Heart Rate Variability (HRV), the Menstrual Cycle, Pregnancy, and Menopause
A look at how hormones impact autonomic regulation.
Our understanding of the relationship between heart rate variability (HRV)and the menstrual cycle, pregnancy, and menopause has evolved significantly in the last decade. Tools like HRV4Training and wearable sensors have made it easier than ever to collect data on HRV in real-life conditions, outside of traditional laboratory settings. This has allowed researchers and athletes alike to get a much clearer picture of how HRV interacts with these life stages.
One of the pioneering studies in this area was conducted by Patricia K. Doyle-Baker’s team back in 2019, using HRV4Training to measure resting heart rate and HRV daily throughout the menstrual cycle. This study was one of the first to look at HRV daily over the course of the cycle, rather than just measuring a single data point during the follicular or luteal phases. This provided insights into how hormonal fluctuations affect autonomic regulation, particularly the parasympathetic nervous system (which we assess through HRV).
This being said, group-level changes in a parameter don’t always translate into useful individual-level information for actionability. This issue has become a major concern of mine as companies are quick at advertising some weak group-level correlation and then using it to build a model and provide “insights” that are simply not applicable to the individual who will use the device. Can we really use resting physiology data in useful and actionable ways in these situations?
The answer is nuanced. While daily HRV data certainly gives us more insight into how the body responds to various physiological changes, the key to understanding this data and its potential utility lies in recognizing the importance of both between-individual and within-individual variability.
Let’s get to it.
Between-Individual vs. Within-Individual
When we look at HRV data from large studies, we’re usually examining population-level trends—the average behavior across a group of individuals. While this gives us important insights into how menstrual phases, pregnancy, and menopause impact the autonomic nervous system on average, it often ignores significant individual differences.
Just because, on average, we see a drop in HRV during the luteal phase of the menstrual cycle or the second trimester of pregnancy, for example, doesn’t mean this is true for everyone. This seems obvious, but the issue is that this is exactly how most apps out there use the information: they assume each individual functions exactly like the average of the group. But do they? (no, the answer is no).
Something else we have learned from looking at data collected over several months for a single person is that we not only have between-individual variability (i.e. people respond differently), but we also need to beware of within-individual variability.
Within-individual variability means that even for a single person, HRV data can vary widely from one cycle to the next based on factors like psychological stress, sleep, physical activity, diet or else. For example, an athlete may notice a drop in HRV during the luteal phase one cycle, but in the next cycle, the exact opposite may occur. This inconsistency makes it difficult to draw reliable conclusions about how hormonal changes are impacting recovery, stress, or training readiness based solely on HRV data.
This highlights a key point: even within an individual, HRV data can fluctuate significantly from one cycle to the next, and sometimes, these fluctuations may not be directly linked to the current menstrual cycle phase due to other stressors. Later, we will see the practical implications in terms of using the data.
HRV and the Menstrual Cycle
As already covered above, when it comes to the menstrual cycle, HRV can indeed show some general trends. In the follicular phase, for example, higher levels of parasympathetic activity are typically associated with higher HRV, whereas in the luteal phase, after ovulation, sympathetic dominance tends to increase, leading to lower HRV.
Research like that of Doyle-Baker’s group shows that HRV data can reveal these shifts, offering valuable insights into how hormonal changes affect recovery and performance (on average!). Specifically, the rise in progesterone is associated with increased sympathetic activity. In contrast, the follicular phase is typically linked with enhanced vagal (parasympathetic) activity, which supports higher HRV (and possibly better recovery).
This phase-related variation means that individual HRV data should be assessed with knowledge of the menstrual cycle. This, however, in my opinion, does not mean that we can have strong expectations on how HRV should change based on the phase, but simply that the phase is additional context - together with all other stressors - that might help us understand how we are responding to stress. Being in the luteal phase does not guarantee a lower HRV, it simply provides context.
I think that this is in line with what Kirsty Elliott-Sale and co-authors have repeatedly shown in terms of the menstrual cycle and training: there is no strong evidence supporting the idea that training should be specifically guided by the menstrual cycle phase.
While there are hormonal fluctuations throughout the cycle, which may have some impact on strength, muscle recovery, and endurance (and HRV and resting heart rate), individual variability plays a much more significant role than cycle phase alone, both for outcomes (performance) and resting physiology.
Personally, having worked much with HRV data, I wonder if these two aspects just discussed go together: maybe we don’t see a consistent change in, e.g. performance or recovery in a specific phase of the cycle because the other underlying stressors impact performance and recovery. Maybe we should be looking at positive responses in HRV during a specific phase in relation to performance and recovery, as well as negative responses in HRV in the same phases, and see if there is something there. Do athletes that show a stable HRV during the luteal phase perform better than athletes that show a suppression? Just some thoughts.
In practical terms, this means that HRV remains an overall - sensitive and generic - marker of our stress response, impacted by the various stressors we face, and not specific to a specific stressor (menstrual cycle or else).
Still, for people with a regular cycle, trying to keep track of it could be useful as additional context.
HRV and Pregnancy
Pregnancy brings about substantial changes to the body’s cardiovascular system, and HRV is no exception. During pregnancy, the body increases blood volume and cardiac output to meet the demands of the developing fetus. At the group level, we can typically expect the following:
First-Second Trimester: Early pregnancy sees hormonal shifts, particularly increases in progesterone, which may lead to increased sympathetic activity and lower HRV. As blood volume increases, we have a higher heart rate and, as it often follows, reduced HRV.
Third Trimester: HRV typically reaches its lowest point as the body prepares for labor, with sympathetic dominance becoming more pronounced. However, recent studies suggest that HRV doesn’t continue to decline uniformly; it may increase slightly in the weeks leading up to childbirth, though the mechanisms behind this are still unclear.
Just as with the menstrual cycle, the changes in HRV during pregnancy must be contextualized within the broader picture, including factors like stress levels, physical activity, and sleep disturbances. However, there are very large changes in this case that are unlikely not to take over, e.g. the elevated heart rate and reduced HRV across pregnancy to meet the demands of the developing fetus. This being said, all other stressors, such as elevated stress or poor sleep can still impact the data in the shorter term.
Just like with the menstrual cycle, HRV data during pregnancy is not always predictable and includes high between-individual variability. Recently, a reversed trend has been documented, with HRV increasing in the last weeks of pregnancy before childbirth. This reverse trend, which has been touted by some wearable companies as an accurate marker of labour, is in fact present in only a fraction of individuals, with no relation to gestational age, preterm birth, pregnancy complications, or individual characteristics (this information comes from personal communication with scientists doing better quality studies and having no financial interests behind). The complexity of these changes makes it difficult to generalize from one pregnancy to the next, let alone between individuals.
In my opinion, when tracking HRV during pregnancy, it is unlikely that the data can be actionable beyond what is the typical use: assessing relative changes with respect to recently collected data as a marker of acute stressors, while simply observing the longer-term variations due to pregnancy itself, which might not be actionable.
HRV and Menopause
Menopause, occurring typically between the ages of 45 and 55, brings additional hormonal changes, particularly the decline in estrogen and progesterone, which have important effects on the autonomic nervous system and HRV. As estrogen levels drop, many experience a reduction in HRV, largely due to decreased parasympathetic activity and increased sympathetic dominance.
Unlike the menstrual cycle, which has a more predictable monthly pattern, or pregnancy, which happens in a well-defined timeframe, menopause is a longer and more variable process, which makes data collection and interpretation significantly more complex. This means that research on menopause and HRV has not made the same progress, though we can expect more clarity over the next decade as more people are collecting data with currently available technologies.
At the group level, we could expect the following:
Perimenopause: During the transition to menopause, HRV often shows a marked decrease as autonomic regulation changes. Sleep disturbances—common during this phase—also might contribute to lower HRV.
Postmenopause: After menopause, HRV tends to stabilize but often at levels that are lower than those seen before menopause.
In postmenopausal women, HRV is often similar to that of men, although women may have a slightly higher HRV when normalized to heart rate before menopause. Hopefully, we will learn more about between-individual differences during and after menopause in the next years, together with what lifestyle factors have a larger impact on our resting physiology (or more importantly, on the outcomes of interest such as health and performance).
Wrap up
While HRV provides valuable insights into the autonomic nervous system’s response to the menstrual cycle, pregnancy, and menopause, it’s important to remember that between-individual variability should always be considered when reading about the latest research findings. What we see at the group level in these phases of life is hardly ever consistent at the individual level (this is unlike other stressors, e.g., training, where we can consistently see reductions in HRV that are intensity-dependent both between and within individuals). Hence, data should be analyzed in relative terms rather than compared across individuals or in absolute values, as there is large between-individual variability across all these phases of life. Recognizing that HRV is highly individual and using tools that report clearly how your data is changing with respect to your own normal range (as we do in HRV4Training) is key.
On top of the between-individual differences, we also have within-individual variability to take into account. Within-individual differences refer to how the same stressors lead to a different response even for the same person over time. These differences can make it difficult to use HRV data as a marker of such stressors (e.g., of a menstrual cycle phase). The lack of repeatability between cycles and individuals, combined with the influence of external factors and other stressors, means that HRV data should always be interpreted with all possible contextual information, and the menstrual cycle should serve as part of that context. HRV data remains a generic marker of stress and as such, is influenced by all other stressors.
All of this means that HRV data might not show the expected group-level behavior when assessed for an individual, and different cycles for the same person can also show different responses over time.
It's essential to remember that HRV is one piece of a much larger puzzle (albeit a possibly important one!), and its real value comes from how it fits into your broader health and performance journey rather than being viewed in isolation. Context is key, and especially during the menstrual cycle, when we can look both at long-term and short-term changes in physiology as a marker of stress, we can interpret our stress response better by adding knowledge of the menstrual cycle as contextual information. For example, if you see a drop in HRV during the luteal phase, and there's no other major stressor present (e.g., training overload or illness), it could be a normal physiological change due to the cycle’s hormonal shifts.
Tools that learn your own normal range from your historical data, as in HRV4Training, automatically account for this added variability, as your normal range might be wider when there are such variations.
Finally, given the underlying, long-term physiological changes that occur both in pregnancy and menopause, HRV in this context might be more practically useful as a tool to track short-term relative changes in relation to various stressors. Short-term data can be helpful as it might be more tightly coupled to certain symptoms (e.g. hot flashes), or reflective of your interventions (e.g. increased exercise), depending on the individual, while long-term data will mostly reflect larger and slower physiological changes.
I hope this was informative, and thank you for reading!
How to Show Your Support
No paywalls here. All my content is and will remain free.
As a HRV4Training user, the best way to help is to sign up for HRV4Training Pro.
Thank you for supporting my work.
Marco holds a PhD cum laude in applied machine learning, a M.Sc. cum laude in computer science engineering, and a M.Sc. cum laude in human movement sciences and high-performance coaching. He is a certified ultrarunning coach.
He has published more than 50 papers and patents at the intersection between physiology, health, technology, and human performance.
He is co-founder of HRV4Training, Endurance Coach, advisor at Oura, guest lecturer at VU Amsterdam, and editor for IEEE Pervasive Computing Magazine. He loves running.
Social:
This is super interesting. I am 33 and my body doesn’t produce any estrogen. I have chronically low HRV (I’m normally below 40) but have recently gone through IVF where I’ve noticed when taking hormone therapy, and particularly when taking progesterone, my HRV drops even further. I’ve always wondered why my HRV is so low but hadn’t connected the hormonal factor!
Thank you Marco for reiterating that many factors influence HRV. The menopause transition to complete estrogen failure can take a long time. Almost all women in this stage - the few years before and sometime many years after complete estrogen failure - report poor sleep. It would be an interesting study to see the HRV response in those women who use hormone replacement therapy and consequently sleep better.