In the claim about tetanic contractions not being set up by currents, which current is identified?

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

Answer: (B)

Tetanic contraction happens when motor units are driven at a rate that makes individual twitches fuse into one smooth, sustained contraction. That requires stimulation at a moderate, repetitive frequency. Very high-frequency currents don’t produce this kind of response—the rapid oscillations don’t allow motor neurons to fire in a way that sustains a fused contraction and they tend to cause heating or conduction effects rather than a controlled muscle contraction. So the current type identified as not setting up tetanic contractions is the high-frequency current. This is why, for strengthening or contraction, therapists use lower frequencies that can produce a true tetanus, while high-frequency currents are used mainly for heating or other effects.