Why is impedance checking important before NMES therapy?

• A. High impedance reduces current delivery and can cause skin heating; ensuring low and stable impedance improves performance and safety.
• B. Impedance has no impact on NMES effectiveness.
• C. Impedance only affects device battery life.
• D. Impedance is only checked for equipment compatibility.

Answer: (A)

Impedance is the pathway the electrical pulses must take from the device through the skin to reach the nerves that drive the muscle. In NMES, the current you rely on to produce a contraction passes across the skin-electrode interface, so how easily it flows matters a lot.

If impedance is high, the current reaching the tissue drops, which can make the stimulation too weak to achieve the intended contraction. The device may respond by raising the voltage to push more current, but that can heat the skin at the electrode and increase the risk of burns or discomfort. Keeping impedance low and stable ensures the prescribed amount of current actually gets to the muscle reliably, giving effective therapy with a safer skin interface.

Impedance can rise due to poor contact, dry or oily skin, hair, dirty electrodes, or old gel. Checking impedance beforehand confirms good contact and an adequate current path, and watching impedance during treatment helps catch shifts that could change dosing. In short, impedance checking protects safety while ensuring the therapy is effective by confirming a clear, stable path for the stimulation.