title: Effect of specific gait modifications on medial knee loading, metabolic cost and perception of task difficulty.
abstract: BACKGROUND
  The metabolic cost and cognitive demand of altering natural gait have not been well studied. The purpose of this investigation was to assess three modified patterns - toe out, ipsilateral trunk lean and a medial weight shift at the foot - on the basis of 1) medial knee joint load reduction, 2) metabolic cost of performance and 3) subject perception of task difficulty.
  
  
  METHODS
  12 healthy individuals underwent 3 dimensional motion analysis and metabolic testing to assess the gait mechanics and energy expenditure of natural gait and the three experimental gait patterns, performed to a self-selected moderate degree. Walking speed was controlled. Perceived workload was assessed using the NASA Task Load Index.
  
  
  RESULTS
  Trunk lean significantly reduced first peak knee adduction moment (↓32%, P<0.001) as well as KAM impulse (↓35%, P<0.001), but was costly in terms of energy expenditure (↑11%, P<0.001) and perceived workload (↑1178%, P<0.001). A moderate toe-out pattern significantly reduced the second peak knee adduction moment (↓32%, P<0.001) and KAM impulse (↓14%, P=0.026), but had no effect on the first peak. Conversely, toe-out was least demanding in terms of additional energy expenditure (↑2%, P=0.001) and perceived workload (↑314%, P=0.001). Medial shift did not reduce knee adduction moment.
  
  
  CONCLUSIONS
  The prioritization of joint load reduction versus additional metabolic and cognitive demands could play a substantial role in the clinical decision making process of selecting a modified gait pattern.
authors.affiliation: Health and Sport Science, University of Dayton, 300 College Park, Dayton, OH 45469, USA. caldwelll1@udayton.edu
authors.forename: Lydia K
authors.initials: LK
authors.lastname: Caldwell
authors.forename: Lloyd L
authors.initials: LL
authors.lastname: Laubach
authors.forename: Joaquin A
authors.initials: JA
authors.lastname: Barrios
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D007717:Knee / Q000502:physiology*; D008297:Male; D011187:Posture / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D013647:Task Performance and Analysis; D060726:Torso / Q000502:physiology; D014481:United States; D016474:Weight-Bearing / Q000502:physiology*; D016526:Workload / Q000523:psychology*; D055815:Young Adult
keywords: Adduction moment; Gait modification; Knee; Metabolic cost