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Ch04-I044963.fm Page 13 Tuesday, August 1, 2006 6:33 PM
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QUANTIFICATION OF DYNAMIC WALKING
STABILITY OF ELDERLY BY USING
NONLINEAR TIME-SERIES ANALYSIS AND
SIMPLE ACCELEROMETRY

1
2
Y. Ohtaki , M. Arii , A. Suzuki 3
4
5
K. Fujita , R. Nagatomi' , H. Inooka 1
x
New Industry Creation Hatchery Center, Tohoku University,
6-6-04 Aza Aoba, Aramaki, Aoba-ku, Sendai 9808579, JAPAN
2
Pakistan Institute of Engineering and Applied Science, PAKISTAN
3
Instruments Technology Research Co. Ltd., Sendai. JAPAN
4
Center for Preventive Medicine and Salutogenesis, Tohoku Fukushi
University, Sendai, JAPAN
"'Graduate School of Medicine, Tohoku University, Sendai, JAPAN
ABSTRACT
This study presented a technique to assess dynamic walking stability utilizing a nonlinear time-
series analysis and a portable instrument. Main objective was to investigate its usefulness in the
assessment of elderly walking. The method was consisted of measurement of three-dimensional
acceleration of the upper body, and estimation of the Lyapunov exponents, thereby directly quan-
tifying local dynamic stability while walking. Straight level walking of young and elderly subjects
was investigated in the experimental study. Effects and efficacies of the interventions for the el-
derly were demonstrated by the proposed method. The experimental results suggested that the
method was useful in revealing degree of improvements on the walking stability.

KEYWORDS

Gait analysis, Walking stability, Portable instrument, Acceleration. Nonlinear time-series analysis,
Aging, Medical application.

INTRODUCTION
Falls cause a serious hazard to elderly people. Impaired mobility due to injuries or a fear of falling
diminish a person's ability to perform activities of daily living (Maki et al. 1991). Hip fracture
due to fall accidents amounts to more than 10 % of bed-bound status of the elderly in Japan.