Document Detail

Measuring robustness of the postural control system to a mild impulsive perturbation.
MedLine Citation:
PMID:  20529754     Owner:  NLM     Status:  MEDLINE    
We propose a new metric to assess robustness of the human postural control system to an impulsive perturbation (in this case, a mild backward impulse force at the pelvis). By applying concepts from robust control theory, we use the inverse of the maximum value of the system's sensitivity function (1/MaxSens) as a measure for robustness of the human postural control system, e.g., a highly sensitive system has low robustness to perturbation. The sensitivity function, which in this case is the frequency response function, is obtained directly using spectral analysis of experimental measurements, without need to develop a model of the postural control system. Common measures of robustness, gain and phase margins, however require a model to assess system robustness. To examine the efficacy of this approach, we tested thirty healthy subjects across three age groups: young (YA: 20-30 years), middle-aged (MA: 42-53 years), and older adults (OA: 71-79 years). The OA group was found to have reduced postural stability during quiet stance as detected by center of pressure measures of postural sway. The proposed robustness measure of 1/MaxSens was also found to be significantly smaller for OA than YA or MA ( p=0.001), implying reduced robustness among the older subjects in response to the perturbation. Gain and phase margins failed to detect any age-related differences. In summary, the proposed robustness characterization method is easy to implement, does not require a model for the postural control system, and was better able to detect differences in system robustness than model-based robustness metrics.
Pilwon Hur; Brett A Duiser; Srinivasa M Salapaka; Elizabeth T Hsiao-Wecksler
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2010-06-07
Journal Detail:
Title:  IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society     Volume:  18     ISSN:  1558-0210     ISO Abbreviation:  IEEE Trans Neural Syst Rehabil Eng     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-08-11     Completed Date:  2010-12-02     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101097023     Medline TA:  IEEE Trans Neural Syst Rehabil Eng     Country:  United States    
Other Details:
Languages:  eng     Pagination:  461-7     Citation Subset:  IM    
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champain, IL 61801, USA.
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MeSH Terms
Aging / physiology
Analysis of Variance
Data Interpretation, Statistical
Middle Aged
Models, Biological
Models, Statistical
Pelvis / physiology
Physical Stimulation
Postural Balance / physiology*
Reproducibility of Results
Young Adult

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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