title: Gait initiation and dynamic balance control in Parkinson's disease.
abstract: OBJECTIVE
  To determine whether the magnitude of the separation between the center of pressure (COP) and the whole-body center of mass (COM) during gait initiation can differentiate patients with varying severity of Parkinson's disease (PD) disability.
  
  
  METHODS
  Cross-sectional, intact groups research design.
  
  
  METHODS
  Biomechanics research laboratory.
  
  
  METHODS
  Forty-three patients were stratified into 2 groups based on the Hoehn and Yahr (H&Y) disability score, which heavily favors balance in determining disability. The 2 groups were: H&Y score of 2.0 or less (n=23; age, 61+/-10y) or H&Y score of 2.5 or higher (n=20; age, 70+/-9y).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  The peak COP-COM distance represents the maximum separation between the location of the whole-body COM and the ground reaction force's COP, and thus is an indicator of dynamic balance control. The peak COP-COM was evaluated during 3 phases of the COP trajectory during a gait initiation task.
  
  
  RESULTS
  The peak magnitude of the COP-COM distance was significantly greater during the end of the single-support phase in the less disabled patients (H&Y score <or=2.0) than in more balance disabled patients (H&Y score >or=2.5) (P=.004).
  
  
  CONCLUSIONS
  The differences in COP-COM distances between these H&Y groups suggest that patients with PD who have impaired postural control produce shorter COM-COP distances than do persons without clinically detectable balance impairment. This method of evaluation could prove a useful quantitative index to examine the impact of interventions designed to improve ambulation and balance in PD.
authors.affiliation: Department of Biobehavioral Sciences, Teachers College Columbia University, New York, NY 10027, USA. hass@exchange.tc.columbia.edu
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Hass
authors.forename: Dwight E
authors.initials: DE
authors.lastname: Waddell
authors.forename: Richard P
authors.initials: RP
authors.lastname: Fleming
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Juncos
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gregor
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005684:Gait / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index