Which test records electrical activity of skeletal muscle?

• A. ECG
• B. EMG
• C. EEG
• D. Endoscopy

Answer: (B)

Recording electrical activity of skeletal muscle is done with electromyography. When a muscle is activated by a motor nerve, its fibers generate small electrical potentials. An EMG uses electrodes—either a needle inserted into the muscle or surface electrodes on the skin—to pick up these signals and display patterns such as insertion activity, motor unit action potentials, and recruitment during contraction. By analyzing these waveforms, clinicians can distinguish problems rooted in the muscle itself from those in the nerves that supply the muscle or at the neuromuscular junction. This is different from ECG, which records heart electrical activity; EEG, which records brain activity; and endoscopy, which visually examines internal structures.