Comparing Oura, Whoop and Garmin in HRV Measurement
Heart rate variability is a great indicator for measuring the amount of stress your body is under. Many wearables can record your HRV overnight and provide you with the data in the morning, along with your resting heart rate, another useful number. But which device does this best? I wore three different devices before bed for three weeks to compare them, and the results were amazing.
The devices I tested were the Oura (3rd generation) ring , the Whoop 4.0 bracelet , and the Garmin Forerunner 265 smartwatch. (By the way, a full review of Forerunner is coming soon. Spoiler alert: I love it.)
What is HRV anyway?
HRV, or heart rate variability, is a measure of how stable your heartbeat is. It’s not how fast or slow it is, but how different the time frames are between beats. The differences can only be measured with precision equipment, but here’s the basic idea: if your heart is beating…beating…beating………..beating…beating…beating…….beating,” you have a high HRV, and that’s a good thing. On the other hand, if your heart beats “beats… beats… beats… beats… beats,” that’s low HRV. We tend to have low HRV when we are stressed or tired, and high HRV when we are either not stressed or recovering well from stressors.
This may seem counterintuitive since most of us think that the ideal heartbeat should be steady and regular, but slight variations from one beat to the next are healthy and normal. Our heart receives orders about how fast to beat from two different parts of our nervous system (sympathetic and parasympathetic). A high HRV is thought to indicate that both systems are active, in some sense counterbalancing each other.
Your HRV will change from day to day, and that’s where these devices come in. You’ll often see a change in your HRV readings immediately after a hard workout or a stressful day at work, giving you a heads-up on what your body is up against. With. This information, if used wisely , can help you adjust your workout schedule and health habits.
What is considered “good” HRV depends on your own medical history; Don’t compare yourself to others. (I don’t mean this in a feel-good sense, but literally, scientifically: your HRV only makes sense in comparison to itself.) Whoop reports that the average 50% of 20-year-olds have an HRV somewhere between 60 and 105 , and their number decreases with age. If you are 60 years old, according to this data set, your HRV scores will likely be somewhere between 30 and 50.
How does HRV differ from resting heart rate (HR)?
Resting heart rate is also an indicator of how stressed your body is, including fatigue and illness. Unlike HRV, a higher resting heart rate means you’re under more stress, while a lower one means you’ve recovered well.
Your resting heart rate can also change over time as you get fitter. Athletes tend to have lower RHR values, and people who begin to exercise often find that their RHR decreases slightly over time. (However, heart rate is not a direct indicator of cardio fitness; there appears to be a significant genetic component to it as well. Take me as an example: my heart rate is always pretty low, even when my cardio fitness sucks. If I If I exercise a lot at stamina, it will drop by two or three points, but no more.)
Most healthy adults have a resting heart rate between 55 and 85 beats per minute (some sources indicate a typical range of 60 to 100). It’s important to note that these numbers typically assume you’re sitting quietly in a doctor’s office. When you sleep in your bed, your heart rate may drop slightly. So it’s quite normal to see smaller numbers than these on a wearable device that records all night.
How to Track HRV and Resting Heart Rate Using Wearables
Gone are the days when you could charge your fitness tracker at night; Wearable fitness devices are now expected to be worn during sleep to track these overnight metrics.
At night, your device monitors your heartbeat. It can sample and average different readings, and each device measures and calculates values slightly differently. (So I didn’t expect much agreement between devices, but more on that in a minute.) When you wake up, you may be presented with a “readiness” or “recovery” meter, but I stand by my position that HRV and HR are the only indicators on which are really worth paying attention to (except for time in bed if you want to monitor your sleep).
The data will be presented to you in the device’s companion application or, in the case of devices with a screen, on the device itself. Often an app or device will tell you how different your numbers are from the average. What you do with this information is up to you.
How I collected data
For this experiment, I wore three devices every night before bed.
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I have an Oura ring and I wear it every night, whether I’m writing about it or not. I’m very used to the numbers I see there. I wore it on the ring finger of my left hand.
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The Forerunner 265 was worn on my left wrist. I’m testing it and plan to review all of its features soon, so it was natural to put it on to bed and see how it compares to the numbers I’m used to from Oura.
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Finally, I added the band Whoop to the mix. I don’t usually wear this (unless I’m writing about it ), and for this experiment I only wore it at night and not during the day.
I tabulated my resting heart rate and HRV data for each day from each device. Whoop and Oura are named by the same number for my nightly HRV; Garmin gives two metrics: “overnight average” and “highest 5-minute average.” So for this device I tracked both. I wore the Oura and Garmin for about a week before I realized I should add Whoop to the mix. In total, I wore at least two devices for about a month, with 24 days of data on all three.
When it comes to using this data, I already have an idea of how the numbers compare to my experience. If my HRV is high and my heart rate is low, I almost always feel good and ready to take on whatever the day throws at me. If my HRV is low and my heart rate is high, then I’m either stressed, sick, or perhaps haven’t gotten enough sleep; I may or may not do an easier workout that day, but I will definitely be focusing more on self-care and good sleep in the future. If my heart rate and HRV are high , it usually means I’m under a lot of stress or fatigue, but I’m handling it well. In this experiment, I didn’t track data about how I felt; I already know that Oura’s data matches my feelings well, so the question was whether other devices were tracking the same trends or not.
Results
It was interesting to watch the results take shape as I added new data to the table. The raw numbers often varied widely: my resting heart rate on a given night could be 45, 47 or 50, depending on what device I’m reading from. But when I logged several weeks of data, the trend lines always told the same story:
In the resting heart rate graph, you can see that although the starting values were always different, with Oura giving the lowest values and Whoop the highest, they all went up and down together.
If I only used one device and decided to switch – say, ditching Oura for Whoop – it would take me a while to adjust to seeing different numbers. 50 is a lot for me on Oura (anything 50+ is “yeah, what did I do?”), but more of an average number as seen on Whoop (“I think I’m a little more stressed than usual”) . But once you get used to the numbers, any of these devices will do a great job of tracking your resting heart rate and letting you notice when it’s particularly high or low.
The same pattern is observed in my HRV readings, although the differences between devices are more dramatic. Whoop and Oura move almost exactly together – it’s hard to see the light gray line in the graph above because it looks almost like a shadow of the blue line.
Garmin looks different: its average is always slightly lower than Whoop and Oura, and its “highest 5-minute average” is often higher than them. Again, I would confidently trust either of these devices, but I wouldn’t compare them. If I used the Oura on some nights and the Garmin on others, I might get the wrong impression. But using any one device will give you useful numbers.
Bottom line
All three Oura (3rd generation) rings , Whoop Band 4.0 and Garmin Forerunner 265 gave consistent and useful readings for both resting heart rate and heart rate variability. The numbers varied from device to device, but all followed the same trend. I was surprised that the trends matched up so well. Based on this data, I would not choose one device over another based on accuracy; all three are suitable for the job.