title: Transcutaneous electrical nerve stimulation and conditioned pain modulation influence the perception of pain in humans.
abstract: BACKGROUND
  Research in animal models suggests that transcutaneous electrical nerve stimulation (TENS) and conditioned pain modulation (CPM) produce analgesia via two different supraspinal pathways. No known studies have examined whether TENS and CPM applied simultaneously in human subjects will enhance the analgesic effect of either treatment alone. The purpose of the current study was to investigate whether the simultaneous application of TENS and CPM will enhance the analgesic effect of that produced by either treatment alone.
  
  
  METHODS
  Sixty healthy adults were randomly allocated into two groups: (1) CPM plus active TENS; (2) CPM plus placebo TENS. Pain threshold for heat (HPT) and pressure (PPT) were recorded from subject's left forearm at baseline, during CPM, during active or placebo TENS, and during CPM plus active or placebo TENS. CPM was induced by placing the subjects' contralateral arm in a hot water bath (46.5 °C) for 2 min. TENS (100 μs, 100 Hz) was applied to the forearm for 20 min at a strong but comfortable intensity.
  
  
  RESULTS
  Active TENS alone increased PPT (but not HPT) more than placebo TENS alone (p = 0.011). Combining CPM and active TENS did not significantly increase PPT (p = 0.232) or HPT (p = 0.423) beyond CPM plus placebo TENS. There was a significant positive association between PPT during CPM and during active TENS (r(2)  = 0.46; p = 0.003).
  
  
  CONCLUSIONS
  TENS application increases PPT; however, combining CPM and TENS does not increase the CPM's hypoalgesic response. CPM effect on PPT is associated with the effects of TENS on PPT.
authors: Master's and Doctoral Programs in Physical Therapy, Universidade Cidade de São Paulo (UNICID), São Paulo, Brazil.
authors: R E
authors: RE
authors: Liebano
authors: C G
authors: CG
authors: Vance
authors: B A
authors: BA
authors: Rakel
authors: J E
authors: JE
authors: Lee
authors: N A
authors: NA
authors: Cooper
authors: S
authors: S
authors: Marchand
authors: D M
authors: DM
authors: Walsh
authors: K A
authors: KA
authors: Sluka
mesh_terms: D000293:Adolescent; D000328:Adult; D000698:Analgesia / Q000379:methods; D001132:Arm / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D010146:Pain / Q000503:physiopathology*; D059408:Pain Management / Q000379:methods; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology; D010465:Perception / Q000502:physiology; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
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