Quantitative Evaluation of Surface Ag/AgCl EMG Electrode Configurations Using Signal-to-Noise Ratio Analysis

The placement of surface electrodes is one of the greatest determinants of the reliability of the surface EMG measurements of muscle electrical activity, and the location of the electrodes can have an effect on the amount of signal captured as well as the amount of noise recorded. In this study, an existing forearm sEMG dataset was used to investigate the electrode location that offers a balance between signal strength and minimal noise. The data consisted of the recordings from 8 channels of electrodes placed in 3 positions around the forearm. The resting and active root mean square (RMS) values were computed, and an SNR was computed for each electrode position. The differences between the electrode positions were determined by a repeated-measures analysis of variance (ANOVA) and a Friedman test. The mean SNR at Electrode 2 at P1 was the highest at 8.3144 with an RMS of 0.0777 at rest and 0.2081 when active. This position resulted in the best SNR, however there were no differences between the electrodes according to either the ANOVA test (p = 0.5275) or Friedman test (p = 0.3028). Thus, the results suggest an emerging descriptive approach that there is better SNR at the estimated muscle-belly position than there is at other positions, and not statistical proof of a true optimal electrode site. The results show that the signal level and the base noise level have to be taken into account for the proper evaluation of the electrode placement for EMG.