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Previous observations suggest that elevated high-pass filter settings (1,600-3,200 HZ) can reveal greater motor unit action potential (MUAP) complexity (turns). We assessed the effect of high-pass filter settings (500, 1,000, 2,000 HZ) on MUAP metrics. MUAPs were recorded with a concentric needle and initially extracted by a decomposition software algorithm at 10 HZ-10 kHZ and further filtered offline at 500, 1,000, and 2,000 HZ. When reanalyzed by the decomposition software there were marked reductions in peak-peak amplitude, area, area-to-amplitude ratio, and duration at the 500 HZ filter with lesser subsequent reductions at higher filter settings. In contrast, turn and phase counts did not change significantly. Individual MUAPs tracked across filter settings showed rare increases in turn count at the 500 HZ setting but a subsequent decrease in counts with higher filter settings. We conclude that the routine use of elevated high-pass filters, as in quantitative EMG analysis, does not enhance turn count.

Quantitative electromyography (QEMG) relies on a number of discharges of the same motor unit action potential (MUAP) from a train to create an averaged MUAP considered to be representative of a true potential. The train of potentials may be affected by changes in position of the electrode relative to contributing muscle fibers of the motor unit due to operator or subject movement. The effect of changes in electrode position, along with consideration for patient comfort, prompted this study to determine the shortest duration of recording time necessary for sufficient data acquisition for QEMG studies. We determined that 10 seconds of moderate muscle activity is the most reasonable acquisition duration to isolate up to 6 MUAPs at a given electrode site and minimize the effects of movement artifact in the signal.