A comparative study of simultaneous vibromyography and electromyography with active human quadriceps

Vibromyographic (VMG) signals, which are low-frequency vibration signals generated during muscle contraction, were studied in comparison with electromyographic (EMG) signals recorded simultaneously during isometric contraction of the human quadriceps muscles. It was found that the VMG and EMG under the same conditions on the same muscle group are, in general, equally sensitive to the levels of muscle contraction. Results show that the RMS value of the VMG signal increases linearly, in a manner similar to the EMG RMS/% maximal voluntary contraction (MVC) relationship, with increasing muscle contraction levels. Furthermore, the study indicates that the averaged mean frequency and peak frequency of the VMG signals are much lower than those of the EMG signals. The results also indicate that certain relationships for the VMG signal, like those of the EMG, may reflect muscle activation patterns, while the difference in frequency content between the VMG and the EMG reflects the morphological differences between the mechanical and electrical responses to muscle activation. The signals exhibit a feature of joint angle dependence.