title: Muscle fatigue in fibromyalgia is in the brain, not in the muscles: a case-control study of perceived versus objective muscle fatigue.
abstract: OBJECTIVE
  To investigate relationships between perceived and objectively measured muscle fatigue during exhausting muscle contractions in women with fibromyalgia (FM) compared with healthy controls (HC).
  
  
  METHODS
  Women with FM and HC completed an isometric muscle exhaustion task at 90° shoulder abduction. Surface electromyographic (EMG) activity in the deltoid muscle was recorded together with self-reported level of muscle fatigue.
  
  
  RESULTS
  25 participants with FM and 23 HC were included. Average time to exhaustion was 254 s shorter in participants with FM than in HC. Participants with FM did not exhibit the same level of objective signs of muscle fatigue, seen as fewer changes in the EMG activity, as the HC during the exhaustion task. The task did not provoke pain in the HC, while participants with FM reported a doubling of pain.
  
  
  CONCLUSIONS
  Women with FM had shorter exhaustion times and showed fewer objective signs of muscle fatigue during an exhausting isometric shoulder abduction compared with younger HC. This indicates that perceived muscle fatigue may be of central origin and supports the notion of central nervous dysfunction as basic pathological changes in FM.
authors.affiliation: Department of Rheumatology, The Parker Institute, Copenhagen University Hospital, Frederiksberg, Copenhagen, Denmark.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bandak
authors.forename: Kirstine
authors.initials: K
authors.lastname: Amris
authors.forename: Henning
authors.initials: H
authors.lastname: Bliddal
authors.forename: Bente
authors.initials: B
authors.lastname: Danneskiold-Samsøe
authors.forename: Marius
authors.initials: M
authors.lastname: Henriksen
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D057645:Deltoid Muscle / Q000502:physiology*; D004576:Electromyography; D005260:Female; D005356:Fibromyalgia / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D010147:Pain Measurement; D010468:Perceptual Disorders / Q000503:physiopathology*; D057566:Self Report; D055815:Young Adult