Using Deliberate Cold Exposure for Health and Performance

00:00:00.000 | - Welcome to the Huberman Lab Podcast,

00:00:02.260 | where we discuss science and science-based tools

00:00:04.900 | for everyday life.

00:00:05.900 | I'm Andrew Huberman,

00:00:10.260 | and I'm a professor of neurobiology and ophthalmology

00:00:13.000 | at Stanford School of Medicine.

00:00:14.940 | Today, we are going to discuss

00:00:16.380 | the use of deliberate cold exposure

00:00:18.460 | for health and performance.

00:00:20.500 | Temperature is a powerful stimulus on our nervous system

00:00:23.660 | and indeed on every organ and system of our body.

00:00:26.780 | And cold in particular can be leveraged to improve

00:00:30.060 | mental health, physical health, and performance,

00:00:33.200 | meaning for endurance exercise,

00:00:35.300 | for recovering from various forms of exercise,

00:00:38.180 | for actually improving strength and power,

00:00:41.440 | and for enhancing mental capacity.

00:00:43.900 | In order to properly leverage deliberate cold exposure

00:00:46.920 | for sake of mental health, physical health, and performance,

00:00:50.260 | you have to understand how cold impacts the brain and body.

00:00:53.220 | So today we are going to discuss that.

00:00:55.300 | We're going to talk about some of the neural circuits

00:00:57.040 | and pathways, some of the hormones involved.

00:00:59.600 | I promise to make it all clear and accessible,

00:01:02.020 | regardless of whether or not

00:01:03.140 | you have a scientific background or not.

00:01:05.500 | We are also going to discuss very specific protocols

00:01:08.040 | that you can apply, which leverage variables

00:01:10.440 | like temperature, how cold, how to deliver the cold.

00:01:14.020 | For instance, whether or not you use a cold shower,

00:01:16.120 | cold immersion, ice bath, circulating water, or still water,

00:01:20.940 | whether or not you're going for walks outside in a t-shirt

00:01:23.860 | when it's cold, or whether or not

00:01:25.460 | you're purposefully using things like cryo,

00:01:28.100 | if you have access to that or not.

00:01:30.340 | One thing I can promise you is that

00:01:31.660 | by the end of today's episode,

00:01:33.520 | you will know a lot about the biology of thermal regulation.

00:01:36.580 | That is how your brain and body regulates its temperature.

00:01:39.960 | You will also have a lot of tools in your arsenal

00:01:42.340 | that you can use and leverage toward

00:01:44.460 | improving mental health, physical health,

00:01:46.620 | reducing inflammation in the body,

00:01:48.280 | improving athletic performance,

00:01:50.180 | improving mental performance.

00:01:51.820 | I promise to spell out all those protocols in detail

00:01:54.540 | as I go along and to summarize them again at the end.

00:01:57.480 | I'd like to make a point now that I'm going to make

00:01:59.700 | several additional times during today's episode.

00:02:02.500 | And that is that temperature is a very potent stimulus

00:02:06.080 | for the brain and body.

00:02:07.700 | That also means that it carries certain hazards

00:02:10.360 | if it's not done correctly.

00:02:12.100 | Now, everyone shows up to the table, meaning to protocols,

00:02:15.340 | with a different background of health status.

00:02:17.380 | And there's simply no way that I can know

00:02:19.140 | what your health status is.

00:02:20.760 | So anytime you are going to take on a new protocol,

00:02:23.260 | that means a behavioral protocol or a nutritional protocol

00:02:26.680 | or a supplementation protocol,

00:02:28.460 | you should absolutely consult a board certified physician

00:02:31.580 | before initiating that protocol.

00:02:34.060 | I don't just say this to protect us.

00:02:35.340 | I also say this to protect you.

00:02:37.660 | If you'd like to see our medical disclaimer,

00:02:39.460 | you can go to our show notes.

00:02:40.840 | It's described there.

00:02:41.680 | In fact, I encourage you to please do that.

00:02:43.900 | And in general, when embarking on new protocols,

00:02:47.780 | in particular, if they involve strong stimuli,

00:02:50.200 | like changing temperature or placing yourself

00:02:52.240 | into unusual temperatures,

00:02:54.680 | I would encourage you to progress gradually.

00:02:56.880 | I would also encourage you to not look at gradual

00:02:59.740 | progression as the kind of weak version of a protocol.

00:03:03.040 | In fact, today I'm going to discuss a really beautiful

00:03:05.660 | peer-reviewed study that involved having people

00:03:08.880 | do deliberate cold exposure.

00:03:10.380 | So they were immersing themselves into water

00:03:12.460 | up to about their neck.

00:03:13.660 | And the water was actually not that cold.

00:03:15.740 | It was only about 60 degrees Fahrenheit,

00:03:17.540 | which for most people is pretty tolerable.

00:03:19.420 | So nowhere near the kinds of extreme temperatures

00:03:22.060 | that one could use in other protocols.

00:03:25.280 | And the interesting thing is,

00:03:26.560 | despite that fairly modest cold temperature,

00:03:29.960 | by simply extending the duration of time

00:03:31.880 | that people were in that water,

00:03:33.380 | they experienced enormous increases in neurochemicals

00:03:36.480 | that ought to translate to improvements in focus and mood.

00:03:40.500 | And indeed that's what's been observed

00:03:42.620 | in subsequent studies.

00:03:44.520 | So again, please see our medical disclaimer

00:03:46.640 | in our show notes.

00:03:47.760 | Please proceed with caution always.

00:03:50.740 | Please also understand that the most potent stimulus

00:03:54.600 | isn't always the one that you experience

00:03:56.500 | as the most intense in the moment.

00:03:58.240 | In fact, I would encourage you to find the minimum threshold

00:04:01.420 | of stimulus that will allow you to derive

00:04:03.640 | the maximum benefit from each protocol.

00:04:06.320 | And indeed, I will point out what those thresholds

00:04:09.100 | ought to be today.

00:04:10.540 | I'll give you some simple formulas,

00:04:12.440 | gauges or guides that you can use in order to navigate

00:04:15.620 | this extremely interesting and potent tool

00:04:18.360 | that we call deliberate cold exposure.

00:04:20.480 | Before we talk about deliberate cold exposure

00:04:22.340 | and its many powerful applications,

00:04:24.860 | I'd like to highlight a study

00:04:26.160 | that I find particularly interesting

00:04:27.800 | and that I think you will find particularly interesting

00:04:30.400 | and useful.

00:04:31.900 | The title of this study is Brief Aerobic Exercise

00:04:35.320 | Immediately Enhances Visual Attentional Control

00:04:37.820 | and Perceptual Speed,

00:04:39.440 | Testing the Mediating Role of Feelings of Energy.

00:04:43.440 | Now, the reason I like this study is first of all,

00:04:46.880 | it's a fairly large size sample group.

00:04:48.940 | They looked at 101 students.

00:04:52.280 | These were college age students and they had two groups.

00:04:55.720 | One group did 15 minutes of jogging at moderate intensity.

00:05:00.720 | So when they did measure percent heart rates, et cetera,

00:05:04.560 | but this would be analogous to zone two cardio,

00:05:08.420 | which I've discussed on this podcast before.

00:05:10.380 | Zone two cardio is cardiovascular exercise

00:05:14.240 | that places you at a level where you can hold

00:05:17.360 | a conversation with a little bit of strain,

00:05:20.060 | meaning that you can get the words out,

00:05:21.440 | but every once in a while, you have to catch your breath.

00:05:23.400 | Whereas if you were to push any harder

00:05:26.120 | by any mechanism going faster or on a steeper incline,

00:05:28.980 | et cetera, that you would have a hard time

00:05:31.440 | carrying out a conversation.

00:05:32.800 | So zone two cardio is a common form of describing

00:05:37.820 | that level of intensity that they call moderate intensity.

00:05:40.620 | So one group did 15 minutes of jogging at moderate intensity,

00:05:44.280 | which I'm translating to roughly zone two cardio.

00:05:47.780 | The other group did 15 minutes of relaxation concentration

00:05:52.000 | that is somewhat akin to mindfulness meditation.

00:05:55.400 | And then they were analyzed for perceptual speed,

00:05:58.960 | visual attentional control, something called working memory,

00:06:01.680 | which is your ability to keep certain batches

00:06:04.440 | of information online.

00:06:06.440 | Just imagine someone telling you their phone number

00:06:08.880 | and you have to remember that sequence of numbers

00:06:10.760 | in your head for some period of time,

00:06:12.920 | that's working memory.

00:06:13.940 | And it depends very heavily

00:06:15.300 | on the so-called prefrontal cortical networks,

00:06:17.960 | which are involved in planning and action.

00:06:19.960 | And they also looked at people's feelings of energy

00:06:23.100 | and they measured that subjectively,

00:06:24.420 | how energetic people felt.

00:06:26.060 | Now, the major takeaways from the study

00:06:27.980 | that I'd like to emphasize are that the 15 minutes

00:06:30.920 | of jogging group experienced elevated levels of energy

00:06:35.280 | for some period of time after they ceased the exercise.

00:06:38.880 | Whereas the group that did mindfulness meditation

00:06:41.760 | actually reported feeling more calm

00:06:44.120 | and having less overall energy.

00:06:46.720 | Now that's very subjective.

00:06:47.860 | And indeed they used subjective measures to analyze energy.

00:06:52.040 | But what gets interesting is when they looked at performance

00:06:55.020 | on these various cognitive tasks.

00:06:57.340 | And the two tasks that they use

00:06:59.240 | were called the trail making tests.

00:07:01.320 | They have different versions of this, version A, version B.

00:07:03.840 | I don't want to go into too much detail,

00:07:05.680 | but version A essentially involves having a page of numbers

00:07:09.920 | that are distributed somewhat randomly.

00:07:11.860 | So one, two, three, four, five, six, seven, eight,

00:07:13.200 | and so on, but distributed randomly across the page.

00:07:15.920 | And people have to use visual search

00:07:17.540 | to circle those numbers in sequence.

00:07:19.480 | So this involves visual attention.

00:07:21.120 | It involves some motor skills.

00:07:23.480 | It involves a number of things

00:07:24.380 | that certainly require energy and focus.

00:07:27.200 | The second test was the trail making test part B,

00:07:30.280 | as I mentioned earlier.

00:07:31.200 | And this involved also circling numbers in sequence,

00:07:34.000 | but intersperse between those numbers were letters.

00:07:36.480 | So rather than just having to circle off numbers in sequence,

00:07:39.760 | they actually had to connect one, then the letter A,

00:07:42.760 | then two, then the letter B, et cetera.

00:07:44.360 | And remember these are randomly distributed across a page.

00:07:47.400 | The major takeaway from the study

00:07:48.800 | is that the group that did the 15 minutes

00:07:51.760 | of moderate exercise prior to these two tests

00:07:55.220 | showed significant decreases in the amount of time required

00:07:58.720 | to complete these tests accurately.

00:08:01.360 | That is interesting and indeed surprising, at least to me,

00:08:05.280 | because there have been many studies

00:08:07.280 | looking at the effects of mindfulness meditation

00:08:09.200 | on the ability to focus.

00:08:11.160 | The key variable in the study turned out to be energy,

00:08:13.960 | this feeling, subjectively measured feeling, I should say,

00:08:17.560 | of having more energy and thereby the ability to focus,

00:08:20.820 | especially in these high cognitive demand tasks.

00:08:23.720 | Now, the takeaway from this study for all of us,

00:08:25.440 | I think is pretty straightforward.

00:08:27.280 | If you are going to sit down to do some work

00:08:30.120 | that requires focus and working memory

00:08:32.520 | and cognitive attention,

00:08:33.600 | and especially if it's some visual spatial control,

00:08:36.800 | meaning you have to search for things on a page,

00:08:38.420 | you have to organize things on a page,

00:08:39.820 | so this would be writing, arithmetic,

00:08:41.420 | basically cognitive work of any kind,

00:08:44.640 | 15 minutes of moderate exercise done prior to that workout

00:08:49.540 | could be very beneficial for you.

00:08:51.560 | This does not mean that mindfulness meditation

00:08:53.900 | would not be of benefit to you.

00:08:55.400 | I wouldn't want you to conclude that,

00:08:57.200 | but if you had to choose between doing

00:08:58.900 | 15 minutes of mindfulness meditation

00:09:00.840 | and doing 15 minutes of moderate exercise

00:09:02.800 | prior to a cognitive workout,

00:09:05.640 | I would say the 15 minutes of moderate exercise

00:09:08.500 | would be more valuable,

00:09:09.920 | at least based on the data in this paper.

00:09:12.240 | In many previous podcasts,

00:09:14.360 | I've talked about the powerful effects

00:09:16.960 | of doing things like mindfulness meditation

00:09:19.700 | and other forms of NSDR, non-sleep deep breaths,

00:09:22.960 | so these could be 20 minute naps

00:09:24.460 | or just lying there quietly with your eyes closed,

00:09:26.660 | or yoga nidra, or NSDR scripts are available on YouTube

00:09:31.460 | and various other places free of cost of any kind,

00:09:34.620 | you can just go to YouTube,

00:09:35.460 | put in NSDR, non-sleep deep rest.

00:09:37.640 | Those protocols have been shown to be very beneficial

00:09:41.500 | for enhancing neuroplasticity,

00:09:43.860 | the changes in the brain and body that encode

00:09:47.080 | or shift the neural circuits that allow for memory to change

00:09:51.660 | that allow for learning to occur after a learning bout.

00:09:55.720 | What I'm referring to today in this particular study

00:09:58.460 | is the use of moderate exercise

00:10:00.800 | in order to increase one's focus and attention

00:10:03.920 | in order to trigger that neuroplasticity.

00:10:06.760 | So the simple sequence here is get energetic and alert,

00:10:11.200 | do that prior to the learning bout,

00:10:14.160 | engage in the cognitive work or learning bout,

00:10:16.320 | and then mindfulness meditation, NSDR,

00:10:18.840 | and so forth should follow.

00:10:20.660 | And if you would like to access this paper

00:10:23.120 | and like to look more at the details in the paper,

00:10:25.540 | we'll be sure to put a link in the show notes.

00:10:27.240 | The first author is Legrand.

00:10:29.180 | And again, the title of this paper is

00:10:30.580 | "Brief Aerobic Exercise Immediately Enhances

00:10:32.620 | Visual Potential Control and Perceptual Speed,

00:10:34.940 | Testing the Mediating Role of Feelings of Energy."

00:10:37.480 | And I also just want to emphasize immediately,

00:10:40.060 | I think most people out there are interested in tools

00:10:42.100 | and protocols that work the first time

00:10:43.860 | and that work every time.

00:10:44.980 | And indeed, I think this protocol fits that bill.

00:10:47.720 | I'm pleased to announce that I'm hosting

00:10:49.220 | two live events this May.

00:10:51.380 | The first live event will be hosted

00:10:52.900 | in Seattle, Washington on May 17th.

00:10:55.580 | The second live event will be hosted

00:10:57.200 | in Portland, Oregon on May 18th.

00:10:59.580 | Both are part of a lecture series entitled

00:11:01.520 | "The Brain-Body Contract,"

00:11:03.180 | during which I will discuss science

00:11:04.900 | and science-based tools for mental health,

00:11:07.060 | physical health, and performance.

00:11:08.860 | And I should point out that while some of the material

00:11:11.300 | I'll cover will overlap with information covered here

00:11:13.960 | on the Huberman Lab Podcast

00:11:15.580 | and on various social media posts,

00:11:17.420 | most of the information I will cover is going to be distinct

00:11:20.580 | from information covered on the podcast or elsewhere.

00:11:23.460 | So once again, it's Seattle on May 17th,

00:11:25.980 | Portland on May 18th.

00:11:27.340 | You can access tickets by going to HubermanLab.com/tour,

00:11:31.460 | and I hope to see you there.

00:11:32.900 | Before we begin, I'd like to emphasize that this podcast

00:11:35.460 | is separate from my teaching and research roles at Stanford.

00:11:38.280 | It is, however, part of my desire and effort

00:11:40.380 | to bring zero cost to consumer information about science

00:11:43.100 | and science-related tools to the general public.

00:11:45.780 | In keeping with that theme,

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00:15:37.260 | Okay, let's talk about the use of cold

00:15:38.860 | for health and performance.

00:15:40.540 | I confess I love this topic

00:15:42.480 | because it takes me back to my undergraduate years

00:15:45.580 | when I worked in a laboratory studying cold physiology,

00:15:49.540 | its effects on the brain and its effects on the body.

00:15:52.620 | And over the years,

00:15:53.980 | I've always kept track of the literature in this area,

00:15:56.740 | and indeed there have been some tremendous discoveries,

00:15:59.780 | both in animal models, so in rodents like mice and rats,

00:16:02.780 | but also in humans.

00:16:04.540 | And today we're going to talk about

00:16:06.080 | both categories of studies,

00:16:07.740 | and I will be careful to point out

00:16:09.460 | when discoveries were made in animal models

00:16:11.880 | and when they were made in humans.

00:16:14.140 | A key point when thinking about the use of cold as a tool,

00:16:19.740 | and the key point is

00:16:21.820 | that you have a baseline level of temperature

00:16:25.080 | that is varying, changing across the 24-hour cycle.

00:16:29.440 | So any use of deliberate cold exposure

00:16:32.220 | is going to be superimposed on that rhythm,

00:16:36.120 | that circadian rhythm, meaning that 24-hour rhythm.

00:16:40.380 | The basic contour of your circadian rhythm in temperature

00:16:44.700 | is that approximately two hours before the time you wake up

00:16:49.520 | is your so-called temperature minimum.

00:16:51.880 | So your temperature minimum is a time

00:16:54.360 | within the 24-hour cycle

00:16:56.140 | when your body temperature is at its lowest, okay?

00:16:59.860 | So if you normally wake up around 6 a.m.,

00:17:03.200 | your temperature minimum is probably about 4 a.m.

00:17:07.380 | If you normally wake up at about 7 a.m.,

00:17:09.960 | your temperature minimum is probably about 5 a.m.

00:17:13.140 | It's not exactly two hours before your wake-up time,

00:17:16.180 | it's approximately two hours before your wake-up time.

00:17:19.220 | Now, as you go from your temperature minimum

00:17:22.660 | to the time in which you are going to awake,

00:17:25.060 | your temperature is rising slightly.

00:17:27.940 | And then at the point where you wake up,

00:17:30.380 | your temperature starts to go up more sharply

00:17:33.280 | and will continue to go up into the early

00:17:35.800 | and sometimes even into the late afternoon.

00:17:38.560 | And then sometime in the late afternoon and evening,

00:17:41.320 | your temperature will start to decline.

00:17:44.700 | And indeed, as you approach sleep,

00:17:46.680 | your body temperature will drop

00:17:48.180 | by anywhere from one to three degrees.

00:17:50.720 | And in fact, that decrease in core body temperature

00:17:53.940 | is important, if not essential,

00:17:55.660 | for getting into and staying in deep sleep, okay?

00:17:58.940 | So temperature rises with waking, that's easy to remember.

00:18:02.780 | It tends to continue to rise throughout the day.

00:18:05.540 | And in the late afternoon and evening,

00:18:07.260 | your temperature will start to go down

00:18:09.500 | and the drop in temperature actually helps you access sleep.

00:18:13.820 | That background, or what we call baseline circadian rhythm

00:18:18.220 | in core body temperature is important to remember

00:18:21.140 | because it helps us frame both the effects

00:18:24.260 | of deliberate cold exposure

00:18:26.340 | and it helps us frame when you might want

00:18:29.620 | to use deliberate cold exposure

00:18:31.060 | in order to access specific states.

00:18:33.540 | It also points to times within the 24 hour cycle

00:18:36.700 | when you might want to avoid using deliberate cold exposure

00:18:39.780 | if your primary goal is to get to sleep.

00:18:42.480 | Okay, so that's the circadian rhythm in temperature.

00:18:45.540 | Now I just briefly want to touch on thermal regulation

00:18:48.780 | at the level of the body and the brain.

00:18:51.060 | And this will be very surprising to many of you.

00:18:55.200 | Let's do what's called a Gedanken experiment,

00:18:57.460 | which is a thought experiment.

00:18:58.920 | Let's say I send you out into the desert heat

00:19:01.880 | for a jog or a run, and it's very hot outside,

00:19:05.220 | you know, 102 degrees or 103 degrees.

00:19:08.680 | And you start to move, you start to sweat,

00:19:12.220 | and of course your core body temperature goes up.

00:19:14.860 | Now, then I offer you a cold towel,

00:19:18.840 | maybe a really, really cold towel,

00:19:21.060 | and this towel is saturated with water

00:19:22.820 | so you could actually squeeze the water out of that

00:19:24.700 | and cool your body off.

00:19:26.320 | And our Gedanken experiment is for me to say,

00:19:28.760 | okay, where are you going to place the towel?

00:19:31.440 | How are you going to cool yourself off?

00:19:33.780 | And I'm guessing that most of you would think

00:19:35.860 | that the best way to cool yourself off

00:19:37.560 | would be to drape that towel over your head,

00:19:39.500 | maybe your neck, over your torso,

00:19:42.000 | that it would feel really, really good

00:19:43.280 | and they would cool you off.

00:19:45.340 | Well, that's exactly the wrong approach

00:19:48.220 | if you want to cool off.

00:19:49.300 | And in fact, if you were to use that approach,

00:19:52.080 | your body temperature would continue to increase even more,

00:19:56.580 | yes, even more than had you not placed that cold towel

00:20:00.300 | on your head or your torso.

00:20:02.540 | And here is why.

00:20:04.440 | Thermal regulation, meaning your brain and body's ability

00:20:07.380 | to regulate your internal core temperature

00:20:10.920 | is somewhat like a thermostat,

00:20:12.500 | and that thermostat resides in your brain.

00:20:15.140 | So if you think about the thermostat

00:20:16.620 | in your home or apartment,

00:20:18.640 | if it's too warm in your home or apartment,

00:20:22.540 | and you were to take a bag of ice

00:20:24.820 | and to put it on that thermostat,

00:20:27.600 | what would the thermostat do?

00:20:29.060 | It would register the environment as artificially cool.

00:20:32.620 | It would think that the environment

00:20:34.640 | was actually much colder than it is.

00:20:37.940 | And so as a consequence, it would trigger a mechanism

00:20:41.000 | to further increase the temperature in the room.

00:20:43.500 | And you have such a thermostat as well.

00:20:45.500 | It's called the medial preoptic area of the hypothalamus,

00:20:48.500 | the hypothalamus is a small region of brain tissue

00:20:52.140 | about over the roof of your mouth

00:20:54.060 | and a little bit in front of that.

00:20:56.180 | So it's basically right behind your nose

00:20:59.500 | and over the roof of your mouth,

00:21:01.200 | and it's a collection of neurons.

00:21:02.620 | Those neurons have a lot of different functions

00:21:04.520 | that include things like the control of aggression,

00:21:07.500 | the control of sex behavior,

00:21:09.200 | the control of temperature regulation, and so on.

00:21:11.680 | The medial preoptic area has connections

00:21:14.960 | with the rest of the brain

00:21:17.240 | or areas within the brain, I should say,

00:21:19.060 | and with many areas within the body,

00:21:21.460 | it receives input from receptors in our skin

00:21:26.100 | and inside our body that register temperature,

00:21:29.560 | and it acts as a thermostat.

00:21:31.280 | So if the surface of your body is made cool,

00:21:34.540 | your medial preoptic area will send signals

00:21:38.380 | by way of hormones and by way of chemicals

00:21:41.700 | that will serve to heat your body up.

00:21:44.620 | So what this means is that if you want to cool down,

00:21:47.220 | the last thing you want to do

00:21:48.980 | is to bring a cold surface of any kind,

00:21:52.780 | towel or splashing water,

00:21:54.560 | to the majority of your body surface.

00:21:57.180 | It might be very, very surprising to you,

00:21:59.060 | and you might say, wait, if I want to cool down,

00:22:00.880 | I should jump into a cold lake or something of that sort.

00:22:02.940 | That's a different thing altogether.

00:22:05.500 | What I'll tell you,

00:22:06.480 | and we'll get into this in more depth later,

00:22:08.280 | is that if you really want to cool down

00:22:09.900 | quickly and efficiently,

00:22:11.320 | you should leverage particular portals,

00:22:14.780 | meaning particular sites on your body

00:22:18.160 | where heat can leave your body more readily

00:22:21.660 | and where cooling can have a dramatic and fast impact

00:22:26.100 | on your core body temperature.

00:22:27.160 | It can even save your life if you're going hyperthermic.

00:22:29.400 | We're going to talk more about the specific protocols

00:22:31.940 | to reduce core body temperature for sake of performance

00:22:34.620 | and avoiding hyperthermia later in the episode.

00:22:37.500 | Hyperthermia, of course, is a very, very dangerous situation

00:22:40.580 | because while your body can drop in core temperature

00:22:44.160 | somewhat and still be safe,

00:22:45.820 | you can't really increase your body temperature that much

00:22:48.440 | before your brain starts to cook

00:22:50.020 | and other organs start to cook.

00:22:51.400 | And by cook, I mean, the cells actually start to die.

00:22:54.140 | So you have to be very, very careful with the use of heat.

00:22:56.900 | Heat stroke is no joke.

00:22:58.420 | People die from heat stroke all the time.

00:23:00.260 | You really want to avoid that.

00:23:02.340 | One way to avoid that

00:23:03.740 | is to cool the appropriate surfaces of your body.

00:23:07.540 | And the appropriate surfaces in this case

00:23:10.020 | are the upper cheeks,

00:23:11.860 | or I would say the upper half of the face,

00:23:14.520 | the palms of your hands, and the bottoms of your feet.

00:23:16.480 | I've talked about this on the podcast before

00:23:18.560 | and in the guest episode with Dr. Craig Heller,

00:23:20.900 | my colleague in the biology department at Stanford.

00:23:23.840 | But just very briefly, these surfaces,

00:23:26.480 | the upper half of the face,

00:23:28.340 | the palms of the hands and the bottoms of the feet

00:23:31.080 | are what we call glabrous skin surfaces,

00:23:34.940 | G-L-A-B-R-O-U-S, glabrous.

00:23:38.340 | And those surfaces are unique

00:23:40.980 | in that just below them,

00:23:42.660 | the vasculature is different than elsewhere in the body.

00:23:46.100 | Normally, the passage of blood

00:23:47.560 | goes from arteries to capillaries to veins,

00:23:50.620 | but just beneath the glabrous skin

00:23:53.860 | on the bottoms of the feet,

00:23:54.700 | the hands and the upper half of the face,

00:23:56.240 | you have what are called arteriovenous astomoses.

00:23:59.940 | These are portals of blood

00:24:02.220 | that go directly from arteries to veins.

00:24:04.140 | And in doing so, allow the body

00:24:07.080 | to dump heat more readily, more quickly.

00:24:10.700 | So as it turns out,

00:24:13.080 | that if you are to cool the palms of the hands,

00:24:15.640 | the bottoms of the feet and the upper half of the face,

00:24:17.440 | you can more efficiently reduce core body temperature

00:24:20.640 | for sake of offsetting hyperthermia

00:24:23.160 | and for improving athletic performance

00:24:25.380 | and maybe even cognitive performance.

00:24:27.280 | So we will return to the specific protocols

00:24:29.120 | for doing that later in the episode.

00:24:31.240 | I'll give you a lot of details about how to do that,

00:24:34.100 | how to do that without the use of any fancy

00:24:36.520 | or expensive technology.

00:24:38.240 | There are some technologies

00:24:39.360 | that are now commercially available.

00:24:41.400 | For instance, the so-called cool-mit

00:24:43.000 | that will allow you to do that with maximum efficiency,

00:24:45.160 | but I'll also give you some at-home methods to do this

00:24:48.560 | either in the gym or on runs or for sake of cognitive work.

00:24:51.640 | Okay, so the two key themes, again,

00:24:54.200 | are understand that baseline circadian rhythm in temperature

00:24:58.480 | and understand that the best way to cool the body

00:25:01.720 | is going to be by making sure that something cold contacts

00:25:06.720 | the bottoms of your feet, the palms of your hands

00:25:09.520 | and the upper half of the face.

00:25:10.480 | Ideally all three if your goal

00:25:11.860 | is to lower core body temperature quickly.

00:25:13.880 | And again, just cooling off the back of your neck

00:25:17.120 | or the top of your head or your torso with a towel

00:25:19.360 | is going to be the least efficient way

00:25:21.360 | to lower core body temperature

00:25:22.920 | and might even increase body temperature

00:25:25.780 | under certain conditions.

00:25:27.040 | Okay, with those two points in mind,

00:25:28.840 | we can start to think about

00:25:30.080 | directed deliberate cold exposure protocols.

00:25:32.640 | And there are a number of different reasons

00:25:34.740 | to use deliberate cold exposure.

00:25:36.800 | And I want to separate those out for you.

00:25:38.840 | There are cold protocols that have been tested

00:25:42.820 | in peer-reviewed studies

00:25:44.040 | that are designed to improve mental performance.

00:25:47.120 | They are designed to improve things like resilience

00:25:49.820 | or your grittiness or your ability to move through challenge

00:25:52.520 | or to regulate your mind and your internal state

00:25:56.280 | under conditions of stress.

00:25:57.800 | And we can define stress very specifically

00:26:00.280 | as times when adrenaline also called epinephrine

00:26:03.800 | and or norepinephrine also called noradrenaline

00:26:09.240 | are elevated in your body.

00:26:10.560 | Forgive me for the noradrenaline, norepinephrine,

00:26:13.460 | adrenaline, epinephrine nomenclature.

00:26:15.240 | I didn't make that up.

00:26:16.480 | It turns out that every once in a while scientists disagree.

00:26:19.040 | Imagine that.

00:26:20.060 | And you'll get multiple scientists

00:26:21.760 | naming the same molecule different things.

00:26:23.560 | Okay, so epinephrine and adrenaline are the same thing.

00:26:26.600 | I will use them interchangeably.

00:26:28.320 | Norepinephrine and noradrenaline are the same thing.

00:26:31.200 | I will use those terms interchangeably.

00:26:34.360 | Noradrenaline and adrenaline are often co-released

00:26:37.120 | in the brain and body.

00:26:38.080 | So they work as kind of a pair

00:26:40.560 | to increase our level of agitation, our level of focus

00:26:44.080 | and our desire and our ability to move.

00:26:47.400 | They are often co-released from different sites

00:26:50.440 | in the brain and body with dopamine,

00:26:52.840 | a molecule that is commonly misunderstood

00:26:56.680 | as the molecule of pleasure,

00:26:58.000 | but is actually the molecule of motivation,

00:27:00.320 | reward and pursuit.

00:27:02.720 | So dopamine, norepinephrine and noradrenaline

00:27:04.920 | tend to be released together under certain conditions.

00:27:08.180 | And today you will learn how deliberate cold exposure

00:27:11.160 | can be used to cause increases in the release of several,

00:27:15.280 | if not all of these in ways that can improve

00:27:17.820 | your levels of attention and your mood.

00:27:20.960 | But the key point is that your mental state is shifted

00:27:25.960 | when you are exposed to certain forms of cold.

00:27:29.800 | And many people use deliberate cold exposure specifically

00:27:33.340 | to shift their body state as a way to train

00:27:36.160 | their mental state so that they can better cope

00:27:38.900 | with stress in real life.

00:27:40.440 | And by real life, I mean,

00:27:41.840 | when life presents stressful events.

00:27:43.880 | And I will give you specific protocols

00:27:45.760 | as to how you can do that.

00:27:47.140 | In other words, how you can become more resilient

00:27:49.640 | through the use of deliberate cold exposure.

00:27:52.160 | Now, because of the ways in which deliberate cold exposure

00:27:55.400 | can increase this category of chemicals

00:27:57.800 | called the catecholamines,

00:27:58.880 | that includes dopamine, norepinephrine and epinephrine.

00:28:01.680 | It can also be used to elevate mood

00:28:05.840 | for long periods of time.

00:28:07.720 | And I'm going to discuss a specific protocol

00:28:10.080 | that has been shown to increase these chemicals

00:28:13.040 | anywhere from 2.5 X, so 250% to as high as 500%

00:28:18.040 | five times over baseline.

00:28:23.040 | Now you might be asking whether or not it's a good thing

00:28:26.300 | to raise chemicals like norepinephrine and dopamine

00:28:29.140 | to such a great degree,

00:28:31.140 | whether or not that's healthy for us,

00:28:32.460 | whether or not they can harm us.

00:28:34.060 | But it turns out that these elevations

00:28:36.020 | in norepinephrine and dopamine are very long lasting

00:28:39.000 | in ways that people report feeling vast improvements

00:28:43.060 | in mood and vast improvements

00:28:45.140 | in levels of cognitive attention

00:28:47.660 | and energy.

00:28:48.720 | So by my read of the literature,

00:28:50.880 | these seem to be healthy increases

00:28:52.980 | in our baseline levels of these chemicals

00:28:56.520 | in ways that can really support us.

00:28:57.720 | So I'll give you a protocol for that.

00:28:59.760 | Now, those are some of the mental effects

00:29:01.720 | of deliberate cold exposure.

00:29:03.200 | But deliberate cold exposure has also been studied

00:29:05.460 | in animal models and in humans

00:29:07.000 | in the context of increasing metabolism.

00:29:09.840 | Even in converting certain fat cells

00:29:12.940 | that we call white fat cells,

00:29:14.280 | which are the ones where energy is stored,

00:29:16.080 | the ones that we typically think of as kind of blubbery fat,

00:29:19.440 | to beige or brown fat, which is thermogenic fat,

00:29:23.280 | meaning that it can increase core body temperature

00:29:25.380 | and serves as kind of the furnace

00:29:27.640 | by which we increase our core metabolism.

00:29:31.000 | So with a very broad stroke,

00:29:33.160 | I can say that white fat is generally the kind of fat

00:29:35.620 | that people want less of,

00:29:37.060 | and beige fat and brown fat is generally the kind of fat

00:29:40.140 | that if you're going to have fat cells

00:29:42.540 | and you certainly need fat cells that you want more of,

00:29:45.300 | they are thermogenic, they help you stay lean,

00:29:47.560 | they actually serve as a reservoir for heating your body up

00:29:50.080 | if you're ever confronted with a cold challenge.

00:29:52.140 | So we're going to talk about how to use cold

00:29:53.920 | for metabolism as well.

00:29:55.540 | And of course, people are using deliberate cold exposure

00:29:57.920 | to reduce inflammation post-exercise,

00:29:59.960 | to reduce inflammation generally.

00:30:01.840 | And people are also using cold to enhance performance

00:30:06.520 | in the context of strength training,

00:30:08.520 | in the context of endurance training,

00:30:10.120 | and we'll talk about those data as well.

00:30:12.440 | But where I'd like to start is with mental performance.

00:30:14.920 | And I'd like to detail what happens

00:30:18.280 | when we deliberately expose ourselves to cold.

00:30:21.420 | It's key to point out the word deliberate.

00:30:24.600 | If I don't say otherwise, then throughout this episode,

00:30:27.600 | if I say cold exposure, I mean deliberate cold exposure.

00:30:30.720 | And the reason I point that out

00:30:32.140 | is that as my colleague David Spiegel

00:30:33.680 | in the Department of Psychiatry at Stanford says,

00:30:36.120 | it's not just about the state that we are in,

00:30:38.560 | it's about the state that we are in

00:30:39.940 | and whether or not we had anything to do

00:30:41.720 | with placing ourselves into that state

00:30:43.880 | and whether or not we did that on purpose or not.

00:30:45.880 | And what he really means by that statement

00:30:48.680 | is that there are important effects of what we call mindset.

00:30:53.080 | Mindset was a topic discussed in the guest episode

00:30:56.340 | with Ali Krum some weeks ago.

00:30:58.620 | If you haven't seen that episode, I highly recommend it.

00:31:01.220 | And the science of mindset tells us

00:31:03.400 | that if we are doing something deliberately

00:31:06.180 | and we believe that it's going to be good for us,

00:31:08.600 | it actually can lead to a different set

00:31:11.400 | of physiological effects than if something is happening

00:31:15.720 | to us against our will or without our control.

00:31:18.800 | Now, this is different than placebo effects.

00:31:20.600 | Placebo effects are distinct from mindset effects.

00:31:23.880 | If you want to learn more about the distinction,

00:31:25.320 | please see the episode with Ali Krum.

00:31:27.240 | But again, when I talk about cold exposure in this episode,

00:31:30.320 | I'm talking about deliberate cold exposure,

00:31:33.240 | meaning that you are placing yourself

00:31:35.260 | into a cold environment on purpose

00:31:37.680 | in order to extract a particular set of benefits.

00:31:41.640 | When we talk about deliberate cold exposure,

00:31:44.960 | almost always that means getting uncomfortable.

00:31:48.080 | And one of the most common questions I get

00:31:50.040 | when discussing the use of cold

00:31:51.880 | for sake of mental or physical performance,

00:31:53.440 | metabolism, et cetera, is how cold should it be?

00:31:57.320 | How cold should the water be?

00:31:58.440 | How cold should the environment be?

00:32:00.900 | And I just will tell you now,

00:32:02.280 | and I'm going to say this again and again

00:32:03.720 | throughout the episode,

00:32:04.560 | 'cause it will continue to be true throughout the episode

00:32:06.820 | and long after the episode is over,

00:32:09.560 | how cold depends on your cold tolerance,

00:32:12.820 | your core metabolism, and a number of other features

00:32:15.920 | that there is simply no way I could know or have access to.

00:32:20.440 | So I would like you to use this rule of thumb.

00:32:22.880 | If you are using deliberate cold exposure,

00:32:27.340 | the environment that you place yourself into

00:32:30.760 | should place your mind into a state of,

00:32:33.260 | "Whoa, I would really like to get out of this environment,

00:32:36.800 | but I can stay in safely."

00:32:39.240 | Okay, now that might seem a little bit arbitrary,

00:32:41.220 | but let's say you were to get into a warm shower

00:32:43.560 | and it would feel really, really nice,

00:32:45.140 | and you were to start turning down the warm

00:32:47.080 | and turning up the cold,

00:32:48.360 | there would be some threshold

00:32:49.700 | at which it would feel uncomfortable to you.

00:32:52.560 | And if you were to continue

00:32:53.700 | to make a little bit colder than that,

00:32:55.540 | you would really want to get out of the shower,

00:32:57.600 | but you were confident that you could stay in

00:33:00.120 | without risking your health, right?

00:33:02.560 | Without risking a heart attack.

00:33:04.040 | Now that's very different

00:33:05.080 | than jumping into a very, very cold lake

00:33:07.820 | or I've seen these images of people

00:33:10.560 | that will cut holes into frozen over lakes

00:33:13.720 | and they'll get into that cold water.

00:33:16.000 | If you are trained to do that

00:33:17.200 | and you have the right conditions, et cetera,

00:33:19.120 | that can be done reasonably safely,

00:33:21.240 | but that's certainly not what I would start with.

00:33:23.740 | And for many people, that will be too cold.

00:33:25.540 | And indeed, some people can go into cold shock

00:33:28.640 | and can die as a consequence of getting

00:33:30.140 | to that extremely cold water very quickly.

00:33:32.200 | Now that's not to scare you away

00:33:33.400 | from deliberate cold exposure.

00:33:34.840 | It's just to say that there's no simple prescriptive

00:33:38.260 | of how cold to make the environment

00:33:39.820 | in order to extract maximum benefit

00:33:43.220 | for mental or physical performance.

00:33:46.220 | So the simple rule of thumb is going to be

00:33:49.220 | place yourself into an environment

00:33:51.120 | that is uncomfortably cold,

00:33:53.540 | but that you can stay in safely, okay?

00:33:55.260 | And you'll have to experiment a bit.

00:33:56.380 | And that number,

00:33:57.940 | meaning that temperature will vary from day to day.

00:34:00.180 | It will vary across the 24 hour cycle

00:34:03.420 | because of that endogenous, meaning that internal rhythm

00:34:06.880 | in temperature that I talked about earlier.

00:34:09.200 | Low early in the day rises

00:34:10.620 | into the afternoon drops at night.

00:34:12.440 | You can actually do this experiment if you like.

00:34:14.860 | Try getting into a cold shower at 11 o'clock at night

00:34:17.680 | if you want versus try doing it

00:34:20.480 | in the middle of the afternoon.

00:34:21.980 | It's quite a different experience.

00:34:24.240 | And by quite a different experience,

00:34:25.580 | I mean it requires quite a different degree of resilience

00:34:29.580 | and leaning into the practice.

00:34:31.060 | Your willpower will have to be higher, I suspect,

00:34:35.620 | late in the day as compared to early in the day.

00:34:39.800 | But that will vary, of course, between individuals as well.

00:34:42.700 | So the most common question I get

00:34:43.940 | about deliberate cold exposure

00:34:45.260 | is how cold should the water be?

00:34:48.060 | And we've answered that with uncomfortably cold

00:34:50.820 | to the point where you want to get out,

00:34:51.920 | but you can safely stay in.

00:34:53.780 | The second most common question I get

00:34:55.460 | about deliberate cold exposure

00:34:57.120 | is whether or not cold showers are as good, better,

00:35:00.140 | or worse than cold water immersion up to the neck.

00:35:03.420 | For instance, I also get a lot of questions

00:35:05.400 | about whether or not cryo chambers

00:35:07.300 | are better than all the others, et cetera, et cetera.

00:35:10.260 | I'm going to make all of that very simple for you

00:35:12.700 | by saying cold water immersion up to the neck

00:35:15.580 | with your feet and hands submerged also

00:35:18.220 | is going to be the most effective.

00:35:20.040 | Second best would be cold shower.

00:35:23.700 | Third best would be to go outside

00:35:26.020 | with a minimum amount of clothing,

00:35:28.720 | but of course, clothing that is culturally appropriate

00:35:32.060 | and that would allow you to experience cold

00:35:35.100 | to the point where you would almost want to shiver

00:35:37.040 | or start shivering.

00:35:38.420 | Now, there are a number of different important constraints

00:35:41.340 | that are going to dictate whether or not

00:35:42.800 | you use one form of cold exposure or the other.

00:35:45.380 | For instance, some people don't have access

00:35:46.980 | to cold water immersion.

00:35:48.000 | They don't have access to ice baths or cold water tanks,

00:35:53.000 | cold ocean or cold lakes, et cetera.

00:35:55.180 | In that case, showers would be the next best solution.

00:35:58.760 | I do want to emphasize that there have been very few,

00:36:01.180 | if any, studies of cold showers.

00:36:04.360 | And you can imagine why this would be the case.

00:36:07.200 | In a laboratory, you want to control

00:36:08.600 | for as many variables as possible.

00:36:10.960 | So placing people into a cold water immersion

00:36:15.440 | or an ice bath up to the neck and insisting

00:36:17.260 | that they keep their hands and feet under

00:36:19.400 | is very easy to control.

00:36:21.240 | It means that everyone can do essentially the same thing,

00:36:23.580 | whereas with cold showers, people are different sized bodies.

00:36:27.280 | Some people are going to put their head under,

00:36:28.580 | some people are going to lean forward.

00:36:31.240 | Measuring the amount of cold water exposure

00:36:33.480 | on the body is very hard to do.

00:36:35.080 | And so there aren't a lot of studies of cold showers,

00:36:38.240 | but of course, a lot of people don't have access

00:36:40.560 | to cold water immersion, so they have to use cold showers.

00:36:43.400 | And if you don't have access to both, of course,

00:36:45.400 | then going outside on a cold day can be of benefit.

00:36:49.520 | But I will point out that the heat transfer

00:36:53.400 | from your body into water is much higher,

00:36:56.980 | four times greater, if not even greater,

00:37:00.720 | depending on the temperature of the water,

00:37:02.400 | in water as opposed to in air.

00:37:04.360 | So it's going to be much more efficient

00:37:05.900 | to do cold water immersion than anything else,

00:37:07.760 | cold showers after that,

00:37:09.160 | and put yourself into a cold environment

00:37:11.680 | would be the third best thing.

00:37:13.380 | I'm not going to get into cryo chambers

00:37:15.000 | because they carry quite a high degree of cost.

00:37:18.240 | And again, there aren't many studies of them.

00:37:20.620 | So if you have access to cryo chambers,

00:37:23.060 | I'm sure that the cryo chamber facility

00:37:24.740 | has told you about all these incredible benefits,

00:37:26.340 | and I don't doubt that some of those benefits truly exist,

00:37:29.040 | but most people just don't have the resources

00:37:31.340 | or the access to those.

00:37:32.380 | So we're going to leave cryo chambers

00:37:33.640 | out of today's discussion.

00:37:34.940 | And of course, I realize there's a fourth category

00:37:37.100 | of cold exposure out there.

00:37:38.400 | People who are wearing ice vests,

00:37:39.860 | believe it or not, those exist.

00:37:40.880 | Ice underwear, yes, those exist.

00:37:43.400 | You can look for them on Amazon if you like.

00:37:46.760 | They are putting cold packs in their armpits

00:37:49.340 | or in their groin or elsewhere in order to stimulate

00:37:52.620 | some of the effects of cold

00:37:54.460 | on mental and physical performance.

00:37:56.780 | I'm not going to address those in too much detail today.

00:37:59.940 | They can be efficient in certain ways,

00:38:02.420 | but as you'll learn about later in the episode,

00:38:04.900 | cooling the palms, the upper face,

00:38:07.460 | and the bottoms of the feet

00:38:08.620 | is going to be far more efficient.

00:38:10.400 | And unfortunately, I think most of the people

00:38:12.860 | that are using ice packs to increase their core metabolism

00:38:15.340 | are not aware of the glabber skin cooling

00:38:18.420 | and how it can be a very, very potent stimulus.

00:38:20.820 | We'll return to that later.

00:38:23.100 | Unless I say otherwise, I'm mainly going to be focusing

00:38:25.820 | on cold water immersion and cold showers.

00:38:28.000 | So let's talk about protocols

00:38:29.460 | for enhancing mental health and performance

00:38:31.700 | using deliberate cold exposure.

00:38:33.540 | What happens when we get into cold

00:38:37.460 | is that we experience an increase in norepinephrine,

00:38:41.460 | in noradrenaline release and in adrenaline release.

00:38:44.500 | The fact that cold exposure, deliberate or no,

00:38:47.180 | increases norepinephrine and epinephrine

00:38:50.140 | in our brain and body

00:38:51.740 | means that it is a very reliable stimulus

00:38:54.400 | for increasing norepinephrine and epinephrine.

00:38:56.540 | That's sort of an obvious statement,

00:38:58.400 | but that obvious statement can be leveraged

00:39:02.020 | to systematically build up what we call resilience.

00:39:05.540 | Now, when we experience a stressor in life,

00:39:08.660 | whether or not it's something bad happens

00:39:10.800 | in our relationship or something bad happens in the world

00:39:14.100 | and we feel stress,

00:39:16.340 | that stress is the consequence of increases

00:39:18.460 | in norepinephrine and epinephrine in our brain and body.

00:39:21.980 | Very similar, if not identical,

00:39:23.660 | to the kinds of increases

00:39:24.720 | that come from deliberate cold exposure.

00:39:27.180 | So deliberate cold exposure is an opportunity

00:39:29.940 | to deliberately stress our body.

00:39:32.940 | And yet, because it's deliberate

00:39:34.520 | and because we can take certain steps,

00:39:36.000 | which I'll describe in a moment,

00:39:38.340 | we can learn to maintain mental clarity.

00:39:41.840 | We can learn to maintain calm

00:39:44.300 | while our body is in a state of stress.

00:39:47.500 | And that can be immensely useful

00:39:49.800 | when encountering stressors in other parts of life.

00:39:53.300 | And that's what we call resilience or grit,

00:39:55.540 | our ability or mental toughness,

00:39:57.460 | our ability to lean into challenge or to tolerate challenge

00:40:01.580 | while keeping our heads straight, so to speak.

00:40:04.140 | So one simple protocol for increasing resilience

00:40:07.700 | is to pick a temperature that's uncomfortable,

00:40:10.400 | of shower or cold immersion,

00:40:12.540 | and then to get in for a certain duration of time

00:40:15.820 | and then to get out.

00:40:17.200 | Now, it's important to understand

00:40:18.240 | that people will experience different levels

00:40:20.160 | of norepinephrine and adrenaline release

00:40:22.320 | when getting into cold water.

00:40:24.140 | Some people, because they dread the cold so much,

00:40:27.980 | will actually experience norepinephrine

00:40:29.880 | and epinephrine increases even before they get

00:40:32.360 | into the cold water or under the cold shower.

00:40:35.100 | Now, you may have experienced this.

00:40:36.240 | I've certainly experienced this.

00:40:37.900 | I'm dreading it, I don't want to do it,

00:40:39.540 | and I have to force myself to do it.

00:40:41.820 | And indeed, epinephrine and norepinephrine and its surges

00:40:45.580 | can be thought of as sort of walls

00:40:47.840 | that we have to confront and go over.

00:40:49.920 | And I'd like you to conceptualize them that way

00:40:52.020 | because it allows us to build protocols

00:40:54.580 | that can be very objective and can allow us

00:40:58.080 | to monitor our progress in terms of building resilience.

00:41:01.240 | So one option is to simply say, okay,

00:41:04.140 | I'm going to force myself to get into the cold shower

00:41:06.500 | for one minute.

00:41:07.700 | How cold?

00:41:08.540 | Again, uncomfortably cold, but you can stay in safely.

00:41:10.440 | Or I'm going to get into the ice bath for one minute.

00:41:13.680 | Ice baths are very cold inevitably.

00:41:16.820 | And what is also inevitable is that when you get

00:41:20.020 | into the cold, you will experience a surge

00:41:22.360 | in epinephrine and norepinephrine.

00:41:24.080 | That's non-negotiable because it's mediated

00:41:26.680 | by cold receptors on the surface of your body and your skin

00:41:30.060 | and the way that they trigger the release of norepinephrine

00:41:32.880 | and epinephrine, not just from the adrenals,

00:41:35.260 | from the adrenal glands above your kidneys,

00:41:37.220 | but also from regions of your brain,

00:41:38.780 | like the locus coeruleus,

00:41:39.940 | which cause increases in attention and alertness,

00:41:42.900 | and from other locations in your body

00:41:45.280 | where epinephrine and norepinephrine are released.

00:41:47.120 | In other words, cold is a non-negotiable stimulus

00:41:51.740 | for increasing epinephrine and norepinephrine.

00:41:55.080 | Even if you are the toughest person in the world

00:41:57.980 | and you love the cold, that increase in epinephrine

00:42:01.780 | and norepinephrine is going to happen.

00:42:04.020 | So the way to think about norepinephrine and epinephrine

00:42:06.700 | in this context of building mental resilience

00:42:09.220 | is that you have two options.

00:42:11.440 | You can either try to extend the duration of time

00:42:15.320 | that you are in the deliberate cold exposure.

00:42:17.440 | So going from one minute to 75 seconds to two minutes

00:42:20.980 | and so on over a period of days,

00:42:23.380 | or one way to approach this

00:42:26.120 | and the way that I particularly favor

00:42:27.840 | is to take the context of the day and the moment

00:42:31.520 | into account, meaning we have different levels of grit

00:42:35.000 | and resilience on different days

00:42:37.160 | and depending on the landscape of our life at the time,

00:42:39.740 | even the time of day that we're doing these protocols

00:42:42.100 | and start to be able to sense

00:42:44.500 | the release of epinephrine, excuse me,

00:42:47.380 | and norepinephrine in our brain and body

00:42:49.620 | and see those as walls that we want to climb over

00:42:52.480 | in order to build resilience

00:42:53.860 | and to start counting the number of walls that we traverse

00:42:57.900 | and the distance between those walls

00:42:59.740 | as we do deliberate cold exposure.

00:43:01.680 | Let me give you an example of the timed protocol

00:43:05.260 | because that one is very straightforward,

00:43:06.840 | although I do not think it is as powerful

00:43:09.560 | for building mental resilience.

00:43:11.000 | The time protocol would be Monday,

00:43:12.880 | I do one minute of deliberate cold exposure

00:43:15.320 | at a given temperature.

00:43:16.160 | Wednesday, I extend that by 50%.

00:43:18.400 | And Friday, I do deliberate cold exposure

00:43:21.680 | for twice as long as I did on Monday.

00:43:23.800 | And if I were to continue that every week,

00:43:26.200 | Monday, Wednesday, Friday,

00:43:27.060 | I would continue to either increase the duration

00:43:29.480 | or I would lower the temperature and reduce the duration.

00:43:34.120 | This kind of thing, very much like sets and reps in the gym.

00:43:36.480 | Now that option is very objective, right?

00:43:38.660 | You could even log it in a book.

00:43:40.280 | And as you develop the ability to stay in cold temperatures,

00:43:44.960 | even progressively colder and colder temperatures

00:43:48.160 | for longer and longer periods of time,

00:43:50.200 | you will become more resilient.

00:43:52.440 | What do I mean by that?

00:43:53.600 | Well, my operational definition of resilience

00:43:55.600 | is that you are able to resist escape from the stressor,

00:43:59.120 | the cold, by virtue of your willpower,

00:44:02.880 | which is really your prefrontal cortex

00:44:05.760 | causing top-down control on your reflexes

00:44:08.800 | and your limbic system and your hypothalamus,

00:44:10.800 | which are basically telling you

00:44:11.820 | to get out of that cold water,

00:44:13.920 | get out of that cold environment.

00:44:16.020 | And in doing so, you are basically getting better

00:44:19.000 | at controlling your behavior when your brain and body

00:44:21.840 | are flooded with norepinephrine and epinephrine.

00:44:24.000 | That's a very reductionist way to explain resilience

00:44:26.600 | or grit or mental toughness,

00:44:28.080 | but it's a reductionist way of explaining it

00:44:30.500 | that is very closely tied to the biology

00:44:32.320 | and to the psychology.

00:44:33.640 | And it is a fact that norepinephrine and epinephrine

00:44:37.680 | release in the brain and body

00:44:39.160 | are the generic universal code for stressor.

00:44:43.500 | There is no unique chemical signature

00:44:45.480 | for different forms of stressors.

00:44:46.840 | That is the only one.

00:44:48.380 | Although, of course,

00:44:49.220 | there are other chemicals involved as well.

00:44:50.800 | So you could go for time

00:44:52.200 | and you could try and reduce the temperature

00:44:53.720 | and increase the time over a period of days or weeks.

00:44:57.440 | Now that's an attractive way to approach things,

00:45:00.000 | but the problem is that you don't have

00:45:02.180 | an infinite amount of room with which to lower temperature

00:45:06.000 | because eventually you will get into temperatures

00:45:08.100 | that are either so-called that they are dangerous,

00:45:10.860 | or you have to stay in cold temperatures

00:45:13.340 | for such long periods that it becomes impractical

00:45:16.940 | because presumably you also have to take care

00:45:19.300 | of other aspects of your life.

00:45:20.440 | You can't just sit all day in the ice bath.

00:45:23.020 | Now, for that reason,

00:45:24.220 | I favor a protocol in which you build mental resilience

00:45:27.600 | and mental toughness

00:45:28.760 | through two different types of protocols.

00:45:31.060 | The first one involves counting walls.

00:45:33.380 | Now, what do I mean by walls?

00:45:34.400 | I mean the sensation of, no, I don't want to do this,

00:45:38.640 | and the idea or the sensation in your brain and body

00:45:42.520 | that you actually want to leave that environment

00:45:44.320 | and go warm up.

00:45:45.520 | Now, again, for some people,

00:45:46.680 | that will be even before getting

00:45:48.280 | into the ice bath or cold shower.

00:45:50.080 | So if you are feeling very resistant

00:45:52.700 | to getting into the ice bath or cold shower

00:45:54.800 | and you manage to do that,

00:45:56.320 | that's going over what I would call one wall, okay?

00:46:00.180 | Then for some period of time,

00:46:01.640 | you might actually feel comfortable in the ice bath,

00:46:05.560 | cold water, or cold shower,

00:46:07.760 | and you feel like you could stay there

00:46:09.540 | for some period of time,

00:46:10.420 | that you could stay there for a minute or two minutes,

00:46:12.220 | but inevitably the next wall will arrive.

00:46:15.860 | And I would encourage you to pay attention

00:46:17.620 | to when that next wall arrives

00:46:19.300 | and actually having an awareness,

00:46:20.960 | that so-called interoceptive awareness, as we call it,

00:46:24.340 | of when that next surge in adrenaline epinephrine comes

00:46:27.640 | or whether or not it reaches a certain threshold

00:46:30.360 | in your brain and body that you feel you want to get out,

00:46:32.360 | and you're able to stay in for even just 10 seconds longer,

00:46:36.240 | that means you've traversed yet another wall.

00:46:39.240 | And if you continue to stay in that cold environment,

00:46:42.140 | you will find that the next wall will come

00:46:44.120 | and the next wall will come.

00:46:45.040 | Now, eventually, of course, you will get very, very numb,

00:46:48.260 | depending on how cold it is,

00:46:49.360 | and you could also place yourself into danger.

00:46:51.180 | So you have to maintain cognitive control,

00:46:54.000 | counting these walls, traversing these walls,

00:46:56.260 | but getting out at some point, of course.

00:46:59.120 | So my favorite protocol for building mental toughness,

00:47:03.880 | AKA grit, AKA resilience, is to take into account

00:47:07.440 | that some days just getting into the ice bath

00:47:10.120 | or cold shower represents a wall, some days it doesn't.

00:47:12.640 | Some days you get in

00:47:13.480 | and you feel like you could go 10 minutes.

00:47:15.700 | Other days you get in

00:47:16.540 | and you feel like you could only go a minute.

00:47:18.640 | And setting a designated number of walls

00:47:20.880 | before you start the protocol

00:47:22.980 | is going to be very beneficial here.

00:47:24.640 | So you say, as long as I can do it safely,

00:47:27.060 | I'm going to do three walls today.

00:47:29.360 | The first wall is getting in,

00:47:30.480 | the second wall will arrive when it arrives,

00:47:32.760 | and the third wall will arrive when it arrives,

00:47:35.380 | and I'll get over that wall and then I'll get out.

00:47:37.100 | The next day, you might do five walls.

00:47:38.700 | The next day, you might do three walls again,

00:47:41.920 | but you might lower the temperature.

00:47:43.480 | This gives you tremendous flexibility,

00:47:45.880 | and indeed, it gives you much more latitude

00:47:48.800 | to be able to use the same temperatures in different ways

00:47:52.480 | or to reduce the temperature only a little bit

00:47:54.720 | and still get a lot of stimulus,

00:47:56.760 | meaning a lot of results out of a given protocol.

00:48:00.140 | Whereas people who are just going for temperature and time

00:48:02.880 | eventually become cold adapted.

00:48:04.920 | They get very, very good at doing three minutes

00:48:07.760 | or six minutes or even 10 minutes at a given temperature.

00:48:10.720 | And so then they feel like they have to lower the temperature

00:48:12.880 | even more and even more,

00:48:14.480 | and eventually they just bottom out.

00:48:16.240 | There's nowhere else to go.

00:48:17.280 | There's nowhere to get improvements out of the protocol,

00:48:21.100 | at least not in terms of mental resilience.

00:48:24.240 | Of course, there's still the positive effects

00:48:26.560 | on inflammation and metabolism, et cetera,

00:48:28.520 | that we'll talk about in a little bit.

00:48:30.800 | But the key thing here is to design protocols

00:48:33.520 | that are going to work for you over time.

00:48:35.600 | And for you very, very hardy, very, very tough guys

00:48:38.480 | and gals out there that can get right into an ice bath

00:48:41.520 | or a very, very cold immersion,

00:48:43.080 | and you can just grind it out for six or 10 minutes,

00:48:45.480 | or you can even do that by remaining peaceful.

00:48:48.680 | Well, more points to you, but guess what?

00:48:51.080 | That's the equivalent of already having loaded up

00:48:53.240 | the barbell with 600 pounds and done your 10 reps.

00:48:56.320 | There's not a whole lot more variable space

00:48:58.960 | with which to get benefits from that stimulus.

00:49:02.300 | And in the weight room,

00:49:03.400 | people understand that you can adjust, for instance,

00:49:05.280 | the speed of the movement,

00:49:06.460 | or you can start combining that movement

00:49:07.960 | with pre-exhaustion, et cetera.

00:49:09.620 | With cold exposure,

00:49:11.060 | you don't have as much variable space to play with.

00:49:13.580 | So if your goal is to build resilience,

00:49:15.660 | either go for time as a function of temperature,

00:49:18.500 | or what I suggest is to start recognizing these walls

00:49:23.220 | as an experience of resistance in you

00:49:25.880 | and going over those walls,

00:49:27.340 | set a certain number of walls

00:49:28.820 | that you're going to go over on a given day

00:49:31.260 | and do that at a given temperature, and then to mix it up.

00:49:34.640 | And ideally, you might even throw in one more wall

00:49:38.420 | at the end if you're really feeling bold and brave,

00:49:41.080 | because that's going to build out further resilience.

00:49:43.420 | But if you want cold exposure to work for you

00:49:45.460 | for sake of building up resilience

00:49:46.900 | and mental toughness over time,

00:49:48.460 | you're going to want to vary this parameter space

00:49:51.340 | in some sort of way,

00:49:52.740 | and you don't have to be super systematic about it.

00:49:56.060 | That's the beauty of this kind of approach,

00:49:58.300 | because you're relying on the fact

00:49:59.900 | that those walls really represent times

00:50:02.860 | in which you are forcing your top-down control,

00:50:05.360 | your prefrontal cortex, to clamp down on your reflex,

00:50:08.140 | and you're learning behavioral control

00:50:10.200 | in the context of your body having elevated levels

00:50:12.940 | of these catecholamines, norepinephrine and epinephrine.

00:50:15.500 | And that translates to real life

00:50:17.460 | in a much more realistic way, I believe,

00:50:19.860 | because in real life, you're not really engaging

00:50:23.280 | in stressors for a given amount of time

00:50:26.220 | that you know how long it's going to last,

00:50:28.000 | and you know the context, no.

00:50:29.420 | Most stressors arrive in the form of surprises we don't like,

00:50:32.400 | text messages that deliver bad news,

00:50:34.800 | information about the outside world or real world

00:50:37.500 | and online interactions that send our system

00:50:39.960 | into a state of increasing norepinephrine and epinephrine.

00:50:42.820 | And if you start to think of those as walls

00:50:44.620 | that you can tolerate and climb over

00:50:46.060 | while staying calm and clear of mind,

00:50:48.460 | then you can really imagine how the ice bath

00:50:52.140 | and other forms of cold exposure are really serving

00:50:54.980 | to train you up for real life stressors.

00:50:57.760 | Okay, the next question that I always get

00:50:59.620 | is what should my mental state be

00:51:02.180 | while I'm exposing myself to this uncomfortable

00:51:04.900 | yet safe condition of cold?

00:51:07.620 | Well, you have two options,

00:51:09.560 | and there are probably other options as well.

00:51:11.580 | One is to try and calm yourself

00:51:13.980 | to remain as mentally still as possible.

00:51:17.640 | The other is to lean into that challenge

00:51:21.100 | and so to grind it out.

00:51:22.620 | And here, I have to say that this is a lot like

00:51:25.060 | teaching someone to drive on a gravel road.

00:51:27.380 | For any of you that have driven on a gravel road,

00:51:29.860 | you know that there is no optimal speed

00:51:32.820 | for all gravel roads.

00:51:33.960 | It depends on the density of the gravel, et cetera,

00:51:36.100 | and the vehicle, et cetera.

00:51:37.720 | So for instance, on some gravel roads,

00:51:40.100 | when you start to drive and the dust starts to kick up,

00:51:42.940 | your best option is to drive fast

00:51:44.660 | and put that dust cloud behind you.

00:51:46.700 | On other gravel roads, if you try and do that,

00:51:49.080 | the dust actually kicks up around the vehicle

00:51:50.740 | and it makes it hard to see.

00:51:51.980 | Sometimes you have to slow down.

00:51:53.920 | The same thing is true for getting

00:51:55.520 | through deliberate cold exposure.

00:51:57.480 | Sometimes it's easier to calm yourself.

00:51:59.500 | One way to do that is through double inhales

00:52:01.700 | through the nose and extended exhales through the mouth,

00:52:03.960 | or simply by trying to control your breathing

00:52:06.740 | and reduce the pace of your breathing

00:52:08.700 | and increase the volume of your breathing.

00:52:12.340 | I have to say that everyone experiences a shortening

00:52:15.380 | of breath when they get into uncomfortably cold water.

00:52:18.300 | That is a universal physiological response.

00:52:21.580 | Everyone also experiences a 30 to 80% decrease

00:52:26.180 | in cognitive function, in particular of the frontal cortex.

00:52:29.400 | The metabolism of your frontal cortex goes down.

00:52:31.400 | The metabolism, meaning the activity of brain areas

00:52:34.400 | associated with stress and panic goes way up.

00:52:36.940 | And so anchoring your mind in cognitive activities

00:52:41.380 | as you get into the cold can be very, very helpful

00:52:44.180 | for maintaining clarity of mind.

00:52:46.820 | In fact, one thing that I sometimes recommend

00:52:48.780 | is that people try and engage

00:52:50.660 | in some sort of cognitive exercise while in the cold,

00:52:53.680 | not as a form of distraction,

00:52:55.580 | but as a way to maintain clarity of thinking

00:52:57.580 | and to learn how to do that when the body is flooded

00:52:59.840 | with all these chemicals that make us stressed.

00:53:02.240 | So for instance, you could do math problems

00:53:04.200 | and not two plus two equals four,

00:53:06.020 | not three times three equals nine,

00:53:08.220 | but things that require a little bit more focus

00:53:10.700 | and attention, working memory and so forth.

00:53:13.340 | You could also start to have thoughts

00:53:16.440 | that you deliberately impose a full sentence structure on.

00:53:20.540 | That's actually quite tough.

00:53:22.100 | You could try and recall specific bouts of information

00:53:25.280 | that are challenging.

00:53:26.120 | This is teaching your mind how to stay online,

00:53:29.240 | or rather I should say,

00:53:30.080 | this is you teaching your prefrontal cortex

00:53:32.460 | how to stay engaged

00:53:33.980 | while you have high levels of stress in your body.

00:53:36.840 | Years ago, I had a friend who works in the neuroscience

00:53:40.760 | world, research neuroscientist,

00:53:42.440 | who was obsessed with this very bizarre sport

00:53:45.680 | that I don't necessarily recommend at all,

00:53:47.660 | which is the combination of boxing and chess.

00:53:50.600 | You may have seen this on YouTube

00:53:51.800 | where people will box around, legitimate boxing around,

00:53:54.580 | they're sparring all out often.

00:53:56.520 | And then at the end of the round,

00:53:58.200 | instead of resting in the corner,

00:53:59.280 | they actually sit down and play chess.

00:54:01.000 | And then they go back to boxing and back to chess.

00:54:03.060 | Again, not a support that I recommend,

00:54:05.540 | but the reason he was obsessed with this

00:54:07.120 | is because he studies the impact of stress

00:54:10.280 | on cognitive performance.

00:54:11.360 | And what that particular very bizarre sport was doing

00:54:14.320 | was toggling back and forth

00:54:15.600 | between different states of mind.

00:54:17.580 | Now it's used both to increase cognitive clarity

00:54:22.040 | for the fighter when they box,

00:54:23.600 | because staying calm and clear thinking

00:54:25.420 | is very important to winning boxing matches.

00:54:27.840 | Believe it or not, it's not an all outrage.

00:54:29.760 | It's a very calculated game of mental chess

00:54:32.180 | and physical chess.

00:54:33.020 | It's quite high stakes, as you can imagine.

00:54:35.440 | It's also used in some circles as a way to teach people

00:54:40.700 | how to engage in cognitive performance

00:54:42.640 | when their body is simply filled with stress.

00:54:44.360 | So in the boxing chess example,

00:54:46.820 | the replacement for the cold water

00:54:49.040 | is actually the boxing, right?

00:54:50.320 | It's the thing that's supposed to induce the stress

00:54:52.280 | 'cause getting hit is stressful

00:54:53.700 | and the risk of getting hit is stressful for most people.

00:54:56.960 | So again, if you think about deliberate cold exposure

00:55:00.700 | as a way of just systematically and reliably

00:55:03.360 | inducing epinephrine and norepinephrine release

00:55:05.420 | and delivering stress,

00:55:07.000 | well, then this idea of maintaining cognitive clarity

00:55:09.720 | and actually engaging in cognitive tasks

00:55:11.600 | while in the ice bath or cold shower

00:55:14.240 | can actually be very beneficial,

00:55:15.600 | even though it might sound a little bit silly.

00:55:16.940 | You're really training up your ability

00:55:18.640 | to keep your brain working

00:55:20.400 | when the reflex is to shut down the parts of your brain

00:55:24.160 | that are involved in deliberate planning and thinking.

00:55:26.300 | Now, another important aspect of deliberate cold exposure

00:55:29.280 | that I rarely, if ever hear discussed,

00:55:32.240 | but is vitally important

00:55:34.480 | is whether or not you move around or not.

00:55:37.640 | And here's the reason.

00:55:38.860 | When you get into cold water

00:55:40.580 | and you remain there for some period of time,

00:55:44.260 | your body is generating heat

00:55:46.500 | and that heat generates what's called a thermal layer

00:55:49.340 | that surrounds your entire body.

00:55:51.240 | So if you stay still,

00:55:54.360 | you are actually warmer than if you move around.

00:55:57.220 | You can try this the next time

00:55:58.420 | you're doing your deliberate cold exposure.

00:55:59.920 | If you're submerged up to the neck,

00:56:01.160 | sit there for about 10, 30 seconds

00:56:03.660 | and be very, very still of body.

00:56:05.480 | In fact, this is the way that most people

00:56:07.360 | start to do deliberate cold exposure.

00:56:09.080 | They give this very stoic look.

00:56:10.420 | They don't blink.

00:56:11.260 | They look very peaceful.

00:56:12.080 | Some of them even look tough,

00:56:13.780 | or they make a very even, A, emotional face,

00:56:17.760 | and so it looks like they're really tough,

00:56:20.140 | but they are so still that, believe it or not,

00:56:22.380 | they're not providing the most potent stimulus.

00:56:26.520 | If they or you were to move around in that water,

00:56:30.660 | what would happen is you'd break up the thermal layer

00:56:32.680 | and that you actually experienced that as much colder.

00:56:35.960 | So if you really want to push the resilience aspect,

00:56:39.100 | or for instance, if you want to use a given temperature

00:56:42.020 | that you're comfortable in,

00:56:43.240 | but that you want to increase the stimulus

00:56:45.500 | and you want to get some more benefit

00:56:47.360 | for mental resilience training,

00:56:49.160 | well, then get into the cold water,

00:56:51.560 | move your body around continuously,

00:56:53.800 | but try and keep your mind still

00:56:55.340 | or even do some sort of cognitive task.

00:56:57.540 | So as you're starting to realize,

00:56:59.160 | there are a bunch of different variables

00:57:00.320 | that you can play with

00:57:01.240 | while maintaining the same temperature of water,

00:57:03.720 | and in doing so, really keep you in the zone

00:57:06.920 | of what should and absolutely has to be safe for you

00:57:10.820 | without having to just continually drop the temperature

00:57:13.120 | from, say, 60 degrees to 55 to 40 to 33,

00:57:15.720 | because as I mentioned before,

00:57:16.640 | eventually you're going to bottom out.

00:57:18.240 | So if you're one of those people that likes to look tough

00:57:20.720 | or really relaxed while you're in the ice bath

00:57:22.880 | or cold water immersion,

00:57:24.080 | just realize that you're actually cheating yourself

00:57:26.760 | out of part of the stimulus.

00:57:28.320 | Keep those limbs moving,

00:57:29.840 | and of course, limbs under the water, feet and hands,

00:57:33.600 | is going to be a more potent stimulus

00:57:35.740 | than hands and feet out

00:57:37.640 | for reasons that should be obvious

00:57:39.180 | based on what we talked about

00:57:40.180 | in terms of glab or skin cooling.

00:57:42.340 | So keep those submerged, move your body, pedal,

00:57:45.420 | maybe move your knees up and down, pedal your feet,

00:57:48.040 | and trust me, it's going to feel a lot colder

00:57:50.080 | than were you to remain stone still.

00:57:52.260 | Another very common question is how often

00:57:54.520 | to do deliberate cold exposure.

00:57:56.720 | It's tough to make a recommendation on that

00:57:59.340 | based on any peer-reviewed study,

00:58:01.740 | although there are a few in humans

00:58:03.220 | that point to a threshold of 11 minutes total per week,

00:58:07.520 | so that's total throughout the week,

00:58:09.400 | divided into two or four sessions

00:58:11.600 | of two or three minutes or so.

00:58:13.540 | Now, that 11-minute cutoff is not a strict threshold

00:58:16.340 | and is actually geared more towards increases in metabolism.

00:58:20.100 | We'll get into this a little bit later in the episode,

00:58:22.940 | but I think the 11-minute threshold,

00:58:25.600 | meaning 11 minutes total of deliberate cold exposure

00:58:28.220 | per week is a pretty good number to use

00:58:31.420 | if you need a number in order to keep you consistent.

00:58:34.940 | But as we talked about earlier,

00:58:36.400 | some of you are going to be in the ice bath

00:58:39.500 | or cold immersion or cold shower for one minute.

00:58:42.020 | Others of you will be in there for 10 minutes,

00:58:44.120 | depending on how frequent and how high, if you will,

00:58:47.540 | those walls of adrenaline are coming.

00:58:50.140 | So for some of you,

00:58:51.980 | getting into a cold shower for three minutes total

00:58:54.260 | for the whole week will represent a tremendous achievement

00:58:58.080 | in terms of willpower and overcoming the resistance

00:59:00.820 | to doing that, overcoming those walls.

00:59:02.340 | For others of you, three minutes is nothing.

00:59:04.980 | So what do I recommend?

00:59:06.880 | I recommend that you get at least 11 minutes total per week,

00:59:11.060 | but at the point where 11 minutes total per week

00:59:13.240 | is very easy for you,

00:59:14.420 | or is no longer representing a significant mental challenge,

00:59:17.180 | meaning you're not experiencing many of these walls,

00:59:19.100 | you're excited to get into the cold shower or immersion,

00:59:21.740 | you're going through it easily, you're cruising basically,

00:59:24.560 | then I would say either lower the temperature safely,

00:59:27.820 | of course, extend the duration safely, of course,

00:59:31.380 | or increase the frequency so that you're doing this

00:59:33.840 | perhaps every day or maybe five days a week

00:59:36.660 | or three days a week.

00:59:37.500 | I personally get tremendous benefit

00:59:39.320 | from doing deliberate cold exposure three times a week

00:59:42.460 | and using the walls method that I described earlier

00:59:45.560 | as my gauge for how long to stay in.

00:59:47.440 | And typically that means that I'm staying in

00:59:49.620 | for anywhere from two minutes to six minutes per session,

00:59:53.740 | and that averages out to about 11 to 15 minutes total

00:59:58.600 | per week.

00:59:59.580 | So again, I do not think that you need to be super strict

01:00:02.860 | about these guidelines.

01:00:04.200 | It's most important when embracing a protocol,

01:00:06.920 | A, that you do it safely,

01:00:08.220 | but secondarily that you do it consistently.

01:00:11.340 | So find what you can do consistently

01:00:13.140 | and then vary the parameters that will allow you

01:00:15.120 | to continue to do deliberate cold exposure consistently,

01:00:18.340 | regardless of whether or not you have access to a shower

01:00:20.500 | or a cold immersion, et cetera.

01:00:22.180 | Okay, so we've been talking about mental effects

01:00:24.380 | and the use of deliberate cold exposure

01:00:26.260 | for sake of building resilience,

01:00:28.060 | which I do believe can be tremendously powerful.

01:00:30.620 | Look, it's no coincidence that the screening

01:00:35.020 | and the training for Navy SEALs involves a lot of exposure

01:00:38.900 | to cold water.

01:00:40.080 | One could argue that it is deliberate

01:00:41.780 | because they elect to go to BUD/S,

01:00:43.740 | but when they get into the cold water at BUD/S

01:00:46.400 | is dictated by the instructors.

01:00:48.660 | And the reason they use cold water exposure as the stressor

01:00:52.260 | is that it does offer considerable leeway

01:00:55.200 | in terms of duration and temperature,

01:00:58.000 | in terms of how you can use it as a stressor,

01:01:00.780 | whereas things like heat don't offer much variable space,

01:01:03.980 | as we say, there isn't a lot of room

01:01:06.640 | beyond which you start injuring or even killing people

01:01:09.620 | by using heat.

01:01:10.720 | So there are a lot of forms of stressors out there,

01:01:12.540 | but cold is one that we can titrate,

01:01:14.540 | that we can adjust in ways that can allow us

01:01:16.420 | to continually build up and/or maintain mental toughness.

01:01:21.420 | Now, deliberate cold exposure also has many effects

01:01:25.580 | on chemicals other than norepinephrine and epinephrine,

01:01:28.760 | most notably the neuromodulator dopamine,

01:01:32.020 | which is involved in elevating our mood,

01:01:34.380 | making us feel energized and enhancing our ability to focus.

01:01:38.140 | And that has a lot to do with how dopamine engages us

01:01:41.180 | in motivated states, tends to narrow our thinking

01:01:44.560 | and our behavior into a particular trench

01:01:46.720 | of goal-directed behavior.

01:01:47.980 | If you want to learn more about dopamine,

01:01:50.540 | you can learn a lot about dopamine

01:01:52.380 | in our episode about dopamine.

01:01:54.140 | It's at hubermanlab.com.

01:01:55.300 | You can find it.

01:01:56.140 | It's a two and a half hour plus kind of deep dive

01:01:59.280 | into all things dopamine, focus, motivation, et cetera.

01:02:02.900 | Deliberate cold exposure has a very powerful effect

01:02:08.700 | on the release of dopamine in our brain and body.

01:02:11.060 | And this is one of the main reasons

01:02:13.000 | why people continue to do deliberate cold exposure.

01:02:16.080 | Basically, it makes us feel good

01:02:19.160 | and it continues to make us feel good

01:02:21.260 | even after we get out of the cold environment.

01:02:23.740 | In fact, some people would say

01:02:25.440 | they don't feel good in the cold environment.

01:02:26.980 | It's all stress for them, but afterwards they feel great.

01:02:30.140 | One of our previous guests, Dr. Anna Lempke,

01:02:32.260 | who's a medical doctor

01:02:33.420 | at Stanford University School of Medicine,

01:02:34.940 | she's a close colleague of mine,

01:02:37.260 | described the use of dopamine in her book, "Dopamine Nation,"

01:02:40.400 | an incredible book about addiction and dopamine,

01:02:42.300 | I should mention,

01:02:43.420 | and the use of dopamine elicited by cold water exposure

01:02:48.420 | by one of her patients.

01:02:50.580 | What I'm referring to is the fact that one of her patients

01:02:53.800 | helped themselves get and stay sober off drugs

01:02:57.100 | by using deliberate cold exposure to increase dopamine.

01:03:01.000 | So a healthier form of dopamine release

01:03:03.100 | than they were engaged in prior to getting sober.

01:03:07.020 | Now, the basis for dopamine release in response

01:03:10.580 | to cold exposure is that the catecholamines,

01:03:12.700 | norepinephrine, epinephrine, and dopamine

01:03:15.140 | tend to be co-released by the same sorts of stimuli,

01:03:18.660 | but most stressors and in particular things

01:03:21.380 | that evoke stress or our feelings of stress internally

01:03:24.800 | that we don't like do not increase dopamine.

01:03:27.980 | They only increase norepinephrine and epinephrine,

01:03:30.520 | but deliberate cold exposure

01:03:32.180 | seems to cause a dramatic increase in dopamine,

01:03:36.020 | and this has actually been substantiated

01:03:37.820 | in a really beautiful study

01:03:39.620 | entitled "Human Physiological Responses to Immersion

01:03:42.520 | into Water of Different Temperatures."

01:03:44.620 | The first author is Sramek,

01:03:46.940 | I'm almost certainly pronouncing that poorly,

01:03:49.740 | if not incorrectly, S-R-A-M-E-K.

01:03:54.180 | This was published in the European Journal

01:03:55.780 | of Applied Physiology in the year 2000.

01:03:58.400 | Really a beautiful study, I love this study.

01:04:00.660 | They took people and they had them sit in chairs underwater,

01:04:04.500 | but their head was out and they were,

01:04:06.140 | so they were immersed up to the neck

01:04:08.020 | in either three different,

01:04:10.020 | either of three different temperatures, excuse me,

01:04:12.100 | 32 degrees Celsius, which is 89 degrees Fahrenheit,

01:04:16.220 | 20 degrees Celsius, which is 68 degrees Fahrenheit,

01:04:19.300 | or 14 degrees Celsius, which is 57.2 degrees Fahrenheit.

01:04:23.720 | So not super cold, but then what they did

01:04:27.380 | is they measured people's core body temperature throughout,

01:04:29.980 | they measured their metabolism,

01:04:31.520 | and they looked at serum levels of things like

01:04:35.020 | norepinephrine, epinephrine, dopamine, and cortisol,

01:04:37.540 | serum meaning within the blood.

01:04:39.360 | So a really nice and quite thorough study.

01:04:42.240 | There were not a huge number of subjects in the study,

01:04:46.240 | but nonetheless, it was a very thorough study

01:04:48.460 | in terms of the number of variables that they explored.

01:04:52.580 | So I just want to briefly highlight some of what they saw

01:04:55.580 | or what they observed in this study.

01:04:57.700 | First of all, all the groups were in the water

01:05:01.640 | of a given temperature for one hour,

01:05:04.480 | which is much longer than most of the deliberate

01:05:06.760 | cold exposure protocols that anyone is using at home.

01:05:09.460 | I mean, maybe you're taking one hour long cold showers,

01:05:12.200 | maybe you're getting into the ice bath for an hour,

01:05:14.440 | although I don't recommend that,

01:05:15.500 | I think you'd probably get badly hypothermic,

01:05:18.360 | or maybe you're getting into a cold water immersion

01:05:21.420 | for some period of time,

01:05:22.480 | but I have a hard time imagining that it would be an hour,

01:05:24.980 | and I don't suggest that if it's very cold.

01:05:27.100 | So this study focused on actually

01:05:28.880 | somewhat moderately cool temperatures,

01:05:31.800 | not what I think most people would consider

01:05:33.960 | very, very cold temperatures,

01:05:35.640 | but extended the duration for quite a while.

01:05:38.380 | So again, 32 degrees Celsius, 20 degrees Celsius,

01:05:42.120 | or 14 degrees Celsius, here's what they observed.

01:05:45.700 | The group that was immersed up to the neck

01:05:48.720 | in 32 degrees Celsius, that is 89 degrees Fahrenheit,

01:05:51.920 | water did not experience a shift in metabolism,

01:05:55.380 | nor a significant increase in dopamine, norepinephrine,

01:05:58.960 | or these other catecholamines.

01:06:01.020 | The group that was in 20 degrees Celsius,

01:06:03.640 | meaning 68 degree Fahrenheit water for an hour,

01:06:08.120 | experienced a 93% increase in metabolic rate,

01:06:12.040 | which is remarkable given that the water wasn't that cold,

01:06:15.920 | and yet an hour is a pretty long time to be in there.

01:06:18.520 | And again, it speaks to the dramatic effect

01:06:21.280 | of heat transfer that water has,

01:06:23.680 | which I mentioned earlier as opposed to being out

01:06:25.580 | in the air at 68 degrees,

01:06:27.340 | it would certainly not cause that increase

01:06:29.580 | in metabolic rate.

01:06:30.560 | The group that was at 14 degrees Celsius,

01:06:34.980 | meaning 57.2 degrees Fahrenheit water for an hour,

01:06:39.140 | experienced a 350% increase in metabolism,

01:06:42.780 | so huge increases in metabolism.

01:06:45.240 | Now, the most interesting data to me,

01:06:48.680 | at least in terms of mental effects

01:06:50.520 | of deliberate cold exposure,

01:06:52.420 | were that the plasma or serum levels

01:06:56.820 | of norepinephrine in the blood increased 530%.

01:07:01.620 | These are huge increases in norepinephrine,

01:07:04.340 | so it suggests that this is a stressful stimulus,

01:07:07.220 | at least neurochemically speaking, stressful,

01:07:10.020 | despite the fact that it's not super, super cold,

01:07:12.300 | although 57.2 degrees Fahrenheit, 14 degrees Celsius,

01:07:15.980 | is not a, you know, it's not a warm environment,

01:07:20.380 | but it's not a ultra, ultra cold environment,

01:07:22.580 | but an hour is a very long time to be in there.

01:07:24.980 | The subjects also experienced a 250% increase

01:07:31.560 | in dopamine concentrations,

01:07:34.060 | which while not 530%, as it was with norepinephrine,

01:07:38.100 | is still a very large increase

01:07:40.620 | in baseline levels of dopamine.

01:07:42.460 | And what was interesting is that those increases

01:07:44.780 | in dopamine persisted for a very long period

01:07:47.860 | of time afterwards, even out to two hours, okay?

01:07:51.500 | And they stopped the study after 120 minutes

01:07:54.400 | of getting out of the cold,

01:07:56.740 | but nonetheless, these increases in norepinephrine

01:07:59.860 | are huge and long-lasting,

01:08:01.780 | and these increases in dopamine

01:08:03.320 | are very large and long-lasting.

01:08:05.800 | And I do believe that these documented effects in humans

01:08:08.860 | explain much of the enhancement of attention

01:08:12.340 | and of feelings of wellbeing and mood

01:08:14.380 | that people typically experience

01:08:16.380 | after doing deliberate cold exposure.

01:08:19.080 | And the reason I say that is that if you were to go back

01:08:22.780 | to the episode that I did on dopamine,

01:08:24.740 | or you were to go back to the episode that I did

01:08:27.020 | with Dr. Anna Lemke on addiction and dopamine,

01:08:29.740 | what you would find is that increases in dopamine

01:08:32.820 | of the sort evoked by deliberate cold exposure

01:08:35.840 | are actually very similar to the kinds of increases

01:08:38.100 | in dopamine that are elicited by things like nicotine

01:08:41.380 | or from other behaviors that are known to be addictive

01:08:44.700 | and bad for us because they lead to other effects

01:08:47.620 | on the brain and body that we simply don't want.

01:08:50.260 | And yet deliberate cold exposure, provided it's done safely,

01:08:53.820 | can create similar, if not greater, increases in dopamine

01:08:57.620 | that are not just fleeting, that don't just occur

01:09:01.460 | during, say, the consumption of some deleterious drug

01:09:04.140 | or activity, but that are very long-lasting

01:09:06.440 | and that can be leveraged toward activities

01:09:09.520 | other than deliberate cold exposure.

01:09:11.820 | So I want to emphasize this.

01:09:13.100 | I'm not suggesting that people do deliberate cold exposure

01:09:15.680 | for an hour a day.

01:09:16.820 | And unfortunately, there are not many studies

01:09:19.680 | yet exploring how shorter colder temperature

01:09:23.780 | environment exposure, say one minute or three minutes

01:09:27.060 | or six minutes at 55 degrees or at 50 degrees,

01:09:32.060 | whether or not that leads to similar, greater,

01:09:35.300 | or reduced levels of dopamine in the brain and body.

01:09:38.780 | And yet almost everybody who does deliberate cold exposure

01:09:42.580 | will say, yeah, it was stressful, I didn't enjoy it,

01:09:45.660 | or I eventually grew to like it,

01:09:47.360 | but that I always feel better afterwards.

01:09:49.620 | And then that feeling lasts a very long period of time.

01:09:52.660 | And I think it's almost certain that those experiences

01:09:56.100 | that people report relate to these increases in dopamine

01:09:58.820 | and in concert with the increases in norepinephrine

01:10:01.980 | also explain the other effect that's commonly reported,

01:10:04.480 | which is an enhancement in mental acuity

01:10:06.940 | and the ability to focus.

01:10:09.140 | Now, here we can extrapolate to the study

01:10:11.720 | that I discussed at the early part of the episode

01:10:14.860 | where I was talking about the use

01:10:15.900 | of short 15 minute exercise,

01:10:18.120 | kind of moderate intensity exercise,

01:10:19.740 | and how that was shown to increase levels of energy

01:10:22.740 | and mental acuity in these working memory

01:10:25.180 | visual attention tasks.

01:10:26.300 | And there again, we have to assume somewhat

01:10:29.300 | because they weren't doing neurochemical measurements,

01:10:31.460 | but we can reasonably assume that those improvements

01:10:35.240 | in cognitive performance were due, at least in part,

01:10:38.380 | to the increase in catecholamines known to accompany

01:10:41.220 | moderate intensity zone to cardio.

01:10:43.720 | So what you're starting to see here is a theme.

01:10:45.780 | The theme is that virtually any stimulus

01:10:49.240 | that delivers more norepinephrine, epinephrine,

01:10:51.660 | and dopamine to our system will sharpen our mental acuity

01:10:54.640 | and elevate our mood, and will do so

01:10:56.380 | for some period of time.

01:10:58.280 | Deliberate cold exposure, it turns out,

01:11:00.480 | is a very potent way to increase these catecholamines,

01:11:03.460 | this category of chemicals, and thereby to improve mood,

01:11:06.700 | mental acuity, and levels of alertness.

01:11:09.160 | And as we'll next see, it not only has that effect,

01:11:13.020 | which can be very beneficial for many people

01:11:15.060 | in a bunch of different circumstances,

01:11:16.900 | but it also has the positive effects that many people seek

01:11:20.960 | in terms of metabolism in lowering inflammation in the body

01:11:24.300 | and other physiological effects as well.

01:11:26.580 | And forgive me, I was almost ready to move on

01:11:28.820 | to effects of deliberate cold exposure on metabolism

01:11:32.740 | and inflammation and so forth,

01:11:34.280 | but I neglected to point out one of the other

01:11:36.660 | very interesting aspects of the study

01:11:39.920 | showing deliberate cold exposure

01:11:41.680 | can increase norepinephrine and dopamine,

01:11:44.160 | which is that they observed no significant increases

01:11:48.140 | in the stress hormone cortisol.

01:11:50.240 | And that is both surprising, interesting, and important,

01:11:53.640 | because what it means is that the quality of stress

01:11:57.460 | that deliberate cold exposure is creating in the body

01:12:00.740 | is likely to be one of what we call eustress.

01:12:04.520 | Hans Selye, the great physiologist,

01:12:07.400 | won a Nobel Prize for distinguishing between distress,

01:12:10.800 | which is stress in the brain and body

01:12:13.200 | that causes the release of things like cortisol

01:12:16.560 | along with the other catecholamines

01:12:17.960 | and that we experience as negative happening to us

01:12:20.720 | and can lead to negative health outcomes.

01:12:22.880 | And he distinguished that from eustress,

01:12:25.400 | which was stress that we now understand

01:12:27.880 | is associated with increases in things

01:12:29.720 | like norepinephrine and dopamine,

01:12:31.440 | but no increases or minimal increases in cortisol

01:12:34.960 | and that can lead to positive health outcomes.

01:12:37.560 | So it appears that deliberate cold exposure

01:12:40.360 | can create what we call or what Hans Selye called eustress.

01:12:44.800 | In other words, it can create a condition

01:12:46.560 | in the brain and body in which we are stressing ourselves,

01:12:49.860 | we are training up resilience,

01:12:51.200 | and yet we are creating a neurochemical milieu

01:12:54.140 | that actually has many health benefits.

01:12:56.380 | Now I'd like to shift our attention

01:12:57.600 | to the effects of deliberate cold exposure on metabolism.

01:13:00.780 | And I'd like to start by detailing a study

01:13:03.320 | that was performed on humans

01:13:05.160 | and published just at the end of last year.

01:13:07.740 | The title of the study is

01:13:08.800 | Altered Brown Fat Thermoregulation

01:13:10.840 | and Enhanced Cold Induced Thermogenesis

01:13:13.620 | in Young Healthy Winter Swimming Men.

01:13:15.980 | And I should point out that

01:13:17.760 | while the study was only performed on male subjects,

01:13:20.600 | there's no reason to think that

01:13:22.300 | the effects that they discovered would only pertain to men.

01:13:25.160 | I would hope that they would also do a study on women

01:13:27.120 | at some point in the future,

01:13:28.800 | but the effects that they describe

01:13:30.840 | are very basic core physiological processes.

01:13:34.700 | What they did is they looked at deliberate cold exposure

01:13:37.200 | in this group of young men,

01:13:38.720 | and they used that 11 minute threshold per week.

01:13:42.960 | So in other words, they had them get into cold water

01:13:46.780 | for approximately 11 minutes per week.

01:13:50.160 | And again, that's 11 minutes total per week.

01:13:53.600 | They divided that into two sessions,

01:13:56.000 | although in speaking with the first author of the study,

01:13:58.760 | Dr. Susanna Soberg,

01:14:00.000 | I learned that it probably is not important

01:14:02.320 | that it be two sessions,

01:14:03.500 | it could be three or even four sessions,

01:14:06.280 | as long as it reaches that 11 minute threshold.

01:14:08.940 | What they discovered was that

01:14:11.520 | by going into these cold environments,

01:14:14.820 | in this case, cold water immersion up to the neck

01:14:17.960 | for 11 minutes total per week,

01:14:21.240 | that these men experienced increases

01:14:23.800 | in so-called brown fat thermogenesis,

01:14:26.660 | I'll talk more about what that is in a moment,

01:14:28.720 | and increases in core body temperature

01:14:30.800 | that translate to increases in core body metabolism.

01:14:34.920 | Now, the overall increases in core body metabolism

01:14:37.820 | that they experienced were not extremely large.

01:14:42.820 | They were statistically significant,

01:14:44.600 | but they weren't extremely large.

01:14:45.960 | However, the changes in brown fat stores

01:14:50.400 | are perhaps what's most interesting about this study,

01:14:53.080 | and I'll tell you why.

01:14:54.420 | The metabolic increases of deliberate cold exposure

01:14:57.580 | are both acute, meaning happening in the short term,

01:15:00.280 | when you get into the cold and immediately after,

01:15:02.900 | one does experience an increase in core metabolism,

01:15:06.440 | you burn some calories, in other words,

01:15:08.380 | and while those might not be very significant increases,

01:15:14.520 | or I should say they can be statistically significant,

01:15:17.740 | but they are not enormously large numbers

01:15:20.720 | of calories burned,

01:15:22.640 | the longer lasting effects of deliberate cold exposure

01:15:27.200 | on metabolism seem to take place by changes that occur

01:15:30.680 | in the types of fat that we store in our body,

01:15:34.100 | and the way that that fat impacts our metabolism

01:15:36.680 | at other times throughout the 24-hour cycle.

01:15:40.120 | This actually has a somewhat anecdotal basis,

01:15:44.660 | in particular in Scandinavia.

01:15:46.880 | I don't speak Swedish nor I speak Danish,

01:15:49.440 | nor do I speak Norwegian,

01:15:51.160 | but I do have Danish relatives,

01:15:52.960 | and they were able to help me decipher

01:15:55.400 | a common Swedish saying,

01:15:58.020 | which essentially translates to the fact that

01:16:01.120 | in preparation for the summer, they say,

01:16:04.300 | one should expose themselves to warm environments

01:16:09.000 | so that one is comfortable in warm environments

01:16:12.240 | in the summer.

01:16:13.120 | That's one half of this traditional Swedish

01:16:16.460 | and also Danish saying.

01:16:17.940 | The other half of this traditional Danish Swedish saying

01:16:22.380 | is that in preparation for winter,

01:16:24.780 | in order to not feel too cold in cold environments,

01:16:28.760 | one should prepare for those in the fall

01:16:31.300 | by not wearing a jacket and exposing oneself

01:16:34.240 | to cold environments.

01:16:36.200 | Now, of course, this is just anecdotal cultural lore,

01:16:40.120 | but it actually has a physiological basis,

01:16:42.200 | which is by exposing oneself to cold environments

01:16:46.380 | on a repeated basis in anticipation of exposure

01:16:50.040 | to more extreme cold environments,

01:16:52.100 | one can feel more comfortable

01:16:53.960 | in those extreme cold environments.

01:16:56.000 | And that's exactly what they observed

01:16:58.180 | in this study by Soberg et al.

01:17:00.380 | The men felt more comfortable in extreme cold

01:17:03.940 | if they had trained through deliberate cold exposure,

01:17:07.360 | which might not seem surprising at all,

01:17:09.880 | but based on what we talked about earlier,

01:17:12.280 | whereby deliberate cold exposure evokes this discomfort

01:17:16.040 | and this experience of norepinephrine release,

01:17:18.640 | at least in the short term,

01:17:20.700 | then you would say, well,

01:17:21.960 | shouldn't that deliberate cold exposure

01:17:23.260 | also make them feel uncomfortable,

01:17:25.240 | like they really want to get out?

01:17:26.680 | Well, that is true at the beginning

01:17:29.600 | of a deliberate cold exposure protocol,

01:17:31.420 | meaning in the first week or in the second week

01:17:33.480 | or the third week.

01:17:34.320 | But what one finds and what you will find

01:17:36.320 | if you do deliberate cold exposure consistently

01:17:38.980 | is that you will then become more comfortable

01:17:42.400 | at cold temperatures

01:17:44.560 | away from the deliberate cold exposure.

01:17:46.720 | So, whereas you might have previously been the person

01:17:49.180 | who was always cold in the room with air conditioning

01:17:51.160 | or always seeking a sweater, always wanting to bundle up,

01:17:54.000 | you will be more comfortable in those cold environments.

01:17:56.040 | And the reason for that is well substantiated

01:17:59.960 | from this study and from animal studies,

01:18:03.240 | whereby deliberate cold exposure

01:18:06.240 | converts one particular kind of fat cell,

01:18:09.520 | the white fat cell,

01:18:11.080 | which is a very low metabolic output cell,

01:18:15.280 | it's basically a storage site for energy in the body,

01:18:17.800 | fat cells, to a different type of fat cell,

01:18:21.260 | which is the beige fat cell,

01:18:23.660 | called beige because it's actually beige

01:18:25.820 | or slightly brown under the microscope,

01:18:28.100 | or even to brown fat cells,

01:18:30.440 | which are very dark under the microscope

01:18:32.420 | and dark because they contain mitochondria

01:18:35.060 | and are very metabolically and thermogenically active.

01:18:40.500 | In other words, white fat doesn't burn many calories.

01:18:43.860 | It's basically a storage site.

01:18:45.520 | It's a bank account for energy.

01:18:47.600 | It's filled with lipids and those lipids can be used

01:18:52.220 | if the body needs energy

01:18:53.480 | and if it goes into a caloric deficit.

01:18:55.680 | Beige fat and brown fat acts as sort of a furnace

01:18:59.660 | or the sort of fat that you would find in a candle,

01:19:03.400 | a fuel that can increase core body temperature.

01:19:06.100 | So beige fat and brown fat

01:19:08.360 | is very good at raising our metabolism

01:19:11.040 | and helps burn white fat.

01:19:13.320 | Now, of course, it does that

01:19:15.080 | only in the context of a caloric deficit,

01:19:18.340 | but it can actually help create that caloric deficit.

01:19:21.960 | Having more beige fat and brown fat

01:19:24.560 | can increase your overall core metabolism.

01:19:27.300 | In other words, the number of calories

01:19:29.040 | that you burn per day,

01:19:30.320 | and therefore the number of calories

01:19:31.700 | that you need to either maintain or to lose weight.

01:19:34.700 | The simple translation of this

01:19:37.420 | is that getting into cold water

01:19:40.060 | for a total of 11 minutes, perhaps more,

01:19:43.040 | but at least 11 minutes per week

01:19:44.980 | divided into two or four sessions

01:19:47.720 | can increase your core metabolism in part

01:19:50.520 | by increasing your beige and brown fat stores.

01:19:54.200 | And we know how that works, at least in animal models.

01:19:57.400 | And there's now reason to suspect

01:19:59.280 | that the exact same mechanisms are occurring in humans.

01:20:02.320 | The primary way in which deliberate cold exposure

01:20:05.340 | converts white fat cells into these more metabolically,

01:20:08.480 | thermogenically active metabolism-increasing

01:20:11.720 | beige and brown fat cells

01:20:14.220 | is because norepinephrine released when we get into the cold

01:20:19.220 | binds to receptors on the surface of white fat cells

01:20:25.000 | and activates downstream pathways such as UCP1.

01:20:30.000 | So this is an uncoupling protein one

01:20:32.640 | that acts on the mitochondrial metabolism of cells

01:20:35.500 | and increases the mitochondrial output of those cells

01:20:39.060 | and the mitochondrial density of those cells.

01:20:41.340 | In other words, it takes a cell

01:20:43.520 | that has a kind of a weak engine

01:20:46.140 | or no engine for generating energy,

01:20:48.860 | although every cell has some mitochondria,

01:20:51.060 | it takes cells that have very few mitochondria

01:20:53.620 | and increases the engine size.

01:20:56.320 | It kind of stokes the furnace of those particular cells

01:20:59.960 | and actually can change gene expression in those cells.

01:21:03.480 | So that's what's really interesting.

01:21:04.640 | Deliberate cold exposure causes increases in norepinephrine,

01:21:08.420 | which bind to receptors on the surfaces of white fat cells,

01:21:12.680 | which triggers the release of things like UCP1.

01:21:16.320 | It also causes the release of things like PPAR gamma

01:21:19.680 | and cofactor PGC1.

01:21:22.040 | I'm going to refer you to a review

01:21:23.540 | if you want to learn more about these.

01:21:25.440 | For those of you that don't want to learn more,

01:21:26.840 | all you need to know is that the downstream of all that

01:21:29.600 | are increases in mitochondria and metabolism

01:21:32.400 | and actual genetic changes in the white fat cells

01:21:36.240 | that convert them into beige and brown fat cells.

01:21:39.480 | This is especially important for adults

01:21:41.400 | because babies and young children

01:21:44.740 | actually don't have the ability to shiver

01:21:47.760 | or they have a less robust capacity to shiver.

01:21:51.520 | Very small babies really can't shiver,

01:21:53.440 | so they have a lot of brown fat in order to keep them warm.

01:21:57.440 | Young children eventually develop the ability to shiver

01:22:00.340 | and maintain these brown fat stores,

01:22:02.920 | mainly around the clavicles, the heart,

01:22:04.720 | the upper spine, and in the upper back.

01:22:07.660 | And it's no coincidence that kids can often run around

01:22:10.840 | with a minimal of clothing and be comfortable

01:22:12.520 | in environments that adults would be cold in.

01:22:15.240 | As life goes on, we tend to lose beige and brown fat,

01:22:21.000 | but this mechanism that I'm referring to

01:22:23.680 | points to the plasticity of white fat,

01:22:25.660 | meaning the ability for white fat

01:22:27.040 | to actually convert its identity

01:22:28.580 | into this metabolically thermogenically enhancing form

01:22:32.100 | of beige and brown fat.

01:22:33.900 | So deliberate cold exposure is a terrific way

01:22:36.520 | to increase your core metabolism.

01:22:38.440 | And oftentimes critics will say,

01:22:39.880 | well, the increase in metabolism isn't that significant,

01:22:42.540 | although I do want to point out again,

01:22:44.440 | the 93% and the 350% increases in metabolism

01:22:49.440 | from that previous study.

01:22:51.040 | But critics then will say,

01:22:53.180 | well, that doesn't really translate

01:22:54.920 | to that big of a caloric burn

01:22:59.000 | during the deliberate cold exposure.

01:23:00.960 | But to that, you should say, ah,

01:23:02.680 | but that's only limiting your optics

01:23:04.840 | to just a portion of the effects

01:23:06.280 | of deliberate cold exposure,

01:23:07.780 | because deliberate cold exposure

01:23:09.080 | can also convert white fat to beige fat and brown fat

01:23:12.840 | and lead to these more lasting increases in metabolism.

01:23:17.000 | So for any of you interested in increasing your metabolism

01:23:19.680 | and/or being comfortable in cold environments

01:23:22.480 | and/or being comfortable in terms of being able

01:23:25.600 | to combat stress mentally,

01:23:27.520 | deliberate cold exposure I do believe is a powerful tool.

01:23:30.960 | And there is simply no reason why you couldn't

01:23:33.560 | and shouldn't use the same protocols

01:23:35.800 | that I described earlier for building resilience

01:23:38.520 | to increase metabolism.

01:23:39.920 | Provided you're hitting that 11 minute per week threshold,

01:23:43.400 | you ought to be stimulating both mechanisms,

01:23:46.160 | increases in resilience and increases in core metabolism.

01:23:51.800 | As I mentioned earlier, most of the detailed studies

01:23:53.820 | on the conversion of white fat to beige fat and brown fat

01:23:57.080 | through the use of cold have been done in animal models,

01:23:59.520 | but the human data are starting to emerge.

01:24:01.480 | And if you'd like to do the deep dive into these mechanisms,

01:24:04.200 | things like UCP1, PPAR gamma, et cetera,

01:24:07.220 | there's a beautiful review that was published recently

01:24:09.640 | in the journal Cell,

01:24:10.600 | which is one of the three apex journals,

01:24:12.120 | Nature Science Cell.

01:24:13.680 | And the title of that paper is

01:24:15.680 | Adipose Tissue Plasticity in Health and Disease.

01:24:18.140 | I love this review.

01:24:19.440 | It has beautiful diagrams detailing all of the pathways

01:24:22.760 | from cold to norepinephrine through UCP1,

01:24:26.460 | downstream of things like cyclic AMP.

01:24:28.200 | If none of those names mean anything to you,

01:24:30.240 | don't worry about it.

01:24:31.080 | You certainly don't need to know these mechanisms

01:24:32.840 | to benefit from deliberate cold exposure protocols.

01:24:35.760 | If those names do mean something to you

01:24:38.140 | or you're interested in exploring the downstream effects

01:24:41.160 | of deliberate cold exposure and something else

01:24:43.600 | that's really nice that's covered in this paper

01:24:45.600 | is how deliberate cold exposure interacts

01:24:48.040 | with fasted states and fed states.

01:24:51.720 | I think you'll also find this review very interesting.

01:24:54.280 | I don't want to go too deeply into fasted states

01:24:56.320 | and fed states right now.

01:24:58.080 | Suffice to say that when we are fasted,

01:25:00.440 | meaning when we haven't eaten for some period of time,

01:25:03.020 | our baseline levels of norepinephrine and epinephrine

01:25:07.100 | are already elevated.

01:25:08.960 | And so cold exposure at those times

01:25:11.360 | ought to have an even greater effect

01:25:13.880 | on metabolism and resilience and so on.

01:25:16.480 | So for you fasters or your intermittent fasters out there,

01:25:20.400 | if you really want to get fancy,

01:25:21.860 | you can do your deliberate cold exposure when you are fasted.

01:25:25.560 | I certainly wouldn't recommend doing it

01:25:27.120 | with a very full stomach in any case.

01:25:29.460 | And as I mentioned before on this podcast,

01:25:32.960 | intermittent fasting is but one way,

01:25:36.200 | and certainly there are other ways

01:25:37.520 | to limit total caloric intake for sake of maintaining

01:25:40.660 | or losing weight if that's your goal.

01:25:43.120 | I know many people are using and benefit

01:25:45.480 | from intermittent fasting, however,

01:25:47.400 | and so it certainly can be combined

01:25:49.680 | with deliberate cold exposures

01:25:51.160 | in order to get even greater increases

01:25:53.000 | in norepinephrine and epinephrine.

01:25:54.860 | So for those of you that are primarily interested

01:25:57.100 | in using deliberate cold exposure

01:25:58.560 | to increase dopamine levels in your brain and body,

01:26:02.220 | you can also do a combined protocol

01:26:04.520 | whereby you ingest caffeine 60 to 120 minutes

01:26:09.140 | before the deliberate cold exposure.

01:26:11.720 | This is based on a study that I've talked about before

01:26:14.660 | entitled Caffeine Increases Striatal Dopamine

01:26:17.540 | D2, D3 Receptor Availability in the Human Brain.

01:26:20.400 | And as the title suggests, this study was done on humans,

01:26:23.760 | looking at the density and or efficacy

01:26:27.560 | of these dopamine receptors in an area of the brain

01:26:29.840 | called the striatum, which is involved in planning and action

01:26:32.500 | and also suppressing planning and action.

01:26:34.320 | It's involved very closely with whether or not

01:26:37.580 | we can engage in behavior and withhold behavior,

01:26:41.080 | the so-called go and no-go pathways in the brain.

01:26:44.240 | Dopamine plays a critical role in that

01:26:45.820 | and many other things as well, as you now know.

01:26:48.360 | So why would you want to ingest caffeine 60 to 120 minutes

01:26:52.620 | before deliberate cold exposure?

01:26:55.020 | Well, as I talked about earlier,

01:26:57.760 | dopamine can increase quite substantially

01:27:00.260 | in response to deliberate cold exposure,

01:27:02.180 | but dopamine on its own doesn't do anything.

01:27:04.000 | It has to bind to receptors.

01:27:05.980 | And this paper shows quite definitively

01:27:08.680 | that ingesting caffeine, in this case,

01:27:10.340 | it was 300 milligram dose of caffeine,

01:27:12.360 | which is about the dose of caffeine

01:27:14.160 | in two or three cups of coffee.

01:27:15.440 | It depends on the strength of the coffee, of course,

01:27:17.560 | but it's not an outrageous amount of caffeine.

01:27:19.800 | That increases the density and or efficacy

01:27:23.800 | of these receptors, which would allow that dopamine

01:27:25.820 | to have its greatest effect.

01:27:28.820 | And for those of you that want to get really, really fancy,

01:27:31.120 | I suppose you could do this fasted,

01:27:32.580 | so you get the further increase in norepinephrine,

01:27:35.000 | then you get the dopamine increase from the cold exposure,

01:27:37.200 | the binding of the dopamine.

01:27:38.880 | Although I do want to point out that at some point,

01:27:42.120 | you start layering together enough protocols

01:27:44.080 | that you would be spending your entire day

01:27:45.680 | trying to get this dopamine pulse.

01:27:47.080 | And I would hope that you would have other activities

01:27:49.560 | that you would engage in.

01:27:50.780 | But if you're getting up in the morning and you're fasted

01:27:53.760 | because you haven't eaten all night

01:27:55.040 | and you have a cup of coffee, and then 60 minutes later,

01:27:57.360 | you take your cold shower, or two hours later,

01:28:00.500 | you do your cold immersion or your cold shower,

01:28:02.880 | you would be layering together these different mechanisms

01:28:05.840 | of dopamine receptors, epinephrine, and so forth

01:28:07.960 | in a way that at least to me doesn't seem incompatible

01:28:11.240 | with having some other life, like going to school

01:28:13.280 | and having relationships, et cetera.

01:28:15.040 | And this increase in dopamine,

01:28:16.720 | particularly in the striatum, is not a trivial one.

01:28:20.740 | I do want to point out, as the authors do,

01:28:23.160 | that preclinical studies have shown that increases

01:28:25.620 | in striatal dopamine induced by things like modafinil,

01:28:29.400 | which is used to treat ADHD and treat narcolepsy,

01:28:33.280 | is necessary for their wake-promoting actions.

01:28:36.120 | What this really says is that just having elevated levels

01:28:38.640 | of dopamine from a drug or from an ice bath

01:28:41.200 | or what have you is not sufficient

01:28:43.280 | to get the effects of dopamine.

01:28:44.560 | You really need the receptors to be available,

01:28:47.400 | and you need those receptors to be available

01:28:49.040 | in the appropriate density,

01:28:50.440 | and you need those receptors to be available

01:28:52.560 | in the appropriate density in the striatum in particular.

01:28:55.320 | So I think there are a number of reasons why,

01:28:57.500 | if it's compatible with the other aspects of your health,

01:29:00.560 | 'cause of course always you have to consider this

01:29:02.280 | on a background of cardiovascular health

01:29:03.920 | and blood pressure, et cetera,

01:29:05.160 | that ingesting a cup or two of coffee

01:29:07.240 | an hour before your ice bath, maybe fasted as well,

01:29:11.240 | could be quite beneficial for increasing dopamine

01:29:13.520 | over quite extended periods of time.

01:29:15.640 | A couple of key points that you'll want to pay attention to

01:29:18.380 | in thinking about deliberate cold exposure and metabolism.

01:29:21.280 | In the Soberg study, they also explored the use of sauna

01:29:25.240 | and how to use sauna, meaning deliberate heat,

01:29:27.960 | in conjunction with cold.

01:29:30.400 | We are going to do an entire episode

01:29:32.240 | about the use of heat for health and performance.

01:29:34.640 | So that is not the focus now.

01:29:37.160 | However, it does raise an important point

01:29:40.160 | that we do need to address at this moment,

01:29:42.100 | which is if you are using sauna

01:29:44.960 | or if you are taking warm showers,

01:29:47.320 | or if you're simply using deliberate cold exposure

01:29:50.040 | of any kind, should you get into the heat afterward

01:29:54.000 | or before or not at all?

01:29:55.840 | And this is where we can point

01:29:58.440 | to the so-called Soberg principle,

01:30:00.680 | at least I call it the Soberg principle.

01:30:02.320 | The Soberg principle named after first author

01:30:04.240 | of this study I referred to earlier,

01:30:06.680 | Dr. Susanna Soberg.

01:30:08.060 | In science, it is appropriate to take a key piece of data

01:30:12.960 | and call it a principle,

01:30:14.480 | if in fact it translates to something larger,

01:30:16.500 | which I believe it does.

01:30:18.160 | It is generally not appropriate

01:30:20.040 | for people to name a principle after themselves,

01:30:21.960 | although there are a few scientists that have done that.

01:30:25.380 | So I have named it the Soberg principle,

01:30:27.000 | but I did that to give it appropriate credit

01:30:30.280 | to Dr. Susanna Soberg, who discovered that

01:30:33.760 | and pointed out quite appropriately

01:30:36.240 | that to achieve the greatest increases in metabolism

01:30:40.380 | through deliberate cold exposure,

01:30:42.720 | you want to force yourself to reheat on your own

01:30:47.460 | after the deliberate cold exposure,

01:30:49.240 | meaning you wouldn't want to go from the cold shower

01:30:52.120 | to a hot shower or from the cold shower to a sauna.

01:30:54.820 | Rather, if you were going to start with a hot shower

01:30:57.140 | or you're going to start with a sauna,

01:30:58.720 | that you would end with the cold

01:31:01.000 | and then you would reheat naturally.

01:31:03.800 | Now, I personally take a cold shower

01:31:06.080 | a few times a week or do cold immersion.

01:31:08.280 | And because I'm not specifically focused

01:31:10.720 | on increasing metabolism, although I probably should be,

01:31:13.880 | that's not what I'm using it for now,

01:31:16.440 | I will take a hot shower afterwards.

01:31:18.040 | And in doing so, I'm short-circuiting

01:31:19.880 | some of the further metabolic increases that I would achieve

01:31:22.760 | were I to just end with the cold.

01:31:25.160 | So the Soberg principle is,

01:31:27.700 | if you want to increase your metabolism, end with cold.

01:31:31.520 | And we can take this a step further and say

01:31:34.560 | that if you want to use deliberate cold exposure

01:31:36.980 | to increase metabolism, that you should make sure

01:31:40.920 | that you get to the point where you shiver.

01:31:43.600 | And the reason for this is that there are a series of studies

01:31:46.400 | but in particular one study published in the journal Nature,

01:31:48.960 | excellent journal in the year 2018,

01:31:51.720 | showing that deliberate cold exposure

01:31:55.700 | that evokes shivering from the muscles

01:31:59.160 | causes the release of a molecule called succinate

01:32:02.080 | from the muscles, and that succinate plays a key role

01:32:06.160 | in activating brown fat thermogenesis,

01:32:08.820 | which you now have heard about and understand

01:32:10.960 | as critical to the increases in metabolism

01:32:13.120 | caused by deliberate cold exposure.

01:32:15.840 | So what this means is if you want to increase

01:32:17.520 | your metabolism, end on cold, that's the Soberg principle,

01:32:20.280 | and as best you can try and get to the point

01:32:23.160 | where you are shivering either when you are

01:32:25.940 | in the cold exposure or immediately afterwards.

01:32:29.240 | Now, one efficient way to do this is to, for instance,

01:32:32.600 | you could get into the cold shower for a minute

01:32:36.080 | or two minutes or three minutes, uncomfortably cold,

01:32:38.920 | but safe to stay in.

01:32:40.060 | Remember, that's our general rule of thumb.

01:32:42.260 | Then turn off the water and stand there.

01:32:45.440 | Make sure that you're not holding yourself

01:32:47.800 | close to your body.

01:32:48.640 | You're not hugging yourself to try and keep yourself warm,

01:32:50.760 | but rather your limbs are extended at your sides.

01:32:53.920 | And then if that fails to induce shiver,

01:32:56.880 | then to turn on the cold water again

01:32:59.660 | and then turn it off again.

01:33:00.920 | So alternating perhaps a minute to three minutes

01:33:03.000 | of cold exposure followed by a minute to three minutes

01:33:05.520 | of drying out in air and going back into the cold exposure,

01:33:09.320 | et cetera.

01:33:10.620 | I can tell you this from experience.

01:33:12.140 | This is a pretty brutal protocol.

01:33:14.100 | If you have never tried getting into an ice bath

01:33:18.680 | or cold water immersion or cold shower for one minute

01:33:21.560 | and then getting out and trying to stand there

01:33:23.340 | with your arms extended in cool or cold air

01:33:26.080 | for one minute and then getting back into the cold shower

01:33:28.800 | or water immersion, you are in for an experience

01:33:32.400 | because even for those of you

01:33:34.280 | that are pretty shiver resistant,

01:33:36.080 | you will find that it is much, much harder

01:33:38.240 | to get out of that cold water and stand their arms extended

01:33:41.880 | and drying off by evaporation,

01:33:43.780 | which further draws heat from the body

01:33:46.600 | than it is to wrap yourself in a towel,

01:33:48.240 | get in a warm shower or a sauna.

01:33:50.160 | So there's certainly no requirement to end on cold.

01:33:54.040 | There's certainly no requirement to induce shiver.

01:33:57.600 | But if your primary goal is to induce increases

01:34:01.720 | in metabolism, both in the short-term and in the long-term

01:34:05.120 | following the cold exposure,

01:34:06.660 | well, then you'll want to end on cold

01:34:07.960 | and you'll want to find a way to shiver

01:34:10.520 | provided that the level of cold

01:34:12.780 | that you're exposing yourself to

01:34:14.080 | is still safe for you overall.

01:34:15.840 | So up until now, I've been talking

01:34:17.080 | about deliberate cold exposure as a potent stimulus

01:34:20.000 | for the release of norepinephrine in the brain and body.

01:34:22.820 | And indeed it is.

01:34:24.400 | But the way I've been describing it

01:34:26.680 | has been in the context of circulating plasma levels

01:34:30.740 | of norepinephrine, meaning circulating within the blood.

01:34:33.640 | What I haven't mentioned, but is absolutely true,

01:34:37.680 | is that the fat cells themselves

01:34:41.700 | actually receive input from neurons.

01:34:44.700 | So there are neurons that release norepinephrine

01:34:47.500 | in response to cold directly into the fat.

01:34:51.060 | So I want to give you this picture

01:34:53.440 | of how the architecture of all this works,

01:34:55.820 | because I think it can help you navigate

01:34:57.980 | and indeed build better deliberate cold exposure protocols.

01:35:01.780 | Your adrenal glands release norepinephrine and epinephrine.

01:35:05.320 | Your brain has sites within it like the locus coeruleus

01:35:08.920 | that release norepinephrine and epinephrine.

01:35:12.000 | But there are also neurons within your skin that sense cold

01:35:16.160 | and other neurons that can directly release norepinephrine

01:35:19.380 | into the fat stores and cause those white fat cells

01:35:22.640 | to convert to beige and brown fat.

01:35:24.400 | And I think this particular aspect of our physiology

01:35:26.920 | is often overlooked in studies.

01:35:29.720 | And when people say, oh, well,

01:35:31.140 | the increases in metabolism aren't that great,

01:35:33.600 | the circulating levels of norepinephrine,

01:35:35.320 | those are very large, but they're very transient and so on,

01:35:39.180 | that fails to understand that neurons

01:35:42.960 | that actually sense cold are in a position to communicate

01:35:46.840 | via other neurons directly to the fat cells

01:35:49.940 | and release norepinephrine into those fat cells,

01:35:51.860 | which as I pointed out earlier,

01:35:53.540 | set off a huge set of immediate and long-term cascades

01:35:56.800 | of even gene expression changes.

01:35:58.880 | So the picture that I'd like you to have in your mind

01:36:02.040 | is that when you get into the cold,

01:36:04.140 | yes, of course you experience that as a experience of,

01:36:07.760 | I don't want to do this, I'm going to overcome this,

01:36:09.540 | I'm going to climb over these mental walls

01:36:11.300 | that represent adrenaline release in my brain and body,

01:36:14.020 | but also that your fat cells are receiving signals,

01:36:17.940 | norepinephrine signals that are changing those fat cells

01:36:21.020 | in the way that they metabolize energy.

01:36:22.860 | Now I'd like to shift our attention

01:36:24.180 | to the use of deliberate cold exposure

01:36:26.240 | for sake of physical performance.

01:36:28.740 | And there are a lot of opinions out there

01:36:30.420 | about the use of deliberate cold,

01:36:32.440 | whether or not it should be done, for instance,

01:36:33.980 | before or after exercise,

01:36:36.160 | whether or not if done immediately after strength training

01:36:39.700 | or hypertrophy training,

01:36:40.800 | meaning training designed to grow muscles

01:36:43.440 | or make them stronger,

01:36:44.340 | whether or not it can inhibit that process

01:36:46.140 | and so on and so forth.

01:36:47.600 | I think today in looking over the literature

01:36:50.640 | and trying to bring forward the simplest

01:36:52.700 | and most straightforward

01:36:53.600 | and yet scientifically grounded protocols,

01:36:56.000 | we can set up some general guidelines

01:36:58.060 | that will allow most if not all of you

01:37:00.140 | to still extract the benefits of deliberate cold exposure

01:37:03.300 | on physical performance

01:37:05.040 | without getting too neurotic about the exact timing.

01:37:08.380 | But for sake of discussion

01:37:10.660 | and because it's a prominent theme in many online communities

01:37:14.860 | let's just start with the big one out there,

01:37:18.140 | meaning the question of whether or not doing an ice bath

01:37:21.960 | or doing deliberate cold exposure

01:37:23.680 | or taking a cold shower after strength/hypertrophy training,

01:37:28.260 | meaning training designed to increase strength

01:37:30.640 | and/or I should say the size of muscles

01:37:34.120 | will somehow short circuit or diminish that process,

01:37:37.800 | whether or not it will reduce

01:37:39.340 | or eliminate those strength gains and hypertrophy gains.

01:37:42.100 | And the short answer that I was able to arrive at

01:37:45.040 | on the basis of a review article

01:37:47.500 | that I'll talk about in a moment

01:37:48.980 | and some other studies as well

01:37:51.140 | is that if your main goal is hypertrophy and strength,

01:37:56.140 | it is probably best to avoid cold water immersion

01:38:00.460 | and ice bath immersion in the four hours

01:38:04.340 | immediately following that strength

01:38:06.860 | and/or hypertrophy training.

01:38:08.660 | Again, if your main goal is to achieve hypertrophy

01:38:12.860 | or strength or some combination of those,

01:38:15.900 | probably best to avoid cold water immersion up to the neck

01:38:20.140 | or ice bath immersion up to the neck

01:38:23.020 | immediately after strength and hypertrophy training

01:38:26.100 | and extending out to about four hours after that training.

01:38:30.100 | If you're really neurotic about this,

01:38:32.940 | then perhaps you'd want to move the cold water exposure

01:38:35.480 | to a different day entirely,

01:38:37.140 | but it all depends on how neurotically attached you are

01:38:39.800 | to getting every last bit of strength and hypertrophy.

01:38:42.380 | And if that's your goal, terrific,

01:38:44.060 | well then probably moving the cold exposure

01:38:47.160 | four hours or more away from that training

01:38:49.040 | is going to be necessary for you.

01:38:50.700 | Now you'll notice I did not talk about cold showers.

01:38:53.700 | And the reason I did not talk about cold showers

01:38:55.820 | is that there simply are not very many studies

01:38:59.340 | of deliberate cold exposure through cold showers

01:39:01.940 | for the reasons I talked about

01:39:03.040 | at the beginning of the episode.

01:39:05.100 | It's hard for me to imagine that taking a brief cold shower

01:39:08.380 | after a strength or hypertrophy training session

01:39:11.020 | would completely reverse or short circuit

01:39:13.240 | the effects of that strength and hypertrophy training.

01:39:15.480 | But again, if you're neurotically attached

01:39:17.860 | to getting every last bit of strength and hypertrophy

01:39:21.100 | out of your training sessions,

01:39:22.580 | then by all means, err on the side of caution

01:39:24.800 | and wait four hours or more to do your cold shower

01:39:27.460 | just as you would wait four hours or more

01:39:29.880 | to do your cold water immersion.

01:39:31.580 | Now there are nice data pointed to the fact

01:39:33.900 | that doing cold water immersion after a hard run,

01:39:37.540 | so endurance training, or even sprint and interval training,

01:39:41.660 | or after a weight workout where your main focus

01:39:45.660 | is on performance of those movements,

01:39:47.500 | or after a skill training workout

01:39:49.180 | where your main focus on performance of those movements,

01:39:52.260 | that there's no reason to think

01:39:54.200 | that that cold water immersion or ice bath or cold shower

01:39:57.380 | would inhibit the progress or the stimulus

01:40:01.540 | that would lead to progress that occurred

01:40:03.820 | during that training session.

01:40:05.260 | In other words, I don't see any reason

01:40:07.460 | based on the literature to avoid deliberate cold exposure

01:40:10.580 | immediately after training,

01:40:12.060 | again, unless your goal is hypertrophy and strength.

01:40:15.900 | And in fact, there's a very nice review

01:40:17.340 | that was recently published on deliberate cold exposure

01:40:21.580 | and how it can impact physical performance,

01:40:24.720 | whether or not it's done before or after

01:40:27.740 | different types of training and so forth.

01:40:30.260 | The paper is entitled, "Impact of Cold Water Immersion

01:40:33.520 | Compared with Passive Recovery

01:40:35.260 | Following a Single Bout of Strenuous Exercise

01:40:37.780 | on Athletic Performance in Physically Active Participants,

01:40:41.280 | a Systematic Review with Meta-analysis and Meta-regression."

01:40:45.080 | So this is a meta-analysis of 52 studies

01:40:49.540 | that looked at a tremendous number of variables

01:40:51.900 | and contexts as you would expect

01:40:54.300 | in a meta-analysis of 52 studies.

01:40:56.820 | I'm going to read you the conclusions of the study

01:40:58.640 | and I will provide a link.

01:40:59.880 | We certainly don't have the time

01:41:00.900 | to go through all the details of the study.

01:41:02.700 | I will highlight a few specific outcomes

01:41:05.120 | that I found particularly interesting,

01:41:07.060 | but here I am paraphrasing their conclusions

01:41:10.400 | that cold water immersion,

01:41:13.420 | I want to emphasize immersion, not cold showers,

01:41:16.440 | but cold water immersion,

01:41:18.080 | they say was an effective recovery tool

01:41:20.040 | after high intensity exercise.

01:41:22.300 | They observed positive outcomes,

01:41:23.860 | meaning improvements in certain variables

01:41:27.360 | for muscular power, muscular soreness,

01:41:30.260 | meaning reduced muscular soreness, increased muscular power,

01:41:33.280 | perceived recovery after 24 hours of exercise.

01:41:36.720 | However, there were certain forms of exercise

01:41:39.340 | that were not benefited by cold water immersion,

01:41:43.320 | such as eccentric exercise,

01:41:45.800 | exercise focusing only on the lowering component

01:41:49.220 | or the so-called eccentric component of resistance exercise.

01:41:52.700 | They saw some very interesting dose-response relationships

01:41:56.620 | for things like endurance training,

01:41:58.400 | meaning the longer the cold exposure

01:42:01.720 | post-endurance training,

01:42:02.780 | the more improvement in endurance performance,

01:42:05.300 | reductions in circulating creatine kinases

01:42:08.740 | and things that relate to muscle damage

01:42:11.260 | under certain conditions.

01:42:13.080 | At some point in the future, by the way,

01:42:14.240 | we'll do an entire episode on creatine and creatine kinases,

01:42:17.220 | which are important not just for muscular function,

01:42:19.700 | but also for brain function.

01:42:21.580 | But the basic takeaway was that cold water immersion

01:42:25.280 | performed after high-intensity exercise

01:42:27.700 | was beneficial from a number of different standpoints

01:42:30.740 | and indicated that shorter duration cold exposure

01:42:35.740 | and lower temperatures can improve

01:42:38.500 | the efficacy of cold water exposure

01:42:40.540 | if used after high-intensity exercise, okay?

01:42:42.940 | There I'm directly pulling from their conclusions.

01:42:45.400 | So what this says is that it's not just those

01:42:47.860 | longer duration 30, 45-minute and 60-minute protocols

01:42:52.420 | of cold water immersion that we discussed earlier,

01:42:54.860 | but also shorter duration, one-minute, three-minute,

01:42:58.100 | five-minute exposures to lower temperatures,

01:43:02.460 | temperatures that would make you psychologically

01:43:04.760 | want to get out as soon as you possibly can,

01:43:07.700 | but again, that you can safely stay in,

01:43:09.980 | done after training really have been shown

01:43:12.640 | to improve outcomes in terms of reducing soreness

01:43:15.940 | and improving training efficacy,

01:43:18.700 | meaning your ability to get back into training more quickly

01:43:22.440 | and thereby deliver more training stimuli

01:43:25.700 | to a given muscle or in your endurance training protocol.

01:43:29.060 | Translating to English,

01:43:29.900 | what this means is that taking a cold shower

01:43:32.100 | or getting into an ice bath

01:43:33.620 | or some other form of cold water immersion

01:43:35.760 | within the immediate minutes

01:43:37.100 | or even the immediate hours following your training

01:43:40.300 | has been shown to be beneficial.

01:43:41.900 | I'm sure a number of you have questions, for instance,

01:43:45.820 | how long should you be in that cold exposure?

01:43:49.020 | Is it the same as the 11-minute threshold described earlier?

01:43:52.720 | To be honest with you,

01:43:53.640 | there are not enough studies

01:43:55.720 | to really point to the critical threshold

01:43:58.180 | for eliminating or reducing delayed onset muscle soreness

01:44:01.800 | or for getting maximal results

01:44:04.480 | from power and endurance training,

01:44:06.560 | but this study does make a couple of key points,

01:44:09.200 | and here I will just paraphrase.

01:44:11.180 | For instance, that cold water immersion

01:44:13.620 | is more likely to positively influence

01:44:16.860 | muscular power performance,

01:44:18.660 | to reduce muscle soreness,

01:44:20.340 | to reduce serum creatine kinase,

01:44:22.700 | and to improve perceived recovery

01:44:24.920 | after high-intensity exercise

01:44:26.780 | as compared with passive recovery.

01:44:29.260 | This can be translated to cold water exposure

01:44:32.260 | after training is beneficial

01:44:34.000 | and probably better than passive recovery

01:44:36.880 | from a number of standpoints.

01:44:38.640 | In addition, they say that dose-response relationships,

01:44:42.040 | meaning the amount and the degree of cold

01:44:47.100 | that people were exposed to,

01:44:48.580 | and how often they did that,

01:44:49.980 | in particular in lower temperature cold immersion,

01:44:53.740 | so these would be the sorts of cold immersion protocols

01:44:57.020 | that are one minute or two minutes,

01:44:59.040 | three minutes, maybe five minutes,

01:45:00.820 | but that one couldn't stay in there longer

01:45:02.780 | because it feels stressful and one wants to get out,

01:45:05.580 | may be more effective after high-intensity exercise

01:45:08.260 | for removal of serum creatine kinase.

01:45:11.380 | As well, that these shorter duration

01:45:13.420 | cold water immersion approaches

01:45:15.180 | may be more effective

01:45:16.100 | after high-intensity endurance performance as well.

01:45:19.820 | So all of this can be translated to say

01:45:22.260 | that unless your main goal is hypertrophy and strength,

01:45:27.140 | that cold exposure, ideally cold immersion

01:45:31.060 | in cold water or ice bath,

01:45:32.540 | but if you don't have access to that,

01:45:34.220 | then cold showers is likely going to be beneficial

01:45:37.180 | if done immediately after

01:45:39.100 | or in the minutes or hours after your training,

01:45:42.460 | especially high-intensity training.

01:45:44.260 | One particularly nice thing about this meta-analysis

01:45:46.540 | is that it included some studies

01:45:48.180 | that involved the use of cooling packs,

01:45:50.740 | so again, vests that can hold essentially ice packs,

01:45:55.400 | and indeed even cryotherapy chambers and so on.

01:45:59.000 | There's a nice table in the study

01:46:00.340 | if you want to get really detailed

01:46:01.860 | and go and look specifically at those studies,

01:46:03.780 | I invite you to do that.

01:46:04.800 | We'll put a link to this study

01:46:06.460 | in the caption for this episode.

01:46:08.600 | But all in all, what this study shows is that

01:46:10.820 | deliberate cold exposure can be very useful

01:46:14.100 | for recovery, likely through reductions in inflammation

01:46:18.140 | in muscle and connective tissue.

01:46:20.660 | And while this study did not look specifically

01:46:22.900 | at the mechanisms of reduced inflammation

01:46:24.900 | caused by deliberate cold exposure,

01:46:27.860 | those mechanisms are somewhat known.

01:46:30.460 | There are a number of studies that have pointed to the fact

01:46:32.660 | that deliberate cold and cold generally

01:46:34.840 | can reduce inflammatory cytokines,

01:46:37.360 | such as IL-6, interleukin-6.

01:46:39.520 | It can increase anti-inflammatory cytokines,

01:46:43.120 | such as interleukin-10 and so on.

01:46:45.260 | Without getting into all those details,

01:46:48.000 | I think it's sufficient to say that

01:46:50.560 | if you are somebody who experiences

01:46:52.140 | a lot of delayed onset muscle soreness,

01:46:54.240 | taking a cold shower after your training

01:46:56.020 | or getting into a cold immersion after your training,

01:46:58.340 | even if it's a few hours later, ought to help.

01:47:01.020 | And if you are doing particularly intense training,

01:47:04.560 | then you probably want to ratchet up

01:47:06.660 | the number of cold exposure sessions that you're doing,

01:47:10.180 | even if those have to be done

01:47:11.460 | on separate days from your training,

01:47:12.980 | because a lot of the inflammatory effects of training,

01:47:15.900 | endurance and strength training,

01:47:16.940 | are actually occurring some hours

01:47:19.040 | away from the training stimulus.

01:47:20.720 | So it's not just that inflammation

01:47:22.020 | goes up radically during training, which it often can,

01:47:25.100 | but that it can occur even in the days

01:47:27.260 | and even weeks afterwards, depending on how intense

01:47:29.580 | and how long duration that training is.

01:47:31.340 | So deliberate cold exposure is very powerful

01:47:33.860 | as an anti-inflammatory tool.

01:47:36.440 | Now I'd like to emphasize a topic that we touched on

01:47:38.580 | at the beginning of the episode,

01:47:40.420 | which are those glabrous skin surfaces,

01:47:43.100 | the hands, the upper face, and the bottoms of the feet,

01:47:45.780 | through which heat is especially good at leaving the body.

01:47:50.420 | And another way of putting that

01:47:52.700 | is that one can cool the body much more efficiently

01:47:56.580 | through the glabrous skin surfaces.

01:47:58.860 | Now, if you want to understand

01:48:00.580 | all of the science behind this

01:48:02.620 | and all of the various applications,

01:48:05.860 | I invite you to please listen to the episode

01:48:07.780 | that I did with Dr. Craig Heller,

01:48:09.860 | again, in the biology department at Stanford.

01:48:12.220 | For sake of this episode,

01:48:14.720 | I'm just going to detail a couple of findings

01:48:17.060 | from his laboratory.

01:48:18.360 | The first one dealing with exercise-induced hyperthermia,

01:48:21.380 | because I think this is very interesting

01:48:22.780 | and it can even save lives

01:48:24.580 | if you understand the way this works.

01:48:26.420 | There's a particular paper that focuses on this

01:48:30.420 | and we will put a link to this as well.

01:48:32.300 | The title of this paper is "Novel Application

01:48:34.160 | of Chemical Cold Packs for Treatment

01:48:35.540 | of Exercise-Induced Hyperthermia,

01:48:37.460 | a Randomized Control Trial."

01:48:39.540 | This is a pretty brutal study,

01:48:42.160 | brutal for the subjects, that is.

01:48:44.820 | What this study involved was having subjects

01:48:47.940 | walk on a treadmill at a pretty significant incline,

01:48:50.960 | anywhere from 9% to 17%,

01:48:53.660 | wearing a substantial amount of clothing

01:48:56.260 | that was not well ventilated,

01:48:58.220 | and the room was kept to 40 degrees Celsius,

01:49:00.700 | which is 104 degrees Fahrenheit.

01:49:03.180 | This is definitely not something to do at home.

01:49:06.680 | This study was designed to induce hyperthermia,

01:49:09.180 | which, as I mentioned earlier, can be quite dangerous.

01:49:11.580 | And they compared two types of cooling.

01:49:14.500 | In the first form of cooling

01:49:16.180 | that they call traditional cooling,

01:49:18.200 | they had ice packs on their neck,

01:49:21.500 | in their armpits, and in their groin.

01:49:23.880 | And in the other group,

01:49:25.500 | there was the so-called glabrous skin cooling.

01:49:27.840 | So the palms, the soles of the feet,

01:49:29.580 | which were actually,

01:49:30.900 | so they were cooling inside the boots or inside of gloves,

01:49:35.440 | and on the upper portion of the face.

01:49:39.040 | And the basic takeaway of this study

01:49:41.220 | is that by cooling the glabrous skin,

01:49:43.240 | the subjects were able to sustain this walking

01:49:47.260 | on these incline treadmills for much longer

01:49:50.880 | than were the people who received traditional cooling.

01:49:54.180 | And also, the return to baseline temperature

01:49:56.380 | was much faster in the glabrous skin cooling group.

01:49:59.820 | So how this translates to the real world

01:50:01.840 | is that if ever you are hyperthermic,

01:50:04.040 | or someone else is hyperthermic,

01:50:05.640 | one way to cool them down quickly

01:50:08.880 | is to cool these palmar glabrous,

01:50:13.260 | soles of the feet glabrous,

01:50:14.500 | and upper portion of the face glabrous portions of the body

01:50:18.020 | using cool rags, using ice packs,

01:50:21.080 | or using any number of different cold objects

01:50:24.680 | or temperatures.

01:50:25.520 | One key thing if you're going to use glabrous skin cooling

01:50:30.100 | is that whatever you use to cool those surfaces

01:50:33.140 | cannot be so cold that it causes vasoconstriction.

01:50:37.060 | Because as I mentioned earlier,

01:50:38.920 | the arteriovenous ostomoses,

01:50:41.660 | these portals of arteries directly to veins

01:50:43.920 | that exist only in these glabrous skin surfaces,

01:50:47.780 | the way that they're able to cool the body

01:50:51.580 | and essentially pass cool into the body,

01:50:53.900 | although that's not really what they're doing,

01:50:55.080 | they're actually extracting heat from the body

01:50:57.420 | to be technical, they're extracting heat from the body,

01:51:00.520 | the only way they can do that

01:51:02.500 | is if those veins don't collapse

01:51:05.100 | and veins will collapse if they are made very, very cold.

01:51:08.780 | So if you want to use glabrous skin cooling

01:51:11.540 | to offset hyperthermia or for the other forms of performance

01:51:14.420 | which we will talk about in a moment,

01:51:16.180 | you need to use a cool object or surface

01:51:19.660 | that is not so cold that it causes vasoconstriction.

01:51:22.260 | And this can be a little bit tough to dial in,

01:51:24.700 | meaning it can be tough to identify such an object.

01:51:27.940 | And for that reason, Dr. Heller and some of his colleagues

01:51:30.340 | have developed a commercial product called the CoolMitt,

01:51:32.480 | you can actually go to their website, coolmitt.com,

01:51:34.580 | I don't have any financial or other relationship to them.

01:51:37.820 | I know they've been developing this technology

01:51:39.540 | for some period of time,

01:51:40.460 | it involves a glove that you put your hand into,

01:51:43.580 | it circulates water of a given temperature

01:51:46.700 | and it does so at a temperature

01:51:49.340 | that is sure to not cause vasoconstriction of the palm.

01:51:53.140 | And you might be asking,

01:51:53.980 | how can you just put your hand into one glove

01:51:56.220 | and have this work?

01:51:57.040 | Well, that's how powerful these glabrous skin surfaces are,

01:51:59.780 | even just by cooling one palm,

01:52:02.840 | the core body temperature drops radically.

01:52:06.300 | Now that's their commercial technology.

01:52:08.900 | I know that some people out there have started

01:52:10.660 | to experiment with a home version of this,

01:52:13.060 | which would be taking a package, for instance,

01:52:15.580 | of frozen blueberries or some other cold drink

01:52:18.920 | or cold metal object and actually bringing it into the gym

01:52:21.760 | or out on a run.

01:52:23.380 | There are even people who are now developing

01:52:25.080 | cooled bicycle handles for long rides.

01:52:29.200 | This might seem a little kooky or crazy to you,

01:52:31.280 | but as you'll soon hear in the study I'm about to describe,

01:52:35.000 | the increases in endurance and in the volume

01:52:38.760 | of strength training that people can conduct

01:52:41.700 | if they appropriately cool their body

01:52:43.740 | through these glabrous skin portals

01:52:46.140 | is actually quite significant.

01:52:48.360 | So again, as it relates to hyperthermia,

01:52:50.500 | if someone is overheating,

01:52:52.220 | by all means try and get them out of that heat,

01:52:54.220 | get them to stop exercising.

01:52:55.700 | You can die from hyperthermia,

01:52:57.600 | try and cool the bottoms of the feet,

01:52:59.040 | the palms of their hands

01:53:01.280 | and the upper portion of their face.

01:53:03.200 | That does not mean that it would be a bad idea

01:53:06.420 | to put cold water on the top of their head.

01:53:08.160 | That probably would also help and perhaps on their neck.

01:53:10.640 | What is probably not going to be a good idea

01:53:13.400 | is to do the more standard thing

01:53:15.720 | of draping someone in cold towels

01:53:17.300 | on the surface of their body.

01:53:18.360 | Because as I mentioned at the beginning of the episode,

01:53:20.460 | that thermostat in the hypothalamus,

01:53:22.360 | the medial preoptic area will typically react to that

01:53:25.660 | by increasing core body temperature further.

01:53:28.240 | The effects of glabrous skin cooling on physical performance

01:53:31.540 | are truly remarkable provided the glabrous skin cooling

01:53:34.200 | is done correctly.

01:53:36.360 | And I want to point out that the main degree of effect

01:53:39.960 | is on volume or the ability to do more work.

01:53:44.160 | And I want to point this out

01:53:45.400 | because I think that many people,

01:53:47.640 | certainly in the exercise science community,

01:53:49.320 | but even in the general public,

01:53:50.520 | when they hear about some of these effects

01:53:52.420 | that are measured in the laboratory,

01:53:54.600 | they sort of look at those effects a bit askance

01:53:59.080 | and they think, well, that's not possible, right?

01:54:01.040 | Effects, for instance, that have been documented

01:54:03.400 | showing doubling or tripling of the number of dips

01:54:05.860 | that one can do in a relatively short amount of time,

01:54:08.760 | or doubling of the number of pull-ups one can do,

01:54:11.760 | or 14% increases in strength,

01:54:13.920 | or even comparable degrees in increase

01:54:16.480 | in weight training output

01:54:18.280 | to people who are on performance enhancing drugs,

01:54:20.400 | et cetera, et cetera.

01:54:22.200 | Part of the confusion is that the effects

01:54:25.000 | of proper Palmer cooling,

01:54:27.380 | because it almost always is done by Palmer cooling

01:54:30.080 | and less often in these experiments

01:54:32.400 | by cooling of the bottoms of the feet

01:54:34.060 | in the upper portion of the face,

01:54:35.520 | but those effects tend to be the ability

01:54:39.840 | to do more work over time.

01:54:42.880 | And just to illustrate some of the major effects

01:54:45.160 | that the Heller lab has seen

01:54:46.320 | and that are documented in this manuscript

01:54:48.080 | that I'll share with you in a moment,

01:54:50.960 | the typical protocol is to have people come in

01:54:53.320 | and do some endurance training, so running on a treadmill,

01:54:56.200 | and to have a condition where one group

01:54:59.440 | is actually doing Palmer cooling

01:55:00.960 | while they are on a bike or on a treadmill.

01:55:03.600 | And inevitably the outcome is that they can do more work.

01:55:06.960 | They can pedal further at a given speed,

01:55:09.920 | or they can run longer at a given speed

01:55:12.780 | than people who are not doing Palmer cooling

01:55:14.800 | or who are receiving cooling by way of cold compress

01:55:18.780 | to the back of the neck or ice pack to the armpits, et cetera.

01:55:22.760 | So the effects of Palmer cooling are very clear

01:55:25.040 | and very robust.

01:55:26.720 | And in the context of endurance exercise,

01:55:29.560 | almost always allow people to do more work,

01:55:31.920 | to go longer with less perceived effort

01:55:34.080 | and to quit later, so to speak.

01:55:36.140 | In terms of strength training,

01:55:38.780 | they've looked at the capacity to perform sets of dips.

01:55:42.540 | So one of the more famous examples of this

01:55:44.780 | that Dr. Heller shares in the episode that we did earlier,

01:55:48.760 | and that you can find at Hubermanlab.com,

01:55:50.940 | involves someone coming in and doing sets of dips,

01:55:54.100 | maybe 40 dips.

01:55:55.900 | This person actually could do 40 dips on their first set,

01:55:58.320 | then resting for a period of two to three minutes

01:56:00.620 | and then doing 35,

01:56:02.420 | and then resting for a period of two or three minutes

01:56:04.500 | and then doing progressively fewer and fewer and fewer

01:56:06.820 | to the point where over a period of time,

01:56:09.380 | they add up the total number of dips that they can do,

01:56:11.820 | and then they have them come back

01:56:14.220 | after a period of recovery.

01:56:15.620 | So not immediately after, but take a couple of days,

01:56:18.700 | come back and do effectively the same protocol,

01:56:21.540 | but during their rest periods,

01:56:22.900 | they're doing two minutes of Palmer cooling,

01:56:25.880 | which essentially allows heat to move out of the body,

01:56:29.300 | lowering core body temperature, in other words.

01:56:31.500 | And what they find is that they see enormous increases

01:56:35.320 | in the total number of dips that people can do,

01:56:37.300 | but that doesn't mean that the person goes

01:56:38.600 | from being able to do 40 dips

01:56:39.860 | to being able to do 50 dips or 60 dips on that first set.

01:56:43.080 | What it means is they are able to do 40 on the first set,

01:56:46.020 | then 40 on the second, then 38 on the third,

01:56:48.880 | and so on and so forth,

01:56:50.040 | so that the total duration of the workout is extended,

01:56:52.900 | and yet they're doing much more work,

01:56:55.500 | even though it takes more time.

01:56:57.300 | So that's an important point,

01:56:59.380 | and I think a point that perhaps wasn't as clear

01:57:02.820 | or as clearly made by me in the previous episodes

01:57:05.380 | that discussed this topic.

01:57:07.420 | For those of you that are interested

01:57:08.700 | in exploring Palmer cooling,

01:57:10.940 | first of all, I recommend taking a brief glance

01:57:13.780 | or even a deep dive into this study,

01:57:17.060 | which is entitled work volume

01:57:18.560 | and strength training responses to resistive exercise

01:57:21.180 | improve with periodic heat extraction from the palm.

01:57:24.280 | In this study, they describe big increases in anaerobic,

01:57:30.360 | meaning strength training output,

01:57:32.620 | things like improvement in dips, improvement in bench press,

01:57:36.960 | improvement in pull-ups, et cetera, in human subjects.

01:57:40.820 | And it's a really nice study

01:57:42.380 | and points to some of the protocols

01:57:43.940 | that you might be able to adapt in your own setup.

01:57:46.780 | For instance, over six weeks of pull-up training,

01:57:48.900 | palm cooling in between sets, improved volume by 144%,

01:57:53.900 | and this was in experienced subjects.

01:57:56.460 | So that's interesting because a lot of studies

01:57:58.860 | of strength training and improvements in hypertrophy

01:58:01.340 | and strength are done in inexperienced untrained athletes,

01:58:04.580 | which changes the picture somewhat

01:58:07.340 | compared to experienced athletes.

01:58:10.640 | They found that strength, meaning the one repetition maximum

01:58:13.440 | increased 22% over 10 weeks in bench press training.

01:58:17.100 | And they point to the particularly strong effects

01:58:20.000 | of using Palmer cooling when people reach plateaus

01:58:23.380 | in endurance and strength training.

01:58:25.080 | And there, I think it's an important point.

01:58:26.660 | I think that if you're going to explore Palmer cooling,

01:58:30.260 | it's probably not the sort of thing

01:58:31.860 | that you're going to do in every run

01:58:34.040 | or in every bout of cycling

01:58:35.980 | or in every strength training session,

01:58:38.600 | but that it might be used to vastly increase your volume

01:58:42.500 | or vastly increase your endurance in a given session

01:58:45.700 | or a set of sessions in order to push through plateaus.

01:58:49.060 | A particularly interesting point in light of that

01:58:51.620 | is Dr. Heller has observed again and again

01:58:54.660 | that Palmer cooling reduces delayed onset muscle soreness

01:58:57.620 | or can eliminate it entirely.

01:58:59.460 | And that's very interesting because it also points

01:59:01.560 | to the fact that reducing core body temperature

01:59:03.900 | may somehow be involved in short circuiting

01:59:06.160 | the normal mechanisms of delayed onset muscle soreness.

01:59:09.620 | And you might say, well, how would temperature be involved

01:59:12.340 | in delayed onset muscle soreness?

01:59:14.320 | Well, I want to refer you back to the meta analysis

01:59:17.540 | that we talked about earlier where the short duration,

01:59:20.380 | very cold temperature exposure after training

01:59:23.040 | did indeed reduce delayed onset muscle soreness

01:59:25.480 | in part through reduction, excuse me, in creatine kinase.

01:59:28.940 | So it's not inconceivable that temperature

01:59:32.280 | and delayed onset muscle soreness are related.

01:59:34.980 | And that raises perhaps the most important point,

01:59:37.160 | which is the way that Palmer cooling can improve performance

01:59:42.160 | by way of reducing core body temperature is known.

01:59:46.080 | And that is because when one engages in exercise

01:59:50.360 | or muscular output of any kind,

01:59:52.060 | strength or endurance exercise,

01:59:54.880 | the range of temperatures under which a muscle can perform

01:59:58.380 | is actually very narrow.

02:00:00.560 | There's an enzyme called pyruvate kinase,

02:00:02.760 | which is critical to muscle contractions

02:00:05.600 | and pyruvate kinase can only function

02:00:07.900 | in a very narrow range of temperatures.

02:00:09.780 | If that temperature gets too hot,

02:00:11.500 | meaning if the muscle heats up locally,

02:00:13.880 | whether or not by running or cycling or swimming

02:00:16.240 | or weightlifting, the ability for that muscle

02:00:19.240 | to continue to contract is reduced

02:00:21.500 | and eventually is short-circuited completely.

02:00:23.880 | And I think this is a much underexplored

02:00:26.760 | or at least a much under-discussed aspect

02:00:29.380 | of so-called muscular failure

02:00:31.000 | or the failure of one to continue to endure in running.

02:00:35.280 | So for instance, when you run

02:00:36.680 | as compared to a bench press or something,

02:00:38.720 | you don't stop running

02:00:39.920 | because you can't actually contract the muscles further,

02:00:42.400 | but somehow signals about the heating up

02:00:46.000 | of muscular tissue are conveyed to the brain.

02:00:48.700 | There's a crosstalk there.

02:00:49.720 | It's probably bi-directional and people stop.

02:00:52.360 | They quit, right?

02:00:53.320 | This is the quitting reflex.

02:00:54.840 | In strength training,

02:00:58.160 | one can no longer perform a repetition

02:01:00.160 | or set of repetitions in part

02:01:01.720 | because of heating up of the muscle locally.

02:01:03.460 | There are other mechanisms as well, of course,

02:01:05.540 | and I realize that.

02:01:06.980 | But what's very clear from the palmar cooling work

02:01:09.620 | is that by simply holding onto a cool object,

02:01:13.220 | remember, not an object so cold

02:01:14.880 | that it constricts the vessels of the palms

02:01:17.080 | or constricts the vessels on the bottoms of the feet,

02:01:20.040 | but by holding onto a relatively cool object

02:01:22.760 | in one or both hands in between sets for two minutes or so,

02:01:26.080 | you can very efficiently reduce your core body temperature.

02:01:29.780 | And in doing so,

02:01:31.160 | reduce the temperature of the muscles

02:01:32.880 | that are doing the work,

02:01:34.080 | increase the capacity for pyruvate kinase

02:01:37.860 | to continue to allow your muscles to contract

02:01:40.760 | and thereby allow you to do more volume of endurance

02:01:43.980 | and strength training.

02:01:45.000 | So a simple protocol that Dr. Heller passed to me

02:01:48.180 | is find a relatively cool object.

02:01:51.560 | So you could, for instance, fill two bottles with cold water,

02:01:54.360 | maybe put a few ice cubes in there, right?

02:01:56.440 | This is not exact because we're not talking

02:01:58.400 | about the commercial cool mint product here,

02:02:00.020 | we're talking about an at-home version,

02:02:01.780 | or use a pack of frozen blueberries or broccoli,

02:02:05.280 | the sort of pack of those as what he described,

02:02:07.800 | and then in between sets to put your hands,

02:02:10.380 | and ideally you'd put the bottoms of your feet,

02:02:12.080 | but that's not always feasible in most gyms

02:02:13.880 | where they won't let you take off your shoes and so forth,

02:02:16.180 | but to put the palms of your hands on that cool surface

02:02:19.120 | for a minute or two minutes between sets

02:02:22.540 | and then returning to your sets of work.

02:02:24.880 | Now, if you are heating up through other mechanisms,

02:02:28.600 | like you're wearing a stocking cap

02:02:29.900 | and you're in a very warm environment,

02:02:31.500 | this might not have as potent an effect

02:02:33.380 | as if you were to do this cooling

02:02:35.080 | in a more moderate environment

02:02:36.740 | wearing lighter clothing, et cetera.

02:02:38.640 | So by all means, warm up to do your exercise,

02:02:41.480 | lubricate your joints and get into a place

02:02:43.240 | where you're not going to injure yourself

02:02:44.320 | doing whatever form of exercise you do,

02:02:46.400 | but then if you'd like to explore Palmer cooling,

02:02:48.920 | I know a number of people who've written to me saying

02:02:51.120 | they heard about Palmer cooling

02:02:52.220 | on the episode with Dr. Heller,

02:02:53.460 | they've tried this and they see quite excellent results.

02:02:56.620 | It does take some discipline, right?

02:02:58.200 | It's one thing to just kind of hang out in the gym

02:02:59.940 | and play on your phone in between sets.

02:03:01.240 | It's another to do deliberate cooling with your palms

02:03:04.100 | or the bottom of your feet

02:03:04.940 | or the upper portion of your face.

02:03:06.520 | You might get some weird looks,

02:03:07.880 | but of course you'll be the one

02:03:09.060 | doing significantly more volume,

02:03:11.040 | not experiencing delayed onset muscle soreness

02:03:13.500 | and achieving better endurance and strength gains

02:03:16.000 | were you to do this properly.

02:03:17.500 | Now, as a final topic related

02:03:19.380 | to the use of deliberate cold exposure

02:03:21.400 | for improving health and performance,

02:03:23.740 | I'd like to touch on this theme that exists online

02:03:27.520 | on social media, on YouTube,

02:03:29.000 | and in various fitness communities

02:03:31.760 | of using deliberate cold exposure to the groin,

02:03:34.280 | in particular to the testicles,

02:03:36.300 | in order to try and increase testosterone.

02:03:39.260 | And while this might sound really kooky,

02:03:41.620 | indeed this practice exists.

02:03:44.360 | Indeed, if you were to go on the Amazon,

02:03:47.100 | there are actually ice pack underwear

02:03:50.360 | that are being marketed

02:03:52.560 | for sake of increasing testosterone.

02:03:54.800 | Now, I am not aware of any specific well-controlled studies

02:03:57.800 | that show that this indeed works.

02:04:00.400 | I can imagine based on what I know about the nervous system,

02:04:03.720 | testosterone and cold, et cetera,

02:04:06.000 | that there are a couple of mechanisms

02:04:07.340 | by which one might experience increases in testosterone

02:04:11.000 | as a consequence of deliberate cold exposure.

02:04:13.120 | First off, let me say,

02:04:14.040 | there is no reason why you would have to apply these ice packs

02:04:17.960 | in the way that I just described.

02:04:20.360 | One could, of course, take a cold shower.

02:04:22.200 | One could, of course, use cold immersion of various kinds,

02:04:26.280 | and you're still going to get that exposure of the groin

02:04:29.720 | and the testicles to cold.

02:04:31.380 | Now, I should point out that people do report,

02:04:34.680 | at least anecdotally, increases in testosterone

02:04:38.460 | as a consequence of this practice.

02:04:40.000 | And I have to imagine

02:04:41.160 | that they are measuring their serum testosterone,

02:04:43.040 | that they're not just guessing

02:04:44.040 | that their testosterone went up.

02:04:46.420 | If you know of a study exploring this directly,

02:04:48.480 | please let me know,

02:04:49.720 | put it in the comment section on YouTube,

02:04:51.520 | or even just email me.

02:04:53.160 | We have a email that you can find at hubermanlab.com.

02:04:57.400 | Please email me the reference.

02:04:58.880 | I wasn't able to find a reference,

02:05:00.600 | but I can imagine two reasonably plausible mechanisms

02:05:04.220 | by which deliberate cold exposure to the groin

02:05:07.520 | and particularly the testicles would increase testosterone.

02:05:10.720 | The first is somewhat direct,

02:05:13.240 | which is that anytime you cool a body surface,

02:05:17.080 | that if it's cold enough,

02:05:18.480 | you're going to get vasoconstriction.

02:05:20.280 | And then subsequently,

02:05:21.280 | you're going to get a rebound increase in vasodilation,

02:05:24.680 | meaning you're going to constrict the blood vessels

02:05:26.620 | in that area.

02:05:27.460 | And then after the cold is removed,

02:05:29.520 | there's going to be more blood flow to that area.

02:05:31.400 | And of course,

02:05:32.240 | blood flow relates to organ health and tissue health,

02:05:35.100 | generally, so perfusion of that region and the gonads,

02:05:40.100 | to be specific, with additional blood,

02:05:42.880 | you could imagine in some ways increasing testosterone.

02:05:46.200 | That's reasonably plausible.

02:05:48.300 | The other probably more likely mechanism

02:05:51.020 | relates to the dopamine increases caused by cold exposure

02:05:54.900 | that we talked about earlier.

02:05:56.300 | Again, anytime you have a somewhat stressful stimulus,

02:05:59.640 | but in particular with cold exposure,

02:06:01.440 | it seems that the catecholamines norepinephrine, epinephrine,

02:06:04.480 | and dopamine all increase.

02:06:07.320 | And dopamine is known to be in the pathway

02:06:10.800 | that can stimulate testosterone.

02:06:13.060 | And so while there isn't a direct relationship

02:06:15.080 | between dopamine stimulating testosterone,

02:06:17.260 | there is an interesting pathway whereby dopamine increases

02:06:20.220 | can trigger increases in things like luteinizing hormone,

02:06:23.320 | which can trigger increases in testosterone,

02:06:26.080 | as well as estrogen for that matter.

02:06:28.140 | So I know that there are a lot of people out there

02:06:30.180 | that are interested in the use of cold exposure

02:06:31.960 | for increasing testosterone.

02:06:33.380 | And some of those people in communities

02:06:35.360 | are indeed using cold exposure directly on the gonads,

02:06:40.240 | on the testes in order to do this.

02:06:42.440 | I'm not certain that that direct contact is necessary.

02:06:46.360 | And in some cases it might actually be quite dangerous

02:06:51.040 | or you at least should be careful

02:06:52.400 | in terms of tissues there and avoiding damage.

02:06:55.760 | But nonetheless, I think that a dopamine impact

02:06:59.880 | on testosterone is very likely given the 250% increases

02:07:04.040 | in dopamine that have been observed with cold water immersion

02:07:06.380 | and all of that points to the fact that cold water immersion

02:07:10.680 | very likely increases testosterone,

02:07:13.320 | but as a downstream consequence

02:07:15.260 | of the cold water immersion effects on dopamine

02:07:18.160 | and luteinizing hormone.

02:07:19.520 | And again, there's no reason to think

02:07:21.080 | that the increases in luteinizing hormone

02:07:23.200 | would also increase estrogen,

02:07:25.240 | probably not too dangerous

02:07:28.000 | or levels that one would want to avoid.

02:07:31.560 | But I don't think that there's anything particularly specific

02:07:34.920 | about cold for inducing testosterone and not other hormones.

02:07:38.140 | I think it's very likely to increase

02:07:39.320 | as a number of different hormones.

02:07:41.540 | I do hope that there will be a systematic study on this

02:07:44.280 | in the not too distant future.

02:07:45.800 | I also hope to not be a subject

02:07:47.720 | in the cooling of the gonads experiment.

02:07:50.360 | Now, I promise you the last topic was the last topic,

02:07:52.540 | but there's one other really important point

02:07:54.580 | that I think everyone should be aware of

02:07:56.400 | if you're going to use deliberate cold exposure.

02:07:59.020 | And that brings us back to the very first thing

02:08:01.920 | that we discussed today

02:08:03.460 | along the lines of deliberate cold exposure,

02:08:05.160 | which is that your baseline temperature

02:08:07.140 | is going to be lowest about two hours before you wake up.

02:08:11.440 | It's going to increase in the morning and as you wake up

02:08:15.040 | and increase throughout the day and afternoon,

02:08:17.240 | and then start to drop in the evening

02:08:19.200 | and come down at night as you head to sleep.

02:08:21.440 | I also want you to remember

02:08:24.520 | that if you are to cool the external portion of your body,

02:08:27.980 | in particular your torso,

02:08:29.500 | the net effect of that

02:08:31.940 | is going to be an increase in body temperature.

02:08:35.480 | So for many people, not all, but for many people,

02:08:38.900 | if you are going to do deliberate cold exposure,

02:08:41.960 | you are going to increase your core body temperature.

02:08:45.180 | And that makes sense if you think about

02:08:46.680 | how deliberate cold exposure can increase metabolism

02:08:50.180 | by increasing thermogenesis.

02:08:52.400 | What that all means is that

02:08:55.020 | if you are doing your deliberate cold exposure

02:08:57.340 | early in the day,

02:08:58.700 | you are going to get yet a further increase

02:09:01.500 | in core body temperature

02:09:03.040 | that would be associated with wakefulness,

02:09:05.620 | your ability to be alert that morning

02:09:07.460 | or throughout the day and so on.

02:09:10.260 | It also means that if you do your deliberate cold exposure

02:09:13.880 | very late in the evening or at night,

02:09:16.280 | so 6 p.m., 7 p.m., 9 p.m., and so on,

02:09:21.280 | you are going to increase your core body temperature.

02:09:23.700 | And if you recall,

02:09:25.780 | a decrease in core body temperature of one to three degrees

02:09:29.500 | is not just beneficial but is necessary

02:09:32.700 | in order to get into deep sleep and remain in deep sleep.

02:09:36.380 | So the takeaway from this is deliberate cold exposure

02:09:39.680 | done properly will increase your core body temperature

02:09:42.240 | and make you feel more alert.

02:09:44.240 | So if you're doing it early in the day,

02:09:46.200 | that's probably terrific,

02:09:48.160 | given that most of us want to be alert during the day.

02:09:50.940 | However, if you do it too late in the day,

02:09:53.220 | evening or night, it can disrupt sleep

02:09:55.880 | by way of disrupting your core body temperature.

02:09:58.780 | Now, the caveat to that is

02:10:00.900 | I myself tend to do my deliberate cold exposure

02:10:04.400 | early in the day,

02:10:05.240 | maybe not first thing in the morning, but mid-morning,

02:10:07.540 | maybe as late as three or four in the afternoon

02:10:09.580 | in some cases.

02:10:10.420 | In the longer days of summer, I might do it even later,

02:10:12.760 | 5 or 6 p.m., and have no trouble sleeping.

02:10:15.600 | I have done deliberate cold exposure very late at night,

02:10:18.940 | 10 p.m., 11 p.m., and so on,

02:10:21.740 | as part of a 30-day challenge

02:10:23.200 | of doing deliberate cold exposure every day for 30 days,

02:10:25.940 | and I got sloppy with my timing,

02:10:27.540 | and then in order to not miss a day,

02:10:29.300 | I would do it at 11 o'clock at night.

02:10:30.940 | And I must say,

02:10:31.900 | I found that I could still fall asleep very easily

02:10:35.340 | even doing deliberate cold exposure very late at night.

02:10:38.060 | However, on those particular days, I was particularly busy,

02:10:42.280 | and so I was particularly exhausted

02:10:44.580 | when I arrived at the deliberate cold exposure,

02:10:46.860 | and I had no trouble falling asleep

02:10:49.100 | after doing deliberate cold exposure

02:10:50.540 | and then taking a nice warm shower and then going to sleep.

02:10:53.020 | But I could imagine

02:10:54.580 | that because of the increases in core body temperature

02:10:56.940 | caused by deliberate cold exposure

02:10:59.340 | that were one to do that too late in the day,

02:11:02.060 | evening or night, that it could indeed disrupt your sleep.

02:11:04.860 | So my recommendation would be for most people,

02:11:07.680 | only do deliberate cold exposure

02:11:09.220 | if you are prepared to be fairly alert

02:11:11.560 | for the next one to four or maybe even six hours

02:11:14.820 | following that deliberate cold exposure.

02:11:17.000 | So for today's episode,

02:11:18.180 | as is the case with most episodes

02:11:20.140 | of the Huberman Lab Podcast, I covered a lot of material.

02:11:23.180 | We talked about mechanisms of catecholamines and stress

02:11:25.940 | and pulsatile release of epinephrine,

02:11:28.580 | metabolism, mental effects, performance,

02:11:31.140 | glabrous skin cooling, and on and on and on.

02:11:33.860 | And while the goal, of course,

02:11:35.480 | is to make sure that everyone arrives at specific,

02:11:38.500 | very clear mechanistic and actionable protocols,

02:11:41.740 | I do realize that it is an immense amount of information.

02:11:44.780 | And for that reason,

02:11:45.640 | I've created a list of deliberate cold exposure protocols

02:11:49.940 | aimed at improving mental toughness and resilience,

02:11:53.660 | mood, performance, metabolism,

02:11:57.000 | reducing inflammation, and so on and so forth.

02:11:59.440 | All of those have been condensed into succinct form

02:12:02.700 | and can be found

02:12:04.180 | at the Huberman Lab Neural Network Newsletter.

02:12:06.860 | This is a monthly or semi-monthly newsletter

02:12:09.380 | that we release that includes takeaways

02:12:11.540 | from the podcast and protocols.

02:12:13.660 | You can access those protocols, zero cost,

02:12:16.460 | by simply going to HubermanLab.com,

02:12:19.060 | signing up for the Neural Network Newsletter.

02:12:20.900 | It's very easy to do.

02:12:21.820 | You just supply your email and you will receive

02:12:23.980 | the newsletter.

02:12:24.940 | We do not share your email with anybody else.

02:12:27.780 | In fact, we have our privacy policy laid out

02:12:30.740 | on the HubermanLab.com website.

02:12:33.100 | So you can find that there.

02:12:34.660 | And the protocols that I've designed

02:12:36.740 | should make it very straightforward for you to create

02:12:39.260 | a set of protocols that you could use with cold showers,

02:12:42.800 | with cold immersion, with or without ice,

02:12:44.820 | in combination with exercise,

02:12:46.300 | specifically for one goal or another,

02:12:47.940 | or to accomplish multiple goals simultaneously.

02:12:50.580 | If you're learning from and/or enjoying this podcast,

02:12:52.780 | please subscribe to our YouTube channel.

02:12:54.560 | That's a terrific zero cost way to support us.

02:12:57.260 | In addition, please subscribe to the podcast

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02:13:10.020 | If you have suggestions for future guests

02:13:12.140 | or topics that you would like us to cover

02:13:14.020 | or feedback generally for the Huberman Lab Podcast,

02:13:16.780 | please put that in the comment section on YouTube.

02:13:19.620 | Please also check out the sponsors mentioned

02:13:21.440 | at the beginning of today's episode.

02:13:23.320 | That is the best way to support this podcast.

02:13:25.880 | In addition, we have a Patreon.

02:13:27.620 | It's patreon.com/andrewhuberman,

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02:13:32.220 | at any level that you like.

02:13:33.740 | On many previous episodes of the Huberman Lab Podcast,

02:13:36.340 | we talk about supplements.

02:13:37.820 | While supplements aren't necessary for everybody,

02:13:39.940 | many people derive tremendous benefit from them

02:13:42.180 | for things like sleep and focus

02:13:43.940 | and other aspects of health and performance.

02:13:46.460 | One issue with the supplement industry

02:13:47.960 | that's very serious, however,

02:13:49.580 | is that many supplement companies

02:13:51.640 | simply do not use high quality ingredients

02:13:53.820 | or the amounts of the ingredients they list on the packaging

02:13:57.180 | does not match what's actually contained in their products.

02:13:59.800 | For that reason, we partner with Thorne,

02:14:02.220 | T-H-O-R-N-E, because Thorne supplements

02:14:04.740 | are known to be of the very highest quality ingredients

02:14:07.340 | and the very highest degree of specificity

02:14:10.100 | in terms of the amounts of the ingredients

02:14:12.140 | that are listed on the packaging

02:14:13.700 | accurately match what's contained in their products.

02:14:16.620 | If you'd like to see the Thorne products that I take,

02:14:18.560 | you can go to Thorne, that's t-h-o-r-n-e.com/u/huberman.

02:14:23.560 | And there you can see the Thorne products that I take

02:14:26.160 | and get 20% off any of those products.

02:14:28.580 | In addition, if you navigate deeper into the Thorne site

02:14:31.040 | through that portal, Thorne,

02:14:32.380 | t-h-o-r-n-e.com/u/huberman,

02:14:36.360 | you can also get 20% off any of the other products

02:14:38.800 | that Thorne makes.

02:14:40.020 | If you're not already subscribed to Huberman Lab

02:14:42.180 | on Instagram and Twitter, please do so.

02:14:44.440 | There I cover science and science-related tools

02:14:46.880 | that sometimes overlap with the content of the podcast,

02:14:49.600 | but oftentimes is distinct

02:14:51.100 | from the information covered on this podcast.

02:14:53.580 | So thank you once again for joining me in the discussion

02:14:56.400 | about the use of deliberate cold exposure

02:14:58.600 | for health and performance.

02:14:59.940 | And last, but certainly not least,

02:15:02.220 | thank you for your interest in science.

02:15:04.060 | [upbeat music]

02:15:06.640 | (upbeat music)

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

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