• S T Palmer, D J Martin, W M Steedman, and J Ravey.
• Department of Physiotherapy, Queen Margaret University College, Edinburgh, Scotland.
• Arch Phys Med Rehabil. 1999 Sep 1;80(9):1065-71.

ObjectivesTo investigate the effects of different interferential current (IC) and transcutaneous electrical nerve stimulation (TENS) frequencies on sensory, motor, and pain thresholds.Study DesignSingle blind, repeated measures design.SettingLaboratory.ParticipantsWomen students 18 to 30 years old (n = 24).InterventionsPremodulated IC and square-wave TENS pulses (125micros phase duration) were applied over the median nerve at a range of frequencies in all subjects.Main Outcome MeasuresThe peak current (in milliamperes) was recorded twice at each threshold for each frequency, and averaged.ResultsBoth IC and TENS displayed a statistically significant effect of frequency for each threshold. However, frequency effects with IC were not well defined and were of small magnitude. Pure 4kHz current (0Hz amplitude modulated frequency) with IC did not produce effects different from those produced when an amplitude modulated frequency was included. With TENS, frequency effects were very clearly observed, with a distinct increase in the current intensity at each threshold as frequency decreased.ConclusionsIt is postulated that the medium frequency component of IC is the main parameter in stimulation, contrary to traditional claims of the amplitude modulated frequency being important. TENS was shown to be a more adaptable method of stimulating these nerve pathways than IC.

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