title: Predicting maximal strength of quadriceps from submaximal performance in individuals with knee joint osteoarthritis.
abstract: OBJECTIVE
  To compare the accuracy of 12 maximal strength (1-repetition maximum [1-RM]) equations for predicting quadriceps strength in people with osteoarthritis (OA) of the knee joint.
  
  
  METHODS
  Eighteen subjects with OA of the knee joint attended a rehabilitation gymnasium on 3 occasions: 1) a familiarization session, 2) a session where the 1-RM of the quadriceps was established using a weights machine for an open-chain knee extension exercise and a leg press exercise, and 3) a session where the subjects performed with a load at which they could lift for approximately 10 repetitions only. The data were used in 12 prediction equations to calculate 1-RM strength and compared to the actual 1-RM data. Data were examined using Bland and Altman graphs and statistics, intraclass correlation coefficients (ICCs), and typical error values between the actual 1-RM and the respective 1-RM prediction equation data. Difference scores (predicted 1-RM--actual 1-RM) across the injured and control legs were also compared.
  
  
  RESULTS
  For the knee extension exercise, the Brown, Brzycki, Epley, Lander, Mayhew et al, Poliquin, and Wathen prediction equations demonstrated the greatest levels of predictive accuracy. All of the ICCs were high (range 0.96–0.99), and typical errors were between 3% and 4%. For the knee press exercise, the Adams, Berger, Kemmler et al, and O'Conner et al equations demonstrated the greatest levels of predictive accuracy. All of the ICCs were high (range 0.95-0.98), and the typical errors ranged from 5.9-6.3%.
  
  
  CONCLUSIONS
  This study provided evidence supporting the use of prediction equations to assess maximal strength in individuals with a knee joint with OA.
authors.affiliation: Health and Rehabilitation Research Institute, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, New Zealand. peter.mcnair@aut.ac.nz
authors.forename: Peter J
authors.initials: PJ
authors.lastname: McNair
authors.forename: Matt
authors.initials: M
authors.lastname: Colvin
authors.forename: Duncan
authors.initials: D
authors.lastname: Reid
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D011237:Predictive Value of Tests; D052097:Quadriceps Muscle / Q000503:physiopathology*