The galvanic-tetanus ratio of normal muscle is

• A. 10-12 to 1
• B. 1 to 1
• C. Applicable only to denervated muscle
• D. None of the above

Answer: (A)

When you compare how normal muscle responds to two types of electrical stimulation, you’re looking at efficiency. Tetanic stimulation uses rapid pulses that summate contractions, so the muscle can produce a strong contraction with relatively less current. Galvanic stimulation uses a direct current, which yields a slower, tonic response and is less efficient at driving a strong, quick contraction. Because of this difference in how the membranes respond to each type of current, the amount of galvanic current needed to produce a contraction comparable to a tetanic contraction is much higher—about ten to twelve times more. That’s why the galvanic-tetanus ratio for normal muscle is around 10-12 to 1. This ratio reflects normal innervated muscle behavior; it wouldn’t apply in the same way to denervated muscle, where responses to stimulation differ.