Which parameter ranges define conventional TENS?

• A. Frequency about 50–100 Hz, pulse width about 50–100 microseconds, amplitude adjusted to sensory threshold or comfortable tingling
• B. Frequency 5–20 Hz, pulse width 200–300 microseconds
• C. Frequency 200–250 Hz, pulse width 400–600 microseconds
• D. Frequency 1–4 Hz, pulse width 20–50 microseconds

Answer: (A)

Conventional TENS aims to stimulate large-diameter sensory fibers to create a comfortable tingling that blocks pain signals at the spinal level, without causing muscle contractions. That effect is best achieved with a relatively high frequency, a short pulse width, and an amplitude set to the sensory threshold. A frequency around 50–100 Hz delivers steady, rapid stimulation; a pulse width of about 50–100 microseconds keeps the pulses short enough to favor A-beta fiber activation over motor fibers; and setting the amplitude so the patient just feels tingling ensures the sensation remains sensory rather than painful or motor.

Other parameter sets tend to align with different TENS approaches: lower frequencies with longer pulse widths can recruit smaller fibers and sometimes produce muscle twitches or longer-lasting analgesia via different mechanisms; extremely high frequencies with long pulse widths are not typical for conventional TENS.