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Biomechanics

Biomechanics - Poster Session C

Poster D6 - Gaze Strategies During Standard and Novel Assessments of Walking

Friday, October 25, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Mobility outside the home is known to decline with age [1]. When mobility impairments restrict individuals from navigating their natural environment and performing daily-life activities, it is referred to as a mobility disability [2]. Rehabilitation and physical therapy are commonly used methods to improve mobility. However, mobility and navigation in laboratory environments may not be representative of how people naturally move in daily life. Navigating an environment requires coordination of gaze behavior and body motion [3]. Specifically, visual information is necessary for planning routes and avoiding obstacles [4]. Domiquez-Zamora et al. reported that older adults use different gaze strategies and had greater difficulty navigating obstacles than younger adults [3]. Evaluation of gaze strategies may reveal information about navigation performance during mobility tasks. The goal of this study is to relate standard laboratory assessments of mobility to novel assessments in a more ecologically valid environment (an outdoor garden). Here, preliminary analysis of gaze data during standard (laboratory) and novel (garden) mobility tasks are presented.

Materials and

Methods:  Ten individuals, without any visual impairments, (N=10, 3 males) ages 55 and above (mean±s.d. 63.0±6.24 years) participated. Subjects performed a variety of balance and gait assessments, including a 2-minute walk in a laboratory environment (Lab-2minWalk), a 2-minute walk in in a garden setting (Gard-2minWalk) and multi-terrain path (garden only). For the 2-minute walk, subjects walked counterclockwise laps (~15ft long) at their comfortable walking pace. For the multi-terrain walk, subjects walked a path of consecutive different terrains, including concrete, gravel, turf, stone, ramps up and down, and stairs down, each of equal distance (~35ft) (Figure 1). Raw gaze data was recorded using Tobii Pro Glasses 3 eye-tracking glasses (50 Hz sample rate) and filtered using Tobii Pro I-VT (Attention) filter (Tobii Pro Lab (Tobii AB, Danderyd, Sweden)). Trials were divided into intervals of straights and turns. For brevity purposes, only straight intervals with no change in elevation (i.e., no stairs/ramps) are considered here. Gaze fixations were manually mapped to custom Areas of Interest (AOIs) using Tobii Pro Lab. AOIs were defined as: directly below, path ahead, path far, forward, side, side forward, and at an object. Objects include computers, chairs, outlets, research personnel, etc. inside and planters, sculptures, railings, research personnel, etc. outside. Total duration, average duration, and percent of total number of fixations were computed for each interval . Here, only qualitative analysis is presented due to reduced sample size.

Results, Conclusions, and Discussions: 

Results: While statistical analyses were not conducted, general patterns were evident. For example, Gard-2minWalk had similar or greater average duration of fixations compared to Lab-2minWalk for all AOIs (Figure 2). Lab-2minWalk and Gard-2minWalk showed similar distributions in percent number of fixations, with path ahead having the greatest percentage followed by path far or object. Lab-2minWalk generally had a greater percentage of forward fixations but less side forward fixations than Gard-2minWalk. Both Lab-2minWalk and Gard-2minWalk intervals averaged less than 2% of fixations for directly below and side.
For the multi-terrain walk, the average duration of fixations for each AOI varied across each terrain, with each terrain having maximum and minimum average durations in different AOIs (Figure 2). Percent number of fixations for the multi-terrain walk had similar distributions to the two-minute walks, with each terrain having the highest average percentage of fixations for path ahead, followed by path far or object. Terrains with lower percentage of path ahead fixations had greater percents of fixations in other AOIs, comparatively. Specifically, turf had the greatest percentage of object fixations, and concrete had higher percentage of path far, forward, and side forward fixations, than other terrains.

Conclusions: Gaze strategies during mobility tasks appear to be affected by the type of terrain and type of environment. Novel mobility assessments in a more ecologically valid environment (outdoor garden) reveal different gaze strategies than standard assessments (indoor laboratory) in healthy older adults.

Discussion: One notable finding is that average duration of fixations in the forward AOI appear to be larger on flat, even surface (concrete, indoor tile) compared to uneven terrain (gravel, stone, turf). This may be indicative of differences in cognitive load required for walking on different surfaces. Specifically, navigating uneven terrain requires continuous cognitive load that is not essential when walking on flat, even surfaces [5].
This pilot study is on-going and will also include older adults with vision loss. Gaze strategies will then be compared both within subjects and across groups. These results will be used to improve the ecological validity of standard rehabilitation and physical therapy interventions, specifically for the low vision population.

Acknowledgements (Optional):  

References: [1] Suri A. et al. (2021). Mobility of Older Adults: Gait Quality Measures are associated with Life-Space Assessment Scores. The journals of gerontology. Series A, Biological sciences and medical sciences. [2] Patla A.E. et al. (1999). Dimensions of Mobility: Defining the Complexity and Difficulty Associated with Community Mobility. Journal of Aging and Physical Activity, 7, 7-19. [3] Domínguez-Zamora, F. J. et al. (2020). Age-related changes in gaze sampling strategies during obstacle navigation. Gait & posture, 76, 252–258. [4] Hamid, S. N. et al. (2010). Gaze patterns in navigation: encoding information in large-scale environments. Journal of vision, 10(12), 28. [5] Liu C. et al. (2023). Electrical Brain Activity during Human Walking with Parametric Variations in Terrain Unevenness and Walking Speed. bioRxiv: the preprint server for biology, 2023.07.31.551289.