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The quality of turning in Parkinson's disease: a compensatory strategy to prevent postural instability?

Mellone S, Mancini M, King LA, Horak FB, Chiari L - J Neuroeng Rehabil (2016)

Bottom Line: Subjects with PD had slower turns and did not widen the distance between their feet for turning, compared to control subjects.Dynamic stability was smaller in the PD, compared to the healthy group, particularly for fast turning angles of 90°.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy.

ABSTRACT

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.

Method: 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.

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Related in: MedlinePlus

Example illustrating trajectory of the COM and ECOM during first 135° turn for a subject with PD at fast speed. Thick grey line represents the path reference traced on the floor. Footprints are aligned to the line joining the marker on the ankle and the marker on the fifth metatarsophalangeal joint; the area between the line on the left foot and the line of the right foot defines the lateral margins of stability. Specific COM and ECOM positions are represented with a black and grey circle, respectively. The black dotted arrow joining the COM and the ECOM represents the COM velocity vector. When the COM or the ECOM is outside the lateral margin of stability, it is represented in red or light red, respectively. Footprints, COM position, ECOM position, and the direction of the COM velocity vector are represented at the time instant of the heel strike; grey dotted double arrows link the COM position to the foot that is hitting the ground. It is interesting to see that the COM and the ECOM were found to be outside the lateral margin of stability at the onset of the turn
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Fig2: Example illustrating trajectory of the COM and ECOM during first 135° turn for a subject with PD at fast speed. Thick grey line represents the path reference traced on the floor. Footprints are aligned to the line joining the marker on the ankle and the marker on the fifth metatarsophalangeal joint; the area between the line on the left foot and the line of the right foot defines the lateral margins of stability. Specific COM and ECOM positions are represented with a black and grey circle, respectively. The black dotted arrow joining the COM and the ECOM represents the COM velocity vector. When the COM or the ECOM is outside the lateral margin of stability, it is represented in red or light red, respectively. Footprints, COM position, ECOM position, and the direction of the COM velocity vector are represented at the time instant of the heel strike; grey dotted double arrows link the COM position to the foot that is hitting the ground. It is interesting to see that the COM and the ECOM were found to be outside the lateral margin of stability at the onset of the turn

Mentions: Dynamic stability during turns: the percentage of time during turning in which the COM (and ECOM) were outside the lateral Margin of Stability (MOS), and the distance between the COM (or ECOM) and the lateral MOS. Lateral MOS was defined as the planar region between the lines through the markers on the lateral malleolus and 5MTJ of the left and right feet. A graphical representation of these variables is illustrated in Fig. 2.Fig. 2


The quality of turning in Parkinson's disease: a compensatory strategy to prevent postural instability?

Mellone S, Mancini M, King LA, Horak FB, Chiari L - J Neuroeng Rehabil (2016)

Example illustrating trajectory of the COM and ECOM during first 135° turn for a subject with PD at fast speed. Thick grey line represents the path reference traced on the floor. Footprints are aligned to the line joining the marker on the ankle and the marker on the fifth metatarsophalangeal joint; the area between the line on the left foot and the line of the right foot defines the lateral margins of stability. Specific COM and ECOM positions are represented with a black and grey circle, respectively. The black dotted arrow joining the COM and the ECOM represents the COM velocity vector. When the COM or the ECOM is outside the lateral margin of stability, it is represented in red or light red, respectively. Footprints, COM position, ECOM position, and the direction of the COM velocity vector are represented at the time instant of the heel strike; grey dotted double arrows link the COM position to the foot that is hitting the ground. It is interesting to see that the COM and the ECOM were found to be outside the lateral margin of stability at the onset of the turn
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4837520&req=5

Fig2: Example illustrating trajectory of the COM and ECOM during first 135° turn for a subject with PD at fast speed. Thick grey line represents the path reference traced on the floor. Footprints are aligned to the line joining the marker on the ankle and the marker on the fifth metatarsophalangeal joint; the area between the line on the left foot and the line of the right foot defines the lateral margins of stability. Specific COM and ECOM positions are represented with a black and grey circle, respectively. The black dotted arrow joining the COM and the ECOM represents the COM velocity vector. When the COM or the ECOM is outside the lateral margin of stability, it is represented in red or light red, respectively. Footprints, COM position, ECOM position, and the direction of the COM velocity vector are represented at the time instant of the heel strike; grey dotted double arrows link the COM position to the foot that is hitting the ground. It is interesting to see that the COM and the ECOM were found to be outside the lateral margin of stability at the onset of the turn
Mentions: Dynamic stability during turns: the percentage of time during turning in which the COM (and ECOM) were outside the lateral Margin of Stability (MOS), and the distance between the COM (or ECOM) and the lateral MOS. Lateral MOS was defined as the planar region between the lines through the markers on the lateral malleolus and 5MTJ of the left and right feet. A graphical representation of these variables is illustrated in Fig. 2.Fig. 2

Bottom Line: Subjects with PD had slower turns and did not widen the distance between their feet for turning, compared to control subjects.Dynamic stability was smaller in the PD, compared to the healthy group, particularly for fast turning angles of 90°.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy.

ABSTRACT

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.

Method: 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.

Show MeSH
Related in: MedlinePlus