There is no single good number. HRV differs widely between healthy people and falls with age, so a value that is normal for you can be low for someone else. What matters is your own baseline and whether you are above or below it.
What is Apple Watch measuring?
HRV, heart rate variability, is the small changes in time between each heartbeat, in milliseconds. It reflects how well your body can handle stress and recover: higher usually means more relaxed and recovered.
Apple Watch samples it while you are still, so most readings come from sleep and quiet moments, and the number of measurements varies with how active your day was. On iPhone it is in the Health app under Browse, Heart, Heart Rate Variability.
Why does my HRV jump around so much?
Because single readings are taken at different times and in different states. One at 3 a.m. in deep sleep and one at your desk after coffee are not comparable. Look at the average over a week, not at individual points.
How do I read it?
- Find your baseline. Your typical weekly average over the last month or two is your normal.
- Below baseline for several days often follows hard training, poor sleep, alcohol, illness or stress. If your resting heart rate is up at the same time, take it seriously and ease off.
- Low after a hard run is normal. It should be back within a day or two.
- A slow rise over months usually goes with improving fitness.
Can I compare it with my friend’s, or with a Garmin or Whoop?
No, for two reasons. HRV is personal, and the devices do not measure the same thing. Apple Watch reports a statistic called SDNN from short samples through the day. Most other wearables report a different one, RMSSD, measured overnight. The numbers are not interchangeable, so treat a change of device as a new baseline.
What does Kiiro show?
Kiiro shows the HRV values your Apple Watch saves in Apple Health as a trend, next to your resting heart rate and your training load status. Seeing them together is the point: a Fatigued status with a falling HRV says more than either one alone. See How can I tell if I’m overtraining?.
Related questions
- Why is my resting heart rate going up?: For a runner the usual causes are fatigue from training, a cold coming on, poor sleep, alcohol, heat or stress. A beat or two is noise. Several beats above your normal for several days is worth acting on.
- What is a good cardio recovery on Apple Watch?: Cardio recovery is how much your heart rate drops after you stop exercising. A bigger drop generally means a fitter heart, and your own trend matters more than any single number.
- How can I tell if I'm overtraining?: No single number tells you. Look for several signs together: training load well above what you are used to, a raised resting heart rate, a lower HRV, and runs that feel harder than they should.
