Falls due to locomotive impairment cause a serious hazard to elderly people. Impaired mobility due to injuries or a fear of falling can diminish a person's ability to perform activities of daily living. Aging effects on the sensory feedback has been hypothesized to be a key factor in adjusting posture to maintain balance against unpredictable external or internal irregularities during walking. Conventionally, clinicians perform posture balance assessments using subjective or quantitative testing, which are mostly focused on quantifying regional amount of kinetic parameters, i.e. region of body sway, variability or geometrical characteristics of motion. However, a measure of variability does not correspond to the sensitivity of the neuromuscular control. This study addresses a quantitative evaluation of personal locomotive ability in terms of stability employing onlinear dynamical analysis. Main objective of this study is to present a reliable technique to assess dynamic stability of walking utilizing a portable accelerometer. Straight level walking of young and elderly subjects was investigated in the experimental study. Elderly subjects generally tended to exhibit higher value suggesting they were less dynamically stable. Significant individual variations were also observed among the elderly subjects, which in part could be explained by their physical conditions. Subjects with higher value were suffering knee pain or had histories of leg fracture, while the subjects with lower value had frequent exercise habit in daily life. Similar tendencies were also found with other direction of acceleration, but not as remarkable as with lateral direction. The experimental results suggested that the present technique might be useful in estimating walking stability and personal risk of falls. This method is easily applicable and reliable in daily living environments and situations. Further application of the present technique may help predicting personal risk of falls.

DESCENTE SPORTS SCIENCE Vol.24/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE