What is the effect of using a longer pulse duration on the amplitude needed to achieve the same contraction?

What is the effect of using a longer pulse duration on the amplitude needed to achieve the same contraction?

• A. Increases amplitude required
• B. Decreases amplitude required
• C. No change in amplitude
• D. Causes unpredictable changes

Answer: (B)

Longer pulse duration delivers more charge per pulse, so you can reach the nerve activation threshold with less current. In NMES, the motor response depends on the total charge delivered (charge ≈ current × time). Increasing the pulse duration increases this charge, allowing the same contraction to be produced at a lower amplitude. So the amplitude required decreases as pulse duration increases. Shorter pulses require higher current to achieve the same contraction, while very long pulses can have other effects (like reduced comfort or increased fatigue), but the direct effect on the threshold motivates a lower current for the same contraction.

Longer pulse duration delivers more charge per pulse, so you can reach the nerve activation threshold with less current. In NMES, the motor response depends on the total charge delivered (charge ≈ current × time). Increasing the pulse duration increases this charge, allowing the same contraction to be produced at a lower amplitude. So the amplitude required decreases as pulse duration increases. Shorter pulses require higher current to achieve the same contraction, while very long pulses can have other effects (like reduced comfort or increased fatigue), but the direct effect on the threshold motivates a lower current for the same contraction.