Bispectral analysis of surface EMG

The objective of this ongoing study is to investigate whether or not bispectral analysis (BS), a particular form of higher order spectra (HOS), may be utilized for analyzing the surface electromyographic signal (SEMG). The bicoherence index was used for characterizing the Gaussianity of the signal. Results indicate that SEMG signal distribution is highly nonGaussian at low and high levels of force whereas the distribution has its maximum Gaussianity at the mid level of maximum voluntary contraction (MVC), i.e. at 50%. A measure of the linearity of the signal, based on deciding whether or not the estimated bicoherence is constant, follows the reverse pattern with the measure of Gaussianity. The power spectrum´s (PS) median frequency, decreases from 105 to 93 Hz with increase of force, whereas the number of turns and the number of zero crosses increase with force. Further work is currently in progress in order to evaluate the usefulness of HOS in normal subjects and subjects suffering from neuromuscular disorders.