Identify the current associated with tetanic contraction.

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

Answer: (A)

Tetanic contraction occurs when muscle fibers are stimulated so rapidly that individual twitches fuse and the muscle remains smoothly contracted. This requires a high rate of stimulation, because each pulse must arrive before the previous twitch has finished relaxing, creating temporal summation. When stimulation is at a lower frequency, each pulse produces a separate twitch with time to relax in between, so you don’t see a fused, tetanic contraction. So, in standard electrotherapy understanding, high-frequency current is what creates tetanus-like, sustained contraction, while low-frequency current yields distinct, individual contractions. Some resources label terminology differently, but the fundamental principle is that rapid, closely spaced pulses produce the fused contraction.