Evidence that older adult fallers prioritise the planning of future stepping actions over the accurate execution of ongoing steps during complex locomotor tasks

Previous research has highlighted differences between older adults determined to be at a low-risk of falling (low-risk) and older adults prone to falling (high-risk) in both where and when they look at stepping targets and the precision with which they subsequently step. On the basis of these findings, we proposed that high-risk older adults prioritise the planning of future stepping actions over the accurate execution of ongoing movements and that adoption of this strategy contributes to increased likelihood of falls. The present experiment was designed to test this hypothesis by manipulating the complexity of the required walking conditions and comparing gaze and stepping performance between young, high-risk and low-risk older adults. Participants walked at a self-selected pace along a 7-m pathway and encountered one of three obstacle conditions: (1) a single stepping target, (2) two stepping targets, (3) two stepping targets separated by a raised obstacle. On average, when there was a single target (Target 1) in the travel path, all groups fixated the target until after heel contact. However, when challenged with additional impending stepping constraints, high-risk older adults transferred their gaze significantly sooner from Target 1 prior to heel contact. On average, low-risk older adults and younger adults maintained gaze on Target 1 until after heel contact, irrespective of future constraints. Premature gaze transfer was associated with decline in stepping accuracy and precision. Our findings suggest that high-risk older adults choose a potentially hazardous gaze strategy when challenged with multiple obstacles. Putative mechanisms underlying this behaviour are discussed. (C) 2006 Elsevier B.V. All rights reserved.