ANALYSIS OF MEASURING CONDITIONS OF SURFACE ELECTROMYOGRAM USING MATHEMATICAL MODEL

To study the measuring conditions of surface electromyogram for work analysis in the field of industrial health, the effect of electrode fixation, electrode distance and electrode-muscle distance were studied using a mathematical model. The results were as follows; 1) The output waveforms of two electrode fixed models, i.e., parallel-fixed model (two electrodes were fixed in parallel to the direction of the muscle fibers) and transverse-fixed model (two electrodes were fixed in transverse to the direction of the muscle fibers) were compared. The maximum output and rectified integrated output of the parallel-fixed model were 2.59 times and 1.2-1.5 times larger than those of transverse-fixed model, respectively. The high output area of the parallel-fixed model was only one round area, but the areas of transverse-fixed model were four round areas which were wider than the area of the parallel-fixed model. The rectified integrated output of the parallel-fixed model was more affected by the location of neuro-muscular junction than that of transverse-fixed model when the electrodes were fixed near the neuro-muscular junction. 2) The rectified integrated output increased by electrode distance, and the changing rate of the rectified integrated output by electrode distance was particularly large when the electrode distance was shorter than 2 cm. The effect was quite similar between the parallel-fixed model and the transverse-fixed model. 3) The rectified integrated output decreased by electrode-muscle distance, and the changing rate of rectified integrated output by electrode-muscle distance also increased when the electrode-muscle distance was short. The effect of electrode-muscle distance was not so large compared with the effect of electrode distance.