title: Reliability and validity of the Performance Recorder 1 for measuring isometric knee flexor and extensor strength.
abstract: BACKGROUND
  Muscular strength is a key parameter of rehabilitation programs and a strong predictor of functional capacity. Traditional methods to measure strength, such as manual muscle testing (MMT) and hand-held dynamometry (HHD), are limited by the strength and experience of the tester. The Performance Recorder 1 (PR1) is a strength assessment tool attached to resistance training equipment and may be a time- and cost-effective tool to measure strength in clinical practice that overcomes some limitations of MMT and HHD. However, reliability and validity of the PR1 have not been reported.
  
  
  METHODS
  Test-retest and inter-rater reliability was assessed using the PR1 in healthy adults (n  =  15) during isometric knee flexion and extension. Criterion-related validity was assessed through comparison of values obtained from the PR1 and Biodex® isokinetic dynamometer.
  
  
  RESULTS
  Test-retest reliability was excellent for peak knee flexion (intra-class correlation coefficient [ICC] of 0.96, 95% CI: 0.85, 0.99) and knee extension (ICC  =  0.96, 95% CI: 0.87, 0.99). Inter-rater reliability was also excellent for peak knee flexion (ICC  =  0.95, 95% CI: 0.85, 0.99) and peak knee extension (ICC  =  0.97, 95% CI: 0.91, 0.99). Validity was moderate for peak knee flexion (ICC  =  0.75, 95% CI: 0.38, 0.92) but poor for peak knee extension (ICC  =  0.37, 95% CI: 0, 0.73).
  
  
  CONCLUSIONS
  The PR1 provides a reliable measure of isometric knee flexor and extensor strength in healthy adults that could be used in the clinical setting, but absolute values may not be comparable to strength assessment by gold-standard measures.
authors.affiliation: PhD Student, School of Population and Public Health, Faculty of Medicine , University of British Columbia , Vancouver, BC , Canada.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Neil
authors.forename: Alec
authors.initials: A
authors.lastname: Myring
authors.forename: Mon Jef
authors.initials: MJ
authors.lastname: Peeters
authors.forename: Ian
authors.initials: I
authors.lastname: Pirie
authors.forename: Rachel
authors.initials: R
authors.lastname: Jacobs
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hunt
authors.forename: S Jayne
authors.initials: SJ
authors.lastname: Garland
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Campbell
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology; D015203:Reproducibility of Results; D055815:Young Adult