Electro-Stimulatory Effects occur within which frequency range?

• A. 100 kHz-3 GHz
• B. 3 Hz-3 kHz
• C. 3 kHz-5 MHz
• D. 3 GHz-300 GHz

Answer: (C)

Electro-stimulatory effects happen when an external field induces currents in neural or muscular tissue large enough to depolarize membranes and trigger action potentials. The likelihood of this depends on frequency because tissue impedance changes with frequency: at very low frequencies the current paths and thresholds are different, and at very high frequencies the membranes can’t respond quickly enough to cause stimulation, with heating becoming the dominant concern. In the mid-range, roughly from a few kilohertz up to a few megahertz, the induced currents can reach excitable tissues effectively without being so high in frequency that stimulation is unlikely or so low in frequency that other effects dominate. That’s why the frequency range from about 3 kHz to 5 MHz is the one associated with electro-stimulatory effects.