What is the primary mechanism by which TENS reduces pain as described?

• A. Sensory stimulation closes the gate to pain
• B. Deep tissue heating
• C. Strong motor contractions relieve pain
• D. Nerve block permanently eliminates pain

Answer: (A)

The main concept is that TENS reduces pain by modulating spinal pain signals through gate control. When TENS delivers sensory-level stimulation, it activates large-diameter A-beta fibers, which in turn excite inhibitory interneurons in the dorsal horn of the spinal cord. This dampens the transmission of pain signals carried by small-diameter A-delta and C fibers to the brain, lowering pain perception. This analgesia is temporary and depends on ongoing stimulation. Deep tissue heating, strong motor contractions, or a permanent nerve block are not how TENS produces relief.