Table 2 Time-Domain features considered in this study

MAV

$\mathit{MA}{V}_k=\frac{1}{N}{\displaystyle \sum _{i=1}^N\left|x_i\right|}$

It adds the absolute value of all the values in a segment divided by the length of the segment.

MAVS

$\mathit{MAV}{S}_k=\mathit{MA}{V}_{k+1}-\mathit{MA}{V}_k$

It estimates the difference between the mean absolute values of the adjacent segments k + 1 and k.

RMS

$\mathit{RM}{S}_k=\sqrt{\frac{1}{N}{\displaystyle \sum _{i=1}^N{x}_{i_2}}}$

It is modeled as amplitude modulated Gaussian random process whose RMS is related to the constant force and non-fatiguing contraction.

VAR

$\mathit{VA}{R}_k=\frac{1}{N}{\displaystyle \sum _{i=1}^N{\left(x_i-\overline{x}\right)}^2}$

It is a measure of how far the numbers in each segment lie from the mean.

WL

$W{L}_k={\displaystyle \sum _{i=1}^{N-1}\left|x_{i+1}-x_i\right|}$

It is the cumulative length of the waveform over the segment. The resultant values indicate a measure of waveform amplitude, frequency and duration.

IEMG

$\mathit{IEM}{G}_k={\displaystyle \sum _{i=1}^N\left|x_i\right|}$

It calculates the summation of the absolute values of EMG signals (Signal Power estimator).

SSC

$\left\{x_i>x_{i-1}\&x_i>x_{i+1}\right\}$ and $\left|x_i-x_{i+1}\right|\ge ϵ$

Given three consecutive samples x_i-1, x_i and x_i+1, the slope sign change is incremented if the equation is satisfied. A Threshold ϵ = 0.02

MV

$\overline{x}=\frac{1}{N}{\displaystyle \sum _{i=1}^N{x}_i}$

It represents the EMG potential from any shift in values of the mean.

SSI

$\mathit{SS}{I}_k={\displaystyle \sum _{i=1}^N\left(\left|x_i^2\right|\right)}$

It determines the energy of EMGs in each segment.

MPV

x _k = max |x _i |

It is used to find the maximum absolute peak value of EMGs.