title: Foot force direction control during a pedaling task in individuals post-stroke.
abstract: BACKGROUND
  Appropriate magnitude and directional control of foot-forces is required for successful execution of locomotor tasks. Earlier evidence suggested, following stroke, there is a potential impairment in foot-force control capabilities both during stationary force generation and locomotion. The purpose of this study was to investigate the foot-pedal surface interaction force components, in non-neurologically-impaired and stroke-impaired individuals, in order to determine how fore/aft shear-directed foot/pedal forces are controlled.
  
  
  METHODS
  Sixteen individuals with chronic post-stroke hemiplegia and 10 age-similar non-neurologically-impaired controls performed a foot placement maintenance task under a stationary and a pedaling condition, achieving a target normal pedal force. Electromyography and force profiles were recorded. We expected generation of unduly large magnitude shear pedal forces and reduced participation of multiple muscles that can contribute forces in appropriate directions in individuals post-stroke.
  
  
  RESULTS
  We found lower force output, inconsistent modulation of muscle activity and reduced ability to change foot force direction in the paretic limbs, but we did not observe unduly large magnitude shear pedal surface forces by the paretic limbs as we hypothesized.
  
  
  CONCLUSIONS
  These findings suggested the preservation of foot-force control capabilities post-stroke under minimal upright postural control requirements. Further research must be conducted to determine whether inappropriate shear force generation will be revealed under non-seated, postural demanding conditions, where subjects have to actively control for upright body suspension.
authors.affiliation: Department of Physical Therapy and Human Movement Sciences, Suite 1100, 645 N, Michigan Avenue, Chicago, IL 60611, USA. JN-Liang@u.northwestern.edu.
authors.forename: Jing Nong
authors.initials: JN
authors.lastname: Liang
authors.forename: David A
authors.initials: DA
authors.lastname: Brown
mesh_terms: D004576:Electromyography; D005260:Female; D005528:Foot / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010291:Paresis / Q000209:etiology / Q000503:physiopathology; D020521:Stroke / Q000150:complications / Q000503:physiopathology*
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