Using Temperature for Performance, Brain & Body Health | Dr. Craig Heller

1. 0:00 – 2:00

   Introducing Dr. Craig Heller, Physiology & Performance

   1. AHAndrew Huberman0:00

      (Instrumental music) Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, I have the pleasure of introducing Dr. Craig Heller as my guest on the Huberman Lab Podcast. Dr. Heller is a professor of biology and neurosciences at Stanford. His laboratory works on a range of topics, including thermal regulation, Down syndrome, and circadian rhythms. Today, we talk about thermal regulation, how the body heats and cools itself and maintains what we call homeostasis, which is an equilibrium of processes that keeps our neurons healthy, our organs functioning well. And as Dr. Heller teaches us, thermal regulation can be leveraged in order to greatly increase our performance in athletics and mental performance as well. Learning to control your core body temperature is one of the most, if not the most powerful thing that you can do to optimize mental and physical performance regardless of the environment that you're in. He also dispels many common myths about heating and cooling the body, including the idea that putting a cold pack on your head or neck is the optimal way to cool down quickly. And in fact, as Dr. Heller tells us, it actually can be counterproductive and lead to hyperthermia. It's a fascinating conversation from which I learned a tremendous amount of new information, and we didn't even get into the other incredibly interesting work that Dr. Heller does on Down syndrome and circadian rhythms and sleep, so we hope to have him back in the future to discuss those topics. As you'll soon see, Dr. Heller is a wealth of knowledge on all things human physiology, biology, and human performance. It's no surprise then that he's been chair of the Biology Department at Stanford for many years, as well as director of the Human Biology Program. So, if you're interested in human biology and how to improve your performance in any context or setting, athletic

2. 2:00 – 6:45

   Sponsors: Roka, Inside Tracker, Athletic Greens

   1. AHAndrew Huberman2:00

      or otherwise, I think you'll very much enjoy today's conversation. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is ROKA. ROKA makes sunglasses and eyeglasses that are of the absolute highest quality. I've spent a lifetime working on the visual system, and I can tell you that the visual system has to go through a lot of work in order to maintain clarity of what you see when there are shadows, when you go into different types of indoor lighting, and so on. 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Unlike a lot of other performance glasses that frankly make people look like cyborgs, the aesthetics on ROKAs are really terrific. You could wear them anywhere you'd like to go. If you'd like to try ROKA glasses, you can go to roka.com, that's R-O-K-A dot-com, and enter the code Huberman to save 20% off your first order. That's ROKA, R-O-K-A dot-com, enter the code Huberman at checkout. Today's podcast is also brought to us by InsideTracker. InsideTracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and help you reach your health goals. I'm a big believer in getting regular blood work done, and now with the advent of modern DNA tests, you can also analyze your DNA to see what you ought to be doing for your immediate and long-term health. 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3. 6:45 – 10:45

   Cold Showers, Ice Baths, Cryotherapy

   1. AHAndrew Huberman6:45

      And now for my discussion with Dr. Craig Heller. Great to have you here.

   2. CHCraig Heller6:49

      It's good to be here.

   3. AHAndrew Huberman6:50

      Yeah. It's, it's been a long time coming. Uh, I know that I and many people have a lot of questions about the use of cold. So one of the things that's happened in recent years is that, for many reasons, people have become interested in things like taking cold showers and taking ice baths for many different purposes.

   4. CHCraig Heller7:13

      Mm-hmm.

   5. AHAndrew Huberman7:13

      You know, sometimes this is introduced as just a general health tonic, you know, but other times people get specific about how it can improve resilience or it can improve one's metabolism. C- could you just tell me a little bit about what happens when I get into a cold shower or an ice bath? What, what are some of the basic responses at the level of metabolism? Obviously, psychologically, we don't know exactly. It'll vary from person to person. But what happens when I submerge myself into an ice bath if I've never done it before?

   6. CHCraig Heller7:49

      Well, first of all, you get a tremendous shock. And what that's going to translate into is a bit of a shot of adrenaline. And I think this is really the, uh, so-called benefit, but I wouldn't call it a benefit of the cryo chambers. You go into a cryo chamber and it's a shock, so you get a shot of adrenaline. So sure, you're gonna feel different when you come out. (laughs) You've had a shot of adrenaline. But it doesn't necessarily translate into any benefit in terms of your physiology or performance and so forth. Now, if you take a cold bath or a cold shower, uh, a couple things are happening. One is you're going to stimulate vasoconstriction. So if anything, it's going to make it a little bit more difficult for your body to get rid of heat, because you're shutting off your avenues of heat loss. Uh, if you're in a true cold bath, the overall surface area of your body is so great that it doesn't matter if you vasoconstricted, you're still going to lose heat.

   7. AHAndrew Huberman8:51

      Okay, so, um, so vasoconstriction, the constriction of... Is it capillaries, vessels, and arteries all constrict? Or just one or two?

   8. CHCraig Heller9:01

      Well, this is an area of controversy. Uh, in general, when people talk of vasoconstriction, they talk of the overall skin surface, and that is not true. Uh, the primary sites of heat loss, which we're going to get into, are the palms of your hands, the soles of your feet, and the upper part of your face. And the reason these are avenues for heat loss is they're underlain by special blood vessels, and these blood vessels are able to shunt the blood from the arteries, which coming from the heart, directly to the veins, which are returning to the heart, and bypassing the capillaries, which are the nutritive vessels but high resistance. So you can tell when you shake someone's hand what his or her thermal status is. The hand's hot or it's cold. Sometimes it's-

   9. AHAndrew Huberman9:51

      Do you think that's part of the reason why humans evolved this practice of, uh, shaking hands?

   10. CHCraig Heller9:55

       (laughs)

   11. AHAndrew Huberman9:56

       Assessing each other's level of anxiety? We all know that a limp handshake is pretty, uh-

   12. CHCraig Heller10:01

       (laughs)

   13. AHAndrew Huberman10:01

       ... indicative of something and a firm handshake is indicative of something, as is the crushing handshake, for that matter. Right.

   14. CHCraig Heller10:07

       Yeah, I really don't know what the evolutionary origin of handshaking is other than to get your hand away from your weapon (laughs) -

   15. AHAndrew Huberman10:14

       Right.

   16. CHCraig Heller10:14

       ... perhaps. (laughs)

   17. AHAndrew Huberman10:15

       Uh, a couple of questions before we get into the specialized, um-

   18. CHCraig Heller10:18

       Yeah.

   19. AHAndrew Huberman10:19

       ... uh, vascular sh- compartments on the soles, the palms, and, and the upper face. Um, you mentioned whole body immersion like into an ice bath or very cold water up to the neck versus a cold shower. Is, is there something fundamentally different about those two besides the fact that they both provide this release of adrenaline? Is there anything that's, that's really important to understand about the difference in the physiological response evoked by th- by sh-

4. 10:45 – 11:55

   Boundary Layers

   1. AHAndrew Huberman10:45

      cold shower versus immersion in cold?

   2. CHCraig Heller10:48

      Well, there are differences that are more physical than anything else. So if you are in a cold bath and you're still, you develop a boundary layer. If you're in a shower, you can't develop a boundary layer.

   3. AHAndrew Huberman11:00

      Could you explain what a boundary layer is?

   4. CHCraig Heller11:01

      Yes, uh, i- i- g- if you... Uh, it's best to explain it in terms of a hot bath, because everybody's experienced that. You get into a hot bath and, oh my god, it's really hot. Almost painful. And then you sit down and eventually it doesn't feel so hot anymore, because the still water, which is close to your skin, is coming into equilibrium with your skin. So it's like having a blanket on you or an insulator on you, and then if you move around, you disturb that still water layer, you feel the hot temperature again.

   5. AHAndrew Huberman11:35

      I see. So if I were to get into a cold ice bath or very cold-

   6. CHCraig Heller11:39

      Right.

   7. AHAndrew Huberman11:40

      ... uh, body of water of some kind and stay still, I'd likely feel warmer, at least until I start-

   8. CHCraig Heller11:45

      Y- you're, you're not going to be losing as much heat.

   9. AHAndrew Huberman11:47

      I see.

   10. CHCraig Heller11:48

       Right.

   11. AHAndrew Huberman11:48

       And then when I move and start-

   12. CHCraig Heller11:49

       If you flail around-

   13. AHAndrew Huberman11:49

       Uh-huh.

   14. CHCraig Heller11:50

       ... flail around, then you're going to lose more heat.

   15. AHAndrew Huberman11:52

       Got it.

   16. CHCraig Heller11:53

       Yeah. But I think getting back to your original

5. 11:55 – 14:45

   Cooling Before Aerobic Activity to Enhance Performance

   1. CHCraig Heller11:55

      question about benefits, uh, you have to keep in mind whether you're talking about aerobic activity or anaerobic activity if you're referring to performance and exercise and so forth. So if you're doing aerobic activity that you can sustain for a long time, your production of heat is rising gradually and is being distributed throughout your body. So eventually, your body temperature is going to come up to a level that's going to impair your performance. So the benefit of a cold bath or a cold shower before aerobic activity is that you increase the capacity of your body mass to absorb that excess heat.

   2. AHAndrew Huberman12:36

      I see. So could you say that, um, in a c- in a rough sense that a protocol that one might use if they're going to head out for a, a long run-

   3. CHCraig Heller12:44

      Yeah.

   4. AHAndrew Huberman12:44

      ... even on a reasonably warm day, not, not super hot-

   5. CHCraig Heller12:48

      Right.

   6. AHAndrew Huberman12:48

      ... or maybe it is super hot, would be to take a cool shower before they go run. Would that be beneficial?

   7. CHCraig Heller12:53

      Sure. It'll take them longer to get to the sweat point and to heat up.

   8. AHAndrew Huberman12:57

      And what will that translate to in terms of a performance benefit?

   9. CHCraig Heller13:00

      I- increase your, well, could increase your speed, uh, or depends on how you use that benefit. Some people are pacers. They will go at the same pace and then they will go farther. Or some people are, um, uh, what I say, pacers and regulators and, uh, no, no, pacers or forcers (laughs) . They will take that advantage and use it up as fast as they can. So they will go faster but not necessarily farther.

   10. AHAndrew Huberman13:27

       I see. As far as I know, not many athletes, at least not the ones that I know, are getting into cool bodies of water, taking cold showers before they head out to train. But it sounds like there could be a real performance benefit there.

   11. CHCraig Heller13:39

       It could be a benefit. Uh, I know our, we're going to talk about our technology for cooling. But, uh, at one point, our, I don't know if they're using it now, but our cross country team, when they would go to compete in a very hot place, they would do their warm-up exercises, their stretching, then they would extract heat before the beginning of the race. So they, I like to think of it is you have greater scope for heat absorption.

   12. AHAndrew Huberman14:04

       Interesting. About how long, uh, would one need to take one of these showers or cold immersions before heading out for run? R- roughly speaking. We don't have to get into details because everyone's performance level and regimen is going to be different, where they live is going to be different, et cetera.

   13. CHCraig Heller14:18

       Right. It's not as long as you think. It's minutes.

   14. AHAndrew Huberman14:21

       Couple minutes?

   15. CHCraig Heller14:22

       Yeah, for, for, because what's going to happen is, uh, as your core temperature goes down, you will eventually shut off your heat loss and that keeps it from going below normal. So, eh, it, you can, if you're, if you've warmed up and your temperature has risen by half a degree, let's say, uh, it doesn't take more than a few minutes to extract that heat

6. 14:45 – 16:45

   Anaerobic Activity Locally Increases Muscle Heat

   1. CHCraig Heller14:45

      if you're vasodilated.

   2. AHAndrew Huberman14:46

      Interesting. And what about for the anaerobic athlete? The strength athlete?

   3. CHCraig Heller14:50

      Right. For the anaerobic athlete, and let's say they're doing several s- several, uh, they're doing several sets, uh, and how many reps, whatever they're doing, um, th- their core temperature's not going to rise that fast because it's only, uh, certain muscles which are being used. But the temperature of those muscles will go up.

   4. AHAndrew Huberman15:11

      So it's a local effect.

   5. CHCraig Heller15:13

      It's a local effect, right.

   6. AHAndrew Huberman15:14

      Okay.

   7. CHCraig Heller15:14

      Because if you're-

   8. AHAndrew Huberman15:14

      So let's say, let's for sake of today, maybe for this discussion, let's, if we assume that the, uh, basic workout, even though people do variation on this, is, you know, five sets of 5 or 10 sets of 10.

   9. CHCraig Heller15:25

      Yeah.

   10. AHAndrew Huberman15:26

       Uh, so for those listening, it would be, um, (laughs) five sets of 10, of five rep- repetitions or 10 sets of 10 repetitions, 10 by 10, five by five.

   11. CHCraig Heller15:35

       Uh-huh.

   12. AHAndrew Huberman15:35

       Yeah. So if somebody, let's say, is doing, um, a large body compound movement like barbell squats where there's, there are a lot of large body movements, hip hinging-

   13. CHCraig Heller15:45

       Yeah.

   14. AHAndrew Huberman15:45

       ... and et cetera. Um, but for instance, the, the biceps are not par- they're involved, but more or less indirectly.

   15. CHCraig Heller15:54

       Right.

   16. AHAndrew Huberman15:55

       So the effect is going to be to heat up the quadriceps, heat up the hamstrings, heat up the glutes, this kind of thing.

   17. CHCraig Heller16:01

       Right.

   18. AHAndrew Huberman16:01

       I see.

   19. CHCraig Heller16:02

       And then during rest, that heat will leave the muscle. Eh, but it's not fast. And certainly the heat can't leave the muscle very fast while you're working out because when the muscle contracts, it squeezes the blood vessels and th- the only way heat gets out of a muscle is in the blood. And your muscle metabolism can go up 50 or 60 fold during anaerobic activity. That means the heat production in the muscle goes up 50 or 60 fold. The blood flow to that muscle cannot go up 50 or 60 fold. So you literally have the capacity to cook your muscles. (laughs)

   20. AHAndrew Huberman16:38

       Mm-hmm. So, um, this is, uh, probably an appropriate time to just, um, mention briefly what the underlying mechanism of

7. 16:45 – 19:00

   Temperature Gates Our Energy Use

   1. AHAndrew Huberman16:45

      this is. Could you just... We, we will return to the specifics of what one can do to mitigate this heating up, but, um, could you just explain the relationship between energy production, ATP and pyruvate kinase, and the role of heat there?

   2. CHCraig Heller17:00

      Sure. Um, we don't get something for nothing. So like a steam engine, most of the energy in our food is lost as heat. So we are roughly about 20% efficient. So of the energy that we take in in our food, about 20% of that can go into doing work and the rest of it is lost as heat. Now, we're mammals, we use that heat to keep our body temperature considerably above the environment. But if you raise body temperature a few degrees higher, you're in trouble. That's hyperthermia. So individual muscles can reach hyperthermic limits before you might experience it in the whole body. So to keep you from damaging your muscle by hyperthermia, we have fail-safe mechanisms. And one of those fail-safe mechanisms is an enzyme which is critical-... for getting fuel, in other words, the results of metabolism of glucose, getting that fuel into the mitochondria, which is making our major coinage of energy exchange, ATP. Okay? So that particular enzyme is temperature-sensitive. So when the muscle temperature gets above 39 or 39.5, it shuts off. And that essentially shuts off the fuel supply to the mitochondria. That's when you cannot do one more rep. You-

   3. AHAndrew Huberman18:29

      So failure, could we say that-

   4. CHCraig Heller18:30

      Muscle failure.

   5. AHAndrew Huberman18:31

      ... one, one component of muscular failure is overheating of the muscle-

   6. CHCraig Heller18:34

      Right.

   7. AHAndrew Huberman18:35

      ... locally?

   8. CHCraig Heller18:36

      Right.

   9. AHAndrew Huberman18:36

      There are probably other things, too. I-

   10. CHCraig Heller18:38

       Well, if you, yeah, if you lack oxygen.

   11. AHAndrew Huberman18:39

       Mm-hmm.

   12. CHCraig Heller18:40

       Yeah. But our oxygen delivery is pretty good to the, to, to the muscle. Uh, if you run out of glucose, yeah, that's going to impair you. But the most immediate, the most immediate impairment of muscle activity, muscle fatigue, in other words, is the rise in temperature of the muscle.

   13. AHAndrew Huberman18:57

       Interesting. Um, I want

8. 19:00 – 22:10

   Local Versus Systemic Fatigue: Heat Is Why We Fail

   1. AHAndrew Huberman19:00

      to talk about how that muscle fails locally, but I have this burning question in my mind that I cannot seem to answer for myself. I'm hoping you can answer it for me. So let's say I'm doing, um, five sets of five with squats.

   2. CHCraig Heller19:13

      Mm-hmm.

   3. AHAndrew Huberman19:14

      I hit f- muscular failure at a given weight.

   4. CHCraig Heller19:16

      Mm-hmm.

   5. AHAndrew Huberman19:17

      And according to what I now know, it's my quadriceps and the muscles associated, I mean, with the squat that have failed because of this heat triggering, this mechanism triggered by heat that shuts off the muscle. But my biceps are nice and cool-

   6. CHCraig Heller19:33

      Yeah.

   7. AHAndrew Huberman19:33

      ... you're telling me. They're not, they're, they're not doing too much work. It's only indirect work.

   8. CHCraig Heller19:37

      Mm-hmm.

   9. AHAndrew Huberman19:37

      So why is it that I can't set the s- the bar down in the squat rack, walk over and do barbell curls with the same intensity that I could if I were to do those barbell curls fresh, w- uh, not having done anything prior?

   10. CHCraig Heller19:53

       Well, you will still have a fatigue curve with your upper body. Okay? And that will be influenced by any rise in temperature that has been generated by your lower body exercise. So-

   11. AHAndrew Huberman20:06

       So, so temperature, in both cases, is the limiting factor. Th- or-

   12. CHCraig Heller20:09

       It's one limiting factor. It's one limiting factor.

   13. AHAndrew Huberman20:13

       I find that amazing. I find that amazing, because, uh, I always thought, naively, that the reason muscles fail is because we, quote, "don't have the strength" to do another repetition, or it's that you lack glycogen or some ability to access that glycogen. But of course we still have glycogen. I, it's naive for me to think that, because if I wait three minutes and go back, I can do those repetitions again.

   14. CHCraig Heller20:35

       Right.

   15. AHAndrew Huberman20:36

       So the glycogen wasn't restored in that three minutes.

   16. CHCraig Heller20:38

       Right.

   17. AHAndrew Huberman20:38

       Obviously, it was there.

   18. CHCraig Heller20:40

       Right.

   19. AHAndrew Huberman20:40

       So I realize there might be other mechanisms involved. Sounds like heat is, if not the dominant mechanism that prevents more work, it's one of them.

   20. CHCraig Heller20:50

       It's one of them, and it's a f- quick one. It's a fast one. Um, so it can happen with, let's say you are a really experienced weightlifter. Okay? You may be doing very, very high weights with sets of five or six.

   21. AHAndrew Huberman21:07

       Yeah, to be clear for the audience, I'm not doing very high weights for sets of five. (laughs)

   22. CHCraig Heller21:11

       (laughs)

   23. AHAndrew Huberman21:11

       I'm not particularly strong. I, I'm not, uh, super weak, but I'm not particularly strong. But Craig's referring in the general sense to, with, to you. So it, why, why is it that if I finish a set of squats, I can't simply cool off my quadriceps by throwing a nice cool towel on my quadriceps? Why would, why is that not the best way to go about it?

   24. CHCraig Heller21:34

       Because your body surface is a very good insulator. Okay? We, we think we don't have fur and therefore we're not insulated. But the skin, the fascia, the, uh, the muscles underlief- underneath, that, they're all very good insulators. And that's why I said earlier that the way the heat gets out of the muscle is in the blood.

   25. AHAndrew Huberman21:56

       So I, I want to step through a couple other portals by which one might think that heating and cooling would be ideal and then get back to these-

   26. CHCraig Heller22:05

       Sure.

   27. AHAndrew Huberman22:06

       ... specialized surfaces on the, the hands, the feet, and the face.

   28. CHCraig Heller22:09

       Yeah.

   29. AHAndrew Huberman22:09

       So if

9. 22:10 – 26:43

   Cooling Off: Most Methods are Counterproductive

   1. AHAndrew Huberman22:10

      throwing a cold towel or ice, even ice-cold towel on my quadriceps isn't going to work or standing in front of the fan because I'm insulated from that cool. I can't cool off my blood fast enough. What about drinking 16 ounces of ice water?

   2. CHCraig Heller22:22

      Uh, sure, you can do that. But you can calculate how much heat that can absorb. Okay? And you can't continue drinking liters of ice water. You're going to dilute your, your blood and have other problems.

   3. AHAndrew Huberman22:34

      Right.

   4. CHCraig Heller22:34

      But yes, it'll help. Sure it will help. But it is not, doesn't have the, the full capacity you will need.

   5. AHAndrew Huberman22:42

      What about an ice pack to the back of my neck or to my head or-

   6. CHCraig Heller22:45

      Okay.

   7. AHAndrew Huberman22:45

      ... squeezing the cold sponge over the head? I'm, I'm deliberately moving through these options, because these are the ones that we see most often. We were actually just watching the Olympic track and field trials-

   8. CHCraig Heller22:54

      Yeah.

   9. AHAndrew Huberman22:54

      ... last night-

   10. CHCraig Heller22:55

       Yep.

   11. AHAndrew Huberman22:55

       ... up in Oregon. I'm a huge track and field fan. And, um, there were a lot of, uh, there were a lot of sponges on the backs of necks, um, before, in between, and after events. And, um, how good is that or how poor is that as a strategy? Since now we know that h- being overheated locally and systemically throughout the body is, is a serious limiting factor on performance.

   12. CHCraig Heller23:18

       Well, you have to understand something about our thermoregulatory system. We have a thermostat just like you have a thermostat in your house. And that thermostat is in the brain. Okay?

   13. AHAndrew Huberman23:30

       Do we know the specific site?

   14. CHCraig Heller23:31

       Yes.

   15. AHAndrew Huberman23:32

       Yes.

   16. CHCraig Heller23:32

       It's called the preoptic anterior hypothalamus. It does many things in terms of physiological regulation. But it serves as a thermostat. Now, that thermostat has to have information. It has to, uh, have input. Where does that input come from? It comes from our overall body surface where we sense temperature. Okay? So one of the things that can happen when you're overheated is that you can send in a cold stimulus to your thermostat...And that's sort of like wanting to cool your house by putting a wet washcloth over your thermostat. You know, it's-

   17. AHAndrew Huberman24:07

       (laughs)

   18. CHCraig Heller24:07

       ... it's doing the wrong thing. So we've actually had experiences where we've had people exercising, getting overheated, and then cooling the body surface and they say, "It feels great. This is fantastic," and their core temperature's going up.

   19. AHAndrew Huberman24:21

       Well, I think this is such an important point. First of all, I wa- I, uh, was weaned in a laboratory where there were always battles over the temperature in the lab.

   20. CHCraig Heller24:29

       (laughs)

   21. AHAndrew Huberman24:29

       So people were always putting ice packs on thermostats-

   22. CHCraig Heller24:32

       To make them hot.

   23. AHAndrew Huberman24:33

       ... or putting fans towards thermostats and trying to play this game. Good to know we were all being foolish, um, even though we're neurobiologists. Um, putting a cold towel over my torso-

   24. CHCraig Heller24:45

       Yeah.

   25. AHAndrew Huberman24:45

       ... or putting ice on the back of my upper back-

   26. CHCraig Heller24:48

       Right.

   27. AHAndrew Huberman24:48

       ... you're saying could actually heat up my core?

   28. CHCraig Heller24:52

       It'll at least decrease your heat loss, your rate of heat loss. As we're, you're going to raise the issue a little later, I, I know, and that is our natural portals for heat loss. So you can think of the natural porters, portals for heat loss as our air conditioners, okay? The thermostat's in the brain and the information from the thermos- to the thermostat is coming from the overall body surface. So what can happen if you, let's say, cool the torso with an ice vest, you can actually cause vasoconstriction of your portals, your heat loss portals. So that's what impairs the rate at which you're losing heat. Feels good. Now back to the head. That's really interesting. The major blood flow to the brain comes up four arteries through the neck. Um, there's the carotid arteries and there's the vertebral arteries. So when you put a cold towel around the neck, you're going to be putting a cold stimulus into the brain. Well, that's great for protecting the brain. You want to protect the brain, but it's also going to make you feel cooler than you are. So you will think you're ready to go again quickly when you've just essentially, uh, cooled the thermostat.

   29. AHAndrew Huberman26:08

       Um, this is an important point and there's a lot of, um, interest nowadays in people doing marathons and-

   30. CHCraig Heller26:14

       Yeah, yeah.
10. 26:43 – 27:45

    Exercise-Induced Brain Fog

    1. AHAndrew Huberman26:43

       it's a bit of a, of a tangent, but many people report after long bouts of exercise-

    2. CHCraig Heller26:48

       Mm-hmm.

    3. AHAndrew Huberman26:48

       ... or even just very intense bouts of exercise, feeling a kind of brain fog or mental fatigue. I, I assumed that that was due to lowered brain oxygenation post-exercise, but is it possible that there are some post-exercise effects on heating and cooling of the brain that might impact cognition, or I should say negatively impact cognition?

    4. CHCraig Heller27:11

       It's certainly possible because we know that, um, a rise in temperature decreases cognitive capacity.

    5. AHAndrew Huberman27:19

       Mm-hmm.

    6. CHCraig Heller27:20

       I mean, you can experience that yourself. You can get on a treadmill, you know, and follow your temperature and then just do a simple activity like adding and subtracting. You get to about 39 degrees, you can't do that anymore. You can't just calculate how m- how long you've been on the treadmill.

    7. AHAndrew Huberman27:36

       So the, the phrase cool, calm and collected is a, is-

    8. CHCraig Heller27:39

       Cool, calm and collected. (laughs)

    9. AHAndrew Huberman27:40

       That's the goal in, in all pursuits.

    10. CHCraig Heller27:42

        That's right. (laughs)

    11. AHAndrew Huberman27:43

        So, um,

11. 27:45 – 31:50

    Hyperthermia

    1. AHAndrew Huberman27:45

       I want to talk about these portals-

    2. CHCraig Heller27:46

       Yeah.

    3. AHAndrew Huberman27:47

       ... 'cause you've mentioned them a few times. Before I ask about what the portals are exactly and how they work and how they can be leveraged for performance, I just, there's a question that my neurobiologist self can't resist but ask. We have this thermostat-

    4. CHCraig Heller28:03

       Yeah.

    5. AHAndrew Huberman28:04

       ... in the preoptic area of the hypothalamus, which is interesting to me that preop- the medial preoptic area is also one that's known to be, um, sexually dimorphic dependent on testosterone exposure early in life, or, uh, et cetera. Although, um, people should just note that it's not actually testosterone that c- creates these sexual dimorphisms, these difference, it's actually testosterone converted into estrogen. Um, it's actually estrogen is the effector, uh, which is fascinating. Nonetheless, we've got this area that acts as a thermostat and you said it's collecting information from the whole body. Does that mean that there are pathways as the neuroscientists like you, you and I refer to them as these, these afferent or input pathways from the body to the preoptic area? Is there a map of our body in the preoptic area? 'Cause that, yeah, I have to imagine that you can't have the information just coming from the left shoulder, just from the right toe. It sounds like you need a pretty, uh, cr- probably a pretty crude map, but that you need a complete map of the body surface there.

    6. CHCraig Heller29:05

       Well, you don't need a complete map in the hypothalamus. I mean, that thermal afferent information that you mentioned, it also goes to the somatosensory cortex. So you know if an ice cube has touched you on the back, but that doesn't necessarily translate into a change in, let's say you're shivering or, or sweating. Uh, so the information that's going to the hypothalamus is more integrated, uh, representation of, of body temperature.

    7. AHAndrew Huberman29:36

       So it's sort of an average of what's happening across the body.

    8. CHCraig Heller29:39

       It's an average. Right.

    9. AHAndrew Huberman29:39

       So if I were to, let's say I get hot on a hot day and, uh, Popsicles when we were in summer camp-

    10. CHCraig Heller29:44

        Yeah.

    11. AHAndrew Huberman29:44

        ... I went to a sports camp near here actually, and we'd run around like crazy and then we get into the shade if we could, but we were, you know, Popsicles, it was all about Popsicles.

    12. CHCraig Heller29:50

        Brain freeze.

    13. NANarrator29:51

        (laughs)

    14. AHAndrew Huberman29:52

        Or the kids were putting ice cubes down each other's-

    15. CHCraig Heller29:54

        Yeah, yeah, yeah.

    16. AHAndrew Huberman29:54

        ... you know, shirts or something. Um, but that's an average because other parts of the body aren't exposed. The mouth is exposed to the ice in the Popsicle case or the, the cold cubes are in the hands.As you said, it feels really good.

    17. CHCraig Heller30:07

        It feels good, yeah.

    18. AHAndrew Huberman30:08

        But it sounds like it- it's feels deceptively good, because in reality could still be quite warm internally.

    19. CHCraig Heller30:16

        Absolutely. Yeah. Yeah.

    20. AHAndrew Huberman30:18

        Interesting.

    21. CHCraig Heller30:18

        Yeah. You can feel great and have a- a dangerously hyperthermic temperature. But I should say that when (laughs) you get into the danger zone, things get bad fast.

    22. AHAndrew Huberman30:29

        What are some of the symptoms that people could be on the lookout for, for hyperthermia?

    23. CHCraig Heller30:34

        Essentially, it's- it's almost ironic that if individuals are trans- trans- transitioning into heatstroke, they actually vasoconstrict and they stop sweating. And th- that's a pathological situation. I- I couldn't begin to explain it. But, uh, essentially, uh, you are just feeling exhausted. You're feeling, uh, miserable. Um, uh, the heart rate is very high. Um, your heart rate goes up as your core temperature goes up, uh, called cardiac drift. Um, so you just feel rotten. Uh, but that's why... since- since it's not an- an- an- it's not a danger signal that you can translate immediately into, "Nope, I'm going into heatstroke." Uh, that's why people can overcome their bad feeling with motivation to continue going, to work harder. So there have been a number of high profile athletic deaths due to heatstroke that were during practice, not in competition when people, you know, are really trying to do it, but in practice-

    24. AHAndrew Huberman31:46

        Yeah.

    25. CHCraig Heller31:46

        ... which shows they were just motivated to push.

12. 31:50 – 38:00

    Best Body Sites for Cooling: Palms, Foot Pads, Upper Face

    1. CHCraig Heller31:50

    2. AHAndrew Huberman31:50

       So let's talk about these magnificent portals-

    3. CHCraig Heller31:53

       Yeah.

    4. AHAndrew Huberman31:53

       ... that not just humans, but other animals, mammals are equipped with.

    5. CHCraig Heller31:58

       Right.

    6. AHAndrew Huberman31:58

       So, um, if putting cold on the neck or on the head or on the torso is not optimal, um, what is optimal? And, um, maybe walk us through a theory as to why we would have these portals located where they are, and then we can talk about how one might leverage them for performance.

    7. CHCraig Heller32:18

       Okay. Where the portals are, are in the glabrous skin, big word, okay? Glabrous just means no hair. So it's the hairless skin. You say, "Well, I'm- you know, most of my body is without hair." No. Your- most of your body has hair follicles. We are mammals. Mammals have fur. We've lost the fur, but we still have those that hairy skin phenotype all over our body, except, except for those skin surfaces where our mammal relatives didn't have fur. So the pads of the feet, and for the primates, upper part of the face. For rabbits, no- portions of the ears, the inner surface of the ears.

    8. AHAndrew Huberman33:03

       Oh, I never thought about that. Yeah.

    9. CHCraig Heller33:04

       For bears, you know, the tongue. Bears have big tongues, huge tongues. (laughs) So-

    10. AHAndrew Huberman33:10

        I didn't know that either. I haven't, I haven't been that close to a bear yet.

    11. CHCraig Heller33:13

        (laughs) Yeah. Haven't had a licking match with a bear.

    12. AHAndrew Huberman33:15

        (laughs) Not yet. No.

    13. CHCraig Heller33:16

        Okay. So anyway, um, our mama- mammalian relatives can't lose heat over their overall body surface. So probably very early on in mammalian evolution, they evolved these special blood vessels in the limited surface areas that don't have fur. And as I said, what these blood vessels are, are shunts between the arteries and the veins. Arteries and veins are both low resistance vessels. So you can have high flow rate. Capillaries, which normally are between arteries and veins, are high resistance, because they're very tiny, okay?

    14. AHAndrew Huberman33:54

        Is it- is it fair to say that, um, what I was taught is that blood flows flo- from arteries then to capillaries and then to veins and then-

    15. CHCraig Heller34:02

        Yes.

    16. AHAndrew Huberman34:02

        ... back to the heart?

    17. CHCraig Heller34:03

        Yes.

    18. AHAndrew Huberman34:03

        So it's sort of like from the heart, through arteries, then through these little capillaries, which are like little estuaries and streams, and then to the veins, back to the heart.

    19. CHCraig Heller34:11

        Right.

    20. AHAndrew Huberman34:11

        Is that- is that generally true?

    21. CHCraig Heller34:12

        Yeah. Abs- absolutely.

    22. AHAndrew Huberman34:13

        Okay. So what I learned in basic physiology is still-

    23. CHCraig Heller34:16

        Is- is still true.

    24. AHAndrew Huberman34:16

        I wouldn't- I wouldn't get an F in your class anyway.

    25. CHCraig Heller34:18

        No. (laughs)

    26. AHAndrew Huberman34:19

        Maybe a D or a C, but not an F. Um-

    27. CHCraig Heller34:22

        (laughs) So that's excellent.

    28. AHAndrew Huberman34:23

        Okay. And so you're saying that in this glabrous or beneath the glabrous skin...

    29. CHCraig Heller34:29

        There are these shunts.

    30. AHAndrew Huberman34:30

        And those go directly from arteries to veins.
13. 38:00 – 41:25

    Cooling Your Brain via The Upper Face; Concussion

    1. CHCraig Heller38:00

       were sweating and were hot.

    2. AHAndrew Huberman38:01

       Oh, amazing, amazing. So these compartments are a real thing. And you mentioned the upper half of the face.

    3. CHCraig Heller38:06

       Upper parts, that's where our primate ancestors don't have fur.

    4. AHAndrew Huberman38:09

       Mm-hmm. And the bottoms of our feet. So, um, let's just take a moment and talk about some of the more amazing results that have been associated-

    5. CHCraig Heller38:18

       Yeah.

    6. AHAndrew Huberman38:19

       ... with proper cooling of these glabrous skin surfaces. Um-

    7. CHCraig Heller38:23

       Let me introduce one more thing-

    8. AHAndrew Huberman38:25

       Sure.

    9. CHCraig Heller38:25

       ... because you asked earlier about the pouring of water on the head, okay? One of the things which is not appreciated fully is that the blood which is perfusing these special blood vessels in the face, above the beard line, that's the non-hairy skin, that blood then returns in the venous supply to the heart, but it actually does it in a very strange way. It actually goes through what are called, um, I'm blocking on the name now.

    10. AHAndrew Huberman38:59

        Take your time.

    11. CHCraig Heller39:00

        Uh, these are blood vessels that go through the skull, okay?

    12. AHAndrew Huberman39:03

        Hmm.

    13. CHCraig Heller39:03

        And that's why the scalp bleeds a lot if you cut-

    14. AHAndrew Huberman39:06

        Mm-hmm.

    15. CHCraig Heller39:06

        ... cut the scalp. And these blood vessels, which are called, I want to say emergent, but it's not emergent. It's a word that means leaving. And these blood vessels were primarily thought to be ways that blood is leaving, uh, the brain. But when you're overheated, the fl, direction of flow in those blood vessels reverses. So the cooled blood that's coming from your facial region goes into that circulation and actually is a cooling source for the brain. So you can cool the brain. You can have a cooling effect on the brain by c, pouring water on, on your head.

    16. AHAndrew Huberman39:45

        Interesting. So that practice, which we, at least for me, I most commonly associate with, um, combat sports-

    17. CHCraig Heller39:52

        Yeah.

    18. AHAndrew Huberman39:52

        ... where someone, the fighter goes to their corner. They usually sit down on a, uh, on a stool, unless they're trying to, um, uh, do some mental, uh, warfare from the corner, in which case they, they don't even take a seat. And they'll, their, um, corner crew will, will squeeze a, a glove, or excuse me, a sponge full of cold water over them, or-

    19. CHCraig Heller40:13

        Over their head.

    20. AHAndrew Huberman40:13

        Um, that you're saying is somewhat effective in cooling the brain.

    21. CHCraig Heller40:17

        Yeah. It's one of the natural mechanisms for, uh, cooling the brain.

    22. AHAndrew Huberman40:21

        I want to return to this at some point as well, but is there any known benefit to cooling the brain in terms of offsetting physical damage, you know, offsetting the negative effects of concussion? Because one of the reasons why, um, fighters will often get a, a, a col- on the back, you know, a cold item on the back of the neck or on the head is not just to cool them down, but the theory is that it might offset some of the damage of neurons.

    23. CHCraig Heller40:49

        Um, I just can't comment on that. I'm aware of those ideas, but they're controversial. Uh, one of the things that you want to do for injury to the brain is to decrease swelling. And, uh, one of the ways that you decrease swelling in many parts of the body is to cool. Uh, uh, uh, it, it decreases inflammation. It decreases the blood flow. Uh, so, you know, I, I think it's a really interesting topic, and it's something that should be investigated. Uh, it's kind of hard to investigate.

    24. AHAndrew Huberman41:23

        Yeah. Um,

14. 41:25 – 45:35

    Extraordinary (Tripling!) Performance by Cooling the Palms

    1. AHAndrew Huberman41:25

       interesting. Okay, so I hear these s- stories and I've seen the data, so I believe the stories. Um, maybe tell us a story about an observation that y- your group has made with respect to anaerobic exercise and the, and this prop- and proper, uh, cooling of the, these glabrous surfaces.

    2. CHCraig Heller41:46

       Yeah.

    3. AHAndrew Huberman41:47

       And we can talk about the technology.

    4. CHCraig Heller41:48

       Yeah, yeah.

    5. AHAndrew Huberman41:49

       Um, maybe give us the dips example first.

    6. CHCraig Heller41:52

       Okay.

    7. AHAndrew Huberman41:52

       Dips, of course, you know, I think most people are familiar with dips. You're supposed to, I guess, get down.

    8. CHCraig Heller41:56

       Raise and lower your body mass.

    9. AHAndrew Huberman41:57

       Yeah, raise and lower your body, raise and lower your body mass, usually with your legs dangling down. Sometimes people are strong enough to attach a weight there and, um, they'll do, it's essentially a compound upper body exercise.

    10. CHCraig Heller42:08

        Right.

    11. AHAndrew Huberman42:09

        Um, uh, one dip would not be particularly impressive for most people. A hundred would be very impressive. Um, 20 would be im- impressive for some, et cetera. What happens when s- a, a skilled athlete comes in and does dips for multiple sets? And then what happens when they cool properly using the glabrous-

    12. CHCraig Heller42:28

        Right.

    13. AHAndrew Huberman42:28

        ... skin surfaces?

    14. CHCraig Heller42:30

        Um, this was a story that occurred early on in our investigations when we first made the discoveries that cooling has a benefit-... to increase your work volume, your capacity to do more reps, okay? So, uh, the word got over, I think, to the 49ers camp and, uh, one of their players, Greg Clark, who was a tight end at the time, he had been tight end at Stanford, um, he decided, or I don't know if he was asked or what, um, to come over and check it out. So, uh, Greg came over and we said, "Greg, what are you good at? What- what ex- activity do you like to do?" He said, "Dips. I can do a lot of dips. I- I can do 40 dips in a first set and I can probably do five sets. That's a usual workout for me." And we said, "Okay." So he came over to the gym one day and that's exactly what he did. He did 40 dips the first set and then maybe 25 and 15 and, you know, down- down from there.

    15. AHAndrew Huberman43:31

        Do you recall wh- roughly what kind of rest periods he was taking between sets?

    16. CHCraig Heller43:35

        Yeah. We- we- and s- we- we standardized the rest period to three minutes.

    17. AHAndrew Huberman43:39

        Mm-hmm.

    18. CHCraig Heller43:40

        Because that's what we had set on for cooling as the interval.

    19. AHAndrew Huberman43:44

        That's a good long rest period for-

    20. CHCraig Heller43:46

        Yeah. It- it is. It- it-

    21. AHAndrew Huberman43:46

        Yeah. Still a lot of dips. I got to-

    22. CHCraig Heller43:48

        Yeah. It's actually-

    23. AHAndrew Huberman43:49

        Yeah.

    24. CHCraig Heller43:49

        ... a longer rest period than many, uh, p- people would prefer during workouts. They want to make the most of their time. (laughs)

    25. AHAndrew Huberman43:54

        Not me. I prefer to take as much rest as I possibly can. (laughs) Yeah.

    26. CHCraig Heller43:58

        (laughs) So several days later, he came back and, uh, his first set he did, I think, maybe 42. Uh, a little bit better, but now people were standing around watching. So there was a little impetus there-

    27. AHAndrew Huberman44:09

        Mm-hmm.

    28. CHCraig Heller44:10

        ... to show off.

    29. AHAndrew Huberman44:10

        Mm-hmm.

    30. CHCraig Heller44:11

        Uh, so then his second d- set was, I don't remember the numbers, but very much above the second set on the control day. This was after we cooled his-
15. 45:35 – 50:00

    Enhancing Recovery, Eliminating Soreness w/Intra-workout Cooling

    1. AHAndrew Huberman45:35

       And in terms of his ability to recover, um, did, was that explored or discussed at all? Um, because my understanding is that if we cause enough stress to a muscle during anaerobic training, we provide the stimulus for compensatory regrowth, et cetera.

    2. CHCraig Heller45:53

       Right. Right.

    3. AHAndrew Huberman45:54

       But if we do more work, we essentially scale up the amount of recovery that's needed or the recovery time. I'm- I'm very curious about whether or not he needed longer to recover between these super performing workouts.

    4. CHCraig Heller46:06

       That's very interesting. That was a major discovery which we didn't realize we were making at the time. There is this phenomenon you're referring to as delayed onset muscle soreness, DOMS.

    5. AHAndrew Huberman46:18

       Mm-hmm.

    6. CHCraig Heller46:19

       And this is due to those little micro tears and so forth that are happening as we extend our workout capacity, volume, okay? So we've had this experience so many times that an athlete or anyone will come in to the lab and they will exceed what their previous goals were, their previous expectations. And I can always see the words coming out of their mouth, "I'm going to be so sore tomorrow." They never are.

    7. AHAndrew Huberman46:49

       Interesting.

    8. CHCraig Heller46:49

       And we've actually demonstrated that, uh, with a naive group. We had a class, a physical conditioning class, and, uh, we had half of them a- uh, well, the first days of the class, we had to establish their true capacity, what they could do. So these were pretty heavy workouts for these new recruits. And, uh, we gave half of them the benefit of cooling and the other half not. And then we had them record their subjective levels of delayed onset muscle soreness. And they, those that were cooled, didn't have significant muscle soreness.

    9. AHAndrew Huberman47:25

       Amazing. And I know there are also published results and we, we will provide links to some of these papers for people, um, seeing similar effects, uh, I should say similar performance enhancing effects using, um, bench presses-

    10. CHCraig Heller47:39

        Right.

    11. AHAndrew Huberman47:39

        ... in a bench press or push-ups or other-

    12. CHCraig Heller47:41

        Yeah.

    13. AHAndrew Huberman47:41

        ... other sorts of things. Maybe you could give us an example from the realm of endurance work or- or-

    14. CHCraig Heller47:47

        Sure.

    15. AHAndrew Huberman47:47

        ... aero- aerobic work. Uh, running, cycling, things of that sort.

    16. CHCraig Heller47:51

        Well, one of the problems with, uh, for us is that our equipment now is not really portable. I mean, it's portable in the sense you can carry it to the gym or to the football field-

    17. AHAndrew Huberman48:04

        But you're not going to run with it.

    18. CHCraig Heller48:04

        ... but you're not going to run with it.

    19. AHAndrew Huberman48:06

        Right.

    20. CHCraig Heller48:06

        (laughs) Right.

    21. AHAndrew Huberman48:06

        Or equip a bicycle with it. Although when are the cooling handles on bicycles coming?

    22. CHCraig Heller48:10

        (laughs) Yeah. That would be- that would be good. But one- one, uh, itinerant activity is golfing and people have put it on their golf carts and, uh, they're out.

    23. AHAndrew Huberman48:18

        Do people really heat up that much in golf?

    24. CHCraig Heller48:20

        They do.

    25. AHAndrew Huberman48:21

        Not to- to be disparaging of the golfers, but I, the way I c- conceptualize golf, it's like a swing and then a walk and then a- and then a cart ride and then a meal. I probably just offended all the golfers out there.

    26. CHCraig Heller48:31

        Well, we, one- one time we had, uh, we were doing work for the, uh, for the, um, Department of Defense. And they wanted to check it out whether or not what we were doing was really worthwhile. So they sent out a team of special...... s- uh, special ops soldiers to be our subjects and test it out. They were here for a week. So, (laughs) they, w- that was a fun week. (laughs)

    27. AHAndrew Huberman48:56

        Yeah. They're, uh, th- I do some work with those guys. They're, they're hard-driving guys.

    28. CHCraig Heller48:59

        (laughs)

    29. AHAndrew Huberman49:00

        They, they also know how to have fun.

    30. CHCraig Heller49:01

        Right. (laughs)
16. 50:00 – 51:00

    Multiple Sclerosis: Heat Sensitivity & Amelioration with Cooling

    1. AHAndrew Huberman50:00

       limiting factor. So-

    2. CHCraig Heller50:01

       Well, you-

    3. AHAndrew Huberman50:01

       ... since they're getting more, more out of their drive, what's, what do you think's going on there?

    4. CHCraig Heller50:06

       Well, they can be heating up. Uh-

    5. AHAndrew Huberman50:08

       And they're wearing gloves, right?

    6. CHCraig Heller50:08

       ... especially, uh, they're wearing gloves-

    7. AHAndrew Huberman50:10

       Yeah.

    8. CHCraig Heller50:10

       ... on a hot day-

    9. AHAndrew Huberman50:11

       Yeah.

    10. CHCraig Heller50:11

        ... and so forth. But let me just tell you one more serious, uh, story about golfers and that is, individuals with multiple sclerosis are exceedingly temperature sensitive.

    11. AHAndrew Huberman50:21

        I didn't know that.

    12. CHCraig Heller50:22

        So they may still be mobile, uh, but they have to stay in cool locations and not increase their exercise to any great extent. But we've had, uh, subjects that have, with multiple sclerosis, who have just essentially put the device on their golf cart and they're back out playing golf in the middle of the summer.

    13. AHAndrew Huberman50:40

        Oh, that's great.

    14. CHCraig Heller50:41

        Yeah.

    15. AHAndrew Huberman50:41

        That's great.

    16. CHCraig Heller50:42

        It doe- does help.

    17. AHAndrew Huberman50:42

        Yeah, anything that allows people to have normal levels-

    18. CHCraig Heller50:45

        Right.

    19. AHAndrew Huberman50:45

        ... of, um, you know, livelihood and, um, and recreation is great. We always think about performance as the, at these kind of like peak and elite levels, and, um, pushing harder. But yeah, anything that allows people to be, to be mobile-

    20. CHCraig Heller50:58

        Right.

    21. AHAndrew Huberman50:58

        ... and functional is great.

17. 51:00 – 53:00

    Enhancing Endurance with Proper Cooling

    1. AHAndrew Huberman51:00

       So, um, w- what's your favorite i- example of endurance? And feel free to give us the extreme one, and then we'll talk about averages at, um, to be, you know, make sure we're thorough about averages versus exceptions.

    2. CHCraig Heller51:12

       Right. We haven't done a lot in the field. I mean, out- outdoors. Uh, most of our endurance has been in, uh, a hot room with treadmill work and so forth. So, the very first experiment we had I think maybe 18 subjects just off the street. I mean, we just recruited people in the hallways, "Come on in and do this." And what we found is we could, for this group, with one trial with and without cooling, we could double their endurance walking on the treadmill, walking uphill on the treadmill in the heat. Like, maybe 40 degrees ambient temperature, 40 degrees Centigrade.

    3. AHAndrew Huberman51:49

       So what does that experiment look like? You're having people walk on an incline. It's really warm. Some people are just going to hit the quit button and say, "I've had enough," and get off the treadmill.

    4. CHCraig Heller51:58

       Right.

    5. AHAndrew Huberman51:59

       With proper cooling, when are they doing the cooling?

    6. CHCraig Heller52:02

       They're, they're doing it continuously.

    7. AHAndrew Huberman52:04

       I see.

    8. CHCraig Heller52:04

       Because in the laboratory, we can suspend devices from the ceiling, for example. Now-

    9. AHAndrew Huberman52:10

       Sure.

    10. CHCraig Heller52:10

        ... now we do have prototype wearable devices. We did them, uh, y- in response to emails from, uh, Ebola workers a number of years ago in, uh, Sierra Leone. They said, "We've read about your work with athletes. Can't you do something for us? I mean, we're in the personal protective gear, and we can't be in the hot zone for more than 15 or 20 minutes." So that was, started us on the, uh, challenge of developing wearable systems that could go under the PPE. Um, we've published that work now. But-

    11. AHAndrew Huberman52:40

        That's great.

    12. CHCraig Heller52:41

        ... there's nothing-

    13. AHAndrew Huberman52:41

        And I'm guessing the military special operators that are out in the desert and other locations-

    14. CHCraig Heller52:45

        Right.

    15. AHAndrew Huberman52:45

        ... are probably excited about this technology.

    16. CHCraig Heller52:48

        Well, once they get it. (laughs)

    17. AHAndrew Huberman52:49

        Once they get it. It's coming.

    18. CHCraig Heller52:50

        It's c-

    19. AHAndrew Huberman52:51

        It's coming. Uh, yeah, you know, I think some people, um, might wonder, you know, if there are all these studies and there are these incredible results over the years, uh, why haven't we heard

18. 53:00 – 58:20

    Cool Mitt, Ice-Cold Is Too Cold, 3 Minutes Cooling

    1. AHAndrew Huberman53:00

       more about it? And I, I will ask your opinion on that as well, but I'll just editorialize a little bit, is that, y- the, the best laboratory work and its practical applications oftentimes requires many studies. Uh, and oftentimes, there isn't a portal, uh, so to speak, uh, to get that information out into the technology sector, so there is a, a company that's developing this technology for people to use and-

    2. CHCraig Heller53:28

       Right.

    3. AHAndrew Huberman53:28

       ... to purchase and use.

    4. CHCraig Heller53:30

       Right.

    5. AHAndrew Huberman53:30

       Um, you might as well just tell us now, what is the name of that company and, and do they have a website? People are going to want to know, um, where can they get this magical technology?

    6. CHCraig Heller53:38

       Right.

    7. AHAndrew Huberman53:38

       And, and is there a poor man's version of it as well?

    8. CHCraig Heller53:42

       Well, the company is Arteria, A-R-T-E-R-I-A, and the website is www.coolmitt.com. So Coolmitt is just C-O-O-L-M-I-T-T.

    9. AHAndrew Huberman53:55

       Mm-hmm. Yeah.

    10. CHCraig Heller53:56

        Coolmitt.com.

    11. AHAndrew Huberman53:57

        Yeah. It's a great website. When I went there, it says that right now, the technology is only available to professional sports teams and military. Is that true?

    12. CHCraig Heller54:04

        Well, where we stand now is, uh, the new version of the technology is sort of in beta test versions. We got it into the hands of people who had used the technology before. So there's, uh, NFL, uh, teams that are using the... There's, uh, uh, college teams. There's, uh, Olympics. There's the, uh, Navy SEALs, uh, uh, Major League Baseball, the NBA, uh, the National Tennis Association. They have locations where now they are trying this out and reporting back, "How's it working? How could you change it? How could you improve it-"

    13. AHAndrew Huberman54:37

        Great.

    14. CHCraig Heller54:38

        "... and so forth." So that's, that's where we are. But, uh, on the website, you can actually sign up for b-... being one who will be able to get one (laughs) when they are finally manufactured. They're now being made in fairly small lots, because you want to change things-

    15. AHAndrew Huberman54:54

        Sure.

    16. CHCraig Heller54:54

        ... as you realize how it can be improved.

    17. AHAndrew Huberman54:57

        Yeah, this is Stanford after all. You want to get the technology right. I, I like to joke that, uh, one of the reasons I like being at Stanford so much is that not only are my colleagues amazing and they're so forward-thinking, but they're all perfectionists. And so, the, the perfectionist mindset is that it has to be perfect before it can go, go live, so to speak. Well, I think there will be a lot of interest. Um, let's talk about the technology in a little more detail for a moment, and then let's talk about whether or not cruder forms of that technology exist, either for sake of safety and/or performance. Um, so what is, um... The, the CoolMitt, as I understand, is it's a, it's a mitt, it's a glove-

    18. CHCraig Heller55:35

        Yeah.

    19. AHAndrew Huberman55:35

        ... you put your hand into. You, you hold onto, uh, a, a surface and that surface, um, cools you, cools your hand and-

    20. CHCraig Heller55:42

        Right.

    21. AHAndrew Huberman55:42

        ... thereby through this, uh, specialized, um, portal, cools your, your core body temperature and all the, all the muscles of the body. Subjectively, if I were to do this right now, would I think that it was ice cold or would I think it was just cool?

    22. CHCraig Heller55:58

        Just cool.

    23. AHAndrew Huberman55:59

        I see.

    24. CHCraig Heller55:59

        Ice cold is too cold. So people always ask, "Well, why can't you just stick your hand in a bucket of ice water?" It's too cold. What that does is that causes reflex vasoconstriction of the very portals that you're trying to maximize the heat loss from. Uh, so you stick your hand in cold water, uh, when it comes out, it's cold.

    25. AHAndrew Huberman56:20

        You just sealed up all the heat in your body.

    26. CHCraig Heller56:22

        You, you... Yeah, right. Uh, so, well, what I sort of recommended to someone at one point, they said, "Well, when I'm running, can't I just carry a frozen juice can and it will gradually melt?" And I said, "Well, no, because that's going to decrease the heat loss from that hand. But if every couple minutes you switched hands-" (laughs)

    27. AHAndrew Huberman56:40

        Exac-

    28. CHCraig Heller56:40

        "... it might work." (laughs)

    29. AHAndrew Huberman56:41

        Well, I have a feeling that there are people now doing that as well as trying, trying this. So, um, how long in, in the CoolMitt at the proper temperature-

    30. CHCraig Heller56:51

        Yeah.
19. 58:20 – 1:01:15

    How You Can Use Palmer Cooling to Enhance Performance

    1. CHCraig Heller58:20

       That's when they use it.

    2. AHAndrew Huberman58:21

       Interesting. So is there a poor person's, uh, poor man or woman's version of this? Uh, you mentioned the juice can passing back and forth. You mentioned cooling the hands. Uh, a number of people said to me after learning a little bit about this science and technology that they've experienced some big effects, uh, positive effects of, of cooling by, uh... And I confess I've done this, taking a, a, a package of frozen blueberries and just kind of passing it back and forth-

    3. CHCraig Heller58:51

       Yeah.

    4. AHAndrew Huberman58:51

       ... between my hands.

    5. CHCraig Heller58:52

       Yeah.

    6. AHAndrew Huberman58:52

       Now talking to you, I realize I probably didn't do it long enough. I probably was... I was only doing maybe 30 seconds passing it back and forth between my hands and then going back into sets. I did see a performance-enhancing effect-

    7. CHCraig Heller59:04

       Uh-huh.

    8. AHAndrew Huberman59:05

       ... ab- absolutely. But, um, I realize I probably wasn't optimizing the protocol. If you were going to give a, um, a crude protocol for, let's just say for the gym, because with running it's a little bit tricky, but, um, what would that look like if people wanted to just play with this in, in some sort of fashion?

    9. CHCraig Heller59:23

       Well, that, it, you know, it's would be experimental. (laughs)

    10. AHAndrew Huberman59:28

        Sure.

    11. CHCraig Heller59:29

        And I-

    12. AHAndrew Huberman59:29

        Yeah, none of that is con- very controlled.

    13. CHCraig Heller59:31

        Your idea of frozen peas is a good idea, uh, and I think s- since there's been no actual study of that, it would have to be you working out what is the best for you. But one way to figure it out is that if after you ho- hold the cold peas in one hand and you switch it to the other hand, if someone then comes and feels your hand, is it warm or cold? If it's cold, it means you vasoconstricted.

    14. AHAndrew Huberman59:59

        Ah.

    15. CHCraig Heller1:00:00

        If it's warm, it means the hot blood is still going there. Okay, so we do that in the lab.

    16. AHAndrew Huberman1:00:06

        And the key is for it to not vasoconstrict?

    17. CHCraig Heller1:00:08

        Right.

    18. AHAndrew Huberman1:00:09

        Okay. So, so there's a test out there, folks. If you're gonna try this in kind of crude fashion, at least until the, uh, the CoolMitt is available more broadly, um, to the general public, you could assess, you want to assess whether or not the ha- your palms actually feel cool to the touch by somebody else-

    19. CHCraig Heller1:00:27

        Right.

    20. AHAndrew Huberman1:00:27

        ... to es- and if it does, that means you sh- you've essentially shut down the portal. You're sealing in more heat-

    21. CHCraig Heller1:00:31

        Right.

    22. AHAndrew Huberman1:00:31

        ... which is bad. What about, um, putting this cold pack of some sort on the face or, um-

    23. CHCraig Heller1:00:39

        Or on the feet.

    24. AHAndrew Huberman1:00:39

        ... or on the feet? I work out at home. I, I don't often work out barefooted, but I suppose I could, like they did in the '70s, you know, when those guys were walking around, uh, without shoes and squatting without shoe- uh, without any shoes or socks on. Could I put my feet on them?

    25. CHCraig Heller1:00:53

        You, you could.Um, if you had- simply had a water-profused pad and you were circulating cool water through it, uh, you could just put your feet on it, okay? Um, part of the problem is, um, that you don't want... I- if, let's say you have just a cold pack

20. 1:01:15 – 1:04:40

    Radiation, Convection, Heat-Transfer, Role of Surface Area

    1. CHCraig Heller1:01:15

       of something. The problem is back to boundary layers again. If you don't have a convective stream of the cooling medium, the heat sink is not as effective, because there'll be a boundary layer developed between the heat sink material and your skin. Uh, so that decreases its, its efficacy.

    2. AHAndrew Huberman1:01:35

       I see, but maybe we should just for a moment talk about convection, uh, radiation and convection, and just make that clear. Like if I put my hands, um... Let's say it's a cold night and I'm at a campfire and I take my hands and I put them out to the fire.

    3. CHCraig Heller1:01:48

       You're getting radiation.

    4. AHAndrew Huberman1:01:49

       You're getting radiation.

    5. CHCraig Heller1:01:50

       Right.

    6. AHAndrew Huberman1:01:50

       Okay.

    7. CHCraig Heller1:01:51

       Right.

    8. AHAndrew Huberman1:01:51

       (laughs) And, and then if it's a windy, warm night... No, I don't know if that's the best example. Give us a good example of convection, um.

    9. CHCraig Heller1:01:59

       Convection, sure, is, is in a cool breeze.

    10. AHAndrew Huberman1:02:01

        Yeah.

    11. CHCraig Heller1:02:01

        You know, the wind chill factor.

    12. AHAndrew Huberman1:02:03

        Sure.

    13. CHCraig Heller1:02:03

        That's due to convection.

    14. AHAndrew Huberman1:02:04

        Mm-hmm.

    15. CHCraig Heller1:02:04

        Okay? But in terms of heat transfer between two objects, uh, if you have convection of the medium, whether it's blood on the inside and water on the outside, you increase the heat exchange if you have convection on both sides.

    16. AHAndrew Huberman1:02:23

        Right, so this is why just planting my feet on two, um, packages of fro- my bare feet on two packages of frozen peas, there's really no opportunity for circulation-

    17. CHCraig Heller1:02:33

        Right.

    18. AHAndrew Huberman1:02:33

        ... of, and, and therefore heat transfer, so it's not really optimal, which is ag- I, and I-

    19. CHCraig Heller1:02:38

        But once again, it depends on the surface area to get any benefit at all. We have a study that we published, um, which was investigating the standard treatment for hyperthermia in the field, and the standard, uh, treatment, the, the, uh, that's recommended by, uh, medical organizations is you take cold packs and you put them in the axilla, the groin.

    20. AHAndrew Huberman1:03:03

        The axilla or the... Are the, are the armpits?

    21. CHCraig Heller1:03:05

        The armpits, yeah, the groin, which is, uh, uh-

    22. AHAndrew Huberman1:03:09

        Thin skin, lots of vasculature.

    23. CHCraig Heller1:03:11

        Right, (laughs) and the f- and the neck. So what we did is we did studies in which we made people hyperthermic and then we measured the rate at which we could cool them by putting those positions in the r- those heat exchange bags in the recommended location versus on the glabrous skin, versus palms, soles, and face. The, the cooling rate was double.

    24. AHAndrew Huberman1:03:36

        Wow, so-

    25. CHCraig Heller1:03:37

        If we put the same ice packs, the same cold packs, uh, on the, uh, heat portals, rather than, uh, the axilla, the groin, and the face.

    26. AHAndrew Huberman1:03:47

        Wow.

    27. CHCraig Heller1:03:48

        Or the neck.

    28. AHAndrew Huberman1:03:49

        Wow, so face, hands, and bottoms of feet will cool you twice as fast-

    29. CHCraig Heller1:03:56

        Th- right.

    30. AHAndrew Huberman1:03:56

        ... as putting cold packs into your armpits, your groin, or back of neck? Amazing.
21. 1:04:40 – 1:11:40

    Hypothermia Story, Ideal Re-Heating Strategy

    1. CHCraig Heller1:04:40

       what the standard operating procedure is.

    2. AHAndrew Huberman1:04:43

       Mm-hmm.

    3. CHCraig Heller1:04:43

       The... That you hit the arteries.

    4. AHAndrew Huberman1:04:45

       Mm-hmm, amazing.

    5. CHCraig Heller1:04:47

       And the veins. The arteries and veins.

    6. AHAndrew Huberman1:04:48

       I'm going to just tell a brief story that, um, illustrates how almost everybody gets this stuff wrong, and then I'm going to use that as an opportunity to ask you about heating. Deliberate heating as opposed to deliberate cooling. So about four months ago, a friend of mine, a- and incidentally a, a guy who did nine years in the SEAL Team, is a really skilled cold water swimmer. We went out for a swim in the morning. Um, I'm not nearly even close to the... Being in the same universe of his, um, output potential. We do these swims. I'm familiar with them. I got enough blubber on me that I'm f- stay warm enough in the cold Pacific, no wetsuits. We do the morning col- cold swim for about a mile or so, and we brought with us a, a young kid that I know real well that hangs out with us sometimes and trains with us who's got very little body fat. He's just exceptionally lean despite eating everything in sight, right?

    7. CHCraig Heller1:05:42

       (laughs)

    8. AHAndrew Huberman1:05:42

       Teenager. Great athlete, great kid. Great swimmer. So we're out there swimming, and at some point, we're talking to him and it's clear that he's gone hyperthermic. He's slurring his words. He's not doing well. So we get him onto the beach. His teeth are turning yellow. He's quaking. He's not... He's got, um, you know, his saliva has taken on that consistency that's clear, like, he's hyperthermic. We go to the lifeguard station. Lifeguard says, "Okay, let's get his vitals. Let's do all this." Meanwhile, trying stand next to him, you know, y- and heat him up by heating up his torso. So there we are, like, pressing against this guy, our friend, trying to heat him up. They get a blanket on him. He's... I'm realizing he was barefoot. His face was exposed, although we did cover his head with the blanket, and he eventually came back. We got some warm liquids into him and he, he was okay. He was fine. I don't know that his mother is ever going to let him swim with us again. Um, if, if I ever-

    9. CHCraig Heller1:06:42

       Yes.

    10. AHAndrew Huberman1:06:42

        ... disappear and go missing, it's because of that incident. Anyway, um, he did great. He recovered. He's back in the water and doing well. But I realized that pretty much everything from the point where we got back on the beach-... Until he was back to normal was, we did incorrectly. We heated his torso, we left his extremities exposed, and we assumed we were doing the right thing. And the lifeguard is a skilled lifeguard at a major public beach. So I guess the simple question is, did we get everything wrong? Did we get anything right? And what would have been the better option to heat up a hypothermic person in that or a similar situation?

    11. CHCraig Heller1:07:26

        Well, it's interesting you ask that, because that is the way we got into this area of investigation. Um, I worked on how the hypothalamus regulates body temperature, neurophysiology. And one day, uh, we were having a discussion with a colleague in the Department of Anesthesia. And, uh, he, he jokingly said to my colleague, he said, "Yeah, you guys think you know so much about temperature. I bet you couldn't solve a problem we have in the recovery room." "What's that?" "Well, the patients come out of surgery, they're hypothermic, and it takes us hours to get them to stop shivering." What do they do in the recovery room? Exactly what you suggested. They put in warm blankets, they put on heat lamps, uh, and it takes them an hour or two hours to get these patients to stop shivering, to bring them back up to... So we say, "Ah, it's a trivial problem." No, it's a hard problem. It's a hard problem because when you're under anesthesia, you're vasodilated. When you come out of anesthesia, you're hypothermic and you vasoconstrict. That makes it very difficult to get heat into the body. So we got the idea that, well, if we could just take one appendage, like an arm, and we put it in a, uh, environment wrapped in a heating pad and a, a negative pressure, you know, suction, uh, that would pull more blood into that limb. That blood would get heated, and it would warm the body up faster. So my colleague built a prototype device. You (laughs) couldn't get such a device into the hospital these days. (laughs) But we were, were with our anesthesiologist friend, we took it into the recovery room, and, and first thing the patient said, (laughs) "No way. (laughs) You're not going to put that on my patient." But he prevailed. And first patient ins- didn't shiver at all. First patient was back to normal temperature, core temperature in, I think it was eight minutes.

    12. AHAndrew Huberman1:09:28

        Amazing.

    13. CHCraig Heller1:09:28

        Eight or nine minutes.

    14. AHAndrew Huberman1:09:29

        Is this now standard practice in hospitals?

    15. CHCraig Heller1:09:31

        No, no, no.

    16. AHAndrew Huberman1:09:32

        So this is another example-

    17. CHCraig Heller1:09:33

        No, no, no.

    18. AHAndrew Huberman1:09:34

        ... where I, I don't get upset about the f- although it, it's upsetting to know that it's not. But I think that it's yet another case where a fundamental problem exists. There's a, a science-based solution that makes sense at the level of physiology, engineering, and practice, and yet it's not being done.

    19. CHCraig Heller1:09:56

        Right.

    20. AHAndrew Huberman1:09:56

        And I mean, we could t- we, that's a whole other discussion as to what the limitations are. Well, perhaps in, and I know a number of our listeners are in the healthcare and medical-

    21. CHCraig Heller1:10:04

        Yeah.

    22. AHAndrew Huberman1:10:04

        ... profession, as well as military athletes, and just also standard other types of jobs, civilians, uh, uh, doing other types of work. Uh, it would be wonderful if people understood this. So, um, once again, is there a, uh, is there a homegrown technology that people could use? If somebody is hypothermic, what is going to be the best way for them to warm up? Is it going to be holding a, a nice warm, um, mug of cocoa or something like that, but not, not too hot, I guess, is-

    23. CHCraig Heller1:10:31

        Yeah, sure.

    24. AHAndrew Huberman1:10:31

        ... again, the idea?

    25. CHCraig Heller1:10:31

        Yeah, um, well, actually, you can go hotter on the, on the glabrous skin, the-

    26. AHAndrew Huberman1:10:37

        Oh, because they don't dilate.

    27. CHCraig Heller1:10:38

        ... bec- because it takes the heat away faster.

    28. AHAndrew Huberman1:10:41

        Mm-hmm.

    29. CHCraig Heller1:10:41

        Okay? But back to the a- anesthesia, what you can do is you can use, uh, warm pads. They have them in, uh, all hospitals. They have circulating water-

    30. AHAndrew Huberman1:10:51

        Mm-hmm.
22. 1:11:40 – 1:12:45

    Paw-lmer Cooling for Dog Health & Performance

    1. CHCraig Heller1:11:40

    2. AHAndrew Huberman1:11:40

       I actually use this technology. I have a bulldog, bulldog mastiff.

    3. CHCraig Heller1:11:43

       Uh-huh.

    4. AHAndrew Huberman1:11:43

       He has a very high, um, propensity for overheating.

    5. CHCraig Heller1:11:47

       Mm-hmm.

    6. AHAndrew Huberman1:11:47

       Because they, they're terrible at dumping heat, and bulldogs are great at pushing themselves-

    7. CHCraig Heller1:11:52

       Yeah.

    8. AHAndrew Huberman1:11:53

       ... to the point of exhaustion or death. It ha- it happens. And so now we do what we call palmar cooling.

    9. CHCraig Heller1:11:59

       (laughs) Ah.

    10. AHAndrew Huberman1:11:59

        Sorry, I couldn't help myself. Where I'll take Costello and lower him into a cool body of water, just the, just the bottoms of his paws. Although I think animals-

    11. CHCraig Heller1:12:07

        Mm-hmm.

    12. AHAndrew Huberman1:12:08

        ... instinctually know to do this, and will go and stand in-

    13. CHCraig Heller1:12:12

        Yeah, yeah.

    14. AHAndrew Huberman1:12:12

        ... bodies of water. They don't often lie down all the way.

    15. CHCraig Heller1:12:15

        Yeah.

    16. AHAndrew Huberman1:12:15

        Some do.

    17. CHCraig Heller1:12:16

        Yeah.

    18. AHAndrew Huberman1:12:16

        Um, but they seem to know that's a great-

    19. CHCraig Heller1:12:19

        Yeah.

    20. AHAndrew Huberman1:12:19

        ... way to cool themselves off.

    21. CHCraig Heller1:12:21

        Mm-hmm. Yeah. Oh, absolutely, yeah.

    22. AHAndrew Huberman1:12:23

        And they get the advantage that their palm, that their palms and their feet are essentially the same thing, so.

    23. CHCraig Heller1:12:27

        We, we actually built devices for dogs-

    24. AHAndrew Huberman1:12:30

        Did you really?

    25. CHCraig Heller1:12:30

        ... and tried them on Iditarod sled dogs, and worked beautifully. They had little backpacks with the equipment and pads on all their feet and, and, uh, it worked beautifully. (laughs)

    26. AHAndrew Huberman1:12:42

        Amazing, amazing. Along the lines of

23. 1:12:45 – 1:17:35

    Warming Up, & Varying Temperature Around the Body

    1. AHAndrew Huberman1:12:45

       heating, deliberate heating, wearing a knit, um, cap is something that you see more of that on the East Coast. You know, people running around Boston and New England-

    2. CHCraig Heller1:12:55

       Yeah.

    3. AHAndrew Huberman1:12:55

       ... you know, with a, with a knit cap. Uh, I've always done that at the start of my runs to try and warm up-

    4. CHCraig Heller1:13:01

       Yeah, yeah.

    5. AHAndrew Huberman1:13:01

       ... more quickly, and then I take it off. I shed layers as I go. Um-Is that a rational practice the way I just described it?

    6. CHCraig Heller1:13:09

       Oh, sure. Yeah.

    7. AHAndrew Huberman1:13:09

       Yeah. 'Cause warming up is important too. Y- you know, there's a certain amount of, uh, quote-unquote, warming up that's required to l- lubricate joints or at least to get the sense that joints are lubricated and, and to be able to move more easily.

    8. CHCraig Heller1:13:21

       Yeah.

    9. AHAndrew Huberman1:13:21

       Do you still recommend that people warm up?

    10. CHCraig Heller1:13:24

        Yeah. Uh, but I think we're misled by the term warm up, as if the major purpose is to raise temperature. Um, I don't, I'm not aware of any data on this, but I, I do think that the major contribution is increasing flexibility. Uh, so you're going to avoid having damage, uh, of joints and, and tendons and ligaments and so forth. Um, but, uh, also, um, the ability of the mitochondria to produce, uh, energy, uh, can be impaired at low- lower temperatures. And you have to keep in mind that we say our body temperature's 37 degrees. But that's not true.

    11. AHAndrew Huberman1:14:06

        Yeah. It varies across the day. It's-

    12. CHCraig Heller1:14:08

        It, it, well, it varies in parts of your body. I mean, my hands and arms are not at 37 degrees right now. They're much lower. (laughs)

    13. AHAndrew Huberman1:14:16

        So that, that raises an interesting question. What is the best way to measure core body temperature?

    14. CHCraig Heller1:14:22

        Well, the best core temperature is the, what we use is esophageal. So we put a thermocouple up the nose, about two feet down the esophagus, (laughs) so that it's about the level of your heart.

    15. AHAndrew Huberman1:14:34

        Not gym or home practical. Although-

    16. CHCraig Heller1:14:37

        (laughs) No.

    17. AHAndrew Huberman1:14:37

        I don't know, some of those COVID swab tests go pretty far.

    18. CHCraig Heller1:14:40

        Too far. (laughs)

    19. AHAndrew Huberman1:14:40

        I can't even imagine going any further.

    20. CHCraig Heller1:14:42

        Too deep.

    21. AHAndrew Huberman1:14:42

        I felt like my brain was getting tickled.

    22. CHCraig Heller1:14:44

        (laughs)

    23. AHAndrew Huberman1:14:44

        Um, and it was really unpleasant.

    24. CHCraig Heller1:14:46

        But tympanic, uh, tympanic is a pretty good...

    25. AHAndrew Huberman1:14:48

        So the ear.

    26. CHCraig Heller1:14:49

        The ear.

    27. AHAndrew Huberman1:14:49

        Yeah.

    28. CHCraig Heller1:14:50

        Uh, it's not foolproof because you have to actually have it aimed properly at the tympanum. And frequently what you're getting is you're getting sort of a mixture of tympanic plus ear canal temperature.

    29. AHAndrew Huberman1:15:02

        And the, and for those listening and for those watching, the tympanic is not gonna be the pinna, the, this part of the ear, the outer part of the ear. The tympanic is gonna be near the tym-

    30. CHCraig Heller1:15:10

        All-
24. 1:17:35 – 1:19:55

    Cooling-Enhanced Performance Is Permanent

    1. AHAndrew Huberman1:17:35

       I realize there was a question that I failed to ask earlier, um, that is y- burning in my mind now, and I think is likely burning in the minds of, of some of the listeners which is, so y- if you do this cooling in between sets in the gym-

    2. CHCraig Heller1:17:49

       Mm-hmm.

    3. AHAndrew Huberman1:17:49

       ... you get this performance enhancing effect.

    4. CHCraig Heller1:17:51

       Mm-hmm.

    5. AHAndrew Huberman1:17:52

       You don't get the delayed onset muscle soreness-

    6. CHCraig Heller1:17:55

       Mm-hmm.

    7. AHAndrew Huberman1:17:55

       ... which is great.

    8. CHCraig Heller1:17:56

       Mm-hmm.

    9. AHAndrew Huberman1:17:56

       So presumably, the body is adapting.

    10. CHCraig Heller1:17:59

        Mm-hmm.

    11. AHAndrew Huberman1:17:59

        You're getting better as a consequence-

    12. CHCraig Heller1:18:00

        Yep, yep.

    13. AHAndrew Huberman1:18:00

        ... of being able to do more work per unit time-

    14. CHCraig Heller1:18:03

        Yep, yep.

    15. AHAndrew Huberman1:18:03

        ... or to go harder in some way-

    16. CHCraig Heller1:18:05

        Right.

    17. AHAndrew Huberman1:18:05

        ... of course. Um, you get that adaptation, does that mean that you see a performance enhancing effect even when you don't cool if you've previously done the cooling workouts?

    18. CHCraig Heller1:18:17

        Yes.

    19. AHAndrew Huberman1:18:17

        So for instance, let's say I can do 10 sets of 10 dips which I, I like to think I can. (laughs) Maybe I need to go try. I don't know if I've done that recently. I do the cooling. I, I cool for three minutes between sets. And let's say I, uh, get to the point where I can do, you know, 20 for 10 sets, n- um, 10 sets of 20 repetitions, and then I don't cool.

    20. CHCraig Heller1:18:37

        Mm-hmm.

    21. AHAndrew Huberman1:18:38

        Will I be able to m- match or approximate my new better performance?

    22. CHCraig Heller1:18:42

        You keep your gains. It's a true conditioning effect. You respond to the increased work volume by all of those mec- mechanisms you mentioned.

    23. AHAndrew Huberman1:18:52

        Amazing.

    24. CHCraig Heller1:18:52

        You increase the number of contractile elements in your muscles.

    25. AHAndrew Huberman1:18:56

        Amazing.

    26. CHCraig Heller1:18:56

        Your muscles get bigger.

    27. AHAndrew Huberman1:18:57

        Amazing.

    28. CHCraig Heller1:18:58

        Uh, we had an experiment that involved some of our, uh, uh, female, uh, students, not athletes, but just regular, they were freshmen actually, and, uh, the experiment was, uh, 10 sets of push-ups to muscle failure with or without cooling.

    29. AHAndrew Huberman1:19:15

        Same regimen, three minutes of r- of cooling in between sets of push-ups?

    30. CHCraig Heller1:19:18

        Right.
25. 1:19:55 – 1:24:00

    Anabolic Steroids versus Palmer Cooling

    1. AHAndrew Huberman1:19:55

       problem to have. Good problem to have. Um, let's talk about steroids, anabolic steroids. Um, we're heading into an Olympics.

    2. CHCraig Heller1:20:04

       Mm-hmm.

    3. AHAndrew Huberman1:20:04

       Um, every time the Olympics rolls around, you hear about these cases of people getting popped, as they call it, or caught for anabolic steroids. There are some accusations out there now. There will be more. They'll, this will get, um, you know, handled in the press and in the various organizations. Clearly, athletes and non-athletes use anabolic steroids, and typically, anabolic steroids are of the testosterone variety. There are derivatives, et cetera, and those derivatives do different things and anabolic versus androgenic, et cetera, but typically, the idea is, at least as I understand it in talking to some of these individuals, um, is that they allow people to train more because they recover faster. They are able to synthesize more protein because they're basically getting a second puberty because as we all know, during puberty, there's a lot of growth of the body, um, and of course, there are a lot of negative effects of abuse of these things, and they are banned from, from various sports organizations, especially I should mention in combat sports, it's, this is especially concerning because in combat sports, a performance enhancement means that you can harm somebody more than you would be able to otherwise.

    4. CHCraig Heller1:21:19

       Mm-hmm.

    5. AHAndrew Huberman1:21:20

       As opposed to in other s- sorts of sports. Just to conceptualize it and, um, and I'm not taking a moral stance on any of this. I just want to ask you, when you compare palmar cooling to anabolic steroids in terms of gym performance, what do you see?

    6. CHCraig Heller1:21:38

       Well, we do not do research on steroids, (laughs) but there is a lot of research in the literature. Uh, a lot of that re- research in the strength conditioning, uh, magazines is not very scientific.

Episode duration: 1:51:35