title: Knee Extensor Power Relates to Mobility Performance in People With Knee Osteoarthritis: Cross-Sectional Analysis.
abstract: BACKGROUND
  Quadriceps femoris muscle strengthening is a common rehabilitation exercise for knee osteoarthritis (OA). More information is needed to determine whether targeting muscle power is a useful adjunct to strengthening for people with knee OA.
  
  
  OBJECTIVE
  The purpose of this study was to identify the predictive ability of knee extensor strength and knee extensor power in the performance of physical tasks in adults with knee OA.
  
  
  METHODS
  This study used a cross-sectional design.
  
  
  METHODS
  Fifty-five participants with clinical knee OA were included (43 women; mean [SD] age=60.9 [6.9] years). Dependent variables were: timed stair ascent, timed stair descent, and the Six-Minute Walk Test (6MWT). Independent variables were: peak knee extensor strength and mean peak knee extensor power. Covariates were: age, body mass index, and self-efficacy. Multiple regression analyses were run for each dependent variable with just covariates, then a second model including strength, and then a third model including power. The R(2) values were compared between models.
  
  
  RESULTS
  Power explained greater variance than strength in all models. Over and above the covariates, power explained an additional 6% of the variance in the 6MWT, increasing the R(2) value from .33 to .39; 8% in the stair ascent test, increasing the R(2) value from .52 to .60; and 3% in the stair descent test, increasing the R(2) value from .44 to .47.
  
  
  CONCLUSIONS
  The sample demonstrated very good mobility and muscle function scores and may not be indicative of those with severe knee OA.
  
  
  CONCLUSIONS
  In adults with knee OA, knee extensor power was a stronger determinant of walking and stair performance when compared with knee extensor strength. Clinicians should consider these results when advising patients on exercise to maintain or improve mobility.
authors: A.J. Accettura, MPT, MSc, School of Rehabilitation Sciences, McMaster University, Hamilton, Ontario, Canada.
authors: Angela J
authors: AJ
authors: Accettura
authors: E.C. Brenneman, MSc, School of Rehabilitation Sciences, McMaster University.
authors: Elora C
authors: EC
authors: Brenneman
authors: P.W. Stratford, PT, MSc, School of Rehabilitation Sciences, McMaster University.
authors: Paul W
authors: PW
authors: Stratford
authors: M.R. Maly, PT, PhD, School of Rehabilitation Sciences, McMaster University, 1400 Main St W, Hamilton, Ontario, Canada L8S 1C7. mmaly@mcmaster.ca.
authors: Monica R
authors: MR
authors: Maly
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D011237:Predictive Value of Tests; D052097:Quadriceps Muscle / Q000503:physiopathology*; D012111:Residence Characteristics; D013647:Task Performance and Analysis
references: Osteoarthritis Cartilage. 2013 Aug;21(8):1042-52
references: 23680877
references: J Sports Sci. 2008 Nov;26(13):1431-6
references: 18923959
references: Phys Ther. 2004 Sep;84(9):822-31
references: 15330695
references: JAMA. 1994 Apr 13;271(14):1093-8
references: 8151851
references: Arthritis Care Res (Hoboken). 2012 Jan;64(1):46-53
references: 22012877
references: J Rehabil Med. 2011 Jun;43(7):572-83
references: 21607295
references: Osteoarthritis Cartilage. 2014 Mar;22(3):363-88
references: 24462672
references: Clin Biomech (Bristol, Avon). 2007 Feb;22(2):203-10
references: 17126461
references: Arthritis. 2012;2012:895495
references: 23008770
references: Eur J Cardiovasc Nurs. 2009 Mar;8(1):2-8
references: 18694656
references: Ann Rheum Dis. 2007 Apr;66(4):433-9
references: 17204567
references: Arthritis Rheum. 1986 Aug;29(8):1039-49
references: 3741515
references: J Am Geriatr Soc. 2002 Mar;50(3):461-7
references: 11943041
references: Arthritis Rheum. 1989 Jan;32(1):37-44
references: 2912463
references: Arch Phys Med Rehabil. 2004 Jul;85(7 Suppl 3):S31-42; quiz S43-4
references: 15221722
references: J Gerontol A Biol Sci Med Sci. 2012 Jan;67(1):41-7
references: 21415261
references: J Physiol. 2003 Oct 1;552(Pt 1):47-58
references: 12837929
references: Phys Ther. 2006 Nov;86(11):1489-96
references: 17079748
references: Obes Rev. 2010 Aug;11(8):568-79
references: 20059707
references: Gait Posture. 2002 Aug;16(1):31-7
references: 12127184
references: JAMA. 2013 Sep 25;310(12):1263-73
references: 24065013
references: Age Ageing. 1998 Jan;27(1):55-62
references: 9504367
references: Am J Epidemiol. 2006 May 15;163(10):950-8
references: 16554351
references: Nat Med. 1998 Nov;4(11):1241-3
references: 9809543
references: Osteoarthritis Cartilage. 2010 Jan;18(1):24-33
references: 19751691
references: Clin Sci (Lond). 1992 Mar;82(3):321-7
references: 1312417
references: Arthritis Care Res (Hoboken). 2011 Nov;63 Suppl 11:S208-28
references: 22588746
references: Eur J Appl Physiol Occup Physiol. 1998 Jun;78(1):59-64
references: 9660157
references: J Strength Cond Res. 2007 May;21(2):518-26
references: 17530980
references: Scand J Med Sci Sports. 2009 Oct;19(5):678-86
references: 18694432
references: Eur J Appl Physiol Occup Physiol. 1990;60(5):385-90
references: 2369911
references: Arthritis Rheum. 2009 Sep 15;61(9):1210-7
references: 19714608
references: Age Ageing. 1994 Sep;23(5):371-7
references: 7825481
references: Phys Ther. 2002 Feb;82(2):128-37
references: 11856064
references: Ann Intern Med. 1997 Jul 15;127(2):97-104
references: 9230035