title: Center of mass trajectories during turning in patients with Parkinson's disease with and without freezing of gait.
abstract: BACKGROUND
  Despite the strong relationship between freezing of gait (FOG) and turning in Parkinson's disease (PD), few studies have addressed specific postural characteristics during turning that might contribute to freezing.
  
  
  METHODS
  Thirty participants with PD (16 freezers, 14 non-freezers) (all tested OFF medication) and 14 healthy controls walked 5 meters and turned 180° in a 3D gait laboratory. COM behavior was analyzed during four turning quadrants of 40° between 10° and 170° pelvic rotation and during 40° before actual FOG episodes. These pre-FOG segments were compared with similar turning sections in turns of freezers without FOG. Outcome parameters were turn time, COM distance, COM velocity, step width and the medial- and anterior COM position.
  
  
  RESULTS
  Turn time was increased in freezers compared to non-freezers (p=.000). No differences were found regarding COM distance and velocity during turning quadrants between groups and between freezers' pre-FOG segments and similar turning segments without FOG. Medial COM deviation was reduced in PD patients compared to controls (p=.004), but no differences were found between freezers and non-freezers. In turns with freezing, turn time increased (p=.005) and step width decreased (p=.025) pre-FOG. Freezers also showed a less medial (p=.020) and more anterior (p=.016) COM position pre-FOG compared to turning sections without FOG.
  
  
  CONCLUSIONS
  Our results revealed no subgroup differences in COM behavior during uninterrupted turning. However, we found a reduced medial deviation, a forward COM shift and a decreased step width in freezers just before FOG episodes. These abnormalities may play a causal role, as they could hamper stability and fluent weight shifting necessary for continued stepping during turning.
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Heverlee, Belgium; Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands. Electronic address: Aniek.Bengevoord@faber.kuleuven.be.
authors.forename: A
authors.initials: A
authors.lastname: Bengevoord
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Heverlee, Belgium. Electronic address: griet.vervoort@faber.kuleuven.be.
authors.forename: G
authors.initials: G
authors.lastname: Vervoort
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Heverlee, Belgium; Hasselt University, Rehabilitation Sciences and Physiotherapy, Hasselt, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Spildooren
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Heverlee, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Heremans
authors.affiliation: Department of Neurology, UZ Leuven, Leuven, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Vandenberghe
authors.affiliation: Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
authors.forename: B R
authors.initials: BR
authors.lastname: Bloem
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Heverlee, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Nieuwboer
mesh_terms: D000368:Aged; D005260:Female; D005684:Gait / Q000502:physiology*; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D012399:Rotation; D016138:Walking / Q000502:physiology*
keywords: Center of mass; Dynamic stability; Freezing of gait; Parkinson's disease; Turning