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Review
. 2008 Apr;18(2):172-8.
doi: 10.1016/j.jelekin.2007.06.008. Epub 2007 Aug 7.

Dynamic stability differences in fall-prone and healthy adults

Kevin P Granata  1 , Thurmon E Lockhart
Affiliations
Review

Dynamic stability differences in fall-prone and healthy adults

Kevin P Granata et al. J Electromyogr Kinesiol. 2008 Apr.

Abstract

Typical stability assessments characterize performance in standing balance despite the fact that most falls occur during dynamic activities such as walking. The objective of this study was to identify dynamic stability differences between fall-prone elderly individuals, healthy age-matched adults, and young adults. Three-dimensional video-motion analysis kinematic data were recorded for 35 contiguous steps while subjects walked on a treadmill at three speeds. From this data, we estimated the vector from the center-of-mass to the center of pressure at each foot-strike. Dynamic stability of walking was computed by methods of Poincare analyses of these vectors. Results revealed that the fall-prone group demonstrated poorer dynamic stability than the healthy elderly and young adult groups. Stability was not influenced by walking velocity, indicating that group differences in walking speed could not fully explain the differences in stability. This pilot study supports the need for future investigations using larger population samples to study fall-prone individuals using nonlinear dynamic analyses of movement kinematics.

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Figures

Fig. 1
Fig. 1
Simulation of two-segment passive dynamic walker (inset) demonstrates limit-cycle dynamics (Granata and Lockhart, 2006; McGeer, 1990). The stable dynamic orbit never intersects a static balance configuration at the origin. Notice how disturbances are attracted toward a common stable orbit. Poincare analyses can be used to characterize the orbital stability (Hurmuzlu and Basdogan, 1994a).
Fig. 2
Fig. 2
Overall mean (solid line at 0.322), individual subject mean values (brief vertical lines), quartile (box) and standard deviation of the mean Floquet multiplier computed from stride differences in the dynamic state at foot-strike. The fall-prone elderly demonstrated poorer dynamic stability of walking then the healthy old and young adults.
Fig. 3
Fig. 3
Overall mean (solid line at 0.552), quartile (box) and standard deviation of the maximum Floquet multiplier computed from stride differences in the dynamic state at foot-strike. The fall-prone elderly demonstrated poorer dynamic stability of walking then the healthy old and young adults.
See this image and copyright information in PMC

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