The quality of turning in Parkinson's disease: a compensatory strategy to prevent postural instability?
BACKGROUND
The ability to turn while walking is essential for daily living activities. Turning is slower and more steps are required to complete a turn in people with Parkinson's disease (PD) compared to control subjects but it is unclear whether this altered strategy is pathological or compensatory. The aim of our study is to characterize the dynamics of postural stability during continuous series of turns while walking at various speeds in subjects with PD compared to control subjects. We hypothesize that people with PD slow their turns to compensate for impaired postural stability.


METHODS
Motion analysis was used to compare gait kinematics between 12 subjects with PD in their ON state and 19 control subjects while walking continuously on a route composed of short, straight paths interspersed with eleven right and left turns between 30 and 180°. We asked subjects to perform the route at three different speeds: preferred, faster, and slower. Features describing gait spatio-temporal parameters and turning characteristics were extracted from marker trajectories. In addition, to quantify dynamic stability during turns we calculated the distance between the lateral edge of the base of support and the body center of mass, as well as the extrapolated body center of mass.


RESULTS
Subjects with PD had slower turns and did not widen the distance between their feet for turning, compared to control subjects. Subjects with PD tended to cut short their turns compared to control subjects, resulting in a shorter walking path. Dynamic stability was smaller in the PD, compared to the healthy group, particularly for fast turning angles of 90°.


CONCLUSIONS
The slower turning speeds and larger turning angles in people with PD might reflect a compensatory strategy to prevent dynamic postural instability given their narrow base of support.
Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy.
Sabato
S
Mellone
Department of Neurology, School of Medicine, Oregon Health and Science University, 3181 Sam Jackson Park Road, Portland, OR, 97239-3098, USA. mancinim@ohsu.edu.
Martina
M
Mancini
Department of Neurology, School of Medicine, Oregon Health and Science University, 3181 Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
Laurie A
LA
King
Department of Neurology, School of Medicine, Oregon Health and Science University, 3181 Sam Jackson Park Road, Portland, OR, 97239-3098, USA.|VA Portland Health Care System (VAPORHCS), 3710 SW US Veterans Hospital Rd, Portland, 97239-9264, OR, USA.
Fay B
FB
Horak
Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy.
Lorenzo
L
Chiari
D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*
Dynamic stability; Parkinson’s disease; Turning