A single-blind investigation into the hypoalgesic effects of different swing patterns of interferential currents on cold-induced pain in healthy volunteers

Objective: To compare the analgesic effects of differing swing patterns of interferential current (IFC) on cold-induced pain. Design: Single-blind intervention study in which subjects completed 6 cycles of the cold-induced pain test-2 pretreatment, 2 during treatment, and 2 posttreatment. Setting: Laboratory. Participants: Forty healthy volunteers. Interventions: Subjects were randomly allocated to receive 1 of 4 IFC treatment interventions: 1integral1, 6integral6, 6boolean AND6, or burst. IFC was administered for 20 minutes via 4 electrodes attached to the forearm (quadripolar application) at a strong but comfortable intensity using amplitude-modulated frequencies of I to 100Hz. Main Outcome Measures: Change in pain threshold and self-report of pain intensity and unpleasantness from pretreatment baseline. Results: Two-way repeated-measure analysis of variance found significant effects for time and group by time interaction (P<.01), but effects for groups failed to reach statistical significance (P=0.1). This suggests that when all groups are considered together, subjects experience a rise in pain threshold when IFC devices are switched on but not when they are switched off. However, the rise in pain threshold was not dependent on the swing pattern employed. Analysis of pain intensity and unpleasantness ratings found no effects for group or group by time interaction. Conclusions: There were no differences in the hypoalgesic effects of different swing patterns.