title: Muscle Fatigability During a Sustained Index Finger Abduction and Depression Scores Are Associated With Perceived Fatigue in Patients With Relapsing-Remitting Multiple Sclerosis.
abstract: BACKGROUND
  Fatigue is a common and debilitating symptom in patients with multiple sclerosis (MS). Self-reported levels of perceived fatigue are associated with both patient characteristics and clinical measures. Pilot analysis indicated that muscle fatigability combined with depression scores was highly associated with perceived fatigue in patients with MS. Studies that combine physiological and psychological constructs to explain MS-related fatigue are scarce. Therefore, the present study aimed to evaluate the robustness of the association between perceived fatigue, muscle fatigability, and depression scores in MS.
  
  
  METHODS
  Eighty-six patients with relapsing-remitting MS completed 2 fatigue questionnaires (Fatigue Severity Scale [FSS] and Modified Fatigue Impact Scale [MFIS]) and a depression questionnaire (Hospital Anxiety and Depression Scale [HADS]). Maximal index finger abduction force (maximum voluntary contraction [MVC]) was measured, as well as muscle fatigability during a 2-minutes sustained maximal contraction. Multivariable regression analyses were used to analyze the association between perceived fatigue, and muscle fatigability and depression scores.
  
  
  RESULTS
  Perceived fatigue was associated with depression, muscle fatigability, and, depending on the questionnaire, to sex or to MVC. The model explained 40% and 48% of the variation in perception of fatigue as indexed with FSS questionnaire (r(partial): HADS 0.45, muscle fatigability 0.45, MVC -0.14, sex 0.32), and MFIS physical questionnaire (r(partial): HADS 0.59, muscle fatigability 0.49, MVC -0.38), respectively.
  
  
  CONCLUSIONS
  The found association accentuates the importance of including both physiological fatigability-related and psychological mood-related constructs in models to explain perceived fatigue in patients with MS. The model also directs future research toward applying effortful conditions and emphasizes the importance of assessing different constructs when evaluating rehabilitation strategies to reduce MS-related fatigue.
authors.affiliation: Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.
authors.forename: Ria
authors.initials: R
authors.lastname: Wolkorte
authors.affiliation: Department of Neurology, University Medical Center Groningen, Groningen, Netherlands.
authors.forename: Dorothea J
authors.initials: DJ
authors.lastname: Heersema
authors.affiliation: Department of Neuroscience, University Medical Center Groningen, University of Groningen, Groningen, Netherlands c.a.t.zijdewind@umcg.nl.
authors.forename: Inge
authors.initials: I
authors.lastname: Zijdewind
mesh_terms: D000328:Adult; D000368:Aged; D003863:Depression / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D005260:Female; D005385:Fingers / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology* / Q000523:psychology; D015999:Multivariate Analysis; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D010465:Perception; D011569:Psychiatric Status Rating Scales; D012044:Regression Analysis; D012720:Severity of Illness Index; D012737:Sex Factors; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Fatigue Severity Scale (FSS); Hospital Anxiety and Depression Scale (HADS); force; motor task; multiple sclerosis; sense of fatigue