An investigation into the analgesic effects of different frequencies of the amplitude-modulated wave of interferential current therapy on cold-induced pain in normal subjects.
OBJECTIVE
To investigate the analgesic effects of different amplitude-modulated frequencies of interferential current therapy (IFT) on cold-induced pain in healthy subjects.


METHODS
Single-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.


METHODS
Laboratory in the United Kingdom.


METHODS
Sixty unpaid, pain-free volunteers without a known pathology that could cause pain.


METHODS
IFT 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).


METHODS
The percentage change in pain threshold, pain intensity, and pain unpleasantness from the pretreatment baseline.


RESULTS
Two-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.


CONCLUSIONS
Experimentally induced cold pain was not influenced by IFT frequencies.
D000328:Adult; D000698:Analgesia / Q000379:methods*; D000704:Analysis of Variance; D001132:Arm; D003080:Cold Temperature; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006225:Hand / Q000503:physiopathology; D006801:Humans; D008297:Male; D010146:Pain / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D059408:Pain Management; D010147:Pain Measurement; D017288:Pain Threshold; D016037:Single-Blind Method; D016896:Treatment Outcome