title: Impact loading following quadriceps strength training in individuals with medial knee osteoarthritis and varus alignment.
abstract: BACKGROUND
  Greater impact loading at initial contact is postulated to play a role in the progression of osteoarthritis. Quadriceps weakness is common in individuals with knee osteoarthritis and may contribute to high impact loading. The purpose of this study was to examine the effects of quadriceps strengthening on impact loading parameters.
  
  
  METHODS
  Data from 97 individuals with knee osteoarthritis who participated in a randomized clinical trial examining effects of a 12-week quadriceps strengthening program was used to conduct this secondary exploratory analysis. Participants completed a three-dimensional gait assessment within 10% of 1.0m/s from which maximum rate of loading (Body Weight/second), average rate of loading (Body Weight/second), and peak vertical ground reaction force during early stance (Body Weight) were determined. Peak isometric quadriceps strength (Nm/kg) was also assessed.
  
  
  RESULTS
  There was a significant increase in quadriceps strength in the training group (mean change (95%CI): 0.35(0.25, 0.045) Nm/kg, P=0.01) with no change in the control group (mean change (95%CI): 0.03(-0.39, 0.45) Nm/kg, P>0.05). There were no changes in impact loading variables. With data from both groups combined, changes in quadriceps strength explained 3% of variance in the change in maximum rate of loading. Change in quadriceps strength was not predictive of the change in peak vertical ground reaction force or average rate of loading.
  
  
  CONCLUSIONS
  While change in strength was predictive of change in maximal loading rate, this explained only a small proportion of the variance. Future research examining the role parameters such as neuromuscular control play in impact loading are warranted.
authors.affiliation: School of Health, Medical, and Applied Sciences, Central Queensland University, Rockhampton, QLD, Australia. Electronic address: c.kean@cqu.edu.au.
authors.forename: Crystal O
authors.initials: CO
authors.lastname: Kean
authors.affiliation: Centre for Health, Exercise and Sports Medicine (CHESM), Department of Physiotherapy, The University of Melbourne, Victoria, Australia.
authors.forename: Rana S
authors.initials: RS
authors.lastname: Hinman
authors.affiliation: Centre for Health, Exercise and Sports Medicine (CHESM), Department of Physiotherapy, The University of Melbourne, Victoria, Australia.
authors.forename: Tim V
authors.initials: TV
authors.lastname: Wrigley
authors.affiliation: School of Sports, Health and Leisure, Republic Polytechnic, Singapore.
authors.forename: Boon-Whatt
authors.initials: BW
authors.lastname: Lim
authors.affiliation: Centre for Health, Exercise and Sports Medicine (CHESM), Department of Physiotherapy, The University of Melbourne, Victoria, Australia.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Bennell
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000534:rehabilitation*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D055070:Resistance Training / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology*
keywords: Impact loading; Osteoarthritis; Quadriceps; Strength training; Vertical ground reaction force