27But again, when I talk about cold exposure in this episode,
31:30I'm talking about deliberate cold exposure,
31:33meaning that you are placing yourself into a
31:36cold environment on purpose in order to extract
31:38a particular set of benefits.
31:42When we talk about deliberate cold exposure, almost always,
31:45that means getting uncomfortable.
31:48And one of the most common questions I get
31:50when discussing the use of cold for sake of mental
31:52or physical performance, metabolism, et cetera,
31:54is how cold should it be?
31:57How cold should the water be?
31:58How cold should the environment be?
32:00And I just will tell you now
32:02and I'm going to say this again and again
32:03throughout the episode,
32:04cause it will continue to be true throughout the episode
32:06and long after the episode is over,
32:09how cold depends on your cold tolerance,
32:12your core metabolism,
32:14and a number of other features that there is simply no way
32:18I could know or have access to.
32:20So I would like you to use this rule of thumb.
32:24If you are using deliberate cold exposure,
32:27the environment that you place yourself into
32:30should place your mind into a state of whoa,
32:34I would really like to get out of this environment,
32:36but I can stay in safely.
32:39Now that might seem a little bit arbitrary,
32:41but let's say you were to get into a warm shower
32:43and it would feel really, really nice
32:45and you were to start turning down the warm
32:47and turning up the cold.
32:48There would be some threshold at which
32:50it would feel uncomfortable to you.
32:52And if you were to continue to make a little bit colder
32:54than that, you would really want to get out of the shower,
32:57but you are confident that you could stay in
33:00without risking your health, without risking a heart attack.
33:04Now that's very different than jumping into
33:05a very, very cold lake or
33:09I've seen these images of people that will cut holes into
33:12frozen over lakes and they'll get into that cold water.
33:16If you are trained to do that
33:17and you have the right conditions, et cetera,
33:19that can be done reasonably safely,
33:21but that's certainly not what I would start with.
33:23And for many people, that would be too cold
33:25and indeed some people can go into cold shock
33:28and can die as a consequence of getting
33:30to that extremely cold water very quickly.
33:32Now that's not to scare you away
33:33from deliberate cold exposure.
33:34It's just to say that there's no simple prescriptive
33:38of how cold to make environment
33:39in order to extract maximum benefit
33:43for mental or physical performance.
33:46So the simple rule of thumb is going to be
33:49place yourself into an environment
33:51that is uncomfortably cold,
33:53but that you can stay in safely.
33:55And you'll have to experiment a bit and that number,
33:57meaning that temperature, will vary from day to day.
34:00It will vary across the 24 hour cycle
34:03because of that endogenous,
34:05meaning that internal rhythm,
34:06in temperature that I talked about earlier.
34:09Low early in the day,
34:10rises into the afternoon, drops at night.
34:12You can actually do this experiment if you like.
34:14Try getting into a cold shower at 11 o'clock at night
34:17if you want versus try doing it
34:20in the middle of the afternoon.
34:22It's quite a different experience
34:24and by quite a different experience,
34:25I mean it requires quite a different degree of resilience
34:29and leaning into the practice.
34:31Your willpower will have to be higher I suspect
34:35late in the day as it compared to early in the day,
34:39but that will vary of course between individuals as well.
34:42So the most common question I get
34:43about deliberate cold exposure
34:45is how cold should the water be?
34:48And we've answered that with uncomfortably cold to the point
34:51where you want to get out,
34:52but you can safely stay in.
34:53The second most common question I get
34:55about deliberate cold exposure is whether or not
34:57cold showers are as good,
34:59better or worse than cold water immersion
35:02up to the neck, for instance.
35:04I also get a lot of questions about whether or not
35:06cryo chambers are better than all the others,
35:08et cetera, et cetera.
35:10I'm going to make all of that
35:12very simple for you by saying cold water immersion
35:14up to the neck with your feet and hands submerged also
35:18is going to be the most effective.
35:20Second best would be cold shower.
35:23Third best would be to go outside
35:26with a minimum amount of clothing, but of course,
35:29clothing that is culturally appropriate
35:32and that would allow you to experience cold to the point
35:35where you would almost want to shiver or start shivering.
35:38Now there are a number of different,
35:40important constraints that are going to dictate
35:42whether or not you use one form of cold exposure
35:44or the other.
35:45For instance, some people don't have access
35:47to cold water immersion.
35:48They don't have access to ice baths or cold water tanks,
35:53cold ocean or cold lakes, et cetera.
35:55In that case, showers would be the next best solution.
35:58I do want to emphasize that there have been very few,
36:01if any, studies of cold showers,
36:04and you can imagine why this would be the case.
36:07In a laboratory,
36:08you want to control for as many variables as possible.
36:11So placing people into a cold water immersion or an ice bath
36:16up to the neck and insisting they keep their hands
36:18and feet under is very easy to control.
36:21It means that everyone can do essentially the same thing
36:23whereas with cold showers,
36:25people are different sized bodies.
36:27Some people are going to put their head under.
36:28Some people are going to lean forward.
36:31Measuring the amount of cold water exposure on the body
36:34is very hard to do
36:35and so there aren't a lot of studies of cold showers,
36:38but of course,
36:39a lot of people don't have access to cold water immersion
36:41so they have to use cold showers.
36:43And if you don't have access to both, of course,
36:45then going outside on a cold day can be of a benefit.
36:49But I will point out that the heat transfer
36:53from your body into water is much higher,
36:57four times greater, if not even greater,
37:00depending on the temperature of the water,
37:02in water as opposed to in air.
37:04So it's going to be much more efficient
37:05to do cold water immersion than anything else,
37:07cold showers after that and put yourself into
37:10a cold environment would be the third best thing.
37:13I'm not going to get into cryo chambers
37:15because they carry quite a high degree of cost.
37:18And again, there aren't many studies of them.
37:20So if you have access to cryo chambers,
37:23I'm sure that the cryo chamber facility
37:24has told you about all these incredible benefits
37:26and I don't doubt that some of those benefits truly exist,
37:29but most people just don't have the resources
37:31or the access to those
37:32so we're going to leave cryo chambers
37:33out of today's discussion.
37:34And of course I realize there's a fourth category
37:37of cold exposure out there.
37:38People are wearing ice vests.
37:39Believe it or not, those exist, ice underwear.
37:41Yes, those exist.
37:44You can look for them on Amazon if you like.
37:46They are putting cold packs in their armpits
37:49or in their groin or elsewhere in order to
37:51stimulate some of the effects of cold
37:54on mental and physical performance.
37:56I'm not going to address those in too much detail today.
37:59They can be efficient in certain ways,
38:02but as you'll learn about later in the episode,
38:04cooling the palms, the upper face
38:07and the bottoms of the feet
38:08is going to be far more efficient
38:10and unfortunately I think most of the people that are using
38:13ice packs to increase their core metabolism
38:15are not aware of the glabrous skin cooling
38:18and how it can be a very, very potent stimulus
38:20so we'll return to that later.
38:23Unless I say otherwise,
38:24I'm mainly going to be focusing on cold water immersion
38:26and cold showers.
38:28So let's talk about protocols for enhancing mental health
38:30and performance using deliberate cold exposure.
38:34What happens when we get into cold is that we experience
38:38an increase in norepinephrine,
38:41in noradrenaline release and in adrenaline release.
38:44The fact that cold exposure, deliberate or no,
38:47increases norepinephrine and epinephrine
38:50in our brain and body means that it is
38:52a very reliable stimulus for increasing
38:54norepinephrine and epinephrine.
38:56That's sort of an obvious statement,
38:58but that obvious statement can be leveraged
39:02to systematically build up what we call resilience.
39:05Now, when we experience a stressor in life,
39:08whether or not it's something bad happens
39:10in our relationship or something bad happens in the world
39:14and we feel stress,
39:16that stress is the consequence of increases
39:18in norepinephrine and epinephrine in our brain and body.
39:22Very similar, if not identical,
39:23to the kinds of increases
39:24that come from deliberate cold exposure.
39:27So deliberate cold exposure is an opportunity
39:29to deliberately stress our body and yet,
39:33because it's deliberate
39:34and because we can take certain steps,
39:36which I'll describe in a moment,
39:38we can learn to maintain mental clarity,
39:41we can learn to maintain calm while our body
39:45is in a state of stress.
39:47And that can be immensely useful
39:49when encountering stressors in other parts of life.
39:53And that's what we call resilience or grit,
39:55our ability or mental toughness,
39:57our ability to lean into challenge or to tolerate challenge
40:01while keeping our heads straight, so to speak.
40:04So one simple protocol for increasing resilience
40:07is to pick a temperature that's uncomfortable
40:10of shower or cold immersion,
40:12and then to get in for a certain duration of time
40:15and then to get out.
40:17Now, it's important to understand
40:18that people will experience different levels
40:20of norepinephrine and adrenaline release
40:22when getting into cold water.
40:24Some people, because they dread the cold so much,
40:28will actually experience norepinephrine
40:29and epinephrine increases
40:31even before they get into the cold water
40:33or under the cold shower.
40:35Now you may have experienced this.
40:36I've certainly experienced this.
40:37I'm dreading it, I don't want to do it
40:39and I have to force myself to do it.
40:41And indeed epinephrine and norepinephrine and its surges
40:45can be thought of as sort of walls that we have to confront
40:48and go over.
40:49And I'd like you to conceptualize them that way,
40:52because it allows us to build protocols
40:54that can be very objective and can allow us
40:58to monitor our progress in terms of building resilience.
41:01So one option is to simply say, okay,
41:04I'm going to force myself
41:05to get into the cold shower for one minute.
41:07How cold, again, uncomfortably cold,
41:09but you can stay in safely
41:10or I'm going to get into the ice bath for one minute.
41:13Ice baths are very cold inevitably.
41:16And what is also inevitable is that
41:19when you get into the cold,
41:20you will experience a surge
41:22in epinephrine and norepinephrine.
41:24That's non-negotiable because it's mediated
41:26by cold receptors on the surface of your body
41:29and your skin and the way that they trigger the release
41:32of norepinephrine and epinephrine,
41:33not just from the adrenals,
41:35from the adrenal glands above your kidneys,
41:37but also from regions of your brain,
41:38like the locus coeruleus,
41:39which cause increases in the tension and alertness,
41:42and from other locations in your body where epinephrine
41:45and norepinephrine are released.
41:47In other words, cold is a non-negotiable stimulus
41:51for increasing epinephrine and norepinephrine.
41:55Even if you are the toughest person in the world
41:58and you love the cold,
42:00that increase in epinephrine and norepinephrine
42:02is going to happen.
42:04So the way to think about norepinephrine and epinephrine
42:06in this context of building mental resilience
42:09is that you have two options.
42:11You can either try to extend the duration of time
42:15that you are in the deliberate cold exposure.
42:17So going from one minute to 75 seconds to two minutes
42:21and so on over a period of days
42:23or one way to approach this
42:25and the way that I particularly favor
42:27is to take the context of the day
42:30and the moment into account,
42:32meaning we have different levels of grit and resilience
42:36on different days and depending on the landscape
42:38of our life at the time,
42:39even the time of day that we're doing these protocols
42:42and start to be able to sense the release of epinephrine,
42:47and norepinephrine in our brain and body and see those
42:50as walls that we want to climb over
42:52in order to build resilience and to start counting
42:55the number of walls that we traverse
42:57and the distance between those walls
42:59as we do deliberate cold exposure.
43:01Let me give you an example of the timed protocol
43:05because that one is very straightforward,
43:06although I do not think it is as powerful
43:09for building mental resilience.
43:11The time protocol would be Monday,
43:12I do one minute of deliberate cold exposure
43:15at a given temperature.
43:16Wednesday, I extend that by 50% and Friday,
43:19I do deliberate cold exposure for twice as long
43:22as I did it on Monday.
43:23And if I were to continue that every week,
43:26Monday, Wednesday, Friday,
43:27I would continue to either increase the duration
43:29or I would lower the temperature and reduce the duration,
43:34this kind of thing, very much like sets and reps in the gym.
43:36Now that option is very objective.
43:38You could even log it in a book
43:40and as you develop the ability to stay in cold temperatures,
43:46even progressively colder and colder temperatures
43:48for longer and longer periods of time,
43:50you will become more resilient.
43:52What do I mean by that?
43:53Well, my operational definition of resilience
43:55is that you are able to resist escape from the stressor,
43:59the cold, by virtue of your willpower,
44:02which is really your prefrontal cortex
44:05causing top down control on your reflexes
44:08and your limbic system and your hypothalamus,
44:10which are basically telling you
44:11to get out of that cold water,
44:13get out of that cold environment and in doing so,
44:17you are basically getting better
44:19at controlling your behavior when your brain and body
44:21are flooded with norepinephrine and epinephrine.
44:24That's a very reductionist way to explain resilience
44:26or grit or mental toughness,
44:28but it's a reductionist way of explaining it
44:30that is very closely tied to the biology end
44:32of the psychology.
44:33And it is a fact that norepinephrine and epinephrine
44:37release in the brain and body
44:39are the generic universal code for stressor.
44:43There is no unique chemical signature
44:45for different forms of stressors, that is the only one,
44:48although of course there are
44:49other chemicals involved as well.
44:50So you could go for time and you could try
44:52and reduce the temperature and increase the time
44:55over a period of days or weeks.
44:57Now that's an attractive way to approach things,
45:00but the problem is that you don't have an infinite amount
45:03of room with which to lower temperature,
45:06because eventually you will get into temperatures
45:08that are either so cold that they are dangerous
45:10or you have to stay in cold temperatures
45:13for such long periods that it becomes impractical
45:16because presumably you also have to
45:18take care of other aspects of your life,
45:20you can't just sit all day in the ice bath.
45:23Now for that reason,
45:24I favor a protocol in which you build mental resilience
45:27and mental toughness through
45:29two different types of protocols.
45:31The first one involves counting walls.
45:33Now, what do I mean by walls?
45:34I mean the sensation of, no,
45:37I don't want to do this and the idea or the sensation
45:41in your brain and body that you actually want to leave
45:43that environment and go warm up.
45:45Now again, for some people,
45:46that will be even before getting into the ice bath
45:49or cold shower.
45:50So if you are feeling very resistant
45:52to getting into the ice bath
45:54or cold shower and you manage to do that,
45:56that's going over what I would call one wall.
46:00Then for some period of time,
46:01you might actually feel comfortable in the ice bath,
46:05cold water or cold shower.
46:07And you feel like you could stay there
46:09for some period of time,
46:10that you could stay there for a minute or two minutes,
46:12but inevitably, the next wall will arrive.
46:15And I would encourage you to pay attention to
46:17when that next wall arrives
46:19and actually having an awareness,
46:21that so-called interceptive awareness as we call it,
46:24of when that next surge adrenaline epinephrine comes
46:27or whether or not it reaches a certain threshold
46:30in your brain and body that you feel you want to get out
46:32and you're able to stay in for even just 10 seconds longer,
46:36that means you've traversed yet another wall.
46:39And if you continue to stay in that cold environment,
46:42you'll find that the next wall will come
46:43and the next wall will come.
46:45Now eventually of course, you will get very, very numb
46:48depending on how cold it is
46:49and you could also place yourself into danger.
46:51So you have to maintain cognitive control,
46:54counting these walls, traversing these walls,
46:56but getting out at some point, of course.
46:59So my favorite protocol for building mental toughness
47:03AKA grit, AKA resilience,
47:06is to take into account that some days,
47:08just getting into the ice bath
47:10or cold shower represents a wall, some days it doesn't.
47:12Some days you get in and you feel you could go 10 minutes,
47:15other days you get in and you feel like
47:17you could only go a minute and setting a designated number
47:20of walls before you start the protocol
47:23is going to be very beneficial here.
47:24So you say, as long as I can do it safely,
47:27I'm going to do three walls today.
47:29The first wall is getting in.
47:30The second wall will arrive when it arrives
47:32and the third wall will arrive when it arrives
47:35and I'll get over that wall and then I'll get out.
47:37The next day, you might do five walls.
47:38The next day, you might do three walls again,
47:41but you might lower the temperature.
47:43This gives you tremendous flexibility
47:45and indeed it gives you much more latitude
47:48to be able to use the same temperatures in different ways,
47:52or to reduce the temperature only a little bit
47:54and still get a lot of stimulus,
47:56meaning a lot of results out of a given protocol.
48:00Whereas people who are just going for temperature and time
48:02eventually become cold adapted.
48:04They get very, very good at doing three minutes
48:07or six minutes or even 10 minutes at a given temperature
48:10and so then they feel like they have
48:12to lower the temperature even more and even more
48:14and eventually they just bought them out.
48:16There's nowhere else to go.
48:17There's no way to get improvements out of the protocol.
48:21At least not in terms of mental resilience.
48:24Of course, there's still the positive effects
48:26on inflammation and metabolism, et cetera,
48:28that we'll talk about in a little bit.
48:30But the key thing here is to design protocols
48:33that are going to work for you over time
48:35and for you very, very hardy,
48:37very, very tough guys and gals out there
48:39that can get right into
48:40an ice bath or a very, very cold immersion
48:43and you can just grind it out for six or 10 minutes,
48:45or you can even do that by remaining peaceful,
48:48well more points to you, but guess what?
48:51That's the equivalent of already having loaded up
48:53the barbell with 600 pounds and done your 10 reps.
48:56There's not a whole lot more variable space
48:59with which to get benefits from that stimulus.
49:02And in the weight room,
49:03people understand that you can adjust, for instance,
49:05the speed of the movement,
49:06or you can start combining that movement
49:08with pre-exhaustion, et cetera.
49:09With cold exposure,
49:11you don't have as much variable space to play with.
49:13So if your goal is to build resilience,
49:15either go for time as a function of temperature,
49:18or what I suggest is to start recognizing these walls
49:23as an experience of resistance in you
49:25and going over those walls, set a certain number of walls
49:28that you're going to go over on a given day and do that
49:31at a given temperature, and then to mix it up.
49:34And ideally you might even throw in one more wall
49:38at the end,
49:39if you're really feeling bold and brave
49:41because that's going to build out further resilience.
49:43But if you want cold exposure to work for you
49:45for sake of building up resilience
49:46and mental toughness over time,
49:48you're going to want to vary this parameter space
49:51in some sort of way.
49:52And you don't have to be super systematic about it.
49:56That's the beauty of this kind of approach
49:58because you're relying on the fact
49:59that those walls really represent times
50:02in which you are forcing your top down control,
50:05your prefrontal cortex to clamp down on your reflex
50:08and you're learning behavioral control in the context
50:11of your body having elevated levels
50:12of these catecholamines, norepinephrine and epinephrine.
50:15And that translates to real life
50:17in a much more realistic way I believe because in real life,
50:21you're not really engaging in stressors
50:24for a given amount of time
50:26that you know how long it's going to last
50:28and you know the context, no.
50:29Most stressors arrive in the form of surprises
50:31we don't like, text messages that deliver bad news,
50:34information about the outside world or real world
50:37and online interactions that send our system
50:40into a state of increased norepinephrine and epinephrine.
50:42And if you start to think of those as walls
50:44that you can tolerate and climb over
50:46while staying and calm and clear of mind,
50:48then you can really imagine how the ice bath
50:52and other forms of cold exposure are really serving
50:55to train you up for real life stressors.
50:58The next question that I always get is
51:00what should my mental state be
51:02while I'm exposing myself to this uncomfortable,
51:04yet safe condition of cold?
51:07Well, you have two options
51:09and there are probably other options as well.
51:11One is to try and calm yourself
51:14to remain as mentally still as possible.
51:17The other is to lean into that challenge
51:21and so to grind it out and here,
51:23I have to say that this is a lot like teaching someone
51:25to drive on a gravel road.
51:27For any of you that have driven on a gravel road,
51:29you know that there is no optimal speed
51:32for all gravel roads.
51:33It depends on the density of the gravel, et cetera,
51:35and the vehicle, et cetera.
51:37So for instance, on some gravel roads,
51:40when you start to drive and the dust starts to kick up,
51:42your best option is to drive fast
51:44and put that dust cloud behind you.
51:46On other gravel roads, if you try and do that,
51:49the dust actually kicks up around the vehicle
51:50and it makes it hard to see
51:52and sometimes you have to slow down.
51:53The same thing is true for getting through
51:55deliberate cold exposure.
51:57Sometimes it's easier to calm yourself.
51:59One way to do that is through double inhales
52:01through the nose and extended exhales through the mouth,
52:04or simply by trying to control your breathing
52:06and reduce the pace of your breath and increase
52:09the volume of your breathing.
52:12I have to say that everyone experiences a shortening
52:15of breath when they get into uncomfortably cold water,
52:18that is a universal physiological response.
52:21Everyone also experiences a 30 to 80% decrease
52:26in cognitive function, in particular, the frontal cortex.
52:29The metabolism of your frontal cortex goes down,
52:31the metabolism meaning the activity of brain areas
52:34associated with stress and panic goes way up.
52:36And so anchoring your mind in cognitive activities
52:41as you get into the cold can be very,
52:43very helpful for maintaining clarity of mind.
52:46In fact, one thing that I sometimes recommend
52:48is that people try and engage
52:50in some sort of cognitive exercise while in the cold,
52:53not as a form of distraction,
52:55but as a way to maintain clarity of thinking
52:57and to learn how to do that when the body is flooded
52:59with all these chemicals that make us stressed.
53:02So for instance,
53:03you could do math problems and not two plus two equals four,
53:06not three times three equals nine,
53:08but things that require a little bit more focus
53:10and attention working memory and so forth.
53:13You could also start to have thoughts
53:16that you deliberately impose a full sentence structure on.
53:20That's actually quite tough.
53:22You could try and recall specific bouts of information
53:25that are challenging.
53:26This is teaching your mind how to stay online,
53:29or rather I should say,
53:30this is you teaching your prefrontal cortex,
53:32how to stay engaged while you have high levels of stress
53:35in your body.
53:36Years ago, I had a friend who works
53:39in the neuroscience world, research neuroscientist,
53:42who was obsessed with this very bizarre sport
53:45that I don't necessarily recommend at all,
53:47which is the combination of boxing and chess.
53:50You may have seen this on YouTube
53:51where people will box around,
53:53legitimate boxing around, they're sparring all out often.
53:56And then at the end of the round,
53:58instead of resting in the corner,
53:59they actually sit down and play chess,
54:01and then they go back to boxing and back to chess.
54:03Again, not a sport that I recommend,
54:05but the reason he was obsessed with this is because
54:08he studies the impact of stress on cognitive performance.
54:11And what that particular very bizarre sport was doing
54:14was toggling back and forth
54:15between different states of mind.
54:17Now it's used both to increase cognitive clarity
54:22for the fighter when they box,
54:23because staying calm and clear thinking
54:25is very important to winning boxing matches.
54:27Believe it or not, it's not an all outrage.
54:29It's a very calculated game of mental chess
54:32and physical chess that's quite high stakes
54:34as you can imagine.
54:36It's also used in some circles as a way to teach people
54:40how to engage in cognitive performance
54:42when their body is simply filled to a stress.
54:44So in the boxing chess example,
54:46the replacement for the cold water is actually the boxing,
54:50it's the thing that's supposed to induce the stress
54:52cause getting hit is stressful and the risk
54:54of getting hit is stressful for most people.
54:57So again, if you think about deliberate cold exposure
55:00as a way of just systematically and reliably
55:03inducing epinephrine and norepinephrine release
55:05and delivering stress,
55:07well then this idea of maintaining cognitive clarity
55:09and actually engaging in cognitive tasks
55:11while in the ice bath or cold shower
55:14can actually be very beneficial.
55:15Even though it might sound a little bit silly,
55:16you are really training up your ability
55:18to keep your brain working
55:20when the reflex is to shut down the parts of your brain
55:24that are involved in deliberate planning and thinking.
55:26Now another important aspect of deliberate cold exposure
55:29that I rarely if ever hear discussed,
55:32but is vitally important is whether or not
55:35you move around or not.
55:37And here's the reason.
55:38When you get into cold water and you remain there
55:43for some period of time,
55:44your body is generating heat and that heat generates
55:47what's called a thermal layer
55:49that surrounds your entire body.
55:52So if you stay still,
55:54you are actually warmer than if you move around,
55:57you can try this the next time
55:58you're doing your deliberate cold exposure.
55:59If you're submerged up to the neck,
56:01sit there for about 10, 30 seconds
56:03and be very, very still of body.
56:05In fact, this is the way that most people start
56:07to do deliberate cold exposure.
56:09They give this very stoic look.
56:10They don't blink, they look very peaceful.
56:12Some of them even look tough
56:13or they make a very even A, emotional face
56:17and so it looks like they're really tough,
56:20but they are so still that believe it or not,
56:22they're not providing the most potent stimulus.
56:26If they or you were to move around in that water,
56:30what would happen is you'd break up the thermal layer
56:32and that you actually experience that as much colder.
56:36So if you really want to push the resilience aspect,
56:39or for instance, if you want to use a given temperature
56:42that you're comfortable in,
56:43but that you want to increase the stimulus
56:45and you want to get some more benefit
56:47for mental resilience training,
56:49well then get into the cold water,
56:51move your body around continuously,
56:53but try and keep your mind still,
56:55or even do some sort of cognitive task.
56:57So as you're starting to realize,
56:59there are a bunch of different variables
57:00that you can play with while maintaining
57:02the same temperature of water and in doing so,
57:05really keep you in the zone of what should
57:08and absolutely has to be safe for you
57:10without having to just continually drop the temperature
57:13from say 60 degrees to 55 to 40 to 33
57:15because as I mentioned before,
57:16eventually you're going to bottom out.
57:18So if you're one of those people that likes to look tough
57:20or really relaxed while you're in the ice bath
57:22or cold water immersion,
57:24just realize that you're actually cheating yourself out
57:26of part of the stimulus.
57:28Keep those limbs moving and of course,
57:31limbs under the water, feet and hands
57:33is going to be a more potent stimulus
57:35than hands and feet out for reasons
57:38that should be obvious based on what we talked about
57:40in terms of glabrous skin cooling.
57:42Keep those submerged, move your body,
57:45maybe move your knees up and down, pedal your feet
57:48and trust me, it's going to feel a lot colder
57:50than were you to remain stone still.
57:52Another very common question
57:53is how often to do deliberate cold exposure.
57:56It's tough to make a recommendation on that
57:59based on any peer reviewed study
58:01although there are a few in humans that point to a threshold
58:04of 11 minutes total per week.
58:07So that's total throughout the week
58:09divided into two or four sessions
58:11of two or three minutes or so.
58:13Now that 11 minute cutoff is not a strict threshold
58:16and is actually geared more towards increases in metabolism,
58:20we'll get into this a little bit later in the episode,
58:22but I think the 11 minute threshold,
58:25meaning 11 minutes total of deliberate cold exposure
58:28per week is a pretty good number to use
58:31if you need a number in order to keep you consistent.
58:34But as we talked about earlier,
58:36some of you are going to be in the ice bath
58:39or cold immersion or cold shower for one minute,
58:42others of you will be in there for 10 minutes,
58:44depending on how frequent and how high, if you will,
58:47those walls of adrenaline are coming.
58:50So for some of you,
58:52getting into a cold shower for three minutes total
58:54for the whole week will represent a tremendous
58:57achievement in terms of willpower and overcoming
59:00the resistance to doing that, overcoming those walls.
59:02For others of you, three minutes is nothing.
59:05So what do I recommend,
59:06I recommend that you get at least 11 minutes total per week,
59:11but at the point where 11 minutes total per week
59:13is very easy for you,
59:14where is no longer representing
59:15a significant mental challenge,
59:17meaning you're not experiencing many of these walls,
59:19you're excited to get into the cold shower immersion,
59:21you're going through it easily, you're cruising basically.
59:24Then I would say either lower the temperature safely,
59:27of course, extend the duration safely, of course,
59:31or increase the frequency so that you're doing this
59:33perhaps every day or maybe five days a week
59:36or three days a week.
59:37I personally get tremendous benefit
59:39from doing deliberate cold exposure three times a week
59:42and using the walls method that I described earlier
59:45as my gauge for how long to stay in
59:47and typically that means that I'm staying in for anywhere
59:50from two minutes to six minutes per session
59:53and that averages out to about
59:5611 to 15 minutes total per week.
59:59So again, I do not think that you need to be super strict
1:00:02about these guidelines.
1:00:04It's most important when embracing a protocol A,
1:00:07that you do it safely,
1:00:08but secondarily that you do it consistently.
1:00:11So find what you can do consistently
1:00:13and then vary the parameters
1:00:14that will allow you to continue to do
1:00:16deliberate cold exposure consistently,
1:00:18regardless of whether or not you have access to a shower
1:00:20or cold immersion, et cetera.
1:00:22So we've been talking about mental effects
1:00:24and the use of deliberate cold exposure
1:00:26for sake of building resilience,
1:00:28which I do believe can be tremendously powerful.
1:00:30Look, it's no coincidence that the screening
1:00:35and the training for Navy Seals
1:00:37involves a lot of exposure to cold water.
1:00:40One could argue that it is deliberate
1:00:41because they elect to go to buds,
1:00:43but when they get into the cold water at buds
1:00:46is dictated by the instructors and the reason
1:00:49they use cold water exposure as the stressor
1:00:52is that it does offer considerable leeway
1:00:55in terms of duration and temperature,
1:00:58in terms of how you can use it as a stressor
1:01:00whereas things like heat don't offer much variable space
1:01:04as we say.
1:01:05There isn't a lot of room beyond which you start injuring
1:01:08or even killing people by using heat.
1:01:10So there are a lot of forms of stressors out there,
1:01:12but cold is one that we can titrate,
1:01:14that we can adjust in ways that can allow us
1:01:16to continually build up and or maintain mental toughness.
1:01:21Now, deliberate cold exposure also has many effects
1:01:25on chemicals other than norepinephrine and epinephrine,
1:01:28most notably the neuromodulator dopamine,
1:01:32which is involved in elevating our mood,
1:01:34making us feel energized and enhancing our ability to focus.
1:01:38And that has a lot to do with how dopamine engages us
1:01:41in motivated states,
1:01:43tends to narrow our thinking in our behavior
1:01:45into a particular trench of goal-directed behavior.
1:01:48If you want to learn more about dopamine,
1:01:50you can learn a lot about dopamine
1:01:52in our episode about dopamine, it's at hubermanlab.com.
1:01:55You can find it, it's a two and a half hour plus
1:01:58kind of deep dive into all things dopamine,
1:02:00focus, motivation, et cetera.
1:02:04Deliberate cold exposure has a very powerful effect
1:02:08on the release of dopamine in our brain and body.
1:02:11And this is one of the main reasons why people continue
1:02:14to do deliberate cold exposure.
1:02:17Basically it makes us feel good
1:02:19and it continues to make us feel good
1:02:21even after we get out of the cold environment.
1:02:23In fact, some people would say
1:02:25they don't feel good in the cold environment,
1:02:27it's all stress for them,
1:02:27but afterwards they feel great.
1:02:30One of our previous guests, Dr. Anna Lembke,
1:02:32who's a medical doctor at Stanford University
1:02:34School of Medicine, she's a close colleague of mine,
1:02:37described the use dopamine in her book, Dopamine Nation,
1:02:40an incredible book about addiction and dopamine
1:02:42I should mention.
1:02:43And the use of dopamine elicited by cold water exposure
1:02:49by one of her patients.
1:02:50What I'm referring to is the fact that one of her patients
1:02:53helped themselves get and stay sober off drugs
1:02:57by using deliberate cold exposure to increase dopamine.
1:03:01So a healthier form of dopamine release
1:03:03than they were engaged in prior to getting sober.
1:03:07Now, the basis for dopamine release
1:03:09in response to cold exposure
1:03:11is that the catecholamines, norepinephrine,
1:03:13epinephrine and dopamine tend to be co-released
1:03:16by the same sorts of stimuli,
1:03:18but most stressors and in particular things
1:03:21that evoke stress or our feelings of stress internally
1:03:24that we don't like do not increase dopamine.
1:03:28They only increase norepinephrine and epinephrine,
1:03:30but deliberate cold exposure
1:03:32seems to cause a dramatic increase in dopamine.
1:03:36And this has actually been substantiated
1:03:37in a really beautiful study entitled
1:03:40human physiological responses
1:03:41to immersion into water of different temperatures.
1:03:44The first author is Sramek.
1:03:46I'm almost certainly pronouncing that poorly
1:03:50and if not incorrectly, S-R-A-M-E-K.
1:03:54This was published in the European Journal
1:03:55of Applied Physiology in the year 2000,
1:03:58really a beautiful study, I love this study.
1:04:00They took people and they had them sit in chairs
1:04:03underwater but their head was out and so they were immersed
1:04:06up to the neck in either of three different temperatures.
1:04:1232 degrees Celsius, which is 89 degrees Fahrenheit,
1:04:1620 degrees Celsius, which is 68 degrees Fahrenheit,
1:04:19or 14 degrees Celsius, which is 57.2 degrees Fahrenheit.
1:04:23So not super cold, but then what they did
1:04:27is they measured people's core body temperature throughout.
1:04:30They measured their metabolism
1:04:31and they looked at serum levels
1:04:33of things like norepinephrine, epinephrine, dopamine,
1:04:36and cortisol, serum meaning within the blood.
1:04:39So a really nice and quite thorough study.
1:04:43There were not a huge number of subjects in the study,
1:04:46but nonetheless, it was a very thorough study
1:04:48in terms of the number of variables that they explored.
1:04:52So I just want to briefly highlight
1:04:54some of what they saw or what they observed in this study.
1:04:57First of all, all the groups were in the water
1:05:01of a given temperature for one hour,
1:05:04which is much longer than most
1:05:06of the deliberate cold exposure protocols
1:05:08that anyone is using at home.
1:05:09I mean, maybe you're taking one hour long cold showers,
1:05:12maybe you're getting into the ice bath for an hour
1:05:14although I don't recommend that.
1:05:15I think you'd probably get badly hypothermic or maybe
1:05:18you're getting into a cold water immersion
1:05:21for some period of time,
1:05:22but I have a hard time imagining that it would be an hour
1:05:25and I don't suggest that if it's very cold.
1:05:27So this study focused on actually somewhat
1:05:29moderately cool temperatures,
1:05:31not what I think most people would consider
1:05:33very, very cold temperatures,
1:05:35but extended the duration for quite a while.
1:05:38So again, 32 degree Celsius,
1:05:4120 degree Celsius or 14 degree Celsius.
1:05:44Here's what they observed.
1:05:45The group that was immersed up to the neck
1:05:48in 32 degrees Celsius, that is 89 degrees Fahrenheit,
1:05:51water did not experience a shift in metabolism
1:05:55nor a significant increase in dopamine,
1:05:58norepinephrine or these other catecholamines.
1:06:01The group that was in 20 degree Celsius,
1:06:03meaning 68 degree Fahrenheit,
1:06:06water for an hour experienced a 93% increase
1:06:10in metabolic rate, which is remarkable
1:06:13given that the water wasn't that cold
1:06:15and yet an hour is a pretty long time to be in there.
1:06:18And again, it speaks to the dramatic effect
1:06:21of heat transfer that water has, which I mentioned earlier,
1:06:24as opposed to being out in the air at 68 degrees,
1:06:27it would certainly not cause that increase
1:06:29in metabolic rate.
1:06:31The group that was at 14 degrees Celsius,
1:06:35meaning 57.2 degrees Fahrenheit,
1:06:37water for an hour experienced a 350% increase in metabolism.
1:06:42So huge increases in metabolism.
1:06:45Now the most interesting data to me,
1:06:48at least in terms of mental effects
1:06:50of deliberate cold exposure,
1:06:52were that the plasma or serum levels of norepinephrine
1:06:58in the blood increased 530%.
1:07:01These are huge increases in norepinephrine
1:07:04so it suggests that this is a stressful stimulus
1:07:07at least neurochemically speaking, stressful,
1:07:10despite the fact that it's not super super cold,
1:07:12although 57.2 degrees Fahrenheit,
1:07:1414 degrees Celsius it's not a warm environment,
1:07:20but it's not a ultra, ultra cold environment,
1:07:22but an hour is a very long time to be in there.
1:07:26The subjects also experienced a 250% increase
1:07:31in dopamine concentrations,
1:07:34which while not 530% as it was with norepinephrine
1:07:38is still a very large increase
1:07:40in baseline levels of dopamine.
1:07:42And what was interesting is that those increases in dopamine
1:07:45persisted for a very long period of time afterwards,
1:07:49even out to two hours.
1:07:51And they stopped the study after 120 minutes
1:07:54of getting out of the cold, but nonetheless,
1:07:58these increases in norepinephrine are huge and long lasting
1:08:01and these increases in dopamine
1:08:03are very large and long lasting.
1:08:05And I do believe that these documented effects in humans
1:08:08explain much of the enhancement of attention and of feelings
1:08:13of wellbeing and mood that people typically experience
1:08:16after doing deliberate cold exposure.
1:08:19And the reason I say that is that
1:08:21if you were to go back to the episode
1:08:23that I did on dopamine,
1:08:24or you were to go back to the episode
1:08:26that I did with Dr. Anna Lembke on addiction and dopamine,
1:08:29what you would find is that increases in dopamine
1:08:32of the sort evoked by deliberate cold exposure
1:08:35are actually very similar to the kinds of increases
1:08:38in dopamine that are elicited by things like nicotine
1:08:41or from other behaviors
1:08:43that are known to be addictive and bad for us
1:08:45because they lead to other effects on the brain
1:08:48and body that we simply don't want.
1:08:50And yet deliberate cold exposure provided is done safely
1:08:53can create similar if not greater increases in dopamine
1:08:58that are not just fleeting, that don't just occur during,
1:09:01say the consumption of some deleterious drug or activity,
1:09:05but that are very long lasting and that can be leveraged
1:09:07toward activities other than deliberate cold exposure.
1:09:11So I want to emphasize this.
1:09:13I'm not suggesting
1:09:14that people do deliberate cold exposure for an hour a day.
1:09:16And unfortunately there are not many studies yet
1:09:20exploring how shorter colder temperature
1:09:23environment exposure, say one minute or three minutes
1:09:27or six minutes at 55 degrees or at 50 degrees,
1:09:32whether or not that leads to similar,
1:09:34greater or reduced levels of dopamine in the brain and body.
1:09:38And yet almost everybody who does deliberate cold exposure
1:09:42will say yeah, it was stressful.
1:09:44I didn't enjoy it, or I eventually grew to like it,
1:09:47but that I always feel better afterwards
1:09:49and then that feeling last a very long period of time.
1:09:52And I think it's almost certain
1:09:54that those experiences that people report
1:09:56relate to these increases in dopamine
1:09:58and in concert with the increases in norepinephrine
1:10:02also explain the other effect that's commonly reported,
1:10:04which is an enhancement in mental acuity
1:10:06and the ability to focus.
1:10:09Now, here we can extrapolate to the study
1:10:11that I discussed at the early part of the episode,
1:10:14where I was talking about the use of
1:10:16short 15 minute exercise,
1:10:18kind of moderate intensity exercise
1:10:19and how that was shown to increase levels of energy
1:10:22and mental acuity
1:10:23in these working memory, visual attention tasks.
1:10:26And there, again, we have to assume somewhat
1:10:29because they weren't doing neurochemical measurements,
1:10:31but we can reasonably assume that those improvements
1:10:35in cognitive performance were due
1:10:37at least in part to the increase in catecholamines
1:10:39known to a company, moderate intensity zone two cardio.
1:10:43So what you're starting to see here is a theme.
1:10:45The theme is that virtually any stimulus
1:10:49that delivers more norepinephrine,
1:10:51epinephrine and dopamine to our system
1:10:53will sharpen our mental acuity and elevate our mood
1:10:55and will do so for some period of time.
1:10:58Deliberate cold exposure, it turns out,
1:11:00is a very potent way to increase these catecholamines,
1:11:03this category of chemicals and thereby to improve mood,
1:11:06mental acuity and levels of alertness.
1:11:09And as we'll next see, it not only has that effect,
1:11:13which can be very beneficial for many people
1:11:15in a bunch of different circumstances,
1:11:16but it also has the positive effects that many people seek
1:11:21in terms of metabolism, in lowering inflammation in the body
1:11:24and other physiological effects as well.
1:11:26And forgive me,
1:11:27I was almost ready to move on to effects
1:11:30of deliberate cold exposure on metabolism
1:11:32and inflammation and so forth,
1:11:34but I neglected to point out one of the other
1:11:36very interesting aspects of the study
1:11:39showing deliberate cold exposure
1:11:41can increase in norepinephrine and dopamine,
1:11:44which is that they observed no significant increases
1:11:48in the stress hormone cortisol
1:11:50and that is both surprising, interesting, and important
1:11:53because what it means is that the quality of stress
1:11:57that deliberate cold exposure is creating in the body
1:12:00is likely to be one of what we call use stress.
1:12:04Hans Selye, the great physiologist,
1:12:07won a Nobel Prize for distinguishing between distress,
1:12:10which is stress in the brain and body
1:12:13that causes the release of things like cortisol
1:12:16along with the other catecholamines,
1:12:18and that we experience as negative happening to us
1:12:20and can lead to negative health outcomes.
1:12:22And he distinguished that from eustress,
1:12:25which was stress that we now understand
1:12:27is associated with increases in things like norepinephrine
1:12:30and dopamine, but no increases or minimal increases
1:12:34in cortisol, and that can lead to positive health outcomes.
1:12:37So it appears that deliberate cold exposure can create
1:12:41what we call or what Hans Selye called eustress.
1:12:44In other words, it can create a condition in the brain
1:12:46and body in which we are stressing ourselves,
1:12:49we are training up resilience,
1:12:51and yet we are creating a neurochemical milieu
1:12:54that actually has many health benefits.
1:12:56Now I'd like to shift our attention
1:12:57to the effects of deliberate cold exposure on metabolism.
1:13:00And I'd like to start by detailing a study
1:13:03that was performed on humans
1:13:05and published just at the end of last year.
1:13:07The title of the study is altered
1:13:09brown fat thermoregulation,
1:13:10and enhanced cold induced thermogenesis
1:13:13in young, healthy winter swimming men.
1:13:16And I should point out that while the study
1:13:18was only performed on male subjects,
1:13:20there's no reason to think that the effects
1:13:22that they discovered would only pertain to men.
1:13:25I would hope that they would also do a study on women
1:13:27at some point in the future,
1:13:28but the effects that they describe
1:13:30are very basic core physiological processes.
1:13:34What they did is they looked at at deliberate cold exposure
1:13:37in this group of young men,
1:13:38and they used that 11 minute threshold per week.
1:13:43So in other words, they had them get into cold water
1:13:46for approximately 11 minutes per week.
1:13:50And again, that's 11 minutes total per week.
1:13:53They divided that into two sessions
1:13:56although in speaking with the first author of this study,
1:13:58Dr. Susanna Søberg,
1:13:59I learned that it probably is not important
1:14:02that it be two sessions,
1:14:03it could be three or even four sessions,
1:14:06as long as it reaches that 11 minute threshold.
1:14:09What they discovered was
1:14:11that by going into these cold environments,
1:14:14in this case cold water immersion up to the neck,
1:14:18for 11 minutes total per week,
1:14:21that these men experienced increases
1:14:23in so-called brown fat thermogenesis,
1:14:26I'll talk more about what that is in a moment,
1:14:28and increases in core body temperature
1:14:30that translate to increases in core body metabolism.
1:14:34Now, the overall increases in core body metabolism
1:14:37that they experienced were not extremely large.
1:14:42They were statistically significant,
1:14:44but they weren't extremely large.
1:14:45However, the changes in brown fat stores
1:14:50are perhaps what's most interesting about this study
1:14:53and I'll tell you why.
1:14:54The metabolic increases of deliberate cold exposure
1:14:57are both acute meaning happening in the short term.
1:15:00When you get into the cold and immediately after,
1:15:02one does experience an increase in core metabolism,
1:15:06you burn some calories, in other words,
1:15:09and while those might not be very significant increases,
1:15:14or I should say they can be statistically significant,
1:15:17but they are not enormously large numbers
1:15:20of calories burned,
1:15:22the longer lasting effects of deliberate cold exposure
1:15:27on metabolism seem to take place by changes that occur
1:15:30in the types of fat that we store in our body
1:15:34and the way that that fat impacts our metabolism
1:15:36at other times throughout the 24 hour cycle.
1:15:41This actually has a somewhat anecdotal basis,
1:15:44in particular in Scandinavia.
1:15:46I don't speak Swedish nor I speak Danish,
1:15:49nor do I speak Norwegian,
1:15:51but I do have Danish relatives
1:15:53and they were able to help me decipher
1:15:55a common Swedish saying,
1:15:58which essentially translates to the fact that
1:16:01in preparation for the summer, they say,
1:16:05one should expose themselves to warm environments
1:16:09so that one is comfortable in warm environments
1:16:12in the summer.
1:16:13That's one half of this traditional Swedish
1:16:16and also Danish saying.
1:16:17The other half of this traditional Danish-Swedish saying
1:16:22is that in preparation for winter,
1:16:24in order to not feel too cold in cold environments,
1:16:28one should prepare for those in the fall
1:16:31by not wearing a jacket and exposing one's self
1:16:34to cold environments.
1:16:36Now, of course, this is just anecdotal cultural lore,
1:16:40but it actually has a physiological basis,
1:16:42which is by exposing oneself to cold environments
1:16:46on a repeated basis in anticipation of exposure
1:16:50to more extreme cold environments,
1:16:52one can feel more comfortable
1:16:54in those extreme cold environments.
1:16:56And that's exactly what they observed
1:16:58in this study by Søberg et al.
1:17:00The men felt more comfortable in extreme cold
1:17:03if they had trained through deliberate cold exposure,
1:17:07which might not seem surprising at all,
1:17:09but based on what we talked about earlier,
1:17:12whereby deliberate cold exposure evokes this discomfort
1:17:16and this experience of norepinephrine release,
1:17:18at least in the short term, then you would say, well,
1:17:21shouldn't that deliberate cold exposure also
1:17:24make them feel uncomfortable
1:17:25like they really want to get out?
1:17:26Well, that is true
1:17:28in the beginning of a deliberate cold exposure protocol,
1:17:31meaning in the first week or in the second week
1:17:33or the third week, but what one finds
1:17:35and what you will find if you do
1:17:36deliberate cold exposure consistently is that you will then
1:17:41become more comfortable at cold temperatures
1:17:44away from the deliberate cold exposure.
1:17:46So whereas you might have previously been the person
1:17:49who is always cold in the room with air conditioning,
1:17:51or always seeking a sweater, always wanting to bundle up,
1:17:54you will be more comfortable in those cold environments.
1:17:56And the reason for that is well substantiated
1:18:00from this study and from animal studies
1:18:03whereby deliberate cold exposure
1:18:06converts one particular kind of fat cell,
1:18:09the white fat cell,
1:18:11which is a very low metabolic output cell.
1:18:15It's basically a storage site for energy
1:18:17in the body fat cells to a different type of fat cell,
1:18:21which is the beige fat cell called beige
1:18:24because it's actually beige or slightly brown
1:18:27under the microscope, or even to brown fat cells,
1:18:30which are very dark under the microscope and dark
1:18:32because they contain mitochondria
1:18:35and are very metabolically and thermogenetically active.
1:18:40In other words, white fat doesn't burn many calories.
1:18:43It's basically a storage site.
1:18:45It's a bank account for energy.
1:18:47It's filled with lipids,
1:18:50and those lipids can be used if the body needs energy
1:18:53and if it goes into a caloric deficit.
1:18:55Beige fat and brown fat acts as sort of a furnace
1:18:59or the sort of fat that you would find in a kindle,
1:19:03a fuel that can increase core body temperature.
1:19:06So beige fat and brown fat is very good
1:19:09at raising our metabolism and helps burn white fat.
1:19:13Now of course,
1:19:14it does that only in the context of a caloric deficit,
1:19:18but it can actually help create that caloric deficit.
1:19:22Having more beige fat and brown fat
1:19:24can increase your overall core metabolism, in other words,
1:19:27the number of calories that you burn per day,
1:19:30and therefore the number of calories
1:19:31that you need to either maintain or to lose weight.
1:19:35The simple translation of this is that getting into
1:19:39cold water for a total of 11 minutes, perhaps more,
1:19:43but at least 11 minutes per week
1:19:45divided into two or four sessions
1:19:47can increase your core metabolism in part
1:19:50by increasing your beige and brown fat stores.
1:19:54And we know how that works at least in animal models
1:19:57and there's now reason to suspect
1:19:59that the exact same mechanisms are occurring in humans.
1:20:02The primary way in which deliberate cold exposure converts
1:20:05white fat cells into these more metabolically
1:20:08thermogenetically active metabolism increasing
1:20:11beige and brown fat cells is because norepinephrine
1:20:18released when we get into the cold binds to receptors
1:20:22on the surface of white fat cells and activates
1:20:25downstream pathways such as UCP1,
1:20:30so this is an uncoupling protein one,
1:20:32that acts on the mitochondrial metabolism of cells
1:20:35and increases the mitochondrial output of those cells
1:20:39and the mitochondrial density of those cells.
1:20:41In other words,
1:20:42it takes a cell that has a kind of a weak engine
1:20:46or no engine for generating energy.
1:20:48Although every cell has some mitochondria,
1:20:51it takes cells that have very few mitochondria
1:20:53and increases the engine size.
1:20:56It kind of stokes the furnace of those particular cells
1:21:00and actually can change gene expression in those cells.
1:21:03So that's what's really interesting.
1:21:04Deliberate cold exposure causes increases in norepinephrine.
1:21:08which bind to receptors on the surfaces of white fat cells,
1:21:12which triggers the release of things like UCP1.
1:21:16It also causes the release of things like P-part gamma,
1:21:19and co-factor PGC1.
1:21:22I'm going to refer you to a review
1:21:23if you want to learn more about these.
1:21:25For those of you that don't want to learn more,
1:21:26all you need to know is that the downstream of all that
1:21:29are increases in mitochondria and metabolism
1:21:32and actual genetic changes in the white fat cells
1:21:36that convert them into beige and brown fat cells.
1:21:39This is especially important for adults
1:21:41because babies and young children actually don't have
1:21:46the ability to shiver
1:21:47or they have a less robust capacity to shiver.
1:21:51Very small babies really can't shiver
1:21:53so they have a lot of brown fat in order to keep them warm.
1:21:57Young children eventually develop the ability to shiver
1:22:01and maintain these brown fat stores,
1:22:02mainly around the clavicles, the heart, the upper spine,
1:22:06and in the upper back.
1:22:07And it's no coincidence that kids can often run around
1:22:10with a minimal of clothing and be comfortable
1:22:12in environments that adults would be cold in.
1:22:16As life goes on, we tend to lose beige and brown fat,
1:22:21but this mechanism that I'm referring to
1:22:23points to the plasticity of white fat,
1:22:25meaning the ability for white fat to actually convert
1:22:27its identity into this metabolically thermogenetically
1:22:31enhancing form of beige and brown fat.
1:22:33So deliberate cold exposure is a terrific way
1:22:36to increase your core metabolism
1:22:38and oftentimes critics will say, well,
1:22:40the increase in metabolism isn't that significant
1:22:42although I do want to point out again,
1:22:44the 93% and 350% increases in metabolism
1:22:49from that previous study.
1:22:51But critics then will say, well,
1:22:53that doesn't really translate to that big of a caloric burn
1:22:59during the deliberate cold exposure.
1:23:00But to that, you should say, ah,
1:23:02but that's only limiting your optics
1:23:04to just a portion of the effects
1:23:06of deliberate cold exposure because deliberate cold exposure
1:23:09can also convert white fat to beige fat and brown fat
1:23:12and lead to these more lasting increases in metabolism.
1:23:17So for any of you interested in increasing your metabolism
1:23:19and or being comfortable in cold environments
1:23:22and or being comfortable in terms of
1:23:25being able to combat stress mentally,
1:23:27deliberate cold exposure, I do believe is a powerful tool.
1:23:31And there is simply no reason why you couldn't and shouldn't
1:23:34use the same protocols that I described earlier
1:23:36for building resilience to increase metabolism.
1:23:39Provided you're hitting that 11 minute per week threshold,
1:23:43you ought to be stimulating both mechanism increases
1:23:47in resilience and increases in core metabolism.
1:23:51As I mentioned earlier,
1:23:52most of the detailed studies on the conversion of white fat
1:23:55to beige fat and brown fat through the use of cold
1:23:57have been done in animal models,
1:23:59but the human data are starting to emerge.
1:24:01And if you'd like to do the deep dive into these mechanisms,
1:24:04things like UCP1, P-part gamma, et cetera,
1:24:07there's a beautiful review that was published recently
1:24:09in the journal cell,
1:24:10which is one of the three apex journals,
1:24:12nature, science, cell.
1:24:13And the title of that paper is adipose tissue plasticity
1:24:17in health and disease.
1:24:18I love this review.
1:24:19It has beautiful diagrams detailing all of the pathways
1:24:22from cold to norepinephrine through UCP1
1:24:26downstream of things like cyclic AMP.
1:24:28If none of those names mean anything to you,
1:24:30don't worry about it.
1:24:31You certainly don't need to know these mechanisms
1:24:32to benefit from deliberate cold exposure protocols.
1:24:35If those names do mean something to you,
1:24:38or you are interested in exploring the downstream effects
1:24:41of deliberate cold exposure and something else
1:24:43that's really nice that's covered in this paper
1:24:45is how deliberate cold exposure interacts
1:24:48with fasted states and fed states.
1:24:51I think you'll also find this review very interesting.
1:24:54I don't want to go too deeply into fasted states
1:24:56and fed states right now,
1:24:58suffice to say that when we are fasted,
1:25:00meaning when we have an eaten for some period of time,
1:25:03our baseline levels of norepinephrine
1:25:06and epinephrine are already elevated.
1:25:09And so cold exposure at those times
1:25:11ought to have an even greater effect on metabolism
1:25:14and resilience and so on.
1:25:16So for you fasters or your intermittent fasters out there,
1:25:20if you really want to get fancy,
1:25:21you can do your deliberate cold exposure
1:25:24when you are fasted.
1:25:25I certainly wouldn't recommend doing it
1:25:27with a very full stomach in any case.
1:25:29And as I mentioned before on this podcast,
1:25:33intermittent fasting is, but one way,
1:25:36and certainly there are other ways
1:25:37to limit total caloric intake for sake of maintaining
1:25:40or losing weight if that's your goal.
1:25:43I know many people are using and benefit
1:25:45from intermittent fasting, however,
1:25:47and so it certainly can be combined
1:25:49with deliberate cold exposures in order
1:25:51to get even greater increases
1:25:53in norepinephrine and epinephrine.
1:25:54So for those of you that are primarily interested
1:25:57in using deliberate cold exposure
1:25:58to increase dopamine levels in your brain and body,
1:26:02you can also do a combined protocol
1:26:05whereby you ingest caffeine 60 to 120 minutes
1:26:09before the deliberate cold exposure.
1:26:11This is based on a study that I've talked about before
1:26:14entitled caffeine increases striatal dopamine D-2,
1:26:18D-3 receptor availability in the human brain.
1:26:20And as the title suggests, this study was done on humans,
1:26:23looking at the density and or efficacy
1:26:27of these dopamine receptors
1:26:29in an area of the brain called the striatum,
1:26:30which is involved in planning in action
1:26:32and also suppressing planning in action.
1:26:34It's involved very closely with whether or not
1:26:37we can engage in behavior and withhold behavior,
1:26:41the so-called go and no go ways in the brain.
1:26:44Dopamine plays a critical role in that
1:26:45and many other things as well as you now know.
1:26:49So why would you want to ingest caffeine 60 to 120 minutes
1:26:52before deliberate cold exposure?
1:26:55Well, as I talked about earlier,
1:26:57dopamine can increase quite substantially
1:27:00in response to deliberate cold exposure,
1:27:02but dopamine on its own doesn't do anything,
1:27:04it has to bind to receptors
1:27:06and this paper shows quite definitively
1:27:08that ingesting caffeine in this case,
1:27:10it was 300 milligram dose of caffeine,
1:27:12which is about the dose of caffeine
1:27:14in two or three cups of coffee,
1:27:15it depends on the strength of the coffee, of course,
1:27:17but it's not an outrageous amount of caffeine,
1:27:21that increases the density and or efficacy
1:27:23of these receptors,
1:27:24which you would allow that dopamine
1:27:25to have its greatest effect.
1:27:28And for those of you that want to get really, really fancy,
1:27:31I suppose you could do this fasted
1:27:32so you get the further increase in norepinephrine,
1:27:35then you get the dopamine increase from the cold exposure,
1:27:37the binding of the dopamine.
1:27:38Although I do want to point out that at some point,
1:27:42you start layering together enough protocols
1:27:44that you would to be spending your entire day
1:27:45trying to get this dopamine pulse
1:27:47and I would hope that you would have other activities
1:27:49that you would engage in,
1:27:50but if you're getting up in the morning and you're fasted
1:27:53because you haven't eaten all night
1:27:55and you have a cup of coffee, and then 60 minutes later,
1:27:57you take your cold shower or two hours later,
1:28:00you do your cold immersion or your cold shower,
1:28:02you would be layering together
1:28:04these different mechanisms of dopamine receptors,
1:28:06epinephrine and so forth in a way that at least to me,
1:28:09doesn't seem incompatible with having some other life
1:28:12like going to school and having relationships, et cetera.
1:28:15And this increase in dopamine,
1:28:16particularly in the striatum is not a trivial one.
1:28:20I do want to point out as the authors do
1:28:23that preclinical studies have shown
1:28:24that increases in striatal dopamine
1:28:27induced by things like modafinil,
1:28:29which is used to treat ADHD and treat narcolepsy,
1:28:33is necessary for their wake promoting actions.
1:28:36What this really says is that just having elevated levels
1:28:38of dopamine from a drug or from an ice bath,
1:28:41or what have you is not sufficient
1:28:43to get the effects of dopamine,
1:28:44you really need the receptors to be available
1:28:47and you need those receptors to be available
1:28:49in the appropriate density
1:28:50and you need those receptors to be available
1:28:52in the appropriate density in the striatum in particular.
1:28:55So I think there are a number of reasons why
1:28:57if it's compatible with the other aspects of your health,
1:29:00cause of course always you have to consider this
1:29:02on a background of cardiovascular health
1:29:03and blood pressure, et cetera,
1:29:05that ingesting a cup or two of coffee
1:29:07an hour before your ice bath may be fasted as well
1:29:11could be quite beneficial for increasing dopamine
1:29:13over quite extended periods of time.
1:29:15A couple of key points that you'll want to pay attention to
1:29:18in thinking about deliberate cold exposure and metabolism.
1:29:21In the Søberg study,
1:29:22they also explored the use of sauna and how to use sauna,
1:29:27meaning deliberate heat in conjunction with cold.
1:29:30We are going to do an entire episode about the use of heat
1:29:33for health and performance.
1:29:34So that is not the focus now, however,
1:29:38it does raise an important point
1:29:40that we do need to address at this moment,
1:29:42which is if you are using sauna
1:29:45or if you are taking warm showers
1:29:47or if you are simply using deliberate cold exposure
1:29:50of any kind,
1:29:51should you get into the heat afterward
1:29:54or before or not at all?
1:29:55And this is where we can point to the so-called
1:29:59Søberg principle, at least I call it the Søberg principle,
1:30:02the Søberg principle named after first author of this study,
1:30:05I referred to earlier, Dr. Susanna Søberg.
1:30:09In science, it is appropriate to take a key piece of data
1:30:12and call it a principle
1:30:14if in fact it translates to something larger,
1:30:16which I believe it does.
1:30:18It is generally not appropriate for people
1:30:20to name a principle after themselves
1:30:22although there are a few scientists that have done that.
1:30:25So I have named it the Søberg principle,
1:30:27but I did that to give it appropriate credit
1:30:30to Dr. Susanna Søberg,
1:30:32who discovered that and pointed out quite appropriately,
1:30:36that to achieve the greatest increases in metabolism
1:30:40through deliberate cold exposure,
1:30:42you want to force yourself to reheat on your own
1:30:47after the deliberate cold exposure,
1:30:49meaning you wouldn't want to go from the cold shower
1:30:52to a hot shower or from the cold shower to a sauna.
1:30:54Rather if you were going to start with a hot shower
1:30:57or you're going to start with a sauna
1:30:58that you would end with the cold,
1:31:01and then you would reheat naturally.
1:31:03Now I personally take a cold shower a few times a week
1:31:06or do cold immersion
1:31:08and because I'm not specifically focused
1:31:10on increasing metabolism, although I probably should be,
1:31:13that's not what I'm using it for now,
1:31:16I will take a hot shower afterwards and in doing so,
1:31:18I'm short circuiting
1:31:19some of the further metabolic increases that I would achieve
1:31:22were I to just end with the cold.
1:31:25So the Søberg principle is
1:31:27if you want to increase your metabolism, end with cold,
1:31:31and we can take this a step further and say
1:31:34that if you want to use deliberate cold exposure
1:31:37to increase metabolism, that you should make sure
1:31:40that you get to the point where you shiver.
1:31:43And the reason in for this is that there are
1:31:45a series of studies, but in particular,
1:31:47one study published in the journal Nature,
1:31:49excellent journal in the year 2018,
1:31:51showing that deliberate cold exposure that evokes shivering
1:31:57from the muscles causes the release of a molecule
1:32:00called succinate from the muscles
1:32:03and that succinate plays
1:32:05a key role in activating brown fat thermogenesis,
1:32:08which you now have heard about and understand
1:32:10as critical to the increases in metabolism
1:32:13caused by deliberate cold exposure.
1:32:15So what this means is if you want to
1:32:17increase your metabolism, end on cold,
1:32:19that's a Søberg principle and as best you can,
1:32:22try and get to the point where you are shivering
1:32:24either when you are in the cold exposure
1:32:27or immediately afterwards.
1:32:29Now one efficient way to do this is to, for instance,
1:32:32you could get into the cold shower for a minute
1:32:36or two minutes or three minutes, uncomfortably cold,
1:32:38but safe to stay in.
1:32:40Remember that's our general rule of thumb.
1:32:42Then turn off the water and stand there,
1:32:45make sure that you're not holding yourself
1:32:47close to your body,
1:32:48you're not hugging yourself to try and keep yourself warm,
1:32:50but rather your limbs are extended at your sides.
1:32:53And then if that fails to induce shiver
1:32:56than to turn on the cold water again,
1:32:59and then turn it off again,
1:33:00so alternating perhaps a minute to three minutes
1:33:03of cold exposure followed by a minute to three minutes
1:33:05of drying out in air
1:33:07and going back into the cold exposure, et cetera.
1:33:10I can tell you this from experience,
1:33:12this is a pretty brutal protocol.
1:33:15If you have never tried getting into an ice bath
1:33:18or cold water immersion or shower for one minute
1:33:21and then getting out and trying to stand there
1:33:23with your arms extended in cool or cold air for one minute,
1:33:27and then getting back into the cold shower
1:33:28or water immersion, you are in for an experience because
1:33:33even for those of you that are pretty shiver resistant,
1:33:36you'll find that it is much, much harder
1:33:38to get out of that cold water and stand there arms extended
1:33:41and drying off by evaporation,
1:33:43which further draws heat from the body
1:33:46than it is to wrap yourself in a towel,
1:33:48get in a warm shower or a sauna.
1:33:50So there's certainly no requirement to end on cold.
1:33:54There's certainly no requirement to induce shiver,
1:33:57but if your primary goal
1:33:59is to induce increases in metabolism,
1:34:02both in the short term and in the long term,
1:34:05following the cold exposure,
1:34:06well then you'll want to end on cold
1:34:08and you'll want to find a way to shiver
1:34:10provided that the level of cold
1:34:12that you're exposing yourself to
1:34:14is still safe for you overall.
1:34:15So up until now,
1:34:16I've been talking about deliberate cold exposure
1:34:18as a potent stimulus for the release of norepinephrine
1:34:21in the brain and body and indeed it is,
1:34:24but the way I've been describing it has been in the context
1:34:27of circulating plasma levels of norepinephrine,
1:34:31meaning circulating within the blood.
1:34:34What I haven't mentioned,
1:34:35but is absolutely true is that the fat cells themselves
1:34:41actually receive input from neurons.
1:34:44So there are neurons that release norepinephrine
1:34:47in response to cold, directly into the fat.
1:34:51So I want to give you this picture of how the architecture
1:34:55of all this works,
1:34:55because I think it can help you navigate
1:34:58and indeed build better deliberate cold exposure protocols.
1:35:01Your adrenal glands release norepinephrine and epinephrine.
1:35:05Your brain has sites within it like the locus coeruleus
1:35:08that release norepinephrine and epinephrine,
1:35:12but there are also neurons within your skin that sense cold
1:35:16and other neurons that can directly release norepinephrine
1:35:19into the fat stores and cause those white fat cells
1:35:22to convert to beige and brown fat.
1:35:24And I think this particular aspect of our physiology
1:35:26is often overlooked in studies.
1:35:29And when people say, oh,
1:35:31well the increases in metabolism aren't that great,
1:35:33the circulating levels of norepinephrine,
1:35:35those are very large, but they're very transient and so on,
1:35:39that fails to understand that neurons
1:35:43that actually sense cold are in a position to communicate
1:35:46via other neurons directly to the fat cells
1:35:49and release norepinephrine into those fat cells,
1:35:51which as I pointed out earlier,
1:35:53set off a huge set of immediate
1:35:55and long term cascades of even gene expression changes.
1:35:59So the picture that I'd like you to have in your mind
1:36:02is that when you get into the cold, yes,
1:36:04of course you experience that as a experience of
1:36:07I don't want to do this, I'm going to overcome this,
1:36:09I'm going to climb over these mental walls
1:36:11that represent adrenaline release in my brain and body,
1:36:14but also that your fat cells are receiving signals,
1:36:18norepinephrine signals that are changing those fat cells
1:36:20and the way that they metabolize energy.
1:36:22Now I'd like to shift our attention to the use
1:36:24of deliberate cold exposure
1:36:26for sake of physical performance.
1:36:28And there are a lot of opinions out there
1:36:30about the use of deliberate cold,
1:36:32whether or not it should be done for instance,
1:36:34before or after exercise,
1:36:36whether or not if done immediately after strength training
1:36:39or hypertrophy training,
1:36:40meaning training designed to grow muscles
1:36:43or make them stronger,
1:36:44whether or not it can inhibit that process
1:36:46and so on and so forth.
1:36:47I think today in looking over the literature
1:36:50and trying to bring forward the simplest
1:36:52and most straightforward,
1:36:53and yet scientifically grounded protocols,
1:36:56we can set up some general guidelines that will allow most,
1:36:59if not, all of you to still extract the benefits
1:37:01of deliberate cold exposure on physical performance
1:37:05without getting too neurotic about the exact timing,
1:37:08but for sake of discussion
1:37:10and because it's a prominent theme
1:37:13in many online communities,
1:37:14let's just start with the big one out there,
1:37:18meaning the question of whether or not doing an ice bath
1:37:22or doing deliberate cold exposure or taking a cold shower
1:37:25after strength slash hypertrophy training,
1:37:28meaning training designed to increase strength
1:37:30and or I should say the size of muscles
1:37:34will somehow short circuit or diminish that process,
1:37:37whether or not it will reduce or eliminate
1:37:39those strength gains and hypertrophy gains.
1:37:41And the short answer that I was able to arrive at
1:37:45on the basis of a review article that I'll talk about
1:37:48in a moment and some other studies as well,
1:37:51is that if your main goal is hypertrophy and strength,
1:37:56it is probably best to avoid cold water immersion
1:38:00and ice bath immersion in the four hours
1:38:04immediately following that strength
1:38:06and or hypertrophy training.
1:38:08Again, if your main goal is to achieve hypertrophy
1:38:12or strength or some combination of those,
1:38:15probably best to avoid cold water immersion up to the neck
1:38:20or ice bath immersion up to the neck
1:38:23immediately after strength and hypertrophy training
1:38:26and extending out to about four hours after that training.
1:38:31If you're really neurotic about this,
1:38:32then perhaps you'd want to move the cold water exposure
1:38:35to a different day entirely,
1:38:37but it all depends on how neurotically attached you are
1:38:39to getting every last bit of strength and hypertrophy.
1:38:42And if that's your goal, terrific,
1:38:44well then probably moving the cold exposure four hours
1:38:47or more away from that training
1:38:49is going to be necessary for you.
1:38:50Now you'll notice I did not talk about cold showers
1:38:53and the reason I did not talk about cold showers
1:38:55is that there simply are not very many studies
1:38:59of deliberate cold exposure through cold showers
1:39:02for the reasons I talked about
1:39:03at the beginning of the episode.
1:39:05It's hard for me to imagine that taking a brief cold shower
1:39:08after a strength or hypertrophy training session
1:39:11would completely reverse or short circuit the effects
1:39:13of that strength and hypertrophy training.
1:39:15But again, if you're neurotically attached
1:39:17to getting every last bit of strength and hypertrophy
1:39:21out of your training sessions, then by all means,
1:39:23err on the side of caution and wait four hours or more
1:39:26to do your cold shower just as you would wait four hours
1:39:29or more to do your cold water immersion.
1:39:31Now there are nice data pointing to the fact
1:39:33that doing cold water immersion after a hard run,
1:39:37so endurance training,
1:39:39or even sprint and interval training
1:39:41or after a weight workout where your main focus
1:39:45is on performance of those movements
1:39:47or after a skill training workout
1:39:49where your main focus on performance of those movements,
1:39:52that there's no reason to think that that
1:39:54cold water immersion or ice bath or cold shower
1:39:57would inhibit the progress or the stimulus
1:40:01that would lead to progress
1:40:03that occurred during that training session.
1:40:05In other words, I don't see any reason
1:40:07based on the literature to avoid deliberate cold exposure
1:40:10immediately after training,
1:40:12again unless your goal is hypertrophy and strength.
1:40:15And in fact,
1:40:16there's a very nice review recently published
1:40:19on deliberate cold exposure
1:40:21and how it can impact physical performance,
1:40:24whether or not it's done before or after,
1:40:27different types of training and so forth.
1:40:30The paper is entitled impact of cold water immersion
1:40:33compared with passive recovery,
1:40:35following a single about of strenuous exercise
1:40:37on athletic performance in physically active participants,
1:40:41a systematic review with meta-analysis and meta regression.
1:40:45So this is a meta-analysis of 52 studies
1:40:49that looked at a tremendous number of variables
1:40:51and contexts, as you would expect in a meta-analysis
1:40:55of 52 studies.
1:40:56I'm going to read you the conclusions of the study
1:40:58and I will provide a link.
1:40:59We certainly don't have the time to go through
1:41:01all the details of the study.
1:41:02I will highlight a few specific outcomes
1:41:05that I found particularly interesting,
1:41:07but here I am paraphrasing their conclusions,
1:41:10that cold water immersion, I want to emphasize immersion,
1:41:15not cold showers, but cold water immersion
1:41:18they say was an effective recovery tool
1:41:20after high intensity exercise.
1:41:22They observed positive outcomes,
1:41:23meaning improvements in certain variables,
1:41:27for muscular power, muscular soreness,
1:41:30meaning reduced muscular soreness,
1:41:31increased muscular power,
1:41:33perceived recovery after 24 hours of exercise.
1:41:36However, there were certain forms of exercise
1:41:39that were not benefited by cold water immersion,
1:41:43such as eccentric exercise,
1:41:45exercise focusing only on the lowering component
1:41:49or the so-called eccentric component of resistance exercise.
1:41:52They saw some very entry dose response relationships
1:41:56for things like endurance training, meaning the longer
1:42:00the cold exposure post-endurance training,
1:42:02the more improvement in endurance performance,
1:42:05reductions in circulating creatine kinases
1:42:08and things that relate to muscle damage
1:42:11under certain conditions.
1:42:12At some point in the future, by the way,
1:42:14we'll do an entire episode on creatine and creatine kinase,
1:42:17which are important not just for muscular function,
1:42:19but also for brain function.
1:42:21But the basic takeaway was that cold water immersion
1:42:25performed after high intensity exercise
1:42:27was beneficial from a number of different standpoints
1:42:30and indicated that shorter duration,
1:42:34cold exposure and lower temperatures
1:42:37can improve the efficacy of cold water exposure
1:42:40if used after high intensity exercise.
1:42:42There I'm directly pulling from their conclusions.
1:42:45So what this says is that it's not just those
1:42:47longer duration, 30, 45 minute and 60 minute protocols
1:42:52of cold water immersion that we discussed earlier,
1:42:54but also shorter duration of one minute, three minute,
1:42:58five minute exposures to lower temperatures.
1:43:02Temperatures that would make you psychologically
1:43:04want to get out as soon as you possibly can,
1:43:07but again that you can safely stay in
1:43:10done after training really have been shown to
1:43:12improve outcomes in terms of reducing soreness
1:43:15and improving training efficacy,
1:43:18meaning your ability to get back into training more quickly
1:43:22and thereby deliver more training stimuli
1:43:25to a given muscle or in your endurance training protocol.
1:43:29Translate to English,
1:43:29what this means is that taking a cold shower or getting into
1:43:33an ice bath or some other form of cold water immersion
1:43:35within the immediate minutes or even the immediate hours
1:43:39following your training has been shown to be beneficial.
1:43:43I'm sure a number of you have questions for instance,
1:43:45how long should you be in that cold exposure?
1:43:49Is it the same as the 11 minute threshold described earlier?
1:43:52To be honest with you,
1:43:53there are not enough studies to really point
1:43:56to the critical threshold for eliminating
1:43:59or reducing delayed onset muscle soreness
1:44:01or for getting maximal results from power
1:44:05and endurance training,
1:44:06but this study does make a couple of key points
1:44:09and here I will just paraphrase.
1:44:11For instance, that cold water immersion
1:44:13is more likely to positively influence
1:44:16muscular power performance,
1:44:18to reduce muscle soreness, to reduce serum creatine kinase,
1:44:22and to improve perceived recovery
1:44:24after high intensity exercise,
1:44:26as compared with passive recovery.
1:44:29This can be translated to cold water exposure after training
1:44:33is beneficial and probably better
1:44:35than passive recovery from a number of standpoints.
1:44:38In addition, they say that dose response relationships
1:44:42meaning the amount and the degree of cold
1:44:47that people were exposed to and how often they did that
1:44:51in particular in lower temperature cold immersion.
1:44:53So these would be the sorts of cold immersion protocols
1:44:57that are one minute or two minutes, three minutes,
1:44:59maybe five minutes,
1:45:00but that one couldn't stay in there longer
1:45:02because it feels stressful
1:45:03and one wants to get out.
1:45:05Maybe more effective after high intensity exercise
1:45:08for removal of serum creatine kinase
1:45:11as well that these shorter duration
1:45:13cold water immersion approaches may be more effective
1:45:16after high intensity endurance performance as well.
1:45:19So all of this can be translated to say that
1:45:22unless your main goal is hypertrophy and strength,
1:45:27that cold exposure, ideally cold immersion
1:45:30and cold water ice bath,
1:45:32but if you don't have access to that,
1:45:34then cold showers is likely going to be beneficial
1:45:37if done immediately after or in the minutes
1:45:39or hours after your training,
1:45:42especially high intensity training.
1:45:44One particularly nice thing about this meta-analysis
1:45:46is that it included some studies that
1:45:48involve the use of cooling packs.
1:45:50So again, vests that can essentially ice packs
1:45:55and indeed even cryotherapy chambers and so on.
1:45:59There's a nice table in the study
1:46:00if you want to get really detailed and go
1:46:02and look specifically at those studies,
1:46:03I invite you to do that.
1:46:04We'll put a link to this study in the caption
1:46:07for this episode, but all in all,
1:46:09what this study shows is that deliberate cold exposure
1:46:12can be very useful for recovery likely through reductions
1:46:17in inflammation, in muscle and connective tissue.
1:46:20And while this study did not look specifically
1:46:22at the mechanisms of reduced inflammation
1:46:25caused by deliberate cold exposure,
1:46:27those mechanisms are somewhat known.
1:46:30There are a number of studies that have pointed to the fact
1:46:32that deliberate cold and cold generally
1:46:34can reduce inflammatory cytokines,
1:46:37such as IL-6, interleukin six.
1:46:39It can increase anti-inflammatory cytokines
1:46:43such as interleukin 10 and so on.
1:46:46Without getting into all those details,
1:46:48I think it's sufficient to say that
1:46:50if you are somebody who experiences
1:46:52a lot of delayed onset muscle soreness,
1:46:54taking a cold shower after your training
1:46:56or getting into a cold immersion after your training,
1:46:58even if it's a few hours later ought to help.
1:47:01And if you are doing particularly intense training,
1:47:04then you probably want to ratchet up the number
1:47:07of cold exposure sessions that you're doing
1:47:10even if those have to be done on separate days
1:47:12from your training,
1:47:13because a lot of the inflammatory effects of training,
1:47:15endurance and strength training are actually occurring
1:47:17some hours away from the training stimulus.
1:47:20So it's not just that inflammation goes up
1:47:22radically during training, which it often can,
1:47:25but that it can occur even in the days
1:47:27and even weeks afterwards,
1:47:28depending how intense and how long duration
1:47:30that training is.
1:47:31So deliberate cold exposure is very powerful
1:47:33as an anti-inflammatory tool.
1:47:36Now I'd like to emphasize the topic that we touched on
1:47:38at the beginning of the episode,
1:47:40which are those glabrous skin surfaces,
1:47:43the hands, the upper face,
1:47:44and the bottoms of the feet through which heat
1:47:47is especially good at leaving the body.
1:47:50And another way of putting that is that one can cool
1:47:54the body much more efficiently
1:47:56through the glabrous skin surfaces.
1:47:58Now, if you want to understand all of the science
1:48:01behind this and all of the various applications,
1:48:05I invite you to please listen to the episode
1:48:07that I did with Dr. Craig Heller, again,
1:48:10in the biology department at Stanford.
1:48:13For sake of this episode,
1:48:14I'm just going to detail a couple of findings
1:48:17from his laboratory.
1:48:18The first one, dealing with exercise induced hyperthermia,
1:48:21because I think this is very interesting
1:48:22and it can even save lives
1:48:24if you understand the way this works.
1:48:28There's a particular paper that focuses on this,
1:48:30and we will put a link to this as well.
1:48:32The title of this paper is novel application
1:48:34of chemical cold packs for treatment
1:48:35of exercise induced hyperthermia,
1:48:37a randomized control trial.
1:48:39This is a pretty brutal study,
1:48:42brutal for the subjects that is.
1:48:45This study involved was having subjects walk on a treadmill
1:48:49at a pretty significant incline and anywhere
1:48:51from nine to 17% wearing a substantial amount of clothing
1:48:56that was not well ventilated
1:48:58and the room was kept to 40 degrees Celsius,
1:49:00which is 104 degrees Fahrenheit.
1:49:03This is definitely not something to do at home.
1:49:06This study was designed to induce hyperthermia,
1:49:09which as I mentioned earlier, can be quite dangerous.
1:49:11And they compared two types of cooling.
1:49:14In the first form of cooling
1:49:16that they call traditional cooling,
1:49:18they had ice packs on their neck,
1:49:21in their armpits and in their groin.
1:49:23And in the other group,
1:49:25there was the so-called glabrous skin cooling.
1:49:27So the palms, the soles of the feet,
1:49:29which were actually so they were cooling inside the boots
1:49:33or inside of gloves and on the upper portion of the face.
1:49:39And the basic takeaway of this study
1:49:41is that by cooling the glabrous skin,
1:49:44the subjects were able to sustain this walking
1:49:47on these inclined treadmills for much longer
1:49:50than were the people who received traditional cooling.
1:49:54And also the return to baseline temperature
1:49:56was much faster in the glabrous skin cooling group.
1:49:59So how this translates to the real world
1:50:01is that if ever you are hyperthermic
1:50:04or someone else's hyperthermic,
1:50:06one way to cool them down quickly is to cool
1:50:10these palmer glabrous, soles of the feet glabrous
1:50:14and upper portion of the face glabrous portions of the body
1:50:18using cool rags, using ice packs or using any number
1:50:22of different cold objects or temperatures.
1:50:26One key thing, if you're going to use glabrous skin cooling,
1:50:30is that whatever you use to cool those surfaces
1:50:33cannot be so cold that it causes vasoconstriction.
1:50:37Because as I mentioned earlier,
1:50:38the arterio-venous anastomoses
1:50:41these portals of arteries directly to veins
1:50:43that exist only in these glabrous skin surfaces,
1:50:49the way that they're able to cool the body
1:50:51and essentially pass cool into the body
1:50:53although that's not really what they're doing,
1:50:55they're actually extracting heat from the body
1:50:57to be technical, they're extracting heat from the body,
1:51:00the only way they can do that is if those veins
1:51:04don't collapse and veins will collapse
1:51:06if they are made very, very cold.
1:51:08So if you want to use glabrous skin cooling
1:51:11to offset hyperthermia
1:51:12or for the other forms of performance,
1:51:14which we'll talk about in a moment,
1:51:16you need to use a cool object or surface
1:51:19that is not so cold that it causes vasoconstriction.
1:51:22And this can be a little bit tough to dial in,
1:51:24meaning it can be tough to identify such an object.
1:51:27And for that reason,
1:51:28Dr. Heller and some of his colleagues have developed
1:51:30a commercial product called the CoolMitt.
1:51:32You can actually go to their website, coolmitt.com.
1:51:34I don't have any financial or other relationship to them.
1:51:37I know they've been developing this technology
1:51:39for some period of time.
1:51:40It involves a glove that you put your hand into,
1:51:43it circulates water of a given temperature and it does so,
1:51:47and does so at a tempera or that is sure to not
1:51:51cause vasoconstriction of the palm.
1:51:53And you may be asking,
1:51:54how can you just put your hand into one glove
1:51:56and have this work?
1:51:57Well, that's how powerful these glabrous skin surfaces are.
1:51:59Even just by cooling one palm,
1:52:02the core body temperature drops radically.
1:52:06Now that's their commercial technology.
1:52:08I know that some people out there have started to experiment
1:52:11with a home version of this,
1:52:13which would be taking a package for instance
1:52:15of frozen blueberries or some other cold drink
1:52:18or cold metal object, and actually bringing it into the gym
1:52:21or out on a run.
1:52:23There are even people who are now developing
1:52:25cooled psych bicycle handles for long rides.
1:52:29This might seem a little kooky or crazy to you,
1:52:31but as you'll soon hear in the study
1:52:33I'm about to describe, the increases in endurance
1:52:37and in the volume of strength training
1:52:39that people can conduct if they appropriately cool
1:52:43their body through these glabrous skin portals
1:52:46is actually quite significant.
1:52:48So again, as it relates to hyperthermia,
1:52:50if someone is overheating by all means,
1:52:52try and get them out of that heat,
1:52:54get them to stop exercising, you can die from hyperthermia,
1:52:57try and cool the bottoms of the feet,
1:52:59the palms of their hands
1:53:01and the upper portion of their face.
1:53:03That does not mean it would be a bad idea
1:53:06to put cold water on the top of their head.
1:53:08That probably would also help and perhaps on their neck.
1:53:10What is probably not going to be a good idea is to do
1:53:14the more standard thing of draping someone in cold towels
1:53:17on the surface of their body because as I mentioned,
1:53:19the beginning of the episode,
1:53:20that thermostat in the hypothalamus,
1:53:22the medial preoptic area will typically react to that
1:53:25by increasing core body temperature further.
1:53:28The effects of glabrous skin cooling on physical performance
1:53:31are truly remarkable
1:53:32provided the glabrous skin cooling is done correctly.
1:53:36And I want to point out that the main degree of effect
1:53:40is on volume or the ability to do more work.
1:53:44And I want to point this out because I think that many people,
1:53:47certainly in the exercise science community,
1:53:49but even in the general public,
1:53:50when they hear about some of these effects
1:53:52that are measured in the laboratory,
1:53:54they sort of look at those effects a bit of scans
1:53:59and they think, well, that's not possible.
1:54:01Effects for instance, that have been documented
1:54:03showing doubling or tripling of the number of dips
1:54:05that one can do in a relatively short amount of time
1:54:08or doubling of the number of pullups one can do
1:54:11or 14% increases in strength or even comparable degrees
1:54:15in increase in weight training output
1:54:18to people who are on performance enhancing drugs,
1:54:20et cetera, et cetera.
1:54:22Part of the confusion is that the effects
1:54:25of proper palmer cooling,
1:54:27because it almost always is done by palmer cooling
1:54:30and less often in these experiments
1:54:32by cooling of the bottoms of the feet
1:54:33and the upper portion of the face,
1:54:35but those effects tend to be the ability to do more work
1:54:41over time and just to illustrate some of the major effects
1:54:45that the Heller lab is seen
1:54:46and they are document entered in this manuscript
1:54:48that I'll share with you in a moment.
1:54:50The typical protocol is to have people come in
1:54:53and do some endurance training
1:54:54so running on a treadmill and to have a condition where
1:54:58one group is actually doing palmer cooling
1:55:01while they are on a bike or on a treadmill
1:55:03and inevitably the outcome is that they can do more work.
1:55:07They can pedal further at a given speed,
1:55:09or they can run longer at a given speed than people
1:55:13who are not doing palmer cooling
1:55:14or who are receiving cooling by way of
1:55:18cold compress to the back of the neck or ice pack
1:55:20to the armpits, et cetera.
1:55:22So the effects of palmer cooling are very clear
1:55:25and very robust.
1:55:26And in the context of endurance exercise
1:55:29almost always allow people to do more work,
1:55:31to go longer with less perceived effort and to quit later
1:55:35so to speak.
1:55:37In terms of strength training,
1:55:38they've looked at the capacity to perform sets of dips.
1:55:42So one of the more famous examples of this
1:55:44that Dr. Heller shares in the episode that we did earlier,
1:55:48and that you can find at hubermanlab.com involves
1:55:51someone coming in and doing sets of dips, maybe 40 dips.
1:55:55This person actually could do 40 dips on their first set,
1:55:58then resting for a period of two to three minutes
1:56:00and then doing 35
1:56:02and then resting for a period of two or three minutes,
1:56:04and then doing progressively fewer and fewer and fewer
1:56:06to the point where over a period of time,
1:56:09they add up the total number of dips that they can do
1:56:11and then they have them come back
1:56:14after a period of recovery, so not immediately after,
1:56:16but take a couple of days,
1:56:18come back and do effectively the same protocol,
1:56:21but during their rest periods,
1:56:22they're doing two minutes of palmer cooling,
1:56:25which essentially allows heat to move out of the body,
1:56:29lowering core body temperature in other words.
1:56:31And what they find is that they see enormous increases
1:56:35in the total number of dips that people can do,
1:56:37but that doesn't mean that the person goes
1:56:38from being able to do 40 dips,
1:56:39to being able to do 50 dips or 60 dips on that first set,
1:56:43what it means is they are able to do 40 on the first set,
1:56:46then 40 on the second,
1:56:47then 38 on the third and so on and so forth
1:56:50so that the total duration of the workout is extended
1:56:52and yet they're doing much more work,
1:56:55even though it takes more time.
1:56:57So that's an important point
1:56:59and I think a point that perhaps wasn't as clear
1:57:02or as clearly made by me in the previous episodes
1:57:05that discuss this topic.
1:57:07For those of you that are interested
1:57:08in exploring palmer cooling, first of all,
1:57:11I recommend taking a brief glance or even a deep dive
1:57:15into this study,
1:57:17which is entitled work volume
1:57:18and strength training responses to resistive exercise
1:57:21improve with periodic heat extraction from the palm.
1:57:25In this study, they describe big increases in anaerobic,
1:57:30meaning strength training output,
1:57:32things like improvement in dips,
1:57:35improvement in bench press,
1:57:37improvement in pull-ups, et cetera, in human subjects.
1:57:40And it's a really nice study and points
1:57:43to some of the protocols that you might be able
1:57:44to adapt in your own setup.
1:57:46For instance, over six weeks of pull up training,
1:57:48palm cooling in between sets improved volume by 144%,
1:57:54and this was in experienced subjects.
1:57:56So that's interesting because a lot of studies
1:57:58of strength training and improvements in hypertrophy
1:58:01and strength are done in inexperienced untrained athletes,
1:58:04which changes the picture somewhat
1:58:07compared to experienced athletes.
1:58:10They found that strength,
1:58:11meaning the one repetition maximum,
1:58:13increased 22% over 10 weeks in bench press training.
1:58:17And they point to the particularly strong effects
1:58:20of using palmer cooling when people reach plateaus
1:58:23in endurance and strength training.
1:58:25And there, I think it's an important point.
1:58:26I think that if you're going to explore palmer cooling,
1:58:30it's probably not the sort of thing that you're going to do
1:58:32in every run or in every about of cycling
1:58:36or in every strength training session,
1:58:38but that it might be used to vastly increase your volume
1:58:42or vastly increase your endurance
1:58:44in a given session or a set of sessions
1:58:46in order to push through plateaus.
1:58:49A particularly interesting point in light of that
1:58:51is Dr. Heller has observed again and again
1:58:54that palmer cooling reduces delayed onset muscle soreness,
1:58:57or it can eliminate it entirely.
1:58:59And that's very interest because it also points to the fact
1:59:02that reducing core body temperature may somehow be involved
1:59:05in short circuiting
1:59:06the normal mechanisms of delayed onset muscle soreness.
1:59:09And you might say, well,
1:59:10how would temperature be involved
1:59:12in delayed onset muscle soreness?
1:59:14Well, I want to refer you back to the meta-analysis
1:59:17that we talked about earlier, where the short duration,
1:59:20very cold temperature exposure after training did indeed
1:59:23reduce delayed onset muscle soreness
1:59:25in part through reduction, excuse me, in creatine kinase.
1:59:28So it's not inconceivable that temperature
1:59:32and delayed onset muscle soreness are related.
1:59:35And that raises perhaps the most important point,
1:59:37which is the way that palmer cooling can improve performance
1:59:42by way of reducing core body temperature is known
1:59:46and that is because when one engages in exercise
1:59:50or muscular output of any kind,
1:59:52strength or endurance exercise,
1:59:54the range of temperatures under which a muscle can perform
1:59:58is actually very narrow.
2:00:00There's an enzyme called pyruvate kinase,
2:00:02which is critical to muscle contractions
2:00:05and pyruvate kinase can only function
2:00:07in a very narrow range of temperatures.
2:00:09If that temperature gets too hot,
2:00:11meaning if the muscle heats up locally,
2:00:13whether or not by running
2:00:14or cycling or swimming or weightlifting,
2:00:17the ability for that muscle to continue
2:00:19to contract is reduced and eventually
2:00:22is short circuited completely.
2:00:23And I think this is a much underexplored
2:00:26or at least a much under discussed aspect
2:00:29of so-called muscular failure or the failure
2:00:32of one to continue to endure in running.
2:00:35So for instance,
2:00:36when you run as compared to a bench press or something,
2:00:38you don't stop running
2:00:39because you can't actually contract the muscles further,
2:00:42but somehow signals about the heating up
2:00:46of muscular tissue are conveyed to the brain.
2:00:48There's a crosstalk there,
2:00:49it's probably bidirectional and people stop, they quit.
2:00:53This is the quitting reflex.
2:00:56In strength training, one can no longer perform a repetition
2:01:00or set of repetitions in part
2:01:01because of heating up of the muscle locally.
2:01:03There are other mechanisms as well, of course,
2:01:05and I realize that,
2:01:07but what's very clear from the palmer cooling work is that
2:01:10by simply holding onto a cool object,
2:01:13remember not an object so cold
2:01:14that it constricts the vessels of the palms
2:01:17or constricts the vessels on the bottoms of the feet,
2:01:20but by holding onto a relatively cool object
2:01:22in one or both hands in between sets for two minutes or so,
2:01:26you can very efficiently reduce your core body temperature
2:01:29and in doing so, reduce the temperature of the muscles
2:01:32that are doing the work,
2:01:35increase the capacity for pyruvate kinase
2:01:37to continue to allow your muscles to contract
2:01:40and thereby allow you to do more volume of endurance
2:01:44and strength training.
2:01:45So a simple protocol that Dr. Heller passed to me
2:01:48is find a relatively cool object.
2:01:51So you could, for instance,
2:01:52fill two bottles with cold water,
2:01:54maybe put a few ice cubes in there.
2:01:56This is not exact because we're not talking about
2:01:58the commercial CoolMitt product here,
2:02:00we're talking about an at home version
2:02:01or use a pack of frozen blueberries or broccoli
2:02:05sort of pack of those as what he described.
2:02:07And then in between sets to put your hands
2:02:10and ideally you'd put the bottoms of your feet,
2:02:12but that's not always feasible in most gyms
2:02:13where they won't let you take off your shoes and so forth,
2:02:16but to put the palms of your hands on that cool surface
2:02:19for a minute or two minutes between sets
2:02:22and then returning to your sets of work.
2:02:24Now, if you are heating up through other mechanisms
2:02:28like you're wearing a stocking cap
2:02:30and you're in a very warm environment,
2:02:31this might not have as potent effect
2:02:33as if you were to do this cooling
2:02:35in a more moderate environment,
2:02:36wearing lighter clothing, et cetera.
2:02:38So by all means warm up to do your exercise,
2:02:41lubricate your joints,
2:02:42and get into a place where you're not going to injure yourself,
2:02:44doing whatever form of exercise you do.
2:02:46But then if you'd like to explore palmer cooling,
2:02:48I know a number of people who've written to me saying
2:02:51they heard about palmer cooling
2:02:52on the episode with Dr. Heller.
2:02:53They've tried this and they see quite excellent results.
2:02:56It does take some discipline.
2:02:58It's one thing to just kind of hang out in the gym
2:02:59and play on your phone in between sets.
2:03:01It's another to do deliberate cooling with your palms
2:03:04or the bottom of your feet
2:03:04or the upper portion of your face.
2:03:06You might get some weird looks,
2:03:07but of course you'll be the one
2:03:09doing significantly more volume,
2:03:11not experiencing delayed onset muscle soreness and achieving
2:03:14better endurance and strength gains
2:03:16were you to do this properly.
2:03:17Now as a final topic related to the use
2:03:19of deliberate cold exposure for improving health
2:03:22and performance, I'd like to touch on this theme
2:03:26that exists online, on social media,
2:03:28on YouTube and in various fitness communities
2:03:31of using deliberate cold exposure to the groin,
2:03:34in particular to the testicles,
2:03:36in order to try and increase testosterone.
2:03:39And while this might sound really kooky,
2:03:42indeed this practice exists.
2:03:44Indeed if you were to go onto Amazon,
2:03:47there are actually ice pack underwear
2:03:50that are being marketed for sake of increasing testosterone.
2:03:54Now, I am not aware of any specific well-controlled studies
2:03:57that show that this indeed works.
2:04:00I can imagine based on what I know about the nervous system,
2:04:03testosterone and cold, et cetera,
2:04:06that there are a couple of mechanisms
2:04:07by which one might experience increases in testosterone
2:04:11as a consequence of deliberate cold exposure.
2:04:13First off, let me say there is no reason why
2:04:15you would have to apply these ice packs
2:04:18in the way that I just described.
2:04:20One could of course take a cold shower.
2:04:22One could of course use cold immersion of various kinds,
2:04:26and you're still going to get that exposure
2:04:28of the groin and the testicles to cold.
2:04:31Now I should point out that people do report
2:04:34at least anecdotally increases in testosterone
2:04:38as a consequence of this practice
2:04:40and I have to imagine
2:04:41that they are measuring their serum testosterone,
2:04:43that they're not just guessing
2:04:44that their testosterone went up.
2:04:46If you know of a study exploring this directly,
2:04:48please let me know, put in the comment section on YouTube,
2:04:51or even just email me.
2:04:53We have a email that you can find it, hubermanlab.com.
2:04:57Please email me the reference.
2:04:58I wasn't able to find a reference,
2:05:00but I can imagine two reasonably plausible mechanisms
2:05:04by which deliberate cold exposure to the groin,
2:05:07in particular the testicles, would increase testosterone.
2:05:10The first is somewhat direct,
2:05:13which is that anytime you cool a body surface,
2:05:17that if it's cold enough,
2:05:18you're going to get vasoconstriction.
2:05:20And then subsequently you're going to get
2:05:21a rebound increase in vasodilation,
2:05:24meaning you're going to constrict
2:05:26the blood vessels in that area.
2:05:27And then after the cold is removed,
2:05:29there's going to be more blood flow to that area.
2:05:31And of course,
2:05:32blood flow relates to organ health
2:05:34and tissue health generally.
2:05:35So perfusion of that region and the gonads to be specific
2:05:41with additional blood,
2:05:42you could imagine in some ways increasing testosterone,
2:05:46that's reasonably plausible.
2:05:48The other probably more likely mechanism
2:05:51relates to the dopamine increases caused by cold exposure
2:05:54that we talked about earlier.
2:05:56Again, anytime you have a somewhat stressful stimulus,
2:05:59but in particular with cold exposure,
2:06:01it seems that the catecholamines,
2:06:03norepinephrine, epinephrine and dopamine all increase
2:06:07and dopamine is known to be in the pathway
2:06:10that can stimulate testosterone.
2:06:13And so while there isn't a direct relationship
2:06:15between dopamine stimulating testosterone,
2:06:17there is an interesting pathway way whereby
2:06:19dopamine increases can trigger increases
2:06:21in things like luteinizing hormone,
2:06:23which can trigger increases in testosterone
2:06:26as well as estrogen for that matter.
2:06:28So I know that there are a lot of people out there
2:06:30that are interested in the use of cold exposure
2:06:32for increasing testosterone.
2:06:33And some of those people in communities are
2:06:36indeed using cold exposure directly on the gonads,
2:06:40on the testees in order to do this.
2:06:42I'm not certain that that direct contact is necessary.
2:06:46And in some cases it might actually be quite dangerous
2:06:51or you at least should be careful in terms of tissues there
2:06:54and avoiding damage.
2:06:55But nonetheless, I think that a dopamine impact
2:06:59on testosterone is very likely given the 250% increases
2:07:04in dopamine that have been observed
2:07:05with cold water immersion and all of that points to the fact
2:07:07that cold water immersion
2:07:10very likely increases testosterone,
2:07:13but as a downstream consequence
2:07:15of the cold water immersion effects on dopamine
2:07:18and luteinizing hormone,
2:07:19and again there's no reason to think that the increases
2:07:22in luteinizing hormone would also increase estrogen.
2:07:25Probably not to dangerous or levels
2:07:29that one would want to avoid,
2:07:31but I don't think that there's anything
2:07:33particularly specific about cold
2:07:35for inducing testosterone and not other hormones.
2:07:38I think it's very likely to increases
2:07:39a number of different hormones.
2:07:41I do hope that there will be a systematic study on this
2:07:44in the not too distant future.
2:07:45I also hope to not be a subject
2:07:47in the cooling of the gonads experiment.
2:07:50Now I promise you the last topic was the last topic,
2:07:52but there's one other really important point
2:07:54that I think everyone should be aware of
2:07:56if you're going to use deliberate cold exposure.
2:07:59And that brings us back to the very first thing
2:08:01that we discussed today,
2:08:03along the lines of deliberate cold exposure,
2:08:05which is that your baseline temperature
2:08:07is going to be lowest about two hours before you wake up,
2:08:11it's going to increase in the morning
2:08:13and as you wake up
2:08:15and increase throughout the day and afternoon,
2:08:17and then start to drop in the evening and come down at night
2:08:20as you head to sleep.
2:08:23I also want you to remember that if you are to cool
2:08:26the external portion of your body, in particular your torso,
2:08:30the net effect of that is going to be an increase
2:08:33in body temperature.
2:08:35So for many people, not all, but for many people,
2:08:38if you are going to do deliberate cold exposure,
2:08:42you are going to increase your core body temperature
2:08:45and that makes sense
2:08:46if you think about how deliberate cold exposure
2:08:48can increase metabolism by increasing thermogenesis.
2:08:52What that all means is that if you are doing
2:08:56your deliberate cold exposure early in the day,
2:08:58you are going to get yet a further increase
2:09:01in core body temperature
2:09:03that would be associated with wakefulness,
2:09:05your ability to be alert that morning
2:09:07or throughout the day and so on.
2:09:10It also means that if you do your deliberate cold exposure
2:09:13very late in the evening, or at night,
2:09:16so 6:00 PM, 7:00 PM, 9:00 PM and so on,
2:09:21you are going to increase your core body temperature
2:09:23and if you recall,
2:09:25a decrease in core body temperature
2:09:27of one to three degrees is not just beneficial,
2:09:31but is necessary in order to get into deep sleep
2:09:34and remain in deep sleep.
2:09:36So the takeaway from this is deliberate cold exposure
2:09:39done properly will increase your core body temperature
2:09:42and make you feel more alert.
2:09:44So if you're doing it early in the day,
2:09:46that's probably terrific
2:09:48given that most of us want to be alert during the day.
2:09:50However, if you do it too late in the day, evening or night,
2:09:54it can disrupt sleep by way of disrupting
2:09:57your core body temperature.
2:09:58Now, the caveat to that is I myself
2:10:02tend to do deliberate cold exposure early in the day.
2:10:05Maybe not first thing in the morning, but mid morning,
2:10:07maybe as late as three or four in the afternoon
2:10:09in some cases.
2:10:10In the longer days of summer, I might do it even later,
2:10:12five or 6:00 PM and have no trouble sleeping.
2:10:15I have done deliberate cold exposure very late at night,
2:10:1810:00 PM, 11:00 PM and so on
2:10:21as part of a 30 day challenge
2:10:23of doing deliberate cold exposure every day for 30 days
2:10:25and I got sloppy with my timing
2:10:27and then in order to not miss a day,
2:10:29I would do it at 11 o'clock at night.
2:10:31And I must say
2:10:31I found that I could still fall asleep very easily,
2:10:35even doing deliberate cold exposure very late at night.
2:10:38However, on those particular days, I was particularly busy
2:10:42and so I was particularly exhausted when I arrived
2:10:45at the deliberate cold exposure
2:10:46and I had no trouble falling asleep
2:10:49after doing deliberate cold exposure,
2:10:50and then taking a nice warm shower and then going to sleep.
2:10:53But I could imagine that because of the increases
2:10:56in core body temperature caused by deliberate cold exposure,
2:10:59that were one to do that too late in the day,
2:11:02evening or night that it could indeed disrupt your sleep.
2:11:04So my recommendation would be
2:11:06for most people only do deliberate cold exposure
2:11:09if you are prepared to be fairly alert for the next one
2:11:12to four or maybe had been six hours
2:11:14following that deliberate cold exposure.
2:11:17So for today's episode,
2:11:18as is the case with most episodes
2:11:20of the Huberman Lab Podcast, I covered a lot of material.
2:11:23We talked about mechanisms of catecholamines and stress
2:11:25and pulsatile release of epinephrine, metabolism,
2:11:29mental effects, performance, glabrous skin cooling
2:11:31and on and on and on.
2:11:33And while the goal of course is to make sure that everyone
2:11:37arrives at specific,
2:11:38very clear mechanistic and actionable protocols,
2:11:41I do realize that it is an immense amount of information.
2:11:44And for that reason,
2:11:45I've created a list of deliberate cold exposure protocols
2:11:49aimed at improving mental toughness and resilience,
2:11:53mood, performance, metabolism, reducing inflammation,
2:11:58and so on and so forth.
2:11:59All of those have been condensed into succinct form
2:12:02and can be found at the Huberman Lab
2:12:05Neural Network Newsletter.
2:12:06This is a monthly or semi-monthly newsletter
2:12:09that we release
2:12:10that includes takeaways from the podcast and protocols.
2:12:13You can access those as protocols zero cost
2:12:16by simply going to hubermanlab.com,
2:12:19signing up for the neural network newsletter.
2:12:20It's very easy to do, you just supply your email
2:12:23and you will receive the newsletter.
2:12:24We do not share your email with anybody else.
2:12:27In fact, we have our privacy policy laid out
2:12:30on the hubermanlab.com website
2:12:32so you can find that there and the protocols
2:12:35that I've designed should make it very straightforward
2:12:38for you to create a set of protocols
2:12:41that you could use with cold showers, with cold immersion,
2:12:43with or without ice in combination with exercise
2:12:46specifically for one goal or another,
2:12:47or to accomplish multiple goals simultaneously.
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2:14:53So thank you once again
2:14:54for joining me in the discussion about the use
2:14:57of deliberate cold exposure for health and performance
2:14:59and last but certainly not least,
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