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. In this paper, this theory has been investigated by studying a sEMG model developed earlier. 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. The model of sEMG of biceps brachii muscle during various levels of isometric voluntary contraction was considered and included details of muscle type, measurable average and individual conduction velocities and the natural variations between motor unit recruitment and firing rates as observed experimentally. The model used the change in the muscle conduction velocity (v) 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 RS parameter in the model. The model was also simulated to generate sEMG at various levels of voluntary isometric contractions. 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 there is large change in MDF with v in the simulated sEMG than in experimental conditions.