“…Examples of such factors are the time of the day to record the data (in the case of short-time recordings); subject-characteristic variables such as age, sex, HR, breathing rate, health and physical activity status, control for medication, food and water consumption, voiding of the bladder; position of the body during short-time recordings; the quality of recorded signals (recording period length, detection or recording method, sampling frequency, breathing pacing-paced or free breathing); as well as the tools used to analyze HRV values (i.e., how HRV metrics were calculated-software, removal of artifacts, frequency band cutoffs, power spectral analysis method, etc.) [33,34,37,40,61,71].…”