Essentials: How to Build Endurance

**Andrew Huberman** (0:00)
Welcome 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. Endurance, 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, et cetera. 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. So our muscles and our neurons use different fuel sources to generate ATP.
The ones that are used first for short bouts of intense activity are things like phosphocreatine. If you've only heard about creatine as a supplement, well, phosphocreatine actually exists on our 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 carbohydrate. It's your sugar that's in your blood. And then if you keep pushing, you start to tap into other fuel sources like glycogen. And 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. You need air, basically, in your system. Now, it's not actual air. You need oxygen molecules in your system. Comes in through your mouth and your nose, goes to your lungs and distributes via the bloodstream.
Oxygen is not a fuel, but like a fire that has no oxygen, you can't actually burn the logs. But when you blow a lot of oxygen onto a fire, basically onto logs with a flame there, then basically it will take fire, it will burn, okay? Oxygen allows you to burn fuel. So today we are going to ask the critical questions. What allows us to perform? What allows us to continue effort for long periods of time? 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. 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. 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. 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, not a physical thing. So why do we quit? Well, an experiment was done a couple of years ago and was published in the journal Cell, Cell Press Journal, excellent journal, showing that there's a class of neurons in our brainstem, 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. 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 churns out more, and then it acts as kind of an alertness signal for the whole brain. We also, of course, have adrenaline epinephrine released in our body, which makes our body ready for things. So think about epinephrine as a readiness signal. And when we are engaged in effort, this readiness signal is being churned into our brain. When we're relaxed and we're falling asleep, epinephrine levels are low. So our desire to continue, or put differently, our willingness to continue and our desire to quit is mediated by events between our two ears. Now, that doesn't mean that the body's not involved, but it means that neurons are critically important. So we have two categories of neurons that are important, the ones in our head that tell us get up and go out and take that run, and the ones that allow us, encourage us to continue that run. And we have neurons that shut things off, 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, that 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, nerve cells to fire, to contract muscle, to say, I'm going to continue, you need sufficient sodium salt because the action potential, the actual firing of neurons is driven by sodium entering the cell, rushing into the cell. And then there's a removal of potassium. And then there's a kind of resetting of those levels by something called the sodium potassium pump. And the sodium potassium pump and sodium and action potentials, even if you don't know anything about that is ATP dependent. It requires energy. So you need energy in order to get neurons to fire. And it is pH dependent. It depends on the conditions or the environment within the brain being of a certain pH or acidity. pH is about how acid or how basic the environment is. 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 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, they're converting that into ATP in order to generate that energy. And 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 will start to mobilize into the bloodstream 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. 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. 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. I'd like to take a quick break and acknowledge our sponsor, AG1. AG1 is a vitamin mineral probiotic drink that also contains adaptogens. I started taking AG1 way back in 2012, long before I even knew what a podcast was. I started taking it and I still take it every single day because it ensures that I meet my quota for daily vitamins and minerals and it helps make sure that I get enough prebiotics and probiotics to support my gut health. Over the past 10 years, gut health has emerged as something that we realize is important, not only for the health of our digestion, but also for our immune system and for the production of neurotransmitters and neuromodulators, things like dopamine and serotonin. In other words, gut health is critical for proper brain function. Now, of course, I strive to eat healthy whole foods from unprocessed sources for the majority of my nutritional intake, but there are a number of things in AG1, including specific micronutrients that are hard or impossible to get from whole foods. So by taking AG1 daily, I get the vitamins and minerals that I need along with the probiotics and prebiotics for gut health and in turn brain and immune system health and the adaptogens and critical micronutrients that are essential for all organs and tissues of the body. So anytime somebody asks me if they were to only take one supplement, what that supplement should be, I always say AG1 because AG1 supports so many different systems in the brain and body that relate to our mental health, physical health and performance. If you'd like to try AG1, you can go to drinkag1.com/huberman.