title: 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.
abstract: 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).
  
  
  METHODS
  Randomised controlled crossover trial with repeated measures.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Forty-six healthy volunteers (23 males, 23 females).
  
  
  METHODS
  Two interferential therapy protocols (with and without amplitude-modulated frequencies) were applied to the lumbar area on two different days.
  
  
  METHODS
  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.
authors.affiliation: Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada. jorgef@ualberta.ca
authors.forename: Jorge
authors.initials: J
authors.lastname: Fuentes C
authors.forename: Susan
authors.initials: S
authors.lastname: Armijo-Olivo
authors.forename: David J
authors.initials: DJ
authors.lastname: Magee
authors.forename: Douglas
authors.initials: D
authors.lastname: Gross
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D018592:Cross-Over Studies; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008161:Lumbosacral Region; D008297:Male; D017288:Pain Threshold; D011312:Pressure; D017211:Treatment Failure; D055815:Young Adult