Physiological Perspectives in endurance sports: A Conversation with Stephen Seiler

This article is a transcription from the Sitkotalks episode that has been published in my Youtube channel. You can watch the interview under the following link:

Sebastian Sitko: Welcome, everybody, to the second season of Sitkotalks. This season comes with many novelties. One of them is that we’ll have international guests in this podcast. Last year, we started with a special guest coming from Spain, Aitor Viribay, nutritionist at Ineos Grenadiers. And this time, I wanted to invite also someone very special. Also, given that we are going to start with international guests, we are here with Stephen Seiler. I think that Stephen doesn’t need any kind of introduction, any kind of presentation. Everybody knows him. But if there is someone who is a little bit lost, Stephen is currently professor at the University of Agder in Norway. He’s a very prolific researcher, in my opinion, one of the biggest researchers in endurance sports physiology in the last decades. And he has also been a consultant for several endurance teams, such as the Uno X cycling team in Norway, and professional athletes and also brands such as Adidas. Many, many thanks for accepting the invitation for this talk.

Stephen Seiler (italics): Thank you. It’s a pleasure.

So I brought Stephen here to talk about several topics regarding endurance sports training and specifically cycling. Some of the research that Stephen has performed is related to training volume and intensity and also external and internal load metrics. So I would like to address these topics because I think that he has a lot to tell us. So first question, Stephen, since the start of the century, we have seen many new advances coming into the field of cycling. We can talk about power meters, which have brought the opportunity to monitor external training load. We can talk about nutritional advances also in the means of carbohydrates, increasing amounts of carbohydrates in training. And this has also changed the training interventions. And here goes my question. Which have been, in your opinion, the biggest advances that we have had in our field in these last two decades, and what kind of changes they have brought in the way we are training the athletes?

Well, obviously, being able to measure power has been a big change. But that’s very specific to cycling. So we have to remember that in most endurance sports, you can’t measure power in the same way in the field, but in cycling we can. And so that’s had quite a bit of impact. However, I also believe that the top teams, we see that they understand a lot more about balancing training, stimuli, and fatigue. And they are reducing the number of races that the athletes do. They’re a bit more careful to give them some periods during the season where they can go back to normal training. So there seems to be a better understanding of the fact that you have to keep your athletes healthy. And so that’s, I see that in the data and in my discussions with teams. Of course, nutrition in cycling has had a huge impact. I mean, we’re seeing dramatic changes in the amount of carbohydrate intake and kind of changing the assumptions about how much carbohydrate can be taken on. Rewriting the nutrition books in a way, you can argue. So that’s not my key area, but when I talk to pro cyclists, they say that nutrition has been a really big change.

Do you think that current athletes are much healthier than what they were two decades ago?

Yeah, I think at least we see that professional teams understand that their biggest resource is their athletes, that they’re a team of 30. That’s the typical size of a world tour team and that they have to distribute that load at any given time of those 30. They’re gonna have athletes that are sick, injured, over fatigued, and they’re, so they have to be constantly managing that resource, which is their team. So I do think that there’s a better understanding of that. And of course, the behaviors of the athletes have also changed. or they think more about being a 24 -hour athlete in the sense that you know sleep nutrition stress recovery and so forth so it’s not just the teams but the athletes also understand this process better.

Related to this one of the of the ways to improve athletes health is to monitor their training load. Yesterday precisely I was reading your chapter in Iñigo Mujika’s book about training where you talk about volume and intensity in endurance sports and here goes my second question: Which is, in your opinio,n the most important one? I know it is not a yes or no answer but if you had to choose one at which parameters would you look at to decide? For example there are people who have not a lot of time to train. So maybe in those cases, you will prefer to choose more intensity versus volume. What’s your opinion on this topic?

Well, I always start with frequency. It’s just say the first thing you have to do is establish a habit of training. So if it was your mother and you wanted to get her off the sofa and she wants to run a 10K in a year, the first thing you’re going to say is, well, mama, let’s agree on how many times you’re going to get out the door. You’re going to put your running shoes on, you’re going to put on the kit I bought you, the warm up suit or whatever. And then she says, well, okay, I can do that three times a week. And so you’re going to try to establish that habit with her of getting out the door and just doing something. And then slowly the something, you’ll stretch it out. And then only after a couple of months would you start talking to your mama about intensity, right? And we’ve learned that from top athletes. We’ve learned that from endurance athletes is that the most important thing is consistency, that they are able to stay healthy and they’re training very regularly. I mean, I’m just looking at data from a absolute world class grand tour winning athlete and looking at their training in a February month. And it’s 94% low intensity, green below the first threshold. And this athlete five months later or six months later is winning a big event. So I think that’s what we see is that intensity is the top of the pyramid. It’s not the bottom. The bottom of the pyramid is frequency and volume. Now that frequency and volume for recreational athletes is going to be a lot lower, but that’s still what you’re trying to make sure that you’re defending. You’re saying, I’m going to get out those four days a week. I’m going to keep my consistency going and if that means I have to reduce the amount of hard training so that I recover I’m going to do that.

One of the main topics of your research is that data from the analysis of top athletes shows that in endurance sports they normally train a lot mostly quite easy and with very specific bouts of high intensity which is what you’re talking about. Would you still apply this to people who have very little time to train?

Well, you know if it’s somebody that only trains three days a week for 45 minutes you know then they can do a lot of things wrong and they can’t get over trained because they’re just not training enough and they have a day of rest between each workout so pretty much they can do whatever they want. But what’s gonna happen is if they train the same way all three days, they’ll stagnate pretty quickly. So even with the three day a week athlete, I would try to have them do one of those workouts, have it be more extensive, longer, to use the effect of duration on the adaptations. And then I would have one of the workouts be more intensity oriented, something like an interval session. And then probably the third workout would be more just in the kind of in the middle. So even with a three day a week athlete, I would try to use both intensity and duration in a way that creates variation for them. It’s not the same every day. And the stimuli are a little bit different. And then clearly we see if an athlete’s training maybe seven or eight hours a week, for sure it makes a difference. Already with that kind of volume, that if they get the intensity distribution right, if they make sure easy stays easy and hard is hard, they tend to get better. We just see it time and time again. So I would say that we do, we can still learn from the 25 hour a week type athletes, even though we’re only training a very small part of that. Because what they show is discipline, making sure that they work their plan. If my plan today is a two hour easy ride, then I’m gonna achieve that. I’m not gonna just turn it into something else, as soon as somebody passes me on the road. That’s the typical recreational rider, right? As soon as somebody cycles past me, here we go. I’m racing, right? I was gonna just do an easy ride, but now my brain just went, whoop. So that’s what we see is the best athletes have better discipline up in their head.

That’s an important take. You have briefly mentioned (I know this is an off topic) overtraining syndrome. Do you really believe in overtraining syndrome as it is stated in science? Have you seen any cases?

Yeah, I have. I’ve seen athlete careers end because of a very clear overtraining syndrome. Now, do I understand it all? No, but I have definitely seen it. It’s rare. I don’t think it happens very often now. I do think that science has come along and the coaches are better, the athletes are better. I mean, the whole system is better at being careful, but it still happens and I have seen it. One very specific athlete, I saw it up close and personal, tried to help and ultimately that athlete retired.

In case anyone wonders, we are talking about months of rest without returning to the previous level.

I would say it’s very rare now. That’s good, obviously. But overreaching and stagnation is not rare at all. In fact, I would probably say that that’s very, very common.

That’s where my question comes from because I’m younger and I haven’t seen any case of overtraining as it is stated in the literature. So I was wondering if, in your case, that’s an important take also. We have briefly mentioned power meters and their role in the training process. And here I would like to talk about internal versus external training load and the impact that power meters have had on the second one. Do you believe that power meters have been a game changer in the world of cycling?

It’s hard for me to say if game changer is the word, but definitely I think it has changed the way they cycle. When I speak with athletes, any top cyclist will be very aware of their power outputs. They’re getting that feedback in races. It’s one of the few variables that are allowed in races at the World Tour level, meaning that they’re not allowed to measure glucose or blood pressure or heart rate. A lot of things, maybe they could. Core temperature. So power is one of their main feedback, heart rate and power. So I think it has had an impact, but the problem is that some of the riders have decided that, well, I don’t need to measure anything internal. I can forget about heart rate, forget about perceived exertion. I’m just going to train to power. I don’t think it is a positive development.

Would you ban power meters from competition?

No, I don’t think I’d ban them. You know, I understand there has been discussion about it would make the racing less predictable. It’d make the racing more interesting because now athletes are so tuned into their powers. You know their threshold powers and so forth that they’re racing kind of somewhat constrained by that there, but I think We still see great racing. I mean We’ve never seen better racing than we have now, so I don’t think it’s hurting racing.

I think that this has been overstated in the media because in the end when you work with pro cyclists normally you will see that they can, even in the absence of a power meter, they are great at knowing the rate of perceived exertion. So I think that this wouldn’t change as much as people believe.

Anything you do 25 hours a week, you know, you get pretty good at. So, yeah, I agree with you 100% they know their bodies extremely well. But the power gives them a calibration, heart rate can give them a calibration too, check and see and that’s where this thing about being able to both measure the external power, the external work and the internal trying to have some calibration of saying well, how is my body responding to that same 350 watts or you know? And when I use 350 for most of us, that would be something close to our maximum six-minute power. But for these athletes, it can be something close to their first threshold power. And that’s the facts that’s how much better they are, you know 350 watts is the first now they finally start to produce some lactate. They go from 1 to 1 .6,  and now they are at 340 350 but also they get tired also they have day bad days. Also, they have to pay attention and then they’re gonna be looking at perceived exertion. They’re gonna be looking at heart rate. How am I, you know are the brakes on is my body in need of an extra day of rest and things? So I do think that we need to measure both, internal, external…

I know this is a weird question, but I want to know your take about this: If you had to choose one single metric to train somebody, which one would you choose: power, heart rate, blood lactate, perceived exertion?

Probably perceived exertion If I only had one, yeah, you only had to use that every day. Yeah, and I would want to make my athlete learn their body. You know and really understand because when in the in the final outcome of it, that’s that’s the best device. They have is their brain so yeah, I would still be and and the research still indicates that the brain is sensitive to these small changes that say I’m getting tired and those changes come earlier than hormonal changes or even heart rate can go up and down so it can be confusing. You know you can manage to hold powers for days, but it’s getting tougher. So I still think perceived exertion is a really important tool yeah.

As an example in one of the previous episodes I interviewed the female trial running world champion and she told me that she basically trained based exclusively on rate of perceived exertion. I know that in trial running We have several problems to monitor for example power output which is an attempt now but is still in the early phase.

Yeah so I think about Kenyan runners and Ethiopian runners and if they have a heart rate monitor that will be about the most advanced piece of equipment they will have but many of the time most of the time they’re going on field so and we know that they’re breaking world records doing that kind of thing so it’s clearly possible.

Okay, last question, Stephen. I think that endurance training comes and goes in trends, so for example I remember several years ago we had like a huge trend of high intensity interval training and you know CrossFit etc. In the last two to three years especially after Covid I have seen like a huge trend in zone two training, this low intensity training many people talking about it and many studies performed on it do you really think that it it’s just another trend or is it really that magical or is it just in line with what you have provided in your previous studies that show that you know the volume at low intensity is really the key to performance. What’s your take on it?

Well, Iñigo San Millan has talked about zone two. In my world zone two the way he describes it is still in that under lactate threshold zone but it’s a you’re basically saying that the green zone or that area you’re you’re you’re pushing up a little bit closer to the the first threshold it’s it’s not a super clear definition for me where zone one ends and zone two begins because I don’t believe there’s a very clear physiological definition of the distinction but but they’re both in that aerobic low lactate region. So in that sense, it’s a positive message. The only problem might be that some people are going to interpret zone two, that they have to be really up next to the edge of their threshold, and then they go over. Because when athletes make a mistake in training, it’s almost always that they push too hard, not that they go too easy. Does that make sense? Recreational athletes, they don’t hit the wall. They don’t stagnate because they go too easy. They stagnate because they go too hard. And then they don’t recover, and they have other stresses in their life, and they just kind of stagnate, doing lots of short, hard workouts.

You have mentioned thresholds, because we have three or five or even seven zone definitions. Do you really believe in these thresholds or we are just talking about physiology as a continuum?

No, I mean definitely you can measure pretty clear break points. Physiologically now, they’re not they’re not exactly precise, but they’re a bit fuzzy. But they are there if you’re good at doing your testing. And if you have athletes that are fairly well trained, they can be quite quite precise quite clear. Now if you’re testing untrained people or people that aren’t very well trained, They’ve been doing a lot of mixed intensities. What we see is they do not have that very clear flat portion of their curve, they tend to kind of just go up from the start but if they’re if their intensity discipline gets better if their low intensity stays low and that then in a period of six or eight weeks their profile changes a lot and it starts to look more like the profiles of elite endurance athletes not the absolute watts, but the shape. So I still do think that it’s it’s more about the clients. So we have you know that if you test well trained athletes man, it’s just really it can be just so clear. Those break points, but it’s because they they have really good metabolic control.

Well, this is very interesting. So would you suggest using different protocols when measuring gas exchange or lactate in highly trained versus moderately or untrained subjects?

Well, I would in some ways I would say well I’m not gonna do a lactate profile on a beginner athlete, someone that hasn’t done anything. I’m first gonna kind of get them down the road six weeks of training try to get them to train just really easy at first. Do a little bit get there just start getting past that initial phase because until we get some training in their body, it’s like that lactate profile just doesn’t tell us much of anything. Does that make sense? So they’re just not ready. Their musculature is not ready. We don’t get a good picture. And basically the picture we get is they don’t have metabolic control. Everything turns on as soon as they go out the door and they don’t have that flat phase. So that’s really the first thing I wanna see is can I get this athlete to the point or this person that started training so that we can actually find a baseline, find an intensity where their lactate stays low and their heart rate flattens out. Those are my two. I wanna see that flat heart rate, which means, hey, I’ve got it under control. I’m in a steady state situation. That doesn’t happen when they first start exercising. But it comes. Within six or eight weeks, we start to see it.

Okay, would you say that the this first visible adaptation to training occurs after six to eight weeks?

I mean you see some things almost immediately, but they get into a habit, their bodies start to show some adaptations, the initial soreness phase goes away. I think six to eight weeks is a good starting point that now we’re ready to really train. Six to eight weeks. You really shouldn’t try to do interval training or anything like that. You should mainly just get the body used to that you know because it’s a huge change to go from not doing anything to an hour running or an hour cycling right. That’s a big change. So let’s do that first okay.

All this conversation evolved around low intensity training and the importance of volume and in several of your papers I have seen that this has a huge limitation. Which is if you want to perform lots of training hours at low intensity you need motivation and I would like you to provide like one two or three bullet points to keep in mind for the amateur athlete who wants to to increase his training hours.

Well, it’s everything we’ve ever seen about doing anything. Well the process has to be enjoyable and so one of the things we see is that you know when I talk with elite athletes, they say yeah, you know we train hard, but we also have fun and especially on our long rides. We’ll stop for coffee. We’re laughing and talking to each other. So there’s some camaraderie. There’s a social environment, those long easy… You can talk to each other. You can enjoy the environment around you because you can be distracted. That’s one of the nice things about low intensity work is your brain doesn’t have to zero in and focus on everything. That’s happening in your body. It can be looking out and seeing the green grass in the spring flowers so, you know when I hear from these wonderful athletes like Kipchoge or Kilian. They are tied into the environment. They love the nature that they’re getting to train in they see that as a joy that they’re allowed to be out in nature. I think that’s one of the things I would encourage recreational athletes to think about is enjoy it, enjoy being outside and or or whatever you’re you know that environment you’re in. Don’t just think of it as work because even the best athletes in the world, they don’t think of it as it’s just work. They love being outside and being able to do what they do. Okay, and there are some hard days, of course. Yeah, but all the days can’t be hard.

So a good advice will be do whatever you want, but that must be something that will keep you training in the long term. The concept of adherence…

Yeah, I think endurance is not just endurance physiologically, but it’s a long term, you know, it’s a long game. Hopefully i’m going to still be cycling when i’m 75 years old. I’m still going to be using my body, I hope if I live that long so that means I have to think about how to make it long game sustainable, right?

Perfect. I think that that’s a very nice summary for this conversation. Again many many thanks for accepting this invitation. It was a pleasure to have you here and hope someday we’ll talk again in my podcast.

Thank you for the good questions. Bye. Bye to all.