Does amplitude-modulated frequency have a role in the hypoalgesic response of interferential current on pressure pain sensitivity in healthy subjects? A randomised crossover study.

摘要

OBJECTIVE: To investigate the hypoalgesic effect of amplitude-modulated frequency during interferential current therapy using an experimentally induced mechanical pain model in normal subjects. This study examined pain pressure sensitivities achieved when the amplitude-modulated frequency parameter was present (100Hz) and absent (0Hz). DESIGN: Randomised controlled crossover trial with repeated measures. SETTING: University research laboratory. PARTICIPANTS: Forty-six healthy volunteers (23 males, 23 females). INTERVENTIONS: Two interferential therapy protocols (with and without amplitude-modulated frequencies) were applied to the lumbar area on two different days. MAIN OUTCOME MEASURES: Pressure pain thresholds over the lumbar area were measured before, during and after application of the interferential therapy protocols. RESULTS: A three-way analysis of variance with repeated measures failed to show any statistically significant difference between the two protocols in modifying pressure pain threshold values (mean difference 0.017kg/cm(2), 95% confidence interval -0.384 to 0.350, P=0.93). Statistically significant differences were identified (P<0.001) between measurements, indicating a comparable decrease in pain sensitivity in both groups. However, the increase in pressure pain thresholds (0.76kg/cm(2)) failed to reach a level of clinical importance. CONCLUSIONS: The addition of an amplitude-modulated frequency parameter to interferential therapy did not influence mechanical pain sensitivity in healthy subjects. Amplitude-modulated frequency is therefore unlikely to have a physiological hypoalgesic effect.