Wavelet analysis of surface EMG signals from three superficial quadriceps muscles under varying levels of contraction intensity and velocity.

摘要

The effects of contraction intensity (100%-, 75%-, 50%-, and 25%- maximum voluntary contraction [MVO]) and movement velocity (50°, 100°, 200°, and 400°/s) on surface electromyography root mean square amplitude (SEMG RMS) and median frequency (SEMGMDF) of rectus femoris (RF), vastus lateralis (VI), and vastus medialis (VM) muscles were investigated, by means of spectral decomposition of the SEMG time waveform with a Continuous Wavelet Transform. To this end, a wavelet spectral decomposition software tool was developed to facilitate effortless transformation of the SEMG signal (or any other given time waveform) into a configuration suitable for statistical analysis.;RF, Vi., and VM muscles displayed increased median frequencies as contraction intensity increased from 25%- to 50%-MVC and from 75%- to 100%-MVC, although each muscle displayed its own frequency shifting patterns to increasing intensities, with velocity displaying no effect on median frequency values; muscle amplitude increased in all three muscles as contraction intensities increased.