Moving approximate entropy applied to surface electromyographic signals

The objective of this study was to investigate the surface electromyographic signals using moving approximate entropy from 20 healthy participants’ wrist muscles (flexor carpi ulnaris and flexor carpi radialis). The participants were required to voluntary performed wrist flexion/extension, co-contraction and isometric contraction. A moving data window of 200 values was applied to the data and a moving approximate entropy series was obtained from the analysis. The results demonstrate that there are distinct drops of the approximate entropy values at the start and end of a contraction, and high (less regularity) approximate entropy in the middle. Mean values of approximate entropy of 0.54 and 0.55 were found for the start of a contraction compared to 0.79 and 0.77 during the middle, for the flexor and extensor, respectively. At the end, there are values of 0.46 and 0.5, respectively.