In order to be qualified as optimum, the stimulation impulse meet meet two indispensable conditions:

• It must bring the quantity of electric charge required to trigger an action potential (modification of the rest potential up to threshold value)
• But it must only bring a quantity of electric charge sufficient to be applied safely and with maximum comfort.

In order to meet these two conditions, the optimum impulse can be defined as that capable of modifying the rest potential up to the threshold value of excitability (according to the fundamental law), while offering maximum comfort to the user. The latter requirement will be fulfilled by minimizing the electrical parameters of the impulse.

After these conditions have been set, the optimum impulse of neurostimulation should have the following characteristics:

• Rectangular wave
• Length of the rectangular wave equal to the chronaxy of the nervous structure that you want to excite
• Compensation of the rectangular wave by a perfectly symmetrical wave with opposite polarity (biphasic impulse with null electrical mean)
• Impulse produced by a constant current generator to maintain a constant impulse shape as it passes through tissue.