Single site electromyograph amplitude estimation.
Previous investigators have experimentally demonstrated and/or analytically predicted that temporal whitening of the surface electromyograph (EMG) waveform prior to demodulation improves the EMG amplitude estimate [1]-[6]. However, no systematic study of the influence of various whitening filters upon amplitude estimate performance has been reported. This paper describes a phenomenological mathematical model of a single site of the surface EMG waveform and reports on experimental studies which examined the performance of several temporal whitening filters. Surface EMG waveforms were sampled during nonfatiguing, constant-force, isometric contractions of the biceps or triceps muscles, over the range of 10-75% maximum voluntary contraction. A signal-to-noise ratio (SNR) was computed from each amplitude estimate (deviations about the mean value of the estimate were considered as noise). A moving average root mean square estimator (245ms window) provided an average +/- standard deviation (A +/- SD) SNR of 10.7 +/- 3.3 for the individual recordings. Temporal whitening with one fourth-order whitening filter designed per site improved the A +/- SD SNR to 17.6 +/- 6.0.
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139.
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Clancy
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Hogan
D000328:Adult; D001696:Biomechanical Phenomena; D002138:Calibration; D004550:Elbow / Q000502:physiology; D004576:Electromyography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008954:Models, Biological; D015233:Models, Statistical; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted