National Physical Therapy Examination (NPTE) Practice Exam

What are the optimal electrode placements for motor stimulation?

1. Electrodes as far away from each other as possible

2. Distal to the muscle fibers

3. One electrode on the functional motor point and the other over a distal site

4. One electrode on the functional motor point and the other on the muscle belly

The correct answer is: One electrode on the functional motor point and the other on the muscle belly

The optimal electrode placement for motor stimulation is when one electrode is placed on the functional motor point and the other on the muscle belly. The functional motor point is the area of a muscle where the largest number of motor nerve fibers enter, making it more responsive to electrical stimulation. This placement helps in achieving a more effective and efficient contraction of the muscle. When one electrode is positioned on the muscle belly, it allows for optimal current flow through the muscle fibers, facilitating stronger contractions and better therapeutic outcomes. Electrodes placed further apart (as suggested in other choices) can lead to a less targeted stimulation and potential stimulation of unwanted adjacent muscles, which may not provide the desired therapeutic effect. Similarly, placing one electrode distal to the muscle fibers may not effectively recruit the motor units necessary for a robust muscle contraction, as it would fail to maximize the stimulation at the site where nerve fibers converge. Therefore, the combination of the functional motor point and the muscle belly allows for a direct and effective path for stimulating motor neurons, ensuring a more efficient therapeutic response.