83. Endurance Performance and the Wild Science of Fatigue Resistance

Woohoo! Welcome to the Some Work, All Play podcast. We are so happy to be with you today. Happy Friday! It's Friday! And it's young on Friday morning. It is dark outside. We are recording early. The day is young. Yeah, we are coming to you live here from the SWAT Podcaster Recording Studios, aka Megan's home office. And it is pitch black outside. It's a little bit like a horror movie in here with the lights turned down low. It's pretty darn exciting for a sexy science corner. I think horror movie is a good way to describe it. So I, last year, decided to paint my walls orange. And I was like, this is the color I want to feel. But the orange actually does give a little bit of a horror show, like jail sort of vibe in here, especially with like the low light and the dark outside. So you just have this orange hue reflecting off your skin. Like our former presidents. So why are we recording early? It's because we have this amazing sexy science corner topic, which is fatigue resistance. We're going to try to open up the vault, tell you all essentially what we've learned, over years of coaching athletes that excel at marathon distances and beyond. Some fascinating data. We'll mix it with a lot of studies. I think you're going to find this one extra sexy today. I am super excited for this. All science is sexy, but this one has particular sex appeal. I put this, I feel like, put this on People Magazine as like the sexiest man or woman of the year or non-binary individual. That is fatigue resistance. And I'm stoked for it. Yeah. As we were doing a brief, like five minute review of some of the science, we've realized just how much overlap there is, in every single topic here, that nothing is straightforward. And what could be more sexy in science than this like amalgamation of just like total incomprehensibility. So we're going to try to make it a little bit more comprehensible, a little bit more interesting and fun in ways you can apply to your own training. And a lot of strong science. And then also our personal hypothesis too. So we'll be, we'll be very cautious about telling you when this is a strong scientific article. And this is our theories because you should trust the strong science. And I think trust our theories too, because we've, we've had a lot of top data, but trust it with a little asterisks. So do you want to get into this right away? Let's do it. Awesome. So as always, the sexy science corners are brought to you by trawnermag.com/outsideplus. Subscribe there to trawnermag. It's only 50 cents a week. They let us open up their vaults to old articles to structure these conversations. We owe a lot to trawnermag and it would be awesome if you subscribed. It's the one of the main ways you can support this podcast. And we love the people there. Two, join.webcast.com/trawnermag, you can find us on Twitter, Instagram, Facebook, Twitter, Twitter, we love them. They've been giving us a lot of interesting information recently as Megan comes back from her heart condition. So yeah, get, get a WHOOP if you don't have one. I was going to say, we've learned a lot about fatigue resistance from WHOOPS. I think that's when we talk about our personal hypotheses on the science journey, it's going to be a lot from WHOOP data. So I'm grateful for them, grateful for them supporting our athletes in this process. And, you know, still grateful for WHOOP, even though it's telling me, right now I have, I have a strong case of piece of shit I did right now, according to WHOOP. I don't know. It doesn't like me. I don't know why it's telling me I'm like very high stressed all the time. And I don't feel that way. It's getting a little bit better. I would say it's, it's improving just by, by a snail's pace. But like the hundred milers we're talking about, the snails can often win. Actually, I guess the tortoise wins, not the snail. The snail is just like in a slimy heap back near the start line. So maybe I messed up that metaphor a little bit. The snail is still sitting in the ultra running chair. Yeah. We need to bring back ultra running memes and the greatness of the ultra running chair, but that's, that is where the snail is right now. That's kind of where my metaphorical WHOOP data is right now, but you can always get off the chair. That's what I've learned in ultra running. It's always possible to get up and keep going. Okay. Well, that's, that's, I think one of the big themes of today is how can you get off the chair and keep your physiology going after you've already put out a lot of work. And that's basically all fatigue resistance is at its core is what happens to your physiology after your physiology has already performed, you know, over 1000 kilojoules of effort. So this can be anything over a couple hours. And the science is really coalescing around this idea that there is some genetic baseline for what happens there. And then from there you get this like butterfly effect of potential outcomes. And you can influence that with training behavior and other things to manipulate your genetics, to perform like a total bad-ass rock star, no matter what your exact baseline might be. And we're being pretty amorphous right now. Intentionally. Intentionally talking about fatigue resistance. We're going to break it down actually in a couple minutes into central fatigue resistance and peripheral fatigue resistance. But maybe let's start actually just start telling our stories of fatigue resistance, because I feel like you got to start any podcast with an anecdote, but also I feel like we, we illustrate interesting points on the, on the standpoint of fatigue resistance. And I think it would be instructive to dive into that. Maybe where I think where we really illustrate is where those baselines, like how that looks in practice. So I'm going to start by telling Megan's story a little bit. So two, two quick stories. One back in 2014, she had just done the short distance world championship. So she was training for a race that was like 40 to 60 minutes long. Her longest run to that point, I believe in your entire life was 16 miles. Was that right? I believe so. Yeah. Yeah. Yeah. So also we've told the story on the podcast before. Side note, sorry, but it illustrates this point perfectly. So bear with us. I feel like every story, it's kind of like, we are your uncles at the Thanksgiving table where we tell a story, but it's told with a slightly different, I don't know. It's a different, different illustration. Everything change changes a little bit to where we're like uncle Rico and Napoleon dynamite, just being like, I threw that football over that mountain over there. I was going to say, I can envision our listeners just being like rolling their eyes and be like, yeah, yeah, we know Megan ran a 50 K after, you know, her longest long run was 16 miles. And it went well, we understand people. Okay. The aunt at the Thanksgiving table, just cut the uncle off. So I'm actually going to go to another story, which is way too cool. So this was either next year or a little bit after. And I heard a story from Rod bean, who's this, you know, legendary ultra runner. And I guess he was running with you at the time. Um, and Rod told me that you guys came together, um, around goat Hill, um, which is, I think mile 24 of that race. And he was running behind you. And all of a sudden this steep Hill at way too cool. You just take the fuck off and he never sees you again. I think you end up being like five or 10 minutes ahead. Um, and that to me is the ultimate example of fatigue resistance. Why does your physiology respond that way at three hours into this tough event? When you never do three hour training runs, you're able to just motor away to where you're at. And I think that's, I think that's the ultimate example of fatigue resistance. But I think that's, I think that's, I think that's the ultimate example of fatigue resistance. Um, and I think that that's just such a cool question because that's essentially what we're all trying to do when you get to these long events, whether it's mile 20 of a marathon or, you know, mild 80 of a hundred miler, it's starting to ask some of the same questions of physiology. Well, if you, if you flip back to when I was running that way too cool race, I never even thought about the concept of fatigue resistance. Like I was not really coaching that much then I was just kind of like, well, I told myself I was going to go with this Hill. So I'm going to go with this Hill. Kind of like when you see, you know, someone's running a mile race and all of a sudden they turn on the jet burners and they've been clearly waiting for that. That was my race strategy going into way too cool. It was like, okay, it's time to go. But at the moment I had convinced myself, I was like, oh, I don't even know anything about fatigue resistance. This is just the idea that I took so many caffeinated gels during that race that as soon as I hit the bottom of that Hill, I was like, oh, thank gosh, I need to like do something with a stored and pent up energy. Yeah. Well, your heart had a lot of experience working very hard before you had these more recent conditions. But you know, I think that's something that I've learned over the last couple of years. And I think that's something that I've learned over the last couple of years. Will my body have it? You know, almost to a certain extent in your body is going to happen in contrast that with my personal experience, which is, you know, my race results have this big scatter in 50 K distance. Like I've been on the podium in the national champs a number of times, but I've also had horrific experiences in, in none of those, even my best races. Did I ever turn it on after two or three hours? Right? Like it's always a slight fade that I'm managing. And I think I could manage that all the way out to even a hundred mile or eventually in my career, but I'm never going to be the type of athlete probably that's able to do an acceleration at that point. And I think that likely comes back to some sort of baseline difference between athletes like you and athletes like me. Well, I think what's interesting is if you look at me in the first mile of a race, you can tell how my race is going to unfold. Like I either have it from mile one or I don't. And there's been, there's been races for sure where I get like one mile in and I'm like, where are my legs today? What is happening? Maybe in some sense it's, it's overlapping with some of the autoimmune stuff I've dealt with. I think almost for sure that's the case with you. It's actually a little bit different. Like I often see you one mile, five miles, 10 miles into a race. And I'm like, oh my gosh, he's having a fantastic day for me. Actually, when I, when I watch you race, the true test is what happens when you come through mile 20. And that's when I really know. And I've seen races where you are smiling, you are like ready to go. And I'm like, oh shoot, this is a podium day. I'm feeling it. And then I've seen other days too, like that day that you're describing where it's obvious to me within one second that the lights are out. And it's just interesting how like with my physiology that we know it immediately, whereas with yours, it takes some time to build up that fatigue to really understand how your day's going to go. Yeah. So a good example would be the 2019 formidable or 2018, one of those years, formidable 58, which was the national champs that year. And I'd been on the podium a few years in a row. I thought, great. I was amazingly trained, had done over a hundred miles a week. And, uh, I get to like mile 20 and I was feeling fine. I was feeling really good. And all of a sudden Tim Tolleson, you know, this amazing ultra runner comes by me. Like I am standing still. And I actually thought I was having a great day at the time. I didn't really realize how much I had actually started to fade until Tim like sprints by me. Tim went on to win, have this like incredible race. And, um, at that moment I really understood, okay, this might not be that exact day. I need to start going into management. And then I ended up seeing Megan, um, at like mile 24, a little bit later. And, uh, she was just like comforting me in the moment, understanding that for whatever reason, this was not a productive day for my fatigue resistance. So, um, what we're going to try to do is we're going to try to do a little bit of a quick analysis of what we've learned from our, from our, from our coaches, how we've started to identify athletes for where they might fall in at baseline. And then, you know, gently direct their physiology. towards the types of fatigue resistance where they can excel at the end of long events, no matter where they're starting from. And I think it gets into some of the most thorny and interesting questions of exercise physiology. And I'm excited that we're doing the science corner now, because I think it overlaps with some of the past science corner episodes that we've done. And also a lot of the topics that we've talked about on the podcast. And as coaches, actually, one of the things that we've done is just continuously refined the input that we put into these algorithms for predicting fatigue resistance, whether it's peripheral or central or both. And so just diving into that and really sharing, like, what are the data that we've collected in this process? So do you want to start first? And I can start highlighting these definitions. What's the difference between peripheral fatigue resistance and central fatigue resistance? Is that a good place to start? I think that's the perfect way to start. So this is like the definition section that starts any good, like, legal article or something. But this is important. I feel like these definitions are going to set the stage for the entire rest of the podcast. It's almost like reading a scientific journal, and you don't catch the acronyms in the first part. Oh, yeah. It's a scientific journal. And then you're going on later, and you're like five pages later, and you're like, what the heck is IKJGH? Like, I don't even know what I'm reading about. So this is like, stay tuned. If you need to fast forward back to understanding these definitions, this will set the stage for the podcast. Awesome. Let's go for it. So what is peripheral fatigue to start? So essentially, peripheral fatigue and peripheral fatigue resistance is the idea that when you have peripheral fatigue, there's essentially impairments that are located in the muscle and characterized by metabolic endpoints. So when we're talking about metabolic endpoints, we're essentially talking about the endpoints that we're actually talking about, largely about, and there's tons of different metabolic endpoints, but essentially byproducts of metabolism like lactate that accumulate in the muscle and make it very hard to continue on. So anyone who has had a significant accumulation of lactate in the muscles understands the legs feel like sludge when this happens. So like when peripheral fatigue really hits, you just feel like you're moving through sludge. Yeah, that lactate corresponds with like hydrogen ions and other things that essentially cause acidosis that make the muscles less likely to fire. One of the, you know, we're not getting into the exact. Peripheral fatigue isn't the focus of this podcast, but there's an interesting question there, maybe in a future science corner on how lactate has been reformulated. We still measure it because it's what corresponds with fatigue, but lactate itself is not the boogeyman. And, you know, so we'll often use lactate as a shorthand for fatigue, even if it's not actually that on the cellular level, but it is like essentially a one-to-one ratio. So it's almost like a distinction without a difference. And so it's important to recognize. I was going to say, it's unfair that we've pinned lactate as the boogeyman. All these years, like, I feel like we need to do a retrial on this and just get lactate out of jail. Like it does not, lactate does not belong in jail. It's actually, it's a kind substance. It's just like, I'm trying to help. And it's like, fuck you. You're here. It's almost like, I don't know, hating firefighters because they're always around fires. But it's like, it's not the firefighter's fault unless it is, in which case firefighters are making business for themselves. Let's go into central fatigue as the next point. And there's a lot of overlap between peripheral fatigue and central fatigue. So central fatigue is essentially the failure of the central nervous system to adequately drive the muscle. And there is a lot that goes on in the central nervous system. Like trying to summarize this would take a whole two and a half, three hour podcast. But essentially when we break it down, we are looking about and we are looking at and talking about ratios of neurotransmitters and neuromodulators in the brain. In this podcast, we're going to talk primarily about serotonin and dopamine. And we've talked about these neurotransmitters and neuromodulators in other podcasts as well. But they play a large role in fatigue in the body and arousal and performance drive and all of these different components. All of so many other bodily processes like serotonin and dopamine make us go in so many different directions in the world. And we're just going to talk about them in the context of the central fatigue resistance. You talking about science makes me quite aroused. But I mean, to simplify, so obviously, Megan, you're a doctor and a researcher to simplify it for a non-doctor like myself, the way I like to think about it, okay, we have these brain processes, which are the chemicals we're doing that, then that is interpreted through the nervous system, which goes out and takes in everything we're experiencing in the outside world, including mechanical forces, things like breaking power on downhills, which we'll talk about how that might impact nerve endings, which then go up to the brain and feedback. So there's all these feedback mechanisms that are have a brain like it stews together in the brain, but it's coming together from everywhere for including things like the peripheral fatigue. So that's where this all is gripped in one thing, and we're going to try to tease it out in ways that can help athletes move forward. So with that in mind, let's get to the article. So the way that we structure these sexy science corners is, we take some of our favorite articles, and we break them down reading through having fun, book club discussions about all the studies within them, and giving you some takeaways that you can use in your own training, hopefully, I like how you describe this as a book club. I love book clubs. But recently, I've been daunted by book clubs. I've had enough homework in my life. And as soon as I hear homework, I'm a little bit traumatized. So guys, this is a book club with no homework. Yeah, I'm on all about that. Oh, yeah. So the article is titled, "10 Training Theories About How to Improve Fatigue Resistance in Ultras." When I wrote this, it was essentially saying, "Okay, here's every secret we've ever developed." I mean, not secrets, but here is what we have seen that is incorporating a field of science that is very weakly understood. And maybe that's the jumping off point before we get to reading it, is that central fatigue is highly debated. We know it matters. We don't know exactly how it works. And that's the hard part when you talk about the nervous system, can't biopsy the neurons. And it reads to a lot of complications that we might not have for quadriceps muscle fatigue or something like that. Actually, side note, you can't necessarily biopsy the neurons, it's not quite a thing you can do. But you can do that in the animal studies. And they're starting to do that more and more, but I don't love animal studies personally. Actually, they give me even more triggers than homework, so not a big fan, but I'm excited to talk about some of the anecdotal facts. I'm excited to talk about some of the anecdotal evidence. Can I start reading the article? Go for it. Let's do it. At mile 90 of the 2019 Western States 100, Claire Gallagher was running a legendary race, one of the fastest times ever through the final checkpoints, still flying. Wow. Almost any other year, it would have been all over except for a victory lap and peeing into a cup while a stranger stood a foot away watching the live stream. But not that year. From behind, a headlamp started bobbing towards her, and the headlamp was moving fast. A few minutes later, Claire realized it was friend, an international superstar, Brittany Peterson, also having a historic day. After nearly 15 hours, the race was officially on. What happens next? I'm not talking about what unfolded in the race. We have talked about that amazing performance before, when Claire proceeded to set the all-time record for the next section of trail. Instead, I'm asking about what influences performance after 15 hours of pushing. They all want it. They all have world-class physiological profiles. They are all winners at countless other races. So what gives? That is the main place to jump off, I think, because Claire's story is fascinating. She is another person like you. That has tested off the charts for this variable. And before that Western States, it is not like she had been doing anomalous training. If you look at athletes at this level of training, it all kind of starts to overlap a little bit. Claire, in fact, spent two weeks before the race in Alaska just doing work with Patagonia for climate resilience. And it is like she wasn't training at that time, and yet she is able to come to Western States and perform this way at mile 95. What is preparing her for mile 95? That is so interesting. And I mean, you could even see it in her eyes when she went through Forest Hill Aid Station at mile 62. It was wild. I agree 100%. Actually, whenever anyone asks me on a podcast or in any other situation, "Who is your mentor in life?" I often go to Claire. I mean, she is a life force of a human. And you talk about seeing that fatigue resistance in her eyes. I see it in her life. Yeah. I mean, what she is doing in terms of the support that she's giving to environmental advocacy while being a runner, while being an awesome person. While just putting out this life force into the world, to me, screams fatigue resistance because she's doing it all. And she's doing it all with so much energy. And I think actually the other interesting side point about Claire is she doesn't need a lot of sleep, from what we've seen. And I think there's actually some interesting, and this is just a side note and not a ton of evidence to look at this, but I think there's a relationship between people who don't need a lot of sleep and high levels of fatigue resistance. Yeah. I think fatigue resistance likely has overlap with other variables that then affect everything in life to some extent. Yeah. And how you exactly see that in different athletes can be really complicated. Like I was thinking John Kelly, another athlete on the team who might have some of the best fatigue resistance ever, like Barkley Marathons finisher, Penine Way, FKT, things like that. I have in his training log, there's a column for sleep and there has been times where he's just hit three hours for two weeks due to being a CTO at his company. And he can buffer that in a way that I could not, for example. Maybe that is sensing something or maybe it's not, maybe it's just an interesting side note. So back to the article. Somewhat surprisingly, we are still unsure of the answer to the question of how athletes can push at that place in a race. There are all of the normal exercise physiology culprits, and this gets to the peripheral fatigue Megan talked about. Aerobic threshold and running economy can be measured with a mask and a treadmill, muscle damage with a blood test, heart rate with a strap. But what about when all of those factors are comparable amongst competitors, or at least within air bars that are extra large and ultra events? Why can some athletes train the same, pace the same, feel the same, yet have different results? I love that this was one of the main points of the article, and especially pushed up front in the article, because it's so true. You think about Western states, and let's go back to Western states in 2021, when Drew proceeded to go into the medical tent and pee in a cup. And if you took his pee in a cup and took it to the Starbucks bar, you could put it on the Starbucks bar with the wrong spelling of Drew, he called that a dark roast. That was how gnarly his pee looked after that race. And we know after the fact, and Drew has been open sharing his story, that his CK levels, his creatine kinase levels, through the freaking. Freaking roof. Yeah. But you would imagine too, and how is Drew able to do that? Everyone else at that point in Western states is like. especially in the top 10 comparable, like these athletes all want it the same. These athletes are all pushing through. Why is Drew able to push through Starbucks colored dark roast that his body is producing when no one else is able to, or no one else at that point in the race? Yeah. Well, I mean, we know from after the fact that his CK levels hit, uh, an extent that was like toxic waste dump, uh, you know, that we need to get the federal government in here to, you know, issue in a formal cleanup. Um, and that's really interesting because if we had been able to biopsy his muscles at mile 90, there would have been nothing left yet. Not only was he performing well at that point, he dropped his pacers and his pacers are, were two world-class athletes. So he wasn't just performing. Okay. He dropped two totally fresh athletes in the heat with no muscles wild. So cool. And also the key thing to remember, it is not how much people want it as much as like some of the world is like, this is about toughness and stuff like that. Everyone at this level is going, doing whatever their physiology can put out. And so it's a cool science experiment. It's kind of the same that you'll see at mile 20 of a marathon. Um, that's mile 80 of Western States. And so this applies to everything. At mile 80 of Western States, everyone is David Goggins hard. And this is about fatigue resistance. It's about what separates them. Like you, you have stratification at that point. And so what is it? Their mental toughness is in gorge as hell. All right, let's get back to the article. The article says the answer may be found in the emergent study in the emerging study of fatigue resistance. Fatigue resistance does not have a definition, but is generally classified as the extent of performance, deterioration, latent events, often unexplained by normal physiological profiling. While fresh a 2021 study in the international journal, sports physiology and performance examined power profiles of elite cyclists with a primary difference between under 23 writers and professionals being that the pros could put out higher bursts of power after hours of hard work, even though their basic power profiles were comparable. Um, and this is because the U 23 writers actually had higher five-second power. The deterioration of the power profile towards the end of races explained some performance differences. And I think this let's dive into this study methodology because it's so important. And I think helps set the stage for conceptualizing this idea of fatigue resistance. Yeah. So essentially what they did is they had power meters on these cyclists and cycling is a great place to look at this in a way we can't in running because the power output is distilled into pressure into a crank. Um, so you can look at the Watts and, you know, put them into a statistical model to determine lots of really interesting things. And so as they put this information to a model, they found that the main thing that they were able to do was to put the power meters on the cyclist. And the main thing separating people was not absolute power. It was not their functional threshold power, let's say, which is lactate threshold or so around one hour effort. It was what they could do after they had put out 1000 to 3000 kilojoules of work already. Um, so we're talking about a couple hours, a few hours of effort. Um, so after that point, the pros didn't have a deterioration in their power profile nearly as much as the under 23s, but even within those groups. So within under 23s or within pros, the best performers were determined not by their absolute power levels, but the amount of deterioration. So in the past, we might have called this endurance or something like that. But endurance is that one hour power like that takes tons of endurance. When you start to get over a few hours, you're talking about something else entirely. And that is most likely this amorphous blob that we're going to call fatigue resistance on this podcast. And one of my favorite sub analyses that they did in this study was they looked at the under 23 writers and under 23 writers are still developing, but they could predict who was going to have success in the pros based off of the stratification in the under 23 writers. So the under 23 writers that were performing very well at this fatigue resistance. So the under 23 writers who are able to hold or maintain better that power after putting out that 1000 to 3000 kilojoules of work were the ones that would go on to be better in the pros. And I think it's really interesting how you can see this variable early. I imagine if we flash back to field day and made, wouldn't that be a terrible field day model where we make young kids put out like a thousand to 3000 kilojoules of work and just like, see what happens. But I imagine because of the genetic components of this, we could stratify even at field day. And yeah, there is a lot of, I think the exciting thing is, is you can modify this. You can train this over time, but I think there is a set genetic range that happens for a lot of people. Yeah. Probably like every single variable. And you know, we're not trying to say that this is the only variable that matters. This interacts with a thousand others, but once you start to get into the limits of human performance, we are saying that in limits of any single human's performance. So like no matter what the level is, this becomes a predominant factor. And so thinking about it and thinking about how to manipulate it, I think is a key element in coaching and performance. And we're going to get into how to manipulate it and how it interacts with some of those other variables. That makes intuitive sense when you consider ultra running. At the Western States 100 in a couple of weeks, so this was written this year in June, 2021, there will be a handful of athletes that would likely have similar lactate thresholds, aerobic engines, and overall training approach. Yet they end up finishing many hours apart, even with smart pacing. And it doesn't just happen at the front of the fields, but all the way to the last finisher and first person to DNF in every ultra. Something that we aren't always measuring is playing a big role. Alex Hutchinson literally wrote the book on fatigue, The Amazing Endure. And he points out that there's a complexity that makes training and understanding this variable difficult. Quote, fatigue, after all, has many different components, metabolic disturbances in your muscles, altered signals from your brain and through your spinal cord, depleted motivation and cognitive resources, end quote. If I had to guess, I imagine there's a high contribution from central fatigue, where the nervous system decreases the neural drive to muscles. A 2012 review in sports medicine on central fatigue just adds more complexity to the picture with a general conclusion that we don't know for sure why it varies, but it likely matters in endurance performance. I love that you highlighted here and Alex Hutchinson highlighted the idea of the complexity. There is a ton of complexity. So I think like one, there's complexity in the nuances of how we understand both of these systems, but also they rely on so many different inputs and variables. So Alex Hutchinson talked about some of them, but if you think about it, like fatigue, just some variables that it relies on would be muscle breakdown or glycogen adaptation or glycogen depletion. And then also like core temperature, brain neurotransmitters, like so many different things, as I said, are being input into this equation and it's very difficult to untangle them and then find also all the correlations associated with them. Yeah. And what I think is fascinating, actually your perspective here is especially unique because you have a background in neuroscience before you went to medical school and then did your PhD in large statistical studying, statistical models. So you've pushed me forward on this topic so much as a coach. And I think a lot of the explanations for why I think I've become a better coach over time, come back to you teaching me more about the brain. And not just for me, I have a temptation to think about it in terms of like power models, output models. And you're thinking about, no, what's actually happening inside the two ears. And that's so cool to me. I feel like in our relationship, you're like the power man and I'm the dopamine girl. And that's kind of where we trend in our relationship. And I mean, I learned a ton from you, so. I am power man here to mansplain the exercise physiology to a doctor. But let's dive into the brain actually. So I think there was a 2012 review that really hit the nail on the head in terms of like talking about fatigue resistance from the central nervous system perspective. And what I think I am just fascinated by this is the idea that neurotransmitters are heavily involved. So one of the theories is, and this is, I mean, I think it's pretty strongly being proved, but again, there's a lot of ambiguity in this field, is that the ratio of serotonin to dopamine is associated with feelings of tiredness and lethargy. So the theory is that having a low ratio, so that would be low serotonin and higher dopamine levels are associated with improved performance through motivation and arousal. And so I think that's really interesting. So high dopamine is beneficial performance and low serotonin in the brain. And so a lot of what we're going to talk about next would be fueling strategies, would be ways about thinking about these dopamine and serotonin levels. Yeah. And a lot of what we're going to talk about is essentially going to be saying, okay, somehow the nervous system is impacted here. We don't know exactly what the intermediary is. And what Megan's talking about with the neurotransmitters is this could be the intermediary. And what's so interesting, and we talked about this on the podcast in the context of numerous other things, that these brain chemicals do have large interpersonal or individual variation. And that could impact everything from how someone performs at mile 80 to how they perform in the heat. And that's wild. I mean, it's so interesting to think that a lot of this isn't training or choice, it's neurotransmitters. And I love that you're bringing up that point. And I actually think there's a lot of inter-individual and intra-individual variation. Because these neurotransmitters are varying widely across. I mean, neurotransmitters in someone could be very different depending upon psychological state, depending even upon what medication someone's taking, depending upon training. So I think it's fascinating when you talk about that in this context. But actually, I love that you also brought up the point of heat. So it's thought that the central fatigue resistance, the idea of dopamine and serotonin being important, are more pronounced in heat. And I think that's interesting when you think about it in terms of Western states. A lot of what we're measuring at Western states, are people who are off the charts with central fatigue resistance, and possibly these neurotransmitters have a role in that. And the theory there is that. So serotonin, there's serotonin and catecholamine projections that innervate areas of the hypothalamus. And that sounds complicated, but essentially the hypothalamus has many roles in the body, including heat and thermal regulation. And these serotonin and dopamine are playing large roles in that level of thermal regulation. And so it's really interesting how fatigue resistance is at the central nervous system level may become more pronounced and more stratified in individuals during periods of heat. Yeah. So to zoom it back from non-doctor perspective, for me, what I like to think about is that there's only so much room in the brain and multiple different things are going on in every different section. A lot is going on in the brain. Yes. This has been brought to you by Mansplain, by Power Man, here to Mansplain. And so when you're talking about something like a hypothalamus, it's doing multiple different things at once. And so we start to get crosstalk in the sense of we're seeing fatigue resistance, we think, in something like heat adaptation and heat buffering. And that's pretty cool. And it is very interesting in the context of R2C, stories, for example. I struggle much more with heat than you. You excel in heat even without heat adaptation. Maybe that's why I might need the sauna more or something. What are we seeing here? Who knows exactly? But it does provide an opportunity to form interventions. And I was going to say, my hypothesis, and again, this is a strong hypothesis and not something that's proven in scientific data, is that I think we can tell a lot about an athlete's natural and genetic fatigue resistance capabilities at the central nervous system level from how they perform in heat. And I think it's an interesting study. And Western States is the ultimate study design for that. And it's truly hard to know until an athlete gets out there how they're going to respond. But Claire Gallagher and Drew Holman, fantastic responders to heat. And also fantastic at this level of fatigue resistance. And I really do think, especially when you look at these possible mechanisms, I think the two go hand in hand. Yeah. And I mean, Drew is from Minnesota. He did not grow up with heat. There's not that explanation. And I think there's some really interesting things here in studies that have been done. On like ephedrine and other, what are they called? Amphetamines. Amphetamines. Boom. That's the word. Thank you. You're so smart. But in football players, for example, many of the heat-related deaths involve amphetamine use. And it's one of the reasons they've been banned, one of the many reasons they've been banned. But that's fascinating because maybe that amphetamines change the neurotransmitters and help someone push past a natural governor that might stop them before they reach those points. And it points that you know, the. How the neurotransmitters act can be individually variable and have massive implications for what happens under fatigue states or heat states, and they're probably the same thing. I think it's actually very interesting that you're bringing up the idea of modulating the neurotransmitters. So one of the purposes of. People have probably heard the term SSRIs before, selective serotonin reuptake inhibitors. Those are a class of antidepressants that actually directly modulate serotonin. And what I find fascinating as a coach is the idea that sometimes when athletes take these antidepressants, and this is like just. A side note, antidepressants, fantastic. We've seen a lot of people helped from anxiety, depression, all kinds of other mental health disease. Sometimes taking a pill is fantastic for life. It's great for improving overall life outlook. And so I think it's important to prioritize your mental health at all costs, but we've seen variable reactions to SSRIs. Sometimes in athletes, I've seen them dramatically improve fatigue resistance. I have seen some athletes come to me after starting an SSRI and they're like, "Meghan, for the first time, I feel like I can just run three, four or five hours in the mountains, and my brain is quiet. I have that motivation. I have drive." Whereas in other athletes, they're like, "I feel like I'm underwater. I don't know what's going on, but I feel so sleepy. I feel like I can't push through anything." And probably what we're seeing there is these selective serotonin reuptake inhibitors are modulating the levels of serotonin in the brain and altering levels of fatigue resistance. And for some athletes it's positive and some athletes it's negative, and perhaps it's neutral for some athletes, but it's hard to predict until someone takes it. And it might also get to addictive personalities more generally, like how people respond to dopamine exposure. We've talked about FACAs in the past. You could be a more addictive personality perhaps than I am, and that likely has to do with how our brains interpret dopamine signals. And that is highly associated with addiction. So maybe one of the things we're seeing in ultra running where some of the best performers might have more addictive personalities doesn't have to do with the fact that they do like a ton of training, which I think has been some of the theory before. It might actually just have to do with, okay, their brains respond slightly differently when these knobs are turned. And yeah, dopamine is heavily implicated in addiction. And for me, I need my dopamine fix. I'm a dopamine junkie and I feel that. I have high, high dopamine needs. And I think there might be something there. I do think I score probably pretty high in this level of fatigue resistance just given how I performed at some of these longer races. You're off the charts in the measurements that I've done as your coach. They're off the charts. And I blame dopamine for that. Something that's actually caused me. I do have an addictive personality. I'm not fantastic. But the flip side of that is that it might be helpful in some of these ultra performances. And for that, I'm grateful. But I think it largely has to do with dopamine. And I'm pretty interested just to continue learning about that and researching about it. Yeah. And it's just. With this obvious bias that I have. Bias. Bias is my middle name. Power man bias roach. Fatigue resistance or something impersonating it is a variable that we noticed was at the forefront of ultra performance right as we started out to the point that we developed the algorithm to determine where athletes might fall at baseline and during training blocks. Or maybe the test measures something else entirely. It's all relatively uncertain still. But whatever is being measured, we have seen the short tests have strong predictive value for 100 milers and beyond. And then in parentheses, and this is something to pay attention to. For those that are curious, the test usually involves a moderate 90 plus minute effort. So getting to like 1,000 plus kilojoules of work, followed by a hard finish, recording the ballpark offset between the hard finish performance and baseline lactate threshold performance. Claire is outstanding, as you'd imagine. So are athletes like Drew Holman and Katie Asmuth, both lining up at Western States in a couple of weeks. You are a fortune teller. You wrote this article before the 2021 Western States when Drew Holman and Katie Asmuth went on to have just remarkable performances and you predicted it. So I think one, you're a fortune teller, but two, it also shows the power of fatigue resistance and the fact that you were seeing that as a coach and then able to go on and predict. But actually one quick question I have is, I think one of the key points that you wrote here is the idea. So you said it's this test, this moderate 90 minute effort followed by a hard finish, and then you record the ballpark offset between the hard finish performance and baseline lactate threshold performance. Can you just, I think that's like one of the cruxes of the entire article. Can you just break that down and spell that out a little bit clearer for our audience? Great. So a good way to think of it is what you would do on a climb at that moderately hard controlled time trials type style. So let's say, a good example is we talk a lot about Walker Ranch here. And so at Walker Ranch, there's a 10 minute ish final climb that's nice and steady and relatively steep. What you would do on that if you were doing it for an hour, if you were doing it like that moderately hard, totally fresh effort in a workout versus what you do at the end of your 90 plus minute moderate effort or your long run. And so running with Drew, I was able to see this firsthand. So at baseline Drew would be fantastic on that climb. After 20 miles, Drew was just a very small amount less fantastic. Whereas for me, I would, you know, to toot my own horn, I would be fantastic at baseline fresh. After a significant amount of work, I would have a relatively large drop off. I'm not that bad. Like I'm, I'm still relatively good in the scope of athletes that we test. But I'm no Drew Holman. I'm no Megan Roach. And you've done the same thing to me at Walker Ranch. And, you know, usually I'm not seeing that in person. I'm doing that via Strava files. So you know, all athletes that are coached by us, they'll get these types of tests without us saying anything. And, you know, I'm not saying that in person, I'm doing that via Strava files. So, you know, all athletes that are coached by us, they'll get these types of tests without us saying anything. And, you know, all athletes that are coached by us, they'll get these types of tests without us saying anything. And it's not that we determine like exactly how they're going to train based on this, it's that we give them more accurate predictions of what they can expect once their body hits the unknown. And those variables can change over time. This is not a baseline that stays the same always, but it is highly predictive of where anyone's at at a given moment. And I think one of the other genetic predictors is how much can someone improve at this? And most likely some people can improve more than others. And that's really exciting too. Like, you know, an athlete that's lining up at Bandera this week, Adam Mary, has improved by like 25% at this number, at this fatigue resistance number, in addition to his raw performance improvement. That's exceedingly exciting, probably indicative of some wildly cool genetics. But what exactly the cause is, who knows? And I think that's one of the coolest things. Just a quick question as an aside. Is it horrifying to do long runs with Drew? Like if you know that Drew is going to be just as good on that final climb, is that going to be a good thing to do? How, I mean, how is that mentally going into long runs with Drew? It's horrifying to do long runs with you. It's probably the best way to end that discussion because you do the same thing to me every single time. Do you want to get back to the article? Let's do it. All right. The article says, and this is the title, "Important overarching training point. Running economy is still the most important variable. The fastest athlete with acceptable endurance has a great shot no matter what their fatigue resistance. 80% of a really big number is still better than being able to hold closer to 100% of a much lesser number. But there's a Holy Grail I want to help athletes achieve. Let's hold close to 100% of a really big number." The problem that I see in ultra training is that some approaches seem almost solely geared to trying to train this amorphous fatigue resistance principle. Yes, it matters, but it's also highly genetic. And whatever amount it can be trained is still subsumed by actual speed, especially over many training cycles when an athlete can get faster and faster. Get fast as heck, then train your body to hold on tight. Yeah. So, you know, that gets back to the general idea that we know running economy can improve long-term, and that can improve for anyone. We think fatigue resistance can improve a ton for almost everyone, but if running economy isn't improved to its maximum, we're just playing at the margins of something that doesn't really matter. So get as fast as you fucking can. And if you can do that, a lot of this stuff smooths out over time. And I think one of the challenges too is it's so easy to measure running economy. And running economy is still amorphous, but it's like much less amorphous than this concept of fatigue resistance. So I feel like I'm curious to see where the scientific field goes in general with this too. I think it's a lot like the microbiome that we talked on Tuesday, where like 10, 15 years from now, we'll probably have much better ways to quantify fatigue resistance. Yeah. And I mean, it gets back to the genetic discussions that we always have. There are probably hundreds of thousands of SNPs of like genetic parts of the genome that correspond to these variables we're looking at. And who knows what ratio of those applies to an individual? So, you know, as you're thinking about it, don't overcomplicate it. Your goal is still to try to get as fast as possible. But the 10 tips in this article, I think, do really help. The problem is we don't know exactly why they help. And whenever you have an intervention without a mechanism, I'm a little cautious. And that's why I always come back to get faster, get faster, get faster, because we can't be sure on the mechanisms here, but we are a little bit more sure on the mechanisms of actually getting faster. I appreciate you highlighting the thousands of SNPs too. And my brain wants to form this decision tree. And if we put only serotonin and dopamine into that decision tree, and those are just two variables that impact central fatigue resistance of the many, many thousands, there are probably thousands of SNPs that impact both serotonin and dopamine levels in the brain amongst numerous other variables. And so you can see where this decision tree is just spanning out to almost infinity of the amount in which genetics can impact fatigue resistance. Coaching is fun. This article provides an overview of some of the ways we have seen what we perceive as fatigue resistance improve over time in advanced athletes. Now is the time when I back up a dump truck of disclaimers. First, as mentioned, well-rounded training designed to improve speed and endurance matters most of all. Being really freaking fast provides a lot of margin for error. I have rarely seen the metrics we use for fatigue resistance improve exponentially in developed athletes outside of athletes like Adam Mary, but I have seen running economy at aerobic threshold take massive leaps over three to five years. Second, different types of things work for every athlete. Fatigue resistance could be connected to muscle fiber typology or similar variables that also implicate different training approaches. So it's one of many things to consider in a training plan. There are likely so many genetic and environmental factors that we're playing a bit of pin the tail on the donkey with training theory. What I am calling fatigue resistance in this article may be something else entirely, a proxy variable obscuring other training adaptations or genetic predispositions. Third, the science is unsettled. So everything you're about to read is based primarily on anecdotes from athletes we have coached and data. Which gives us insight into trends over time. Clara was a fatigue resistance boss when we met her, so her training might be a bit less instructive. Other athletes have traveled different paths that provide some clues. But as you can imagine, there's a certain amount of truthiness mixed in with this sort of analysis, where our guts are telling us what patterns are most important. Take what you want and leave the rest. Ten tips, trying to give away any special information we might have gathered over time, and all for free. Our business model is just six babies with a toy abacus. I love it. I haven't heard the term. I haven't heard the term truthiness in a long time. Yeah. It's been too long. Blast from the past, right? I also like the abacus reference there. Not sure exactly what part of my brain that came from. So I mean, to really zoom that out a little bit, this is for two plus hours events. This includes road marathons. It includes even road half marathons for some athletes. And essentially all endurance performance. This is us trying to say, okay, this is everything we have seen. And we've been taking these baseline metrics of fatigue resistance over time and then charting it out with different interventions. So this includes so many data points that we've found and data points that end up for athletes that improve from run-walk to being really good, but also athletes that improve from being good to the best in the world. And athletes also that have regressed. We don't want to act like it just is this pure upward trajectory. Do you want to dive into it? Let's start with the first tip one. So tip one says, fully fuel and hydrate most training. Glycogen depletion endurance-induced performance decrease is an element in peripheral rather than central fatigue, but it likely feeds back into how the brain processes efforts over time. Hutchinson interviewed the authors of the cycling study, who said that being low in carbohydrates worsens fatigue resistance, which makes sense. What happens when you're often practicing being low in fatigue resistance based on what I've seen, it only gets worse from there. So practice giving your body and brain the chance to feel and perform better late in runs with full fueling and hydration, including electrolytes. It might make sense to occasionally do long, slow runs or hikes with some depletion, which may provide a training hack for some of these processes, but almost never for female athletes. That last point, almost never for female athletes. Thank you for including that. I feel like of this section, that's the most important takeaway because fasted training for fueling athletes has the potential to just create a bomb amongst all the fatigue resistance systems. Oh, so true. I mean, all of these studies come back to energy availability is key for actual performance in these metrics. And so if we're looking for a direct way to improve it, it's to make sure you have energy availability during, especially in your long efforts. Um, because if you're, if you, you're not, you're just getting better at being depleted and depleted athletes perform worse. There might be slight fatigue hacks that some men, male athletes can do with like ketosis. Um, but that is extremely risky. And even then athletes that excel in ketosis are limiting their max performance. And if the goal is to raise max performance as high as possible, to not have to worry too much about this variable at all, they're selling themselves short. And it's why that even the ketosis athletes, like you're never seeing them have success. You know, the 50 Ks. As much as they possibly could, um, especially when there's hills and you have to raise your heart rate really high. Like you need to make sure that fire is burning super hot. And as we've talked about before in other podcasts too, there's, there's links between prolonged depletion and overtraining and overtraining also takes a bomb to fatigue resistance. Like if you think about perturbations and like thyroid hormones, sex hormones, those have heavy implications for central nervous system fatigue, as well as peripheral fatigue in ways that make it just hard to perform. And so like, that's the ultimate goal is, is like, let's not deplete the body. Let's not have these, you know, these states that may contribute to overtraining syndrome because fatigue resistance becomes almost impossible in those, in those states. Yeah. And there's tons of studies on that. Our favorite is a 2019 review in current opinion in endocrine and metabolic research, um, that you can look at to understand how the endocrine and nervous systems really start to play a role here. Um, but there are theories that go into fueling on every single variable you can imagine, and it gets to how complex some of this stuff can actually be. Actually, can we dive into one of my favorites? And this is how fueling relates to serotonin. And this is something that I've. I mean, I find this like very interesting and I might just be weird. And in fact, I actually, I know I'm weird in this aspect, but can I just share it? Cause I think it's really interesting. It's so sexy to me when you go down rabbit holes, random science, rabbit holes of tryptophan, this is like a Thanksgiving gift of, uh, not sexiness, but tryptophan is essentially a precursor to serotonin and a lot of the, um, what we've derived in terms of fueling mechanisms actually relate to serotonin. So one of the theories is that carbohydrate intake at rest actually increases serotonin, which, um, but via increasing tryptophan. So tryptophan crosses the blood brain barrier when consuming carbohydrates at rest and, um, is known to increase serotonin levels in the brain. Interestingly, it's thought that during exercise, carbohydrate intake actually decreases levels of tryptophan and thus reduces the levels of serotonin in the brain, making an athlete potentially, um, more energized or aroused, which I think is super cool. Yes. Incredibly cool. Like I wonder, I bet there's some evolutionary principles that underscore that. I'm not gonna, I'm not gonna speculate. Um, but it's fascinating when you think about, okay, during exercise, you want to, you know, reduce this, like, essentially serotonin bombs that can come from things like other things as well. Um, and there are probably ways to do that. One is just consuming carbohydrates, plain and simple. That really helps. And another potentially more complicated way, and this is one where the mechanism is known, but we haven't quite seen it transfer to the way of, of exercise physiology studies in the way that, like, it was thought to be so, so exceptional. So BCAAs, branched chain amino acids, there's been a lot of talk about them recently. In the scientific field, you can take them in numerous forms. A lot of them come in supplements. You can take pills, there's all different ways to get BCAAs, but BCAAs actually compete with tryptophan, um, for crossing into the blood brain barrier at that receptor. So the theory is, is that if you take BCAAs, it reduces the level of tryptophan in the brain, thus reducing serotonin and thus increasing, um, you know, energy, energy and arousal. And I think that's fascinating. Interestingly enough, the exercise physiology studies haven't shown that like truly exceptional level. Of BCAAs and the theory is, is that there's probably some like other competing processes that happen, including a much more complicated process involving ammonia, but it's, I mean, I think there's a lot of work to be done on BCAAs and they have very few side effects. So I'm actually kind of pro BCAAs, but again, it's, it hasn't shown that like transformational level and exercise physiology that we would expect based off of the mechanism. Well, I mean, I've seen a really big impact personally in terms of what athletes do and what I do. That's why, um, actually, and, and this isn't something that's just a supplement. I mean, goo, rock. Tame gels have BCAAs in them and it's because, you know, they're harnessing some of this same, uh, aspect and a lot of other gels too, but it's something to look at. So, you know, in addition to carbohydrate and normal fueling and electrolytes, think about BCAAs if it's something that, um, you struggle with a little bit or you haven't had the best experiences over events over two hours long. And what's your framework for taking BCAAs? Are you taking them during exercise, after exercise? Um, and again, there's not, not a lot of evidence to go around with like, what's the best framework, but what have you found works for you? Suppository at every stage. Um, no, just, um, ideally taking something on the recommendations of the nutrition company that you trust. So a good example would be goo. They have very specific recommendations for BCAAs, um, sticking with that or nutritionist recommendations since because it is an amorphous zone, um, I'm assuming that there is a lot of data that underscores those types of, of ideas. Um, and all of this relates back to how cortisol and hormones, um, function. So we haven't really talked about stress hormone cortisol, but that's playing a role in all of this. If cortisol is super duper elevated, con chronically, an athlete's going to struggle with fatigue resistance. They're also going to be tired all the time. They're also going to underperform in life. So think about how fueling impacts those, uh, baseline stress levels. Um, okay. So onto tip two, tip two, increased vert in the six to eight weeks before long events, emerging theories about delayed onset muscle soreness indicate that it's not just what you might think muscle breakdown from eccentric muscle contractions. It might also involve nervous system changes from the same exact stress and whenever I see nervous system implicated in breakdown. Processes, my ears perk up constantly listening for clues, aroused ears to use our word of the day vert makes the legs more resilient, and there may be some weekly understood nervous system impacts as well, which could improve fatigue resistance. That's one reason why we ask athletes to do some vert even before flat ultras. Usually that includes two to five weekends of back-to-back long runs with vert with midweek vert for mountain races. And I, I think this topic is so cool. So, uh, zooming out that 2020 study, I think was, uh, it was one that when I first saw it, uh, it sent like. a shiver down my fucking spine because it was something I had never considered. And the basic theory there is that delayed onset muscle soreness also relates to an acute compression exonopathy. I can't say that word. Oh my God, you're so smart. Of the nerve endings in the muscle spindle. So let's just think about that in a more simplistic way that there's these compressions that cause the nervous system itself to be interpreting something that isn't just muscle breakdown. It's just the nerves being essentially fucked. That's a great exercise sociology term. Yeah, yeah. But the idea being, okay, well, we can train these and maybe that will have, that the nervous system isn't just happening in the brain. It's also happening in these mechanical forces. So train the mechanical forces. We love athletes, especially those that struggle a little bit more with this to really ramp up the vert in the six weeks before events, particularly on weekends. You don't need to do it all week, but a couple back-to-back long runs with vert profiles at the race level or greater usually prepares them to. Avoid some of this, maybe compression exonopathy, that exact word that you just said. What I find curious also too is the relationship between inflammation and delayed onset muscle soreness and central fatigue resistance. So inflammation is actually known to enhance delayed onset muscle soreness. And I'm actually really curious between how those three relate in a triangle, because what I've seen anecdotally, and this makes sense intuitively when you think about the mechanisms, is immune-mediated inflammation or other types of inflammation, actually wreak havoc on central nervous system fatigue resistance. And it's interesting how DOMS is implicated in that process as well, delayed onset muscle soreness. And so I think the three form a fascinating triangle that we'll continue to read more and more about in the literature. I think inflammation is kind of this buzzword, I feel like, of this decade. And there's a lot more research coming out about preventing inflammation, how inflammation is also needed for adaptation and recovery. And so I think just pay attention to that. There'll be a lot more coming out on this topic. It's a menage a trois I can get behind. Do you want to go on tip three? Awesome. So tip three is consider consistent higher rep strength training to fatigue after runs. In the annals of, I don't know why it works, but it seems to, is the mountain legs routine. An incredible athlete and life superstar on the team named Julie has improved more in the fatigue resistance proxy variable than anyone I have seen, with the caveat that we may be measuring something else entirely, all in her late 40s. One of the main things she does differently than others is the one-legged step-ups three to five times per week. Perhaps any type of strength training would work, but we generally, I don't know, don't do it. So I think it's a good idea to do it. Ask our ultra athletes to avoid heavy strength training to failure, except in the off season. And that is unless they are purely slow twitch athletes doing the higher rep strength training after runs, including long runs may stress some of the same variables that play a role in fatigue resistance. And I think this is such an important point. Also, as I was reading this paragraph started with annals and that word, whenever I see it, even like there's a bunch of journals that are like the annals. How do you even, I don't even know actually how you appropriately say that. Am I going to get like hot and flustered? I'm like looking at my Garmin right now, my heart rate's up to one Oh five. I'm like, am I saying that right? It feels wrong. Yeah. It's like a herd of anuses is actually the definition. So there's so many interesting things here. I think one thing to think about is muscle fiber typology. So reference it just in passing there with slow twitch athletes. So slow twitch athletes who much of training theory is formed around because they are often the Olympic champions or, you know, the baseline people that are champions, no matter what they do. Slow twitch athletes respond to strength training in a very different way than athletes that might have more intermediate muscle fibers or fast twitch muscle fibers. So Megan and I, for example, likely more, we have at least some intermediate fibers because we were both athletes that sprinted as kids and other things. We spend our entire life training, trying to get those intermediate fibers to behave more like slow twitch fibers. And that is like a lot of endurance training. So much of endurance training is revolving around this. This is why we do short strides and not long sprints and swap. And, you know, I think that's one of the reasons why it's so important that you use your strength training to then make your intermediate fibers behave like fast twitch fibers. The problem is there are people that have success doing that, but they're almost always going to be slow twitch athletes. And so make sure you're asking yourself that question. Physiologist Alan Cusions, one of my favorite people to follow on Twitter in the world, calls it endurance strength training, that you spend your whole life trying to train these intermediate fibers to behave like slow twitch. Don't ruin it in the weight room. And, you know, I think what we have seen in swap is that, in fact, the weight room might be a huge opportunity to push everything more towards adequate fast twitch. Yeah, I think that's a really good point. I agree. And I think it's a great way to mentally break it up. Let's get back to the article. So the article said, tip five, periodically do steady running on tired legs, like after long run tempos. Connected to the long run tempo point, stressing glycogen recovery after high glycogen depletion stress without actually going over the edge could have some positive impacts on ability to withstand fatigue on race day. Moderate long runs and training races play the same role. Similar principles apply to running on tired legs. So, you know, the quality is much higher, even as we're not going over 20 miles. And then within hard training blocks, you know, John Kelly never went over 25 miles, but he might do 25 miles with 30 to 60 minutes moderate to moderately hard at the start. And you combine those two variables, and he's able to step up at mile 200 and accelerate. And I think that that's kind of what we're trying to find is how can we hack these variables to get the adaptations without having to go excessively long in training, which is going to cause injury or loss of confidence. So the hormonal impacts or impact brain chemicals and other things we don't want to do. And front loading that tempo stimulus really has a strong role in that. So getting back to the article, tip six, consider doubles that can progress to steady effort. Doubles sometimes have a neuromuscular context that approximately makes longer efforts. Add a workout component, revert and tremble, and it may supercharge the adaptations. We have a theory that doubles are connected to this concept of fatigue resistance, that doing doubles might help build fatigue resistance. And you can do that in the context. The nice thing about doubles is they don't necessarily deplete the glycogen well. Athletes are doing them, you know, if athletes are executing them well in terms of getting in good fuel between between workouts. And also, too, they might not have they might not be taking the sledgehammer to like the potential hormonal context, because you don't have to do these massive training stimuli all at once. You can split them up. And it could even improve the hormonal context. In fact, I love the Ingritson and Canova approaches to training, which now forms the basis of how most elite athletes in the track world are going. And almost all of them include some concept of double workouts, even where they're occasionally in a training block, there will be a PM workout in addition to an AM one, both controlled, usually, you know, the tempo style efforts, the threshold style efforts, why those work, we are not exactly sure we do know they work based on the amount of data we have now. And it's something we incorporate often with treadmill uphills or something where the last 15 minutes of a treadmill uphill might be around threshold in the evenings, occasionally, I was gonna say only if an athlete is not stress limited. Yes, if an athlete is stress limited, it it's interesting how you insert those for 123 weeks, and it causes almost rapid implosion. And so it's very dependent upon the athlete. And all of this stuff becomes you're playing at the razor's edge. But we talk about someone like Adam Mary. he has started to incorporate this variable as one of the main changes. And I've seen his fatigue resistance go off the charts relative to what it was before. Maybe that's part of what we're seeing in these doubles, in these double workouts, or maybe not. The hard part becomes, can't really trace the intervention to the outcome because there are 20 interventions going on at once at any given time in any athlete's training, which is why coaching is so fun. It's fun. It's like doing a stew of interventions. And we got stew in one more podcast this week, that word, we're just rolling with it. Tip seven, periodically end longer runs with hard efforts. Often to end a big training week, we'll have athletes put out short bursts of high power, usually through four to eight by 20 to 30 second hill strides. The idea is to stress the neuromuscular system close to maximum, but without it being long enough so that the inefficiency of doing it on a tired body risks creating a more inefficient athlete. So we were talking about this before the podcast. You disagree. I actually strongly disagree. Okay, yeah. So it shows that we're not in perfect alignment. I might have slight bias because, my hamstring injury actually started after doing strides at the end of a long week. I think for me, I think this is grasping at like 0.5% performance improvements, but it comes at like a 20% injury risk because you're doing these faster strides at the end of a training week on a tired body. And so I think for me, it heavily depends on the athlete. I think 95 to 99% of the time, I wouldn't go along with a situation unless there's like a special situation in which an athlete is pretty injury resilient. And we're also looking to grasp that 0.25% 0.25, that 0.5% performance benefit. Do you have any, do you ever do hard efforts at the end of runs? Oh, for sure. At the end of runs. Yeah, just not. So I think strides at the end of long runs. So strides after more than 10 or 12 miles, just come with an injury risk that I think is not, I mean, you could just do strides four miles in and doesn't come with the same injury risk. And I think, I think you're really grasping at performance straws there. So to me, it just, I heavily weigh that situation, but tend to not do it. Maybe a good compromise that we both use is sometimes ending the last climb of your run a little harder. Um, it's very, it almost mirrors the test that we use for fatigue resistance and anything that you're using for tests likely stimulates that thing you're testing for. So, uh, that's a good, good compromise here, um, is, you know, much like we would do at Walker ranch, you know, the last time you can start to put on the gas a little on these long runs. And if you do that, uh, maybe you'll be hitting this note directly. And I actually do that often. And what I like about that is because you're not putting on the gas for 20 or 30 seconds, the build and the acceleration, build into it is much more controlled and much more gradual. And so you don't have that same injury risk that you necessarily have. If you're putting out like 20 to 30% burst of high power at the end of 15, 16, 20 miles. But caveat, we actually, we really do deemphasize that we do not do fast finish long runs as a specific focus too often because we want athletes to be performing at their peak. Like the reason that the long run tempos happen near the start of runs is because that's when athletes are freshest and put out the most power and the goal is to improve running economy as much as possible. So this becomes something that happens more closer, the races, or as an athlete is really focusing on specific adaptations where we've gotten the running economy high already. And we're just saying, okay, now we're preparing the brain for this weird event that you're about to go under. And specifically before a races as well. So I think there's a lot of like nuances and to, as to when I give this fast finish, long runs. Awesome. Um, so another little nuance, one tippy avoid excessively hard efforts or recruitment of fast twitch muscle fibers in two weeks before events, muscle fiber typology is largely genetic with most endurance, having some slow Twitch and some faster Twitch fibers, the pure, slow Twitch athletes might not need to have too many concerns with this variable. But if you may be faster Twitch, we have seen athletes Excel removing most intensity above lactate threshold in the last few weeks, with the exception of some short Hill strides and avoid going too hard on workouts throughout a training build. And let's that's unless that's the goal of a session. I appreciate that you worked this point in here. It's I think in medicine, it's curious because they're really heading into this world of personalized medicine. And I feel like an exercise physiology, there's actually similar corollaries where like we're heading into the world of personalized exercise. Physiology. And I think a big component of that, and that's how we try to coach. And we're just kind of guessing at these variables. But over time, as we start to measure these things easier in athletes, I think part of that personalization will be dividing athletes into like muscle fiber tip hot typology and really developing exercise interventions that are, that are different across typology. And there's a lot of different ways. We actually, in our book, we talk about a way to estimate this much like the fatigue resistance model that you could check out. If you haven't there's a lot of interesting things on here. Basically it doesn't hurt before at events over two hours, make sure you stay relative. We fast with things like strides and health strides being your friend, but you can take out intense variables over one hour effort due to the risk of the recruitment of the wrong muscle fibers that you were not going to need. And that will not respond well after a substantial amount of work. Let's go back to the article. The tip is tip nine, consider one or two longer ultra efforts or training races, but don't overdo it. Now we are getting to the two most important variables. There's a lot of disagreement here. So remember this is one of the many approaches that can work. The first time athletes step up to an entirely new distance, it usually ends with a long fatigue cycle. After I see this most often with professional runners at the Western States, 100 who earned their entry from golden tickets given to winners of shorter races, whether the 100 goes awesomely or horribly, it's usually a month or two or longer of waiting through fatigue and lethargy. And I actually, I think this is a point that's not talked about enough in the world of ultra running is what happens to the body after that first harder, longer effort. And I think there is a corollary here actually with someone who steps up and does their first hard, fast road marathon too, is like, what are this fatigue? Fatigue cycles. The body is going through, we see it after Western States, 100. I've seen it too off after Leadville, 100. I think there's something about that high altitude, hard 100 mile race that for athletes doing a 100 mile for the first time, their body is like cellularly like what the freak just happened. Like, I mean, and that's, it's, and it's, I almost see it consistently across athletes. Yeah. And I think that question is fascinating. What happens to the body, but what we're getting at in, in, in coaching is what happens to the brain that we've, what we've been saying is what happens to the body is probably the nervous system thing or both. Yeah. Yeah. And how they interact and, you know, how the nervous system can actually adapt over many training cycles. And that gets back to how you train for these long events. And so back to the article. That fatigue is present long after the musculoskeletal system heals and hormones stabilize. You usually can't spot it in blood work at all. So what is it? Because longer term fatigue and adaptation cycles likely have the root, at least partially in the nervous system. Well, we can't measure exactly what's happening. What's coolest of all is what happens. Next. The athlete might go back to Western States in the next year after top 10 finish accepting more of the same fatigue post-race and they'll be fine. A few weeks later, they might even be setting PRS and local segments. That story isn't ubiquitous, but clearly there are some long-term adaptation cycles going on that could involve the nervous system and thus could have an impact on fatigue resistance. If you're stepping up in distance to 100 milers training races and or two to four 30 plus mile long runs are especially important to get some of those adaptations before the start line for experienced athletes though, it might be less, I think a question every ultra athlete needs to ask themselves is this, what added patients actually happened at mile 40 of a long training run. Maybe the answer lies in the nervous system, but most evidence indicates those adaptations are longer term and come with risk of fatigue cycles and injuries aerobically and musculoskeletal musculoskeletal. There could be some endurance benefit, particularly for resilience, but most of those adaptations come from normal training to particularly harder efforts of a few hours on top of solid weekly mileage. Add in the ultimate risk. Even if an athlete, avoids injury doing super long runs, completing them often requires going pretty slow and speed still matters. Most of all for our athletes first time, 100 mile races racers usually do a 50 mile or 100 K plus a 50 K and a few back-to-backs experienced racers sometimes do a long training race, but some never go beyond 50 K focusing instead on being the fastest they can be. As long as they can remain confident without epic long runs, they usually find that stepping into the unknown is way better with health and speed at the forefront. So this is much more controversial than it might seem when it's just us presenting, uh, the, the data here. Um, once we, so the first time an athlete steps up, it's extremely difficult on the body. And I think that almost happens no matter what drew Holman being an example of that, you know, he didn't race for six months after Western states this year, and it was because he couldn't. Um, but the next time drew does this, like I've been trying to tell him like, you're going to be fine. Um, and why is that most likely something is happening with the nervous system. So the big takeaway here is if you were training for ultras, do not emphasize doing tons of very long runs, like that is not going to get you the, uh, you know, the adaptations you need for your speed. It's probably also not going to get the adaptations you need for the nervous system, because that's not one of those moments where you kind of just have to put your hand in the fire and afterwards you come out resistant to fire, but you need to make it happen once for that, to, for that to happen at all. And you also need to believe in that process too. So I've seen so many athletes have put their hand in the fire and they'll be like, I'm on fire. I never want to do this again. This was terrible, but. I that's where like our role as a coach comes in and we're like, we're promised the next time we'll be better. Let me not promise, but like it's highly likely the next time we'll be better. And the next time after that will be better and better and better from there. And, um, but the, the first taste of fire is tough. Yeah. But you know, in to make this extremely, like the reason ultra running can be so inclusive and marathon running at the top level is that you don't need to simulate the race too often to be ready for it. Like for a hundred mile or 50 K is all you need to do for, for a lot of athletes. You're, it's going to be tough. Um, but you can get through it and you can excel at the very, very top level of the sport. Um, this emphasis on going very long and often very slow, I think causes athletes to regress over multiple year cycles in a way that focusing on being fast and limiting your long run distance. And often through these like tempo principles and things can actually cause humongous breakthroughs. The hard part is you might face a little bit more uncertainty that first time out. So I think you have to be kind of comfortable with that uncertainty to avoid making your body just go into a shit stew. So this, This next tip, I think, might be the most important at all and gets into the really world of how fatigue resistance interacts with fitness development over time. And that's tip 10, which is do not overtrain. Whatever causes fatigue resistance differentiation, it's clear that the nervous system plays a role. When you step into the unknown on race day, a flickering nervous system bulb will never be able to light the course on fire. Chronic training stress, like weekly miles, matters some, and it's key to maximize stress totals and pulses during an ultra training block. But tracking tons of successful ultras over time, there doesn't seem to be much correlation between sustained weekly miles and performance, as long as an athlete is being consistent and not at a strikingly low volume based on their background, parentheses, and has some of those bigger pulses, like training camps, races, and or 7 to 10 day overload cycles. That's likely related to the same nervous system points as in tip 9. I'd argue that way more miles are needed for a peak potential road marathon, where it's actually possible to train the exact stresses you'll see on race day. Meanwhile, long ultras are stepping into the unknown in a unique way. Try to train the best you can, and if you can do it right, you'll see the best you can do in the future. And even if an athlete survives that for a few cycles, it's playing with physiological fire and could impede speed development. I think there's lots of interesting things here. I mean, just for a quick flash into what an athlete can do, Scotty Hawker was on the podium at UTMB off of 40 miles per week. You know, he came back to CCC the next year and was second at CCC, one of the most competitive races in the world, again at 40-ish miles per week. And the point being, he understood his body. He understood his body. And he understood his body. Yes, it would be great if he could do 100 miles a week. But for him, that caused this fatigue resistance principle to actually get worse because it led to that flickering bulb. And so pay attention to your body. That's where feeling good comes in as a proxy for what you're actually adapting to and what is good for your physiology. And I think that's where also understanding the context of your body in terms of life stress matters a lot too. So oftentimes I see athletes that are carrying high life stress just have to be lower mileage by definition. And that often works for them. And I think that's where you're going to often work for them and it's successful. And so that's also something that we consider in this equation as well. Yeah. So as you're adding volume, it's great, but keep it really aerobic at first. Make sure you're responding well. If you feel super fatigued for more than a week or two at a time, that's not a great thing. And especially for ultra performance, I think in road marathons or even road 10Ks, there can be more benefit to that than there might be in these super long races where we're worried about fatigue resistance, which means you need that nervous system turned up to 11. 10 won't cut it. You need it all the way up. One of my favorite things in life is turning things past 10. It gives me such like, I don't know. There's something about it and I'm like, I'm all for it, but let's get back to the article. Putting it another way, it's still good to feel good. Like with tip one on glycogen depletion, you probably have grown a castaway beard by now. There's likely some feedback between how you feel for a majority of training and how your body adapts to chronic stress loads. Spend too much time training in the physiological ditch and you might just become the ditch dwelling version of yourself over time. Every athlete is different though. Maybe a special talent of some of the outliers is being able to adapt under immense chronic training stress. Most of us though are not outliers, no matter what my mom says. So run plenty, but stay in touch with your speed and don't overdo it. Take your rest days, taper with confidence, always eat enough, balance life stress and training stress. Try to get to bed early, but don't sweat it when you don't. And most of all, give yourself lots of love. At mile 80, you are no longer running on lactate threshold or VO2 max. You're running on something else. We're not 100% sure what that something else is, but I am 100% sure. That love can't hurt. That's a beautiful way to end this article, man. A little bit of a love mic drop, right? A little bit of a love train. I'm all about love trains. That's exactly the thesis of this podcast. Actually, the joke there about my mom is really relevant because I went to our podcast today and there's a new review and it's from my mom, Roach Woman. I don't know if she knew that her name- Oh my gosh, that's amazing. But the best part of all is that in her review, she's like, I had to get used to them talking pretty fast at first. Did she say that? Yeah. That's hilarious. She nagged us in her house, but it was five stars. So thank you, mom. And hey, anyone else? Give this five stars if you like it. But yeah, I mean, I think that this really gets into the nuances of adaptation. So as we're talking about performance in a long race, what we really care about is not the performance in this immediate long race, six weeks or 12 weeks from now. It's what about the one three years from now? And once we start thinking about multiple cycles, we really need that nervous system tuned up because the same thing we're seeing at mile 80 of a race likely is going to influence how the body actually adapts to the training it's doing. That's the wild thing about the nervous system. It's not just determining output. It's determining then how things at the cellular level actually adapt. And so fatigue itself is something in an acute way that can be fine, but in a chronic way, probably sends you into that ditch. And even if the ditch leads to one good race, it's not going to lead to too many good races. I agree 100%. I love the idea that the nervous system is just intimately connected to everything. Like how cool is that? Cool and scary. And I think that's one of the reasons that like gifting yourself that love, gifting yourself like the approach of being cautious with training, of not overdoing it is so important because the nervous system is connected to so many different things. And maybe that's the final takeaway here is that it's connected to so many different things, which gives you so much opportunity to improve. One of the coolest things in coaching is we have seen athletes fundamentally alter their profiles over time. So no matter what that starting point is, and even if that fatigue resistance starts at the very low end, which there are definitely people listening just based on statistics that are, it can improve everything. It can improve a ton. So where you are right now, it might be a nonlinear trajectory to the amazing places you can go. So have hope for what's beyond the horizon, have belief. If you're able to invest that over time, using some of these principles, then also listening to your body and your coach, wherever that is, who knows what you're capable of. We have been fortunate to see athletes go from thinking that they could never race these long distance races to being absolutely fantastic and crushing their wildest dreams. So your wildest dreams are out there, but you got to give yourself a chance. You got to believe and you got to do it over a bunch of years. And one, one other important takeaway is if you are at this point of the podcast, congratulations, because you have podcast fatigue resistance, you are doing it. This is a good proxy for your endurance fatigue resistance. And we are excited about that. We are barely, I mean, we're like talking over here, like, oh my gosh, it's hard to speak at this point. We are building our podcast. It's a lot of science. A lot, a lot of sexy science though, to be fair. There are so many anals of science, just a herd of anuses of science lined up. So we absolutely subscribe, rate, review, if you can, like this is a labor of love and it really means a lot if you let other people know about this podcast, because you know, that is what has helped it really grow exponentially in the last few months. So thank you for that. We appreciate you all so much. We love you.