Comparison of the analgesic efficacy of interferential therapy and transcutaneous electrical nerve stimulation

ObjectiveTo compare the analgesic efficacy of interferential therapy (IFT) and transcutaneous electrical nerve stimulation (TENS) using an experimental cold pain model.DesignRandomised controlled trial with repeated measures design.SettingUniversity research laboratory.ParticipantsTwenty healthy subjects.InterventionsIFT and TENS applied to each subject on different days.Main outcome measuresCold pain threshold (time), intensity and unpleasantness (visual analogue scales).ResultsThe mean cold pain threshold with a TENS intervention was higher than that with IFT. A training effect was evident as subjects’ responses become more consistent with repeated exposure to stimulation and the testing procedure. Using data from the second testing sessions, the differences in pain threshold between IFT and TENS for the two during-intervention (T3 and T4) measures were statistically significant (T3 difference in the means 5.9 seconds, 99% confidence interval 3.1 to 8.7 seconds; T4 difference in the means 6.6 seconds, 99% confidence interval 3.8 to 9.4 seconds). No significant differences were identified in pain intensity and unpleasantness ratings.ConclusionsTENS is more effective than IFT at increasing cold pain thresholds in healthy subjects, and this effect increases with repeated exposures. Future trials should include a familiarisation session prior to testing to increase the consistency of subjects’ responses. The clinical implications of these effects need investigation.