title: Fibromyalgia and related conditions: electromyogram profile during isometric muscle contraction.
abstract: OBJECTIVE
  To evaluate electromyogram (EMG) profiles in patients with three related conditions: fibromyalgia, chronic fatigue syndrome, and depression.
  
  
  METHODS
  We studied 44 healthy volunteers, 22 patients with fibromyalgia, 11 patients with chronic fatigue syndrome, and 10 patients admitted for depression. The trapezius electromyogram was recorded during maximally sustained, bilateral, 90 degrees abduction of the shoulders. EMG signal frequency and amplitude were measured throughout the test.
  
  
  RESULTS
  In the fibromyalgia group, isometric contraction duration was significantly shorter than in the other two patient groups (P<0.001) and the EMG frequency and amplitude pattern indicated premature discontinuation of the muscle contraction. Findings in the chronic fatigue patients were similar to those in the healthy controls. The patients with depression had a distinctive EMG profile characterized by excessive initial motor-unit recruitment with a shift in the frequency spectrum.
  
  
  CONCLUSIONS
  Fibromyalgia was associated with a specific EMG pattern indicating premature discontinuation of the muscle contraction. Therefore, maximal voluntary muscle contraction tests may be of limited value for assessing function in fibromyalgia patients. Chronic fatigue syndrome patients had similar EMG findings to those in the healthy controls. The EMG alterations in the patients with depression were consistent with manifestations of psychomotor retardation.
authors.affiliation: Department of Motricity Sciences, University of Liege, University Hospital Centre of Liege, ISEPK, B21, 4, allée des Sports, 4000 Liege, Belgium. d.maquet@ulg.ac.be
authors.forename: Didier
authors.initials: D
authors.lastname: Maquet
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Croisier
authors.forename: Catherine
authors.initials: C
authors.lastname: Dupont
authors.forename: Michel
authors.initials: M
authors.lastname: Moutschen
authors.forename: Marc
authors.initials: M
authors.lastname: Ansseau
authors.forename: Bernard
authors.initials: B
authors.lastname: Zeevaert
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Crielaard
mesh_terms: D000328:Adult; D003863:Depression / Q000175:diagnosis / Q000503:physiopathology; D004525:Efferent Pathways / Q000503:physiopathology; D004576:Electromyography / Q000379:methods*; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology; D014836:Volition / Q000502:physiology; D055815:Young Adult