• Myrto D Dounavi, Linda S Chesterton, and Julius Sim.
• Bioengineering Unit, University of Strathclyde, Glasgow, United Kingdom.
• Phys Ther. 2012 Jul 1;92(7):911-23.

BackgroundLittle evidence exists regarding parameter selection for hypoalgesia using interferential therapy (IFT).ObjectiveThis study investigated segmental and extrasegmental hypoalgesic effects of different IFT parameter combinations upon experimentally induced pressure pain threshold (PPT) in pain-free volunteers.DesignThe participants were randomly assigned to 6 groups: control, placebo, bipolar constant amplitude modulation frequency (AMF), bipolar sweep AMF, quadripolar constant AMF, and quadripolar sweep AMF.SettingThe study was conducted in a university laboratory.ParticipantsOne hundred eighty adults who were healthy and pain-free participated in the study.InterventionInterferential therapy was delivered to all groups at high, to-tolerance intensity and at high AMF. Stimulation to the dominant forearm was delivered for 30 minutes, with monitoring for a further 30 minutes.MeasurementsPain pressure threshold was measured at the area of first dorsal interosseous muscle of the dominant and nondominant hands (segmental measurements) and over the tibialis anterior muscle (extrasegmental measurement) at baseline and at 10-minute intervals using a pressure algometer. Square root transformed PPT data were analyzed using repeated-measures analysis of variance.ResultsThere was a significant change in PPT over time, but no significant between-subjects difference in segmental or extrasegmental PPT between any of the IFT groups and the placebo or control group. Thus, IFT delivered in any of these parameter combinations did not significantly affect the PPT of pain-free participants compared with the control or placebo group.LimitationsSuccess of blinding was not evaluated.ConclusionsThis study showed that IFT delivered at high, to-tolerance intensity and high AMF does not produce significant segmental and extrasegmental hypoalgesic effects on PPT in participants who were healthy compared with a control or placebo group. Further research is warranted to investigate the hypoalgesic effect of different IFT parameter combinations and to explain its possible mechanism of action.

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