Conventional and acupuncture-like transcutaneous electrical nerve stimulation excite similar afferent fibers

The purpose of our study was to determine whether similar or different peripheral afferent fiber(s) is(are) activated by "conventional" transcutaneous electrical nerve stimulation (TENS) applied at low intensity-high frequency, as opposed to "acupuncture-like" TENS administered at high intensity-low frequency. The electrical stimulation was delivered to the median nerve at the wrist of 17 healthy subjects. For conventional TENS, single pulses were applied at an intensity of 3 X T (sensory threshold). Two kinds of acupuncture-like TENS were studied: single pulses at 0.1Hz, and trains of 100Hz pulses at 4Hz, both delivered at an intensity greater than 3 X T. Thirty compound action potentials per type of stimulation were recorded over the median nerve in the cubital fossa and averaged. The results showed that the mean conduction velocities of the afferent fibers excited by conventional TENS, single pulse, and short-train acupuncture-like TENS ranged from 50.3 to 65.4, 50.0 to 63.5, and 41.3 to 54.8m/s, respectively. Thus, conventional and acupuncture-like TENS activated similar fiber types, predominantly in the A alpha beta range. Our findings suggested that the effects of these two types of TENS may be mediated by the activation of similar peripheral afferent fibers.