How to Build Endurance in Your Brain & Body

Andrew Huberman:

Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.

Andrew Huberman:

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.

Andrew Huberman:

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 nonshiver, 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. 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.

Andrew Huberman:

This was going to be the time that we moved 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've previously imagined.

Andrew Huberman:

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.

Andrew Huberman:

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. Today we will talk about the four kinds of endurance.

Andrew Huberman:

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. If that sounds like a simple thing like, "Oh, just tap off water until your 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 not that's increasing hypertrophy, whether or not that's running, swimming, even mental performance. Even if you're not an athlete or a recreational athlete at all, I encourage you to stay tuned for the part about hydration. 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.

Andrew Huberman:

Before 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, creatine or sleep or ice bath or sauna, it will take you to the specific episodes that contain that information.

Andrew Huberman:

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 an 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 make any announcements about live lectures, which at some point I'll probably start doing in various cities in the U.S. 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. 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. I hope you will join. as a final announcement, if you're not already following us on Instagram, you can go to Huberman Lab on Instagram. If you do that, I often make announcements and release protocols and links to protocols and things there as well.

Andrew Huberman:

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.

Andrew Huberman:

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. 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. I describe the reasons for that and the mechanisms in the previous episode.

Andrew Huberman:

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. I do believe that our ability to engage in activities that we call endurance training, or physical endurance activities, do have carry over to mental performance of things that require long-term effort. I'll touch on that at the end and why 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.

Andrew Huberman:

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, and 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. I want to dive into the topic of endurance. I want to just begin by addressing something that's vital to any kind of effort, whether not it's mental effort or physical effort. As always, a little bit of science, then we'll get right into protocols.

Andrew Huberman:

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 little factories that make energy, if you will. ATP is required for anything that requires energy, for anything that you do that requires effort. There are different ways to get ATP. We have been gifted as a species with the ability to convert lots of things into ATP.

Andrew Huberman:

We can convert carbohydrates, literally the kinds of carbohydrates, you eat a bagel, you eat a piece of pizza. Pizza usually has dough and it has cheese and some other things. Costello hears when you talk 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. Our muscles and our neurons use different fuel sources to generate ATP.

Andrew Huberman:

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. That's why people take creatine. You can load your muscles with more creatine. Phosphocreatine is great for short, intense bouts of effort. So when you 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, that's going to be phosphocreatine that's going to be your main fuel source.

Andrew Huberman:

Then you start to tap into things like glucose, which is literally just carbohydrate, just sugar that's in your blood. Then if you keep pushing on that car, you keep 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, it's like a little pack, just like 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.

Andrew Huberman:

And you have fats stored in adipose tissue. Even if you have very, very low body fat percentage, like you're one of these people 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.

Andrew Huberman:

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 to complete that process of taking these fuels and converting them into energy, most of the time you need oxygen.

Andrew Huberman:

You need air, basically, in your system. Now, it's not actual air. You need oxygen molecules in your system. It 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 logs with a flame there, then basically it will take fire, it will burn. Okay? Oxygen allows you to burn fuel.

Andrew Huberman:

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? That effort could be a run, it could be a swim, it could be studying, 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.

Andrew Huberman:

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? Whether or not you're somebody who has a lot of what we would 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 in specific neurons.

Andrew Huberman:

So, we have to ask the question, what is the limiting factor on performance. Right? 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, 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."

Andrew Huberman:

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. 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:

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. He 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. I'm going to mention a key review for any of you of aficionados who really want to get down into the weeds.

Andrew Huberman:

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. If you hear the word intellectual and you kind of back up and cringe from that, understand that he's also a practitioner. Thank you Andrew Galpin, Andy Galpin, for your support in these episodes. We hope to have you as a guest on the podcast soon.

Andrew Huberman:

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 experiment that's going to make it very clear why quitting is a mental thing and not a physical thing. Why do we quit? Well, an experiment was done a couple years ago and was published in the journal Cell, Cell Press journal, an 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. Anytime we are engaged in effort of any kind, we are releasing epinephrine.

Andrew Huberman:

Anytime we're awake, really, we are releasing epinephrine into our brain. In fact, this little group of neurons in the back of our brain, it's called the locus coeruleus, if you like, is churning out epinephrine all the time. But if something stresses us out, it turns 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. 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.

Andrew Huberman:

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. 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? 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.

Andrew Huberman:

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 kind that pulls you out to ocean. 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.

Andrew Huberman:

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, "Ah, enough," if they could release more adrenaline into the system, then subjects would keep going. 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. 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, that 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.

Andrew Huberman:

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, "I hear that sports or effort or fighting or — it's 90% mental, 10% physical." 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. You're 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? When people say mental or physical, understand it's 100% neural. I'd love for the "how much of it is mental and how much is physical" to just disappear. That argument means nothing and it's not actionable.

Andrew Huberman:

Now, what do nerves need in order to continue to fire? What do you need in order to get neurons to say, "I will persist"? Well, they need glucose. Unless you're a keto and ketogenic adapted, you need carbohydrate; it's 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.

Andrew Huberman:

The sodium-potassium pump and sodium and action potentials, even if you don't know anything about that, is ATP dependent. It requires energy. 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. We will talk a little bit about pH in simple terms that you can understand. 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. 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, that's how nerves work. You need carbohydrate, you need sodium, potassium and magnesium in order to drive the brain.

Andrew Huberman:

Muscle. Muscle is going to engage and generate energy first by using this phosphocreatine system. High bouts of effort, really intense effort, short-lived, seconds to minutes, but probably more like seconds, is 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. 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.

Andrew Huberman:

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. 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.

Andrew Huberman:

We've got nerve, muscle, and then there's stuff in our blood that's available as an energy source. In blood, we've got glucose, so literally blood sugar that's floating around. 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, you're bringing oxygen into your blood. 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 induce effort, whether or not it's a run or a swim or writing or talking.

Andrew Huberman:

Now, there are some other factors that are important, and those are the heart, which is going to move blood — 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. Your heart is vitally important to 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. 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.

Andrew Huberman:

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 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?

Andrew Huberman:

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 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.

Andrew Huberman:

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? The way we do that is with energy, and the way to get energy to it is to buy those five things.

Andrew Huberman:

Now we're going to talk about how you can actually build different types of endurance and what that does at the level-

Andrew Huberman:

... 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 through them.

Andrew Huberman:

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. I 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, Ellefsen, 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 paywall, and we will link to it. And it gets really deep into all the signaling cascades, the genetic changes within muscle with high-intensity interval training; short-term, super-high-intensity training; weight training. So if you're a real nerd for this stuff and you want to get right down into how PGC-1 alpha p53 and PH 20 change the adaptation features of muscle and gene regulation, that is definitely the review for you.

Andrew Huberman:

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 figures and pictures. But I do want to offer that as a resource. In addition to discussions with Dr. Andy Galpin, it's been a primary resource for the content of this episode.

Andrew Huberman:

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.

Andrew Huberman:

Now for many people, they think, Endurance exercise, that means what? An hourlong run, or I got to get on the StairMaster or I have to treadmill for hours on end each week. 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 because they're very interesting and they each have very different protocols that you use in order to build and maximize them. And now you'll understand what fuel sources they use in order to build that thing we call endurance.

Andrew Huberman:

So first of all, we have muscular endurance. Muscular endurance is the ability 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. 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 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'll talk about the mental pursuits that it supports as well.

Andrew Huberman:

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 easy repetition.

Andrew Huberman:

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 a hundred 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. If you were to get on the floor and start 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.

Andrew Huberman:

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 it follows.

Andrew Huberman:

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 might be 25, but you could go all the way up to 100. 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.

Andrew Huberman:

The other thing you could do is something like a plank. A plank position is actually a way to build muscular endurance, not strength. 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, because you're not doing repetitions, it's an isometric hold, as we say, a 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 or 180 seconds and then repeat. So things like pushing a sled, push-ups, isometric, planks, 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.

Andrew Huberman:

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.

Andrew Huberman:

Some people will be more susceptible to this 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, 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 chest touches 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.

Andrew Huberman:

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 likely climb metrics 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, not a 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.

Andrew Huberman:

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 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 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. These days everyone seems to have text neck. Everyone's basically staring at their toes all the time. It has a default towards their toes. So isometric holds can be very good for building muscular endurance.

Andrew Huberman:

You can spot people, including yourself, perhaps, with poor muscular endurance in the postural muscles because anytime 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 rubbing my lower back, and indeed I have some asymmetries in my postural muscle, 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 wanted to improve those, I could improve those by really focusing on symmetry and isometric symmetry, meaning holding my hands at equivalent positions in planks and doing isometric holds for building muscular endurance of the postural muscles.

Andrew Huberman:

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 exercises 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 and repeatedly. I'm sure there are some out there, but it's hard to imagine. So you can do this with isometrics; you can do this with more standard nonisometric-type movements, but make sure there isn't a strong eccentric load.

Andrew Huberman:

So now let's talk about the science briefly of why this works. Well that takes us back to this issue of fuel utilization and what fails. So if we were say, okay, let's say you do a plank, and you're planking, 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 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 it's something called mitochondrial respiration, respiration because of the involvement of oxygen.

Andrew Huberman:

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. So even though 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. Continually, if you're using isometric holds, repeatedly, if you're using repetition-type exercise where there's a contraction and an extension of the muscle, essentially 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.

Andrew Huberman:

It was recommended, I should say by Andy Galpin, that you not use Olympic lifts for this because once you get past eight 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 lifts like snatches and dead lifts 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 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, or your lungs.

Andrew Huberman:

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 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.

Andrew Huberman:

This is going to be at less than a hundred percent 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.

Andrew Huberman:

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 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. 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.

Andrew Huberman:

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 perseverate 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.

Andrew Huberman:

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. 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 30 minutes or 60 minutes or an hour. We'll talk about programming later in the episode. This is going to be less than a hundred percent of your maximum 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.

Andrew Huberman:

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 are becoming more efficient. 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.

Andrew Huberman:

Now, why do this long-duration effort? Why would you want to do it? Why 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 yet, but if you have seen the episode on supercharging performance, we talked about AVAs, these arterio-venous anastomoses, where blood moves from arteries directly into veins, but that's unusual. That only takes place in the so-called glabrous skin 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.

Andrew Huberman:

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 for increasing the mitochondria, the energy-producing elements of the cells, the actual muscle cells.

Andrew Huberman:

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 fluid flow, but basically it's the difference between taking a hose and sticking it into some dirt just directly and turning on the faucet at a given rate, 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.

Andrew Huberman:

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 five 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.

Andrew Huberman:

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 three times a week, pretty soon it would become easy because you're building these vascular microbeds, or microvascular beds, as they're called. 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 long-duration endurance.

Andrew Huberman:

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 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.

Andrew Huberman:

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 endurance first. Anaerobic endurance, from a protocol perspective, is going to be three to 12 sets. 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. 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 does 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 12 sets, and it's going to have a ratio of work to rest of anywhere from three to one — to one to five.

Andrew Huberman:

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 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 weighted squats, if you will, provided you can manage that. Thirty 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.

Andrew Huberman:

The opposite 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 a hundred 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.

Andrew Huberman:

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 1, 2, 3, 4, maybe even as many as 12 sets if you're really in good condition, that you'll be able to do all those because peddling 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.

Andrew Huberman:

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 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-

PART 1 OF 3 ENDS [00:30:04]

Andrew Huberman:

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 using weights, maybe you're doing squats — so you're going to do 20 seconds on and 100 seconds of rest.

Andrew Huberman:

Maybe it's even a barbell-loaded squat. Maybe you're doing kettlebells, maybe you've got 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.

Andrew Huberman:

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, 100 seconds rest, and you might do that twice a week and then each week you're adding one or two sets. Okay?

Andrew Huberman:

In doing that, you will build up what we call anaerobic endurance. What is anaerobic endurance? Well, let's ask why we fail. Anaerobic 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 effects that are going to lead to fatigue at some point in the workout, and that fatigue will trigger an adaptation.

Andrew Huberman:

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 ... 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.

Andrew Huberman:

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 there's a mental component to this as well, a motivational component after that third or fourth or sixth set of 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 and ATP, and the adaptation is in the mitochondria's ability to use oxygen, and this has tremendous carryover effects for other types of exercise.

Andrew Huberman:

So while I know and appreciate that people are using high-intensity interval training of this kind or similar in order to just burn fat, "do their workouts," 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 generate short bouts of very intense work.

Andrew Huberman:

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 putting you back on your heels and you have to really make the maximum amount of effort to run to the net and to get the ball across — things of that sort. Okay?

Andrew Huberman:

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.

Andrew Huberman:

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.

Andrew Huberman:

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. So HIIT has these two forms, anaerobic and aerobic, and you just heard about anaerobic. High-intensity aerobic conditioning also involves about three to 12 sets.

Andrew Huberman:

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. Twenty seconds on or 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?

Andrew Huberman:

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, 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, then 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.

Andrew Huberman:

You can build this up. Many people find that using this type of training allows them to do things like go run half marathons in 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 and then resting for an equivalent amount of time, running a mile, resting for equivalent amount of time for seven miles allows you to run continuously for 13 miles or for 26 miles?

Andrew Huberman:

Well, I'm not discouraging people from ever doing the long-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 engage, excuse me, the nerve-to-muscle firing. It improves 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.

Andrew Huberman:

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? Well, it's really a question for these workouts of asking how much work can one do in eight to 12 minutes and then rest and then repeat.

Andrew Huberman:

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 program 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 we're 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.

Andrew Huberman:

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 do a one-to-one mile repeats — 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 really kind of advanced or elite athlete and/or, dare I say, you're using tools to enhance your performance at the level of blood or hormones, and now I'm actually going to talk about those at the end and why they work.

Andrew Huberman:

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 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 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 nonathletes in order to improve oxygenation and energy utilization of the brain and the heart.

Andrew Huberman:

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 our 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.

Andrew Huberman:

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 because 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.

Andrew Huberman:

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.

Andrew Huberman:

So your heart is muscle, it's cardiac muscle. We have skeletal muscle attached to our bones, and 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 pushing of the wall. I realized I'm not using the strict anatomy here, but I don't want to get into all the structural features of the heart, but the left ventricle, essentially, getting slammed back and then having to push back in an 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.

Andrew Huberman:

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 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, so and so has a ..." Or maybe, "You have a nice low heart rate." That maybe you're one of these really extreme folks, 30 or 40 beats per minute, although most people are sitting at 50, 60, 70, 80; that's your resting heart rate.

Andrew Huberman:

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 mile run repeats that I described a minute ago, so you do that twice a week for three or four, and I said it could go all the way up to 12 sets, which is a lot. I don't recommend people start there.

Andrew Huberman:

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 with brain function. Now, weight training does have some positive effects on brain function also. When I say weight training, I should be more specific. I really am referring to strength and hypertrophy training.

Andrew Huberman:

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, nonhuman primates, I should say, and it's hard to get mice to do resistance training. Okay?

Andrew Huberman:

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, 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.

Andrew Huberman:

However, it's very clear, and you should now understand intuitively why the 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 your memory over time; you might.

Andrew Huberman:

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 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 develop ... Excuse me, to deliver neurons more nutrients.

Andrew Huberman:

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 microstrokes. 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, increased stroke volume of the heart and is going to improve brain function.

Andrew Huberman:

This has been supported by many, many quality peer-reviewed studies. So that's one form of positive adaptation. I also talked about just performance adaptations, how doing high-intensity aerobic conditioning of the 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 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, 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 five repetitions up to 12, or 12 to 25 reps, and you're going out for long jogs.

Andrew Huberman:

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.

Andrew Huberman:

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.

Andrew Huberman:

Most people need, I should say, one to two full rest days per week. I know there are people going to say that's ridiculous, and okay, maybe you have amazing recovery abilities. It 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 and 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 type of training with other types of training, and I'll talk about a variety of combinations of those toward the end of the episode.

Andrew Huberman:

I do want to talk about how to deliver more energy and oxygen. These are tools that are extremely useful, I believe, and that are grounded in physiology. The three things I'd like to talk about are how to breathe, what to do immediately after training and hydration. And I promise, I will get back into programming and protocols, but these are vitally important to your ability to perform endurance work in particular, and they are grounded in how neurons and blood and oxygen and your heart work together.

Andrew Huberman:

So let's first talk about breathing or respiration. We breathe a couple of different ways, but let's just remind ourselves why we breathe. We breathe to bring oxygen into our system and we breathe to get rid of carbon dioxide, and we need both oxygen and carbon dioxide in order to utilize fuel and for our brain and body to work. It's not that oxygen is good and carbon dioxide is bad. They have to be present in the appropriate ratios.

Andrew Huberman:

So one thing that is very clear is our ability to deliver oxygen to working muscles and to our brain is going to be important for our ability to generate muscular effort, especially of the kind of I was talking about today, but also weight training and other forms of skill-based effort, et cetera, and our ability to think. If you're holding your breath for too long; if you're breathing too much; if you're what they call overbreathing or underbreathing; if you're shallow breathing; if you're mouth breathing; these are all things that can really impede mental and physical performance.

Andrew Huberman:

So let's make it really simple, and then I promise to do a future episode all about respiration. There are two main sources of air for your body, and it's air coming in through your nose and air coming in through your mouth. In general, nasal breathing is better. It scrubs the air of bacteria and viruses. You have a microbiome in your nose that benefits. There are a number of reasons. It's also just a more efficient system, believe it or not; even though it feels like you can gulp more air with your mouth, getting good at nasal breathing is useful.

Andrew Huberman:

A gear system of the type that Brian McKenzie and colleagues have developed I think is a good way to conceptualize this. If you're doing long-duration work, try and do it all nasal breathing. If you have deviated septum, it's probably because you don't nasal breath enough. Mouth breathing is something that many people suffer from. You're more prone to infections; it's not as efficient, et cetera. There is a place for mouth breathing, however, it's usually if you need to do a strong exhale, oftentimes you can discard more volume through the mouth, unless you're very trained at nasal breathing.

Andrew Huberman:

So if you're doing high-intensity training, a good way to conceptualize this is to exhale on the max effort and then to inhale on the less intense part. So that might be as you're generating the movement, in the concentric part of the movement, you exhale just like on a bat swing, or something like that, or fighters and martial artists do this differently, depending on how they were trained and the different purposes, but the kind of exhaling during the effort and then inhaling on the portion of the repetition that is not the highest effort portion.

Andrew Huberman:

Usually that's the eccentric phase of anything involving weights or rowing and things of that sort. So nasal breathing is great, but as you increase the intensity of your endurance work, you will need to incorporate the mouth. So a gear system would look something like first gear would be just nasal breathing, or second gear would also be just nasal breathing, but with more effort. Third gear, again, Power Speed Endurance has a lot more about this. You can go to their website. I think it's a very intelligent way to conceptualize this.

Andrew Huberman:

As you go into more max effort, then you're going into third and fourth and fifth gear, and at some point you're not thinking about nose or mouth. You're just trying to hang on for dear life and complete the work safely. And that means breathe through whatever orifice works for you. So that's one aspect, nose versus mouth. The other aspect is whether or not you're using your ribs, the intercostal muscles or these muscles that Bruce Lee had, these remarkable intercostal muscles that allow you to lift the rib cage or the diaphragm, which is a skeletal muscle that sits below the lungs.

Andrew Huberman:

Just to remind you, when you inhale, the diaphragm moves down. When you exhale, the diaphragm moves up. Okay, here's something that most people don't do and would benefit tremendously from. And I can say this because Andy Galpin's lab has done work on this — exploring how warming up the intercostals and the nerve-to-diaphragm pathways before any kind of endurance work or in the first few minutes of endurance work can allow you to breathe more deeply and to deliver more oxygen to the blood and, excuse me, and to the muscles and to be able to do more work more efficiently.

Andrew Huberman:

So what that involves is sometimes sitting, sometimes standing and just really concentrating on two things. We always hear about how we should diaphragmatic breathe, and that means our belly moves out when we inhale. So our stomach expands, but also expanding the intercostals, which means actually raising the ribs, chest breathing. We're all told in yoga class, "Don't breathe with your chest — this ..." But actually, that is warming up the intercostal muscles.

Andrew Huberman:

So this is also a great way to generate adrenaline if you do it a little bit intensely. So let's say you're feeling unmotivated to train. I don't particularly like doing endurance training until I'm actually doing it. So I use and benefit from having a practice while I'll just sit there, and for about three minutes I'll just breathe very deeply, trying to raise my chest as much as I can for maybe a minute and then expanding, contracting my diaphragm and expanding my stomach outward when I inhale.

Andrew Huberman:

By the end of that, you're actually delivering more oxygen to your system. My lab has looked at this in a totally different context. Andy's lab has looked at it in the context of physical performance. So warming up the breathing muscles should make sense given that you now know that muscles and neurons need glucose and they need oxygen in order to function, and so that's a great warmup. You can also do this while walking or while getting on the bike and starting to pedal, really starting to think about warming up the breathing system. And then you can decide if you want to do pure nasal or a combination of nasal and mouth breathing, and so on.

Andrew Huberman:

So that's something that we don't often hear about. The other one, the other tool, rather, that I've talked about in a previous episode I'll just mention again is some people when they do endurance type work, they get a stitch in their side. They feel like they've got a side cramp. Very rarely is it actually a skeletal muscular cramp. Oftentimes it's a referenced pain of the phrenic nerve that innervates the liver. So the phrenic nerve is responsible for the movement of the diaphragm. It is a very important system, but it has a number of what we call collateral.

Andrew Huberman:

So it branches to other organs, runs over other organs. Sometimes when we're breathing shallow and we are in physical motion and we're engaging in physical effort, we'll feel that side stitch and we think, "Oh, I've got a cramp." Or "Maybe I'm dehydrated." Or "Maybe I need to run with my hands over my head." Excuse me. Typically, you can relieve that side cramp, which isn't a cramp at all — that side stitch — by doing the double inhale, exhale, really breathing deeply and then sneaking a little bit more air in.

Andrew Huberman:

That's a double firing, or what we call volley of action potentials, sent from the phrenic nerve to the diaphragm, which will also activate that collateral, that branch, literally, of the nerve that innervates the liver. And then when you exhale, you offload a bunch of carbon dioxide. But if you repeat that a few times, often, in fact for me, every time, but often what will happen is that side stitch will just naturally disappear; it just means you're not breathing properly.

Andrew Huberman:

The phrenic nerve is firing in a way that's aggravating that referenced pain. There's nothing voodoo or mysterious about this. It just has to do with the way that the different nerves travel in the body. So as you set out on your run, or maybe you're going to do some muscular endurance work or high-intensity work, warming up the intercostals, warming up the diaphragm is good, and there are exercises, there is work that you can do to strengthen the intercostals and to strengthen the diaphragm during bouts of this kind of effort. And I would say that one of the ways that you can do that best is by really focusing on getting the maximum diaphragmatic expansion and chest lifting, what we're all told now not to do — don't chest breathe, belly breathe. The intercostals are there for a reason, and they are perfectly good at filling your lungs. They work best when they collaborate with your diaphragm. But when you are starting to fatigue, to start to really inhale deeply and try and really expand those to deliver more oxygen to your system. While we're talking about delivering more oxygen to your system, I want to share with you a useful tool that will now make total sense mechanistically why it works, which is oftentimes when we are on a long run or in long duration bouts of effort, we will hit the so-called wall, right?

Andrew Huberman:

We will "bonk," I think they used to call it, or maybe — do they still call it that, Costello? He's asleep. We bonk; we think, "No, we can't continue." It's a curious thing as to whether or not that's neural or whether or not it's fuel based. There's certainly going to be a psychological or motivational component, but one way that you can reveal this extra gear, the capacity to-

PART 2 OF 3 ENDS [01:00:04]

Andrew Huberman:

One way that you can reveal this kind of extra gear, the capacity to push on, is by understanding the way that different muscle fibers use energy differently. Remember the fast-twitch phosphocreatine system and the slow twitch system that relies mainly on lipids and glucose? Okay, well, even if you don't remember all that, if you've been running steadily for a long time, and you're starting to fatigue, and you feel like it's time to quit, you may have not tapped into an alternative fuel source. One thing that you can do is you can actually increase your speed. This is also true of work where you're doing repetitions with kettlebells or something — you can start to increase your speed. So run faster, pedal faster, row faster, swim faster. Not all-out sprint. But in doing that, you're shifting the muscles and the nerves over towards utilizing a separate fuel source, or a distinct fuel source. Maybe the phosphocreatine system, if it's a quick bout of intense acceleration. Or maybe it's a combination of lipids and carbohydrates in your system that weren't available to you prior. Now of course, if you completely deplete your liver glycogen, you completely deplete everything, you're only going to be running on stored fuel and fats, and eventually you'll start metabolizing protein, muscles themselves. But this is a kind of unique way to realize that, oh, you weren't out of energy at all. You were just overrelying on one fuel source.

Andrew Huberman:

And this is the reason why, especially elite athletes, are starting to both rely on carbohydrates — so they're doing the whole carb depletion, then carb loading thing; they're loading up their liver and their muscles with plenty of glycogen by eating pastas and rice and stuff before races — but they are also ingesting ketones during races, during long bouts of effort, because ketones can be a quick form of energy.

Andrew Huberman:

There's no reason why you can't use ketones if they are taken, exogenous ketones, and carbohydrate and in combination. Remember, the body is accustomed to using multiple fuel sources, fatty acids, carbohydrates, all these things. It's only in the kind of Internet age that we think in terms of, "Oh, well you're either keto, or you're burning sugar, or you're fat adapted or you're fat fasting or fast fasting or fat fating."

Andrew Huberman:

Costello woke up when I said fat fating. I'm not talking about you, Costello. So the point is that your body's used to using multiple fuel sources. So if you're kind of hitting that wall, sometimes accelerating can actually allow you to tap into a new fuel source, or combination of fuel sources, just based on the way that muscles use fuel. So that's another tool.

Andrew Huberman:

The other thing that's really important to think about in terms of endurance-type work is hydration. And I think hydration is important for all forms of physical work and exercise, not just endurance. The deal with hydration is that we've been taught about hydration all wrong. But let's remember what neurons work on. What do they use in order to fire? Well, they certainly need water, right? We need water in our system, I should say. But remember, they use electrolytes, sodium and potassium, to generate those action potentials to actually get neurons to contract, to be able... Excuse me, muscles to contract. And for our brain to function and to be able to think.

Andrew Huberman:

Typically, we're going to lose anywhere from one to five pounds of water per hour of exercise. And that's going to vary tremendously. It's going to vary on weather; it's going to vary on intensity, probably more like five pounds if it's a hot day and you're exercising very intensely. So about one to five pounds per hour. Now you know how much you weigh. So if you think about your weight in pounds, once you lose about 1% to 4% of your body weight in water, you are going to experience about a 20% to 30% reduction in work capacity and your ability to generate effort of any kind — strength, endurance, et cetera.

Andrew Huberman:

You are also going to experience a significant drop in your ability to think and perform mental operations. So hydration is key. Now, many people have been told, "Well, if you urinate and your urine is clear, well then you're hydrated enough." Sometimes that's true, sometimes that's not true. Also, and this isn't a topic I enjoy discussing, but urine is a biological phenomenon. It's actually filtered blood. Every once in a while, and if there's a kid and it's a family friend, I'll say, "Did you know that your pee is actually filtered blood?" And they usually kind of go wide-eyed, but then they go, "Oh, that's kind of cool."

Andrew Huberman:

Like kids have this natural curiosity about blood and pee and stuff that's not contaminated by our preconceived notions of those things being gross. Because urine being filtered blood can give you some indication as to whether or not you're hydrated enough or not. And in order to really assess that, it's not going to be sufficient to urinate into another volume of water and assess whether or not your urine is very dark or very light. It actually requires urinating into a small volume and saying, "Well, is it darker or lighter than before?" It's not something you really want to do most places. The etiquette of most gyms and environments is not suitable for that. But one of the things that you can just do is you can figure, "Well, I'm going to lose one to five pounds of water per hour." You can show up to exercise reasonably hydrated with electrolytes.

Andrew Huberman:

So potassium, sodium and magnesium, are really key. Yes, it's true. You can die from drinking too much water, in particular because it forces you... If you drink too much water, you'll excrete too many electrolytes, and your brain will shut off. Your heart will stop functioning properly. So you don't want to overconsume water to the extreme, either. But, there are a number of equations that go into figuring out how much water you need based on how intense you're training, et cetera, body size, et cetera. Just remember, you burn — you lose, excuse me, about one to five pounds of water per hour, depending on how hot it is and how intensely you're exercising. Once your body weight drops by 1% to 4%, so you can just figure it, well, if you lose five pounds per hour, you exercise for two hours. Let's say you're about 200 pounds, that's about 10%.

Andrew Huberman:

Okay, well you want to replace that very quickly. You want to replace that all along before you start experiencing this massive 20% to 30% reduction in work capacity of muscles and the brain. A simple formula, what I call the Galpin equation, hereafter referred to as the Galpin equation, is a formula that gets you close to the exact amount that you would want, that Dr. Andy Galpin came up with, which is your body weight in pounds, divided by the number 30. And that is how many ounces you should drink for every 15 minutes of exercise.

Andrew Huberman:

So once again, the Galpin equation, your body weight in pounds divided by 30, that's the amount of fluid to drink in ounces, right? Every 15 minutes of exercise. Now, if you are sweating a lot, you may need more, okay? If you're already very well hydrated, you may need less. But that's a good rule of thumb to begin and to start to understand the relationship between hydration and performance.

Andrew Huberman:

There is a phenomenon in which gastric emptying, the ability to move stuff out of your gut, including water and electrolytes, out of your gut and into the bloodstream and for delivery to the tissues of your body for effort, is hindered when you get above 70% of your VO2 max.

Andrew Huberman:

In other words, when you're doing high-intensity training, sometimes people will experience that ingesting water during intense training is difficult. It is something that can be actually trained up. It's a matter of learning to kind of relax your abdominal muscles. And there's some other aspects of adaptation that will allow you to drink during higher-intensity work.

Andrew Huberman:

As Galpin says, don't try and ingest fluids when you're working out or competing at higher than 70% of VO2 max if you've never done it before. You want to train up this capacity. People can learn how to consume fluids during a race, or consume fluids during bouts of exercise that are very intense. And a lot of people don't want to do that, because they don't want to have to stop to urinate, et cetera. But given the crucial role of hydration for muscular performance and for brain performance, it seems that if you're going to be doing a lot of high-intensity interval training of the various kinds I talked about today, or high-intensity training of any kind, that hydration is key, and learning, or in other words getting your system to adapt to ingesting fluids in the middle of these workouts is something that seems beneficial, at least to me, in terms of the trade-off between being dehydrated and the somewhat discomfort of maybe drinking some fluid.

Andrew Huberman:

So you sip small amounts of fluid initially, and then you're able to take bigger and bigger gulps as time goes on, and pretty soon you're able to drink mid set or be... Excuse me, not mid set. Please don't do that. Between sets in your workout, or while you're still breathing hard after a mile repeat, or something of that sort, without much disruption, or any at all, to your performance.

Andrew Huberman:

Last episode, we talked about how to assess recovery and things that you might want to do to improve recovery, how exposure to ice baths and cold showers can reduce inflammation, which can be great for recovery but can inhibit some of the adaptations for strength and hypertrophy because inflammation isn't good or bad. Inflammation isn't a nice person or a mean person, it's both. It's a great thing for stimulating adaptations, but you don't want it around too long.

Andrew Huberman:

And so we suggested that you not do ice baths within probably six hours of any training where the goal was hypertrophy or strength training. There is some evidence that getting yourself into an ice bath or cold shower after endurance training can actually improve the mitochondrial aspects of endurance exercise, that you can get improvements in mitochondrial density and you can get improvements in mitochondrial respiration by doing that afterwards, and that it can facilitate recovery. That's still a bit of a controversial area. I do think that what I mentioned earlier, that waiting at least six hours and probably more like 24 hours between workouts is a good idea. That getting at least one full day of rest each week, for some people that'll be two. I have to say I'm one of these people that after two days of absolutely no exercise, I do perform better, consistently, across all aspects of physical performance.

Andrew Huberman:

And mentally I feel better, as well. Even though I loathe to take those days off, unless I'm really exhausted, it does seem to help my training. Some people can train seven days a week and they're fine. I think it just is, there's a lot of individual variation.

Andrew Huberman:

You want to work on sleep and maximizing sleep for recovery. Nutrition, of course, as well. I talked about sleep in the first four episodes of the podcast. So if you have trouble with sleep, definitely check out those episodes. It's very clear, and a number of sports teams, even some folks that I work with, and Andy Galpin and others, are starting to incorporate what's called a parasympathetic downregulation after training of any kind, as a way to accelerate recovery and enable you to do more work. In other words, get back to work out sooner. What is parasympathetic downregulation?

Andrew Huberman:

It means finishing your training. And instead of just hopping on the phone or hopping into your car and heading off, to take five minutes minimum, maybe ideally more like 10 or 20, but for sake of time, five minutes minimum. And doing just some slow, pure nasal long-exhale-devoted breathing. Or lying down and just kind of zoning out. That, it seems, can accelerate recovery and allow you to get back into other types of work, mental work or physical work, more quickly. Which makes total sense, because, remember, your nervous system and recovery and work is a local phenomenon. Which muscles were you using? Were you using your glutes, your hams and your back, or were you using your shoulders, et cetera. But it's also a systemic thing. It's also about those neurons and the locus coeruleus that are releasing epinephrine. You want to quiet all that down after training.

Andrew Huberman:

You want to really just zone out. Think Costello, channel your inner Costello. And just mellow out for five to 20 minutes, and then move into the rest of your day. Five minutes should be manageable, even if it's just sitting in the car with your eyes closed, doing that downregulation breathing. I think you'll see big benefits in terms of allowing yourself to come back sooner, do more work over time, and just perform and feel better generally, as well as be able to think about other things besides just how much the previous workout kind of beats you up.

Andrew Huberman:

A couple more things I think are going to be useful, and I do want to just pack these in, because we are closing out the month on physical performance, and that's about programming and about pacing and the kind of mental aspects of endurance. So let's start with pacing and mental aspects of endurance.

Andrew Huberman:

I learned from a friend and colleague here at the podcast who's very active in triathlon and marathon, and knows a lot about that whole world and the competitive landscape there, that pacing — and literally, physical pacers have a laser on the ground — or visualizing it or having a pace car or a pace runner in front, is actually not allowed in many competitions. And if those are present, doesn't allow the race times to qualify as legitimate record holding times. And that's very interesting to me, because what we know is that the visual system has this capacity to switch back and forth between what we call panoramic vision, where we're not really focused on anything; things are just flowing past us or our eyes are just kind of zoned out. So I can do this right now, and you won't be able to tell, but I'm looking at the corners of the room.

Andrew Huberman:

I see Costello down there on the floor, I see my podcast team here, and I can also see the microphone. I can see myself in this environment. That's panoramic vision. Whereas if I draw my eyes to one location, like right there in the center of the camera, it's what's called a vergence eye movement. So I'm contracting my visual window. The contraction of the visual window, when that's done, is the same thing that would happen if I was tracking, say, a pace car or a pace runner or a laser on the ground. The mere bringing our eyes together to what we call a vergence point has the impact of triggering the activation of neural circuits in the thalamus. Things like zona incerta, if you really want to know what their names are, of these brain areas as well as in the brain stem, that activate the so-called alertness system, things like locus coeruleus.

Andrew Huberman:

Whereas panoramic vision tends to bring us into states of relaxation. You can actually leverage this during your runs. Let's say you're out for a long run, or you're swimming, or you're cycling, this is probably easiest to imagine out of the water, but you could probably do in the water as well. If you focus your attention on a landmark that you're going to run to, you'll find that it's much easier than if you don't actually have a set milestone or landmark that you're going to run to.

Andrew Huberman:

However, if you were to continue that repeatedly, just going milestone after milestone after milestone, you would feel more mentally fatigued, and you would actually be able to generate less work overall. One thing that can be useful is focusing on a milestone, running to that milestone or biking, whatever it is the activity happens to be, and then dilating your field of view to relax this system, and then continuing again.

Andrew Huberman:

So it's this kind of active contraction of the visual window and then dilation of the visual window. Contraction of the visual window allows you to generate more effort, but there's a cost to doing that, because neurons consume energy, and now you know how they do that. Whereas dilation allows you to, essentially, be more efficient, right?

Andrew Huberman:

Now, pacing is not allowed or having a pacer, a visual pacer, because it does allow you to access systems in the brain and body that allow you to create more energy, more effort. And so I find it interesting that, I think, in a kind of subconscious genius, the race officials and the governing bodies of these races have said, "Okay, sure, having a pacer there or someone in front, you can draft off of them." There's actually a kind of aerodynamic effect of having someone in front of you that makes it easier to run in the wake of their airstream, so to speak.

Andrew Huberman:

Same as true in cycling. This is why the cycling teams are so good at maneuvering in packs in very specific ways. You can go faster with less effort if you're drafting, as it's called, behind somebody. But as well, where you place your vision will allow you to generate more effort. And so it's interesting that they've taken out this kind of, if you will, performance-enhancing tool. I have to imagine it's the appropriate word here, that good runners, good cyclists, have the ability to create a kind of pacer in their mind's eye. I have to imagine that they're not just completely allowing their attention to drift, although they do that when they want to be in highly efficient mode, generating effort without having to tax their mental capacity. And remember, mental capacity is neural energy and consumes glucose —energy that they could devote to the functioning of their body. But that when needed, that they can focus their energy in and actually kind of chase a mental pacer or pick milestones.

Andrew Huberman:

So this is a mental game that you can play as well. It's a little bit hard to do in the context of weightlifting in the gym. It's more of a moving-through-space kind of thing. But some people do this by counting reps, et cetera. I think it's especially suitable for endurance type of exercise, especially done outside. One of the reasons I hate running on a treadmill is it just feels like it's never ending. And I've never tried one of these Peleton things. I try and avoid looking at screens as much as I possibly can. But if you try this next time you're out for a run or a swim, what you'll find is that you have a capacity to engage a system of higher energy output when you focus your eyes on a particular location. But you want to use that judiciously. Because your goal, of course, is to become efficient at moving through space over time, and not taxing your brain and body to the point where you arrive at the end of that, unless it's race day, just completely tapped out.

Andrew Huberman:

So that's a kind of interesting aspect of running. If you're a fan of running, which I am, and you get the chance to look at any of the documentaries or docudramas made about Steve Prefontaine, it was clear that he was mostly in a battle with himself, but that he was also a highly competitive individual. And you'll see this in some of his races. I do encourage you to look some of those up on YouTube or see the docudramas. They're quite good. Where he ran, essentially, was 12 laps on a track. It is the 5,000 meter race, which is, essentially, three miles. And he, essentially, tried to sprint the whole thing, which is ridiculous. Actually knowing what you know today, you'll realize that Steve Prefontaine, basically, was pulling from strength, speed, power, muscular endurance, long-duration effort, high-intensity aerobic, anaerobic as he sort of tried to maximize every fuel system.

Andrew Huberman:

And you'll see that in the races that he runs. But that when runners are nearing the final lap, the so-called bell lap of a race, they'll often look to one another to see where somebody is, obviously to assess their progress and how close somebody is. But when somebody gets passed, oftentimes you'll see someone access this mysterious kick, this ability to tap into some additional gear that allows them to run forward or faster, when they themselves actually thought that they were maxed out.

Andrew Huberman:

So someone could be running for the finish line, they're convinced they're going to win, they're going max effort, or at least they perceive max effort, someone passes them. And all of a sudden, max effort has changed. Because of that visual target, they are able to access higher levels of speed and output and effort and performance. They don't always catch up to that person and win. But having a target, a milestone, is a powerful way that we can generate more force and energy in anything. And the visual system is the way that we bring those milestones into our brain, which then brings about epinephrine, which brings about neural firing, which allows us to access whatever resources happen to be available to us.

Andrew Huberman:

So I find this fascinating, because people often wonder, Where does the kick come from? Where is this kind of gift of an additional gear? Where is that deeper resource? And we often express it and talk about it in kind of psychological terms, like heart or willpower or that something kind of got transplanted into us or descended into us. And not to remove any of the spiritual aspects of sport or running or effort or the human heart, but it's very clear that the nervous system, when it has a specific visual target, can generate the sorts of intense effort that it couldn't otherwise. And it sometimes even comes as a surprise to the person generating the effort.

Andrew Huberman:

I promised that I would talk about programming, meaning when and how many times a week to do the various workouts related to endurance and how to merge those with other types of exercise that you might be doing for strength or yoga or other things that you might be doing, like work and other things unrelated to exercise. Since that's a vast space with many different parameters, and you all have different lives and lifestyles and backgrounds with fitness, et cetera, what I'm going to do is I'm going to put three different levels, if you will, or protocols that one could adopt in a link on the show notes. So in the caption on YouTube, if you click on that link, you'll be able to see three possible combinations of endurance work, strength and hypertrophy work, or endurance work, flexibility and hypertrophy work, that are grounded in many of the major publications that Dr. Andy Galpin and colleagues, and other people, have described, including this review that's also linked there on concurrent training and how one can use concurrent training, meaning training for endurance, training for strength, training for hypertrophy, training for all these different things without having to train constantly every day, twice a day, etcetera.

Andrew Huberman:

So if you are interested in taking the protocols that you learned about in this episode and in previous episodes and combining those, we've placed them there for you as a completely zero-cost resource. Please understand they are not holy. Costello agrees. They are not holy. There will be variation in terms of what people can tolerate and what they have time for. But I think they'll serve as a useful guideline in getting started, or in continuing with and expanding on existing endurance work, strength work, hypertrophy work, and so forth.

Andrew Huberman:

Just really quickly, we didn't talk about supplements much today. In the previous episodes, I talked about the phosphocreatine system and supplementing with creatine. Talked about beta-alanine for kind of moderate duration work. Really, the only things that have been shown to really improve endurance work across the four varieties of endurance work I described today, they have essentially two forms. One are stimulants, so things like caffeine will definitely improve endurance work and power output. There's a little bit of evidence that caffeine intake can actually inhibit the function of the creatine system, but it's just one study. But that's interesting. If you want to read that study, you can put caffeine into examine.com and it will take you to that study. Many people get sore after workouts and particularly workouts that involve a lot of eccentric loading, or workouts that are very novel, where they've kind of pushed it instead of moving gradually, as I suggest, into say, high-intensity anaerobic endurance work of three sets of 20 seconds on, 100 second rest.

Andrew Huberman:

Maybe you get overambitious and you do eight sets, in which case you are extremely sore. Certain forms of magnesium, in particular magnesium malate, M-A-L-A-T-E, have been shown to be useful for removing or reducing the amount of delayed-onset muscle soreness. That form of magnesium is distinctly different than the sorts of magnesium that are good for getting us into sleep. Things like magnesium threonate and bisglycinate.

Andrew Huberman:

And then there's this whole thing about beet powder and beet juices, and things that increase nitric oxide and allow for more vasodilation, and therefore delivery of blood to muscle and neurons and other tissues for long bouts of endurance work. Some people like beet juice and the related compounds that increase arginine and vasodilation. Some people don't. Some people don't feel good when they take those. Some people also don't feel good when they take beta-alanine, because it can give them this feeling of itchy creepy-crawlies under the skin, kind of the niacin phenomenon, the niacin flush.

Andrew Huberman:

Some people don't mind that or some people don't experience that. So when it comes to supplementation, there's a lot of variety. But magnesium malate has been shown to reduce soreness. So sometimes that's good. Cold and hot contrast therapy for soreness, things of that sort. But in general, we focused mainly today on behavioral tools. You'll notice that all of the tools are accessible without the need for lots of equipment. So I didn't say you need a rower or you need a kettlebell, though those will work. And I hope I was able to illustrate for you that endurance isn't just one thing. It's not just the ability to go for long bouts of exercise of different kinds, that there's also this mental component because of the way that neurons work. And also that there are these different forms of endurance, of muscular endurance, that ... where you're going to fail because of the muscles and muscle energy utilization and the nerves that innervate those muscles locally, not because of a failure to bring in oxygen or blood.

Andrew Huberman:

Whereas long-duration effort, it's going to be more about being below your VO2 max and your ability to be efficient for long bouts of more than 12 minutes of exercise. One set, as they say, of 12 minutes to maybe several hours. I should just mention with long-duration-type work, you could even imagine raking in the yard or mowing a lawn, depending on how big that lawn is. I used to have job when I was a kid mowing lawns, and I'll tell you, we didn't have many neighbors with very big lawns, but a few of them felt huge because they were really convoluted. And if you're pushing that mower, and these were the old fashioned mowers, not electric mowers, it's work. That's also of the sort that we call long-duration endurance work. High-intensity training will tap into yet other fuel sources and mechanisms, as we learned today.

Andrew Huberman:

So if you are enjoying this podcast and you're finding the information useful, it would be great if you would subscribe to the YouTube channel. That really helps us quite a lot. And if you like, you can click the notifications button on YouTube as well — that way you're sure to never miss an episode. We always release episodes on Monday, but we also sometimes release episodes in between Mondays. So please do subscribe to the YouTube channel. Please also give us feedback in the comment section on the YouTube channel. That's where you can tell us about topics that you want to hear more about. Or if you have questions about a given episode or content within an episode, that's where you want to put that feedback. If you're not already subscribing on Apple and Spotify as well, please do that. On Apple, you can give us up to a five-star review.

Andrew Huberman:

We like to think that you would give us a five-star review, but you can also leave comments on Apple about the podcast more generally. And again, those are all zero-cost ways that you can really help support the podcast. Please also check out our sponsors that we mentioned at the beginning of the podcast. I know ad reads are not the first thing that people want to hear when they're getting ready to consume scientific information. Please understand that the ads and the sponsors allow us to bring the zero-cost-to-consumer information about science and science-related tools to everybody. So if you have the means, check out the sponsors. We only work with sponsors whose products we really believe in and that I actually use and really love. There's no obligation, however.

Andrew Huberman:

If you know people that might be interested in the podcast and benefit from the information, please recommend it to them. That really helps us. If you're on Instagram, check us out at Huberman Lab. If you're on Twitter, it's also Huberman Lab. And please check out our new website, which is hubermanlab.com. There you can find all the episodes of all the podcasts batched according to topic in every format, YouTube, Apple and Spotify, with links out to those. It's searchable by keywords that you're interested in. So sleep or exercise, weight training, strength, fat loss, et cetera. And you can subscribe to our newsletter, the Neural Network, which will allow you to get zero-cost updates about speaking events, about any book releases or exciting things that I'm reading that I think you would enjoy reading as well, as well as protocols related to science and some summary and important notes from the podcast. And last but not least, on behalf of myself and Costello, who's finally waking up for... Oh no, he went back to sleep. Thank you for your interest in science.

PART 3 OF 3 ENDS [01:30:04]

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