In late 2024, several female listeners of our show reached out because of something they had been seeing online and hearing from coaches. New advice was being given based on the belief that, because the benefits of long slow zone 2 training came from research on men, it didn’t necessarily apply to women. The explanation offered was that women naturally have much better developed mitochondrial density and fat metabolism, so they shouldn’t need to do the same training as men to develop those attributes.
The question we were asked by our listeners was whether there was any truth to this notion, and whether they should change their training accordingly. These particular athletes stated that they want to do what’s best for their fitness, but substantially reducing their zone 2 training would be a big change. Understandably, they didn’t want to make a change like that unless it would be prudent to do so.
To debate this topic, joining us today are two top physiologists who are very familiar with working with female endurance athletes. We’re joined by coach Julie Young, whose voice you may recognize as the host of the Fast Talk Femmes podcast, and who is also the owner of Julie Young Training. And we’re also joined by Dr. Dana Lis, the owner of Summit Sports Nutrition.
Together, we’ll dive into the recent research that is being used to make the case that women should do less zone 2 training, to help you assess whether it is a valid argument. Many people like to state their case with “research says” but one of the biggest questions we aim to answer today is whether the research really does say that—or not.
Then, we’ll pivot to analyze the arguments both for less zone 2 training and for doing as much zone 2 training as male counterparts. Finally, we’ll offer our own suggestions on what we think female athletes should do for training.
Joining our primary guests, we’ll also hear from Dr. Kate Bennett, the founder of Athlete Insight, and coach Isaiah Newkirk, the director of the Project Echelon professional cycling team.
So, get ready to question the science, and let’s make you fast!
Episode Transcript
Griffin McMath 00:04
Hello and welcome to Fast Talk: your source for the science of endurance performance. I’m your host, Dr. Griffin McMath, here with Trevor Connor. Not too long ago, several female listeners of our show reached out because of something they had been seeing online and hearing from coaches. There was apparently new science showing that the belief in lots of long, slow, zone two training came from research on men and may not apply to women. The explanation offered was that women naturally have much better developed mitochondrial density and fat metabolism, so they shouldn’t need to do the same work as men to develop those attributes. The question we were asked by our listeners is whether there’s any truth to this and should they change their training? They want to do what’s best for their fitness, but substantially reducing their zone two training is a big change, and understandably, they don’t want to make a change like that unless it makes sense. We wanted to make sure we gave the best answer we could to that question. So joining us today are two top physiologists who are very familiar with working with female endurance athletes across the lifespan. We’re talking with Coach Julie Young, whose voice you may recognize as the host of the Fast Talk Fem podcast, also the owner of Julie Young Training and Dr. Dana Lis, the owner of Summit Sports Nutrition. Together, we’ll dive into the recent research that is being used to make the case that women should do less zone two training, and then help you assess whether it truly makes a strong case or not. Many like to start their case with “research says”, but one of the biggest questions we aim to answer today is whether their research really does say that or not. Listen to hear our thoughts on how strong the science actually is. Then we’ll pivot to make the arguments both for less zone two training and for doing as much zone two training as male counterparts. Finally, we’ll offer our own suggestions on what we think female athletes should do with their training. Joining our primary guests, we’ll also hear from Dr. Kate Bennett, the founder of Athlete Insight, and Coach Isaiah Newkirk, the director of the Project Echelon Professional Cycling Team. So get ready to question the science, and let’s make you fast.
Trevor Connor 02:04
Well, Julie, Dr. Lis, pleasure to have you on the show. I know we’ve got a kind of controversial subject here, so I hope you’re excited to dive into this.
Dr. Dana Lis 02:13
These are my favorite types. Yeah, definitely.
Zone 2 Training, Defined
Trevor Connor 02:15
Good. Well, the topic on hand is whether women need zone two training. I think it’s an important question. It has been challenged. Obviously, there are a lot of high level women endurance athletes out there who are doing a lot of long, slow and it’s been raised the question of whether, “hey, that works for men, but does that actually really work for women?” And there does seem to be some science saying actually that might not apply to women. So we’re gonna dive into this. But I guess the place to start just let’s get right back to the basics: how would you define zone two training, and what are the perceived benefits to it?
Julie Young 02:16
I guess it depends, like if you’re going off of heart rate or power, in terms of kind of dialing in that intensity. But you know, in terms of – if you’re going off, like threshold, which has kind of become a common marker for, like, devising the different training zones, you know, for heart rate, it’s, I think it’s like 69 to 83% of that threshold and for the power, it’s 55 to, I believe 70 or 56 to 75 something like that – but I think generally, just, you know that that intensity, where it’s super comfortable, there’s not a lot of stress, you know, lungs, legs, it’s something you could do forever. Just that cruise type intensity, I think the standard benefits, it’s just kind of, to me, where you’re developing your foundation to be able to do the harder work, like in terms of the physiology and metabolism, and just developing that durability for the long season ahead. I think just like some specific things, it’s where we’re developing that mitochondrial density, the capillary density, also developing those shuttles which will transport the lactate from those fast twitch fibers into that slow twitch that can then consume that as an energy source. So that’s kind of my basic – I don’t know, does anybody have anything else to add?
Trevor Connor 04:13
So the only other thing I’ll add to that is the other perceived very large benefit of this type of training is it improves your ability to use fat for fuel, as opposed to carbohydrates. So it’s carbohydrate sparing. We don’t have a lot of carbs in our muscles. We want to save those from when we’re doing harder, more intense work, where fat stores are somewhat unlimited. So the higher intensity we can go, where we’re relying exclusively on fat, the better. The fitter we are. Dr. Lis, anything you want to add to that?
Dr. Dana Lis 04:43
Yeah, I think just one thing I always look at when I’m working with coaches and riders I always look at, you know, exactly, what the training, the training design, what the goal of training session, each sort of micro to macro cycle goals in terms of training adaptations and you know, if I’m looking at a program that Julie’s doing, for example, and she has, you know, zone two, programmed in and periodized in, I’m always looking at, you know, what are the – what’s the goal? What are the training adaptations? What are the performance determinants of this rider sport – whether it’s mountain biking or road cycling – and then what are the nutrition strategies that underpin those adaptations? So you know that are going to maximize those adaptations? So I think the question I always ask, too, when I’m looking at a training program is it’s not just black or white what’s best for females or males or whatever it’s you know, in a way, what are the performance determinants of a sport, and what level is that athlete as well, in terms of development?
Arguments for Less Zone 2 Training
Trevor Connor 05:39
Well, let’s dive into the argument that’s being made, which is: women don’t need zone two training, or they don’t need a lot of it – I shouldn’t take it to that extreme – the people who have been saying this aren’t saying no zone two, they’re just saying need a lot less than what’s been recommended, because the recommendations are based more on what men need. And it seems like there’s been two arguments that have been made for why women don’t need nearly as much zone two: one is they have much better ability to already burn fat for fuel and to spare carbohydrates, so not really something that women need to train. Another, more recent explanation, you were talking about: lactate transporters. There’s two important transporters, MCT1 and MCT4. MCT1 is what you find on a lot of your slow twitch muscle fibers that take in lactate so that it can be used to power oxidative phosphorylation, basically power the whole aerobic machinery within those cells. And there’s a belief that this long, slow training really increases the density of MCT1 transporters on the surface of those type one muscle fibers. But there’s also an argument being made that, no, the science is showing that that might work for men, but in women, you don’t see an increase in the MCT ones. Is there anything I’m leaving out here, and anything you want to expand on with those arguments for why women shouldn’t be doing zone two?
Dr. Dana Lis 07:02
Yeah, I think a couple of the other is just general arguments that are are more theoretical in backing is one has to just do well so with the presence of higher estrogen levels, and theoretically, some beliefs around estrogen improving mitochondrial efficiency and reducing muscle damage – you know, which could theoretically speed up recovery – and that women have, again, like, just already, as you mentioned, like better lactate clearance. So I think, just, yeah, some of the hormonal arguments that are used, kind of as a framework, are still very generalized and very theoretical. I’ve done some work in in a molecular physiology lab, in the Barr lab, with Keith Barr’s lab for several years and as a practitioner, it was amazing learning for me to really step back and you know, we get this information that comes in, these kind of blanket statements, like, for example, exactly what we’re talking about. And my role in this lab was to basically take research and nutritional interventions that started in with cells up to tissue, like connective tissue, into rodents and then my role was to take what we saw in terms of these molecular mechanisms and see if they worked in humans in athletes. So I think a lot of times when we base these blanket recommendations and exercise recommendations on wide human populations based on molecular mechanisms, I think that’s a massive, massive jump, even when it has to do with factors that we’re pretty confident in, like estrogen. We’ve measured estrogen in females over months and months, and there’s huge variability. Not everyone follows this exact trend in terms of the extra extremes that we see in the peaks and valleys with progesterone and estrogen. So I think just being careful when we’re making those massive assumptions.
Griffin McMath 08:46
I so appreciate you saying immediately, right off the bat, let’s exercise caution, especially when it comes to these hormones, because Trevor and I, in preparation, for this episode yesterday – which, I just have to say credit to you for wanting to walk into a room, figurative room, full of women to talk about the science on women. That takes a confident man and scientist. But one of the things I kept telling him was like, I feel like we do be really careful about who we’re talking about when we say women, and for a variety of reasons. One of those many reasons is across the lifespan. I mean, Julie, you coach young, young female athletes, right? And their hormones going through a certain phase, when we talk about endurance athletes postpartum, when we talk about the impact after menopause, like there’s just so many different things. And then, to your point, person to person, then there’s all this variation too, right? I’m really interested in this conversation and maybe quiet too, because I’m just really fascinated at how we’re gonna do this dance but I so appreciate you saying we’re not the bat, “Let’s exercise caution”.
Trevor Connor 09:51
Well, thank you for the compliment and yeah, I walked into this room also under the weather, so kind of whammy against me. But, I do love that you brought that up because I agree with you. We have to be really careful about how to interpret that science and I’m going to take it a step further and say we also have to be really careful about taking a scientific study and stretching it to the point where you’re making it say something it doesn’t say so, for example, a quote I’ve seen several times in this debate, this is right out of a scientific study which says “physical activity is essential for males to maintain mitochondrial integrity in conjunction with more coupled respiration like females, even though their bioenergetic capacity may remain lower than females”. So basically the gist of this is females have a fantastic mitochondrial density and capability within their cells, and males actually have to train just to be on par with females. So why would females train? My issue with this quote, and this particular study is: it’s not a study in humans, it’s a study in mice, and there’s plenty of evidence showing that mitochondria function differently in mice. More importantly, it’s a study of mitochondria in the livers of mice. It isn’t looking at the mitochondria in their muscle and the impact of physical activity on that mitochondria. So it is a bit of a stretch to take this study, which has been used to say women don’t need to train their mitochondria, it’s already fully developed. But Julie, Dr. Lis?
Dr. Dana Lis 11:27
Yeah, I think I totally, completely, 110% agree with you. With regards to just some mitochondrial studies in in liver cells, there are some mechanisms, or some studies or some questions, basically, that can, essentially – in terms of mechanisms – translate to other mitochondrial cells, like looking at some of the mitochondrial enzymes, some of that information from liver cells can translate to muscle cells. That’s just cell to cell in terms of rodent data scaling up to humans, yeah. I mean, we all we have these calculations that look at allometric scaling, which is like, you know, body size and metabolic rate of a rodent being seven times faster. We always have to be very careful when we’re calculating interventions and assumptions with anything from, you know, metabolic rates or mitochondrial biogenesis from these little rodents that are very different to humans, but they do offer really valuable insight into mechanisms, but I would never base any recommendation off of a rodent study for humans.
Trevor Connor 12:34
Yeah and they even say in that study that mice have a very fast metabolism. The reason they saw no adaptations in the female mice is because, basically, the mitochondria are already maxed out. Humans don’t have that fast a metabolism. I’m not sure we can say that about humans.
Griffin McMath 12:51
When I hear that, though – and especially because that’s one of the big pillars that I think some of this argument is rested upon – since we are, and please correct me if I’m wrong, shy of the sufficient evidence for women in endurance sports, when a study like this comes out, what conclusion can be drawn and implemented in the meantime? Like in the meantime, of us not having this in human models, then what can be taken away from that for coaches and athletes now?
Julie Young 13:18
I mean I guess I personally feel like it’s quite a stretch, you know, and it’s one study on mice and it’s – as Trevor said – it’s hepatic versus muscle tissue and I guess, I don’t know, I just have a hard time, just because I do understand that a lot of the studies have done been done on men, and there might be some differences, but we don’t at this point have anything conclusive to to think otherwise. And I just kind of, I don’t know if this is the place to mention this, but I did want to mention, you know, just my work in the lab, and I see a variety of athletes in the lab and doing resting metabolic rate assessments and metabolic efficiency assessments and, you know, I kind of see this – I see this population of these women that are really all in on this high intensity work, you know, whether they’re like CrossFitters, and everything they’re doing is kind of high intensity, and they’re doing very little, kind of aerobic zone two type work. And this is, I mean, it’s a generalization, but it seems like it’s a pattern. These women come in, they do these resting metabolic rate assessments, and they have high respiratory quotients, meaning, like a high like, they’re burning quite a bit of fat, you know? And here they are, fasted, 12 hour fast, no activity, and burning – excuse me, burning quite a bit of carbs with that high respiratory quotient. So I don’t know this thing that it’s just a given that women are really good at burning fats, I just like – again, I see that also in these metabolic efficiency assessments, where we have the athletes, you know, kind of fueled appropriately, but doing kind of a lower intensity, and gradually increasing that, and watching that respiratory exchange ratio, again, that you know, understanding the kind of substrate they’re burning, carbs or fats, and understanding the percentages of that. And again, I see these women that you know, maybe they fudge on their zone too, maybe they’re not as disciplined as they should be, not doing quite as much, and they have a high respiratory exchange ratio, meaning burning quite a bit of carbs at a low intensity. I also see this even in lactate tests, where these young riders that I work with maybe not being as disciplined as they should be, in their zone two, and not having a really efficient lactate profile, you know, not being as efficient at consuming that lactate for energy as they can be. So I guess I feel like I don’t see it being a truth that women just – it’s a given that they burn fats really well and I think Dana had kind of alluded to this but to me, I guess, it’s not necessarily just about, you know, that intensity, but it’s also how they’re coupling their nutrition with that intensity to amplify the response.
Griffin McMath 16:06
Let’s take a minute to hear from Dr. Kate Bennett, who echoes what we’ve been saying about the labs versus life.
Endurance Training in Women
Dr Kate Bennett 16:13
So I’m a female, right? So I have a very unique perspective to this. I respect Dr. Sims, and I think she’s got fantastic physiology research out there. Sometimes what I find, and this is no disrespect to Stacey or anybody else there, but when we put things in laboratories, they sound great, and then when we bring them to real life, they don’t always show up the way we hope they do or intend to. From my perspective, is that zone two would do two things in one. It could give that athlete some space and time that they need or just some quiet space and time, mindful riding, mindful running and so from that perspective, psychologically, I think it’s beneficial, even if physiologically, we’re not seeing some giant benefit and, too, sometimes just learning how to be moving slow is harder than it is to be moving fast. And so there is, again, a psychological benefit to moving slow as well as like cycling seat time, just being on the bike for that long. If you’re going to be doing an Ironman and you’re going to be on your bike for hours on end, even if there’s not a lot of physiological adaptation, being comfortable on your bike for that amount of time is important, too. So maybe it’s not the physiology we’re always chasing, but the psychology and the adaptations in other ways that we need to meet.
Trevor Connor 17:17
I’m looking right now at a study called “Maximal fat oxidation rates and endurance trained and untrained women”, and they do say in the study that there is some evidence that women burn fat a little better than men, but there’s been studies both ways. But Julie, the thing you would appreciate is when they compared the untrained women to trained women, you saw graphs that you’d be very familiar with whether you’re looking at a woman or a man, which is: in the trained women, they had a much greater capacity to burn fat, and they were able to continue using fat at much higher intensities than the untrained women. So there is definite evidence that women can improve their fat burning capacity through training.
Dr. Dana Lis 18:01
I believe it, and I appreciate that, you know, that the transitional piece is – what you asked about Griffin in terms of, like, what can coaches take away – I’ve worked with tons of different coaches, like throughout Europe, as well as has Julie with World Tour cycling, and I think one of the struggles sometimes with coaches, especially some of the old school, old school cycling cultures, is they really like to latch on to some of these, like novel concepts, like, really latch on to this zone two, less zone two thing, and then go full gas with it about in terms of implementing it into their team’s training strategies and really jumping on to this concept and, you know – “the newest and best thing” – and I just really encourage, yeah, to people to pull back in terms of, like, how is this – is what the study is telling you, how is this actionable? How would you take this and action it in what you do in your role with an athlete? Like, if you’re programming training, and you have any of these athletes that you have data on, you have that data to then make more informed decisions of – in terms of looking at what their oxidation rates are and seeing changes in that athlete as well – especially if you’re testing them regularly, you have the information to make more informed, individualized decisions. But then for general population too – and I think this is where some of the zone two stuff is really, in a way, catching and getting a lot of traction in the social media space – is like the general, you know, general exercise or CrossFit. There are a lot of elite CrossFitters too, but we’re sort of targeting more of a Gen pop, I think, with this zone two and a lot of sort of social media channels, and that’s where there’s a lot of difference between our general everyday active person/athlete versus a trained endurance athlete. And we don’t really have exact cutoffs in terms of you fall in this category, in that category, in terms of defining an athlete, but I think it’s important to really, also really take into context what an endurance trained athlete is versus an active endurance person like myself. (laughs) I don’t race bikes anymore.
Shallow Conclusions in Deep Science
Griffin McMath 20:07
It is. It’s true of this audience, so interested in what you called latching onto novel concepts. There’s a reason on this podcast we’ve had so many episodes about talking about cutting-edge science or technology, because it feels like you got to put a governor on it with this audience, like, “Okay, we know you’re excited about it, that does not mean you need to stop, drop $2,000 and immediately change your personality when it comes to training because of this one thing that comes out”. And that’s why, you know, I asked this question in science and in healthcare, a study like what Trevor mentioned with mice comes out, our initial thing is “okay, if it proves this, then it justifies further research down this line”. We know what to do with it when it comes to that, but for a coach who’s working with a human in that exact moment who sees something like what you said on social media and then goes “oh, well, let’s change what it means for that particular audience” to implement it or not, because for us, it justifies further nerding out, not implementation with a real human.
Trevor Connor 21:05
That’s kind of what I was getting at before, which is we really have to be careful with the research. When I read the argument for why women shouldn’t be doing much zone two, there were a bunch of references there. And if you read it at face value, you go “boy, there’s a lot of science behind this”. But then I took the time, and I went into the studies, and they’re just being stretched. You know, another one that made the case for those MCT1 transporters said that you don’t really see endurance work improving it in women. There was a scientific – or improving the density of MCT1 transporters. There was a reference for that, and I check out the reference. That study was in weightlifting. And you go “how can you make a statement about endurance sports, long, slow training on a study that came out of weight training” – it’s completely different. So again, it got stretched a bit. And where I’m extraordinarily sympathetic is – and I think this is the really valid criticism – is the research hasn’t been done that does need to be done. So I did a hunt for anything, any sort of research I could find on mitochondria in the skeletal muscles of women, on MCT1 in women, these various sides of the physiology and women. And those couple studies that were being cited just kept coming up again because they’re the only studies. But I think that’s where we need to say “we just don’t know”. The research needs to be done. We need to do the research on women, but it hasn’t been done yet, so we really can’t say anything one way or the other, because the research isn’t there yet. I think that’s, to me, what needs to be said right now.
Dr. Dana Lis 22:40
But that doesn’t catch on social media. That doesn’t make you money!
Griffin McMath 22:44
I’ll admit too that sometimes hearing that is so unsatisfying, or it almost feels like, “well, that’s a lazy thing, or maybe you don’t have the same sense of urgency that I have for women to have just as much…. access to this information”, where it’s like “no, no, actually, by saying no, we don’t have enough information to draw this conclusion, we’re doing our due diligence, because we know this population has had a lot of crap happen to them historically with recommendations”. So it’s not a sense – a lack of urgency. It’s not a lack of prioritization or dismissing something. It’s saying “actually, let’s do the same due diligence we would give to any other population, and be careful about the conclusions we’re drawing”. Which, actually, I think is an important question for the audience to understand, is, when we’re talking about this, is the scope of potential impact of just taking those – to what Julie said – like allowing that stretch of logic, are we talking about something that could lead to harm or just not optimal performance? Where’s the scope of impact? What direction could that involve?
Julie Young 23:47
I personally think, at this point, like taking something like that and implementing it is almost more harmful. And I kind of, I guess, I’ve felt this way, kind of across the board with this movement of, you know, staking that claim that women are different than men. And I guess generally, for me, it just feels like jumping the gun on science for like, commercial purposes. But I do feel like, you know, whether it’s stating kind of this big claim that fasting is bad for women, and it’s like, “well, what constitutes fasting?” Because I think – and then I believe that claim was also based on a study of immature mice using a really aggressive fasting protocol. So anyway, I just think generally, like what I found, and then also just, you know, kind of manipulating the training around the menstrual cycle. And I totally understand, like everybody’s individuals, some people have really lousy menstrual cycles, and that might be great, you know, those times they’re just feeling lousy, like, do that. But I just feel like, generally, we’re kind of jipping women. We’re like, at this point, in terms of what we know, best practices for training, like we’re really neglecting the training principles. And I just feel like we’re not training them to our best ability, if we’re going to kind of go, like, grab onto this one study on mice on hepatic mitochondria.
Dr. Dana Lis 25:08
With the menstrual cycle and hormonal piece, I think that’s something that I really want to stress to females and female athletes, because I’ve had athletes – and quite a few that have started focusing so much on their menstrual cycle and their potential individual hormone fluctuations and the symptoms and side effects they’ve been told that they’re supposed to have at these various phases in their menstrual cycle – that they forget to race their bikes and then also fall back on where they are in their menstrual cycle as a reason for why they did not race well that day, when really we know it was six other factors. They were under fueled or whatever. And I just think, like, I really do agree with Julie that some of these blanket recommendations are harmful, and they’re doing more of a disservice, rather than empowering females to really take it like an individualized approach to their training and nutrition. It’s actually a lot of it is actually introducing unnecessary risk and doing a disservice.
Griffin McMath 25:59
It’s so interesting too, right, about the idea of training to your cycle is, in one way, that’s like, such a romantic idea of like, “oh, all of life can follow my cycle”. But you know what? A race day does not check and say, “is this a good date for you? Can we all sink on the same cycle? Please? So that this is optimal?” Like that life and training plans do not work that way so if we only were to train to our cycle, to your point about neglecting the actual bike, it neglects all these other factors and that life does not stop for a woman’s cycle. I mean, first off, no. Secondly, you might not – you may not menstruate, or whatever the thing is, so if we were just so, you know, bowed down always to our cycle, then it does not understand how we can mitigate other factors, or how we can actually participate in the season the same way alongside everyone else.
Julie Young 26:55
I totally agree with you guys. I mean, I think that’s one thing for me as a coach like, we know how there’s such a huge psychological component to performing and I think when these racers, these athletes, are told, like, like, “yeah, you’re bowing down to your menstrual cycle, and you don’t have control, and it has control over you”, but you don’t have control over your race calendar, you know? And I think it’s far better – Griffin, as you and Dana said – like, you know, like, empower that athlete. Like, give that athlete the tools that they can mitigate and deal with those situations. And, you know, again, like, kind of back to these studies, like the studies I’ve seen, like, there isn’t a performance difference. I mean, the sensations might not feel that great, but physiologically, there isn’t really an impact on that performance based on like that hormonal – I think we’re just so much more capable than we give ourselves credit just to kind of buck up and rise to the occasion.
Griffin McMath 27:50
And how empowering to have a coach like you, Julie – oh my gosh, if I had a coach like you around that age and been like, “Yes, I’m ovulating”, or “I’m at this like – I’m PMSing at this particular point in my cycle” and to get a pep talk from you of like, “hey, been there, this is how to manage this aspect of training”. Occasionally, you take the day off because stuff just sucks, sure, but if we could not neglect and incorporate and lean into our coaches and have that ability to say, “Okay, what do I do when I’m this deep into a race and life sucks”. We have to be able to learn. So not dropping it is so great.
Arguments for More Zone 2 Training
Trevor Connor 28:27
I mean, that was the thing I was going to bring up – and yes, I am hiding heavily behind the research right now – probably the best study that I found was a very recent review called “The effect of exercise training on mitochondrial and capillary growth in human skeletal muscles”. So this is really what we’re getting at, and it’s a systematic review and meta regression. So Dr Lis, you’ll appreciate this – your jaw’s gonna drop – it was a meta analysis, and they used 353 studies. Can you imagine pulling all that data together?
Dr. Dana Lis 29:00
Several years of work. Who were the grad students – who put that work in?
Trevor Connor 29:04
(laughs) Poor people. So, 5,973 participants in this. It is a great review. It’s worth reading just in general because it has some really good information in it, but they did address “is there a sex difference in mitochondrial development?”, which has been this whole argument, that women have fully developed mitochondria, so there’s no real use in zone two training. And they have a great graph here showing the change in women versus the change in men. And in men, you see about a 25% improvement in mitochondrial density. In women, it’s about 23%, 23 and a half, and it’s not a significant difference. So that was – the only thing that they found was different between men and women was, you saw, when doing high intensity training, a greater percent change in vO2 max in women than you did in men. But, basically, the argument of this study, pooling all this data together from studies where they have used both men and women – and as you said, these poor grad students who had to pool all this data together – ultimately, their conclusion was the biggest factor in the differences you saw was in the fitness level. But they said this is right out of the study, so the differences are largely determined by the initial fitness level and not influenced by age, sex, disease and menopause.
Griffin McMath 30:28
I like that one got a specific shout out.
Trevor Connor 30:30
Yes.
Julie Young 30:30
I mean, I think that’s more conclusive. For me, that’s way more conclusive than a study on mice, on hepatic mitochondria. Again, at this point, I just don’t see anything conclusive to really change our methods with training women.
Trevor Connor 30:45
So then let’s flip this around, and what is your argument for why women should be doing a fair amount of zone two training?
Dr. Dana Lis 30:53
Sanity.
Trevor Connor 30:53
(Laughs) Good argument.
Griffin McMath 30:59
That’s so true.
Dr. Dana Lis 31:00
For the peace of the world and the well being of people closest to me.
Julie Young 31:04
I think one thing that I always keep in mind with the training is – I’m pretty sensitive to this – is keeping that balance of, you know, understanding that it takes quite a bit of volume to get those adaptations with the zone two, but also understanding that you need just a finite amount of that high intensity work, and that there really is a tipping point, you know, like over – however people want to say it – 15, 20% of that overall volume of training, you know, we really can start adversely affecting, like, the autonomic nervous system, endocrine system, you know, the immune system – all those things that are really just those balancing systems for us. And, you know, sometimes it’s hard with athletes because it’s not something they can actually tangibly feel, but yet, you know, it’s so important, like, I think one of the most important things with athletes is keeping them healthy so they’re not missing training. They can stay on that trajectory versus kind of these dips due to illness. So to me, when I’m doing training, I’m always very mindful of that. Like, we don’t need more of this high intensity. It’s like, kind of finding this balance point. But I also think, like, there are so many other benefits – and Trevor, we’ve talked a lot about this – like, I think sometimes with training, we can get really fixated on the physiologic metabolic mechanisms, but yet there is such a huge psychological, like, mental component to training too. And you know, again, it depends on what kind of athlete we’re talking about. Like, are we talking about athletes doing unpound? Well, you know, if you’re going to be doing that, like, you have to understand what to expect. And I think that is such a huge part of, you know, spending time on the bike, you know, really kind of mentally, physically, knowing what to expect, because that will increase confidence going into these events. There’s also benefit, like your fueling right? Having those days and really dialing in those fueling strategies, dialing in your comfort on the bike, you know – like again, like I remember the first time I did Leadville, it was like, all the things I would never, ever have expected that started being the limiters, you know – and I think those times where you have those days where you’re doing that zone two, you’re spending time on the bike, and you’re working out all those things like the shammy is uncomfortable, you know, I feel not right on my bike. You’re dialing it all in. And I just think you need that time, just for that mental and physical confidence.
Dr. Dana Lis 33:30
The argument, too, I think that’s been made for reducing zone two, it also has to do with, like, an argument for unnecessarily having a factor that increases cortisol levels, so a factor that, you know, we talk about cortisol and inflammation, and that’s bad, we don’t want that and why would we do something that’s not going to give us any sort of physiological benefit? But we’re going to have increased cortisol levels. So that’s, you know, one of the arguments in terms of reducing zone two is that okay, you’re not really seeing those mitochondrial adaptations, but you’re getting increases in cortisol theoretically. So we should decrease zone two. It’s sort of one of the arguments against – sorry, for zone two reduction. But it’s a very limited, limited argument. If you’ve ever tried to measure cortisol, even if you have a point-of-care thing, you could measure cortisol onsite with your athletes? It’s a simple but complicated marker to try an action on. There are so many factors that affect your like immediate cortisol levels that to base your training structure on one measure of cortisol. It’s a stretch.
Griffin McMath 34:38
That’s being nice (laughs).
Trevor Connor 34:40
I agree with you, and I think that point made earlier on, that you know, this is true of men and women, we can only handle so much intensity before we start dealing with a lot of autonomic stress that is going to cause all sorts of issues in our bodies, that really one thing men and women definitely have in common is we need to keep the amount of intensity we do limited. And I will – going back to that huge meta analysis I was telling you about – the one thing I didn’t mention from it is, they said, really the biggest factor. So they looked at volume, they looked at intensity, and they looked at frequency, and their impact on training adaptations. And they said the most important one was frequency. And so again, if you have a limit in how much high intensity you can do, and frequency is really important, then it doesn’t matter. For all of us, we’re necessarily going to have to do a lot of slow training.
Griffin McMath 35:29
You said a few things, a few times, where I’ve just been like, I’m going to need to sit with that for a second. Think we’re all feeling Friday.
Dr. Dana Lis 35:36
I guess, with some of the general messaging that I think – and that’s where, you know, I think the greater impact is with, you know, some of these community these communications around nutrition and training for Gen pop – is, I’ve seen some of the trends in this messaging around female athlete training and physiology and nutrition change a bit from targeting the female athlete to targeting the middle-aged female athlete or active person, and so I think that’s also just a context that it’s important for people to kind of sift out a bit, too, is like we’re seeing this information online or wherever, but the target audience has like from somebody sort of watching this, this evolution of this communication for female athletes change, the target audience has changed as the claims have become challenged with real evidence, or lack thereof.
Trevor Connor 36:28
Now, I have to sit with that one. That’s a good point (laughs).
Dr. Dana Lis 36:32
And I guess what I’m trying to say is, like, you know, some of these claims around female athletes must turn like this because of X, Y and Z and these molecular adaptations and, you know, we all got on a lot of people got on this and, like, “oh, I can’t do this on this day because I’m not gonna actually see muscular training adaptations, because I’m on day 21 of my cycle, or whatever” and I think that was kind of popular for a bit. And then once more, of the science was better communicated around female athletes, and whether it’s training in accordance with your cycle or not, I think that kind of dissipated when the sort of social media concepts were overcome with more research. But now I see with this zone two piece, what’s happening, sort of, with communications is as people are starting to question, you know, the blanket recommendations, the proponents of this are sort of targeting their recommendations more towards not necessarily female athletes and younger female athletes, but more towards female athletes that are experiencing some of the changes that happen with perimenopause and menopause, and sort of changing that target audience a bit too – which, in a way, adds a whole other layer of complication.
Trevor Connor 36:33
I’m going to go back to something you said earlier – because you just reminded me of it, and I think it was such a great point – that we got to be careful about, kind of getting our nose into looking at molecular pathways and saying that gives the conclusion, because I do think that’s part of what’s going on when they’re talking about “women shouldn’t train at this point in their cycle, or talk about the different effects we’re often looking at, well, it has this particular effect on this particular pathway”. But I think of an episode we did not all that long ago with Dr. Egan, where – here’s another review for you. He had a 300 page review with over 1200 citations describing all the different pathways of adaptation that we know of. And we brought him on the show, the first thing he said is, yeah, that 300 page review is a summary, and we don’t even know all the different pathways. And he made the point of “we get a little too simplistic”, like we go, “it’s all about the PGC1 Alpha pathway, so something impacts that it’s a benefit, and if it doesn’t impact that, then there’s no gains to be had here”. But he goes, “we really focus on that one, just because we’ve done a ton of research on it, there are a bunch of others that impact our endurance adaptations and a lot that we don’t know about”. And so I think it’s the same thing where you say, “Oh, well, when you’re in this phase of your cycle, this particular pathway is impacted so training has no benefit?” I think, is looking at it too simplistically, where there’s many other pathways involved, where you might actually get adaptations. You can’t really say this for certain, so I think it’s something we do have to be careful about.
Dr. Dana Lis 39:17
Absolutely. And I think too, just, you know, we look to the experts in different fields, whoever we see as those experts, and that’s something I think I kind of learned as – like working with some of the leading molecular physiologists – is just being able to sit back and observe how somebody who’s really fixated on that specific area of research, how they then translate that to the media or to practitioners, and it was a good learning experience in terms of like, we have just kind of take for face value sometimes what some of these experts will say. But I think just taking a step back and really trying to filter out some of the biases that even the best researchers in the world may not mean to communicate, but just inadvertently do because they’re very fixated on this specific area of research. And that’s where I think, you know, you find that nice match between practitioner and researcher, and that’s where you know the best communications kind of come out from to the general public and athletes and coaches, etc.
Griffin McMath 40:20
Curious and passionate does not a great communicator make, necessarily. And I think that’s you know – if we’ve learned anything from social media – people who are sharing their curiosities or something, they’re really excited that they read, very passionate about helping our particular population, like people who’ve, you know, shared this particular belief, ultimately, they’re doing it because they’re passionate about women, taking care of women, and doing those things. I just think even if science eventually says, “Hey, this is the truth” and then I just hope the way that we get there is sound. And I think that, to me, is the thing I keep hearing over and over, in different ways, from each of you too, is “Yeah, but the methods” or like “this particular detail, and until we get there, do not start making this, you know, claim”.
Trevor Connor 41:08
Well, this goes back to – I mean, Julie, this is why it’s great that you have the in-lab experience and see what actually does impact people and this is why we actually need to do the research because we can sit here and I can go “Well, we do see improvements in fat burning and you know, that’s one particular pathway” and one of you might be sitting there going, “but there’s no improvements in mitochondria, because it’s already maxed out”. And we can argue this to death, but at the end of the day, you need to do the research and say, “Hey, they went out and did 10 weeks of training. Did we see improvements? Did we not see improvements? Because, as you said, we’re each going down our own rabbit holes, and we kind of get fixated on that, but ultimately, doing the research, having people actually do the work and see the impact, is going to account for all pathways. You’re going to see the true results.
Julie Young 41:55
I think too, you know, I think it’s been said that – and I know Dana probably you feel this way – but a lot of times, practice leads science. And, you know, I think we still, even though, you know, we admire and respect experts, you know, I think still we can learn, like with the nutrition, you know, like all the things, like, it’s still individual. And I think we really have to be confident in, that we really can. Obviously, we want good we want sound, like, principles, but also we can learn for ourselves too. Trevor, to your point, like, what’s working? Like, what are we actually seeing translate into better performance? Because at the end of the day, that’s what it’s all about. It’s not about these values in the lab necessarily.
Trevor Connor 42:40
Agreed. And that actually brings up the last study, which I’m going to mention, which was a four year study where they looked at the difference in training between male and female professional road cyclists. And this actually kind of goes towards the maybe a little less zone two. The big difference that they found between men and women was men did more volume, and women did a little more intensity. We’re not talking huge amounts, it wasn’t like the women were doing all intensity and the men were doing all volume, but you just saw women doing a little more intensity and you saw men doing more volume.
Julie Young 43:12
Were they World Tour riders, Trevor, or…?
Trevor Connor 43:14
It just says 20 male and 10 female professional cyclists. They didn’t give much details beyond that.
Dr. Dana Lis 43:20
I just see flags right away (laughs). That’s a really small sample size.
Trevor Connor 43:26
Yes.
Dr. Dana Lis 43:28
I mean, Julie has been – I’d say she probably has first hand experience in terms of, like, trading camps with men’s teams and women’s teams, etc. – I would say, yeah, like the volume sometimes is less, but the races are also different. The demands are different. And I encourage, you know, coaches and athletes to look at, again, what are the performance determinants of their sport? What do they need to win a race or do their job on a team, rather than focusing on their sex as the main focus of determining their training? Julie, what are your thoughts on that piece?
Julie Young 43:58
I guess it’s exactly what you said. Dana – I was thinking as Trevor was talking about that study -you know, obviously, if we just use World Tour, you know, look at it, Tour de France versus the Men’s Tour de France versus the Women’s, and the volume of that of that race. So obviously the trading demand would be different to meet the demands of that race.
Trevor Connor 44:17
That was exactly where I went with this study, because it is an older study. It’s not like it just came out. It came out at a time when women’s races were shorter. Women didn’t have three week stage races. There wasn’t a reason for women to put in the sort of volume that men were putting in. But that doesn’t necessarily mean that they wouldn’t see the same benefits and gains if they did.
Dr. Dana Lis 44:38
I definitely have worked with women who can ride just as much volume as any of the men’s team riders. It’s just not necessary in a lot of context.
Griffin McMath 44:48
This is a good place to hear from Isaiah Newkirk, who points out that women do race long events, among other things.
Isaiah Newkirk 44:57
I personally believe that zone two training is still going to be valuable for female athletes. I can understand the thought process of why you might want to focus more on intensity, but I would kind of argue back that this is when planning training around their menstrual cycle will be advantageous, and that is when timing of intensity and or volume will be best benefited. And I lean on that with my female athletes in particular. But outside of that, you still need to really be specific towards an athlete’s goals and what they’re trying to achieve. And oftentimes, you know, you still have female athletes pursuing long endurance events. And you know, what’s really fascinating is women do tend to be strong suited with endurance, but we still want to train our strengths too, so that’s when I think it’s still important to keep it in play.
Recommendations for Female Athletes
Trevor Connor 45:49
Well, I think it’s time we shift gears a little bit, because I do want to spend some time talking about the practical side. Taking what we do know, what recommendations do you have for women endurance athletes?
Dr. Dana Lis 46:03
I think the main questions I get in terms of everyone working in endurance sport – from coaches to trainers to the athletes themselves, to the physiologists- is, what do we need to do differently with with female athletes? If I had, you know, the men’s and women’s side of a World Tour program, you know what needs to be different between these two groups? And I just encourage everyone to first just start with what are the biggest differences in what these riders need to do for health, for race performance, and their progression as a rider. So I’m talking sort of in an elite performance space of stepping back and breaking it up into kind of those pieces as well, rather than starting with what do we know that’s different, and how do we shape training around hormones or mitochondrial differences that may or may not exist? And I think just with general pop, just really stepping back again and not blanket-recommending across the board with every female athlete. It’s also more about your lifestyle and the context what you’re able to get in for training. Not everyone is training for World Tour. Not everyone’s training for any of the like Grand Fondos. Some of us are just trying to get decent workouts in, and it’s better to get a zone two workout in than nothing at all when, you know, you have 20 minutes or an hour or whatever. So I think it’s definitely taking in the context of real life.
Trevor Connor 47:30
I think that’s good advice. Julie, what do you have to add to that?
Julie Young 47:33
I think it’s just reiterating, probably what I’ve said earlier, but just along, you know, the lines of what Dana said too, it’s, again, I think it just goes back to individuality. And no matter who I’m working with, every single athlete – like, I want to listen and learn about that athlete. And again, just learn like, “Hey, what are our weak links and in our fitness and performance, and what do we need to do to reach the goals?” And to me, I just, I guess I’m just not thinking along the lines of gender, you know, I’m really, again, just learning each individual athlete and, you know, again, what exactly they need. And I guess for me personally, I’m still sticking to just the principles of training, you know, just like those good principles, and again, just tailoring them to each individual.
Trevor Connor 48:20
I’m actually really glad to hear you say that, because I’ve worked with a lot of female athletes, but I’ve never with my athletes said, “Oh, you’re a male athlete, therefore I coach you this way, and you’re a female athlete, therefore I coach you that way”. It’s always been “I just want to get to know the person as an individual and figure out what does and doesn’t work for them”. You know, you start with the basic principles, but then you just see what’s effective. And sure, gender may have some influence on that, but it has an influence on we tried something and, gee, that didn’t work for you. It’s worked for other people, so we try something different for you.
Julie Young 48:52
Yep, exactly.
Griffin McMath 48:53
I do really appreciate what was just said, too, about still taking this as an opportunity to say, “Okay, we do still need to make sure our training programs are individualized”. The way that looks could still very, very much differ from biological female to biological female, and coaches and athletes still should spend time understanding things about the biologically-female body, the hormones, the different fluctuations that happen. But to Julie’s point, really saying, “Okay, now I have a baseline foundation understanding that may end up getting tossed out the window when I understand this specific athlete”. And so none of this is to say that it’s not worth time learning about those hormones, learning about, you know, all the things that could come with that, but sitting down and understanding your athlete trumps all of that.
Trevor Connor 49:51
Well, it’s been a good conversation. I’ve actually been looking forward to this. Julie, always fun getting you on the show and Dr. Lis, it’s a joy of getting you on to Fast Talk. I know you’ve been on Fast Talk Fem a bunch of times.
Dr. Dana Lis 50:03
Thanks for having me. I appreciate it.
Takeaways and Final Remarks
Trevor Connor 50:04
We’ve enjoyed having you. So I think it’s time to round it out. To start with, we do have a question for our forum. Hope we can get some of the women who listen to our show to join this forum. Question, how much zone two training do you do and what have you found most effective for your individual training? So go to our forum, we’ll have that question up there. We’d love to hear your responses. And with that, we finish out our shows with take homes. Dr. Lis, this is a first time for you. This is where each of us has one minute to say the thing that we think is most important for the listeners to take from this episode. So give us some thought. Julie, you think you’re ready to lead us out here?
Julie Young 50:45
I guess I feel like I kind of just said it with in terms of just really respecting each individual athlete and really taking the time to learn about each individual athlete. I also think it’s super important to always think about like context and relevancy, even though something is, you know, stated as a study or science based, I think you, you know, have to be pretty critical in your thinking and just see, does it apply to me? You know, I think too, like I was thinking about this, like, in terms of zone two, like, to me, one of the most important things about training is keeping it fun. And I think, like, zone two rides with your friends can be some of the best memories, and the best parts – like Dana said, sanity. Like to me, that’s the sanity. And I think like training is just – it extends mental and physical benefits. So I guess that’s my wrap up.
Dr. Dana Lis 51:34
I would have no social life and no friends if I didn’t do any zone two on my bike.
Julie Young 51:38
There you go.
Dr. Dana Lis 51:38
It’s the only time I socialize (laughs). My take home is not necessarily related exactly to zone two training, yes or no, but more of sort of the broader concept piece of just trying to empower people to be scientific skeptics. I think that we get really excited and it’s human nature to really want to get excited about a solution or an idea or the newest and latest way I should train. And generally speaking, if you’re hearing something really hot and that’s really prescriptive and blanket recommendation, it’s probably going to die out in a year or two max, and it’s probably not founded in any decent science that you want to make personal decisions around in terms of your training and nutrition and health. Generally, the people with the largest voices and the loudest voices in social media are not the ones in the lab actually doing the work. When I’m in the lab and I don’t have time to make lots of social media things, don’t have that much time in a day, so usually someone’s got a really loud voice and lots of content, they’re probably not the expert in that area – which doesn’t mean you don’t need to take what they’re saying in or not listen to what they’re saying – but just be a bit of a scientific skeptic with how much you take that into your life and your decisions.
Trevor Connor 52:54
Mine is very similar. So I’ll go next, which is there has been a very, very valid criticism that so far, most of the research has been done on men and we haven’t done the research on women. And that is a very fair criticism, and that needs to be corrected, that research needs to be done. But what we have to be careful about right now is saying, “well, the research was done on men, therefore it doesn’t apply to women”. What we can say is “the research was done on men, therefore we don’t know until the research is done on women, it might apply to them. It might not. We don’t know”. But what we have to be really careful about, in my opinion, right now, is saying, “well, that research was done on men, try to find one or two studies that get really stretched to therefore say, well, that’s not right for women, and women have to do something different”. That’s where I think you can get into a dangerous space of giving recommendations that do more harm than good. That’s a place where I would default to saying, “What have really experienced, really capable women been doing in their training? And let’s go with their experience until the proper research has been done.”
Griffin McMath 54:04
That was so well said.
Trevor Connor 54:05
Thank you. Yeah, every once while I do that.
Griffin McMath 54:08
I know – Trevor and I have gone back and forth in this topic in the office, and that was the most eloquent that you put it. I’m like, yeah, exactly that. Well, besides copy/paste that, everything else you’ve all said, I think something that really struck me, and I believe – I think both of you actually talked about this one point – was some of the notes about, “hey, some of this research is actually based on strength, not necessarily endurance”. And then, if we are talking about endurance, how are we defining that? You both said this. I’m just gonna say one of you really pinpointed on the fact that, are you just a fit person who does endurance activities, or are you an endurance athlete, and what does that look like, and how this relates to you. And social media – there’s a character limit and captions, and no one reads the fine print. And the flashiest, first carousel slide gets the headline, so I think being able to have all of us stop and be curious and go, “okay, tell me more”. I think that I would love to see conversations go that route, rather than the inflammatory, “well, that’s a lot of… “And you know, because then we get lost in the sauce of whether or not the science – and it’s like no to Trevor’s point – we want more science with women as the subjects. We want better science in this area. But rather than getting shut down or launching off, it’s saying, “Okay, tell me more. How is this done? Who does this pertain to?” Rather than immediately applying it or getting up in arms. So I really like that once again, we have to define endurance, to define the level of athleticism or how this pertains to you, and that’s my takeaway. All right, it’s about that time. Here’s our question for the forum. For the women on our forum, how much zone two training do you do, and what have you found most effective for your training?
Trevor Connor 56:01
There we go.
Dr. Dana Lis 56:02
Can I add just one more thing? I think just, you know, leaving people with like, “yeah, we have to do more science”, I think it’s also just encouraging that there is a ton of research going on right now in terms of really focused female athlete research. There’s a ton of funding – and directly in the US as well, like UK, Europe – but there’s a big funding body supporting female athlete research. Dr. Kate Ackerman is leading a huge push there, with Boston Children’s and Women’s Hospital, I think is where she her position is? Along with like Louise Burke, who’s, you know, one of the OGs of sport nutrition, Kirsty Elliot Sale, like these are a lot of the female researchers who have been leading the charge in this space and they – I know they’re running a huge study out of the USOC in the next couple months. So there is, like, a lot of research that is evolving and a lot of funding. I do think in the next few years, this conversation will be very different.
Griffin McMath 56:53
What an encouraging note to end on, like, we’re like, “don’t complain we need more science, let me tell you about who’s doing it, and then you just laid out, like, multiple bad (bleeped) women leading the charge. That’s great.
Dr. Dana Lis 57:05
And some dudes too, yeah.
Julie Young 57:07
And I do think it is important to say, like, we can kind of get critical, but it is great that this conversation has started. And to your point, Dana, it’s fueled all this, like, interest and funding. And another program is Stanford, their faster program, yeah, the translational science and Dr. Krauss. Got a lot of good things happening.
Griffin McMath 57:28
Well, the last thing I’d say is even to the credit of the people who are making the argument that maybe we dissected today, I think the heart being in the right place of women deserve to have – like I can really appreciate the sentiment, and I can really appreciate the attention and focus that they’ve drawn to female athleticism and what’s required so, you know, even this conversation isn’t a bash at anyone specifically making that, it’s saying, “wow, I’m so glad this conversation is happening, where it’s the next part of this conversation?” So thanks for having it with us today.
Trevor Connor 58:01
Thanks for joining us.
Griffin McMath 58:03
And that was another episode of Fast Talk. The thoughts and opinions expressed on Fast Talk are those of the individual. Subscribe to Fast Talk wherever you prefer to find your favorite podcasts. Be sure to leave us a rating and a review. As always, we love your feedback. Join the conversation at forums.fasttalklabs.com or learn from our experts at fasttalklabs.com. You can find us on all your favorite social platforms. For Julie Young, Dr. Dana Lis, Dr. Kate Bennett, Isaiah Newkirk and Trevor Connor, I’m Dr, Griffin McMath. Thanks for listening.
