nerves can be stimulated using either surface (transcutaneous) or subcutaneous (percutaneous or implanted) electrodes. the surface electrodes are placed on the skin surface above the nerve or muscle that needs to be "activated". they are noninvasive, easy to apply, and generally inexpensive. until recently the common belief in the fes field has been that due to the electrode-skin contact impedance, skin and tissue impedance, and current dispersion during stimulation, much higher-intensity pulses are required to stimulate nerves using surface stimulation electrodes as compared to the subcutaneous electrodes.