Table 1.

Description of the electroencephalogram (EEG) and heart rate variability (HRV) features used in the stress assessments.

Feature	Description	Unit	Equation
nLAP	Normalized left hemisphere alpha band power	%	$\frac{\mathrm{Summation}\mathrm{of}\mathrm{power}\mathrm{from}8\mathrm{to}13\mathrm{Hz}}{Total power} \times 100$
nRAP	Normalized right hemisphere alpha band power	%
nLBP	Normalized left hemisphere beta band power	%	$\frac{\mathrm{Summation}\mathrm{of}\mathrm{power}\mathrm{from}13\mathrm{to}30\mathrm{Hz}}{Total power} \times 100$
nRBP	Normalized right hemisphere beta band power	%
DPA	Delta band power asymmetry	-	$\frac{EEG band powe{r}_R-EEG band powe{r}_L}{EEG band powe{r}_R+EEG band powe{r}_L}$
TPA	Theta band power asymmetry	-
APA	Alpha band power asymmetry	-
BPA	Beta band power asymmetry	-
mRR	Mean of R–R interval	msec	$\frac{{{\displaystyle \sum }}_{i=1}^N\left(R{R}_i\right)}{N}$
SDRR	Standard deviation of R–R interval	msec	$\sqrt{\left(\frac{{{\displaystyle \sum }}_{i=1}^N{\left(R{R}_i-mRR\right)}^2}{N-1}\right)}$
RMSSD	Root mean square difference of successive R–R interval	msec	$\sqrt{\frac{{{\displaystyle \sum }}_{i=1}^{N-1}{\left(R{R}_{i+1}-R{R}_i\right)}^2}{N-1}}$
nLF-HRV	Normalized low frequency power of HRV	%	$\frac{\mathrm{Summation}\mathrm{of}\mathrm{power}\mathrm{from}0.04\mathrm{to}0.15\mathrm{Hz}}{Total power} \times 100$
nHF-HRV	Normalized high frequency power of HRV	%	$\frac{\mathrm{Summation}\mathrm{of}\mathrm{power}\mathrm{from}0.15\mathrm{to}0.4\mathrm{Hz}}{Total power} \times 100$
LF/HF	The ratio between nLF-HRV and nHF-HRV	-	$\frac{nLF-HRV}{nHF-HRV}$