Assessment of walking stability by Lyapunov exponent estimation

This paper presents a unique technique to estimate walking stability utilizing a small and light-weight portable instrument. Lyapunov exponent estimation, a method of nonlinear time series analysis, was applied to quantify the dynamic stability of body sway during walking as measured by accelerometry. Fourteen young and twenty-one elderly subjects participated this study. Lyapunov exponent of the elderly subjects tended to be higher suggesting lower stability as compared to the younger subjects. Moreover, the elderly subjects suffering knee pain or frequent history of fall presented higher value as compared to those having exercise habit. The results suggest that Lyapunov exponent estimation of walking stability is useful to assess locomotive ability.