Two-dimensional dynamic walking stability of elderly females with a history of falls.

Injuries related with falls are a major health risk for the elderly. Accurate evaluation of the dynamic walking stability of elderly people is the key to fall prevention. A two-dimensional (2-D) model is proposed in this study given that the custom method is mainly focused on the dynamic walking stability along the antero-posterior axis. An inverted pendulum model was utilised to calculate the region of stability at toe-off, and stability conditions were evaluated first along the antero-posterior and medio-lateral axes. The analysis was then extended to the 2-D plane. In the 2-D case, the region of stability was determined based on the use of the information of the envelope of the foot. Twenty-four female participants, categorised as healthy young, healthy elderly, and elderly with a history of falls, were examined. Significant differences among the three groups were demonstrated with the 2-D analysis method, but not in the antero-posterior or medio-lateral analyses. The centre-of-masses of elderly fallers were significantly closer to the foot-supporting boundary compared with that of healthy young and elderly adults at toe-off. A 2-D analysis method using the envelope-of-foot could evaluate the dynamic stability of elderly females based on a more accurate scale.