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Quantifying ataxia: ideal trajectory analysis--a technical noteWe describe a quantitative method to assess repeated stair stepping stability. In both the mediolateral (ML) and anterioposterior (AP) directions, the trajectory of the subject's center of mass (COM) was compared to an ideal sinusoid. The two identified sinusoids were unique in each direction but coupled. Two dimensionless numbers-the mediolateral instability index (IML) and AP instability index (IAP)-were calculated using the COM trajectory and ideal sinusoids for each subject with larger index values resulting from less stable performance. The COM trajectories of nine nonimpaired controls and six patients diagnosed with unilateral or bilateral vestibular labyrinth hypofunction were analyzed. The average IML and IAP values of labyrinth disorder patients were respectively 127% and 119% greater than those of controls (p<0.014 and 0.006, respectively), indicating that the ideal trajectory analysis distinguishes persons with labyrinth disorder from those without. The COM trajectories also identify movement inefficiencies attributable to vestibulopathy.
Document ID
Document Type
Reprint (Version printed in journal)
McPartland, M. D. (Harvard Medical School, Massachusetts General Hospital Biomotion Laboratory Department of Orthopaedics, Boston, MA 02114, United States)
Krebs, D. E.
Wall, C. 3rd
Date Acquired
August 21, 2013
Publication Date
July 1, 2000
Publication Information
Publication: Journal of rehabilitation research and development
Volume: 37
Issue: 4
ISSN: 0748-7711
Subject Category
Life Sciences (General)
Distribution Limits
Non-NASA Center
Clinical Trial
NASA Discipline Neuroscience
Controlled Clinical Trial