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[015] Citation: B. Hannaford, S. Lehman, 'Short Time Fourier Analysis of the Electromyogram: Fast Movements and Constant Contraction,'
IEEE Transactions on Biomedical Engineering, vol. BME-33, pp. 1173-1181, Dec. 1986.
Abstract
We applied short-time Fourier analysis to surface electromyograms (EMG)
recorded during rapid movements, and during isometric contractions at constant
forces. We selected a portion of the data to be transformed by multiplying
the signal by a Hamming window, then computed the discrete Fourier transform.
Shifting the window along the data record, we computed a new spectrum each 10
ms. We displayed the transformed data in spectrograms or "voiceprints." This
short-time technique allowed us to see time-dependencies in the EMG that are
normally averaged in the Fourier analysis of these signals. Spectra of EMG's
during isometric contractions at constant force vary in the short (10-20 ms)
term. Moments of the spectral distribution show this variability. Short-time
spectra from EMG's recorded during rapid movements were much less variable. The
windowing technique picked out the typical "three-burst pattern" in EMG's from
both wrist and head movements. Spectra during the bursts were more consistent
than those during isometric contractions. Furthermore, there was a consistent
shift in spectral statistics in the course of the three bursts. Both the
center frequency and the variance of the spectral energy distribution grew from
from the first burst to the second burst in the same muscle. We discuss this
pattern with respect to the origin of the EMG bursts in rapid movement. We
also extend the analogy between electromyograms and speech signals to argue for
future applicability of short-time spectral analysis of EMG.
["I would like a hard copy of this report"]
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Updated: Tue Jul 15 23:54:48 2008
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