How to Build Endurance in Your Brain & Body

Andrew Huberman 0:00 (music) Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. 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, and I'm delighted that they're a partner and a sponsor for the podcast. As some of you may already know, I've spent two decades or more studying the visual system, how we see. Vision is absolutely the most important sense by which humans navigate the world and survive, and our eyes, as two pieces of our brain, do many other important things as well. So taking good care of our eyesight is essential. Founded by two all-American swimmers from Stanford, ROKA was born out of an obsession for performance. They've carefully put science and purpose behind their design choices, and they built absolutely terrific products as a result. The glasses are amazing. I love them because they look great, they are super comfortable, and the optical clarity is incredible. They filter out sunlight in a way that still allows you to see contrast and shadows the way you need to. You know, for me, one of the things that's really irritating is if I have a pair of sunglasses that don't allow me to see all the things I want to see. And with ROKA glasses, I get incredible contrast, but then I can also relax and be outdoors in bright light, and as the amount of light changes with cloud cover and things of that sort, my ability to see my surroundings is, is still really sharp and really clear. 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InsideTracker is a personalized nutrition platform that analyzes data from your blood and DNA to help you better understand your body and reach your health goals. I'm a big believer in getting regular blood work done for the simple reason that many of the important things that are vital to our immediate and long-term health can only be detected in a good quality blood test. The problem with blood tests is that most blood tests, you get a lot of information back about levels that are too high or too low of this thing or the other thing, but making sense of that and what to do with that information is very challenging. Even if you have a really attentive physician, oftentimes it's mysterious as to what to do with all this data. With InsideTracker, they make it very easy to understand what all the metabolic factors, hormone factors, et cetera mean for you and what to do about those markers. 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With Athletic Greens, you get a ton of factors that are good for you mixed into this one really good-tasting drink. I like to mix mine with water and a little bit of lemon juice, and I drink that once or twice a day, typically once early in the day and sometimes also in the afternoon or even evening. I'm able to sleep after drinking in the evening just fine. The reason I've been using Athletic Greens for so long, that I continue to use Athletic Greens, is that, one, I feel better when I take it, I just do, psychologically, physically, I feel better. But also, it covers all my bases of the things that I need for my general health. It's sort of a foundational supplement, as I like to call it. In fact, when people ask me, "What should I take?" If I were to recommend just one supplement that people take, it would be Athletic Greens. 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Andrew Huberman 5:45 offer. For the last month, four episodes to be exact, we've been discussing physical performance and skill learning. We've talked about how to learn skills faster, whether or not those are skills for athletic performance, dance, music.Things of that sort. We've also talked about how to gain strength and how to lose fat faster by leveraging the nervous system, things like shiver and non-shiver, non-exercise activity-induced thermogenesis. We talked about how neurons can actually trigger accelerated fat loss. We talked about hypertrophy, also called muscle growth, and we covered everything from sets and reps, protocols, how long to stay in a cold ice bath, when to get out, how to keep shivering. We've covered a lot of tools and a lot of science. So, if you're interested in those things and you even perhaps want to learn a little bit about how we make energy, ATP, from carbohydrates or from fats, it's all covered in the previous four episodes. This was going to be the time that we move to a new topic entirely, but we are going to do one more episode in this series on physical performance for the simple reason that you asked many questions about something that's vitally important, both for physical performance and long-term and short-term health, and that's endurance. And so today, we are going to talk about endurance. Now, if you're a strength athlete or you're not interested in endurance, don't depart just yet because it turns out that there are ways to train endurance that are very different than I would have previously imagined. If you only think about long runs, long swims, marathons, half-marathons, 10Ks, 5Ks, and that sort of thing puts you to sleep, kind of like Costello is snoring in the background right now. He's not a long-distance endurance athlete, that's for sure. If you're interested in those things or if you are averse to those things, I encourage you to continue listening because we are going to talk about a little bit of science and then some specific protocols that really define what endurance is, the four types of endurance and ways to train those in concert with the other things that you might be doing like weight training or skill training or yoga. And if you are an endurance athlete, we are going to cover a lot of tools and science that I'm certain will also help enhance your training and performance in races or even just recreationally. The topic of endurance, I think has been badly misrepresented, frankly, online, and when you start digging into the science and you start talking to real experts in this area, what you discover, what I've discovered is that it's an incredibly interesting area because it teaches us so much about how our body and our brain use fuels and how we can control which fuels are used by our body and brain. So, today we will talk about the four kinds of endurance. We will also cover the topic of hydration, which might sound incredibly boring, like, okay, just drink more water, but it's really interesting because not only is hydration a limiting factor on performance, but there is a right way to hydrate and there is a wrong way to hydrate. There actually is a formula that I'll teach you to know how much water to be drinking depending on your activity levels, and if that sounds like a simple thing, like, oh, just, you know, tap off water until your ru- urine runs clear, that's actually the wrong advice. It turns out that if you don't hydrate properly, you can see 20 to 30% reductions in performance, whether or not that's strength, whether or not that's y- you know, increasing hypertrophy, whether or not that's running, swimming, even mental performance. So, even if you're not an athlete or a recreational athlete at all, I encourage you to stay tuned for the part about hydration. So, we're going to cover as usual a little bit of science and then we're going to dive right into protocols that you can apply if you like and if you deem those correct and safe for you. Before

Andrew Huberman 9:49 we dive into all that, I want to make an important announcement which is, all the episodes of the Huberman Lab Podcast are now housed on a single website, which is hubermanlab.com. If you go to hubermanlab.com, you can find all the episodes in YouTube, Apple, and Spotify format with links there. The website is also searchable, so if you go into the little search function, which you'll find very easily and you put in, for instance, uh, creatine or sleep or ice bath or sauna, it will take you to the specific episodes that contain that information. And in addition, if you go to the website hubermanlab.com, you have the opportunity to sign up for what we call the Huberman Lab Neural Network. The Huberman Lab Neural Network is a zero-cost resource where once a month, perhaps more often, you'll receive a email newsletter and that newsletter will contain specific protocols, announcements, attachments of PDFs and things of that sort, of protocols, tools and science from the podcast. We will also a- make any announcements about live lectures, which at some point I'll probably start doing in various cities in the US and probably around the world as well, as well as other things that I think would be really useful to you, all of course at zero cost. So, that's hubermanlab.com. Sign up for the Neural Network Newsletter. You can find that in the menu tab or it might pop up when you get there, and I hope you will join, and as a final announcement, if you're not already following us on Instagram, you can go to @hubermanlab on Instagram, and if you do that, I often make announcements and release protocols and links to protocols and things there as well.

Andrew Huberman 11:28 I briefly want to touch on something from the previous episode, which is that if you are somebody that is trying to increase muscle strength and/or size or if you're simply somebody who doesn't want to increase muscle strength and size and you just want to maintain the musculature that you have, it's vital that you perform at least five sets of resistance training per muscle per week. If we don't do that, we lose muscle over time, and that is one reason among many to have a regular resistance training protocol. Nobody wants to start resembling a folded-over envelope or a melted candle-No one wants to have challenges getting up out of a chair or off the ground. Maintaining musculature is vital, not just to our immediate health, but to our long-term health trajectory, so I just want to emphasize that point. If you're curious about the sets, the reps, how close to failure to go or not go, whether or not you should be doing your cardiovascular training before or after your weight training, all of that is in the previous episode, right down to the details, and I like to think made simple for you to understand. But I do strongly believe that resistance training, whether or not it's with body weight or bands or weights or simply lifting rocks in the yard or logs in the yard, is vital for our systemic physiology and our overall health, and that includes our brain health, and I described the reasons for that and the mechanisms in the previous episode.

Andrew Huberman 12:56 Today, I'd like to talk about endurance and how to build endurance and how to use endurance for the health of your entire body. Endurance, as the name suggests, is our ability to engage in continuous bouts of exercise or continuous movement or continuous effort of any kind, and I do believe that our ability to engage in activities that we call endurance training or physical endurance activities do have carryover to mental performance of things that require long-term effort. I'll touch on that at the end and why th- there's reason to believe that there's a biological crossover between those two things. I don't think it's simply the case that if you train yourself to be a strength and speed athlete and to do short bouts of exercise that are very intense that you can only do mental work that's of short bouts and very intense, but it is clear that cardiovascular exercise, exercise where you're getting your heart rate up continuously for a period of time, and endurance exercise, we will define what that is in a moment, is vital for tapping into and enhancing various aspects of our biology in the body and in the brain such that our brain can perform work for longer periods of time, focused work, learning, et cetera. So, I want to dive into the topic of endurance and I want to just begin by addressing something that's vital to any kind of effort, whether or not it's mental effort or physical effort, so as always, a little bit of science, then we'll get right into protocols.

Andrew Huberman 14:38 So the key thing to understand about energy production in the body, meaning your ability to think, your ability to talk, your ability to walk, your ability to run, is this thing that we call ATP. ATP and mitochondria, which are just little what we call organelles within cells, these are little factories that make energy, if you will, ATP is required for anything that requires energy, for anything that you do that requires effort, and there are m- different ways to get ATP, and we have been gifted as a species with the ability to convert lots of things into ATP. We can convert carbohydrates, literally the kinds of carbohydrates, you eat a bagel, you eat a piece of pizza, pizza usually is dough and it has cheese and some other things, Costello hears me talking about pizza, Costello loves pizza by the way, eating a piece of pizza, it gets converted into various things, fatty acids from the fats, glucose from the bread, and those things get converted into ATP within cells through things like glycolysis, things like lipolysis. I talked about this in previous episodes. So our muscles and our neurons use different fuel sources to generate ATP. The ones that are used first, for short bouts of intense activity, are things like phosphocreatine. If you've only heard about creatine as a supplement, well, phosphocreatine actually exists in our muscles and that's why people take creatine, you can load your muscles with more creatine and th- and, excuse me, phosphocreatine is great for short, intense bouts of effort. So when you're really pushing hard on something physical, let's say you see a car on the side of the road and that car is stalled and a person says, "Hey, can you help me push my car?" and you start to push, it's going to be phosphocreatine that's going to be your main fuel source. Then you start to tap into things like glucose, which is literally just carbohydrate, it's just sugar that's in your blood, and then if you keep pushing on that car or you keep in- engaging in a particular effort or you keep studying or you keep listening to this podcast, you start to tap into other fuel sources like glycogen from your liver, which is just, it's like a little pack just like, you know, you might have packed a sandwich or something for work, you have a little pack of glycogen in your liver that you can rely on, and you have fat stored in adipose tissue. Even if you have very, very low body fat percentage, like you're one of these people who has, like, 3% or 5% body fat, really thin skin, very little body fat, you can extract lipids, fatty acids from that body fat, it's like a storage pack, it is a storage pack for energy that can be converted to ATP. So without going into any more detail, when I say today energy or I say ATP, just remember that regardless of your diet, regardless of your nutritional plan, your body has the capacity to use creatine, glucose, glycogen, lipids, and if you're ketogenic, ketones, we'll talk about ketosis, in order to generate fuel, energy. Now, the other crucial point is that in order

Andrew Huberman 18:00 to complete that process of taking these fuels and converting them into energy, most of the time, you need oxygen.You need air basically in your system. Now, it's not actual air, you need oxygen molecules in your system, comes in through your mouth and your nose, goes to your lungs and distributes via the bloodstream. Oxygen is not a fuel, but like a fire that has no oxygen, you can't actually burn the logs, but when you blow a lot of oxygen onto a fire, basically onto, uh, uh, logs with a flame there, then basically it will take fi- f- it will take fire, it will burn, okay? Oxygen allows you to burn fuel. So today, we are going to ask the critical questions, what allows us to perform? What allows us to continue effort for long periods of time? And that effort could be a run, it could be a swim, it could be studying,

Andrew Huberman 19:00 it could be anything that extends over a long period of time. Well, you're going to need energy and you're going to need oxygen. But the way to answer a question like what allows us to endure, right? Endurance. What allows us to keep going? Well, we think of things like willpower, but what's willpower? Willpower is neurons, it's neurons in our brain, we have this thing called the central governor which decides whether or not we should or could continue or whether or not we should stop, whether or not we should quit, okay? So whether or not you're somebody who has a lot of what we call resilience and endurance or whether or not you're somebody who taps out early and quits early or can't handle frustration, that has to do with your fuel utilization and specific neurons. So we have to ask the question, what is the limiting factor on performance, right? So instead of saying, what allows us to endure? We should say, what prevents us from enduring? What prevents us from moving forward? What are the factors that say, "You know what? No more. I'm not going to continue this run." Or, "You know what? I've had a really long hard day or maybe I've had an easy day or I'm feeling lazy, I just don't even really feel like getting up and moving." So what we're going to talk about today actually gets right down to the heart of motivation and fuel use, motivation and fuel allocation, and we are going to talk about specific training protocols that you can follow that have carryover between the bodily systems of running, swimming, et cetera, and the way that your brain works. So let's talk about endurance by asking first, what are the limiting factors on endurance? What stops us? Because in addressing that and answering that, we will understand what allows us to get into effort and to continue effort.

Andrew Huberman 20:46 There are five main categories of things that allow us to engage in effort and they are neurons, nerves, muscle, muscle, blood, things in our blood, our heart, and our lungs. Now, I don't want to completely write off things like the immune system and other systems of the body, but nerve, muscle, blood, heart, and lungs are the five that I want to focus on today because that's where most of the data are. As we go forward into this, I want to acknowledge Dr. Andy Galpin, who as with the last episode, has been tremendously helpful and informative in terms of the exercise physiology, is a true expert, he has a laboratory, he's a full professor who does work on muscle biopsy, who understands the science but who also works with athletes and works with recreational athletes, professional athletes, really understands at a variety of levels how all these systems work. He's the person I consulted with about today's episode, although I did access other literature as well and I'm going to mention a key review for any of you aficionados who really want to get down into the weeds, but I encourage you if you want more detail to check out Dr. Andy Galpin's YouTube page, I think he's also on Twitter, he's definitely on Instagram. His content is excellent and he really understands. I have learned and I really believe that an intellectual is somebody who understands a topic at multiple levels of specificity, of detail, and can communicate that and Andy is a true intellectual of muscle physiology and performance and if you hear the word intellectual and you kind of back up and cringe from that, understand that he's also a practitioner. So thank you, Andrew Galpin, Andy Galpin, um, for your support in these episodes and we hope to have you as a guest on the podcast soon. So nerve, muscle, blood, heart, and lungs, let's talk about neurons and how they work, okay? But I want to tell you about an

Andrew Huberman 22:50 experiment that's going to make it very clear why quitting is a mental thing, not a physical thing so why do we quit? Well, an experiment was done a couple years ago and was published in the journal Cell, Cell Press Journal, excellent journal, showing that there is a class of neurons in our brain stem, in the back of our brain, that if they shut off, we quit. Now, these neurons release epinephrine. Epinephrine is adrenaline and anytime we are engaged in effort of any kind, we are releasing epinephrine, anytime we're al- awake really, we are releasing epinephrine into our brain. In fact, this little group of neurons in the back of our brain is called the locus coeruleus if you like, is churning out epinephrine all the time but if something stresses us out, it churns out more and then it acts as kind of an alertness signal for the whole brain. We also, of course, have adrenaline epinephrine released in our body which makes our body ready for things. So think about epinephrine as a readiness signal and when we are engaged in effort this readiness signal is being churned into our brain, when we're relaxed and we're falling asleep epinephrine levels are low. Okay, so they did a really interesting experiment where...They had subjects engage in bouts of effort, of trying to move forward toward a goal, but they manipulated the visual environment with these stripes, kind of like fences passing on both sides of them, and by doing that, they could trick subjects into thinking that their effort was either allowing them to move forward, right? Because these rungs on the fence were moving past, or that their effort was futile, that they were no longer moving forward because they would make the rungs move slowly even though the subjects were making a lot of effort to move forward, okay? So y- this is analogous or similar to being on a treadmill and you're trying to walk on this treadmill and you just can't move the conveyor, right? Or you're in virtual reality and you're putting a ton of effort, but it seems like you're moving excruciatingly slow. I had this experience recently in real life, I was doing a swim in the Pacific, I was trying to go south, and I was swimming and I was caught in a current, not the ki- that pulls you out to ocean, and I kept looking to my left and I saw this hotel on the shoreline, and then I was swimming and swimming and swimming and swimming and 20 minutes later, I looked to my left and the hotel is still exactly where it was before, which meant that I wasn't moving. It felt futile. Eventually, either the current changed or something changed and I eventually swam past the hotel, got back on the beach, and eventually drove home. That's essentially what they did in this experiment, but what they found was these neurons that release epinephrine, there's another cell type called glia, which actually means glue in Latin, that is paying attention to how much epinephrine is being released, and at some point the system reaches a threshold, it reaches this threshold and it shuts off the release of more epinephrine. It's like a "I quit, that's it, no more effort" signal. If they could extend the time before those glia said, "Uh, enough," if they could release more adrenaline into the system, then subjects would keep going. So our desire to continue, or put differently, our willingness to continue and our desire to quit, is mediated by events between our two ears. Now, that doesn't mean that the body's not involved, but it means that neurons are critically important. So we have two categories of neurons that are important, the ones in our head that tell us, "Get up and go out and take that run," and the ones that allow us, encourage us to continue that run, and we have neurons that shut things off and say, "No more." And we of course have the neurons that connect to our muscles and control our muscles. But the reason we quit is rarely because our body quits. Our mind quits. Now, I would never want to encourage people to drive themselves to the point of injury, that's not going to be good for anybody, but it is good to know that it's neural, our ability to persist is neural. So when people say, "Is it... I hear that, you know, sports or effort

Andrew Huberman 27:19 or fighting or, um, it's 90% mental, 10% physical." You know, that, that whole discussion about how much is mental, how much is physical is absolutely silly. It just proves that there's no knowledge of the underlying biology behind that statement. It's neither mental nor physical. Everything is physical, everything is neurons. Your thinking is the responsibility of chemicals and electrical signals in your head, so it's not 90% mental, 10% physical, it's not 50/50, it's not 70/30, it's 100% nervous system. It's neurons, okay? So when people say mental or physical, understand it's 100% neural, and I'd love for the how much of, of it is mental and how much is physical to just disappear. That, th- that argument means nothing and it's not actionable.

Andrew Huberman 28:10 Now, what do nerves need in order to continue to fire? What do you need in order to get neurons to say, "I p- I will persist"? Well, they need glucose. Unless you're keto and ketogenic-adapted, you need carbohydrate, is glucose, that's what neurons run on, and you need electrolytes. Neurons have what's called a sodium-potassium pump, blah, blah, blah, they generate electricity, we could go into all this, I will probably do an entire lecture about the action potential, but basically, in order to get nerves, nerve cells to fire, to contract muscle, to say, "I'm going to continue," you need sufficient sodium, salt, because the action potential, the actual firing of neurons is driven by sodium entering the cell, rushing into the cell, and then there's a removal of potassium and then there's a kind of resetting of those levels by something called the sodium-potassium pump, and the sodium-potassium pump and sodium and action potentials, even if you don't know anything about that, is ATP dependent, it requires energy. So you need energy in order to get neurons to fire. And it is pH dependent, it depends on the conditions or the environment within the brain being of a certain pH or acidity. pH is about how acid or how basic the environment is, and we will talk a little bit about pH in simple terms that you can understand. So nerves need salt, they need potassium, and it turns out they need magnesium and you need glucose and carbohydrates in order to power those neurons unless you are running on ketones, and to run on ketones you have to make sure that you're fully keto-adapted. I will talk about adding in ketones on top of carbohydrate at the end of the episode. Okay, so that's how nerves work. You need carbohydrate, you need sodium, potassium, and magnesium in order to drive the brain. Muscle. Muscle is going to engage and generate energy first by using this phosphocreatine

Andrew Huberman 30:10 system. High bouts of effort, really intense effort, short-lived....seconds to minutes, but probably more like seconds. There's going to be this phosphocreatine, literally a fuel source in the muscle that you're going to burn just like you would logs on a fire. And glycogen, which is stored carbohydrate in the muscle, that also can be burned just like logs on a fire to generate energy. So, let me make this crystal clear. If you move your wrist towards your shoulder and contract your bicep really hard, muscle fibers are burning up their own carbohydrate, they're converting that into ATP in order to generate that energy, okay? And pH is important and temperature is important. In the episode on Supercharge Your Physical Performance, I talked all about how by using cooling, specifically of the palms or the bottoms of the feet or the cheeks of the face using particular methods, you can adjust the temperature of the body and of muscle in a way that allows you to do more work, to do more reps, to run further, to keep going, and to persist. And that's because if temperature is too low or too high, then ATP is not going to be available because of this whole thing called the pyruvate kinase pathway and the temperature dependence of pyruvate kinase. Check out that episode if you want to learn more about that, but temperature is important and pH is also important. So, we got nerve, muscle, and then there's stuff in our

Andrew Huberman 31:36 blood that's available as an energy source, and in blood we've got glucose, so literally blood sugar that's floating around. So, let's say you have fasted for three days, your blood glucose is going to be very low, so that's not going to be a great fuel source, but you will start to liberate fats from your adipose tissue, from your fat, fatty acids will start to mobilize into the bloodstream and you can burn those for energy, and oxygen in your blood. When you inhale, (inhales deeply) you're bringing oxygen into your blood. So, these are all fuel sources in your neurons, in your muscle, in your blood, in your various tissues that are providing the opportunity to give effort, to pr- to induce effort, whether or not it's a run or a swim or writing or talking. Now, there are some other factors that are important and those are the heart, which is going to move blood. So, the more that the heart can move blood and oxygen, well, the more fuel that's going to be available for you to engage in muscular effort and thinking effort. So, your heart is vitally important to your, your muscle's ability to work and your brain's ability to work. And as I've mentioned oxygen a few times, it should be obvious then that the lungs are very important. You need to bring oxygen in and distribute it to all these tissues because oxygen is critical for the conversion of carbohydrates and the conversion of fats, and we could get into the discussion about whether or not oxygen is important for ketogenic metabolism, but you need oxygen there, you need to breathe and you need to breathe properly. So, I just covered what would normally be about four lectures of energy consumption and energy utilization, I didn't go into much detail at all, but what I want you to imagine is that you've got these different cell types. You've got neurons, you've got muscle, they need to collaborate in order to generate effort or to make the decision to do something or to think hard or to run hard or to run far, and then you've got fuel sources both in the neurons, in the muscle, in your blood, and then the heart and lungs are, are going to help distribute the oxygen and those fuels. And of course, you have that little energy pack that we call the liver that will allow you to pull out a little more carbohydrate if you need it for work, okay? So, that's as much as I want to cover about energy consumption because that's a lot, but what it tells you is that when you eat and you use food as a fuel source, that f- food can be broken down and you can immediately burn the glucose that's in your bloodstream or you can rely on some of the stored fuel in your liver, or you can rely on stored fuel in the muscle, so-called glycogen, and there are a lot of different ways that we can generate ATP. So, when we ask the question, "What's limiting for performance? What is going to allow us to endure, to engage in effort and endure long bouts of effort or even moderately long bouts of effort?" we need to ask which of those things, nerve, muscle, blood, heart, and lungs, is limiting? Or put differently, we ask, what should we be doing with our neurons, what should we be doing with our muscles, what should we be doing with our blood, what should we be doing with our heart, and what should we be doing with our lungs that's going to allow us to build endurance for mental and physical work and to be able to go longer, further, with more intensity? That's the real question. How can we do more work? And the way we do that is with energy, and the way to get energy to it is by those five things, and so now we're going to talk about how you can actually build different types of endurance and what that does at the level of your blood, your heart, your muscles, and your neurons. So, we're going to skip back and forth between protocols, tools, and the underlying science. So rather than heavy stack the science at the front end and then just give you all the tools at the end, we're going to talk about the protocols, the four kinds of endurance and how to achieve them, and we are going to talk about the underlying science as we move

Andrew Huberman 35:40 through that. If you would like a lot of detailed science, I encourage you to check out a review that we've linked in the show notes, and the review is called Adaptations to Endurance and Strength Training. This is a review article with many excellent citations. It's from Cold Spring Harbor Perspectives in Medicine. The Cold Spring Harbor Press is an excellent scientific press. Spent the last 21 years doing summers at Cold Spring Harbor teaching neuroscience, but Cold Spring Harbor is involved in all sorts of themes and topics related to neuroscience and medicine. This review by Hughes, Elefson, El-Elafesin, that's the name, Elafesin and Baar, B-A-A-R, Adaptations to Endurance and Strength Training, is rich with citations. It can be downloaded as a complete PDF, there's no pay wall, and we will link to it, and it gets really deep into all the signaling cascades, the genetic changes within muscle, uh, with high intensity interval training, short-term hi- super high intensity training, uh, weight training. So if you're a real nerd for this stuff and you want to get right down into how PGC-1alpha, P53, and PH20 change the adaptation features of muscle and gene regulation, that is definitely the review for you. If you're like most people and you're not really interested in that level of detail, no reason to pick up the review unless you just want to check out some of the, the figures and pictures, but I do want to offer that as a resource. It's been a, in addition to discussions with Dr. Andy Galpin, it's been a, a primary resource for the content of this episode.

Andrew Huberman 37:15 So let's talk about the four kinds of endurance and how to achieve those. I do believe that everybody should have some sort of endurance practice, regular endurance practice. It's clear that it's vital for the functioning of the body and the mind, and there are clear longevity benefits. There are a lot of reasons why that's true, but the main one is that if we have good energy utilization in our musculature and in our blood, in our vascular system, and in our oxygenating system, our lungs, the so-called cardiovascular system, respiratory system, and musculature, the body and brain function much better. There are so many papers now, so much data to support that. So I do believe everyone should either try to maintain the muscle that they have, provided they've already gone through puberty and development, and they should be engaged in regular endurance exercise. Now, for many people they think endurance exercise, that means, what? An hour-long run or I got to get on the StairMaster or I have to treadmill for hours on end each week, and it turns out that's not the case. There are four kinds of endurance and you can train specifically for any one of those, and you can vary your training. So let's talk about those four kinds of endurance 'cause they're very interesting and they each have very different protocols that you use in order to build and maximize them, and now you will understand what fuel sources they use in order to build that thing we call endurance. So first of all,

Andrew Huberman 38:53 we have muscular endurance. Muscular endurance is the ability t- for our muscles to perform work over time, and our failure to continue to be able to perform that work is going to be due to muscular fatigue, not to cardiovascular fatigue. So not because we're breathing too hard or we can't get enough blood to the muscles or because we quit mentally, but because the muscles themselves give out, okay? One good example of this would be if you had to pick up a stone in the yard and that stone is not extremely heavy for you and you needed to do that anywhere from 50 to 100 times, and you were picking it up and putting it down, and picking it up and putting it down, and picking it up and putting it down. At some point, your muscles will fatigue, they will fail to endure. Muscular endurance is incredibly useful for a variety of physical pursuits, and we will talk about the mental pursuits that it supports as well. In terms of physical pursuits, the ability for a given muscle to perform repeated work is going to improve your golf swing, it's going to improve your tennis swing, it's going to improve your posture, your ability to dance, your ability to repeatedly engage in an activity that requires effort in a way that's very different from the kind of endurance that you will build simply by increasing your cardiovascular fitness, your ability to generate kind of easy repetition. So let's talk about muscular endurance and what it is. Muscular endurance is going to be something that you can perform for anywhere from 12 to 25 or even up to 100 repetitions, and that's actually how, if you like, you would train muscular endurance, and I will give the specific protocol in a few moments. So, a good example is push-ups, all right? If you were to get on the floor and start ch- doing push-ups, even if you're somebody who has to do knees-down push-ups, and you're doing your push-ups, eventually you won't be able to do any more push-ups, and that's not going to be because you couldn't get enough oxygen into your system or your heart wasn't pumping enough blood. It's going to be because the muscles fail, that's why. So if you want to be able to do more push-ups or even more pull-ups, muscular endurance is really what it's about. It's actually no coincidence that a lot of military boot camp style training is not done with weights, it's done with things like push-ups, pull-ups, sit-ups, and running, because what they're really building is muscular endurance, the ability to perform work repeatedly over time for a given set of muscles and neurons. So what's a good protocol to build muscular endurance? Let's just give that to you now and explain some of the underlying science as th- as it follows.

Andrew Huberman 41:50 So, a really good muscular endurance training protocol, according to the scientific literature, would be three to five sets of anywhere from 12 to 100 repetitions. That's a huge range. Now, 12 to 25 repetitions is going to be more reasonable for most people, and the rest periods are going to be anywhere from 30 to 180 seconds of rest, so anywhere from half a minute to three minutes of rest. So this might be five sets of push-ups.done getting your maximum push-ups. So for some people that might be zero and you have to do it knees down. For some people, it might be 10 push-ups, for some people it might be 25, but you could go all the way up to a hundred, rest anywhere from 30 to 180 seconds, and then do your next set for a total of three to five sets. So it doesn't actually sound like a ton of work. The other thing you could do is something like a plank. A plank position is actually a way to build muscular endurance, not strength, okay? It's, I'm sure it could be used to develop strength, but it's really about muscular endurance. So you would do three to five sets of planks. Those planks would probably, you, because you're not doing repetitions, it's an isometric hold as we say, it's kind of static hold, or a wall sit would be another example, and you would do that probably for a minute or two minutes, take some rest of anywhere from 30 to 60 s- or 180 seconds, and then repeat. So things like pushing a sled, push-ups, isometric planks, um, even pull-ups, those will all work, and as with other forms of training, you would want to do this until you approach failure or actually fail and where you're unable to perform another repetition, that would mark the end of a set. The one critical feature of building muscular endurance is that it has no major eccentric loading component. Now, I haven't talked much about eccentric and concentric loading, but concentric loading is when you are shortening the muscle typically or lifting a weight, and eccentric movements are when you are lengthening a muscle typically or lowering a weight. So if you do a pull-up and you get your chin over the bar, or a chin-up, that's the concentric portion of the effort, and then as you lower yourself, that's the eccentric portion. Eccentric portion of resistance training of any kind, whether or not it's for endurance or for strength, is one of the major causes of soreness. Some people will be more susceptible to, of this, t- to this, excuse me, than others, but it does create more damage in muscle fibers. Muscular endurance and building muscular endurance should not include any movements that include major eccentric loads. So if you're going to do push-ups, it doesn't mean that you want to drop, you know, smash your chest into the floor. And by the way, your chest should touch the ground on every push-up. That's a real push-up, okay? It's not about breaking 90 with the elbows, it's about pushing down till your chests touch the floor and straightening out, that's a proper push-up. And a pull-up is where you pull your chin above the bar. Neither of those should include a slow, eccentric, or lowering component if you are using those to train muscular endurance, the three to five sets of 12 to 25 and maybe even up to 100 repetitions with 30 to 180 seconds of rest in between. That means that jumping also is going to be a very poor tool for building muscular endurance, because jumping has a slowing down component as you land. So things like plyometrics or agility work where you're moving from side to side and you're decelerating, you're slowing yourself down a lot, not going to be good for muscular endurance. Terrific for cardiovascular training and conditioning of other kinds and skill training and agility and all that, but if you want to build muscular endurance, you want to make your muscles able to do more work for longer, it's going to be this three to five sets of 12 to 100 reps, 30 to 180 seconds of mainly concentric movement, okay? Not a, uh, slow lowering phase or a heavy lowering phase. So that might be kettlebell swings and things of that sort. Isometrics, as I mentioned, things like plank and wall sits will work. Now, what's interesting about this is that it doesn't seem at all like what people normally think of as endurance, and yet it's been shown in nice, quality, peer-reviewed studies, several of which are cited in the review I mentioned earlier, that muscular endurance can improve w- our ability to engage in long bouts of what we call long duration, low intensity endurance work. So this can support long runs, it can support long swims, and it can build also, it can build postural s- strength and endurance simultaneously, and that's mainly accomplished through isometric holds. So things like planks are actually quite good for building endurance of the spinal erector muscles that provide posture of the abdominal muscles that are helpful for posture, for being upright, for the upper neck muscles and things of that sort. We, uh, these days everyone seems to have text neck, everyone's basically staring at their toes all the time as a default towards their toes, so isometric holds can be very good for building muscular endurance. You can spot people, including yourself perhaps, with poor muscular endurance in the postural muscles because any time they stop moving, they have to lean against a wall or their hip will move to one side or they're always leaned to one side. I am guilty of this too. Some of you have actually pointed out, I like to think out of concern, that I often am t- uh, rubbing my lower back, and indeed I have some asymmetries in my postural muscles, some of which are probably genetic and some of which are probably just from excessive work or something of that sort that have my right shoulder sit lower than my left and things of that sort. If I were, wanted to improve those, I could improve those by really focusing on symmetry and isometric, uh, symmetry meaning hold my, holding my hands at equivalent positions in planks and doing isometric holds for building muscular endurance of the postural muscles. But this can also be done with, as I mentioned, kettlebell swings for the lower back and legs and posterior chain. So there are a number of different exercise you could do this with, but it should be compound exercises mainly. It's rare for people to do this kind of muscular endurance work specifically for things like bicep curls or triceps, and there aren't many activities that really rely on isolation of those muscles repeatedly, all right? It's hard, I'm sure there are some out there but it's kind of hard to imagine.So, you can do this with isometrics, you can do this with more standard non-isometric type movements, but make sure there isn't a strong eccentric load. So, now let's talk about the science

Andrew Huberman 48:40 briefly of why this works. Well, that takes us back to this issue of fuel utilization and what fails. So, if we were to say, okay, uh, let's say you do a plank, uh, and you're planking for, you know, maybe you're able to plank for a minute or two minutes or three minutes, at some point you will fail. You're not going to fail because the heart gives out, you're not going to fail because, uh, you can't get enough oxygen because you can breathe while you're doing that, you're going to fail because of local muscular failure, which means that as you do, if you choose, to do this protocol of three to five sets, et cetera, et cetera, to build muscular endurance, mainly what you are going to be building is you're going to be building the ability of your mitochondria to use oxygen to generate energy locally, and that it's something called mitochondrial respiration, respiration because of the- the involvement of oxygen and it's also going to be increasing the extent to which the neurons control the muscles and provide a stimulus for the muscles to contract, but this is independent of power and strength, okay? So even though the- the low sets, like three to five sets, and the fact that you're doing repetitions and you're going to failure, even though it seems to resemble power and strength and hypertrophy-type training, it is distinctly different, it's not going to generate strength, hypertrophy, and power, it's going to mainly create this ability to endure, to continually contract muscles or repeatedly contract muscles, okay? Continually if you're using isometric holds, repead- repeatedly, excuse me, if you're using repetition-type exercise where there's a l- a contraction and an extension of the muscle, essentially con- uh, uh, concentric and an eccentric portion, but remember that you want the eccentric portion to be light and relatively fast, not so fast that you injure yourself but certainly not deliberately slowed down. It was recommended, I should say, by Andy Galpin that you not use Olympic lifts for this because once you get past 8 or 12 or 25 repetitions, especially, form on those Olympic lifts is key for not getting injured, and while some people can perform those sorts of- of lifts, like, you know, snatches and deadlifts and cleans and jerks and overhead presses, probably not a great idea if the goal is to push the body to points of fatigue because you do open yourself up to injury unless you're very skilled at doing that or you have a really good coach who can help you guide through those lifts. So, that's one form of e- of endurance, which is muscular endurance and it's mainly going to rely on neural energy, so nerves and muscle, and it's not going to rely quite so much on what's available in your blood, your heart,

Andrew Huberman 51:31 or your lungs. So, now let's talk about the other extreme of endurance, which is long-duration endurance. This is the type that people typically think about when they think about endurance, you're talking about a long run, a long swim, a long bike ride, well, how long? Well, anywhere from 12 minutes to several hours or maybe even an entire day, maybe eight or nine hours of hiking or running or biking, some people are actually doing those kinds of really long events, marathons for instance, so anything longer than 12 minutes and this type of work builds on fuel utilization in the muscles, it builds on the activity of neurons in the brain that are involved in what we call central pattern generators, we talked about this in a previous episode or several previous episodes, these are groups of neurons that allow our body to engage in re- regular rhythmic effort without having to think about the movement too much, so running and stepping or swimming if you already know how to swim or pedaling on a bike or walking upstairs and hiking, you're not thinking about right, left, right, left, it's all carried out by central pattern generators. This is going to be at less than 100% of your maximum oxygen uptake, your VO2 max, I'll talk about what VO2 max is, but I just want to give a sense of what the protocol is and the underlying science. How many sets? One. Long-duration effort is one set of 12 minutes or longer, so you're not counting repetitions, I sure hope that if you're going out on a 30-minute run or even a 15-minute run that you're not counting steps, that you're not counting pedal strokes, that you're not on the rower counting pulls on the rower, I suppose you could but I think that would be pretty dreadful, seems like a poor utilization of cognitive brain space. You're getting into regular repeated effort and your ability to continue that effort is going to be dependent mainly on the efficiency of the movement, on your ability to strike a balance between the e- the movement itself, the generation of the muscular movements that are required and fuel utilization across the different sources of nerve, muscle, blood, heart, and lungs. So, let's ask the question, why would you fail on a long run? Why would you quit? Well, as you set out on that long run, assuming you have some glycogen in your liver and in your muscles, you're going to use that energy first even if it's very low intensity, okay? So, we're not talking about sprinting, we're talking about heading out the door or starting off on a marathon, you're starting to, assuming you have some conditioning or even if you don't, you're going to burn carbohydrate, you're going to burn glucose in the bloodstream, you're going to burn carbohydrate as those muscles contract, those what we call slow twitch muscles, they're contracting, they start burning up fuel to make ATP to continue to contract.Your mind is going to use more or less energy depending on how much willpower, how much of a fight you have to get into with yourself in order to generate the effort. I really want to underscore this. If you're somebody that's thinking, "Maybe I go for the run. Maybe I don't go for the run. I'll do it at 2:00. Okay, 2:05. No, I only want to go on the half hour or maybe on the main hour," and you're going through all that, guess what? You're burning up useful energy that you could use either for the run, for example, or for something else. When we think about something hard, when we ruminate, when we perse- perseverate on a, on an idea or on a decision, we are burning neural energy, and neural energy is glucose and epinephrine and all the things we talked about before. So willpower, in part, is the ability to devote resources to things, and part of that is making decisions to just either do it or not do it. I'm not of the just do it mindset. I think there's a right time and a place to train, but I also think that it is not good, in other words, it utilizes excessive resources to churn over decisions excessively and you probably burn as much cognitive energy deciding about whether or not to do a given training or not as you do in the actual training, okay? So we'll talk more about how this long duration effort can relate to mental performance but the long duration effort should be one set, 12 minutes or longer, it could go for s- 30 minutes or 60 minutes or an hour, we'll talk about programming later in the episode. This is going to be less than 100% of your maximum, uh, oxygen uptake. Your heart rate is not going to be through the ceiling or maxed out, but it's all about efficiency of movement. That's what you're building. When you go out for a run that's 30 minutes, you are building the capacity to repeat that performance the next time while being more efficient, actually burning less fuel, and that might seem a little bit counterintuitive but every time you do that run, what you're doing is you're building up mitochondrial density. It's not so much about mitochondrial oxidation and respiration, you're building up mitochondrial density, you're actually increasing the amount of ATP that you can create for a given bout of effort. You're becoming more efficient, okay? You're burning less fuel overall doing the same thing. That's really what these long slow distance or long bouts of effort are really all about. Now, why do this long duration effort? Why would you want to do it? Why

Andrew Huberman 57:00 is it good for you? Well, it does something very important which is that it builds the capillary beds within muscles. So let's talk a little bit about vasculature. We haven't done this too much, uh, yet but if you have seen the episode on Supercharging Performance, we talked about AVAs, these arteriovenous anastomoses where blood moves from arteries directly into veins, but that's unusual. That only takes place i- in the so-called, um, glabrous skin of the po- of the palms, the face and the bottoms of the feet. Typically, for most all other areas of the body, what happens is arteries bring blood to a given tissue like a muscle and veins return that blood back to the heart. There are exceptions, but in general... And in between arteries and veins are these little tiny what are called capillary beds or microcapillaries. So these are tiny little avenues, like little tiny streams and estuaries between the bigger arteries and veins. Now, those are actually contained within muscle and what's amazing is that you can increase the number of them. You can literally build new capillaries, you can create new little streams within your muscles, and the type of long duration effort that I was talking about before, 12 minutes or more of steady effort, is very useful for doing that and is very useful in- for increasing the mitochondria, the energy producing elements of the cells, the actual muscle cells, and the reason is when blood arrives to muscles, it has oxygen, the muscles are going to use some of that oxygen and then some of the deoxygenated blood is going to be sent back to the heart and to the lungs. Now, the more capillaries that you build into those muscles, the more oxygen available to those muscles. I don't want to get too much into the physics of, of fluid flow but basically it's the difference between taking a hose and sticking it into some dirt, um, just directly, like, and turning on the faucet at a given rate, uh, the spigot rather, or having a bunch of little hoses like a sprinkler system that go out and irrigate the whole yard. The irrigation is equivalent to this capillary bed system and it's very good at using energy sources within blood. So the simple way to think about this is when you go out for a run, let's say it's the first run you've done for a while and you go out for 12 or 15 minutes and somewhere right around 20 minutes you're like, "That's it. I just can't continue." Well, when you come back the next time to do that run, you've built endurance largely because you've built these capillary beds, you've expanded these little streams in which blood can deliver oxygen to the muscles and so it's going to feel relatively straightforward to either go a little bit quicker for the same duration, the same distance or to extend that run for another 5 to 10 minutes. So this long duration work, unlike muscular endurance like planks and everything that we were talking about before, is really about building the capillary systems and the mitochondria, the energy utilization systems within the muscles themselves and that's very important to understand. It's distinctly different than, say, building the neurons that fire the muscles. The neurons are already there, they're going to fire those muscles just fine. In fact, if your life depended on it today you could probably run a marathon. You'd probably get injured, it would be very psychologically and physically painful, I don't recommend you do that unless you're trained for it but if you were to train properly for it, if you were to do long duration bouts of effort-... once or twice a week or e- three times a week, pretty soon it would become easy because you're building these vascular microbeds or microvascular beds as they're called. Okay? So you're able to bring more energy to the muscles and they're able to utilize more energy. So that's long duration. So we've got muscular endurance and we've got

Andrew Huberman 1:01:00 long-duration endurance. And then there are two kinds in between that in recent years have gotten a lot of attention and excitement, but most people are not distinguishing between these two kinds of endurance, and that's a shame because in failing to distinguish between the two kinds of what we call high-intensity training, sometimes called high-intensity interval training, most people, perhaps you, are not getting nearly as much physical and mental benefit out of high-intensity training as you could. So, I want to talk about the two kinds of high-intensity interval training and what each of them does for your brain and body and what sorts of adaptations they cause because in doing that, you can really start to build up specific energy systems in your brain and body in ways that are g- best serve you for your cognitive work and for other sorts of things like strength and speed or hypertrophy or for running marathons for that matter. So there are two kinds of high-intensity training for endurance, sometimes called high-intensity interval training. One is anaerobic, so-called anaerobic endurance, so no oxygen, and the other is aerobic endurance, both of which qualify as HIIT, high-intensity interval training. So let's talk about anaerobic

Andrew Huberman 1:02:20 endurance first. Anaerobic endurance from a protocol perspective is going to be three to twelve sets, okay? And these repetitions, and I'll talk about what the repetitions are, are going to be performed at whatever speed allows you to complete the work in good, safe form. Okay? So it could be fast, it could be slow. As the work continues, your repetitions may slow down or it may speed up. Chances are it's going to slow down. So what is this work? What do these sets look like? Remember, long slow distance is one set, muscular endurance is three to five sets, high-intensity anaerobic endurance is going to be somewhere between three and twelve sets, and it's going to have a ratio of work to rest of anywhere from three-to-one to one-to-five. Okay? So what would a three-to-one ratio set look like? Well, it's going to be 30 seconds of hard pedaling on the bike, for instance, or running or r- on the rower. These are just examples. It could be in the pool swimming, it could be any number of things, or air squats or, you know, or weighted squats, if you will, provided, uh, you can manage that. 30 seconds on, 10 seconds off. That's a very brief rest. So three-to-one is just a good example would be 30 seconds on, 10 seconds off. The opposite r- extreme on that ratio would be one-to-five, so 20 seconds on, 100 seconds off. So you do the work for 20 seconds, then you rest 100 seconds. Now, what's the difference? What ... Should you do three-to-one ratio, so 30 seconds on, 10 seconds off? Or should you do one-to-five, 20 seconds on to 100 seconds off? Well, that will depend on whether or not the quality of the movement is important to you. So let's just take a look at the three-to-one ratio. So in the three-to-one ratio, if you're going to do 30 seconds of hard pedaling on a bike followed by 10 seconds, so maybe one of these what they call assault bikes, and then you stop for 10 seconds and then repeat, chances are you will be able to do one, two, three, four, maybe even as many as twelve sets if you're really in good condition, that you'll be able to do all those because pedaling on the bike doesn't require a ton of skill, and if you do it incorrectly, if your elbow flares out a little bit or something, it's very unlikely that you'll get injured unless it's really extreme, okay? But the same movement done, for instance, with kettlebells, so 30 seconds on, 10 seconds off, the first set will probably be in good form, the second one will be in pretty good form, but let's say you're getting to the fifth and sixth set and you're going 30 seconds on, 10 seconds off, chances are y- the quality of your repetitions will degrade significantly, and you increase the probability that you're going to get injured or that you're going to damage yourself in some way, or that you can't complete the movement, or that some smaller muscles like your grip muscles might give out. Okay? So the quality of repetitions is going to drop considerably with the three-to-one approach. If you're just doing it for effort, and we'll talk about what this builds in your system in a moment, that's fine, but for most people, if quality of form is important, so maybe this is, uh, using weights, maybe you're doing squats, so you're going to do 20 seconds on and 100 seconds of rest, maybe it's even a barbell loaded squat, maybe you're doing kettlebells, maybe you've got, um, some other resistance there that's allowing you to do this. What you'll find is that the longer rest, even though it's 20 seconds of intense effort followed by a longer rest of about 100 seconds will allow you to perform more quality repetitions safely over time. So, what does building anaerobic endurance look like? And then I'll tell you what it's actually good for in the true practical sense. What anaerobic endurance exercise generally looks like is that if you decide to do this for the first week, you might do this two or three times a week, maybe even just once a week depending on the other things you're doing, we'll talk about programming at the end, and you would generate just three sets. So it might be three sets of 20 seconds of hard effort followed by 100 seconds rest. Then you repeat, 20 seconds of hard effort, 100 seconds rest, 20 seconds of effort, hard ... 100 seconds rest. And you might do that twice a week, and then each week you're adding one or two sets.Okay? In doing that, you will build up what we call anaerobic endurance. What is anaerobic endurance? Well, let's ask why we fail. Anaerobic

Andrew Huberman 1:07:00 endurance is going to be taking your system into greater than 100% of your VO2 max. It's going to be taking your heart rate up very high and it's going to maximize your oxygen utilization systems. That is going to have ef- effects that are going to lead to fatigue at some point in the workout and that fatigue will trigger an adaptation, so let's ask what adaptation it's triggering. Well, it's triggering both mitochondrial respiration, the ability of your mitochondria to generate more energy by using more oxygen because you're bringing so m- you're maxing out, literally you're getting above your VO2 max, you're hitting that threshold of how much oxygen you can use in your system. One of the adaptations will be that your mitochondria will shift such that they can use more oxygen, and you're going to also increase the capillary beds but not as much as you're going to be able to increase the amount of neuron engagement of muscle. So normally when we start to hit fatigue, when we're exhausted, when we're breathing really hard, because the systems of the body are linked and we- there's a mental component to this as well, a kind of motivational component, after that third or fourth or sixth set of h- you know, 20 seconds on, 100 seconds off or if you're at the other extreme, 30 seconds on and 10 seconds off, there's going to be a component of you want to stop and by pushing through and repeating another set, safely of course, what you're doing is you are training the neurons to be able to access more energy, literally, convert that into ATP and for the muscles therefore to access more energy in ATP and the adaptation is in the m- the mitochondria's ability to use oxygen and this has tremendous carryover effects for other types of exercise. So while I know and appreciate that people are using high intensity interval training of this kind or similar in order to just like burn fat, you know, do their workouts, quote unquote, it's very useful for building a capacity to engage in short bouts of effort repeatedly to really lock in, I don't want to use the word focus because it's not strictly mental focus, but to be able to in- to generate short bouts of very intense work. This can be beneficial in competitive sports or team sports where there's a sprinting component, where the field opens up and you need to dribble the ball down the field, for instance, and shoot on goal, or where you're playing tennis and it's a long rally and then all of a sudden somebody really starts, you know, putting you back on your heels and you have to really t- make the maximum amount of effort to run to the net and to get the ball across the net, things of that sort, okay? There are a variety of places where there's carryover from this type of training but it does support endurance. It's about muscle endurance, it's about these muscles' ability to generate a lot of force in the short term but repeatedly. Okay, so that's the way to conceptualize this, and it is different than maximum power. Even though it feels like maximum effort, it is not the same as building power and speed into muscles, those are distinctly different protocols. So the key elements again are that you're bringing your breathing and your oxygen utilization way up above your max, it's not quite hitting failure but you're really pushing the system to the point where you are not ready to do another set and yet you begin another set, you're not necessarily psychologically ready. I'll talk more about some of the adaptations that this causes in terms of stroke volume in a few minutes when we talk about how it is that work of this sort can increase our heart's ability to deliver blood and oxygen to our lungs and other tissues. I'm going to get very specific about how to breathe during these different types of protocols and what's happening at the level of the heart but I want to make sure I touch on the fourth protocol which is high intensity aerobic conditioning.

Andrew Huberman 1:10:59 So HIT has these two forms, anaerobic and aerobic, and you just heard about anaerobic. High intensity aerobic conditioning also involves about three to 12 sets starting off of course with fewer sets as you're getting into this training and then extending into more sets as one parameter you could expand, has again the same ratio of three to one, so 30 seconds on, 10 seconds off, or one to five, 20 seconds on, 100 seconds off, or a very powerful tool for building up aerobic conditioning is a one-to-one ratio. A one-to-one ratio is powerful for building on average most of the energy systems involving... Remember we had these nerve, muscle, blood, heart, and lungs? A one to- a one-to-one ratio might be you run a mile and however long that takes, let's say it takes you six minutes or seven minutes, then you rest for an equivalent amount of time then you repeat i- and then you rest for an equivalent amount of time so you might run first mile is let's say seven minutes, then you rest for seven minutes, then you run a mile again and it might take eight minutes and you rest for eight minutes and you continue that for a total of four miles of work for four miles of running work I should say, or seven miles of work, you can build this up. Many people find that using this type of training allows them to do things like go run half marathons and marathons even though prior to the race date they've never actually run a half marathon or marathon. Now that might seem incredible, it's like how could it be that running a mile on and then e- and then resting for running a mile and then resting for an equivalent amount of time, running a mile, resting for an equivalent amount of time for seven miles allows you to run continuously for 13 miles or for 26 miles? Well, I'm not discouraging people from ever doing the long d- duration endurance, I think that is very important but it's because it builds up so many of these energy utilization systems, it really teaches you to eng- engage, excuse me, the nerve to muscle firing. It improves t-ATP and mitochondrial function in muscle. It allows the blood to deliver more oxygen to the muscle and to your brain, and I'll explain how that is, and it allows your heart to deliver more oxygen overall, and it builds a tremendous lung capacity, and we will talk about exactly how to breathe and how to build lung capacity both for sake of warming up and for performance. So what would this look like and when should you do this? Um, well, it's really a question for these workouts of asking how much work can one do in eight to 12 minutes, right? And then rest and then repeat. How much work can you do for eight to 12 minutes, then rest, and then repeat? And how many times should you do this? Well, this is the sort of thing, it's pretty intense, and so you would probably only want to do this two, maybe three times a week if you're not doing many other things. I will talk about how this programming can be moved in with other forms of training, but I'll just give you a little hint now. It's very clear and it's described in the review article referred to, and we will link another article as well, that concurrent training, doing strength training and the endurance training of any of the four kinds that I'm describing today can be done, you can program those in the same week, but you want to get four and ideally six or even better 24 hours between these workouts because it is very hard, for instance, to, to do a one-to-one mile repeats, like, r- run a mile, rest for equivalent time, run a mile, rest for equivalent time, to do that two or three times a week and also do weight training before or do a long run afterwards. That would quickly lead to breakdown for most people unless you have very, very good energy utilization systems, you're a really kind of advanced or elite athlete and/or, um, dare I say you're using tools to enhance your performance at the level of blood or hormones, and I'm actually going to talk about those at the end and why they work. So we have four kinds of endurance, muscular endurance, we have long duration endurance, we have high-intensity interval training of two kinds, anaerobic and aerobic, and this last type, the aerobic one works best it seems if you kind of do this one-to-one ratio. So how would you use these and what are they actually doing? Let's talk about the heart and the

Andrew Huberman 1:15:20 lungs and oxygen because that's something that we can all benefit from understanding, and it will become very clear in that discussion why this type of training is very useful even for non-athletes in order to improve oxygenation and e- energy utilization of the brain and the heart. The brain and the heart are probably the two most important systems that you need to take care of in your life. Yes, your musculature needs to be maintained. If you want to build it, that's up to you, but you should try and maintain your musculature, but maintaining or enhancing a brain function and cardiovascular function, it's absolutely clear are key for health and longevity in the short and long term, and the sorts of training I talked about today has been shown again and again and again to be very useful for enhancing the strength of the mind. Yes, I'll talk about that, as well as the health of the brain and the body. So let's talk about the sorts of adaptations that are happening in your brain and body that are so beneficial in these different forms of training. If you are breathing hard and your heart is beating hard, so this would be certainly in the high-intensity anaerobic and aerobic conditioning 'cause you're getting up near your VO2 max in high-intensity aerobic conditioning and you're exceeding your VO2 max in high-intensity anaerobic conditioning. What's going to happen is as, of course, your heart beats faster, your blood is going to be circulating faster in principle. Oxygen utilization in muscles is going to go up, and over time, not long, very quickly what will happen when those capillary beds start to expand, we talked about that, but in addition, because of the amount of blood that's being returned to the heart when you engage in these really intense bouts of effort repeatedly, the amount of blood being returned to the heart actually causes an eccentric loading of one of the muscular walls of the heart. So your heart is muscle, it's cardiac muscle. We have skeletal muscle attached to our bones, then we have cardiac muscle, which is our heart. When more blood is being returned to the heart because of the additional work that your muscles and nerves are doing, it actually has the effect of creating an eccentric loading, a kind of pushing of the w- wall, the left w- I realize I'm not using the, the strict anatomy here, but I don't want to get into all the features of the, structural features of the heart, but the left ventricle essentially getting slammed back and then having to push back in a kind of eccentric loading of the cardiac muscle, and the muscle thickens, but not because the heart thickens overall. It's actually a strengthening of the cardiac muscle in a way that increases what we call stroke volume, meaning as more blood is returned to the heart, there's an adaptation where the heart muscle actually gets stronger and therefore can pump more blood per stroke, per beat, and as it does that, it delivers, because blood cont- contains glucose and oxygen and other things, it delivers more fuel to your muscles, which allows you to do yet more work per unit time. Okay? So when we hear that, oh, you know, s- uh, so-and-so has a, or maybe you have a nice low heart rate that, you know, maybe you're one of these really extreme folks like 30 or 40 beats per minute, although most people are sitting at 50, 60, 70, 80, that's your resting heart rate. If you exercise regularly and you do long duration aerobic work, your heart rate will start to go down, your resting heart rate. It will increase the stroke volume of your heart. If you do this high-intensity type training where your heart is beating very hard, so maybe the one-to-one ratio, uh, mile run repeats that I described a minute ago, let's say you do that twice a week.... for three or four, and I said it could go all the way up to 12 re- uh, sets, which is a lot. I don't recommend people start there. Pretty soon the stroke volume of your heart will really increase and as a consequence, you can deliver more fuel to your muscles and to your brain and you will notice that you can do more work, meaning you can do the same work you were doing a few days or weeks ago with relative ease. Your cognitive functioning will improve. This has been shown again and again because there's an increase in vasculature, literally capillary beds within the brain, the hippocampus, areas that support memory, but also areas of the brain that support respiration, that support focus, that support effort. This isn't often discussed, but the ability to deliver more blood and therefore more glucose, remember neurons run on glucose, and oxygen to the brain is a big feature of why exercise of the kind I'm describing helps

Andrew Huberman 1:20:10 with brain function. Now, weight training does have some positive effects on brain function also. When I say weight training, I'm really, uh, I should be more specific. I really am referring to strength and hypertrophy training. Strength and hypertrophy training, especially if it's of the sort where you get into the burn as we talked about last episode and you start generating lactate as a hormonal signal that can benefit your brain, et cetera, it can have positive effects on the brain. And frankly, there haven't been as many studies of resistance training, strength and hypertrophy training on brain function mainly because most of those experiments are done in mice or primates, non-human primates I should say, and, um, it's hard to get mice to do resistance training, okay? It's hard to get humans to do resistance training. It's definitely hard to get mice to do resistance training. There are ways to do it but it's hard to get them to do, say, you know, uh, three sets of eight on the deadlift and then do some curls and then do some chin-ups and this kind of thing, okay? It's pretty easy to get a mouse to run on a treadmill and you can set the tension on that treadmill to make it so that it's easier or harder for the mouse to turn that wheel. So that's one of the reasons. However, it's very clear and you should now understand intuitively why the kind of standard strength and hypertrophy type workouts are not going to activate the blood oxygenation and the stroke volume increases for the heart that the sorts of training I'm talking about today will. It just doesn't have the same positive effects. Now, that isn't to say that if you just weight train that you'll be dumb or that you'll lose, uh, your, your memory over time. You might, but it is to say that endurance work, in particular the high-intensity and long-duration work that I've talked about today, the two high-intensity protocols and the long-duration work has been shown again and again and again to have positive effects on brain function. Not through the addition of new neurons. Sorry to break, break it to you but that's not a major event in the exercised or non-exercised human brain for reasons we can talk about in a future episode, but it still has many positive effects through the delivery of things like IGF-1 but also just through plain oxygenation of the brain and the way it promotes the development of microvasculature to devel- to, excuse me, to deliver ner- neurons more nutrients. If neurons don't get oxygen and glucose, they do die unless there's another fuel source like ketones which can replace the glucose. If you don't give oxygen to neurons, if you don't deliver enough to them, you get what's called ischemia. You get little micro-strokes. So the type of exercise I'm talking about today in generating intense heart rate increases provided that's safe for you to do, breathing hard, that's going to deliver oxygen and blood, increase stroke volume of the heart and is going to improve brain function. This has been supported by many, many quality peer-reviewed studies. So that's one form of positive adaptation. I also talked about just sort of performance adaptations, how doing high-intensity aerobic conditioning of the, you know, mile repeats type training can actually improve your ability to do long bouts of intense work. It also seems like it dovetails or is compatible with

Andrew Huberman 1:23:25 resistance training that's aimed towards strength and hypertrophy. Now, in full disclosure, the data seem to indicate that if people just weight train or train for strength, so three reps, um, rest five minutes, three reps of heavy weights, et cetera, yeah, you'll get much stronger than you would if you're doing things like, you know, five repetitions up to 12 or 12 to 25 reps and you're, you know, and you're going out for long jogs. There's always going to be a compromise in adaptations unfortunately. It does seem like you can do concurrent training as I mentioned before if you allow anywhere from four to six or ideally 24 hours between workouts. As I mentioned in the previous episode, if you want to know if you are recovered from a workout, a great way to do that is to apply the carbon dioxide tolerance test, which is four breaths in and out, inhale, exhale, inhale, exhale, inhale, exhale, inhale, exhale, then a big inhale and then a slow controlled exhale. If that slow controlled exhale is 60 seconds or longer, it means that your parasympathetic, your calming nervous system is under your control and it's likely, I should say likely that systemically your whole nervous system has recovered from whatever it is that you've been doing and experiencing in life including work and relationships. If not, you might want to take a rest day, dare I say, or Costello's on his, what? He's 10 now. I think he's on his 12,000th rest day. Um, most people need, I should say, one to two full rest days per week. I know there are people who are going to say that's ridiculous, and okay, maybe you have, uh, amazing recovery abilities. Also depends on training intensity. Many people benefit from having one or two full rest days per week, at least one. Some people don't need to. But if you are not able to extend that exhale on the carbon dio- dioxide tolerance test past 60 seconds or so, 45 seconds, 60 seconds, chances are your so-called sympathetic nervous system, your stress system is chronically elevated and you're not really putting the brake on that system enough, and that's a subconscious thing. There are ways that you can accelerate recovery but I would encourage you to listen to the previous episode. It's timestamped for how to assess recovery.So how often to program these things will depend on the other things you're doing. I think it's perfectly reasonable to do this