back to indexUsing Deliberate Cold Exposure for Health and Performance | Huberman Lab Podcast #66
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Welcome to the Huberman Lab Podcast,
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where we discuss science and science-based tools
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for everyday life.
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I'm Andrew Huberman,
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and I'm a professor of neurobiology and ophthalmology
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at Stanford School of Medicine.
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Today, we are going to discuss
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the use of deliberate cold exposure
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for health and performance.
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Temperature is a powerful stimulus on our nervous system
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and indeed on every organ and system of our body.
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And cold in particular can be leveraged to improve
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mental health, physical health, and performance,
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meaning for endurance exercise,
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for recovering from various forms of exercise,
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for actually improving strength and power,
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and for enhancing mental capacity.
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In order to properly leverage deliberate cold exposure
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for sake of mental health, physical health, and performance,
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you have to understand how cold impacts the brain and body.
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So today we are going to discuss that.
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We're going to talk about some of the neural circuits
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and pathways, some of the hormones involved.
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I promise to make it all clear and accessible,
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regardless of whether or not
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you have a scientific background or not.
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We are also going to discuss very specific protocols
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that you can apply, which leverage variables
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like temperature, how cold, how to deliver the cold,
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for instance, whether or not you use a cold shower,
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cold immersion, ice bath, circulating water, or still water,
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whether or not you're going for walks outside in a t-shirt
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when it's cold, or whether or not
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you're purposefully using things like cryo,
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if you have access to that or not.
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One thing I can promise you is that
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by the end of today's episode,
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you will know a lot about the biology of thermal regulation.
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That is how your brain and body regulates its temperature.
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You will also have a lot of tools in your arsenal
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that you can use and leverage toward
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improving mental health, physical health,
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reducing inflammation in the body,
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improving athletic performance,
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improving mental performance.
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I promise to spell out all those protocols in detail
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as I go along and to summarize them again at the end.
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I'd like to make a point now that I'm going to make
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several additional times during today's episode,
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and that is that temperature is a very potent stimulus
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for the brain and body.
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That also means that it carries certain hazards
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if it's not done correctly.
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Now, everyone shows up to the table, meaning to protocols,
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with a different background of health status,
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and there's simply no way that I can know
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what your health status is.
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So anytime you are going to take on a new protocol,
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that means a behavioral protocol or a nutritional protocol
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or a supplementation protocol,
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you should absolutely consult a board-certified physician
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before initiating that protocol.
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I don't just say this to protect us.
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I also say this to protect you.
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If you'd like to see our medical disclaimer,
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you can go to our show notes.
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It's described there.
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In fact, I encourage you to please do that.
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And in general, when embarking on new protocols,
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in particular, if they involve strong stimuli
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like changing temperature
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or placing yourself into unusual temperatures,
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I would encourage you to progress gradually.
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I would also encourage you to not look at gradual progression
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as the kind of weak version of a protocol.
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In fact, today I'm going to discuss
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a really beautiful peer-reviewed study
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that involved having people do deliberate cold exposure,
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so they were immersing themselves into water
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up to about their neck,
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and the water was actually not that cold.
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It was only about 60 degrees Fahrenheit,
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which for most people is pretty tolerable,
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so nowhere near the kinds of extreme temperatures
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that one could use in other protocols.
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And the interesting thing is,
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despite that fairly modest cold temperature,
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by simply extending the duration of time
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that people were in that water,
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they experienced enormous increases in neurochemicals
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that ought to translate to improvements in focus and mood,
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and indeed, that's what's been observed
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in subsequent studies.
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So again, please see our medical disclaimer in our show notes
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please proceed with caution always.
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Please also understand that the most potent stimulus
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isn't always the one that you experience
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as the most intense in the moment.
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In fact, I would encourage you
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to find the minimum threshold of stimulus
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that will allow you to derive the maximum benefit
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from each protocol, and indeed,
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I will point out what those thresholds ought to be today.
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I'll give you some simple formulas,
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gauges or guides that you can use
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in order to navigate this extremely interesting
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and potent tool that we call deliberate cold exposure.
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Before we talk about deliberate cold exposure
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and its many powerful applications,
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I'd like to highlight a study
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that I find particularly interesting
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and that I think you will find
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particularly interesting and useful.
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The title of this study is brief aerobic exercise
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immediately enhances visual attentional control
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and perceptual speed,
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testing the mediating role of feelings of energy.
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Now, the reason I like this study is,
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first of all, it's a fairly large size sample group.
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They looked at 101 students.
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These were college age students, and they had two groups.
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One group did 15 minutes of jogging at moderate intensity.
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So when they did measure percent heart rates, et cetera,
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but this would be analogous to zone two cardio,
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which I've discussed on this podcast before.
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Zone two cardio is cardiovascular exercise
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that places you at a level
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where you can hold a conversation
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with a little bit of strain,
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meaning that you can get the words out,
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but every once in a while, you have to catch your breath.
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Whereas if you were to push any harder
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by any mechanism going faster
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or on a steeper incline, et cetera,
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that you would have a hard time
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carrying out a conversation.
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So zone two cardio is a common form
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of describing that level of intensity
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that they call moderate intensity.
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So one group did 15 minutes of jogging
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at moderate intensity,
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which I'm translating to roughly zone two cardio.
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The other group did 15 minutes of relaxation concentration
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that is somewhat akin to mindfulness meditation.
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And then they were analyzed for perceptual speed,
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visual attentional control,
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something called working memory,
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which is your ability to keep certain batches
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of information online.
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Just imagine someone telling you their phone number
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and you have to remember that sequence of numbers
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in your head for some period of time.
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And that's working memory.
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And it depends very heavily
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on the so-called prefrontal cortical networks,
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which are involved in planning and action.
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And they also looked at people's feelings of energy
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and they measured that subjectively,
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how energetic people felt.
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Now, the major takeaways from the study
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that I'd like to emphasize
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are that the 15 minutes of jogging group
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experienced elevated levels of energy
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for some period of time after they ceased the exercise.
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Whereas the group that did mindfulness meditation
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actually reported feeling more calm
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and having less overall energy.
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Now that's very subjective
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and indeed they used subjective measures to analyze energy.
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But what gets interesting is when they looked at performance
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on these various cognitive tasks
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and the two tasks that they use
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were called the trail making tests.
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They have different versions of this,
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version A, version B,
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I don't want to go into too much detail,
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but version A essentially involves having a page of numbers
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that are distributed somewhat randomly.
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So one, two, three, four, five, six, seven, eight,
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and so on, but distributed randomly across the page.
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And people have to use visual search
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to circle those numbers in sequence.
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So this involves visual attention,
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it involves some motor skills,
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involves a number of things
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that certainly require energy and focus.
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The second test was the trail making test part B,
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as I mentioned earlier,
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and this involved also circling numbers in sequence,
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but interspersed between those numbers were letters.
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So rather than just having to circle off numbers
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in sequence, they actually had to connect one,
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then the letter A, then two, then the letter B, et cetera.
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And remember, these are randomly distributed across a page.
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The major takeaway from the study
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is that the group that did the 15 minutes
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of moderate exercise prior to these two tests
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showed significant decreases in the amount of time
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required to complete these tests accurately.
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That is interesting and indeed surprising, at least to me,
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because there have been many studies
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looking at the effects of mindfulness meditation
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on the ability to focus.
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The key variable in the study turned out to be energy,
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this feeling, subjectively measured feeling, I should say,
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of having more energy and thereby the ability to focus,
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especially in these high cognitive demand tasks.
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Now, the takeaway from this study for all of us,
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I think is pretty straightforward.
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If you are going to sit down to do some work
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that requires focus and working memory
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and cognitive attention,
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and especially if it's some visual spatial control,
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meaning you have to search for things on a page,
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you have to organize things on a page,
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so this would be writing, arithmetic,
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basically cognitive work of any kind,
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15 minutes of moderate exercise done prior to that work bout
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could be very beneficial for you.
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This does not mean that mindfulness meditation
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would not be of benefit to you.
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I wouldn't want you to conclude that,
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but if you had to choose between doing
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15 minutes of mindfulness meditation
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and doing 15 minutes of moderate exercise
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prior to a cognitive work bout,
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I would say the 15 minutes of moderate exercise
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would be more valuable,
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at least based on the data in this paper.
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In many previous podcasts,
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I've talked about the powerful effects of doing things like
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mindfulness meditation and other forms of NSDR,
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non-sleep deep rest, so these could be 20 minute naps
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or just lying there quietly with your eyes closed
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or yoga nidra or NSDR scripts are available on YouTube
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and various other places free of cost of any kind.
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You can just go to YouTube, put in NSDR,
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non-sleep deep rest.
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Those protocols have been shown to be very beneficial
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for enhancing neuroplasticity,
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the changes in the brain and body that encode
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or shift the neural circuits that allow for memory to change
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that allow for learning to occur after a learning bout.
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What I'm referring to today in this particular study
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is the use of moderate exercise
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in order to increase one's focus and attention
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in order to trigger that neuroplasticity.
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So the simple sequence here is get energetic and alert,
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do that prior to the learning bout,
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engage in the cognitive work or learning bout,
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and then mindfulness meditation, NSDR and so forth
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And if you would like to access this paper
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and like to look more at the details in the paper,
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we'll be sure to put a link in the show notes.
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The first author is Legrand.
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And again, the title of this paper is
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"'Brief Aerobic Exercise Immediately Enhances
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Visual Attention Control and Perceptual Speed,
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Testing the Mediating Role of Feelings of Energy.'"
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And I also just want to emphasize immediately,
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I think most people out there are interested in tools
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and protocols that work the first time
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and that work every time.
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And indeed, I think this protocol fits that bill.
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I'm pleased to announce that I'm hosting
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two live events this May.
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The first live event will be hosted
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in Seattle, Washington on May 17th.
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The second live event will be hosted
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in Portland, Oregon on May 18th.
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Both are part of a lecture series entitled
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The Brain-Body Contract,
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during which I will discuss science
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and science-based tools for mental health,
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physical health, and performance.
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And I should point out that while some of the material
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I'll cover will overlap with information covered here
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on the Huberman Lab Podcast
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and on various social media posts,
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most of the information I will cover
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is going to be distinct from information covered
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on the podcast or elsewhere.
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So once again, it's Seattle on May 17th,
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Portland on May 18th.
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You can access tickets by going to hubermanlab.com slash tour
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and I hope to see you there.
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Before we begin, I'd like to emphasize
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that this podcast is separate from my teaching
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and research roles at Stanford.
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It is, however, part of my desire and effort
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to bring zero cost to consumer information about science
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and science-related tools to the general public.
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In keeping with that theme,
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I'd like to thank the sponsors of today's podcast.
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Our first sponsor is Athletic Greens, also called AG1.
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I started taking AG1 way back in 2012,
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so I'm delighted that they're sponsoring the podcast.
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The reason I started taking AG1
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and the reason I still take AG1 once or twice a day
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is that it covers my foundational vitamin, mineral,
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and probiotic needs.
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It also has adaptogens and things like zinc
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for immune system function,
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but the probiotics are one of the key features in there.
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I've done several podcasts on the gut microbiome,
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which are these trillions of microbiota
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that live in our digestive tract
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and that are crucial for our immune system,
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brain function, and so on.
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One way to enhance our gut microbiome
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to ensure that it's healthy
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is to make sure that we get the correct probiotics.
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And Athletic Greens has the correct prebiotics
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and probiotics that ensure a healthy gut microbiome.
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If you'd like to try Athletic Greens,
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you can go to athleticgreens.com slash Huberman
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to claim a special offer.
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They'll give you five free travel packs
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that make it very easy to mix up Athletic Greens
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while you're on the road, so in the car and on the plane.
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I should mention that Athletic Greens is delicious.
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I love the way it tastes.
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I mix mine with some water
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and a little bit of lemon or lime juice.
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The special offer is the five free travel packs
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Vitamin D3 has been shown to be important
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Many of us who get sunlight get enough vitamin D3.
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Many of us, even if we do get sunlight,
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do not get enough vitamin D3.
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So the year supply of vitamin D3 also has K2,
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which is important for cardiovascular function,
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for calcium regulation.
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Again, go to athleticgreens.com slash Huberman
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to get the five free travel packs
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and the year supply of vitamin D3K2.
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Today's episode is also brought to us by Roca.
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Roca makes eyeglasses and sunglasses
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that are of the absolute highest quality.
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The company was founded
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and everything about their eyeglasses and sunglasses
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Now, the glasses were initially designed
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They're very lightweight.
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They have a terrific aesthetic,
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Today's episode is also brought to us by Helix Sleep.
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Helix Sleep makes mattresses and pillows
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Everybody knows the importance of sleep
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Okay, let's talk about the use of cold
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for health and performance.
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I confess I love this topic because it takes me back
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to my undergraduate years when I worked in a laboratory
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studying cold physiology,
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its effects on the brain and its effects on the body.
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And over the years,
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I've always kept track of the literature in this area,
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and indeed there have been some tremendous discoveries,
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both in animal models, so in rodents like mice and rats,
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but also in humans.
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And today we're going to talk about
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both categories of studies,
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and I will be careful to point out
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when discoveries were made in animal models
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and when they were made in humans.
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A key point when thinking about the use of cold as a tool,
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and the key point is that you have a baseline level
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of temperature that is varying,
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changing across the 24-hour cycle.
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So any use of deliberate cold exposure
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is going to be superimposed on that rhythm,
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that circadian rhythm, meaning that 24-hour rhythm.
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The basic contour of your circadian rhythm in temperature
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is that approximately two hours before the time you wake up
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is your so-called temperature minimum.
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So your temperature minimum is a time
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within the 24-hour cycle
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when your body temperature is at its lowest, okay?
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So if you normally wake up around 6 a.m.,
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your temperature minimum is probably about 4 a.m.
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If you normally wake up at about 7 a.m.,
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your temperature minimum is probably about 5 a.m.
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It's not exactly two hours before your wake-up time.
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It's approximately two hours before your wake-up time.
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Now, as you go from your temperature minimum
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to the time in which you are going to awake,
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your temperature is rising slightly.
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And then at the point where you wake up,
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your temperature starts to go up more sharply
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and will continue to go up into the early
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and sometimes even into the late afternoon.
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And then sometime in the late afternoon and evening,
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your temperature will start to decline.
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And indeed, as you approach sleep,
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your body temperature will drop
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by anywhere from one to three degrees.
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And in fact, that decrease in core body temperature
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is important, if not essential,
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for getting into and staying in deep sleep, okay?
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So temperature rises with waking.
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That's easy to remember.
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It tends to continue to rise throughout the day.
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And in the late afternoon and evening,
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your temperature will start to go down
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and the drop in temperature actually helps you access sleep.
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That background, or what we call baseline circadian rhythm
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in core body temperature is important to remember
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because it helps us frame both the effects
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of deliberate cold exposure
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and it helps us frame when you might want
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to use deliberate cold exposure
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in order to access specific states.
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It also points to times within the 24-hour cycle
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when you might want to avoid using deliberate cold exposure
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if your primary goal is to get to sleep.
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Okay, so that's the circadian rhythm in temperature.
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Now I just briefly want to touch on thermal regulation
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at the level of the body and the brain.
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And this will be very surprising to many of you.
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Let's do what's called a Gedanken experiment,
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which is a thought experiment.
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Let's say I send you out into the desert heat
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for a jog or a run, and it's very hot outside,
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you know, 102 degrees or 103 degrees.
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And you start to move, you start to sweat,
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and of course your core body temperature goes up.
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Now, then I offer you a cold towel,
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maybe a really, really cold towel.
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And this towel is saturated with water
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so you could actually squeeze the water out of that
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and cool your body off.
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And our Gedanken experiment is for me to say,
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okay, where are you going to place the towel?
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How are you going to cool yourself off?
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And I'm guessing that most of you would think
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that the best way to cool yourself off
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would be to drape that towel over your head,
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maybe your neck, over your torso,
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that it would feel really, really good
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and they would cool you off.
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Well, that's exactly the wrong approach
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if you want to cool off.
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And in fact, if you were to use that approach,
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your body temperature would continue to increase even more,
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yes, even more than had you not placed that cold towel
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on your head or your torso.
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Thermal regulation, meaning your brain and body's ability
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to regulate your internal core temperature
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is somewhat like a thermostat
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and that thermostat resides in your brain.
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So if you think about the thermostat
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in your home or apartment,
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if it's too warm in your home or apartment
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and you were to take a bag of ice
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and to put it on that thermostat,
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what would the thermostat do?
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It would register the environment as artificially cool.
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It would think that the environment
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was actually much colder than it is.
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And so as a consequence,
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it would trigger a mechanism
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to further increase the temperature in the room.
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And you have such a thermostat as well.
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It's called the medial preoptic area of the hypothalamus.
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The hypothalamus is a small region of brain tissue
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about over the roof of your mouth
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and a little bit in front of that.
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So it's basically right behind your nose
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and over the roof of your mouth.
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And it's a collection of neurons.
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Those neurons have a lot of different functions
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that include things like the control of aggression,
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the control of sex behavior,
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the control of temperature regulation and so on.
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The medial preoptic area has connections
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with the rest of the brain
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or areas within the brain, I should say,
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and with many areas within the body.
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It receives input from receptors in our skin
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and inside our body that register temperature,
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and it acts as a thermostat.
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So if the surface of your body is made cool,
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your medial preoptic area will send signals
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by way of hormones and by way of chemicals
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that will serve to heat your body up.
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So what this means is that if you want to cool down,
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the last thing you want to do
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is to bring a cold surface of any kind,
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towel or splashing water,
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to the majority of your body surface.
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It might be very, very surprising to you.
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And you might say, wait, if I want to cool down,
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I should jump into a cold lake or something of that sort.
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That's a different thing altogether.
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What I'll tell you,
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and we'll get into this in more depth later,
link |
is that if you really want to cool down
link |
quickly and efficiently,
link |
you should leverage particular portals,
link |
meaning particular sites on your body
link |
where heat can leave your body more readily
link |
and where cooling can have a dramatic and fast impact
link |
on your core body temperature.
link |
It can even save your life if you're going hyperthermic.
link |
We're going to talk more about the specific protocols
link |
to reduce core body temperature for sake of performance
link |
and avoiding hyperthermia later in the episode.
link |
Hyperthermia, of course, is a very, very dangerous situation
link |
because while your body can drop in core temperature
link |
somewhat and still be safe,
link |
you can't really increase your body temperature that much
link |
before your brain starts to cook
link |
and other organs start to cook and by cook,
link |
I mean the cells actually start to die.
link |
So you have to be very, very careful with the use of heat.
link |
Heat stroke is no joke.
link |
People die from heat stroke all the time.
link |
You really want to avoid that.
link |
One way to avoid that
link |
is to cool the appropriate surfaces of your body
link |
and the appropriate surfaces in this case
link |
are the upper cheeks,
link |
or I would say the upper half of the face,
link |
the palms of your hands and the bottoms of your feet.
link |
I've talked about this on the podcast before
link |
and in the guest episode with Dr. Craig Heller,
link |
my colleague in the biology department at Stanford,
link |
but just very briefly, these surfaces,
link |
the upper half of the face,
link |
the palms of the hands and the bottoms of the feet
link |
are what we call glabrous skin surfaces,
link |
G-L-A-B-R-O-U-S, glabrous.
link |
And those surfaces are unique in that just below them,
link |
the vasculature is different than elsewhere in the body.
link |
Normally, the passage of blood goes from arteries
link |
to capillaries to veins,
link |
but just beneath the glabrous skin
link |
on the bottoms of the feet,
link |
the hands and the upper half of the face,
link |
you have what are called arteriovenous ostomoses.
link |
These are portals of blood
link |
that go directly from arteries to veins.
link |
allow the body to dump heat more readily, more quickly.
link |
So as it turns out,
link |
that if you are to cool the palms of the hands,
link |
the bottoms of the feet and the upper half of the face,
link |
you can more efficiently reduce core body temperature
link |
for sake of offsetting hyperthermia
link |
and for improving athletic performance
link |
and maybe even cognitive performance.
link |
So we will return to the specific protocols
link |
for doing that later in the episode.
link |
I'll give you a lot of details about how to do that,
link |
how to do that without the use of any fancy
link |
or expensive technology.
link |
There are some technologies
link |
that are now commercially available.
link |
For instance, the so-called Coolmit
link |
that will allow you to do that with maximum efficiency,
link |
but I'll also give you some at-home methods to do this
link |
either in the gym or on runs or for sake of cognitive work.
link |
Okay, so the two key themes again
link |
are understand that baseline circadian rhythm in temperature
link |
and understand that the best way to cool the body
link |
is going to be by making sure that something cold
link |
contacts the bottoms of your feet,
link |
the palms of your hands and the upper half of the face.
link |
Ideally all three if your goal
link |
is to lower core body temperature quickly.
link |
And again, just cooling off the back of your neck
link |
or the top of your head or your torso with a towel
link |
is going to be the least efficient way
link |
to lower core body temperature
link |
and might even increase body temperature
link |
under certain conditions.
link |
Okay, with those two points in mind,
link |
we can start to think about
link |
directed deliberate cold exposure protocols.
link |
And there are a number of different reasons
link |
to use deliberate cold exposure.
link |
And I want to separate those out for you.
link |
There are cold protocols that have been tested
link |
in peer reviewed studies
link |
that are designed to improve mental performance.
link |
They are designed to improve things like resilience
link |
or your grittiness or your ability to move through challenge
link |
or to regulate your mind and your internal state
link |
under conditions of stress.
link |
And we can define stress very specifically
link |
as times when adrenaline also called epinephrine
link |
and or norepinephrine also called noradrenaline
link |
are elevated in your body.
link |
Forgive me for the noradrenaline nor epinephrine
link |
adrenaline epinephrine nomenclature.
link |
I didn't make that up.
link |
It turns out that every once in a while,
link |
scientists disagree, imagine that.
link |
And you'll get multiple scientists
link |
naming the same molecule different things, okay?
link |
So epinephrine and adrenaline are the same thing.
link |
I will use them interchangeably.
link |
Norepinephrine and noradrenaline are the same thing.
link |
I will use those terms interchangeably.
link |
Noradrenaline and adrenaline
link |
are often co-released in the brain and body.
link |
So they work as kind of a pair to increase our level
link |
of agitation, our level of focus
link |
and our desire and our ability to move.
link |
They are often co-released from different sides
link |
in the brain and body with dopamine,
link |
a molecule that is commonly misunderstood
link |
as the molecule of pleasure,
link |
but is actually the molecule of motivation,
link |
reward and pursuit.
link |
So dopamine, norepinephrine and noradrenaline
link |
tend to be released together under certain conditions.
link |
And today you will learn how deliberate cold exposure
link |
can be used to cause increases in the release of several,
link |
if not all of these,
link |
in ways that can improve your levels of attention
link |
But the key point is that your mental state is shifted
link |
when you are exposed to certain forms of cold.
link |
And many people use deliberate cold exposure specifically
link |
to shift their body state
link |
as a way to train their mental state
link |
so that they can better cope with stress in real life.
link |
I mean when life presents stressful events.
link |
And I will give you specific protocols
link |
as to how you can do that.
link |
In other words, how you can become more resilient
link |
through the use of deliberate cold exposure.
link |
Now, because of the ways in which deliberate cold exposure
link |
can increase this category of chemicals
link |
called the catecholamines,
link |
that includes dopamine, norepinephrine and epinephrine,
link |
it can also be used to elevate mood
link |
for long periods of time.
link |
And I'm going to discuss a specific protocol
link |
that has been shown to increase these chemicals
link |
anywhere from 2.5X, so 250%,
link |
to as high as 500% five times over baseline.
link |
Now you might be asking whether or not it's a good thing
link |
to raise chemicals like norepinephrine and dopamine
link |
to such a great degree,
link |
whether or not that's healthy for us,
link |
whether or not they can harm us.
link |
But it turns out that these elevations
link |
in norepinephrine and dopamine are very long lasting
link |
in ways that people report feeling vast improvements in mood
link |
and vast improvements in levels of cognitive attention
link |
So by my read of the literature,
link |
these seem to be healthy increases
link |
in our baseline levels of these chemicals
link |
in ways that can really support us.
link |
So I'll give you a protocol for that.
link |
Now, those are some of the mental effects
link |
of deliberate cold exposure.
link |
But deliberate cold exposure has also been studied
link |
in animal models and in humans
link |
in the context of increasing metabolism.
link |
Even in converting certain fat cells
link |
that we call white fat cells,
link |
which are the ones where energy is stored,
link |
they're the ones that we typically think of
link |
as kind of blubbery fat,
link |
to beige or brown fat, which is thermogenic fat,
link |
meaning that it can increase core body temperature
link |
and serves as kind of the furnace
link |
by which we increase our core metabolism.
link |
So with a very broad stroke,
link |
I can say that white fat is generally the kind of fat
link |
that people want less of,
link |
and beige fat and brown fat is generally the kind of fat
link |
that if you're going to have fat cells
link |
and you certainly need fat cells that you want more of.
link |
They are thermogenic.
link |
They help you stay lean.
link |
They actually serve as a reservoir for heating your body up
link |
if you're ever confronted with a cold challenge.
link |
So we're going to talk about how to use cold
link |
for metabolism as well.
link |
And of course, people are using deliberate cold exposure
link |
to reduce inflammation post-exercise,
link |
to reduce inflammation generally,
link |
and people are also using cold to enhance performance
link |
in the context of strength training,
link |
in the context of endurance training,
link |
and we'll talk about those data as well.
link |
But where I'd like to start is with mental performance,
link |
and I'd like to detail what happens
link |
when we deliberately expose ourselves to cold.
link |
It's key to point out the word deliberate.
link |
If I don't say otherwise, then throughout this episode,
link |
if I say cold exposure, I mean deliberate cold exposure.
link |
And the reason I point that out is that as my colleague,
link |
David Spiegel in the Department of Psychiatry at Stanford
link |
says, it's not just about the state that we are in,
link |
it's about the state that we are in
link |
and whether or not we had anything to do
link |
with placing ourselves into that state
link |
and whether or not we did that on purpose or not.
link |
And what he really means by that statement
link |
is that there are important effects
link |
of what we call mindset.
link |
Mindset was a topic discussed in the guest episode
link |
with Ali Krum some weeks ago.
link |
If you haven't seen that episode, I highly recommend it.
link |
And the science of mindset tells us
link |
that if we are doing something deliberately
link |
and we believe that it's going to be good for us,
link |
it actually can lead to a different set
link |
of physiological effects than if something is happening
link |
to us against our will or without our control.
link |
Now, this is different than placebo effects.
link |
Placebo effects are distinct from mindset effects.
link |
If you want to learn more about that distinction,
link |
please see the episode with Ali Krum.
link |
But again, when I talk about cold exposure in this episode,
link |
I'm talking about deliberate cold exposure,
link |
meaning that you are placing yourself
link |
into a cold environment on purpose
link |
in order to extract a particular set of benefits.
link |
When we talk about deliberate cold exposure,
link |
almost always that means getting uncomfortable.
link |
And one of the most common questions I get
link |
when discussing the use of cold for sake of mental
link |
or physical performance, metabolism, et cetera,
link |
is how cold should it be?
link |
How cold should the water be?
link |
How cold should the environment be?
link |
And I just will tell you now,
link |
and I'm going to say this again and again
link |
throughout the episode,
link |
because it will continue to be true throughout the episode
link |
and long after the episode is over,
link |
how cold depends on your cold tolerance,
link |
your core metabolism, and a number of other features
link |
that there is simply no way I could know or have access to.
link |
So I would like you to use this rule of thumb.
link |
If you are using deliberate cold exposure,
link |
the environment that you place yourself into
link |
should place your mind into a state of,
link |
whoa, I would really like to get out of this environment,
link |
but I can stay in safely.
link |
Okay, now that might seem a little bit arbitrary,
link |
but let's say you were to get into a warm shower
link |
and it would feel really, really nice,
link |
and you were to start turning down the warm
link |
and turning up the cold,
link |
there would be some threshold
link |
at which it would feel uncomfortable to you.
link |
And if you were to continue
link |
to make a little bit colder than that,
link |
you would really want to get out of the shower,
link |
but you were confident that you could stay in
link |
without risking your health, right?
link |
Without risking a heart attack.
link |
Now that's very different
link |
than jumping into a very, very cold lake,
link |
or I've seen these images of people
link |
that will cut holes into frozen over lakes
link |
and they'll get into that cold water.
link |
If you are trained to do that
link |
and you have the right conditions, et cetera,
link |
that can be done reasonably safely,
link |
but that's certainly not what I would start with.
link |
And for many people, that will be too cold.
link |
And indeed, some people can go into cold shock
link |
and can die as a consequence of getting
link |
to that extremely cold water very quickly.
link |
Now that's not to scare you away
link |
from deliberate cold exposure.
link |
It's just to say that there's no simple prescriptive
link |
of how cold to make the environment
link |
in order to extract maximum benefit for mental
link |
or physical performance.
link |
So the simple rule of thumb is going to be,
link |
place yourself into an environment
link |
that is uncomfortably cold,
link |
but that you can stay in safely, okay?
link |
And you'll have to experiment a bit.
link |
And that number, meaning that temperature
link |
will vary from day to day.
link |
It will vary across the 24 hour cycle
link |
because of that endogenous, meaning that internal rhythm
link |
in temperature that I talked about earlier,
link |
low early in the day, rises into the afternoon,
link |
You can actually do this experiment if you like.
link |
Try getting into a cold shower at 11 o'clock at night,
link |
if you want, versus try doing it
link |
in the middle of the afternoon.
link |
It's quite a different experience.
link |
And by quite a different experience,
link |
I mean it requires quite a different degree of resilience
link |
and leaning into the practice.
link |
Your willpower will have to be higher, I suspect,
link |
late in the day as compared to early in the day.
link |
But that will vary, of course, between individuals as well.
link |
So the most common question I get
link |
about deliberate cold exposure is,
link |
how cold should the water be?
link |
And we've answered that with uncomfortably cold
link |
to the point where you want to get out,
link |
but you can safely stay in.
link |
The second most common question I get
link |
about deliberate cold exposure is whether or not
link |
cold showers are as good, better,
link |
or worse than cold water immersion up to the neck.
link |
For instance, I also get a lot of questions
link |
about whether or not cryo chambers are better
link |
than all the others, et cetera, et cetera.
link |
I'm going to make all of that very simple for you
link |
by saying cold water immersion up to the neck
link |
with your feet and hands submerged also
link |
is going to be the most effective.
link |
Second best would be cold shower.
link |
Third best would be to go outside
link |
with a minimum amount of clothing,
link |
but of course clothing that is culturally appropriate
link |
and that would allow you to experience cold
link |
to the point where you would almost want to shiver
link |
or start shivering.
link |
Now, there are a number of different important constraints
link |
that are going to dictate whether or not you use
link |
one form of cold exposure or the other.
link |
For instance, some people don't have access
link |
to cold water immersion.
link |
They don't have access to ice baths or cold water tanks,
link |
cold ocean or cold lakes, et cetera.
link |
In that case, showers would be the next best solution.
link |
I do want to emphasize that there have been very few,
link |
if any, studies of cold showers,
link |
and you can imagine why this would be the case.
link |
In a laboratory, you want to control
link |
for as many variables as possible.
link |
So placing people into a cold water immersion
link |
or an ice bath up to the neck and insisting
link |
that they keep their hands and feet under
link |
is very easy to control.
link |
It means that everyone can do essentially the same thing.
link |
Whereas with cold showers, people are different size bodies.
link |
Some people are going to put their head under.
link |
Some people are going to lean forward.
link |
Measuring the amount of cold water exposure on the body
link |
is very hard to do.
link |
And so there aren't a lot of studies of cold showers,
link |
but of course, a lot of people don't have access
link |
to cold water immersion, so they have to use cold showers.
link |
And if you don't have access to both, of course,
link |
then going outside on a cold day can be of benefit.
link |
But I will point out that the heat transfer
link |
from your body into water is much higher,
link |
four times greater, if not even greater,
link |
depending on the temperature of the water,
link |
in water, as opposed to in air.
link |
So it's going to be much more efficient
link |
to do cold water immersion than anything else,
link |
cold showers after that,
link |
and put yourself into a cold environment
link |
would be the third best thing.
link |
I'm not going to get into cryochambers
link |
because they carry quite a high degree of cost.
link |
And again, there aren't many studies of them.
link |
So if you have access to cryochambers,
link |
I'm sure that the cryochamber facility
link |
has told you about all these incredible benefits,
link |
and I don't doubt that some of those benefits truly exist,
link |
but most people just don't have the resources
link |
or the access to those.
link |
So we're going to leave cryochambers
link |
out of today's discussion.
link |
And of course, I realize there's a fourth category
link |
of cold exposure out there.
link |
People who are wearing ice vests,
link |
believe it or not, those exist.
link |
Ice underwear, yes, those exist.
link |
You can look for them on Amazon if you like.
link |
They are putting cold packs in their armpits
link |
or in their groin or elsewhere
link |
in order to stimulate some of the effects of cold
link |
on mental and physical performance.
link |
I'm not going to address those in too much detail today.
link |
They can be efficient in certain ways,
link |
but as you'll learn about later in the episode,
link |
cooling the palms, the upper face,
link |
and the bottoms of the feet
link |
is going to be far more efficient.
link |
And unfortunately, I think most of the people
link |
that are using ice packs to increase their core metabolism
link |
are not aware of the glabber skin cooling
link |
and how it can be a very, very potent stimulus.
link |
So we'll return to that later.
link |
Unless I say otherwise, I'm mainly going to be focusing
link |
on cold water immersion and cold showers.
link |
So let's talk about protocols for enhancing mental health
link |
and performance using deliberate cold exposure.
link |
What happens when we get into cold
link |
is that we experience an increase in norepinephrine,
link |
in noradrenaline release and in adrenaline release.
link |
The fact that cold exposure, deliberate or no,
link |
increases norepinephrine and epinephrine
link |
in our brain and body
link |
means that it is a very reliable stimulus
link |
for increasing norepinephrine and epinephrine.
link |
That's sort of an obvious statement,
link |
but that obvious statement can be leveraged
link |
to systematically build up what we call resilience.
link |
Now, when we experience a stressor in life,
link |
whether or not it's something bad happens
link |
in our relationship or something bad happens in the world,
link |
and we feel stress, that stress is the consequence
link |
of increases in norepinephrine and epinephrine
link |
in our brain and body.
link |
Very similar, if not identical,
link |
to the kinds of increases
link |
that come from deliberate cold exposure.
link |
So deliberate cold exposure is an opportunity
link |
to deliberately stress our body.
link |
And yet, because it's deliberate
link |
and because we can take certain steps,
link |
which I'll describe in a moment,
link |
we can learn to maintain mental clarity.
link |
We can learn to maintain calm
link |
while our body is in a state of stress.
link |
And that can be immensely useful
link |
when encountering stressors in other parts of life.
link |
And that's what we call resilience or grit,
link |
our ability or mental toughness,
link |
our ability to lean into challenge or to tolerate challenge
link |
while keeping our heads straight, so to speak.
link |
So one simple protocol for increasing resilience
link |
is to pick a temperature that's uncomfortable,
link |
of shower or cold immersion,
link |
and then to get in for a certain duration of time,
link |
and then to get out.
link |
Now, it's important to understand
link |
that people will experience different levels
link |
of norepinephrine and adrenaline release
link |
when getting into cold water.
link |
Some people, because they dread the cold so much,
link |
will actually experience norepinephrine
link |
and epinephrine increases
link |
even before they get into the cold water
link |
or under the cold shower.
link |
Now, you may have experienced this.
link |
I've certainly experienced this.
link |
I'm dreading it, I don't want to do it,
link |
and I have to force myself to do it.
link |
And indeed, epinephrine and norepinephrine and its surges
link |
can be thought of as sort of walls
link |
that we have to confront and go over.
link |
And I'd like you to conceptualize them that way
link |
because it allows us to build protocols
link |
that can be very objective
link |
and can allow us to monitor our progress
link |
in terms of building resilience.
link |
So one option is to simply say,
link |
okay, I'm going to force myself
link |
to get into the cold shower for one minute.
link |
Again, uncomfortably cold, but you can stay in safely.
link |
Or I'm going to get into the ice bath for one minute.
link |
Ice baths are very cold inevitably.
link |
And what is also inevitable is that when you get
link |
into the cold, you will experience a surge
link |
in epinephrine and norepinephrine.
link |
That's non-negotiable because it's mediated
link |
by cold receptors on the surface of your body and your skin
link |
and the way that they trigger the release
link |
of norepinephrine and epinephrine,
link |
not just from the adrenals,
link |
from the adrenal glands above your kidneys,
link |
but also from regions of your brain,
link |
like the locus coeruleus,
link |
which cause increases in attention and alertness,
link |
and from other locations in your body
link |
where epinephrine and norepinephrine are released.
link |
In other words, cold is a non-negotiable stimulus
link |
for increasing epinephrine and norepinephrine.
link |
Even if you are the toughest person in the world
link |
and you love the cold, that increase in epinephrine
link |
and norepinephrine is going to happen.
link |
So the way to think about norepinephrine and epinephrine
link |
in this context of building mental resilience
link |
is that you have two options.
link |
You can either try to extend the duration of time
link |
that you are in the deliberate cold exposure.
link |
So going from one minute to 75 seconds to two minutes
link |
and so on over a period of days,
link |
or one way to approach this
link |
and the way that I particularly favor
link |
is to take the context of the day and the moment
link |
into account, meaning we have different levels of grit
link |
and resilience on different days
link |
and depending on the landscape of our life at the time,
link |
even the time of day that we're doing these protocols,
link |
and start to be able to sense the release
link |
of epinephrine, excuse me,
link |
and norepinephrine in our brain and body,
link |
and see those as walls that we want to climb over
link |
in order to build resilience,
link |
and to start counting the number of walls that we traverse
link |
and the distance between those walls
link |
as we do deliberate cold exposure.
link |
Let me give you an example of the timed protocol
link |
because that one is very straightforward,
link |
although I do not think it is as powerful
link |
for building mental resilience.
link |
The time protocol would be Monday,
link |
I do one minute of deliberate cold exposure
link |
at a given temperature.
link |
Wednesday, I extend that by 50%.
link |
And Friday, I do deliberate cold exposure
link |
for twice as long as I did on Monday.
link |
And if I were to continue that every week,
link |
Monday, Wednesday, Friday,
link |
I would continue to either increase the duration
link |
or I would lower the temperature and reduce the duration,
link |
this kind of thing,
link |
very much like sets and reps in the gym.
link |
Now that option is very objective, right?
link |
You could even log it in a book.
link |
And as you develop the ability to stay in cold temperatures,
link |
even progressively colder and colder temperatures
link |
for longer and longer periods of time,
link |
you will become more resilient.
link |
What do I mean by that?
link |
Well, my operational definition of resilience
link |
is that you are able to resist escape from the stressor,
link |
the cold, by virtue of your willpower,
link |
which is really your prefrontal cortex
link |
causing top-down control on your reflexes
link |
and your limbic system and your hypothalamus,
link |
which are basically telling you
link |
to get out of that cold water,
link |
get out of that cold environment.
link |
And in doing so, you are basically getting better
link |
at controlling your behavior when your brain and body
link |
are flooded with norepinephrine and epinephrine.
link |
That's a very reductionist way to explain resilience
link |
or grit or mental toughness,
link |
but it's a reductionist way of explaining it
link |
that is very closely tied to the biology
link |
and to the psychology.
link |
And it is a fact that norepinephrine and epinephrine release
link |
in the brain and body
link |
are the generic universal code for stressor.
link |
There is no unique chemical signature
link |
for different forms of stressors.
link |
That is the only one.
link |
Although, of course,
link |
there are other chemicals involved as well.
link |
So you could go for time
link |
and you could try and reduce the temperature
link |
and increase the time over a period of days or weeks.
link |
Now that's an attractive way to approach things,
link |
but the problem is that you don't have
link |
an infinite amount of room with which to lower temperature
link |
because eventually you will get into temperatures
link |
that are either so-called that they are dangerous,
link |
or you have to stay in cold temperatures
link |
for such long periods that it becomes impractical
link |
because presumably you also have to
link |
take care of other aspects of your life.
link |
You can't just sit all day in the ice bath.
link |
Now, for that reason,
link |
I favor a protocol in which you build mental resilience
link |
and mental toughness
link |
through two different types of protocols.
link |
The first one involves counting walls.
link |
Now, what do I mean by walls?
link |
I mean, the sensation of, no, I don't want to do this,
link |
and the idea or the sensation in your brain and body
link |
that you actually want to leave that environment
link |
Now, again, for some people,
link |
that will be even before getting into
link |
the ice bath or cold shower.
link |
So if you are feeling very resistant
link |
to getting into the ice bath or cold shower
link |
and you manage to do that,
link |
that's going over what I would call one wall, okay?
link |
Then for some period of time,
link |
you might actually feel comfortable in the ice bath,
link |
cold water, or cold shower,
link |
and you feel like you could stay there
link |
for some period of time,
link |
that you could stay there for a minute or two minutes,
link |
but inevitably the next wall will arrive.
link |
And I would encourage you to pay attention
link |
to when that next wall arrives
link |
and actually having an awareness,
link |
that so-called interoceptive awareness, as we call it,
link |
of when that next surge in adrenaline epinephrine comes
link |
or whether or not it reaches a certain threshold
link |
in your brain and body that you feel you want to get out,
link |
and you're able to stay in for even just 10 seconds longer,
link |
that means you've traversed yet another wall.
link |
And if you continue to stay in that cold environment,
link |
you will find that the next wall will come
link |
and the next wall will come.
link |
Now, eventually, of course, you will get very, very numb,
link |
depending on how cold it is,
link |
and you could also place yourself into danger.
link |
So you have to maintain cognitive control,
link |
counting these walls, traversing these walls,
link |
but getting out at some point, of course.
link |
So my favorite protocol for building mental toughness,
link |
AKA grit, AKA resilience, is to take into account
link |
that some days just getting into the ice bath
link |
or cold shower represents a wall.
link |
Some days it doesn't.
link |
Some days you get in
link |
and you feel like you could go 10 minutes.
link |
Other days you get in
link |
and you feel like you could only go a minute.
link |
And setting a designated number of walls
link |
before you start the protocol
link |
is going to be very beneficial here.
link |
So you say, as long as I can do it safely,
link |
I'm going to do three walls today.
link |
The first wall is getting in,
link |
the second wall will arrive when it arrives,
link |
and the third wall will arrive when it arrives,
link |
and I'll get over that wall and then I'll get out.
link |
The next day, you might do five walls.
link |
The next day, you might do three walls again,
link |
but you might lower the temperature.
link |
This gives you tremendous flexibility,
link |
and indeed, it gives you much more latitude
link |
to be able to use the same temperatures in different ways,
link |
or to reduce the temperature only a little bit
link |
and still get a lot of stimulus,
link |
meaning a lot of results out of a given protocol.
link |
Whereas people who are just going for temperature and time
link |
eventually become cold adapted.
link |
They get very, very good at doing three minutes
link |
or six minutes or even 10 minutes at a given temperature.
link |
And so then they feel like they have to lower the temperature
link |
even more and even more,
link |
and eventually they just bottom out.
link |
There's nowhere else to go.
link |
There's nowhere to get improvements out of the protocol,
link |
at least not in terms of mental resilience.
link |
Of course, there's still the positive effects on inflammation
link |
and metabolism, et cetera,
link |
that we'll talk about in a little bit.
link |
But the key thing here is to design protocols
link |
that are going to work for you over time.
link |
And for you very, very hardy,
link |
very, very tough guys and gals out there
link |
that can get right into an ice bath
link |
or a very, very cold immersion,
link |
and you can just grind it out for six or 10 minutes,
link |
or you can even do that by remaining peaceful.
link |
Well, more points to you, but guess what?
link |
That's the equivalent of already having loaded up
link |
the barbell with 600 pounds and done your 10 reps.
link |
There's not a whole lot more variable space
link |
with which to get benefits from that stimulus.
link |
And in the weight room,
link |
people understand that you can adjust, for instance,
link |
the speed of the movement,
link |
or you can start combining that movement
link |
with pre-exhaustion, et cetera.
link |
With cold exposure,
link |
you don't have as much variable space to play with.
link |
So if your goal is to build resilience,
link |
either go for time as a function of temperature,
link |
or what I suggest is to start recognizing these walls
link |
as an experience of resistance in you
link |
and going over those walls,
link |
set a certain number of walls
link |
that you're going to go over on a given day
link |
and do that at a given temperature,
link |
and then to mix it up.
link |
And ideally, you might even throw in one more wall
link |
at the end if you're really feeling bold and brave,
link |
because that's going to build out further resilience.
link |
But if you want cold exposure to work for you
link |
for sake of building up resilience
link |
and mental toughness over time,
link |
you're going to want to vary this parameter space
link |
in some sort of way,
link |
and you don't have to be super systematic about it.
link |
That's the beauty of this kind of approach,
link |
because you're relying on the fact
link |
that those walls really represent times
link |
in which you are forcing your top-down control,
link |
your prefrontal cortex, to clamp down on your reflex,
link |
and you're learning behavioral control
link |
in the context of your body having elevated levels
link |
of these catecholamines, norepinephrine and epinephrine.
link |
And that translates to real life
link |
in a much more realistic way, I believe,
link |
because in real life,
link |
you're not really engaging in stressors
link |
for a given amount of time
link |
that you know how long it's going to last,
link |
and you know the context.
link |
No, most stressors arrive in the form of surprises
link |
we don't like, text messages that deliver bad news,
link |
information about the outside world
link |
or real world and online interactions
link |
that send our system into a state
link |
of increasing norepinephrine and epinephrine.
link |
And if you start to think of those as walls
link |
that you can tolerate and climb over
link |
while staying calm and clear of mind,
link |
then you can really imagine how the ice bath
link |
and other forms of cold exposure
link |
are really serving to train you up for real life stressors.
link |
Okay, the next question that I always get
link |
is what should my mental state be
link |
while I'm exposing myself to this uncomfortable
link |
yet safe condition of cold?
link |
Well, you have two options,
link |
and there are probably other options as well.
link |
One is to try and calm yourself
link |
to remain as mentally still as possible.
link |
The other is to lean into that challenge
link |
and so to grind it out.
link |
And here, I have to say that this is a lot
link |
like teaching someone to drive on a gravel road.
link |
For any of you that have driven on a gravel road,
link |
you know that there is no optimal speed
link |
for all gravel roads.
link |
It depends on the density, the gravel, et cetera,
link |
and the vehicle, et cetera.
link |
So for instance, on some gravel roads,
link |
when you start to drive and the dust starts to kick up,
link |
your best option is to drive fast
link |
and put that dust cloud behind you.
link |
On other gravel roads, if you try and do that,
link |
the dust actually kicks up around the vehicle
link |
and it makes it hard to see,
link |
and sometimes you have to slow down.
link |
The same thing is true for getting
link |
through deliberate cold exposure.
link |
Sometimes it's easier to calm yourself.
link |
One way to do that is through double inhales
link |
through the nose and extended exhales through the mouth,
link |
or simply by trying to control your breathing
link |
and reduce the pace of your breathing
link |
and increase the volume of your breathing.
link |
I have to say that everyone experiences
link |
a shortening of breath
link |
when they get into uncomfortably cold water.
link |
That is a universal physiological response.
link |
Everyone also experiences a 30 to 80% decrease
link |
in cognitive function,
link |
in particular of the frontal cortex.
link |
The metabolism of your frontal cortex goes down,
link |
the metabolism, meaning the activity of brain areas
link |
associated with stress and panic goes way up.
link |
And so anchoring your mind in cognitive activities
link |
as you get into the cold can be very, very helpful
link |
for maintaining clarity of mind.
link |
In fact, one thing that I sometimes recommend
link |
is that people try and engage
link |
in some sort of cognitive exercise while in the cold,
link |
not as a form of distraction,
link |
but as a way to maintain clarity of thinking
link |
and to learn how to do that when the body is flooded
link |
with all these chemicals that make us stressed.
link |
So for instance, you could do math problems
link |
and not two plus two equals four,
link |
not three times three equals nine,
link |
but things that require a little bit more focus
link |
and attention, working memory and so forth.
link |
You could also start to have thoughts
link |
that you deliberately impose a full sentence structure on.
link |
That's actually quite tough.
link |
You could try and recall specific bouts of information
link |
that are challenging.
link |
This is teaching your mind how to stay online,
link |
or rather I should say,
link |
this is you teaching your prefrontal cortex
link |
how to stay engaged
link |
while you have high levels of stress in your body.
link |
Years ago, I had a friend who works in the neuroscience
link |
world, research neuroscientist,
link |
who is obsessed with this very bizarre sport
link |
that I don't necessarily recommend at all,
link |
which is the combination of boxing and chess.
link |
You may have seen this on YouTube
link |
where people will box around, legitimate boxing around,
link |
they're sparring all out often.
link |
And then at the end of the round,
link |
instead of resting in the corner,
link |
they actually sit down and play chess.
link |
And then they go back to boxing and back to chess.
link |
Again, not a sport that I recommend,
link |
but the reason he was obsessed with this
link |
is because he studies the impact of stress
link |
on cognitive performance.
link |
And what that particular very bizarre sport was doing
link |
was toggling back and forth
link |
between different states of mind.
link |
Now it's used both to increase cognitive clarity
link |
for the fighter when they box
link |
because staying calm and clear thinking
link |
is very important to winning boxing matches.
link |
Believe it or not, it's not an all outrage.
link |
It's a very calculated game of mental chess
link |
and physical chess that's quite high stakes,
link |
as you can imagine.
link |
It's also used in some circles as a way to teach people
link |
how to engage in cognitive performance
link |
when their body is simply filled with stress.
link |
So in the boxing chess example,
link |
the replacement for the cold water
link |
is actually the boxing, right?
link |
It's the thing that's supposed to induce the stress
link |
because getting hit is stressful
link |
and the risk of getting hit is stressful for most people.
link |
So again, if you think about deliberate cold exposure
link |
as a way of just systematically
link |
and reliably inducing epinephrine
link |
and norepinephrine release and delivering stress,
link |
well, then this idea of maintaining cognitive clarity
link |
and actually engaging in cognitive tasks
link |
while in the ice bath or cold shower
link |
can actually be very beneficial,
link |
even though it might sound a little bit silly.
link |
You're really training up your ability
link |
to keep your brain working
link |
when the reflex is to shut down the parts of your brain
link |
that are involved in deliberate planning and thinking.
link |
Now, another important aspect of deliberate cold exposure
link |
that I rarely, if ever hear discussed,
link |
but is vitally important
link |
is whether or not you move around or not.
link |
And here's the reason.
link |
When you get into cold water
link |
and you remain there for some period of time,
link |
your body is generating heat
link |
and that heat generates what's called a thermal layer
link |
that surrounds your entire body.
link |
So if you stay still,
link |
you are actually warmer than if you move around.
link |
You can try this the next time
link |
you're doing your deliberate cold exposure.
link |
If you're submerged up to the neck,
link |
sit there for about 10, 30 seconds
link |
and be very, very still of body.
link |
In fact, this is the way that most people
link |
start to do deliberate cold exposure.
link |
They give this very stoic look.
link |
They look very peaceful.
link |
Some of them even look tough,
link |
or they make a very even, A, emotional face
link |
and so it looks like they're really tough,
link |
but they are so still that, believe it or not,
link |
they're not providing the most potent stimulus.
link |
If they or you were to move around in that water,
link |
what would happen is you'd break up the thermal layer
link |
and that you actually experienced that as much colder.
link |
So if you really want to push the resilience aspect,
link |
or for instance, if you want to use a given temperature
link |
that you're comfortable in,
link |
but that you want to increase the stimulus
link |
and you want to get some more benefit
link |
for mental resilience training,
link |
well, then get into the cold water,
link |
move your body around continuously,
link |
but try and keep your mind still
link |
or even do some sort of cognitive task.
link |
So as you're starting to realize
link |
there are a bunch of different variables
link |
that you can play with
link |
while maintaining the same temperature of water,
link |
and in doing so, really keep you in the zone
link |
of what should and absolutely has to be safe for you
link |
without having to just continually drop the temperature
link |
from say 60 degrees to 55 to 40 to 33,
link |
because as I mentioned before,
link |
eventually you're going to bottom out.
link |
So if you're one of those people that likes to look tough
link |
or really relaxed while you're in the ice bath
link |
or cold water immersion,
link |
just realize that you're actually cheating yourself
link |
out of part of the stimulus.
link |
Keep those limbs moving,
link |
and of course, limbs under the water, feet and hands,
link |
is going to be a more potent stimulus
link |
than hands and feet out
link |
for reasons that should be obvious
link |
based on what we talked about
link |
in terms of glab or skin cooling.
link |
So keep those submerged, move your body, pedal,
link |
maybe move your knees up and down,
link |
pedal your feet, and trust me,
link |
it's going to feel a lot colder
link |
than were you to remain stone still.
link |
Another very common question
link |
is how often to do deliberate cold exposure.
link |
It's tough to make a recommendation on that
link |
based on any peer reviewed study,
link |
although there are a few in humans
link |
that point to a threshold of 11 minutes total per week.
link |
So that's total throughout the week,
link |
divided into two or four sessions
link |
of two or three minutes or so.
link |
Now that 11 minute cutoff is not a strict threshold
link |
and is actually geared more towards increases in metabolism.
link |
We'll get into this a little bit later in the episode,
link |
but I think the 11 minute threshold,
link |
meaning 11 minutes total of deliberate cold exposure per week
link |
is a pretty good number to use
link |
if you need a number in order to keep you consistent.
link |
But as we talked about earlier,
link |
some of you are going to be in the ice bath
link |
or cold immersion or cold shower for one minute.
link |
Others of you will be in there for 10 minutes
link |
depending on how frequent and how high, if you will,
link |
those walls of adrenaline are coming.
link |
So for some of you getting into a cold shower
link |
for three minutes total for the whole week
link |
will represent a tremendous achievement
link |
in terms of willpower and overcoming the resistance
link |
to doing that, overcoming those walls.
link |
For others of you, three minutes is nothing.
link |
So what do I recommend?
link |
I recommend that you get at least 11 minutes total per week,
link |
but at the point where 11 minutes total per week
link |
is very easy for you or is no longer representing
link |
a significant mental challenge,
link |
meaning you're not experiencing many of these walls,
link |
you're excited to get into the cold shower or immersion,
link |
you're going through it easily, you're cruising basically,
link |
then I would say either lower the temperature safely,
link |
of course, extend the duration safely, of course,
link |
or increase the frequency so that you're doing this
link |
perhaps every day or maybe five days a week
link |
or three days a week.
link |
I personally get tremendous benefit
link |
from doing deliberate cold exposure three times a week
link |
and using the walls method that I described earlier
link |
as my gauge for how long to stay in.
link |
And typically that means that I'm staying in for anywhere
link |
from two minutes to six minutes per session.
link |
And that averages out to about 11 to 15 minutes total
link |
So again, I do not think that you need to be super strict
link |
about these guidelines.
link |
It's most important when embracing a protocol,
link |
A, that you do it safely,
link |
but secondarily that you do it consistently.
link |
So find what you can do consistently
link |
and then vary the parameters that will allow you
link |
to continue to do deliberate cold exposure consistently,
link |
regardless of whether or not you have access to a shower
link |
or a cold immersion, et cetera.
link |
Okay, so we've been talking about mental effects
link |
and the use of deliberate cold exposure
link |
for sake of building resilience,
link |
which I do believe can be tremendously powerful.
link |
Look, it's no coincidence that the screening
link |
and the training for Navy SEALs involves a lot of exposure
link |
One could argue that it is deliberate
link |
because they elect to go to BUDs,
link |
but when they get into the cold water at BUDs
link |
is dictated by the instructors.
link |
And the reason they use cold water exposure as the stressor
link |
is that it does offer considerable leeway
link |
in terms of duration and temperature,
link |
in terms of how you can use it as a stressor,
link |
whereas things like heat don't offer much variable space.
link |
As we say, there isn't a lot of room
link |
beyond which you start injuring or even killing people
link |
So there are a lot of forms of stressors out there,
link |
but cold is one that we can titrate,
link |
that we can adjust in ways that can allow us
link |
to continually build up and or maintain mental toughness.
link |
Now, deliberate cold exposure also has many effects
link |
on chemicals other than norepinephrine and epinephrine,
link |
most notably the neuromodulator dopamine,
link |
which is involved in elevating our mood,
link |
making us feel energized and enhancing our ability to focus.
link |
And that has a lot to do with how dopamine engages us
link |
in motivated states, tends to narrow our thinking
link |
and our behavior into a particular trench
link |
of goal-directed behavior.
link |
If you want to learn more about dopamine,
link |
you can learn a lot about dopamine
link |
in our episode about dopamine.
link |
It's at hubermanlab.com.
link |
It's a two and a half hour plus kind of deep dive
link |
into all things dopamine, focus, motivation, et cetera.
link |
Deliberate cold exposure has a very powerful effect
link |
on the release of dopamine in our brain and body.
link |
And this is one of the main reasons
link |
why people continue to do deliberate cold exposure.
link |
Basically, it makes us feel good
link |
and it continues to make us feel good
link |
even after we get out of the cold environment.
link |
In fact, some people would say
link |
they don't feel good in the cold environment.
link |
It's all stress for them, but afterwards they feel great.
link |
One of our previous guests, Dr. Anna Lempke,
link |
who's a medical doctor
link |
at Stanford University School of Medicine,
link |
she's a close colleague of mine,
link |
described the use of dopamine in her book,
link |
dopamine nation, an incredible book
link |
about addiction and dopamine, I should mention,
link |
and the use of dopamine elicited by cold water exposure
link |
by one of her patients.
link |
What I'm referring to is the fact that one of her patients
link |
helped themselves get and stay sober off drugs
link |
by using deliberate cold exposure to increase dopamine.
link |
So a healthier form of dopamine release
link |
than they were engaged in prior to getting sober.
link |
Now, the basis for dopamine release
link |
in response to cold exposure
link |
is that the catecholamines, norepinephrine, epinephrine,
link |
and dopamine tend to be co-released
link |
by the same sorts of stimuli,
link |
but most stressors, and in particular things
link |
that evoke stress or our feelings of stress internally
link |
that we don't like, do not increase dopamine.
link |
They only increase norepinephrine and epinephrine,
link |
but deliberate cold exposure
link |
seems to cause a dramatic increase in dopamine,
link |
and this has actually been substantiated
link |
in a really beautiful study
link |
entitled Human Physiological Responses to Immersion
link |
into Water of Different Temperatures.
link |
The first author is Sramek.
link |
I'm almost certainly pronouncing that poorly,
link |
if not incorrectly, S-R-A-M-E-K.
link |
This was published in the European Journal
link |
of Applied Physiology in the year 2000.
link |
Really a beautiful study.
link |
I love this study.
link |
They took people and they had them sit in chairs underwater,
link |
but their head was out and so they were immersed
link |
up to the neck in either of three different temperatures,
link |
excuse me, 32 degrees Celsius,
link |
which is 89 degrees Fahrenheit, 20 degrees Celsius,
link |
which is 68 degrees Fahrenheit, or 14 degrees Celsius,
link |
which is 57.2 degrees Fahrenheit.
link |
So not super cold, but then what they did
link |
is they measured people's core body temperature throughout.
link |
They measured their metabolism
link |
and they looked at serum levels
link |
of things like norepinephrine, epinephrine,
link |
dopamine, and cortisol, serum meaning within the blood.
link |
So a really nice and quite thorough study.
link |
There were not a huge number of subjects in the study,
link |
but nonetheless, it was a very thorough study
link |
in terms of the number of variables that they explored.
link |
So I just want to briefly highlight some of what they saw
link |
or what they observed in this study.
link |
First of all, all the groups were in the water
link |
of a given temperature for one hour,
link |
which is much longer than most
link |
of the deliberate cold exposure protocols
link |
that anyone is using at home.
link |
I mean, maybe you're taking one hour long cold showers.
link |
Maybe you're getting into the ice bath for an hour,
link |
although I don't recommend that.
link |
I think you'd probably get badly hypothermic.
link |
Or maybe you're getting into a cold water immersion
link |
for some period of time,
link |
but I have a hard time imagining that it would be an hour
link |
and I don't suggest that if it's very cold.
link |
So this study focused on actually
link |
somewhat moderately cool temperatures,
link |
not what I think most people would consider
link |
very, very cold temperatures,
link |
but extended the duration for quite a while.
link |
So again, 32 degrees Celsius, 20 degrees Celsius,
link |
or 14 degrees Celsius, here's what they observed.
link |
The group that was immersed up to the neck
link |
in 32 degrees Celsius, that is 89 degrees Fahrenheit,
link |
water did not experience a shift in metabolism
link |
nor a significant increase in dopamine norepinephrine
link |
or these other catecholamines.
link |
The group that was in 20 degrees Celsius,
link |
meaning 68 degree Fahrenheit water for an hour,
link |
experienced a 93% increase in metabolic rate,
link |
which is remarkable given that the water wasn't that cold
link |
and yet an hour is a pretty long time to be in there.
link |
And again, it speaks to the dramatic effect
link |
of heat transfer that water has,
link |
which I mentioned earlier as opposed to being out
link |
in the air at 68 degrees,
link |
it would certainly not cause that increase
link |
in metabolic rate.
link |
The group that was at 14 degrees Celsius,
link |
meaning 57.2 degrees Fahrenheit water for an hour,
link |
experienced a 350% increase in metabolism.
link |
So huge increases in metabolism.
link |
Now, the most interesting data to me,
link |
at least in terms of mental effects
link |
of deliberate cold exposure,
link |
were that the plasma or serum levels of norepinephrine
link |
in the blood increased 530%.
link |
These are huge increases in norepinephrine.
link |
So it suggests that this is a stressful stimulus,
link |
at least neurochemically speaking, stressful,
link |
despite the fact that it's not super, super cold,
link |
although 57.2 degrees Fahrenheit, 14 degrees Celsius
link |
is not a, you know, it's not a warm environment,
link |
but it's not a ultra, ultra cold environment,
link |
but an hour is a very long time to be in there.
link |
The subjects also experienced a 250% increase
link |
in dopamine concentrations, which while not 530%,
link |
as it was with norepinephrine,
link |
is still a very large increase
link |
in baseline levels of dopamine.
link |
And what was interesting is that those increases
link |
in dopamine persisted for a very long period of time
link |
and afterwards, even out to two hours, okay?
link |
And they stopped the study after 120 minutes
link |
of getting out of the cold, but nonetheless,
link |
these increases in norepinephrine are huge and long lasting,
link |
and these increases in dopamine
link |
are very large and long lasting.
link |
And I do believe that these documented effects in humans
link |
explain much of the enhancement of attention
link |
and of feelings of wellbeing and mood
link |
that people typically experience
link |
after doing deliberate cold exposure.
link |
And the reason I say that is that if you were to go back
link |
to the episode that I did on dopamine,
link |
or you were to go back to the episode that I did
link |
with Dr. Anna Lemke on addiction and dopamine,
link |
what you would find is that increases in dopamine
link |
of the sort evoked by deliberate cold exposure
link |
are actually very similar to the kinds of increases
link |
in dopamine that are elicited by things like nicotine
link |
or from other behaviors that are known to be addictive
link |
and bad for us because they lead to other effects
link |
on the brain and body that we simply don't want.
link |
And yet deliberate cold exposure, provided it's done safely,
link |
can create similar, if not greater, increases in dopamine
link |
that are not just fleeting,
link |
that don't just occur during, say,
link |
the consumption of some deleterious drug or activity,
link |
but that are very long lasting
link |
and that can be leveraged toward activities
link |
other than deliberate cold exposure.
link |
So I want to emphasize this.
link |
I'm not suggesting that people do deliberate cold exposure
link |
for an hour a day,
link |
and unfortunately there are not many studies
link |
yet exploring how shorter,
link |
colder temperature environment exposure,
link |
say one minute or three minutes or six minutes
link |
at 55 degrees or at 50 degrees,
link |
whether or not that leads to similar,
link |
greater or reduced levels of dopamine in the brain and body.
link |
And yet almost everybody who does deliberate cold exposure
link |
will say, yeah, it was stressful, I didn't enjoy it,
link |
or I eventually grew to like it,
link |
but that I always feel better afterwards.
link |
And then that feeling lasts a very long period of time.
link |
And I think it's almost certain that those experiences
link |
that people report relate to these increases in dopamine
link |
and in concert with the increases in norepinephrine
link |
also explain the other effect that's commonly reported,
link |
which is an enhancement in mental acuity
link |
and the ability to focus.
link |
Now, here we can extrapolate to the study
link |
that I discussed at the early part of the episode
link |
where I was talking about the use
link |
of short 15 minute exercise,
link |
kind of moderate intensity exercise,
link |
and how that was shown to increase levels of energy
link |
in these working memory visual attention tasks.
link |
And there again, we have to assume somewhat
link |
because they weren't doing neurochemical measurements,
link |
but we can reasonably assume
link |
that those improvements in cognitive performance
link |
were due at least in part to the increase in catecholamines
link |
known to accompany moderate intensity zone to cardio.
link |
So what you're starting to see here is a theme.
link |
The theme is that virtually any stimulus
link |
that delivers more norepinephrine, epinephrine,
link |
and dopamine to our system will sharpen our mental acuity
link |
and elevate our mood,
link |
and will do so for some period of time.
link |
Deliberate cold exposure, it turns out,
link |
is a very potent way to increase these catecholamines,
link |
this category of chemicals,
link |
and thereby to improve mood, mental acuity,
link |
and levels of alertness.
link |
And as we'll next see, it not only has that effect,
link |
which can be very beneficial for many people
link |
in a bunch of different circumstances,
link |
but it also has the positive effects
link |
that many people seek in terms of metabolism
link |
in lowering inflammation in the body
link |
and other physiological effects as well.
link |
And forgive me, I was almost ready to move on
link |
to effects of deliberate cold exposure
link |
on metabolism and inflammation and so forth,
link |
but I neglected to point out
link |
one of the other very interesting aspects
link |
of the study showing deliberate cold exposure
link |
can increase norepinephrine and dopamine,
link |
which is that they observed no significant increases
link |
in the stress hormone cortisol.
link |
And that is both surprising, interesting, and important,
link |
because what it means is that the quality of stress
link |
that deliberate cold exposure is creating in the body
link |
is likely to be one of what we call eustress.
link |
Hans Selye, the great physiologist,
link |
won a Nobel Prize for distinguishing between distress,
link |
which is stress in the brain and body
link |
that causes the release of things like cortisol
link |
along with the other catecholamines
link |
and that we experience as negative happening to us
link |
and can lead to negative health outcomes.
link |
And he distinguished that from eustress,
link |
which was stress that we now understand
link |
is associated with increases in things
link |
like norepinephrine and dopamine,
link |
but no increases or minimal increases in cortisol,
link |
and that can lead to positive health outcomes.
link |
So it appears that deliberate cold exposure
link |
can create what we call,
link |
or what Hans Selye called eustress.
link |
In other words, it can create a condition
link |
in the brain and body in which we are stressing ourselves,
link |
we are training up resilience,
link |
and yet we are creating a neurochemical milieu
link |
that actually has many health benefits.
link |
Now I'd like to shift our attention
link |
to the effects of deliberate cold exposure on metabolism.
link |
And I'd like to start by detailing a study
link |
that was performed on humans
link |
and published just at the end of last year.
link |
The title of the study is
link |
Altered Brown Fat Thermoregulation
link |
and Enhanced Cold Induced Thermogenesis
link |
in Young Healthy Winter Swimming Men.
link |
And I should point out that
link |
while the study was only performed on male subjects,
link |
there's no reason to think that
link |
the effects that they discovered
link |
would only pertain to men.
link |
I would hope that they would also do a study on women
link |
at some point in the future,
link |
but the effects that they describe
link |
are very basic core physiological processes.
link |
What they did is they looked at deliberate cold exposure
link |
in this group of young men,
link |
and they used that 11 minute threshold per week.
link |
So in other words, they had them get into cold water
link |
for approximately 11 minutes per week.
link |
And again, that's 11 minutes total per week.
link |
They divided that into two sessions,
link |
although in speaking with the first author of the study,
link |
Dr. Susanna Soberg,
link |
I learned that it probably is not important
link |
that it be two sessions.
link |
It could be three or even four sessions
link |
as long as it reaches that 11 minute threshold.
link |
What they discovered was that
link |
by going into these cold environments,
link |
in this case, cold water immersion up to the neck
link |
for 11 minutes total per week,
link |
that these men experienced increases
link |
in so-called brown fat thermogenesis.
link |
I'll talk more about what that is in a moment
link |
and increases in core body temperature
link |
that translate to increases in core body metabolism.
link |
Now, the overall increases in core body metabolism
link |
that they experienced were not extremely large.
link |
They were statistically significant,
link |
but they weren't extremely large.
link |
However, the changes in brown fat stores
link |
are perhaps what's most interesting about this study.
link |
And I'll tell you why.
link |
The metabolic increases of deliberate cold exposure
link |
are both acute, meaning happening in the short term,
link |
when you get into the cold and immediately after,
link |
one does experience an increase in core metabolism.
link |
You burn some calories, in other words.
link |
And while those might not be very significant increases,
link |
or I should say they can be statistically significant,
link |
but they are not enormously large numbers
link |
of calories burned,
link |
the longer lasting effects of deliberate cold exposure
link |
on metabolism seem to take place by changes that occur
link |
in the types of fat that we store in our body
link |
and the way that that fat impacts our metabolism
link |
at other times throughout the 24-hour cycle.
link |
This actually has a somewhat anecdotal basis,
link |
in particular in Scandinavia.
link |
I don't speak Swedish nor I speak Danish,
link |
nor do I speak Norwegian, but I do have Danish relatives.
link |
And they were able to help me decipher
link |
a common Swedish saying,
link |
which essentially translates to the fact that
link |
in preparation for the summer, they say,
link |
one should expose themselves to warm environments
link |
so that one is comfortable
link |
in warm environments in the summer.
link |
That's one half of this traditional Swedish
link |
and also Danish saying.
link |
The other half of this traditional Danish Swedish saying
link |
is that in preparation for winter,
link |
in order to not feel too cold in cold environments,
link |
one should prepare for those in the fall
link |
by not wearing a jacket and exposing oneself
link |
to cold environments.
link |
Now, of course, this is just anecdotal cultural lore,
link |
but it actually has a physiological basis,
link |
which is by exposing oneself to cold environments
link |
on a repeated basis in anticipation of exposure
link |
to more extreme cold environments,
link |
one can feel more comfortable in those extreme
link |
cold environments.
link |
And that's exactly what they observed
link |
in this study by Soberg et al.
link |
The men felt more comfortable in extreme cold
link |
if they had trained through deliberate cold exposure,
link |
which might not seem surprising at all,
link |
but based on what we talked about earlier,
link |
whereby deliberate cold exposure evokes this discomfort
link |
and this experience of norepinephrine release,
link |
at least in the short term,
link |
then you would say, well, shouldn't that deliberate
link |
cold exposure also make them feel uncomfortable,
link |
like they really want to get out?
link |
Well, that is true at the beginning
link |
of a deliberate cold exposure protocol,
link |
meaning in the first week or in the second week
link |
or the third week, but what one finds and what you will find
link |
if you do deliberate cold exposure consistently
link |
is that you will then become more comfortable
link |
at cold temperatures away from the deliberate cold exposure.
link |
So, whereas you might have previously been the person
link |
who was always cold in the room with air conditioning
link |
or always seeking a sweater, always wanting to bundle up,
link |
you will be more comfortable in those cold environments.
link |
And the reason for that is well substantiated
link |
from this study and from animal studies
link |
whereby deliberate cold exposure
link |
converts one particular kind of fat cell,
link |
the white fat cell,
link |
which is a very low metabolic output cell,
link |
it's basically a storage site for energy in the body,
link |
fat cells to a different type of fat cell,
link |
which is the beige fat cell called beige
link |
because it's actually beige or slightly brown
link |
under the microscope, or even to brown fat cells,
link |
which are very dark under the microscope
link |
and dark because they contain mitochondria
link |
and are very metabolically and thermogenically active.
link |
In other words, white fat doesn't burn many calories,
link |
it's basically a storage site,
link |
it's a bank account for energy,
link |
it's filled with lipids and those lipids can be used
link |
if the body needs energy
link |
and if it goes into a caloric deficit.
link |
Beige fat and brown fat acts as sort of a furnace
link |
or the sort of fat that you would find in a candle,
link |
a fuel that can increase core body temperature.
link |
So beige fat and brown fat is very good
link |
at raising our metabolism and helps burn white fat.
link |
Now, of course, it does that only in the context
link |
of a caloric deficit,
link |
but it can actually help create that caloric deficit.
link |
Having more beige fat and brown fat
link |
can increase your overall core metabolism.
link |
In other words, the number of calories
link |
that you burn per day and therefore the number of calories
link |
that you need to either maintain or to lose weight.
link |
The simple translation of this is that getting
link |
into cold water for a total of 11 minutes, perhaps more,
link |
but at least 11 minutes per week,
link |
divided into two or four sessions
link |
can increase your core metabolism in part
link |
by increasing your beige and brown fat stores.
link |
And we know how that works, at least in animal models.
link |
And there's now reason to suspect
link |
that the exact same mechanisms are occurring in humans.
link |
The primary way in which deliberate cold exposure
link |
converts white fat cells into these more metabolically,
link |
thermogenically active metabolism increasing beige
link |
and brown fat cells is because norepinephrine
link |
released when we get into the cold,
link |
binds to receptors on the surface of white fat cells
link |
and activates downstream pathways such as UCP1.
link |
So this is an uncoupling protein one
link |
that acts on the mitochondrial metabolism of cells
link |
and increases the mitochondrial output of those cells
link |
and the mitochondrial density of those cells.
link |
In other words, it takes a cell that has a kind
link |
of a weak engine or no engine for generating energy,
link |
although every cell has some mitochondria,
link |
it takes cells that have very few mitochondria
link |
and increases the engine size.
link |
It kind of stokes the furnace of those particular cells
link |
and actually can change gene expression in those cells.
link |
So that's what's really interesting.
link |
Deliberate cold exposure causes increases in norepinephrine,
link |
which bind to receptors on the surfaces of white fat cells,
link |
which triggers the release of things like UCP1.
link |
It also causes the release of things like PPAR gamma
link |
and cofactor PGC1.
link |
I'm going to refer you to a review
link |
if you want to learn more about these.
link |
For those of you that don't want to learn more,
link |
all you need to know is that the downstream of all that
link |
are increases in mitochondria and metabolism
link |
and actual genetic changes in the white fat cells
link |
that convert them into beige and brown fat cells.
link |
This is especially important for adults
link |
because babies and young children
link |
actually don't have the ability to shiver
link |
or they have a less robust capacity to shiver.
link |
Very small babies really can't shiver,
link |
so they have a lot of brown fat in order to keep them warm.
link |
Young children eventually develop the ability to shiver
link |
and maintain these brown fat stores,
link |
mainly around the clavicles, the heart, the upper spine,
link |
and in the upper back.
link |
And it's no coincidence that kids can often run around
link |
with a minimal of clothing
link |
and be comfortable in environments
link |
that adults would be cold in.
link |
As life goes on, we tend to lose beige and brown fat,
link |
but this mechanism that I'm referring to
link |
points to the plasticity of white fat,
link |
meaning the ability for white fat
link |
to actually convert its identity
link |
into this metabolically thermogenically
link |
enhancing form of beige and brown fat.
link |
So deliberate cold exposure is a terrific way
link |
to increase your core metabolism.
link |
And oftentimes critics will say,
link |
well, the increase in metabolism isn't that significant,
link |
although I do want to point out again,
link |
the 93% and the 350% increases in metabolism
link |
from that previous study.
link |
But critics then will say,
link |
well, that doesn't really translate to that big
link |
of a caloric burn during the deliberate cold exposure.
link |
But to that, you should say, ah,
link |
but that's only limiting your optics
link |
to just a portion of the effects
link |
of deliberate cold exposure,
link |
because deliberate cold exposure
link |
can also convert white fat to beige fat and brown fat
link |
and lead to these more lasting increases in metabolism.
link |
So for any of you interested in increasing your metabolism
link |
and or being comfortable in cold environments
link |
and or being comfortable
link |
in terms of being able to combat stress mentally,
link |
deliberate cold exposure, I do believe is a powerful tool.
link |
And there is simply no reason why you couldn't
link |
and shouldn't use the same protocols
link |
that I described earlier for building resilience
link |
to increase metabolism.
link |
Provided you're hitting that 11 minute per week threshold,
link |
you ought to be stimulating both mechanisms,
link |
increases in resilience and increases in core metabolism.
link |
As I mentioned earlier, most of the detailed studies
link |
on the conversion of white fat to beige fat and brown fat
link |
through the use of cold have been done in animal models,
link |
but the human data are starting to emerge.
link |
And if you'd like to do the deep dive into these mechanisms,
link |
things like UCP-1, PPAR-gamma, et cetera,
link |
there's a beautiful review that was published recently
link |
in the journal Cell,
link |
which is one of the three apex journals,
link |
Nature Science Cell.
link |
And the title of that paper
link |
is Adipose Tissue Plasticity in Health and Disease.
link |
I love this review.
link |
It has beautiful diagrams detailing all of the pathways
link |
from cold to norepinephrine through UCP-1,
link |
downstream of things like cyclic AMP.
link |
If none of those names mean anything to you,
link |
don't worry about it.
link |
You certainly don't need to know these mechanisms
link |
to benefit from deliberate cold exposure protocols.
link |
If those names do mean something to you,
link |
or you're interested in exploring the downstream effects
link |
of deliberate cold exposure,
link |
and something else that's really nice
link |
that's covered in this paper
link |
is how deliberate cold exposure interacts
link |
with fasted states and fed states.
link |
I think you'll also find this review very interesting.
link |
I don't want to go too deeply into fasted states
link |
and fed states right now.
link |
Suffice to say that when we are fasted,
link |
meaning when we haven't eaten for some period of time,
link |
our baseline levels of norepinephrine and epinephrine
link |
are already elevated.
link |
And so cold exposure at those times
link |
ought to have an even greater effect
link |
on metabolism and resilience and so on.
link |
So for you fasters or your intermittent fasters out there,
link |
if you really want to get fancy,
link |
you can do your deliberate cold exposure
link |
when you are fasted.
link |
I certainly wouldn't recommend doing it
link |
with a very full stomach in any case.
link |
And as I mentioned before on this podcast,
link |
intermittent fasting is but one way,
link |
and certainly there are other ways
link |
to limit total caloric intake
link |
for sake of maintaining or losing weight,
link |
if that's your goal.
link |
I know many people are using and benefit
link |
from intermittent fasting, however,
link |
and so it certainly can be combined
link |
with deliberate cold exposures
link |
in order to get even greater increases
link |
in norepinephrine and epinephrine.
link |
So for those of you that are primarily interested
link |
in using deliberate cold exposure
link |
to increase dopamine levels in your brain and body,
link |
you can also do a combined protocol
link |
whereby you ingest caffeine 60 to 120 minutes
link |
before the deliberate cold exposure.
link |
This is based on a study that I've talked about before
link |
entitled Caffeine Increases Striatal Dopamine D2D3
link |
Receptor Availability in the Human Brain.
link |
And as the title suggests, this study was done on humans.
link |
Looking at the density and or efficacy
link |
of these dopamine receptors in an area of the brain
link |
called the striatum, which is involved in planning and action
link |
and also suppressing planning and action.
link |
It's involved very closely with whether or not
link |
we can engage in behavior and withhold behavior,
link |
the so-called go and no-go pathways in the brain.
link |
Dopamine plays a critical role in that
link |
and many other things as well, as you now know.
link |
So why would you want to ingest caffeine 60 to 120 minutes
link |
before deliberate cold exposure?
link |
Well, as I talked about earlier,
link |
dopamine can increase quite substantially
link |
in response to deliberate cold exposure,
link |
but dopamine on its own doesn't do anything.
link |
It has to bind to receptors.
link |
And this paper shows quite definitively
link |
that ingesting caffeine, in this case,
link |
it was 300 milligram dose of caffeine,
link |
which is about the dose of caffeine
link |
in two or three cups of coffee.
link |
It depends on the strength of the coffee, of course,
link |
but it's not an outrageous amount of caffeine.
link |
That increases the density and or efficacy
link |
of these receptors,
link |
which would allow that dopamine to have its greatest effect.
link |
And for those of you that want to get really, really fancy,
link |
I suppose you could do this fasted.
link |
So you get the further increase in norepinephrine,
link |
then you get the dopamine increase from the cold exposure,
link |
the binding of the dopamine.
link |
Although I do want to point out that at some point
link |
you start layering together enough protocols
link |
that you would be spending your entire day
link |
trying to get this dopamine pulse.
link |
And I would hope that you would have other activities
link |
that you would engage in.
link |
But if you're getting up in the morning and you're fasted
link |
because you haven't eaten all night
link |
and you have a cup of coffee,
link |
and then 60 minutes later you take your cold shower,
link |
or two hours later you do your cold immersion
link |
or your cold shower,
link |
you would be layering together these different mechanisms
link |
of dopamine receptors, epinephrine, and so forth
link |
in a way that at least to me doesn't seem incompatible
link |
with having some other life,
link |
like going to school and having relationships, et cetera.
link |
And this increase in dopamine,
link |
particularly in the striatum, is not a trivial one.
link |
I do want to point out, as the authors do,
link |
that preclinical studies have shown
link |
that increases in striatal dopamine
link |
induced by things like modafinil,
link |
which is used to treat ADHD and treat narcolepsy,
link |
is necessary for their wake promoting actions.
link |
What this really says is that
link |
just having elevated levels of dopamine from a drug
link |
or from an ice bath or what have you
link |
is not sufficient to get the effects of dopamine.
link |
You really need the receptors to be available,
link |
and you need those receptors to be available
link |
in the appropriate density,
link |
and you need those receptors to be available
link |
in the appropriate density in the striatum in particular.
link |
So I think there are a number of reasons why,
link |
if it's compatible with the other aspects of your health,
link |
because of course always you have to consider this
link |
on a background of cardiovascular health
link |
and blood pressure, et cetera,
link |
that ingesting a cup or two of coffee
link |
an hour before your ice bath, maybe fasted as well,
link |
could be quite beneficial for increasing dopamine
link |
over quite extended periods of time.
link |
A couple of key points that you'll want to pay attention to
link |
in thinking about deliberate cold exposure and metabolism.
link |
In the Soberg study, they also explored the use of sauna
link |
and how to use sauna, meaning deliberate heat,
link |
in conjunction with cold.
link |
We are going to do an entire episode
link |
about the use of heat for health and performance.
link |
So that is not the focus now.
link |
However, it does raise an important point
link |
that we do need to address at this moment,
link |
which is if you are using sauna
link |
or if you are taking warm showers,
link |
or if you're simply using deliberate cold exposure
link |
of any kind, should you get into the heat afterward
link |
or before or not at all?
link |
And this is where we can point
link |
to the so-called Soberg principle,
link |
at least I call it the Soberg principle.
link |
The Soberg principle named after first author
link |
of this study I referred to earlier, Dr. Susanna Soberg.
link |
In science, it is appropriate to take a key piece of data
link |
and call it a principle,
link |
if in fact it translates to something larger,
link |
which I believe it does.
link |
It is generally not appropriate
link |
for people to name a principle after themselves,
link |
although there are a few scientists that have done that.
link |
So I have named it the Soberg principle,
link |
but I did that to give it appropriate credit
link |
to Dr. Susanna Soberg, who discovered that
link |
and pointed out quite appropriately
link |
that to achieve the greatest increases in metabolism
link |
through deliberate cold exposure,
link |
you want to force yourself to reheat on your own
link |
after the deliberate cold exposure,
link |
meaning you wouldn't want to go
link |
from the cold shower to a hot shower
link |
or from the cold shower to a sauna.
link |
Rather, if you were going to start with a hot shower
link |
or you're going to start with a sauna,
link |
that you would end with the cold
link |
and then you would reheat naturally.
link |
Now, I personally take a cold shower
link |
a few times a week or do cold immersion.
link |
And because I'm not specifically focused
link |
on increasing metabolism, although I probably should be,
link |
that's not what I'm using it for now,
link |
I will take a hot shower afterwards.
link |
And in doing so, I'm short-circuiting
link |
some of the further metabolic increases
link |
that I would achieve were I to just end with the cold.
link |
So the Soberg principle is
link |
if you want to increase your metabolism, end with cold.
link |
And we can take this a step further and say
link |
that if you want to use deliberate cold exposure
link |
to increase metabolism, that you should make sure
link |
that you get to the point where you shiver.
link |
And the reason for this is that
link |
there are a series of studies, but in particular,
link |
one study published in the journal Nature,
link |
excellent journal in the year 2018,
link |
showing that deliberate cold exposure
link |
that evokes shivering from the muscles
link |
causes the release of a molecule called succinate
link |
from the muscles, and that succinate plays a key role
link |
in activating brown fat thermogenesis,
link |
which you now have heard about and understand
link |
as critical to the increases in metabolism
link |
caused by deliberate cold exposure.
link |
So what this means is if you want to increase
link |
your metabolism, end on cold, that's the Soberg principle,
link |
and as best you can, try and get to the point
link |
where you are shivering either when you are
link |
in the cold exposure or immediately afterwards.
link |
Now, one efficient way to do this is to, for instance,
link |
you could get into the cold shower
link |
for a minute or two minutes or three minutes,
link |
uncomfortably cold, but safe to stay in.
link |
Remember, that's our general rule of thumb.
link |
Then turn off the water and stand there,
link |
make sure that you're not holding yourself
link |
close to your body, you're not hugging yourself
link |
to try and keep yourself warm,
link |
but rather your limbs are extended at your sides.
link |
And then if that fails to induce shiver,
link |
then to turn on the cold water again
link |
and then turn it off again.
link |
So alternating perhaps a minute to three minutes
link |
of cold exposure followed by a minute to three minutes
link |
of drying out in air and going back
link |
into the cold exposure, et cetera.
link |
I can tell you this from experience,
link |
this is a pretty brutal protocol.
link |
If you have never tried getting into an ice bath
link |
or cold water immersion or cold shower for one minute
link |
and then getting out and trying to stand there
link |
with your arms extended in cool or cold air
link |
for one minute and then getting back into the cold shower
link |
or water immersion, you are in for an experience
link |
because even for those of you
link |
that are pretty shiver resistant,
link |
you will find that it is much, much harder
link |
to get out of that cold water and stand their arms extended
link |
and drying off by evaporation,
link |
which further draws heat from the body
link |
than it is to wrap yourself in a towel,
link |
get in a warm shower or a sauna.
link |
So there's certainly no requirement to end on cold.
link |
There's certainly no requirement to induce shiver,
link |
but if your primary goal is to induce increases
link |
in metabolism, both in the short-term and in the long-term
link |
following the cold exposure,
link |
well, then you'll want to end on cold
link |
and you'll want to find a way to shiver
link |
provided that the level of cold
link |
that you're exposing yourself to
link |
is still safe for you overall.
link |
So up until now, I've been talking
link |
about deliberate cold exposure as a potent stimulus
link |
for the release of norepinephrine in the brain and body.
link |
And indeed it is, but the way I've been describing it
link |
has been in the context of circulating plasma levels
link |
of norepinephrine, meaning circulating within the blood.
link |
What I haven't mentioned, but is absolutely true
link |
is that the fat cells themselves
link |
actually receive input from neurons.
link |
So there are neurons that release norepinephrine
link |
in response to cold directly into the fat.
link |
So I want to give you this picture
link |
of how the architecture of all this works
link |
because I think it can help you navigate
link |
and indeed build better deliberate cold exposure protocols.
link |
Your adrenal glands release norepinephrine and epinephrine.
link |
Your brain has sites within it like the locus coeruleus
link |
that release norepinephrine and epinephrine.
link |
But there are also neurons within your skin
link |
that sense cold and other neurons
link |
that can directly release norepinephrine
link |
into the fat stores and cause those white fat cells
link |
to convert to beige and brown fat.
link |
And I think this particular aspect of our physiology
link |
is often overlooked in studies.
link |
And when people say, oh, well,
link |
the increases in metabolism aren't that great,
link |
the circulating levels of norepinephrine,
link |
those are very large, but they're very transient and so on,
link |
that fails to understand that neurons
link |
that actually sense cold are in a position
link |
to communicate via other neurons
link |
directly to the fat cells
link |
and release norepinephrine into those fat cells,
link |
which as I pointed out earlier,
link |
set off a huge set of immediate and long-term cascades
link |
of even gene expression changes.
link |
So the picture that I'd like you to have in your mind
link |
is that when you get into the cold,
link |
yes, of course you experience that as a experience of,
link |
I don't want to do this, I'm going to overcome this,
link |
I'm going to climb over these mental walls
link |
that represent adrenaline release in my brain and body,
link |
but also that your fat cells are receiving signals,
link |
norepinephrine signals that are changing those fat cells
link |
and the way that they metabolize energy.
link |
Now I'd like to shift our attention
link |
to the use of deliberate cold exposure
link |
for sake of physical performance.
link |
And there are a lot of opinions out there
link |
about the use of deliberate cold,
link |
whether or not it should be done, for instance,
link |
before or after exercise,
link |
whether or not if done immediately after strength training
link |
or hypertrophy training,
link |
meaning training designed to grow muscles
link |
or make them stronger,
link |
whether or not it can inhibit that process
link |
and so on and so forth.
link |
I think today in looking over the literature
link |
and trying to bring forward the simplest
link |
and most straightforward
link |
and yet scientifically grounded protocols,
link |
we can set up some general guidelines
link |
that will allow most, if not all of you
link |
to still extract the benefits of deliberate cold exposure
link |
on physical performance without getting too neurotic
link |
about the exact timing.
link |
But for sake of discussion,
link |
and because it's a prominent theme
link |
in many online communities,
link |
let's just start with the big one out there,
link |
meaning the question of whether or not doing an ice bath
link |
or doing deliberate cold exposure
link |
or taking a cold shower after strength
link |
slash hypertrophy training,
link |
meaning training designed to increase strength
link |
and or I should say the size of muscles
link |
will somehow short circuit or diminish that process,
link |
whether or not it will reduce
link |
or eliminate those strength gains and hypertrophy gains.
link |
And the short answer that I was able to arrive at
link |
on the basis of a review article
link |
that I'll talk about in a moment
link |
and some other studies as well
link |
is that if your main goal is hypertrophy and strength,
link |
it is probably best to avoid cold water immersion
link |
and ice bath immersion in the four hours
link |
immediately following that strength
link |
and or hypertrophy training.
link |
Again, if your main goal is to achieve hypertrophy
link |
or strength or some combination of those,
link |
probably best to avoid cold water immersion up to the neck
link |
or ice bath immersion up to the neck
link |
immediately after strength and hypertrophy training
link |
and extending out to about four hours after that training.
link |
If you're really neurotic about this,
link |
then perhaps you'd want to move the cold water exposure
link |
to a different day entirely,
link |
but it all depends on how neurotically attached you are
link |
to getting every last bit of strength and hypertrophy.
link |
And if that's your goal, terrific,
link |
well then probably moving the cold exposure
link |
four hours or more away from that training
link |
is going to be necessary for you.
link |
Now you'll notice I did not talk about cold showers.
link |
And the reason I did not talk about cold showers
link |
is that there simply are not very many studies
link |
of deliberate cold exposure through cold showers
link |
for the reasons I talked about
link |
at the beginning of the episode.
link |
It's hard for me to imagine that taking a brief cold shower
link |
after a strength or hypertrophy training session
link |
would completely reverse or short circuit
link |
the effects of that strength and hypertrophy training.
link |
But again, if you're neurotically attached
link |
to getting every last bit of strength and hypertrophy
link |
out of your training sessions,
link |
then by all means, err on the side of caution
link |
and wait four hours or more to do your cold shower
link |
just as you would wait four hours or more
link |
to do your cold water immersion.
link |
Now there are nice data pointed to the fact
link |
that doing cold water immersion after a hard run,
link |
so endurance training, or even sprint and interval training,
link |
or after a weight workout where your main focus
link |
is on performance of those movements,
link |
or after a skill training workout
link |
where your main focus on performance of those movements,
link |
that there's no reason to think
link |
that that cold water immersion or ice bath or cold shower
link |
would inhibit the progress or the stimulus
link |
that would lead to progress that occurred
link |
during that training session.
link |
In other words, I don't see any reason
link |
based on the literature to avoid deliberate cold exposure
link |
immediately after training,
link |
again, unless your goal is hypertrophy and strength.
link |
And in fact, there's a very nice review
link |
that was recently published on deliberate cold exposure
link |
and how it can impact physical performance,
link |
whether or not it's done before or after
link |
different types of training and so forth.
link |
The paper is entitled impact of cold water immersion
link |
compared with passive recovery
link |
following a single bout of strenuous exercise
link |
on athletic performance in physically active participants,
link |
a systematic review with meta-analysis and meta-regression.
link |
So this is a meta-analysis of 52 studies
link |
that looked at a tremendous number of variables
link |
and contexts as you would expect
link |
in a meta-analysis of 52 studies.
link |
I'm going to read you the conclusions of the study
link |
and I'll provide a link.
link |
We certainly don't have the time
link |
to go through all the details of the study.
link |
I will highlight a few specific outcomes
link |
that I found particularly interesting,
link |
but here I am paraphrasing their conclusions
link |
that cold water immersion,
link |
I want to emphasize immersion, not cold showers,
link |
but cold water immersion,
link |
they say was an effective recovery tool
link |
after high intensity exercise.
link |
They observed positive outcomes,
link |
meaning improvements in certain variables
link |
for muscular power, muscular soreness,
link |
meaning reduced muscular soreness, increased muscular power,
link |
perceived recovery after 24 hours of exercise.
link |
However, there were certain forms of exercise
link |
that were not benefited by cold water immersion,
link |
such as eccentric exercise,
link |
exercise focusing only on the lowering component
link |
or the so-called eccentric component
link |
of resistance exercise.
link |
They saw some very interesting dose response relationships
link |
for things like endurance training,
link |
meaning the longer the cold exposure
link |
post-endurance training,
link |
the more improvement in endurance performance,
link |
reductions in circulating creatine kinases
link |
and things that relate to muscle damage
link |
under certain conditions.
link |
At some point in the future, by the way,
link |
we'll do an entire episode on creatine
link |
and creatine kinases,
link |
which are important not just for muscular function,
link |
but also for brain function.
link |
But the basic takeaway was that cold water immersion
link |
performed after high-intensity exercise
link |
was beneficial from a number of different standpoints
link |
and indicated that shorter duration cold exposure
link |
and lower temperatures can improve
link |
the efficacy of cold water exposure
link |
if used after high-intensity exercise, okay?
link |
There I'm directly pulling from their conclusions.
link |
So what this says is that it's not just those
link |
longer duration 30, 45-minute and 60-minute protocols
link |
of cold water immersion that we discussed earlier,
link |
but also shorter duration, one-minute, three-minute,
link |
five-minute exposures to lower temperatures,
link |
temperatures that would make you psychologically
link |
want to get out as soon as you possibly can,
link |
but again, that you can safely stay in,
link |
done after training really have been shown
link |
to improve outcomes in terms of reducing soreness
link |
and improving training efficacy,
link |
meaning your ability to get back into training more quickly
link |
and thereby deliver more training stimuli to a given muscle
link |
or in your endurance training protocol.
link |
Translating to English, what this means is that
link |
taking a cold shower or getting into an ice bath
link |
or some other form of cold water immersion
link |
within the immediate minutes
link |
or even the immediate hours following your training
link |
has been shown to be beneficial.
link |
I'm sure a number of you have questions, for instance,
link |
how long should you be in that cold exposure?
link |
Is it the same as the 11-minute threshold
link |
described earlier?
link |
To be honest with you, there are not enough studies
link |
to really point to the critical threshold
link |
for eliminating or reducing delayed onset muscle soreness
link |
or for getting maximal results
link |
from power and endurance training,
link |
but this study does make a couple of key points,
link |
and here I will just paraphrase.
link |
For instance, that cold water immersion is more likely
link |
to positively influence muscular power performance,
link |
to reduce muscle soreness, to reduce serum creatine kinase,
link |
and to improve perceived recovery
link |
after high-intensity exercise
link |
as compared with passive recovery.
link |
This can be translated to cold water exposure
link |
after training is beneficial and probably better
link |
than passive recovery from a number of standpoints.
link |
In addition, they say that dose-response relationships,
link |
meaning the amount and the degree of cold
link |
that people were exposed to and how often they did that,
link |
in particular in lower temperature cold immersion,
link |
so these would be the sorts of cold immersion protocols
link |
that are one minute or two minutes,
link |
three minutes, maybe five minutes,
link |
but that one couldn't stay in there longer
link |
because it feels stressful and one wants to get out,
link |
may be more effective after high-intensity exercise
link |
for removal of serum creatine kinase,
link |
as well that these shorter duration
link |
cold water immersion approaches may be more effective
link |
after high-intensity endurance performance as well.
link |
So all of this can be translated to say
link |
that unless your main goal is hypertrophy and strength,
link |
that cold exposure, ideally cold immersion
link |
in cold water or ice bath,
link |
but if you don't have access to that,
link |
then cold showers is likely going to be beneficial
link |
if done immediately after or in the minutes or hours
link |
after your training, especially high-intensity training.
link |
One particularly nice thing about this meta-analysis
link |
is that it included some studies
link |
that involved the use of cooling packs,
link |
so again, vests that can hold essentially ice packs
link |
and indeed even cryotherapy chambers and so on.
link |
There's a nice table in the study
link |
if you want to get really detailed
link |
and go and look specifically at those studies,
link |
I invite you to do that.
link |
We'll put a link to this study
link |
in the caption for this episode.
link |
But all in all, what this study shows
link |
is that deliberate cold exposure can be very useful
link |
for recovery, likely through reductions in inflammation
link |
in muscle and connective tissue.
link |
And while this study did not look specifically
link |
at the mechanisms of reduced inflammation
link |
caused by deliberate cold exposure,
link |
those mechanisms are somewhat known.
link |
There are a number of studies that have pointed to the fact
link |
that deliberate cold and cold generally
link |
can reduce inflammatory cytokines,
link |
such as IL-6, interleukin-6.
link |
It can increase anti-inflammatory cytokines,
link |
such as interleukin-10 and so on.
link |
Without getting into all those details,
link |
I think it's sufficient to say that if you are somebody
link |
who experiences a lot of delayed onset muscle soreness,
link |
taking a cold shower after your training
link |
or getting into a cold immersion after your training,
link |
even if it's a few hours later, ought to help.
link |
And if you are doing particularly intense training,
link |
then you probably want to ratchet up
link |
the number of cold exposure sessions that you're doing,
link |
even if those have to be done on separate days
link |
from your training.
link |
Because a lot of the inflammatory effects of training,
link |
endurance and strength training,
link |
are actually occurring some hours away
link |
from the training stimulus.
link |
So it's not just that inflammation goes up radically
link |
during training, which it often can,
link |
but that it can occur even in the days
link |
and even weeks afterwards, depending on how intense
link |
and how long duration that training is.
link |
So deliberate cold exposure is very powerful
link |
as an anti-inflammatory tool.
link |
Now I'd like to emphasize a topic that we touched on
link |
at the beginning of the episode,
link |
which are those glabrous skin surfaces,
link |
the hands, the upper face and the bottoms of the feet,
link |
through which heat is especially good at leaving the body.
link |
And another way of putting that is that
link |
one can cool the body much more efficiently
link |
through the glabrous skin surfaces.
link |
Now, if you want to understand all of the science
link |
behind this and all of the various applications,
link |
I invite you to please listen to the episode that I did
link |
with Dr. Craig Heller, again, in the biology department
link |
For sake of this episode, I'm just going to detail
link |
a couple of findings from his laboratory.
link |
The first one dealing with exercise-induced hyperthermia,
link |
because I think this is very interesting
link |
and it can even save lives
link |
if you understand the way this works.
link |
There's a particular paper that focuses on this
link |
and we will put a link to this as well.
link |
The title of this paper is novel application
link |
of chemical cold packs for treatment
link |
of exercise-induced hyperthermia,
link |
a randomized control trial.
link |
This is a pretty brutal study,
link |
brutal for the subjects, that is.
link |
What this study involved was having subjects
link |
walk on a treadmill at a pretty significant incline,
link |
anywhere from nine to 17%,
link |
wearing a substantial amount of clothing
link |
that was not well-ventilated,
link |
and the room was kept to 40 degrees Celsius,
link |
which is 104 degrees Fahrenheit.
link |
This is definitely not something to do at home.
link |
This study was designed to induce hyperthermia,
link |
which as I mentioned earlier, can be quite dangerous.
link |
And they compared two types of cooling.
link |
In the first form of cooling
link |
that they call traditional cooling,
link |
they had ice packs on their neck,
link |
in their armpits and in their groin.
link |
And in the other group,
link |
there was the so-called glabrous skin cooling.
link |
So the palms, the soles of the feet,
link |
which were actually,
link |
so they were cooling inside the boots or inside of gloves.
link |
And on the upper portion of the face.
link |
And the basic takeaway of this study
link |
is that by cooling the glabrous skin,
link |
the subjects were able to sustain this walking
link |
on these incline treadmills for much longer
link |
than were the people who received traditional cooling.
link |
And also the return to baseline temperature
link |
was much faster in the glabrous skin cooling group.
link |
So how this translates to the real world
link |
is that if ever you are hyperthermic
link |
or someone else is hyperthermic,
link |
one way to cool them down quickly
link |
is to cool these palmar glabrous,
link |
soles of the feet, glabrous,
link |
and upper portion of the face,
link |
glabrous portions of the body,
link |
using cool rags, using ice packs,
link |
or using any number of different cold objects
link |
One key thing if you're going to use glabrous skin cooling
link |
is that whatever you use to cool those surfaces
link |
cannot be so cold that it causes vasoconstriction.
link |
Because as I mentioned earlier,
link |
the arteriovenous osteomoses,
link |
these portals of arteries directly to veins
link |
that exist only in these glabrous skin surfaces,
link |
the way that they're able to cool the body
link |
and essentially pass cool into the body,
link |
although that's not really what they're doing,
link |
they're actually extracting heat from the body
link |
to be technical, they're extracting heat from the body.
link |
The only way they can do that
link |
is if those veins don't collapse,
link |
and veins will collapse if they are made very, very cold.
link |
So if you want to use glabrous skin cooling
link |
to offset hyperthermia,
link |
or for the other forms of performance,
link |
which we will talk about in a moment,
link |
you need to use a cool object or surface
link |
that is not so cold that it causes vasoconstriction.
link |
And this can be a little bit tough to dial in,
link |
meaning it can be tough to identify such an object.
link |
And for that reason, Dr. Heller and some of his colleagues
link |
have developed a commercial product called the CoolMitt.
link |
You can actually go to their website, coolmitt.com.
link |
I don't have any financial or other relationship to them.
link |
I know they've been developing this technology
link |
for some period of time.
link |
It involves a glove that you put your hand into.
link |
It circulates water of a given temperature,
link |
and it does so at a temperature
link |
that is sure to not cause vasoconstriction of the palm.
link |
And you may be asking,
link |
how can you just put your hand into one glove
link |
and have this work?
link |
Well, that's how powerful these glabrous skin surfaces are,
link |
even just by cooling one palm,
link |
the core body temperature drops radically.
link |
Now that's their commercial technology.
link |
I know that some people out there
link |
have started to experiment with a home version of this,
link |
which would be taking a package, for instance,
link |
of frozen blueberries or some other cold drink
link |
or cold metal object and actually bringing it into the gym
link |
There are even people who are now developing
link |
cooled bicycle handles for long rides.
link |
This might seem a little kooky or crazy to you,
link |
but as you'll soon hear in the study I'm about to describe,
link |
the increases in endurance
link |
and in the volume of strength training
link |
that people can conduct
link |
if they appropriately cool their body
link |
through these glabrous skin portals
link |
is actually quite significant.
link |
So again, as it relates to hyperthermia,
link |
if someone is overheating,
link |
by all means, try and get them out of that heat,
link |
get them to stop exercising.
link |
You can die from hyperthermia.
link |
Try and cool the bottoms of the feet,
link |
the palms of their hands
link |
and the upper portion of their face.
link |
That does not mean that it would be a bad idea
link |
to put cold water on the top of their head.
link |
That probably would also help and perhaps on their neck.
link |
What is probably not going to be a good idea
link |
is to do the more standard thing
link |
of draping someone in cold towels
link |
on the surface of their body
link |
because as I mentioned at the beginning of the episode,
link |
that thermostat in the hypothalamus,
link |
the medial preoptic area,
link |
will typically react to that
link |
by increasing core body temperature further.
link |
The effects of glabrous skin cooling
link |
on physical performance are truly remarkable
link |
provided the glabrous skin cooling is done correctly.
link |
And I want to point out that the main degree of effect
link |
is on volume or the ability to do more work.
link |
And I want to point this out
link |
because I think that many people,
link |
certainly in the exercise science community,
link |
but even in the general public,
link |
when they hear about some of these effects
link |
that are measured in the laboratory,
link |
they sort of look at those effects a bit askance
link |
and they think, well, that's not possible, right?
link |
Effects, for instance, that have been documented
link |
showing doubling or tripling of the number of dips
link |
that one can do in a relatively short amount of time,
link |
or doubling of the number of pull-ups one can do,
link |
or 14% increases in strength,
link |
or even comparable degrees in increase
link |
in weight training output
link |
to people who are on performance enhancing drugs,
link |
et cetera, et cetera.
link |
Part of the confusion is that the effects
link |
of proper Palmer cooling,
link |
because it almost always is done by Palmer cooling
link |
and less often in these experiments
link |
by cooling of the bottoms of the feet
link |
in the upper portion of the face,
link |
but those effects tend to be the ability
link |
to do more work over time.
link |
And just to illustrate some of the major effects
link |
that the Heller lab has seen
link |
and that are documented in this manuscript
link |
that I'll share with you in a moment,
link |
the typical protocol is to have people come in
link |
and do some endurance training,
link |
so running on a treadmill,
link |
and to have a condition where one group
link |
is actually doing Palmer cooling
link |
while they are on a bike or on a treadmill.
link |
And inevitably the outcome is that they can do more work.
link |
They can pedal further at a given speed,
link |
or they can run longer at a given speed
link |
than people who are not doing Palmer cooling
link |
or who are receiving cooling by way of, you know,
link |
cold compress to the back of the neck
link |
or ice pack to the armpits, et cetera.
link |
So the effects of Palmer cooling are very clear
link |
And in the context of endurance exercise,
link |
almost always allow people to do more work,
link |
to go longer with less perceived effort
link |
and to quit later, so to speak.
link |
In terms of strength training,
link |
they've looked at the capacity to perform sets of dips.
link |
So one of the more famous examples of this
link |
that Dr. Heller shares in the episode that we did earlier
link |
and that you can find at Hubermanlab.com
link |
involves someone coming in and doing sets of dips,
link |
this person actually could do 40 dips on their first set,
link |
then resting for a period of two to three minutes
link |
and then resting for a period of two or three minutes
link |
and then doing progressively fewer and fewer and fewer
link |
to the point where over a period of time,
link |
they add up the total number of dips that they can do,
link |
and then they have them come back
link |
after a period of recovery.
link |
So not immediately after, but take a couple of days,
link |
come back and do effectively the same protocol,
link |
but during their rest periods,
link |
they're doing two minutes of Palmer cooling,
link |
which essentially allows heat to move out of the body,
link |
lowering core body temperature, in other words.
link |
And what they find is that they see enormous increases
link |
in the total number of dips that people can do,
link |
but that doesn't mean that the person goes
link |
from being able to do 40 dips
link |
to being able to do 50 dips or 60 dips on that first set.
link |
What it means is they are able to do 40 on the first set,
link |
then 40 on the second, then 38 on the third
link |
and so on and so forth,
link |
so that the total duration of the workout is extended
link |
and yet they're doing much more work,
link |
even though it takes more time.
link |
So that's an important point.
link |
And I think a point that perhaps wasn't as clear
link |
or as clearly made by me in the previous episodes
link |
that discussed this topic.
link |
For those of you that are interested
link |
in exploring Palmer cooling,
link |
first of all, I recommend taking a brief glance
link |
or even a deep dive into this study,
link |
which is entitled work volume
link |
and strength training responses to resistive exercise
link |
improve with periodic heat extraction from the palm.
link |
In this study, they describe big increases in anaerobic,
link |
meaning strength training output,
link |
things like improvement in dips, improvement in bench press,
link |
improvement in pull-ups, et cetera, in human subjects.
link |
And it's a really nice study
link |
and points to some of the protocols
link |
that you might be able to adapt in your own setup.
link |
For instance, over six weeks of pull-up training,
link |
palm cooling in between sets, improved volume by 144%.
link |
And this was in experienced subjects.
link |
So that's interesting because a lot of studies
link |
of strength training and improvements in hypertrophy
link |
and strength are done in inexperienced untrained athletes,
link |
which changes the picture somewhat
link |
compared to experienced athletes.
link |
They found that strength, meaning the one repetition maximum
link |
increased 22% over 10 weeks in bench press training.
link |
And they point to the particularly strong effects
link |
of using Palmer cooling when people reach plateaus
link |
in endurance and strength training.
link |
And there, I think it's an important point.
link |
I think that if you're going to explore Palmer cooling,
link |
it's probably not the sort of thing that you're going to do
link |
in every run or in every bout of cycling
link |
or in every strength training session,
link |
but that it might be used to vastly increase your volume
link |
or vastly increase your endurance in a given session
link |
or a set of sessions in order to push through plateaus.
link |
A particularly interesting point in light of that
link |
is Dr. Heller has observed again and again
link |
that Palmer cooling reduces delayed onset muscle soreness
link |
or can eliminate it entirely.
link |
And that's very interesting because it also points
link |
to the fact that reducing core body temperature
link |
may somehow be involved in short circuiting
link |
the normal mechanisms of delayed onset muscle soreness.
link |
And you might say, well, how would temperature
link |
be involved in delayed onset muscle soreness?
link |
Well, I want to refer you back to the meta analysis
link |
that we talked about earlier where the short duration,
link |
very cold temperature exposure after training
link |
did indeed reduce delayed onset muscle soreness
link |
in part through reduction, excuse me, in creatine kinase.
link |
So it's not inconceivable that temperature
link |
and delayed onset muscle soreness are related.
link |
And that raises perhaps the most important point,
link |
which is the way that Palmer cooling can improve performance
link |
by way of reducing core body temperature is known.
link |
And that is because when one engages in exercise
link |
or muscular output of any kind,
link |
strength or endurance exercise,
link |
the range of temperatures under which a muscle can perform
link |
is actually very narrow.
link |
There's an enzyme called pyruvate kinase,
link |
which is critical to muscle contractions
link |
and pyruvate kinase can only function
link |
in a very narrow range of temperatures.
link |
If that temperature gets too hot,
link |
meaning if the muscle heats up locally,
link |
whether or not by running or cycling or swimming
link |
or weightlifting, the ability for that muscle
link |
to continue to contract is reduced
link |
and eventually is short-circuited completely.
link |
And I think this is a much under explored
link |
or at least a much under discussed aspect
link |
of so-called muscular failure
link |
or the failure of one to continue to endure in running.
link |
So for instance, when you run
link |
as compared to a bench press or something,
link |
you don't stop running
link |
because you can't actually contract the muscles further,
link |
but somehow signals about the heating up
link |
of muscular tissue are conveyed to the brain.
link |
There's a crosstalk there.
link |
It's probably bi-directional and people stop, they quit.
link |
This is the quitting reflex.
link |
In strength training,
link |
one can no longer perform a repetition
link |
or set of repetitions in part
link |
because of heating up of the muscle locally.
link |
There are other mechanisms as well, of course,
link |
and I realize that.
link |
But what's very clear from the palmar cooling work
link |
is that by simply holding onto a cool object,
link |
remember not an object so cold
link |
that it constricts the vessels of the palms
link |
or constricts the vessels on the bottoms of the feet,
link |
but by holding onto a relatively cool object
link |
in one or both hands in between sets for two minutes or so,
link |
you can very efficiently reduce your core body temperature.
link |
reduce the temperature of the muscles
link |
that are doing the work,
link |
increase the capacity for pyruvate kinase
link |
to continue to allow your muscles to contract
link |
and thereby allow you to do more volume of endurance
link |
and strength training.
link |
So a simple protocol that Dr. Heller passed to me
link |
is find a relatively cool object.
link |
So you could, for instance, fill two bottles with cold water,
link |
maybe put a few ice cubes in there, right?
link |
This is not exact because we're not talking
link |
about the commercial cool mint product here,
link |
we're talking about an at-home version,
link |
or use a pack of frozen blueberries or broccoli,
link |
the sort of pack of those as what he described,
link |
and then in between sets to put your hands,
link |
and ideally you'd put the bottoms of your feet,
link |
but that's not always feasible in most gyms
link |
where they won't let you take off your shoes and so forth,
link |
but to put the palms of your hands on that cool surface
link |
for a minute or two minutes between sets
link |
and then returning to your sets of work.
link |
Now, if you are heating up through other mechanisms,
link |
like you're wearing a stocking cap
link |
and you're in a very warm environment,
link |
this might not have as potent an effect
link |
as if you were to do this cooling
link |
in a more moderate environment
link |
wearing lighter clothing, et cetera.
link |
So by all means, warm up to do your exercise,
link |
lubricate your joints and get into a place
link |
where you're not going to injure yourself
link |
doing whatever form of exercise you do,
link |
but then if you'd like to explore Palmer cooling,
link |
I know a number of people who've written to me saying
link |
they heard about Palmer cooling
link |
on the episode with Dr. Heller,
link |
they've tried this and they see quite excellent results.
link |
It does take some discipline, right?
link |
It's one thing to just kind of hang out in the gym
link |
and play on your phone in between sets.
link |
It's another to do deliberate cooling with your palms
link |
or the bottoms of your feet
link |
or the upper portion of your face.
link |
You might get some weird looks,
link |
but of course you'll be the one
link |
doing significantly more volume,
link |
not experiencing delayed onset muscle soreness
link |
and achieving better endurance and strength gains
link |
were you to do this properly.
link |
Now, as a final topic related to the use
link |
of deliberate cold exposure
link |
for improving health and performance,
link |
I'd like to touch on this theme that exists online
link |
on social media, on YouTube,
link |
and in various fitness communities
link |
of using deliberate cold exposure to the groin,
link |
in particular to the testicles,
link |
in order to try and increase testosterone.
link |
And while this might sound really kooky,
link |
indeed this practice exists.
link |
Indeed, if you were to go on the Amazon,
link |
there are actually ice pack underwear
link |
that are being marketed
link |
for sake of increasing testosterone.
link |
Now, I am not aware of any specific well-controlled studies
link |
that show that this indeed works.
link |
I can imagine based on what I know about the nervous system,
link |
testosterone and cold, et cetera,
link |
that there are a couple of mechanisms
link |
by which one might experience increases in testosterone
link |
as a consequence of deliberate cold exposure.
link |
First off, let me say there is no reason
link |
why you would have to apply these ice packs
link |
in the way that I just described.
link |
One could, of course, take a cold shower.
link |
One could, of course, use cold immersion of various kinds,
link |
and you're still going to get that exposure
link |
of the groin and the testicles to cold.
link |
Now, I should point out that people do report,
link |
at least anecdotally, increases in testosterone
link |
as a consequence of this practice.
link |
And I have to imagine
link |
that they are measuring their serum testosterone,
link |
that they're not just guessing
link |
that their testosterone went up.
link |
If you know of a study exploring this directly,
link |
please let me know,
link |
put it in the comment section on YouTube,
link |
or even just email me.
link |
We have a email that you can find at hubermanlab.com.
link |
Please email me the reference.
link |
I wasn't able to find a reference.
link |
But I can imagine two reasonably plausible mechanisms
link |
by which deliberate cold exposure to the groin
link |
and particularly the testicles would increase testosterone.
link |
The first is somewhat direct,
link |
which is that anytime you cool a body surface,
link |
that if it's cold enough,
link |
you're going to get vasoconstriction.
link |
And then subsequently,
link |
you're going to get a rebound increase in vasodilation,
link |
meaning you're going to constrict the blood vessels
link |
And then after the cold is removed,
link |
there's going to be more blood flow to that area.
link |
And of course, blood flow relates
link |
to organ health and tissue health generally,
link |
so perfusion of that region and the gonads, to be specific.
link |
With additional blood,
link |
you could imagine in some ways increasing testosterone.
link |
That's reasonably plausible.
link |
The other probably more likely mechanism relates
link |
to the dopamine increases caused by cold exposure
link |
that we talked about earlier.
link |
Again, anytime you have a somewhat stressful stimulus,
link |
but in particular with cold exposure,
link |
it seems that the catecholamines norepinephrine, epinephrine
link |
and dopamine all increase.
link |
And dopamine is known to be in the pathway
link |
that can stimulate testosterone.
link |
And so while there isn't a direct relationship
link |
between dopamine stimulating testosterone,
link |
there is an interesting pathway whereby dopamine increases
link |
can trigger increases in things like luteinizing hormone,
link |
which can trigger increases in testosterone,
link |
as well as estrogen for that matter.
link |
So I know that there are a lot of people out there
link |
that are interested in the use of cold exposure
link |
for increasing testosterone.
link |
And some of those people in communities
link |
are indeed using cold exposure directly on the gonads,
link |
on the testes in order to do this.
link |
I'm not certain that that direct contact is necessary.
link |
And in some cases it might actually be quite dangerous
link |
or you at least should be careful
link |
in terms of the tissues there and avoiding damage.
link |
But nonetheless, I think that a dopamine impact
link |
on testosterone is very likely given the 250% increases
link |
in dopamine that have been observed
link |
with cold water immersion.
link |
And all of that points to the fact
link |
that cold water immersion very likely increases testosterone,
link |
but as a downstream consequence
link |
of the cold water immersion effects
link |
on dopamine and luteinizing hormone.
link |
And again, there's no reason to think
link |
that the increases in luteinizing hormone
link |
would also increase estrogen,
link |
probably not too dangerous or levels
link |
that one would want to avoid.
link |
But I don't think that there's anything
link |
particularly specific about cold for inducing testosterone
link |
and not other hormones.
link |
I think it's very likely to increase
link |
as a number of different hormones.
link |
I do hope that there will be a systematic study on this
link |
in the not too distant future.
link |
I also hope to not be a subject
link |
in the cooling of the gonads experiment.
link |
Now, I promise you the last topic was the last topic,
link |
but there's one other really important point
link |
that I think everyone should be aware of
link |
if you're going to use deliberate cold exposure.
link |
And that brings us back to the very first thing
link |
that we discussed today
link |
along the lines of deliberate cold exposure,
link |
which is that your baseline temperature
link |
is going to be lowest about two hours before you wake up.
link |
It's going to increase in the morning and as you wake up,
link |
and increase throughout the day and afternoon,
link |
and then start to drop in the evening
link |
and come down at night as you head to sleep.
link |
I also want you to remember
link |
that if you are to cool the external portion of your body,
link |
in particular your torso,
link |
the net effect of that
link |
is going to be an increase in body temperature.
link |
So for many people, not all, but for many people,
link |
if you are going to do deliberate cold exposure,
link |
you are going to increase your core body temperature.
link |
And that makes sense if you think about
link |
how deliberate cold exposure can increase metabolism
link |
by increasing thermogenesis.
link |
What that all means is
link |
that if you are doing your deliberate cold exposure
link |
you are going to get yet a further increase
link |
in core body temperature
link |
that would be associated with wakefulness,
link |
your ability to be alert that morning
link |
or throughout the day, and so on.
link |
It also means that if you do your deliberate cold exposure
link |
very late in the evening or at night,
link |
so 6 p.m., 7 p.m., 9 p.m., and so on,
link |
you are going to increase your core body temperature.
link |
And if you recall,
link |
a decrease in core body temperature of one to three degrees
link |
is not just beneficial,
link |
but is necessary in order to get into deep sleep
link |
and remain in deep sleep.
link |
So the takeaway from this is
link |
deliberate cold exposure done properly
link |
will increase your core body temperature
link |
and make you feel more alert.
link |
So if you're doing it early in the day,
link |
that's probably terrific,
link |
given that most of us want to be alert during the day.
link |
However, if you do it too late in the day,
link |
evening or night, it can disrupt sleep
link |
by way of disrupting your core body temperature.
link |
Now, the caveat to that is I myself
link |
tend to do my deliberate cold exposure early in the day,
link |
maybe not first thing in the morning, but mid-morning,
link |
maybe as late as three or four in the afternoon
link |
In the longer days of summer, I might do it even later,
link |
5 or 6 p.m., and have no trouble sleeping.
link |
I have done deliberate cold exposure very late at night,
link |
10 p.m., 11 p.m., and so on,
link |
as part of a 30-day challenge of doing
link |
deliberate cold exposure every day for 30 days,
link |
and I got sloppy with my timing,
link |
and then in order to not miss a day,
link |
I would do it at 11 o'clock at night.
link |
And I must say, I found that I could still fall asleep
link |
very easily, even doing deliberate cold exposure
link |
very late at night.
link |
However, on those particular days, I was particularly busy,
link |
and so I was particularly exhausted
link |
when I arrived at the deliberate cold exposure,
link |
and I had no trouble falling asleep
link |
after doing deliberate cold exposure
link |
and then taking a nice warm shower and then going to sleep.
link |
But I could imagine that because of the increases
link |
in core body temperature caused by deliberate cold exposure,
link |
that were one to do that too late in the day,
link |
evening or night, that it could indeed disrupt your sleep.
link |
So my recommendation would be for most people,
link |
only do deliberate cold exposure
link |
if you are prepared to be fairly alert
link |
for the next one to four or maybe even six hours
link |
following that deliberate cold exposure.
link |
So for today's episode, as is the case
link |
with most episodes of the Huberman Lab Podcast,
link |
I covered a lot of material.
link |
We talked about mechanisms of catecholamines and stress
link |
and pulsatile release of epinephrine,
link |
metabolism, mental effects, performance,
link |
glabrous skin cooling, and on and on and on.
link |
And while the goal of course is to make sure
link |
that everyone arrives at specific, very clear,
link |
mechanistic and actionable protocols,
link |
I do realize that it is an immense amount of information.
link |
And for that reason, I've created a list
link |
of deliberate cold exposure protocols
link |
aimed at improving mental toughness and resilience,
link |
mood, performance, metabolism,
link |
reducing inflammation, and so on and so forth.
link |
All of those have been condensed into succinct form
link |
at the Huberman Lab Neural Network Newsletter.
link |
This is a monthly or semi-monthly newsletter
link |
that we release that includes takeaways
link |
from the podcast and protocols.
link |
You can access those protocols, zero cost,
link |
by simply going to HubermanLab.com,
link |
signing up for the Neural Network Newsletter.
link |
It's very easy to do.
link |
You just supply your email and you will receive
link |
We do not share your email with anybody else.
link |
In fact, we have our privacy policy laid out
link |
on the HubermanLab.com website,
link |
so you can find that there.
link |
And the protocols that I've designed
link |
should make it very straightforward for you to create
link |
a set of protocols that you could use with cold showers,
link |
with cold immersion, with or without ice,
link |
in combination with exercise, specifically for one goal
link |
or another, or to accomplish multiple goals simultaneously.
link |
If you're learning from and are enjoying this podcast,
link |
please subscribe to our YouTube channel.
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That's a terrific zero cost way to support us.
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In addition, please subscribe to the podcast
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link |
That is the best way to support this podcast.
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In addition, we have a Patreon.
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link |
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On many previous episodes of the Huberman Lab Podcast,
link |
we talk about supplements.
link |
While supplements aren't necessary for everybody,
link |
many people derive tremendous benefit from them
link |
for things like sleep and focus and other aspects
link |
of health and performance.
link |
One issue with the supplement industry
link |
that's very serious, however,
link |
is that many supplement companies simply do not use
link |
high quality ingredients or the amounts of the ingredients
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they list on the packaging does not match
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There I cover science and science-related tools
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So thank you once again for joining me in the discussion
link |
about the use of deliberate cold exposure
link |
for health and performance.
link |
And last, but certainly not least,
link |
thank you for your interest in science.
link |
I'll see you next time.