• Mark I Johnson and Ghazala Tabasam.
• Scool of Health Sciences, Faculty of health and Environment, Leeds Metropolitan University, Leeds, UK.
• Arch Phys Med Rehabil. 2003 Sep 1; 84 (9): 1387-94.

ObjectiveTo investigate the analgesic effects of different amplitude-modulated frequencies of interferential current therapy (IFT) on cold-induced pain in healthy subjects.DesignSingle-blind parallel group methodology was used. Subjects completed 6 cycles of the cold-induced pain test (2 pretreatment, 2 during treatment, 2 posttreatment). During each cycle, subjects plunged their hand into iced water and the time taken to reach pain threshold was recorded. The hand remained immersed in the iced water for a further 30 seconds, after which the self-reports of pain intensity and pain unpleasantness were recorded.SettingLaboratory in the United Kingdom.ParticipantsSixty unpaid, pain-free volunteers without a known pathology that could cause pain.InterventionsIFT delivered on the nondominant arm at a "strong but comfortable" intensity without visible muscle twitches, using a quadripolar application technique at 1 of 6 possible amplitude modulated "beat" frequencies (20, 60, 100, 140, 180, 220Hz).Main Outcome MeasuresThe percentage change in pain threshold, pain intensity, and pain unpleasantness from the pretreatment baseline.ResultsTwo-way repeated-measures analyses of variance found no effects for groups for pain threshold (P=.11) or pain ratings (P>.05). There were no effects for cycle for any of the outcome measures. Effects for group by cycle interaction were noted for pain intensity and unpleasantness ratings (P<.05), although post hoc analysis failed to determine the nature of this interaction.ConclusionsExperimentally induced cold pain was not influenced by IFT frequencies.

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