title: Freezing of gait in Parkinson's disease: further insights into pathophysiological mechanisms.
abstract: BACKGROUND
  Freezing of gait in Parkinson's disease (PD) was found to occur in the presence of the sequence effect (a decrease in length of consecutive footsteps) and a shortened step length. Gait asymmetry and reduced coordination of gait have also been implicated in freezing of gait. The aim of this study was to determine the effect of controlling for step length on asymmetry and coordination of gait. A second aim was to determine if asymmetry and bilateral coordination predicted freezing.
  
  
  METHODS
  Data for sixteen participants with PD and freezing of gait, ten people with PD but no history of freezing and ten controls was analyzed. Participants, in their 'off' state, had their gait recorded walking at preferred and normalized step lengths of 100%, 75%, 50% and 25%.
  
  
  RESULTS
  Asymmetry of swing time increased in all groups as step length decreased from 100% to 25% and did not differ between the PD group with freezing compared to the PD group without freezing in the preferred and normalized step length conditions after adjusting for step length and disease severity. Coordination of walking worsened in all groups at the shorter normalized step lengths with no difference between PD groups in the 25% condition where the frequency of freezing was highest. Asymmetry and coordination of gait were not predictive of freezing in the 25% condition.
  
  
  CONCLUSIONS
  These results suggest asymmetry and decreased coordination of gait are affected by step length and may not be factors in determining freezing of gait in PD.
authors.affiliation: Clinical Research Centre for Movement Disorders and Gait, Kingston Centre Southern Health, Melbourne, Australia.
authors.forename: Mary
authors.initials: M
authors.lastname: Danoudis
authors.forename: Robert
authors.initials: R
authors.lastname: Iansek
authors.forename: Pamela
authors.initials: P
authors.lastname: Simpson
mesh_terms: D005163:Factor Analysis, Statistical; D005260:Female; D046352:Freezing Reaction, Cataleptic / Q000502:physiology*; D020233:Gait Disorders, Neurologic / Q000209:etiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D010300:Parkinson Disease / Q000150:complications*; D011597:Psychomotor Performance / Q000502:physiology; D012720:Severity of Illness Index; D013997:Time Factors; D016138:Walking