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

Abstract

OBJECTIVE To determine if interferential current (IFC) or transcutaneous electric nerve stimulation (TENS) alters C and A delta fiber-mediated thermal perception thresholds. DESIGN Single-blind, randomized controlled trial. SETTING Laboratory. PARTICIPANTS One hundred forty healthy women volunteers (mean age +/- standard deviation, 20.6+/-2.7 y). INTERVENTIONS Subjects were randomly and exclusively assigned to 1 of 7 groups (n=20 in each): 0, 5, and 100 Hz of IFC; 5 and 100 Hz 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. MAIN OUTCOME MEASURES Warm sensation, cold sensation, hot pain, and cold pain thresholds (degrees C) before, during, and after stimulation. RESULTS 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<.001). There were no statistically significant differences between experimental groups, nor any interaction effects (all P>.05). CONCLUSIONS 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.

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