In EMG biofeedback, placing electrodes close together has what effect on detecting undesired activity from adjacent muscles?

• A. Increases detection of adjacent muscle activity
• B. Decreases likelihood of detecting undesired motor unit activity from adjacent muscles
• C. Has no effect on detection
• D. Increases overall EMG amplitude

Answer: (B)

Focusing on a smaller area with electrodes improves spatial selectivity in EMG readings. When the two sensing points are close together, the recorded signal mainly reflects activity from the small region of the target muscle, so activity from adjacent muscles contributes less to what you measure. The differential signal emphasizes local potentials and attenuates distant sources, which means cross-talk from nearby muscles is reduced. In biofeedback, this helps ensure the feedback represents the intended muscle activation rather than undesired motor unit activity from neighboring muscles. If the electrodes were farther apart, you’d pick up more cross-talk, making it harder to separate the target activity from adjacent muscle activity.