A two dimensional electrode current density model for subthreshold electrical stimulation

Transcutaneous electrical neuromuscular stimulation (TENS) is finding increasing applicability. One use is a new therapy using subthreshold TENS to promote growth and neuron sprouting in target muscles. Heretofore, models used to examine the current distribution in long strip electrodes were one dimensional. These models do not represent the dynamics accurately, particularly within 3 cm of the center wire of the electrode. When stimulating children or specific muscle groups using small rectangular electrodes, this discrepancy becomes of greater concern. This paper characterizes the current density flowing out of an electrode by modeling the electrode as a two dimensional surface. Mathematically, the family of cable equations is incorporated into the form of a solution. Further, this paper develops an equivalent circuit incorporating the actual shape of the electrode, the effects of subcutaneous fat, and the muscle´s atrophy level