Mechanical model of the recovery from stumbling

Abstract

Several strategies have been described as a reaction to a stumble during gait. The elevating strategy, which tries to proceed with the perturbed step, was executed as a response to a perturbation during early swing. The lowering strategy, bringing the perturbed leg to the ground and overtaking the obstacle with the contralateral limb, was executed more frequently when the perturbation appeared at mid or late swing. The goal of this paper is to analyze which mechanical factors determine the most advantageous strategy. In order to determine these factors, a mechanical model of the recovery was developed and used to analyze a series of perturbation experiments. It was assumed that the goal of the recovery reaction was to control the trunk as an inverted pendulum during the double-stance phase. In order to be able to control the trunk angle, one foot should be up front and one foot should be behind the hips; otherwise it would be impossible to generate the required trunk torques. The trunk dynamics were expressed in terms of the ground reaction forces and their application point. A larger step (elevation strategy) gives the opportunity to dissolve the perturbation in one step. A small step (lowering strategy) necessarily results in a second quick step, after which the perturbation energy can be dissipated in the second double-stance phase. If a recovery step is too slow, it becomes impossible to counteract the forward flexion of the trunk. It is suggested that a measure of the ability to recover from a stumble could be based on the ability to perform quick steps.

The impact of a systematic reduction in shoe–floor friction on heel contact walking kinematics—A gait simulation approach

“…Although dynamic models have been used in a wide range of gait and neuro-rehabilitation research applications, there have been very few reports on the use of forward dynamic simulations in investigations of postural reactions generated in response to external perturbations during walking (Yang et al, 2008;Cordero et al, 2004;van den Bogert et al, 2002;Zhou et al, 2002). Modeling investigations described in these studies demonstrate how such an approach can play an important role in focusing therapeutic interventions on factors that contribute to an increased chance of recovering from external perturbations.…”

Simulating balance recovery responses to trips based on biomechanical principles

“…Regarding the swing ankle joint, a tibialis anterior burst can often be observed about 75 msec after the collision and acts for ankle dorsiflexion. After the push-off reaction, a flight phase [PBvD04] or a double sup- port phase [CKvdH04,CKvdH05] might occur followed by touchdown on the ground with the tripped leg.…”

Detecting stumbles with a single accelerometer

“…For example, it was established that there are two general strategies of recovery from stumbling: elevating and lowering. The elevating strategy occurs as a response to a perturbation during the early swing phase of gait, whereas the lowering strategy occurs during the late swing phase of gait [17] [4]. It was established that one's ability to perform such recovery methods after a stumble could be determined by one's ability to perform quick steps [4].…”