title: TauG-guidance of dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia.
abstract: Impaired postural control has been reported in static conditions in chronic fatigue syndrome and fibromyalgia, but postural control in dynamic tasks have not yet been investigated. Thus, we investigated measurements from a force plate to evaluate dynamic balance control during gait initiation in patients with chronic fatigue syndrome and fibromyalgia compared to matched healthy controls.
  
  
  
  Thirty female participants (10 per group) performed five trials of gait initiation. Center of pressure (CoP) trajectory of the initial weight shift onto the supporting foot in the mediolateral direction (CoPX) was analyzed using General Tau Theory. We investigated the hypothesis that tau of the CoPX motion-gap (τCoPx) is coupled onto an intrinsic tauG-guide (τG) by keeping the relation τCoPx=KτG, where K is a scaling factor that determines the relevant kinematics of a movement.
  
  
  
  Mean K values were 0.57, 0.55, and 0.50 in fibromyalgia, chronic fatigue syndrome, and healthy controls, respectively. Both patient groups showed K values significantly higher than 0.50 (P<0.05), indicating that patients showed poorer dynamic balance control, CoPX colliding with the boundaries of the base of support (K>0.5).
  
  
  
  The findings revealed a lower level of dynamic postural control in both fibromyalgia and chronic fatigue syndrome compared to controls.
authors.affiliation: Institute of Health Science, Faculty of Health and Social Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Electronic address: omid.rasouli@ntnu.no.
authors.forename: Omid
authors.initials: O
authors.lastname: Rasouli
authors.affiliation: Institute of Health Science, Faculty of Health and Social Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Electronic address: ann-katrin.stensdotter@ntnu.no.
authors.forename: Ann-Katrin
authors.initials: AK
authors.lastname: Stensdotter
authors.affiliation: Developmental Neuroscience Laboratory, Department of Psychology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Electronic address: audrey.meer@svt.ntnu.no.
authors.forename: Audrey L H
authors.initials: ALH
authors.lastname: Van der Meer
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D001837:Body Weights and Measures; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology*; D005260:Female; D005356:Fibromyalgia / Q000503:physiopathology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult
keywords: Base of support; Chronic widespread pain; Myalgic encephalomyelitis; Postural control; TauG analysis