title: Alternating frequencies of transcutaneous electric nerve stimulation: does it produce greater analgesic effects on mechanical and thermal pain thresholds?
abstract: OBJECTIVE
  To determine whether alternating frequency transcutaneous electric nerve stimulation (TENS) at 2 and 100Hz (2/100Hz) has a more potent hypoalgesic effect than a fixed frequency at 2 or 100Hz in healthy participants.
  
  
  METHODS
  A single-blind randomized controlled trial with a convenience sample.
  
  
  METHODS
  University physiotherapy department.
  
  
  METHODS
  Sixty-four healthy volunteers (32 men [mean age, 28.1+/-5.9y], 32 women [mean age, 27.7+/-5.6y]) were recruited and randomly divided into 4 groups.
  
  
  METHODS
  The 4 groups received TENS delivered at (1) 2Hz; (2) 100Hz; (3) 2/100Hz alternating frequency; and (4) no treatment (control group), respectively. Electric stimulation was applied over the anterior aspect of the dominant forearm for 30 minutes.
  
  
  METHODS
  Mechanical pain thresholds (MPTs) and heat pain thresholds (HPTs) were recorded before, during, and after TENS stimulation. The data were analyzed using linear mixed models, with group treated as a between-subject factor and time a within-subject factor.
  
  
  RESULTS
  During and shortly after electric stimulation, HPT increased significantly in the alternating frequency stimulation group (P=.024). MPT increased significantly in both the 100Hz (P=.008) and the alternating frequency groups (P=.012), but the increase was substantially larger in the 100Hz group.
  
  
  CONCLUSIONS
  Alternating frequency stimulation produced a greater elevation in the HPT, but a greater increase in the MPT was achieved using 100Hz stimulation.
authors.affiliation: Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong SAR, China.
authors.forename: K C
authors.initials: KC
authors.lastname: Tong
authors.forename: Sing Kai
authors.initials: SK
authors.lastname: Lo
authors.forename: Gladys L
authors.initials: GL
authors.lastname: Cheing
mesh_terms: D000328:Adult; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology; D059408:Pain Management; D017288:Pain Threshold; D010812:Physical Stimulation; D016037:Single-Blind Method; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*