Essentials: How to Build Endurance

0:00Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science -based tools for mental health, physical health, and performance. 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. 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.

0:38Endurance, as the name suggests, is our ability to engage in continuous bouts of exercise or continuous movement or continuous effort of any kind. It is clear that cardiovascular exercise, exercise where you're getting your heart rate up continuously for a period of time, 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, etc. The key thing to understand about energy production in the body is this thing that we call ATP. ATP is required for anything that requires energy, for anything that you do that requires effort.

1:28So our muscles and our neurons use different fuel sources to generate ATP. The ones that are used first for short bouts of intense activity are things like phosphocreatine. If you've only heard about creatine as a supplement, well, phosphocreatine actually exists on a muscles, and that's why people take creatine, you can load your muscles with more creatine. Phosphocreatine is great for short intense bouts of effort. Then you start to tap into things like glucose, which is literally just carbohydrates, your sugar that's in your blood. And then if you keep pushing, you start to tap into other fuel sources like glycogen.

2:06And you have fat stored in adipose tissue, even if you have very, very low body fat percentage, 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. 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 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.

2:58You need air, basically, in your system. Now, it's not actual air. You need oxygen molecules in your system comes in through your mouth and your nose goes to your lungs and distributes via the bloodstream. Oxygen is not a fuel, but like a fire that has no oxygen, you can't actually burn the logs. But when you blow a lot of oxygen onto a fire, basically onto logs with a flame there, then basically it will take fire. It will burn. Oxygen allows you to burn fuel. So today, we are going to ask the critical questions. What allows us to perform? What allows us to continue effort for long periods of time?

3:43Well, 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. So we have to ask the question, what is the limiting factor on performance? 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. There are five main categories of things that allow us to engage in effort. 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.

4:33Let's talk about neurons and how they work. But I want to tell you about an experiment that's going to make it very clear why quitting is a mental thing, not a physical thing. So why do we quit? Well, an experiment was done a couple years ago and was published in the journal Cell, Cell Press Journal, excellent journal showing that there's a class of neurons in our brain stem in the back of our brain. That if they shut off, we quit. Now these neurons release epinephrine epinephrine is adrenaline and anytime we are engaged in effort of any kind, we are releasing epinephrine anytime we're awake really we are releasing epinephrine into our brain.

5:22In fact, this little group of neurons in the back of our brain is called the locus serulius 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. So think about epinephrine as a readiness signal. And when we are engaged in effort, this readiness signal is being churned into our brain when we're relaxed and we're falling asleep epinephrine levels are low. So our desire to continue or put differently our willingness to continue and our desire to quit is mediated by events between our two ears.

6:07Now that doesn't mean that the body is not involved, but it means that neurons are critically important. So we have two categories of neurons that are important. The ones in our head that tell us get up and go out and take that run and the ones that allow us encourage us to continue that run and we have neurons that shut things off 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. So when people say, is it, I hear that, you know, sports or effort or fighting or it's 90 % mental, 10 % physical.

6:44That whole discussion about how much is mental, how much is physical is absolutely silly. It's 100 % nervous system. It's neurons. Okay. So when people say mental or physical, understand it's 100 % neural. 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 is glucose. That's what neurons run on. And you need electrolytes. Neurons have what's called a sodium potassium pump blah blah blah. They generate electricity in order to get nerves, nerves cells to fire to contract muscle to say, I'm going to continue.

7:32You need sufficient sodium salt because the action potential, the actual firing of neurons is driven by sodium entering the cell rushing into the cell. And then there's a removal of potassium and then there's a kind of resetting of those levels by something called the sodium potassium pump and the sodium potassium pump and sodium and action potentials. Even if you don't know anything about that is ATP dependent. It requires energy. So you need energy in order to get neurons to fire. And it is pH dependent. It depends on the conditions or the environment within the brain being of a certain pH or acidity.

8:12pH is about how acid or how basic the environment is. 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. Muscle. Muscle is going to engage and generate energy first by using this phosphocreatine system. High vows 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, they're converting that into ATP in order to generate that energy.

8:55And then there's stuff in our blood that's available as an energy source. And in blood we've got glucose so literally blood sugar that's floating around. So let's say you have fasted for three days, your blood glucose is going to be very low. So that's not going to be a great fuel source. But you will start to liberate fats from your adipose tissue, from your fat fatty acids. We'll start to mobilize into the blood stream and you can burn those for energy. Now there are some other factors that are important and those are the heart which is going to move blood. So the more that the heart can move blood and oxygen, well the more fuel that's going to be available for you to engage in muscular effort and thinking effort.

9:37And 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. 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?

10:16What 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. As many of you know, I've been taking AG1 daily for more than 13 years. However, I've now found an even better vitamin mineral probiotic drink. That new and better drink is the new and improved AG1, which just launched this month. This next gen formula from AG1 is a more advanced clinically backed version of the product that I've been taking daily for years.

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12:02Right now, AG1 is giving away an AG1 welcome kit with five free travel packs and a free bottle of vitamin D3 K2. Again, go to drink AG1 .com slash Huberman to claim the special welcome kit with five free travel packs and a free bottle of vitamin D3 K2. So let's talk about the four kinds of endurance and how to achieve those. 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.

12:56Okay. 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. At some point, your muscles will fatigue. Muscular endurance is going to be something that you can perform for anywhere from 12 to 25 or even up to 100 repetitions. So a good example is pushups. It's actually no coincidence that a lot of military bootcamp style training is not done with weights. It's done with things like pushups, pullups, situps 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.

13:52So 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. The one critical feature of building muscular endurance is that it has no major eccentric loading component. 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.

14:40And eccentric movements are when you are lengthening a muscle typically or lowering a weight. So if you do a pullup 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. Ecentric portion of resistance training of any kind, whether or not for endurance or for strength, is one of the major causes of soreness. Some people will be more susceptible to this to this, excuse me, than others. But it does create more damage in muscle fibers. Muscular endurance and building muscular endurance should not include any movements that include major eccentric loads.

15:20So if you're going to do pushups, doesn't mean that you want to drop, you know, smash your chest into the floor. And by the way, your chest should touch the ground on every pushup. That's a real pushup. It's about pushing down until your chest, touch the floor and straightening out. That's a proper pushup. And a pullup is where you pull out 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.

15:55But 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. Isometric, as I mentioned, things like plank and wall sits will work. Now, what's interesting about this is that it doesn't seem at all like what people normally think of as endurance. And yet it's been shown in nice quality peer reviewed studies that muscular endurance can improve our ability to engage in long bouts of what we call long duration low intensity endurance work.

16:44So this can support long runs, it can support long swims and it can build also it can build postural strength and endurance simultaneously. 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 to say, okay, let's say you do a plank and you're planking for, you know, maybe you're able to plank for a minute or two minutes or three minutes. At some point you will fail. You're not going to fail because the heart gives out. You're not going to fail because you can't get enough oxygen because you can breathe while you're doing that.

17:24You're going to fail because of local muscular failure, which means that as you do, if you choose to do this protocol of three to five sets, et cetera, et cetera, to build muscular endurance. Mainly what you are going to be building is you're going to be building the ability of your mitochondria to use oxygen to generate energy locally. And that it's something called mitochondrial respiration respiration because of the involvement of oxygen. And it's also going to be increasing the extent to which the neurons control the muscles and provide a stimulus for the muscles to contract. But this is independent of power and strength.

18:08Okay. 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. Okay. Continually if you're using isometric holds, repeatedly, repeatedly, excuse me if you're using repetition type exercise where there's a contraction and an extension of the muscle essentially concentric and an eccentric portion.

18:47But 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. I'd like to take a quick break and thank one of our sponsors, Element. Element is an electrolyte drink that has everything you need and nothing you don't. That means the electrolytes sodium magnesium and potassium in the correct ratios, but no sugar. We should all know that proper hydration is critical for optimal brain and body function. In fact, even a slight degree of dehydration can diminish your cognitive and physical performance to a considerable degree.

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19:50And electrolytes. There are a bunch of different great tasting flavors of Element. I like the watermelon, I like the raspberry, I like the citrus. Basically, I like all of them. If you'd like to try Element, you can go to drinkelement .com slash Huberman to claim an Element sample pack with the purchase of any Element drink mix. Again, that's drink element spelled LMNT. So it's drinkelement .com slash Huberman to claim a free sample pack. Today's episode is also brought to us by 8 Sleep. 8 Sleep makes smart mattress covers with cooling, heating, and sleep tracking capacity. Now, I've spoken before on this podcast about the critical need for us to get adequate amounts of quality sleep each and every night.

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22:15Some people are actually doing those kinds of really long events, marathons, for instance. 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, your mind is going to use more or less energy depending on how much will power, how much of a fight you have to get into with yourself in order to generate the effort.

23:03I really want to underscore this. Will power 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. 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.

23:50And that might seem a little bit counterintuitive, but every time you do that run what you're doing is you're building up mitochondrial density. It's not so much about mitochondrial oxidation and respiration. You're building up mitochondrial density. You're actually increasing the amount of ATP that you can create for a given bout of effort. You're becoming more efficient. You're burning less fuel overall doing the same thing. That's really what these long slow distance or long bouts of effort are really all about. Now why do this long duration effort? Why would you want to do it? Why is it good for you?

24:28Well, it does something very important, which is that it builds the capillary beds within muscles. So these are tiny little avenues like little tiny streams and estuaries between the bigger arteries and veins. 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. And the reason is when blood arrives to muscles, it has oxygen.

25:12The 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. So this long duration work, unlike muscular endurance, like planks and everything that we were talking about before, is really about building the capillary systems and the mitochondria, the energy utilization systems within the muscles themselves. And then there are two kinds in between that in recent years have gotten a lot of attention and excitement, sometimes called high intensity interval training.

25:52One is anaerobic, so called anaerobic endurance, so no oxygen, and the other is aerobic endurance, both of which qualify as HII, high intensity interval training. So let's talk about anaerobic endurance first. Anaerobic endurance from a protocol perspective is going to be three to twelve sets. And these are going to be performed at whatever speed allows you to complete the work in good, safe form. Okay, so it could be fast, it could be slow, as the work continues, your repetitions may slow down or it may speed up. Chinsar, it's going to slow down. So what does this work, what do these sets look like?

26:37Remember, long slow distance is one set. Muscular endurance is three to five sets, high intensity anaerobic endurance is going to be somewhere between three and twelve sets. And it's going to have a ratio of work to rest of anywhere from three to one to one to five. Okay, so what would a three to one ratio set look like? Well, it's going to be 30 seconds of hard pedaling on the bike, for instance, or running, or on the roller. 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. 30 seconds on, 10 seconds off.

27:22That's a very brief rest. So three to one is just a good example would be 30 seconds on, 10 seconds off. 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 100 seconds. So let's just take a look at the three to one ratio. So in the three to one ratio, if you're going to do 30 seconds of hard pedaling on a bike, followed by 10 seconds, so maybe one of these what they call assault bikes, and then you stop for 10 seconds and then repeat. Chances are you will be able to do one, two, three, four, maybe even as many as twelve sets, if you're really in good condition, that you'll be able to do all those because pedaling on the bike doesn't require a ton of skill.