Which statement about electrode sizes is true in electrical stimulation?

Which statement about electrode sizes is true in electrical stimulation?

• A. Active pad is larger than the dispersive pad.
• B. Size has no effect on the number of motor units stimulated.
• C. Active pad is smaller than the dispersive pad.
• D. All electrodes are the same size.

Answer: (C)

The effectiveness of electrical stimulation hinges on how current concentrates under each electrode, which is governed by electrode size. Current density is basically current divided by electrode area, so a smaller active pad creates a higher current density at the target tissue, focusing stimulation on the desired muscles and improving motor unit recruitment. A larger dispersive pad spreads the return current over a wider area, lowering peak current density away from the target and reducing unwanted stimulation and skin irritation. This combination—active pad smaller than the dispersive pad—lets you target the muscle more efficiently while keeping comfort and safety in check.

The effectiveness of electrical stimulation hinges on how current concentrates under each electrode, which is governed by electrode size. Current density is basically current divided by electrode area, so a smaller active pad creates a higher current density at the target tissue, focusing stimulation on the desired muscles and improving motor unit recruitment. A larger dispersive pad spreads the return current over a wider area, lowering peak current density away from the target and reducing unwanted stimulation and skin irritation. This combination—active pad smaller than the dispersive pad—lets you target the muscle more efficiently while keeping comfort and safety in check.