title: Reliability of contractile properties of the knee extensor muscles in individuals with post-polio syndrome.
abstract: OBJECTIVE
  To assess the reliability of contractile properties of the knee extensor muscles in 23 individuals with post-polio syndrome (PPS) and 18 age-matched healthy individuals.
  
  
  METHODS
  Contractile properties of the knee extensors were assessed from repeated electrically evoked contractions on 2 separate days, with the use of a fixed dynamometer. Reliability was determined for fatigue resistance, rate of torque development (MRTD), and early and late relaxation time (RT50 and RT25), using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM, expressed as % of the mean).
  
  
  RESULTS
  In both groups, reliability for fatigue resistance was good, with high ICCs (>0.90) and small SEM values (PPS: 7.1%, healthy individuals: 7.0%). Reliability for contractile speed indices varied, with the best values found for RT50 (ICCs>0.82, SEM values <2.8%). We found no systematic differences between test and retest occasions, except for RT50 in healthy subjects (p = 0.016).
  
  
  CONCLUSIONS
  In PPS and healthy individuals, the reliability of fatigue resistance, as obtained from electrically evoked contractions is high. The reliability of contractile speed is only moderate, except for RT50 in PPS, demonstrating high reliability.
  
  
  CONCLUSIONS
  This was the first study to examine the reliability of electrically evoked contractile properties in individuals with PPS. Our results demonstrate its potential to study mechanisms underlying muscle fatigue in PPS and to evaluate changes in contractile properties over time in response to interventions or from natural course.
authors.affiliation: Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Voorn
authors.affiliation: Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Merel A
authors.initials: MA
authors.lastname: Brehm
authors.affiliation: Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Anita
authors.initials: A
authors.lastname: Beelen
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Arnold
authors.initials: A
authors.lastname: de Haan
authors.affiliation: Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Frans
authors.initials: F
authors.lastname: Nollet
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Karin H L
authors.initials: KH
authors.lastname: Gerrits
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007719:Knee Joint; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue; D016262:Postpoliomyelitis Syndrome / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D019415:Torque