in: Fitness, Health & Fitness, Podcast

• Last updated: September 29, 2021

Podcast #382: How to Lift More, Run Faster, and Endure Longer

How long can a human run without stopping? What’s the most weight a human can deadlift? Will someone ever run a mile in less than three minutes and thirty seconds?

My guest explores these questions in his latest book, and along the way uncovers insights into all the factors that go into pushing the limits of human athletic performance. His name is Alex Hutchinson and he’s the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance

Today on the show, Alex and I discuss the history of the science of human performance and the three competing theories about how to measure and improve it. Alex first explains the interplay between physiology and psychology when it comes to humans pushing themselves. We then spend the rest of the conversation discussing factors that have an influence on our performance including pain, thirst, muscle strength, diet, and mental fatigue. Alex finally shares insights from the latest research on how you can manipulate these factors to run faster and longer and lift heavier weights. 

Show Highlights

  • The competing theories that try to determine the limits of human performance 
  • What is VO2 max? Does it determine your physical limits?
  • Why isn’t VO2 max held in the same regard as it was 1o or 20 years ago?
  • The central governor theory, and the brain science behind endurance 
  • How great coaches help you build your endurance 
  • Samuele Marcora’s theory of human endurance
  • Why perceived effort has such an affect on our performance  
  • How mental fatigue impacts your physical performance 
  • Can you train yourself to ignore pain? Can you separate that pain from your perceived effort?
  • How should you fuel yourself for optimal performance? 
  • Does high-fat/low-carb diet work? What happened to carbo-loading?
  • The hydration debate — what does the science really say?
  • What can we do to train our brains to endure longer and push the limits of our own physical performance?
  • Why you should embrace training when you’re mentally tired 

Resources/People/Articles Mentioned in Podcast

Book cover of " Endure" by Alex Hutchinson.

Connect With Alex 

Alex on Twitter

Alex’s website

Alex’s Sweat Science column

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Read the Transcript

Brett McKay: Welcome to another edition of the Art of Manliness Podcast. How long can a human run without stopping? What’s the most weight a human can deadlift? Will someone ever run a four minute mile in less than three minutes and 30 seconds, and will someone ever run a marathon in less than two hours? My guest explores these questions in his latest book and along the way uncovers insights to all the factors that go into pushing the limits of human athletic performance. His name is Alex Hutchinson, and he’s the author of the book Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance.

Today on the show, Alex and I discuss the history of the science of human performance, and the three competing theories about how to measure and improve it. Alex first explains the interplay between physiology and psychology when it comes to humans pushing themselves. We then spend the rest of the conversation discussing various factors that have influence on our performance, including pain, thirst, muscle strength, diet, and mental fatigue.

Alex then shares insights into the latest research and how you can manipulate these factors to run faster and longer, and life heavier. After the show’s over, check out the show notes at AOM.IS/endure.

Alex Hutchinson, welcome to the show.

Alex Hutchinson: Thanks a lot Brett, I’m glad to be here.

Brett McKay: So you had a book out called Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. And it is about how we’re able to push ourselves to do these amazing physical feats, and we’ll talk about some of the ones you highlighted in the book, but before we do that, can you tell us a bit about your background? And how it inspired you to research the science of human performance and endurance?

Alex Hutchinson: Yeah, so these days I call myself a science journalist, or sometimes if I’m being really specific, I’m a science of endurance journalist. But that all started probably 20 years ago, I was a competitive track and field athlete. I ran for the Canadian National team for a number of years. And there was this sort of ongoing mystery of was I really approaching my limits? And there was this one night where I ran … I’d been trying to break four minutes for 1500 meters, which is a sort of decent high school time, for a number of years, for like years I’ve been stuck just over that barrier. And one day, I was running a race where the timekeeper was calling out the splits that were wrong, and he tricked me basically, accidentally, into thinking I was running super fast, and I ran a nine second personal best, which totally changed the trajectory of my running career.

And basically since that moment … and nothing had changed in my physical training, so there was this moment where a mental change created a total difference in my apparent physical endurance. So I’ve been sort of wondering about that for a long time, and when I became a journalist about 10 years later, I started to dig into the research about the science of endurance, trying to understand what it was that set limits, and that’s the long and winding answer, but it was a long and winding road that sort of got me to this point.

Brett McKay: So then as we’ll see in this conversation, is that we really don’t know, we have some ideas, but some of it, it’s confounding. So let’s talk about sort of the overall … give like a big picture view. You talked about in the book, there’s three competing theories that determines the limits of human endurance. The first is a physical limit, and that is primarily VO2 max. Now I’m sure our listeners have heard that acronym thrown around a lot, so what exactly is VO2 max? And why have physiologists thought that that’s the thing that determines how long you can run, or push yourself physically?

Alex Hutchinson: Yeah, so VO2 max, so the science definition is that it’s the maximum amount of oxygen that you can breathe in from the air, use your heart to pump to the muscles, extract from your blood, and use it to help fuel aerobic exercise. So it’s the maximum aerobic quantity. And it goes back about a century, almost a century now, to when scientists were first figuring out how muscles actually work. And there was this dawning realization that oh, you know, if you take an individual muscle fiber, basically we can understand, it’s just like a machine, and we can understand what the rules that govern this machine are. And so, there was this hope that we could extrapolate that up to the human body, and think of the body, literally, the guy who invented the O2 max, wrote these articles for Scientific American saying the human body is a machine, and we can calculate its limits.

So, VO2, definitely … no one ever thought the VO2 max was the only factor dictating endurance, but they thought it was a big factor that tells you … so at a certain point, the harder I run, the more oxygen I need, right, and the harder I start to breath. But at a certain point, you just can’t breathe any harder, and you can’t bring any more oxygen in. And the idea was that that’s what determines the level of your endurance, that you reach this maximum, or this plateau in oxygen.

And so, that turned out to be a really influential idea, philosophically, for most of the 20th century.

Brett McKay: Right. So when did people start figuring out, well VO2 max really isn’t the determining factor of human performance?

Alex Hutchinson: Well, some of the first skepticism was in the late 70s and early 80s. And there’s a scientist named Tim Noakes, in South Africa, who’s been both tremendously influential and tremendously controversial, about a number of topics. And I visited him six or seven years ago, and I asked him, “When did you first start having doubts about VO2 max?” And he said, “Well, we had just started our lab in the early 80s.” And he was testing a lot of elite athletes, and so he brought in two very good athletes, one of whom was a sub four minute miler, of one of the best milers that South Africa had ever produced. And the other was a woman who had won a very famous ultra marathon in South Africa, which is … I think it’s 55 miles long, or something like that, a totally different race. So she was a very slow miler, but a good long distance runner. And he was a very good miler. And he tested them both in the same day, and they both had exactly the same VO2 max. And he thought, “Well, if this test can’t tell the difference between this like six foot two sprinting, middle distance runner, and this tiny, petite ultra runner, then obviously there’s something that we’re not understanding here.”

And so, I would say, in the last 30 years there’s been doubts, and in the last 20 years there’s been controversy. And in the last 10 years, people have kind of moved away from the idea that VO2 max … it’s almost … the pendulum sometimes swings too far, and now people are like, “Oh, VO2 max is meaningless.” And that’s not true, VO2 max has meaning. It’s just the sort of … sometimes, one way of thinking of it is, if I have a bucket, and I want to know how much water can fit in that bucket, we understand geometry well enough to know that if I know tall the bucket is, and how wide it is, I know exactly how much water it will hold, and it doesn’t matter how hard the bucket tries, it can’t hold more water than that. And we now understand … and there was the hope that VO2 max would allow us to calculate the sort of capacity of human endurance in the same way. And now we understand that we’re not buckets, we’re more like balloons. You can kind of squeeze more air, or more water, into the balloon, and the balloon’s capacity isn’t infinite. You can’t fit the whole in the balloon, but it’s also very hard to define a limit of how much air you can squeeze into a balloon. At some point, it’s going to pop, but you don’t really know when in advance.

Brett McKay: Okay, so, speaking of Tim Noakes, that leads us to the next theories of what allows us to push ourself, and these are more psychological. And Tim Noakes, he’s the guy that developed the central governor theory. What is that?

Alex Hutchinson: Yeah, so he … and this is probably, when you think of alternatives to the human machine view of endurance, the most famous one is this central governor theory, which was proposed by Noakes in the late 1990s. And basically what he argues is that the brain is protecting you in some way. There are physical limits, but if you reach those physical limits, you would die, because your heart wouldn’t be getting enough oxygen. If you were really limited by a lack of oxygen, your heart would stop pumping, and you would die. That’s maybe a little bit hyperbolic, but the point is, he argues that we never quite reach our limits, and that’s because the brain is looking out for you in all sorts of different ways. It’s monitoring your temperature, it’s monitoring your brain oxygen levels, and if it detects that things are getting a little too crazy, it automatically sort of throttles down the signals that are going from your brain to your muscles. So you’re still trying just as hard, but you’re not getting as much force out of your muscles. And that’s to make sure you never quite hit those limits.

And that theory has been really influential, but also controversial, because the obvious question is, “Okay, lets find a brain scanner and lets see this central governor.” But it’s not that simple, there isn’t a part of the brain called the central governor. So that theory has been attacked, or debated a lot in the last few years.

Brett McKay: Well if there’s no like single part of it, they have ideas of parts of the brain that might play a role in this central governor?

Alex Hutchinson: Absolutely. And the sort of interesting thing is the more advanced these studies get, the more brain areas get implicated. So there’s some really interesting studies looking at, for instance, the insular cortex, which is responsible for monitoring signals from within the body, so it’s a logical place for this function to be located.

But there’s all sorts of other parts of the brain that are involved with assessing future risk, or monitoring the outside environment. And so, I’ve been following this area of research really closely, and maybe five years ago if you had asked me, I would’ve said, “Oh, it’s pretty cool, they’re really zeroing in on the insular cortex and its links to the motor cortex, which is what sends the signals out to your muscles, and I think that’s where it’s going to be.” But as time has gone on, more studies come out, and it’s like, “Okay, but you also have to include the prefrontal cortex, and you also have to include the anterior singular cortex, which assess your perception of effort.” And all the sudden it’s like, “Well hang on, we’ve now listed all regions of the brain.” So is there a central governor, or is this just … is this a behavior that describes how our brains work, to make sure that we don’t push ourselves absolutely to our limits?

And one of the sort of vivid images that Noakes uses, when he gives talks, he’ll put up a slide of just after the finish of the 1996 Olympic marathon, which is when a South African runner won it, so he likes that picture. But the guy who came second was, I think, from South Korea and maybe just three seconds behind. And the two of them are jogging around the track, waving with their flags. And he says, “Well look, what do you notice about the guy in second place? He’s not dead.” And you think about that, if you’re finishing a marathon, your three seconds from being immortal as the Olympic champion, of course you’re going to be trying as hard as you can. This guy didn’t leave anything on reserve, at least he tried not to, but obviously he still had enough reserve, his heart was still working and his muscles were still working, because he crossed the line and he kept jogging.

Brett McKay: Well so if there is a central governor there, and there’s a reserve, it’s accessible, right? So does Noakes thing you can override the central governor, like through training? Or are you hamstrung by that no matter what you do?

Alex Hutchinson: Yeah, so there’s no doubt that that reserve is negotiable, and it’s accessible to different degrees by different people. It’s hard to … when I asked him, “So, what do you do? How do you get to this reserve?” One of his answers was, “You know what, I think the great coaches of the world, they always work on the brain.” So before he became a sort of running guru, he was actually a very accomplished collegiate rower in South Africa. And he said one of his turning points was this workout that he did as a college rower. They would usually do six times 500 meter pull, or something like that, as hard as they could, and once they finished it, one day, and the coach said, “Okay, go back and do another one.” And they were like, “What? We can’t do another one, we just went as hard as we could.” And the coach said, “No, no, no, you have another one in you, so go back and do another one.” And they did another one, in fact, they did four more, I think, until they had done 10. And it was one of those watershed moments of all of them realizing, “Oh yeah, we had pushed as hard as we could, but it turns out there was still a reserve there.”

And so, maybe that’s a little wishy washy, but Noakes would argue that good coaches help athletes learn what they’re capable of, and learn how to access that reserve. And I think the process of regular training also teaches us that naturally. When you first start an activity, like running, and you get all out of breath, and your legs are burning and you think, “Man, I went as hard as I could,” but gradually you learn that those signals aren’t really … that signal doesn’t mean that you’re about to die, it means that it’s just a warning, that you can’t continue indefinitely, and you can start to push those limits back a little bit, gradually. And I don’t … part of my book, the last part of my book, as you know, is kind of asking the question are there shortcuts to that process? Can we learn to access those reserves without the hard work? And the answer to that is maybe, but I think the most reliable way is still go through that long process. While you’re training your body, you’re also training your mind, and if you’re conscious of that, you can make sure to bring out those lessons, and help be aware of the ways that sometimes we hold ourselves back, or we trick ourselves into thinking that we’ve reached a limit, when it’s really not.

Brett McKay: Okay, so we’ve talked about the first theory, VO2 max, which is the body is basically a machine, and you can figure out those limits, and push into those limits. The second theory is psychological, it’s the central governor theory, developed by Noakes. There’s a third theory, also psychological, but this one is developed by an Italian guy named Marcora. Marcora? Is that how you say his name?

Alex Hutchinson: Marcora.

Brett McKay: Tell us about his theory, and how it’s different from the central governor theory.

Alex Hutchinson: Yeah, so this is Samuele Marcora, and his basic claim is that the central governor is a super complicated idea that relies on all these subconscious control mechanisms, and it relies on your brain knowing in advance how far you’re going to go, or what the temperature’s going to be. And he says, “Look, it’s simpler than that. There’s not all these subconscious mechanisms.” We go until it feels too hard, relative to our level of motivation for a given task, and when it’s harder than we want to, we either slow down or stop. And that sounds sort of obvious, like that’s not a scientific theory, that’s like grade two pseudo psychology. But it’s actually a lot deeper than it might appear at first glance, because what he’s saying is that VO2 max, lactate, oxygen consumption, glycogen stores, all that stuff just feeds into something more important, which is your sense of effort. How hard does it feel? And how hard it feels when it reaches a maximum, when you’re pushing as hard as you’re willing to push, or hard as you’re able to push, then you either have to slow down or stop.

And the reason that’s actually … what grabbed me about this theory, or what struck me as remarkable, is that he said, “Look, here’s a prediction based on this theory. If it’s true that your sense of effort is the final arbiter as to how far you can push, then we should be able to change your endurance just by working on the mind, without affecting the body.” So, I first saw him at a conference about seven years ago, and he said … and he was giving a talk, and as an aside, when he was explaining his theory, he said, “Look, I should be able to sit people down at a computer for a few months, have them do some computer tasks that work on specific mental traits,” like response inhibition, which is the thing that you work on in the marshmallow test, or the thing that you test with the marshmallow test. “And if I improve your response inhibition, I should be able to improve your marathon time without doing any physical training.” And I thought that sounds crazy, if you’re willing to make a crazy statement like that, you should test it. And that’s what he’s done with some remarkable results.

And so, I’ve come around to the idea that Marcora’s theory actually has some very interesting implications that, so far, seem to be supported by some of his experiments. He did another experiment with subliminal messages. He had cyclists doing a ride to exhaustion, and he flashed up images, 16 milliseconds at a time, so the cyclists weren’t even aware that there were images. But he flashed up smiling faces and frowning faces, and when there was a smiling face, the cyclist’s were able to push longer before they reached exhaustion. And his explanation is that the smile … we see a smile, it puts it at ease, and the sense of ease kind of bleeds into our sense that things are okay and not as hard as we might think of them, and so our sense of effort is a little bit lower, and we’re able to keep pushing.

So, I don’t know what that final answer, or the right answer is. But I find Marcora’s theoretical work, and also the predictions that he’s able to make based on this seemingly very simple theory, to be really interesting.

Brett McKay: So the Marcora thing, I’m familiar with, or somewhat familiar with it. With weight training, I sometimes do what’s called RPE training. Basically my coach assigns me a program and he says, “Be an RPE eight.” Which means, like rate of perceived effort. So it should feel like an eight, which means that I could do maybe two more reps.

But what’s interesting abour RPE, is that it changes on a day to day basis, like you said. Like some days it just … a weight, maybe like 400 pounds, feels like an eight. Then on another day it could feel like a nine. And nothing’s really changed, but … I don’t know, it’s crazy how effort really does … like how hard something feels determines whether I can get a weight up or not.

Alex Hutchinson: Well that’s exactly it. And so, Marcora would say RPE is what counts. And so you might say, “Why is lifting 400 pounds an eight one day, and a nine the next day?” And there are a lot of potential explanations. It could be you didn’t sleep well, it could be that you’re stressed about a very exciting interview with Alex Hutchinson, or it could be … there’s all sorts of possibilities that could be tweaking your sense of perceived effort.

But the point is, if you’re trying to figure out what your limits are, the RPE is what matters. You can calculate, we could go and measure your muscles and do physiological tests, but ultimately, the determinate of whether you’re going to be able to do eight reps or ten reps this weight is how you feel. And so, Marcora’s point is that’s not a defect in the system, that’s not like a problem, that’s actually a sign that RPE, or perceived effort, is exactly what ultimately determines our limits.

Brett McKay: But he would also argue you can ignore that perceived effort, right? Just like … how bad do you want it, would be like the … if it feels really hard, if you just really, really want to accomplish this thing, if you want to a four minute mile or whatever, if you want it bad enough, you can overcome that feeling of perceived effort and actually push beyond a bit, right?

Alex Hutchinson: Up to a point, yeah. So, in Marcora’s model, there’s actually two, there’s the sort of the yin and the yang. Effort, as it climbs, you’re more likely to quit. Motivation is what determines the ceiling. So, lets say you’re thinking of effort on a one to ten scale. If I go out, I went out, it was pretty this morning and I did a workout with a friend, a running workout, it was snowy and slushy, it was not the greatest day. And so, the level I was willing to get to was maybe an eight out of ten, I wasn’t willing to go 10 of 10 on this crappy, slushy day, when it’s not a super important workout, and there’s cars that are trying to run me over, and so on.

If this was the Olympics this morning, I would’ve pushed to 9.99999999 out of 10, or maybe 10 out of 10. So, most of us, in most situations are not really reaching 10 out of 10. So in that sense, the how bad do you want it is how high are you willing to go on this rating scale? But once you … there’s a point at which ratings, your effort, reaches a maximum. And in scientific studies, they pay volunteers in scientific studies not because out of the goodness of their heart, they want to make sure that people are maximumly motivated so that when they’re taking these tests, they’re willing to go up to an effort of 10 out of 10. Unless you are at an effort of 10 out 10, there’s not really any further you can push no matter how badly you want it.

So, it’s only up a point. We do reach limits eventually.

Brett McKay: So what’s interesting about Marcora’s theory is that the psychological has its influence on the physical, right? And I thought it was interesting that research you highlight is how even mental fatigue, right, if you just had a rough day at work, stressed day with the kids, or whatever, that can actually diminish physical performance. Even though you didn’t really exert yourself physically, the fact that you had to endure this mental fatigue, that’s going to hamper your ability to perform your run, or your workout, whatever it is.

Alex Hutchinson: Yeah, to me that was, again, one of the really most fascinating results that got me interested in his work, because it’s … on the one hand, it’s like yeah, if I’m doing complicated mental arithmetic, or stressful negotiations or something, all day, and then I go and do a workout, definitely I’m going to notice a decrement in my performance. But if you say, “Okay, so why is that? How do I explain that in the context of sort of textbook physiology?” It’s not obvious. Because if I’m been sitting at my desk all day, you’d think I’d be rearing to go, and ready to … and I used to notice this, I would meet friends to do a workout at 5:00, and if I had a story due, if I was on deadline til like 4:45, I would always have a terrible workout. Even though my job is like the least physically demanding job in history.

So, it’s obvious in an intuitive sense, but it’s not easy to explain scientifically. And so, what Marcora would say is that yeah, your muscles haven’t changed at all. All that’s happened is that because your mentally fatigued, everything feels a little harder, it’s one point harder on the sort of perceived effort scale, and that’s exactly what he found.

He did a study where it’s like the people either had to do this computer task, where you’re sitting at a screen and tapping buttons depending on which letters flash on the screen, but you have to focus, and so it takes your attention, versus just watching a documentary about trains, or something like that. And then they had to cycle to exhaustion at a given pace. And right from the very start, so it’s not just something that shows up at the point where they quit, as soon as they started peddling, they had to say, “Okay, how hard is this?” And the people who were mentally tired, immediately they were rating it as sort of five out of 10, rather than four out of 10. Then halfway through the test, they’re at like seven out of ten, rather than six out of ten. And then everyone quits when they reach 10, or 9.5 or whatever, depending … roughly 10. It’s just that the people who started at a higher rating of perceived exertion, they’re hitting 10 earlier, not because their muscles are more tired or there’s more lactic acid, or there’s not enough oxygen, or anything like that. Just simply because it feels harder, because their brain’s a little tired.

Brett McKay: We’ll talk a little bit later, like what Marcora thinks you can do to train. Basically increase your body, or your … I don’t know what you want to call it, the motivation you’re … mental capacity to keep going even when you’re fatigued. But let’s talk about, you highlighted in the book that there is this ardent, strident debate between Marcora’s camp and Noakes camp. Why the acrimony between the two?

Alex Hutchinson: Yeah, it’s interesting, and I wish it wasn’t, because I think both sides … but both groups have done really, really fascinating research. And any time I talk to scientists from one camp, I come away thinking, “Man, these guys are amazing, they must be right.” Then I’ll talk to the other camp, and it’ll be like, “Oh, no, those guys are full of crap.” So it’s difficult when science gets kind of polarized like this.

Ultimately, I think it’s worth remembering that science is a human endeavor. As one of the scientists I was speaking to, the sort of guy in the middle, that’s what he told me, he said, “You’ve just got to remember, it’s a human endeavor, people have egos and motivation to advance their own ideas, and no one takes kindly when it’s suggested that their ideas are wrong, or not original.” And so sometimes the debates are as much personal as they are scientific.

And there are some actual differences in the two theories, in terms of what’s proposed, and how it’s supposed to work. And ultimately, experiments are going to decide which theory, if either of them, is the right one. My suspicion is that it’s going to end up being kind of a mix of both. And I think both of them are kind of moving towards each other in terms of … they both now recognize that effort is really a key … a really, really important parameter. So even the scientists who have been developing Noakes’ ideas, they would now argue the way the brain keeps track of whether your body is in danger is through sense of effort. That sense of effort is this warning signal that tells you, “You better slow down, because we’re getting pretty close to 10 out of 10.”

So, yeah, at the end of the day, in any field, you’re never going to have everyone getting along with everyone else. And I guess, just the one other thing to mention on this, is that it’s really hard to challenge established theories. Like in science, and in any field, to be the one who says, “You know what, I think we’ve been doing this wrong for the last century,” is really hard, and you get a lot of pushback. And so I think there’s something to the fact that the people who’ve successfully proposed these new ideas, they have to have a certain personality that’s willing to push hard, and to be abrasive, and to put forward new ideas despite criticism. And so, as a result, when you get two people, or two groups who are both putting forward new ideas, that maybe don’t necessarily have the temperament to want to cooperate, they’re just naturally inclined to push, and to kind of question everything.

Brett McKay: So lets talk about some of the … before we get to the mental things, that’s interesting. But what I thought was interesting and very useful for me, is the physiological factors that you highlight in the book, that contribute to our sense of effort. Whether something feels hard or not. And one interesting one was pain, right. So if you’re doing a long run, an ultra marathon, mid distance run, or you’re a competitive lifter, you’re going to feel pain when you’re training. So how does … I mean, I guess it makes sense when something hurts, you want to stop, but the question is can you train yourself to ignore that pain?

Alex Hutchinson: Yeah, so the first thing I’d say about pain is that if you’d asked me when I was a runner, “Why do you slow down in the third lap of a mile race. I’d say well, it hurts. It really, really, really hurts. And we sort of naturally think of endurance … when you’re really pushing your limits, it’s a painful task. And one of the things that Marcora argues, and I think he’s generally right, is that you have to learn to separate the feelings of pain and effort. And definitely, if you’re running a marathon, it hurts, but is the pain really what holds you back, or is it the effort, that it feels too hard? That you don’t go faster, not because you’re worried about hurting a little more, but actually because you just can’t it feels too hard.

And so, he’s done some interesting studies where … so first of all, he’ll have a subject dip their hand … there’s a classic pain test called the cold pressor test, basically it’s a measure of how long you can hold your hand in an ice bucket, until the pain gets too much. And so, he’ll have people dip their hand in an ice bucket and rate their sense of pain over time, until they reach 10 out of 10 and have to pull it out. So then they know what maximum pain feels like. Then he has them do a cycling test to exhaustion. And he has then both their pain and their effort. And what he finds is that the point where they get to the end of the … where they’re on the bike and they say, “Okay, I can’t keep this pace anymore, I have to stop. I cannot continue.” At that point, they’re rating their effort very close to 10 out of 10. But their pain might only be six out of 10. Now six out of 10 hurts, but it suggests that what limits us usually is not pain, it’s effort.

So from Marcora’s perspective, pain is kind of … it’s there, and it hurts, but it’s not that important. But there are lines of evidence that suggest that pain does play some sort of role in our limits. And in fact, there’s a bunch of evidence showing that athletes are better at tolerating pain than non athletes. And that isn’t necessarily something you’re born with, it’s something you can train. And there was a recent study out of a university in England, where they compared two different cycling training programs, one was a sort of steady, just ride at a steady pace, and the other was a high intensity interval program, which involves enduring a bunch of discomfort, a bunch of pain. And they designed the programs to be exactly the same in terms of how much physical improvement they produced. So both groups improved their VO2 max by exactly the same amount. But the high intensity interval group increased their pain tolerance more, and also increased their performance more. And so it was like they both had the same physiological improvement, but by being forced to cope with a painful stimulus, they were able to endure a little bit more discomfort during a competition.

And so, one way to think of that is that pain isn’t the be all and end all. You don’t quit because the pain is just absolutely so excruciating. But pain is something that contributes to your sense of effort. And so if something is six out of 10 on pain, it’s not limiting you directly, but it’s also making your effort maybe a point, or half a point higher, so it’s getting you to that maximum effort a little bit more quickly.

Brett McKay: So when you say pain tolerance, it’s not the athlete feels pain less, like the pain still feels like a seven, he just has trained themselves to ignore that, and push their … and like again, effort becomes the limiting factor.

Alex Hutchinson: Yeah, that’s exactly it. So there’s a bunch of studies on athletes, and what they all find is lets say you give people electric shocks with progressively increasing intensity on their arm, or something. And athletes and non athletes will both say, “Okay, that hurts,” at the same point. They’ll say, “Yeah,” the point where … that’s pain threshold. Or pain sensitivity, rather. They detect pain in the same way. It’s just that as you keep turning up the shocks, the non athletes are the first ones to say, “Okay, I want to stop now.” And the athletes will keep going for, in some cases, substantially longer.

And so, no one really knows the full answer as to how that happens, but the prevailing thinking is that it’s not there’s some physiological change, that athletes have some sort of magical anti-pain molecule circulating in their body. It’s just a question of psychological coping mechanisms. Athletes, because they train in ways that are uncomfortable, they’re used to, on a daily basis, dealing with some discomfort, and they understand that pain doesn’t mean your arm’s going to fall off, it just hurts. It’s information for your brain. And so they’re willing to tolerate that information a little bit longer, until it really gets intense, and then they say, “Okay, yeah … ” like pain still affects them, it’s just they’ve learned to cope. And that’s actually one of the most transferrable things, I think, about athletic training, and playing sports, is that you learn these psychological coping mechanisms without even being aware of it, that allow you to handle discomfort, whether it’s being stuck in an uncomfortable plane seat, airplane seat for four hours, or whether it’s running the last five miles of a marathon. The coping skills, I think, are really transferrable.

Brett McKay: So another factor is … physiological factor is the muscles themselves. And this was … I thought the experiments done, throughout the history of this science, was interesting. Like one of the interesting ones, where they just take frog legs, and just put electricity through them, and just watch them twitch up and down until they’d stop, to see how long muscle tissue can move. So what does the research say about that? How long can muscles contract, fully, before they just … they won’t move anymore?

Alex Hutchinson: Yeah, so the answer is longer than you will ever be able to inflict damage on them. So yeah, again, the frog leg experiments, they started in the late 1800s, and the classic ones were in the early 1900s. And they’re zapping frog legs, and finding that yeah, eventually you get to this point where the legs don’t even twitch anymore, and it’s like, oh, so that’s what fatigue is, that’s … But the problem is, the frog legs aren’t attached to anything. And they later did experiments with what’s called decelebrate cats, which is basically cats whose brains have been removed. And they found the same thing. You could make them twitch until their muscles wouldn’t move anymore. But in reality, we never get to that point, because, with what we’ve been talking about, the brain is like, “Nah, we’re not going to let you twitch that muscle anymore.”

And so one of the … there’s a guy named Gio Milei, he’s a French researcher, he’s currently at the University of Calgary, and he’s also an accomplished ultra endurance athlete, he was an ultra runner and a national team cross country skier. And he got interested in this topic about 15 years ago, and there’s techniques you can use that are sort of similar to this, the zapping the frog legs, you can use them on humans now.

So you can, first of all, you can ask someone to say, lets say you want to test leg muscles. You can say, “Okay, contract your leg muscle, or push out with your leg muscles as hard as you can.” So then you know that the maximum voluntary contraction is. Then you can say, “Okay, we’re going to apply an electrical jolt to the nerve at the top of your leg, and we’re going to make your leg twitch, just like the frogs’ legs, and we’re going to see how strongly you can twitch that muscle. And then we’re going to take a magnetic stimulator and apply it to your brain, right at the region where the nerves go down to the leg muscle, and we’re going to make it twitch there.” So then we’re going to be able to find out where is the fatigue? Is it in your brain, like from the voluntary desire to twitch, is it in the muscle, in the muscle not twitch, or is it somewhere in the spinal cord, because there’s a lot of sort of potential fatigue mechanisms in the spinal cord, where the nerve signal was traveling down.

And so, he said, “Okay, well let’s … ” he started out with experiments where it’s like, “Okay, lets put someone on a treadmill for four hours, and lets see how much muscle fatigue versus central fatigue … “, which is brain or spinal cord, “there is, lets compare, by comparing the voluntary maximum with the electrically stimulated maximum.” And then he said, “Okay, four hours isn’t enough, let’s try eight hours, let’s try 12 hours. Let’s try … ” And then he went to a race in Europe called the Ultra Trail Mont Blanc, which it’s something like … I think the winning time this year was just under 20 hours, and it’s up and down, you climb sort of more than the height of Everest, and go back down. So it’s a really long race. And at this point, he’s still finding yeah, the muscles get tired, but they don’t get totally maxed out.

So then he said, “Well, that’s not extreme enough.” So there’s another trail race called the . . . which is … it takes about … for the guys they were studying, it takes at least 80 hours, sometimes the winners are 80 to 100 hours to run this race, and they sleep almost not at all. They basically go for three or four days straight, just running it the whole time. And the shocking result was that the actual amount of fatigue in the muscles was less after this 80 hour race, than it was after the 20 hour race, or the 25 hour race.

And so, this was a sort of headline result, it’s like oh, you’re less tired after you run 200 miles through the mountains than when you run 100 miles through the mountains. But the real lesson was that, no matter how far you go, because your brain is kind of holding the brakes, you never get to that point, like the frogs’ legs, where there’s just no more twitch left in your muscle. And in fact, if you go long enough, it’s so long that you have to slow down just to get there, and so you actually get a little bit less fatigue, so the maximum amount of fatigue in your muscles is actually from quite a short duration. It may even be from just a couple minutes, you can push so hard that you’ll get a high level of muscle fatigue, but you never reach that point where the muscles can’t twitch anymore.

Brett McKay: So you can always keep going, you can always keep your legs moving?

Alex Hutchinson: Yeah … yeah, I’m sure if I was to test, stand at the of altar and say, “Hey, you can keep going, you can run another mile,” I might get some negative comments from the people. Because the legs aren’t the limiting factor, but other things are starting to fail, and you’re probably sleep deprived, and your brain just wants to stop. And your legs are probably sore too, but they could still twitch if you were … if a lion jumps out from behind the tree, you’ll discover you can still sprint down the street.

Brett McKay: So, related to muscles is how we fuel our muscles, and this has been a topic of just a lot of controversy and debate in the past, I’d say, 15 years. So, when I was growing up, carb loading was all the rage. Like before a football game, before a run, my mom was like, “Here’s a big bowl of pasta, you’ve got to eat this so you have carbs for running.” But then, of course, the whole paleo things happened in the past 15 years or so, and saying … and endurance runners will pick this up, “No, actually, we want to go high fat, low carb because we want to be in aerobic, using oxygen and not glycogen.” So, what does the research actually say about high fat, low carb diets and human performance and endurance?

Alex Hutchinson: So, the short answer is it doesn’t say a whole lot. These are hard things to study, and so a lot of the arguments are not really based on scientific research, but more on just like, “I tried this, and it worked for me.” Now, I should emphasize that if a lot of people say, “I tried this, and it worked for me,” is something you have to pay attention to, and you have to think carefully about, maybe there’s something here. But, like you said, the carb loading thing, which really emerged in the 60s in Scandinavia, it sort of became the dominant paradigm. And so, for a long time, people, including me, would’ve said, “There’s no way you can do good endurance performance without good carbohydrate levels.” And so there were some studies in the 80s, for example, a few isolated studies that suggest that hey, if you take the time to adapt to a high fat, low carb diet, you can actually sustain your endurance pretty well. The evidence wasn’t super strong or anything like that, but there were these studies and they got mostly ignored, because the idea was so entrenched that carbs were the way to go.

And what’s happened over the last, I would say, five years, is there’s been an acceptance that the idea of a low carb, high fat diet was dismissed too quickly for endurance performance. And that a lot of the studies that suggested that it’s actually really bad for you, they were too short. Or there were other flaws in the studies, so if you switched to a high fat diet for a week, and then try and run a marathon or whatever, you’re definitely going to have problems, because your body hasn’t fully adapted.

So the big question is what happens if you take longer, so that your body has really learned to make the best use possible of your fat stores. So there’s two questions you can ask, one is, is it possible to do this, and have reasonable performance? And the other is, is it better than the current carbohydrate based approach? And I would say the big revolution, to me, has been the idea that it is possible to go low carb, high fat, and to have very good endurance performance. To run marathons successfully, to run ultra marathons successfully, to do Iron Man triathlons and so on. All the while, while consuming virtually no carbohydrates. And that’s a big surprise, and it’s been confirmed in some studies too. There’s been some studies at the Australian Institute of Sport, that have shown yeah, it is possible to maintain performance in a relatively meaningful way. Whether it’s better than carbs is were I think the argument has gotten pushed a little farther than the evidence suggests.

And there’s definitely a bit of a food fight, if you will, among scientists, for and against this idea, debating sort of subtleties of whether the efficiency is increased by a few percent, or decreased by a few percent. But the bottom line, just to simplify it from my perspective, is nobody has shown that low carb, high fat is better than carbs for most endurance performance. There’s some evidence that it might be worse. Where the advantage might be is if you’re talking about ultra endurance performance, where … it’s one thing to say, “Hey, just take in 60 grams of carbohydrate per hour, and you will be fine.” It’s another thing to do that for 12 hours. It’s very hard to keep choking down gels for 12 hours. So if you can switch to a fat based fuel, so that you don’t have to eat as much during a long competition, that may well be an advantage, in terms of avoiding stomach upset, and things like that, and just feeling better.

So, I’m definitely open to the idea that this low carb, high fat approach has some advantages for some people in certain contexts. If you look at the Olympic marathon, or something like that, I would be surprised if you found anyone, really in history, who’s taken that approach. So to me there’s a long way to go before anyone can claim that it’s better for competitive events of, say, three hours or less.

Brett McKay: Yeah, as you point out, when you’re doing a competitive event, there’s always at that end, you have that kick. Where you have to go really fast, you’re doing that sprint, and that requires … you’re probably going to switch from an aerobic to anaerobic, and that requires glycogen, which requires carbohydrates. So, if you’re doing a 5k, probably don’t … the high fat, low carb’s not going to do much for you, but if you’re doing an ultra marathon, definitely try that out.

Alex Hutchinson: Yeah, and if you’re in the Tour de France, then it’s a very, very long race. But every time there’s a breakaway, every time there’s a significant hill climb, you’re having to dig deep and rely on carbohydrates. And if you’ve sort of down regulated your ability to use carbohydrates, you’re not going to be competitive. Now some people still disagree and say that, “Oh, you can still use your carbohydrates, you can have your cake and eat it too.” But I think that remains to be proven.

And the other thing is, I guess we can look very narrowly at how does it affect your endurance? But you can also look more broadly at how does this fit in with your lifestyle? And so, for some people, going low carb, high fat is wonderful, and it’s really changed their lives, and that’s great, but I wouldn’t recommend if someone is just looking for a performance boost to have this radical overhaul of their lifestyle, unless they’re looking to do some sort of overhaul for other reasons. Because it’s a big ask to suddenly cut out all carbohydrates for something that may or may not help you in this one small facet of your life.

Brett McKay: Right, and as you point out too, a lot of the big marathon runners, they’re from Kenya, and they pretty much just like eat corn porridge, is their diet. So they’re not getting the high fat-

Alex Hutchinson: Yeah, they’re the definite sort of ultimate example of … it’s like, if you listen to mainstream sports and nutritionists these days, they’re like, “Yeah, you need carbohydrates, but of course it’s got to be complex, organic vegetable, blah, blah … ” It’s like you’ve got to eat high quality, of course we don’t recommend sugar. And you look at what the Kenyan marathoners are eating, and they’re getting like 20% of their calories from the sugar they pour into their … from the simple sugar that they pour into their tea, and their porridge.

Now, their lifestyle is such that they seem to be able to … they seem to thrive off that. But it’s … even I would like … I don’t think I would be able to eat that much sugar without feeling this tremendous sense of guilt, which maybe says something about our attitudes towards food in the west or something.

Brett McKay: Right. So related to food is water, hydration. And that’s another thing, like in the past, I think, 15 years, has been this just debate. Like if you’re watching the news, one year they’re telling you, “Oh, you need to drink eight gallons … ” whatever, “A gallon of water a day,” and then the next thing, “No, you actually don’t need that much water, because that’s going to kill you.”

So, what’s the science say? How much water do we really need, particularly when we’re competing in an endurance event or exercising?

Alex Hutchinson: Yeah, so I would say the science says you need to drink as much as you feel you need to drink. And whether it’s sitting at your desk at the office, or while running a marathon. And, as you said, this debate has gotten really polarized to where it’s almost sort of caricature. One side is saying, “You basically have to have an IV hooked up to at all times or you’re going to die.” And the other side is saying, “Water is terrible, you’re going to get water poisoning, you’re going to get hyponatremia.” Which is this condition that can arise if you do drink too much water, although it’s very rare. And both of these are kind of scare tactics, and the truth is somewhere in the middle.

For the most part, in most contexts, we don’t really need to worry at all about hydration, other than being aware that when you’re thirsty, you should drink. That said, it’s not that hydration is totally irrelevant. If you get severely dehydrated, you are likely to have changes in your performance, and so you have to be aware, and there’s some contexts where you have to be more than just aware, you have to be planning ahead. If you’re running a marathon, you can’t just drink whenever you’re thirsty, because you can only drink when there’s a water station, and if you’re running you may not want to drink even though you’re thirsty, because it’s uncomfortable to drink. So there’s these situations where you do have to kind of be aware. But for the most part, if you are just simply making an effort to listen to the signals from your body, to the listen to the signals that for millions of years of evolution have made sure that we get enough water, and if we fall behind on the amount of water we have, we’ll catch up with it later, then you’ll be okay.

One little stat that I like to cite is, the first man to run sub 2:04 for a marathon was Haile Gabresalasie in 2008. And during that race, he lost about 10% of his body weight. He was, I think 128 pounds when he started, and something like 116 when he finished, from dehydration. Now, not all of us can do that, but if mild dehydration, if 2% dehydration was a problem, we wouldn’t have these world record setting marathoners losing 10% of their weight. So I think the hydration message has been pushed a little harder than it needs to, and the performance effects, and also the sort of health effects are not as severe as thought, because a lot of the studies are like, “Okay, we’re going to give you a diathetic, put you in a heat chamber for six hours, and then we’re going to test your performance.” And it’s like, “Oh look, you didn’t perform as well.” It’s like well, that’s not a real world situation. If I’m in my office, if I’m thirsty I’ll drink, it’s not like I’m being forced not to drink in some of these studies.

Brett McKay: So, we’ve talked about some of the physiological factors that play into rate of perceived effort. There’s a lot more people can take out of the book, but as you’ve discussed, none of them really … a lot of people think they matter, and they’re going to make the difference in their training, but basically the argument you’re making is like well, they don’t actually make that much of a difference. And it all comes back to that mentality, and the psychological factors. So, what can we do to train our brains so that even when things feel hard, we keep going? Or we’re able to push yourself even further before things start feeling hard, right? Like what happened to you, when you’re with your run, where you thought you were running faster than you really were, so you thought it was easy, but it wasn’t. So how can we do that in our own … whatever our activity is, whether it’s running or weight lifting, or whatever it is?

Alex Hutchinson: Yeah, so, let me start with the caveat, which is I think the most powerful thing to do is to be aware of these things. And one of the studies that I found fascinating is investigating the effects of heat on cycling performance. And they put cyclists in a room where it was 100 degrees Fahrenheit, but in some cases they rigged the thermometer so that it only read like 90 degrees Fahrenheit. And the cyclists went faster. And it’s not that heat didn’t have an effect, it still had some effect, but it had much less of an effect. So there’s always this … it’s this halfway thing, it’s not all in your head, you can’t just pretend that heat doesn’t exist. But the effects we feel are always greater than … the ultimate effect on our performance is always greater than pure physiology would suggest, there’s always a mental component.

And so, if you’re aware of that, I think you can choose to not … to kind of disobey some of the signals, to say, “Yeah, I feel hot, but you know what, it doesn’t mean I’m dying, it just means that I’m being warned that I’m hot.” So, that’s the starting point, is be aware that there’s more.

But there’s also specific ways you can kind of try and strengthen certain kinds of mental muscle. And I mentioned before the marshmallow test, which is this famous thing were they gave four year olds, they said basically, “You can have one marshmallow now, or you can, if you wait maybe 15 minutes, you can have two marshmallows.” And then they tracked … people who could … the longer kids could wait at age four for an extra marshmallow, the better they did in all sorts of life outcomes 20 or 30 years later in terms of … there’s studies linking this sort of response inhibition, not just to things like educational attainment and income, but also to like crack addiction, and stuff like that.

So, response inhibition, being able to keep doing something when you don’t want to, or to avoid doing something that you’re not supposed to, to suppress your initial urge, which in the context of endurance, your initial urge is like, “This is hard, I should stop.” Or, “I should slow down.” If you can suppress that urge, you will be able to do better. So how can you train response inhibition? Well, there are certain computer tasks, these things like something called the Stroop task, which are designed to measure cognitive traits like response inhibition.

And so, what Samuele Marcora argued is like, “Okay, if you’re doing this task, which is supposed to measure response inhibition, that means you’re using your response inhibition.” And think about physical training, if I want to get faster … or if I want to be able to lift a weight, a heavier weight, then what I should do is lift weights, and make my arm tired, and then let it recover, and then lift more weights and let it recover, and by lifting that weight, I’ll eventually be able to lift more weight. And so he applies the same logic to mental training. If you keep doing tasks that tax your response inhibition, your response inhibition should ultimately get better. And so you should increase your ability to stick at a task when it’s uncomfortable, and ultimately be able to sustain … ultimately what this will do is kind of reduce your perceived sense of effort, because you’re getting better at handling mental fatigue.

And so he’s done some studies, over the last three or four years, they were funded by the British Ministry of Defense, because they felt like this would be pretty useful for soldiers who are in combat for sometimes a couple days at a time. And they’ve had intriguing results. So he’s found if you train people physically, and you give half of them this additional brain training on the computer, and the people who get the brain training improve their physical performance by a far greater amount than the people who did just the physical training.

So, there’s a kind of proof of principle that you can specifically train the brain with these specific kinds of cognitive tasks. You don’t just go do the crossword puzzle, it’s a very specifically chosen kind of cognitive task that attacks certain mental traits like response inhibition. And so I tried this out a couple years ago before running a marathon. And I wasn’t doing a study, so I can’t really assess whether it worked or not, but what I can say is my god, those mental tasks are boring. And they’re time consuming. So I found it a real challenge. So there’s a maybe gap between saying, this is what you can do, but it’s not necessarily what I would recommend everyone rush out and start doing.

Brett McKay: As you highlight in the book, this stuff, what he recommends doing, Marcora, is like you have to do these brain drain exercises for an hour, and then go train. A lot of people don’t have an hour of their time, plus an hour to train. So I guess he’s coming up with some ideas of things you can do while you’re training to fatigue the brain, sort of cut down on the time?

Alex Hutchinson: Yeah, so he has a couple of ideas. One thing he said to me is like, “Look, from a practical perspective, one thing you could do is just embrace the idea of training when you’re mentally tired sometimes.” So, personally, I run most days, and do some other stuff too, lift weights and stuff like that. I do it almost always in the morning, because that’s when I feel fresh and it just feels more pleasant to me that way. And he’s saying, “Look, maybe if you do a workout after a long day of work, or even after a night when you haven’t slept as well as you’d like, that may … the results of the workout may seem worse physically, but you’re actually training your brain.” Like sleep deprivation and mental fatigue, learning to push through that is a mental training exercise.

So, in some ways it’s kind of a positive way of framing when you have a crappy workout. You’re like, “Well, I was pretty stressed and tired, so my time and the workout was crappy, but I sure as heck trained my brain today.” So that’s a kind of practical approach to keep in mind. He’s been developing an app, or working with app developer, to create a form of mental training that, as I understand it, it’s sound based rather than … like it’s an auditory brain training app rather than one with a screen in front of you, so it’s something you could do, have it on your phone and be doing it while you’re out training, and hopefully not be hit by a car in the process, but … So he’s working on trying to make this available. But I think one key … and he’s doing some studies where you do the brain training task while you’re sitting on a stationary bike, so you’re combining the time of physical training and mental training. But personally, I still have no interest in sitting on a stationary bike for my training, I’d rather be outside.

So, there’s ways that he’s trying to make it more accessible, and ways that you can kind of work on this indirectly through your mental training. But it’s still, I think it’s still … I guess I want to be cautious about over hyping it, because it’s still like early days yet, and it would be good to see other labs reproduce the results. Because that was the other thing that I took from my own personal experiment with it, because I’m a busy guy too, in some ways, and it was not easy for me to find time to do this brain training, and it would’ve felt a lot … it was much harder to find time for brain training because of the voice in my head that was saying, “This is ridiculous, how is this going to help me run a faster marathon?” So you kind of want to make sure that it’s legit and really works before you try and invest a bunch of time in it.

Brett McKay: Well Alex, there’s a lot more we could talk about, there’s a chapter about zapping your brain that we didn’t get to, but where do people go to find out more about the book and your work?

Alex Hutchinson: So, the easiest place to find me is on Twitter. My handle is SweatScience, all one word. And my website is And both of those places will guide you to articles that I write about this topic, and the book, and hopefully people will have been working on their mental endurance just by listening to me ramble on the podcast today.

Brett McKay: There you go. Well Alex Hutchinson, thank you so much for your time, it’s been a pleasure.

Alex Hutchinson: I really enjoyed it, thanks Brett.

Brett McKay: My guest today was Alex Hutchinson, he’s the author of the book Endure, it’s available on and bookstores everywhere. You can find out more information about his work at Also check out our show notes at AOM.IS/Endure, where you can find links to resources where you can delve deeper into this topic.

Well that wraps up another edition of The Art of Manliness podcast. For more manly tips and advice, make sure to check out The Art of Manliness at While you’re there, check out our podcast archives, we almost have over 400 episodes there in the archives. It’s While you’re there, make sure to subscribe via one of your favorite services, whether Stitcher, iTunes, whatever. And one thing else you need to do to help us out, if you have a minute, give us a review on iTunes or Stitcher, it helps out a lot and if you’ve done that already, thank you. Please share the show with others so that others can get the benefit from The Art of Manliness.

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