title: Energy flow analysis of the lower extremity during gait in persons with chronic stroke.
abstract: BACKGROUND
  A decline in walking capacity and high energy cost can limit mobility following stroke. Mechanical energy exchange between lower limb and trunk segments can reflect gait inefficiencies, but reveals little about active energy flow between adjacent segments through muscle actions. This study evaluated mechanical energy expenditures (MEEs) during walking in stroke and healthy groups to understand movement control and explore the impact of walking speed on mechanical energy exchanges.
  
  
  METHODS
  Thirteen adults with hemiparesis and six healthy controls walked at self-selected speed. Power curves for each lower limb joint were segmented into concentric and eccentric sources of muscle power and transfer/no-transfer modes to calculate MEEs during stance.
  
  
  RESULTS
  MEEs were lower in the stroke group on the affected side compared to the less affected side and compared to controls. Specifically, the affected plantarflexors transferred less energy distally via concentric action in late stance compared to the less affected side. However, the stroke group generated greater energy at the ankle in the absence of transfer compared to controls. Less concentrically transferred energy through midstance and absorbed in late stance was evident by the knee extensors bilaterally in stroke. At the hip, the total energy (no transfer) was reduced on the affected side. Classifying stroke subjects by walking speed (<.6m/s, >.6m/s) revealed disruptions in harnessing energy through motion and transfer energy across segments in the slower group.
  
  
  CONCLUSIONS
  The limited ability of those with stroke to exploit intersegmental energy transfer to optimize efficiency may limit endurance and functional independence.
authors.affiliation: Toronto Rehabilitation Institute, Toronto, ON, Canada; School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada.
authors.forename: Alison C
authors.initials: AC
authors.lastname: Novak
authors.affiliation: Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada.
authors.forename: Shuozhi
authors.initials: S
authors.lastname: Yang
authors.affiliation: School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada. Electronic address: brouwerb@queensu.ca.
authors.forename: Brenda
authors.initials: B
authors.lastname: Brouwer
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D002908:Chronic Disease; D004734:Energy Metabolism / Q000502:physiology*; D004735:Energy Transfer / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020521:Stroke / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Biomechanics; Disability; Joint kinetics; Mechanical energy transfer