title: Test-retest reliability of lower limb isokinetic endurance in COPD: A comparison of angular velocities.
abstract: BACKGROUND
  The purpose of this study was to determine and compare the test-retest reliability of quadriceps isokinetic endurance testing at two knee angular velocities in patients with chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  After one familiarization session, 14 patients with moderate to severe COPD (mean age 65±4 years; forced expiratory volume in 1 second (FEV1) 55%±18% predicted) performed two quadriceps isokinetic endurance tests on two separate occasions within a 5-7-day interval. Quadriceps isokinetic endurance tests consisted of 30 maximal knee extensions at angular velocities of 90° and 180° per second, performed in random order. Test-retest reliability was assessed for peak torque, muscle endurance, work slope, work fatigue index, and changes in FEV1 for dyspnea and leg fatigue from rest to the end of the test. The intraclass correlation coefficient, minimal detectable change, and limits of agreement were calculated.
  
  
  RESULTS
  High test-retest reliability was identified for peak torque and muscle total work at both velocities. Work fatigue index was considered reliable at 90° per second but not at 180° per second. A lower reliability was identified for dyspnea and leg fatigue scores at both angular velocities.
  
  
  CONCLUSIONS
  Despite a limited sample size, our findings support the use of a 30-maximal repetition isokinetic muscle testing procedure at angular velocities of 90° and 180° per second in patients with moderate to severe COPD. Endurance measurement (total isokinetic work) at 90° per second was highly reliable, with a minimal detectable change at the 95% confidence level of 10%. Peak torque and fatigue index could also be assessed reliably at 90° per second. Evaluation of dyspnea and leg fatigue using the modified Borg scale of perceived exertion was poorly reliable and its clinical usefulness is questionable. These results should be useful in the design and interpretation of future interventions aimed at improving muscle endurance in COPD.
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Ribeiro
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Pierre-Alexis
authors.initials: PA
authors.lastname: Lépine
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Corine
authors.initials: C
authors.lastname: Garceau-Bolduc
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Valérie
authors.initials: V
authors.lastname: Coats
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Étienne
authors.initials: É
authors.lastname: Allard
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Maltais
authors.affiliation: Centre de recherche de l'Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Didier
authors.initials: D
authors.lastname: Saey
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue; D010807:Physical Endurance; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013997:Time Factors; D019415:Torque; D014797:Vital Capacity
keywords: chronic obstructive pulmonary disease; isokinetic endurance; lower limb; test-retest reliability