Open Access Postural Control in a Fall Risk Situation in the Elderly: Stepping Over an Obstacle Under Dual-Task Conditions

Abstract: Avoiding and negotiating obstacles is a common cause of falling in the elderly. There is also evidence that walking under dual-task conditions, which requires a high level of attention, is associated with an elevated risk of falls in older adults. To better understand the role of dual-tasking in the disturbance of postural control when subjects are faced with obstacles, we used a simple quantification method to assess postural control after obstacle clearance. Sixty healthy elderly volunteers (aged 66-85 years) were tested for their postural stabilization on a force platform under the five follow-ing conditions: i) simple walking, ii) walking and stepping over an obstacle, and iii to v) walking and stepping over the obstacle under dual or triple-task conditions, the secondary task being either motor or cognitive for the dual-task and a combination of both for the triple-task. Postural control was assessed by determining both the distance covered by the cen-ter of pressure (COP) and the root-mean-square of the medio-lateral COP displacement. Only the latter differed signifi-cantly between walking conditions. In the “walking plus stepping ” conditions, the motor and cognitive secondary tasks led to opposite effects, the motor task perturbed whereas the cognitive task improved postural control. These findings highlight the adverse effects of performing a secondary motor task while walking under challenging conditions, and con-firm the appropriate prioritization of postural control over a cognitive task in cognitively unimpaired older subjects. Thes