Table 4 HRV parameters used in the selected papers

Time-domain measure

 Standard deviation, SD (ms) [40, 41]

Standard deviation of RR-interval

Total HRV

Frequency-domain measure

 Low frequency power, LF (ms²) [35]

Spectral power in the low frequency band (0.04–0.15 Hz)

Cardiac sympathetic modulation

 High frequency power, HF (ms²) [35]

Spectral power in the high frequency band (0.15–0.4 Hz)

Cardiac vagal modulation

 Total power, TP (ms²) [35]

Total spectral power (0.01–0.5 Hz)

–

 LF/HF ratio [35]

Ratio of LF power to HF power

Cardiac sympathovagal balance

 Spectral power density at frequency of 0.1Hz (in absolute unit, ms²/Hz, and relative units) [40, 41]

–

Likely due to the baroreceptor reflex, which reflects the 0.1 Hz arterial blood pressure oscillations (Mayer wave) [52]