If the pulse duration is increased, what happens to the amplitude needed to achieve the same contraction?

If the pulse duration is increased, what happens to the amplitude needed to achieve the same contraction?

• A. Amplitude required increases
• B. Amplitude required decreases
• C. Amplitude remains the same
• D. Amplitude becomes unpredictable

Answer: (B)

Increasing pulse duration lowers the amplitude needed to reach the same contraction because the longer pulse delivers more charge per pulse. Muscle and nerve fibers reach their activation threshold when enough charge is delivered; by extending the duration, you can reduce the current while still achieving that threshold. This is the strength–duration relationship: as duration increases toward the fiber’s excitability window, the required current decreases. So, to get the same contraction, you can use a lower amplitude when you lengthen the pulse duration. (Be mindful that very long durations can affect comfort and selectivity, but the basic idea is that longer pulses reduce the needed amplitude.)

Increasing pulse duration lowers the amplitude needed to reach the same contraction because the longer pulse delivers more charge per pulse. Muscle and nerve fibers reach their activation threshold when enough charge is delivered; by extending the duration, you can reduce the current while still achieving that threshold. This is the strength–duration relationship: as duration increases toward the fiber’s excitability window, the required current decreases. So, to get the same contraction, you can use a lower amplitude when you lengthen the pulse duration. (Be mindful that very long durations can affect comfort and selectivity, but the basic idea is that longer pulses reduce the needed amplitude.)