Analysis of Skip Motion as a Recovery Strategy after an Induced Trip

Abstract

Falls are one of the main causes of decreased quality of life and activities of daily living among the elderly individuals. Because tripping is the most common cause of falls, some types of recovery motions have been reported after tripping induced by a flat plate or block. Common recovery strategies observed under these conditions included elevating and lowering strategies. Especially, in case that the swinging leg contacts an obstacle at its early phase, the elevating strategy has been considered as a typical recovery motion. In this study, we performed a tripping experiment using a crossbar in the early and middle of swing phase. As a result, a new recovery strategy, which differed from those previously reported, was observed. In the new strategy, referred to as the skip strategy, the subjects lifted and moved the standing leg forward after tripping. The subjects utilized this strategy to recover from an early phase trip. The participants had to exert enough knee flexion and ankle plantar flexion torques of recovery leg with the skip strategy and enough knee extension, hip extension, and ankle plantar flexion torques of recovery leg with the lowering strategy. Especially for the elderly who cannot perform large joint torques, gait assistant devices such as physical assistant robots are required to compensate such joint torques in order to perform these recovery motions.

Fall Inducing Movable Platform (FIMP) for Overground Trips and Slips

“…Common across them was the stiffening of the perturbed leg while the recovery leg attempted to lower itself to impose a flat-foot configuration. Overall, FIMP has proven to be capable of inducing ecologically valid overground walking gait and falls similar to those reported in the literature [6,7,9,38,39,8].…”

“…The contralateral leg transitions to the swing phase before the perturbed leg has touchdown [8], unlike in the lowering strategy where the contralateral switches phase only after the touchdown of the perturbed leg [6]. The rapid transition from stance to swing in the skipping strategy is shown in events (c) through (e) in Fig.…”

“…An elevating strategy is utilised when the swing leg encounters an easy to overcome perturbation during the early to mid-swing gait phase [6,7]. If the obstacle or perturbation is sufficiently large, a skipping strategy is utilised [8]. This is due to the perturbed leg being arrested from forward mo-tion, requiring the contralateral leg to skip forward to reinstate a suitable base of support and regain stability.…”

Fall Inducing Movable Platform (FIMP) for Overground Trips and Slips

“…This difference is likely attributed to the duration of the brake activation duration. This phenomenon has previously been reported but with the use of a different fall inducing method [31]. Since the current experiment arrested the ankle for 250 ms, the duration for fall recovery has already been expended by more than half.…”

“…For trips, an elevating strategy is used when an easy to overcome external perturbation occurs at the early to mid-swing gait phase [12,30]. When the obstacle or perturbation becomes large enough, a skipping strategy is utilised [31]. This is due to the perturbed leg being arrested from moving forward by the perturbation.…”