Use a heart rate monitor, ECG, chest strap, or validated wearable that records beat-to-beat intervals
Record a resting measurement in a quiet setting, ideally at the same time each day
Measure during a consistent posture, such as lying down or seated
Collect a clean RR or NN interval series for a set duration, commonly 1 to 5 minutes
Remove artifacts, missed beats, and ectopic beats from the recording
Calculate time-domain metrics such as RMSSD, SDNN, and pNN50
Calculate frequency-domain metrics such as LF, HF, and LF/HF ratio if needed
Use the same device, protocol, and conditions for repeated measurements
Review trends over time rather than relying on a single reading
Follow the device or software’s HRV measurement method and output format