During EMG biofeedback, why are electrodes initially placed close together?

• A. Increase signal amplitude
• B. Decrease likelihood of detecting undesired motor units from adjacent active muscles
• C. Increase volume of monitored muscle
• D. Increase crosstalk

Answer: (B)

During EMG biofeedback, the aim is to monitor activity from a specific target muscle and provide feedback based on that muscle’s activation. Surface electrodes can pick up signals not only from the muscle beneath but also from nearby muscles through volume conduction. Placing the electrodes close together narrows the sensing field to a small area of the target muscle, which improves spatial selectivity and reduces the pickup of signals from adjacent muscles. In other words, it lowers the likelihood of detecting undesired motor unit activity from neighboring muscles, decreasing cross-talk. If the electrodes were farther apart, signals from nearby muscles would contribute more, muddying the signal for the target muscle.