A double blind placebo controlled investigation into the analgesic effects of inferential currents (IFC) and transcutaneous electrical nerve stimulation (TENS) on cold-induced pain in healthy subjects

Abstract

Transcutaneous electrical nerve stimulation (TENS) and interferential currents (IFC) are used by physiotherapists for the management of painful conditions. It is claimed that the analgesic profiles of TENS and IFC differ although no studies have directly compared the analgesic effects of the two modalities. The aim of this double blind placebo controlled study was to compare the analgesic effects of TENS and IFC on cold-induced pain in healthy volunteers. Twenty one subjects completed six cycles of the cold-induced pain test (two pre-treatment, two during treatment, and two post-treatment). During each cycle pain threshold was recorded as the time from immersion of the subject's hand in cold water to the first sensation of pain and pain intensity and unpleasantness ratings were recorded using visual analogue scales. Subjects received one of the following treatments during the two treatment cycles: IFC, TENS, or sham electrotherapy. IFC and TENS were delivered at a ''strong but comfortable'' intensity via two electrodes applied over the anterior aspect of the forearm. Sham electrotherapy was administered by a ''dummy'' stimulator with no current output. All stimulators were visually identical. Analysis of the results found that IFC and TENS significantly elevated pain threshold when compared to sham electrotherapy (P <. 05). There were no significant differences in the magnitude of the increase in pain threshold between IFC and TENS. No significant changes in pain intensity or unpleasantness ratings were found between the three treatment groups. We conclude that there were no differences in the analgesic effects of IFC and TENS under the present experimental conditions.