Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds

Palmer ST, Martin DJ, Steedman WM, Ravey J. Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds. Arch Phys Med Rehabil 2004;85:119–28. To determine if interferential current (IFC) or transcutaneous electric nerve stimulation (TENS) alters C and A delta fiber-mediated thermal perception thresholds. Single-blind, randomized controlled trial. Laboratory. One hundred forty healthy women volunteers (mean age ± standard deviation, 20.6±2.7y). Subjects were randomly and exclusively assigned to 1 of 7 groups (n=20 in each): 0, 5, and 100Hz of IFC; 5 and 100Hz of TENS; placebo and control stimulation. Stimulation was applied through 2 electrodes placed over the median nerve. Warm sensation, cold sensation, hot pain, and cold pain perception thresholds were measured from the thenar eminence by using a quantitative sensory testing device and a method of limits algorithm. Warm sensation, cold sensation, hot pain, and cold pain thresholds (°C) before, during, and after stimulation. There was a statistically significant effect of time for all 4 thermal perception thresholds (separate 2-way analyses of variance with repeated measures, all P.05). Neither IFC nor TENS altered C and A delta fiber-mediated thermal perception thresholds. The results suggest that any analgesic mechanisms with these modalities are likely to be complex.