Optimizing the stimulus current in a surface based stimulation device

A method for ensuring firing of an action potential in an intended physiological target activated by a stimulus pulse generated by an electrode of a non-invasive surface based stimulation device irrespective of skin-to-electrode impedance, comprising the steps of:

• sensing the skin-to-electrode impedance;
• deriving from the sensed skin-to-electrode impedance a current decay;
• detecting a strength-duration curve of the intended physiological target and a Chronaxie in the strength-duration curve of the intended physiological target;
• detecting based on the Chronaxie in the strength-duration curve of the intended physiological target when the derived current decay is insufficient to fire the action potential in the intended physiological target;
• increasing internal impedance of the stimulation device;
• and
• generating the stimulus pulse using the electrode;
• wherein the increased internal impedance widens a duration of the stimulus pulse so as to ensure firing of the action potential of the intended physiological target irrespective of the sense skin-to-electrode impedance.