Use a heart rate monitor, ECG, or wearable device that records beat-to-beat intervals
Record a resting measurement in a quiet, stable state
Collect RR intervals or interbeat intervals for a set period
Ensure the recording is free from movement artifacts and signal noise
Calculate time-domain metrics such as SDNN, RMSSD, and pNN50
Calculate frequency-domain metrics such as LF, HF, and LF/HF ratio
Calculate non-linear metrics such as Poincaré plot measures if needed
Use the same device, time of day, and conditions for repeated measurements
Compare results against your own baseline rather than a single universal value