Knee extensor torque and perceived discomfort during symmetrical biphasic electromyostimulation

The purpose of this study was to examine the effects of simultaneously delivering 2 channels of electromyostimulation (EMS) current using 2 different electrode arrangements. Ten men and 10 women university students had 4 reusable electrodes placed (2 proximal, 2 distal) medial and lateral on the quadriceps muscle group. Isokinetic voluntary peak torque (VPT) of the quadriceps was determined at 60 degrees x s(-1). A symmetrical biphasic square wave current was applied using 2 independent channels in either a parallel (P) or a crossed (X) electrode arrangement. Subjects increased the current until maximal tolerance was achieved. No significant differences in percent VPT or perceived discomfort (PD) were observed between men and women. Percent VPT was significantly greater using the X (57.2 +/- 11.3%) vs. the P (46.5 +/- 10.7%) pad placement; however, pad placement did not affect peak PD. Data from this study suggest that a 2-channel application of EMS using a crossed electrode arrangement provides greater knee extensor force without greater discomfort.