For NMES, what is the typical aim of biphasic pulses (symmetrical or asymmetrical)?

• A. They are not used in NMES
• B. They deliver nerve conduction tests
• C. They produce long-term nerve damage
• D. They deliver safe, efficient muscle contraction with minimal skin irritation

Answer: (D)

In NMES, biphasic pulses are used to drive a muscle contraction while protecting the skin and underlying tissues. A major concern with electrical stimulation on the skin is net charge buildup, which can cause undesirable electrochemical reactions at the electrode-skin interface and skin irritation or tissue damage. Biphasic pulses are designed to be charge-balanced, so the positive and negative phases cancel out over time and the net charge is near zero. This reduces skin irritation, lowers the risk of tissue damage, allows for more comfortable, higher currents, and supports a stronger, more reliable contraction. The symmetry or asymmetry of the two phases refers to how the pulse is shaped, but the crucial point is that the overall charge is balanced. The aim is to deliver safe, efficient muscle contraction with minimal skin irritation.