title: The characterization of a base-width neutral step as the first step for balance recovery in moderate Parkinson's disease.
abstract: OBJECTIVE
  The purpose of this study is to characterize the base-width neutral step (BNS) as the first step in a compensatory step response in persons with moderate Parkinson's disease (PD), and its effect on balance recovery.
  
  
  METHODS
  Ten PD and 10 healthy controls (HCs) responded to a posterior waist pull. A BNS was defined if the first step was less than 50 mm. The length, height, duration and velocity of the BNS and its effect on balance recovery time and center of mass location at recovery were compared to the first step within other stepping strategies (single step (SS), multiple step (MS)). A linear mixed model was used to compare across strategies.
  
  
  RESULTS
  Six of ten persons with PD compared to zero HC used a BNS. The BNS was shorter in length and duration compared to MS responses in HC, and shorter in duration compared to MS responses in PD. The BNS was slower in velocity compared to every other strategy. BNS use resulted in a longer recovery time compared to all strategies in HC and SS responses in PD, and trended toward a longer recovery time compared to MS responses in PD.
  
  
  CONCLUSIONS
  The BNS as the first step in a MS response may be an unreported strategy for compensatory stepping in PD. This study suggests that the cost of utilizing the BNS may be a longer time for recovery, but further work is necessary to understand the progression of the BNS as PD severity increases.
authors.affiliation: a 1 Department of Mechanical Engineering , University of Kansas , Lawrence, Kansas , KS , USA.
authors.forename: Molly A
authors.initials: MA
authors.lastname: McVey
authors.affiliation: b 2 Bioengineering, University of Kansas , Lawrence, Kansas , KS , USA.
authors.forename: Annaria N
authors.initials: AN
authors.lastname: Barnds
authors.affiliation: c 3 Department of Neurology , University of Kansas Medical Center , Kansas City , KS , USA.
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Lyons
authors.affiliation: c 3 Department of Neurology , University of Kansas Medical Center , Kansas City , KS , USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Pahwa
authors.affiliation: d 4 Department of Biostatistics , University of Kansas Medical Center , Kansas City , KS , USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Mahnken
authors.affiliation: a 1 Department of Mechanical Engineering , University of Kansas , Lawrence, Kansas , KS , USA.|b 2 Bioengineering, University of Kansas , Lawrence, Kansas , KS , USA.
authors.forename: Carl W
authors.initials: CW
authors.lastname: Luchies
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*
keywords: Parkinson's disease; balance recovery; compensatory stepping; motor control