Dynamical structure of center-of-pressure trajectories in patients recovering from stroke

Faculty of Human Movement Sciences, Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands.
Experimental Brain Research (Impact Factor: 2.04). 10/2006; 174(2):256-69. DOI: 10.1007/s00221-006-0441-7
Source: PubMed


In a recent study, De Haart et al. (Arch Phys Med Rehabil 85:886-895, 2004) investigated the recovery of balance in stroke patients using traditional analyses of center-of-pressure (COP) trajectories to assess the effects of health status, rehabilitation, and task conditions like standing with eyes open or closed and standing while performing a cognitive dual task. To unravel the underlying control processes, we reanalyzed these data in terms of stochastic dynamics using more advanced analyses. Dimensionality, local stability, regularity, and scaling behavior of COP trajectories were determined and compared with shuffled and phase-randomized surrogate data. The presence of long-range correlations discarded the possibility that the COP trajectories were purely random. Compared to the healthy controls, the COP trajectories of the stroke patients were characterized by increased dimensionality and instability, but greater regularity in the frontal plane. These findings were taken to imply that the stroke patients actively (i.e., cognitively) coped with the stroke-induced impairment of posture, as reflected in the increased regularity and decreased local stability, by recruiting additional control processes (i.e., more degrees of freedom) and/or by tightening the present control structure while releasing non-essential degrees of freedom from postural control. In the course of rehabilitation, dimensionality stayed fairly constant, whereas local stability increased and regularity decreased. The progressively less regular COP trajectories were interpreted to indicate a reduction of cognitive involvement in postural control as recovery from stroke progressed. Consistent with this interpretation, the dual task condition resulted in less regular COP trajectories of greater dimensionality, reflecting a task-related decrease of active, cognitive contributions to postural control. In comparison with conventional posturography, our results show a clear surplus value of dynamical measures in studying postural control.

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Available from: Peter J Beek, Oct 09, 2015
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    • "In contrast with findings in other pathologies (Cavanaugh et al., 2006; Donker et al., 2008; Roerdink et al., 2006; Schmit et al., 2006), subjects with current LBP in the present study showed a more irregular sway pattern with a higher frequency content, when standing on foam. The subjects in these other studies had pathologies that contain larger threats to postural balance than LBP does, such as CVA and Parkinson disease. "
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    Human Movement Science 02/2015; 39:109-20. DOI:10.1016/j.humov.2014.05.011 · 1.60 Impact Factor
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    • "It should be noted that the above set of findings may not be unique to motor CD, but that other motor abnormalities could have resulted in similar patterns of results. For example, Roerdink et al. [44] found effects of attentional distraction (mental arithmetic) on COP dynamics in patients recovering from stroke, highlighting the cognitive contributions to postural control in this patient group. Future studies should not only directly compare CD to controls, but should also include a group of disease controls such as multiple sclerosis [16], so that it can be established whether postural measures provide a useful diagnostic tool. "
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    Journal of Psychosomatic Research 11/2014; 78(3). DOI:10.1016/j.jpsychores.2014.11.009 · 2.74 Impact Factor
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    • "To employ the SampEn algorithm, the parameters m (template length) and r (tolerance level) must be defined. A guideline to select m and r was first developed to examine the SampEn of cardiac dynamics [40], and this has been used previously to examine dynamics of the CoP in other posture tasks [19] [41]. As per these guidelines, a variety of m and r value combinations were examined to determine the set of values that lead to the lowest acceptable variance. "
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