You’ve probably heard of basal body temperature and OPKs. But the Ava Bracelet provides information that you might never have heard of before. Why does Ava measure more than just temperature?
In fertility tracking, there is a lot of focus on using urine tests and the temperature method to pinpoint ovulation. There are downsides to these methods: temperature can only tell you after you’ve already ovulated, when your fertile window is over. And OPKs only give you a very small fertile window of 12 – 48 hours, when your fertile window is actually six days long.
Changes in other physiological parameters, such as resting pulse rate and breathing rate, can help give a more comprehensive view of the cycle and contribute to earlier detection of the fertile window.
To help you make sense of the new parameters that Ava monitors, we put together this in-depth guide. (Ava also measures several parameters that are not displayed in your daily results. Read more about them here.)
What is it?
The number of breaths you take per minute (bmp).
What kind of pattern should I see in my breathing rate?
Several publications confirm that breathing rate is higher in the mid-luteal phase compared to the mid-follicular phase1.
What’s a normal breathing rate?
Breathing rate can vary widely during the course of a day due to your activities, but typical breathing rates during sleep range from 10 – 25 bpm.
Resting Pulse Rate
What is it?
It’s basically the same thing as resting heart rate. Your resting pulse rate is lowest when you are completely at rest.
What kind of pattern should I see in my resting pulse rate?
Ava’s research partner, the University Hospital of Zurich, conducted a clinical study looking at resting pulse rate (RPR) throughout the menstrual cycle. RPR is lowest during menstruation, but several days before ovulation, it begins to increase. In our clinical study, we found an average increase of about two beats per minute (bmp) compared to the menstrual phase, but the amount of increase will vary from woman to woman. We found that resting pulse rate tends to increase again after ovulation, often reaching a peak in the mid-luteal phase.2.
In cycles that end in pregnancy, resting pulse rate tends to remain elevated beyond the usual luteal phase length.
This is the pattern we observed in most ovulatory cycles in the clinical study, but there were some ovulatory cycles where pulse rate did not behave in this manner. Sometimes, resting pulse rate drops during the luteal phase, even though the cycle is still ovulatory. We are looking further into why this is, but so far, it appears that this doesn’t indicate a problem—it’s just a less typical, though still normal, type of pattern.
What’s a healthy resting pulse rate?
Typical resting pulse rates are between 40 and 80 bpm. If you are very physically active, your resting pulse rate may be even lower than 40 bpm. Stress, illness, and alcohol can cause temporary increases in resting pulse rate.
What it is?
Ava measures the temperature of your skin at your wrist. Your skin temperature is lower and more variable than your oral or vaginal temperature.
Even though your temperature reading in Ava is much lower than traditional BBT, it’s still useful for tracking your fertility. During the day, when you’re going about your usual activities, your skin temperature is even lower and it is highly influenced by the environment you’re in. But when you go to sleep, your skin temperature rises. It never gets as high as your oral or vaginal temperature, but it stabilizes enough that you should be able to see it rise slightly after ovulation.
What kind of pattern should you see in Ava?
In clinical testing, Ava’s skin temperature data was shown to behave similarly to oral/vaginal temperature readings. That is, it increases after ovulation, stays high during the luteal phase, and decreases again around the time you get your next period. If you become pregnant, it will remain high throughout your pregnancy.
It may be a little bit harder to see the rise in Ava compared with oral or vaginal temperatures, but the Ava algorithm uses a filtering technique that can allow it to detect the rise even when it is difficult for the naked eye.
Contrary to popular belief, temperature doesn’t always increase the day after ovulation. For some women, temperature does not increase until several days after ovulation. That’s why we think it’s important to monitor other things besides temperature—like resting pulse rate, which Ava also measures (read more about it below).
If Ava is measuring your skin temperature all night long, you might be wondering why you only see a single number on your health dashboard, and what that number represents. It’s not quite as simple as the lowest temperature of the whole night, because remember, when you first get into bed, your skin temperature will be quite low, then it begins to rise and becomes more stable. We use a complex temperature extraction algorithm in order to identify your true BBT as reflected in your skin temperature during the night.
What should your skin temperature range be?
If you’ve ever taken your basal body temperature orally or vaginally, you’re probably used to seeing a number that’s somewhere between 96.0 – 99.0 degrees Fahrenheit. But your skin temperature reading on Ava will be significantly lower than this, usually in the range of 92.0 – 95.0.
Heart Rate Variability Ratio
What is it?
TLDR: Higher HRV ratio indicates higher stress, lower HRV ratio indicates lower stress.
Heart rate variability, or HRV, is the variation in the time interval from one heartbeat to the next. It can be used as an indicator of physiological stress: when there is a lot of variation in the time interval between heartbeats—high HRV—it means you are more resilient and less stressed.
However, this variability is hard to quantify in a single number. Ava has chosen to measure the ratio between low frequency and high frequency waves in your heart rate. We call this number HRV ratio, which is not the same as overall HRV. Because Ava measures your heart rate variability using this ratio, a lower number in the app actually indicates that you are less stressed.
Why is HRV important?
Stress can impact your cycle and your overall health. But sometimes, you can be physiologically stressed without actually feeling stressed out. Intense exercise, travel, tiredness, and coming down with an illness can all be interpreted by your body as a form of stress—even if you feel as cool as a cucumber!
Physiological stress can have a variety of impacts on your body, affecting your mood, your immunity, and even your fertility. Stress can delay ovulation, contribute to anovulation, or shorten your luteal phase.
What’s a healthy HRV ratio?
A universal scale for healthy HRV ratio does not exist—it varies widely from person to person. The best way to use your HRV data is to observe it for one cycle to get a sense of what your personal baseline is, and then notice when you are higher or lower than normal.
What kind of pattern should I see in my HRV ratio?
There isn’t any particular pattern you should be looking for: just try and connect your HRV ratio to possible stressors in your life.
The quality and quantity of sleep you’re getting each night are important parameters to track for your fertility. Your menstrual cycle can affect your sleep, and your sleep, in turn, can affect your menstrual cycle. Pregnancy can also influence sleep.
Ava records the amount of sleep you get each night. Additionally, Ava tracks the percentage of combined deep and REM sleep. Deep sleep is important for feeling rested the next morning, while REM sleep is important for learning and storing memories.
Typical sleep cycles for adults are 50 – 65 percent light sleep and 35 – 50 percent deep sleep + REM.