back to indexDr. Craig Heller: Using Temperature for Performance, Brain & Body Health | Huberman Lab Podcast #40
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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, I have the pleasure of introducing Dr. Craig Heller
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as my guest on the Huberman Lab Podcast.
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Dr. Heller is a professor of biology
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and neurosciences at Stanford.
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His laboratory works on a range of topics,
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including thermoregulation, down syndrome,
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and circadian rhythms.
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Today, we talk about thermoregulation,
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how the body heats and cools itself
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and maintains what we call homeostasis,
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which is an equilibrium of processes
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that keeps our neurons healthy,
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our organs functioning well.
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And as Dr. Heller teaches us,
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thermoregulation can be leveraged
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in order to greatly increase our performance in athletics
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and mental performance as well.
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Learning to control your core body temperature
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is one of the most, if not the most powerful thing
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that you can do to optimize mental and physical performance
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regardless of the environment that you're in.
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He also dispels many common myths
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about heating and cooling the body,
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including the idea that putting a cold pack
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on your head or neck is the optimal way
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to cool down quickly.
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And in fact, as Dr. Heller tells us,
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it actually can be counterproductive
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and lead to hyperthermia.
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It's a fascinating conversation
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from which I learned a tremendous amount
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of new information,
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and we didn't even get into the other
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incredibly interesting work that Dr. Heller does
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on Down syndrome and circadian rhythms and sleep.
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So we hope to have him back in the future
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to discuss those topics.
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As you'll soon see,
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Dr. Heller is a wealth of knowledge
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on all things human physiology, biology,
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and human performance.
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It's no surprise then that he's been
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chair of the biology department at Stanford for many years,
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as well as director of the human biology program.
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So if you're interested in human biology
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and how to improve your performance
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in any context or setting, athletic or otherwise,
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I think you'll very much enjoy today's conversation.
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I'd like to emphasize that this podcast
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is separate from my teaching 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
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about science and science related tools
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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 Roca.
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Roca makes sunglasses and eyeglasses
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that are of the absolute highest quality.
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I've spent a lifetime working on the visual system.
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I can tell you that the visual system
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when there are shadows,
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Today's episode is also brought to us by Athletic Greens.
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I've been using Athletic Greens since 2012,
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so I'm delighted that they're sponsoring the podcast.
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And now for my discussion with Dr. Craig Heller.
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Great to have you here.
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It's good to be here.
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It's been a long time coming.
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I know that I and many people have a lot of questions
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about the use of cold.
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So one of the things that's happened in recent years
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is that for many reasons,
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people have become interested in things
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like taking cold showers and taking ice baths
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for many different purposes.
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Sometimes this is introduced as just a general health tonic,
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but other times people get specific
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about how it can improve resilience
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or it can improve one's metabolism.
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Could you just tell me a little bit about what happens
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when I get into a cold shower or an ice bath?
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What are some of the basic responses
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at the level of metabolism?
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Obviously, psychologically, we don't know exactly.
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It'll vary from person to person,
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but what happens when I submerge myself into an ice bath
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if I've never done it before?
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Well, first of all, you get a tremendous shock.
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And what that's going to translate into
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is a bit of a shot of adrenaline.
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And I think this is really the so-called benefit,
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but I wouldn't call it a benefit of the cryochambers.
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You go into a cryochamber and it's a shock,
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so you get a shot of adrenaline.
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So sure, you're going to feel different when you come out.
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You've had a shot of adrenaline,
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but it doesn't necessarily translate into any benefit
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in terms of your physiology or performance and so forth.
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Now, if you take a cold bath or a cold shower,
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a couple of things are happening.
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One is you're going to stimulate vasoconstriction.
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So if anything, it's going to make it
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a little bit more difficult for your body
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to get rid of heat because you're shutting off
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your avenues of heat loss.
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If you're in a true cold bath,
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the overall surface area of your body is so great
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that it doesn't matter if you've vasoconstricted,
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you're still going to lose heat.
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Okay, so vasoconstriction, the constriction of,
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is it capillaries, vessels, and arteries all constrict
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or just one or two?
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Well, this is an area of controversy.
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In general, when people talk of vasoconstriction,
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they talk of the overall skin surface,
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and that is not true.
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The primary sites of heat loss,
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which we're going to get into,
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are the palms of your hands, the soles of your feet,
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and the upper part of your face.
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And the reason these are avenues for heat loss
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is they're underlain by special blood vessels.
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And these blood vessels are able to shunt the blood
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from the arteries, which are coming from the heart,
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directly to the veins, which are returning to the heart,
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and bypassing the capillaries,
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which are the nutritive vessels, but high resistance.
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So you can tell when you shake someone's hand
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what his or her thermal status is,
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the hand's hot or it's cold.
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And sometimes it's-
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Do you think that's part of the reason
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why humans evolved this practice of shaking hands,
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assessing each other's level of anxiety?
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We all know that a limp handshake
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is pretty indicative of something,
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and a firm handshake is indicative of something,
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as is the crushing handshake for that matter, right?
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Yeah, I really don't know
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what the evolutionary origin of handshaking is
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other than to get your hand away from your weapon, perhaps.
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Right, a couple of questions
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before we get into these specialized vascular compartments
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on the soles, the palms, and the upper face.
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You mentioned whole body immersion, like into an ice bath
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or very cold water up to the neck versus a cold shower.
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Is there something fundamentally different about those two
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besides the fact that they both provide
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this release of adrenaline?
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Is there anything that's really important to understand
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about the difference in the physiological response
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evoked by cold shower versus immersion in cold?
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Well, there are differences that are more physical
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than anything else.
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So if you are in a cold bath and you're still,
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you develop a boundary layer.
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If you're in a shower, you can't develop a boundary layer.
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Could you explain what a boundary layer is?
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Yes, it's best to explain it in terms of a hot bath
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because everybody's experienced that.
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You get into a hot bath and oh my God, it's really hot,
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almost painful, and then you sit down
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and eventually it doesn't feel so hot anymore
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because the still water, which is close to your skin,
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is coming into equilibrium with your skin.
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So it's like having a blanket on you or an insulator on you.
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And then if you move around, you disturb that still water
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layer, you feel the hot temperature again.
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So if I were to get into a cold ice bath
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or a very cold body of water of some kind and stay still,
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I'd likely feel warmer, at least until I start-
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You're not going to be losing as much heat.
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And then when I move it, I'll say-
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If you flail around, if you flail around,
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then you're going to lose more heat.
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But I think getting back to your original question
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about benefits, you have to keep in mind
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whether you're talking about aerobic activity
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or anaerobic activity, if you're referring to performance
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and exercise and so forth.
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So if you're doing aerobic activity that you can sustain
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for a long time, your production of heat is rising gradually
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and is being distributed throughout your body.
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So eventually your body temperature is going to come up
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to a level that's going to impair your performance.
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So the benefit of a cold bath or a cold shower
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before aerobic activity is that you increase the capacity
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of your body mass to absorb that excess heat.
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So could you say that in a rough sense that a protocol
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that one might use if they're going to head out
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for a long run, even on a reasonably warm day,
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not super hot, or maybe it is super hot,
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would be to take a cool shower before they go run?
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Would that be beneficial?
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Sure, it'll take them longer to get to the sweat point
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And what will that translate to
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in terms of a performance benefit?
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Well, could increase your speed,
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or it depends on how you use that benefit.
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Some people are pacers, they will go at the same pace
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and then they will go farther.
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Or some people are, I want to say, pacers and regulators.
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And no, no, pacers or forcers, they will take that advantage
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and use it up as fast as they can.
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So they will go faster, but not necessarily farther.
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As far as I know, not many athletes,
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at least not the ones that I know,
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are getting into cool bodies of water,
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taking cold showers before they head out to train.
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But it sounds like there could be
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a real performance benefit there.
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It could be a benefit.
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I know we're going to talk about our technology for cooling,
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but at one point, I don't know if they're using it now,
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but our cross-country team,
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when they would go to compete in a very hot place,
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they would do their warmup exercises, their stretching,
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then they would extract heat
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before the beginning of the race.
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So I like to think of it as you have greater scope
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for heat absorption.
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Interesting, about how long would one need
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to take one of these showers or cold immersions
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before heading out for a run?
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Roughly speaking, we don't have to get into details
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because everyone's performance level and regimen
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is going to be different,
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where they live is going to be different, et cetera.
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Right, it's not as long as you think, it's minutes.
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Yeah, because what's going to happen
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is as your core temperature goes down,
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you will eventually shut off your heat loss
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and that keeps it from going below normal.
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So if you've warmed up and your temperature has risen
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by half a degree, let's say,
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it doesn't take more than a few minutes
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to extract that heat if you're vasodilated.
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Interesting, and what about for the anaerobic athlete,
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the strength athlete?
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Right, for the anaerobic athlete,
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and let's say they're doing several sets
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and how many reps, whatever they're doing,
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their core temperature is not going to rise that fast
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because it's only certain muscles which are being used,
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but the temperature of those muscles will go up.
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So it's a local effect?
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It's a local effect, right.
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So let's say for sake of today, maybe for this discussion,
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if we assume that the basic workout,
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even though people do variation on this,
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is five sets of five or 10 sets of 10.
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So for those listening, it would be five sets
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of five repetitions or 10 sets of 10 repetitions,
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10 by 10, five by five, yeah.
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So if somebody, let's say,
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is doing a large body compound movement
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like barbell squats where there are a lot
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of large body movements, hip hinging and et cetera,
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but for instance, the biceps are not,
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they're involved, but more or less indirectly.
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So the effect is going to be to heat up the quadriceps,
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heat up the hamstrings, heat up the glutes,
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this kind of thing.
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And then during rest, that heat will leave the muscle,
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but it's not fast, and certainly the heat
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can't leave the muscle very fast while you're working out
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because when the muscle contracts,
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it squeezes the blood vessels, and the only way heat gets
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out of a muscle is in the blood,
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and your muscle metabolism can go up 50
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or 60 fold during anaerobic activity.
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That means the heat production
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in the muscle goes up 50 or 60 fold.
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The blood flow to that muscle cannot go up 50 or 60 fold.
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So you literally have the capacity to cook your muscles.
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So this is probably an appropriate time
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to mention briefly what the underlying mechanism of this is.
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Could you just, we will return to the specifics
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of what one can do to mitigate this heating up,
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but could you just explain the relationship
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between energy production ATP and pyruvate kinase
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and the role of heat there?
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We don't get something for nothing.
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So like a steam engine,
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most of the energy in our food is lost as heat.
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So we are roughly about 20% efficient.
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So of the energy that we take in in our food,
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about 20% of that can go into doing work,
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and the rest of it is lost as heat.
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Now, we're mammals.
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We use that heat to keep our body temperature
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considerably above the environment.
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But if you raise body temperature a few degrees higher,
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you're in trouble.
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That's hyperthermia.
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So individual muscles can reach hyperthermic limits
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before you might experience it in the whole body.
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So to keep you from damaging your muscle by hyperthermia,
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we have fail-safe mechanisms.
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And one of those fail-safe mechanisms is an enzyme
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which is critical for getting fuel,
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in other words, the results of metabolism of glucose,
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getting that fuel into the mitochondria,
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which is making our major coinage of energy exchange ATP.
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So that particular enzyme is temperature sensitive.
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So when the muscle temperature gets above 39 or 35,
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And that essentially shuts off the fuel supply
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to the mitochondria.
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That's when you cannot do one more rep.
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So failure, could we say that one component
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of muscular failure is overheating of the muscle locally?
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There are probably other things too.
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Well, yeah, if you lack oxygen,
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but our oxygen delivery is pretty good to the muscle.
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If you run out of glucose, yeah, that's going to impair you.
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But the most immediate impairment of muscle activity,
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muscle fatigue, in other words,
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is the rise in temperature of the muscle.
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I want to talk about how that muscle fails locally,
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but I have this burning question in my mind
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that I cannot seem to answer for myself.
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I'm hoping you can answer it for me.
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So let's say I'm doing five sets of five with squats.
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I hit muscular failure at a given weight.
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And according to what I now know,
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it's my quadriceps and the muscles associated
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with the squat that have failed
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because of this mechanism triggered by heat
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that shuts off the muscle.
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But my biceps are nice and cool, you're telling me.
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They're not doing too much work.
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It's only indirect work.
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So why is it that I can't set the bar down
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in the squat rack, walk over and do barbell curls
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with the same intensity that I could
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if I were to do those barbell curls fresh,
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not having done anything prior?
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Well, you will still have a fatigue curve
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with your upper body, okay?
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And that will be influenced by any rise in temperature
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that has been generated by your lower body exercise.
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So temperature in both cases is the limiting factor.
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It's one limiting factor.
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It's one limiting factor.
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I find that amazing.
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I find that amazing because I always thought naively
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that the reason muscles fail is because we, quote,
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"'Don't have the strength to do another repetition'
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or it's that you lack glycogen
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or some ability to access that glycogen."
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But of course we still have glycogen.
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It's naive for me to think that
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because if I wait three minutes and go back,
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I can do those repetitions again.
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So the glycogen wasn't restored in that three minutes.
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Obviously it was there.
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So I realized there might be other mechanisms involved.
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Sounds like heat is if not the dominant mechanism
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that prevents more work.
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It's one of them and it's a quick one, it's a fast one.
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So it can happen with,
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let's say you are a really experienced weightlifter, okay?
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You may be doing very, very high weights
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with sets of five or six.
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Yeah, to be clear for the audience,
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I'm not doing very high weights with sets of five.
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Not particularly strong, I'm not super weak,
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but I'm not particularly strong.
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But Craig's referring in the general sense to you.
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So why is it that if I finish a set of squats,
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I can't simply cool off my quadriceps
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by throwing a nice cool towel on my quadriceps?
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Why is that not the best way to go about it?
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Because your body surface is a very good insulator, okay?
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We think we don't have fur
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and therefore we're not insulated.
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But the skin, the fascia, the muscles underneath,
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underneath, they're all very good insulators.
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And that's why I said earlier
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that the way the heat gets out of the muscle
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So I want to step through a couple other portals
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by which one might think that heating and cooling
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would be ideal and then get back
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to these specialized surfaces on the hands,
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the feet, and the face.
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So if throwing a cold towel or even ice cold towel
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on my quadriceps isn't going to work
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or standing in front of the fan
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because I'm insulated from that cool,
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I can't cool off my blood fast enough.
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What about drinking 16 ounces of ice water?
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Sure, you can do that,
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but you can calculate how much heat that can absorb.
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And you can't continue drinking liters of ice water.
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You're going to dilute your blood and have other problems.
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But yes, it'll help.
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Sure, it will help.
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But it doesn't have the full capacity you will need.
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What about an ice pack to the back of my neck
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or to my head or squeezing the cold sponge over the head?
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I'm deliberately moving through these options
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because these are the ones that we see most often.
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We were actually just watching
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the Olympic track and field trials last night
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I'm a huge track and field fan.
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And there were a lot of sponges on the backs of necks
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before and between and after events.
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And how good is that or how poor is that as a strategy?
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Since now we know that being overheated
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locally and systemically throughout the body
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is a serious limiting factor on performance.
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Well, you have to understand something
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about our thermoregulatory system.
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We have a thermostat,
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just like you have a thermostat in your house.
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And that thermostat is in the brain, okay?
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Do we know the specific site?
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It's called the preoptic anterior hypothalamus.
link |
It does many things in terms of physiological regulation,
link |
but it serves as a thermostat.
link |
Now that thermostat has to have information.
link |
It has to have input.
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Where does that input come from?
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It comes from our overall body surface
link |
where we sense temperature, okay?
link |
So one of the things that can happen when you're overheated
link |
is that you can send in a cold stimulus to your thermostat.
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And that's sort of like wanting to cool your house
link |
by putting a wet washcloth over your thermostat.
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No, it's doing the wrong thing.
link |
So we've actually had experiences
link |
where we've had people exercising, getting overheated,
link |
and then cooling the body surface.
link |
And they say, it feels great.
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This is fantastic.
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And their core temperature's going up.
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Well, I think this is such an important point.
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First of all, I was weaned in a laboratory
link |
where there were always battles
link |
over the temperature in the lab.
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So people were always putting ice packs on thermostats
link |
or putting fans towards thermostats
link |
and trying to play this game.
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Good to know we were all being foolish,
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even though we were neurobiologists.
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Putting a cold towel over my torso
link |
or putting ice on the back of my upper back,
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you're saying could actually heat up my core.
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It'll at least decrease your heat loss,
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your rate of heat loss.
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You're going to raise the issue a little later, I know,
link |
and that is our natural portals for heat loss.
link |
So you can think of the natural portals for heat loss
link |
as our air conditioners, okay?
link |
The thermostats in the brain
link |
and the information to the thermostat
link |
is coming from the overall body surface.
link |
So what can happen if you, let's say,
link |
cool the torso with an ice vest,
link |
you can actually cause vasoconstriction of your portals,
link |
your heat loss portals.
link |
So that's what impairs the rate at which you're losing heat.
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Now back to the head.
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That's really interesting.
link |
The major blood flow to the brain
link |
comes up four arteries through the neck.
link |
There's the carotid arteries
link |
and there's the vertebral arteries.
link |
So when you put a cold towel around the neck,
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you're going to be putting a cold stimulus into the brain.
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Well, that's great for protecting the brain.
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You want to protect the brain,
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but it's also going to make you feel cooler than you are.
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So you will think you're ready to go again quickly
link |
when you've just essentially cooled the thermostat.
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This is an important point.
link |
And there's a lot of interest nowadays
link |
in people doing marathons
link |
and there are even some people do these ultras,
link |
ultra running, which I guess is everything longer
link |
than a marathon and last man standing,
link |
last man, last woman standing kind of thing.
link |
So you're saying that if somebody is hyperthermic,
link |
they could trick themselves into subjectively thinking
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that they are cooling off by putting a cold towel
link |
and that they can go further, but their brain could cook.
link |
Well, if they stop the cooling,
link |
then that hot blood from the body core
link |
is going to go to the brain.
link |
Well, it's a bit of a tangent,
link |
but many people report after long bouts of exercise
link |
or even just very intense bouts of exercise,
link |
feeling a kind of brain fog or mental fatigue.
link |
I assumed that that was due
link |
to lowered brain oxygenation post-exercise,
link |
but is it possible that there are some post-exercise effects
link |
on heating and cooling of the brain
link |
that might impact cognition
link |
or I should say negatively impact cognition?
link |
It's certainly possible because we know
link |
that a rise in temperature decreases cognitive capacity.
link |
I mean, you can experience that yourself.
link |
You can get on a treadmill and follow your temperature
link |
and then just do a simple activity
link |
like adding and subtracting.
link |
You get to about 39 degrees,
link |
so you can't do that anymore.
link |
You can't just calculate
link |
how long you've been on the treadmill.
link |
So the phrase cool, common, collected is-
link |
Cool, common, collected.
link |
That's the goal in all pursuits.
link |
So I want to talk about these portals
link |
because you've mentioned them a few times.
link |
Before I ask about what the portals are exactly
link |
and how they work and how they can be leveraged
link |
for performance, there's a question
link |
that my neurobiologist self can't resist but ask.
link |
We have this thermostat in the preoptic area
link |
of the hypothalamus, which is interesting to me.
link |
The medial preoptic area is also one
link |
that's known to be sexually dimorphic
link |
depending on testosterone exposure early in life, et cetera.
link |
Although people should just note
link |
that it's not actually testosterone
link |
that creates these sexual dimorphisms, these differences.
link |
It's actually testosterone converted into estrogen.
link |
It's actually estrogen is the effector,
link |
which is fascinating.
link |
Nonetheless, we've got this area that acts as a thermostat,
link |
and you said it's collecting information
link |
from the whole body.
link |
Does that mean that there are pathways
link |
as the neuroscientists like you and I refer to them
link |
as these afferent or input pathways
link |
from the body to the preoptic area?
link |
Is there a map of our body in the preoptic area?
link |
Because I have to imagine that you can't have
link |
the information just coming from the left shoulder,
link |
just from the right toe.
link |
It sounds like you need probably a pretty crude map,
link |
but that you need a complete map of the body surface there.
link |
Well, you don't need a complete map in the hypothalamus.
link |
I mean, that thermal afferent information that you mentioned,
link |
it also goes to the somatosensory cortex.
link |
So you know if an ice cube has touched you on the back,
link |
but that doesn't necessarily translate into a change
link |
in let's say you're shivering or sweating.
link |
So the information that's going to the hypothalamus
link |
is more integrated, representation of body temperature.
link |
So it's sort of an average of what's happening
link |
across the body. It's an average.
link |
So if I were to, let's say I get hot on a hot day
link |
and popsicles when we were in summer camp,
link |
I went to a sports camp near here actually,
link |
and we'd run around like crazy,
link |
and then we'd get into the shade if we could,
link |
but we were popsicles.
link |
Or the kids were putting ice cubes down each other's shirts
link |
or something, but that's an average
link |
because other parts of the body aren't exposed.
link |
The mouth is exposed to the ice in the popsicle case
link |
or the cold cubes or in the hands.
link |
As you said, it feels really good.
link |
It feels good, yeah.
link |
But it sounds like it feels deceptively good
link |
because in reality, it could still be quite warm internally.
link |
You can feel great and have a dangerously
link |
hyperthermic temperature.
link |
But I should say that when you get into the danger zone,
link |
things get bad fast.
link |
What are some of the symptoms
link |
that people could be on the lookout for, for hyperthermia?
link |
Essentially, it's almost ironic
link |
that if individuals are transitioning into heat stroke,
link |
they actually vasoconstrict and they stop sweating.
link |
And that's a pathological situation.
link |
I couldn't begin to explain it.
link |
But essentially, you are just feeling exhausted.
link |
You're feeling miserable.
link |
The heart rate is very high.
link |
Your heart rate goes up as your core temperature goes up,
link |
called cardiac drift.
link |
So you just feel rotten.
link |
But that's why, since it's not a danger signal
link |
that you can translate immediately into,
link |
nope, I'm going into heat stroke,
link |
that's why people can overcome their bad feeling
link |
with motivation to continue going, to work harder.
link |
So there have been a number of high profile athletic deaths
link |
due to heat stroke that were during practice,
link |
not in competition when people are really trying to do it,
link |
which shows they were just motivated to push.
link |
So let's talk about these magnificent portals
link |
that not just humans, but other animals,
link |
mammals are equipped with.
link |
So if putting cold on the neck or on the head
link |
or on the torso is not optimal, what is optimal?
link |
And maybe walk us through a theory
link |
as to why we would have these portals
link |
located where they are,
link |
and then we can talk about how one might leverage them
link |
Okay, where the portals are are in the glabrous skin,
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Glabrous just means no hair.
link |
So it's the hairless skin.
link |
You say, well, most of my body is without hair.
link |
No, most of your body has hair follicles.
link |
We've lost the fur, but we still have those,
link |
that hairy skin phenotype all over our body,
link |
except, except for those skin surfaces
link |
where our mammal relatives didn't have fur.
link |
So the pads of the feet.
link |
And for the primates, upper part of the face.
link |
For rabbits, no portions of the ears,
link |
the inner surface of the ears.
link |
No, I never thought about that.
link |
For bears, not the tongue.
link |
Bears have big tongues, huge tongues.
link |
I didn't know that either.
link |
I'm in that close to a bear yet.
link |
Yeah, I've had a licking match with a bear.
link |
So anyway, our mammalian relatives
link |
can't lose heat over their overall body surface.
link |
So probably very early on in mammalian evolution,
link |
they evolved these special blood vessels
link |
in the limited surface areas that don't have fur.
link |
And as I said, what these blood vessels are
link |
are shunts between the arteries and the veins.
link |
Arteries and veins are both low resistance vessels.
link |
So you can have high flow rate.
link |
Capillaries, which normally are between arteries and veins,
link |
are high resistance because they're very tiny, okay?
link |
Is it fair to say that what I was taught
link |
is that blood flows from arteries, then to capillaries,
link |
and then to veins, and then back to the heart.
link |
So it's sort of like from the heart through arteries,
link |
then through these little capillaries,
link |
which are like little estuaries and streams,
link |
and then to the veins, back to the heart.
link |
Is that generally true?
link |
So what I learned in basic physiology is still,
link |
I wouldn't get an F in your class.
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Maybe a D or a C, but not an F.
link |
So that's excellent.
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Okay, and so you're saying that in this glabrous,
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or beneath the glabrous skin.
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There are these shunts.
link |
And those go directly from arteries to veins.
link |
So you skip the capillaries.
link |
And is it actually, as long as I say that in the skin,
link |
you know, when I feel the pads in my hands,
link |
how deep to the surface do these vessels reside?
link |
They're below the, obviously, the epidermis.
link |
So if you are warm and you look at the palms of your hands,
link |
they are fairly red.
link |
The backs of your hands aren't.
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You don't have these vessels in the backs of your hands.
link |
Now, if you take a glass, like a water tumbler, right,
link |
and you grab it, you can see if you squeeze a little bit,
link |
the hand goes white.
link |
That's because you've shut off that blood flow.
link |
I'm going to do that little home experiment.
link |
So if you're bicycling on a hot day,
link |
you don't want to be grabbing your handlebars all the time.
link |
You want to periodically.
link |
Well, this is important.
link |
I know you're privy to some really amazing results
link |
that we're going to talk about,
link |
but I actually heard you say this during this lecture
link |
recently that Stanford held about human performance
link |
that we're both part of.
link |
And you mentioned this, that if you're cycling
link |
and you're working hard and you want to be able
link |
to do more work, we now know why you want to remain cool
link |
in order to continue to do work.
link |
And if you get too warm, that's bad.
link |
That gripping the handlebars too tightly
link |
will actually limit your performance.
link |
And that's probably also true on the Peloton
link |
or any other kind of device,
link |
or the skier or anything like that.
link |
So loosen the grip, or if you safely can,
link |
you want to actually expose your hands to the world.
link |
Now, what about for people wearing gloves?
link |
What about the, to me, that just seems crazy
link |
based on everything you're telling me?
link |
Well, gloves definitely impede heat loss from the hands,
link |
just as socks impede heat loss from the feet, okay?
link |
So if you want to maximize your heat loss,
link |
you want to have as thin a protectors
link |
as possible on your hands.
link |
And of course the feet are more problematical
link |
because you have to be using them in certain ways.
link |
Some people run barefoot.
link |
That's become somewhat popular.
link |
It seems like it kind of came and went.
link |
They had those toe shoes things,
link |
but they looked so ridiculous that I think most people
link |
just were willing to take the performance hindrance
link |
Actually, we had a track coach here at Stanford
link |
who for a while was famous for introducing training
link |
without shoes running.
link |
And he thought it was because it changed the posture
link |
And I think it was just due to the fact
link |
that he was increasing the capacity
link |
of his runners to lose heat.
link |
Yeah, so heating up at the level of the hands
link |
obviously is going to hinder performance.
link |
So if I can, how about with running?
link |
I noticed I ran across the country briefly in high school
link |
and not particularly well at that,
link |
but that we were told to run as if we were holding crackers
link |
in our fingers or something, like very lightly,
link |
and to keep hands kind of loose.
link |
So running like this would actually be more beneficial
link |
performance than, or gripping a phone,
link |
which is probably what most people are doing nowadays.
link |
And I once, I'll tell you an experience I had once.
link |
I was in Alaska in the winter
link |
and I went out running
link |
and I absentmindedly forgot gloves.
link |
And I realized this after a short period running
link |
because the backs of my hands were aching from the cold.
link |
The palms of my hands were sweating and were hot.
link |
So these compartments are a real thing.
link |
And you mentioned the upper half of the face.
link |
That's where our primate ancestors don't have fur.
link |
And the bottoms of our feet.
link |
So let's just take a moment and talk about
link |
some of the more amazing results
link |
that have been associated with proper cooling
link |
of these glabrous skin surfaces.
link |
Let me introduce one more thing.
link |
Because you asked earlier
link |
about the pouring of water on the head.
link |
One of the things which is not appreciated fully
link |
is that the blood which is perfusing
link |
these special blood vessels in the face above the beard line,
link |
that's the non-hairy skin.
link |
That blood then returns in the venous supply to the heart
link |
but it actually does it in a very strange way.
link |
It actually goes through what are called,
link |
I'm blocking on the name now.
link |
These are blood vessels that go through the skull, okay?
link |
And that's why the scalp bleeds a lot
link |
if you cut the scalp.
link |
And these blood vessels which are called,
link |
I want to say emergent but it's not emergent,
link |
it's a word that means leaving.
link |
And these blood vessels were primarily thought
link |
to be ways that blood is leaving the brain.
link |
But when you're overheated,
link |
the direction of flow in those blood vessels reverses.
link |
So the cooled blood that's coming from your facial region
link |
goes into that circulation
link |
and actually is a cooling source for the brain.
link |
So you can cool the brain,
link |
you can have a cooling effect on the brain
link |
by pouring water on your head.
link |
Interesting, so that practice which we,
link |
at least for me, I most commonly associate
link |
with combat sports where someone,
link |
the fighter goes to their corner,
link |
they usually sit down on a stool
link |
unless they're trying to do some mental warfare
link |
from the corner in which case they don't even take a seat.
link |
And their corner crew will squeeze a glove,
link |
excuse me, a sponge full of cold water over them.
link |
That you're saying is somewhat effective
link |
in cooling the brain.
link |
Yeah, it's one of the natural mechanisms
link |
for cooling the brain.
link |
I want to return to this at some point as well,
link |
but is there any known benefit to cooling the brain
link |
in terms of offsetting physical damage,
link |
offsetting the negative effects of concussion?
link |
Because one of the reasons why fighters
link |
will often get a cold on the back,
link |
cold item on the back of the neck or on the head
link |
is not just to cool them down,
link |
but the theory is that it might offset
link |
some of the damage of neurons.
link |
I just can't comment on that.
link |
I'm aware of those ideas, but they're controversial.
link |
One of the things that you want to do
link |
for injury to the brain is to decrease swelling.
link |
And one of the ways that you decrease swelling
link |
in many parts of the body is to cool.
link |
It decreases inflammation.
link |
It decreases the blood flow.
link |
So I think it's a really interesting topic
link |
and it's something that should be investigated.
link |
It's kind of hard to investigate.
link |
Yeah, interesting.
link |
Okay, so I hear these stories and I've seen the data,
link |
so I believe the stories.
link |
Maybe tell us a story about an observation
link |
that your group has made with respect to anaerobic exercise
link |
and proper cooling of these glabrous surfaces.
link |
And we can talk about the technology.
link |
Maybe give us the dips example first.
link |
Dips, of course, I think most people are familiar with dips.
link |
You're supposed to, I guess, get down.
link |
Raise and lower your body mass.
link |
Yeah, raise and lower your body mass,
link |
usually with your legs dangling down.
link |
Sometimes people are strong enough to attach a weight there
link |
and they'll do, it's essentially
link |
a compound upper body exercise.
link |
One dip would not be particularly impressive
link |
100 would be very impressive.
link |
20 would be impressive for some, et cetera.
link |
What happens when a skilled athlete comes in
link |
and does dips for multiple sets?
link |
And then what happens when they cool properly
link |
using the glabrous skin surfaces?
link |
This was a story that occurred early on
link |
in our investigations when we first made the discoveries
link |
that cooling has a benefit to increase your work volume,
link |
your capacity to do more reps, okay?
link |
So the word got over, I think, to the 49ers camp
link |
and one of their players, Greg Clark,
link |
who was a tight end at the time,
link |
he had been tight end at Stanford,
link |
and he decided, or I don't know if he was asked or what,
link |
to come over and check it out.
link |
So Greg came over and we said, Greg, what are you good at?
link |
What activity do you like to do?
link |
I can do a lot of dips.
link |
I can do 40 dips in a first set
link |
and I can probably do five sets.
link |
That's a usual workout for me.
link |
And we said, okay.
link |
So he came over to the gym one day
link |
and that's exactly what he did.
link |
He did 40 dips the first set and then maybe 25 and 15
link |
and down from there.
link |
Do you recall roughly what kind of rest periods
link |
he was taking between sets?
link |
Yeah, we standardized the rest period to three minutes
link |
because that's what we had set on for cooling
link |
That's a good long rest period.
link |
It's still a lot of dips.
link |
Yeah, it's actually a longer rest period
link |
than many people would prefer during workouts.
link |
They want to make the most of their time.
link |
Not me, I prefer to take as much rest as I possibly can.
link |
So several days later, he came back
link |
and his first set he did, I think maybe 42.
link |
A little bit better,
link |
but now people were standing around watching.
link |
So there was a little impetus there to show off.
link |
So then his second set was, I don't remember the numbers,
link |
but very much above the second set on the control day.
link |
This was after we cooled his-
link |
When is he doing the cooling?
link |
He's sitting down and putting his hands
link |
in the devices that we had built,
link |
which were cooling the palms of his hands.
link |
For how long does that cooling take?
link |
Can he do it inside of a three-minute rest period?
link |
Yeah, that's what we were doing.
link |
We standardized the interval
link |
for resting or cooling to three minutes.
link |
Okay, but the point is he got to his fifth set
link |
and all of the sets were above
link |
what he had done on the previous day.
link |
And he said, you know, I'm not tired.
link |
I can do another set.
link |
And then I can do another set.
link |
I can do another set.
link |
I can do another set.
link |
So from one day to two or three days later with cooling,
link |
he doubled the total work volume.
link |
He doubled the total number of dips.
link |
By adding more sets and more repetitions to each set.
link |
So then he kept coming back for four more weeks,
link |
And by the end of that month,
link |
he was doing 300 dips.
link |
Wow, so what percentage?
link |
He essentially tripled.
link |
And so here's a professional athlete
link |
at peak physical conditioning
link |
and he triples what he can do.
link |
And in terms of his ability to recover,
link |
was that explored or discussed at all?
link |
Because my understanding is that
link |
if we cause enough stress to a muscle
link |
during anaerobic training,
link |
we provide the stimulus for compensatory regrowth, et cetera.
link |
But if we do more work,
link |
we essentially scale up the amount of recovery that's needed
link |
or the recovery time.
link |
I'm very curious about whether or not
link |
he needed longer to recover
link |
between these super performing workouts.
link |
That's very interesting.
link |
That was a major discovery,
link |
which we didn't realize we were making at the time.
link |
There is this phenomenon you're referring to
link |
as delayed onset muscle soreness, DOMS.
link |
And this is due to those little micro tears
link |
and so forth that are happening
link |
as we extend our workout capacity, volume.
link |
So we've had this experience so many times
link |
that an athlete or anyone will come in to the lab
link |
and they will exceed what their previous goals were,
link |
their previous expectations.
link |
And I can always see the words coming out of their mouth.
link |
I'm going to be so sore tomorrow.
link |
And we've actually demonstrated that with a naive group.
link |
We had a class, a physical conditioning class,
link |
and we had half of them.
link |
The first days of the class,
link |
we had to establish their true capacity,
link |
what they could do.
link |
So these were pretty heavy workouts for these new recruits.
link |
And we gave half of them the benefit of cooling
link |
and the other half not.
link |
And then we had them record their subjective levels
link |
of delayed onset muscle soreness.
link |
And those that were cooled
link |
didn't have significant muscle soreness.
link |
And I know there are also published results
link |
and we will provide links to some of these papers
link |
for people seeing similar effects,
link |
I should say similar performance enhancing effects
link |
using bench presses, bench press or pushups
link |
or other sorts of things.
link |
Maybe you could give us an example
link |
from the realm of endurance work or aerobic work,
link |
running, cycling, things of that sort.
link |
Well, one of the problems for us
link |
is that our equipment now is not really portable.
link |
I mean, it's portable in the sense
link |
you can carry it to the gym or to the football field.
link |
But you're not going to run with it.
link |
But you're not going to run with it, right.
link |
Or equip a bicycle with it.
link |
Although when are the cooling handles on bicycles coming?
link |
Yeah, that would be good.
link |
But one itinerant activity is golfing
link |
and people have put it on their golf carts
link |
Do people really heat up that much in golf?
link |
Not to be disparaging of the golfers,
link |
but the way I conceptualize golf,
link |
it's like a swing and then a walk
link |
and then a cart ride and then a meal.
link |
I probably just offended all the golfers out there.
link |
Well, one time we were doing work
link |
for the Department of Defense
link |
and they wanted to check it out
link |
whether or not what we were doing was really worthwhile.
link |
So they sent out a team of special ops soldiers
link |
to be our subjects and test it out.
link |
They were here for a week.
link |
So that was a fun week.
link |
Yeah, I do some work with those guys.
link |
They're hard driving guys.
link |
They also know how to have fun.
link |
But yeah, they definitely have,
link |
if they have an off or a quit switch,
link |
it's buried deep within their nervous system.
link |
They don't like to hit that quit switch.
link |
So the guy who wrote the final report,
link |
he gave an addendum to the report and he said,
link |
well, I'll tell you this, after I've gotten home,
link |
it's added that technology.
link |
They took the technology with them.
link |
They wanted to keep it.
link |
Oh yeah, that sounds about right.
link |
I said, and using it,
link |
it has added 20 yards to every club in my bag
link |
and that's no effing small deal.
link |
So it's allowing people to hit further,
link |
hit the golf ball further.
link |
All right, so for the golf players out there,
link |
then that's the reward you get back from Craig
link |
for all my little knocks on golf.
link |
I actually, I don't have any knock on golf.
link |
I just don't think about it as a sport
link |
where heating up is a limiting factor.
link |
So since they're getting more out of their drive,
link |
what do you think is going on there?
link |
Well, they can be heating up.
link |
And they're wearing gloves, right?
link |
They're wearing gloves on a hot day and so forth.
link |
But let me just tell you one more serious story
link |
about golfers and that is individuals with multiple sclerosis
link |
are exceedingly temperature sensitive.
link |
I didn't know that.
link |
So they may still be mobile,
link |
but they have to stay in cool locations
link |
and not increase their exercise to any great extent.
link |
But we've had subjects that have with multiple sclerosis
link |
who have just essentially put the device on their golf cart
link |
and they're back out playing golf
link |
in the middle of the summer.
link |
Anything that allows people to have normal levels
link |
of livelihood and recreation is great.
link |
We always think about performance
link |
at these kind of like peak and elite levels
link |
and pushing harder.
link |
But yeah, anything that allows people
link |
to be mobile and functional is great.
link |
So what's your favorite example of endurance?
link |
And feel free to give us the extreme one
link |
and then we'll talk about averages to be,
link |
make sure we're thorough about averages versus exceptions.
link |
We haven't done a lot in the field.
link |
Most of our endurance has been in a hot room
link |
with treadmill work and so forth.
link |
So the very first experiment we had,
link |
I think maybe 18 subjects just off the street.
link |
I mean, we just recruited people in the hallways,
link |
come on in and do this.
link |
And what we found is we could,
link |
for this group with one trial with and without cooling,
link |
we could double their endurance,
link |
walking on the treadmill,
link |
walking uphill on the treadmill in the heat,
link |
like maybe 40 degrees ambient temperature,
link |
40 degrees centigrade.
link |
So what does that experiment look like?
link |
You're having people walk on an incline, it's really warm.
link |
Some people are just going to hit the quit button
link |
and say, I've had enough and get off the treadmill.
link |
With proper cooling.
link |
When are they doing the cooling?
link |
They're doing it continuously.
link |
Because in the laboratory,
link |
we can suspend devices from the ceiling, for example.
link |
Now we do have prototype wearable devices.
link |
We did them in response to emails from Ebola workers
link |
a number of years ago in Sierra Leone.
link |
They said, we've read about your work with athletes.
link |
Can't you do something for us?
link |
I mean, we're in the personal protective gear
link |
and we can't be in the hot zone
link |
for more than 15 or 20 minutes.
link |
So that was started us on the challenge
link |
of developing wearable systems that could go under the PPE.
link |
We've published that work now.
link |
And I'm guessing the military special operators
link |
that are out in the desert and other locations
link |
are probably excited about this technology.
link |
Well, once they get it.
link |
It's coming, it's coming.
link |
Yeah, I think some people might wonder
link |
if there are all these studies
link |
and there are these incredible results over the years,
link |
why haven't we heard more about it?
link |
And I will ask your opinion on that as well,
link |
but I'll just editorialize a little bit.
link |
Is that the best laboratory work
link |
and its practical applications
link |
oftentimes requires many studies.
link |
And oftentimes there isn't a portal, so to speak,
link |
to get that information out into the technology sector.
link |
So there is a company that's developing this technology
link |
for people to use, to purchase and use.
link |
We might as well just tell us now,
link |
what is the name of that company?
link |
And do they have a website?
link |
People are going to want to know
link |
where can they get this magical technology?
link |
And is there a poor man's version of it as well?
link |
Well, the company is Arturia, A-R-T-E-R-I-A.
link |
And the website is www.coolmit.com.
link |
So coolmit is just C-O-O-L-M-I-T-T, coolmit.com.
link |
It's a great website.
link |
When I went there, it says that right now
link |
the technology is only available
link |
to professional sports teams and military.
link |
Well, where we stand now is the new version
link |
of the technology is sort of in beta test versions.
link |
We got it into the hands of people
link |
who had used the technology before.
link |
So there's NFL teams that are using,
link |
there's college teams, there's Olympics,
link |
there's the Navy Seals, Major League Baseball,
link |
the NBA, the National Tennis Association.
link |
They have locations where now they are trying this out
link |
and reporting back, how's it working?
link |
How could you change it?
link |
How could you improve it?
link |
So that's where we are.
link |
But on the website, you can actually sign up
link |
for being one who will be able to get one
link |
when they are finally manufactured.
link |
They're now being made in fairly small lots
link |
because you want to change things
link |
as you realize how it can be improved.
link |
Yeah, this is Stanford after all.
link |
You want to get the technology right.
link |
I like to joke that one of the reasons
link |
I like being at Stanford so much is that
link |
not only are my colleagues amazing
link |
and they're so forward thinking,
link |
but they're all perfectionists.
link |
And so the perfectionist mindset has to be perfect
link |
before it can go live, so to speak.
link |
Well, I think there will be a lot of interest.
link |
Let's talk about the technology
link |
in a little more detail for a moment.
link |
And then let's talk about whether or not
link |
cruder forms of that technology exist,
link |
either for sake of safety and or performance.
link |
So what is, the cool mitt, as I understand,
link |
is it's a mitt, it's a glove.
link |
You put your hand into, you hold on to a surface
link |
and that surface cools your hand
link |
and thereby through this specialized portal,
link |
cools your core body temperature
link |
and all the muscles of the body.
link |
Subjectively, if I were to do this right now,
link |
would I think that it was ice cold
link |
or would I think it was just cool?
link |
Ice cold is too cold.
link |
So people always ask,
link |
well, why can't you just stick your hand
link |
in a bucket of ice water?
link |
What that does is that causes reflex
link |
vasoconstriction of the very portals
link |
that you're trying to maximize the heat loss from.
link |
So you stick your hand in cold water
link |
and when it comes out, it's cold.
link |
You just sealed up all the heat in your body.
link |
So what I sort of recommended to someone at one point,
link |
they said, well, when I'm running,
link |
can I just carry a frozen juice can
link |
and it will gradually melt?
link |
And I said, well, no, because that's going to decrease
link |
the heat loss from that hand.
link |
But if every couple of minutes you switched hands,
link |
Well, I have a feeling that there are people now doing that
link |
as well as trying this.
link |
So how long in the cool mitt at the proper temperature,
link |
how long are people putting their hands into the mitt?
link |
We, once again, had just standardized on three minutes.
link |
And part of the reason for that is that the rate of heat
link |
loss is an exponentially declining curve, okay?
link |
And three minutes sort of gets the best part of the curve.
link |
So you can go longer and get more benefit,
link |
but the biggest bang for the buck
link |
is in the first two, three minutes.
link |
You mentioned a number of impressive organizations,
link |
sports teams, and military that are using this.
link |
This is not something that I typically see
link |
on the sidelines of games, although to be honest,
link |
I haven't looked very carefully.
link |
I'm guessing that they are probably keeping the technology
link |
somewhat under wraps.
link |
Where and how are they doing this?
link |
Are they running back to the locker room?
link |
I mean, the military special operators
link |
are doing their thing, but in terms of the athletes,
link |
is it possible, hypothetically,
link |
the athletes are doing this somewhat incognito?
link |
It's possible, but I really don't know.
link |
People have mentioned here at Stanford,
link |
they don't see the football team using it.
link |
Well, the football team here at Stanford
link |
is mostly playing in cold weather, cool weather.
link |
The night games are cool.
link |
Even date games are not very hot frequently here,
link |
but when they go to a hot place like Arizona or Utah,
link |
at least our coach, Shaw, says that they take it with them,
link |
and that's when they find the benefit.
link |
That's when they use it.
link |
So is there a poor man or woman's version of this?
link |
You mentioned the juice can passing back and forth.
link |
You mentioned cooling the hands.
link |
A number of people said to me
link |
after learning a little bit about this science
link |
and technology that they've experienced some big effects,
link |
positive effects of cooling by,
link |
and I confess I've done this,
link |
taking a package of frozen blueberries
link |
and just kind of passing it back and forth between my hands.
link |
Now, talking to you,
link |
I realize I probably didn't do it long enough.
link |
I probably was, I was only doing maybe 30 seconds,
link |
passing it back and forth between my hands
link |
and then going back into sets.
link |
I did see a performance enhancing effect, absolutely,
link |
but I realized I probably wasn't optimizing the protocol.
link |
If you were going to give a crude protocol for,
link |
let's just say for the gym,
link |
because with running, it's a little bit tricky,
link |
but what would that look like
link |
if people wanted to just play with this
link |
in some sort of fashion?
link |
Well, it would be experimental.
link |
Sure, yeah, none of that is very controlled.
link |
Your idea of frozen peas is a good idea.
link |
And I think since there's been no actual study of that,
link |
you would have to be you working out
link |
what is the best for you.
link |
But one way to figure it out is that
link |
if after you hold the cold peas in one hand
link |
and you switch it to the other hand,
link |
if someone then comes and feels your hand,
link |
is it warm or cold?
link |
If it's cold, it means you've as a constricted.
link |
If it's warm, it means the hot blood is still going there.
link |
Okay, so we do that in the lab.
link |
And the key is for it to not vasoconstrict.
link |
Okay, so there's a test out there, folks.
link |
If you're going to try this in kind of crude fashion,
link |
at least until the cool mitt is available more broadly
link |
to the general public,
link |
you could assess, you want to assess
link |
whether or not your palms actually feel cool
link |
to the touch by somebody else.
link |
that means you've essentially shut down the port
link |
or you're sealing in more heat, which is bad.
link |
What about putting this cold pack of some sort on the face?
link |
I work out at home.
link |
I don't often work out barefooted,
link |
but I suppose I could, like they did in the 70s,
link |
you know, when those guys were walking around
link |
without shoes and squatting without any shoes or socks on.
link |
Could I put my feet on them?
link |
If you had simply had a water-perfused pad
link |
and you were circulating cool water through it,
link |
you could just put your feet on it.
link |
Part of the problem is that you don't want,
link |
if, let's say you have just a cold pack of something.
link |
The problem is back to boundary layers again.
link |
If you don't have a convective stream of the cooling medium,
link |
the heat sink is not as effective
link |
because there'll be a boundary layer developed
link |
between the heat sink material and your skin.
link |
So that decreases its efficacy.
link |
Maybe we should just for a moment talk about convection,
link |
radiation and convection, and just make that clear.
link |
Like if I put my hands, let's say it's a cold night
link |
and I'm at a campfire and I take my hands
link |
and I put them out to the fire.
link |
You're getting radiation.
link |
You're getting radiation.
link |
And then if it's a windy, warm night,
link |
no, I don't know if that's the best example.
link |
Give us a good example of convection.
link |
Convection sure is in a cool breeze.
link |
You know, the wind chill factor, that's due to convection.
link |
But in terms of heat transfer between two objects,
link |
if you have convection of the medium,
link |
whether it's blood on the inside and water on the outside,
link |
you increase the heat exchange if you have convection
link |
Right, so this is why just planting my feet
link |
on two packages of, my bare feet on two packages
link |
of frozen peas, there's really no opportunity
link |
for circulation and therefore heat transfer.
link |
So it's not really optimal, which is, and I-
link |
But once again, it depends on the surface area
link |
to get any benefit at all.
link |
We have a study that we published,
link |
which was investigating the standard treatment
link |
for hyperthermia in the field.
link |
And the standard treatment that's recommended
link |
by medical organizations is you take cold packs
link |
and you put them in the axilla, the groin.
link |
The axilla or the armpits?
link |
The armpits, yeah, the groin, which is-
link |
Thin skin, lots of vasculature.
link |
Right, and the neck.
link |
So what we did is we did studies in which we made people
link |
hyperthermic, and then we measured the rate
link |
at which we could cool them by putting those positions
link |
in those heat exchange bags in the recommended location
link |
versus on the glabrous skin, versus palms, soles, and face.
link |
The cooling rate was double.
link |
So we put the same ice packs, the same cold packs
link |
on the heat portals rather than the axilla,
link |
the groin, and the face.
link |
So face, hands, and bottoms of feet
link |
will cool you twice as fast
link |
as putting cold packs into your armpits,
link |
your groin, or back of neck.
link |
So I like to give the analogy of if your car is overheating,
link |
okay, and you have a hose, a garden hose,
link |
where should you spray your cooling system?
link |
Should you spray the radiator or should you spray the tubes
link |
going in and out of the radiator?
link |
Well, the rationale with putting these cold packs
link |
in the axilla, the groin, and the neck
link |
is that you're getting close to the major arteries.
link |
Sure, that's going to be effective,
link |
but it's much more effective if you actually increase
link |
the heat loss capacity of the radiating surface,
link |
So you cool the hot stuff heading toward the core.
link |
That's essentially what the standard operating procedure is,
link |
that you hit the arteries.
link |
And the veins, the arteries and veins.
link |
I'm going to just tell a brief story
link |
that illustrates how almost everybody gets this stuff wrong,
link |
and then I'm going to use that as an opportunity
link |
to ask you about heating, deliberate heating,
link |
as opposed to deliberate cooling.
link |
So about four months ago, a friend of mine, incidentally,
link |
a guy who did nine years in the SEAL teams,
link |
really skilled cold water swimmer.
link |
We went out for a swim in the morning.
link |
I'm not nearly even close to being in the same universe
link |
of his output potential.
link |
We do these swims, I'm familiar with them.
link |
I got enough blubber on me that I stay warm enough
link |
in the cold Pacific, no wetsuits.
link |
We do the morning cold swim for about a mile or so.
link |
And we brought with us a young kid that I know real well
link |
that hangs out with us sometimes and trains with us,
link |
who's got very little body fat.
link |
He's just exceptionally lean,
link |
despite eating everything inside, right?
link |
Teenager, great athlete, great kid, great swimmer.
link |
So we're out there swimming,
link |
and at some point we're talking to him
link |
and it's clear that he's gone hypothermic.
link |
He's slurring his words, he's not doing well.
link |
So we get him onto the beach, his teeth are turning yellow,
link |
he's quaking, he's not, he's got, you know,
link |
his saliva is taking on that consistency that's clear,
link |
like he's hypothermic.
link |
We go to the lifeguard station.
link |
Lifeguard says, okay, let's get his vitals,
link |
let's do all this.
link |
Meanwhile, trying stand next to him, you know,
link |
and heat him up by heating up his torso.
link |
So there we are, like pressing against this guy, our friend,
link |
trying to heat him up.
link |
They get a blanket on him.
link |
He's, I'm realizing he was barefoot.
link |
His face was exposed,
link |
although we did cover his head with the blanket.
link |
And he eventually came back.
link |
We got some warm liquids into him and he was okay.
link |
I don't know that his mother is ever going to let him swim
link |
If I ever disappear and go missing,
link |
it's because of that incident.
link |
Anyway, he did great.
link |
He's back in the water and doing well.
link |
But I realized that pretty much everything from the point
link |
where we got back on the beach until he was back to normal
link |
was we did incorrectly.
link |
We heated his torso.
link |
We left his extremities exposed.
link |
And we assumed we were doing the right thing.
link |
And the lifeguard is a skilled lifeguard
link |
at a major public beach.
link |
So I guess the simple question is,
link |
did we get everything wrong?
link |
Did we get anything right?
link |
And what would have been the better option
link |
to heat up a hypothermic person in that
link |
or a similar situation?
link |
Well, it's interesting you asked that
link |
because that is the way we got into this area
link |
I worked on how the hypothalamus regulates body temperature
link |
And one day we were having a discussion with a colleague
link |
in the department of anesthesia.
link |
And he jokingly said to my colleague, he said,
link |
yeah, you guys think you know so much about temperature.
link |
I bet you couldn't solve a problem we have
link |
in the recovery room.
link |
Well, the patients come out of surgery,
link |
they're hypothermic and it takes us hours
link |
to get them to stop shivering.
link |
What do they do in the recovery room?
link |
Exactly what you suggested.
link |
They put in warm blankets.
link |
They put in heat lamps.
link |
And it takes them an hour or two hours
link |
to get these patients to stop shivering
link |
to bring them back up.
link |
So we say, ah, it's a trivial problem.
link |
No, it's a hard problem.
link |
It's a hard problem because when you're under anesthesia,
link |
you're vasodilated.
link |
When you come out of anesthesia,
link |
you're hypothermic and you vasoconstrict.
link |
That makes it very difficult to get heat into the body.
link |
So we got the idea that, well,
link |
if we could just take one appendage, like an arm,
link |
and we put it in a environment wrapped in a heating pad
link |
and a negative pressure, you know, suction,
link |
that would pull more blood into that limb.
link |
That blood would get heated
link |
and it would warm the body up faster.
link |
So my colleague built a prototype device.
link |
You couldn't get such a device into the hospital these days.
link |
But we were with our anesthesiologist friend.
link |
We took it into the recovery room
link |
and the first thing the patient said, no way.
link |
You're not gonna put that on my patient.
link |
But he prevailed and first patient didn't shiver at all.
link |
First patient was back to normal temperature,
link |
core temperature in, I think it was eight minutes,
link |
eight or nine minutes.
link |
Is this now standard practice in hospitals?
link |
So this is another example where I don't get upset
link |
about the, although it's upsetting to know that it's not,
link |
but I think that it's yet another case
link |
where a fundamental problem exists.
link |
There's a science-based solution
link |
that makes sense at the level of physiology,
link |
engineering and practice, and yet it's not being done.
link |
And I mean, that's a whole other discussion
link |
as to what the limitations are.
link |
Well, perhaps in, I know a number of our listeners
link |
are in the healthcare and medical profession
link |
as well as military athletes,
link |
and just also standard other types of jobs,
link |
civilians doing other types of work.
link |
It would be wonderful if people understood this.
link |
So once again, is there a homegrown technology
link |
that people could use?
link |
If somebody is hypothermic, what is going to be the best way
link |
for them to warm up?
link |
Is it going to be holding a nice warm mug of cocoa
link |
or something like that?
link |
But not too hot, I guess, is again the idea.
link |
Yeah, well, actually you can go hotter on the glabrous skin.
link |
Oh, because it'll dilate.
link |
Because it takes the heat away faster, okay?
link |
But back to the anesthesia,
link |
what you can do is you can use warm pads.
link |
They have them in all hospitals.
link |
They have circulating water perfused pads.
link |
Hot water bottle type stuff.
link |
Put them on the feet.
link |
So typically they'll slide them under your lower back
link |
or something like that?
link |
Yeah, put them on the feet.
link |
Okay, sure, that will do it.
link |
But it turns out that we discovered through this work
link |
that it had nothing to do with the whole arm.
link |
It was only the hand.
link |
And that's when we came to the realization
link |
of these special blood vessels.
link |
We didn't discover the blood vessels.
link |
They're described in Grey's Anatomy,
link |
but nobody knew what they were for.
link |
And you mentioned bears earlier and other hairy animals.
link |
Do they have these AVAs as well?
link |
And I suppose we haven't defined AVAs.
link |
We've been pretty good about the no acronyms rule.
link |
AVAs is arteriovenous anastomosis.
link |
So a connection between the arteries and the veins, yeah.
link |
I actually use this technology.
link |
I have a bulldog, bulldog mastiff.
link |
He has a very high propensity for overheating
link |
because they're terrible at dumping heat
link |
and bulldogs are great at pushing themselves
link |
to the point of exhaustion or death.
link |
And so now we do what we call palmer cooling.
link |
Sorry, I couldn't help myself.
link |
Where I'll take Costello and lower him
link |
into a cool body of water,
link |
just the bottoms of his paws.
link |
Although I think animals instinctually know to do this
link |
and will go and stand in bodies of water.
link |
They don't often lie down all the way.
link |
But they seem to know that's a great way
link |
to cool themselves off.
link |
Oh, absolutely. Yeah.
link |
And they get the advantage that their palms
link |
and their feet are essentially the same thing.
link |
So we actually built devices for dogs.
link |
And tried them on.
link |
I did a rod sled dogs and it worked beautifully.
link |
They had little backpacks with the equipment
link |
and pads on all their feet and it worked beautifully.
link |
Along the lines of heating, deliberate heating,
link |
wearing a knit cap is something that,
link |
you see more of that on the East Coast.
link |
People run around Boston and New England with a knit cap.
link |
I've always done that at the start of my runs
link |
to try and warm up more quickly.
link |
And then I take it off, I shed layers as I go.
link |
Is that a rational practice the way I just described it?
link |
Because warming up is important too.
link |
There's a certain amount of quote unquote warming up
link |
that's required to lubricate joints
link |
or at least to get the sense that joints are lubricated
link |
and to be able to move more easily.
link |
Do you still recommend that people warm up?
link |
Yeah, but I think we're misled by the term warm up
link |
as if the major purpose is to raise temperature.
link |
I'm not aware of any data on this,
link |
but I do think that the major contribution
link |
is increasing flexibility.
link |
So you're going to avoid having damage
link |
of joints and tendons and ligaments and so forth.
link |
But also the ability of the mitochondria
link |
to produce energy can be impaired at lower temperatures.
link |
And you have to keep in mind
link |
that we say our body temperature is 37 degrees,
link |
but that's not true.
link |
Yeah, it varies across the day.
link |
Well, it varies in parts of your body.
link |
I mean, my hands and arms are not at 37 degrees right now.
link |
They're much lower.
link |
So that raises an interesting question.
link |
What is the best way to measure core body temperature?
link |
Well, the best core temperature
link |
is that what we use is esophageal.
link |
So we put a thermocouple up the nose
link |
about two feet down the esophagus
link |
so that it's about the level of your heart.
link |
Not gym or home practical, although I don't know.
link |
Some of those COVID swab tests go pretty far.
link |
I can't even imagine it going any further.
link |
I felt like my brain was getting tickled.
link |
And it was really unpleasant.
link |
Timpaniq is a pretty good-
link |
It's not foolproof because you have to actually
link |
have it aimed properly at the tympanum.
link |
And frequently what you're getting
link |
is you're getting sort of a mixture
link |
of tympanic plus ear canal temperature.
link |
And for those listening and for those watching,
link |
the tympanic is not going to be the pinna
link |
that this part of the ear, the outer part of the ear,
link |
the tympanic is going to be near the tympanic.
link |
All headed towards the tympanic membrane.
link |
And yes, I'm sticking my finger in my ear
link |
because that's where the laser would actually have to go
link |
to measure your temperature.
link |
So when we're walking into restaurants
link |
and other places nowadays,
link |
and they're shining the laser at our forehead,
link |
that's probably giving a pretty crude readout of temperature.
link |
It is, but there's much less insulation
link |
between your brain and your forehead skin
link |
than there is between your biceps and your arm skin.
link |
So if you're going to measure a surface temperature,
link |
that's where you would do it.
link |
And we do temperatures in the infrared.
link |
We take infrared videos of athletes and our subjects.
link |
And of course, the face lights up.
link |
Okay, so if we're not,
link |
I imagine there's going to be a technology coming soon
link |
where you can point your smartwatch
link |
or your smartphone at yourself
link |
and you're going to get a heat map.
link |
That's got to, if somebody out there
link |
hasn't already invented this
link |
for the typical folks outside military,
link |
somebody please invent that
link |
because I think there's growing interest in temperature
link |
based on the work that you're doing.
link |
And also for sake of something I do want to touch on,
link |
which is sleep and metabolism,
link |
although we don't want to open up those portals all the way
link |
because we'd need several days to cover it.
link |
Okay, so putting on the cap,
link |
what about some of the helmets and gloves
link |
that are used in typical sports?
link |
Do you think that those can be improved
link |
in order to improve performance
link |
in terms of their ventilation ability
link |
or keeping Palmer surfaces open, for instance?
link |
Well, you mentioned about the knit cap
link |
in cold weather especially,
link |
and that is significant
link |
because you do lose a lot of heat from your head,
link |
but it's a constant heat loss.
link |
It's not variable like your glibrous skin.
link |
So if you decrease that heat loss,
link |
you're going to be warmer.
link |
So sure, that has an impact.
link |
Now, in terms of helmets, they should be ventilated.
link |
I mean, they should have enough space in them
link |
and holes in them so that air can circulate.
link |
You don't want to thermally insulate your scalp.
link |
That's going to decrease heat loss quite considerably.
link |
You know, just for a resting individual,
link |
the brain is about 20% of your metabolism.
link |
So that's a lot of heat production.
link |
I realized there was a question that I failed to ask earlier
link |
that is burning in my mind now,
link |
and I think is likely burning in the minds
link |
of some of the listeners, which is,
link |
so if you do this cooling in between sets in the gym,
link |
you get this performance-enhancing effect.
link |
You don't get the delayed onset muscle soreness,
link |
So presumably, the body is adapting.
link |
You're getting better as a consequence
link |
of being able to do more work per unit time
link |
or to go harder in some way, of course.
link |
You get that adaptation.
link |
Does that mean that you see a performance-enhancing effect
link |
even when you don't cool
link |
if you've previously done the cooling workouts?
link |
So for instance, let's say I can do 10 sets of 10 dips,
link |
which I like to think I can.
link |
Maybe I need to go try.
link |
I don't know if I've done that recently.
link |
I cool for three minutes between sets.
link |
And let's say I get to the point
link |
where I can do 20 for 10 sets,
link |
10 sets of 20 repetitions, and then I don't cool.
link |
Will I be able to match or approximate
link |
my new, better performance?
link |
You keep your gains.
link |
It's a true conditioning effect.
link |
You respond to the increased work volume
link |
by all of those mechanisms you mentioned.
link |
You increase the number of contractile elements
link |
The muscles get bigger.
link |
We had an experiment that involved
link |
some of our female students, not athletes,
link |
but just regular, they were freshmen actually.
link |
And the experiment was 10 sets of pushups
link |
to muscle failure with or without cooling.
link |
Same regimen, three minutes of cooling
link |
in between sets of pushups?
link |
Some of those young ladies reached over 800 pushups.
link |
Now, the total duration of the workout
link |
could be getting much longer as a consequence
link |
of doing more work.
link |
No, it doesn't take you longer.
link |
I mean, a pushup is pretty fast.
link |
Yeah, it's pretty fast.
link |
So you do 10 sets, the maximum 45 minutes total.
link |
That's a lot of pushups.
link |
That's a lot of pushups.
link |
So the interesting thing is they came in one day
link |
and they said, Dr. Heller, you cost us a lot of money.
link |
Well, we had a formal dance this weekend.
link |
We all had to buy new sleeveless dresses.
link |
It's a good problem to have.
link |
Good problem to have.
link |
Let's talk about steroids, anabolic steroids.
link |
We're heading into an Olympics.
link |
Every time the Olympics rolls around,
link |
you hear about these cases of people getting popped,
link |
as they call it, or caught for anabolic steroids.
link |
There are some accusations out there now.
link |
This will get handled in the press
link |
and in the various organizations.
link |
Clearly athletes and non-athletes use anabolic steroids.
link |
And typically anabolic steroids
link |
are of the testosterone variety.
link |
There are derivatives, et cetera.
link |
And those derivatives do different things
link |
in anabolic versus androgenic, et cetera.
link |
But typically the idea is, at least as I understand it,
link |
in talking to some of these individuals,
link |
is that they allow people to train more
link |
because they recover faster.
link |
They are able to synthesize more protein
link |
because they're basically getting a second puberty.
link |
Because as we all know, during puberty,
link |
there's a lot of growth of the body.
link |
And of course there are a lot of negative effects
link |
of abuse of these things.
link |
And they are banned from various sports organizations.
link |
Especially, I should mention, in combat sports,
link |
it's especially concerning because in combat sports,
link |
a performance enhancement means that you can harm somebody
link |
more than you would be able to otherwise,
link |
as opposed to in other sorts of sports,
link |
just to conceptualize it.
link |
And I'm not taking a moral stance on any of this.
link |
I just want to ask you,
link |
when you compare Palmer cooling to anabolic steroids
link |
in terms of gym performance, what do you see?
link |
Well, we do not do research on steroids,
link |
but there is a lot of research in the literature.
link |
A lot of that research in the strength conditioning
link |
magazines is not very scientific.
link |
Or it might not even be scientific at all.
link |
But we did do an analysis of reputable papers.
link |
And we did find, I think it was probably eight or nine,
link |
10 studies on bench press, increase in bench press
link |
performance on steroids or not.
link |
These were males or females?
link |
Well, these were all males,
link |
but I'll get back to the females.
link |
The bottom line is that in all of these independent studies,
link |
their rate of improvement was approximately 1% per week.
link |
And I just told you about studies
link |
in which we've had 300% increase in a month.
link |
It's an enormous, enormous difference.
link |
So why would you endanger your health
link |
as well as your legal ability to compete
link |
with such an ineffective tool?
link |
No, I think the notion of performance enhancement
link |
is a really interesting one,
link |
because people clearly pay attention to nutrition.
link |
Sleep is now something that I think everybody,
link |
but especially athletes are paying attention to.
link |
And I predict that temperature will be one
link |
of the more powerful parameters
link |
that people are going to be focusing on.
link |
Because of the magnitude of the effects
link |
that you're describing.
link |
And also because so much of the variability
link |
around performance, as you mentioned,
link |
has to do with when you go to a new environment.
link |
Everyone has their home environment worked out pretty well.
link |
Sleep well in your own bed at home.
link |
When you can control everything,
link |
your performance is always great.
link |
This is why I think military special operators
link |
are a particularly interesting group,
link |
because their whole world is centered around elite
link |
and high performance with very high risk, high consequence,
link |
under variable conditions.
link |
The essence of their work
link |
is variable, unpredictable conditions.
link |
So you mentioned female athletes and steroids.
link |
I'm curious about this.
link |
Yeah, because everybody has always said to us,
link |
well, you only use male subjects,
link |
and obviously they have this testosterone background.
link |
They have higher levels of testosterone.
link |
That's why you get these results.
link |
So we did a comparative study on females.
link |
We get the same results.
link |
And these are our Stanford athletes or also-
link |
No, these were not Stanford athletes.
link |
They were Stanford students, but not athletes.
link |
Well, we have done, of course, work on some athletes,
link |
but in general, we don't do research on our teams,
link |
our varsity teams, so they have their own protocols.
link |
They have their own training programs.
link |
Yeah, they don't like us to get too close to them.
link |
No, I work with some of these folks and the coaches,
link |
and they are very skeptical, with good reason.
link |
Also, and the reason I ask is that when you see these PAC-10
link |
or Division I college athletes,
link |
and then you see their peers,
link |
there's clearly a difference, right?
link |
I mean, they are pedigreed throughout, right?
link |
And more typical folks also have different goals.
link |
They may not want to get infinitely stronger
link |
or perform more endurance work.
link |
So I want to ask you a couple of things
link |
about shivering and metabolism,
link |
because I think they're very interesting
link |
and sufficiently related.
link |
So my understanding is that shiver is an adaptation
link |
that's designed to heat us up,
link |
that we have brown fat that's in compartments
link |
around our body that are activated by shiver
link |
or coactivated by shiver,
link |
and that shivering is useful for increasing metabolism.
link |
And does it require that cold be the stimulus?
link |
So two scenarios, I'll give you an experiment.
link |
I put someone into cold water of some sort,
link |
and then I make them get out or I have them stand near it,
link |
and then they start shivering.
link |
My understanding is that their metabolism will increase.
link |
What if I take someone and I just have them shiver,
link |
but they're not exposed by cold?
link |
It's kind of a deliberate shivering.
link |
Will that also create a substantial increase in metabolism?
link |
So deliberate shivering without cold
link |
is essentially what happens when you get a fever.
link |
Your set point goes up and you're hypothalamus,
link |
and you actually, even though you're normal body temperature
link |
your thermostat is telling you you're too cold,
link |
increase your metabolism, so shiver.
link |
So sure, shivering is a good way of increasing metabolism,
link |
but it only can take metabolism up
link |
maybe three or four times resting.
link |
Whereas exercise can take you up 10 times.
link |
All right, I'm gonna ask a couple of more random questions
link |
and seemingly random.
link |
Do bears actually hibernate?
link |
The true hibernation?
link |
Well, it depends on how you define true.
link |
A bear, actually we've done a lot of work on bears.
link |
Do you also put the nose thermocouple down in the esophagus?
link |
We implant them surgically.
link |
Okay, they're anesthetized when you implant them.
link |
What kind of bears are these?
link |
And did this with colleagues at University of Alaska,
link |
and we're analyzing the data now,
link |
but what we've done is we've had now a total of 18 bears,
link |
and we implant them with EEG, EKG, temperature sensors,
link |
and sometimes we actually measure their oxygen consumption.
link |
These are bears in the wild.
link |
These are bears in the wild,
link |
but they're brought in to University of Alaska
link |
where we keep them in an outdoor enclosure,
link |
so they're hibernating in a nest box in an enclosure,
link |
and we're recording this electrophysiological data
link |
continuously for six months.
link |
How do I get on this protocol?
link |
Craig and I are doing some work together going forward,
link |
and maybe you can slide me onto this protocol too.
link |
That sounds amazing.
link |
Right now, it's a matter of just analyzing the gigabytes,
link |
terabytes of data that have been collected.
link |
But anyway, you asked about hibernation.
link |
So bears only go down to about 33, 34 degrees centigrade
link |
in core temperature, and that's been argued that,
link |
well, they can't go lower
link |
because they have so much insulation.
link |
They're so big, their surface volume ratio and so forth,
link |
and that's not true.
link |
So if we have a day like minus 40,
link |
which you get up in Alaska,
link |
they will go through periods of shivering
link |
and maintain a core temperature on 33, 34.
link |
Now, the ground squirrels and the marmots,
link |
which are smaller animals,
link |
they will drop down to a body temperature,
link |
maybe within a degree of the environment.
link |
So they can go down to one or two degrees centigrade,
link |
just above freezing during bouts of hibernation.
link |
So they'll stay in hibernation for seven or eight days,
link |
and they'll come back up to normal body temperature
link |
Then they'll go back down and do another job.
link |
What do they do during that day
link |
when they're warming up again?
link |
Do they go around?
link |
They rearrange their nests, eat, if they've stored food.
link |
Some species store lots of food.
link |
Others just depend on their fat.
link |
A former mentor of mine, my master's degree mentor,
link |
and a colleague and friend of yours,
link |
Irving Zucker at UC Berkeley, told me a story once,
link |
told me a lot of stories.
link |
He tells great stories, as you know.
link |
He told me that when an animal comes out of hibernation
link |
periodically, that it's a very dramatic thing to observe.
link |
That it's not like they wake up and yawn and look around,
link |
but it's like a complete epileptic seizure.
link |
What's going on there?
link |
It's just a very dramatic shiver.
link |
So at the low temperatures, they cannot shiver
link |
because the effect of temperature on the conduction
link |
of the nerves and the muscle fibers.
link |
So they're shut down, basically.
link |
They're shut down.
link |
So there they use brown fat.
link |
So activate brown fat.
link |
And then when they get up to a temperature
link |
of maybe 15, 16 degrees centigrade,
link |
then the shivering starts and it gets very, very violent.
link |
But they're still asleep.
link |
Do we shiver in our sleep?
link |
I would imagine we do, but it probably wakes us up.
link |
So the brown fat is kind of like kindling.
link |
The brown fat is a tissue which has lots of stored energy
link |
But unlike our white fat, our regular fat,
link |
it also has lots of these little powerhouses,
link |
mitochondria, and lots of blood supply.
link |
So essentially it is a tissue just to produce heat.
link |
That's what it's there for.
link |
Now, in these hibernators,
link |
there are big patches of brown fat at certain locations
link |
that are critical, like around the heart, for example.
link |
For us, the brown fat is sort of distributed.
link |
So for many, many years,
link |
it was thought humans don't have brown fat,
link |
It's just not localized into discrete fat pads
link |
like it is in ground squirrels, marmots.
link |
I don't know why the phrase fat pads is so satisfying to say,
link |
but it is fat pads.
link |
Speaking of fat pads, I was taught that we have,
link |
by the internet, I should say,
link |
I was taught by the internet that we have brown fat
link |
between our scapulae and our upper neck.
link |
Is that truly a source of brown enrichment for brown fat?
link |
If you're a ground squirrel.
link |
So it's completely, this is all the drawings out there.
link |
Okay, so what I'm hearing you say is that brown fat
link |
is actually distributed in patches.
link |
In humans, it's distributed along with other fat tissue.
link |
It's not as discrete.
link |
So the reason I'm kind of shocked and amused
link |
and troubled by this
link |
is because there is a somewhat standard protocol
link |
in the performance wellness, whatever, world,
link |
whatever you want to call it,
link |
of putting ice packs on the upper back
link |
as a way to stimulate brown fat thermogenesis.
link |
I'm hearing some inhales of concern from the physiologist.
link |
So tell me why, it sounds like that's probably not
link |
the best way to stimulate brown fat activation.
link |
Well, let's put it this way.
link |
You're not attacking anyone specifically
link |
because the whole world believes this.
link |
But it may not be totally facetious or false.
link |
Think of what that's doing.
link |
If you put ice right there where your spinal cord
link |
is close to the surface,
link |
that's where you're going to hit the vertebral arteries.
link |
So you're essentially putting a cold source
link |
into the brain to the hypothalamus.
link |
The hypothalamus says you're too cold,
link |
so it is going to turn on shivering and brown fat.
link |
Would there be a better site
link |
for sake of activating brown fat?
link |
You know, I can't say because the activation of brown fat
link |
is a sympathetic nervous system response.
link |
So any lowering of core temperature
link |
that will let the thermostat say you're too cold
link |
is going to turn on sympathetic.
link |
Now, people will have perhaps different amounts
link |
So newborn have more brown fat than adults.
link |
Because newborns can't shiver, correct?
link |
Okay, that's what I read.
link |
I don't know if it's true.
link |
Yeah, I don't know.
link |
I read that in what I believe to be credible sources,
link |
Yeah, it could be.
link |
I just don't know.
link |
It depends on if it's really newborn.
link |
I can agree because you don't have
link |
all of the motor pathways connected up yet.
link |
That's something that occurs in early days of life
link |
and is probably one of the functions of REM sleep,
link |
which infants have a lot of.
link |
But how to activate brown fat?
link |
If you are consistently exposed to cold,
link |
so if you live in the Arctic
link |
and you go out jogging in the winter,
link |
maybe that will increase the amount of brown fat you have.
link |
If you live in the tropics, maybe you have less brown fat.
link |
I don't know of any studies which have looked into that.
link |
Sometimes I'll drink a cold beverage
link |
or I'll eat ice cream and my head will-
link |
And speaking of special forces, I was talking to,
link |
we all see the images, the SEAL training slash screening
link |
in Coronado where they're going in and out of the Pacific,
link |
which is very cold.
link |
But I know they also spend some time
link |
in the very cold waters of Kodiak, Alaska.
link |
You mentioned Alaska.
link |
Brain freeze, so-called ice headache,
link |
is a common occurrence there in those situations.
link |
But we all have experienced this.
link |
We eat ice cream, we get that brain freeze.
link |
I can feel it right now a little bit subjectively.
link |
What's going on there?
link |
And I would always just rub my tongue
link |
on the roof of my mouth.
link |
Is there something that I'm doing that's functional there
link |
just to try and alleviate it?
link |
The thing is that the roof of your mouth
link |
is very close to your hypothalamus.
link |
So if indeed it's a popsicle
link |
that's giving you the brain freeze,
link |
it may be a direct cooling effect
link |
from the roof of your mouth.
link |
You put your tongue there,
link |
you're insulating the roof of your mouth.
link |
But what's the source of the brain freeze?
link |
Is it a vasoconstriction?
link |
It's a vasomotor change.
link |
Whether it's constriction,
link |
I think it's more likely a vaso,
link |
an increase in blood pressure,
link |
which will essentially cause an expansion of the arteries
link |
and activate pain receptors.
link |
We don't have pain receptors in the neural tissue,
link |
We have them in the meninges
link |
and predominantly associated with the blood vessels,
link |
the walls of the blood vessels.
link |
So if you have something
link |
which will dramatically increase your blood pressure
link |
going to the brain, you're likely to get a...
link |
We've had some preliminary data.
link |
I even hate to mention this
link |
because we have not been able to pursue it systematically,
link |
but we've had some experience with people with migraine
link |
that say if they use one of our devices to heat,
link |
that the migraine goes away.
link |
You know, the idea-
link |
It's very interesting.
link |
A lot of people suffer from migraine.
link |
I know there are a lot of different types of migraine.
link |
I've been reading a lot about this lately
link |
because I get so many questions about migraine.
link |
I hate to say anything.
link |
And we'll just underscore this as preliminary.
link |
And people have been great about understanding
link |
that when we say preliminary,
link |
we mean it has not passed through the required filters
link |
to call it hard fact yet.
link |
We don't even have a decent data set.
link |
These are anecdotal reports.
link |
Anecdata, as people like to call it.
link |
But I don't even like to call it that
link |
because then we don't want to give it more weight
link |
That's interesting.
link |
The ice headache and the increase in blood pressure
link |
is interesting because the only thing that I've heard
link |
is similar to it is something that comes from,
link |
you know, they have these competitions
link |
where people eat these very hot chili peppers.
link |
You know, it's kind of a-
link |
An ego thing, I guess, for reasons that escape me,
link |
that eating really hot peppers.
link |
And every once in a while, someone will eat one of these
link |
and get what's called thunderclap headache,
link |
where a headache comes on extremely quickly.
link |
And so quickly that it's caused,
link |
so severe, rather, that it's been known
link |
to cause stroke and brain damage.
link |
So these very, very hot peppers,
link |
if you're not acclimated to them,
link |
and maybe even if you are,
link |
have been shown to actually cause brain damage.
link |
Some good evidence for this.
link |
I do want to talk about something
link |
that we have not touched on yet,
link |
which is NEAT, non-exercise induced thermogenesis.
link |
So non-activity associated thermogenesis
link |
and the fidgeters, right?
link |
So the classic work of like Rothwell and Stock
link |
and the idea that some people who overeat
link |
are burning off that energy by way of shaking their knee
link |
or moving around a lot.
link |
These are the kind of nerve, they quote,
link |
you know, quote unquote nervous types.
link |
But they quoted in those studies,
link |
a huge degree of caloric burn, you know,
link |
800, 2,500 calories per day burned
link |
above those who sit rather still.
link |
Does that seem far-fetched?
link |
Those are older data, but any comment on NEAT
link |
or non-exercise induced thermogenesis?
link |
Well, I do think it's pretty straightforward
link |
that if you increase muscle activity of any kind,
link |
you're increasing your energy consumption
link |
and your heat production.
link |
And no, the really extreme example
link |
is hyper and hypothyroidism.
link |
People that are hyperthyroid are fidgety
link |
and you know, they have a high metabolic rate
link |
And people that are hypothermic are cool.
link |
They're not, they don't move very much.
link |
So any kind of muscle activity increases.
link |
And when you say, you know, it's not much activity,
link |
but remember it's only 20% effective.
link |
80% of the energy is going to heat.
link |
So it may not exert much energy to tap your foot,
link |
but four times the amount of energy
link |
that is going into the movement is being lost as heat.
link |
That's very interesting.
link |
A couple more quick questions.
link |
There's a lot of excitement these days,
link |
or at least usage these days of so-called energy drinks
link |
or pre-workout drinks.
link |
Many of these contain thermogenic compounds.
link |
So caffeine, things, there's a culture now
link |
of taking arginine, things that support arginine.
link |
So, you know, beet juice and L-citrulline,
link |
things to dilate the blood vessels.
link |
Sometimes this is for sake of increasing blood flow
link |
to the muscles during resistance exercise.
link |
But a lot of these are thermogenic.
link |
It's to increase body temperature.
link |
And is it possible that some of these energy drinks
link |
are actually, or similar, you know,
link |
six espresso or whatever it is,
link |
are acting to prevent optimal performance
link |
or reduce performance?
link |
I don't think that the temperature rise is that.
link |
I really don't know.
link |
But what it does is it makes you more jittery
link |
and you're going to increase that neat
link |
that you were talking about.
link |
Or it's another thing, and that is that
link |
when you are exercising your muscle
link |
and it becomes slightly hypoxic,
link |
I mean, the oxygen supply is not enough,
link |
the muscle releases adenosine.
link |
And what adenosine does in the muscle
link |
is cause the blood vessels to open up, to dilate.
link |
So it's a way of increasing the blood flow to the muscle
link |
and therefore the oxygen supply to the muscle.
link |
And caffeine is essentially an adenosine antagonist.
link |
An adenosine antagonist, right.
link |
So under the strict logic, ingesting caffeine
link |
will reduce adenosine release
link |
and will reduce oxygen utilization at the muscle.
link |
So that would lead me to believe
link |
that motivational support aside,
link |
that caffeine will hinder muscular performance.
link |
but I can't give you an authoritative answer on that.
link |
Okay, we're just going through the logic
link |
and the gymnastics around that.
link |
I think it's a fascinating area that deserves attention
link |
because the question of what one can ingest
link |
in order to perform better,
link |
to say nothing of hormone augmentation,
link |
but has often leads back to stimulants.
link |
And if those stimulants,
link |
most of which include caffeine of some sort,
link |
are inhibiting the adenosine system
link |
and the adenosine system
link |
is supporting the oxygenation of muscle,
link |
then I would imagine that avoiding them
link |
might be the better option.
link |
Yeah, I just am not aware of data that would...
link |
So this is a general phenomenon of adenosine
link |
It has, of course, a different effect in the brain.
link |
Adenosine causes sleep, so caffeine keeps you awake.
link |
And if you stay awake,
link |
you're going to have a higher metabolic rate
link |
than if you go to sleep.
link |
So, and the thing is you say energy drinks.
link |
The question is, what really is in them?
link |
It's usually a cocktail of things.
link |
I don't take these.
link |
I don't like them at all,
link |
but they're usually a combination of vasodilators,
link |
stimulant, caffeine, some sort of stimulant.
link |
And a source of glucose.
link |
Sometimes a source of glucose and sometimes not.
link |
And oftentimes there are vasodilators
link |
and there are compounds
link |
that are thought to be so-called nootropics, smart drugs,
link |
that basically increase acetylcholine
link |
or norepinephrine transmission.
link |
You know, in the 80s and 90s,
link |
the beta-3 agonists like clambuterol were very popular,
link |
but they were all banned.
link |
So those are all banned from...
link |
Although people use them recreationally,
link |
which I do not recommend.
link |
There were actually a number of deaths
link |
due to dehydration, overheating,
link |
as well as cardiac effects.
link |
Before we wrap up,
link |
I know you've done a ton of work on sleep.
link |
I think we're going to have to do another episode
link |
about your work on sleep
link |
because the amount of data that you produce there
link |
is vast, actually.
link |
So I first got to know you and your work
link |
related to sleep and temperature.
link |
We all hear nowadays that it's good to keep the room
link |
that you sleep in cool, keep it dark.
link |
I've talked a number of times on podcast episodes
link |
about the role of light and shifting in circadian rhythms.
link |
I have two questions related to sleep.
link |
One is, are there any things
link |
that may or may not relate to temperature,
link |
but that you think are very useful for getting better sleep
link |
that you don't hear that much about,
link |
that people might want to consider or try,
link |
realizing that there are a lot of reasons
link |
why people don't sleep great,
link |
but what are some things that you don't hear
link |
that much about these days that you wish people knew?
link |
Well, the sleep medicine community
link |
now puts a lot more emphasis on cognitive behavioral therapy
link |
than on pharmacology.
link |
So what cognitive behavioral therapy does
link |
is it essentially increases your sleep hygiene.
link |
So there are certain just general rules.
link |
So have a regular bedtime and a regular arousal time.
link |
Don't be skipping back and forth all the time.
link |
Arousal, you mean wake-up time.
link |
Wake-up time, yeah.
link |
Spoken like a true physiologist.
link |
Another thing is don't use screens
link |
within a couple hours of bedtime
link |
because screens are predominantly rich in blue light.
link |
And what that does is you mentioned the circadian system.
link |
That affects your circadian system.
link |
That pushes off your circadian stimulus for sleep, okay?
link |
Another thing is, of course, relax.
link |
I mean, don't work right up till the time
link |
you're going to bed.
link |
Take some time to do something relaxing.
link |
And then temperature, you've mentioned that.
link |
And for many people, a warm bath is really conducive
link |
And people are now swearing by a cooler environment
link |
And that makes sense in terms of the circadian effect
link |
on body temperature.
link |
So our circadian clock is affecting our thermostat.
link |
So at the time we go to bed, our thermostat
link |
is on its way down to a lower set point, okay?
link |
You go to bed and you're feeling a little bit cool.
link |
So you pile on lots of blankets.
link |
And then what happens is you wake up a little bit later
link |
and you're hot, so you throw them off.
link |
It's because your thermostat has set downward.
link |
Now, why is it better to have a cool environment?
link |
It's better to have a cool environment
link |
because it's easier to thermoregulate.
link |
So you can go to Europe in the summertime
link |
and the hotel rooms still have these big comforters,
link |
these down comforters.
link |
So how do you deal with that?
link |
You stick out your hands and your legs, okay?
link |
I've always slept with, I have one leg
link |
that just kind of hangs out of the, yeah.
link |
But that's, they're your heat loss surfaces, right?
link |
So if you're in a cool environment,
link |
you can take advantage of that.
link |
You can take advantage by passively
link |
regulating your body temperature.
link |
You don't have to get up and wake up and say,
link |
oh my God, I got to change the covers
link |
or blankets or what have you.
link |
If you're in a warm environment, what can you do?
link |
You need to sleep with one hand in the cool mitt, right?
link |
And right now that's not available yet.
link |
Right, it's not available.
link |
I've never heard about it that way.
link |
I've always heard you want to sleep in a cool room
link |
or keep the room cold.
link |
But I never realized why that's useful,
link |
which is, as you're saying,
link |
that then you can move these glabrous surfaces in and out.
link |
You could even, I'll sometimes even wake up
link |
under the blanket completely.
link |
Very, very interesting.
link |
That finally a rational science grounded explanation
link |
for why we need to sleep in a cool room.
link |
Because I always thought, well,
link |
if your temperature is going down anyway,
link |
why do you have to sleep in a cool room?
link |
What about wearing socks while you sleep?
link |
That was big a few years ago where they said,
link |
you know, you should put socks on.
link |
Now I would think that's probably the wrong advice.
link |
You probably just-
link |
Well, I don't know if it's wrong advice.
link |
There's an old, old study that was supported by,
link |
I think, Eddie Bauer, the sleeping bag company.
link |
And what the study showed, what the study was asking is,
link |
what are the most temperature sensitive spots in the body?
link |
Where do you feel cold?
link |
And what that showed was it was the toes.
link |
So when you sample water with your toe,
link |
you always see that.
link |
So the socks essentially are promoting thermal comfort
link |
by insulating that area that's quite sensitive.
link |
Now, of course, if it's too warm,
link |
you're not going to put socks on.
link |
Well, Craig, thank you so much.
link |
You gave so much information
link |
that's actionable and interesting.
link |
I know a lot of people are going to be really interested
link |
in the Palmer Cooling Technology from Coolmit.
link |
We will be sure to provide resources to the website
link |
so that people can register interest.
link |
I do encourage people to play around with, so to speak,
link |
the Palmer Cooling Technology that we all have,
link |
which are these glabrous surfaces.
link |
And I also just want to thank you
link |
for taking time out of your busy schedule
link |
to share this information.
link |
It was lots of fun.
link |
I certainly learned a lot,
link |
and I know a lot of people are going to learn a lot
link |
that's useful to them.
link |
Well, fabulous answers.
link |
Thank you for joining for my discussion
link |
with Dr. Craig Heller.
link |
If you're enjoying this podcast and learning from it,
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please subscribe to our YouTube channel.
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As well, you can give us feedback
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Also, please subscribe to the podcast
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That's a terrific way to support our podcast.
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In addition, if you're interested in supporting research
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you can go to hubermanlab.stanford.edu slash giving,
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and there you can make a tax-deductible donation
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If you're not already following us at Huberman Lab
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On Instagram, I do short neuroscience tutorials
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that are separate from the tutorials
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that I tend to do on the podcast.
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Often on this podcast, we discuss supplements.
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One of the really important things
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if you're going to take supplements
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is that the supplements be of the highest quality ingredients
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and that the amount of those ingredients
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We've partnered with Thorne, T-H-O-R-N-E,
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If you'd like to see the supplements that I take,
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You can get 20% off any of those supplements
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So it's Thorne, T-H-O-R-N-E.com
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slash the letter U slash Huberman.
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And last, but certainly not least,
link |
thank you for your interest in science.
link |
I'll see you next time.