Heart rate variability, or HRV, describes variation in the time between heartbeats. It is different from heart rate, which counts beats per minute. A low reading on a wearable does not identify a diagnosis or explain fatigue on its own.[1]
Before interpreting the result, find out what the device measured and how.
HRV is not one universal number
There are several ways to calculate HRV. The length of the recording, the metric used, and characteristics such as age affect interpretation. Values from a short recording cannot simply be compared with values collected over a full day.[1]
That makes a universal internet target unhelpful when the method is unknown. It also makes comparisons between different apps or devices harder to interpret.
Higher is not always better. Some abnormalities in heart rhythm can increase measured variability, so the direction of change alone is not a complete health assessment.[1]
A trend needs its surroundings
If a pattern concerns you, keep the device name, measurement dates, and any associated symptoms together. Note changes in sleep, travel, illness, exercise, or medicines rather than assuming the app has identified the cause.
Optical wearables also have measurement limitations. A study of wearable heart-rate sensors found differences in accuracy between devices and activity conditions.[2]
Symptoms deserve their own attention
Fatigue that persists despite adequate rest can have several causes, including sleep disorders, anemia, thyroid problems, and medicines.[3] A wearable trend may add context, but it cannot decide which explanation fits.
Bring the original record rather than only the app's recovery label.
