Table 1 Description of heart rate variability (HRV) stress indices
Heart rate variability (HRV) stress indices | Description | Value |
|---|---|---|
Average heart rate (HR) | Average absolute heart rate in time window | Higher: higher stress Lower: lower stress |
Sample entropy (SE) | Complexity of the HRV: assumes a complexity loss under constraints (e.g. stress) | Higher: lower stress Lower: higher stress |
Low frequency/high frequency ratio (LF/HF) | Balance between sympathetic and parasympathetic nervous systems. LF: associated with sympathetic nervous system, HF: associated with parasympathetic nervous system | Higher: higher stress Lower: lower stress |
Standard deviation of RR Intervals (SDRR) | Variation of RR intervals around a mean value | Higher: lower stress Lower: higher stress |
Root mean squared of successive differences (RMSSD) | Absolute variation of RR intervals | Higher: lower stress Lower: higher stress |
Percentage of RR interval pairs with difference > 50 ms (PRR50) | Compares each pair of adjacent RR intervals and considers the difference between them; if it is larger than 50 ms a counter is increased by one. The ratio of the counter and the number of RR intervals in one time window is pRR50 | Higher: lower stress Lower: higher stress |