Full Transcript: How to Prevent & Treat Colds & Flu
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0:00 - Welcome to the Huberman Lab Podcast,
0:01 where we discuss science
0:03 and science based tools for everyday life.
0:09 I'm Andrew Huberman,
0:10 and I'm a professor of neurobiology
0:11 and ophthalmology at Stanford School of Medicine.
0:15 Today, we are going to discuss the use
0:16 of deliberate cold exposure
0:18 for health and performance.
0:20 Temperature is a powerful stimulus on our nervous system
0:23 and indeed on every organ and system of our body
0:26 and cold in particular can be leveraged
0:29 to improve mental health, physical health, and performance,
0:33 meaning for endurance exercise, for recovering
0:36 from various forms of exercise,
0:38 for actually improving strength and power
0:41 and for enhancing mental capacity.
0:43 In order to properly leverage deliberate cold exposure
0:46 for sake of mental health, physical health and performance,
0:50 you have to understand how cold impacts the brain and body.
0:53 So today we are going to discuss that.
0:55 We're going to talk about some of the neural circuits
0:57 and pathways, some of the hormones involved.
0:59 I promise to make it all clear and accessible
1:02 regardless of whether or not
1:03 you have a scientific background or not.
1:05 We are also going to discuss very specific protocols
1:08 that you can apply,
1:09 which leverage variables like temperature,
1:11 how cold, how to deliver the cold, for instance,
1:14 whether or not you use a cold shower,
1:16 cold immersion, ice bath, circulating water, or still water,
1:20 whether or not you're going for walks outside in a t-shirt
1:23 when it's cold or whether or not
1:25 you're purposefully using things like cryo,
1:28 if you have access to that or not.
1:30 One thing I can promise you
1:31 is that by the end of today's episode,
1:33 you will know a lot about the biology of thermal regulation,
1:36 that is how your brain and body regulates its temperature.
1:40 You will also have a lot of tools in your arsenal
1:42 that you can use and leverage
1:44 toward improving mental health,
1:45 physical health, reducing inflammation in the body,
1:48 improving athletic performance,
1:50 improving mental performance.
1:51 I promise to spell out all those protocols in detail
1:54 as I go along and to summarize them again at the end.
1:57 I'd like to make a point now that I'm going to make
1:59 several additional times during today's episode
2:02 and that is that temperature is a very potent stimulus
2:06 for the brain and body.
2:07 That also means that it carries certain hazards
2:10 if it's not done correctly.
2:12 Now, everyone shows up to the table,
2:14 meaning to protocols,
2:15 with a different background of health status
2:17 and there's simply no way that I can know
2:19 what your health status is.
2:20 So anytime you are going to take on a new protocol,
2:23 that means a behavioral protocol or a nutritional protocol
2:26 or a supplementation protocol,
2:28 you should absolutely consult a board certified physician
2:31 before initiating that protocol.
2:34 I don't just say this to protect us,
2:35 I also say this to protect you.
2:37 If you'd like to see our medical disclaimer,
2:39 you can go to our show notes, it's described there.
2:41 In fact, I encourage you to please do that.
2:43 And in general,
2:45 when embarking on new protocols in particular,
2:48 if they involve strong stimuli like changing temperature
2:51 or placing yourself into unusual temperatures,
2:54 I would encourage you to progress gradually.
2:56 I would also encourage you to not look at
2:59 gradual progression as the kind of weak version
3:02 of a protocol.
3:03 In fact, today I'm going to discuss
3:04 a really beautiful peer reviewed study
3:06 that involved having people do deliberate cold exposure
3:10 so they were immersing themselves into water
3:12 up to about their neck
3:13 and the water was actually not that cold.
3:15 It was only about 60 degrees Fahrenheit,
3:17 which for most people is pretty tolerable.
3:19 So nowhere near the kinds of extreme temperatures
3:22 that one could use in other protocols.
3:25 And the interesting thing is despite
3:27 that fairly modest cold temperature,
3:30 by simply extending the duration of time
3:31 that people were in that water,
3:33 they experienced enormous increases in neurochemicals
3:36 that ought to translate to improvements in focus and mood.
3:40 And indeed, that's what's been observed
3:42 in subsequent studies.
3:44 So again, please see our medical disclaimer
3:46 in our show notes, please proceed with caution always,
3:50 please also understand that the most potent stimulus
3:54 isn't always the one that you experience
3:56 as the most intense in the moment.
3:58 In fact, I would encourage you to you find
3:59 the minimum threshold of stimulus
4:02 that will allow you to drive the maximum benefit
4:05 from each protocol and indeed,
4:07 I will point out what those thresholds ought to be today.
4:10 I'll give you some simple formulas,
4:12 gauges or guides that you can use in order to navigate
4:15 this extremely interesting and potent tool
4:18 that we call deliberate cold exposure.
4:20 Before we talk about deliberate cold exposure
4:22 and its many powerful applications,
4:24 I'd like to highlight a study
4:26 that I find particularly interesting,
4:27 that I think you will find
4:29 particularly interesting and useful.
4:31 The title of this study is brief aerobic exercise
4:35 immediately enhances visual attentional control
4:37 and perceptual speed,
4:39 testing the mediated role of feelings of energy.
4:43 Now, the reason I like this study is first of all,
4:46 it's a fairly large size sample group.
4:48 They looked at 101 students.
4:52 These were college-aged students and they had two groups.
4:55 One group did 15 minutes of jogging at moderate intensity.
5:01 So they did measure percent heart rates, et cetera,
5:04 but this would be analogous to zone two cardio,
5:08 which I've discussed on this podcast before.
5:10 Zone two cardio is cardiovascular exercise
5:14 that places you at a level where you can hold a conversation
5:18 with a little bit of strain,
5:20 meaning that you can get the words out,
5:21 but every once in a while you have to catch your breath
5:23 whereas if you were to push any harder by any mechanism
5:27 going faster or on a steeper incline, et cetera,
5:30 that you would have a hard time carrying out a conversation.
5:32 So zone two cardio is a common form of describing
5:37 that level of intensity that they call moderate intensity.
5:40 So one group did 15 minute of jogging at moderate intensity,
5:44 which I'm translating to roughly zone two cardio.
5:47 The other group did 15 minutes of relaxation concentration
5:52 that is somewhat akin to mindfulness meditation.
5:55 And then they were analyzed for perceptual speed,
5:59 visual attentional control, something called working memory,
6:01 which is your ability
6:02 to keep certain batches of information online.
6:06 Just imagine someone telling you their phone number,
6:08 and you have to remember that sequence of numbers
6:10 in your head for some period of time, that's working memory.
6:13 And it depends very heavily on the so-called
6:15 prefrontal cortical networks,
6:18 which are involved in planning and action.
6:20 And they also looked at people's feelings of energy
6:23 and they measured that subjectively,
6:24 how energetic people felt.
6:26 Now the major takeaways from this study
6:28 that I'd like to emphasize are that
6:30 the 15 minutes of jogging group
6:32 experienced elevated levels of energy
6:35 for some period of time after they ceased the exercise
6:38 whereas the group that did mindfulness meditation
6:41 actually reported feeling more calm
6:44 and having less overall energy.
6:46 Now that's very subjective and indeed they used
6:48 subjective measures to analyze energy,
6:52 but what gets interesting is when they looked at performance
6:55 on these various cognitive tasks and the two tasks
6:58 that they use were called the trail making tests,
7:01 they have different versions of this,
7:02 version A, version B,
7:03 I don't want to go into too much detail,
7:05 but version A essentially involves having a page of numbers
7:09 that are distributed somewhat randomly.
7:11 So one, two, three, four, five, six, seven, eight and so on,
7:14 but distributed randomly across the page
7:15 and people have to use visual search
7:17 to circle those numbers in sequence.
7:19 So this involves visual attention,
7:21 it involves some motor skills,
7:23 involves a number of things
7:24 that certainly require energy and focus.
7:27 The second test was the trail making test part B,
7:30 as I mentioned earlier,
7:31 and this involved also circling numbers in sequence,
7:34 but interspersed between those numbers were letters.
7:36 So rather than just having
7:37 to circle off numbers in sequence,
7:39 they actually had to connect one,
7:41 then the letter A, then two, then the letter B, et cetera
7:44 and remember these are randomly distributed across the page.
7:47 The major takeaway from the study is that the group that did
7:50 the 15 minutes of moderate exercise prior to these two tests
7:55 showed significant decreases in the amount of time required
7:58 to complete these tests accurately.
8:01 That is interesting and indeed surprising at least to me,
8:05 because there have been many studies looking at the effects
8:08 of mindfulness meditation on the ability to focus.
8:11 The key variable in the study turned out to be energy.
8:14 This subjectively measured feeling I should say
8:17 of having more energy and thereby the ability to focus,
8:20 especially in these high cognitive demand tasks.
8:23 Now the takeaway from this study for all of us
8:25 I think is pretty straightforward.
8:27 If you are going to sit down to do some work
8:30 that requires focus and working memory
8:32 and cognitive attention
8:33 and especially if it's some visual spatial control,
8:36 meaning you have to search for things on a page,
8:38 you have to organize things on a page,
8:39 so some writing, arithmetic,
8:41 basically cognitive work of any kind,
8:44 15 minutes of moderate exercise done prior
8:48 to that work about could be very beneficial for you.
8:51 This does not mean that mindfulness meditation
8:53 would not be a benefit to you.
8:55 I wouldn't want you to conclude that,
8:57 but if you had to choose between doing
8:58 15 minutes of mindfulness meditation
9:00 and doing 15 minutes of moderate exercise
9:02 prior to a cognitive work about,
9:05 I would say the 15 minutes of moderate exercise would be
9:09 more valuable at least based on the data in this paper.
9:12 In many previous podcasts,
9:14 I have talked about the powerful effects of doing things
9:17 like mindfulness meditation, and other forms of NSDR,
9:21 non-sleep deep rest.
9:23 So these could be 20 minute naps or just lying there quietly
9:25 with your eyes closed or yoga nidra
9:28 or NSDR scripts are available on YouTube
9:31 and various other places free of cost of any kind.
9:34 You just go to YouTube, put in NSDR,
9:36 non-sleep deep rest.
9:38 Those protocols have been shown to be very beneficial
9:41 for enhancing neuroplasticity,
9:43 the changes in the brain and body that encode
9:47 or shift the neural circuits that allow
9:49 for memory to change,
9:51 that allow for learning to occur after a learning about.
9:55 What I'm referring to today in this particular study
9:58 is the use of moderate exercise
10:00 in order to increase one's focus and attention
10:03 in order to trigger that neuroplasticity.
10:06 So the simple sequence here is get energetic and alert,
10:12 do that prior to the learning about,
10:14 engage in the cognitive work or learning about,
10:16 and then mindfulness meditation,
10:18 NSDR and so forth should follow.
10:20 And if you would like to access this paper
10:23 and like to look more at the details in the paper,
10:25 we'll be sure to put a link in the show notes.
10:27 The first author is Legrand.
10:29 And again, the title of this paper is brief aerobic exercise
10:31 immediately enhances visual potential control
10:33 and perceptual speed,
10:34 testing the mediating role of feeling of energy.
10:37 And I also just want to emphasize immediately.
10:40 I think most people out there are interested in tools
10:42 and protocols that work the first time
10:43 and that work every time
10:45 and indeed, I think this protocol fits that bill.
10:47 I'm pleased to announce
10:48 that I'm hosting two live events this May.
10:51 The first live event will be hosted
10:52 in Seattle, Washington on May 17th.
10:55 The second live event
10:56 will be hosted in Portland, Oregon on May 18th,
10:59 both are part of a lecture series entitled
11:01 the Brain Body Contract during which I will discuss science
11:04 and science-based tools for mental health,
11:07 physical health and performance.
11:08 And I should point out that while some of the material
11:11 I'll cover will overlap with information covered here
11:14 on the Huberman Lab Podcast
11:15 and on various social media posts,
11:17 most of the information I will cover is going to be distinct
11:20 from information covered on the podcast or elsewhere.
11:23 So once again, it's Seattle on May 17th,
11:26 Portland on May 18th.
11:27 You can access tickets by going to hubermanlab.com/tour
11:31 and I hope to see you there.
11:32 Before we begin,
11:33 I'd like to emphasize that this podcast is separate
11:36 from my teaching and research roles at Stanford.
11:38 It is however part of my desire and effort
11:40 to bring zero cost to consumer information about science
11:43 and science-related tools to the general public.
11:45 In keeping with that theme,
11:46 I'd like to thank the sponsors of today's podcast.
11:49 Our first sponsor is Athletic Greens, also called AG One.
11:53 I started taking AG One way back in 2012
11:56 so I'm delighted that they're sponsoring the podcast.
11:59 The reason I started taking AG One
12:00 and the reason I still take AG One
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12:07 It also has adaptogens and things like zinc
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12:12 but the probiotics are one of the key features in there.
12:14 I've done several podcasts on the gut microbiome,
12:17 which are these trillions of microbiota
12:18 that live in our digestive tract,
12:20 and that are crucial for our immune system,
12:22 brain function and so on.
12:24 One way to enhance our gut microbiome
12:26 to ensure that it's healthy is to make sure
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15:37 Let's talk about the use of cold for health and performance.
15:40 I confess I love this topic
15:42 because it takes me back to my undergraduate years
15:45 when I worked in a laboratory studying cold physiology,
15:49 its effects on the brain and its effects the body.
15:52 And over the years,
15:54 I've always kept track of the literature in this area
15:56 and indeed there have been some tremendous discoveries,
15:59 both in animal models, so in rodents like mice and rats,
16:02 but also in humans
16:04 and today we're going to talk about both categories
16:07 of studies and I'll be careful to point out when discoveries
16:10 were made in animal models
16:11 and when they were made in humans.
16:15 A key point when thinking about the use of cold as a tool,
16:19 and the key point is that you have a baseline level
16:23 of temperature that is varying,
16:26 changing across the 24 hour cycle.
16:29 So any use of deliberate cold exposure
16:32 is going to be super imposed on that rhythm,
16:36 that circadian rhythm, meaning that 24 hour rhythm.
16:40 The basic contour of your circadian rhythm in temperature
16:44 is that approximately two hours before the time you wake up
16:49 is your so-called temperature minimum.
16:51 So your temperature minimum is a time
16:54 within the 24 hour cycle
16:56 when your body temperature is at its lowest.
16:59 So if you normally wake up around 6:00 AM,
17:03 your temperature minimum is probably about 4:00 AM.
17:07 If you normally wake up at about 7:00 AM,
17:10 your temperature minimum is probably about 5:00 AM.
17:13 It's not exactly two hours before your wake up time,
17:16 it's approximately two hours before your wake up time.
17:19 Now, as you go from your temperature minimum
17:22 to the time in which you're going to awake,
17:25 your temperature is rising slightly.
17:27 And then at the point where you wake up,
17:30 your temperature starts to go up more sharply
17:33 and will continue to go up into the early
17:36 and sometimes even into the late afternoon.
17:38 And then sometime in the late afternoon and evening,
17:41 your temperature will start to decline.
17:44 And indeed, as you approach sleep,
17:46 your body temperature will drop
17:48 by anywhere from one to three degrees.
17:50 And in fact that decrease in core body temperature
17:53 is important if not essential for getting into
17:56 and staying in deep sleep.
17:59 So temperature rises with waking, that's easy to remember.
18:02 It tends to continue to rise throughout the day
18:05 and in the late afternoon and evening,
18:07 your temperature WILL start to go down and the drop
18:10 in temperature actually helps you access sleep.
18:13 That background or what we call baseline circadian rhythm
18:18 in core body temperature is important to remember
18:21 because it helps us frame both the effects
18:24 of deliberate cold exposure and helps us frame
18:28 when you might want to use deliberate cold exposure
18:31 in order to access specific states.
18:33 It also points to times within the 24 hour cycle
18:36 when you might want to avoid using deliberate cold exposure,
18:39 if your primary goal is to get to sleep.
18:42 So that's the circadian rhythm in temperature.
18:45 Now I just briefly want to touch on
18:47 thermal regulation at the level of body and the brain.
18:51 And this will be very surprising to many of you.
18:55 Let's do what's called a Gedanken experiment,
18:57 which is a thought experiment.
18:58 Let's say I send you out into the desert heat
19:01 for a jog or a run and it's very hot outside,
19:05 102 or 103 degrees, and you start to move,
19:11 you start to sweat
19:12 and of course your core body temperature goes up.
19:14 Now, then I offer you a cold towel,
19:18 maybe a really, really cold towel
19:21 and this towel is saturated with water
19:22 so you could actually squeeze the water out of that
19:24 and cool your body off.
19:26 And our Gedanken experiment is for me to say okay,
19:29 where are you going to place the towel?
19:31 How are you going to cool yourself off?
19:33 And I'm guessing that most of you would think
19:35 that the best way to cool yourself off
19:37 would be to drape that towel over your head,
19:39 maybe your neck, over your torso,
19:42 that it would feel really, really good,
19:43 and it would cool you off.
19:45 Well, that's exactly the wrong approach
19:48 if you want to cool off.
19:49 And in fact, if you were to use that approach,
19:52 your body temperature would continue to increase even more.
19:56 Yes, even more than had you not placed
19:59 that cold towel on your head or your torso.
20:02 And here is why.
20:04 Thermal regulation meaning your brain and body's ability
20:07 to regulate your internal core temperature
20:10 is somewhat like a thermostat and that thermostat
20:13 resides in your brain.
20:15 So if you think about the thermostat
20:16 in your home or apartment,
20:18 if it's too warm in your home or apartment
20:22 and you were to take a bag of ice
20:24 and to put it on that thermostat,
20:27 what would the thermostat do?
20:29 It would register the environment as artificially cool.
20:32 It would think that the environment
20:34 was actually much colder than it is.
20:37 And so as a consequence,
20:39 it would trigger a mechanism
20:41 to further increase the temperature in the room.
20:43 And you have such a thermostat as well.
20:45 It's called the medial preoptic area of the hypothalamus.
20:48 The hypothalamus is a small region of brain tissue
20:52 about over the roof of your mouth
20:54 and a little bit in front of that.
20:56 So it's basically right behind your nose and over the roof
21:00 of your mouth and it's a collection of neurons.
21:02 Those neurons have a lot of different functions
21:04 that include things like the control of aggression,
21:07 the control of sex behavior,
21:09 the control of temperature regulation and so on.
21:11 The medial preoptic area has connections with
21:15 the rest of the brain
21:17 or areas within the brain, I should say
21:19 and with many areas within the body,
21:21 it receives input from receptors in our skin
21:26 and inside our body that register temperature
21:29 and it acts as a thermostat.
21:31 So if the surface of your body is made cool,
21:34 your medial preoptic area will send signals
21:38 by way of hormones
21:40 and by way of chemicals that will serve
21:42 to heat your body up.
21:44 So what this means is that if you want to cool down,
21:47 the last thing you want to do is to bring a cold surface
21:52 of any kind, towel or splashing water,
21:54 to the majority of your body surface.
21:56 It might be very, very surprising to you.
21:59 And you might say, wait, if I want to cool down,
22:00 I should jump into a cold lake or something of that sort.
22:02 That's a different thing altogether.
22:05 What I'll tell you,
22:06 and we'll get into this in more depth later,
22:08 is that if you really
22:09 want to cool down quickly and efficiently,
22:11 you should leverage particular portals,
22:14 meaning particular sites on your body
22:18 where heat can leave your body more readily
22:21 and where cooling can have a dramatic and fast impact
22:26 on your core body temperature,
22:27 can even save your life if you're going hyperthermic.
22:29 We're going to talk more about the specific protocols to reduce
22:32 core body temperature for sake of performance
22:34 and avoiding hyperthermia later in the episode.
22:37 Hyperthermia of course is a very, very dangerous situation
22:40 because while your body can drop in core temperature
22:44 somewhat and still be safe,
22:45 you can't really increase your body temperature that much
22:48 before your brain starts to cook
22:50 and other organs start to cook and by cook,
22:52 I mean the cells actually start to die.
22:54 So you have to be very, very careful with the use of heat.
22:56 Heat stroke is no joke.
22:58 People die from heat stroke all the time.
23:00 You really want to avoid that.
23:02 One way to avoid that is to cool the appropriate surfaces
23:06 of your body and the appropriate surfaces in this case
23:10 are the upper cheeks
23:11 or I would say the upper half of the face,
23:14 the palms of your hands and the bottoms of your feet.
23:16 I've talked about this on the podcast before
23:18 and in the guest episode with Dr. Craig Heller,
23:20 my colleague in the biology department at Stanford,
23:23 but just very briefly, these surfaces,
23:26 the upper half of the face,
23:28 the palms of the hands and the bottoms of the feet
23:31 are what we call
23:32 glabrous skin surfaces, G-L-A-B-R-O-U-S, glabrous.
23:38 And those surfaces are unique in that just below them,
23:42 the vasculature is different than elsewhere in the body.
23:46 Normally the passage of blood goes from
23:48 arteries to capillaries to veins,
23:50 but just beneath the glabrous skin on the bottoms
23:54 of the feet, the hands in the upper half of the face,
23:56 you have what are called arterio-venous anastomoses.
23:59 These are portals of blood that go directly
24:03 from arteries to veins and in doing so,
24:05 allow the body to dump heat more readily, more quickly.
24:11 So as it turns out that if you are to cool the palms
24:15 of the hands, the bottoms of the feet
24:16 and the upper half of the face,
24:17 you can more efficiently reduce core body temperature
24:20 for sake of offsetting hyperthermia
24:23 and for improving athletic performance
24:25 and maybe even cognitive performance.
24:27 So we will return to the specific protocols
24:29 for doing that later in the episode,
24:31 I'll give you a lot of details about how to do that,
24:34 how to do that without the use of
24:35 any fancy or expensive technology.
24:38 There are some technologies
24:39 that are now commercially available, for instance,
24:41 the so-called CoolMitt
24:43 that will allow you to do that with maximum efficiency,
24:45 but I'll also give you some at home methods to do this
24:48 either in the gym or on runs or for sake of cognitive work.
24:52 So the two key themes again
24:54 are understand that baseline circadian rhythm
24:57 in temperature, and understand that the best way to cool
25:01 the body is going to be
25:02 by making sure that something cold contacts
25:07 the bottoms of your feet,
25:08 the palms of your hands and the upper half of the face.
25:10 Ideally all three
25:11 if your goal is to lower core body temperature quickly,
25:13 and again, just cooling off the back of your neck
25:17 or the top of your head or your torso with a towel
25:19 is going to be the least efficient way
25:21 to lower core body temperature and might even increase
25:24 body temperature under certain conditions.
25:27 With those two points in mind,
25:28 we can start to think about directed deliberate
25:31 cold exposure protocols,
25:32 and there are a number of different reasons
25:34 to use deliberate cold exposure.
25:36 And I want to separate those out for you.
25:40 There are cold protocols that have been tested
25:42 in peer reviewed studies that are designed
25:45 to improve mental performance.
25:47 They are designed to improve things like resilience
25:49 or your grittiness,
25:50 or your ability to move through challenge
25:52 or to regulate your mind and your internal state
25:56 under conditions of stress
25:57 and we can define stress very specifically as times
26:01 when adrenaline also called epinephrine
26:04 and or norepinephrine also called noradrenaline,
26:09 are elevated in your body.
26:10 Forgive me for the noradrenaline,
26:12 norepinephrine, adrenaline, epinephrine nomenclature,
26:15 I didn't make that up.
26:16 It turns out that every once in a while,
26:17 scientists disagree, imagine that,
26:20 and you'll get multiple scientists
26:21 naming the same molecule different things.
26:23 So epinephrine and adrenaline are the same thing.
26:26 I will use them interchangeably.
26:28 Norepinephrine and noradrenaline are the same thing.
26:31 I will use those terms interchangeably.
26:34 Noradrenaline and adrenaline
26:36 are often co-released in the brain and body.
26:38 So they work as kind of a pair to increase
26:41 our level of agitation,
26:42 our level of focus and our desire and our ability to move.
26:47 They are often co-released from different sites
26:50 in the brain and body with dopamine,
26:52 a molecule that is commonly misunderstood
26:56 as the molecule of pleasure,
26:58 but is actually the molecule of motivation,
27:00 reward and pursuit.
27:02 So dopamine, norepinephrine and noradrenaline
27:04 tend to be released together under certain conditions
27:08 and today you'll learn how deliberate cold exposure
27:11 can be used to cause increases in the release of several,
27:15 if not, all of these in ways
27:16 that can improve your levels of attention and your mood.
27:21 But the key point is that your mental state is shifted
27:26 when you are exposed to certain forms of cold,
27:29 and many people use deliberate cold exposure
27:32 specifically to shift their body state as a way
27:35 to train their mental state so that they can better cope
27:38 with stress in real life and by real life,
27:41 I mean when life presents stressful events,
27:43 and I will give you specific protocols
27:45 as to how you can do that, in other words,
27:47 how you can become more resilient
27:49 through the use of deliberate cold exposure.
27:52 Now, because of the ways in which deliberate cold exposure
27:55 can increase this category of chemicals
27:57 called the catecholamines,
27:58 that includes dopamine, norepinephrine and epinephrine,
28:02 it can also be used to elevate mood
28:05 for long periods of time.
28:07 And I'm going to discuss a specific protocol
28:10 that has been shown to increase these chemicals
28:13 anywhere from 2.5X to 250%, to as high as 500%,
28:21 five times over baseline.
28:23 Now you might be asking whether or not it is a good thing
28:26 to raise chemicals like norepinephrine and dopamine
28:29 to such a great degree,
28:31 whether or not that's healthy for us,
28:32 whether or not they can harm us.
28:34 But it turns out that these elevations in norepinephrine
28:36 and dopamine are very long lasting in ways
28:39 that people report feeling vast improvements
28:43 in mood and vast improvements
28:45 in levels of cognitive attention and energy.
28:48 So by my read of the literature,
28:50 these seem to be healthy increases in our baseline levels
28:55 of these chemicals in ways that can really support us
28:57 so I'll give you a protocol for that.
28:59 Now, those are some of the mental effects
29:01 of deliberate cold exposure,
29:03 but deliberate cold exposure has also been studied
29:05 in animal models and in humans
29:07 in the context of increasing metabolism,
29:09 even in converting certain fat cells
29:12 that we call white fat cells,
29:14 which are the ones where energy is stored,
29:16 they're the ones that we typically think of
29:17 as kind of blubbery fat, to beige or brown fat,
29:21 which is thermogenic fat,
29:23 meaning that it can increase core body temperature
29:25 and serves kind of the furnace
29:27 by which we increase our core metabolism.
29:31 So with a very broad stroke,
29:33 I can say that white fat is generally the kind of fat
29:35 that people want less of and beige fat and brown fat
29:38 is generally the kind of fat that
29:40 if you're going to have fat cells and
29:42 you certainly need fat cells that you want more of.
29:45 They are thermogenic, they help you stay lean.
29:47 They actually serve as a reservoir for heating your body up
29:50 if you're ever confronted with a cold challenge.
29:52 So we're going to talk about how to use cold
29:53 for metabolism as well.
29:55 And of course,
29:56 people are using deliberate cold exposure
29:57 to reduce inflammation post exercise,
30:00 to reduce inflammation generally.
30:02 And people are also using cold to enhance performance
30:06 in the context of strength training,
30:08 in the context of endurance training
30:10 and we'll talk about those data as well,
30:12 but where I'd like to start is with mental performance
30:14 and I'd like to detail what happens
30:18 when we deliberately expose ourselves to cold.
30:21 It's key to point out the word deliberate.
30:24 If I don't say otherwise, then throughout this episode,
30:27 if I say cold exposure, I mean deliberate cold exposure.
30:30 And the reason I point that out is that as my colleague,
30:33 David Spiegel, and the department of psychiatry
30:34 at Stanford says,
30:36 it's not just about the state that we are in,
30:38 it's about the state that we are in and whether or not
30:40 we had anything to with placing ourselves into that state
30:43 and whether or not we did that on purpose or not.
30:45 And what he really means by that statement is that
30:50 there are important effects of what we call mindset.
30:53 Mindset was a topic discussed in the guest episode
30:56 with Ali Crumb some weeks ago.
30:58 If you haven't seen that episode, I highly recommend it.
31:01 And the science of my mindset tells us that if we are doing
31:04 something deliberately and we believe
31:06 that it's going to be good for us,
31:08 it actually can lead to a different set
31:11 of physiological effects than if something
31:15 is happening to us against our will or without our control.
31:18 Now, this is different than placebo effects.
31:20 Placebo effects are distinct from mindset effects.
31:23 If you want to learn more about that distinction,
31:25 please see the episode with Ali Crumb.
31:27 But again, when I talk about cold exposure in this episode,
31:30 I'm talking about deliberate cold exposure,
31:33 meaning that you are placing yourself into a
31:36 cold environment on purpose in order to extract
31:38 a particular set of benefits.
31:42 When we talk about deliberate cold exposure, almost always,
31:45 that means getting uncomfortable.
31:48 And one of the most common questions I get
31:50 when discussing the use of cold for sake of mental
31:52 or physical performance, metabolism, et cetera,
31:54 is how cold should it be?
31:57 How cold should the water be?
31:58 How cold should the environment be?
32:00 And I just will tell you now
32:02 and I'm going to say this again and again
32:03 throughout the episode,
32:04 cause it will continue to be true throughout the episode
32:06 and long after the episode is over,
32:09 how cold depends on your cold tolerance,
32:12 your core metabolism,
32:14 and a number of other features that there is simply no way
32:18 I could know or have access to.
32:20 So I would like you to use this rule of thumb.
32:24 If you are using deliberate cold exposure,
32:27 the environment that you place yourself into
32:30 should place your mind into a state of whoa,
32:34 I would really like to get out of this environment,
32:36 but I can stay in safely.
32:39 Now that might seem a little bit arbitrary,
32:41 but let's say you were to get into a warm shower
32:43 and it would feel really, really nice
32:45 and you were to start turning down the warm
32:47 and turning up the cold.
32:48 There would be some threshold at which
32:50 it would feel uncomfortable to you.
32:52 And if you were to continue to make a little bit colder
32:54 than that, you would really want to get out of the shower,
32:57 but you are confident that you could stay in
33:00 without risking your health, without risking a heart attack.
33:04 Now that's very different than jumping into
33:05 a very, very cold lake or
33:09 I've seen these images of people that will cut holes into
33:12 frozen over lakes and they'll get into that cold water.
33:16 If you are trained to do that
33:17 and you have the right conditions, et cetera,
33:19 that can be done reasonably safely,
33:21 but that's certainly not what I would start with.
33:23 And for many people, that would be too cold
33:25 and indeed some people can go into cold shock
33:28 and can die as a consequence of getting
33:30 to that extremely cold water very quickly.
33:32 Now that's not to scare you away
33:33 from deliberate cold exposure.
33:34 It's just to say that there's no simple prescriptive
33:38 of how cold to make environment
33:39 in order to extract maximum benefit
33:43 for mental or physical performance.
33:46 So the simple rule of thumb is going to be
33:49 place yourself into an environment
33:51 that is uncomfortably cold,
33:53 but that you can stay in safely.
33:55 And you'll have to experiment a bit and that number,
33:57 meaning that temperature, will vary from day to day.
34:00 It will vary across the 24 hour cycle
34:03 because of that endogenous,
34:05 meaning that internal rhythm,
34:06 in temperature that I talked about earlier.
34:09 Low early in the day,
34:10 rises into the afternoon, drops at night.
34:12 You can actually do this experiment if you like.
34:14 Try getting into a cold shower at 11 o'clock at night
34:17 if you want versus try doing it
34:20 in the middle of the afternoon.
34:22 It's quite a different experience
34:24 and by quite a different experience,
34:25 I mean it requires quite a different degree of resilience
34:29 and leaning into the practice.
34:31 Your willpower will have to be higher I suspect
34:35 late in the day as it compared to early in the day,
34:39 but that will vary of course between individuals as well.
34:42 So the most common question I get
34:43 about deliberate cold exposure
34:45 is how cold should the water be?
34:48 And we've answered that with uncomfortably cold to the point
34:51 where you want to get out,
34:52 but you can safely stay in.
34:53 The second most common question I get
34:55 about deliberate cold exposure is whether or not
34:57 cold showers are as good,
34:59 better or worse than cold water immersion
35:02 up to the neck, for instance.
35:04 I also get a lot of questions about whether or not
35:06 cryo chambers are better than all the others,
35:08 et cetera, et cetera.
35:10 I'm going to make all of that
35:12 very simple for you by saying cold water immersion
35:14 up to the neck with your feet and hands submerged also
35:18 is going to be the most effective.
35:20 Second best would be cold shower.
35:23 Third best would be to go outside
35:26 with a minimum amount of clothing, but of course,
35:29 clothing that is culturally appropriate
35:32 and that would allow you to experience cold to the point
35:35 where you would almost want to shiver or start shivering.
35:38 Now there are a number of different,
35:40 important constraints that are going to dictate
35:42 whether or not you use one form of cold exposure
35:44 or the other.
35:45 For instance, some people don't have access
35:47 to cold water immersion.
35:48 They don't have access to ice baths or cold water tanks,
35:53 cold ocean or cold lakes, et cetera.
35:55 In that case, showers would be the next best solution.
35:58 I do want to emphasize that there have been very few,
36:01 if any, studies of cold showers,
36:04 and you can imagine why this would be the case.
36:07 In a laboratory,
36:08 you want to control for as many variables as possible.
36:11 So placing people into a cold water immersion or an ice bath
36:16 up to the neck and insisting they keep their hands
36:18 and feet under is very easy to control.
36:21 It means that everyone can do essentially the same thing
36:23 whereas with cold showers,
36:25 people are different sized bodies.
36:27 Some people are going to put their head under.
36:28 Some people are going to lean forward.
36:31 Measuring the amount of cold water exposure on the body
36:34 is very hard to do
36:35 and so there aren't a lot of studies of cold showers,
36:38 but of course,
36:39 a lot of people don't have access to cold water immersion
36:41 so they have to use cold showers.
36:43 And if you don't have access to both, of course,
36:45 then going outside on a cold day can be of a benefit.
36:49 But I will point out that the heat transfer
36:53 from your body into water is much higher,
36:57 four times greater, if not even greater,
37:00 depending on the temperature of the water,
37:02 in water as opposed to in air.
37:04 So it's going to be much more efficient
37:05 to do cold water immersion than anything else,
37:07 cold showers after that and put yourself into
37:10 a cold environment would be the third best thing.
37:13 I'm not going to get into cryo chambers
37:15 because they carry quite a high degree of cost.
37:18 And again, there aren't many studies of them.
37:20 So if you have access to cryo chambers,
37:23 I'm sure that the cryo chamber facility
37:24 has told you about all these incredible benefits
37:26 and I don't doubt that some of those benefits truly exist,
37:29 but most people just don't have the resources
37:31 or the access to those
37:32 so we're going to leave cryo chambers
37:33 out of today's discussion.
37:34 And of course I realize there's a fourth category
37:37 of cold exposure out there.
37:38 People are wearing ice vests.
37:39 Believe it or not, those exist, ice underwear.
37:41 Yes, those exist.
37:44 You can look for them on Amazon if you like.
37:46 They are putting cold packs in their armpits
37:49 or in their groin or elsewhere in order to
37:51 stimulate some of the effects of cold
37:54 on mental and physical performance.
37:56 I'm not going to address those in too much detail today.
37:59 They can be efficient in certain ways,
38:02 but as you'll learn about later in the episode,
38:04 cooling the palms, the upper face
38:07 and the bottoms of the feet
38:08 is going to be far more efficient
38:10 and unfortunately I think most of the people that are using
38:13 ice packs to increase their core metabolism
38:15 are not aware of the glabrous skin cooling
38:18 and how it can be a very, very potent stimulus
38:20 so we'll return to that later.
38:23 Unless I say otherwise,
38:24 I'm mainly going to be focusing on cold water immersion
38:26 and cold showers.
38:28 So let's talk about protocols for enhancing mental health
38:30 and performance using deliberate cold exposure.
38:34 What happens when we get into cold is that we experience
38:38 an increase in norepinephrine,
38:41 in noradrenaline release and in adrenaline release.
38:44 The fact that cold exposure, deliberate or no,
38:47 increases norepinephrine and epinephrine
38:50 in our brain and body means that it is
38:52 a very reliable stimulus for increasing
38:54 norepinephrine and epinephrine.
38:56 That's sort of an obvious statement,
38:58 but that obvious statement can be leveraged
39:02 to systematically build up what we call resilience.
39:05 Now, when we experience a stressor in life,
39:08 whether or not it's something bad happens
39:10 in our relationship or something bad happens in the world
39:14 and we feel stress,
39:16 that stress is the consequence of increases
39:18 in norepinephrine and epinephrine in our brain and body.
39:22 Very similar, if not identical,
39:23 to the kinds of increases
39:24 that come from deliberate cold exposure.
39:27 So deliberate cold exposure is an opportunity
39:29 to deliberately stress our body and yet,
39:33 because it's deliberate
39:34 and because we can take certain steps,
39:36 which I'll describe in a moment,
39:38 we can learn to maintain mental clarity,
39:41 we can learn to maintain calm while our body
39:45 is in a state of stress.
39:47 And that can be immensely useful
39:49 when encountering stressors in other parts of life.
39:53 And that's what we call resilience or grit,
39:55 our ability or mental toughness,
39:57 our ability to lean into challenge or to tolerate challenge
40:01 while keeping our heads straight, so to speak.
40:04 So one simple protocol for increasing resilience
40:07 is to pick a temperature that's uncomfortable
40:10 of shower or cold immersion,
40:12 and then to get in for a certain duration of time
40:15 and then to get out.
40:17 Now, it's important to understand
40:18 that people will experience different levels
40:20 of norepinephrine and adrenaline release
40:22 when getting into cold water.
40:24 Some people, because they dread the cold so much,
40:28 will actually experience norepinephrine
40:29 and epinephrine increases
40:31 even before they get into the cold water
40:33 or under the cold shower.
40:35 Now you may have experienced this.
40:36 I've certainly experienced this.
40:37 I'm dreading it, I don't want to do it
40:39 and I have to force myself to do it.
40:41 And indeed epinephrine and norepinephrine and its surges
40:45 can be thought of as sort of walls that we have to confront
40:48 and go over.
40:49 And I'd like you to conceptualize them that way,
40:52 because it allows us to build protocols
40:54 that can be very objective and can allow us
40:58 to monitor our progress in terms of building resilience.
41:01 So one option is to simply say, okay,
41:04 I'm going to force myself
41:05 to get into the cold shower for one minute.
41:07 How cold, again, uncomfortably cold,
41:09 but you can stay in safely
41:10 or I'm going to get into the ice bath for one minute.
41:13 Ice baths are very cold inevitably.
41:16 And what is also inevitable is that
41:19 when you get into the cold,
41:20 you will experience a surge
41:22 in epinephrine and norepinephrine.
41:24 That's non-negotiable because it's mediated
41:26 by cold receptors on the surface of your body
41:29 and your skin and the way that they trigger the release
41:32 of norepinephrine and epinephrine,
41:33 not just from the adrenals,
41:35 from the adrenal glands above your kidneys,
41:37 but also from regions of your brain,
41:38 like the locus coeruleus,
41:39 which cause increases in the tension and alertness,
41:42 and from other locations in your body where epinephrine
41:45 and norepinephrine are released.
41:47 In other words, cold is a non-negotiable stimulus
41:51 for increasing epinephrine and norepinephrine.
41:55 Even if you are the toughest person in the world
41:58 and you love the cold,
42:00 that increase in epinephrine and norepinephrine
42:02 is going to happen.
42:04 So the way to think about norepinephrine and epinephrine
42:06 in this context of building mental resilience
42:09 is that you have two options.
42:11 You can either try to extend the duration of time
42:15 that you are in the deliberate cold exposure.
42:17 So going from one minute to 75 seconds to two minutes
42:21 and so on over a period of days
42:23 or one way to approach this
42:25 and the way that I particularly favor
42:27 is to take the context of the day
42:30 and the moment into account,
42:32 meaning we have different levels of grit and resilience
42:36 on different days and depending on the landscape
42:38 of our life at the time,
42:39 even the time of day that we're doing these protocols
42:42 and start to be able to sense the release of epinephrine,
42:47 and norepinephrine in our brain and body and see those
42:50 as walls that we want to climb over
42:52 in order to build resilience and to start counting
42:55 the number of walls that we traverse
42:57 and the distance between those walls
42:59 as we do deliberate cold exposure.
43:01 Let me give you an example of the timed protocol
43:05 because that one is very straightforward,
43:06 although I do not think it is as powerful
43:09 for building mental resilience.
43:11 The time protocol would be Monday,
43:12 I do one minute of deliberate cold exposure
43:15 at a given temperature.
43:16 Wednesday, I extend that by 50% and Friday,
43:19 I do deliberate cold exposure for twice as long
43:22 as I did it on Monday.
43:23 And if I were to continue that every week,
43:26 Monday, Wednesday, Friday,
43:27 I would continue to either increase the duration
43:29 or I would lower the temperature and reduce the duration,
43:34 this kind of thing, very much like sets and reps in the gym.
43:36 Now that option is very objective.
43:38 You could even log it in a book
43:40 and as you develop the ability to stay in cold temperatures,
43:46 even progressively colder and colder temperatures
43:48 for longer and longer periods of time,
43:50 you will become more resilient.
43:52 What do I mean by that?
43:53 Well, my operational definition of resilience
43:55 is that you are able to resist escape from the stressor,
43:59 the cold, by virtue of your willpower,
44:02 which is really your prefrontal cortex
44:05 causing top down control on your reflexes
44:08 and your limbic system and your hypothalamus,
44:10 which are basically telling you
44:11 to get out of that cold water,
44:13 get out of that cold environment and in doing so,
44:17 you are basically getting better
44:19 at controlling your behavior when your brain and body
44:21 are flooded with norepinephrine and epinephrine.
44:24 That's a very reductionist way to explain resilience
44:26 or grit or mental toughness,
44:28 but it's a reductionist way of explaining it
44:30 that is very closely tied to the biology end
44:32 of the psychology.
44:33 And it is a fact that norepinephrine and epinephrine
44:37 release in the brain and body
44:39 are the generic universal code for stressor.
44:43 There is no unique chemical signature
44:45 for different forms of stressors, that is the only one,
44:48 although of course there are
44:49 other chemicals involved as well.
44:50 So you could go for time and you could try
44:52 and reduce the temperature and increase the time
44:55 over a period of days or weeks.
44:57 Now that's an attractive way to approach things,
45:00 but the problem is that you don't have an infinite amount
45:03 of room with which to lower temperature,
45:06 because eventually you will get into temperatures
45:08 that are either so cold that they are dangerous
45:10 or you have to stay in cold temperatures
45:13 for such long periods that it becomes impractical
45:16 because presumably you also have to
45:18 take care of other aspects of your life,
45:20 you can't just sit all day in the ice bath.
45:23 Now for that reason,
45:24 I favor a protocol in which you build mental resilience
45:27 and mental toughness through
45:29 two different types of protocols.
45:31 The first one involves counting walls.
45:33 Now, what do I mean by walls?
45:34 I mean the sensation of, no,
45:37 I don't want to do this and the idea or the sensation
45:41 in your brain and body that you actually want to leave
45:43 that environment and go warm up.
45:45 Now again, for some people,
45:46 that will be even before getting into the ice bath
45:49 or cold shower.
45:50 So if you are feeling very resistant
45:52 to getting into the ice bath
45:54 or cold shower and you manage to do that,
45:56 that's going over what I would call one wall.
46:00 Then for some period of time,
46:01 you might actually feel comfortable in the ice bath,
46:05 cold water or cold shower.
46:07 And you feel like you could stay there
46:09 for some period of time,
46:10 that you could stay there for a minute or two minutes,
46:12 but inevitably, the next wall will arrive.
46:15 And I would encourage you to pay attention to
46:17 when that next wall arrives
46:19 and actually having an awareness,
46:21 that so-called interceptive awareness as we call it,
46:24 of when that next surge adrenaline epinephrine comes
46:27 or whether or not it reaches a certain threshold
46:30 in your brain and body that you feel you want to get out
46:32 and you're able to stay in for even just 10 seconds longer,
46:36 that means you've traversed yet another wall.
46:39 And if you continue to stay in that cold environment,
46:42 you'll find that the next wall will come
46:43 and the next wall will come.
46:45 Now eventually of course, you will get very, very numb
46:48 depending on how cold it is
46:49 and you could also place yourself into danger.
46:51 So you have to maintain cognitive control,
46:54 counting these walls, traversing these walls,
46:56 but getting out at some point, of course.
46:59 So my favorite protocol for building mental toughness
47:03 AKA grit, AKA resilience,
47:06 is to take into account that some days,
47:08 just getting into the ice bath
47:10 or cold shower represents a wall, some days it doesn't.
47:12 Some days you get in and you feel you could go 10 minutes,
47:15 other days you get in and you feel like
47:17 you could only go a minute and setting a designated number
47:20 of walls before you start the protocol
47:23 is going to be very beneficial here.
47:24 So you say, as long as I can do it safely,
47:27 I'm going to do three walls today.
47:29 The first wall is getting in.
47:30 The second wall will arrive when it arrives
47:32 and the third wall will arrive when it arrives
47:35 and I'll get over that wall and then I'll get out.
47:37 The next day, you might do five walls.
47:38 The next day, you might do three walls again,
47:41 but you might lower the temperature.
47:43 This gives you tremendous flexibility
47:45 and indeed it gives you much more latitude
47:48 to be able to use the same temperatures in different ways,
47:52 or to reduce the temperature only a little bit
47:54 and still get a lot of stimulus,
47:56 meaning a lot of results out of a given protocol.
48:00 Whereas people who are just going for temperature and time
48:02 eventually become cold adapted.
48:04 They get very, very good at doing three minutes
48:07 or six minutes or even 10 minutes at a given temperature
48:10 and so then they feel like they have
48:12 to lower the temperature even more and even more
48:14 and eventually they just bought them out.
48:16 There's nowhere else to go.
48:17 There's no way to get improvements out of the protocol.
48:21 At least not in terms of mental resilience.
48:24 Of course, there's still the positive effects
48:26 on inflammation and metabolism, et cetera,
48:28 that we'll talk about in a little bit.
48:30 But the key thing here is to design protocols
48:33 that are going to work for you over time
48:35 and for you very, very hardy,
48:37 very, very tough guys and gals out there
48:39 that can get right into
48:40 an ice bath or a very, very cold immersion
48:43 and you can just grind it out for six or 10 minutes,
48:45 or you can even do that by remaining peaceful,
48:48 well more points to you, but guess what?
48:51 That's the equivalent of already having loaded up
48:53 the barbell with 600 pounds and done your 10 reps.
48:56 There's not a whole lot more variable space
48:59 with which to get benefits from that stimulus.
49:02 And in the weight room,
49:03 people understand that you can adjust, for instance,
49:05 the speed of the movement,
49:06 or you can start combining that movement
49:08 with pre-exhaustion, et cetera.
49:09 With cold exposure,
49:11 you don't have as much variable space to play with.
49:13 So if your goal is to build resilience,
49:15 either go for time as a function of temperature,
49:18 or what I suggest is to start recognizing these walls
49:23 as an experience of resistance in you
49:25 and going over those walls, set a certain number of walls
49:28 that you're going to go over on a given day and do that
49:31 at a given temperature, and then to mix it up.
49:34 And ideally you might even throw in one more wall
49:38 at the end,
49:39 if you're really feeling bold and brave
49:41 because that's going to build out further resilience.
49:43 But if you want cold exposure to work for you
49:45 for sake of building up resilience
49:46 and mental toughness over time,
49:48 you're going to want to vary this parameter space
49:51 in some sort of way.
49:52 And you don't have to be super systematic about it.
49:56 That's the beauty of this kind of approach
49:58 because you're relying on the fact
49:59 that those walls really represent times
50:02 in which you are forcing your top down control,
50:05 your prefrontal cortex to clamp down on your reflex
50:08 and you're learning behavioral control in the context
50:11 of your body having elevated levels
50:12 of these catecholamines, norepinephrine and epinephrine.
50:15 And that translates to real life
50:17 in a much more realistic way I believe because in real life,
50:21 you're not really engaging in stressors
50:24 for a given amount of time
50:26 that you know how long it's going to last
50:28 and you know the context, no.
50:29 Most stressors arrive in the form of surprises
50:31 we don't like, text messages that deliver bad news,
50:34 information about the outside world or real world
50:37 and online interactions that send our system
50:40 into a state of increased norepinephrine and epinephrine.
50:42 And if you start to think of those as walls
50:44 that you can tolerate and climb over
50:46 while staying and calm and clear of mind,
50:48 then you can really imagine how the ice bath
50:52 and other forms of cold exposure are really serving
50:55 to train you up for real life stressors.
50:58 The next question that I always get is
51:00 what should my mental state be
51:02 while I'm exposing myself to this uncomfortable,
51:04 yet safe condition of cold?
51:07 Well, you have two options
51:09 and there are probably other options as well.
51:11 One is to try and calm yourself
51:14 to remain as mentally still as possible.
51:17 The other is to lean into that challenge
51:21 and so to grind it out and here,
51:23 I have to say that this is a lot like teaching someone
51:25 to drive on a gravel road.
51:27 For any of you that have driven on a gravel road,
51:29 you know that there is no optimal speed
51:32 for all gravel roads.
51:33 It depends on the density of the gravel, et cetera,
51:35 and the vehicle, et cetera.
51:37 So for instance, on some gravel roads,
51:40 when you start to drive and the dust starts to kick up,
51:42 your best option is to drive fast
51:44 and put that dust cloud behind you.
51:46 On other gravel roads, if you try and do that,
51:49 the dust actually kicks up around the vehicle
51:50 and it makes it hard to see
51:52 and sometimes you have to slow down.
51:53 The same thing is true for getting through
51:55 deliberate cold exposure.
51:57 Sometimes it's easier to calm yourself.
51:59 One way to do that is through double inhales
52:01 through the nose and extended exhales through the mouth,
52:04 or simply by trying to control your breathing
52:06 and reduce the pace of your breath and increase
52:09 the volume of your breathing.
52:12 I have to say that everyone experiences a shortening
52:15 of breath when they get into uncomfortably cold water,
52:18 that is a universal physiological response.
52:21 Everyone also experiences a 30 to 80% decrease
52:26 in cognitive function, in particular, the frontal cortex.
52:29 The metabolism of your frontal cortex goes down,
52:31 the metabolism meaning the activity of brain areas
52:34 associated with stress and panic goes way up.
52:36 And so anchoring your mind in cognitive activities
52:41 as you get into the cold can be very,
52:43 very helpful for maintaining clarity of mind.
52:46 In fact, one thing that I sometimes recommend
52:48 is that people try and engage
52:50 in some sort of cognitive exercise while in the cold,
52:53 not as a form of distraction,
52:55 but as a way to maintain clarity of thinking
52:57 and to learn how to do that when the body is flooded
52:59 with all these chemicals that make us stressed.
53:02 So for instance,
53:03 you could do math problems and not two plus two equals four,
53:06 not three times three equals nine,
53:08 but things that require a little bit more focus
53:10 and attention working memory and so forth.
53:13 You could also start to have thoughts
53:16 that you deliberately impose a full sentence structure on.
53:20 That's actually quite tough.
53:22 You could try and recall specific bouts of information
53:25 that are challenging.
53:26 This is teaching your mind how to stay online,
53:29 or rather I should say,
53:30 this is you teaching your prefrontal cortex,
53:32 how to stay engaged while you have high levels of stress
53:35 in your body.
53:36 Years ago, I had a friend who works
53:39 in the neuroscience world, research neuroscientist,
53:42 who was obsessed with this very bizarre sport
53:45 that I don't necessarily recommend at all,
53:47 which is the combination of boxing and chess.
53:50 You may have seen this on YouTube
53:51 where people will box around,
53:53 legitimate boxing around, they're sparring all out often.
53:56 And then at the end of the round,
53:58 instead of resting in the corner,
53:59 they actually sit down and play chess,
54:01 and then they go back to boxing and back to chess.
54:03 Again, not a sport that I recommend,
54:05 but the reason he was obsessed with this is because
54:08 he studies the impact of stress on cognitive performance.
54:11 And what that particular very bizarre sport was doing
54:14 was toggling back and forth
54:15 between different states of mind.
54:17 Now it's used both to increase cognitive clarity
54:22 for the fighter when they box,
54:23 because staying calm and clear thinking
54:25 is very important to winning boxing matches.
54:27 Believe it or not, it's not an all outrage.
54:29 It's a very calculated game of mental chess
54:32 and physical chess that's quite high stakes
54:34 as you can imagine.
54:36 It's also used in some circles as a way to teach people
54:40 how to engage in cognitive performance
54:42 when their body is simply filled to a stress.
54:44 So in the boxing chess example,
54:46 the replacement for the cold water is actually the boxing,
54:50 it's the thing that's supposed to induce the stress
54:52 cause getting hit is stressful and the risk
54:54 of getting hit is stressful for most people.
54:57 So again, if you think about deliberate cold exposure
55:00 as a way of just systematically and reliably
55:03 inducing epinephrine and norepinephrine release
55:05 and delivering stress,
55:07 well then this idea of maintaining cognitive clarity
55:09 and actually engaging in cognitive tasks
55:11 while in the ice bath or cold shower
55:14 can actually be very beneficial.
55:15 Even though it might sound a little bit silly,
55:16 you are really training up your ability
55:18 to keep your brain working
55:20 when the reflex is to shut down the parts of your brain
55:24 that are involved in deliberate planning and thinking.
55:26 Now another important aspect of deliberate cold exposure
55:29 that I rarely if ever hear discussed,
55:32 but is vitally important is whether or not
55:35 you move around or not.
55:37 And here's the reason.
55:38 When you get into cold water and you remain there
55:43 for some period of time,
55:44 your body is generating heat and that heat generates
55:47 what's called a thermal layer
55:49 that surrounds your entire body.
55:52 So if you stay still,
55:54 you are actually warmer than if you move around,
55:57 you can try this the next time
55:58 you're doing your deliberate cold exposure.
55:59 If you're submerged up to the neck,
56:01 sit there for about 10, 30 seconds
56:03 and be very, very still of body.
56:05 In fact, this is the way that most people start
56:07 to do deliberate cold exposure.
56:09 They give this very stoic look.
56:10 They don't blink, they look very peaceful.
56:12 Some of them even look tough
56:13 or they make a very even A, emotional face
56:17 and so it looks like they're really tough,
56:20 but they are so still that believe it or not,
56:22 they're not providing the most potent stimulus.
56:26 If they or you were to move around in that water,
56:30 what would happen is you'd break up the thermal layer
56:32 and that you actually experience that as much colder.
56:36 So if you really want to push the resilience aspect,
56:39 or for instance, if you want to use a given temperature
56:42 that you're comfortable in,
56:43 but that you want to increase the stimulus
56:45 and you want to get some more benefit
56:47 for mental resilience training,
56:49 well then get into the cold water,
56:51 move your body around continuously,
56:53 but try and keep your mind still,
56:55 or even do some sort of cognitive task.
56:57 So as you're starting to realize,
56:59 there are a bunch of different variables
57:00 that you can play with while maintaining
57:02 the same temperature of water and in doing so,
57:05 really keep you in the zone of what should
57:08 and absolutely has to be safe for you
57:10 without having to just continually drop the temperature
57:13 from say 60 degrees to 55 to 40 to 33
57:15 because as I mentioned before,
57:16 eventually you're going to bottom out.
57:18 So if you're one of those people that likes to look tough
57:20 or really relaxed while you're in the ice bath
57:22 or cold water immersion,
57:24 just realize that you're actually cheating yourself out
57:26 of part of the stimulus.
57:28 Keep those limbs moving and of course,
57:31 limbs under the water, feet and hands
57:33 is going to be a more potent stimulus
57:35 than hands and feet out for reasons
57:38 that should be obvious based on what we talked about
57:40 in terms of glabrous skin cooling.
57:42 Keep those submerged, move your body,
57:45 maybe move your knees up and down, pedal your feet
57:48 and trust me, it's going to feel a lot colder
57:50 than were you to remain stone still.
57:52 Another very common question
57:53 is how often to do deliberate cold exposure.
57:56 It's tough to make a recommendation on that
57:59 based on any peer reviewed study
58:01 although there are a few in humans that point to a threshold
58:04 of 11 minutes total per week.
58:07 So that's total throughout the week
58:09 divided into two or four sessions
58:11 of two or three minutes or so.
58:13 Now that 11 minute cutoff is not a strict threshold
58:16 and is actually geared more towards increases in metabolism,
58:20 we'll get into this a little bit later in the episode,
58:22 but I think the 11 minute threshold,
58:25 meaning 11 minutes total of deliberate cold exposure
58:28 per week is a pretty good number to use
58:31 if you need a number in order to keep you consistent.
58:34 But as we talked about earlier,
58:36 some of you are going to be in the ice bath
58:39 or cold immersion or cold shower for one minute,
58:42 others of you will be in there for 10 minutes,
58:44 depending on how frequent and how high, if you will,
58:47 those walls of adrenaline are coming.
58:50 So for some of you,
58:52 getting into a cold shower for three minutes total
58:54 for the whole week will represent a tremendous
58:57 achievement in terms of willpower and overcoming
59:00 the resistance to doing that, overcoming those walls.
59:02 For others of you, three minutes is nothing.
59:05 So what do I recommend,
59:06 I recommend that you get at least 11 minutes total per week,
59:11 but at the point where 11 minutes total per week
59:13 is very easy for you,
59:14 where is no longer representing
59:15 a significant mental challenge,
59:17 meaning you're not experiencing many of these walls,
59:19 you're excited to get into the cold shower immersion,
59:21 you're going through it easily, you're cruising basically.
59:24 Then I would say either lower the temperature safely,
59:27 of course, extend the duration safely, of course,
59:31 or increase the frequency so that you're doing this
59:33 perhaps every day or maybe five days a week
59:36 or three days a week.
59:37 I personally get tremendous benefit
59:39 from doing deliberate cold exposure three times a week
59:42 and using the walls method that I described earlier
59:45 as my gauge for how long to stay in
59:47 and typically that means that I'm staying in for anywhere
59:50 from two minutes to six minutes per session
59:53 and that averages out to about
59:56 11 to 15 minutes total per week.
59:59 So again, I do not think that you need to be super strict
1:00:02 about these guidelines.
1:00:04 It's most important when embracing a protocol A,
1:00:07 that you do it safely,
1:00:08 but secondarily that you do it consistently.
1:00:11 So find what you can do consistently
1:00:13 and then vary the parameters
1:00:14 that will allow you to continue to do
1:00:16 deliberate cold exposure consistently,
1:00:18 regardless of whether or not you have access to a shower
1:00:20 or cold immersion, et cetera.
1:00:22 So we've been talking about mental effects
1:00:24 and the use of deliberate cold exposure
1:00:26 for sake of building resilience,
1:00:28 which I do believe can be tremendously powerful.
1:00:30 Look, it's no coincidence that the screening
1:00:35 and the training for Navy Seals
1:00:37 involves a lot of exposure to cold water.
1:00:40 One could argue that it is deliberate
1:00:41 because they elect to go to buds,
1:00:43 but when they get into the cold water at buds
1:00:46 is dictated by the instructors and the reason
1:00:49 they use cold water exposure as the stressor
1:00:52 is that it does offer considerable leeway
1:00:55 in terms of duration and temperature,
1:00:58 in terms of how you can use it as a stressor
1:01:00 whereas things like heat don't offer much variable space
1:01:04 as we say.
1:01:05 There isn't a lot of room beyond which you start injuring
1:01:08 or even killing people by using heat.
1:01:10 So there are a lot of forms of stressors out there,
1:01:12 but cold is one that we can titrate,
1:01:14 that we can adjust in ways that can allow us
1:01:16 to continually build up and or maintain mental toughness.
1:01:21 Now, deliberate cold exposure also has many effects
1:01:25 on chemicals other than norepinephrine and epinephrine,
1:01:28 most notably the neuromodulator dopamine,
1:01:32 which is involved in elevating our mood,
1:01:34 making us feel energized and enhancing our ability to focus.
1:01:38 And that has a lot to do with how dopamine engages us
1:01:41 in motivated states,
1:01:43 tends to narrow our thinking in our behavior
1:01:45 into a particular trench of goal-directed behavior.
1:01:48 If you want to learn more about dopamine,
1:01:50 you can learn a lot about dopamine
1:01:52 in our episode about dopamine, it's at hubermanlab.com.
1:01:55 You can find it, it's a two and a half hour plus
1:01:58 kind of deep dive into all things dopamine,
1:02:00 focus, motivation, et cetera.
1:02:04 Deliberate cold exposure has a very powerful effect
1:02:08 on the release of dopamine in our brain and body.
1:02:11 And this is one of the main reasons why people continue
1:02:14 to do deliberate cold exposure.
1:02:17 Basically it makes us feel good
1:02:19 and it continues to make us feel good
1:02:21 even after we get out of the cold environment.
1:02:23 In fact, some people would say
1:02:25 they don't feel good in the cold environment,
1:02:27 it's all stress for them,
1:02:27 but afterwards they feel great.
1:02:30 One of our previous guests, Dr. Anna Lembke,
1:02:32 who's a medical doctor at Stanford University
1:02:34 School of Medicine, she's a close colleague of mine,
1:02:37 described the use dopamine in her book, Dopamine Nation,
1:02:40 an incredible book about addiction and dopamine
1:02:42 I should mention.
1:02:43 And the use of dopamine elicited by cold water exposure
1:02:49 by one of her patients.
1:02:50 What I'm referring to is the fact that one of her patients
1:02:53 helped themselves get and stay sober off drugs
1:02:57 by using deliberate cold exposure to increase dopamine.
1:03:01 So a healthier form of dopamine release
1:03:03 than they were engaged in prior to getting sober.
1:03:07 Now, the basis for dopamine release
1:03:09 in response to cold exposure
1:03:11 is that the catecholamines, norepinephrine,
1:03:13 epinephrine and dopamine tend to be co-released
1:03:16 by the same sorts of stimuli,
1:03:18 but most stressors and in particular things
1:03:21 that evoke stress or our feelings of stress internally
1:03:24 that we don't like do not increase dopamine.
1:03:28 They only increase norepinephrine and epinephrine,
1:03:30 but deliberate cold exposure
1:03:32 seems to cause a dramatic increase in dopamine.
1:03:36 And this has actually been substantiated
1:03:37 in a really beautiful study entitled
1:03:40 human physiological responses
1:03:41 to immersion into water of different temperatures.
1:03:44 The first author is Sramek.
1:03:46 I'm almost certainly pronouncing that poorly
1:03:50 and if not incorrectly, S-R-A-M-E-K.
1:03:54 This was published in the European Journal
1:03:55 of Applied Physiology in the year 2000,
1:03:58 really a beautiful study, I love this study.
1:04:00 They took people and they had them sit in chairs
1:04:03 underwater but their head was out and so they were immersed
1:04:06 up to the neck in either of three different temperatures.
1:04:12 32 degrees Celsius, which is 89 degrees Fahrenheit,
1:04:16 20 degrees Celsius, which is 68 degrees Fahrenheit,
1:04:19 or 14 degrees Celsius, which is 57.2 degrees Fahrenheit.
1:04:23 So not super cold, but then what they did
1:04:27 is they measured people's core body temperature throughout.
1:04:30 They measured their metabolism
1:04:31 and they looked at serum levels
1:04:33 of things like norepinephrine, epinephrine, dopamine,
1:04:36 and cortisol, serum meaning within the blood.
1:04:39 So a really nice and quite thorough study.
1:04:43 There were not a huge number of subjects in the study,
1:04:46 but nonetheless, it was a very thorough study
1:04:48 in terms of the number of variables that they explored.
1:04:52 So I just want to briefly highlight
1:04:54 some of what they saw or what they observed in this study.
1:04:57 First of all, all the groups were in the water
1:05:01 of a given temperature for one hour,
1:05:04 which is much longer than most
1:05:06 of the deliberate cold exposure protocols
1:05:08 that anyone is using at home.
1:05:09 I mean, maybe you're taking one hour long cold showers,
1:05:12 maybe you're getting into the ice bath for an hour
1:05:14 although I don't recommend that.
1:05:15 I think you'd probably get badly hypothermic or maybe
1:05:18 you're getting into a cold water immersion
1:05:21 for some period of time,
1:05:22 but I have a hard time imagining that it would be an hour
1:05:25 and I don't suggest that if it's very cold.
1:05:27 So this study focused on actually somewhat
1:05:29 moderately cool temperatures,
1:05:31 not what I think most people would consider
1:05:33 very, very cold temperatures,
1:05:35 but extended the duration for quite a while.
1:05:38 So again, 32 degree Celsius,
1:05:41 20 degree Celsius or 14 degree Celsius.
1:05:44 Here's what they observed.
1:05:45 The group that was immersed up to the neck
1:05:48 in 32 degrees Celsius, that is 89 degrees Fahrenheit,
1:05:51 water did not experience a shift in metabolism
1:05:55 nor a significant increase in dopamine,
1:05:58 norepinephrine or these other catecholamines.
1:06:01 The group that was in 20 degree Celsius,
1:06:03 meaning 68 degree Fahrenheit,
1:06:06 water for an hour experienced a 93% increase
1:06:10 in metabolic rate, which is remarkable
1:06:13 given that the water wasn't that cold
1:06:15 and yet an hour is a pretty long time to be in there.
1:06:18 And again, it speaks to the dramatic effect
1:06:21 of heat transfer that water has, which I mentioned earlier,
1:06:24 as opposed to being out in the air at 68 degrees,
1:06:27 it would certainly not cause that increase
1:06:29 in metabolic rate.
1:06:31 The group that was at 14 degrees Celsius,
1:06:35 meaning 57.2 degrees Fahrenheit,
1:06:37 water for an hour experienced a 350% increase in metabolism.
1:06:42 So huge increases in metabolism.
1:06:45 Now the most interesting data to me,
1:06:48 at least in terms of mental effects
1:06:50 of deliberate cold exposure,
1:06:52 were that the plasma or serum levels of norepinephrine
1:06:58 in the blood increased 530%.
1:07:01 These are huge increases in norepinephrine
1:07:04 so it suggests that this is a stressful stimulus
1:07:07 at least neurochemically speaking, stressful,
1:07:10 despite the fact that it's not super super cold,
1:07:12 although 57.2 degrees Fahrenheit,
1:07:14 14 degrees Celsius it's not a warm environment,
1:07:20 but it's not a ultra, ultra cold environment,
1:07:22 but an hour is a very long time to be in there.
1:07:26 The subjects also experienced a 250% increase
1:07:31 in dopamine concentrations,
1:07:34 which while not 530% as it was with norepinephrine
1:07:38 is still a very large increase
1:07:40 in baseline levels of dopamine.
1:07:42 And what was interesting is that those increases in dopamine
1:07:45 persisted for a very long period of time afterwards,
1:07:49 even out to two hours.
1:07:51 And they stopped the study after 120 minutes
1:07:54 of getting out of the cold, but nonetheless,
1:07:58 these increases in norepinephrine are huge and long lasting
1:08:01 and these increases in dopamine
1:08:03 are very large and long lasting.
1:08:05 And I do believe that these documented effects in humans
1:08:08 explain much of the enhancement of attention and of feelings
1:08:13 of wellbeing and mood that people typically experience
1:08:16 after doing deliberate cold exposure.
1:08:19 And the reason I say that is that
1:08:21 if you were to go back to the episode
1:08:23 that I did on dopamine,
1:08:24 or you were to go back to the episode
1:08:26 that I did with Dr. Anna Lembke on addiction and dopamine,
1:08:29 what you would find is that increases in dopamine
1:08:32 of the sort evoked by deliberate cold exposure
1:08:35 are actually very similar to the kinds of increases
1:08:38 in dopamine that are elicited by things like nicotine
1:08:41 or from other behaviors
1:08:43 that are known to be addictive and bad for us
1:08:45 because they lead to other effects on the brain
1:08:48 and body that we simply don't want.
1:08:50 And yet deliberate cold exposure provided is done safely
1:08:53 can create similar if not greater increases in dopamine
1:08:58 that are not just fleeting, that don't just occur during,
1:09:01 say the consumption of some deleterious drug or activity,
1:09:05 but that are very long lasting and that can be leveraged
1:09:07 toward activities other than deliberate cold exposure.
1:09:11 So I want to emphasize this.
1:09:13 I'm not suggesting
1:09:14 that people do deliberate cold exposure for an hour a day.
1:09:16 And unfortunately there are not many studies yet
1:09:20 exploring how shorter colder temperature
1:09:23 environment exposure, say one minute or three minutes
1:09:27 or six minutes at 55 degrees or at 50 degrees,
1:09:32 whether or not that leads to similar,
1:09:34 greater or reduced levels of dopamine in the brain and body.
1:09:38 And yet almost everybody who does deliberate cold exposure
1:09:42 will say yeah, it was stressful.
1:09:44 I didn't enjoy it, or I eventually grew to like it,
1:09:47 but that I always feel better afterwards
1:09:49 and then that feeling last a very long period of time.
1:09:52 And I think it's almost certain
1:09:54 that those experiences that people report
1:09:56 relate to these increases in dopamine
1:09:58 and in concert with the increases in norepinephrine
1:10:02 also explain the other effect that's commonly reported,
1:10:04 which is an enhancement in mental acuity
1:10:06 and the ability to focus.
1:10:09 Now, here we can extrapolate to the study
1:10:11 that I discussed at the early part of the episode,
1:10:14 where I was talking about the use of
1:10:16 short 15 minute exercise,
1:10:18 kind of moderate intensity exercise
1:10:19 and how that was shown to increase levels of energy
1:10:22 and mental acuity
1:10:23 in these working memory, visual attention tasks.
1:10:26 And there, again, we have to assume somewhat
1:10:29 because they weren't doing neurochemical measurements,
1:10:31 but we can reasonably assume that those improvements
1:10:35 in cognitive performance were due
1:10:37 at least in part to the increase in catecholamines
1:10:39 known to a company, moderate intensity zone two cardio.
1:10:43 So what you're starting to see here is a theme.
1:10:45 The theme is that virtually any stimulus
1:10:49 that delivers more norepinephrine,
1:10:51 epinephrine and dopamine to our system
1:10:53 will sharpen our mental acuity and elevate our mood
1:10:55 and will do so for some period of time.
1:10:58 Deliberate cold exposure, it turns out,
1:11:00 is a very potent way to increase these catecholamines,
1:11:03 this category of chemicals and thereby to improve mood,
1:11:06 mental acuity and levels of alertness.
1:11:09 And as we'll next see, it not only has that effect,
1:11:13 which can be very beneficial for many people
1:11:15 in a bunch of different circumstances,
1:11:16 but it also has the positive effects that many people seek
1:11:21 in terms of metabolism, in lowering inflammation in the body
1:11:24 and other physiological effects as well.
1:11:26 And forgive me,
1:11:27 I was almost ready to move on to effects
1:11:30 of deliberate cold exposure on metabolism
1:11:32 and inflammation and so forth,
1:11:34 but I neglected to point out one of the other
1:11:36 very interesting aspects of the study
1:11:39 showing deliberate cold exposure
1:11:41 can increase in norepinephrine and dopamine,
1:11:44 which is that they observed no significant increases
1:11:48 in the stress hormone cortisol
1:11:50 and that is both surprising, interesting, and important
1:11:53 because what it means is that the quality of stress
1:11:57 that deliberate cold exposure is creating in the body
1:12:00 is likely to be one of what we call use stress.
1:12:04 Hans Selye, the great physiologist,
1:12:07 won a Nobel Prize for distinguishing between distress,
1:12:10 which is stress in the brain and body
1:12:13 that causes the release of things like cortisol
1:12:16 along with the other catecholamines,
1:12:18 and that we experience as negative happening to us
1:12:20 and can lead to negative health outcomes.
1:12:22 And he distinguished that from eustress,
1:12:25 which was stress that we now understand
1:12:27 is associated with increases in things like norepinephrine
1:12:30 and dopamine, but no increases or minimal increases
1:12:34 in cortisol, and that can lead to positive health outcomes.
1:12:37 So it appears that deliberate cold exposure can create
1:12:41 what we call or what Hans Selye called eustress.
1:12:44 In other words, it can create a condition in the brain
1:12:46 and body in which we are stressing ourselves,
1:12:49 we are training up resilience,
1:12:51 and yet we are creating a neurochemical milieu
1:12:54 that actually has many health benefits.
1:12:56 Now I'd like to shift our attention
1:12:57 to the effects of deliberate cold exposure on metabolism.
1:13:00 And I'd like to start by detailing a study
1:13:03 that was performed on humans
1:13:05 and published just at the end of last year.
1:13:07 The title of the study is altered
1:13:09 brown fat thermoregulation,
1:13:10 and enhanced cold induced thermogenesis
1:13:13 in young, healthy winter swimming men.
1:13:16 And I should point out that while the study
1:13:18 was only performed on male subjects,
1:13:20 there's no reason to think that the effects
1:13:22 that they discovered would only pertain to men.
1:13:25 I would hope that they would also do a study on women
1:13:27 at some point in the future,
1:13:28 but the effects that they describe
1:13:30 are very basic core physiological processes.
1:13:34 What they did is they looked at at deliberate cold exposure
1:13:37 in this group of young men,
1:13:38 and they used that 11 minute threshold per week.
1:13:43 So in other words, they had them get into cold water
1:13:46 for approximately 11 minutes per week.
1:13:50 And again, that's 11 minutes total per week.
1:13:53 They divided that into two sessions
1:13:56 although in speaking with the first author of this study,
1:13:58 Dr. Susanna Søberg,
1:13:59 I learned that it probably is not important
1:14:02 that it be two sessions,
1:14:03 it could be three or even four sessions,
1:14:06 as long as it reaches that 11 minute threshold.
1:14:09 What they discovered was
1:14:11 that by going into these cold environments,
1:14:14 in this case cold water immersion up to the neck,
1:14:18 for 11 minutes total per week,
1:14:21 that these men experienced increases
1:14:23 in so-called brown fat thermogenesis,
1:14:26 I'll talk more about what that is in a moment,
1:14:28 and increases in core body temperature
1:14:30 that translate to increases in core body metabolism.
1:14:34 Now, the overall increases in core body metabolism
1:14:37 that they experienced were not extremely large.
1:14:42 They were statistically significant,
1:14:44 but they weren't extremely large.
1:14:45 However, the changes in brown fat stores
1:14:50 are perhaps what's most interesting about this study
1:14:53 and I'll tell you why.
1:14:54 The metabolic increases of deliberate cold exposure
1:14:57 are both acute meaning happening in the short term.
1:15:00 When you get into the cold and immediately after,
1:15:02 one does experience an increase in core metabolism,
1:15:06 you burn some calories, in other words,
1:15:09 and while those might not be very significant increases,
1:15:14 or I should say they can be statistically significant,
1:15:17 but they are not enormously large numbers
1:15:20 of calories burned,
1:15:22 the longer lasting effects of deliberate cold exposure
1:15:27 on metabolism seem to take place by changes that occur
1:15:30 in the types of fat that we store in our body
1:15:34 and the way that that fat impacts our metabolism
1:15:36 at other times throughout the 24 hour cycle.
1:15:41 This actually has a somewhat anecdotal basis,
1:15:44 in particular in Scandinavia.
1:15:46 I don't speak Swedish nor I speak Danish,
1:15:49 nor do I speak Norwegian,
1:15:51 but I do have Danish relatives
1:15:53 and they were able to help me decipher
1:15:55 a common Swedish saying,
1:15:58 which essentially translates to the fact that
1:16:01 in preparation for the summer, they say,
1:16:05 one should expose themselves to warm environments
1:16:09 so that one is comfortable in warm environments
1:16:12 in the summer.
1:16:13 That's one half of this traditional Swedish
1:16:16 and also Danish saying.
1:16:17 The other half of this traditional Danish-Swedish saying
1:16:22 is that in preparation for winter,
1:16:24 in order to not feel too cold in cold environments,
1:16:28 one should prepare for those in the fall
1:16:31 by not wearing a jacket and exposing one's self
1:16:34 to cold environments.
1:16:36 Now, of course, this is just anecdotal cultural lore,
1:16:40 but it actually has a physiological basis,
1:16:42 which is by exposing oneself to cold environments
1:16:46 on a repeated basis in anticipation of exposure
1:16:50 to more extreme cold environments,
1:16:52 one can feel more comfortable
1:16:54 in those extreme cold environments.
1:16:56 And that's exactly what they observed
1:16:58 in this study by Søberg et al.
1:17:00 The men felt more comfortable in extreme cold
1:17:03 if they had trained through deliberate cold exposure,
1:17:07 which might not seem surprising at all,
1:17:09 but based on what we talked about earlier,
1:17:12 whereby deliberate cold exposure evokes this discomfort
1:17:16 and this experience of norepinephrine release,
1:17:18 at least in the short term, then you would say, well,
1:17:21 shouldn't that deliberate cold exposure also
1:17:24 make them feel uncomfortable
1:17:25 like they really want to get out?
1:17:26 Well, that is true
1:17:28 in the beginning of a deliberate cold exposure protocol,
1:17:31 meaning in the first week or in the second week
1:17:33 or the third week, but what one finds
1:17:35 and what you will find if you do
1:17:36 deliberate cold exposure consistently is that you will then
1:17:41 become more comfortable at cold temperatures
1:17:44 away from the deliberate cold exposure.
1:17:46 So whereas you might have previously been the person
1:17:49 who is always cold in the room with air conditioning,
1:17:51 or always seeking a sweater, always wanting to bundle up,
1:17:54 you will be more comfortable in those cold environments.
1:17:56 And the reason for that is well substantiated
1:18:00 from this study and from animal studies
1:18:03 whereby deliberate cold exposure
1:18:06 converts one particular kind of fat cell,
1:18:09 the white fat cell,
1:18:11 which is a very low metabolic output cell.
1:18:15 It's basically a storage site for energy
1:18:17 in the body fat cells to a different type of fat cell,
1:18:21 which is the beige fat cell called beige
1:18:24 because it's actually beige or slightly brown
1:18:27 under the microscope, or even to brown fat cells,
1:18:30 which are very dark under the microscope and dark
1:18:32 because they contain mitochondria
1:18:35 and are very metabolically and thermogenetically active.
1:18:40 In other words, white fat doesn't burn many calories.
1:18:43 It's basically a storage site.
1:18:45 It's a bank account for energy.
1:18:47 It's filled with lipids,
1:18:50 and those lipids can be used if the body needs energy
1:18:53 and if it goes into a caloric deficit.
1:18:55 Beige fat and brown fat acts as sort of a furnace
1:18:59 or the sort of fat that you would find in a kindle,
1:19:03 a fuel that can increase core body temperature.
1:19:06 So beige fat and brown fat is very good
1:19:09 at raising our metabolism and helps burn white fat.
1:19:13 Now of course,
1:19:14 it does that only in the context of a caloric deficit,
1:19:18 but it can actually help create that caloric deficit.
1:19:22 Having more beige fat and brown fat
1:19:24 can increase your overall core metabolism, in other words,
1:19:27 the number of calories that you burn per day,
1:19:30 and therefore the number of calories
1:19:31 that you need to either maintain or to lose weight.
1:19:35 The simple translation of this is that getting into
1:19:39 cold water for a total of 11 minutes, perhaps more,
1:19:43 but at least 11 minutes per week
1:19:45 divided into two or four sessions
1:19:47 can increase your core metabolism in part
1:19:50 by increasing your beige and brown fat stores.
1:19:54 And we know how that works at least in animal models
1:19:57 and there's now reason to suspect
1:19:59 that the exact same mechanisms are occurring in humans.
1:20:02 The primary way in which deliberate cold exposure converts
1:20:05 white fat cells into these more metabolically
1:20:08 thermogenetically active metabolism increasing
1:20:11 beige and brown fat cells is because norepinephrine
1:20:18 released when we get into the cold binds to receptors
1:20:22 on the surface of white fat cells and activates
1:20:25 downstream pathways such as UCP1,
1:20:30 so this is an uncoupling protein one,
1:20:32 that acts on the mitochondrial metabolism of cells
1:20:35 and increases the mitochondrial output of those cells
1:20:39 and the mitochondrial density of those cells.
1:20:41 In other words,
1:20:42 it takes a cell that has a kind of a weak engine
1:20:46 or no engine for generating energy.
1:20:48 Although every cell has some mitochondria,
1:20:51 it takes cells that have very few mitochondria
1:20:53 and increases the engine size.
1:20:56 It kind of stokes the furnace of those particular cells
1:21:00 and actually can change gene expression in those cells.
1:21:03 So that's what's really interesting.
1:21:04 Deliberate cold exposure causes increases in norepinephrine.
1:21:08 which bind to receptors on the surfaces of white fat cells,
1:21:12 which triggers the release of things like UCP1.
1:21:16 It also causes the release of things like P-part gamma,
1:21:19 and co-factor PGC1.
1:21:22 I'm going to refer you to a review
1:21:23 if you want to learn more about these.
1:21:25 For those of you that don't want to learn more,
1:21:26 all you need to know is that the downstream of all that
1:21:29 are increases in mitochondria and metabolism
1:21:32 and actual genetic changes in the white fat cells
1:21:36 that convert them into beige and brown fat cells.
1:21:39 This is especially important for adults
1:21:41 because babies and young children actually don't have
1:21:46 the ability to shiver
1:21:47 or they have a less robust capacity to shiver.
1:21:51 Very small babies really can't shiver
1:21:53 so they have a lot of brown fat in order to keep them warm.
1:21:57 Young children eventually develop the ability to shiver
1:22:01 and maintain these brown fat stores,
1:22:02 mainly around the clavicles, the heart, the upper spine,
1:22:06 and in the upper back.
1:22:07 And it's no coincidence that kids can often run around
1:22:10 with a minimal of clothing and be comfortable
1:22:12 in environments that adults would be cold in.
1:22:16 As life goes on, we tend to lose beige and brown fat,
1:22:21 but this mechanism that I'm referring to
1:22:23 points to the plasticity of white fat,
1:22:25 meaning the ability for white fat to actually convert
1:22:27 its identity into this metabolically thermogenetically
1:22:31 enhancing form of beige and brown fat.
1:22:33 So deliberate cold exposure is a terrific way
1:22:36 to increase your core metabolism
1:22:38 and oftentimes critics will say, well,
1:22:40 the increase in metabolism isn't that significant
1:22:42 although I do want to point out again,
1:22:44 the 93% and 350% increases in metabolism
1:22:49 from that previous study.
1:22:51 But critics then will say, well,
1:22:53 that doesn't really translate to that big of a caloric burn
1:22:59 during the deliberate cold exposure.
1:23:00 But to that, you should say, ah,
1:23:02 but that's only limiting your optics
1:23:04 to just a portion of the effects
1:23:06 of deliberate cold exposure because deliberate cold exposure
1:23:09 can also convert white fat to beige fat and brown fat
1:23:12 and lead to these more lasting increases in metabolism.
1:23:17 So for any of you interested in increasing your metabolism
1:23:19 and or being comfortable in cold environments
1:23:22 and or being comfortable in terms of
1:23:25 being able to combat stress mentally,
1:23:27 deliberate cold exposure, I do believe is a powerful tool.
1:23:31 And there is simply no reason why you couldn't and shouldn't
1:23:34 use the same protocols that I described earlier
1:23:36 for building resilience to increase metabolism.
1:23:39 Provided you're hitting that 11 minute per week threshold,
1:23:43 you ought to be stimulating both mechanism increases
1:23:47 in resilience and increases in core metabolism.
1:23:51 As I mentioned earlier,
1:23:52 most of the detailed studies on the conversion of white fat
1:23:55 to beige fat and brown fat through the use of cold
1:23:57 have been done in animal models,
1:23:59 but the human data are starting to emerge.
1:24:01 And if you'd like to do the deep dive into these mechanisms,
1:24:04 things like UCP1, P-part gamma, et cetera,
1:24:07 there's a beautiful review that was published recently
1:24:09 in the journal cell,
1:24:10 which is one of the three apex journals,
1:24:12 nature, science, cell.
1:24:13 And the title of that paper is adipose tissue plasticity
1:24:17 in health and disease.
1:24:18 I love this review.
1:24:19 It has beautiful diagrams detailing all of the pathways
1:24:22 from cold to norepinephrine through UCP1
1:24:26 downstream of things like cyclic AMP.
1:24:28 If none of those names mean anything to you,
1:24:30 don't worry about it.
1:24:31 You certainly don't need to know these mechanisms
1:24:32 to benefit from deliberate cold exposure protocols.
1:24:35 If those names do mean something to you,
1:24:38 or you are interested in exploring the downstream effects
1:24:41 of deliberate cold exposure and something else
1:24:43 that's really nice that's covered in this paper
1:24:45 is how deliberate cold exposure interacts
1:24:48 with fasted states and fed states.
1:24:51 I think you'll also find this review very interesting.
1:24:54 I don't want to go too deeply into fasted states
1:24:56 and fed states right now,
1:24:58 suffice to say that when we are fasted,
1:25:00 meaning when we have an eaten for some period of time,
1:25:03 our baseline levels of norepinephrine
1:25:06 and epinephrine are already elevated.
1:25:09 And so cold exposure at those times
1:25:11 ought to have an even greater effect on metabolism
1:25:14 and resilience and so on.
1:25:16 So for you fasters or your intermittent fasters out there,
1:25:20 if you really want to get fancy,
1:25:21 you can do your deliberate cold exposure
1:25:24 when you are fasted.
1:25:25 I certainly wouldn't recommend doing it
1:25:27 with a very full stomach in any case.
1:25:29 And as I mentioned before on this podcast,
1:25:33 intermittent fasting is, but one way,
1:25:36 and certainly there are other ways
1:25:37 to limit total caloric intake for sake of maintaining
1:25:40 or losing weight if that's your goal.
1:25:43 I know many people are using and benefit
1:25:45 from intermittent fasting, however,
1:25:47 and so it certainly can be combined
1:25:49 with deliberate cold exposures in order
1:25:51 to get even greater increases
1:25:53 in norepinephrine and epinephrine.
1:25:54 So for those of you that are primarily interested
1:25:57 in using deliberate cold exposure
1:25:58 to increase dopamine levels in your brain and body,
1:26:02 you can also do a combined protocol
1:26:05 whereby you ingest caffeine 60 to 120 minutes
1:26:09 before the deliberate cold exposure.
1:26:11 This is based on a study that I've talked about before
1:26:14 entitled caffeine increases striatal dopamine D-2,
1:26:18 D-3 receptor availability in the human brain.
1:26:20 And as the title suggests, this study was done on humans,
1:26:23 looking at the density and or efficacy
1:26:27 of these dopamine receptors
1:26:29 in an area of the brain called the striatum,
1:26:30 which is involved in planning in action
1:26:32 and also suppressing planning in action.
1:26:34 It's involved very closely with whether or not
1:26:37 we can engage in behavior and withhold behavior,
1:26:41 the so-called go and no go ways in the brain.
1:26:44 Dopamine plays a critical role in that
1:26:45 and many other things as well as you now know.
1:26:49 So why would you want to ingest caffeine 60 to 120 minutes
1:26:52 before deliberate cold exposure?
1:26:55 Well, as I talked about earlier,
1:26:57 dopamine can increase quite substantially
1:27:00 in response to deliberate cold exposure,
1:27:02 but dopamine on its own doesn't do anything,
1:27:04 it has to bind to receptors
1:27:06 and this paper shows quite definitively
1:27:08 that ingesting caffeine in this case,
1:27:10 it was 300 milligram dose of caffeine,
1:27:12 which is about the dose of caffeine
1:27:14 in two or three cups of coffee,
1:27:15 it depends on the strength of the coffee, of course,
1:27:17 but it's not an outrageous amount of caffeine,
1:27:21 that increases the density and or efficacy
1:27:23 of these receptors,
1:27:24 which you would allow that dopamine
1:27:25 to have its greatest effect.
1:27:28 And for those of you that want to get really, really fancy,
1:27:31 I suppose you could do this fasted
1:27:32 so you get the further increase in norepinephrine,
1:27:35 then you get the dopamine increase from the cold exposure,
1:27:37 the binding of the dopamine.
1:27:38 Although I do want to point out that at some point,
1:27:42 you start layering together enough protocols
1:27:44 that you would to be spending your entire day
1:27:45 trying to get this dopamine pulse
1:27:47 and I would hope that you would have other activities
1:27:49 that you would engage in,
1:27:50 but if you're getting up in the morning and you're fasted
1:27:53 because you haven't eaten all night
1:27:55 and you have a cup of coffee, and then 60 minutes later,
1:27:57 you take your cold shower or two hours later,
1:28:00 you do your cold immersion or your cold shower,
1:28:02 you would be layering together
1:28:04 these different mechanisms of dopamine receptors,
1:28:06 epinephrine and so forth in a way that at least to me,
1:28:09 doesn't seem incompatible with having some other life
1:28:12 like going to school and having relationships, et cetera.
1:28:15 And this increase in dopamine,
1:28:16 particularly in the striatum is not a trivial one.
1:28:20 I do want to point out as the authors do
1:28:23 that preclinical studies have shown
1:28:24 that increases in striatal dopamine
1:28:27 induced by things like modafinil,
1:28:29 which is used to treat ADHD and treat narcolepsy,
1:28:33 is necessary for their wake promoting actions.
1:28:36 What this really says is that just having elevated levels
1:28:38 of dopamine from a drug or from an ice bath,
1:28:41 or what have you is not sufficient
1:28:43 to get the effects of dopamine,
1:28:44 you really need the receptors to be available
1:28:47 and you need those receptors to be available
1:28:49 in the appropriate density
1:28:50 and you need those receptors to be available
1:28:52 in the appropriate density in the striatum in particular.
1:28:55 So I think there are a number of reasons why
1:28:57 if it's compatible with the other aspects of your health,
1:29:00 cause of course always you have to consider this
1:29:02 on a background of cardiovascular health
1:29:03 and blood pressure, et cetera,
1:29:05 that ingesting a cup or two of coffee
1:29:07 an hour before your ice bath may be fasted as well
1:29:11 could be quite beneficial for increasing dopamine
1:29:13 over quite extended periods of time.
1:29:15 A couple of key points that you'll want to pay attention to
1:29:18 in thinking about deliberate cold exposure and metabolism.
1:29:21 In the Søberg study,
1:29:22 they also explored the use of sauna and how to use sauna,
1:29:27 meaning deliberate heat in conjunction with cold.
1:29:30 We are going to do an entire episode about the use of heat
1:29:33 for health and performance.
1:29:34 So that is not the focus now, however,
1:29:38 it does raise an important point
1:29:40 that we do need to address at this moment,
1:29:42 which is if you are using sauna
1:29:45 or if you are taking warm showers
1:29:47 or if you are simply using deliberate cold exposure
1:29:50 of any kind,
1:29:51 should you get into the heat afterward
1:29:54 or before or not at all?
1:29:55 And this is where we can point to the so-called
1:29:59 Søberg principle, at least I call it the Søberg principle,
1:30:02 the Søberg principle named after first author of this study,
1:30:05 I referred to earlier, Dr. Susanna Søberg.
1:30:09 In science, it is appropriate to take a key piece of data
1:30:12 and call it a principle
1:30:14 if in fact it translates to something larger,
1:30:16 which I believe it does.
1:30:18 It is generally not appropriate for people
1:30:20 to name a principle after themselves
1:30:22 although there are a few scientists that have done that.
1:30:25 So I have named it the Søberg principle,
1:30:27 but I did that to give it appropriate credit
1:30:30 to Dr. Susanna Søberg,
1:30:32 who discovered that and pointed out quite appropriately,
1:30:36 that to achieve the greatest increases in metabolism
1:30:40 through deliberate cold exposure,
1:30:42 you want to force yourself to reheat on your own
1:30:47 after the deliberate cold exposure,
1:30:49 meaning you wouldn't want to go from the cold shower
1:30:52 to a hot shower or from the cold shower to a sauna.
1:30:54 Rather if you were going to start with a hot shower
1:30:57 or you're going to start with a sauna
1:30:58 that you would end with the cold,
1:31:01 and then you would reheat naturally.
1:31:03 Now I personally take a cold shower a few times a week
1:31:06 or do cold immersion
1:31:08 and because I'm not specifically focused
1:31:10 on increasing metabolism, although I probably should be,
1:31:13 that's not what I'm using it for now,
1:31:16 I will take a hot shower afterwards and in doing so,
1:31:18 I'm short circuiting
1:31:19 some of the further metabolic increases that I would achieve
1:31:22 were I to just end with the cold.
1:31:25 So the Søberg principle is
1:31:27 if you want to increase your metabolism, end with cold,
1:31:31 and we can take this a step further and say
1:31:34 that if you want to use deliberate cold exposure
1:31:37 to increase metabolism, that you should make sure
1:31:40 that you get to the point where you shiver.
1:31:43 And the reason in for this is that there are
1:31:45 a series of studies, but in particular,
1:31:47 one study published in the journal Nature,
1:31:49 excellent journal in the year 2018,
1:31:51 showing that deliberate cold exposure that evokes shivering
1:31:57 from the muscles causes the release of a molecule
1:32:00 called succinate from the muscles
1:32:03 and that succinate plays
1:32:05 a key role in activating brown fat thermogenesis,
1:32:08 which you now have heard about and understand
1:32:10 as critical to the increases in metabolism
1:32:13 caused by deliberate cold exposure.
1:32:15 So what this means is if you want to
1:32:17 increase your metabolism, end on cold,
1:32:19 that's a Søberg principle and as best you can,
1:32:22 try and get to the point where you are shivering
1:32:24 either when you are in the cold exposure
1:32:27 or immediately afterwards.
1:32:29 Now one efficient way to do this is to, for instance,
1:32:32 you could get into the cold shower for a minute
1:32:36 or two minutes or three minutes, uncomfortably cold,
1:32:38 but safe to stay in.
1:32:40 Remember that's our general rule of thumb.
1:32:42 Then turn off the water and stand there,
1:32:45 make sure that you're not holding yourself
1:32:47 close to your body,
1:32:48 you're not hugging yourself to try and keep yourself warm,
1:32:50 but rather your limbs are extended at your sides.
1:32:53 And then if that fails to induce shiver
1:32:56 than to turn on the cold water again,
1:32:59 and then turn it off again,
1:33:00 so alternating perhaps a minute to three minutes
1:33:03 of cold exposure followed by a minute to three minutes
1:33:05 of drying out in air
1:33:07 and going back into the cold exposure, et cetera.
1:33:10 I can tell you this from experience,
1:33:12 this is a pretty brutal protocol.
1:33:15 If you have never tried getting into an ice bath
1:33:18 or cold water immersion or shower for one minute
1:33:21 and then getting out and trying to stand there
1:33:23 with your arms extended in cool or cold air for one minute,
1:33:27 and then getting back into the cold shower
1:33:28 or water immersion, you are in for an experience because
1:33:33 even for those of you that are pretty shiver resistant,
1:33:36 you'll find that it is much, much harder
1:33:38 to get out of that cold water and stand there arms extended
1:33:41 and drying off by evaporation,
1:33:43 which further draws heat from the body
1:33:46 than it is to wrap yourself in a towel,
1:33:48 get in a warm shower or a sauna.
1:33:50 So there's certainly no requirement to end on cold.
1:33:54 There's certainly no requirement to induce shiver,
1:33:57 but if your primary goal
1:33:59 is to induce increases in metabolism,
1:34:02 both in the short term and in the long term,
1:34:05 following the cold exposure,
1:34:06 well then you'll want to end on cold
1:34:08 and you'll want to find a way to shiver
1:34:10 provided that the level of cold
1:34:12 that you're exposing yourself to
1:34:14 is still safe for you overall.
1:34:15 So up until now,
1:34:16 I've been talking about deliberate cold exposure
1:34:18 as a potent stimulus for the release of norepinephrine
1:34:21 in the brain and body and indeed it is,
1:34:24 but the way I've been describing it has been in the context
1:34:27 of circulating plasma levels of norepinephrine,
1:34:31 meaning circulating within the blood.
1:34:34 What I haven't mentioned,
1:34:35 but is absolutely true is that the fat cells themselves
1:34:41 actually receive input from neurons.
1:34:44 So there are neurons that release norepinephrine
1:34:47 in response to cold, directly into the fat.
1:34:51 So I want to give you this picture of how the architecture
1:34:55 of all this works,
1:34:55 because I think it can help you navigate
1:34:58 and indeed build better deliberate cold exposure protocols.
1:35:01 Your adrenal glands release norepinephrine and epinephrine.
1:35:05 Your brain has sites within it like the locus coeruleus
1:35:08 that release norepinephrine and epinephrine,
1:35:12 but there are also neurons within your skin that sense cold
1:35:16 and other neurons that can directly release norepinephrine
1:35:19 into the fat stores and cause those white fat cells
1:35:22 to convert to beige and brown fat.
1:35:24 And I think this particular aspect of our physiology
1:35:26 is often overlooked in studies.
1:35:29 And when people say, oh,
1:35:31 well the increases in metabolism aren't that great,
1:35:33 the circulating levels of norepinephrine,
1:35:35 those are very large, but they're very transient and so on,
1:35:39 that fails to understand that neurons
1:35:43 that actually sense cold are in a position to communicate
1:35:46 via other neurons directly to the fat cells
1:35:49 and release norepinephrine into those fat cells,
1:35:51 which as I pointed out earlier,
1:35:53 set off a huge set of immediate
1:35:55 and long term cascades of even gene expression changes.
1:35:59 So the picture that I'd like you to have in your mind
1:36:02 is that when you get into the cold, yes,
1:36:04 of course you experience that as a experience of
1:36:07 I don't want to do this, I'm going to overcome this,
1:36:09 I'm going to climb over these mental walls
1:36:11 that represent adrenaline release in my brain and body,
1:36:14 but also that your fat cells are receiving signals,
1:36:18 norepinephrine signals that are changing those fat cells
1:36:20 and the way that they metabolize energy.
1:36:22 Now I'd like to shift our attention to the use
1:36:24 of deliberate cold exposure
1:36:26 for sake of physical performance.
1:36:28 And there are a lot of opinions out there
1:36:30 about the use of deliberate cold,
1:36:32 whether or not it should be done for instance,
1:36:34 before or after exercise,
1:36:36 whether or not if done immediately after strength training
1:36:39 or hypertrophy training,
1:36:40 meaning training designed to grow muscles
1:36:43 or make them stronger,
1:36:44 whether or not it can inhibit that process
1:36:46 and so on and so forth.
1:36:47 I think today in looking over the literature
1:36:50 and trying to bring forward the simplest
1:36:52 and most straightforward,
1:36:53 and yet scientifically grounded protocols,
1:36:56 we can set up some general guidelines that will allow most,
1:36:59 if not, all of you to still extract the benefits
1:37:01 of deliberate cold exposure on physical performance
1:37:05 without getting too neurotic about the exact timing,
1:37:08 but for sake of discussion
1:37:10 and because it's a prominent theme
1:37:13 in many online communities,
1:37:14 let's just start with the big one out there,
1:37:18 meaning the question of whether or not doing an ice bath
1:37:22 or doing deliberate cold exposure or taking a cold shower
1:37:25 after strength slash hypertrophy training,
1:37:28 meaning training designed to increase strength
1:37:30 and or I should say the size of muscles
1:37:34 will somehow short circuit or diminish that process,
1:37:37 whether or not it will reduce or eliminate
1:37:39 those strength gains and hypertrophy gains.
1:37:41 And the short answer that I was able to arrive at
1:37:45 on the basis of a review article that I'll talk about
1:37:48 in a moment and some other studies as well,
1:37:51 is that if your main goal is hypertrophy and strength,
1:37:56 it is probably best to avoid cold water immersion
1:38:00 and ice bath immersion in the four hours
1:38:04 immediately following that strength
1:38:06 and or hypertrophy training.
1:38:08 Again, if your main goal is to achieve hypertrophy
1:38:12 or strength or some combination of those,
1:38:15 probably best to avoid cold water immersion up to the neck
1:38:20 or ice bath immersion up to the neck
1:38:23 immediately after strength and hypertrophy training
1:38:26 and extending out to about four hours after that training.
1:38:31 If you're really neurotic about this,
1:38:32 then perhaps you'd want to move the cold water exposure
1:38:35 to a different day entirely,
1:38:37 but it all depends on how neurotically attached you are
1:38:39 to getting every last bit of strength and hypertrophy.
1:38:42 And if that's your goal, terrific,
1:38:44 well then probably moving the cold exposure four hours
1:38:47 or more away from that training
1:38:49 is going to be necessary for you.
1:38:50 Now you'll notice I did not talk about cold showers
1:38:53 and the reason I did not talk about cold showers
1:38:55 is that there simply are not very many studies
1:38:59 of deliberate cold exposure through cold showers
1:39:02 for the reasons I talked about
1:39:03 at the beginning of the episode.
1:39:05 It's hard for me to imagine that taking a brief cold shower
1:39:08 after a strength or hypertrophy training session
1:39:11 would completely reverse or short circuit the effects
1:39:13 of that strength and hypertrophy training.
1:39:15 But again, if you're neurotically attached
1:39:17 to getting every last bit of strength and hypertrophy
1:39:21 out of your training sessions, then by all means,
1:39:23 err on the side of caution and wait four hours or more
1:39:26 to do your cold shower just as you would wait four hours
1:39:29 or more to do your cold water immersion.
1:39:31 Now there are nice data pointing to the fact
1:39:33 that doing cold water immersion after a hard run,
1:39:37 so endurance training,
1:39:39 or even sprint and interval training
1:39:41 or after a weight workout where your main focus
1:39:45 is on performance of those movements
1:39:47 or after a skill training workout
1:39:49 where your main focus on performance of those movements,
1:39:52 that there's no reason to think that that
1:39:54 cold water immersion or ice bath or cold shower
1:39:57 would inhibit the progress or the stimulus
1:40:01 that would lead to progress
1:40:03 that occurred during that training session.
1:40:05 In other words, I don't see any reason
1:40:07 based on the literature to avoid deliberate cold exposure
1:40:10 immediately after training,
1:40:12 again unless your goal is hypertrophy and strength.
1:40:15 And in fact,
1:40:16 there's a very nice review recently published
1:40:19 on deliberate cold exposure
1:40:21 and how it can impact physical performance,
1:40:24 whether or not it's done before or after,
1:40:27 different types of training and so forth.
1:40:30 The paper is entitled impact of cold water immersion
1:40:33 compared with passive recovery,
1:40:35 following a single about of strenuous exercise
1:40:37 on athletic performance in physically active participants,
1:40:41 a systematic review with meta-analysis and meta regression.
1:40:45 So this is a meta-analysis of 52 studies
1:40:49 that looked at a tremendous number of variables
1:40:51 and contexts, as you would expect in a meta-analysis
1:40:55 of 52 studies.
1:40:56 I'm going to read you the conclusions of the study
1:40:58 and I will provide a link.
1:40:59 We certainly don't have the time to go through
1:41:01 all the details of the study.
1:41:02 I will highlight a few specific outcomes
1:41:05 that I found particularly interesting,
1:41:07 but here I am paraphrasing their conclusions,
1:41:10 that cold water immersion, I want to emphasize immersion,
1:41:15 not cold showers, but cold water immersion
1:41:18 they say was an effective recovery tool
1:41:20 after high intensity exercise.
1:41:22 They observed positive outcomes,
1:41:23 meaning improvements in certain variables,
1:41:27 for muscular power, muscular soreness,
1:41:30 meaning reduced muscular soreness,
1:41:31 increased muscular power,
1:41:33 perceived recovery after 24 hours of exercise.
1:41:36 However, there were certain forms of exercise
1:41:39 that were not benefited by cold water immersion,
1:41:43 such as eccentric exercise,
1:41:45 exercise focusing only on the lowering component
1:41:49 or the so-called eccentric component of resistance exercise.
1:41:52 They saw some very entry dose response relationships
1:41:56 for things like endurance training, meaning the longer
1:42:00 the cold exposure post-endurance training,
1:42:02 the more improvement in endurance performance,
1:42:05 reductions in circulating creatine kinases
1:42:08 and things that relate to muscle damage
1:42:11 under certain conditions.
1:42:12 At some point in the future, by the way,
1:42:14 we'll do an entire episode on creatine and creatine kinase,
1:42:17 which are important not just for muscular function,
1:42:19 but also for brain function.
1:42:21 But the basic takeaway was that cold water immersion
1:42:25 performed after high intensity exercise
1:42:27 was beneficial from a number of different standpoints
1:42:30 and indicated that shorter duration,
1:42:34 cold exposure and lower temperatures
1:42:37 can improve the efficacy of cold water exposure
1:42:40 if used after high intensity exercise.
1:42:42 There I'm directly pulling from their conclusions.
1:42:45 So what this says is that it's not just those
1:42:47 longer duration, 30, 45 minute and 60 minute protocols
1:42:52 of cold water immersion that we discussed earlier,
1:42:54 but also shorter duration of one minute, three minute,
1:42:58 five minute exposures to lower temperatures.
1:43:02 Temperatures that would make you psychologically
1:43:04 want to get out as soon as you possibly can,
1:43:07 but again that you can safely stay in
1:43:10 done after training really have been shown to
1:43:12 improve outcomes in terms of reducing soreness
1:43:15 and improving training efficacy,
1:43:18 meaning your ability to get back into training more quickly
1:43:22 and thereby deliver more training stimuli
1:43:25 to a given muscle or in your endurance training protocol.
1:43:29 Translate to English,
1:43:29 what this means is that taking a cold shower or getting into
1:43:33 an ice bath or some other form of cold water immersion
1:43:35 within the immediate minutes or even the immediate hours
1:43:39 following your training has been shown to be beneficial.
1:43:43 I'm sure a number of you have questions for instance,
1:43:45 how long should you be in that cold exposure?
1:43:49 Is it the same as the 11 minute threshold described earlier?
1:43:52 To be honest with you,
1:43:53 there are not enough studies to really point
1:43:56 to the critical threshold for eliminating
1:43:59 or reducing delayed onset muscle soreness
1:44:01 or for getting maximal results from power
1:44:05 and endurance training,
1:44:06 but this study does make a couple of key points
1:44:09 and here I will just paraphrase.
1:44:11 For instance, that cold water immersion
1:44:13 is more likely to positively influence
1:44:16 muscular power performance,
1:44:18 to reduce muscle soreness, to reduce serum creatine kinase,
1:44:22 and to improve perceived recovery
1:44:24 after high intensity exercise,
1:44:26 as compared with passive recovery.
1:44:29 This can be translated to cold water exposure after training
1:44:33 is beneficial and probably better
1:44:35 than passive recovery from a number of standpoints.
1:44:38 In addition, they say that dose response relationships
1:44:42 meaning the amount and the degree of cold
1:44:47 that people were exposed to and how often they did that
1:44:51 in particular in lower temperature cold immersion.
1:44:53 So these would be the sorts of cold immersion protocols
1:44:57 that are one minute or two minutes, three minutes,
1:44:59 maybe five minutes,
1:45:00 but that one couldn't stay in there longer
1:45:02 because it feels stressful
1:45:03 and one wants to get out.
1:45:05 Maybe more effective after high intensity exercise
1:45:08 for removal of serum creatine kinase
1:45:11 as well that these shorter duration
1:45:13 cold water immersion approaches may be more effective
1:45:16 after high intensity endurance performance as well.
1:45:19 So all of this can be translated to say that
1:45:22 unless your main goal is hypertrophy and strength,
1:45:27 that cold exposure, ideally cold immersion
1:45:30 and cold water ice bath,
1:45:32 but if you don't have access to that,
1:45:34 then cold showers is likely going to be beneficial
1:45:37 if done immediately after or in the minutes
1:45:39 or hours after your training,
1:45:42 especially high intensity training.
1:45:44 One particularly nice thing about this meta-analysis
1:45:46 is that it included some studies that
1:45:48 involve the use of cooling packs.
1:45:50 So again, vests that can essentially ice packs
1:45:55 and indeed even cryotherapy chambers and so on.
1:45:59 There's a nice table in the study
1:46:00 if you want to get really detailed and go
1:46:02 and look specifically at those studies,
1:46:03 I invite you to do that.
1:46:04 We'll put a link to this study in the caption
1:46:07 for this episode, but all in all,
1:46:09 what this study shows is that deliberate cold exposure
1:46:12 can be very useful for recovery likely through reductions
1:46:17 in inflammation, in muscle and connective tissue.
1:46:20 And while this study did not look specifically
1:46:22 at the mechanisms of reduced inflammation
1:46:25 caused by deliberate cold exposure,
1:46:27 those mechanisms are somewhat known.
1:46:30 There are a number of studies that have pointed to the fact
1:46:32 that deliberate cold and cold generally
1:46:34 can reduce inflammatory cytokines,
1:46:37 such as IL-6, interleukin six.
1:46:39 It can increase anti-inflammatory cytokines
1:46:43 such as interleukin 10 and so on.
1:46:46 Without getting into all those details,
1:46:48 I think it's sufficient to say that
1:46:50 if you are somebody who experiences
1:46:52 a lot of delayed onset muscle soreness,
1:46:54 taking a cold shower after your training
1:46:56 or getting into a cold immersion after your training,
1:46:58 even if it's a few hours later ought to help.
1:47:01 And if you are doing particularly intense training,
1:47:04 then you probably want to ratchet up the number
1:47:07 of cold exposure sessions that you're doing
1:47:10 even if those have to be done on separate days
1:47:12 from your training,
1:47:13 because a lot of the inflammatory effects of training,
1:47:15 endurance and strength training are actually occurring
1:47:17 some hours away from the training stimulus.
1:47:20 So it's not just that inflammation goes up
1:47:22 radically during training, which it often can,
1:47:25 but that it can occur even in the days
1:47:27 and even weeks afterwards,
1:47:28 depending how intense and how long duration
1:47:30 that training is.
1:47:31 So deliberate cold exposure is very powerful
1:47:33 as an anti-inflammatory tool.
1:47:36 Now I'd like to emphasize the topic that we touched on
1:47:38 at the beginning of the episode,
1:47:40 which are those glabrous skin surfaces,
1:47:43 the hands, the upper face,
1:47:44 and the bottoms of the feet through which heat
1:47:47 is especially good at leaving the body.
1:47:50 And another way of putting that is that one can cool
1:47:54 the body much more efficiently
1:47:56 through the glabrous skin surfaces.
1:47:58 Now, if you want to understand all of the science
1:48:01 behind this and all of the various applications,
1:48:05 I invite you to please listen to the episode
1:48:07 that I did with Dr. Craig Heller, again,
1:48:10 in the biology department at Stanford.
1:48:13 For sake of this episode,
1:48:14 I'm just going to detail a couple of findings
1:48:17 from his laboratory.
1:48:18 The first one, dealing with exercise induced hyperthermia,
1:48:21 because I think this is very interesting
1:48:22 and it can even save lives
1:48:24 if you understand the way this works.
1:48:28 There's a particular paper that focuses on this,
1:48:30 and we will put a link to this as well.
1:48:32 The title of this paper is novel application
1:48:34 of chemical cold packs for treatment
1:48:35 of exercise induced hyperthermia,
1:48:37 a randomized control trial.
1:48:39 This is a pretty brutal study,
1:48:42 brutal for the subjects that is.
1:48:45 This study involved was having subjects walk on a treadmill
1:48:49 at a pretty significant incline and anywhere
1:48:51 from nine to 17% wearing a substantial amount of clothing
1:48:56 that was not well ventilated
1:48:58 and the room was kept to 40 degrees Celsius,
1:49:00 which is 104 degrees Fahrenheit.
1:49:03 This is definitely not something to do at home.
1:49:06 This study was designed to induce hyperthermia,
1:49:09 which as I mentioned earlier, can be quite dangerous.
1:49:11 And they compared two types of cooling.
1:49:14 In the first form of cooling
1:49:16 that they call traditional cooling,
1:49:18 they had ice packs on their neck,
1:49:21 in their armpits and in their groin.
1:49:23 And in the other group,
1:49:25 there was the so-called glabrous skin cooling.
1:49:27 So the palms, the soles of the feet,
1:49:29 which were actually so they were cooling inside the boots
1:49:33 or inside of gloves and on the upper portion of the face.
1:49:39 And the basic takeaway of this study
1:49:41 is that by cooling the glabrous skin,
1:49:44 the subjects were able to sustain this walking
1:49:47 on these inclined treadmills for much longer
1:49:50 than were the people who received traditional cooling.
1:49:54 And also the return to baseline temperature
1:49:56 was much faster in the glabrous skin cooling group.
1:49:59 So how this translates to the real world
1:50:01 is that if ever you are hyperthermic
1:50:04 or someone else's hyperthermic,
1:50:06 one way to cool them down quickly is to cool
1:50:10 these palmer glabrous, soles of the feet glabrous
1:50:14 and upper portion of the face glabrous portions of the body
1:50:18 using cool rags, using ice packs or using any number
1:50:22 of different cold objects or temperatures.
1:50:26 One key thing, if you're going to use glabrous skin cooling,
1:50:30 is that whatever you use to cool those surfaces
1:50:33 cannot be so cold that it causes vasoconstriction.
1:50:37 Because as I mentioned earlier,
1:50:38 the arterio-venous anastomoses
1:50:41 these portals of arteries directly to veins
1:50:43 that exist only in these glabrous skin surfaces,
1:50:49 the way that they're able to cool the body
1:50:51 and essentially pass cool into the body
1:50:53 although that's not really what they're doing,
1:50:55 they're actually extracting heat from the body
1:50:57 to be technical, they're extracting heat from the body,
1:51:00 the only way they can do that is if those veins
1:51:04 don't collapse and veins will collapse
1:51:06 if they are made very, very cold.
1:51:08 So if you want to use glabrous skin cooling
1:51:11 to offset hyperthermia
1:51:12 or for the other forms of performance,
1:51:14 which we'll talk about in a moment,
1:51:16 you need to use a cool object or surface
1:51:19 that is not so cold that it causes vasoconstriction.
1:51:22 And this can be a little bit tough to dial in,
1:51:24 meaning it can be tough to identify such an object.
1:51:27 And for that reason,
1:51:28 Dr. Heller and some of his colleagues have developed
1:51:30 a commercial product called the CoolMitt.
1:51:32 You can actually go to their website, coolmitt.com.
1:51:34 I don't have any financial or other relationship to them.
1:51:37 I know they've been developing this technology
1:51:39 for some period of time.
1:51:40 It involves a glove that you put your hand into,
1:51:43 it circulates water of a given temperature and it does so,
1:51:47 and does so at a tempera or that is sure to not
1:51:51 cause vasoconstriction of the palm.
1:51:53 And you may be asking,
1:51:54 how can you just put your hand into one glove
1:51:56 and have this work?
1:51:57 Well, that's how powerful these glabrous skin surfaces are.
1:51:59 Even just by cooling one palm,
1:52:02 the core body temperature drops radically.
1:52:06 Now that's their commercial technology.
1:52:08 I know that some people out there have started to experiment
1:52:11 with a home version of this,
1:52:13 which would be taking a package for instance
1:52:15 of frozen blueberries or some other cold drink
1:52:18 or cold metal object, and actually bringing it into the gym
1:52:21 or out on a run.
1:52:23 There are even people who are now developing
1:52:25 cooled psych bicycle handles for long rides.
1:52:29 This might seem a little kooky or crazy to you,
1:52:31 but as you'll soon hear in the study
1:52:33 I'm about to describe, the increases in endurance
1:52:37 and in the volume of strength training
1:52:39 that people can conduct if they appropriately cool
1:52:43 their body through these glabrous skin portals
1:52:46 is actually quite significant.
1:52:48 So again, as it relates to hyperthermia,
1:52:50 if someone is overheating by all means,
1:52:52 try and get them out of that heat,
1:52:54 get them to stop exercising, you can die from hyperthermia,
1:52:57 try and cool the bottoms of the feet,
1:52:59 the palms of their hands
1:53:01 and the upper portion of their face.
1:53:03 That does not mean it would be a bad idea
1:53:06 to put cold water on the top of their head.
1:53:08 That probably would also help and perhaps on their neck.
1:53:10 What is probably not going to be a good idea is to do
1:53:14 the more standard thing of draping someone in cold towels
1:53:17 on the surface of their body because as I mentioned,
1:53:19 the beginning of the episode,
1:53:20 that thermostat in the hypothalamus,
1:53:22 the medial preoptic area will typically react to that
1:53:25 by increasing core body temperature further.
1:53:28 The effects of glabrous skin cooling on physical performance
1:53:31 are truly remarkable
1:53:32 provided the glabrous skin cooling is done correctly.
1:53:36 And I want to point out that the main degree of effect
1:53:40 is on volume or the ability to do more work.
1:53:44 And I want to point this out because I think that many people,
1:53:47 certainly in the exercise science community,
1:53:49 but even in the general public,
1:53:50 when they hear about some of these effects
1:53:52 that are measured in the laboratory,
1:53:54 they sort of look at those effects a bit of scans
1:53:59 and they think, well, that's not possible.
1:54:01 Effects for instance, that have been documented
1:54:03 showing doubling or tripling of the number of dips
1:54:05 that one can do in a relatively short amount of time
1:54:08 or doubling of the number of pullups one can do
1:54:11 or 14% increases in strength or even comparable degrees
1:54:15 in increase in weight training output
1:54:18 to people who are on performance enhancing drugs,
1:54:20 et cetera, et cetera.
1:54:22 Part of the confusion is that the effects
1:54:25 of proper palmer cooling,
1:54:27 because it almost always is done by palmer cooling
1:54:30 and less often in these experiments
1:54:32 by cooling of the bottoms of the feet
1:54:33 and the upper portion of the face,
1:54:35 but those effects tend to be the ability to do more work
1:54:41 over time and just to illustrate some of the major effects
1:54:45 that the Heller lab is seen
1:54:46 and they are document entered in this manuscript
1:54:48 that I'll share with you in a moment.
1:54:50 The typical protocol is to have people come in
1:54:53 and do some endurance training
1:54:54 so running on a treadmill and to have a condition where
1:54:58 one group is actually doing palmer cooling
1:55:01 while they are on a bike or on a treadmill
1:55:03 and inevitably the outcome is that they can do more work.
1:55:07 They can pedal further at a given speed,
1:55:09 or they can run longer at a given speed than people
1:55:13 who are not doing palmer cooling
1:55:14 or who are receiving cooling by way of
1:55:18 cold compress to the back of the neck or ice pack
1:55:20 to the armpits, et cetera.
1:55:22 So the effects of palmer cooling are very clear
1:55:25 and very robust.
1:55:26 And in the context of endurance exercise
1:55:29 almost always allow people to do more work,
1:55:31 to go longer with less perceived effort and to quit later
1:55:35 so to speak.
1:55:37 In terms of strength training,
1:55:38 they've looked at the capacity to perform sets of dips.
1:55:42 So one of the more famous examples of this
1:55:44 that Dr. Heller shares in the episode that we did earlier,
1:55:48 and that you can find at hubermanlab.com involves
1:55:51 someone coming in and doing sets of dips, maybe 40 dips.
1:55:55 This person actually could do 40 dips on their first set,
1:55:58 then resting for a period of two to three minutes
1:56:00 and then doing 35
1:56:02 and then resting for a period of two or three minutes,
1:56:04 and then doing progressively fewer and fewer and fewer
1:56:06 to the point where over a period of time,
1:56:09 they add up the total number of dips that they can do
1:56:11 and then they have them come back
1:56:14 after a period of recovery, so not immediately after,
1:56:16 but take a couple of days,
1:56:18 come back and do effectively the same protocol,
1:56:21 but during their rest periods,
1:56:22 they're doing two minutes of palmer cooling,
1:56:25 which essentially allows heat to move out of the body,
1:56:29 lowering core body temperature in other words.
1:56:31 And what they find is that they see enormous increases
1:56:35 in the total number of dips that people can do,
1:56:37 but that doesn't mean that the person goes
1:56:38 from being able to do 40 dips,
1:56:39 to being able to do 50 dips or 60 dips on that first set,
1:56:43 what it means is they are able to do 40 on the first set,
1:56:46 then 40 on the second,
1:56:47 then 38 on the third and so on and so forth
1:56:50 so that the total duration of the workout is extended
1:56:52 and yet they're doing much more work,
1:56:55 even though it takes more time.
1:56:57 So that's an important point
1:56:59 and I think a point that perhaps wasn't as clear
1:57:02 or as clearly made by me in the previous episodes
1:57:05 that discuss this topic.
1:57:07 For those of you that are interested
1:57:08 in exploring palmer cooling, first of all,
1:57:11 I recommend taking a brief glance or even a deep dive
1:57:15 into this study,
1:57:17 which is entitled work volume
1:57:18 and strength training responses to resistive exercise
1:57:21 improve with periodic heat extraction from the palm.
1:57:25 In this study, they describe big increases in anaerobic,
1:57:30 meaning strength training output,
1:57:32 things like improvement in dips,
1:57:35 improvement in bench press,
1:57:37 improvement in pull-ups, et cetera, in human subjects.
1:57:40 And it's a really nice study and points
1:57:43 to some of the protocols that you might be able
1:57:44 to adapt in your own setup.
1:57:46 For instance, over six weeks of pull up training,
1:57:48 palm cooling in between sets improved volume by 144%,
1:57:54 and this was in experienced subjects.
1:57:56 So that's interesting because a lot of studies
1:57:58 of strength training and improvements in hypertrophy
1:58:01 and strength are done in inexperienced untrained athletes,
1:58:04 which changes the picture somewhat
1:58:07 compared to experienced athletes.
1:58:10 They found that strength,
1:58:11 meaning the one repetition maximum,
1:58:13 increased 22% over 10 weeks in bench press training.
1:58:17 And they point to the particularly strong effects
1:58:20 of using palmer cooling when people reach plateaus
1:58:23 in endurance and strength training.
1:58:25 And there, I think it's an important point.
1:58:26 I think that if you're going to explore palmer cooling,
1:58:30 it's probably not the sort of thing that you're going to do
1:58:32 in every run or in every about of cycling
1:58:36 or in every strength training session,
1:58:38 but that it might be used to vastly increase your volume
1:58:42 or vastly increase your endurance
1:58:44 in a given session or a set of sessions
1:58:46 in order to push through plateaus.
1:58:49 A particularly interesting point in light of that
1:58:51 is Dr. Heller has observed again and again
1:58:54 that palmer cooling reduces delayed onset muscle soreness,
1:58:57 or it can eliminate it entirely.
1:58:59 And that's very interest because it also points to the fact
1:59:02 that reducing core body temperature may somehow be involved
1:59:05 in short circuiting
1:59:06 the normal mechanisms of delayed onset muscle soreness.
1:59:09 And you might say, well,
1:59:10 how would temperature be involved
1:59:12 in delayed onset muscle soreness?
1:59:14 Well, I want to refer you back to the meta-analysis
1:59:17 that we talked about earlier, where the short duration,
1:59:20 very cold temperature exposure after training did indeed
1:59:23 reduce delayed onset muscle soreness
1:59:25 in part through reduction, excuse me, in creatine kinase.
1:59:28 So it's not inconceivable that temperature
1:59:32 and delayed onset muscle soreness are related.
1:59:35 And that raises perhaps the most important point,
1:59:37 which is the way that palmer cooling can improve performance
1:59:42 by way of reducing core body temperature is known
1:59:46 and that is because when one engages in exercise
1:59:50 or muscular output of any kind,
1:59:52 strength or endurance exercise,
1:59:54 the range of temperatures under which a muscle can perform
1:59:58 is actually very narrow.
2:00:00 There's an enzyme called pyruvate kinase,
2:00:02 which is critical to muscle contractions
2:00:05 and pyruvate kinase can only function
2:00:07 in a very narrow range of temperatures.
2:00:09 If that temperature gets too hot,
2:00:11 meaning if the muscle heats up locally,
2:00:13 whether or not by running
2:00:14 or cycling or swimming or weightlifting,
2:00:17 the ability for that muscle to continue
2:00:19 to contract is reduced and eventually
2:00:22 is short circuited completely.
2:00:23 And I think this is a much underexplored
2:00:26 or at least a much under discussed aspect
2:00:29 of so-called muscular failure or the failure
2:00:32 of one to continue to endure in running.
2:00:35 So for instance,
2:00:36 when you run as compared to a bench press or something,
2:00:38 you don't stop running
2:00:39 because you can't actually contract the muscles further,
2:00:42 but somehow signals about the heating up
2:00:46 of muscular tissue are conveyed to the brain.
2:00:48 There's a crosstalk there,
2:00:49 it's probably bidirectional and people stop, they quit.
2:00:53 This is the quitting reflex.
2:00:56 In strength training, one can no longer perform a repetition
2:01:00 or set of repetitions in part
2:01:01 because of heating up of the muscle locally.
2:01:03 There are other mechanisms as well, of course,
2:01:05 and I realize that,
2:01:07 but what's very clear from the palmer cooling work is that
2:01:10 by simply holding onto a cool object,
2:01:13 remember not an object so cold
2:01:14 that it constricts the vessels of the palms
2:01:17 or constricts the vessels on the bottoms of the feet,
2:01:20 but by holding onto a relatively cool object
2:01:22 in one or both hands in between sets for two minutes or so,
2:01:26 you can very efficiently reduce your core body temperature
2:01:29 and in doing so, reduce the temperature of the muscles
2:01:32 that are doing the work,
2:01:35 increase the capacity for pyruvate kinase
2:01:37 to continue to allow your muscles to contract
2:01:40 and thereby allow you to do more volume of endurance
2:01:44 and strength training.
2:01:45 So a simple protocol that Dr. Heller passed to me
2:01:48 is find a relatively cool object.
2:01:51 So you could, for instance,
2:01:52 fill two bottles with cold water,
2:01:54 maybe put a few ice cubes in there.
2:01:56 This is not exact because we're not talking about
2:01:58 the commercial CoolMitt product here,
2:02:00 we're talking about an at home version
2:02:01 or use a pack of frozen blueberries or broccoli
2:02:05 sort of pack of those as what he described.
2:02:07 And then in between sets to put your hands
2:02:10 and ideally you'd put the bottoms of your feet,
2:02:12 but that's not always feasible in most gyms
2:02:13 where they won't let you take off your shoes and so forth,
2:02:16 but to put the palms of your hands on that cool surface
2:02:19 for a minute or two minutes between sets
2:02:22 and then returning to your sets of work.
2:02:24 Now, if you are heating up through other mechanisms
2:02:28 like you're wearing a stocking cap
2:02:30 and you're in a very warm environment,
2:02:31 this might not have as potent effect
2:02:33 as if you were to do this cooling
2:02:35 in a more moderate environment,
2:02:36 wearing lighter clothing, et cetera.
2:02:38 So by all means warm up to do your exercise,
2:02:41 lubricate your joints,
2:02:42 and get into a place where you're not going to injure yourself,
2:02:44 doing whatever form of exercise you do.
2:02:46 But then if you'd like to explore palmer cooling,
2:02:48 I know a number of people who've written to me saying
2:02:51 they heard about palmer cooling
2:02:52 on the episode with Dr. Heller.
2:02:53 They've tried this and they see quite excellent results.
2:02:56 It does take some discipline.
2:02:58 It's one thing to just kind of hang out in the gym
2:02:59 and play on your phone in between sets.
2:03:01 It's another to do deliberate cooling with your palms
2:03:04 or the bottom of your feet
2:03:04 or the upper portion of your face.
2:03:06 You might get some weird looks,
2:03:07 but of course you'll be the one
2:03:09 doing significantly more volume,
2:03:11 not experiencing delayed onset muscle soreness and achieving
2:03:14 better endurance and strength gains
2:03:16 were you to do this properly.
2:03:17 Now as a final topic related to the use
2:03:19 of deliberate cold exposure for improving health
2:03:22 and performance, I'd like to touch on this theme
2:03:26 that exists online, on social media,
2:03:28 on YouTube and in various fitness communities
2:03:31 of using deliberate cold exposure to the groin,
2:03:34 in particular to the testicles,
2:03:36 in order to try and increase testosterone.
2:03:39 And while this might sound really kooky,
2:03:42 indeed this practice exists.
2:03:44 Indeed if you were to go onto Amazon,
2:03:47 there are actually ice pack underwear
2:03:50 that are being marketed for sake of increasing testosterone.
2:03:54 Now, I am not aware of any specific well-controlled studies
2:03:57 that show that this indeed works.
2:04:00 I can imagine based on what I know about the nervous system,
2:04:03 testosterone and cold, et cetera,
2:04:06 that there are a couple of mechanisms
2:04:07 by which one might experience increases in testosterone
2:04:11 as a consequence of deliberate cold exposure.
2:04:13 First off, let me say there is no reason why
2:04:15 you would have to apply these ice packs
2:04:18 in the way that I just described.
2:04:20 One could of course take a cold shower.
2:04:22 One could of course use cold immersion of various kinds,
2:04:26 and you're still going to get that exposure
2:04:28 of the groin and the testicles to cold.
2:04:31 Now I should point out that people do report
2:04:34 at least anecdotally increases in testosterone
2:04:38 as a consequence of this practice
2:04:40 and I have to imagine
2:04:41 that they are measuring their serum testosterone,
2:04:43 that they're not just guessing
2:04:44 that their testosterone went up.
2:04:46 If you know of a study exploring this directly,
2:04:48 please let me know, put in the comment section on YouTube,
2:04:51 or even just email me.
2:04:53 We have a email that you can find it, hubermanlab.com.
2:04:57 Please email me the reference.
2:04:58 I wasn't able to find a reference,
2:05:00 but I can imagine two reasonably plausible mechanisms
2:05:04 by which deliberate cold exposure to the groin,
2:05:07 in particular the testicles, would increase testosterone.
2:05:10 The first is somewhat direct,
2:05:13 which is that anytime you cool a body surface,
2:05:17 that if it's cold enough,
2:05:18 you're going to get vasoconstriction.
2:05:20 And then subsequently you're going to get
2:05:21 a rebound increase in vasodilation,
2:05:24 meaning you're going to constrict
2:05:26 the blood vessels in that area.
2:05:27 And then after the cold is removed,
2:05:29 there's going to be more blood flow to that area.
2:05:31 And of course,
2:05:32 blood flow relates to organ health
2:05:34 and tissue health generally.
2:05:35 So perfusion of that region and the gonads to be specific
2:05:41 with additional blood,
2:05:42 you could imagine in some ways increasing testosterone,
2:05:46 that's reasonably plausible.
2:05:48 The other probably more likely mechanism
2:05:51 relates to the dopamine increases caused by cold exposure
2:05:54 that we talked about earlier.
2:05:56 Again, anytime you have a somewhat stressful stimulus,
2:05:59 but in particular with cold exposure,
2:06:01 it seems that the catecholamines,
2:06:03 norepinephrine, epinephrine and dopamine all increase
2:06:07 and dopamine is known to be in the pathway
2:06:10 that can stimulate testosterone.
2:06:13 And so while there isn't a direct relationship
2:06:15 between dopamine stimulating testosterone,
2:06:17 there is an interesting pathway way whereby
2:06:19 dopamine increases can trigger increases
2:06:21 in things like luteinizing hormone,
2:06:23 which can trigger increases in testosterone
2:06:26 as well as estrogen for that matter.
2:06:28 So I know that there are a lot of people out there
2:06:30 that are interested in the use of cold exposure
2:06:32 for increasing testosterone.
2:06:33 And some of those people in communities are
2:06:36 indeed using cold exposure directly on the gonads,
2:06:40 on the testees in order to do this.
2:06:42 I'm not certain that that direct contact is necessary.
2:06:46 And in some cases it might actually be quite dangerous
2:06:51 or you at least should be careful in terms of tissues there
2:06:54 and avoiding damage.
2:06:55 But nonetheless, I think that a dopamine impact
2:06:59 on testosterone is very likely given the 250% increases
2:07:04 in dopamine that have been observed
2:07:05 with cold water immersion and all of that points to the fact
2:07:07 that cold water immersion
2:07:10 very likely increases testosterone,
2:07:13 but as a downstream consequence
2:07:15 of the cold water immersion effects on dopamine
2:07:18 and luteinizing hormone,
2:07:19 and again there's no reason to think that the increases
2:07:22 in luteinizing hormone would also increase estrogen.
2:07:25 Probably not to dangerous or levels
2:07:29 that one would want to avoid,
2:07:31 but I don't think that there's anything
2:07:33 particularly specific about cold
2:07:35 for inducing testosterone and not other hormones.
2:07:38 I think it's very likely to increases
2:07:39 a number of different hormones.
2:07:41 I do hope that there will be a systematic study on this
2:07:44 in the not too distant future.
2:07:45 I also hope to not be a subject
2:07:47 in the cooling of the gonads experiment.
2:07:50 Now I promise you the last topic was the last topic,
2:07:52 but there's one other really important point
2:07:54 that I think everyone should be aware of
2:07:56 if you're going to use deliberate cold exposure.
2:07:59 And that brings us back to the very first thing
2:08:01 that we discussed today,
2:08:03 along the lines of deliberate cold exposure,
2:08:05 which is that your baseline temperature
2:08:07 is going to be lowest about two hours before you wake up,
2:08:11 it's going to increase in the morning
2:08:13 and as you wake up
2:08:15 and increase throughout the day and afternoon,
2:08:17 and then start to drop in the evening and come down at night
2:08:20 as you head to sleep.
2:08:23 I also want you to remember that if you are to cool
2:08:26 the external portion of your body, in particular your torso,
2:08:30 the net effect of that is going to be an increase
2:08:33 in body temperature.
2:08:35 So for many people, not all, but for many people,
2:08:38 if you are going to do deliberate cold exposure,
2:08:42 you are going to increase your core body temperature
2:08:45 and that makes sense
2:08:46 if you think about how deliberate cold exposure
2:08:48 can increase metabolism by increasing thermogenesis.
2:08:52 What that all means is that if you are doing
2:08:56 your deliberate cold exposure early in the day,
2:08:58 you are going to get yet a further increase
2:09:01 in core body temperature
2:09:03 that would be associated with wakefulness,
2:09:05 your ability to be alert that morning
2:09:07 or throughout the day and so on.
2:09:10 It also means that if you do your deliberate cold exposure
2:09:13 very late in the evening, or at night,
2:09:16 so 6:00 PM, 7:00 PM, 9:00 PM and so on,
2:09:21 you are going to increase your core body temperature
2:09:23 and if you recall,
2:09:25 a decrease in core body temperature
2:09:27 of one to three degrees is not just beneficial,
2:09:31 but is necessary in order to get into deep sleep
2:09:34 and remain in deep sleep.
2:09:36 So the takeaway from this is deliberate cold exposure
2:09:39 done properly will increase your core body temperature
2:09:42 and make you feel more alert.
2:09:44 So if you're doing it early in the day,
2:09:46 that's probably terrific
2:09:48 given that most of us want to be alert during the day.
2:09:50 However, if you do it too late in the day, evening or night,
2:09:54 it can disrupt sleep by way of disrupting
2:09:57 your core body temperature.
2:09:58 Now, the caveat to that is I myself
2:10:02 tend to do deliberate cold exposure early in the day.
2:10:05 Maybe not first thing in the morning, but mid morning,
2:10:07 maybe as late as three or four in the afternoon
2:10:09 in some cases.
2:10:10 In the longer days of summer, I might do it even later,
2:10:12 five or 6:00 PM and have no trouble sleeping.
2:10:15 I have done deliberate cold exposure very late at night,
2:10:18 10:00 PM, 11:00 PM and so on
2:10:21 as part of a 30 day challenge
2:10:23 of doing deliberate cold exposure every day for 30 days
2:10:25 and I got sloppy with my timing
2:10:27 and then in order to not miss a day,
2:10:29 I would do it at 11 o'clock at night.
2:10:31 And I must say
2:10:31 I found that I could still fall asleep very easily,
2:10:35 even doing deliberate cold exposure very late at night.
2:10:38 However, on those particular days, I was particularly busy
2:10:42 and so I was particularly exhausted when I arrived
2:10:45 at the deliberate cold exposure
2:10:46 and I had no trouble falling asleep
2:10:49 after doing deliberate cold exposure,
2:10:50 and then taking a nice warm shower and then going to sleep.
2:10:53 But I could imagine that because of the increases
2:10:56 in core body temperature caused by deliberate cold exposure,
2:10:59 that were one to do that too late in the day,
2:11:02 evening or night that it could indeed disrupt your sleep.
2:11:04 So my recommendation would be
2:11:06 for most people only do deliberate cold exposure
2:11:09 if you are prepared to be fairly alert for the next one
2:11:12 to four or maybe had been six hours
2:11:14 following that deliberate cold exposure.
2:11:17 So for today's episode,
2:11:18 as is the case with most episodes
2:11:20 of the Huberman Lab Podcast, I covered a lot of material.
2:11:23 We talked about mechanisms of catecholamines and stress
2:11:25 and pulsatile release of epinephrine, metabolism,
2:11:29 mental effects, performance, glabrous skin cooling
2:11:31 and on and on and on.
2:11:33 And while the goal of course is to make sure that everyone
2:11:37 arrives at specific,
2:11:38 very clear mechanistic and actionable protocols,
2:11:41 I do realize that it is an immense amount of information.
2:11:44 And for that reason,
2:11:45 I've created a list of deliberate cold exposure protocols
2:11:49 aimed at improving mental toughness and resilience,
2:11:53 mood, performance, metabolism, reducing inflammation,
2:11:58 and so on and so forth.
2:11:59 All of those have been condensed into succinct form
2:12:02 and can be found at the Huberman Lab
2:12:05 Neural Network Newsletter.
2:12:06 This is a monthly or semi-monthly newsletter
2:12:09 that we release
2:12:10 that includes takeaways from the podcast and protocols.
2:12:13 You can access those as protocols zero cost
2:12:16 by simply going to hubermanlab.com,
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2:12:20 It's very easy to do, you just supply your email
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2:12:24 We do not share your email with anybody else.
2:12:27 In fact, we have our privacy policy laid out
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2:12:32 so you can find that there and the protocols
2:12:35 that I've designed should make it very straightforward
2:12:38 for you to create a set of protocols
2:12:41 that you could use with cold showers, with cold immersion,
2:12:43 with or without ice in combination with exercise
2:12:46 specifically for one goal or another,
2:12:47 or to accomplish multiple goals simultaneously.
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2:14:53 So thank you once again
2:14:54 for joining me in the discussion about the use
2:14:57 of deliberate cold exposure for health and performance
2:14:59 and last but certainly not least,
2:15:02 thank you for your interest in science.