Different heart rate - egc v monitor
the apple watch monitor heart rate is noticeably less than the rate when i run ECG - why please?
Question marked as
I just tested with my Apple Watch Series 7, both methods show some variability but I would not consider the differences to be significant. For the record,
Heart Rate app 57-61 bpm over about 1 minute
ECG app 55-59 bpm over 30 second ECG trace.
The numbers varied up and down during each test, and the HR reading was the first test, followed a few moments later by the ECG app.
If you are seeing big differences between the 2 methods I suggest you take a look at
Monitor your heart rate with Apple Watch - Apple Support
Get the most accurate measurements using your Apple Watch - Apple Support
noting particularly the comments about the correct fit of the watch band/strap. I know I can get really wild results for HR if the optical sensor is allowed to move too much during measurement. Also note the comments in the second document about blood flow, and things like tattoos or skin tone. These may affect optical measurement but would not impair sensing of your heart's electrical impulses for the ECG app.
Further checks
Clean the back of your Apple Watch and wash/dry your arm to be sure it is not something as simple as moisture interfering with the measurements.
Sit and relax for 5 minutes before you make your repeat test, to give your heart time to settle to a steady rate after any exercise.