Dr. Craig Heller: Using Temperature for Performance, Brain & Body Health | Huberman Lab Podcast #40

welcome to the hubermann lab podcast where we discuss science and science-based tools for everyday life i'm andrew hueberman 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 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 main clarity of what you see when there are shadows when you go into different types of indoor lighting and so on and a lot of glasses don't work well because you put them on and then you're in bright light and you can see fine but then you move into a shadow and then you have to take them off and they don't adjust or they don't adjust quickly enough with roka their 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of vitamin d3k2 there's now ample evidence that vitamin d3k2 is supportive of the immune system and a bunch of other biological functions and k2 has been shown to be important for cardiovascular health so again if you go to athletic greens.com huberman you'll get the athletic greens the five free travel packs and the year's supply of vitamin d3k2 and now for my discussion with dr craig heller great to have you here it's good to be here it's been a long time coming 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 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 could you just tell me a little bit about what happens when i get into a cold shower or an ice bath 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 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 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 going to feel different when you come out 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 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've acid constricted you're still going to lose heat okay so um so vasoconstriction the constriction of is it capillaries vessels and arteries all constrict or just one or two 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 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 do you think that's part of the reason why humans evolved this practice of shaking hands assessing each other's level of anxiety we all know that a limp handshake is pretty uh indicative of something and a firm handshake is indicative of something as is the crushing handshake for that matter right yeah i really don't know what the evolutionary origin of handshaking is other than to get your hand away from your weapon perhaps right a couple of questions before we get into these specialized uh vascular 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 by cold shower versus immersion in cold 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 can you explain what a boundary layer is yes if you 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 i see so if i were to get into a cold ice bath or a very cold uh body of water of some kind and stay still i'd likely feel warmer at least until i started you're not going to be losing as much heat i see right and then whenever you move around flail around then you're going to lose more heat got it yeah but i think getting back to your original 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 i see so could you say that um in a in a rough sense that a protocol that one might use if they're gonna head out for a long run even on a reasonably warm day not not super hot right or maybe it is super hot would be to take a cool shower before they go run would that be beneficial sure it'll take them longer to get to the sweat point and to heat up and what will that translate to in terms of a performance increase your well could increase your speed uh or it 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 uh i want to say pacers and regulators and no no pacers or forcers they will take that advantage and use it up as fast as they can so they will go faster but not necessarily farther 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 it could be a benefit uh i know our we're going to talk about our technology for cooling but 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 as you have greater scope for heat absorption interesting about how long uh would one need to take one of these showers or cold immersions before heading out for run 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 etc right it's not as long as you think it's minutes a couple minutes yeah 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 it you can if you're if you've warmed up and your temperature has risen by half a degree let's say it doesn't take more than a few minutes to extract that heat if you're vasodilated interesting and what about for the anaerobic athlete the strength right for the anaerobic athlete and let's say they're doing several several they're doing several sets uh and how many reps whatever they're doing um their core temperature is 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 so it's a local effect it's a local effect right so let's say for sake of today of 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 five or ten sets of ten uh so for those listening it would be um five sets of ten of five rep repetitions or ten sets of ten repetitions ten by ten five by five 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 hinges etc um but for instance the the biceps are not they're involved but more or less indirectly right so the effect is going to be to heat up the quadriceps heat up the hamstrings heat up the glutes this kind of thing right i see and then during rest that heat will leave the muscle 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 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 so um this is a probably an appropriate time to just mention briefly what the underlying mechanism of this is could you just 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 sure 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 percent 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 hypothermia 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 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 so failure could we say that muscle one one component of muscular failure is overheating of the muscle right locally right probably other things too right well if you yeah if you lack oxygen 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 interesting um i want 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 five sets of five with squats i hit muscular failure at a given weight 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 they're telling me they're they're they're not doing too much work it's only indirect work so why is it that i can't set this 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 not having done anything prior 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 so temperature in both cases is the limiting factor it's one limiting factor it's one limiting i find that amazing i find that amazing because 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 it's naive for me to think that because if i wait three minutes and go back i can do those repetitions again so the glycogen wasn't restored in that three minutes right obviously it was there right so i realized there might be other mechanisms involved sounds like heat is if not the dominant mechanism that prevents more work it's one of them it's one of them and it's a quick one it's a fast one so it can happen with let's say you are a really experienced weight lifter okay you may be doing very very high weights with sets of five or six yeah to be clear for the audience i'm not doing very high weights for the sense of fun i'm not particularly strong i'm not 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 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 the muscles underneath 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 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 sure specialized surfaces on the the hands the feet and the face so if 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 sure you can do that but you can calculate how much heat that can absorb and you can't continue drinking liters of ice water you're going to dilute your your blood and have other problems but yes it'll help sure it will help but it is not doesn't have the the full capacity you will need what about an ice pack to the back of my neck or to my head or 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 last night yep 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 neck's um before and between and after events and um how good is that or how poor is that as a strategy since now we know that being overheated locally and systemically throughout the body is is a serious limiting factor on performance 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 do we know the specific site yes yes it's called the pre-optic 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 have input where does that input come from it comes from our overall body surface where we sense temperature 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 no it's 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 is going up well i think this is such an important point first of all i i was weaned in a laboratory where there were always battles over the temperature in the lab so people were always putting ice packs on thermostats or putting fans towards thermostats and trying to play this game good to know we were all being foolish um even though we were neurobiologists um putting a coal towel over my torso or putting ice on the back of my upper back you're saying could actually heat up my core 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 porter's portals for heat loss as our air conditioners okay the thermostats 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 it 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 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 cooled the thermostat this is an important point and there's a lot of um interest nowadays and people doing marathons and there are even some people do these ultras ultra running which i guess is everything longer than a marathon and go and go last man standing uh last man last woman standing kind of things so you're saying that if somebody's hyperthermic they could trick themselves into subjectively thinking that they are cooling off by putting a quartal and then they can go further but their brain could cook well if they stop the cooling then that hot blood from the body core is going to go to the brain interesting well many um it's a bit of a of a tangent but many people report after long bouts of exercise 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 it's certainly possible because we know that a rising temperature decreases cognitive capacity i mean you can experience that yourself you can get on a treadmill 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 how long you've been on the treadmill so that the phrase cool calm and collected is a whole common connection that's the goal in in all pursuits that's right so um i want to talk about these portals yeah because 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 in the pre-optic area of the hypothalamus which is interesting to me the pre the medial pre-optic area is also one that's known to be um sexually dimorphic dependent on testosterone exposure early in life etc although um people should just note that it's not actually testosterone that creates these sexual dimorphisms these differences it's actually testosterone converted into estrogen um it's actually estrogen is the effector 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 pre-optic area is there a map of our body in the pre-optic area because 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 probably a pretty crude map but that you need a complete map of the body surface there well you don't need a complete map in the hypothalamus i mean that thermal afferent information that you mention 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 so it's sort of an average of what's happening so if i were to let's say i get hot on a hot day and uh popsicles when we were in summer camp yeah i went to a sports camp near here actually and we'd run around like crazy and then we'd get into the shade if we could but we were you know popsicles or the kids were putting ice cubes down each other's 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 cold cubes or in the hands as you said it feels really good it feels good yeah but it sounds like it it feels deceptively good because in reality it could still be quite warm internally absolutely yeah interesting yeah you can feel great and have a dangerously hypothermic temperature but i should say that when you get into the danger zone things get bad fast what are some of the symptoms that people could be on the lookout for for hyperthermia essentially it's it's almost ironic that if individuals are trans transitioning into heat stroke they actually vasoconstrict and they stop sweating and that's a pathological situation i i couldn't begin to explain it but essentially you are just feeling exhausted you're feeling miserable uh the heart rate is very high your heart rate goes up as your core temperature goes up called cardiac drift so you just feel rotten but that's why since since it's not an and it's not a danger signal that you can translate immediately into nope i'm going into heat stroke 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 heat stroke that were during practice not in competition when people you know are really trying to do it but in practice which shows they were just motivated to push so let's talk about these magnificent portals yeah that not just humans but other animals mammals are equipped with 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 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 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 surfaces of the ears for bears and at the tongue bears have big tongues huge dunks i didn't know that either i've been that close to a marriott i've had a licking match with a bear not yet okay so anyway um our 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 is it is it fair to say that um what i was taught is that blood flows fl from arteries then to capillaries and then to veins and back to the heart 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 is that is that generally yeah absolutely so what i learned in basic physiology is still it's still i wouldn't i wouldn't get an f in your class no okay maybe a d or c but not enough um so that's excellent okay and so you're saying that in this glabrous or beneath the glabrous skin there are these shunts and those go directly from arteries to veins so you skip the the capillaries yeah and is it actually as long as i as i um say that in the skin you know when i feel the pads in my hands um how deep to the surface do these to these vessels residing they're below the obviously the sure the the the epidermis uh so so if you are warm and you look at your palms your hands they are fairly red the backs of your hands aren't you don't have these vessels in the backs of your hands now if you take a glass like a water tumbler right and you grab it you can see if you squeeze a little bit the hand goes white that's because you've shut off that blood flow oh interesting i'm going to do that little homework so if you're bicycling on a hot day you don't want to be grabbing your handlebars all the time you want to periodically well this is important i know you um you're privy to some really amazing results that we're going to talk about but i actually heard you say this during this lecture recently uh that stanford held about human performance that we were both part of and you mentioned this that if you're cycling and you're working hard and you want to be able to do more work it we now know why you want to remain cool in order to continue to do work and if you get too warm that's bad that gripping the handlebars too tightly will actually limit your performance right and that's probably also true on the peloton or any other kind of device or the skier or anything like that right so loosen the grip or if you safely can you want to actually expose your hands right to the world now what about for people wearing gloves what about the to me that just seems crazy based on everything you're telling me well gloves definitely impede heat loss uh from the hands just as socks impede heat loss from the feet okay so if you want to maximize your heat loss you want to have as thinner protectors as possible on your hands and of course the feet are more problematical because you have to be using them in certain ways some people run barefoot yeah well yeah yeah that's that's become somewhat popular it seems like it kind of came and went they had those toe shoes things but they looked so ridiculous that i think most people just were willing to take the performance hindrance of regular shoes actually we had a track coach here at stanford who for a while was famous for introducing uh training without shoes running and he thought it was because it changed the posture of the runner and i think it was just due to the fact that he was increasing the capacity of his runners to lose heat interesting yeah so heating up at the level of the hands obviously is going to hinder performance so if i can how about with running i noticed um i ran across the country briefly in high school and and not particularly well at that but that we were told to run as if we were holding you know crackers in our in our fingers or something like very lightly and to keep hands kind of loose so running like this would actually be more beneficial performance than oh then which is probably what most people are doing nowadays right right interesting and um i once i'll tell you an experience i had once i was in alaska in the winter and i went out running and i absent-mindedly forgot gloves and i realized this after a short period running because the backs of my hands were aching from the cold the palms of my hands were sweating and were hot oh amazing amazing so these compartments are a real thing and you mentioned the upper half of the face that's where our primate ancestors don't have fur and the bottoms of our feet so um let's just take a moment talk about some of the more amazing results that have been associated with proper cooling of these glabrous skin surfaces let me introduce one more thing sure because you asked earlier about the pouring of water on the head 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 uh blocking on the name now take your time these are blood vessels they go through the skull okay and that's why the scalp bleeds a lot if you cut 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 these blood vessels were primarily thought to be ways that blood is leaving the brain but when you're overheated the direction of flow in those blood vessels reverses so the cool 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 pouring water on on your head interesting so that practice which we at least for me i most commonly associate with um combat sports where someone the fighter goes to their corner they usually sit down on a 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 squeeze a glove excuse me a sponge full of cold water over them or um that you're saying is somewhat effective in cooling the brain yeah it's one of the natural mechanisms for cooling the brain 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 coal on the back in 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 um i just can't comment on that i'm aware of those ideas but they're controversial one of the things that you want to do for injury to the brain is to decrease swelling and one of the ways that you decrease swelling in many parts of the body is too cool it decreases inflammation it decreases the blood flow 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 yeah um interesting okay so i hear these stories and i've seen the data so i believe the stories maybe tell us a story about an observation that your group has made with respect to anaerobic exercise and and this prop and proper uh cooling of the these glabrous surfaces and we can talk about the technology um maybe give us the dips example first of course you know i think most people are familiar with dips you're supposed to i guess get raise and lower your raising 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 right um one dip would not be particularly impressive for most people a hundred would be very impressive um 20 would be impressive for some etc what happens when a skilled athlete comes in and does dips for multiple sets and then what happens when they cool properly using the glabrous skin surfaces 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 the word got over i think to the 49ers camp and one of their players greg clark who was a tight end at the time he had been tight end at stanford he decided or i don't know if he was asked or what uh to come over and check it out so greg came over and we said greg what are you good at what what activity do you like to do he said dips i can do a lot of dips 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 do you recall roughly what kind of rest periods he was taking between yeah we ins we we standardized the rest period to three minutes because that's what we had set on for cooling as the internet that's a good long rest period yeah it is still a lot of dips i got it yeah it's actually a longer rest period than many uh people would prefer during workouts they want to make them not me i prefer to take as much stress as i possibly can yeah so several days later he came back and uh his first set he did i think maybe 42 a little bit better but now people were standing around watching so there was a little impetus there to show off uh so then his second 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 okay so he does when is he doing the cooling he's he's sitting down and putting his hands in the devices that we had built which were cooling the palms of his hands for how long does that cooling take can you do it inside of a three-minute rest period yeah that's what we were doing we standardized the the interval for resting or cooling uh to three minutes okay but the the point is he got to his fifth set and he's and all of the sets were above what he had done on the previous day and he said you know i'm not tired i can do another set and then i can do another set i can do another set i can do another set so from one day to two or three days later with cooling he doubled the total work volume he doubled the total number of dips by adding more sets and more repetitions to each set right so then he kept coming back for four more weeks twice a week and by the end of that month uh he was doing 300 dips wow so what percentage he tripled he tripled and so here's here's a professional athlete at peak physical conditioning and he triples what he can do amazing 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 etc right but if we do more work we essentially scale up the amount of recovery that's needed or the recovery time i'm very curious about whether or not he needed longer to recover between these super performing workouts 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 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 interesting and we've actually demonstrated that with a naive group we had a class a physical conditioning class and we had half of them 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 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 cool didn't have significant muscle soreness amazing and i know there are also published results and 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 in a bench press or push-ups or other other sorts of things maybe you could give us an example from the realm of endurance work or or aerobic work uh running cycling things of that sort 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 but you're not gonna run but you're not gonna run with it right or equip a bicycle with it although when are the cooling handles on bicycles coming 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 their that people really heat up that much in golf they do not to be disparaging of the golfers but the way i 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 well we what one time we had we were doing work for the uh for the 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 special ops soldiers to be our subjects and test it out they were here for a week so they that was a fun week yeah they're i do some work with those guys they're they're hard driving guys they also know how to have fun right there yeah they they definitely have um if they have an off or a quit switch it's buried deep within their nervous system they don't like to hit that that quit switch so the guy who wrote the final report he gave an addendum to the report he said well i'll tell you this after i've gotten home it's added that technology they took the technology with them they wanted to yeah that sounds about right and using it it has added 20 yards to every club in my bag and that's no effing small so it's allowing people to hit further hit the golf ball further right interesting um all right so for the for the uh golf um players out there and the um it then uh that's the um that's a reward you get back from craig for all my my little knocks on golf i actually i i don't have any knock on golf i just don't think about it as a sport where heating up is a limiting factor so well since they're getting more more out of their drive what what do you think is going on there well they can be heating up uh and there were specialties right there one hot day 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 i didn't know 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 just essentially put the device on their golf cart and they're back out playing golf in the middle of the summer oh that's great yeah that's great it does anything that allows people to have normal levels right 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 or functional is great so um what's your favorite example of endurance and feel free to give us the extreme one and then we'll talk about averages to be you know make sure we're thorough about averages versus exceptions right we haven't done a lot in the field i mean outdoors uh most of our endurance has been in 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 and 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 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 right with proper cooling when are they doing the cooling they're they're doing it continuously i see because in the laboratory we can suspend devices from the ceiling for example now we do have prototype wearable devices we did them uh in response to emails from ebola workers a number of years ago in 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 challenge of developing wearable systems that could go under the ppe uh we've published that work now but that's great i'm guessing the military special operators that are out in the desert and other locations are probably excited about this technology well once they get it once they get it it's coming it's coming 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 why haven't we heard more about it and i i will ask your opinion on that as well but i'll just editorialize a little bit that you the the best laboratory work and its practical applications oftentimes requires many studies and oftentimes there isn't a portal so to speak to get that information out into the technology sector see there is a company that's developing this technology for people to use right to purchase and use um right 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 right and and is there a poor man's version of it as well well the company's arteria a-r-t-e-r-i-a and the website is www.coolmit.com so coolmit is just c-o-o-l-m-i-t-t 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 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 there's uh college teams there's olympics there's the navy seals major league baseball the nba 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 great and so forth so that's that's where we are but uh on the website you can actually sign up for being one who will be able to get one when they are finally manufactured they're now being made in fairly small lots because you want to change things so you realize how it can be improved 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 that the perfectionist mindset is 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 that the cool mid as i understand is it's a it's a mitt it's a glove you put your hand into you you hold on to a surface and that surface um cools you cools your hand and thereby through this uh specialized um portal cools your core body temperature and 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 just cool i see 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 so you stick your hand in cold water and when it comes out it's cold you just sealed up all the heat yeah right so what i sort of recommended to someone at one point they said well when i'm running can 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 it might work well i have a feeling that there are people now doing that as well as trying trying this so um how long in the cool mid at the proper temperature um how long are are people putting their hands into the mitt we once again had just standardized on three minutes and part of the reason for that is that the heat law the rate of heat loss is an exponentially declining curve okay and three minutes sort of gets the best part of the curve so you can go longer and get more benefit but the biggest bang for the buck is in the first two three minutes okay you mentioned a number of impressive organization sports teams in military that are using this this is not something that i typically see on the sidelines of games although to be honest i haven't looked very carefully um i'm guessing that they are probably keeping the technology somewhat under wraps uh where and how are they doing this are they running back to the locker room i mean the military special operators are doing their thing but in terms of the athletes um is it possible hypothetically that athletes are doing this um somewhat incognito it's possible but i really don't know people have mentioned here at stanford they don't see the football team using it well the football team here at stanford is mostly playing in cold weather cool weather night games are cool even date games are not very hot frequently here but when they go to a hot place like arizona or utah at least our coach shaw says that they take it with them and that's when they find the benefit that's when they use it 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 package of frozen blueberries i'm just kind of passing it back and forth between my hands now talking to you i realized 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 absolutely but um i realized 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 well that you know it's would be experimental sure yeah none of that is kind of very controlled your idea of frozen peas is a good idea and i think since there's been no actual study of that you 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 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've as a constricted if it's warm it means the hot blood is still going there okay so we do that in the lab and the key is for it to not vasoconstrict right 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 cool mit is available more broadly um to the general public you could assess you want to assess whether or not the your palms actually feel cool to the touch by somebody else to us and if it does that means you you've essentially shut down the portal you're sealing in more heat which is bad what about um putting this cold pack of some sort on the face or um or the feet more 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 and without shoes and squatting without without any shoes or socks on could i put my feet on them you you could um if you had simply had a water perfused pad and you were circulating cool water through it you could just put your feet on it okay part of the problem is that you don't want if let's say you have just a cold pack 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 so that decreases its its efficacy i see 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 you're getting radiation you're getting radiation right okay right 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 convection sure is is in a cool breeze yeah with the wind chill factor that's due to convection okay but in terms of heat transfer between two objects 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 right so this is why just planting my feet on two um packages of throat my bare feet on two packages of frozen peas there's really no opportunity for circulation right of and therefore heat transfer so it's not really optimal which is i and i but once again it depends on the surface area to get any benefit at all we have a study that we published which was investigating the standard treatment for hyperthermia in the field and the standard treatment the the that's recommended by medical organizations is you take cold packs and you put them in the axilla the groin the axel are the are they are the armpits the armpits yeah the groin which is uh uh thin skin lots of acid glitter right and the and the neck so what we did is we did studies in which we made people hypothermic and then we measured the rate at which we could cool them by putting those positions in the those heat exchange bags in the recommended location versus on the glamorous skin versus palm soles and face the the cooling rate was double wow so we put the same ice packs the same cold packs on the uh heat portals rather than uh the axilla the groin in the face wow for the neck wow so face hands and bottoms of feet will cool you twice as fast as putting cold packs into your armpits your groin or back of neck so so i like to give the analogy of if your car is overheating okay and you have a hose a garden hose where should you spray your cooling system should you spray the radiator or should you spray the tubes going in and out of the radiator well the rationale with putting these cold packs in the axle of the groin in the neck is that you're getting close to the major arteries sure that's going to be effective but it's much more effective if you actually increase the heat loss capacity of the radiating surface the radiators so you cool the hot stuff heading toward the core that that's essentially what the standard operating procedure is the that you hit the arteries amazing and the veins the arteries and veins i'm going to just tell a brief story that um illustrates how almost everybody gets this stuff wrong and i'm gonna 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 incidentally a guy who did nine years in the seal teams 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 stay warm enough in the cold pacific no wetsuits we do the morning cold swim for about a mile or so and we brought with us 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 inside right 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 hypothermic 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 is taking on that consistency that's clear like he's hypothermic we go to the lifeguard station lifeguard says okay let's get his vitals let's do all this meanwhile try and stand next to him you know 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 he 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 gonna let him swim with us again um if if i ever 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 similar situation well it's interesting you asked that because that is the way we got into this area of investigation i worked on how the hypothalamus regulates body temperature neurophysiology and one day we were having a discussion with a colleague in the department of anesthesia and uh 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 in heat lamps uh and it takes them an hour or two hours to get these patients to stop shivering to bring them back up 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 environment wrapped in a heating pad and a negative pressure you know suction 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 couldn't get such a device into the hospital these days but we were with our anesthesiologist friend we took it into the recovery room and and first thing the patient said no way 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 eight or nine minutes is this now standard practice hospitals no no so this is another example where i i don't get upset about the 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 right and i mean we could we that's a whole other discussion as to what the limitations are well perhaps in i know a number of our listeners are in the healthcare and medical profession as well as military athletes and just also standard other types of jobs civilians of 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 home-grown technology that people could use if somebody's hypothermic what is going to be the best way for them to warm up is it gonna be holding a nice warm uh mug of cocoa or something like that but not not too hot i guess is that again the idea yeah well actually you can go hotter on the on the glabrous skin there oh because it'll dilate because it takes the heat away faster okay but back to the anesthesia what you can do is you can use uh warm pads they have them in all hospitals they have circulating water perfused pads hot water bottles put them on the feet so typically they'll slide them under your lower back or something like that put them and put them on the feet okay sure that that will do it but uh it turns out that we discovered through this work that it had nothing to do with the whole arm it was only the hand and that's when we came to the realization of these special blood vessels we didn't discover the blood vessels they're described in grey's anatomy but nobody knew what they were for and you mentioned bears earlier and other hairy animals um do they have these avas oh yeah as well oh and i suppose we haven't defined avas we've been pretty good about the no acronyms real avias is arteria venus anastomoses so a connection between the arteries and the veins yeah i actually use this technology i have a bulldog bulldog mastiff he has a very high um propensity for overheating because they they're terrible at dumping heat and bulldogs are great at pushing themselves to the point of exhaustion or death it happens and so now we do what we call palmer cooling sorry i couldn't help myself where i'll take costello and lower him into a cool body of water just just the bottoms of his paws although i think animals instinctually know to do this and will go and stand in bodies of water they don't often lie down all the way some do yeah um but they seem to know that's a great way to cool themselves off yeah oh absolutely yeah and they get the advantage that they're pop that their palms and their feet are essentially the same thing we actually built devices for dogs did you really and tried them on i did a rod sled dogs and it worked beautifully they had little backpacks with the equipment and pads on all their feet and and uh it worked beautifully amazing amazing along the lines of heating deliberate heating wearing a knit um cap is something that you see more of that on the east coast you know people run around boston and new england 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 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 yeah because warming up is important too you know there's a certain amount of quote unquote warming up that's required to lubricate joints or at least to get the sense that joints are lubricated and to be able to move more easily yeah do you still recommend that people warm up yeah but i think we're misled by the term warm up as if the major purpose is to raise temperature i don't i'm not aware of any data on this but i i do think that the major contribution is increasing flexibility so you're going to avoid having damage of joints and and tendons and ligaments and so forth but also 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 is 37 degrees but that's not true yeah it varies across the day it's 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 so that raises an interesting question what is the best way to measure core body temperature well the best core temperature is that what we use is a savage gel so we put a thermocouple up the nose about two feet down the esophagus so that it's about the level of your heart not gym or home practical although i know i don't know some of those coveted swab tests go pretty far i can't even imagine going any further i felt like my brain was getting tickled um tympanic is a pretty good so the ear the year yeah 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 dympanic plus ear canal temperature and the and for those listening and for those watching the tympanic is not going to be the pinna that this part of the ear the outer part of the tympanic is going to be near the top headed towards the tympanic membrane and yes i'm sticking my finger in my ear because that's where the laser would actually have to go to measure your temperature right so when we're walking into restaurants and other places nowadays and they're shining the laser at our forehead that's probably giving a pretty crude readout of temperature it is but there's much less insulation between your brain and your forehead skin than there is between your biceps and your arm skin so if you're going to measure a surface temperature that's where you would do it and uh we do temperatures in the infrared we we take infrared videos of athletes and and our our subjects and of course the face lights up okay so if we're not i imagine there's going to be a technology coming soon where you can point your um smart watch or your smartphone or yourself and you're going to get a heat map right right that's got it if somebody out there hasn't already invented this for the typical folks outside military somebody please invent that because i think there's growing interest in temperature based on the work that you're doing and also for sake of something i do want to touch on which is sleep and metabolism although we don't want to open up those portals all the way because we'd need uh several days to cover it um okay so putting on the the cap um what about some of the helmets and gloves that are used in typical sports do you think that those can be improved in order to improve performance in terms of their ventilation ability or keeping palmer surfaces um open for instance well you mentioned about the the knit cap in cold weather especially and that is significant because you do lose a lot of heat from your head but it's a constant heat loss it's not variable like your glamorous skin so if you decrease that heat loss you're going to be warmer so sure that that that has an impact now in terms of helmets they should be ventilated i mean they should have enough space in them and holes in them so that air can circulate you don't want to insulate thermally insulate your your scalp that's going to decrease heat loss quite considerably you know just for a resting individual the brain is about 20 percent of your metabolism so that's that's a lot of heat production yeah absolutely um i realized there was a question that i failed to ask earlier um that is it burning in my mind now and i think is likely burning in the minds of of some of the listeners which is so you if you do this cooling in between sets in the gym you get this performance enhancing effect you don't get the delayed onset muscle soreness which is great so presumably the body is adapting you're getting better as a consequence of being able to do more work per unit time or to go harder in some way 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 so for instance let's say i can do 10 sets of 10 dips which i like to think i can maybe i need to go try i don't know if i've done that recently i do the cooling 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 10 sets of 20 repetitions and then i don't cool will i be able to match or approximate my new better performance you keep your gains it's a true conditioning effect you respond to the increased work volume by all of those mechanisms you mentioned amazing you increase the number of contractual elements in your muscles muscles get bigger amazing uh we had an experiment that involved some of our uh female 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 same regimen three minutes of of cooling in between sets of push-ups right some of those young ladies reached over 800 push-ups now the total duration of the workout could be getting much longer as a consequence of doing more work no it doesn't take you longer well minor i mean a push-up is pretty fast yes pretty fast yeah so you do 10 sets the maximum and 45 minutes total that's a lot of push-ups that's a lot of push-ups yeah and so the interesting thing is they came in one day and they said dr heller you cost us a lot of money why well we had a formal dance this weekend we all had to buy new sleeveless dresses nice it's a good problem to have good problem to have um let's talk about steroids anabolic steroids um we're heading into an olympics 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 then the various organizations clearly athletes and non-athletes use anabolic steroids and typically anabolic steroids are of the testosterone variety there are derivatives etc and those derivatives do different things and anabolic versus androgenic etc 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 is especially concerning because in combat sports a performance enhancement means that you can harm somebody more than you would be able to otherwise as opposed to in other 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 palmer cooling to anabolic steroids in terms of gym performance what do you see well we do not do research on steroids but there is a lot of research in the literature a lot of that was research in the strength conditioning uh magazines is not very scientific no okay or it might not even be scientific at all right right but we did do an analysis of reputable papers and we did find uh i think it was probably eight or nine ten studies on bench press uh increase in bench press performance on steroids or not okay a lot of males or females well these were all males but i'll get back to the females okay the bottom line is that in all of these independent studies their rate of improvement was approximately one percent per week okay okay now i've just told you about studies in which we've had 300 percent increase in a month uh and so it's an enormous enormous difference so so why would you endanger your health as well as your legal ability to compete with such an ineffective tool yeah no i i think it's the the notion of performance enhancement is is a really interesting one because people clearly pay attention to nutrition sleep is now something that i think everybody but especially athletes are paying attention to right um and i predict that temperature will be one of the more um powerful uh parameters that people are going to be focusing on yeah because because of the magnitude of the effects that you're describing and and also because so much of the variability around performance as you mentioned has to do with when you go to a new environment you know everyone has their home environment worked out pretty well sleep well in your own bed at home you when you can control everything your performance is always great this is why i think military special operators are particularly interesting group because their whole world is centered around elite and high performance at with very high risk high consequence under variable conditions the essence of their work is variable unpredictable conditions so um you mentioned female athletes and steroids i'm curious about this yeah because everybody has always said to us well you only use male subjects and obviously they have this testosterone background you know they have higher levels of testosterone that's why you get these results so we did a comparative study on females we get the same results impressive and these are our stanford athletes or also no these were not stanford they were stanford students but not athletes well we we have done of course work on some athletes but in general we don't do research on our teams our varsity teams so they have their own protocols they have their own training programs that they don't like us to i work with some of these folks and the coaches and they're very skeptical with good reason also and the reason i ask is that uh i when you see these um pac-10 or or division one college athletes and then you see their peers there's there's clearly a uh a difference right i mean they they are pedigreed that throughout right um and more typical folks uh also have different goals they may not want to get infinitely stronger or perform more endurance work so i want to ask you a couple of things about shivering and metabolism because i think they're very interesting and um sufficiently related so my understanding is that shiver is an adaptation that's designed to heat us up yes uh that we have brown fat that's in compartments around our body that are activated by shiver or co-activated by shiver and that shivering is useful for increasing metabolism is that true and does it require that cold be the stimulus so two scenarios i'll give you an experiment i put someone into cold water of some sort and then i make them get out or i have them stand near it and then they start shivering my understanding is that their their metabolism will increase what if i take someone and i just have them shiver but they're not exposed by coal it's kind of a deliberate shivering will that also create a substantial increase in metabolism sure so deliberate shivering without cold is essentially what happens when you get a fever your set point goes up in your hypothalamus and you actually even know your normal body temperature your thermostat is telling you you're too cold increase your metabolism so shiver so sure shivering is uh is a good way of increasing metabolism but it only can take metabolism up maybe three or four times resting okay whereas exercise can take you up you know ten times got it all right i'm gonna ask a couple of more random questions and um seemingly random do bears actually hibernate oh yeah the true hibernation well it depends on how you define true uh a bear actually we've done a lot of work on bears we we've do you also put the nose thermocouple down in the esophagus oh we implant them surgically okay they're anesthetized when you implant them yes what kind of bears are these black bears okay and did this with colleagues at university of alaska and we're analyzing the data now but what we've done is we've we've had now a total of 18 bears and we implant them with eeg ekg temperature sensors and sometimes we actually measure their oxygen consumption these are bears in the wild these are bears in the wild but they're brought in to university of alaska where we keep them in an outdoor enclosure so they're hibernating in a nest box in a enclosure and we're recording this electrophysiological data continuously for six months amazing how do i get on this protocol craig and i are doing some work together going forward and uh maybe you can slide me onto this protocol too right sounds amazing right now it's a matter of just analyzing the gigabytes terabytes of data that have been collected so but anyway you asked about hibernation so bears only go down to about 33 34 degrees centigrade and core temperature and that's been argued that well they can't go lower because they have so much insulation they're so big their surface volume ratio and so forth and that's not true they shiver so if if we have a day like minus 40 which you get up in in alaska they will go through periods of shivering uh and maintain a core temperature on 33 34. now the ground squirrels and the marmots which are small smaller animals they will drop down to a body temperature maybe within a degree of the environment so they can go down to one or two degrees centigrade just above freezing during bouts of hibernation so they'll stay in hibernation for seven or eight days and they'll come back up to normal body temperature for a day then they'll go back down and what are they doing that day when they're warming up again do they rearrange their nests uh eat if they've stored food some species store lots of food others just depend on their fat a former mentor of mine my master's degree mentor and uh a colleague and friend of yours irving zucker at uc berkeley told me a story once told me a lot of stories tells great stories as you know he told me that when an animal comes out of hibernation periodically that it's a very dramatic thing to observe that it's not like they wake up and yawn and look around but it's like a like a complete epileptic seizure right what what's going on it's just a very dramatic shiver so at the low temperatures they cannot shiver because the effective temperature on the conduction of the of the nerves and the muscle fibers so they're shut down basically shut down so there they use brown fat so activate brown fat and then when they get up to a temperature of maybe 15 16 degrees centigrade then the shivering starts and it gets very very violent but they're still asleep do we shiver in our sleep i would imagine we do but it probably wakes us up interesting so the brown fat is kind of like kindling the brown fat is a tissue which has lots of stored energy because it's fat but unlike our weight fat our regular fat it also has lots of these little powerhouses mitochondria and lots of blood supply so essentially it is a tissue just to produce heat that's what it's there for now in these hibernators there are big patches of brown fat at certain locations that are critical like around the heart for example for us the brown fat is sort of distributed so for many many years it was thought humans don't have brown fat but indeed we do it's just not localized into discrete fat pads like it is in ground squirrels marmots i don't know why the phrase fat pads is so satisfying to say but it is fat pads um speaking of fat pads um i was taught that we have by the internet i should say i was taught by the internet that we have brown fat between our scapulae and our upper neck is is that truly a source of brown enrichment for brown fat if you're a ground squirrel so it's complete this is all the drawings out there okay so what i'm what i'm hearing you say is that brown fat is actually distributed in humans it's distributed uh along with other uh fat tissue it's it's not as discreet so the reason i'm i'm kind of shocked and amused and um uh troubled by this is because there is a somewhat standard protocol in the performance wellness whatever world whatever you want to call it of putting ice packs on the upper back as a way to stimulate brown fat thermogenesis i'm i'm hearing some some uh inhales of concern from from the physiologist so tell me why it sounds like that's probably not the best way to stimulate brown fat activation well let's put it this way you're not attacking anyone specifically because the whole world believes this so it does but it may not be totally um facial or false think of what that's doing if you put ice right there where your spinal cord is close to the surface that's where you're going to hit the vertebral arteries so you're essentially putting a cold source into the brain to the hypothalamus the hypothalamus says you're too uh cold so it is going to turn on shivering and brown fat so would there be a better site for sake of activating brown fat um polymer cooling uh you know i i can't say because the activation of brown fat is a sympathetic nervous system response so any lowering of core temperature that will let the thermostat say you're too cold is going to turn on sympathetic now people will have perhaps different amounts of brown fat so um newborn have more brown fat than adults because newborns can't shiver correct i don't know okay that's that's what i read i don't know i read that in what i believe to be credible sources yeah it could be i i just don't know it depends on if it's really newborn i can agree because you don't have all of the uh motor pathways connected up yet that's something that occurs in early days of life and it's probably one of the functions of rem sleep which infants have a lot of right okay but how to activate brown fat if you are consistently exposed to cold so if you live in the arctic and you go out jogging in the winter maybe that will increase the amount of brown fat you have if you live in the tropics maybe you have less brown i don't know i don't know of any studies which have looked into that okay ice headache sometimes i'll drink a cold beverage or all um eat ice cream and my head will brain freeze brain freeze and speaking of special forces i was talking to um you know we all see the images uh the seals seal training slash uh screening and coronado where they're going in and out of the pacific which is very cold but uh i know they also spend some time in the very cold waters of kodiak alaska you mentioned alaska brain freeze so-called ice headache is um a common occurrence there uh in those situations but we all have experienced this we i scream we get that brain freeze i can feel it right now a little bit subjectively i can induce it uh what's going on there and um i would always just rub my tongue on the roof of my mouth is there something that i'm doing that's uh functional there just to try and alleviate it a good question the thing is that the roof of your mouth is very close to your hypothalamus so if indeed it's a popsicle that's giving you the brain freeze it may be a direct cooling effect from the roof of your mouth you put your tongue there you're insulating the roof of your mouth i don't know i'm guessing but what's it but the so what's the source of the brain freeze is it a vasoconstriction it's a it's it's a vasomotor change whether it's constriction i think it's more likely a vaso an increase in blood pressure which will essentially cause an expansion of the arteries and activate pain receptors we don't have pain receptors in the neural tissue in the brain we have them in the meninges and predominantly associated with the blood vessels the walls of the blood vessels so if you have something which will dramatically increase your blood pressure going to the brain you're likely to get a we've had some preliminary data i even hate to mention this because we have not been able to pursue it systematically but we've had some experience with people with migraine that say if they use one of our devoi devices to heat that the migraine goes away and uh i don't know it's a very injury a lot of people suffer from migraine i know there are a lot of different types of migraine right been reading a lot about this lately because i get so many questions about migraine um but i hate to say anything sure and we'll just underscore this as preliminary and people are have been great about um understanding that when we say preliminary we mean has not passed through the the um required filters to call it um hard fact yeah we don't we don't even have a decent data set right it's just this these are anecdotal reports anecdotally but i don't even like to call it that because then if you we don't want to give it more weight than it deserves but that's interesting um the ice headache and the increase in blood pressure is interesting because the only thing that i've heard is similar to it is something that um comes from you know they have these competitions where people eat these very hot chili peppers you know it's kind of a yeah an ego thing i guess um for reasons that that escaped me that eating really hot peppers and every once in a while some will eat one of these and get what's called thunderclap headache where a headache comes on extremely quickly and so quickly that it's caused it's so severe rather that it's been known to cause stroke and brain damage so these very very very hot peppers if you're not acclimated to them and maybe even if you are have been shown to cause actually cause brain damage yeah some good evidence for this um i do want to talk about um something that we have not touched on yet which is meat non-exercise induced thermogenesis right the um so non-activity-associated thermogenesis and the fidgeters right so the classic work of like rothwell in stock and the idea that some people who overeat are burning off that energy by way of shaking their knee or moving around a lot these are the kind of they quote you know they're quote unquote nervous types but um they quoted in those studies a huge degree of caloric burn you know 800 2500 calories per day burned above those who sit rather still does that seem far-fetched those are older data but any any comment on neat or non exercise induced thermogenesis well i do think it's a pretty straightforward that if you increase muscle activity of any kind you're increasing your energy consumption and your heat production and no the the really extreme example is hyper and hypothyroidism uh people that are hyperthyroid or fidgety and you know they have very metabolic rate and they're hot and people that are hypothermic are cool they're not they don't move very much so any kind of muscle activity increases and when you say you know it's not much activity but remember it's only 20 percent effective 80 percent of the energy is going to heat so it may not exert much energy to tap your foot but four times the amount of energy that is going into the movement is being lost as heat that's very interesting a couple more quick questions there's a lot of excitement these days or at least usage these days of so-called energy drinks or pre-workout drinks many of these contain thermogenic compounds so caffeine things there's a culture now of taking um arginine things that support arginine so you know beet juice and uh citrulline things to dilate the blood vessels sometimes this is for sake of of increasing blood flow to the muscles during resistance exercise but a lot of these are thermogenic it's to increase body temperature and are so is it possible that some of these energy drinks are actually or similar you know six espresso or whatever it is are acting to prevent optimal performance or reduce performance i don't think that the the temperature rise is that i really don't know but what it does is it makes you more jittery and you're going to increase that neat that you were talking about or it's another thing and that is that when you are exercising your muscle and it becomes slightly hypoxic i mean it's the oxygen supply is is not enough the muscle releases adenosine and what adenosine does in the muscle is cause the blood vessels to open up to dilate so it's a way of increasing the blood flow to the muscle and therefore the oxygen supply to the muscle so caffeine in is an essentially an adenosine enzyme that's a venison antagonist right so it's so under the strict logic ingesting caffeine will reduce adenosine release and we will reduce oxygen utilization of the muscle right so that would lead me to believe that motivational support aside that caffeine will hinder muscular performance i would think so but i i i can't give you an authoritative answer on that okay we're just we're just um going through the yeah the logic and the gymnastics around that um i think it's a fascinating area that deserves attention because the question of what one can ingest in order to perform better to say nothing of you know hormone augmentation but uh has often leads back to stimulants yeah and if those stimulants most of which include caffeine of some sort are inhibiting the adenosine system and the adenosine system is supporting the oxygenation of muscle then i would imagine that avoiding them might be the better option yeah i just i'm not aware of of data that would so this is a general phenomenon of adenosine and uh and blood flow it has of course a different effect in the brain adenosine causes sleep so caffeine keeps you awake and if you stay awake you're going to have a higher metabolic rate than if you uh go to sleep so and the thing is you say you know energy drinks the question is you know what really is is in them it's usually a cocktail of things um i don't take these i don't like them at all but they're usually a combination of vasodilators stimul caffeine some sort of stem and a source of glucose usually sometimes a source of glucose and sometimes not and oftentimes there are um there are vasodilators um and there are compounds that are thought to be so-called nootropics smart drugs that basically increase acetylcholine or norepinephrine transmission um you know in the in the 80s and 90s um the beta 3 agonists like clem buteral were very popular but they were all banned so those are all banned from from uh although people use them recreationally which i do not recommend uh there are actually a number of deaths due to dehydration overheating as well as cardiac effects um before we wrap up i i know you've done a ton of work on sleep i think we're gonna have to do another episode about your work on sleep because the amount of data that you produce there is vast actually so i first got to know you and your work um uh relate to sleep and temperature we all hear nowadays that it's good to keep the room that you sleep in cool keep it dark i've talked a number of times on podcast episodes about the role of light and shifting and circadian rhythms i have two questions related to sleep one is are there any things that may or may not relate to temperature but that you think are very useful for getting better sleep that you don't hear that much about um that people might want to consider or try realizing that there are a lot of reasons why people don't sleep great but what are some things that you don't hear that much about these days that you wish people knew well the sleep medicine community now puts a lot more emphasis on cognitive behavioral therapy than on pharmacology so what cognitive behavioral therapy does is it essentially increases your sleep hygiene so there are certain just general rules so have a regular bedtime and a regular arousal time don't be skipping back and forth all the time arousal you mean wake up time wake up time yeah spoken like a true physiology yeah um another thing is don't use screens uh within a couple hours of bedtime because screens are predominantly rich in blue light and what that does is you mention the circadian system that affects your circadian system that pushes off your circadian stimulus for sleep okay another thing is of course uh relax i mean don't work right up till the time you're going to bed take some time to do something relaxing and then temperature you you've mentioned that and for many people a warm bath you know is is really conducive to to to good sleep and people are now swearing by a cooler environment for sleep and that makes sense in terms of the circadian effect on body temperature so our circadian clock is affecting our thermostat so at the time we go to bed our thermostat is on its way down to a lower set point so what happens you go to bed and you're feeling a little bit cool so you pile on lots of blankets and then what happens is you wake up a little bit later and you're hot so you throw them off it's because your thermostat has set downward now why is it better to have a cool environment it's better to have a cool environment because it's easier to thermal regulate so you go to europe in the summertime and the hotel rooms still have these big comforters these down comforters so how do you deal with that you stick out your hands and your legs okay i've always slept with you i have one leg that just kind of hangs out of the yeah but that's they're your heat loss surfaces right so if you're in a cool environment you can take advantage of that you can take advantage by passively regulating your body temperature you don't have to get up and wake up and say oh my god i gotta change the covers or blankets or what have you if you're in a warm environment what can you do you need to sleep with one hand in the cool mitt right right and right now that's not available yet it's not available i've never i've never heard about it that way i've always heard you want to sleep in a cool room or keep the room cold yeah but i never realized why that's useful which is as you're you're saying that then you can move your these glabrous surfaces in and out you could even sometimes wake up under the blanket completely very very interesting that finally a rational science grounded explanation for why we need to sleep in a cool room because i always thought well if your temperature is going down anyway why do you have to sleep in a cool room what about wearing socks while you sleep that was big a few years ago where they said you know you should put socks on now i would think that's probably the wrong advice you probably well i don't know if it's wrong advice uh there's an old old study that was supported by i think uh eddie bauer the the sleeping bag company and what the study showed what the study was asking is where what are the most temperature sensitive spots in the body where do you feel cold and what that showed was it was the toes so exactly so when you sample water with your toe you always see that so so the the socks essentially are promoting thermal comfort by insulating that area that's quite sensitive now of course if it's too warm you're not going to put socks on right well craig thank you so much you gave so much information that's actionable and interesting i know a lot of people are going to be really interested in the polymer cooling technology from coolmit we will be sure to provide resources to the website so that people can register interest i do encourage people to play around with so to speak the uh the palmer cooling technology that we all have which are you know these glabrous surfaces and um i also just want to thank you for taking time out of your busy schedule to share this welcome it was fun it was lots of fun i certainly learned a lot and i know a lot of people are going to learn a lot that's useful to them good questions well fabulous answers thank you thank you thank you for joining for my discussion with dr craig heller if you're enjoying this podcast and learning from it please subscribe to our youtube channel as well you can give us feedback in the comments section on youtube as to topics you would like us to cover future guests and so on also please subscribe to the podcast on apple and on spotify and on apple you have the opportunity to leave us up to a five star review and you can leave us a comment or feedback there as well please also check out our sponsors that we mentioned at the beginning of the podcast that's a terrific way to support our podcast in addition if you're interested in supporting research in the hubermann lab at stanford you can go to hubermannlab.stanford.edu giving and there you can make a tax deductible donation to support research in my laboratory on stress human performance sleep and trauma and topics of that sort if you're not already following us at hubermann lab on instagram or twitter you're welcome to do so on instagram i do short neuroscience tutorials that are separate from the tutorials that i tend 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Channel: Andrew Huberman

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Keywords: andrew huberman, huberman lab podcast, huberman podcast, dr. andrew huberman, neuroscience, huberman lab, palmer cooling, recovery, performance, strength training, Craig Heller

Id: 77CdVSpnUX4

Length: 111min 35sec (6695 seconds)

Published: Mon Oct 04 2021

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talk starts at 6:45