Table 2.

Characteristics of commonly used waveforms for electrical stimulation therapy.

Type of Exogenous ES	Characteristics
Direct current (DC)	Continuous flow of electric charge in a monophasic waveform (in one direction). Currents of 20–200 µA can be supplied at a low voltage.
Alternating current (AC)	Has a biphasic waveform, with two symmetrical electrical pulses alternating one after the other. Voltages typically 50–150 V dependent on tissue hydration.
Pulsed current (PC)	Intermittent flow of charged particles with gaps in current flow. This can have a monophasic or biphasic waveform. Currents of 1.2–1.5 mA can be supplied to the tissue at high voltage.
Degenerate wave (DW)	A type of waveform used in certain biofeedback devices. A constant current of 0.3 mA, which delivers an electric field of 10 mV/mm between the electrodes can be used.