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Postural control in the elderly: An analysis of test-retest and interrater reliability of the COP-COM variable,☆☆,

https://doi.org/10.1053/apmr.2001.18678Get rights and content

Abstract

Corriveau H, Hébert R, Prince F, Raîche M. Postural control in the elderly: an analysis of test-retest and interrater reliability of the COP-COM variable. Arch Phys Med Rehabil 2001;82:80-5. Objectives: To estimate the test-retest and interrater reliability of the center of pressure-center of mass (COP-COM) variable of postural control in the elderly. Design: The biomechanic variable COP-COM, which represents the distance between the COP and the COM, was determined from 2 AMTI force platforms and 3 OPTOTRAK® position sensors. Measurements were taken in quiet position, double leg stance, and eyes open and eyes closed conditions. Setting: Laboratory environment. Participants: Forty-five healthy subjects, 8 patients with diabetes neuropathy, and 7 stroke survivors, all of whom were at least 60 years old. Interventions: Subjects were evaluated on 2 separate occasions within 7 days by the same evaluator to determine test-retest reliability. Interrater reliability was determined the same day. Main Outcome Measures: The biomechanic variable COP-COM, which represents the distance between the COP and the COM in terms of root mean square. The mean of 4 trials of the COP-COM variable for each condition was used for statistical analysis. Intraclass correlation coefficients (ICCs) were used. Results: The COP-COM variable has good reliability for both the test-retest and interrater studies, but its reliability varies according to the direction of the COP-COM. For the test-retest and interrater studies, the ICC ranged from.89 to.93 in the anteroposterior direction and from.74 to.79 in the mediolateral direction. Conclusion: The equivalence of the test-retest and interrater coefficients obtained suggests that the measurement error of the COP-COM variable is mainly linked to the biologic variability of this measure over a short period of time. Using the mean of 4 trials stabilizes the COP-COM variable enough to be potentially used to evaluate clinical change. © 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Section snippets

Subjects

Healthy elderly subjects were recruited from a database of people who showed an interest in studies carried out at the research center.21 They were then contacted by phone to verify their eligibility and to make an appointment if they were interested in participating. The eligibility criteria were to be at or over the age of 60 years, living independently in the community, and having no neurologic or musculoskeletal impairments (eg, history of stroke, transient ischemia attacks, Parkinson's

Results

The study sample consisted of 45 healthy elderly persons and 15 elderly persons with impaired postural control from PDN or stroke. Careful examination of data collection and processing procedures showed a technical problem in the record of 1 impaired subject at the first evaluation. Consequently, test-retest reliability was estimated on 59 subjects. Interrater reliability was estimated using all the subjects because there were no technical problems. The subjects' characteristics are in table 1.

Discussion

The results obtained indicated good reliability of the COP-COM variable for both the test-retest and interrater studies, but varied significantly according to the direction of the COP-COM (AP vs M/L). It is accepted in the literature that postural measures are split in the AP and M/L directions because of the differences between balance control in the sagittal and frontal planes, both from a biomechanic18 and a neural control perspective.30 In the present study, the directional difference in

Conclusion

Postural control is a dynamic phenomenon that changes from day to day. Using the mean of 4 trials of the COP-COM variable stabilizes the COP-COM variable enough to get a reliable measure over a short period of time. An inverted pendulum model involving simultaneous COM and COP records is required to understand how the trajectory and acceleration of the COM in both AP and M/L directions is controlled to maintain postural balance. Using the COP-COM variable provides the opportunity to measure

Acknowledgements

We thank Lise Trottier for the statistical analysis.

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    Supported in part by the Medical Research Council of Canada (grant no. MT4343), and the Fonds de la recherche en santé du Québec.

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    No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

    Reprint requests to Hélène Corriveau, PT, MSc, Schl of Rehabilitation Sciences, Physiotherapy, University of Ottawa, 451 Smyth Rd, Ottawa, Ont K1H 8M5 Canada, e-mail: [email protected].

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