Chaotic Characteristics of Joint Motions during Normal Gait

S.-M. Ye, K. Son, J.-H. Park, and K.-W. Seo (Korea)


Chaotic characteristics, Joint motions, Lyapunov exponent, Normal gait, Time series analysis


The purpose of this study is to investigate chaotic characteristics of joint motions during the level walking. The chaos analysis was used to quantify nonlinear motions of eleven human joints. The joints analyzed were the neck and the right and left shoulders, elbows, hip joints, knees and ankles. Gait experiments were carried out by a total of twenty subjects: ten males and ten females. Each was asked to walk on a treadmill with his/her natural speed. Eight video cameras were used to capture flexion-extension angles of the joints. In order to evaluate joint characteristics the Lyapunov exponent was calculated from a state space created by time series and embedding dimensions. The maximal Lyapunov exponent had the smallest mean value at the neck both for both male and female. The mean values of the maximal exponents ranged from 1.183 to 1.959 for the upper extremities and from 0.585 to 1.722 for the lower extremities. The results obtained can be used to establish a database on the normal gait and to estimate joint stability for diagnostic purposes.

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