For eliciting a motor contraction, where should the electrodes be placed?

• A. Muscle Belly or Motor Points
• B. Around the Joint
• C. Over a Bony Prominence
• D. Directly Over Fat Tissue

Answer: (A)

To reliably evoke a motor contraction with electrical stimulation, you want the current to reach the motor nerves that innervate the target muscle with minimal impedance. The ideal placement is at the muscle belly or at a motor point—the spot where motor endplates are concentrated and where nerves are closest to the surface. This lets the current depolarize the motor units efficiently, producing a strong, localized contraction with lower current.

Placing electrodes around the joint tends to excite nerves in the area rather than the specific muscle, leading to less controlled or less specific contractions. Placing over a bony prominence reduces skin contact and increases impedance, making stimulation uncomfortable and less effective. Directly over fat tissue also raises impedance and keeps current from reaching the muscle well, requiring higher intensities and giving a weaker contraction.

So, muscle belly or motor points is the best choice.