Interrupted direct current (IDC) involves delivering unidirectional current pulses separated by intervals of no current. The pulses can have different durations, frequencies, rise/fall times, and waveforms (rectangular, trapezoidal, triangular, sawtooth). IDC is used therapeutically for sensory stimulation, pain relief, accelerating healing, and muscle stimulation. It works on nerves and muscles depending on pulse duration and intensity. Techniques like labile and group stimulation are used to target all muscle fibers. IDC has physiological effects like hyperaemia and contraindications like metal implants or risk of injury.