Learn more about the heart rate variability (HRV) measurements taken by the Oura Ring.
What Is Heart Rate Variability?
Heart rate variability (HRV) is a measure of variation in time (milliseconds) between your heartbeats. HRV provides a snapshot into how your body is balancing between the two branches of your autonomic nervous system: your sympathetic ("fight-or-flight") and parasympathetic ("rest-and-digest").
Normal HRV can range anywhere from below 20 to over 200 milliseconds, depending on various factors such as age, sex, physical fitness, and genetics. The HRV value provided by Oura falls within this same range. HRV differs for everyone, so be sure to compare changes in your HRV to your baseline and not others. Oura supplies you with a personalized baseline so you know what your normal HRV is.
As a general rule:
- High HRV (relative to your baseline) is associated with activation of your "rest-and-digest" branch, general physical fitness, and good recovery. Higher average nighttime HRV measurements have also been linked to better sleep quality and vice-versa.
- Low HRV (relative to your baseline) is associated with activation of your "fight-or-flight" branch, stress (both good and bad), illness, and overtraining.
How Oura Measures HRV
Oura calculates your nighttime HRV using rMSSD, a well-known HRV parameter that provides a reliable and accurate view of your autonomic nervous system’s activity. The average HRV you see on your Readiness tab is the mean of all five-minute samples measured while you sleep. What’s unique about Oura is that changes in your HRV are accounted for every five minutes throughout the night in comparison to other wearables that only take HRV measurement at a single point during the night. Having continual measurements throughout the night not only results in greater accuracy but gives you a more detailed perspective into how your body is responding to the previous day’s stressors and how well it’s preparing for the next.
As displayed in the Readiness tab view shown below, Oura provides you with the following heart rate variability metrics:
- Average HRV: Your average HRV captured over the entire night
- Max HRV: Your highest HRV value captured over the entire night
- Your HRV Trace: Your HRV values captured every five minutes throughout the night, displayed in a graph.
You can find this data in your Readiness tab, as well as in Trends. Trends can be found by tapping on the menu located in the upper left-hand corner of your Home tab.
Observing your HRV in the Trend view is a great way to identify how well you've recovered over the past week and if you may want to draw more awareness to any internal or external stressors in your life.
Please see our article on using Trends for more information on how to get started with this feature.
Interpreting Long-Term HRV
HRV can’t get rid of your stress or improve your cardiovascular fitness on its own, but it can offer insight into how your behavior, environment, emotions, thoughts, and feelings are impacting your bodily functions. In this sense, measuring and tracking HRV can be the first step necessary to jumpstart a healthier lifestyle: whether that be helping you to respond to stress in a more meaningful way, building more physical activity into your weekly routines, or bringing awareness to how your diet selections may be placing your body into fight-or-flight mode, monitoring your HRV is an amazing place to start.
If you’re interested in evaluating your HRV for long-term changes, we suggest you read more about HRV balance, which happens to be one of your Readiness contributors.
Check out The Pulse article, "What is HRV Balance" for everything you’ll need to know about this powerful metric.
Interpreting Short-Term HRV
1. Interpret Your HRV Trace
- Higher HRV values tend to occur during REM sleep.
- Lower HRV values tend to occur during deep sleep.
2. Interpret Your HRV Values (High & Low)
HRV levels that are high or slightly higher than your normal range tend to be signs of good recovery. A higher HRV may be the result of:
- A much-needed rest day
- A cool bedroom at night
- Participation in more mindful, low-to-moderate-intensity activities like hiking or yoga
- Engagement in mindfulness meditation
HRV levels that are lower than your normal range are signs of excessive strain on the body. Lower HRV may be the result of:
- Consumption of alcohol
- A late night meal or workout
- Acute and prolonged stress
- A hot bedroom at night
- Jet lag and inconsistent sleep patterns
Note: naturally, after a hard workout, your HRV will likely decline. As you recover, your HRV should rebound. If it doesn't return to your baseline or takes an extended period of time to, this can be an indication that you’re training too often or too hard.
Considerably higher HRV levels are not necessarily a good thing. These may be an indication of low autonomic nervous system stimulation, which can be felt as low energy and lethargy. Overly high HRV scores are a sign from your body that you’re ready to take on a physical challenge to build cardiovascular fitness in pursuit of greater health.
The Importance of HRV
Your autonomic nervous system is divided into two branches: sympathetic ("fight-or-flight") and parasympathetic ("rest-and-digest"). Heart rate variability is produced by competing inputs from these two branches.
When both of these branches are giving inputs to your heart, you’ll see increases and decreases in your heart rate, which naturally causes variation between beats. Heart rate and heart rate variability tend to be inversely connected. Having a slower heart rate means that there is more room for variability between each beat, which typically results in a higher HRV. In contrast, having a faster heart rate limits space for variability between each beat, which usually results in a lower HRV.
Having variation between your heartbeats demonstrates that your autonomic nervous system is balanced and capable of responding to a wide variety of stimuli in a healthy manner.
New Sleep Staging Algorithm
In May 2023, Oura began rolling out a new sleep staging algorithm for the Oura Ring Gen3. This new algorithm was developed to take advantage of the Gen3 ring's extra sensors and increased memory capacity in order to provide even more refined sleep stage detection.
Some Oura members with Gen3 rings may see changes to their data. With the added sensitivity of the new algorithm, it’s perfectly normal to see a different ratio of your sleep stages, especially an increase in light sleep. For most healthy individuals, light sleep accounts for >50% of a typical night of sleep and can account for up to 60% in older individuals.
While a lot of factors determine the magnitude of changes you’ll see in your data, HRV has a large impact depending on whether you have higher, average, or lower HRV.
- Members with higher HRV may see a large decrease in Deep, large increase in Light, small increase in REM, and little or no change in awake
- Members with average HRV may see a large decrease in Deep, large increase in Light, small decrease in REM, and little or no change in awake
- Members with lower HRV may see a large decrease in REM, large increase in Light, small decrease in Deep, and small increase in awake
Learn more about the heart rate variability (HRV) measurements taken by the Oura Ring here.
When Does Oura Measure Heart Rate Variability?
Oura focuses on measuring heart rate variability during sleep, in order to block out confusing "noise" during daytime hours that would otherwise impact your data and make them challenging to interpret. Heart rate and heart rate variability are two very sensitive metrics, meaning they’re easily subject to change via activities as simple as drinking a glass of water, getting up to go to the bathroom, or watching an exciting television show.
For Gen2 owners: Certain unguided sessions will provide heart rate, HRV, and skin temperature snapshots upon completion. These sessions can be used at any time of the day.
For Gen3 owners: The Explore tab contains meditation sessions and stories, some of which will also measure your heart rate, HRV, and skin temperature.