What effect do surface electrodes have on compound muscle action potential (CMAP) amplitude?

Surface electrodes can actually increase the compound muscle action potential (CMAP) amplitude and improve the morphology when properly applied. This is because surface electrodes can provide a more optimal contact with the skin, generating a more significant and representative recording from the underlying muscle fibers. By capturing a broader area of muscle activity, surface electrodes can enhance the amplitude of the detected signal.

Additionally, surface electrodes are less affected by muscle movement and can provide a clearer signal compared to needle electrodes in certain scenarios, which contributes to better morphology. Proper placement and techniques with surface electrodes can help to reduce artifacts and improve the overall quality of the signal captured.

In contrast, while other options may suggest negative effects or no effect, they do not account for the specific advantages of surface electrodes in capturing the CMAP effectively when utilized correctly.