Coaches have known about the importance of durability for years, but researchers are only just starting to catch up. We discuss why it is the fourth pillar of performance.
Episode Transcript
Trevor Connor 00:05
hello and welcome to fast. Doc, your source for the science of endurance performance. I’m your host. Trevor Connor, here with Chris case in the 1990s Dr, Joyner defined the three pillars of endurance performance, VO two Max, economy and threshold, expressed as a percentage of vO two, Max. He felt that these three pillars were so central to an athlete’s performance that he created the joiner model, which used the three pillars to predict how an endurance athlete would perform. He used it to predict marathon times, and was able to make his predictions with surprising accuracy. There was just one problem, the formula almost always predicted a better time than what the runner could actually do. Something was missing, and researchers didn’t have an answer. But even back then, in the 90s, coaches could have told you what it was. Top cyclists and coaches love to say it’s not about how hard you can go for five minutes, but how hard you can go for five minutes after four hours, some athletes can maintain their strength better than others. Coaches called this a lot of things, but it wasn’t until 2021 that researchers finally put an official name to it, durability. Durability is about how long you can maximally sustain your other three pillars, VO two, Max economy and threshold before they start to decline. It has been called the fourth pillar. In today’s episode, we’re going to dive into what the newest science is saying about it, including why it’s so important, the three potential ways to measure durability, the physiology behind why we lose durability, and of course, ways we can train durability and things we can do in events to delay the decline. Today’s episode is just myself and Chris reviewing the science, but we’ll also hear from ex Tour de France writer levimer, who is helping to revive North American cycling with the growler at the Levi Leipheimer Gran Fondo. And before we dive into today’s episode, I want to thank our sponsor, Trainingpeaks, as we’re going to talk about later in this episode, the biggest challenge that researchers are facing with durability is figuring out how to measure it. There’s a lot of different ways. And right now, I’d say the two most popular are looking at drifts and looking at decline in maximal power. So that first one drifts, that’s when you see a change in heart rate relative to an athlete’s power, or if you’re talking about a runner, relative to their pace, meaning if they were going to steady wattage, that heart rate slowly drifting upwards, which means they’re actually working harder to maintain that same power. That’s a really good indicator that the durability is starting to decline. And this is something that didn’t surprise me to see training peaks has already worked into their platform. If you use the online version of training peaks, they have something that’s called their aerobic decoupling factor. It basically looks at the start of your ride, the first half of the ride, and then the second half of the ride, looks at the power relative to heart rate, and then shows the percent change. So if you only see a one or 2% change, that means that the durability was really good. If you start seeing a 25 30% change, that means durability might be something that you or your athlete needs to work on. It’s a great number a lot of people have missed it in training peaks. It’s a really good thing to take a look at, because that’s an attribute that you can really train. And if you’re a coach or even an athlete who uses training peak sister application, W, K, o5, there’s even more sophisticated charts. We have two, and if you go to our website, go the show notes for this episode. We’ve provided links to those charts for anybody who’s using Wk 05 The first one is a chart that I built with Dr silo, and he was doing his research on durability, and it shows that change in heart rate relative to power as a line over the course of a workout. So you can see where that decoupling starts. You can see how much decoupling there is. You can see what’s affecting it, so it allows you to make better decisions as an athlete or a coach. So please use that chart. The other chart that we’re making available to you is a chart that looks at the power duration curve of an athlete. So this is their maximal wattages at all the different time frames. It has the power duration curve when the athlete is fresh, but then it shows their best power duration curve after 1000 kilojoules, after 1500 kilojoules, 2000 kilojoules. So you’re basically seeing how much power they can put out after they’ve expended a lot of energy, and in a really fit athlete who’s got great durability, you’re not going to see a lot of change in those charts. And somebody who could work on their durability, you’re going to see a big drop. So please again, go to our website, download those charts and upload them to your Wk 05 platform. And while you’re at it, if you want to start a free coach trial, visit trainingpeaks.com/fasttalk and get your free trial. Thanks again to training peaks for being our sponsor. And with that, let’s see how durable your podcast listening skills are, and let’s make it fast.
Trevor Connor 04:56
So we are going to dive into this concept that’s very new in the. Science World. But as Chris said, You ask any coach, they’ve known about this for decades. There’s a great expression in cycling, which is, it’s not how hard you can go for five minutes, it’s how hard you can go for five minutes after four hours, right? Exactly. That is exactly coaches way of defining durability.
Chris Case 05:16
Well, give us a little bit more about what we’re going to talk about here today.
Trevor Connor 05:21
So I’m going to quickly mention this. What motivated this? And Chris, this was you. You found these very recent reviews that dived into durability and said, Hey, this would be a really interesting conversation. So again, they’ll go on the show notes. The first one, lead author is Ben Hunter, and it’s durability as an index of endurance exercise performance methodological considerations. We have one that I brought in that was looking at how to train durability, and we’ll get to that in a minute, which is durability is improved by both low and high intensity endurance training. The other review that you brought in, these are both from 2025 is by a Andrew Jones as the lead author, and it’s physiological resilience. What is it and how might it be trained? And then, of course, the study that started all this was Dr Munder and Dr Seiler, the importance of durability and the physiological profile of endurance athletes. As Chris said, this is becoming kind of one of the big things in research right now. A bunch of studies have been coming out looking at durability or resilience, and I’m going to read to you the technical definition of each we’re going to use them interchangeably, but durability is defined as the time of onset and magnitude of deterioration and physiological profiling characteristics during prolonged exercise. Resilience is the ability to resist functional decline following acute and or chronic stressors. So durability is, how long can you sustain before you start to see those declines in those whatever parameters we’re talking it’s measuring it. Resilience is, how good is your ability to maintain your durability? How long can you go
Chris Case 07:07
resisting the declines that are inevitable in anybody but where and when do they come? Is the question like, how far can you go before you see those declines? Yep,
Trevor Connor 07:18
so those are the definitions. But for the rest of this, we’re just gonna basically use them in orchard. Use them interchangeably. But yeah, you touched on something really important, which is so they call this joiners three pillars. And Dr Joyner wrote about this in the early 90s, really saying that there were three things that contributed to the performance of an endurance athlete. The first one was VO, two, Max, the second one was economy or efficiency. And we’re not going to dive this episode into the difference between those two. We’re just going to use them interchangeably. And then the third one is that functional threshold. But what Dr Joyner was really talking about is how close you can get your threshold to your VO two max so one of the biggest adaptations I see in elite athletes is so let’s talk cycling. We’ll just use power right now. But in runners, you would use speed, their threshold power is actually remarkably close to their vo two max power. Or somebody who’s less fit, their threshold power is much, much lower as a percentage than their vo two max power. And Dr Joyner came up with a formula for predicting marathon speed using these three factors, but interestingly, it almost always overestimated performance
Chris Case 08:38
because it didn’t take into account durability. Is that, what where you’re going
Trevor Connor 08:41
with this way to open the Christmas gift the day before? Chris, sorry, that’s exactly where we were going. Yes, the problem was that was all these things in endurance athletes for years were measured in a fresh state. They would bring an athlete into the lab and go, let’s measure your VO, two Max and rest, and then we’re going to measure it. Let’s measure your economy fresh. Let’s measure your threshold fresh. You go and run a marathon at a very high pace, you’re not going to be fresh near the end of that marathon. And for some marathoners, you would see a decline, and the formula doesn’t account for that. The only person, sorry, I’m blanking on the name right now, but the runner who just recently broke the two hour mark, who was part of that two hour Oh, gay, thank you. He was the only one that the formula got spot on, because he just,
Chris Case 09:35
he doesn’t fatigue. He’s a specimen, for sure. He is unique.
Trevor Connor 09:38
And so, yeah, there was a realization that there’s something else going on here, and it’s all these parameters. So this is this whole idea of durability. At a certain point, these parameters are going to decline. So VO, two, Max will come down. As you fatigue, your economy will worsen, and even your threshold power. Will come down, because generally, an athlete can hold a certain percentage of their vo two max. So let’s use runners as example. Let’s say a runner’s critical speed is a five minute mile, and that’s 90% of their vo two Max. You know, the speed of vO two Max? Yeah, they can generally hold 90% but if the VO two max speed comes down, and they continue to try to hold a five minute mile, they’re now above their critical speed. So in order to be able to still sustain that speed has to come down.
Chris Case 10:33
Something to clarify here, because we’re talking about various sports, and what’s long in cycling is not necessarily what’s long and running and athletes are built differently. What duration are we talking about before durability becomes a thing, or is that relative to every individual based on their training, their sort of specialty as an athlete and the sport in which they’re partaking?
Trevor Connor 10:59
So that’s one of the key questions, and a great question to ask, because a you look at the research, huge range of what they use. Some of them will just look at an hour and call that a really long endurance workout. Others will look at 3456, hours. There is a recognition that when we’re talking about durability, you need to use longer, which I love to see, because you look at research prior to looking at durability. You rarely saw studies that were going over an hour, because it’s tough in a lab. Yeah, you do see it becomes a factor sooner with running than it does with cycling. So for example, I saw some studies where, if they’re looking at runners, they’re looking at about an hour, hour and a half before this starts to become a factor. Or a cyclist, they really need to do three, four hours before it starts to become a factor. So you do need to go longer with a cyclist to start
Chris Case 11:53
to see those effects. And that makes sense. Yeah, I would say. But when
Trevor Connor 11:57
you’re dealing with somebody coming off of the couch, or somebody who’s not very fit, versus a Tour de France athlete, it’s very different. Somebody off the couch, yeah, you’re gonna start seeing durability be a factor an hour or two in Tour de France athlete. You can put them on a train for eight hours, and you’re gonna still be going, okay, when’s the durability gonna start kicking? Yeah, when’s this, where’s this decline? And they’re gonna be sitting there on the train or whistling, going, huh, whatever. Okay,
Chris Case 12:22
so why is durability a fourth pillar? Why has it become so important in both the research world and as we’ve expressed, it’s been important in the athletic world, in the performance world,
Trevor Connor 12:36
so we just talked about joiners three pillars. So that’s the VO two Max, that’s economy, and then it’s the threshold you are seeing the research kind of an acceptance now that this is a fourth pillar, but in some ways it’s a unique pillar. You know, first of all, part of the reason they’re saying it’s another pillar is because you look at studies where they’ve looked at the training effect on durability, where you can improve durability, but you saw no improvement in vo two Max. Likewise, you can see vo two Max change without a change in durability. So they know that there’s different mechanisms going on here. So this isn’t just the same physiology. What makes durability unique is it is the one that affects the other three pillars, right? So it’s kind of a fourth pillar, but in the same way, it’s the pillar that the other three sit upon, because it’s literally defined as the point where those other three pillars start to
Chris Case 13:29
decline. In my mind, as I try to visualize this, it’s not so much a pillar as it is. There are three pillars, and then this is an interconnected web between the three of them. In some way, it all is interrelated through durability, but all the other three are independent of one another,
Trevor Connor 13:50
the way I was looking as I was reading this is it’s the strength of those three pillars. Like you might have a good VO, two, Max, but your pillars, are they made of paper, or are they made of marble? Yes, there’s a certain point where it’s going to start cracking. And if it’s made of marble, it’s going to go a long time. If it’s made of let’s paper is probably a bad example. Made of wood. Pillars are going to start cracking pretty quick under the weight. And as you mentioned, there’s huge individual variants. So in studies, they’ve seen anywhere from a decline of just 1% up to 33% and a lot of these studies on durability, they kind of average it out, but they always say it’s hard to average it out, because there is such a huge individual
Chris Case 14:37
variation, and 1% would be considered a significant, statistically significant decline, or you were just throwing that number
Trevor Connor 14:43
out there. No, this is literally so I saw multiple reviews that mentioned this from studies that the range was 1% to 33% okay, so you know, 1% decline in vo two Max. Let’s put it this way. If you’re doing a four hour race and your VO two Max only declines 1% you probably got to. Good shot at winning that race, right? Sure. 33% Yeah, you’re getting popped. Yep,
Chris Case 15:05
yep. That’s a big range. So then, how does one measure whether one is durable or not? How does it done in the lab? So I
Trevor Connor 15:15
am going to give you the answer that I’m going to be giving you to all the questions that we’re going to ask through this episode, which is, we don’t have a reliable answer yet.
Chris Case 15:24
Okay, yeah, that’s how new this line of questioning in the research world is, right? This
Trevor Connor 15:31
is just incredibly new to the research world. And the whole time I was reading this, I remember, you know, we had Dr Seiler on the show not all that long ago, where he talked about when he was giving a presentation to a room of coaches and researchers. This was like 10 years ago, and as he was presenting, all the researchers in the room are just going, No, that’s wrong. And the coaches were all nodding their head, going, spot on, right, yeah. And this is the same sort of thing where researchers are going, Oh, this is a whole new concept, and we got to figure this out where coaches are going, seriously, duh. Yeah. We’ve known this since the 70s. This is, yeah, this is what makes a champion endurance athlete versus somebody who can’t perform well. You can take literally, a very mediocre endurance athlete and an elite and put them at the, say, base of a couple minute climb, and have them go at one another. They will actually fresh, be very close to one another. Actually, I’ll give you a perfect example of that. This is back when I was living in Toronto. Michael Barry lived in Toronto. There was a group ride that I always went on in the mornings, and it was this loop that we did five times is there’s this one minute climb in the middle of the loop, and everybody was expecting that the first time at that climb, Barry was just gonna drop everybody. He didn’t. And afterwards, I was talking to riders, and they’re like, oh, he was just holding back. And I was like, No, he wasn’t. You guys go up that hill extraordinarily hard like but he’s a tour athlete. I went right. We did five laps for five laps. You guys can put out the same power. If we did that 30 times, which would be on par with some stages at the Tour de France, then he’d be killing you. But fresh one minute up that climb, no, he couldn’t drop you guys, yeah, yeah. And that’s, again, this concept of durability, and athletes and coaches have known it for a while.
Chris Case 17:27
Yeah, it’s also why amateurs can out perform or get close to performances on Strava segments, because it’s a one off. Amateur X can go just as hard as Sep in a 12 minute effort once, but put that person in any stage of any tour, and they’re getting dropped, or they’re not even getting to the point where the decisive move happens four or five hours into that stage.
Trevor Connor 17:53
Well, we got a guy here in Boulder, full credit to him. He’s phenomenally gifted, who has gone and taken every single one of sep kusistrava records here in Boulder. And I’ve had the conversation with him, and he’s like, yeah, fresh going up Flagstaff, I can give him a run. Does that mean that I can go and beat him at the Tour de France? Probably not, right, yeah. So it’s a whole different game. Yeah.
Chris Case 18:14
Was there in the coaching community? What was the name that people gave to this aspect of performance, of fitness, before durability was coined. Was it grit? Was
Trevor Connor 18:27
it, honestly, durability was thrown out a lot, okay, stamina, grit, yeah, all these terms were used. And I think as the research world is grabbing onto it, they obviously want a term that they can define, and that’s what they’ve landed on, is durability and resilience.
Chris Case 18:45
Yeah, to have that common language, whatever you choose to
Trevor Connor 18:49
call it, past Tour de France rider Levi lightheimer knows all about the importance of being able to sustain your efforts day after day. Here’s Levi talking about the importance of durability and some of his suggestions on how to train it.
Levi Leipheimer 19:03
The concept of durability is very important, but I think that comes with years of training and racing, and I truly think maybe the only way to test it, I know you could try and test it in the lab, or go out ride four hours and then do a lactate threshold test, whether inside or outside, or just a straight up power test for any number of minutes, but really, the best way to test it is through racing and history. A great example of that is, you know, the best champions throughout the history of cycling have shined in the monuments or the queen stages of Grand Tours, where it’s seven hours, where you’re sitting at near threshold most of the time, and then it comes down to the crux of the race towards the end, the last hour, where it’s a five minute effort, for example, and who can make the difference. I don’t know if you’re able to replicate that in a laboratory. I mean, it takes intense racing for hours and hours to get to that level.
Trevor Connor 19:58
And what’s your. Thought and how you train this, because that’s what the physiologists are now kind of scratching their head at, is what is the best way to train that durability.
Levi Leipheimer 20:06
I think it’s not a secret that you want to train all of your zones, right? And you want to train some anaerobic power, for example, some sprints, some VO, two, some threshold work. But you need long rides. You still need volume. Volume is it kind of has this stigma of being old school, but it’s still the staple of endurance cycling. You have to do volume. There’s just no replacement for it,
Trevor Connor 20:34
which is important, but we got way off topic. So measurements,
Chris Case 20:39
yes, measurements, and you said it’s not well defined yet. How this is done?
Trevor Connor 20:44
They’re still trying to figure this out, of how do you measure it? And they’ve landed on what they think are three good metrics, but they still need to be standardized. We’ll have references in the show notes. There’s some really good reviews on this, some really good studies, including, we forgot to mention this earlier, but it was actually a study that Dr Maunder and Dr Seiler wrote in 2021 that started all this, where they defined durability and the importance of this. And now a bunch of other researchers are jumping on it, but it was really those two who came up with this. One of the reviews made the good point that these three things, which I’m about to tell you, seem like good ways to measure it, but we haven’t standardized or figured out the best way to measure them, and there’s a lot of potential issues with them, so we know the right direction. It’s the details that become really important. So number one, which is a great metric, is drifts. So this is an idea that we have various physiological internal measures that you can look at, like energy expenditure, oxygen consumption, heart rate, that when you are fresh. So let’s use cyclists. You’re going at a given power. You’re holding power steady. All these metrics will also hold steady. So power is an external measure. These things are internal measures. At a certain point they are going to uncouple, and that’s called a drift. So for example, most of us can see this if you’re a cyclist and you have a power meter where you can look at your heart rate relative to power, and for first hour or two of your ride, it’s going to be very consistent with one another. Certain point heart rate is going to start going up. And that’s the concept of durability. How long before you hit that drift? And what is the magnitude of that drift? So somebody who doesn’t have very good durability. That drift is going to start very early on in their ride, and you’re going to see a very large drift, a very large increase in heart rate, where, amazingly, you look at a Tour de France athlete, even on one of those killer six hour stages, you probably don’t start seeing the drift until late in the stage. And you’re not going to see that much drift, right? Yeah. So we know that the drifts are a great way to look at it, but there’s all sorts of other things that contribute, like hydration, like what’s the temperature outside? Heat increases cardiac drift. Dehydrating increases cardiac drift. So if you’re going to properly measure this, you need to control all these things, right? So that’s what they really got into with that. But said drift is a great way to do it, because it’s also something you can see out on the road. The second measure is looking at maximal performances before and after a long, fatiguing ride, right? Any endurance workout. Yeah. And what are the questions they bring up is, do you do it all in one day, or do you do an effort fresh on one day, then the second day, you do the three, four or five hour ride, or the two hour run, and then do it, and then immediately do the effort at the end. So again, these are some of the questions they’re getting at, I see. But the idea is, if you have really good resilience, that maximal effort after that long ride or run is going to be pretty close to what it was when you were fresh. And for anybody listening to this who doesn’t want to do that, there’s actually a great chart that you can get in some of the training software that will you take your power duration curve shows your peak wattages from one second to many hours. And you can create a chart where you show what they are fresh and then after you’ve expended 2000 kilojoules, or 4000 kilo whatever the case, after a certain number of kilojoules, and in a an elite lead cyclist, those graphs are going to be very close to one another, and somebody with poor resilience, you’re going to see those charts really start separating. There
Chris Case 24:48
will be drift, yeah, yep.
Trevor Connor 24:50
And then the final one, which I think you saw less focus on, is just the, really the self report. You know, did it start feeling harder? Though? It. Part One here we had Dr Seiler talking about measuring breathing, and that seems to match up with RPE. And so same sort of thing is, if you’re at a steady wattage and you’re seeing so this is more adrift, you’re seeing that increase in ventilation, that’s a sign that you’re losing durability.
Chris Case 25:20
Question I have is these other three pillars. We have now a very defined unit. We can say your VO two Max is 75 and that’s in a particular unit, and it’s universally recognized. And everybody knows what that means, volume of oxygen, lactate threshold, it’s at x watts, if you’re on a bike, or if it’s at x pace, if you’re a runner or whatever. Economy. I don’t know if you can put a number on that, but I guess my question is, this is a speculation on your part. What would be the number you’re given for your durability score, if you will. Like, what’s it going to express? You know, what I’m saying? Is it going to be a like four, as in, Trevor can go four hours before he sees declines. I mean, that’s too vague, I would think, right. So
Trevor Connor 26:14
there’s the question of, what are the numbers that you’re going to look at in the lab? Is what we can use. So in the lab, you can measure oxygen consumption, you can measure vo two max. So what they’ve been using these studies is, what was the percent drop in vo two max? So they literally will do the VO two max test fresh, then they’ll do it after that fatiguing ride or run, and then say, we saw X percent drop in vo two max. So easy to use percentages when you’re looking at something like that. I actually remember having this conversation with Dr Seiler because I tried to come up with a number in my training platform of start of the ride versus end of the ride. And he went, I don’t like that. He’s like, I think this is more dynamic. We need to see this over time. I see and what we actually created was a chart, and I can tell you, we played a lot with this formula until we finally got something that looked right or gave us what we wanted. And so it’s pretty complex formula, but basically what we did is divide heart rate by power, but not just straight heart rate by power. What we did is with heart rate, we took heart rate reserve at that particular moment in the ride and expressed it as a percent of max heart rate. Then we took power and expressed it well. We first did a 2/42 smoothing, because heart rate’s not instantaneous, but power is so by doing that 2/42 smoothing, you get a similar effect to heart rate, or that’s the idea. So we did a 2/42 smoothing, and then we expressed that power as a percent of the athlete’s five minute max power, which is pretty equivalent to the sort of power you should be putting out as you hit max heart rate. So if all this is done right, what you end up seeing is that those two should divide to one when the athlete is 100% and we just create this line that goes across the ride. And if you’re seeing good durability, if you’re seeing no drift, that line is going to stay right around one. I mean, you see little variances in it down hills cause it to drop a little bit, things like that, but it’s mostly gonna sit right around one. And when you see drift start to occur, that line will start picking up. So now be 1.1 then 1.2 1.3 and that’s when you know durability is starting to break. You’re seeing a drift. And there isn’t really a metric. You’re just looking at the dynamics of the ride. But to me, that’s actually extremely valuable, because I can see, when did you start seeing that separation? So that’s the uncoupling. And how big is the uncoupling?
Chris Case 29:00
It seems like it needs a little tweaking, and some marketing genius needs to come up with the like, flashy number that everybody’s like, Ooh, my durability score is, but maybe it’s never going to be that simple, because it’s a dynamic metric rather than a static thing. Okay, now my brain is wanting to go a little bit deeper and understand durability at a more cellular level, what’s going on physiologically. Here? Do we have answers? There? We have some answers, I bet, but we don’t have all of them.
Trevor Connor 29:38
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Use the code fast 20 or go directly to their website at to Fauci optics.com, that’s t, i, f, O, S, I O, P, T, i, c, s.com/discount/fast, 20, and get your glasses today. One of these studies basically said, We don’t currently know the cause of high and low resilience, but we have some thoughts. There are a lot of factors that can contribute to this. So what they were looking at is, what are things that can cause that uncoupling? What are things that can cause that drift? And they had a very large list. So it’s what can cause that uncoupling. What can also start to cause a decline in vo two Max, a decline in economy, a decline in your threshold. So one is basically glycogen depletion and an increase in fat burning glycogen is more efficient than fat, so it requires more oxygen to burn fat for fuel. So when you have good glycogen stores in your liver and your muscle tissues, you’re going to be more efficient. As that starts to deplete, your cells are going to start relying more on fat burning, and that is just going to make you less efficient. So that affects efficiency. It can also affect not necessarily, I think, VO two Max, but how much power you can produce at VO two max. So it’s going to have an impact on that sort of threshold power. That said, they pointed out very high level endurance athletes, like tour level cyclists are really good fat burners. Even though it’s a less efficient fuel, they’re very good at storing glycogen. So there’s some complexity to that side of it. To me, a more important one, which we’ve been talking about for a long time, is fast twitch muscle fiber activation. So it’s always great when you’re trying to do an aerobic sport, to rely on slow twitch muscle fibers, because they are effectively infatigable. They can just keep going and keep going. Truth of matters that’s not actually true, they will start to get damaged. They’ll start to have issues. There’s a certain point when you’re doing extended exercise where, even if you’re at a power or running speed or pace, where fresh you would rely entirely on slow touch muscle fibers, you will hit a point where you can no longer just rely on slow touch muscle fibers, and you’re gonna start bringing some of those fast touch muscle fibers in. And again, fast touch muscle fibers can work oxidatively, but they’re not as good at it, and so that’s gonna increase oxygen demand. That’s going to hurt your efficiency, right? And that’s going to start to cause some of those drifts. The other one is just simple neuromuscular technique. When you’re fresh, you might have a really good running stroke, you might have a really good pedal stroke. As you get tired, that can fall apart, and that’s going to affect your economy, right? Another one is blood flow. VO two Max is a measure of how much oxygen you can deliver to muscles and use so ideally you want most of that blood flow going to the working muscles. But things can impact that. One is a drop in blood volume. So if your blood volume goes down, your heart rate’s going to increase just to match the same blood flow, yeah. So that’s going to affect your ability to deliver oxygen. It’s going to bring your VO two Max down. Likewise, as you start to get hot, your body starts to get hot, some of that blood flow is going to be diverted to the skin so that you can sweat, so you can get rid of some of that heat, which means there’s less going to the working muscles. And again, blood flow is going to stay the same, but the oxygen delivery to the working muscles is going to be less, right? And then in runners, there’s elasticity, so you could be a lot more efficient by having that elasticity in your tendons, particularly your Achilles tendon, that allows you to do a lot of the running stroke without expending any energy. As you lose that elasticity, you’re going to have to do more and more work to keep your stroke up. And damage from running can impact your elasticity. So they talked in one of these reviews about the Super shoes that they were trying to do the sub two hours with, and shared it out probably one of the biggest benefits there is you saw less damage, so they were able to maintain the elasticity. And there’s more than that, but those are the big ones that you saw again and again and again and I. Try not to dive too deep into any of them, but I hope that gave a decent explanation.
Chris Case 35:04
It’s very clear that it’s complicated. Yep, there’s a lot of factors. There’s a lot of research yet to be done that’s gonna help tease some of this out, but it’s gonna take a long time, I would imagine.
Trevor Connor 35:16
Yeah, so this is another form of fatigue, and for years, I remember reading research studies on what causes fatigue, and in one of the reviews, they did say durability is different from fatigue. When they think about fatigue, they think about high intensity, you’re going really hard, what causes you to basically hit that point where you crack. This is still fatigue, but it’s a different type, and so they prefer to use the term durability. What durability is when you’re talking about that long, slow distance, yeah, and fatigue is when you’re talking about high intensity, okay, and so I’ve read multiple studies looking at what causes fatigue. And I think at one point they were probably trying to say, is there one cause and where they landed on is, oh, no, right? There are ton of factors, and any one of them could cause so one is, you’ve seen where if your core temperature goes above a certain temperature, you’re just done. Another one, if you’re going really hard, is when your blood hits a certain acidity, it just shuts you down. Another one is glycogen depletion, right? All the glycogen in your muscles, and you just hit the wall, yeah? And there’s many others. So the answer was, many different causes of fatigue. They all had the same result. You’re done, yeah,
Chris Case 36:35
right? And there might be a need for more nuanced, more specific language around these things, because the cause of them is all different. So to call them fatigue, even though they have different causes, is a little bit confusing. One is a bonk. One is something else, one is something else. To call them all fatigue just leads people to believe that they’re all the same thing, but they’re not. You know
Trevor Connor 37:00
where I go to is what we discussed before. And I love that Dr Seiler came onto the show and basically said he doesn’t fully believe in homeostasis. That’s the first time I’ve ever disagreed with Dr Seiler on something. I still think homeostasis is the driving principle of the body, but where the compromise point I would come up with is homeostasis is aspirational, meaning your body is always trying to maintain homeostasis, but it’s an impossibility. Eventually homeostasis is going to break, yeah, particularly when you’re exercising. So the idea of homeostasis when you’re exercising is your body is trying to stay in balance against a large insult to maintaining balance, and as long as it’s able to maintain that balance, you can keep going, but when it can no longer maintain it, that’s when you start the fatigue. That’s either you crack or durability starts to decline, but that’s basically your body can no longer mean a homeostatic balance, and now you’re in trouble, and slow down, right?
Chris Case 38:04
It’s sort of like zones are a range, and homeostasis is a range. It’s not a single point, and we’re never going to remain at 98.6 degrees, you know, like there is a range there, and it depends on whatever you’re talking about, whether it’s core temperature or glycogen level or whatever, there’s a range of acceptance, if you will. And outside that gray area is where you kind of fall off the cliff. But within that range that I mean, is that homeostasis or Yes,
Trevor Connor 38:39
and I actually, when I listened to that episode with Dr Seider, I was sitting there going, Oh, I wish I had said that. So I’m really glad you brought it, yeah, because Dr Seiler said he doesn’t believe in a set point, that our body’s trying to hold an exact number, right? And I agree that is not the definition of homeostasis. Homeostasis is we have this range that is acceptable. And if you go above or below that range, you are doing damage to your body. And that point, we’re going to do everything possible to try to get you to stop taking us out of that range. You’re right. Body temperature, it can go up and down, particularly when you’re exercising, but you get above a certain number, your body says you’re now denaturing proteins. You are doing damage to me. Yeah, I’m gonna try to stop you. Yeah, that, to me, is the definition of homeostasis. Yes,
Chris Case 39:27
gotcha, right. Well, let’s turn our attention to sort of the practical side here, because who wouldn’t want, really, to be a more durable athlete, who wouldn’t want to be able to attack and have a five minute power that’s as good at hour four as it was at hour zero. Who wouldn’t want to be able to sprint all out at the end of a marathon and put in that last big dig that takes durability? So how do we get it? How do we train durability? Is this something that can be trained
Trevor Connor 40:02
so am I answer for the research world? You want to guess what
Chris Case 40:05
this is. I know what it is. I know what it is. We don’t know exactly yet what can be done to train durability.
Trevor Connor 40:12
The best way to train this, though, I think if we brought any experienced coaches on this, they would go seriously. We’ve known about this for years, and we got a pretty good idea how to train it. Yeah, what was a theme in all those studies that I just mentioned? They said we’re not still not certain how to train it, but there are good indicators, and one of the best ways is to look at experienced athletes versus amateurs, because one thing we know for certain is very high level endurance athletes have great durability, and amateurs have poor durability. And actually, one of the really interesting things I brought up that I loved hearing them say, because we’ve always been looking at where are the biggest improvements. And again, they were always looking at joiners, three pillars, VO, two Max economy, percent of, you know, lactate threshold, the lactate threshold, what percentage of vO two max it is. And there was a lot of kind of scratch in the head, because vo two Max, you max out pretty early on. So we see, even in amateur athletes, if you start training them, you see big improvements in vo two Max really quickly. And you see it max out really quickly. So you go, okay, that’s not really it. For decades, so much research on, how do we improve vo two Max when they’re also going you have it you kind of max it out in the first year, but you’re not winning the Tour de France in your first year. Something else is going on, right, right. There’s still arguments on, can you improve efficiency in economy? And evidence is still mixed, so that’s not necessarily it. They have certainly shown that elite athletes, you see that continual rise in their threshold as a percentage of vO two max. So we knew that was one, yeah, but I’m going to make the argument. And again, this is where I think you bring in any elite coach, and they’re going to go, Well, duh, durability was a really key factor. And again, it’s the good old. You take a top level marathoner and you take a moderately decent marathon runner, that moderately decent marathon runner can probably keep up with the elite marathon runner for the first 1520, 30 minutes, but then they’re going to start to decline. Yeah, because they don’t have the durability.
Chris Case 42:33
Yeah? Is this just a giant blind spot in the research? Then, in some ways,
Trevor Connor 42:38
kind of is yes, yeah, and they brought up in one of the reviews, again, I love them bringing it up, going, Well, geez, all these other pillars seem to have a very different training timeline from durability, where you see most of them improve very rapidly in amateurs, but also Peak very early, where durability, well, it’s trainable and amateurs, and you see it improve. It’s something that you see improve over years, right? So there was even one study where they took high level Junior cyclists and tested their durability versus elite Elite, like Tour de France, Olympic level cyclists, and basically said you would see the juniors just absolutely crack at something that wouldn’t even break a sweat on the elite.
Chris Case 43:29
Yeah, there’s no surprise in that. It’s just putting a name to it and understanding the mechanism of it that’s been the blind spot.
Trevor Connor 43:37
So the question then is, what was the training these elite athletes were doing over years. Yeah, that gave them such great durability. And one of the reviews looked at studies of African marathon runners, because that’s one of the you know, certainly, it was an African marathon runner who finally broke the two hour mark and there was no decline in his markers. His durability is phenomenal. And when you look at African marathon runners, you saw a couple things. One was just huge volume. Yes, not hard, just huge volume. They tended to train twice daily. And then one other thing they pointed out is they often train fasted. Ah,
Chris Case 44:19
interesting, but we wouldn’t necessarily recommend that to the amateur out there, would
Trevor Connor 44:23
we? No, we would yet, for whatever it’s worth. Yeah, when you look at these amazing Ethiopian runners, they often train fasted, yeah, so I think the fasted training is still something that I think there’s a danger to it. We know there’s some potential to it. I think a lot more research needs to be done on that. Yeah, before we have any recommendations, but I do think it’s volume. And what you were seeing was kind of a common trend in all these reviews that we looked at, was they were saying it’s a lot of volume over years and consistency. But one of the things that could really. Help is doing volume, where towards the end of it, you start putting in efforts. So go out and do a four hour bike ride and then do your intervals. Or go ahead a hell, really hard, but try to do those high intensity efforts when you’ve fatigued your body. Yeah, I wouldn’t say do that in every single long effort, yeah, but there’s certainly a value to that.
Chris Case 45:23
You would struggle to follow the polarized training method if every six hour ride ended with a 20 minute all out time trial, yes,
Trevor Connor 45:35
then you start pushing over reach Yes. Another thing that I think is really important, I’ve talked about this on the show, but it was a long time ago. I’ve always made the argument that there are some training adaptations that are structural, there are some training adaptations that are biochemical, and often you can produce the same results with both, but the structural changes take a lot longer, but could have a bigger impact. So for example, improving your stroke volume is really important to endurance athletes, yeah, cardiac output, yep, there’s two ways to do that. One is increase your blood volume, which you can do in weeks. The other one is remodel your heart to increase the size of your left ventricle right that’s a structural thing that takes time. It also doesn’t detrain In the same way. You know, if you stop training, blood volume can drop in a week. And so you have to be careful with some of these studies. I’m about to get to this in a second of are they looking at the structural changes, or are they looking at the biochemical because I think when we are talking about durability, true durability, it’s much more structural changes. So one of the reviews pointed out, probably what you are seeing in these really elite athletes is a transition of fast twitch muscle fibers to slow twitch muscle fibers, which takes years. But we know those slow twitch muscle fibers are more efficient and they don’t really fatigue in the same way, the short term adaptation is you can get your fast twitch muscle fibers to work more oxidatively. So you can do 10 weeks of training, get those fast switch muscle fibers to work more oxidatively, and that might help your durability, but only go so far, and it could detrain Quickly, where, if you actually cause a fiber type transition. That’s more of a permanent thing, and I think has a bigger impact. It’s the sort of thing that you’re going to see in more of those tour level type athletes after years. I bring all this up because one of these studies looked at whether high intensity or low intensity training can improve durability in athletes, and addressing their conclusion was, yeah, after 10 weeks of training, both improved durability, but important to know they were studying basically college students who are recreationally fit. A lot of them, when they came into the study, were maybe training three hours a week, and they built them up to training 10 to 12 hours a week. But this was essentially amateur athletes, and you did see a little bigger and improvement from the high intensity training and their durability, but they raised that as well. Of how much of this is biochemical changes in that 10 weeks is the 10 weeks enough to really see those important structural changes, because it’s certainly not claiming that after 10 weeks, these athletes had the durability of an elite marathon runner or a Tour de France cyclist,
Chris Case 48:27
as you’ve been describing all of this. It really makes me think back to an article that you wrote that has to do with this general, simple concept of training and how this goes back to your mentor, Glenn swan. I don’t know if this is appropriate to bring into this conversation, but it seems like I’ll have you explain that if it’s appropriate, that concept goes to the heart of durability without naming durability.
Trevor Connor 48:58
Yeah. So that was Thank you. We have this on the website. I’m going to try to describe this. It’s a really simple concept that’s just a really elegant way to understand the basics of how our bodies adapt, which is, if you look at training stress relative to performance improvement, it’s not a straight line relationship, it’s not a the harder you train, the fitter you’re going to get. It starts with a very steep curve where, if you’re an unfit person, it doesn’t take a lot of training to see big improvements, but then it starts to level out. It eventually, it doesn’t matter how much harder you train, you’re really not going to see any performance gains. Yeah, it plateaus. And what I drew this graph, the point I made was, each season you have a different potential, correct, and that graph will rise with each season. So how high you can get into your performance is going to improve year to year because of these structural changes that take time. Yeah, and I do think the durability is an important part of that for two. Reasons. One is, as we’ve been talking about, durability is one of the pillars, and is one of the things that really separates that endurance athlete. Going back to that example of Michael berry fresh up a one minute climb, local amateurs are going to do just as well as him. You hit that climb 20 times, he’s going to be dropping them pretty damn hard. Yeah, yeah. So durability is actually it’s not your one minute power that separates really separates you from a Tour de France level athlete. It’s that durability, that ability to sustain it. But likewise, if you improve your durability, you can train harder, because I do think once you start getting to that point where everything’s declining, you are putting stressors on your body, where if you do too much of that, you’re probably going to start pushing your body into overreach, yeah, where as long as you’re training in that point where durability hasn’t kicked In that much, you can keep training, and that is something I look at with my athletes. So I have that graph that shows the uncoupling. And what I like to look for when I have my athletes do their long rides, I want to see them get to the point of uncoupling and maybe go 30 minutes into that atom coupling. What I don’t want to see them do is start uncoupling at two hours and go for six hours. Yes, unless you’re in a race or because I think if you do that too much, you’re going to start pushing yourself into overreach.
Chris Case 51:30
Would you say then that the simple act of doing rides where you force cardiovascular drift is a method to improve your ability to prevent that from happening.
Trevor Connor 51:45
It’s just like anything else that you train. In order to improve it, you have to stress it, but it’s how much do you stress it?
Chris Case 51:52
And of course, there are other factors that could lead to it, so trying to do these under similar conditions is going to be a pretty critical so that you know you’re doing it, quote, unquote, the right way, without other factors leading to that drift.
Trevor Connor 52:08
Yeah. So be this is if I could add one thing to bike computers or running watches or whatever that I would love to have in real time, is that graph that we were talking about that shows that one line of your power to heart
Chris Case 52:24
rate, yeah, the relationship there,
Trevor Connor 52:26
and that you can see it when it changes. So you can be out, do it a long ride and go, Okay, I’m starting to see the drift. I’m starting to uncouple. It’s time to start going home. You know, let’s get my good quality 3040, minutes there, but then bring it home so that I’m getting a stressor on it, but not too much, but not too much. So it’s just, you know, we’ve talked about this with interval training. You want to stress your body, but you go to a bad place if you’re finishing every single interval workout destroyed. Yeah, right. So this is the same thing you want the stress you don’t want to destroy your body.
Chris Case 53:05
Is there a place for weight training, strength and conditioning? Is that something that we know anything about in terms of its ability to improve durability? So
Trevor Connor 53:16
this has been one of the big changes you’ve really seen in the research, and this is where I really tip my hat to Dr ronistad, who changed the conversation about weight training, because for years they said weight training doesn’t help endurance athletes. Yeah. And now we really have the context of which to discuss that, because the earlier research on weight training, what do you measure? Of course, we’ve got the three pillars. Let’s see if weight training improves, VO two Max, doesn’t improve your VO two Max, right? How would an endurance athlete train? Yeah, in the weight room. What Dr ronistad showed is it is really helpful for this durability. Weight training literally damages muscle tissue, and you are doing a lot of work in the weight room on those slow twitch muscle fibers. And he’s demonstrated that the weight training improves the resilience of your slow twitch muscle fibers, and that over time, where somebody who isn’t in the weight room, you start seeing that fatigue of the slow twitch muscle fibers and the recruitment of the fast twitch people who are in the weight room, don’t see that same fatigue. They can continue to rely exclusively on slow touch muscle fibers for much longer, plus those slow touch muscle fibers get stronger, so you can put out a higher wattage or run at a faster pace, relying exclusively on slow touch muscle fibers, which will improve durability.
Chris Case 54:41
Here’s a maybe a silly question, Does every endurance athlete need durability
Trevor Connor 54:47
if you do it shorter events, not necessarily, yeah, if you’re a track racer, yeah, I think this is one of the things that goes into this would be great research to do. So are you a track racer? Does it factor in if your time trial is doing a 20 minute time trial doesn’t matter, yeah, or if you’re a 10k runner, doesn’t matter if you’re doing something closer to an hour, does it matter? Then, you know, I think these are all important questions. I don’t have an answer for you, yeah, so, but I will go back to that whole training. If you improve your durability, you can train harder without the risk of overreaching. So I think for the sake of your training, that’s important. I’ve seen this. I’ve taken athletes with no durability, put them through what I would consider a pretty easy training camp, and it kills them, but with years of working on their durability, all of a sudden they can do a training camp that’s three times longer and come out of it actually feeling better? Yeah, yeah.
Chris Case 55:45
This might be another question you cannot answer. Is there a genetic component to one’s durability? I would assume so if all these other things that we’re talking about, there’s a genetic component to basically everything, right? And is there a gender component here
Trevor Connor 56:01
the genetic I haven’t seen any studies on genetics and durability. I’m not sure they’d even know where to start with. Yeah, not yet, but I would be shocked. Sure. Yeah. My guess is, what makes somebody who can win the Tour de France is just a genetically gifted resilience,
Chris Case 56:18
yeah, yeah, and a lot of hard work, yeah, I
Trevor Connor 56:22
think it could definitely be trained. But I do think to be at that elite level, you probably need the genetics for that really good resilience. There is a gender difference. Definitely female athletes have better natural so there’s evidence of genetics as well, have better natural resilience than male athletes. All right, so and then, yeah, two other things to quickly bring up with this that we kind of hinted at, but are important to mention, nutrition can have a big impact. So again, we talked about the fact that when you start to deplete glycogen, you rely more on fat for fuel. That’s less efficient, you’re going to start to see that, that uncoupling. You’re going to start to see that drop in durability. And they have done studies where they’ve shown if you are consuming carbohydrates through the ride, you can maintain your durability longer, and the magnitude of the change the drop in your durability is less.
Chris Case 57:19
Do you think that because professional athletes are able to consume more carbohydrates, not because they’ve trained their gut, just because it’s more readily available to them in races versus amateur racers, that, in and of itself, leads them to have better performances over the long term?
Trevor Connor 57:40
You know, I’m gonna give you a bit of a different answer to this. So Jared Berg, our physiologist here, yeah, I was riding with him at the local Wednesday group ride yesterday, and we were talking during the ride, and he said, he’s good a big ride with some buddies. That’s like 120 miles and 15,000 feet of climbing. He’s biking from Boulder to Breckenridge. Okay, sure, not taking the straight route. He’s doing the hilly, crazy route. And I said, you know, what’s the longest ride you’ve done so far this year? He’s like, Oh, three hours. And I went, are you worried? And he goes, No, because I know if I am just cramming the carbohydrates down my gullet throughout the ride that I’ll be able to survive it. It’s like I might not perform amazing
Chris Case 58:26
as long as his butt lasts, but he said,
Trevor Connor 58:29
I’ll be able to survive it. So there is a dedicated physiologist who advises athletes on this, and is an RD sports rd basically saying, yeah, if you are keeping that consumption up, goes a long way, a
Chris Case 58:44
long way, yeah. So, I mean, okay, I don’t know, like, I want to go down that rabbit hole maybe, maybe that’s inappropriate for the episode. But if he’s not at a level where he’s needing to consume, like, if he’s just at a moderate pace the entire time. Why does he need to consume so many carbohydrates to remain durable throughout a ride at that length, you
Trevor Connor 59:07
will even at the moderate pace if you’re going for a long time, you’re going to start depleting that glycogen, yeah, and then you’re going to start recruiting fast twitch muscle fibers. You’re going to start relying more on fat for fuel. Your durability is going to go down, and you’re going to start struggling. So that said, you want to add a little complexity to this, and this is getting thrown out, but one of the common wisdoms among tour level athletes was the coffee ride, which was sure, six hour ride, don’t eat anything. Trained your body to be able to handle it. But now there’s a lot of questions of, does that do more damage? Isn’t good, but it was certainly something they did for years and thought it really benefited you, yeah, which is the exact opposite approach. The other factor is just environmental factors. We know that heat, obviously, is going to cause you to sweat more, so that’s going to divert blood flow away from muscle tissue. It’s going to. Drop your blood volume over time, so that’s also going to shorten the onset of the decline in durability. All right, durability isn’t a guess, it’s data, and when it comes to data, training peaks leads the pack. The best coaches trust training peaks to track athlete performance with real metrics, not just gut feel, cut through the noise and coach with purpose. Visit trainingpeaks.com/fast, talk to start your free coach trial.
Chris Case 1:00:32
I think the way to close this episode out is really to go back to the beginning, which is Trevor Connor has been doing this for basically his entire life as an endurance athlete, and so many other athletes have too, and so many other coaches have been coaching athletes to train their durability without naming it that they might have called it something else. They might just have known from experience that this is what it takes to win races. But what’s really fun is that science has caught on. Science wants to learn more about it, specific details about what underlies this physiologically and that would inform how we train it in a more specific way, rather than, Oh, you need five years and you need, you know, 500 hours a year to do your base training, to get durability. Could be something else out there that would help you earn your way to durability without just LSD rides. Are you in agreement with that? Is that how you see it too, like, are you excited? Hugely
Trevor Connor 1:01:36
excited. So I’ll share a story with you. I remember right after I took my first exercise physiology class, and have been exposed to PubMed and all these tools to search for the research. I remember right after exams ended, I was lying in bed with my computer on a Saturday morning.
Chris Case 1:01:54
This is a laptop or a desktop. Okay, not
Trevor Connor 1:01:59
that crazy. I did
Chris Case 1:02:00
that’s I was thinking it was so old laptops didn’t exist. You’re welcome. You’re welcome.
Trevor Connor 1:02:05
Okay, we’ll go there. And I wanted to, I was like, Yeah, I knew from all my time as an athlete that the huge value of these long, slow endurance work. And so I was like, Okay, I want to finally read all the research on this. And I remember just searching on PubMed and going, where’s the research? You know, the research was all high intensity, and there’s a reason for that. It’s easier to study in a lab, absolutely. And researchers didn’t want to bring people in and say, do the four or five, six hour ride? And I think another factor in this is they had defined those three pillars and really focused in on those three things, VO two Max, this economy, this threshold, percentage of vO two Max, and we’re looking at how intervals improve that. And there was just this understanding I had it back then, and this is right when I was just starting to study exercise physiology, but as a coach, as an athlete, that there was this other factor, there was this durability, and the long, slow, just lots of time, is how you do it. And again, the evidence is, look at the Ethiopian runners. That’s how they train. Talks with Dr Enugu sau Milan, the way he was training today, and a lot of these top level cyclists was he almost didn’t give them interval work. It was just lots of zone two training. So we kind of had this understanding of it. But I remember just looking at the research and going, it’s not existent. Why is that? And so I find it fascinating now that I love this. I love that it’s now hit the research. And they went, Oh, there’s this fourth factor that we had never really considered before. It is the fourth pillar. And it’s also the one that they’re going, not sure high intensity is the way to this. And so for the first time, you’re seeing them actually doing studies where they’re going, Okay, we got to bring them into the lab and do a four lab and do a four hour bike ride. So I love seeing that, because decades ago, I was looking for that, going, Why isn’t there? You know, it’s a little late to the game for the science community, but they’re there better later than ever. It’s great, and I’m actually really excited to see as they figure out how to research this, what they discover in the research, I think this is going to be some pretty novel
Chris Case 1:04:26
stuff. And it goes without saying. There’s no question about it that if you want to win long bike races, you kind of have to have durability, and so it is something that we put an aim to today in a way that we haven’t ever on the show, but we’ve talked about the type of training that will get you there a lot on the
Trevor Connor 1:04:45
show. But again, it’s any endurance sport. It’s not just cycling. Sure. You know, I have to point to that example of the person who finally broke the two hour marathon.
Chris Case 1:04:57
You want to try to say his name, you’re pretty good. I
Trevor Connor 1:04:59
better. Avoid it, because, you know how good I am at saying names. I don’t want to embarrass myself. He was the only person that the joiner equation predicted perfectly, and that’s because he has phenomenal resilience. There was probably no decline in his durability. Yeah, very good. That was another episode of fast talk. The thoughts and opinions expressed on fast talk are those of the individual subscribe to fast talk wherever you prefer to find your favorite podcast, be sure to leave us a radiant review. As always, we love your feedback. Tweet us at at fast talk labs, join the conversation at forums dot fast talk labs.com or learn from our experts at fast talk labs.com for Levi lightheimer and Chris case. I’m Trevor Connor. Thanks for listening. You.
