In settings intended to increase muscle strength with electrical stimulation, which waveform is used?

• A. Symmetrical Biphasic
• B. Asymmetrical Biphasic
• C. Monophasic Pulse
• D. Pulsed Direct Current

Answer: (A)

For strengthening with electrical stimulation, the waveform should deliver strong, repeatable muscle contractions with minimal risk of skin irritation or tissue damage. A symmetrical biphasic pulse does this well because it has equal positive and negative phases, resulting in near-zero net charge per pulse. This charge balance prevents electrode polarization, reduces skin irritation, and lowers the chance of tissue damage during repeated sessions, allowing longer, more productive strengthening programs. The balanced waveform also promotes smooth, consistent motor unit recruitment, which is important for building strength. In contrast, monophasic pulses create net charge and can irritate the skin or cause burns, pulsed direct current has DC components that are uncomfortable and less safe for repeated use, and asymmetrical biphasic can introduce a residual charge that may increase discomfort or alter recruitment. Thus, the symmetrical biphasic waveform is the best fit for muscle strengthening with electrical stimulation.