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   -> Volume 7, Issue 7

Thesis: The analysis of electromyography using wavelets
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"Jae S. Lee" (

PostPosted: Wed Jul 08, 1998 8:20 pm    
Subject: Thesis: The analysis of electromyography using wavelets
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#6 Thesis: The analysis of electromyography using wavelets

Hello, I'd like to share my Ph.D. work with you. I've got my degree
at the University of Iowa (Biomedical Engineering) and currently
working at the California State University at Long Beach, California
as a post-doc fellow in Electrical Engineering Dept. I've mainly
worked on the analysis of Surface Electromyography (EMG) signals using
both discrete and continuous wavelet transforms. If you have specific
questions, like the detailed informations about my publications,
please e-mail me, or simply visit my home page


Abstract: Electromyography (EMG) is a well-established technique that
provides an indication of a level of muscle activity. The analysis
used in my work is mainly based on wavelet transform, a recently
developed advanced mathematical technique. Three criteria, wavelet
filtering, window width and scale comparison index, were used to
detect onset time from sudden load experiment. The wavelet based
onset detection algorithm showed precision, consistency and
reproducibility not only in clear signals but also in signals that
have considerable background activity. The onset detection error in
wavelet based method was about 5 ms while those of traditional methods
were about 20 ms. The reaction time of low back muscles to sudden
loads has been measured and compared for various lumbar supports. No
statistically significant effect in reaction time was detected as a
result of wearing various lumbar supports. The relative muscular
activity, however, did show apparent differences when different lumbar
supports were used. The properly worn Chase Lumbar support produced
the least overcompensation. The effect of lumbar supports in fatigue
has also been demonstrated using median frequency shift measure during
the Sorenson test. Wide, circumferential compression applied around
the pelvis by wearing lumbar support snugly was shown to reduce muscle
fatigue. In the whiplash study, it was demonstrated that cervical
muscle activity exists shortly after the initial motion of the sled
using two different techniques: continuous wavelet transform and
multiresolution analysis. Both techniques gave approximately the same
results for the times and frequency of occurrences of muscle activity.
The reaction time measured in this study was shorter than those
reported previously by other researchers. This finding is significant
because it suggests that such muscle activity may be a contributing
factor in the creation of a more accurate whiplash biomechanical
model. Multiresolution analysis has been successfully applied for the
automatic onset time determination from low back surface EMG signals.
The results indicated that the reaction time from the erector spinae
muscle after rehabilitation was faster than the reaction time before
rehabilitation for about half of the cases.

Jae S. Lee, Ph. D.
California State Univ. at Long Beach
1213 E. Cordova St. Apt. 6
Pasadena, California 91106
Tel: 626)844-4520
All times are GMT + 1 Hour
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