Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/18033
Title: Oscillations in the power spectra of motor unit signals caused by refractoriness variations
Authors: Hu, XL
Tong, KY
Hung, LK
Issue Date: 2004
Source: Journal of neural engineering, 2004, v. 1, no. 3, p. 174-185 How to cite?
Journal: Journal of Neural Engineering 
Abstract: The refractory period of a motor unit is an important mechanism that regulates the motor unit firing, and its variation has been found in many physiological cases. In this study, a new observation that an increase in the motor unit refractoriness results in an enhancement of oscillations, or ripple effects, in the motor unit output power density spectra (PDS) has been identified and studied. The effects of the refractoriness variation on the PDS of motor unit firing were investigated on three levels: theoretical modeling, simulation and electromyographic (EMG) experimentation on human subjects. Both theoretical modeling and simulation showed the enhanced oscillations, ripple effects, in MUAPT PDS, given the increase in the refractoriness. It was also found that the extent of the increment in output PDS oscillation could be related to the motor unit size and the mean firing rate of the stimulation. A needle EMG experiment on biceps brachii muscles of five healthy human subjects was carried out during isometric contraction at 20% maximum voluntary contraction (MVC) for 20 s with a fatigue effort proceeded by MVC. The increased oscillations in the PDS of the real MUAPTs were observed with the rising of the motor unit refractoriness due to fatigue. The study gives new information for EMG spectra interpretation, and also provides a potential method for accessing neuromuscular transmission failure (NTF) due to fatigue during voluntary contraction.
URI: http://hdl.handle.net/10397/18033
ISSN: 1741-2560
DOI: 10.1088/1741-2560/1/3/007
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