Table 3.

Definitions of the physiological parameters and their physiological relevance.

Name	Definitions and Physiological Relevance
Systolic blood pressure (SYS)	The blood pressure when the heart contracts to pump blood to the body, with a normal value ranging between 90 and 140.
Diastolic blood pressure (DIA)	The blood pressure when the heart rests between beats, with a normal value ranging between 50 and 90.
Pulse pressure	The gap between SYS and DIA, with a normal value being 30–50 mmHg.
Number of heartbeats per minute (HR)	The average number of times the heart beats per minute within 5 min.
Number of occurrences of arrhythmia	The number of occurrences of arrhythmia within 5 min. If the value is >20, participants should undergo a physical examination to understand the causes of the arrhythmia.
Activity of the autonomic nervous system (HRV)	The variation in the time interval between heartbeats.
LF power of the autonomic nervous system (LF)	Spectral power of the LF R–R interval (0.04–0.15 Hz), which is related to the activity of the sympathetic nerves.
HF power of the autonomic nervous system (HF)	Spectral power of the HF R–R interval (0.15–0.4 Hz), which is related to the activity of the sympathetic nerves.
LF power ratio of the autonomic nervous system (LF%)	Spectral power ratio of the LF R–R interval. LF% = LF / (LF + HF). The normal range is 30–70%.
Age of the autonomic nervous system activity (HRV age)	The age that the HRV data norm corresponds to. HRV decreases as age increases ([19], Figure 1).