Nerd Lab: Geeking Out on Dr. Paul Laursen’s HIIT Research

We cover some of the seminal research from Dr. Laursen on high-intensity interval training and dehydration. 

Female training cyclists

You may not recognize all of the names, but throughout the last 100 years since exercise science became a science, there have been key researchers and coaches who have been critical to what we think of as the modern approach to endurance sport training.  

A few, such as Izumi Tabata, were lucky enough to have a popular interval workout or training method named after them. But whether you’re doing 5 x 5-minute intervals or taking a block periodization approach to your season, there was a researcher who proved the benefits, so in this Nerd Lab episode we’re going to focus on one of those key researchers—Dr. Paul Laursen—and talk about a few of his seminal studies.  

Dr. Laursen has been a researcher for over two decades and literally wrote the book on high intensity interval training. Some of his reviews are required reading in exercise science programs and in this show we talk about two of those. The first, The Scientific Basis for High Intensity Interval Training, published in 2002, summarized the existing science on interval work. It then went a step further trying to explain the gains and detail the best approach to high-intensity work with recommendations that still stand today. 

RELATED: Fast Talk Podcast 261: Diving Deep into the Pain Cave 

A second 2010 review titled Training for Intense Exercise Performance: High-Intensity or High-Volume Training? addressed the fact that while there was little scientific evidence for low-intensity training, elite athletes still do a lot of it. The review then goes on to detail how both high- and low-intensity training activate the critical PGC-1α pathway and it’s the combination that produces the best gains.  

Finally, we talk about a 2013 study titled Current Hydration Guidelines Are Erroneous: Dehydration Does Not Impair Exercise Performance in Heat, a study that shows how research can bring into question what was considered resolved science.  

RELATED: Fast Talk Podcast 221: Addressing Sweat and Electrolyte Loss with Dr. Robert Kenefick 

So, look up your favorite high-intensity intervals—Dr. Laursen probably researched them—and let’s make you fast! 

Key Takeaways

  • High-intensity interval training (HIIT) trains both the oxidative and glycolytic pathways, making it a highly efficient form of training. Multiple studies indicate that doing high-intensity intervals can improve fat oxidation, lower the respiratory exchange ratio (RER) during exercise, and preserve the substrate or glycogen in your muscles. HIIT is not just about cramming as much sugar as possible and running through glycolytic processes as fast as possible. Even VO2 max efforts or sprint interval training can improve power at lactate threshold and other more durable measures of performance.
  • The rest interval is critical, as it allows the anaerobic system to recharge, ATP stores to be rebuilt, and the anaerobic energy system to be hit hard. However, if done incorrectly, as in the case of Tabata, the anaerobic energy stores can be depleted quickly, and the workout becomes mostly aerobic. Depending on the goal of your workout, this may actually be beneficial.
  • Higher volumes of exercise training are likely to signal adaptations through calcium calmodulin kinase, while higher intensity of endurance training, which lowers ATP concentration and raises AMP levels, appears more likely to signal for mitochondrial biogenesis through the AMPK pathway.
  • The pathway used by high intensity has a rapid response but seems to plateau, while the pathway used by long, slow endurance training is much slower in its adaptations but does not plateau as much and produces continuing gains over time. The right mix of the two is the ultimate explanation for the polarized approach to training. If you only do long, slow, you will miss out on gains, and if you only do high intensity, you will miss out on gains. The combination of the two produces a much more significant effect.
  • It is not that athletes who drink during exercise are getting dehydrated, which hurts performance. Instead, drinking has a stimulus that allows them to go harder. Research studies that do not blind athletes to the rehydration status may be studying a placebo effect more than a physiological one.

Episode Transcript

Rob Pickels  00:05

Today we’re discussing Dr. Paul Laursen has whose research spans two decades and who’s literally written the book on high intensity interval training. Today we’re covering three of his papers. The first titled, “The scientific basis for high-intensity interval training”, was published in 2002 and after 20 years it’s detailed best approaches for high-intensity training are still relevant today. A second 2010 review titled “Training for intense exercise performance: high-intensity or high-volume training?” details how high and low intensity training can both lead to improvements aerobic performance. Finally, we’ll talk about a 2013 study titled “Current hydration guidelines are erroneous: Dehydration does not impair exercise performance in heat” – a study that highlights the complexity of physiological research and how nuance can have a meaningful impact to our knowledge and best practices. So, get ready to dive into the science of Dr. Laursen, and let’s make you fast.   Hello and welcome to Fast Talk, your source for the science of endurance performance! I’m your host Rob Pickels and I’m here with Coach Connor.  There have been key researchers who have been critical to our understanding of endurance sports science. And, while we’ll never be able to cover everyone who has had a lasting impact, Trevor and I have decided that we want to focus on some key researchers with a variation on our “Nerd Lab” style episodes.  These “Seminal Study” episodes will focus on one researcher; highlighting their contributions that made a lasting impact in sport science knowledge.  Hey listeners, it’s Rob Pickels, co-host of Fast Talk. We have some exciting news to share—Fast Talk is now on Patreon! Patreon is a social platform that helps us to keep creating the Fast Talk podcasts you know and love. As a Fast Talk supporter, you can help us stay independent—just log on to and search Fast Talk Podcast. Personally, I’ve really loved creating Fast Talk. Being able to share a little bit of myself with you every week has been a lot of fun and happy that I’m able to give back to a community that means so much to me. I’m inspired every day by your emails, comments, and feedback and I’m constantly looking for ways to improve the podcast experience for our listeners. Honestly, we couldn’t do any of this without all of you. So, thank you for your support, and thanks for listening.


Trevor Connor  02:35

Well, hello, welcome to Fast Talk. It’s actually getting a little unusual, Rob. It’s just you and me in the studio today.


Rob Pickels  02:44

I think it’s unusual because it’s a Wednesday and it’s not snowing outside right now, Trevor.


Trevor Connor  02:48

Yeah, but that’s been kind of the routine here hasn’t it been? Snowstorm every Wednesday.


Rob Pickels  02:52

It has been it’s incredible. Hey, you know, do you ever feel, Trevor when we’re putting together more of these Nerd Lab episodes that you feel like you’re cramming for a midterm?


Trevor Connor  03:02

I feel like that for every single episode.


Rob Pickels  03:04

Well, I don’t feel like that for every single episode, but good lord, getting ready for this one, I was knee deep in research. And each paper that I read—we’re talking about three papers today—I kept looking at other papers to backup my thoughts and it was like 100 papers deep. I think I did my own meta analysis to get ready for this episode.


Trevor Connor  03:25

Yeah.  I hope I get an A. I’ll let you know at the end. I might be giving you a B+.


Rob Pickels  03:31

We’ll see, B+ I’m happy with actually tell you the truth. A solid B student. I’m okay with that.


Trevor Connor  03:36

There we go. My nephew used to intern, help us out with the show a little bit, and he asked me about the preparations for the show. And he’s like, “So what’s your secret to that?” And I just looked and him and went, “Remember when you were in college, when you had to research for an exam or research for a paper and then write the paper? He’s like, “Yeah, that was really hard.” I’m like, “That’s every episode.”


Rob Pickels  03:55

That’s our life. Yep. Don’t podcast people, leave it to the pros.


Trevor Connor  04:00

Leave it to the people who don’t mind spending a Friday night reading research. There you go. That’s what it comes down to.


Rob Pickels  04:06

There you go. What’s this research we’re covering today, Trevor?


Trevor Connor  04:08

So this is a new type of episode, we do these Nerd Labs where we talk about some recent research. But Rob, you have this great idea of we should be talking about some of the big names in exercise science research. And there’s one that we keep referencing on show after show after show that we felt, let’s talk about some of the seminal research that this person’s done, and this is Dr. Paul Larsen. And give a little bit of background Dr. Larsen. He doesn’t put out a ton of information about his history out on the—goodness I was about to use the term worldwideweb back in the 90s.


Rob Pickels  04:42

How about interwebs? I think that’s what the cool kids say today.


Trevor Connor  04:47

So we were looking up Dr. Larsen because some of my favorite reviews, some of my favorite research is from him and discovered some interesting things about him. I believe he is Canadian. So he did his schooling in British Columbia—that’s where I did some of my work—he actually was a researcher and still a researcher at the Auckland University of Technology. So at some point he went over to, I know he’s worked with Australia, New Zealand, and done a lot of his research over there. But he’s now actually moving into being a bit of a businessman. He has a company called Athletica that’s doing AI training software. He’s also co founder and CEO of what’s called HIIT Science. And he, on top of all his research, wrote a fantastic book that if you are looking for the full science, the full explanation of high intensity interval work, that is the book. So we’re actually going to talk about one of his reviews today that cover that, but this is a book that kind of, is that review on steroids.


Rob Pickels  05:53

Yeah, Dr. Larsen is without question, the real deal. I’m super excited that we’re talking about him today. Maybe not him, we’re talking about the work that he has done. And what is a little bit different about this episode is that we’re actually kicking it old school, because we’re talking about some research from the early 2000s. You know, we might have some updates that have occurred in the last 20 years, but this is some of the more seminal things, at least I think in Trevor and I’s life, in terms of understanding. But before we dive into that research, I want to share one quick anecdote that that’s pretty funny. You know, a few years ago, TrainingPeaks put on the Endurance Sports Coaching symposium or something like that, right? It was at CU Sports Medicine, where I was a physiologist at the time. And as part of that symposium, everyone could come down to my lab and get an education in lactate testing, and exercise prescription and everything else. And so I’m in this room with a dozen people. And you know of course you get questions, and life is grand and answering questions is fun, but I started getting question after question from this one individual, and they got deeper and more complex every time it was asked. And in my head, I’m going, “Who is this guy? He knows exactly what he is talking about.” And I was sweating at times, I hope that I answered his questions sufficiently. And after he walked up, shook my hand and said, “Hey, I’m Paul Larsen. Nice to meet you.” And I was like, “Oh, now I get it.” So that’s my one run in with Dr. Larsen, but hopefully we can get him on the show, Trevor, and we’ll be talking with him, maybe about some new research?


Trevor Connor  07:40

That’d be absolutely fascinating. And it was really interesting, looking at what his most recent research is, because a lot of what I’ve read and keep going back to is some of his older stuff. But he’s been actually still—this is what’s fascinating to me—he is just known as the high intensity interval guy. He wrote the book on it, literally. And all of his research has been on low carbohydrate, high fat diets. And he seems to be a bit of a proponent, particularly from a health perspective.


Rob Pickels  08:07

It’s interesting to rectify those two things together, right?


Trevor Connor  08:10

Because and you’ve hopefully already heard our episode on carbohydrates with Dr. Jeukendrup. And we talked about in that episode, it’s pretty definitive science, that to be able to do that really high intensity work, you need glucose, you need those carbohydrates. So Rob, we have two reviews on a study from Dr. Larsen. What’s our first one?

“The scientific basis for high intensity interval training” Review

Rob Pickels  08:31

Well, the first one that we’re going to do is all the way back to 2002. And it’s titled, “The scientific basis for high intensity interval training.” Some people might call this review, I would call it a knowledge drop to tell you the truth. If I remember right, 170 references. But what was really interesting and why this is an important article is that he really tried to fill in the blanks between what is just typically a meta analysis— explaining the research that’s out there—but also trying to close some of those loops or proposed things for the future. It read in such an informative manner that I think everyone needs to read this paper at some point in their life.


Trevor Connor  09:14

What was really interesting for me is I mean, I read this back when it came out. And this was just this review was a big deal, because finally somebody had kind of collected all this information on interval work.; what does work, what doesn’t work, giving recommendations on how to do interval work. And as I’m going through that, I’m like, “Yeah, whether it was from this review or people were reading the same research, this is really, when you think of the last 20 years and what we focused on an interval work, it’s all kind of in here. So at the time, it was just huge. You know, here it is, here’s the paper talking about high intensity interval work. What I found really interesting reading it—and this is 21 year old paper—you do start to see some of the age in it. It’s not to take anything away from it, it was a fantastic review at the time. But you do certainly see a little bit of that age. One of my favorite parts is he talks in the beginning about how a lot more of the research has been done on running because you can control pace, and you don’t really have anything that’s controllable in cycling. And you’re sitting there going, “Power?”


Rob Pickels  10:21

Yeah, I got a power meter on every part of my bike right now.


Trevor Connor  10:23

Right, but 2002, it was a lot less common.


Rob Pickels  10:27

I was a sophomore in college.


Trevor Connor  10:29

Yeah, I’m trying to think of where I was in 2002. I actually have to think about that for a minute.


Rob Pickels  10:35

I know, I know, it’s incredible to think back. And it doesn’t feel like this research know—I know that you’re mentioning some of it is dated—it feels like it was a long time ago that I was a sophomore in college. But this still feels very relevant and very important to me today. Hey Trevor, can I ruffle your feathers for a second? How do you feel about this? Increase training volume does not cause further improvement in highly trained athletes.


Trevor Connor  11:03

So Rob actually picked the three studies from Dr. Larsen that we’re going to talk about. And what I really like is when we get into the next one—which is one of my all time favorite reviews, I’ve probably mentioned that 30 times on the show— is another review from Dr. Larsen in 2010. And we’re going to do a little bit of contrast between these two because he makes statements in this 2002 paper that you see kind of an evolution of his thinking by the 2010 review, and some changes. So in this one, he says pretty definitively, as you said, that when you’re talking about elite athletes, doing low intensity work doesn’t provide any more gains.


Rob Pickels  11:43

But I didn’t read it that way. I read it as elite athletes doing more low intensity work doesn’t improve their gains. And one of the studies that he references, and I actually I saw this one kicking around Twitter the other day which is just fortuitous. It was a study by Costal that looked at swimmers. And essentially for one group of swimmers, they doubled their training program by having them do two a days. So their volume literally increased twofold. And they saw little to no improvement in any physiological markers. And if anything, the athletes just got really frickin tired and they struggled to do the training in general. And I wonder at what point does that kick in, right? Because in this study, or in this review, Dr. Larsen clearly says, “Hey, if you’re an untrained or recreational train person, increasing your low intensity volume, totally worthwhile. But if you’re a highly trained athlete, and it was defined as someone with a VO2 max greater than 60 milliliters per kilogram, that increase low intensity time probably isn’t doing anything for you.” And yeah, let’s put that into a practical perspective. If you’re doing two hours a week of training, and you go to 10 hours a week, you’re going to get better. If you go to 10 hours a week, but you increase to 15 hours a week, are you going to get better? Probably. But if you’re at 15 hours a week, can you go to 20 hours a week? Are you going to see major improvements? I don’t know.


Trevor Connor  13:17

See, that’s the difference between the two reviews, I agree with you. And he I think he says it a little more eloquently in the 2010 review, which is if all you do is low intensity work, you’re gonna miss out on potential gains. But he also states in that review that if all you do is high intensity, you’re gonna miss out on gains. And really, it’s the balance between the two. But in that 2010 review, he first cites some of the similar research that he cites on this 2002 saying, we don’t really see any gains from adding volume to high level athletes. But for some reason, all the high level athletes do it anyway. And by the way, this 2002 review, there were multiple authors; It was Dr. Larsen and Dr. David Jenkins. 2010 was just Dr. Larsen.


Rob Pickels  14:07

And the title, because we’re talking about it now, the title for that 2010 review is “Training for intense exercise performance: high-intensity or high volume training?”


Trevor Connor  14:17

And what he gets into is, A, the limitations of the research that is much harder to study; the high volume, low intensity, because it takes often months to years to see the gains from that. And it’s also when you’re dealing with the lab, it’s very easy to get somebody to come in and do 30 minutes of intervals. It’s much harder to get somebody to come in and do a bunch of six hour rides in the lab. So it’s just hard to control. So basically, he admits there might be gains that we just can’t see because the research just is having a harder time addressing this.


Rob Pickels  14:49

Yeah and I think that that’s a similar sentiment that’s shared by other researchers. Dr. Larsen heavily references Dr. Seiler throughout these papers and we’re obviously seeing that.


Trevor Connor  14:59

Well in 2010.


Rob Pickels  15:01

In 2002 it wasn’t quite, you know, Seilier time yet at that point


Trevor Connor  15:05

Dr. Seiler first introduced the polarized training model in 2006. And yes, I agree that 2010, the underlying message of it is polarized training and seems to fit with the science.


Rob Pickels  15:16

Yeah and Dr. Seiler recognizes there an optimized training intensity distribution, if I remember right. That there’s long-term athlete development here that takes a decade, right? Before we’re seeing major improvements or people reaching high levels of fitness. And that’s where it becomes interesting to compare the high-intensity versus the low-intensity adaptations. Universally, I think everyone agrees that there are relatively rapid improvements from high intensity-training without question. But based on Dr. Seiler’s work, we know that a high percent of time spent at low-intensity training is essential. It’s critical to high-level endurance performance.

Central Adaptations Versus Peripheral Adaptations

Trevor Connor  16:04

And I think we should dive a little more into the 2002 review, but when we get to the 2010 review, Dr. Larsen actually gives some of the physiological explanation behind it. In the 2002 review, you see him really talking about central adaptations versus peripheral adaptations. And that was pretty dominant in the science and the idea, when you’re particularly going back to maybe 80s, 90s, there was this notion that you have central adaptations, which is basically your heart’s ability to deliver blood. So that’s what we’re talking about stroke volume, cardiac output. And then peripheral adaptations are the muscles ability to take in that oxygen and use it for energy. So it’s what’s going on at the at the muscle level. And there, there used to be a bit more of a belief that that long, slow volume that you do, that trains your central adaptations, that’s training your stroke volume, and it’s the high intensity that trains the peripheral side. So that was the explanation behind why you need both. But as we’ll see, when we get into 2010 review, we’ve learned more about how the the physiology works, that kind of got thrown out, because he even has in the 2010 review this great diagram with PGC-1alpha at the center…my favorite term. And showing that actually both high-intensity and low-intensity hit that same pathway. So it’s not one trains central, one trains peripheral, it seems to be they both hit the same pathway, and then that produces adaptations at both levels. So a lot of this old central versus peripheral got thrown out.


Rob Pickels  17:40

You know in this 2002, obviously the title “Scientific basis for high intensity interval training,” it’s focused on high intensity intervals without question. The thing that I found really interesting, and I think that this is applicable, is there’s the continued mentioned that high intensity interval training trains both oxidative and glycolytic pathways, and that because of that, it’s a highly efficient form of training. And I do want to emphasize this because there are multiple studies that indicate doing high intensity intervals improves things like fat oxidation, lowering your RFQ during exercise, preserving the substrate the or glycogen in your muscles. Doing high intensity is not all about cramming as much sugar as possible in running through glycolytic processes as fast as possible. It’s not just about your finishing sprint, that high intensity, even vo two Max efforts, even sprint interval training has the ability to improve the power at lactate threshold, these other more durable measures of performance.


Trevor Connor  18:56

So the final part of this 2002 review, he talks about what’s the best prescriptions for interval type work and talks about the different types and the sort of benefits they’ve seen from them. And you really saw the makings of what’s become some of the standard ways of doing high intensity work. Coming out of this review was sort of his thought experiments which made a lot of sense, where he talked about the importance of, you know, back before this review, if you go back to the training in the the 80s and 90s you saw a lot more of that just steady threshold work. It hadn’t been too long since Tabata had introduced the Tabata type intervals which is that really high intensity; the traditional Tabata is a really high intensity for 20 seconds, then a 10 second rest, then 20 seconds, then 10 seconds. He also talked a lot in this review about 30 30s, which is 30 seconds, 30 minutes would be really tough. 30 seconds at most of the studies he was looking at we’re running. So he’s talking about at your VO2 max pace, then 30 seconds easy, then 30 seconds of your VO2 max pace. But what I found really interesting is he said that that rest interval is really important. Because if you have that long rest, you recharge that anaerobic system, your ATP stores can be rebuilt, and you’re really just hitting your anaerobic energy system. But he flipped it around and actually said, one of the issues with something like that Tabatas is very quickly, you deplete the anaerobic energy stores. And you’re actually most—even though you’re trying to do this high intensity work—you’re mostly aerobic. And so he was talking about that great balance where you hit both the high intensity, but the recoveries are short enough that you have to start bringing in some aerobic energy, and he was talking about some of the best high intensity intervals are going to both hit that anaerobic and the aerobic systems. And that’s, I think, why he quite frequently went back to the 30 30s. And I can’t help the point out, but your mentor, who we’ve had on the show many times, Neil Henderson, he loves 30 30s.


Rob Pickels  21:02

Yeah. And revolver was a workout written by him that people are probably quite familiar with if they’ve ever done Sufferfestt, or I guess it’s Wahoo System at this point. Yeah, I’ve been doing that workout for years and years and years before it was ever a publicly shared workout, and it hits you hard, certainly.


Trevor Connor  21:21

Yeah. So it was really interesting to hear that expressed in his review. And like you said, it was kind of a knowledge dump. It wasn’t just reviewing studies and saying, “Here’s what they showed,” it was him. And it was also very interesting to see in 2002,  how little research on interval work had actually been done. I think the person who had really been hitting it hard was Dr. Belay, if I’m pronouncing that correctly,


Rob Pickels  21:45

Veroniqueblah, yeah.


Trevor Connor  21:47

You know, you had to kind of make a lot of logical leaps here, because a ton of the research hadn’t been done yet. But you really saw him kind of thinking through, “Here’s what would make the most effective intervals.” And I still know a lot of top-level coaches that are really doing what you see at the end of the study.

Buffering Capacity

Rob Pickels  22:04

Yeah. One of the bigger takeaways for me, Trevor, from this research was that Dr. Larsen really made the point that, at least at this point in time, there was not a lot of research on high-level athletes—the ones that have VO2 max greater than 60, as defined in here—in that the research or the recommendations created for everyone else, for the recreational for the non athlete, they don’t necessarily apply to the highly trained athlete, because they’ve already achieved a lot of the adaptations. And that there’s some factors are not ready to change. I’ll say, in very layman’s terms, some factors are not ready to change within their body. And by going off the recommendations typically given to people this high intensity or this high performance athlete, I should say, the high performance athlete isn’t able to see the gains, like we would expect for a less fit athlete.


Trevor Connor  23:02

Agreed. And to your point about the lack of research., at one point, he goes specifically to look at cycling studies when there was only one. And it’s a great study where they took five very divergent types of interval workouts. I think it was like super long thresholds, they had four-minute intervals, the more that VO2 max intervals, the other 30 30s, I think they had a sprint and then one other. And you’re kind of left scratching your head from the study, because they showed the two that were the most effective and had produced very similar gains were the 30 30s and the four minutes. And they look at and go, “Those are pretty divergent intervals. How are they doing the same thing?” But yeah, you’re getting to what I found really interesting about this review, which is he spends a lot of time trying to say, we see that high intensity interval work produces gains in elite athletes, but how? What is it changed? And he goes through physiological system after physiological system and keeps going, “Don’t really see anything.”


Rob Pickels  24:06

Yeah, exactly. Or a couple where he’s like, “Maybe it’s this, but we don’t know.” There needs to be more research. I thought it was interesting how he focused on increased buffering capacity.


Trevor Connor  24:19

I’m glad that you bring that up. That’s really the one where he’s like, “There’s something here.”


Rob Pickels  24:23

And for me, it’s like, oh, increase buffering capacity. Yeah, I took a lot of sodium bicarbonate when I was a 400-meter hurdler, I can see how increased buffering improved my 52nd effort time. But how he related the increased buffering capacity of the hydrogen ions to an increased ability or an increased function of PFK— phosphofructokinase which is one of the first steps in the Krebs cycle— that ultimately can support aerobic energy production. And that was a link—I don’t like admitting that I didn’t know something—that’s a link I had never made.


Trevor Connor  25:00

It’s a really interesting link, but yeah. I thought it was quite perceptive to go to the buffering. And this is where I would point at, you know, look at Dr. San Milan. Look at the amount of research he’s done on buffer and he loves to talk about MCT1 and MCT4, which are your transporters for lactate and really focus on that, you want to be able to go hard for a long period of time, you need that ability to buffer. So Rob, before we move to the second review, I’m going to throw this to you. So this is 22 years, 21 years old. A lot of research has come out since then. He was obviously left at the end of this review, kind of scratching his head on what changes. Any thoughts on 20 years of research since? What it is or how we see the adaptations in elite athletes?


Rob Pickels  25:47

Well, it’s funny, because this is 21 years old, and I was about 22 years old at the time, I know that I’ve had a lot of changes in the subsequent years. And you had pointed this out, so you’re stealing my thunder a little bit. The work of Dr. Seiler that has come out has really augmented, I’ll say this research to date, mostly because at this time in 2002, it was easy to say, we did long continuous training and nothing happened. And we did high intensity training and people got better. So therefore, we must put our eggs in the high intensity basket. And the work of Dr. Seiler really showed that that’s not how people train, and that we have to lend credence to the fact that long, low intensity as a major component, not a component, the major component of training is ultimately essential to high performance. That’s the major one for me. Trevor, what are your thoughts in the past 20 some odd years?

Maintaining Homeostasis

Trevor Connor  26:52

So I’m actually going to point to two; one is, at the same time that this review came out, it’s really important to point out another top researcher, Dr. Lucia, was doing some of his best study. So actually two of the ones of the reviews, physiology, professional road cycling, and kinetics of VO2 and professional cyclists. And what I actually found interesting, I went back to find those to compare them to Dr. Larsen’s review, and notices that Dr. Larsen’s review is 2002. Both of these were 2001, I believe. So this is all right, about the same time. And what Dr. Lucia was trying to get at is how do top athletes improve? And he kind of said, there’s three big physiological things that we look at. One is your Vo2 max. One is your threshold. One is your economy efficiency—for right now we’ll just combine those even though that are not the same thing. And what he stated was, you don’t really see much improvement in economy. VO2 max tends to peak pretty early on in your careers, you don’t see a lot of improvements in that, and pros. What he said was the difference is you see that threshold. So if we’re talking power and cyclists, for example, that threshold power gets very close to their VO2 max power. So they’re able to just sustain a very close to their VO2 max. So keep that thought. The other thing that I want to bring up is a lot of research on fatigue that’s happened in the last 20-30 years, where they were trying to figure out what causes fatigue in athletes, what causes them to finally slow down? And the answer is, it’s not one thing. It’s many, many different things that can lead to fatigue. And ultimately, what I got out of that is the importance of homeostasis of basically when you are going hard, your body is trying to stay in balance, that’s homeostasis. And when your body stops be able to maintain homeostasis, then it starts to shut down. Then it can’t maintain the pace and multiple different ways homeostasis can shut down. So my theory is it’s not one thing that improves. What you see when you’re doing this high intensity work. And the long slow in elite athletes is they’re improving their ability to maintain homeostasis. And it’s hard to measure because it’s 30 different things, all of which improved just a little bit. But what it adds up to is we’ll use power again because power is really easy. Take an amateur cyclist and a pro cyclist, they can both get on the bike and put out 300 watts. The difference is the pro, you’re seeing no buildup of lactate, you see no acid buildup. You’re seeing them produce most of that energy aerobicly, so they’re tapping into their fat stores which are basically unlimited. So they can sustain that 300 watts. That amateur, they’re producing a lot of that energy anaerobically and those stores are very, very limited. They are producing a lot of acid, they’re producing a lot of lactate, which they can’t buffer very well. So you’re seeing that build up. And so they can only do that 300 watts for a short period of time before homeostasis shuts down. And it’s not one thing. It’s a whole lot of things.


Rob Pickels  30:10

Trevor, I think that you’re on a really interesting point. We oftentimes look at these determinants of performance and kind of a reductionist state, because that makes it easy to understand. Does the training improve my mitochondrial density? No, wasn’t worthwhile…we can measure that. Well, but if it improved something else, then maybe it improves performance and vice versa. Sometimes we see training or any intervention—it could be a supplement, it could be the time of day—we see that this intervention improves things in the laboratory, no effect whatsoever when it comes to performance. So we always have to remember how complex the situation is, not throw the baby out with the bathwater, so to say, but try to understand the bigger picture here.


Trevor Connor  31:02

Right. And I think when you’re talking about that, talking about maintaining homeostasis, you have to bring in a big mental component. Again, when you talk about fatigue, there’s that central governor theory of fatigue, which is, all these different signals are being sent to your brain. And it’s actually your brain that at some point says, “This is too much, I’m going to slow you down.” I think we can learn to control that. So an amateur they’re gonna get those signals very quickly, the brain is gonna go, “Enough, stop.” I think an elite athlete has a an ability to go “Yeah, this is really hurting. There’s a lot of things that are starting to break down a little bit. I can keep going. I can push through that.” One of the classic examples was they always said, once your core temperature hits 40 degrees Celsius, you’re done. That’s that’s just a definite, you’re fatigued. But then they did studies on elite like Olympic level cyclists, and we’re showing that in races—races that they really cared about—they were hitting 43, they were hitting 44, and they were just able to push through it.


Rob Pickels  32:01

Yeah. You know, I think that this is a super interesting topic. Instead of getting too off track from what we’re talking about today, we have a couple more studies. I’m going to encourage people to go back and listen to episode 261 that we did on pain tolerance with Scott Frey because we talk a lot about this in that episode.


Ryan Kohler  32:22

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“Training for intense exercise performance: high-intensity or high volume training?” Review

Trevor Connor  32:54

So let’s move to the 2010 review. This is “Training for intense exercise performance: high-intensity or high volume training?” And this is one of my all time favorite reviews,


Rob Pickels  33:04

Should I just sit back and let you go. Here, I’m gonna drink a little water.


Trevor Connor  33:09

We’re going to do the dummy thing where you’re actually talking as my mouth moving. So you’ll one thing that I love to see in here was he actually, in this review, brings up the whole purpose of training is to better handle what he called homeostatic deviation. Exactly what I was talking about. And it was kind of nice to see because Dr. Larsen is a much smarter person than me, but at least twice as smart. At least twice as smart. But when I was reading the 2002 review, I came up with that idea that I just expressed to you. Then I went back and reviewed the 2010 and went, “Oh, he had the same idea.” Or more, “I had the same idea as him.”


Rob Pickels  33:49

Let’s call a spade a spade on this one. It’s documented when he had the idea.


Trevor Connor  33:53

Yes, exactly. So what I love about this review is a couple things. So I’ll kind of give the quick summary and then Rob, let’s go wherever you’d like to go. So we already talked about the fact that first he addresses, hey, there isn’t a ton of research that high volume does much for you. But then admits, here’s the limitations of the research. And we have this fact that even though there isn’t any evidence, you see again and again and again—and remember this is 2010—Dr. Seiler proposed the whole polarized theory, which he referenced multiple times in this review in 2006 and 2007. He said, but for some reason, elite athletes are spending 75% or higher their time doing long, slow. So what’s the reason? And just said, essentially, what’s probably going on here is there are gains that we just can’t see in the research because it’s really hard to do that study. They just take too long and it’s hard to do in a controlled setting. So that was one thing that I loved to see him talk about. But then he goes into what are the possible physiological mechanisms? And he explains the whole PGC one Alpha pathway, which is fantastic, as a great diagram of it showing both high intensity and high volume hitting PGC-1alpha, how they do it, and then the gains that you see, which is increase in type one fibers, increase in mitochondrial biogenesis, increase in fat oxidation capacity, and an increase in your GLUT4 transporters for sugars and glycogen. And what he gets into—and you’ve heard me say this multiple times on the show—is there are four mechanisms that seem to activate PGC-1alpha, that seemed to elevate it. One is mechanical stretch or muscle tension. The second one is an increase in reactive oxygen species that occurs when oxygen is processed through respiratory pathways.


Rob Pickels  35:49

And we’re not going to talk much about it, but I will say this is what’s behind the theory of antioxidants. Taking a large amount of vitamin C might diminish adaptation.


Trevor Connor  36:02

Three, an increase in muscle calcium concentrations as required by excitation contraction coupling. By the way, I’m not interpreting these I’m reading the study right now. And then four is the altered energy status, i.e. lower ATP and muscles. Now, here’s what’s really important and the thing that I got out of this review, and why go back to it again, and again and again, and again; that increase in calcium concentrations in the muscle. So calcium is used to help muscles contract and the ideas, the sarcoplasmic reticulum, which I just mispronounced. Rob is laughing.


Rob Pickels  36:40

Close enough man, it’s cool.


Trevor Connor  36:43

Close enough. It releases calcium that causes the muscle to contract, and then all that calcium suck back up, which gets the muscle to relax. You do that enough times even at low intensity, and it gets harder and harder and harder to suck all that calcium back up, and you get some build up.


Rob Pickels  36:58

So it breaks down


Trevor Connor  36:58

So things break down. That’s what long slow does, and that activates PGC-1alpha. The high intensity work causes that buildup of ADP. So the drop in ATP, which also activates PGC-1alpha.


Rob Pickels  37:13

And as a quick refresher, whenever we talk about burning fat, burning carbohydrate during exercise, the whole reason we’re doing that is to create more ATP. To add phosphate back on to the ADP—the dye, that’s what the D is dye means two—and bring it back to an adenosinetri, three, phosphate. So ADP and ATP are ultimately what we’re talking about when we talk about energy for the muscle cell.


Trevor Connor  37:43

So here I’m gonna read right out of the study. So first, he says, “Higher volumes of exercise training are likely to signal for these adaptations through the calcium calmodulin kinase, while higher intensity of endurance training, which lowers ATP concentration and raises ANP levels, appear more likely to signal for mitochondrial biogenesis through the ANP activated protein kinase pathway ANPK.” So that’s what we were just saying.


Rob Pickels  38:10

For what it’s worth, AMP is M is mono. So now we only have one phosphate. So ATP ADP, AMP, is three to one phosphates.


Trevor Connor  38:20

Then he goes on to say, “With these two secondary phenotypic adaptation signals identified, it becomes apparent how different types of endurance training modes might elicit similar adaptive responses.” So basically, he’s saying they’re hitting PGC-1alpha—they’re both are—but they’re hitting it differently through different means. And then how we finishes the review is to say, “A, the pathway that high intensity seems to use has a rapid response, but seems to plateau, where the pathway that’s used by the long slow seems to be much slower in his adaptations, but doesn’t seem to plateau as much. It seems to produce continuing gains over time.” Ultimately, what he says is, it’s the additive effect that these two work in conjunction to produce a much bigger game. So if all you ever do is long slow, you’re gonna miss out on gains. If all you ever do is high intensity, you’re gonna miss out on gains. It’s the right mix of the two, which is really the ultimate explanation of the polarized approach to training.


Rob Pickels  39:27

Yeah, I really enjoy this paper, this knowledge drop, because of the practicality that is inside of it. Dr. Larsen clearly says training above LT1, VT1— however you want to define it—training above base, it induces a lot of stress through the autonomic nervous system and athletes can only handle so much of that systemic stress. We know that training at high levels or high intensities causes great gains and adaptations, but we should also know that it’s pretty limited, the amount of work that we can handle there. And that we might not see as rapid of a change at low intensity, but man, we can do a lot of low intensity work before it overwhelms the body. And that balance between the two, that’s the balance that we need to be the best athletes we can.


Trevor Connor  40:20

And he also brings up in this review, as you were saying, the overwhelming your body, the importance of that autonomic stress. That high intensity work produces a lot of stress on us that if you do too much of that can push you over into an overtrained state, where the long slow does not. And that’s part of the reason that you see these elite athletes do a lot of long, slow because they can only handle so much high intensity.


Rob Pickels  40:43

Yeah, to put this into perspective, I think that this came out of a Seiler paper. I don’t think it was in this one, Trevor, let me know. There was a study on race horses that was using alternating high intensity and low intensity days. And they train the racehorses up, they got pretty good with this alternating high and low intensity. And then they said, “Hey, we’re gonna keep the low intensity as it is, we’re gonna make the high intensity a bit more intense.” The horses got better. They didn’t get overtrained. Perfect. When they changed up the structure though, and they said, “We’re going to take out the low intensity and we’re going to move that to really what was a moderate intensity plus the high intensity,” Those horses were overtrained before you could drop a hat, they couldn’t complete the training anymore, all of their performance came down. So showing that polarize difference, keeping the low, low and the high high, even in horses is worthwhile.


Trevor Connor  41:34

Yep, agreed. Now, one thing that’s worth pointing out here, and I do apologize, because I’ve read this review for the life of me, I couldn’t find it. I spent 30-40 minutes looking for it last night, I will keep looking for it. So yeah, I can’t remember the name of that review. I apologize, as I said, I spent a long time looking for it last night, we’ll put it in the show notes if I can find it. But they did add some complexity to this conversation. We always talk on the show about PGC-1alpha and I tried to keep it simple, not throw too many terms at you, so we talk a lot about that pathway. But more and more they’re showing that obviously, whenever you’re talking about the body is always more complicated. And PGC-1alpha seems to work in conjunction with another signaling protein called P53. And it does complicate the conversation a little more. And I do at some point want us to do an episode talking about how these two proteins produce a lot of our aerobic adaptations and a lot of the complexity of this conversation.


Rob Pickels  42:33

Yeah, I think that would be interesting. I’ve certainly read a bit about P53, but I’m not an expert yet, but when I cram for that episode, I hopefully will be.


Trevor Connor  42:41

Well, let’s get on the calendar. I think this would be a fun one.


Rob Pickels  42:44



Trevor Connor  42:44

All right Rob, should we move to our final study from Dr. Larsen?


Rob Pickels  42:49

I think we should. In this study, it’s different than the first two. The 2002 and the 2010 study that we talked about are both on this high intensity, low intensity training spectrum.


Trevor Connor  42:59

They’re also reviews.

“Current hydration guidelines are erroneous: Dehydration does not impair exercise performance in heat” Review

Rob Pickels  43:00

They are also reviews correct. This is a study in which Dr. Larsen was the lost author. And so presumably, some students carried out this work, Dr. Larsen was overseeing it. But this is a 2013 study, that I don’t know if it’s inflammatory, but the title is “Current hydration guidelines are erroneous: Dehydration does not impair exercise performance in heat.” Go figure.


Trevor Connor  43:26

I love this study. I’ve actually never read this before.


Rob Pickels  43:29

Really? You’re glad I picked it out. Great.


Trevor Connor  43:32

So I’m just going to say this as somebody who did race at a high level and had to suffer through five hour races in extreme heat. I’m gonna go back to this is 2008 when they were getting ready for the Olympics and China and they were expecting a lot of heat there. And I remember the Canadian national team was putting all the riders in these kind of mobile homes to do their training because they could heat it up. And we’re just obsessing about their bail to handle the heat and getting into this hole. So the belief is, once you lose 2% of your body weight in dehydration, your performance drops. So they’re obsessing the 2% loss. And I remember one of the Canadian Olympians—I’ll let them remain anonymous—griping to me about all this time in these heated buildings. And just saying, “We’re athletes, we’re tough, we’ll figure it out. Just let us race the damn race.” And that’s what I’ve always felt. I’m like, “I am certain I have done many races where I’ve lost way more than 2% of my bodyweight.”


Rob Pickels  44:38

Think about how much faster you go up a climb.


Trevor Connor  44:42

And look, certainly there’s a point where you see a drop in performance, but I find it hard to believe at 2%, you’re falling off.


Rob Pickels  44:48

Yeah, you know, I will say that there is research supporting the fact that heat training or heat adaptation increases things like plasma volume and that that can Improve stroke volume and you can get better performance. I think that is a topic for a different show, but I do like research like this, that’s like “Haha, you thought you knew, but you probably don’t know.” And what’s unique about this, and they open the paper by saying, previous hydration research, essentially how it’s done, you have somebody exercise in the heat, you get them really thirsty, you get them really dehydrated, and then you put them on a bike and tell them go as hard as they possibly can, right? Maybe you give them some water to drink during this time. And you say, “Hey, look in the people we didn’t give a drink to, they did terribly. And the ones that we handed the water bottle to and they replaced all of their dehydration, they did great.” But this is research and usually what we try to do is blind people to what’s going on. And when you hand somebody a nice, cool water bottle, they’re gonna do better.


Trevor Connor  45:56

And it’s as you said, it’s not blinded. The group that’s been rehydrated versus the group tha not, they know it.


Rob Pickels  46:04

The poor people not getting rehydrated are sitting there like, “What about me?”


Trevor Connor  46:07

So whenever I read things like this, I always think there’s this movie that I enjoyed, a  Canadian movie called, “Brain Candy” from the 90s, where they come up with this drug that just makes everybody feel really good. It’s kind of a satire about the drugs, but they’re doing a controlled experiment of it. And you have this group of people that are still miserable, and their faces are covered in zits. And they’re yelling at the researcher, “The minute you’re given us the sugar pill.”


Rob Pickels  46:36

That was an episode that Dr. Juekendrup could have been a part. You know, so this study, what did they do if they didn’t give someone a water bottle? They gave them an IV. And this is pretty ingenious, I think because they gave everyone an IV, they hid the IV bag from the subjects so they couldn’t see it.


Trevor Connor  46:59

And they went down to the detail of when you get a saline solution, you feel coolness, right where the needle side is. So they’re literally putting cold towels on the site, so you wouldn’t know.


Rob Pickels  47:10

And the other thing they did was they changed the rate of infusion, so that people didn’t know how quickly they were getting fluids. So they created three different conditions with this. The first condition, everybody went through a warm exercise dehydration trial that dehydrated them 3%. And then out of that three conditions occurred, they either replaced everything so they were back to a hydrated, a normal 0% dehydrated, or they replaced 1%, or they replaced nothing, right? But people didn’t know that they got nothing, they very well could have gotten the 2% or they could have been back to totally normal again. And that was super unique about this. Another thing that was unique about this study, is they point out when you blow more air on someone, lo and behold, they don’t feel as hot and they don’t feel as though they’re working that hard. And in our day and age of everybody riding the indoor trainer, especially in the winter time, you know exactly what this feels like.


Trevor Connor  48:10

Yeah, try doing your intervals on the trainer with no fan. I’ve tried it once.


Rob Pickels  48:13

Yeah, that’s heat training. Maybe that’s good for you.


Trevor Connor  48:16

Yeah, maybe.


Rob Pickels  48:17

I will say prior to this when I was at Pearl Azumi, you know Trevor, I used to go visit you in Toronto every once in a while, and the reason that I was up there was working in an environmental wind tunnel in Canada to test clothing on cycling subjects. And the reason I flew to Canada for this was it was an environmental wind tunnel. Everybody getting tested was getting blasted by an appropriate amount of air just like they were riding their bike outside. And when I’m testing clothing, you better believe that that’s important. Not just having a fan blowing on somebody’s head, really not doing anything to cool them off.


Trevor Connor  48:53

Yep. By the way, what I loved about the wind tunnel you’re in was it was designed for cars. So this wasn’t the little wind tunnel where you’re doing one subject at a time, you’re that giant room where you could put 10 athletes in there and test them all at the same time.


Rob Pickels  49:07

Yeah the room was big enough to hold eight coach buses, to put the size in perspective. And I measured the wind flow everywhere. I could put 10 athletes and each would have laminar airflow, meaning not buffeted by other people hitting them. I could also control the humidity, the temperature, the radiant heating, which is one thing they didn’t do in this study. That is like if they’re going to the thing of increasing the airflow, they should probably shine some sun on these people. So I will knock the study for that aspect, but these environmental conditions getting them right, if you want to compare this to outside free living, you got to get them right.


Trevor Connor  49:44

And so getting to the results of the study, I love seeing this because I agree with this. And look, I’m not saying there’s no such thing as dehydration. I think you get somebody down to 6-8% loss of body weight, yeah, you’re gonna see a decrement in performance. It’s more this rule of 2% that you never want to drop below. So they had the 2%, they had the 3%, they had the getting you back to normal hydration level and basically showed no difference in perceived effort. No difference in performance. No difference in heart rate, the only thing that they saw a slight difference in was core temperature. And it was only in the group that was dehydrated to 3%. And you only saw them start to diverge after 17 kilometers of this 25 Kilometer time trial. Wow,


Rob Pickels  50:36

Wow, go figure. No change in presumably sweat rate, because skin temperature was the same. No change in thermal sensation, people didn’t necessarily feel hotter. But I did find it interesting and reassuring that they did see a change in core temperature. So we are getting some precision of data here. It’s not like they had an agenda, so to say, and they’re just like, dehydration doesn’t matter. We work for the drinks and Corporation. But it was in line with what we would expect. Typically, it’s reported that a 1% change in hydration status causes a 1/10 of a change in core temperature in degrees Celsius. So 3% dehydration was about three tenths of a degree Celsius hotter a core temperature than in the normal. But I will say the 2%. If you look at the data, the 2% was right there with the 3%. And this is my issue with statistical significance and practical significance, because I would say they were practically the same. But statistically, there was no difference at 2%. But I think that there was.


Trevor Connor  51:45

Yep, no, I agree with you. So what I loved is again, you know, this is something you see in Dr. Larsen studies is then he’ll he’ll go into let’s try to explain what’s going on. Let’s talk about the physiology. And I loved his theory on this, which is the oral sensing. Yeah. So he cited some really interesting studies where they were taking people that were getting a little glycogen depleted, and had them wash their mouse with a carbohydrate drink, but not swallow it. So they rinse their mouth, and then spit it out. And that would actually improve performance. Just the sensing of carbohydrates. Yes, allowed athletes to go harder when they were doing a time trial to fatigue.


Rob Pickels  52:27

And for what it’s worth practically. Let’s say you’re at the end of a long race, you’re feeling like you’re bonking. But you can’t possibly stomach any more food because you’re just nauseous. Go ahead and rinse that sports drink and spit it out. It’s probably going to help you. But when we talk about hydration, Trevor, it wasn’t the same.


Trevor Connor  52:44

Right? So what he gets out here, I think you’re getting out as well is. So he was trying to explain those other studies that saw a difference. And his point is, it’s not dehydration. It’s not that they’re getting dehydrated. And that’s hurting performance. More of what you’re seeing as the group that were drinking, that drinking has a stimulus that allowed them to go harder. Frankly, they


Rob Pickels  53:07

weren’t thirsty. And what’s interesting in this study is Dr. Larson’s subjects weren’t thirsty either. And that potentially, or what I should say is this. They were no more thirsty, depending on the group they were in. Because if you do look, they were more thirsty after the test. Yeah, all of them than they were before the test. But because in the saline that normalize the osmolality of their blood, which decreases one of the drives for thirst. Another study you know, I’m glad that you brought up the mouth rinsing one another study that was really interesting that he references is they had subjects drink water, they had subjects get water injected into their stomach through a nasal gastric tube. And they had subjects drink water and have the water sucked out of their stomach by the can you are a match it


Trevor Connor  54:02

paid to be a volunteer in this study.


Rob Pickels  54:04

I have to wonder if this is a military study because the military has an unlimited supply of very willing volunteers there. In that study. If the subject drank the water, they didn’t get thirsty. If it was injected into their stomach by their nose, they did get thirsty. But what was super interesting is if they drank it, and then it got sucked out. They didn’t get thirsty. So it had nothing to do their thirst had nothing to do with the hydration or the water and everything to do with the act of drinking.


Trevor Connor  54:35

Well, this is this gets at something that I’ve brought up before that’s really important to remember. You know, they keep bringing up 2% body weight loss. So you you lose that weight and water. You can step on a scale and see that your body has no ability to know how much water it has lost. The way your body actually keeps track of hydration stuff. itis is that concentration of electrolytes in the fluid. So if theoretically, if you’re losing a lot of fluid, because you tend to lose more fluid and electrolytes, your your blood is going to become more concentrated. And then your body goes, I need more fluid. Let’s drink. Yep, that’s really the only way your body knows if you lose eight pounds and water, but you’ve maintained the the osmotic balance in your blood, so you’re losing proportionally equivalent electrolytes. Theoretically, you wouldn’t be that thirsty, because you just wouldn’t know.


Rob Pickels  55:33

And I think that’s especially important to point out because of something else they mentioned in here, there was no change in heart rate. So that means presumably, there was no change in stroke volume, right, because the cardiac output required is the same, because they’re all going the same workload, right. And if the heart rate is the same, then the cardiac output must be the same. And the stroke while you must be the same, they all have to be the same. So if there’s no change in stroke volume, there was probably no change in the volume in their vascular system. And he points out that the body does everything it can to preserve the fluid in the vascular space, it will take out of the extra vascular space, it’ll take it out of your skin out of your muscles, everything it can do before you take it out of the vascular space. So you might see a decrease in that blood volume when you’re more dehydrated, but at 3%, probably hasn’t changed yet.


Trevor Connor  56:28

So what you see is what they call cellular dehydration, where actually your cells will shrink a little bit because the fluids been pulled out to your cells into your blood to maintain that balance. And this is this is a whole nother conversation because this gets really complicated. But this is why the science of hydration is actually really complicated. And why just slamming a bunch of electrolyte with some water with a sugary drink might not always be the best solution because it’s what state is your body in is Have you finally lost blood volume, or Has it just been the cells that have shrunk because if the blood is staying in balance, and then you you drink a highly concentrated fluid, even though you have cellular dehydration, the cells have lost fluid, if you have a more concentrated fluid in your gut, because somebody convinced you this huge electrolyte drink is great for you, then water always goes to decrease the concentration, even though you’re dehydrated, and your blood volume is okay, right now, you’re actually going to pull fluid out of your blood in your gut to reduce the concentration of fluid there, and then you’re gonna get bloated, and you’ve actually made yourself more dehydrated.


Rob Pickels  57:38

Now, coming out of this study, I’m a little perplexed on the recommendations. Because in a 25 kilometer time trial, it probably doesn’t matter, right? And Dr. Larsen or I shouldn’t say this group, I shouldn’t just refer to Dr. Larson here. But this group says or suggests that drinking to thirst is probably what you need. Because thirst itself seems like the limiter, which if you’re familiar with Dr. Noakes, you can go read about drinking to thirst, you know, based on Dr. Noakes, his work, but I will say I am someone who enjoys very long, very arduous adventures. And I am someone who’s really nerdy to the point that I have made a spreadsheet that calculates blood osmolality, based on hours, fluid consumption, the concentration of sodium within that fluid. And, Trevor, as you know, I like to color code things. So it’s green, when it’s in a good place that changes to red when it’s outside the recommendation. There’s a reason I like having I’ll maybe share that sheet at one point. But I don’t know that the recommendation dehydration doesn’t matter, is the right recommendation to give, especially in people in my place. Because of this. I think on short duration stuff, you can certainly drink to thirst and be totally fine. If I’m legitimately in the middle of the desert three hours in and three hours from home and I’m thirsty, I’m probably not able to catch back up and quench my thirst, so to say at that point. So I do even though I know this, even though I know that dehydration doesn’t necessarily matter, at least a 3%. I’m still very diligent about calculating what I’m taking in to make sure that I don’t end up at 6 or 8%. Because when you sweat like a pig like I do, you get there real fast. Let me tell you,


Trevor Connor  59:26

And I don’t think Dr. Larsen would disagree with that. I think the point that he’s making which I agree with is a we have become obsessed with dehydration, right? And we think it takes very little for us to get dehydrated and lose performance and you see people obsessing, rehydrating. And the worst consequence of this has been in amateurs like recreational athletes who are doing something like a marathon and so worried about dehydration, that they over consume, they drink too much fluid. And that leads to something called hyponatremia that can kill people and you had cases As of people dying in marathons because they were over hydrating. So I think the point that I agree with here is we’re a little tougher than we think. We can handle dehydration a little better than we think. You know, take care of yourself. Be smart about it. Don’t dramatically dehydrate. I’ve been there. It’s a bad place. Yeah. But don’t think that you know, we’re this fragile. Yeah.


Rob Pickels  1:00:23

We talk a lot about this back in episode 221 with Dr. Kenefick. It was called “Addressing sweat and electrolyte loss.” Great episode that goes really deep on that side of it.


Ryan Kohler  1:00:35

Hey, listeners, this is Ryan Kohler, coach, physiologist and owner of Rocky Mountain Devo. Whether you’re a competitive athlete or a fitness focused individual, Rocky Mountain Devo has a place for you. We provide coaching nutrition, lactate and metabolic testing and training plan guidance so that you can get to where you want to be. Check us out today at


Trevor Connor  1:01:00

Well Rob, we’re at about an hour.


Rob Pickels  1:01:03

I think I got an A-, what do you think?


Trevor Connor  1:01:05

Oh, I was gonna grade you wasn’t I?


Rob Pickels  1:01:07

I graded myself because that’s how you do it in this day and age. You score yourself Trevor.


Trevor Connor  1:01:12

Am I grading on the final episode are all the stuff that you cut out.


Rob Pickels  1:01:16

I already gave you went off more than I did. I already gave myself an A- you got to grade yourself man. Are you better than me? Are you worse than me? Others say I’m better looking. A- for you too.


Trevor Connor  1:01:33

Can you recover for that? When are we?


Rob Pickels  1:01:35

Nope. We’re done. That’s it. Mic drop.  That was another episode of Fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcasts. Be sure to leave us a rating and a review. The thoughts and opinions expressed on Fast Talk are those of the individual. As always we love your feedback, tweet at us at @fasttalklabs or join the conversation at As always, you can learn from our experts at, or help keep us independent by supporting us on Patreon. For Trevor Connor and Rob Pickels. Thanks for listening!


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