MULTIFREQUENCY CHARACTERISTICS OF DISPOSABLE AND NONDISPOSABLE EMG NEEDLE ELECTRODES

The physical properties of recording electrodes coupled with the input characteristics of recording amplifiers can affect motor unit paramet ers. In recent years, there has been increased use of disposable needl e electrodes; thus, a comparison of impedance characteristics with dis posable types is of interest. Impedances at 10, 100, 1000, and 10,000 Hz of eight different electrode models including concentric and monopo lar, both disposable and reusable, were measured. For all models of mo nopolar electrodes, no significant difference in impedance was found b etween disposable and nondisposable types. Intramodel variability was seen, however, with a twofold difference between minimum and maximum i mpedances for each model. For concentric electrodes, a moderate differ ence in impedance was found between disposable and nondisposable types , but less intramodel variability was seen; there was also more interm odel variability. To determine whether the measured impedances could a ffect recorded motor unit potentials, a theoretical analysis was condu cted using typical waveforms along with circuit analysis techniques. E lectrode impedances as high as 50 times nominal values caused no signi ficant waveform distortion.