Recent Research on Sprinting, Overtraining Your Cells, and Durability

Nerd Lab! In this episode, Mr. Pickels nerds out with Coach Trevor Connor for a deep dive into new scientific research findings.

laboratory scientist examines a tray of blue petri dishes
Scientist examines the result of a plaque assay. Photo: Unsplash/CDC

Rob Pickels is the Advanced Development Project Manager at PEARL iZUMi, but more importantly, he can out-nerd Trevor as you’ll hear in today’s deep-dive into some new scientific research in sports physiology.

Even though the findings of one of these studies may not appear to directly apply to your weekly training plan, understanding the questions that have been asked by scientists can hopefully give you context into what is known and knowable by science as it relates to human performance.

Trevor gives a brief overview of each study and then he and Rob point out key components of each study and translate the scientific jargon.

In case you missed it and enjoy this depth of conversation about research, we did a “Nerd-Lab” episode a while back, Fast Talk 155: Recent Research on Interval Types, Timing Effects on Performance, Health Benefits of Endurance, and Pacing Strategies.

Aerobic vs Anaerobic Contribution in Sprints

First up is “The Aerobic and Anaerobic Contribution During Repeated 30-s Sprints in Elite Cyclists” by researchers Nicki Winfield Almquist, Øyvind Sandbakk, Bent R. Rønnestad, and Dionne Noordhof. Sometimes, because of the way a study is conducted, the findings are not very well applied to real-world training. Trevor points out some of these methods used which a training athlete would never use in their own workouts. It could be argued that science sometimes needs to ask and answer questions for itself that simply show the bounds of human potential.

Mitochondrial Impairment

Next, we try to understand more about mitochondrial impairment in a study titled “Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers.”

Durability in Endurance Athletes

The final review of the day leaves Rob asking for more from scientists and friends of the podcast, Stephen Seiler and Ed Maunder in their Review article, “The Importance of ‘Durability’ in the Physiological Profiling of Endurance Athletes.” Rob asks the questions he wants answers to and looks for more valuable information.

Let’s make you fast!


  • Aguiló, A., Tauler, P., Guix, M. P., Villa, G., Córdova, A., Tur, J. A., & Pons, A. (2003). Effect of exercise intensity and training on antioxidants and cholesterol profile in cyclists. The Journal of Nutritional Biochemistry, 14(6), 319–325. Retrieved from 
  • Almquist, N. W., Ettema, G., Hopker, J., Sandbakk, Ø., & Rønnestad, B. R. (2020). The Effect of 30-Second Sprints During Prolonged Exercise on Gross Efficiency, Electromyography, and Pedaling Technique in Elite Cyclists. International Journal of Sports Physiology and Performance, 15(4), 562–570. Retrieved from 
  • Almquist, N. W., Sandbakk, Ø., Rønnestad, B. R., & Noordhof, D. (2021). The Aerobic and Anaerobic Contribution During Repeated 30-s Sprints in Elite Cyclists. Frontiers in Physiology, 12, 692622. Retrieved from 
  • Flockhart, M., Nilsson, L. C., Tais, S., Ekblom, B., Apró, W., & Larsen, F. J. (2021). Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers. Cell Metabolism. Retrieved from 
  • Hawley, J. A., & Bishop, D. J. (2021). High-intensity exercise training — too much of a good thing? Nature Reviews Endocrinology, 17(7), 385–386. Retrieved from 
  • Hernando, B., Gil-Barrachina, M., Tomas-Bort, E., Martinez-Navarro, I., Collado-Boira, E., & Hernando, C. (2020). The effect of long-term ultra-endurance exercise and SOD2 genotype on telomere shortening with age. Journal of Applied Physiology (Bethesda, Md. : 1985). Retrieved from 
  • Hopker, J. G., O’Grady, C., & Pageaux, B. (2017). Prolonged constant load cycling exercise is associated with reduced gross efficiency and increased muscle oxygen uptake. Scandinavian Journal of Medicine & Science in Sports, 27(4), 408–417. Retrieved from 
  • Lewis, N. A., Towey, C., Bruinvels, G., Howatson, G., & Pedlar, C. R. (2016). Effects of exercise on alterations in redox homeostasis in elite male and female endurance athletes using a clinical point-of-care test. Applied Physiology, Nutrition, and Metabolism, 41(10), 1026–1032. Retrieved from 
  • Maunder, E., Seiler, S., Mildenhall, M. J., Kilding, A. E., & Plews, D. J. (2021). The Importance of ‘Durability’ in the Physiological Profiling of Endurance Athletes. Sports Medicine, 1–10. Retrieved from 
  • Péronnet, F., & Massicotte, D. (1991). Table of nonprotein respiratory quotient: an update. Canadian Journal of Sport Sciences = Journal Canadien Des Sciences Du Sport, 16(1), 23–9. 
  • Serrano, E., Venegas, C., Escames, G., Sánchez-Muñoz, C., Zabala, M., Puertas, A., … Acuna-Castroviejo, D. (2010). Antioxidant defence and inflammatory response in professional road cyclists during a 4-day competition. Journal of Sports Sciences, 28(10), 1047–1056. Retrieved from 
  • Serresse, O., Lortie, G., Bouchard, C., & Boulay, M. (1988). Estimation of the Contribution of the Various Energy Systems During Maximal Work of Short Duration. International Journal of Sports Medicine, 09(06), 456–460. Retrieved from 
  • Tiidus, P. M., Pushkarenko, J., & Houston, M. E. (1996). Lack of antioxidant adaptation to short-term aerobic training in human muscle. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 271(4), R832–R836. Retrieved from 

Episode Transcript

Chris Case  00:12

Hey everyone, welcome to another episode of Fast Talk, your source for the science of endurance performance.


Chris Case  00:18

I’m your host Chris Case, sitting down today with Coach Trevor Connor in the studio, as well as Rob Pickels, he is the advanced development project manager at PEARL iZUMi, which means he’s a scientist, but he also likes to get crazy and creative. Let’s make you fast.


Dr. Stephen Seiler  00:39

Hi, I’m Dr. Stephen Seiler of the University of Augsburg in Norway. I’m a longtime contributor to and a fan of Fast Talk and now Fast Talk Labs. So, I’m really happy to be involved and I think Fast Talk Labs with Chris and Trevor, and their team exemplify some aspects of the coaching and the process that I value. So, I’m proud to be part of it, and I hope you will enjoy it.


Trevor Connor  01:06

That was Dr. Seiler from Fast Talk Episode 139 when we introduced Fast Talk Laboratories and our new virtual Performance Center. If you enjoy Dr. Seiler’s appearances on our show, we have really good news for you. We just unlocked all 40 of Dr. Seiler’s webinars, lectures, and interviews on our website They are now free for members, join at and you can get Dr. Seiler’s pioneering work in one convenient place. Sign up for a free listener membership today at


Introduction to Rob Pickels

Chris Case  01:38

You used to work at the University of Colorado Sports Medicine and Performance Center as well. He’s been on Fast Talk, but it’s been years and years. So, welcome back to the program, Rob.


Rob Pickels  01:54

Thanks for having me, Chris. Glad to be here, it has been too long, frankly, to sit in this room with you guys.


Trevor Connor  01:59

I agree. We got to get you back in again.


Chris Case  02:02

So, today, we want to dive into several interesting studies. Trevor, I think you actually have a little short story you’d like to kick off the episode with. This pertains maybe more to Rob than the studies themselves, so let’s hear it.


Trevor Connor  02:20

This is one of my favorite moments that I want to share about Rob, I’m probably going to really embarrass him.


Chris Case  02:26



Trevor Connor  02:27

A few years ago, this company, I’m not going to name the company, this company that had developed this brand new, whole new metrics training device came to Boulder and they were doing a presentation on it, and Rob sent me an email saying, “Hey, we got to go check this out.” So, we went there. Now, Rob, you’re one of the best physiologists I’ve ever met, I love discussing this stuff with you. You went to this just to watch, see what this is about, we all went to this do that. So, they came in with their product, and they had a rider on a trainer, and they were doing a whole lactate test in front of us, you can tell they’ve been traveling around the country, trying to wow people by doing the lactate test and in front of all these coaches. At the beginning, Rob, you asked a very reasonable question about their test protocol, and they turned around you and will if you understood exercise testing the way we do, shot down your question. I just looked at you and could see, Oh, it’s on. For the rest of this, you took them apart, their protocol, their device, what they were claiming to the point that you could tell they just wanted this to be over and get out of the place. I have never seen such a good dissection of the physiology to, unfortunately, their discipline.


Rob Pickels  03:53

And Trevor, where is that company today?


Trevor Connor  03:55

I don’t know.


Rob Pickels  03:56



Trevor Connor  03:57

I haven’t seen them.


Rob Pickels  03:58

I haven’t seen them either. Thank you for that Trevor, I do remember that day, It was interesting. I love, I don’t want to say being critical, because critical has a negative connotation, right?


Trevor Connor  04:11



Rob Pickels  04:12

But asking why? And having a deeper understanding of what’s going on not necessarily taking things at face value.


Chris Case  04:19

I think being skeptical and having a critical eye is a very valid attribute for a scientist.


Rob Pickels  04:25

Yeah, absolutely without question. It’s an unbiased manner, right? It’s not to be negative, it’s not to say no, it’s not to disprove things for the sake of disproving it, but it’s to just find that deeper truth, right? And that deeper understanding. On the other side of that, I’ll go up against anybody when it comes to lactate testing and laboratory-based physiological testing. I’ve had a long career of doing that, I’ve picked a lot of fingers and I’ve analyzed a lot of results, It’s something I’ve enjoyed doing quite a bit.


Trevor Connor  04:56

You have taken blood from my fingers many times, every time commenting on how old I am. So, but this is why I was really excited to get you to this episode. So, we’re going to talk about a couple of recent studies. I really am excited to just present this study and have you do what you did at that presentation of let’s dissect these studies, let’s see how well they hold up, and really want to hear what you have to say. I love the fact I’m looking at the table here, and Rob has like eight studies spread across our podcast table. So, not only the studies that we’re going to talk about but he’s come with other stuff. So, we’re about to go to war.


Chris Case  05:37

Excellent. Well, shall we dive into the first one? It is entitled, can I read the title, Trevor? Do you want to read the title? I get to? Okay. Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers, this is out of Sweden, Mikael Flockhart is the lead author here. So, yeah, tell us a bit more about it.


Study 1: Excessive Exercise Training Causes Mitochondrial Functional Impairment and Decreases Glucose Tolerance in Healthy Volunteers

Trevor Connor  06:06

Okay, well, I’ll start by saying that this is a complex study, that involves multiple muscle biopsies and measures of a whole bunch of different metabolic markers. So, right now, what I’m going to do is give you the two-minute summary, which is not going to do at full credit. I’m just going to say, if you really want to get into the fine details of this study, download it, read it, it’s an interesting one. The short of it is what they were trying to do is look at the effects, what happens if you overload an athlete with high-intensity work? What does it do to them metabolically? And particularly, what does it do to the mitochondria in the muscles? I haven’t seen a lot of research on that, so at least not done this way. So, it is a really interesting study to see, we overloaded or overreach the athlete, what does that look like? The protocol here, they had six women, six men, all recreationally active, this was not high-level cyclists, and they put them through a four-week overload protocol. So, basically, the first week, they did light training with limited interval work. The next week, they did what they called moderate training with three or four, I can’t quite read that right, but basically a few high-intensity sessions, but then they had the fifth week where the goal was to overload the athletes and basically hit them five days in a row with hard, high-intensity work. Now, I already know Rob has some issues with this, because this is while they were trying to show here are the effects of doing too much high-intensity work, this really isn’t the way an athlete would train. So, you’re getting some interesting information, but it’s always good to do a protocol, you say, let’s see the effects of the way you would actually have an athlete train. Then finally, they had a recovery week where they had them back down, and they wanted to see how much of these physiological markers return to baseline by the end of that recovery week. So, that was the four-week protocol. As I said, they were taking biopsies throughout and really looking at the markers of mitochondrial activity. I should say, they were doing more than biopsies, they’re also taking blood samples, there were multiple markers that were being checked. The big ones were looking at mitochondrial activity, which is the powerhouses of our cells in terms of working with oxygen. They were looking at glucose metabolism, so our glucose, the changes in the glucose tolerance of these athletes, changes in insulin. They also looked at markers of oxidative stress. What was really interesting, I know we’re going to dive into this I’m not going to cover too much right now is what stayed in balance, and what didn’t stay in balance. There were a few surprising things here, and I’ll quickly go through the list right now, but as I said, I think the most interesting part of this conversation is going to be what they found changed and what didn’t. So, their main conclusion, and I’m really using their wording here, so we might, later on, give our opinion on this, but their main conclusion was that there is an upper limit on the amount of intense exercise that you can do before it hurts metabolic health. Again, their wording, we’ll dive into that. A couple of things that they saw that did get out of balance when you’ve hit that high-intensity week or got to the end of that high-intensity week, first of all, a drop in what they called intrinsic mitochondrial respiration. I’m not going to dive into what that is, again, if you’re really interested go read the study, but basically, it’s a way of measuring how functional the mitochondria remained. What they are saying is, by the end of that high-intensity week, you are seeing some dysfunction in the mitochondria. Another thing that was quite interesting is they saw a reduction in glucose tolerance and an increase in insulin resistance. So, this is basically the body’s ability to manage glucose.


Trevor Connor  10:49

A decrease in glucose tolerance and an increase in insulin resistance is something that you would see in somebody who’s pre-diabetic. So, normally, our bodies maintain glucose, blood glucose levels, within a tight range, and what they were seeing in this study after all this high-intensity work was the athletes were having a harder time staying in that range. So, sometimes glucose was going below, sometimes it was going above, and that’s significant, and that’s why they’re tying all this back to this sort of high-intensity work hurting metabolic health because you are essentially seeing the same sort of symptoms you’d see in pre-diabetes. Now, whether in an athletic situation that is truly an issue with metabolic health or not, I think another thing we’ll probably dive into here. Finally, and I’ll fly through this so that we can get to Rob and his interpretations. One of the good things that they saw was there was still that classic slight overreach and then a super-compensation, so these athletes definitely got stronger. While there was a dysfunction in the mitochondria, in the short run, there was still mitochondrial biogenesis, which is a fancy way of saying you saw some mitochondrial growth. The big thing that was surprising was they expected to see a big increase in oxidative stress, since mitochondria are giant aerobic machinery, and if they’re being overtaxed, you would expect they’d be pumping out a ton of reactive oxygen species, but what they found was that oxidative stress stayed in balance. That was because the mitochondria actually reduced the quantity or concentration of H2O2 that they were pumping out. So, that was really interesting, and again, I really hope we dive into that. So, a couple of really interesting things for this study that we’re going to dive into, but I am just going to start with saying, I found it fascinating, even if the protocol was a little different from what an athlete would normally do, I found it really interesting to say, okay, we’ve overreached an athlete, we eventually saw a super-compensation, let’s look back at all the biomarkers and see what was actually going on in the body. So, Rob, what did I get wrong in that explanation?


Rob Pickels  13:23

I don’t think that you got anything wrong.


Chris Case  13:25

What did they get wrong?


What the Study Got Wrong

Rob Pickels  13:26

What they got wrong? That’s a great question, Chris. I’m gonna back up to the statement that I made a little bit earlier of looking at things in an agnostic sort of fashion. I’m going to admit, when I first saw the title of this paper, I don’t know how agnostic I was at that point in time, I was a little flared up, right? Because here we are a bunch of exercise physiologists sitting in a room and you see something like this excessive training, you know, is leading to this negative sort of consequences. You know, and so I had to back up for a second, I had to understand this study a little bit more deeply. But to that point, what I wish the paper had been titled is, An Increase in Glucose Transport, in an increase in Lipid Oxidation in Mitochondrial Content and Enzymatic Activity in Glycogen in hexokinase and glucagon synthase, mitofusin to remodeling, no Decrease in Antioxidant Activity. All of these really positive things came out of this excessive training protocol and based on the title, I felt like it was almost you know, they were reaching out to be a little inflammatory to get people interested because so many positive things did come out of this, and so that’s the first thing I think they got wrong.


Trevor Connor  14:42

That’s a good point, right? At the start of the study, they talk about recent research that has been showing mitochondrial dysfunction is associated with type two diabetes, and raise the question of is the mitochondrial dysfunction a consequence of impaired glucose tolerance, or is mitochondrial dysfunction causing glucose intolerance? So, they actually tried to address that with this study, which I don’t think is appropriate because somebody who’s training really hard is very different from somebody who’s going into diabetes. But certainly, as you said, Rob, what they’re really implying is, you see some of the dysfunction, some of the health consequences that you would see in diabetics if you train too hard, and you don’t want those consequences. That’s what they were at least implying.


Chris Case  15:26

Let me ask a question that is a little bit of a tangent, how much control do the authors of a study have over what the title is versus the publisher of the journal that might want to elicit more attention to their publication?


Dissecting the Title of the Study

Rob Pickels  15:44

I feel like I’ve titled all my papers.


Chris Case  15:46



Rob Pickels  15:47

Personally, I don’t know, Trevor, in your experience is different? I haven’t published in cell metabolism previously.


Trevor Connor  15:56

Well, I know in our website, I tend to give Chris titles like this in my articles, and then the title that ends up,


Chris Case  16:03

A little bit different.


Trevor Connor  16:05

It ends up very different, so yeah, I think these are written by a bunch of scientists like me who don’t know how to title of the paper, and nobody ever fixes it.


Chris Case  16:14

Well, I’m getting at the point of it sounds like they’re skewing the title to be a little bit like you said, Rob, inflammatory, whereas they could have gone a much different route, and, obviously, what you just read off is a complete mouthful, and would take up an entire page if they were put it on. So, that wouldn’t have worked, but they went the excessive training causes bad things, whereas they could have put excessive training causes some of the good things or, you know, they could have taken a different direction.


Rob Pickels  16:45

Yeah, I think that they certainly could have without question, but at the same time, as I said before, when I took a step back, and I started to actually read the study, and to, you know, settle down and let my blood pressure come down and take a little extra blood pressure medication,


Chris Case  16:59



Rob Pickels  17:00

I do think they actually had a lot of really good stuff within this study, and one thing that I found that was interesting was that when they had a finding, they delved a little deeper into that finding, they tried to understand why they had that finding. It ended up creating a very robust study, from an exploratory sort of sense.


Chris Case  17:21

Can you give an example of one of those findings that they went a little deeper on?


Rob Pickels  17:26

Well, what I’ll say is when they saw that the IMR, or the intrinsic mitochondrial respiration, which is essentially a measure of how well each mitochondrion itself is functioning, when they had that finding, then they said, oh, we oftentimes see this in a glucose intolerance situation, let’s go ahead and understand if that’s happening in these athletes. Then from there, and this is what I think is the most interesting finding of this study, is they said, we saw this glucose intolerance with our excessive training group, I wonder if we see this in just elite athletes in general? So, they went out and they did 24-hour glucose monitoring on just individual elite athletes who weren’t a part of the initial study, and they said, wow, they spent more time in a hyperglycemic, so too much blood sugar, and a hypoglycemic, two little blood sugar, as compared to the controls, you know, who were either, Trevor, were they non-athletes or were they recreationally active? I don’t remember.


Trevor Connor  18:29

So, in that they were recreationally fit.


Rob Pickels  18:32



Trevor Connor  18:33

They weren’t comparing the people off the couch, but certainly not highly trained athletes.


Chris Case  18:38

So, what you’re saying is that elite athletes, these random, quote, unquote, random elite athletes they tested, were showing signs that their glucose levels were fluctuating high and low, and they weren’t stabled really?


Rob Pickels  18:52

Exactly. Yeah, you want glucose to be controlled within a relatively narrow window, or what I’ll say is the traditional view is that you want glucose controlled within a relatively narrow window. For me, personally, I don’t know, I’m not knowledgeable enough to know, if this glucose intolerance is a result of training and heavy activity, if that’s truly a negative thing, or is that a very normal, healthy response?


Chris Case  19:14



Rob Pickels  19:15

Because we know that athletes have this level tend to have a decrease in all-cause mortality, you know, ultimately, they’re healthier throughout the rest of their life, and if this was truly a negative situation, I don’t think that we would necessarily see that.


Trevor Connor  19:28

Right. It’s a really interesting question, as you said, that was one of the most intriguing parts of this study, and this is why every study ends with more research is needed.


Chris Case  19:37



Trevor Connor  19:37

I think this is the part where you go, that’s intriguing, there does seem to be a health consequence to these elite cyclists, yet we’re not seeing them with higher levels of diabetes, as you said, we’re not seeing them dying younger so is that actually a negative health effect? More research is needed.


Chris Case  19:55

More research is needed, always. Alright, Rob, tell us a little bit more about some of the findings they had here, maybe oxidative stress, that was one of the points that Trevor made at the beginning.



Rob Pickels  20:07

Yeah, you know, with the oxidative stress I found it interesting that they were surprised that there wasn’t much of a change. Looking at the results, they also didn’t see a decrease in antioxidant activity. I think that the two of those things go hand in hand. For me, what I found most interesting, though, was that they predicted that the H2O2 production decreased, almost to help balance that oxidative stress in that it was done more prophylactically, so to say, ahead of time to maintain that level of oxidative stress. Trevor, I’m not familiar enough to know, does the bodywork in that manner? I would have thought that we would have seen the increased oxidative stress, H2O2 production would have continued until there was a negative sort of feedback loop and then things perhaps would have dropped off.


Trevor Connor  21:02

So, we’ve talked about another study that actually addressed this with really high-level athletes in some of our previous episodes, they did a study with best of the best. So, this was at the dofana, looking at their overall oxidative stress levels. So, the combination in both production and antioxidants, and showed over the course of the dofana, these athletes actually saw a net decrease in oxidative stress. Now, they compare that to amateur athletes and showed how quickly amateur athletes could get overwhelmed by oxidative stress. So, one of the major adaptations you see in high-level cyclists, and this is a study with higher-level cyclists, or at least higher-level endurance athletes is a very robust antioxidant system that can really keep oxidative stress in balance.


Rob Pickels  21:53

Now, Trevor, did they see a decrease in mitochondrial respiration similar to what we saw in this study?


Trevor Connor  22:00

They didn’t address it in that study.


Rob Pickels  22:01

They didn’t address it, yeah. Part of the reason they’re saying that there was no change in stress, is that perhaps there was a decrease in the mitochondrial respiration and that that is also helping balance the equation.


Trevor Connor  22:18

That previous study didn’t talk about mitochondrial dysfunction, but what it did really address is a dramatic rise in SOD2 and all these other natural antioxidants, basically saying that increase in natural antioxidants exceeded the increase that you were seeing in reactive oxygen species. So, the net was actually a decrease in oxidative stress.


Rob Pickels  22:44

So, it’s interesting that they found that, Trevor, because, you know, I think one of the strategies employed by a lot of professional cyclists, especially in these multi-day, multi-week events, is supplementation with NAC, to increase glutathione production, right? And to decrease, you know, reactive oxidative species from that increase in antioxidant profile. Do you think that something like that is warranted if the body is naturally producing more antioxidants, and we’re not necessarily seeing an increase in overall stress?


Trevor Connor  23:14

That’s a really good question because that was a study at the dofana, and they did not bring up if any of these cyclist supplementing. So, what I got out of this, I always look for what is an interesting story that I hear from a study, this whole antioxidant, the fact that oxidative stress stayed fairly stable, and they were surprised by that it led to a bigger picture for me of so you see oxidative stress stay level, where basically the mitochondria stopped pumping out as much, ROSS in order to maintain that level, you saw that drop in insulin, you saw that slight glucose intolerance, but what also happened was you saw an increase in GLUT4, which is the transporter used in muscles, so muscles can take up glucose. So, even though insulin wasn’t being produced as well, so insulin normally is what causes cells to take up the glucose to keep blood sugar at normal levels, you’re almost seeing this secondary mechanism stepping up to say, we’re still going to keep glucose in balance.


Trevor Connor  24:21

There were several things like this that you saw on the study where there were changes that ultimately led to the body staying in balance, even though it wasn’t the normal way. So, this goes back to something we talked about a lot in the show, which is homeostasis, body likes to stay in homeostasis, it likes to stay in balance. What I really saw here is during that excessive training week, the really interesting ways in which the body was saying you are stressing me there are certain things that I can’t keep normal, but I’m going to find creative ways to do my best to maintain homeostasis. So, it maintained oxidative stress. It did its best to maintain blood glucose levels by up-regulating GLUT4, so it was addressing these stressors. What you might be seeing is when you have too much training, we’ll get to the methods in a minute, this was a ridiculous week, when you have too much training, the body’s going to do its best to maintain homeostasis, but it’s going to prioritize the things that it sees is most damaging. So, it doesn’t want access raw, so it’s going to prioritize that. When blood sugar levels get too high or too low can be very damaged to you, so it’s gonna prevent that, but it might come at a cost of other things in the body just says I can’t maintain those. I think that’s what they’re getting at with some of this mitochondrial dysfunction. Ultimately, what they said is, some of these things explain why when you really train very hard, you see that ability to go hard, to do that big jump, that 30-second effort kind of goes away. So, that’s what I found really interesting, I’ve seen a picture of the body trying to maintain homeostasis, saying I can’t do it perfectly, so making decisions of what it’s ultimately going to let fall apart a little bit.


Rob Pickels  26:10

If you make rats do prolonged swimming, which is drop them in the tank and make sure they don’t die.


Chris Case  26:18



Rob Pickels  26:18

For hours, then you see a 50% increase in GLUT4 transport within like 16 hours or something like that, and within two days, there’s a 200% increase in GLUT4 transporters. Because of that very short time course to adaptation there, I would almost argue that the GLUT4 increase comes prior to any changes within the insulin side of things. I think that GLUT4 is really important, right? Because from this study, even though they did excess training, they didn’t necessarily see a decrease in glycogen content within the muscles, right?


Trevor Connor  26:58

That was the other thing that surprised them, you saw decrease in glycolysis, but glycogen stayed quite robust.


Rob Pickels  27:08

Yeah, exactly. We have to understand that we’re talking about healthy volunteers, right? These are individuals who did less than five hours of endurance training but were otherwise pretty active. So, the systems that they have are not say up to snuff with maybe a lot of people that are listening here that are training more regularly, or anything else, you know, but because of this increase in GLUT4, because of the increase in hexokinase, which helps lock that glucose within the muscle, you know, they were able to adapt very, very quickly to the energy expenditure that they were doing, to the high-intensity work they were doing, and to trap a lot of that glucose that’s floating around their bloodstream to trap that within the working muscle itself, to prepare their body for the next day, for the next hard session that’s going to be coming along. With the insulin side of things, is it possible that the insulin resistance is coming from almost this lower blood sugar because things were getting pulled into the muscle more? Or do you think maybe the glucose intolerance is just coming from a different system that’s getting worn out down the line?


Trevor Connor  28:17

That’s a really good question. So, you’re right, they just compare the different stages. So, they compared the excessive training to the moderate training to the light training, they didn’t say. So, they certainly said, you saw this rise in GLUT4, and you saw the decrease in glucose tolerance during the excessive training phase, but they didn’t say which came first. They just said it was during that phase. So, I can’t tell you which of those two came first. My initial interpretation, this is just a thought, and please give me a reaction to this is these athletes are training really hard, they’re doing high intensity every single day, again, their body’s trying to stay in balance, and to a degree their body is basically saying, I really need to prioritize getting glucose to these muscles, because they’re having a high demand right now, I don’t want as much glucose goes into other tissues because the muscles needed the most right now. So, I was interpreting it as kind of a simultaneous decrease in insulin, with a rise in the GLUT4 to really prioritize where the glucose. Insulin is indiscriminate, when you release insulin, all cells respond and start taking it.


Rob Pickels  29:32

Yeah, Trevor, I think that might be the smartest thing you’ve ever said, and I fully 100% agree. Let’s end the show with a high note, there’s no more to talk about.


Trevor Connor  29:43

I think I take that as a compliment? But I’m detecting some sarcasm.


Rob Pickels  29:47

No sarcasm, no sarcasm, I fully agree. I would love some research to back that up, I think that that’s a really interesting theory, I can see that being 100% plausible. But at the same time, we can’t necessarily really know anything until we, you know, disprove some null hypotheses on this one.


Trevor Connor  30:04



Chris Case  30:04

My question, I know you wouldn’t encourage anyone to maybe change how they train based on a single study, but we’re talking to an audience that is looking for takeaways and messages here, what is the message based on this study? Is there anything you should do differently? Obviously, don’t train like a ding, dong, and do five-hit sessions in a row, we didn’t actually talk about those methods, but that’s what we’re getting at here, and we’re essentially saying that’s more than excessive in a sense.


Trevor Connor  30:46

So, my first conclusion from all this discussion is, Rob is the only person that rivals you, Chris, in terms of making fun of me for being old and Canadian, I’m a little disturbed by the fact that you’re just complimented me. I’m waiting for it to come back around.


Chris Case  31:03

It will.


Rob Pickels  31:04

I do to keep you off balance, always guessing, you know.


Trevor Connor  31:07

I’m really off balance right now.


Chris Case  31:10

You’re trying to stay in homeostasis, and you’re struggling.


Trevor Connor  31:13

I need my insults, quick somebody make fun of me.


Chris Case  31:16

You’re Canadian by the way.


Trevor Connor  31:17

Thank you.


Chris Case  31:18

Okay, there we go. Is there any solid message you would take from this study in terms of how you should change? Or would change training?



Rob Pickels  31:29

Yeah, it’s a great question. Why did we talk about this? Sometimes I struggle with this because I’m not in the world of pure laboratory physiology anymore. I’m more in the world of applied physiology, how do we take this and actually utilize the information? That was one of my initial issues with this study, and I think that that’s why we have issue perhaps with the methods that were chosen, right? Because of the insane amount of high intensity that they did in a serial manner, right? one week of low, one week of moderate, one week of excessive, nobody would ever train in that manner, there would be maybe some lower intensity days, it would maybe be weeks between these sessions, it’s not practical. What this is helping us understand is all of that training methodology was a perturbation to the system, it was never intended to be training. They never said, doing three by ten, by 30/30s, it’s not about training. It was what can we do to really stress out this system? And how does the body respond? I think that when we talk about, you know, the nuance of it, it leads to a deeper understanding, right? We would not have perhaps found these negative results, I’m going to call them, right? The glucose intolerance, some of the mitochondrial function impairment, if they hadn’t gone out and done something silly to tell you the truth. So, I think that just from a truly deep understanding, then this is incredible knowledge. From a how does this affect my training? I don’t think that was ever the purpose or the function of this research.


Trevor Connor  33:17

Rob, that was damn smart. Not the smartest thing I’ve ever heard you say, but close.


Chris Case  33:22

Pretty close.


Rob Pickels  33:23

Are we gonna have a compliment-off?


Chris Case  33:26



Trevor Connor  33:27

This is actually scaring me more than the insult-off I was expecting.


Chris Case  33:32

Nobody can see it, but Trevor’s hair is on point right now.


Trevor Connor  33:45

So, yes I really did mean that. I fully agree.


Chris Case  33:50

Of course, you meant it, you’re Canadian.


Trevor Connor  33:52

So, it is Canada Day today? Today is July 1st, isn’t it?


Rob Pickels  33:58

But America day is coming in two more.


Chris Case  34:00

An American told us that it was Canada Day, not the Canadian.


Trevor Connor  34:07

This is the anniversary of the day a bunch of Canadians went to England and said, could we please sort of have independence, you can still have ultimate authority over us, but we sort of want to have our own government. Is that okay?


Rob Pickels  34:19

You didn’t shoot anybody to get that?


Trevor Connor  34:21



Rob Pickels  34:22

You missed out.


Trevor Connor  34:25

Where were we?


Rob Pickels  34:27

We were talking about the takeaways from this and what our listeners learn.


Trevor Connor  34:32

Right. I think Rob, you were spot on, and that’s what I got from this. There is nothing that you can take from this and say this will impact your training. I think they did want to say there’s such a thing as too much training, but he even did point out there was evidence of super-compensation from this. What I took from this is we talk all the time about training is about exactly that, you have to put a stress on the body that the body can’t tolerate, and then have a rest period where the body repairs and super-compensates. This is one of the first studies that says when we talk about putting stress on the body that the body can’t handle, what exactly does that stress look like? Which I found fascinating. Seeing this body trying to stay in homeostasis, not able to fully be able to do that, but finding really creative ways to make sure the really important thing stay in homeostasis. To me, that was all very fascinating, as we said, that now raised a whole bunch of now we need to study this, we need to study this, and we need to study this, which is I think the biggest thing to get out of this study.



Chris Case  35:38

So, Trevor, as a final note, it seems like this study has caused a few waves. Do you want to comment on that? There have been some responses by some prominent names.


Trevor Connor  35:47

Yeah, I found this really interesting. This study came out two months ago, and Dr. John Holley, we’ve actually had on the show, who’s a very respected physiologist, has already written a response to it. We won’t go into it, but if anybody’s interested, so it’s in the Journal of, I’m not looking at it, Nature reviews. So, it was just a two-page response, and he pointed out the key findings of the study but also raised a few criticisms. One of them was basically what Rob was saying was, this isn’t really the way people train. So, you have to factor that in, he also brought up a valid point that this is muscle biopsies looking in vitro. So, it wasn’t looking at the full muscle, full-body response, it was just taking a very small part of the muscle.


Trevor Connor  36:42

Hey listeners, if you’ve been listening to Fast Talk for a while, you’ve probably heard a few of my hot weather racing stories like the time I tricked a rival team into feeding me some of their water bottles, or a few of the times where I didn’t do quite so well. Stories like those show how critical it is to beat the heat and stay hydrated. In our new pathway, we explore exercise in the heat. We show how to manage heat, dial-in hydration, and fuel for performance in hot conditions. This new pathway taps Dr. Stephen Cheung, the internationally recognized expert in thermal physiology, and sport sciences Robert Pickels, Lindsey Golich, Dr. Stephen Seiler, plus of course, Ryan Kohler and myself. This pathway busts myths and reveal science-based best practices for beating the heat. Topics include rider body types, mental strategies, sports strength salinity, drinking versus dosing, muscle cramping, where you know I have a strong bias, getting acclimated, drink to thirst, and how heat affects sports nutrition. Take a look at our new exercise in the heat pathway at


Study 2: The Importance of ‘Durability’ in the Physiological Profiling of Endurance Athletes

Chris Case  37:52

Alright, let’s move on to the next study we want to discuss. This one was in Sports Medicine, The Importance of ‘Durability’ in the Physiological Profiling of Endurance Athletes. The lead author here is Ed Maunder; the second author here is Dr. Stephen Seiler. Maunder is in New Zealand, Seiler, as we know, is in Norway. Tell us a little bit about this study, Trevor.



Trevor Connor  38:19

So, again, I’ll give the two-minute summary, and then we’ll let Rob dive into this. So, important first to define durability, because they talk a lot about it in this study, and we’ve discussed this. So, durability or repeatability, we use a variety of terms, but they define it here as the time of onset and magnitude of deterioration and physiological characteristics overtime during prolonged exercise. So, that’s a mouthful, basically saying there’s a certain point, if you train long and hard enough, where things are going to change, physiology is going to change, and perhaps the numbers that you were using at the start of that workout, don’t really apply anymore. That’s really what they’re trying to get at is saying, the gist of the study is they start by talking about the different ways of profiling athletes. So, the key metrics that we tend to measure, VO2 max, anaerobic capacity, economy, substrate utilization threshold, and you can tell I’m trying to rush through this, I want to get to rob because this is his wheelhouse.



Trevor Connor  39:25

Basically, talked about the different ways of testing it, such as doing critical power, doing intermittent exercise tests, during an MLSS test. I’d actually seen a previous draft of this where they wrote a very thorough explanation of each, in the final published copy, they really quick explaining each. The gist of this is basically saying, all of these test methods, all these things that we tend to measure are always done fresh, and they don’t account for the fact that over time, these variables might change. We actually don’t know how they change and the sort of impact they have on you. So, the classic one they talked about was cardiac drift, you do a long, semi-hard training ride, at a certain point, you’re going to see heart rate go up relative to power or pace. They said it could be that’s completely benign drift and whatever training zones you were using the beginning, you can keep using those, or it’s possible that means that if you’re doing your training zones by heart rate, they have shifted, and if you don’t shift with them, you could start under training, or conversely, they have shown a really long exercise. So, up to six hours, you can actually see heart rate decline a little bit, and if you stay with your heart rate zones, in that scenario, you would actually be overtraining a little bit. So, and they basically said we don’t know, so we need to look at this.


Chris Case  40:59

More research is needed.


Trevor Connor  41:00

Exactly. This is another more research is needed.


Chris Case  41:03



Trevor Connor  41:03

And see this impact of durability. The other thing they brought up, that we can discuss, is durability is different in everybody. They actually showed a chart of different athletes where you saw some, there was quite dramatic change in that cardiac drift over time, while other athletes actually maintained it pretty well throughout the four-hour ride. So, Rob, that’s my really short summary, because I really am excited to hear your response to all this.


Rob Pickels  41:35

I don’t know what to say about this study.


Chris Case  41:37

He’s left speechless.


Rob Pickels  41:40

I’m left speechless by this because I think it was a great half-step to tell you the truth. The reason I say it’s a half step is I wish that they had just done the study, of does this stuff matter or not? To tell you the truth.


Chris Case  41:54

So, you’re saying that they’ve kind of defined that this is an area that needs more research without actually taking a step forward into that research?



Rob Pickels  42:02

Yeah, I agree with that. The reason for that is I think that a lot of people know and understand this already. Did this need to be said? What physiologist sort of doesn’t think about these concepts? I know that I certainly do and did, the cardiac drift question has been asked on internet forums around the world for as long as internet forums have been online. Here’s the thing, I fully agree with everything in this study, as I typically do with Dr. Seiler, he’s terrific, and life is grand. What’s new in this? Trevor, I guess, is really my question. I don’t want to be overly critical of it like that, but as I said, this is sort of just known in common knowledge, right? I think that it’s important that it’s gotten out there, maybe it’s gotten out there officially, maybe it spurs somebody to actually do the research at this point in time, and maybe this is a struggle that I have as a scientist, right? One of the most difficult things, when I was working directly with athletes, is knowing what was common knowledge for myself, and common knowledge for people in the industry, and that wasn’t actually common knowledge for everyone else. oftentimes, I would sort of forget or I would assume incorrectly, and so yeah, there is the positive benefit of getting that information out there, asking the question to make sure everybody knows that we need to ask the question, but I would have loved if this group just kind of got down to it and started figuring these things out.


Trevor Connor  43:35

So, they did share some data from unpublished studies, I actually recognize some of this data because I know that Dr. Seiler has been working on this. Matter of fact, there is one chart here of a particular ride, which looks an awful lot like a ride that Dr. Seiler sent me that he did on Zwift.


Rob Pickels  43:56

I remember this from the Twittersphere if I remember correctly. If I think back a few months, it crossed my mind to that’s exactly what this was.


Trevor Connor  44:05

So, I think you have this spot on. I don’t think they wrote this to say we have some answers. I do know that Dr. Seiler has been spending a ton of time focusing on this trying to come up with some of these answers, particularly, he’s been trying to find a way of how do we measure this? Which is actually surprisingly hard. I think ultimately, this was just about here’s where we’re at and raising that red flag of, yes, we’ve all talked about this, but we really do need to dive into this and figure this out.



Rob Pickels  44:37

Yeah, I think that if we get into the question of how do we do it? Is it a training study? Is it choosing one method of constant heart rate or constant power? Or you know, dealing with the drift and then seeing the outcome, you know, 12 weeks later, whatever that is. The other thing that would be really interesting to me is analyzing lactate data. I think that perhaps these profiles exist if we do a deeper dive into say, the lactate profile or even the critical power graph, you know, the power duration chart, and more of an analysis than just saying, oh, what is your watt per kilo at four millimoles? What is your power at LT1? For me, when I was doing a lot of interpretation of lactate graphs and physiology results, if you looked at, you know, Trevor, someone like yourself or Chris, you know, you guys are both, you know, really, really strong cyclists. I would know that just by the shape of your graph without ever seeing your weight, or your power, or anything else, and how your baselines react, and how you step between different stages, and what your maximal lactates were. I would be able to tell that you guys likely have more durability because of your higher training status than someone else who came into the lab, and again, this is without actually seeing the numbers, so to say, but just how the tests progress from stage to stage. I believe it would be the same thing if we look at critical power. Now, all of this is anecdotal, something that I’ve learned from testing numerous, numerous athletes, and what was very fortunate for me was that I was able to work with athletes of all levels, literally somebody beginning cycling, never doing activity, to people that were world-class, you know, absolute peloton riders, and you begin to see these nuances and these differences. I’ve always said that with lab testing, anyone can prick a finger, it takes literally no skill to get a little blood sample and put it in a pipette and put it in your YSI or the handheld ones now, I’m still old school in my lactate analyzer preferences, the real knowledge comes from the interpretation of that graph. What does this actually mean? I do believe and challenge anyone that’s doing these physiological tests to go deeper than just looking at what threshold is, you know, to understand, how are you choosing thresholds? And what does that actually mean in terms of that interpretation?


Trevor Connor  47:22

So, I just want to take a wild guess here and see if I got this right or not, but I think I know one of the ways that you could see better durability in a lactate curve, and I’m wondering if this is what you were thinking about. So, I’ve seen lactate curves, in some highly trained athletes where, four, five, six stages, those lactate levels are just absolutely flat, and then as they approach that LT2, that anaerobic threshold, that’s where you see it suddenly just kind of kick up, and then the graph quickly goes up to well over four millimoles. I’ve seen other athletes who are less trained where even though they stay below two millimoles, even at very low stages, you see a very slow rise in the lactates, you don’t see that nice flat curve, and then it just kind of gradually goes into the curve that you would see as they approach threshold. My guess is those athletes would not have as good durability, because even though it’s very, very small, you’re seeing even at low wattages they’re already dealing with a very small stressor.


Rob Pickels  48:31

Yeah, Trevor, I think that I would refer to that as an upward sloping baseline, right? We can infer some understanding about lactate production and lactate clearance from that. I think that also those athletes that have the upward sloping baselines, you know, they probably have an increased anaerobic contribution, even at relatively low workloads, it’s not overwhelming, because they are able to clear at that point in time. If you take that person that has the higher anaerobic contribution, you know, I think that you take them out into the field, and you do a 20-minute test on them, and then you do a 30-minute test on them, and then you have them do an hour time trial, you’re going to see a relatively large delta between those scores on those individuals. For myself, I kind of in some regard fall into this category, because I’m a sprinter. I grew up racing 400 hurdles and 110 hurdles and switch to cycling later in life, and if you look at my build, I’m bigger than I should be in the thighs and the calves, you know, to be an endurance cyclist, because of those type two muscle fibers. If we take sort of field testing from me, my 20-minute and 30-minute, you know, deltas between my performances there, it’s a bigger drop-off than it should be. If we take individuals like this, and this is getting into a bit of a tangent, if I were to do 95% of my 20-minute effort to determine FTP, it would be way, way above what it actually should be, way above a truly sustainable FTP number for me, and that’s, again because of that anaerobic contribution. So, when I’m determining my numbers, if I only have 20 minutes in me, then I’ll take 92% of that, if I got a good 30-minute effort in me, then I can take 95% of a 30-minute effort, right? But through this field testing through lab testing, I think that we can begin to understand the durability, right? Durability, as they’re sort of pointing out is very individual. For me, if you ask my durability in a repeated sprint test, I could be pretty durable there, you know, in a crit race, I’m going to be faring better, right? But if you put my durability in the context, kind of as they’re discussing, you know, high-intensity effort levels or drift throughout a long duration ride, then my durability is going to be relatively low, especially compared to somebody like yourself and Chris, and like I said, a lot of more, you know, people with an aerobic sort of makeup as a general statement.


Chris Case  51:07

So, you’re saying that with more research, there might be a way to give someone a durability profile? You could be durable on one end of the spectrum, or on the other end of the spectrum, you could be durable, quote, unquote, durable for sprints, or durable for long-distance, and maybe there’ll be some people that would kind of be that all around, or that’d be somewhat durable at everything?


Rob Pickels  51:34

Yeah, I think that you could do that, and I also think that you could do it from relatively common measures that we’re doing today. I don’t think that this is a brand-new test, I think this is a reinterpretation of a lot of the data that we’re already gathering on people.


Trevor Connor  51:47

Well, the thing that comes to mind for me, and I can’t remember, did you overlap with Dr. Inigo San Millan?


Rob Pickels  51:51

I did, yeah. Certainly.


Trevor Connor  51:52

So, he was very big on his 10-minute lactate test protocol, because he was trying to get at that durability.


Chris Case  51:59

It’s not just stages. Yeah.


Trevor Connor  52:00

Right. It’s not just what sort of lactate are you hitting at a stage, but can you sustain those lactates across that stage and found that’s really one of the biggest difference he saw on the top cyclists versus lower level cyclists is, they might start a stage very similar lactates, but that top-level cyclists is not really gonna change over the 10-minutes or somebody who’s not as good. They just don’t have the durability there, lactates are going to go up over 10 minutes, and you might not see that in a three- or five-minute stage. I never did ask you what you thought of that protocol.


Rob Pickels  52:34

It was interesting, it was an interesting mix of the more traditional, you know, say a four-minute stepwise test, and then also the protocol utilized for maximal lactate steady state, it was a way to kind of understand an MLSS number, but in one laboratory visit. I think that it produced perhaps slightly different results, if you looked at the interpretation of it, but I also don’t think that it produced anything that was dramatically different from a more traditional stepwise test. So, in this one, it’s certainly a personal preference, I’ve used both to great success, and I would definitely support the use of it, but I’m not going to say that it’s an absolute necessary protocol.


Trevor Connor  53:15

For any of our listeners who don’t know, the MLSS test, is just brutal, you do 30 minutes, so you try to basically approximate what your MLSS is. Then you do a series of 30-minute tests right around that range, and it’s the highest one wherein the 10-to-30-minute part of the test, you see a rise in lactates as less than one millimole. It is a tough test, to do one all-out 30-minute effort at a given wattage is tough to have to do multiple, it takes a little time.


Rob Pickels  53:52

In my understanding of the test, it’s traditionally multiple days.


Trevor Connor  53:56



Rob Pickels  53:56

Day one is a traditional stepwise test to kind of understand the range that you’re then going to have to test on day two because you can’t go out and do that, you know, 30-minute or long-duration stages, you know, at 25-watt increments like you might normally do, because otherwise, the person would be there for four or five hours in the lab.


Trevor Connor  54:17

This is also why it’s used in studies, so used in the lab, you would never see elite cyclists agree to do this because it would kill their training for over a week.


Rob Pickels  54:29

Trevor, I’m a big picture sort of guy and I need to ask the question, does this matter? Does the durability concept matter? The reason that I bring that up, is we kind of understand that this is happening in the background, I can understand it maybe being important for characterizing someone for identifying a strength or a weakness, but in day in and day out training, does it matter? I’m going to pause it that, I went on prescribing training zones, most everybody describes a range, right? Base is not say, 200 watts, we would typically say that a base or zone one or whatever system you want to use, you know, is between, 175 and 205 watts, and I’ve always advocated that somebody trains toward the middle of their zone, right? Because we’re understanding sort of that the stimulus in that range is about the same, and then we’re accumulating that stress over time. So, if somebody is getting a recommendation of training in the middle of their zone, say 190 watts, does cardiac drift? Does any of this stuff moving up or down matter if we’re staying within that range that we know is appropriate?


Trevor Connor  55:47

That’s a good question. You know getting the athletes to actually train in the middle of the zone versus one watt below the top end of the zone is really hard to do, because that’s what they tend to like to do.


Rob Pickels  55:58

That’s why you cheat their zones down without telling them.


Chris Case  56:01

Assuming that the zone is actually accurate, right?


Trevor Connor  56:04

Well, so my answer to the question, because I am a big believer in the importance of durability, I think it’s an important thing to train. I think as a coach, it’s a really important thing to have a metric of is this improving because it goes back to the good old expression of it’s not how hard you can hit a five-minute climb, it’s how hard you can hit a five-minute climb after four hours, and you have a lot of people who can be super strong on the start line, but when they get to the end of the race, it’s not there because they don’t have the durability. So, I think it’s really important to train, and as a coach, I want to be able to see are my athletes improving?


Rob Pickels  56:43

Trevor, that’s because you’re still stuck in the peloton. Frankly, when I’m trying to snipe a Strava KOM, I’m not doing it after four hours. I’m warming up on the trainer and I’m riding straight to the climb.


Chris Case  56:54

With your skin suit on.


Rob Pickels  56:56

That I need to haul myself up, so you’re looking at it from the wrong perspective. Our listeners, Trevor, they’re not in the pro peloton, man.


Chris Case  57:06

He said, “our listeners.” Wow.


Rob Pickels  57:08

I’m not part of the team now?


Chris Case  57:10

You can be, you’re doing a great job today.


Trevor Connor  57:12

I’m liking this, yes, smack me down. So, yes, if you ride no more than 30 minutes and in those 30 minutes, you go for multiple Strava KOM’s, screw all this, why did we even talk about this study?


Chris Case  57:25

Durability is irrelevant for you.


Rob Pickels  57:27

Is that a running theme? Why are we even talking about it?


Trevor Connor  57:31

I’m starting to wonder that myself.


Chris Case  57:36

With that, should we move on to the final study?


Trevor Connor  57:41

This is kind of the simplest of all them.


Chris Case  57:43

Alright. Well, Frontiers in Physiology is the journal it published in back in May of 2021. So, not too long ago. Titled, The Aerobic and Anaerobic Contribution During Repeated 30-s Sprints in Elite Cyclists. This comes from a Norwegian group, the lead author being Nicki Winfield Almquist.


Study 3: The Aerobic and Anaerobic Contribution During Repeated 30-s Sprints in Elite Cyclists

Trevor Connor  58:07

But you will notice the third author is Dr. Rønnestad.


Chris Case  58:11

Yes, he’s buried in there, and that is a name that probably a lot of listeners have heard of, because he has this famous, somewhat famous, Rønnestad protocol. We’ve had Dr. Cehung, do some workshops on our site to pick apart some of the studies he’s done and some of these protocols that he’s sort of innovated. So, tell us a little bit about this particular study, Trevor.



Trevor Connor  58:34

So, the short version is they’re really trying to look at the impact of repeated sprints on high-level cyclists. In one of the studies, they do at the end of it, compare them to amateur cyclists to see if there’s a difference, but in the particular protocols here, they only used elite cyclists. So, they had two protocols. One was just a single day, it was a three-hour ride, so they’re actually getting into this durability concept here, too. Towards the end of each hour, the cyclists would do three, 30-second sprints, separated by four minutes, so you’d really bring down the power and recover in those four minutes, and then ride at about 50% for the next hour, and then repeat the three sprints, so they did this three times. What they were looking at was whether they were able to maintain power, and they were also looking at how much of that sprint power came from aerobic energy systems versus anaerobic energy systems.



Trevor Connor  58:34

The short version is, you actually in these elite cyclists saw from set to set, so from the first set to the third set, there was really no change, but within the sets, you saw a decrease in the power from the first, to the second, to the third, and most of that loss was from anaerobic sources. In the second study, so they use similar protocol, at the very beginning before they did their intervention, they did a series of four sprints separated by four minutes to measure their total power and then their anaerobic and aerobic contribution. Then these cyclists would do a 14-day training camp, high volume, so one group just did all the volume, the other group added in a total, so not sets of, but a total of 12, 30-second sprints every third day during the 14-day camp. So, that was the only difference between the two groups, then they had a recovery and then they retested them with those four, 30-second sprints separated by four minutes to see if their power improved and to see if their energy contributions changed at all. The short version of it is, you saw no improvement in the group that didn’t do sprints during the camp, in the group that did add those sprints, and again, not a lot of sprints during that camp, you saw improvement in their overall power, a that mostly came from anaerobic sources. That’s the short version of it, did I miss anything, Rob?


Rob Pickels  1:01:15

No, I don’t think that you did it all, and interestingly, I read this study after reading the Seiler study. I just kind of went like favorite authors like down the list, I’m taking these two first. I honestly thought that you were doing a durability theme, Trevor, when I read these two, back-to-back because, you know, I immediately saw that durability concept breaking out in here, even though it wasn’t necessarily named.


Trevor Connor  1:01:41

I saw that too, that was accidental.


Rob Pickels  1:01:43

Perfect. It was serendipitous.


Trevor Connor  1:01:45

Yes. No, it’s kind of neat, isn’t it?



Rob Pickels  1:01:47

Yeah. I think the big takeaway from this, for me is training specificity, right? I mean, if you train sprints, you’re gonna sprint better. While I agree that it wasn’t a lot of sprint training, multiple 30-second sprints throughout a multi-hour ride is actually quite grueling, if you think about it. We’ve all sort of been there, 30 seconds is a really difficult time to hit because you’re all in and you are hurting by the end of that. So, yeah, these riders put in work, and they got better at what they were doing, right? Their durability increased. What I thought was interesting was that throughout the course of the ride, the average power of the three sprints did not necessarily diminish, right? So, they did three sprints at hour one, at hour two, and hour three, essentially, and the average of those so they were able to fully recover in the low-end intensity riding in between there, even though we saw a detrimental effect within each sprint set.


Trevor Connor  1:03:00

So, that, again, goes back to the durability concept, and yeah, they really pointed out when you are talking about elite cyclists, this shows that in a race, they have this ability to keep going hard, as long as they get some recovery time, they aren’t going to see that big a drop in their power, if any at all, they can keep doing this. Now, they did compare this, and I didn’t remember if they said whether this was previous studies that they had done, this group have done or another group have done, but they did have similar results from another study in amateurs and you did not see the same thing. You actually saw a big drop in the anaerobic contribution, you saw a big drop in power, and you didn’t see them fully restore their power. So, that’s one of the big differences.


Chris Case  1:03:42

Could we help listeners out there understand, how did they define amateur versus elite? Is that worth mentioning?


Defining an Amateur vs. Elite Athlete

Rob Pickels  1:03:52

It is and the reason it’s interesting is I don’t know that these were really elite riders. To tell you the truth, if we go through the demographics of these riders,


Trevor Connor  1:04:05

They were strong, not amazing.


Rob Pickels  1:04:06

Exactly. They’re better than I am, but we’re talking body mass of 76 kilos, that’s about 167 pounds, height was 183 centimeters, that’s about six feet tall. So, relatively tall and relatively skinny. Their training volume was 55 hours over 30 days, so we’re talking about 13ish hours per week, and their power output at four millimoles of lactate was 4.3 watts per kilo, if we take the average kilo then that’s about 326 watts. Their VO2 max was 73.4, at their body size that’s 5.5 liters, which is good but not incredible. In their watt max at the end of their VO2 protocol was 6.3 watts per kilo or 480 watts. These riders in my opinion were almost in a no man’s land, they weren’t strong enough to be a strong larger rider that’s a powerful one-day classic sort of rider, and they weren’t small enough to be more of a GC type of rider. They’re sort of like me, not quite small enough, not quite strong enough.


Trevor Connor  1:05:18

So, particularly look at that 4.3 watts per kilogram and four millimoles, if you want to be racing in the professional peloton, you need to be well over five.


Chris Case  1:05:29

So, these are more like elite amateur racers, perhaps?


Trevor Connor  1:05:31

It’d be like a decent, probably really good CAT2, maybe an okay CAT1.


Chris Case  1:05:37



Rob Pickels  1:05:38

I agree with that.


Trevor Connor  1:05:39

So, I just looked through and I couldn’t find anything about the selection, how they particular selected these athletes. Later, when they compare it to amateurs, they just said amateurs, you know, that wasn’t part of this study, so they really didn’t go into the details there.


Chris Case  1:05:53

Very good.


Trevor Connor  1:05:54

So, unfortunately, I can’t answer that question for you.


Rob Pickels  1:05:57

Trevor, can we talk a little bit about the aerobic versus the anaerobic contribution of this?


Aerobic Versus Anaerobic Contribution

Trevor Connor  1:06:02

Yes, I was hoping you would go there.


Rob Pickels  1:06:04

I found the results to be certainly understandable, I would assume that a decrease in the anaerobic contribution is what’s leading to the decrease in sprint performance, and the aerobic would maintain relatively similar in terms of contribution just because of the durability if we use that word again, of the aerobic versus the anaerobic system. I’d love to get your comment on that, but I’d also love to talk more about the gross efficiency method that they used for determining this. I don’t want to get in the weeds too much, but I found this to be a very interesting and perhaps difficult manner to try to elucidate the aerobic versus anaerobic situation. I understand that they chose it, I’m sure they had great reasons to, but there were other things that seemed a little bit more obvious to me that might have been a more straightforward choice.


Trevor Connor  1:06:58

Rob, that is the smartest thing I’ve ever heard you say.


Rob Pickels  1:07:01

And you guys have heard the second and the smartest thing ever.


Trevor Connor  1:07:04

In one day. We got it all right here.


Rob Pickels  1:07:06

That’s because I had three shots of espresso this morning, the extra one was for good luck. There we go.



Trevor Connor  1:07:14

Yeah, I actually circled the same part and actually put a big question mark beside it. They do point out, it’s very easy to figure out the aerobic contribution, you just hook them up to a metabolic cart, you can actually measure that, there is no direct way to measure the anaerobic contribution. So, they talk about the different methods. There are multiple ways in the literature to do this, and as you said, they went with this efficiency method and brought up essentially that durability concept of saying efficiency changes over time, so we chose to use this efficiency method to determine the anaerobic contribution. Maybe I should read those because I actually want to hear your responses, let me find this. The “aerobic contribution during the first 30 seconds sprint was calculated using the GE determined immediately before the first sprint, the aerobic contribution during the last 30-second sprint was calculated using the GE determined six minutes after the last sprint. Subsequently, the anaerobically attributable mechanical power was calculated by subtracting the aerobically attributable mechanical power from the mean power output of each 30 seconds sprint.” Basically, saying they calculated the aerobic and then the anaerobic contribution was total power minus the aerobic. The whole figuring out the aerobic contribution, why 30 seconds before the sprint? Why six minutes after the sprint?


Rob Pickels  1:08:39

And why the second one was the average of the two, right? They weren’t able to calculate the middle sprint that they did in these sets, and so they average the two. That’s just assuming a linear decrease between them, and we don’t even know that that’s a correct assumption.


Trevor Connor  1:08:55

Yeah, I put a big question mark beside this, and I admit I left it there. You actually brought another study that brings up this question of efficiency. It sounds like you really had big questions about this and dived into it. So, why don’t you jump into that?


Rob Pickels  1:09:11

Trevor, I brought two additional studies, actually, one was the study that they referenced when they chose this gross efficiency, they had referenced some previous work that had been done, and frankly, this gross efficiency method was foreign to me prior to this. So, I wanted to understand that a little bit more. The second study that I brought, you know, because this is essentially, I feel like me going back to grad school, I feel like I walked in today to take a grad school exam. So, I threw it back old school. I threw it back old school and grabbed a study that we had covered in my grad school days with my advisor, Dan Heil, so thanks, Dan, your education is coming back, full circle. That study was actually from 1975, and it was from Glenn Geyser and George Brooks, right? So, two just amazing founders of this and that was looking at muscular efficiency during steady rate cycling. If we go back to the gross efficiency concept, you know, this wasn’t even like a true gross efficiency in the whole scheme of things, right? What they were doing, and I need to sort of read this equation, its GE, gross efficiency, can be defined as the ratio between the mechanical power output and power input in which power input can be calculated from VO2, which is expressed in liters per second, and the oxygen equivalent. So, that power input now they go even deeper. It’s VO2 times 4940, times RER, times 16,040. I just feel like there’s a lot of assumptions and equations here, right? Not even talking about good old fashioned gross efficiency, they’re sort of trying to extrapolate this based on the indirect calorimetry that’s happening with the person in the RER, and they’re trying to maybe make it more robust than gross efficiency, but at the same time, we’re introducing so many unknown variables into, you know, a research protocol where we’ve already had questions about why did they do it immediately before? Why do they do it six minutes after? Why was the middle taken as the average of those two? We just have multiple layers of questions stacking up on top of each other.


Trevor Connor  1:11:30

I totally understand this is a more challenging problem than you would think, you would just go, why not just measure oxygen consumption, and then, as they said, subtract that from the total power? The issue is there’s a thing called oxygen deficit, when you’re talking about 30 seconds sprint, if you measure the oxygen consumption during that 30 second sprint and say that was the total aerobic contribution to the 30 seconds, you’re gonna get it wrong, because there is a delay effect. So, you have to figure out how long after that sprint do you keep measuring to get the true aerobic contribution to the sprint effort? That’s what they’re trying to figure out here, but I agree with you, they had to make a whole lot of assumptions.


Rob Pickels  1:12:14

So, the question is why didn’t they just take it out of the oxygen conversation in general? I almost feel like this is a single issue, right? They chose this gross efficiency method, because of the change in gross efficiency over time, and they wanted almost to understand, again, that durability issue without naming the durability issue in this, and so they were looking for a measure that might change over time, as these riders rode, you know, for three hours. I think a much cleaner way of doing this would have been from the mechanical side of things and would have gone with critical power, and W-prime, you know, your anaerobic capacity. It’s interesting, because the paper that they reference that they got this gross efficiency, you know, sort of validated in was actually a paper where the second author was Phil Skiba, right? Who does a lot of work in the critical power sort of theory? That paper laid out a lot of the amazing benefits or how critical power can be accurate across so many different situations, and there were also questions that they had raised about the gross efficiency in this paper that they’re referencing to support their use of gross efficiency, and how you need certain considerations, and how things change, and how it might not be accurate in these different situations.


Trevor Connor  1:13:31

So, my question to you, Rob, is since they were consistent with the methodology here, putting aside that there are a lot of assumptions here since they are consistent, do you feel they are able to draw the conclusions they drew?


Rob Pickels  1:13:51

Trevor, I’m going to say yes and no. Reading from the results part here, it says, “the relative anaerobic contribution decreased from the first to the second sprint, and from the first to the third sprint.” Big picture, I think that we can understand that, and we can say, yeah, that makes sense, we know their performance is decreasing, and we know that a decrease anaerobic is likely going to happen there. But if I continue, it says, “while the relative aerobic contribution increased from the first to the second, and from the first to the third,” this is a nuance that I have to question because we’re questioning their methodology and actually defining what the contribution is for both of these, you know, and they’re claiming a relatively small increase, we’re talking you 36.4 to 38 and 36.4 to 37.6%, we’re talking about a change of 3%?


Trevor Connor  1:14:51



Rob Pickels  1:14:51

I don’t think that we can go that significant, to tell you the truth. Not without validating this perhaps with a different methodology to see if we arrive at the same conclusion. So, big picture yes, fully agree with the study think it’s terrific, think it’s great information, think it explains a lot of the concepts that we’ve been talking about today, but the deep sort of nuance, I wouldn’t hang my hat, on a 3% change in aerobic contribution.


Trevor Connor  1:15:20

That is the third smartest thing I’ve ever heard you say.


Chris Case  1:15:54

Thanks for joining us, Rob.


Rob Pickels  1:15:56



Trevor Connor  1:16:00

That was another episode of Fast Talk, subscribe to Fast Talk wherever you prefer to find your favorite podcast, be sure to leave us a rating and a review when you do. The thoughts and opinions expressed on Fast Talk are those of the individual. As always, we’d love your feedback, join the conversation at to discuss each and every episode. Become a member of Fast Talk laboratories at and become a part of our education and coaching community. For Rob Pickles and Chris Case, I’m Trevor Connor. Thanks for listening.