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Dynamic Analysis of Posture Profiles in Quiet Stance on Carpets through Fractional Brownian Motion

Division of Kinesiology, University of Michigan, Ann Arbor, MI 48109, U.S.A.

Ning Pan

Division of Textiles and Clothing, Department of Biological and Agricultural Engineering, University of California, Davis, CA 95616, U.S.A., npan{at}ucdavis.edu

Keith R. Williams

Exercise Biology Program, University of California, Davis, CA 95616, U.S.A.

In this study we examine the dynamic characteristics of the center of pressure (COP) profiles in quiet stance on various carpets through the framework of fractional Brownian motion. Four different carpets plus the force platform (which served as a control floor) were tested. Six healthy young subjects stood stationary in bare feet on each flooring condition under both eyes-open (EO) and eyes-closed (EC) conditions. A stabilogram diffusion analysis (SDA) was conducted in both anteroposterior and mediolateral directions to extract the dynamic features of the COP profiles. Two approximately linear regions (short-versus long-term regions) were found for all of the flooring conditions in the double logarithmic plot of the mean-square displacements versus time intervals, implying that a two-stage control scheme exists in regulating the posture. In general, a more compliant carpet was found to be associated with a shorter transitional time interval and a lower H_L value (Hurst coefficient in the long-term region) under the EO condition, but to be correlated with a higher H_S (Hurst coefficient in the short-term region) and a higher H_L under the EC condition. While the hard floor of the force platform significantly decreased H_L from the EO to the EC conditions, the alteration of visual environments did not substantially influence H_L for a compliant carpet.

Key Words: carpet • quiet stance • posture • center of pressure • fractional Brownian motion

Textile Research Journal, Vol. 78, No. 1, 45-52 (2008)
DOI: 10.1177/0040517507081909


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