Changes in motor unit action potential parameters in monopolar recordings related to filter settings of the EMG...

We studied the effect of different electromyographic amplifier settings on various parameters of motor unit potentials (MUPs) as recorded by the monopolar needle. Of the four filter settings used--2Hz-10kHz, 20Hz-10kHz, 20Hz-2kHz and 500Hz-10kHz--2Hz-10kHz yielded longest duration recordings. Reductions of all parameters of the MUP except for phases and turns were demonstrated with the 500Hz-10kHz filter. No significant differences were noted between recordings obtained with 20Hz-10kHz and 20Hz-2kHz filters. Frequencies below 500Hz were more significant in determining the various parameters of the MUP than were those above 2kHz. Most suitable filter settings for recording MUPs were 2Hz-10kHz and 20Hz-10kHz. Measurements of MUPs were shown to be specific for a given filter setting.