Age-related changes in gait adaptability in response to unpredictable obstacles and stepping targets

Highlights

• Novel test paradigm incorporating precision steps and obstacle avoidance.

• Compared to young, older adults adopt a conservative gait adaptability strategy.

• Older adults also make less accurate steps and make more stepping errors.

• Older adults are affected by the possibility of a hazard appearing on the pathway.

• Poor gait adaptability might contribute to falls in older people.

Abstract

Background

A large proportion of falls in older people occur when walking. Limitations in gait adaptability might contribute to tripping; a frequently reported cause of falls in this group.

Objective

To evaluate age-related changes in gait adaptability in response to obstacles or stepping targets presented at short notice, i.e.: approximately two steps ahead.

Methods

Fifty older adults (aged 74 ± 7 years; 34 females) and 21 young adults (aged 26 ± 4 years; 12 females) completed 3 usual gait speed (baseline) trials. They then completed the following randomly presented gait adaptability trials: obstacle avoidance, short stepping target, long stepping target and no target/obstacle (3 trials of each).

Results

Compared with the young, the older adults slowed significantly in no target/obstacle trials compared with the baseline trials. They took more steps and spent more time in double support while approaching the obstacle and stepping targets, demonstrated poorer stepping accuracy and made more stepping errors (failed to hit the stepping targets/avoid the obstacle). The older adults also reduced velocity of the two preceding steps and shortened the previous step in the long stepping target condition and in the obstacle avoidance condition.

Conclusion

Compared with their younger counterparts, the older adults exhibited a more conservative adaptation strategy characterised by slow, short and multiple steps with longer time in double support. Even so, they demonstrated poorer stepping accuracy and made more stepping errors. This reduced gait adaptability may place older adults at increased risk of falling when negotiating unexpected hazards.

Introduction

The ability to adjust gait is crucial when performing daily living activities such as crossing a busy street or avoiding obstacles. In older age, limited sensorimotor and cognitive functions [1] may lead to poor gait adaptability which might contribute to tripping; a frequently reported cause of falls in this group [2].

Obstacle negotiation tests have previously been used to measure gait adaptability performance. Compared with young, older adults initiate adjustments in step length and step time one or two steps earlier when approaching a fixed obstacle [3] and display shorter step lengths, slower gait speed and smaller obstacle-heel distance when crossing an obstacle [4]. In addition, gait protocols involving the sudden-appearance of an obstacle on a treadmill reveal that older adults have longer avoidance reaction times, larger toe clearances [5] and lower obstacle avoidance success rates compared with young adults [5], [6]. Adaptive gait experiments have also found that compared with young, older adults were less accurate when stepping on targets [7] and made slower stepping adjustments to visual target moving to unpredictable locations [8].

More recent research has used stepping paradigms including an inhibitory component [6], [9], [10] that may reflect the cognitive load challenges required for walking in many daily life situations. Yamada et al. [10] used an overground multi-target stepping task which required participants to step on squares with an assigned colour while avoiding other coloured squares and demonstrated that stepping failures were associated with an increased risk of falling. However, the target panels were present at all times so participants were able to pre-plan their stepping trajectories. This limits the ability to draw conclusions about an individual's ability to adapt gait in response to changes in the pathway. Response inhibition has also been incorporated in a treadmill stepping test [6], [9] requiring precision steps and avoidance of obstacles. This research showed that shorter available response time contributes to increased stepping failures [9] with the largest failure rates occurring when participants had to perform a secondary inhibitory task [6]. Although these studies provide good insights into adaptive gait failures, no studies have investigated gait adaptation strategies during an over-ground walking task combining both precision steps and obstacle avoidance.

We, therefore, devised an overground walking task that assessed the ability to adapt gait in response to obstacles and targets appearing on the walkway two steps ahead of the individual. Walk-through trials in which no stimulus appeared (catch trials) were included as a way to estimate the extent of the effects of expectation of a gait perturbation. Our aim was to compare the gait adaptability strategies of young and older adults when performing this task. We hypothesised that compared with young, older adults would (a) make more mistakes and demonstrate lower accuracy in negotiating the targets/obstacle, and/or (b) use a more cautious/conservative strategy when approaching the targets/obstacle.