The analgesic effects of interferential (IF) current on cold-pressor pain in healthy subjects: a single blind trial of three IF currents against sham IF and control

Abstract

Interferential (IF) therapy is well documented as a therapeutic medium for pain relief. Despite widespread use by physiotherapists, there remains very limited laboratory or clinical evidence for the analgesic effect of IF.Fifty volunteers were randomly allocated to one of five groups ( n =10): control group (no treatment throughout); IF 100 Hz applied to the ipsilateral limb; IF 100 Hz applied to the contralateral limb; IF 30 Hz applied to the ipsilateral limb; Sham IF applied to the ipsilateral limb. Subjects were given repeated (six) cycles of cold-pressor pain and pain threshold scores were recorded for each cycle and compared using repeated measure ANOVA. Mean pain threshold values for all groups increased with the exception of the control group: where pain threshold values decreased across the cycles. Pain thresholds within IF treatment groups repeatedly increased, but no more than sham IF. IF at 30 Hz and 100 Hz applied to the contralateral limb offered more consistency in the rise in mean values, with the sham group demonstrating more variation in performance. However, statistical analysis failed to show any significant differences for the treatment effects either within groups across repeated cycles (P=0.123) or between the groups across cycles (P=0.552). IF does not significantly alter pain threshold.