The Food Medic - The Latest Insights On Menstrual Cycle Research For Active Women | With Kelly McNulty

Episode Date: June 25, 2025

If the menstrual cycle affects everything from strength to sleep, why are we ignoring it in sport? In this episode of The Food Medic Podcast, Dr Hazel Wallace, a women’s health nutritionist, sits down with researcher Kelly McNulty to discuss the challenges of researching female physiology, the importance of individualised training, and the role of cycle tracking for athletes.  The episode covers: How do the menstrual cycle and hormonal contraceptives affect women’s health, athletic performance, and recovery?   What challenges exist in researching female physiology and why is more high-quality research needed?   Why is individualised training important for women, especially athletes?   What is the role of cycle tracking in optimising athletic performance and recovery for women?   How can women be empowered to better understand and work with their bodies throughout all stages of life? The episode emphasises the need for more high-quality research, encourages a balanced approach to training, and aims to empower women to better understand and work with their bodies throughout all stages of life. The more you understand your body, the more power you have to train, perform, and live on your own terms. So ask yourself: how much could change if you truly knew what your body needs? — If you have a question you'd like us to answer on the podcast, simply send a voice note to [e-mail] – we'd love to hear from you! Stay up to date with the latest health advice, recipes, insights, and updates from Dr. Hazel Wallace and The Food Medic community. Dr. Hazel Wallace Instagram: https://www.instagram.com/drhazelwallace/ The Food Medic Instagram: https://www.instagram.com/thefoodmedic/ Facebook: https://www.facebook.com/thefoodmedic/ Twitter: https://twitter.com/Thefoodmedic Explore More from The Food Medic Not Just A Period – New Book A groundbreaking guide to understanding your cycle, hormones, and health.Coming 22nd May 2025. Pre-order now: https://linktr.ee/notjustaperiod The Food Medic App Learn more: https://www.thefoodmedic.co.uk/about-the-food-medic-hub Weekly Newsletter Subscribe here: https://view.flodesk.com/pages/62b5a28d76b1bf772c403012 Get in Touch For inquiries or collaborations: General: [e-mail] Partnerships: [e-mail] Learn more about your ad choices. Visit podcastchoices.com/adchoices

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There is a huge debate within even the scientific community, and also I think people who are not in that space are even taking it upon themselves to create their own assumptions as to how women should be training across the menstrual cycle. If we look at, you know, gold medal winning performances, personal records, whatever else have been set at all phases of the menstrual cycle, you know, there's not a specific phase where all of these optimal things are happening. Does the pill reduce training adaptation, particularly strength? So there's a lot of theory that it might because of those chronically low estrogen and progesterone. But actually when we looked at the data and it was

another systematic review and meta-analysis, apparently I love to do this. But basically we found... Hello everyone and welcome back to the FoodMedic podcast. I'm Dr. Hazel Wallace, a women's health nutritionist and former NHS doctor, and I'm back for a special women's health series of the Food Medic podcast. In this mini series, we're diving into all things women's health, from expert insights and myth-busting chats to mini Ask Dr. Hazel episodes, where I answer questions submitted by you. Expect accessible, evidence-backed tips to help you feel empowered, not held back by your menstrual cycle and more. Today, I'm joined by Kelly McNulty,

researcher, educator, and founder of The Period of the Period. Kelly's work focuses on female physiology across the lifespan, including the menstrual cycle, hormonal contraception, perimenopause, and how these factors impact performance and recovery. She's on a mission to change the narrative around women's health in sport.

And today, we're diving into the research, the nuance, and what really matters when it comes to training with your cycle. If you're enjoying these conversations and want to go beyond just understanding your hormones and your menstrual cycle and actually learn how to work with them, my latest book Not Just a Period is available. It's a practical science-backed roadmap that helps you align your cycle in every area of your life, from nutrition and mood to body image, skin, hair and more.

If you're ready to feel more in tune with your body and supported by your hormones, rather than confused by them, I'd love for you to check it out. You might notice a QR code floating around if you're watching the video, free to scan. Or if you're listening to the audio version, you can find the link at the bottom of the episode show notes. Kelly, welcome back to the Food Medic podcast. Thank you so much. It's nice to be back in a nice, fancy place.

Yes, I know. We were just talking about how the last time we spoke was probably during COVID times. So it's a lot further along now. And I would love to kind of talk about your journey since we spoke last because you were doing your PhD at the time and you've since done a ton of research in the menstrual cycle in terms of sports performance and recovery. So I would love to talk about what you've been working on since we spoke last. Great question.

So I finished my PhD, it was September, December time in 2022. And that was like what I mentioned on the podcast previously, looking at the effects of the menstrual cycle and hormonal contraceptive use on how we perform and recover mainly. And it wasn't just in elite female athletes, it was recreational all the way through to that top tier as well. After that, I made the packed everything up and moved to Ireland for postdocs. So that was part of the SHE research, the Ascenta now, not a research group, at the TUS. And that was a different life stage, so another female health, but lacking at the effects

of perimenopause and postmenopause. So it's specifically designing programs involving exercise, nutrition, education, from managing perimenopausal symptoms. I then did a whole 180 back to the menstrual cycle after that, so I was a research scientist at Kyniska Innovation Hub for a while. At Desjardins Insurance, we know that when you're a building contractor, your company's foundation

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from 1.74 percent and save up to $4,000. Condition Supply. Visit your GTA Volvo retailer or go to volvocars.ca for full details. No Frills delivers. Get groceries delivered to your door from No Frills with PC Express. Shop online and get $15 in PC Optimum Points on your first five orders. Shop now at nofrills.ca. Well, again, working on not only the research side, but that was a bit more of the applied practice as well. So working across the three teams that they've got there as well. And then, yeah, right now I'm a research assistant at Northumbria University,

so all the way back at Northumbria and also at Bangor University in Wales. And they're two different projects, but in female health as well. So one of them is a female health brain study at Northumbria and the other one is looking at, it's called active periods and it's looking at teen girls and trying to, we know that 78% report any kind of like period pain, menstrual cycle symptoms and even just bleeding is a reason why that reduces their exercise. So it's one of the biggest barriers. So yeah, that's a project trying to reduce some of them barriers and it's quite exciting. It's

co-designing the sessions with them as well, what they want. So it's a bit different as well. But yeah, so just researching any kind of female physiology, menstrual cycles, through to menopause. But yeah, definitely finished the PhD. Amazing. Such important work as well, especially, you know, working from those teenage years, which are so crucial as we know, right up to the perimenopause and the menopause. But, you know, you know better than anyone how difficult, how notoriously difficult it is to do research related to the menstrual cycle. And it's really why women of a reproductive age have been excluded from any health sciences for a really long time because we have that fluctuating 28-day or so cycle. So I would love to just kind of shine some light on what considerations do we need to

take into account when we are looking at research around the menstrual cycle? And why is it so difficult to get really good data? Just so we can start there before we actually talk about what's the science saying now. Yeah, I know that's such a good question as well. And I think when we think about this kind of research area that highlights on that we've got a lack of research, we all know that 6% of sport and exercise science start. And we've all heard that before by the group of Dr. Emma Cowley, and we were part of that group, the Invisible Sportswomen series.

But actually, not only do we have a research in terms of the quantity gap, but there's a quality gap as well. So I think if we go look at one of our studies we did as part of my PhD that was looking at the effects of the menstrual cycle on performance, and only 8% of those studies reached a quality stat of high quality. 42%, if that's correct off the top of my head, was low quality and then the rest was kind of very low. So you can see that it's really difficult to achieve that kind of what we consider high quality research. And you mentioned a few of the reasons why we have that gap.

In the first place, it's expensive and it's not just expensive from a cost, like when we think about consumables and everything that has to go with it, but a cost of both researcher and participant burden as well. If we think about menstrual cycle research, often it's done across three time points across the cycle, so that's three extra visits compared to men. Actually the female brain health study we're doing has got a population of men and women at the minute. And I'm so not used to testing on male participants. You see them once and that's it. The women are always coming back for extra sessions. So it is, you know, that burden on participants and the researchers to be there and then the

cost of the bloods and everything else as well. But I also think we've got this awareness gap. So when we're taught at kind of undergraduate level or even postgraduate level, it's not really taught in kind of research methods in terms of how to do it around female physiology, you know, fluctuating hormones and everything else as well. So not only is it taught and then when we get to PhD level, we have to learn all of that. Or if you're a researcher, have to learn all of those different methods that have to come with it.

And maybe sometimes it's just a gap in knowledge in terms of what methods to use and then for the research produced as normally or typically can be low quality. So yeah, it's just kind of that education gap as well contributing to it. As part of the Invisible Sportswoman series with Emma, we did a paper and sometimes we don't like to mention these stats because people get angry about them. But we actually looked at who was doing the research and on terms of female specific topics, but also who was producing the highest quality research. And we found that when you got like an author pairing of female author, main author and

female last author, they were producing the best quality female specific research compared to any other combination in terms of if that involved in male and male was actually the least quality, but we don't like it because it causes everyone to like complain about it. But yeah, I guess that comes from that potential awareness of maybe women and girls are more, I don't know, used to knowing about menstrual cycle and how that might affect your research design potentially is what we said in the paper as well. So yeah, there's a lot of different reasons why we've got that gap. And I guess it makes it when you're reading a research paper, not only have we got that gap of actually

using potentially big words that people don't understand, but then also, you know, people don't know about these methods of what is high quality and what's potentially low quality and things to look out for there as well. So I think the biggest thing is looking at just the generic study quality, you know, is this study aims, the title, the methods all explained well. And do you know what's going on in the study? Have they done like sample size calculations? Is there anything like a familiarization session or looking at kind of what they've eaten before or exercise before?

Like, have all of those factors been taken into consideration consideration and then we get into the more female specific stuff. So if we're looking specifically at menstrual cycle research, you know, have they defined, you know, the phase of the cycle instead of just being like follicular phase or luteal phase? Is it what point in that follicular phase was the early follicular phase when they were bleeding? Or was it during the late follicular phase when oestrogen is rising, did they use an ovulation kit to identify that as well? Was it the midluteal phase or the late luteal? There's lots of

different specific things you can look at there as well. I guess also the biggest one when we talk about quality is this kind of three-step method that we do in terms of identifying menstrual cycle phase and then verifying it. So we use calendar based counting, that's quite straightforward, quite simple. And then urinary ovulation detection kits as well. So the luck and that luteinizing hormone and that really allows us to kind of guess or predict where we are in the cycle. And then we use the blood's hormonal analysis to confirm everything as well. So that's kind of where most studies are falling down in terms of using that three step or that kind of gold standard is what we call it at the minute in terms of the best practice.

But that said, you know, there is such a need for high quality research, but we can't just ignore all the research that doesn't fall into that bucket as well. It is so valuable and you know, it's got us to where we are today as well in terms of what we know. And there's no need to just discard it, but be aware of those limitations and how they might work or apply to whatever you're doing as well. So yeah, just how we classify everything. So that research pyramid where systematic reviews and meta-analysis are at the top and case studies are at the bottom, it's similar to that. We need to reframe it in a different way. It's not valuable if it's low quality, there's still some takeaways from it, but just consider it in terms of the limitations as well.

And I completely agree with you. I think that like three step approaches, gold standard and amazing when we are getting that in the research and we need to push for more of that. But as you said, that's a lot more expensive than just a calendar based method. And so now that we have like smart devices and or rings and whoops and garments and whatever you have, we're able to collect a lot of data that way. But it is dependent on the user to really log when their cycle is starting or when their period is starting, when their period is ending. And, you know, even if you are having a regular period, that doesn't mean you're ovulating and it doesn't mean you're ovulating on day 14. So there's so many drawbacks from that.

But I agree with you. I think like, we have to take what we can get, but take into consideration like how good quality that evidence is. There's actually a great paper by, she's now a Dr. Ella Smith. It basically has a tiered approach. I normally actually have it alongside if I'm reading any papers, but it's like gold, silver, bronze, and then unclassified. But she's got a few bullet points in each one in terms of how to classify a study.

If someone's reading it first time and they don't know what to look for, it's a nice paper to actually include. Yeah, nice. Let's circle back to what we know in terms of the current research base when we're looking at the menstrual cycle and performance in sport and exercise. Now, that's a really big question and we've covered it before on the podcast, but years ago and since then, quite a few studies have come out. And there is a huge debate within even the scientific community. And also, I think people who are not in that space are even taking it upon themselves to

create their own assumptions as to how women should be training across the menstrual cycle. So let's start with what we know with the science that we have right now. Yeah, such a huge question. And like you say, there has been more research since the last time we were on the podcast. But again, it is still very conflicting. Some studies do show an effect, some studies show still absolutely no effect, whatever. And then we've got to consider the quality of the research that that was done on as well. So I guess the takeaway for talking about performance, and when I talk about performance,

I mean, does your performance, whether exercise metric or, you know, running a marathon, PR, whatever it might be, change on any given day of your menstrual cycle? And right now, no, it shouldn't really have that much of an impact. For instance, if we look at, you know, gold medal winning performances, personal records, whatever else have been set at all phases of the menstrual cycle. There's not a specific phase where all of these optimal things are happening. That said, if we go back to kind of, it is more nuanced and more complex than that. So if we go back to the kind of theory of how this comes about, so we know estrogen and progesterone don't just influence the reproductive system, they affect the entire body and when it comes to performance and training, obviously that is crucial. All of them systems involved can be influenced by estrogen and progesterone.

So there is that theory or that theory behind why performance might change across the cycle, but whether that actually influence our actual performance on that given day, we still don't really fully know. I know we talked about it last time on the podcast in terms of that systematic review we did, but it's still very much applicable in terms of we showed that trivial effect in terms of exercise performance and that was both strength and endurance during that early follicular phase of the menstrual cycle. So when people were bleeding, so normally during days one to five, but it was really, really small and it did come with all those caveats of, you know, the really small effect really small effect size, the poor quality of the research and everything else in between, but

it's still very much the key takeaway right now of that individualized approach. Some people might notice performance changes across the menstrual cycle and others might see no difference at all as well. I think when it comes to performance, there's so much happening on any given day that can influence performance and menstrual cycle might potentially be washed out. But that said, if it's something that's had a lot of symptoms, there's a lot of pain or you're worried about bleeding, it's obviously going to have an impact in some potential way as well. So yeah, mixture between the theory and the research and that perception effect as well, it's difficult at the minute.

When we look at training as well, it gets even more muddier. So when I talk about training, I mean, can we program certain training sessions across the menstrual cycle to maximize adaptation? And mainly people, when we enter this phase, talk about sort of phase-based training, particularly phase-based strength training. There's been one more study since we talked about it and the last time on the podcast. So there was four then, there are five studies looking at it now. Again, it's that same takeaway, treat it with a bit of caution in terms of, yes, there are five studies that show follicular phase-based training. So strength training more on that follicular phase is better than luteal phase-based strength training or straight training

equally across the whole cycle. But take it with a bit of pinch of salt. It's a bit like, you know, how the method considerations and everything that's been taken into account with those studies. So some of mixed menstrual cycles with hormonal contraceptive users still. So it's still potentially something to consider, but we don't know a lot from the research right now. Unfortunately, it's kind of the similar story, and I think, you know, it won't be until another 10 or even 20 years where we get research in that pipeline as well. So yeah, nothing's really

changed from a research perspective, but you know, hopefully there's more we can learn soon as well. Yeah, absolutely. And I think I have recently been thinking about that systematic review that you did been thinking about that systematic review that you did. And just to reiterate for anyone who hasn't read it or hasn't listened to the podcast in that you found that in the early follicular phase, so during menstruation, there may be a small dip in performance in strength and endurance. But it was such a small effect that we don't know like how this is going to actually practically impact someone on a given day. But I think you make a really good point because practically speaking, just being on your period,

if you do have a match or race or whatever is not fun. Like if you've got cramps, you're going to experience some pain, you know, like just the practical aspects of it. I've just run Paris Marathon on day four of my cycle. It was meant to be day one and I don't know why it came early because it's usually clockwork for me. But the practical aspect of that was a little bit of a nightmare.

It meant I had to stop at least once in the race. If it happened a week later, I wouldn't have had to stop. So I think there are some considerations we have to think about practically, but whether our hormones are actually influencing us and impairing our performance or enhancing our performance is another question. And I do think it's super individual because I work one-to-one with clients and I know some just even really struggle to have the energy to get to the gym during that first week of their period or first week of their menstrual cycle.

And some that like really just don't notice and they're super happy. Some who feel better in that follicular phase, that early follicular phase than they did in the luteal phase. And sometimes I'm like that. I'm like, thank God my period came. Can we pass the luteal? Yeah. So I think there's so many things to chat about. And I think one of the studies that I'd love to chat about was, I came out and I know that you and I discussed it since then. And essentially to summarize, they said there was no effect whatsoever when it comes to

performance in the menstrual cycle. And I think there's a few things to talk about there that I would love to pick your brains on. Yeah, no, definitely. And I agree. And I think what you said before in terms of if we're lacking at, and I was probably at the start of my PhD, this was probably my kind of blinkering effect as well as we were obsessed with ovarian hormones and you know what is it that what concentrations of estrogen and progesterone and is it when they're low low at the early follicular phase when we see a decrease in performance or training adaptation or is it when their estrogen is high and progesterone is low do we see that performance and it was very much taking that

ovarian hormonal profile what's happening what the hormone is doing and how is that having an influence on X or Y outcome. And whilst that's, you know, crucial and hugely important and really exciting, actually, you know, we're not just hormones and we don't just perform at this phase when that's exactly low and that's exactly high or whatever else as well. It's a whole cycle of performance on any given day. And there's a lot more to factor in than just sex hormones. So if you think about,

and probably where the body of research has gone, and probably thanks to COVID, but a lot more in terms of the perceptual effects of how women and girls believe or think that the periods influence them. And we've got a lot more studies that are showing that I think it's something like 36 to 100 percent, if you include all the different studies together, that women and girls, percent of them think that their performance is impaired or enhanced by the menstrual cycle. So there's something going on. And then like what we talked about the practical stuff as well. So you know, just if you come on your period, like in the middle of a race or whatever else,

it is all that managing around it. And I've worked a lot with golfers and normally their rounds are say five, six hours where they're out on a golf course. Sometimes they don't have access to toilets and fear of leaking and everything else. And if your brain's not on your performance and it's elsewhere, you're probably not going to be thinking about, you know, like them like pawing a birdie in a hole when their brain's thinking, have I leaked through my shorts as well? So yeah, I think one of the reasons why they might be the perceptual effects as well is obviously symptoms. So we know that if these indirect effects of these sex hormones can produce the likes

of cramps or bloating or breast pain and all of those, you know, the chances are if you've got breast pain and you're running and it's not going to be very comfortable and all of them can influence performance as well. So yeah, I guess a lot of the focus has been on the ovarian hormones and what they're doing rather than those lived experiences right now. And that's where we've got this kind of clash or this almost gap in terms of what the objective measures are saying in terms of this maybe no effect of the menstrual cycle versus the subjective measures of actually, I'm noticing a change in my cycle.

And there's a whole kind of spectrum of that as well in terms of people who actually don't notice any difference as well. So yeah, I think what's really interesting is moving forward, we do need to merge those kind of two sides together. So a lot more research with the objective measures alongside the subjective measures. And maybe it's something that actually we manage. You don't want to say to someone it's all in your head because it's absolutely not.

It's such a difficult conversation to have, but you know, around managing symptoms and managing those perceived effects rather than actually potentially those ovarian hormone levels and what they're doing. So I guess it's a good sign that we can manage things as well rather than just thinking, oh, it's our hormones and we can't do anything about it. So yes. Yeah, yeah. I think like it is, it's empowering to think that it's not holding you back as well.

I think it's, it is a fine balance because you don't want to like frisk for some of them including myself. It's a very, there's a very big difference between different phases of my cycle and how I perform. But one of the studies that I came across when researching my new book was related to a group of female athletes and they believe that they performed worse during menstruation, but actually their tests were faster. So their reaction times are faster and they perform better. And that was a really

good kind of reminder for me going into Paris Marathon thinking, you know, like, I don't want to overthink this and tell myself that I'm going to perform really bad because it's during my period. Yes, I might need to stop and that's a little bit of an inconvenience, but I'm also strong and capable. And like, you know, we watch people at like, who are on Team GB and people at the Olympics who performed during their period and get gold medals. And I think that's testament to like how strong and powerful we are, irrespective of where we are in our cycles. Yeah, absolutely. I think that's such a great message for everyone to kind of take home

in terms of that as well. And I know probably touch on it a bit later, but that kind of more taking that strengths based approach to everything as well. So empowering and, you know, saying that we are, you know, just as strong or just as capable at any point in the menstrual cycle rather than facing it as a limitation or we have to, your performance might be reduced, you might have to manage this symptom and just taking that more positive side of it as well. Yeah, absolutely. I would love to know your thoughts on how this has been, I guess, extrapolated into social media because I've seen a couple of, you know, I've seen multiple videos on cycle phase-based workouts, I've seen PDFs that you can download. I've seen apps integrate this. And I have watched quietly. So I'd love to know what are your thoughts

on this? And are there any potential benefits to it? Are there any potential downsides that women should be aware of before signing up to these cookie cutter approaches to the menstrual cycle in training? Yeah, absolutely. And I guess it starts with, and I don't know, it's probably going to sound controversial, but right now there isn't any science to guide any of the cycle-syncing reels and TikToks and everything else in between as well. But it is a little bit more nuanced than that as well. And I guess that's where, you know, we've got that polarizing view of if it affects everything versus and do X, Y, Z versus it has no difference at all. And I'm kind of, you know,

somewhere in the middle of what everything has to happen. So if we look at those cycle syncing workouts, and this is kind of being very generic across the board, but they generally typically say, you know, low intensity walking, yoga on your period, then it goes into that maybe they classify it as ovulation or late follicular, where you do more strength training and it's more high intensity. Moving into those kind of that luteal phase where typically you see longer endurance type

activities and then into the late luteal pre-per period where it's more. I came back to those lower intensities, walking, maybe not doing as much as well. I do want to sound like I'm not, you know, yoga and all of that does have a place in every kind of program as well. But that is normally the kind of cookie cutter approach that you do tend to see. And it's funny because as you know, a research scientist or all of us were all like, where did this actually start and come from and how did it originate? And I guess it's difficult for us to understand because it takes roughly about 17 years for research to kind of translate into practice. But yet these kind of this hot trend of topics of menstrual cycle sinking seems to just taking off and everyone kind of knows about this kind

of approach as well. But yeah, right now there isn't that high quality body of research to really support any of that, which is really interesting in terms of how, like I mentioned, how it stems and how it's come about. But then, you know, I don't want to sound like I'm so anti cycle thinking. I do think we need to stay away from misinformation and disinformation in the menstrual cycle. There's like a huge amount of that as you know. But I do think if we look at cycle awareness instead of cycle thinking, maybe it's, I don't know, maybe that term's just had a bad rep. But if we think about the positives, it does really make people aware of their cycle.

And it's not just maybe not following the cookie cutterura approach but actually you might notice your performance dip so you might have this symptom and it's actually how can you then use that to like auto-regulate your own kind of training and performance rather than taking the kukikura. So I think my issues or the science community's issues with kind of the cycle syncing is that there's not really high quality evidence to support it right now and we're all happy to change that opinion when we get more evidence. Potentially, it might be more problematic if that makes sense in terms of if it's kind of saying, oh, do this kind of training and you might get better adaptation. Actually, right now, if we're thinking about if we lower our intensity to yoga or walking for two weeks of the cycle

in an already chronically under trained population of women and girls, you probably aren't meeting the recommended physical activity guidelines, then we're actually going to end up probably in a worse place as well. And then I guess it kind of ignores the whole individualized asian of everything as well. So you're going to have different needs compared to someone else as well and taking that just kind of almost and replicating it isn't potentially always going to work out. So I think the focus on the cycle syncing should be more on getting the basic fundamentals

of training and basic training principles rather than the menstrual cycle being at the forefront. It's one issue that we do need to talk about, but it's not the only issue when it comes to training and performance as well. I guess a good way to think about it is use your menstrual cycle as one factor when it comes to thinking about your training. So let it guide you, not dictate what you need to do. Because I completely agree with you, especially when we think about things like muscle mass

and bone strength, which really drops off after the menopause. But what we do now will determine how strong and how fit we're going to be in the menopause. And if we are following cycles thinking workouts that are telling us to only do strength training or any high intensity training, one week of the cycle, that's really not enough to create any strength adaptation. So I think I agree with you. I love that the conversation is happening. And I feel this movement, well, excuse the pun, but like empowerment phase that's happening throughout social media when it comes to women in the health and fitness

space and how they really want to listen to their bodies, regardless of, you know, they have a cycle, they're on contraception, they're postmenopausal, like that's happening. And we definitely need to have more research and support women better in that space. But I almost feel like we're creating barriers by telling them like, only do this on this week, only do this particular workout on that week.

So I'm really glad that you've said that because I know that there's a lot of confusion regarding what women should be doing right now. Yeah. And I think that's it as well. You know, like the whole should thing as well, like women should be doing this, like actually women should, well, do whatever kind of training or performance or whatever suits them best at whatever cycle phase that they might be as well. So yeah, and I think you're totally right. And I guess it's that, you know, I get where we get those polarizing views is like when people are at the extremes of that, you know, like people who maybe cycle syncing has worked and that

is great and whatever and that's great for them. But actually, for the most people, maybe it doesn't work and they don't need to follow it as well. So it's difficult. And I think that's where a lot of the social media friction comes from as well. Like, I know when we put out different studies, there would be like a backlash because that's not what people are experiencing. Or it might be different to what they're experiencing. And that all comes down to those individual differences which are, yeah. Yeah. And I think, I mean, it can be confusing for people because I do feel like there is like two camps which even within the research community where there's a group of people

saying, you know, there is definitely an impact to the menstrual cycle, whether that's perceived or it's objective, subjective. And then there's a camp that says there's no effect. And I often see like those posts get shared a lot and people really want to really want to jump into one camp and not move from there. And I think, and I'm sure people are getting this from our conversation, that it's not black and white and it's a bit more gray and not all studies have found an effect and not all studies have found an effect and not all studies have found no effect. So it's about gathering more data and also considering like, what are we actually looking

at here? Are we looking at the impact of those hormones on muscle mass or strength or performance? Or is it because of symptoms? Is it certain women who experience PMS have different effects? Like so many other things to consider. And I think the best piece of advice is like learning about what works for you and like how your cycle impacts your training. And if it has no impact, like that's amazing.

And like do not change what you're doing. But if it does, and you're really struggling to keep up a momentum across your month, maybe that allows you to be more compassionate towards yourself. And actually, you're not going to do your hardest or your longest run on day two of your cycle because you know that that's just too exhausting for you for obvious reasons. Yeah, no, exactly. And I think what we talked about earlier in terms of those perception studies and the symptom studies, they're not anything particularly groundbreaking, but actually they could have such a huge difference

in terms of how someone's performing or training. So when I think about going back to the start of my PhD, when we were looking at ovarian hormone profiles and we did a study looking at satellite cells from muscle biopsies across the cycle and actually really the output of that in terms of actual practice was so minuscule in terms of how it's going to affect people, but actually our symptoms work. Although we didn't think it was anything that was, like I said before, groundbreaking, actually the practical implications from it are so much bigger than potentially that biopsy study that had all the bells and whistles compared to actually a very basic symptom study that liked to actually, you know, was symptom frequency and severity having an influence on, it was

mainly recovery at the time. And yeah, we actually, and that's where most of the research is lacking is actually, you know, negative cycle related symptoms, having that more correlation with performance and training than the sex hormones, which is, yeah, you know, it might not sound as exciting, but actually, it's probably going to be more beneficial to more women and girls as well. And I'm conscious that we talked a lot about performance, but you just mentioned recovery, which is like another side of the coin. And I know for a fact that my recovery changes, I use a web to track my data. And it's like a perfect, it like perfectly matches with my cycle in terms of like how my heart rate just slightly creeps up towards that like late utile phase.

And then my HRV just slightly starts dropping down and then recovers like on day one of my cycle. And I know that that is reflective of the most of the whoop cohort that Stacey Sims and the rest of the whoop team looked at. But we have other metrics of recovery that we can look at, like they're just crude measures. What else are we seeing in the recovery space when it comes to the menstrual cycle? Yeah, and I actually think potentially the recovery space is possibly the most exciting,

unless that's just me being biased with where my PhD was as well. But I do think, again, theoretically, there is that whole body of research that shows that estrogen and progesterone might influence recovery metrics, whether that's actually reducing the effects of exercise-induced muscle damage or helping muscles repair and regenerate after that as well. Again, as with everything we've spoken about, the research base is very mixed. Some studies show an effect, some studies show no difference whatsoever, but actually there's probably, if I'm being totally, I don't know, maybe I'm just being biased,

but there does seem to be something more of an effect happening in that recovery phase as well. So if I go back to that biopsy study that we looked at, so we were looking at satellite cells, which basically help the muscle repair and recover their like muscle stem cells almost. So we were looking at the early follicular phase. So people came in, they were on their period. So it was day two of their period. They had to do a really heavy strength training session. It was mainly a lot of like press exercise. But pre and post that we took some muscle biopsies and then we tracked their recovery for 24, 48 and 72 hours after as well. So we were looking at neuromuscular measures and then they had the biopsy at 72 hours post. So there was a

lot going on, I saw potestons a lot and they then came back in that late follicular phase just before ovulation we tried to catch people. So when estrogen was really high, did it again and then they also came back in the mid-luteal phase. So seven to nine days after a positive ovulation test and did everything again. What we did see was changes in the satellite cells, how they were going from resting to they then go to proliferation stage and then a differentiation stage. They were different across the menstrual cycle. When we were looking at the early follicular phase, the stem cells were still very much in a resting phase after, so they

hadn't really done much. But when we compared it, the satellite cell response at that late follicular phase, it was much different. They were differentiating and potentially creating more satellite, or contributing to the satellite cell pool or, you know, turning into muscle fibers that way as well. So it's exciting. And we compared that with the hormonal contraceptive group as well that showed like no difference compared to those who were naturally menstruating. But we only did it in 15 participants and like what's that going to inform? Probably

nothing. But hopefully it's something, it's quite a nice pilot study to then hopefully get more research funding for that study. As you can imagine, it's quite a big study, which has a lot of consumables and a lot of research and participant burden. But it is quite exciting that there is still research on them, sex hormones and recovery as well. But yeah, right now, the message is very much, notice if you're any like what you said about you tracking the metrics and everything, lacking at your individual recovery and how that might change across, rather than a blanket recommendation on recovery across phases.

But yeah, I think it's exciting. We just need more funding into that. Yeah, definitely. So I realize we've been talking about naturally cycling women and a huge portion of women who have menstrual cycles are on hormonal based contraception, which obviously impacts those hormone levels and then impacts everything that we're talking about. What do we know in terms of performance and recovery when it comes to hormonal contraceptives?

Yeah, I guess probably keeping it along the same lines of the menstrual cycle in a quite short summary is we still don't really know that much. In terms of actually being able to give blanket recommendations on this type of hormonal contraception X or Y, Z might happen. So yeah, I think when it comes to hormonal contraception the majority of the research has been done on the combined monophasic or contraceptive pill which, and I guess the reason for that is it was predominantly the most used, but that could be changing especially in female athletes. I know from

when we're working in the applied world it's not actually all about the combined pill anymore and I do see more people on those like longer term progestin only type forms. A lot more on the kind of copper coil which obviously has no impact on sex hormones or varian hormones in that way as well. So I think it's really important for those people to understand what their hormonal profile looks like. So yes, it differs from naturally menstruating, but actually it also differs between all the different types that we have. We actually have a paper where we show those hormonal potential concentrations with each

different pill type. And it's actually really interesting to see because you don't normally see a figure that shows you know you see the combined pill and how that kind of spikes daily and then the low natural estrogen progesterone but actually what does it look like on all the other different forms as well. So yeah definitely I think people just knowing and understanding more about what their homeowner profile looks like on that type and then diving into the research on potentially how that might influence bearing in mind that the bulk of research is in the combined pill and you're probably struggling to find anything else that's on it and any research on any of the other types, unfortunately right now.

But yeah, I think it's very much again tracking all the same kind of metrics. You can do that across the hormonal contraceptive cycle, just as you can with the menstrual cycle metrics and what you might do. Some might be different, but yeah, it's very similar in terms of looking out for your individualized patterns and then making any adjustments to performance training recovery that way as well. One study that we did do recently with Dr. David Nolan, so we were looking at does the hormone of contraception, it's quite a big one on social media in terms of does the pill reduce training adaptation, particularly strength. So there's a lot of theory that it might because of those chronically

low estrogen and progesterone. But actually when we looked at the data and it was another systematic review and meta-analysis, apparently I love to do this. But basically we found no difference in terms of taking Hormone and Contraception versus naturally menstruating women in terms of actual training adaptations. And that was all looking at the hypertrophy, muscle strength, muscle size as well. So that is, you know, a really positive finding that it doesn't really have that much of an influence. But obviously, like everything else, it's a lot more nuanced than that as well. So yeah, one paper to potentially go away and read, it did create a bit of a

stir again, like what you mentioned in terms of people thinking that when they were on hormonal contraception, it did reduce their adaptations. So it is again, really individual and yeah, it comes down to your performance and training again. Yeah. We'll grab those papers off you, pop them in the show notes for anyone who wants to do any extra reading. We're integrating these conversations a lot when it comes to high performing athletes. And I'm seeing this even in the sports nutrition space, like perhaps how carbohydrate utilization changes across the menstrual cycle.

And I think for most people like you and I, who are not going to the Olympics, unfortunately, we probably don't need to be looking at it in that much of a granular way. Well, at least we think so at this point, we don't need to. But for those people who are maybe high performing athletes, maybe it's like high rocks, marathons, again, even higher than that championship levels. How can we squeeze out that extra 1% by using the menstrual cycle? What would be your kind of top tips there? You know, when it comes to elite performance, we do often think that they're all doing everything so differently and everything's different and better and whatever. But actually,

at the most elite level, in terms of menstrual cycle specific, we're doing the same things as what everyday people might be doing, but we're just doing it at kind of a more consistent and just doing the basics much better, if that makes sense. So if we think about kind of cycle tracking and the benefits that has, that is something that is implemented at the elite level as well. Before we get the ovarian hormonal profiling is huge in terms of actually identifying if they have a menstrual cycle, has it been verified with sex hormones, and how long ago was that? Was it six months? Was it 12 months? And continuously or routinely updating that as well. Are they on hormonal contraception? What type? Were

they pregnant? How long postpartum? And all of answering those questions, and we just had a paper, it was led by Dr. Kirsty Elliott-Sale that had this ovarian hormonal profile and classification tool. So it's a pretty infographic, but it's also an online tool. And a lot of the elite level at the minute are using that to get to that ovarian hormonal profile. And then from there, we do the data collection and the data and the monitoring as well. So daily cycle monitoring. And that again could be not just using that top level of urinary ovulation kits and blood testing.

That's not feasible and practical in especially elite environments where you're doing it daily. But what is the aura ring or the whoop or whatever else, how we're collecting cycle tracking, so cycle day, and then overlaying all of that with any kind of symptoms. So we were doing something like a symptom frequency time severity where they were looking at rolling symptoms going into performance. And if that was high, what can we do to reduce that because that was having the biggest impact. So those people who had a bigger frequency and a bigger symptom index score typically

are the ones who've noticed performance changes or kind of anything else in the training as well. So how can we reduce those? So it is very much the basics of everything as well. And then staying away from people who notice no difference whatsoever, you know. And I think that is difficult within the elite space as well. So when we think about kind of performance or training, anything small can potentially have a huge or massive output if we think about performance. So it's very careful. Like, yes, cycle tracking is great and there are a lot of positives,

but also we do need to potentially factor in when we're working that, especially at the elite level, the potential negatives. So if an athlete does realize or notice a symptom such as bloating, that actually they were blissfully unaware of it previously and now we've potentially created an issue that has to be overcome. And that could get into their mind a bit more as well. So it's balancing that in terms of cycle tracking. And I think we need a lot more education at the start

before we do any cycle tracking of, yes, these are the benefits, we all know the benefits and they're cited a lot, but actually, what are we doing and what potentially are the negatives? I don't want to say that, but like what are the potential negative aspects and negative sides of it. But also I do think we have a long way to go in terms of the policies of cycle tracking as well.

So data governance protection, who has the access to all of that information and who's the person on the ground leading it. So I do think all of that stuff's not as exciting, but I do think athletes, especially at the elite level, where potentially cycle tracking is a group based rather than opt in at the minute. So yeah, I think it's just something to consider. But yeah, going back to the question, it's probably just doing the basics really, really well, but with that understanding of, you know, we saw that trivial effect in performance and that systematic review we keep talking about.

But actually, if you think a trivial performance effect at the elite level is potentially that difference between winning and losing. So it is something that's being considered, but probably no different from how average people, I don't want to say that, but recreational people who are training are considering it in the same way. Yeah, absolutely. I would love to wrap up by asking you one question, which is what's one myth about women's health or hormones that you would love to see busted?

I do think at the minute when we're talking about it, we need to be careful of talking about, you know, women and girls have menstrual cycles or have a period and they have to manage that or they have to or their performance might be reduced by that or it's mainly kind of framing it in a kind of negative aspect or they might, if we go back to the cycle syncing, your body might have to do ex-training because it's not as capable if that makes sense. So I do think women and girls, we're strong, we're capable, we can be fast, whatever, at any point in the cycle as well. So I think it's changing that kind of more negative, if we're talking about more, let's try and

be more empowering about it as well at the same time, but also, you know, like so it doesn't spread misinformation. And I get that there are challenges with it. Absolutely. People are going to struggle with symptoms, etc. as well. But actually, how can we frame that, like I mentioned earlier, in a more strengths-based, what they are capable of rather than what they're not capable of? Yeah, so I think that's probably the big one as well. And that occurs throughout all female life cycles, puberty and then pregnancy, postpartum, perimenopause, postmenopause. Can we frame it in that kind of positive aspect of everything rather than a yeah, a

negative one. Absolutely. Amazing. Thank you so much for your time, Kelly. Thank you. Thanks. Before we leave each other, I would love if you could just take a moment to rate the podcast, leave a review or share it with a friend or a loved one that you think would learn a lot

from this episode. If today's conversation resonated, my book, Not Just a Period is available and it's packed with practical advice to help you understand your hormones, manage tricky periods and work with your cycle for better energy, mood and overall health. You can grab a copy now through the link in the show notes or via the QR code on your screen. I hope you all have a great week and thank you so much for listening. Hi there. I wanted to tell you about a podcast that I think every single one of you will benefit from. It's called Therapy Works and it's hosted by me, Julia Samuel. I'm a bestselling author and psychotherapist. I invite you into my therapy room where I speak to either a known or unknown guest.

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