00:03
Welcome, hi, I'm Mikki and this is Mikkipedia, where I sit down and chat to doctors, professors, athletes, practitioners, and experts in their fields related to health, nutrition, fitness, and wellbeing, and I'm delighted that you're here.

00:24
Hey everyone, it's Mikki here, you're listening to Mikkipedia, and this week on the podcast I welcome back Dr. Guillaume Millet to discuss sex differences in ultra endurance events. Now as someone who is just in a 50k, barely seems like an endurance event to be honest, or an ultra, I'm very much interested in this topic, particularly given that I managed to beat out a couple of my

00:53
most fierce competitors, one of them being Hubster and the other one being my mate Christian. And actually to be fair, in both cases, there were very clear reasons as to why I could possibly do better. One, because Christian is a very good technical runner and this was largely a road runner's course. And of course, Hubster had just arrived back the day before from the UK. So, you know, it probably wasn't just down to sex differences alone, which allowed me to beat them out.

01:20
But it does raise that interesting question. What would it take or what is it that potentially creates an advantage for females in that ultra-endurance space? And so Dr. Guillaume and I discussed the interplay between biology and behavior and how females are different from men and what possible advantages and disadvantages this may have over the longer distance. We also discussed biomechanics.

01:50
and how much of the differences in performance may be due to sociological differences. We discuss a ton more actually, and it includes Guillem's dream event where true sex differences could be put to the test if money was no object, which was a super fun exercise and I think that you'll really love it. For those of you unfamiliar or who didn't catch my first episode with Guillem, we'll put a note in the show notes along with the studies that we discuss here.

02:18
Dr. Guillem Millet is a professor at Jean Monnet University. From 1998 to 2013, he held various academic positions in France, including a four-year full-time research contract at the French National Institute for Medical Research. And in 2013, he moved to the University of Calgary, where he directed a research team of around 15 trainees in the neuromuscular fatigue lab. He was also the vice chair of research of the Canadian Society for Exercise Physiology.

02:47
2014-2016. Upon returning back to France in 2018, he received a very competitive IDEX-Léon fellowship, which is a program that aims to attract outstanding scientists with a strong international track record and now leads the ACT-DFS, Physical Activity in Fatigue Health academic chair. His general research area investigates the physiological, neurophysiological and biomechanical factors associated with fatigue.

03:17
both in extreme exercise and in patients of neuromuscular diseases, cancer in the ICU. His research is focusing on understanding fatigue in order to create tailored rehabilitation programs for clinical populations. In 2021, he had published five books and over 260 journal articles, and he has supervised 37 post-doctoral fellows and PhD students from 13 different countries.

03:46
and he has served as an external reviewer for over 60 PhD candidates. And he is pretty much very well revered in his field of study, which is super unsurprising. So I've put links to Guillaume's profile and his research gates. You can catch up on all of the research that we discuss in this interview, in the previous interview and all of the other research projects that Guillaume has going on to date.

04:13
Just before we crack on in though, a reminder that the best way to support this podcast is to hit the subscribe button on your favourite podcast listening platform and leave a 5 star review. That way it'll increase the visibility of the podcast out there in amongst the literally thousands of podcasts so more people get the opportunity to learn from the guests that I have on this show including Dr. Gere Millay. So please enjoy this conversation.

04:42
Happy New Year, Giam. Thank you so much for taking time again out of your busy schedule to come and speak to me about sex differences. Interesting though, on the basis of our previous conversation on fatigability and the flush model, I was chatting to a friend yesterday telling them that I had recently downscaled my next race from the 100 kilometer to the 50 kilometer because I'm having some calf issues.

05:11
And we both were like, oh, well, that mental burden's just like completely diminished now. And I thought of what we were discussing with stress in the athlete and how these things can sort of blow up in your head. So yeah, timely. And interesting on the basis of our conversation this morning. Do you know Kamil Heron or know the name Kamil Heron?

05:40
way that I know the name of you, so yeah. Yeah, and so I was just having a look at some of her Instagram posts, and she posted quite recently that she has the number three record in the world for the 48 hour run distance time, which sort of blew me away. She said there were just two men in front of me. And I imagine actually, I'm not sure how surprised you are by that, but I did also think

06:10
48 hours is a very long time to be running. It is. And that's probably one of the reasons why, first, she's exceptional. She's a fantastic athlete. But the fact that she's ranked third in the world is probably because this distance is so long that there are not that many marks about 48 hours. So I can't remember on top of my mind how...

06:36
is she's ranked on 24 hours, but it's a bit more popular. So I doubt that she's so well ranked, but yeah, but still, still third is quite amazing. Yeah, in fact, that's such a good point as well, right? When you get into the, I'm not sure how you would define that, like extreme ultra endurance events, like there are just far few people who...

07:02
probably mentally and physically able to line up on the start line for that kind of event? There is no definition. I mean, you can put the line wherever you like. To me, I would say that 100 miles is still reasonable. Yes. And then over that, at least for me personally, that was my limit. I was fine with UTMB, Western States, etc.

07:29
But when I tried, it was only once the Tour de Géant, which is twice as much. To me, that was too much. For me, at least, the limit is here. For people like Camille, I'm sure it's much further. For other people, it may be less. It really depends on the person, your physiology, of course, your training history, etc. I will put the mark at 100 miles for me.

07:58
Yeah, now I totally appreciate that. And as far as I'm concerned, right here and now, I haven't even done 100 kilometers. And I don't think that's going to happen anytime soon. But so that's fine. I'm actually okay with that, which is actually a big thing. Anyway, to our conversation today on sex differences in endurance performance. And it's interesting, and I'm sure I mean, you'll be involved in the conversation.

08:26
particularly over the last couple of years, looking at sex differences in performance in general. And so, though we've had a couple of big meta-analyses that have been published, maybe it was in 2021, I think, in British Medical Journal, that essentially says that at the minute, we can't really make any sort of sweeping sex-based recommendations for performance.

08:54
But this doesn't necessarily mean that there aren't differences which do impact outcomes over time. Would that be sort of how you would frame it, Guillaume? So I'm not sure I fully understood your question. So you are saying that there are good meta-analyses, recent meta-analyses on six differences, but I didn't get the question. So what, Penny, can you repeat? Yeah. So despite the fact that we can't make...

09:22
training recommendations based on sex differences, this doesn't necessarily mean that there aren't differences between men and women and their ability to perform, particularly over that long distance. Well, first, I'm not sure we cannot make training recommendations based on sex differences because some people try to do that. For instance, some coaches try to consider

09:51
to train their athletes. It's not very popular. I'm not sure this is actually needed, but I know that some coaches take that into consideration. But for sure, there are many, many differences between the sexes, and I guess this is the topic of today. So we're going to cover that in details. But of course, yeah, there are so many differences and so many things in common as well. So yeah, we can start talking about that. It's a fascinating topic.

10:21
And I came across this, it was a graph or a paper that was written in Aske, Juppentrop, I can never say his name, but I think you know what I'm talking about. Yeah, he did a lovely summary of sort of how women's performance times and men's performance times have changed over the years. And there was a sort of graph included that sort of showed a

10:50
was that didn't, I mean, of course it changed over the time, but not in the same sort of trajectory that women's performance changed, and particularly in that longer distance. There was slight, or seemed to be much more slight improvement over the years in the shorter distances. Then when we came to the longer distances, there appeared to be quite a steep performance jump. Do you think that that's

11:20
a cultural sort of change in, you know, more people, more women are running and therefore there's more possibility to get greater times. Do we think it's more biologically sort of related? But when you see something like that, Guillaume, what's your initial understanding? Well, this is definitely cultural. I mean, there is no reason that the change in performance, I mean, let me rephrase that.

11:47
You're right that if you look at the performance in Marathon and the evolution with time, and if you consider only the last 40 years, you will see, wow, females are improving so much their time while males are not. So is it biological? The answer is no, definitely not. The answer is that females have started to run.

12:10
only a couple of decades ago. So of course there is much more room for improvement when you don't have so much of a history in performance. And for males it was of course in 1900. So this is actually one of the reasons why we had this paper published in Nature in 1992.

12:37
And I insist it was published in Nature, so probably the best scientific journal. And this paper published in 1992, they were guessing that females will actually beat males in on the marathon in 1998. So it was six years from where the, from the time that the paper was published. And of course, we are now in 2023. So of course we know that it did not happen. And in my opinion, it will never happen for real.

13:06
that we are going to discuss later. And the reason why they made this mistake is that they actually consider in this paper, it was, now when you think about it, it seems crazy, but again, it was in nature and so it was published. Anyway, so they consider the evolution of the marathon record, like they took the best performance for each decade in the last, I can't remember off the top of my mind, I haven't read the paper for a while, but in the last maybe five or six decades.

13:35
And of course you have this slow decrease in males and this steep, I mean, this low increase in performance in males and this steep increase in performance in females. And of course you, you cross the line, very, very soon, like it was in six years from, from the time that the paper was published. And this is, but the reason, this is, this is crazy. And it didn't happen is that the analysis itself was crazy because this is not a linear, it looks like it was a linear increase for females.

14:04
simply because they consider only one performance per decade and it was a performance history from only a couple of decades. So now we know that rather than continuing, of course, to increase linearly, the performance increases non-linearly. So you have this asymptote in females like you have in males. So now the two lines are parallel.

14:32
And the difference is around 10%, 10% to 12%, as in many other distances, actually. So yeah, it was a very funny, and they were the respected scientists, published in Nature, again. But it was a funny story. Yeah, well, that's interesting, actually. So the gap of 10% to 12% in the marathon isn't actually that different if you compare the gap in a shorter distance. Is that what you're sort of saying?

15:02
Yes. Yeah. So, contrary to what we think, and again, this is something we're going to cover later in this discussion, I believe. But contrary to what we think, the difference in top athlete is not reduced when you increase the distance. Yeah. Yeah. So interesting. And one of the papers that

15:32
You published a paper that had quite an extensive database looking at running endurance in women compared to men and looking at sort of matching up similar men and women in terms of their performance times to sort of have a look at the differences. Is that how you would describe the genesis of that paper, Guillaume? Yes, so we were basically questioning

16:01
sex differences in endurance. And this is what we discussed. So if you... Okay, so if we... Now we have discussed this cultural and historical bias. Okay, now that females have started for more years to run at high level, okay, now we can definitely consider the sex differences in performance and on different distances.

16:31
However, as we just said, if you consider the top athletes and you look at the difference between 100 meters, 400, 10K marathon and refer marathon, and you look at the sex differences, there is actually no reduction of the gap. So if you look that way, you will tend to conclude, okay, so females are actually not more endurance because the gap is not reduced.

17:00
However, when you do that, you still have to consider that despite the cultural things is reduced, it's still there. What I mean by that is that if you look for instance in Marathon, there is not 50% females at the start. It's getting closer. It's more like 35 to 40%, but it's still not 50%.

17:28
And if you look at your terminal fund like the UTMB, now we are very far from 50%. We are at 10%. So, yeah, yeah. So in the US, maybe, I don't know, in New Zealand, but in other countries, it might be a bit more, it might be like 20, 25%. But it's, I mean, I'm talking about 100k, 100 miles races. But in Europe, but still, it's still very low. And in Europe, it's actually even lower.

17:57
at the UTMB again, and it has been like that from the beginning in 2003. The percentage female at the start is 10%. Wow. And Giam, and just on that Giam, and I know that I don't know how much of this you know, but I'm just interested. Is it something to do with the way that they set up the entries to the event or the way that they, that you can qualify for that event? Or is it literally that only 10% of women on basis?

18:27
the participants who enter are only sort of 10%. Like there aren't women being turned away because... I don't know. Obviously not. I mean, you have the same chance to be accepted if you're a man or a woman, of course. However, there are much less women who applied to enter in the race. So, and the reason for that, I mean, of course I don't have the definitive answer for that, but the reason...

18:57
is and this is what I was going to discuss is cultural in my opinion. I'd be a bit psychological like if some maybe females are less inclined to do, they don't, I would say they don't need that to prove anything to anybody contrary to males but I don't think this is the main reason. To me, the main reason is that they have less time to train because they have to take care of the family, the roles in the society is not

19:26
fully balanced still nowadays. And anyway, and I'm pretty sure this is the reason anyway, so 10% at the end of the day, we have 10% females at the start. So in terms of probability, you have much less chance to find a woman gifted to run ultras than a man. Yeah, right. So of course, there is no reduction in the gap, as I said, but it doesn't mean that endurance is not better in females because

19:56
if you have, if the percentage stays the same, but you have less chance to have good women, then you may think, okay, maybe if you were at 50-50 at the start, maybe the, the, a neutral marathon, the, the gap will be reduced. And we have reasons to think that actually a woman are, in terms of physiology, are particularly gifted for endurance performance. And again, something we're going to discuss in a couple of minutes.

20:25
Anyway, so if you look at the top performance, there is no reduction of the gap as the distance increases. Now, if you look, but I don't think if you consider that way, I don't think this is fair for women because of the reason I explained. I mean, there is not the same pool of persons to compete. Now, if you consider the average time of men and women in function of distance, then...

20:55
you will conclude the exact opposite, meaning that you will conclude that the gap is reduced to a point that females tend to be even better than males. But now I don't think this is fair for men. What I mean by that is that, okay, maybe there are only 10% females at the start, but I can tell you that when they are here, they are here for a reason and they are super well prepared.

21:25
very specific characteristics. They are super tough, super well trained. This is, of course, the case for many men, but this is much less the case for the average man, I would say. Some people are going to do UTMB, for instance, like, yeah, I want to do UTMB. I'm not super well prepared, but anyway, I do it. This is much less the case for women. So, analyzing the average performance of men and women is not fair for men, in my opinion.

21:54
So back to your initial question of the reason why we decided to analyze the performance by doing pairs is because if you consider top performance versus mean performance, the conclusion is completely opposite. Now we wanted to find another way to examine this question and this is the way we decided to examine the question. So in this paper we took pairs and we were able, thanks to the UTMB group, who were able

22:24
kindly gave us their database. We're able to make from hundreds of thousands of results. We're able to make 7,000 pairs of males and females who have run two races the same year, one short, one long. And so we matched the performance on the short distance and we examined

22:54
further. And with the hypothesis that it will, they will close the gap, the females will close the gap and this is exactly what we found. And I think this is, to me, of course, this is my paper, this is our paper, so of course I'm a bit biased, but to me this is the best way to examine this question. I'm not saying this is a perfect method, but I think this is much better than the other two methods that I explained. Yeah, for sure. And Guillaume, when you say short,

23:22
you're talking about less than 60 kilometers, is that right? So there were some races in there in the short category, which was still significantly long compared to say 10k. Yeah, exactly. Now this is trail running. So there are no very short trail running races. So yeah, this is a short, you're right, 30 to 50k, something like that.

23:48
And long doesn't mean necessarily 100 miles. It's longer, it could be 80k, 100k, etc. So, depending on the pairs, the difference in terms of distances was not the same. But overall, with the statistical analysis, we're able to estimate that when you increase, if you take a man and a woman with the same performance, actually it was not...

24:15
the same performance in terms of absolute performance, so not the same running speed, it was the same relative performance in percentage of the winning time for males and females. But anyway, it doesn't change the, if we had chosen the absolute performance, it wouldn't have changed the final outcome. But anyway, so if you took a man and a woman with the same performance, relative performance, and they...

24:44
both run a short and a long run, then the gap will be closer for the long race. Yeah. Guillaume, were you surprised by the finding or did you expect that this is what you would see based on those biological and physiological differences between men and women? No, that was, again, that was our hypothesis. We were hoping to see that.

25:12
Still, this is the first time that it has been shown in my life. And so, yeah, we are, well, not happy or unhappy. I mean, at the end of the day, we are not here to... We don't have anything to win or to lose. Yeah, yeah, yeah. But I was... Yeah, this is what we anticipated, for sure. And the reasons are because I...

25:36
said a few times that we're going to discuss. Here we are. So the reasons are, there are actually quite a few reasons. Yeah, let's talk about them. Yeah. So maybe we can start by saying why females are slower. So on very short distances or other disciplines where muscle strength and power is very important, I guess it is quite obvious to guess why males are slower.

26:05
faster and stronger, they have more muscle mass. Well, not me in particular, I'm not that strong. I'm joking, but yeah, we have testosterone, obviously, and this is super important, and we have a much higher muscle mass, much higher power, maximal power, and so that it's relatively obvious. Now, if we look at the endurance performance, males,

26:32
and we know that strength and power is not important anymore. But yeah, testosterone has another very important role, is that it triggers erythropoiesis. So because of that, we have more red blood cells and we have more capacities to carry oxygen in our blood. And this is one of the reasons why we have a higher view to max. So in average,

27:01
men have a higher view to max, like 10% higher, even if you normalize by body mass. And even if you normalize by lean body mass, if you consider the body fat percentage, you still have a 5 to 10% difference between males and females in average. Can I ask you a question, Guillaume? When you're talking about, when you were talking about muscle mass and sort of strength and power, so even the power to weight ratio, so even relative, like you've got a small female runner who might...

27:31
have a lot of muscle mass for her size. Similarly, a male who might be the same relative, he will still be stronger and will still have a bit more power. Yeah, no, it's a good point. I should have said that, but it's, yeah, yeah. No, it's not only because we are taller, bigger, even if you normalize to body mass, this is the same. And this is the same for view to max, as I was saying, if you normalize to, of course, if you consider absolute view to max for the same reason, because we have more muscle mass, the view to max in average

28:01
difference is like 30%. But of course, this is not the way we should consider that. So if you normalize by body mass, then we have 10 to 15% difference. Now if you consider the body fat, because you have in average a higher, like 15% higher body fat, then the difference is still there. I mean, it's lower, obviously, but still there. And it's more like between 5 and 10%. But this is still huge, right?

28:30
The first reason why males are faster, even in endurance performance, where power and strength doesn't matter anymore, do not matter anymore, is because of this bigger utumax. So again, larger utumax is due to the fact that we have higher hematocrit, so more red hotels. Also, we have a bigger heart, especially left ventricles. Again, this is due to the role of testosterone.

29:00
So we have a greater cardiac output, etc. So because of those reasons, VU2 max is higher and this is one of the main reasons why in endurance performance, because VU2 max is such an important factor in performance, we have better performance as a, I mean males have better performance. So, and so back to the question, why females are closing the gap?

29:28
when the distance increases. The reason I'm starting with View2Max is because actually View2Max takes less and less importance as the distance increases. So we have shown that. In neutral and alpha it's still important to have a good View2Max and if you look at the best neutral runners like Kylian Jornet, Jim Wamslay, etc. they still have a very good View2Max. But this is not as important as on shorter distances.

29:57
I would say that for females, if you consider ultramarathons, because they have a lower VO2 max, of course, this is not a good thing, but this is less of a problem as compared to shorter distances. Okay. Guillaume, do we have, this is a slight tangent, but are there cutoffs that define what an elite VO2 max is versus a good age grouper and things like that? Do we have those sort of numbers?

30:27
of interest? Yeah, so the top view to marks in males are probably around 95 milliliters per minute per kilogram and in females it's more like 80. Wow. So yeah, there is a huge gap. There is huge. But again, this is not, I don't have the data in kilogram lean body mass, but it is, so the gap is a bit smaller as we discussed, but yeah, the five times some difference is still there.

30:57
event for the top. And this is true for any level of performance. This is very consistent. So this is not only for elite. In average, View2Max is lower for females mainly for the two reasons that I mentioned, so left ventricle size and hematoprotein.

31:20
In my opinion, females are closing the gap is because they have a lower view to max, but view to max is less important as the distance increases. So this is like a kind of a negative reason. I get it. Yeah, yeah, yeah. It's less important. So it's sort of almost, let's say, that's important in the shorter distance, but here, we've removed that barrier, I suppose. Yes, not completely removed, but less important. Okay, less important. Yeah. It's still there.

31:50
too short to see one day a female winning UTMB or big ultra because it's still too short and View2Max is still relatively important, less than on shorter distance but still relatively important even for 100 miles races. Do you think Courtney might prove you wrong at some point? No, I wish. Yeah. I actually know her personally and I will be.

32:17
super happy to see her winning the UTMB. That would be amazing. Yeah. Okay. Cool. Anyway, the second reason is because they have a better endurance and endurance is probably related to differences in terms of muscle fiber composition. So females in general have a greater percentage type 1 fibers.

32:45
When you come to it's not like the number of fibers is different between males and females It is the surface occupied by the type one fibers is greater in females. So this is At the end of the day, this is what matters And so this isn't like like a detail, but I still wanted to make sure that this is very clear to everyone anyway, so the the the volume that's

33:11
put it that way, the volume of type 1 fibers is like, relative volume is greater in percentage in females compared to males. And of course, we know that this is important in terms of fatigue resistance and endurance. Yeah, for sure. And can you remind us or tell the listener what the differences between those type 1 and type 2 fibers, which I know that you talk about all the time in your work, but people may be less familiar with what that actually is.

33:41
Yeah, so we all have different fiber types in our muscles. And there are basically three main fiber types, type one, type 2A, and type 2B, or 2X. 2X, not that many, especially in endurance runners. So it's mainly type 2B, sorry, 2A, which are still fast twitch fibers. So.

34:08
The fast-twitch fibers are more powerful, they have a greater shortening contraction velocity, a greater glycolytic activity, so those fibers are here to do a high intensity performance. On the contrary, you have type 1 fibers, they are fatigue resistant, less glycolytic, so more aerobic sources of energy. They have a greater concentration of...

34:37
of mitochondria, etc. etc. So, and those fibers are, of course, designed to for long distance, long duration exercises. And this is the type of fibers that females have in a greater quantity in terms of course in percentage. Yeah. This is a slight tangent, and I don't know if you do know

35:06
the type 1 fibers compared to the type 2 from I don't know yeah like has what would the reason be do we know? Yes it's probably because training and any type of training but of course particularly like kind of high intensity doesn't mean to be like super high intensity but high intensity training tend to to increase the the type 2 fibers.

35:35
And because males have more type 2 fibers, the effect of training, well, in general on muscle mass, but particularly on type 2 fibers, is greater on males. So that it's not like, it's almost like the other way around, meaning that it's not like females have, of course, this is the same, the same conclusion, but it's not like females have more type 1 fibers. It's more like the other way around, like males have more type 2 fibers.

36:01
And again, this is related to testosterone probably. So when we train, because of testosterone, we are increasing muscle mass much more than females. And this is the reason why we have a greater muscle mass. Because if you consider muscle mass before puberty, there is no difference between the boys and girls. And then after puberty, when testosterone comes in, then of course, the males tend to increase their muscle mass because of that.

36:30
and this is particularly true for type 2 fibers. This is the reason why the distribution, again not in terms of number but in terms of volume of type 2 and type 1 fibers, tend to change and males have more type 2 and females have more type 1 fibers. But anyway, long distance short, at the end females have more type 1 fibers so they are particularly suited for endurance performance.

36:57
It goes with greater capillarity, so they are more able to deliver oxygen to their muscle and as well as the substrates such as lipids. I was looking for a word, but anyway, so, and they also have, so this is another very important reason.

37:24
and explaining why they also have probably a better resistance to fatigability, as we demonstrated in a couple of papers. And they also have, which is probably also important to explain, the fact that they are closing the gap, as we showed in the paper we discussed earlier, is the fact that they have a better, what we call, metabolic flexibility. So they are able to use more fat for a given...

37:52
intensity at a given intensity. We know that for males and females when you increase intensity, you are using more and more carbohydrates and less fat, but at a given percentage of you to max, females use more fat than males, meaning that they can save their glycogen and also they are using less amino acids. And this is probably one of the reasons, maybe it's not like that clear, but it could be one of the reasons why.

38:21
This is probably another good thing in terms of ultra endurance performance, because if you have to use less amino acid, maybe this is also a good thing for your muscle. And Guillaume, is any of this changeable that we're talking about with those muscle fibers? I mean, this is a little bit of a tangent as well. I appreciate that. But it's interesting. I remember doing for Z and talking about fiber types, but...

38:48
not really engaging that much in it because I was like 18 or 19 or something. But I remember knowing or thinking I knew that you could sort of shift from one type to another type of training. Like, so is that, is that true? Is that still what we think happens with fibers? Do you detrain and you end up with more type one as opposed to type two? Well, you can, you can definitely, definitely change your typology, but this is because the changes are relatively minor. So meaning that you have to train a lot.

39:17
observe significant changes but this is still possible. What happens very early in training is that if you are completely sedentary you may have, and this is almost counter-intuitive, but you may have a greater percentage of type 2x, so the fastest fiber types that I was mentioning earlier. If you start to train, and funny enough, if you start to train in

39:45
resistance type activities or endurance type activities, this is the same. It's usually, of course, the training effects are very different for those two types of activity. But here, this is one of the rare cases where you have the same consequence. The percentage of type 2X is reduced in favor of the percentage of type 2A. Oh, interesting. Now, if you train in endurance for many years, you can...

40:15
increase your percentage of type 1 fibers. But it's like super slow, like 1% per year, 1.5% per year. So this is very slow. This is still possible. And this is true for males. I mean, in males you can probably, I mean, not probably, it has been shown that you can also increase your percentage of type 1 fibers. But still, at the end, if you take, well,

40:41
We don't have actually that many data in Elites. So what I'm saying here in terms of males versus females difference in terms of typology is for the general population or trend population, but not Elites. So we don't even know, like we don't know the fiber type composition of Francois Dane or Kilian Jornet. So maybe they have like, and it's likely that actually they have a super high percentage of type one fibers. It's quite obvious, but it has never been measured in my, to my knowledge.

41:09
But is it still lower than Kourtney or Camille Heron? We don't know. It's possible. So what I'm saying here is like a general physiology. And as usual, when you talk about physiology, you still have to keep in mind that in elite, it might be a bit different. And again, another example of this is different, but still, since we're talking about difference between elite and non-elite, is that...

41:35
but this is still related to the topic of the day, because it is sex differences in terms of pacing. So you have this common idea that females have a better pacing than males, meaning that they start slower. Maybe we can get that to that later, but still they start slower, so they are basically smarter. And this is true. If you look at the paper, oh, well, this is less true in your trauma fund, but generally speaking, this is true, that the pacing is more even for females than males.

42:05
But this is true for the general athletic population. If you look at the marathon pacing in elite males and females, you have no difference anymore. Because in the males, maybe a typical average marathon runner will make the mistake of starting too fast for different reasons. That could be actually related to testosterone. Yeah. Anyway.

42:32
And not females. I still have positive speak for females on marathon, but less. However, if you look at the pasting strategies of top marathon runners, males and females, then there are no differences anymore. Oh, it's interesting. So, Guillaume, I think what you need is a big budget in your lab to then go and get muscle biopsies from all of the professional runners that you know, so you can...

43:00
get actual data, but I can't imagine how many of them will want to be able to get something stuck in the middle. It's funny that you're talking about that because if I was able to find, let's say, $100 million, not that much money for some people. So if Jeff Pezos hears this podcast, maybe he can contact me. Yes. Well, I'm sure, I think Jeff actually listens to Micropedia, to be honest.

43:26
So, so, I'll take him when this comes out. Of course, it's a joke, but this is the reason why I'm saying this joke. If I'm able to find this budget, what I will do is organize a race to see the real capacities of women in the trans-durance. So the race will be 500k without any headstation and the winner will win $10 million.

43:56
Oh, amazing. In five years, so that the females have time to prepare. Now we'll see if it attracts lots of females to get this amount of money. Now we have a reason to think that if we do that, maybe we'll have much more than 10% female entering this race. So we have a larger pool of females, so more chance to have a good genetic, like genetics such as Camille and Kourtney. Because this is

44:24
so long that view to max is even less important and endurance and all the positive aspects related to good endurance in females are even more important then we'll see if females cannot win this race and not as I said I'm pretty certain I hope to be wrong but I'm pretty certain that I will never see a woman winning the UTMB but this type of race it could be different.

44:54
Yeah, you might expect it. And Guillaume, why would you take out the aid stations? Because of this advantage, again, to favor females because they have this better ability to use fats. So they need less carbohydrate during the race. So this is again to favor females. And this is the right idea for human beings, right? There were in the past, there were no aid stations where you're going for hunting, right? Yeah.

45:23
Yeah, that's super interesting. And actually on that then, does that then sort of speak to over the longer distance, females may not need as much fuel going in at any given time compared to males? Like, is that what you're thinking? Probably, yes. Yeah, yeah. Which would of course be advantageous from a GI issue perspective. Yeah, it is. In theory, the reality is that...

45:51
This is not the case. There are not that many good studies on that topic, but from what I know, the differences between males and females in terms of GI distress is not that pronounced. And if there is a difference, it's actually the other way around. I mean, females tend to have more GI distress, as far as I know. Yes. Yeah, yeah, interesting. But still, in theory, they need to...

46:20
they need to eat less. Yeah. So if we move to the pacing side of things before we come to biomechanical, because you did mention it. So in your research, have you discovered that men tend to confuse their ambition with their ability? So they go out way too quick and end up sort of dying off, but women are much more sensible. Yes. Again,

46:49
As we discussed earlier, this is not true for elite athletes, but for average runners, this is true. Even so, this is, as I said, I believe less true in ultra for some reasons. I don't know why exactly, but anyway, so generally speaking, this is true. So yeah, one way to analyze this result is to say, okay, women are smarter. So they start slower because they know this is better for them.

47:17
for performance, which is probably true. I mean, that you are smarter. Seriously speaking, I think this is, it could be that, but it could also be related to the physiological differences that we discussed. I mean, if you have a greater power, higher maxima aerobic power, so a greater view to max, it makes also sense that you start faster than if you have a lower view to max and a better endurance. So at the end of the day, the

47:46
differences in pacing strategies between males and females may at least partly reflect the fact that sexes have different physiological abilities. You know what I mean? So it makes sense. It makes sense that if you have a greater endurance and a lower view to max, you start slower. And if you look at the, like among females and among males, like of course there are also differences. We are talking about the differences.

48:14
in between males and females, but we also of course have to always have to remember that among females and among males, there are much larger differences like among a given sex than between the average difference between males and females. Of course, if you look at the view to max, the lowest and the greatest view to max in males and females, of course this is huge. So anyway, so if you took two males or two females with a different view to max and different

48:43
that their pacing strategy will be different, like naturally different. And so again, it probably explains why we have this difference in terms of pacing strategies between sexes. Now the cognitive issue, the fact that you're really doing your best to not start too fast may exist, may still exist. It's difficult to differentiate between the two.

49:12
cognitive and the physical, if you wish. And I was joking by saying maybe this is you to test us wrong, but I'm actually thinking that this is for real, like you, that we don't want to be. And especially if you start to see a woman overpassing you, then you will tend to factor in. And this is probably one of the reasons why men are starting too fast, because they don't want to be passed. But at the end, so it just makes things worse at the end of the day, because they

49:41
but even uh faster and that's it. Yes, I have had many races where I have sort of started out conservatively but I would do that anyway and then across the course of the event pass several people including a lot of males to then have them run past me again and then absolutely fade. It's always like quite hilarious at the time and quite satisfying actually.

50:10
Yeah, there are many stories like that. Yeah. Guillaume, what about the biomechanical differences? Because I do understand that just the way that the woman's sort of pelvis or her hip angle or something, does that change performance outcomes or endurance outcomes? It is a difficult question. There is no definitive answer to my knowledge.

50:40
But one thing you need to remember, something we haven't discussed in terms of performance, we have talked about the differences in V2 Max, in endurance, but we haven't talked about the last pillar of performance, which is running economy. So V2 Max in favor of males, endurance in favor of females, running economy, it's a new game. I see.

51:06
Yeah, so, no, basically there is no, not a great difference in terms of running economy between males and females. Some people have said that because this is a complicated issue, but because of a scaling question, like if you normalize, usually running economy like view to max, you divide by kilogram body mass. But this is less an advantage if you do that.

51:36
is less an advantage for smaller runners and average females are smaller. So if you were normalizing by kilogram exponents, 0.75, so this is a bit technical, but anyway, so again, long story short, the difference between the sexes is minimal. If there is a difference, it will tend to be in favor of females.

52:05
again, I think we should consider that the differences is almost okay. Yeah, so it's not the place to look for. Yeah, so biomechanics. The reason I'm talking about rene economy, well, first, because I think it's important to mention that there is no differences, no set differences at this level. And the other reason is that yeah, biomechanics, if it's the impact of biomechanics will be throughout rene economy.

52:35
And we know that as you started to discuss that there are biomechanical differences that can be spatiotemporal, like in terms of contact time, strike frequency, but also it could be kinematics or kinetics. And as you started to discuss, of course, the cue angle, the cue angle is different between males and females because females have a wider pelvis, et cetera.

53:04
So yeah, there are definitely differences. The functional consequence, the biomechanical consequences of that and the impact on performance and on injuries is much less certain. It's a debated issue. And it is, well, first, as usual, we don't have a definitive answer because there are not that many studies that have studied females. Of course, more and more, but still.

53:34
still not that many. Another issue is the fact that if you consider, let's take for instance contact time or strike frequency. It has been shown that at a given speed, females have a shorter contact time and a greater strike frequency. But it has been often measured at a given speed. Since the maximal speed is, in average, slower for females,

54:02
At a given speed, it means that they are at a greater percentage of their max. And we know that if you increase your speed, if you approach your maximal speed, you will have a shorter contact time and a greater stress frequency. So if you normalize in terms of percentage, maximal speed or maximal aerobic speed, then the differences disappear. You know, so this is a, you know, this is a complex issue. Yeah, sounds like it. Yes, definitely does. And again, what about...

54:30
Thermoregulatory differences, as I understand it, across the menstrual cycle at least, there are changes in how a woman might be able to sort of cool off in sort of extreme heat or environments or something like that. So does any of that play a role in fatigability over endurance when we're comparing men and women? Not that much. Cool. Yeah. Again, this is an area where the answer is not...

55:00
that clear. But if I had to say something, I would say that the differences like running economy is not very important. So definitely not the main issue. I mean, men and women can do fantastic jobs in the heat, but it's not more like women than men. It's both. We know that as human beings, we are very good compared to other species to run in the heat. But this is for males and females.

55:30
That's reassuring I think. I don't think this is... and in terms of menstrual cycles, again, I'm not saying that this is not an issue. Of course, we know that something happened during... I'm not an expert in hormones, but of course there are changes over the cycle, but the changes are relatively minimal compared to, for instance, males and females differences and sometimes...

55:58
I can read that there are not that many studies in females because of that, it makes things more complicated, et cetera. Yeah, but we should not overestimate the effects of menstrual cycles on the form. So this is definitely not a reason to not study females. Yes. Yeah. No, I appreciate what you're saying there. And I think it's probably reassuring to know for women out there listening that actually it's, you know, because again,

56:26
If I think about stress and an event in training, like if you turn something into a big deal, but in fact it isn't, like that actually, that will change how you perform on any given sort of day in itself really. No, no, we should not underestimate the effect, but we should not overestimate it as well. Yeah, yeah, nice. Nice. And then finally, what about neuromuscular fatigue, Guillaume? Like, you know, how does that differ between men and women?

56:56
So we have done a couple of studies to study this particular question. The first one at UTMB in 2012, and what we found is that the race was 110 kilometers, and we compared males and females in terms of neuromuscular fatigue or fatigability. We call that fatigability nowadays, but it's the same, neuromuscular fatigue, which is defined as a reduction in maximal strength.

57:26
the race. And what we found by then is that females were less fatty at the end and particularly at the muscle level because we, as we discussed in the previous episode, we differentiate central and peripheral components of neurosklerotic fatigue. So it was mainly due to the fact that the muscle fatigue was attenuated in female and because it was in a way expected because of this

57:55
what we discussed today, like better endurance, a greater percentage of type 1 fibers that are fatigue-free, etc. So it was expected, but we were like, okay, is it only true in ultras or is it true on shorter distances as well? So we went back to ETMB in 2019, sorry, in 2019, and we did the study again, so comparing males and females, but over different distances.

58:24
from 40k to 170k. And what we found is that again, females tended to have attenuated fatigability, but that was true for short and long distances. So it was not specific to ultra. And again, it was mostly muscle.

58:50
fatigability that was attenuated. And we did another thing, even though we are physiologists, we still kind of investigated very basic but still investigated the psychological aspects. So what we did was only ask our subjects, males and females, okay, did you go to do your best in terms of performance to really race competitively?

59:20
Did you do it more for fun just to finish the race? With this idea that maybe there will be sex differences again with this testosterone component, et cetera. And actually we definitely have to conduct more studies on that topic, but because the answer was, there was a difference. Females, at least they pretended that they were more here for fun and males pretended that they were more here for performance.

59:49
But I must add that if we now compare their finishing or their average speed in percentage of maximal aerobic speed that we measured in the lab in the weeks before, there was no difference anymore between males and females. So maybe it's just, maybe they were, I don't know. So we are at this point now.

01:00:16
The reality is that maybe this is only males pretending that they are not pushing, because they are like, no, I'm doing it for fun, you know, I'm not super serious about performance, but baby they are. And for males, this is the opposite. I'm here to do the, I'm tough. So yeah, I'm doing the race and maybe they are not pushing as much as they are pretending. They've got much more of a competitive edge to them.

01:00:41
Yeah, so we but okay, now, but the reason this is the reason I was talking about this. But again, we are physiologists, we are not psychologists. But the reason I was talking about this result is that when we talk about fatigability, it may not be 100% due to differences in physiology, the psychological aspect not pushing because we are measuring at the end of the race. So of course, if you push less, you're going to be to be less fatigued. So maybe this plays a role.

01:01:09
But I still believe that the physiology is the major component to explain the difference in sexes in terms of fatigability. Yeah, completely. So, Guillaume, with all of this sort of information and, you know, for the potential reasons why at some point in the future, over the longer distances, that gap is obviously shortening to a point that maybe women will overtake men.

01:01:39
Is there any practical application from this information that I can take as an athlete or coaches can take and use with their athletes? Yes, so first we have to remember that we have this reduction in the gap between males and females. So this is, I think, a very important information. We haven't completely discussed that, but we have in a way.

01:02:06
The fact that it doesn't mean that women are better in your trust than men, as some journalists are saying. If you look at even Courtenay or Camille, it may be the exception of these 48 hours, because this is a very specific race, but if you take races such as 100 miles, etc., the best performance like Courtenay basically, she was able to...

01:02:34
be at six to seven percent behind the best males. And I'm talking about races where the best males were present, like UTMB, Western states. Because of course, if you look at the results, sometimes you will see, yeah, females won the race. So does it mean that females are better in your trial than males? No, this is most of the time because there was no good man at the start.

01:03:03
But if you take top, top races such as Western States and UTMB, this is where we are at, like 6 to 7% for the best females. And Courtney, I think, is quite exceptional. Maybe she's exceptional because there are not that many women at the start, but no, she's very exceptional. She's just exceptional, yeah. Anyway, back to your question. I think we have discussed a couple of things that could be...

01:03:31
applied in terms of training. First, in terms of feeding strategies, nutritional strategies, probably females do not have to eat as much as males. Maybe, and this is a common mistake probably done by males and females to over hydrate or overheat during ultra. So I think it should be avoided and particularly in females maybe. And also in terms of training.

01:03:59
because they are naturally gifted for endurance, maybe they need to do less super long endurance training sessions and more maximal aerobic power development sessions. But I'm not a coach, so this is a very difficult recommendation that if I had to train the males and the females, maybe I will ask my female athletes to do more interval training

01:04:29
endurance type sessions. So this is what I would say. And then there are some discussion in terms of injury prevention that should be also specific between men and women, but I'm less a specialist on this area, but I know that some injuries are more specific to females. So you also have to really read this literature and make sure that you do the right prevention for females and males.

01:04:58
this is not exactly the same types of injuries. So yeah, there are a couple of things here. Yeah, no, that's super helpful. And with regards to the distance then, so are we talking about 100 miles and beyond where this sort of might kick in? Or is actually, when you looked at your research, you found that sort of above 60 kilometers, this is where some of these sort of principles may be applied, like the

01:05:27
of change in training or the feeding strategies? Yeah, I was talking about trail running. Yeah, yeah. Oh, no, for sure. Yeah. Yeah. But I think this is applicable to all endurance distances. Like even if you are training for a half marathon, for instance, I think this is still true. Okay. And is it applicable? I know we're talking about trail running. Do you see this? Do we know if this also applies in, say, endurance cycling or those other?

01:05:55
and long endurance sports, would you expect it to be different? Well, most of the topics that we discussed today are applicable to other sports. Yeah. Even though the differences in terms of performance is not the same, for instance, if let's take swimming. The fact, so when I was talking about this six, seven percent difference for now in terms of the best females, keeping in mind that

01:06:25
there are much less women at the start. But still, this is the data we have at the moment. If you look at the super long swimming races, by super long, I mean over 30 kilometers. Like 10 kilometers is too short, because if you look at the results at the Olympics, I'm not sure the open water is at the Olympics, I believe it is, but at least for the world championships, the performance in males and females are still...

01:06:54
different like males are faster even on 10k swimming distance. So this is too short. But if you, too short, if you, if you consider like even longer, like 30 kilometers and longer distances in swimming, then females actually are very close to the best males. And one of the reasons is probably the fact that this greater percentage body fat, that is of course

01:07:24
not a disadvantage and actually almost an advantage in terms of buoyancy in swimming. So this is probably the reason why the gap is closed is smaller in swimming than in rain. Yeah, no, that makes perfect sense. And Guillaume, if I have to put you on the spot, as I will with my final question, in what year will we see women surpass men in the ultra running event, in a long ultra running event? Never.

01:07:54
my opinion. No, but depending on the distance, as I said, I want Jeff Bezos to give me 10 million dollars so that I can have my race on 500 kilometers. And then maybe we'll see the best woman overcoming the best men. Yeah, nice. I love it. Again, I'm joking, but I'm half serious. Yes, no, I appreciate it. We need longer, so...

01:08:23
to be a bit more serious if you take UTMB, you know, this kind of, and this is back to the very first part of the discussion where you are asking me to define what I consider extreme exercise. So for races like 100 miles, like UTMB, I think it will never happen. Again, I don't think I will see a man, I mean a woman winning UTMB. But now if you consider Tour de Géant or even longer races,

01:08:53
maybe this is a different story. I would love to see Courtenay preparing very seriously the Tour des Giants and beating again François Dain or the top top top. I think this is even too short, but how about two loops of the Tour des Giants? I know it seems crazy, but it's not. Because the longer you are, the better it is for women.

01:09:23
So we just need to find a distance that is long enough so that we can see the woman overpassing all the men. Yeah, that would be amazing, Guillaume. And I'll put that note out to Jeff to tell him to contact you after our conversation today. I can give you my phone number if he wants to contact me. Fantastic. Guillaume, thank you so much for your time this morning. I really appreciate it. And where can people...

01:09:52
Find your research. Is ResearchGate the best place? No, I have my personal website. That's right. www. Perfect. And I will pop that in the show notes along with a link to our first conversation on the flush model and the fatigue ability game.

01:10:18
Always a really lovely pleasure to speak to you today. Have a fabulous rest of your day. My pleasure. Thank you for the invitation. Bye bye. Take care.

01:10:38
Alright team, hopefully you enjoyed that and I think that the idea of having a race that extends for hundreds of kilometres with absolutely no support would really put to test the sex differences between male and females in that ultra endurance space and my goodness wouldn't that be super cool if that was to ever go down. Anyway hopefully you enjoyed that and next week on the podcast we speak to Professor

01:11:07
also already been on the show all about amino acids and protein. Number two, a whole heap of new information covering different material. I think you're really going to love it. Until then though, you can catch me over on Instagram, threads and Twitter @mikkiwilldien, Facebook @mikkiwillidennutrition. Head to my website, mikkiwilliden.com. Book a one-on-one call with me. All right, team, you have the best week. See you later.