TABLE 1. List of Parameters That are Used in the Current Study to Compare the HRV Measurements From a Tilt Table and a Zero-Gravity Chair.

Parameter	Domain	Definition
SDNN	Time	Standard deviation (SD) of NN intervals.
SDNN5	Time	5-minute SD of NNs.
RMSSD	Time	The RMS of the successive differences.
SDSD	Time	The SD of the successive differences.
pNN50	Time	The proportion of NN50 divided by total number of NNs.
LF	Frequency	Spectral power in the range of 0.04 to 0.15 Hz.
HF	Frequency	Spectral power in the range of 0.15 to 0.4 Hz.
LF/HF	Frequency	The ratio of power between LF and HF bands.
SD1/SD2	Non-linear	Poincare plot features