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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

Representative examples of CoM and ankle trajectories for the three requested speeds of trial execution: slow, preferred, and fast. The COM trajectory and its velocity (color code), together with the right and left ankle trajectory (dashed) for a representative control subject a and a subject with PD b. Solid black line represents the path reference traced on the floor with direction of walking indicated by arrows and numbers. The box insert for the fast trajectory shows a zoomed 90° turn trajectory in which the subject with PD has the COM outside the base of support longer than the control subject
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Fig1: Representative examples of CoM and ankle trajectories for the three requested speeds of trial execution: slow, preferred, and fast. The COM trajectory and its velocity (color code), together with the right and left ankle trajectory (dashed) for a representative control subject a and a subject with PD b. Solid black line represents the path reference traced on the floor with direction of walking indicated by arrows and numbers. The box insert for the fast trajectory shows a zoomed 90° turn trajectory in which the subject with PD has the COM outside the base of support longer than the control subject

Mentions: Subjects were instructed to walk following a path traced on the floor with tape, which was composed of a route mixed with short straight paths interspersed within eleven turns ranging from 30 to 180° (see Fig. 1). Specifically, the planned sequence of turns was: 1) 90° left, 2) 135° right, 3) 135° left, 4) 180°, 5) 90° right, 6) 30° right, 7) 165° right, 8) 45° left, 9) 180°, 10) 45° right, 11) 135° right. Here we report results about seven of these turns, only: 180°, and left and right turns of 90 and 135°. We focused on such turns because they were always consistently taken, while other turns, due to the design of the route, often induced subjects to avoid them (45°) or to merge two consecutive turns into a single turn (30 and 165°). Subjects were asked to perform the route 12 times at three different speeds: four at their comfortable (preferred) speed, four at faster, and four at slower speeds. To calculate body kinematics and COM trajectories, subjects wore a set of 15 reflective markers placed bilaterally on the fifth metatarsophalangeal joints (5MTJ), lateral malleolus, knees, shoulders, anterior- and posterior-superior iliac spines, and anterior to ears. Body kinematics (acquired with a 8-camera Motion Analysis system, Santa Rosa, CA; sample rate 60 Hz) and anthropometric tables [21, 22] were used to estimate the instantaneous position of the COM in the sagittal, frontal and transverse planes as a weighted sum of all segments’ COM positions. COM velocity was calculated as the first derivative of the COM position. Figure 1 illustrates the route superimposed on the body COM and footfall trajectories in two representative subjects (one control and one PD subject) walking at slow, comfortable, and fast speeds.Fig. 1


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)

Representative examples of CoM and ankle trajectories for the three requested speeds of trial execution: slow, preferred, and fast. The COM trajectory and its velocity (color code), together with the right and left ankle trajectory (dashed) for a representative control subject a and a subject with PD b. Solid black line represents the path reference traced on the floor with direction of walking indicated by arrows and numbers. The box insert for the fast trajectory shows a zoomed 90° turn trajectory in which the subject with PD has the COM outside the base of support longer than the control subject
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Representative examples of CoM and ankle trajectories for the three requested speeds of trial execution: slow, preferred, and fast. The COM trajectory and its velocity (color code), together with the right and left ankle trajectory (dashed) for a representative control subject a and a subject with PD b. Solid black line represents the path reference traced on the floor with direction of walking indicated by arrows and numbers. The box insert for the fast trajectory shows a zoomed 90° turn trajectory in which the subject with PD has the COM outside the base of support longer than the control subject
Mentions: Subjects were instructed to walk following a path traced on the floor with tape, which was composed of a route mixed with short straight paths interspersed within eleven turns ranging from 30 to 180° (see Fig. 1). Specifically, the planned sequence of turns was: 1) 90° left, 2) 135° right, 3) 135° left, 4) 180°, 5) 90° right, 6) 30° right, 7) 165° right, 8) 45° left, 9) 180°, 10) 45° right, 11) 135° right. Here we report results about seven of these turns, only: 180°, and left and right turns of 90 and 135°. We focused on such turns because they were always consistently taken, while other turns, due to the design of the route, often induced subjects to avoid them (45°) or to merge two consecutive turns into a single turn (30 and 165°). Subjects were asked to perform the route 12 times at three different speeds: four at their comfortable (preferred) speed, four at faster, and four at slower speeds. To calculate body kinematics and COM trajectories, subjects wore a set of 15 reflective markers placed bilaterally on the fifth metatarsophalangeal joints (5MTJ), lateral malleolus, knees, shoulders, anterior- and posterior-superior iliac spines, and anterior to ears. Body kinematics (acquired with a 8-camera Motion Analysis system, Santa Rosa, CA; sample rate 60 Hz) and anthropometric tables [21, 22] were used to estimate the instantaneous position of the COM in the sagittal, frontal and transverse planes as a weighted sum of all segments’ COM positions. COM velocity was calculated as the first derivative of the COM position. Figure 1 illustrates the route superimposed on the body COM and footfall trajectories in two representative subjects (one control and one PD subject) walking at slow, comfortable, and fast speeds.Fig. 1

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