The effects of oral contraceptives and hormonal intrauterine devices on strength and recovery across the menstrual cycle phases. BIO: Hannah Cabre is a registered dietitian and a postdoctoral fellow at Pennington Biomedical Research Center. Her research focuses on the effects female sex hormones across the lifespan on nutrition, health, and performance. Her current work seeks to evaluate the importance of skeletal muscle maintenance for long-term health during the menopause transition.
The effects of oral contraceptives and hormonal intrauterine devices on strength and recovery across the menstrual cycle phases. BIO: Hannah Cabre is a registered dietitian and a postdoctoral fellow at Pennington Biomedical Research Center. Her research focuses on the effects female sex hormones across the lifespan on nutrition, health, and performance. Her current work seeks to evaluate the importance of skeletal muscle maintenance for long-term health during the menopause transition.
Today I'm going to be presenting on some of my dissertation work that I did at the University of North Carolina and then bringing a little bit to the field kind of call to action in terms of next steps with female physiology research. So these are my objectives for the talk today, and we will first be going through what the menstrual cycle is for those of you who might not be as familiar with it and introducing some hormonal contraception mix into the mix with this and really trying to understand their potential influence on performance. And then we'll look at the literature that exists for strength and recovery and I'll discuss why I wanted to focus on those two specifically for my dissertation and then go into some next steps and practical applications. So it's important to understand female physiology because females are different than males. So on this schematic we can see that there are differences in our respiratory system, our circulatory systems, skeletal muscles, the way that our motor neurons influence contractions and even the way that things are processed on the neural level, and so this can have large implications for exercise performance and that amounts to women being less fatigual. And this is in terms of just the whole systems and I'm not going to walk through every single part of the schematic here, but if you look at it, you can see that parts of this can be very directly influenced by what we're eating, how we're training and the menstrual cycle itself, and that relates to looking at estrogen and progesterone and how that is different than testosterone in males. So, looking at just this difference in physiology, we would think that we would want to know what females and how females specifically respond to exercise and nutrition. But this review by Cowley et al from 2021 looked at about 5,000 different papers and exercise physiology journals and they found that only about 6% had only female participants. There was a large percentage that included both males and females, but that percentage did not always include sex-based differences. In their analysis, and in that only 6%, we see that about 64 publications looked at female-specific factors within their research, so that includes things like pregnancy, what phase of the menstrual cycle they were in and if they were using hormonal contraception. So OC here stands for oral contraceptives, and then the UM is eumenereic women. So the difference between those who are using some form of hormonal contraception versus not was only about 42 in that total of the 328 publications in females, and none of these studies looked at hormonal intrauterine devices, and so this has really large implications for performance, injury, nutrition and recovery and looking at how we as practitioners and researchers can influence our females.
Speaker 1:So this is a human reac menstrual cycle and you may have seen this before, you may not have. So I'm just going to walk through this briefly so you can see that, beginning at day one, this is the onset of menstruation, so the bleeding period and at this time point the estrogen and progesterone are really low, so there's not a lot going on hormonally. Things are basically resetting in the body after pregnancy does not occur and across about 14 days. This is just an average, so it varies between women on how long their menstrual cycle lasts, but just the kind of standard is 28 days and right about before ovulation, at 14 days, we see that there's this peak in estrogen and that's what triggers the ovulation, which is where the egg drops, and then that's how a woman can become pregnant. And if that does not occur, if pregnancy does not occur, we see that there is a huge increase in progesterone and in estrogen in that mid luteal phase and this is where women will start to feel bad. They'll have pretty much like bad symptoms. They'll feel bad. They have differences in their cravings and what they might be intaking and then that kind of resets again. So this happens every month and most of research will look at the earlier follicular phase and the mid luteal phase as the time points within their study. So we can see that this leads to some changes within our oxidation specifically. So a lot of the research that's been done has been looking at resting, energy expenditure and then oxidation rates. And I just want to call into your attention the luteal phase specifically, because we see that there's this increase in fat oxidation, increase in protein oxidation, decrease in carbohydrate oxidation and then the ability to store glycogen is higher. So in this phase we could see that there could be potential implications for aerobic exercise and this study by um Hackney et al in 1994 does a really good job of demonstrating this. So we see at the lower exercise intensity of 35% in the mid luteal phase, so the um black box right here, uh, the uh black box at the top there is going to be the fat oxidation and that is really high and as the exercise intensity increases we would expect that it decreases and carbohydrate increases too. But we can see that it's pretty consistent across the board in terms of being higher in that mid luteal phase. So knowing what to eat and how to eat and how to feel your aerobic exercise is going to be important here.
Speaker 1:But uniquely, women can manipulate their menstrual cycle with hormonal contraception. So this is CDC data for 2020, demonstrating different contraception types to prevent pregnancy, and the most common ones are the oral contraceptive pill and then long-acting reversible contraception, and that includes intrauterine devices. And in preparation for my dissertation, I conducted a study of 670 females a survey study, and we were asking them what contraception type they mostly use and, as you can see by the results, about 48% said that they were using the oral contraceptive pill, which is what we expected to see, and then about 40% said they were using a hormonal intrauterine device. So this was pretty surprising that this percentage was as high as it is, and pretty concerning, considering that there is not really any literature that is specific towards hormonal intrauterine device users. And just a quick kind of picture here of what this looks like comparatively to the last slide on pneumonorrheic menstrual cycles there's a consistent amount of hormones that are being released across the 21 days in females, and then you can see that in our IUD users. It looks basically the same to what we would expect to see with the human ureic menstrual cycle, but a little bit higher in that progesterone here. So this calls into question would our performance outcomes in intrauterine devices users be similar to human ureic women? So a lot of information was just given.
Speaker 1:Just wanted to recap here before we move on. So understanding that female physiology should be considered preferred for performance, specifically looking at the nutrition and aerobic outcomes. And then we can also see that there is a large hormonal landscape differences when we look at hormonal contraception and how that could potentially change some of these performance outcomes. So specifically I was interested in looking at strength and recovery and that anaerobic piece of exercise, since a lot of literature has been done in the aerobic side of things, and so the theoretical model that we were proposing is that when we see that these different hormones are introduced, whenever the hormones were lower in any of these forms, we would see that strength would be higher and that recovery wouldn't really change between hormonal contraception types in pneumatic women. And then when we got into the high hormone phase, that luteal phase where progesterone is higher, we would see that there'd be a decrease in strength and then the same things where recovery wasn't really changed.
Speaker 1:So, looking at the literature here, we see that there is some data from 2019 looking at the effects of the menstrual cycle on strength and outcomes, and so they had 13 females come in and these were very well-trained women, they were triathletes, they were not using any oral contraceptives and we see that they tested them at that the three time periods the early follicular phase, the late follicular phase and the mid luteal phase. And this is really important and unique because sometimes we don't see that late follicular phase being examined, but here they did. And overall, on these figures here we see that the mean force, so their power output, did not change at any of these time points, suggesting that the strength was very similar between them. And again, these were very well trained women. So this is good to see that there may not be strength outcome differences when looking at the menstrual cycle.
Speaker 1:Now, this next study took a little bit of a different approach and they did a training outcome. So they had women 18 women come in and do 10 weeks of resistance training and endurance training and they had a hormonal contraceptive group and then a humanureic group. So this study wasn't necessarily looking at phase differences between these. They were looking at the differences between hormonal contraceptive users and non-users, and this data presented on the slide is looking at the post visit, so after the training was completed, what they saw. So in our isometric leg press they saw that there was not really any significant differences these graph figures look like there might be, but there wasn't any significance between these and both groups did improve over time. So we see that they were both able to respond to the stimulus very well and that there weren't any differences between the groups in terms of performance outcomes. And that was the same for the leg press one repetition max. We see that the E-menorheic women might have had a little bit higher, but only about five kilograms there, and then the counter movement jump was pretty much similar between them. And one thing that I want to point out on this slide is the error bars. The error bars are very large in this study.
Speaker 1:So we're looking at group means here and that kind of brings into question the use of the group means when we look at individual effects and possibly differences across the menstrual cycle and between these hormonal contraceptive types. So in my dissertation we had 60 females come into the lab for a cross-sectional study and we tested them once in their early follicular phase, so during menstruation, and then once in their gluteal phase, and we confirmed ovulation to make sure that we were testing them within each of their respective phases. And we had 21 oral contraceptive users, 20 hormonal IUD users and 19 eumenoreic women and so we did a one repetition max leg press. So the LP1RM is leg press, one repetition max. And we saw some interesting data when we looked at the differences between the groups. Looked at the differences between the groups, the positive value here shows that in the change score shows that the group means were more positive within the luteal phase and this negative value here shows that the hormonal IUD users actually had a greater leg press 1RM in their follicular phase. So these group means do show that there might be possible differences between hormonal contraceptive types and compared to human or women across these phases. But interestingly we plotted out the individual effects here and this shows, I think, a really interesting picture. When we look at the data, so up on the top of this figure here, we see that this is the change scores for each of these. So that would mean that this specific participant performed better in the luteal phase, while this specific participant performed better in the follicular phase. So there is a great diversity in the response of each individual person that isn't necessarily captured within this group means. So, moving forward, it would be very important to look at some of our individual effects and at least present these data and be cautious about what these group means are showing us.
Speaker 1:In my dissertation we also looked at all of these other outcomes of strength. So we did a bench press, one repetition max, some isometric diamometry and countermovement jump and reactive strength index, and between groups there were no significant differences on any of these outcomes. And again we did see that there were group mean diversity between the menstrual cycle phases. So here this negative value shows that there was the improvement in the follicular phase and then a higher value within the luteal phase. So the values weren't consistent across each contraception type or across the phases as well. So when we look at it as a whole, even outside of these studies that I've presented today, it seems that there are equivocal findings with strength and that it's possible that large muscle groups and the athletic status of these women could be influencing some of these outcomes, specifically when we look at hormonal contraception type.
Speaker 1:And so, moving on to recovery, we see that this really nice review by Parari et al showed that eight studies show women were less fatigable, meaning that they had better recovery on subsequent exercise bouts luteal phase. So the results are pretty mixed and a large reason for that was some of the differences in methodologies and techniques to use to find the menstrual cycle phase. Specifically, when we look at some of the differences in recovery markers and so a lot of the previous literature has looked from biomarkers such as IL-6 all the way down to total workloads. So this kind of creates a non-consensus with terms of recovery and performance between or fatigue ability between bouts. But overall it seems that it is kind of mixed.
Speaker 1:So one study here in six humanoreic females so not using any oral contraceptives but using workload as their primary outcome, showed that there was greater work within their luteal phase versus follicular phase and then that the recovery VO2 is also greater in the luteal phase and the follicular phase. So this is interesting, especially when going back to looking at some of these oxidation rates and how nutrient oxidation can impact our exercise outcomes. And there was no differences in peak power or blood lactate between these menstrual cycle phases, suggesting that there may be some differences when we look at workload as the main outcome for recovery and ability to perform. So in my dissertation we had the women also perform a 10, 10, six seconds sprints at the highest amount of power that they could muster and we saw that overall the follicular phase was not the benefit for recovery. So the peak power, the time to peak power, average power, the fatigue index and blood lactate clearance were not as high within the follicular phase compared to that luteal phase.
Speaker 1:So our research does align with some of the previous research, showing that the luteal phase may be a little bit better for recovery pieces, and going into this paper is in press right now with JSCR, and so we show a lot of our individual effects within this paper for the same reason of transparency between our specific participants. So, going back to this objective, looking at our current state of strength and recovery, it seems that for both of these there still needs to be a lot more research and right now there's not a clear outcome with which phase or hormonal contraceptive type may be better. This could suggest that research does not only need to be limited to human or yuck women in that follicular phase, that we should expand this to include more women, whether they are using hormonal contraception or not, and then also really focusing on this individual effects versus the group means. So when we look at what our practical applications are for practitioners and for people working with female athletes, we see that this is a conversation that should be had and it really should be driven by the participant, the female athlete themselves. And looking at personal autonomy first. So if you are on social media of any type, you may have been very familiar with this new kind of wave of cycle syncing in terms of what you should be doing with exercise and nutrition in each cycle, and also looking at is hormonal contraception even good for you, should you just be not using anything at all? And so, as those conversations come up, with your clients and your athletes being able to have an open conversation about what's works best for them because in terms of pregnancy, working with a pregnant athlete is going to be a lot harder than working with someone who is using an oral contraceptive pill and also looking at if they're comfortable with cycle tracking and being able to manage some of these symptoms with that, and oral contraceptives and hormonal IUDs can be very helpful with the mediation of some of the negative side effects of the menstrual cycle, like heavy bleeding or premenstrual syndrome. So again, they are not all bad. We do not have enough data to support cycle syncing or changing in our differences of our phases for exercise and then for sports nutrition. This is a little outside of the scope of this presentation specifically, but this is a really great review published in the JSSN and I would highly recommend reading this. There's a nice infographic discussing some of the applications for the differences in oxidation we do see across the menstrual cycle. That would be really great to refer to.
Speaker 1:And then, in terms of future research considerations, the first one would be did you include females? We should absolutely be including them and then, within that, adequately describing them. So you might not need to be excluding women if they're using hormonal contraception. But it can be very useful to report that within your study characteristics, demographics and then also reporting the time of testing, so you might not have to only test in the follicular phase, but it can be helpful to show some of those data in your papers and then also reporting sex-based differences and individual differences, making sure you're powered appropriately to do that so that if you are including males and females, there can be this discussion between the differences in sex and then reports other than group means.
Speaker 1:So, even if it is something like the individual effect figures, to clearly show how these participants are responding to the interventions that you are conducting, and then also considering if your primary aim does require specific menstrual cycle testing, thinking about the time of testing, if they are looking at large versus small muscle groups, repeated measures, all of this can be led to inform some of your research practices, led to inform some of your research practices. So here are my acknowledgements and my contact information. I would definitely like to thank Dr Abby Smith-Ryan, who is my advisor for my PhD, and all of her expertise, and the rest of the lab team that helped me conduct my dissertation, to Dr Antonia, the ISSN, for inviting me to speak today, my participants and the National Strength and Conditioning Association Foundation, who supported my dissertation.