Sept. 29, 2022

"Muscle Glycogen in Elite Soccer" with Professor Magni Mohr

"Muscle Glycogen in Elite Soccer" with Professor Magni Mohr

Episode 175 of the Institute of Performance Nutrition's "We Do Science" podcast! In this episode, I (Laurent Bannock) discuss "Muscle Glycogen in Elite Soccer" with Professor Magni Mohr PhD (University of Southern Denmark).

Discussion Topics Include:

  • Review of what we know, and likely don't know regarding muscle glycogen and football performance, fatigue, and recovery
  • Physiological loading, end-game fatigue and glycogen depletion in soccer
  • Muscle glycogen and potential fatiguing mechanisms
  • Implications for between-game recovery
  • Points to consider in future soccer

Podcast Episode Transcript: Download PDF Copy

Key Paper(s) Discussed / Referred to:

Related Podcast Episodes:

Check out our other podcasts, publications, events, and professional education programs for current and aspiring sports nutritionists at www.TheIOPN.com and follow our social media outputs via @TheIOPN

Transcript

EPISODE 175

 

[INTRODUCTION]

 

[00:00:00] LB: Hi, and welcome to episode 175 of the Institute of Performance Nutrition’s We Do Science podcast. I'm Laurent Bannock. And today, I had a great chat with Professor Magni Mohr. Some of you will know who Magni is. Some of you won't of course. He is going to tell you all about himself as we kick off our discussion for you in a minute. And what we talked about was muscle glycogen in elite soccer. Now, those of you that are fans of, have followed Magni’s work over the years, of course you'll know he's been heavily involved in soccer and football as a researcher and also as a practitioner in various settings, which is something we discuss as we explore Magni’s own academic and professional journey, which I think is particularly relevant to how our conversation opened up when we talk about his perspectives, and mine, to a certain extent, but his perspectives on the implications that muscle glycogen an elite soccer needs to have as it relates to performance, fatigue, and recovery. 

 

Whether you're a practitioner, a researcher, a strength conditioning coach, and of course, a nutritionist, we get into a number of different aspects of this topic that I think you'll find particularly interesting. So, for example, the evolution of football as a game has changed quite a bit over the years. It's a crazy bonkers sport. But of course, now, particularly in the elite setting, it's the congested fixture schedules, the nature and number of all international competitions, the tournaments, which I am particularly familiar with, of course. But also, the sheer volume of training sessions and the types of training. And of course, the gadgetry that's involved, whether it's from research, or whether it's in the club, or in a traveling team setting. And I'm thinking things like match analysis, as well as methods to assess body composition, of course, in the lab. The more regular use of things like the muscle biopsy technique and so on changes the way in which we see this information come out. How we see the value of that knowledge and the relevance of it in different contexts. I love all that stuff. And we're going to get into that as it relates to elite football, elite soccer, in just a minute. 

 

But before you listen to this conversation, I am aware that I haven't done a podcast in a little while. I've just been super busy. We got some massive things happening at the IOPN. In fact, if you go to our website now, you will see that we've just launched the latest version of the IOPN diploma, or our advanced professional diploma in sports nutrition. It's evolved to another level. And there's a massive new excitement that are associated with that program. So, you can learn about that on the website with the new course overview, new prospectus. 

 

And in the very near future, there's going to be some very exciting announcements that relates to our flagship program there and some associated things that we're about to launch. And also, that relates to us as a status as an institute. I just can't wait. But anyway, I can't say it now, because I'm not quite ready. But depending on when you listen to this podcast, do go to our website, because you'll definitely see some changes as it relates to that program, where you can also, of course, find all of the past episodes of this podcast, and access the notes and various other things that we reference throughout our conversations, including this very episode. 

 

And also, you can learn about SENPro, our software platform that enables practitioners to work with individual athletes or a group of athletes online, or as I do, for example, with my football and rugby teams that I work with. It's a fantastic tool. I know, I would be biased because it's our program that we've developed. But we keep evolving it based on real-world elite practice, and also successful effective private practice. And if that's what you're after, then do check out SENPro, because I know you'll find it useful because I use it myself, and so do many of our graduates, and students, and our staff and so on. You can learn all about that at www.theiopn.com. 

 

Now anyway, let's get you to this conversation I had with Professor Magni Mohr. All about muscle glycogen in elite soccer. Enjoy. 

 

[INTERVIEW]

 

[00:04:31] LB: Hi, and welcome back to the Institute of Performance Nutrition’s We Do Science podcast. I am Laurent Bannock. And today, I have Magni Mohr. Magni, how are you? 

 

[00:04:41] MM: I'm good. Thanks.

 

[00:04:42] JBH: Now, in the history of this podcast – and I need to find some woods somewhere, which I'll use my head to tap right now. We never had this many challenges trying to have a conversation. We've been plagued with technical issues over the past few months. But here we are. And I'm very grateful for your time. I have been particularly keen to have this conversation with you, because some time ago now, I had read your perspective paper with your colleagues. I'm not going to try and pronounce all the names here. 

 

But Peter Krustrup was one of your colleagues there on muscle glycogen in elite soccer. And I'm interested in this topic for a number of reasons. One of which is, I've worked a lot in elite soccer, particularly in tournament football, where we're constantly chasing this concept of trying to fuel up and recover our athletes. But also, part of my own personal mission, particularly with this podcast, is to bridge the pretty significant gap that does exist between the science and the evidence that we draw upon out in the sports science world, sports nutrition world, to what we want to be doing with our clients, with our athletes, in very chaotic applied settings, that is day to day practice. 

 

And for me personally, the chaos of a tournament is just mind boggling. And I can't think of a greater difference than what I see in a textbook than what I see happening day to day in a tournament setting. But of course, you know exactly what I'm talking about because you've done all of this stuff yourself, which I want to get into. 

 

But before we get there, Magni, let's have you tell us, the audience, just a little bit about who you are, your background as – How you got to where you are today basically as both an academic and as a researcher, practitioner, and so on. I know that'll be an interesting start to our conversation.

 

[00:06:42] MM: Yeah, thanks. Yeah, I'm a professor in exercise physiology at the University of the Faroe Islands. And professor in football at the University of Southern Denmark. Yeah, how I got into this, I grew up on the Faroe Islands. Small country in the North Atlantic Ocean. And did a lot of sports when I was a child. Many different sports, which is very normal in the Scandinavian region. And started playing football more seriously during my teenage years and played in the best league. Followed football like many young boys do at that age. 

 

And then I went to the University of Copenhagen when I was around 20 years old. And like many Faroe Islanders, they travel abroad for educational purposes. And that was a fantastic experience. I studied at university, which is among the world's leading sports science or exercise physiology universities. 

 

And yeah, I worked there after my studies. I did my PhD. I was employed there. Then I traveled to England, to South of England, Devon. Aery nice place as well. And worked at the University of Exeter for a period. And now I'm sharing my time between the University of the Faroes and the University of Southern Denmark. 

 

And in Denmark, I'm part of a research group that works primarily with football and team sports, both from the health point of view, but also in relation to performance. So yeah, this is like more or less my academic CV. 

 

But over the years, I've had breaks from university. And I've been working in clubs, clubs in the best Danish league for a period when I was still a student. That was – I became involved in an Italian team, Juventus. Very famous team. I was doing much analysis and helping with individual profiling of players. This was because my supervisor at university [inaudible 00:08:42] was their assistant coach. So, I became his assistant. 

 

And then I was working for Chelsea Football Club in the English Premier League for a period, in La Liga with Deportivo de La Coruña. Yeah, and then other teams as well. And I've also been in national team scenarios with the Danish national team, the national team of Cameroon. And currently, I'm part of the staff of the Faroese national team.

 

[00:09:12] LB: Yeah. And you just had a good result, haven't you? We just discussed. 

 

[00:09:14] MM: Yeah, yeah, yeah. We drew against Lithuania away, which was okay for us. Should have won that game. And then we beat Turkey at home, which was quite an achievement from taking into account that we're a small country. That's something we're really proud of.

 

[00:09:31] LB: Well, yes. And rightly so. Actually, you've mentioned a couple of things there that I find interesting that hopefully we'll get into more as our conversation gets on. Because I try and sort of not just humanize these topics in sport and exercise nutrition. And I say humanize, because a key issue in evidence-based practice is to take into account the individual needs and preferences of the individuals we're trying to impact. It's not just about doing research and applying whatever we found from a cohort of our participants and just throwing that at a group of people who are numbers or labeled as athletes. They’re actually individuals. And there's some interesting stuff there that goes as far as something you just mentioned about working, everywhere from you Juventus, to Chelsea, of course. 

 

There’s this joke in the English Premier League, that there aren't actually that many English people playing in the English Premier League. But where I was going with that is just how international this sport is. Obviously, it's the big game, football. I mean, you have – If one's title of professor of football is like royalty possibly out there. But the concept of a football player being this easily defined sort of character with the same individual needs and preferences and so on is as far from the truth as you can get. And of course, you'll have known that. 

 

But also, with your national team experiences from Lithuania to Cameroon, it makes me think of myself. In the 2018 World Cup, I was with Egypt. And then most recently with the Belgian team. And boy, was there some massive differences there. But the challenges that that presents, the nutritionist, for example, which is my specific perspective, in trying to influence what we're going to talk about today is muscle glycogen levels. Has all sorts of interesting challenges that is influenced along with factors like fatigue. You have to communicate actually with people. 

 

And then there's factors like players trying to understand why they're being told to eat certain foods. Or why they shouldn't be doing something. It's more than just a case of knowing that muscle glycogen is important. We have to have actual impact that results in players actually consuming this stuff, the right stuff at the right times, and so on. So, I think we can go down some interesting rabbit holes on this topic. 

 

But listen, it's a fascinating background that you've got. It fits what I'm trying to do with this podcast particularly well, where you have both that background of the very strong scientific pedigree behind you in great institutions. But also, you've really been at the coalface of practice, as we say, which helps you, I think, understand from both perspectives. 

 

Just before we get into this topic, because I've mentioned that, since you are somebody who has had a great deal of impact through your publications, and so on, you have a perspective on the quality and the relevance of research that should be used to inform practice. Well, what have been your perspective? Because you've obviously had some great mentors. But you've also had to see the practical application of this, so you can see how certain types of science may not be so relevant. I'd be interested to hear what your thoughts are on that, Magni.

 

[00:12:49] MM: I can go back to when I was a student at University of Copenhagen, because that’s a really strong institution where it's a sports science institution, but it's also a physiological institution. And that's where the traditions are dating back to Nobel Prize winner [inaudible 00:13:06], who won the Nobel Prize some 100 years ago. And after that, Ben [inaudible 00:13:11], who was there, and lead that institution for decades. There are really, really strong traditions in basic exercise physiology from that institution where I studied. 

 

And I think that throughout my career that has been really important that to have a more mechanistic approach to even practical stuff. And that's some of the things that I'm observing or have observed over the years, is that many things become truths in the practical scenario maybe without having the scientific evidence. And I see a lot of people working only with practical issues, or only with descriptive research and may have difficulties in understanding the mechanistic link between exercise physiology, and in this case, football. What goes on on the game? How can we link that to certain mechanisms that are of importance for performance? 

 

I guess, if there's something that I'm lucky to be part of, or have to be part of over the years, has been a group that has worked in both camps. Both with the practical issues, doing math analysis, sensing, training loads, and so on, but also going into the laboratory sometimes, because there are questions that we can't understand just by monitoring players on the field and try to understand some of the more basic underlying mechanisms. I think there are some pitfalls there in how people are approaching exercise physiology in general. And also, some of these things I see it also in the practical communities where sometimes we are as well.

 

[00:15:00] LB: Sure. I mean, listen, we've talked about football as the biggest thing there is in terms of a sport globally. But also, it's a relatively easy area for people to do research in in terms of finding people to participate in your studies. Chances are the students themselves know how to play a little bit of football. 

 

The universities, or at least at the very least, the towns or the cities that institutions are based in will have football teams in the local area. The thing though is, is there's a big difference between an elite athlete as an international player relative to an elite college athlete. But of course, also, we could really get into this and say, "Well, there's the elite of the elite." And not everyone in the Premier League is at the same level. And as I said earlier, there's massive differences. How do you try and account for that when you look at your own – setting up your own research? 

 

[00:16:01] MM: Yeah, we always tried – when we are trying to answer questions or scientific research questions on elite populations, we try to use players that are as close to the elite as possible. And I fully agree that there are many studies and many findings from college athletes, from sub-elite athletes, that over the years have been translated into procedures maybe at the elite level. 

 

I think sometimes you can do a study on a sub-elite population to describe something that has never been described before. But then you need to test it in elite population before you can draw firm conclusions, because we're talking, as you said, about completely different groups of athletes. 

 

What we do sometimes is that if we're doing studies, for example, invasive studies where we have difficulties having the best players in the world participating, we try to take test results and try to recruit players that are competitive at the close to the elite level, but that have a physical capacity that resembles those at the highest level. 

 

But in general, in Denmark and in Sweden, partly in Norway as well, it's quite easy to get access to elite populations. For example, in Denmark, we're working very closely with Team Denmark, which is the elite organization for lead athletes in the country. And that's a huge possibilities to work with the federations, with the men federations, on projects. And then we can use the national team level athletes.

 

[00:17:47] LB: Yeah. And of course, there's value in everything as long as you understand how to position that and then learn whether or not you should be casting that piece of information aside or not, which is, in my podcast, I’m well known for talking about things like context, and relevance, and so on. And this conversation is a tool that helps people understand that further, rather than just read a paper. 

 

Now, speaking of papers, what brought us together here in particular was this perspective in Frontiers in Sports and Active Living, which is muscle glycogen in elite soccer, and you and your group's perspective on the implication performance fatigue and recovery. 

 

I’m interested to know what led to you guys wanting to bring this paper out into the public domain. What was the impetus behind this paper? 

 

[00:18:41] MM: Yeah, the interest, or the reason for writing this paper is there are a number of reasons. But one of the reasons is that few – And this is on football obviously. But during the Corona period where the world was locked down, and we as researchers also had to reinvent ourselves during that period, because the laboratory were closed down. So, we were not able to do many of the studies that we had planned. So, we had some time on our hands to do other stuff that we normally don't have time to do. 

 

So, one of the things that we did was that we gathered a group of international football researchers and then we included some practitioners, for example, from Liverpool Football Club. And then we wrote a paper, an editorial, on how will football look in 2030. So, it was like looking at how has the game developed over the last decades. And then we cystically calculated ourselves into the future, that if we're on the same trajectory of development, how will it look in 2030? 

 

And doing that, we were quite amazed how much more intense football has become just from the – or the last two decades players are using 2.5 more time on training and games. And the number of games has exploded. The general intensity. The tempo of the games is higher. And this obviously something that we need to take into account. 


So, this was one of the reasons that we started to think about doing some new studies. And then also the rule changes that have been made over the last years, for example, with a higher number of international tournaments. But also, the abolishment of the home or away goal advantage has also led to a higher probability of playing 120 minutes games. So, this was part of the reason that we wrote this because we see that football is developing so fast. Can the players actually follow the development? 

 

And we have seen changes with the five substitutions that we have now possibilities for. So, we wrote this paper basically based on we have a discussion on how we are approaching football. And when we have a World Cup around the corner, that also makes sense. Yeah, that's part of the reason why we – 

 

[00:21:08] MM: But that's fascinating. And I love it. And actually, it's that opportunity that arose. I mean, let's face it. There's lots of negative stuff that happened in the last few years. But that opportunity arose, and it allowed you some space to think about these things. And I think this is particularly interesting for various reasons, particularly when it makes you think back how far we are basing our decision-making – The evidence upon which we make decisions comes from knowledge, from information, that is quite old now, at least within the spectrum of sports science or even, more niche, sports nutrition, which it's a very young field. The evolution of that knowledge is – I mean, there's an acceleration, obviously, of production of studies and research and so on that's coming to place. But obviously, we've had this past few years, as you say, where there's been a bit of a break on that. And of course, you and others have had a bit of time to reflect on that and look at what have we got? Because the game, as it is, is nuts, as you said. It's just bonkers where football has got. Particularly in tournament football. 

 

At the end of a professional season, you then got this hugely congested period within these tournaments like the World Cup that's coming up. That also includes crazy amounts of travel. And it makes me think, of course, of the ones that I did with all the Covid restrictions and all the other stuff that was going on. 

 

But let's just quickly talk about that, because in order to have a real appreciation for where the science has been in the past and how we've used that to understand, in this case, muscle glycogen needs in athletes, and where the changes have and are going in terms of what impacts those muscle glycogen demands. The status, if you like, of muscle glycogen within elite soccer players. Maybe you could just help illustrate where some of those changes have gone in the last few years in terms of the implications for performance fatigue and recovery. And then we can talk about how we should actually be approaching muscle glycogen strategies. 

 

[00:23:20] MM: Yeah. There was a really interesting study done in the 1939 by a Danish researchers, Christensen and Hansen, where they, for the first time, explained that in an exercise scenario you are utilizing fat as fuel. And you are utilizing carbohydrates. So, they made this really nice study nearly 100 years ago, or 80 years ago. 

 

And then why what happened was that in the 1960s, Swedish researchers started to measure glycogen for the first time. The muscle biopsy technique was invented by Bergstrom and colleagues. And that was for the first time that you actually measured muscle glycogen. 

 

There actually is a study done by Van Sultan from 1973, actually the year I was born, looking at muscle glycogen during a football game for the first time. Showing a huge decline in glycogen and also showing some relationships between the performance at the end of a game for players who started the game with high levels compared to low levels. This is a knowledge that is 50 years old as such. 

 

And then during the 1980s, especially, there was some really nice studies from research groups around the world looking at the relationships between glycogen and performance. Also, in the 1990s, some manipulation studies with diet and with glycogen depletion prior to exercise, and so on. And then we have come into the area, after the Millennium, where football research is exploding completely out of this world. And a lot of studies have been made with nutritional interventions and different types of intervention. 

 

But if we look through the literature, we know that muscle glycogen is related to performance. It's associated. But the real mechanisms of that have not really been elucidated fully. And during now, the corona period, or after the corona period. So, over the last year or so, we started also to do some studies going back to some of those problems on what is the actual cause of fatigue associated with. How does glycogen affect performance? What is the mechanism? 

 

And we did some really nice studies that were published this year, last year, on that. And those tests were also by we chose to write this editorial, trying to start these discussions again. But there a lot of studies. We also wrote a review paper on muscle glycogen and fatigue during intense exercise. And when you sit there and you go through the entire literature on this topic, you also see how much information is lacking. And there are a lot of studies stating that muscle glycogen is important where most of glycogen wasn't actually measured. 

 

So, a lot of study where they not necessarily measured muscle glycogen, but they manipulated diet, and so on. And on the other hand, there are also a lot of studies that are very descriptive in nature. So, this is actually where we are within this field. And obviously, the possibility of doing more sophisticated analysis has been important for approaching that more in depth. But still, most of glycogen – the real cause of fatigue because most of glycogen is not fully understood, which is quite interesting. Because if you go to the practical community, it's like old news. Just like yesterday's news, “Oh, my God. Now they come back and they start preaching about carbohydrates and muscle glycogen again. But it's an area that is not fully understood still.

 

[00:27:13] LB: And you see, that's the thing. That's the thing that I think will blow most people's minds, is we actually aren't totally sure yet. And I've gone out of my way in this podcast. I've done a hundred and – I should know the total number. Nearly 200 podcasts. A lot of them are with people like yourself. Professors, people with lots of publications, have done a lot of applied work, but also a lot of mechanistic stuff. A lot of, in this particular topic, studies that involve things like biopsies, and so on and so forth. 

 

And actually, not only is the consensus of, “Well, we think it's this.” But we still have a lot more work that we need to do to find out where we're at. Relative to, if you go out there, and you pick up some books in the past, or listen to conversations between people who aren't aware of this stuff, that there is a sort of matter of fact consensus that exists, isn't there? Which, of course, is why this paper is so important. But why does that persist, Magni? Why are we still in this situation where what you've just said may be a surprise to somebody that's listening? Well, it will be a surprise to somebody that's listening. Why are we in this situation, you think?

 

[00:28:20] MM: I don't know why we are. But I think that, for example, in the football community, and maybe also in the sports, lead sports community, there is – I see it, not everywhere, but many places. There is a need always to have something that is really new and sexy when you start to. It needs to be – because if you come into a club and you want to improve performance and procedures, sometimes people expect that you bring something really, really, really new that they never heard before to the table every time. And that's not how science or knowledge work. It takes years, decades, maybe centuries sometimes to understand things in their depth. 

 

And often – we can take another example. And that's the 10,000 hours of training that people have to do to become good at something. That's maybe the best example of something that just becomes a truth in a community, in elite community. And people start to apply it without actually going back and look at the evidence. I think it's an expectation from elite athletes that that you should bring something new to the table every time.

 

[00:29:37] LB: Yeah, well, especially in football, of course, where sexy stuff is linked heavily to the old branding and marketing side of things. And football at the elite level sells a lot of things beyond just football, of course. And that's nutrition is rife with supplements and all this sort of thing, which we'll come to in a minute.

 

But I guess we can envisage the concept of knowledge on this topic is a bit like the football being dribbled up and down the pitch. And there's a few goals and a few things are lost. And of course, the problem with the scientific structure of knowledge gets out primarily on the basis of what is published. But of course, there's a lot of things that we really should know and we'd like to know that are those failed studies or things that didn't work. And we've got this issue, of course, of certain negative findings won't be published or put out into the public arena. 

 

I know you as a practitioner, that I spend half my time trying to deal with things that are compensating for the realization that, “Dammit! That's just not going to work.” Well, I would like to have known that in the first place. What are your thoughts about that side of where we're at in terms of developing knowledge that's applied into practice?

 

[00:30:53] MM: Yeah, I fully agree on what you're saying about publication bias in the literature. And I know that when you have negative findings, it's really difficult to publish them compared to positive findings. And that creates a mismatch when you are doing overview, systematic reviews, and meta analysis, that the things, such as supplements, for example, is a good example. They appear in the literature to work maybe better than they are actually do. 

 

I think it's important that we sometimes step back and analyze things more in depth. And that's back to what I said before, that I think it's really, really important that we have a mechanistic overview or approach to football training. Yeah. So, that's it.

 

[00:31:39] LB: And I just want to go back to your comment about 10,000 hours. I think it’s absolutely fascinating to see the journey of an elite football player, for example. I've certainly seen them through settings that will go from academy all the way up to playing for Chelsea, Juventus, national teams, Cameroon, Belgium, whatever. And there's a lot of players that don't get that far. 

 

And there's all sorts of factors, of course, that goes behind sort of the successful evolution, if you like. And by successful, I mean, achieving that level of being a super famous football player, or being particularly well-known for being one of the best football players in the world. There's just a fascinating backstory that goes behind it. And of course, football is far more complicated than one might imagine, for example. A straight 100-meter sprint, for example. Or the world's strongest man in a particular given Olympic lift, or whatever. Football is a crazy game. That's a mixture of many different factors, including what the weather's like, or what mood certain people are in, including their head coach or whatever. 

 

But as sports scientists or sports nutritionists in this particular bias that I have for this conversation, we know that we can have an impact on factors from performance, fatigue, and recovery. And of course, what we're talking about here is muscle glycogen. Why is muscle glycogen in the elite football setting? Because that extraordinary talent and those 10,000, 20,000, 30,000 hours of training or whatever takes him so far. But we still need to get this muscle glycogen bit right. Why do we still need to have this as a key consideration for our athletes, Magni?

 

[00:33:30] MM: Yeah, if we look at studies that especially our group have done over the last two decades, is that we have done studies where we have taken muscle biopsies during real football games. Both games like experimental games that we have organized ourselves with relatively trained players. And then also game simulations. Some years ago, we did a test called the Copenhagen Soccer Test, which is actually a test that the simulating football on the pitch wearing boots. So, you're in your natural scenario, and you're doing the physical part of what football is. 

 

And then we have done studies where we have taken muscle biopsies before and after an injury recovery period after real competitive games in and best Danish League, the best Swedish League and so on. And if we look at those data, we see that football is a very glycogen-consuming activity. So, because of the amount of intense work that you do as a football player, and especially going back to that editorial that I mentioned before, the football has become markedly more intense than it was in the past. The importance of glycogen may become maybe even more important today than it was years ago. 

 

So, if we look at these studies, I think these are really fundamental studies for understanding the demands of football and also the role of glycogen. Because if you put people on a bike and you test them on a bike and you try to look at recovery and how fast you can fill your glycogen stores, it's completely different than playing football. 

 

And what we'll also see in these studies is that, because of the nature of football, because of the nature of the characteristics of the movement pattern, you are utilizing both your main muscle fiber types, the slow-twitch fibers primarily being used for endurance exercise. And the fast-twitch fibers primarily being used for intensive explosive actions. You see a huge glycogen depletion in both those fiber types. 

 

And recently, we started to look more in depth. So, looking at glycogen localization in the muscle cell. We know from previous study, primarily done by Niels Ørtenblad from the University of Southern Denmark, that glycogen is stored heterogeneously in cell, and at least three different pools of glycogen are present. And we see also that after football game, you have a huge depletion pattern in all of those pools that are very close to some of the key steps in the excitation contraction coupling. So, when muscle force is being produced. So, that's why football is of interests, or most of glycogen is of interest in football, because of this huge glycogen depletion that you have in all fiber types and in all three clients in pools. 

 

But then, another interesting aspect is that when we follow the muscle glycogen kinetics after a football game, we see some results that are very different from what you see after running, after cycling, after swimming. We see that the muscle glycogen resynthesis after the football game is markedly slower. And even if we try to provide athletes or players with the optimal diet, we still see that it's really, really, really difficult to get back to the baseline values. So, that also put an emphasis on the recovery aspect of muscle glycogen.

 

[00:37:04] LB: This is fascinating on many levels. But again, I'm quite a visual person. I imagine a lot of the listeners are as well. There's what you see in terms of these various tests that you'll do from biopsies and so on. But for us, we can't see anything. Of course, there isn't a dial on the muscle. It's not driving your car. I'm imagining, you've got your fuel gauge. 

 

We appreciate that there's going to be differences between individuals. But generally speaking, whether it's – and in the context of a football player, who is training during the week. And as they build up to that game, there's going to be an impact on those fuel supplies, fuel reserves. And then of course, there's the game itself. And there might be extra time, there might be another game the very next day. There're certain situations there. What's that dial doing throughout the course of that process, Magni? Help us understand. Help us visualize what's going on in that respect.

 

[00:38:10] MM: Yeah. If we take like a normal week for a player, then what we see in some of these biopsy studies that we're doing, that when we’re taking baseline biopsies of football players, their baseline values are quite low compared to, for example, if we take a muscle biopsy from a Tour de France cyclist just prior to starting the race, he will be very, very high. 

 

This is also something that we see in other team sport athletes that, in general, the baseline values are markedly lower. And this is like a result of constant training where you have to do football movements, which I’m referring to that football is a very glycogen-consuming activity, and then you have this very slow recovery of glycogen. 

 

So, this means that it's very easy for players to constantly have suboptimal glycogen levels. And we know that going through some of the basic research that have been done over the years, over the last few decades, at least, we see that there appears to be a threshold for muscle glycogen where it becomes really, really critical. There's quite strong evidence for that. And that limit of 250 millimole hours per kilo driving muscle. We know that some of the important steps in having a proper muscle function become compromised when you fall below that level. 

 

When we look at those studies, where we have had players starting maybe with levels of 400 or even below 400, they fall in a normal game below that level, which means that they are much more prone to become fatigued and much more at risk of injuries and so on. And a few weeks ago, we published a paper in Medicine & Science in Sports & Exercise where it was actually the first study done on 120 minutes football. 

 

So, where we took biopsies before, after a game, and after additional time in a study done in Greece with trained Greek players. And in that additional time, we see that players are falling really, really low in muscle glycogen. And we see an extreme fatigue response on so many levels. And we see high degree of inflammation, muscle damage, and so on, which often follow the glycogen depletion. 

 

If you consider this player and that is going to perform over a week playing two games and training, which is resembling of the game again, it's really, really challenging for players to even be at a reasonable level in relation to muscle glycogen prior to games and prior to training.

 

[00:40:54] LB: In various podcasts over the years, we've talked about things like various perspectives on substrate utilization, and the various things that influenced this. But if we draw that out over to sort of days, weeks, months, that's one perspective. But particularly in football, there's this acute – there's interest in the acute impact, the fuel reserves, the fuel supplies, and the status, that status constantly changes throughout the game. And yes, it's influenced by how many minutes a player will play. What are the pregame during game, halftime strategies? There're all sorts of stuff. And we've discussed that with various experts. 

 

But I'm particularly interested in the fact that, again, there's this issue about generalizing. In science, of course, we like to generalize. But there are various implications to an individual's glycogen status that could be impacted by, for example, the training they've done the day before, the types of warm-ups potentially. And what about even something that's becoming more popular of late is the concept of the types of muscle fiber types that players have, which is not evenly distributed equally per person. And there's some ideas that you can test muscle fiber types in individuals and then actually come up with individualized nutrition strategies to deal with that. 

 

I mean, what are the considerations from your perspective that – and I'm going to be on the nutritionist at this point, the fitness coaches, the coach themselves, who's deciding what the players are going to do on the day of a game even, the warm ups and so on? What are your thoughts on that, that we should bear in mind?

 

[00:42:38] MM: Yeah, on your point on individual variability in these issues like – and every other biological issues there, there are huge, huge differences. And this is also something that we see and also report in some of the studies that I've referred to before. And if you look at those papers, most of them are showing individual values. And we see that there are huge differences. And we also see that it depends on if we look at muscle glycogen depletion during a game, we see that it's really highly linked to the amount of work that you do, obviously. So, the players that covered longest ground or that run the most, they also are the players that are more compromised. This is something that you, as a fitness coach, can use directly, because you have access to training data to match data so that you can have more individual focus on those players that are at the highest risk of being low on glycogen. 

 

Yeah, and then how do you train during the week? What about procedures on the match day? It's really, really important that you take these things into account to how much anaerobic exercise or anaerobic training should you do the day before the game. You need to calculate some of these things. And you can do that based on basic studies that have done. Because doing intense work, high intensity exercise, even if you train for a really, really short period of time, it's very easy to deplete your muscle glycogen, especially in type two fibers. These are also things that you need to consider. 

 

And you mentioned the players that really fast and explosive. These players also are players that you have a special focus on in relation to these issues. Yeah, warm up procedures – I remember I used to play football as well. And I remember when we warmed up in my days, we went out to pitch nearly an hour before. And sometimes when you started the game, you will have maybe covered three or four kilometers of warm up. 

 

So, what has happened over the years is that the warm-up today is really, really short and precise. And the reason for that is not to use unnecessary glycogen prior to the start of the game. So, doing too much intense work, too much anaerobic work in your warm up is not recommended.

 

[00:45:00] LB: I mean, look, it's clear that glycogen status is pretty critical. And yes, we can agree that there are many factors that will influence the outcome of a game or a tournament. And notwithstanding skills and strategy and all these other things, it's quite clear that preserving or optimizing glycogen status throughout the game, not just at the beginning of the game, is something that becomes the obsession, of course, of the nutritionist in particular, because that's our job. We got to do what we can. 

 

There're all sorts of things we do throughout the season, preseason, from body composition, and so on. But when it comes to the game in the tournament, it's all about glycogen. Let's get that carbohydrate in one way or another. And of course, there's a lot of strategies for that with your match day minus one or even match day minus two type approaches with nutrition and feeding all the way through to halftime strategies, which may involve more supplements rather than food potentially. Although, I think back to working, for example, with the Egyptian team, supplements really weren't that popular. It was all about foods. 

 

And of course, how do we differentiate a food from a supplement legally or practically? There're just different perspectives there. And as you mentioned before, actually, sometimes we think about things on the basis of it being an approach or a strategy, just because that's how it was done in the research. Well, there's a reason why it was done in the research, because it was an easier to control approach, as opposed to what is realistic or practical in the real world, but might just be just as effective if not more effective. We just don't need to understand those mechanism maybe as much. 

 

But we want to talk about the nutritional impact here, Magni. And we've already been talking for a while. And it's been a mind sort of blowing insight already thus far. But let's just talk about something that all human beings need to do, which is eat and drink. And inevitably, there was also the concept of special feeding, drinking strategies where that can impact glycogen status. 

 

I want listeners to read our link to all the different papers that we've mentioned so they can get into that. And there's plenty of resources out there to help them understand that. But from your perspective, what are the key areas that we need to be factoring in on this?

 

[00:47:28] MM: Yeah. The key area in relation to the topic of the day, as you mentioned, is to time and to control to a certain degree your intake of carbohydrates. And studies are showing that a really nice review came out a couple of years ago by UEFA, suggesting strategies for football players, and they are also an industry review we're referring to that if we look at the carbohydrate intake of players, a lot of players they are under consuming carbohydrates in general. And this may also be a challenge of the day because of sometimes we forget that the players are also young people. They are being affected by the media, by the social media. And since we are living in the area of protein is good and carbohydrates is bad, that has been sold to the general public, players will also get affected by this. And I think that I see it in payers today that they are sometimes reluctant to consume the required amount of carbohydrates. 

 

And studies are showing that many players are maybe being 25% below what they should consume in relation to amounts and concentrations. So, this is a challenge that we also need to take into account. But when you have the short time in between the games, three days between the game, you need to have a really high focus on consuming as much as possible, after the game, leading up to the game, on the day of the game, during the game, and so on. So, it's really, really important – these things are really, really important to take into account especially when you have games where 72 hours between.

 

[00:49:16] LB: I'm pleased you mentioned that bit about the players being young humans, males, females. I certainly had a lot of that with my players. But also, a few years ago, we did a case study on an international player that ultimately had frequent upper respiratory tract infection. So, we had to come up with a solution to reduce the infection incidents. And ultimately though, that did come down to the player not consuming carbohydrates. And one of the reasons for that was because they had bought into this business of carbohydrates are bad. But also an interest in their body composition. 

 

And they as a brand on things like Instagram or whatnot, inevitably, there is the odd shirt off type scenario and the link that that has to food and body composition. But also, the difference between their perspective on how nutrition impacts body composition relative to performance, rather than just aesthetics. And of course, a football player needs to be functional, not just aesthetic. And that, for the nutritionist, is a big challenge, because we're not in a position where we can sit over their shoulder all day long telling them what to do. Yes, of course, we have advantages now with digital tools, coaching tools, apps, and various other things to help coach the athlete. But ultimately, it does come down to having the athlete buy in to what they may see is a risky strategy of increasing carbohydrate. What are your thoughts on that? And are there any – and I'm just throwing this at you, because it's interesting, maybe some of the sexy side of carbohydrates. How do you perceive the selling points of the sexy side of it? What would your thoughts beyond that?

 

[00:51:14] MM: Normally, when I've been working with players, we sit down with the players, and we try to educate them on nutritional strategies. When I was at Chelsea Football Club, I worked together with a really good nutritionist called Nick Broad, who unfortunately is not among us anymore. And I think they had a really good strategy at that time with – it was an 80-20 strategy. So that 80% of the time you do as we suggest that you should do. And then you have the 20% just your own thing, because the psychological part of nutrition, of consuming food, and so on, and the enjoyment of consuming food is also something that you need to take into account, especially when we can say some of the things that I mentioned earlier that players today are using 2.5 more time on training and time and because they are constantly of interest in the media. The psychological stress is immense. So, if you also add to the area of controlling everything you eat. 

 

So, I think it's really important when you plan for this and when you try to sell these messages to players that you take into account these issues as well, that the players already are under a really, really high stress. And that you educate them that there are maybe many roads reasonable result. That you can consume food that you find pleasurable, and not only be on the constant control of the club.

 

[00:52:56] LB: Yeah. And, I think, again, we talked about the evolution of the game. We've talked about the evolution of science, and knowledge, and so on. But also, since we're talking about elite football players, we now have something relatively new also, which is the concept of personal chefs, which is a big thing that I've spent a lot of my time actually interacting with players’ personal chef. But also – and this is difficult for the team nutritionist to deal with, is they've also got their own nutritionist. So, we all really need to be singing from the same hymn sheet. And it gets a bit complicated. 

 

That's why this conversation and the work, for example, that you've published that we're talking about, it's important that this awareness is out there because of that myth that carbohydrates are bad for you, and so on, so forth. And we've had this debate many times, and it does of course – there are angles there for maybe ultra-endurance athletes. There're angles there maybe for non-athletes. There’re just different perspectives. But in the context of an elite football player, this stuff is critical. 

 

I've already mentioned there's all these different papers. You've referred to the UEFA position statement, which Professor Mike Gleason and I talked about a while ago now. These are all great resources. Where do you think things are going go in the future? I know that you yourself are working on this. No doubt you've already got studies underway. You're planning more studies. Where do we need to go, Magni, in order to keep furthering our knowledge on this to help add additional weight that overrides all the noise and the mess that exists in the world on this topic of carbohydrates and so on, particularly for elite soccer players?

 

[00:54:41] MM: Yeah, it's difficult to predict precisely where things would go. I can mention that – before I answer your question, I can also mention that some years ago we did a study where we were trying to correlate some of the physiological variables that we are normally measuring in our biopsies, in our testing procedures, and so on, to match activities performance. 

 

So, we did a correlation study where we looked at, for example, skeletal muscle profile or phenotype compared to how good you are at doing accelerations. How much ground you can cover? How much high intensity running you can do on the pitch, and so on? 

 

And in that study, we saw – and this is something that has been shown to both men and women. And we saw some really nice correlations between how much of the endurance part of football you can do, and your ability to utilize fat as fuel. And we saw also the ability to do high intensity exercise at the end of a game is highly correlated to your fat burning capacity, or some of the key enzymes in the beta oxidation. 

 

I think that we should also maybe discuss that it may sometimes be an advantage to train on low glycogen. That you can have an adaptation, an adaptive response from doing that. And there are some evidence also suggesting this. But I think that, one, the direction that I think we will be moving is the role of fat in this whole concept. And what about reducing protein? What if we go low on protein, which some of my colleagues that are experts are suggesting that we should do? 

 

I think that we are going to see different manipulations. I would suggest that exploring more in depth, the role of fat and fat supplementation, and so on, and certain types of fats. Again, I know there will be a lot of studies focusing on optimizing glycogen resynthesis after games. How can we train for that? Can we train your glycogen resynthesis? And then I think that these theories about reducing protein are also highly interesting.

 

[00:56:58] LB: You know, not everyone listening – Like, if my wife was listening, she'd be like, “This is so boring, this stuff.” It is so exciting to see where things can go. The explosion that we're already seeing is just going to become more nuclear in terms of where the stuff can go. And the things that you've touched upon, like, whether we're talking about periodizing in terms of how we impact feeding patterns, and so on. All the way through to nutritional training, things like metabolic flexibility, that influencing substrate utilization capacities. The ability to switch from one fuel supply to another. Concepts like nutrient priming. Physical or nutritional strategies to influence that acute selection of fuel supplies, and so on, is just utterly amazing stuff, which, for nutritionists, and sports scientists, and so on, is undoubtedly going to get the juices going.

 

But we have to bring this conversation to an end, I think, because we're in danger of pushing our luck, Magni, given how hard it was to have this chat in the first place. But I just wanted to thank you so much for sharing your time. You're an incredibly busy guy, but we've managed to get you in on this. And I personally just selfishly really enjoyed this conversation. And I know that the listeners will have done also. 

 

As I said, I'll link to all the papers and various things that we've discussed for people to really take even deeper dives into some of those topics. If people want to follow you, I'm not sure if you consider yourself a social media influencer, Magni. But if people do want to follow you and your work or even come and do a PhD with you guys or whatever, what's the best ways for them to stay in touch with you?

 

[00:58:46] MM: Yeah, I'm not on social media. 

 

[00:58:48] LB: Very wise. 

 

[00:58:49] MM: Not even on Twitter, which most of my colleagues are. But email me if you have any questions or if you find some of this stuff interesting. Or if you have ideas for collaboration, you are always welcome to drop me an email. And you can find my email address on some of my papers. 

 

[00:59:08] LB: Yeah, I'll link to that. Well, look, thank you, Magni. Thank you so much for your time today. It's been an absolute pleasure to have you on the podcast today. And thank you everyone for listening. I hope you enjoyed it. I am Laurent Bannock. And I look forward to bring another episode of We do science back to you all very soon. Take care, everyone.

 

[END]