Spectral properties of surface electromyogram signal and change in muscle conduction velocity during isometric muscle contraction

It is well known that there is a change in the spectrum of surface electromyogram (sEMG) with the onset of muscle fatigue. This change has largely been attributed to the change in muscle conduction velocity. We have investigated this theory by using our previously developed sEMG model with the various neuromuscular parameters. The change of spectrum of the experimental results has been compared with simulated sEMG in response to the change in muscle conduction velocity using similar conditions. In this study, the designed model implemented the change in the muscle conduction velocity ( ) as a parameter to simulate the sEMG. The shift in spectrum was identified by computation of the median frequency (MDF) of the sEMG before and after the implementation of the rate of the slow down (RS or ) parameter in the model. The results based on the simulation of the model show that the rate of change in MDF was consistent in all levels of contractions and it is not same with experimental conditions. The results also suggest that the large change in MDF in the simulated sEMG than in experimental conditions may be attributable to other factors such as change in the recruitment pattern and the level of contraction not only due to the change in the muscle conduction velocity ( ).