Wearable devices can offer impressive insights into sleep, heart rate, body temperature, activity and more. These are all measures that may fluctuate with, or impact, a person’s cycle. Wearable users may be interested in how their measures change across their individual cycle, and how those changes play out in their day-to-day lives—from sleep quality, to strength building, to endurance, to recovery after a workout. Some people may notice cycle-related variations they didn’t know were there. People may also find they’ve overestimated the role of the cycle for certain things, like mood, and underestimated the role of sleep.
A bunch of us here at Clue are nerds about wearables and what we can learn about our bodies from them — you’ll see various devices on our hands and wrists when you walk around the office.
Wearables also have the potential to advance reproductive health research, something we’re particularly excited about. We have partnered with ŌURA, a new ring that measures body temperature with a higher degree of accuracy than devices worn on the wrist. Our partnership means that users of the ŌURA ring can now sync their ring with the Clue app to help our researchers learn more about female health, and to eventually improve tracking and personal insights within Clue.
(In the interest of transparency, a disclaimer: It is also a financial partnership, and Clue will receive a portion of any sales of the ŌURA ring with our promo code. This post was written independently by Clue’s team of researchers and writers.)
Here are a few cycle-related changes that you might look out for when using ŌURA or another wearable:
What you can learn will depend on the measures and accuracy of the wearable you use.
1. How quickly you fall asleep (sleep latency)
Sleep is tied closely to hormones. Women are more likely to report sleep disturbances and insomnia than men, and people with irregular cycles are more likely to report problems falling, and staying, asleep (1, 2).
Some research suggests some people may fall asleep more quickly and easily during the follicular phase (the first part of the cycle, between ovulation and menstruation)(3). These changes may be influenced by the hormone progesterone, which is dominant during the luteal phase, and low during the follicular phase (the first part of the cycle). Not all studies agree — others have found the timing of sleep across the cycle to be stable. Tracking can help you learn what’s true for you (2, 4).
Certain cycle symptoms, such as cramps, might also make falling asleep more difficult for some people. Cyclical troubles with falling asleep are also a complaint with premenstrual dysphoric disorder (PMDD) (5). ŌURA shows you how long you laid in bed before falling asleep.
2. How long you spend in REM sleep
Research has found that the amount of REM sleep a person gets changes over the cycle (6, 7). During the luteal phase you may enter REM sleep more quickly after falling asleep, but spend less time in it overall. People also tend to report lower overall sleep quality during this phase, which could, in part, be influenced by an increased body temperature, but more research is needed (6, 7, 9). ŌURA tracks how much time you spend in REM sleep each night.
People may also notice that they are sleepier during the second half of their cycle, despite how much sleep they get (10). This is likely related to the hormone progesterone, which is sometimes called the “calming hormone.” Luteal-phase drowsiness may be especially noticeable for people who’ve been diagnosed with PMDD (4).
3. How many sleep disturbances you have
In research, people tend to report lower subjective sleep quality around the time of menstruation (11). They also report more sleep disturbances, which could be because symptoms like cramps and bloating affect overall sleep quality. Despite these findings, overall sleep quality doesn’t necessarily change with the cycle for most people (11). For those with PMDD, frequent wakings are commonly reported and may be due to altered hormone production, and/or sensitivity to certain hormones (5).
Tracking can give you insight into differences between perception and what’s actually measurable.
The details and reasons for sleep changes across the menstrual cycle (and across hormonal life phases) remain understudied and unclear. Many studies are contradictory or inconclusive. In some studies, significance of the attribution has been found to go away after adjusting for factors like perceived stress and socializing (11). There is a need for more systematic and large-scale research. Tracking your sleep can help you learn what is true for you.
4. How your workout feels
Body temperature tends to be slightly higher after ovulation, and resting heart rate may also fluctuate with the cycle (Clue has been researching this as well). For athletes, these changes may affect how a workout, and recovery after a workout, feels. There is some evidence that endurance sports may feel slightly more difficult during the mid-luteal phase (between ovulation and menstruation) (12). There is also some new evidence that suggests people may build more muscle mass when training during the follicular phase (before ovulation) (13).
5. The interplay between your sleep, mood and cycle
There are a loooottttt of cultural messages around PMS as it relates to mood and emotions. While the tone of these messages tends to be strong, the evidence behind them is not (14). Negative mood changes with the cycle may be far less common (and more diverse) than once thought (although for some people, for example those with PMDD, it’s a different story). Expectations of mood changes can also influence how people experience different cycle phases (14).
The impact of sleep on mood is more clear. Depression and anxiety are tied to experiences of poor sleep, and studies have shown that not getting enough can lead to irritability, vulnerability and stress. A study at UPenn found that subjects getting 4.5 nightly hours of sleep for a week reported feeling more sad, angry and stressed — mood changes that virtually resolved when normal sleep resumed (15).
Tracking your cycle and sleep might help you determine whether changes in mood are related to cycle phase, sleep quality, some combination of both, or neither.
6. Some possible effects of new hormonal contraception
If you’re tracking your hormonal pills in Clue or getting ready to start a new pill, using ŌURA or another wearable may give you insights into how a method affects your body. Hormonal contraceptives may influence your body temperature (possibly increasing it) as well as impacting your sleep patterns and heart rate variability (16, 17). Changes may be more of a consideration for some than others, such as for professional athletes.
If you’re interested in learning more about your sleep, mood, athletic performance and cycle—or if you have concerns and are looking to better understand the root of a problem—using a wearable in combination with tracking your cycle may be helpful to understand what is cyclical and what isn’t. The way abnormalities are treated will depend on their causes. The direction someone takes to “optimize” their fitness will also depend on the reason behind any day-to-day variations.
What Clue staffers have learned so far
We’ve been testing out the ŌURA ring for the last few weeks. Here’s what Caro and Erica have learned:
As a CrossFit athlete, I need to pay a lot of attention to my sleep, because it is a big part of my recovery.
After using the ŌURA ring, I learned that I wasn’t sleeping as much as I thought I was and that my deep sleep was not optimal. I also realized how important resting heart rate is for recovery.
Also interesting is that the ŌURA app notified me recently that the time it took me to fall asleep was shorter than my usual. Research suggests a link to the fact that I was entering the follicular phase.
Combining both my data tracked with ŌURA and Clue’s knowledge about cycle science is very valuable to me as a female athlete.
The ŌURA ring has totally enhanced the way I look at my health. I’m more aware of my resting heart rate, quality of sleep and how to improve both. I’ve noticed that the more I sweat, the lower my RHR (~50 bpm) and the better I sleep (with 2–3 hours of REM sleep per night). I’m pretty competitive with myself, so I’m constantly trying to increase my “readiness” score — a combination of my previous night’s sleep, resting heart rate, recovery time and activity. And so far, I feel better as a result.