The Effects of Subcutaneous Fat, Electrode Size and Inter-Electrode Distance During Transcutaneous Electrical Stimulation

Transcutaneous electrical stimulation is used as an adjunct therapy for obesity, where it can enable increased levels of voluntary exercise. Due to the high resistivity of subcutaneous fat tissue, however, high stimulus currents are required to evoke muscle contraction in obese subjects, possibly leading to patient discomfort. In this study, a three-dimensional finite element model of the human thigh, including skin, fat, muscle and bone, was developed to examine the effects of fat thickness, electrode size and inter-electrode distance on the level of evoked muscle activation, examined using the activating function, during monopolar and bipolar stimulation. The results indicate that increased electrode size may reduce patient discomfort while maintaining the efficacy of the electrical stimulation in obese patient populations. Additionally, muscle activation appeared to be less sensitive to inter-electrode distance as fat thickness increased.