Table 3 Stress explanation features

ECG

\(\mu _{HR}, \sigma _{HR}\)

Mean, standard deviation,

\(Max_{HR},Min_{HR}\)

Maximum and minimum heart rate (bpm)

\(HF_{HRV}\)

Variance in HRV in the high frequency range (.15–.40 Hz)

\(LF_{HRV}\)

Variance in HRV in the low frequency range (.04–.15 Hz)

\(\vert \mu \vert _{NN}, \sigma _{NN},Mad_{NN}\)

Mean of the absolute values, standard deviation, median absolute deviation

\(Med_{NN},MCV_{NN}\)

Median, and median-based coefficient of variation of the successive differences between the RR intervals

\(RMSSD_{NN}\)

Root mean square(RMS) of the RR interval

\(PNN_{20}\), \(PNN_{50}\)

Number of interval differences of successive RR intervals greater than 20 ms or greater than 50 ms

EMG

\(\mu _{EMG}, \sigma _{EMG}\)

Mean, standard deviation, maximum, and minimum

\(Max_{EMG}, Min_{EMG}\)

Values of EMG activity in the lower trapezius

\(Peaks_{EMG},RMS_{EMG}\)

Number of peaks in signal, normalized RMS value

\(RMS50P_{EMG},RMS90P_{EMG}\)

50th, 90th percentile of rank-ordered RMS values

EDA

\(\mu _{WristEDA},\sigma _{WristEDA}\)

Mean, standard deviation, maximum, and minimum

\(Max_{WristEDA}, Min_{WristEDA}\)

Values of EDA connected to the user’s wrist

\(\mu _{ChestEDA},\sigma _{ChestEDA}\)

Mean, standard deviation, maximum, and minimum

\(Max_{ChestEDA}, Min_{ChestEDA}\)

Values of EDA connected to the user’s chest

\(\mu _{ChestSCL},\sigma _{ChestSCL}\)

Means and standard deviations of the skin

\(\mu _{ChestSCR},\sigma _{ChestSCR}\)

Onductance level and skin conductance response

Respiration

\(\mu _{RespRate},\sigma _{RespRate}\)

Mean, standard deviation, maximum

\(Max_{RespRate}, Min_{RespRate}\)

and minimum of the respiration rate

Temperature

\(\mu _{WristTemp},\sigma _{WristTemp}\)

Mean, standard deviation,

\(Max_{WristTemp}, Min_{WristTemp}\)

Maximum and minimum values of the temperature measured from the user’s wrist