Electrode configurations for transcutaneous stimulation of forearm muscles

Abstract

Electrode arrays facilitate customized stimulation delivery by modulating the shape and size of the stimulation area. Still, it is challenging to achieve an ideal response as several factors influence the overall stimulation. Thus, characterizing these factors to optimize stimulation performance is of interest to FES applications. This study evaluates the influence of electrode configurations on transcutaneous stimulation of forearm muscles. For a desired muscle response, different configurations were studied by changing the location of active and return electrodes, and the distance between them. The resulting muscle response was quantified as minimum evocable contraction (MEC). Firstly, the availability of more than one unique electrode configuration to achieve a target response was demonstrated. Secondly, an optimal interelectrode distance for forearm muscles was ~ 80 mm (range of 34.4 to 126.4 mm), which evoked 60–100% MEC. These inferences can help with improving electrode array-based stimulation. The availability of more than one electrode configuration implies the possibility of switching electrodes to emulate asynchronous stimulation that mitigates the onset of fatigue. Also, identifying the optimal distance between the electrodes simplifies electrode calibration and placement routines.