In motor stimulation, electrode size should be chosen based on the size of the targeted muscle.

• A. Big for big muscle
• B. Small for small muscle
• C. Depends on the size
• D. It does not matter

Answer: (C)

Electrode size changes current density and how localized the stimulation will be. When targeting a muscle, you choose the electrode size to match what you’re trying to activate. A larger electrode spreads the current over a bigger area, lowering current density and producing a more diffuse, less focal contraction, which can be appropriate for activating a large muscle group with greater comfort. A smaller electrode concentrates the current, giving a more focused activation on a specific muscle or motor point, but can increase discomfort and skin impedance if the current is high. Because you must balance effective activation with comfort and selectivity, the right choice depends on the size and location of the targeted muscle (and other factors like depth and desired precision). That’s why the correct idea is that it depends on the size.