To obtain a stimulated muscular contraction, we are obliged to produce a depolarisation of one or more motor units.
The better way is to apply a current flow on a motor point, that is to say the point where the nervous fibre innervates the muscle fibre.
Being the human tissues very similar to a capacitor, from the electric point of view, it has been stated that the better effectiveness for the electro stimulation is obtained by using a pulse wave, having a very steep rising front.
The better pulse width will match the chronaxy value of the muscle to be stimulated.
A monophasic pulse could be used, but it has been demonstrated that a biphasic pulse is more comfortable, without reduction of the effectiveness.
The biphasic pulse has no galvanic effect, so it is also suitable to be used over areas including metallic prosthesis.