Motor unit action potentials(MUAPs) were recorded from the biceps and first dorsal interosseous muscles to identify the electrode effect on the properties of MUAPs between concentric and monopolar electrode in 25 healthy adults. The parameters of MUAPs such as amplitude, area, spike amplitude and number of phases recorded with monopolar electrode were larger than those recorded with concentric needle, but in contrast there were no significant difference on mean MUAP duration between two electrode types in both muscles. The most common shape of MUAPs were triphasic in both electrode recordings and the incidence of polyphasic and polyturn MUAPs were higher in monopolar recordings than concentric.
The rise time was inverse relationship with the amplitude, and number of phases and turns. And in general there were significant positive correlation between the duration, the amplitude, the area, the spike amplitude and area, the number of phases and turns.
Therefore different reference values must be used in analyzing the MUAP recorded by concentric and monopolar electrodes.
