Research and analysis on the effect of joint angle on EMG in thigh muscles

In this paper the effect of joint angle on EMG is analyzed qualitatively for finding the controlling mechanism of knee joint swing velocity and flexion angle. Wavelet transformation (WT) and wavelet packet transformation (WPT) are used to eliminate the noises of surface EMG sampled from the lower limb during the subjects of study walked normally on the flat. By comparing the denoise result, WPT wins an advantage of WP with the same threshold. And the result shows that if the suitable scale and the threshold are selected, the high-frequency noises can be eliminated effectively. According to the characteristic of WPT, the motion features are extracted during the stance phase and the swing phase using the WPT. The figures show the fine extraction result in this paper. While discrete Fourier transform (DFT) illustrates that the primary frequency band is from 20Hz to 200Hz whether flexion or extend.