title: Obesity is associated with prolonged activity of the quadriceps and gastrocnemii during gait.
abstract: OBJECTIVE
  To examine the effect of obesity and its potential interaction with knee OA presence on the electromyography patterns of the major knee joint periarticular muscles during walking.
  
  
  METHODS
  One hundred and eighteen asymptomatic adults and 177 adults with moderate knee osteoarthritis were subdivided into categories of healthy weight (n = 77; 20 kg/m(2) < BMI < 25 kg/m(2)), overweight (n = 117; 25 kg/m(2) ⩽ BMI < 30 kg/m(2)), and obese (n = 101; BMI ⩾ 30 kg/m(2) based on their body mass index (BMI). All individuals underwent a three-dimensional gait analysis. Surface electromyograms from the lateral and medial gastrocnemii, lateral and medial hamstrings, vastus lateralis, vastus medialis, and rectus femoris were recorded during self-selected speed walking. Principal component analysis was used to extract major features of amplitude and temporal pattern variability from the electromyograms of each muscle group (gastrocnemii, quadriceps, hamstrings separately). Analysis of variance models tested for main BMI category effects and interaction effects for these features (α = 0.05). Statistically significant BMI category (i.e. obesity) effects were found for features that described more prolonged activations of the gastrocnemii and quadriceps muscles during the stance phase of gait with obesity (P < 0.05).
  
  
  CONCLUSIONS
  Obesity was associated with prolonged activation of quadriceps and gastrocnemii, which can result in prolonged knee joint contact loading, and thereby may contribute to the predisposition of knee OA development and progression in obese individuals.
authors.affiliation: School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Amiri
authors.affiliation: School of Physiotherapy, Dalhousie University, Halifax, NS, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada.
authors.forename: C L
authors.initials: CL
authors.lastname: Hubley-Kozey
authors.affiliation: School of Kinesiology, Acadia University, Wolfville, NS, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada.
authors.forename: S C
authors.initials: SC
authors.lastname: Landry
authors.affiliation: Department of Surgery, Division of Orthopedics, Dalhousie University, Halifax, NS, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada.
authors.forename: W D
authors.initials: WD
authors.lastname: Stanish
authors.affiliation: School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada. Electronic address: Janie.Wilson@Dal.Ca.
authors.forename: J L
authors.initials: JL
authors.lastname: Astephen Wilson
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D009765:Obesity / Q000503:physiopathology*; D016138:Walking
keywords: Electromyography; Gait; Knee osteoarthritis; Obesity; Principal component analysis