title: Anticipatory postural adjustments prior to step initiation are hypometric in untreated Parkinson's disease: an accelerometer-based approach.
abstract: OBJECTIVE
  Anticipatory postural adjustments (APAs), prior to step initiation, are bradykinetic in advanced Parkinson's disease (PD) and may be one of the factors associated with 'start hesitation'. However, little is known about APAs in the early stage of PD. In this study, we determined whether body-worn accelerometers could be used to characterize step initiation deficits in subjects with early-to-moderate, untreated PD.
  
  
  METHODS
  Eleven PD and 12 healthy control subjects were asked to take two steps. Postural adjustments were compared from center of pressure (COP) and from acceleration of the trunk at the center of mass level (L5).
  
  
  RESULTS
  Our findings show that APAs measured from the peak COP displacement toward the swing leg and the peak trunk acceleration toward the stance leg were smaller in untreated PD compared with control subjects. The magnitude of APAs measured from peak COP displacements and accelerations were correlated.
  
  
  CONCLUSIONS
  These results suggest that quantitative analysis of step initiation from one accelerometer on the trunk could provide useful information for the characterization of patients in early stages of PD, when clinical evidence of start hesitation may not be detectable. Ambulatory monitoring of step initiation is also promising for monitoring patient progression in the home environment, and eventually providing feedback for preventing freezing of gait episodes.
authors.affiliation: Biomedical Engineering Unit, Department of Electronics, Computer Science & Systems, Alma Mater Studiorum, Universita' di Bologna, Bologna, Italy. martina.mancini@unibo.it
authors.forename: M
authors.initials: M
authors.lastname: Mancini
authors.forename: C
authors.initials: C
authors.lastname: Zampieri
authors.forename: P
authors.initials: P
authors.lastname: Carlson-Kuhta
authors.forename: L
authors.initials: L
authors.lastname: Chiari
authors.forename: F B
authors.initials: FB
authors.lastname: Horak
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001696:Biomechanical Phenomena / Q000502:physiology; D005684:Gait / Q000502:physiology*; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology; D011434:Proprioception / Q000502:physiology; D012815:Signal Processing, Computer-Assisted