Objective: The present study aimed to test the effect of the electrode position and inter-electrode distance on the evoked force by neuromuscular electrical stimulation (NMES) with a low current intensity and a single pair of electrodes. Knee extensor forces during NMES to quadriceps femoris muscles were compared among four different electrode configurations in seven healthy men. Electrodes were located at 10 cm proximal and 15 cm distal (P10-D15), 10 cm proximal and 10 cm distal (P10-D10), 5 cm proximal and 15 cm distal, and 5 cm proximal and 10 cm distal (P5-D10) to the center of the longitudinal axis of the quadriceps femoris muscles.
Results: The evoked force-time area for P5-D10 was significantly higher than those for P10-D15 and P10-D10 (p < 0.05). When using NMES devices with a low current intensity, a shorter inter-electrode distance and relatively distal locations can promote greater evoked forces in the quadriceps femoris muscles.
Keywords: Electrical muscle stimulation; Electrode location; Innervation zone; Knee extensor; Quadriceps femoris muscles; Stimulation parameter.