title: The effect of weight-bearing asymmetry on dynamic postural stability in healthy young individuals.
abstract: BACKGROUND
  In people with lateralized disorders, such as stroke, Weight-Bearing Asymmetry (WBA) is common. It is associated with postural instability, however, WBA is one of several abnormalities that may affect postural stability in these disorders. Therefore, we investigated the isolated effects of WBA on dynamic postural stability in healthy individuals.
  
  
  METHODS
  Ten young participants were subjected to multidirectional stance perturbations by support surface translations at three levels of WBA (0, 10 and 20% of body weight unloading of one leg). The stepping threshold was determined iteratively for each condition and in four perturbation directions (forward, backward, leftward and rightward). The stepping threshold was defined as the highest perturbation intensity recovered from with a feet-in-place response. The Margin of Stability (MOS) at the stepping threshold was defined as the smallest distance between the vertical projection of the Extrapolated Center of Mass (XCOM) and the edge of the base of support.
  
  
  RESULTS
  WBA decreased the stepping threshold (stability decreased) for perturbations towards the loaded side (translations towards the unloaded side), whereas it increased stepping thresholds for perturbations towards the unloaded side. No significant effects of WBA were found on the MOS. WBA increased the frequency of stepping with the unloaded leg upon forward and backward perturbations.
  
  
  CONCLUSIONS
  WBA increased dynamic stability towards the unloaded leg following external balance perturbations and resulted in a greater probability of stepping with this leg. Future studies are needed to evaluate the functional significance of these WBA-related effects on postural stability in people with lateralized disorders.
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands. Electronic address: digna.dekam@radboudumc.nl.
authors.forename: Digna
authors.initials: D
authors.lastname: de Kam
authors.affiliation: ViaReva, Centre for Rehabilitation, Apeldoorn, The Netherlands.
authors.forename: Jip F
authors.initials: JF
authors.lastname: Kamphuis
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands; Sint Maartenskliniek Research, Nijmegen, The Netherlands.
authors.forename: Vivian
authors.initials: V
authors.lastname: Weerdesteyn
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands; Sint Maartenskliniek Research, Nijmegen, The Netherlands.
authors.forename: Alexander C H
authors.initials: AC
authors.lastname: Geurts
mesh_terms: D000328:Adult; D005260:Female; D005528:Foot / Q000502:physiology*; D020233:Gait Disorders, Neurologic; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*
keywords: Balance perturbations; Dynamic stability; Weight-bearing asymmetry