National Physical Therapy Examination (NPTE) Practice Exam

For pain modulation, what set of parameters best describes conventional TENS?

1. 50-100 pps, short phase duration, low intensity

2. 150-200 pps, long phase duration, low intensity

3. 200-250 pps, short phase duration, high intensity

4. 100-150 pps, short phase duration, high intensity

The correct answer is: 50-100 pps, short phase duration, low intensity

Conventional TENS (Transcutaneous Electrical Nerve Stimulation) is primarily used for pain relief through a mechanism known as the "gate control theory" of pain modulation. This theory suggests that the application of electrical stimulation can help block pain signals to the brain. The parameters that best describe conventional TENS generally include higher pulse frequencies, ranging from 50 to 100 pulses per second (pps), which allows for the quick activation of large-diameter A-beta fibers that can inhibit pain transmission via smaller A-delta and C fibers. The phase duration is short, typically around 50 microseconds, as this is sufficient to stimulate sensory nerves without causing discomfort. Intensity during conventional TENS is kept at a low level, just below the threshold of pain, enabling a comfortable sensory experience without causing muscle contractions. The selected parameters not only optimize pain relief through the stimulation of sensory fibers but also ensure patient comfort, making this the most effective description for conventional TENS. Other options either adjust the frequency to levels not typical of conventional TENS or suggest longer durations and higher intensities, which can lead to discomfort and alterations in the expected pain modulation response.