Which current is listed as correct in the statement that tetanic contractions are not set up by currents?

• A. Low Frequency Current
• B. High Frequency Current
• C. Both
• D. Neither

Answer: (B)

The main idea is how the frequency of electrical stimulation influences muscle contraction and whether a sustained, tetanic contraction can be produced. Tetanic contraction happens when impulses arrive fast enough that the muscle fibers don’t relax between stimuli, creating a smooth, ongoing contraction. Very high-frequency currents, in typical electrotherapy use, do not produce this kind of summated contraction. They either don’t recruit motor units effectively, or they can cause nerve conduction block and rapid fatigue, so they don’t generate the sustained tetanus described. That’s why high-frequency current is the option listed as the one that does not set up tetanic contractions. Lower to mid-range frequencies, by contrast, are the ones capable of producing tetany through temporal summation, which is why they wouldn’t fit the statement in the same way.