HRV, a measure of how variable the time is between heartbeats, is crucial for assessing bodily stress levels. Many wearables now track HRV overnight, alongside resting heart rate, to provide users with valuable morning data. But which device performs best? To find out, I wore three different devices—Oura ring (gen 3), Whoop 4.0 band, and Garmin Forerunner 265 smartwatch—to bed for three weeks, yielding some surprising results.

HRV, Explained

HRV reflects heartbeat consistency, not speed—higher variability generally indicates less stress or better recovery. This metric derives from the balance between the body’s sympathetic and parasympathetic nervous systems.

What Differentiates HRV from Resting Heart Rate (RHR)?

RHR signifies stress; higher rates denote more stress, lower rates indicate better recovery. Athletes often exhibit lower RHR, influenced by fitness and genetics.

Using Wearables to Track HRV and RHR

Modern wearables now monitor these metrics throughout sleep, presenting data via apps or device screens upon waking. Each device calculates data slightly differently; hence, comparisons can vary.

Data Collection Method

I collected nightly HRV and RHR readings from each device—Oura (finger-worn), Garmin (wrist-worn), and Whoop (wrist-worn, night-only)—over 24 days, entering results into a spreadsheet.

Results

While raw numbers differed (e.g., RHR readings varied between devices), trends across weeks were consistent. Oura typically provided lower RHR values, while Whoop tended higher, yet both showed synchronized trends. Garmin’s averages often fell between the two, with its “highest 5-min average” occasionally exceeding them.

Conclusion

All three devices—Oura ring (gen 3), Whoop band 4.0, and Garmin Forerunner 265—yielded reliable, comparable readings for both RHR and HRV. Although numerical disparities exist, each device tracked similar trends over time. Therefore, selecting a device hinges less on absolute accuracy and more on user preference and comfort with interpreting specific metrics.