Algorithm 1. Detecting the onset of muscle activity in the EMG signal

Input: x—EMG signal, N—signal length

/* Step 1: Determine the area of activity */

1  Peak ← local maxima detection(x)

2  Cluster ← Separation into 2 groups using EM

- muscle activity

- background noise

3  PDFactivity ← Kernel Density Estimation (KDE) for muscle activity

4  PDFnoise ← KDE for background noise

5   for n ← 1 to N do

6       if PDFactivity[n] > PDFnoise[n] then

7           activeregion ← n

8       end

9   end

10  onsetrough ← activeregion starting point

/ Stage 2: Onset clarification /

11  W ← signal window around onsetrough

12  Energy ← Teager–Kaiser energy operator

13  onsetfinal ← the point where energy changes the most

14  return onsetfinal

Output: onsetfinal—starting point of muscle activity