title: Fatigue perceived by multiple sclerosis patients is associated with muscle fatigue.
abstract: BACKGROUND
  Fatigue is a debilitating symptom in multiple sclerosis (MS). Previous studies showed no association between fatigue as perceived by the patient and physiological measures of fatigability.
  
  
  OBJECTIVE
  The authors investigated associations between perceived fatigue and measures of fatigability after correction for differences in maximal voluntary contraction (MVC).
  
  
  METHODS
  A total of 20 people with relapsing-remitting MS with an Extended Disability Severity Score less than 5.5 and 20 healthy controls filled out the Fatigue Severity Score questionnaire of perceived fatigue. The authors obtained the MVC from the first dorsal interosseus muscle, voluntary muscle activation, and force decline during a sustained MVC (124 s, muscle fatigue).
  
  
  RESULTS
  Patients perceived increased levels of fatigue compared with controls (P < .001). Although patients and controls developed similar amounts of muscle fatigue during the sustained contraction, a linear regression model that included both muscle fatigue and MVC was positively associated with perceived fatigue in patients only (R (2) = 0.45; P = .01). Voluntary activation during the sustained contraction was negatively associated with perceived fatigue (R (2) = 0.25; P = .02).
  
  
  CONCLUSIONS
  The data indicate that fatigue perceived by MS patients is associated with measures of fatigability. This observation helps in the understanding of mechanisms underlying the increased levels of fatigue perceived by MS patients. These data also emphasize that for comparison of fatigue-related parameters between groups, correction for individual maximal force is essential.
authors.affiliation: Deptartment of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.
authors.forename: Anneke
authors.initials: A
authors.lastname: Steens
authors.forename: Astrid
authors.initials: A
authors.lastname: de Vries
authors.forename: Jolien
authors.initials: J
authors.lastname: Hemmen
authors.forename: Thea
authors.initials: T
authors.lastname: Heersema
authors.forename: Marco
authors.initials: M
authors.lastname: Heerings
authors.forename: Natasha
authors.initials: N
authors.lastname: Maurits
authors.forename: Inge
authors.initials: I
authors.lastname: Zijdewind
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005221:Fatigue / Q000209:etiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000150:complications* / Q000503:physiopathology; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology; D010465:Perception / Q000502:physiology*; D013116:Spinal Cord / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation