Table 3: The putative relationship between NAU properties and needling sensation.

NAU properties Components of needling sensation Aching/soreness/warmth Numbness/heaviness/distension Type of NAUs Cutaneous-receptor-rich NAUs with a predominance of nociceptors. Muscle-spindle- and tendon-organ-rich NAUs. NAU reactions Biochemical reaction Biophysical reaction Dominant afferent fibers Aδ and C Aβ and Aδ Acupuncture stimulation modesa Prick; shallow needling; high-frequency EA; laser acupuncture; heat acupuncture. Most manual techniques in gentle and repetitive manipulation; low-frequency, high-intensity EA and TENS.

aLow-frequency, high-intensity EA and TENS is thought to dominantly activates myelinated fibers (Aβ and Aδ), whereas high-frequency EA mainly activate small-diameter myelinated Aδ fibers and unmyelinated C fibers [133, 134]. bEA, electroacupuncture; TENS, transcutaneous electrical nerve stimulation.