In interferential current therapy, which beat-frequency is most associated with acupuncture-like analgesia?

• A. Conventional pain relief with high frequency.
• B. Acupuncture-like analgesia.
• C. Muscle contraction.
• D. Tissue heating.

Answer: (B)

Interferential therapy works by crossing two medium-frequency currents to create a beat frequency, the difference between the two. The physiological effect depends on how fast that beat is perceived. Very low beat frequencies, in the range of a couple of hertz (around 2 Hz), stimulate endogenous opioid pathways in a manner similar to acupuncture, producing acupuncture-like analgesia. Higher beat frequencies tend to produce other types of analgesia or effects, but the distinctive acupuncture-like analgesia is tied to that low-frequency beat. So the beat frequency most associated with acupuncture-like analgesia is the low one, about 2 Hz.