Effects of aging and dual tasking on step adjustments to perturbations in visually cued walking.

Masood Mazaheri,Melvyn Roerdink,Zrinka Potocanac,Jacques Duysens,Peter J Beek,Wouter Hoogkamer,C E Peper,Sabine Verschueren

doi:10.1007/s00221-015-4407-5

Masood Mazaheri, Melvyn Roerdink + Show 6 more

Open Access

https://doi.org/10.1007/s00221-015-4407-5

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Abstract

Making step adjustments is an essential component of walking. However, the ability to make step adjustments may be compromised when the walker’s attentional capacity is limited. This study compared the effects of aging and dual tasking on step adjustments in response to stepping-target perturbations during visually cued treadmill walking. Fifteen older adults (69.4 ± 5.0 years; mean ± SD) and fifteen young adults (25.4 ± 3.0 years) walked at a speed of 3 km/h on a treadmill. Both groups performed visually cued step adjustments in response to unpredictable shifts of projected stepping targets in forward (FW), backward (BW) or sideward (SW) directions, at different levels of task difficulty [which increased as the available response distance (ARD) decreased], and with and without dual tasking (auditory Stroop task). In both groups, step adjustments were smaller than required. For FW and BW shifts, older adults undershot more under dual-task conditions. For these shifts, ARD affected the age groups differentially. For SW shifts, larger errors were found for older adults, dual tasking and the most difficult ARD. Stroop task performance did not differ between groups in all conditions. Older adults have more difficulty than young adults to make corrective step adjustments while walking, especially under dual-tasking conditions. Furthermore, they seemed to prioritize the cognitive task over the step adjustment task, a strategy that may pose aging populations at a greater fall risk. For comparable task difficulty, the older adults performed considerably worse than the young adults, indicating a decreased ability to adjust steps under time pressure.

Highlights

The study of mechanisms behind the occurrence of falls in elderly has recently received a lot of attention
Step adjustments were elicited by means of sudden positional shifts of stepping targets during visually cued treadmill walking
Both age groups could perform this task successfully, the step adjustments were smaller than the actual target shifts

Summary

Introduction

The study of mechanisms behind the occurrence of falls in elderly has recently received a lot of attention. In an observational study, based on video footage of real-life falls, it has been shown that the most frequent cause of falling (accounting for 41 % of falls) is an incorrect shift in body weight (including, for instance, misplaced steps during walking; Robinovitch et al 2013) This finding highlights the importance of assessing behaviors like step adjustments during walking, which are highly dependent on weight shift strategies. Step adjustments to sudden shifts in stepping targets have been studied extensively in relation to step initiation from standstill situations (Melzer and Oddsson 2004; Reynolds and Day 2005; Tseng et al 2009; Melzer et al 2010; Kim and Brunt 2013) This complex behavior requires two integrated motor skills: control of foot trajectory and control of balance (Reynolds and Day 2005; Tseng et al 2009). Healthy young adults have shown fast and accurate step adjustments to unpredictable stepping-target

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