Everything you need to know about the HRV insights on your wearable.
Heart rate variability (HRV) is an increasingly key metric in wearables, with brands such as Whoop, Oura, Garmin, and Apple using it to help measure and advise on training and recovery.
In the new era of advanced health and fitness trackers, HRV is often at the heart of distinct algorithms designed to track the wearer’s stress, readiness, and fatigue.
But what is it, actually, and why is it so important? This guide answers these questions and more.
We’ll cover all the basics surrounding HRV, frequently asked questions about the metric, and how each major brand measures and presents the data.
What is heart rate variability?
Heart rate variability is the measurement of the time interval between heartbeats.
Unlike measuring heart rate, which is about the average number of heartbeats per minute, HRV focuses on the slight fluctuations of the heartbeat and usually measures the variation time in milliseconds.
Most academic studies agree that a higher HRV figure is better than a lower one, but this metric isn’t as simple as VO2 max or resting heart rate (as we’ll explain below).
Those fluctuations can be affected by a host of things, including age, body position, the time of day, emotional wellbeing, and physical status. A lot can impact your HRV.
The benefits of tracking HRV
Why is it useful to measure or monitor it? Well, particularly for fitness, it helps you understand when you’re putting too much stress or strain on your body and serves as an indicator of whether you’re physically and mentally ready to work out again.
So if you’re a runner and you’ve just put in a tough 2-hour run, it can help you decide whether you’re ready to go again the following day or if you should take a day off from training. When you’re working out, your HRV decreases as your heart rate and exercise intensity rise.
But it’s not just about serious athletes; HRV measurements have started to trickle down into devices like fitness trackers, which can also be used to check in on how stressed you are.
What is a normal, high, or low HRV?
So, what does it mean to have a low or high HRV reading? There’s no ideal HRV score, and like resting heart rate, it’s hugely personal.
Generally speaking, high HRV is associated with healthy longevity and the part of the nervous system that promotes relaxation, digestion, sleep, and recovery.
A low HRV reading is commonly associated with stress, overtraining, inflammation, and illness. Diabetes, coronary heart disease, and high cholesterol are also commonly linked to having a low HRV.
What is a high, low, or normal HRV reading? A blog post on that subject by Oura, makers of the Oura Ring smart ring, which measures HRV during sleep to assess your readiness, explains:
“High and low HRV is relative for each person. HRV is a highly sensitive metric, which responds uniquely for everyone.
“Some individuals have steady HRV scores, while others fluctuate greatly. HRV is an evolving tool, which means, at every HRV level, your personal scores and body status observations are especially important.”
While Oura has calculated what its research and studies interpret as a normal HRV, it emphasizes that each person’s HRV is unique, and you should compare your averages rather than others to best understand the data.
Wearables and HRV
As we mentioned, most major wearable manufacturers are utilizing HRV measurements for various insights. We’ve outlined how the key players are leveraging this data to enhance features on your smartwatch or fitness tracker.
Apple Watch (all versions)
HRV is a staple feature of the Series 10, Ultra 2, and Apple Watch SE.
Apple’s native handling of HRV tracking involves continuously recording it with its optical heart rate sensor for as long as you wear the device. This allows you to view trends in the Apple Health app on your paired iPhone. Through the Health app, you can observe daily, weekly, monthly, and yearly trends to identify increases and decreases in HRV measurements.
If you want to delve deeper into what the measurement can tell you, third-party HRV Apple Watch apps like HRV4Training can help you interpret the data and provide more actionable insights.
Interestingly, HRV isn’t part of the Vitals app introduced in watchOS 11—the metrics for that only include sleep duration, respiratory rate, blood oxygen, resting heart rate, and skin temperature.
Fitbit (and Google Pixel Watch)
Most new Fitbit fitness trackers and smartwatches (as well as Google’s Pixel Watch devices, which use Fitbit’s tracking platform) can measure heart rate variability and closely observe those variations between heartbeats, mainly during sleep.
You’ll find it on everything from the Fitbit Inspire 3 to the Sense 2.
Fitbit reports HRV directly to the Health Metrics section of the Fitbit app. From there, you’ll see the latest HRV measurement, which is measured in milliseconds (ms) from the longest sleep period over the past 24 hours.
Basic Fitbit users can see the HRV trend over the past 7 days, but Premium users can track it for 30 and 90 days. If you see a significant decrease in HRV, it could be a sign of significant stress, illness, or fatigue.
In addition to measuring HRV, that metric is used in Fitbit’s Daily Readiness Scores (shown above on the Pixel Watch 3) to guide you on whether you’re in good shape to train hard or should take a day off.
Whoop
HRV underpins the Whoop experience, featuring in its recovery, health, and stress features.
The all-important daily percentage of readiness that Whoop offers users is majorly weighted to your HRV, but it also lives within the Health Monitor. This data dashboard shows a range of measurements and your average daily baseline.
Anything within range or over will get you a green status. However, if your HRV is significantly lower, you’ll get an orange or red warning.
Finally, HRV is also a major part of Whoop’s Stress Monitor, which shows a live estimation of stress levels throughout the day (shown throughout).
Samsung
Heart rate variability and measurements fuel the stress monitoring features on the Samsung Galaxy Watch. This monitoring can be done continuously and lets you see on-the-spot stress measurements directly on the watch.
However, there’s nothing in the way of recovery or training insights, meaning it’s behind the competition when it comes to harnessing HRV as a metric. With the ever-expanding Samsung Health app, though, which is expected to deliver more AI prompts in 2025, this could be improved for the next generation of devices (and trickle back to older models).
Garmin
Garmin has increasingly embraced HRV measurements across a range of its watches.
Most new watches (see Venu 3, Forerunner 265, Vivoactive 5) show HRV Status (shown above) which takes an average HRV reading from the night, and a 7-day average both compared to your baselines.
On its premium watches (such as Fenix 7 and Epix), Garmin interprets HRV as a Training Readiness metric. Much like Whoop and Oura, this gives you a score on how ready your body is for a tough workout – or a signal that you might need a rest day.
For sleep, it uses HRV to improve the accuracy of determining when you’ve been awake and the time you’ve spent in the different sleep stages it can recognize.
Like Samsung, Garmin also uses HRV data to track stress levels.
From an exercise and training point of view, it’s also a metric that fuels data such as your VO2 max, performance condition, and lactate threshold and it powers Garmin’s Body Battery energy monitor too.
Polar
Polar also uses HRV to help you better assess when to train and when to spend time recovering. Watches like the Polar Vantage V3 offer an Orthostatic test, which is based on HRV and requires an external heart rate monitor chest strap to conduct the test.
The test results fuel Polar’s Recovery Pro features and if you’re doing the tests regularly, it can help you better understand whether fatigue is training-based or based on another factor.
Oura
We’ve already spoken about Oura, whose smart rings center around sleep and recovery needs.
The current and previous generations of Oura’s rings track HRV overnight, using these continuous measurements to inform how your body responds to stress and strain.
In its companion app, you can then view average, maximum, and a trace graph, which can be handy to delve into to understand your stability throughout the night.
In addition to those, you can also explore ‘HRV balance’, which looks at a longer-term comparison of your current HRV trend and your baseline to understand whether you’re recovering well or putting your body under serious stress.
Regarding stress, HRV is also integral to the brand’s two major features in this area—Stress Resilience (shown above) and Daytime Stress.
How accurate is HRV tracking and what’s coming next?
We’ve discussed this earlier, but it’s important to revisit. For accurate heart rate variability measurements, the sensors must perform effectively. This brings us back to the ongoing debate of wrist versus chest heart rate monitoring.
When we spoke to biometrics experts at Valencell, they told us: “It’s really difficult to deliver heart rate variability from the wrist when you have so much movement of the wrist.”
Like most aspects of wearable data, HRV trends can be a useful window into our wellness. But relying on the numbers as absolute gospel can be subjective. Not only is it dependent on accuracy, but also on how and when the HRV figure is taken and averaged.
