Age-related changes in avoidance strategies when negotiating single and multiple obstacles

Abstract

The aim of this research was to describe age-related changes in locomotor adjustments during obstructed gait and expand and build from the current body of literature describing single obstacle avoidance strategies by including trials in which the subjects stepped over two identical obstacles placed in series. We observed young adults (YA: N = 8; aged 23.1 +/- 2.0 years) and older adults (OA: N = 8; aged 76.1 +/- 4.3 years) as they walked along a 5 m long instrumented pathway (GAITRite) and stepped over one or two obstacles that were scaled to their lower leg length. Infrared markers, tracked using the Optotrak motion analysis system (60 Hz; Northern Digital Inc, Canada), were fixed to subjects' trunk and feet, and several anatomical landmarks were digitized for each segment (e.g. toes). Data analyses included lead and trail toe clearance values, take-off and landing distance, step time, length, width and velocity, and three-dimensional trunk angles. Both age groups were able to successfully complete the obstacle avoidance task, and the presence of a second obstacle did not affect clearance strategies of either OA or YA. OA crossed the obstacles with a reduced step velocity and stepped closer to the trailing edge, although take-off distances were not different between the age groups. Additionally, OA used similar ranges of trunk motion as YA when crossing the obstacle, but did so while using smaller step lengths and step widths compared to YA, effectively, using a narrower base of support. Together, these findings suggest that older adults adopted a more cautious crossing strategy in that they reduced their crossing step velocity. However, other aspects of the avoidance strategy used by the older adults, specifically the shortened landing distances and the use of similar ranges of trunk motion within a narrowed BOS, could potentially put them at risk for tripping or imbalance when stepping over an obstacle.

Obstacle crossing deficits in older adults: A systematic review

“…Of the 13 studies that reported spatiotemporal data, five reported no difference in spatiotemporal variables between young and older adults [17,[22][23][24][25]. In the eight that reported differences, older adults walked slower during obstacle crossing [13,14,15,20,21,26], with smaller steps [13,14,18,21]. Older adults landed closer to the obstacle with their lead limb after crossing in three studies [14,21] however, only a significant difference between older and younger females was reported in the study by Chen et al [20].…”

“…In the eight that reported differences, older adults walked slower during obstacle crossing [13,14,15,20,21,26], with smaller steps [13,14,18,21]. Older adults landed closer to the obstacle with their lead limb after crossing in three studies [14,21] however, only a significant difference between older and younger females was reported in the study by Chen et al [20]. In contrast, Lu et al [16] reported that older adults placed their foot closer to the obstacle prior to crossing and landed further from the obstacle after crossing.…”

“…Both Chen et al [20] and Lowrey et al [21] reported that Hahn and Chou [24] No obstacle contacts occurred No --Hahn et al [25] No obstacle contacts occurred No --Lowrey et al [21] One older adult and one YA contacted the second obstacle in the two-obstacle condition lead limb toe clearance was unaffected by age. Lu et al [16] however, reported an interaction of lead limb toe clearance with age and obstacle height, whereby older adults increased their toe clearance with increasing obstacle height and younger adults did not.…”

“…No obstacle contacts occurred for either age group in four of these studies. In the two investigations that obstacle contacts occurred, Chen et al [20] reported four older adults hit the obstacle and both an older and young adult contacted the second of two obstacles in a study by Lowrey et al [21]. Several obstacle crossing studies that were reviewed did not state whether any obstacle contact events occurred during testing.…”

Computational Streetscapes

“…Aspects of the weighting that occurs in estimating collision potential involves spacing and timing of movement [371], and the affordances that individual people associate with the things that they see around them [20], including the information conveyed by gait and body language [372]. Much of this information is inaccurate in human sensing, however, as are people's estimates of the relative influence of conflicting factors [240], and inaccuracies may grow more cumbersome as we age [373,374], or when we encounter things that are unfamiliar [375,376]. Visual information is also often highly dependent upon the state and position of the person doing the looking, and in this regard gaze has been shown to be of particular importance [238,371,377]; indeed, this component of vision is now readily testable using eye tracking technology and has therefore received considerable attention [9].…”