title: Nonvolitional assessment of muscle endurance in idiopathic inflammatory myopathies: there is no relationship between patient-reported fatigue and muscle fatigability.
abstract: BACKGROUND
  We investigated whether muscle endurance differs between IIM patients and controls and if a relationship exists between perceived fatigue and poor muscle endurance.
  
  
  METHODS
  Quadriceps contractility, measured using femoral nerve stimulation (TwQ), and strength, measured using maximal voluntary contraction (MVCQ), were assessed in 20 IIM patients and matched controls. Quadriceps endurance was assessed using repetitive electrical stimulation (3 minutes). Time for force to fall to 70% initial force was determined (T70). Reported fatigue was measured using the FACIT-F/Fatigue Severity Scales.
  
  
  RESULTS
  TwQ and MVCQ were lower and perceived fatigue greater for patients. There was no difference in T70 between groups. No relationships were observed between perceived fatigue and endurance (T70).
  
  
  CONCLUSIONS
  IIM patients reported more fatigue and were weaker than controls, but there was no difference in muscle endurance. Endurance and strength were unrelated to reported fatigue measures. Mechanisms driving perceived IIM fatigue are likely to be multifactorial.
authors.affiliation: Department of Academic Rheumatology, King's College London, Weston Education Centre, Cutcombe Road, London SE5 9RJ, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Campbell
authors.forename: Patrick
authors.initials: P
authors.lastname: Gordon
authors.forename: Katie
authors.initials: K
authors.lastname: Ward
authors.forename: Charles
authors.initials: C
authors.lastname: Reilly
authors.forename: David L
authors.initials: DL
authors.lastname: Scott
authors.forename: Gerrard F
authors.initials: GF
authors.lastname: Rafferty
mesh_terms: D000328:Adult; D000368:Aged; D003402:Creatine Kinase / Q000378:metabolism; D003627:Data Interpretation, Statistical; D003882:Dermatomyositis / Q000503:physiopathology; D004558:Electric Stimulation; D005260:Female; D005267:Femoral Nerve / Q000502:physiology; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009135:Muscular Diseases / Q000503:physiopathology*; D009220:Myositis / Q000503:physiopathology*; D010807:Physical Endurance / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology; D011795:Surveys and Questionnaires
chemical_list: D003402:Creatine Kinase
keywords: dermatomyositis; fatigue; idiopathic inflammatory myopathy; myositis; polymyositis