Age-related kinematic changes in late visual-cueing during obstacle circumvention

Effects of direction cue time and walking speed on spatial-temporal gait adaptations in healthy older and young adults upon approach of turns

BACKGROUND

Hurrying and turning are each associated with falls in older adults. Losing balance sideways when turning increases the likelihood of hip fracture. Yet 99 % of failures when turning unexpectedly have been traced to an inability to curb forward momentum regardless of age.

RESEARCH QUESTION

Do age-based differences exist in spatial-temporal gait adaptations related to medial-lateral (M-L) balance and posterior-anterior (P-A) propulsion upon approach of turns relative to continuing straight, across walking speeds and whether direction is known in advance?

METHODS

Healthy young (n=10) and older adults (n = 10) walked at preferred and fast test speeds while randomly cued for direction either early upon initiating gait or late 1-2 steps before entering a spatially defined turning area. An instrumented 4.6 m carpet recorded spatial-temporal changes up to the penultimate footfall prior to turning 900 or continuing straight.

RESULTS

When approaching the turning zone across interactions of walking test speed, cue time and direction, other than stride-length being shorter in older adults, both age-groups showed similar adjustments in gait speed and stride-length in managing P-A deceleration perturbations, and similar adaptations in right and left heel-to-heel base of support (BOS) in managing M-L balance destabilizing forces. A three-way interaction (p<.027) suggests a similar foot strategy of BOS narrowing may be used approaching turns relative to straight walks when direction is cued early walking fast (p<.020) and late walking preferred speed (p<.014).

SIGNIFICANCE

The findings were interpreted within the context of regulating center of mass acceleration and processing environmental regulatory conditions to maintain a personal space safety margin. The study supports that in otherwise healthy older adults, gait training for turns include practice to not only manage perturbations which accelerate the body sideways but also those which decelerate forward progression.

Relationship between adaptability during turning and the complexity of walking before turning in older adults

In this study, the relationship between behavioral complexity (sample entropy, SEn) during steady walking and the quickness of subsequent turning performance in older adults. Herein, healthy older and younger adults (n = 12 each) were instructed to walk straight and then turn into an intersection surrounded by four pylons. This walking task was performed under two turning conditions: reactive and pre-planned turning, where the direction of turning was unknown until immediately before turning or was informed beforehand, respectively. For older adults, behavioral complexity was comparable under both conditions, but was higher under reactive than pre-planned turning condition for younger adults. This suggests that older adults cannot adapt their walking patterns in response to turning conditions. Correlation analysis showed that older adults with lower SEn had more difficulty in turning rapidly under reactive turning condition, indicating a relationship between the two variables. Thus, deterioration of the reactive turning performance in older adults is related to stereotyped movements during steady walking.

Effects of age on the visuo-locomotor control used to circumvent a virtual pedestrian with different limb movements

It is known that young adults (YA) circumvent pedestrians differently than inanimate obstacles and that limb movements of the pedestrian influence minimum clearance for predictable pedestrian paths. Although older adults (OA) use more cautious strategies for general pedestrian avoidance compared to YA, how pedestrian movements influence circumvention by OAs is unknown. The aim of this study was to understand how limb movements of a pedestrian with an initially unpredictable trajectory affect circumvention control in younger vs older healthy adults. Fourteen YA and 14 OA (> 70 years) were immersed in a virtual shopping mall and instructed to circumvent a virtual pedestrian (VP) approaching with either normal locomotor movements, upper limbs fixed, lower limbs fixed, or both upper and lower limbs fixed. Onset distance for trajectory deviation, minimum clearance, walking speed, body segment yaw angles and gaze behaviour were analysed. When the VP lacked local limb movements, both age groups initiated their trajectory deviations farther away, but significantly more so for OA. Minimal clearance was unchanged across conditions and similar for both age groups. OA walked slower, produced smaller head and trunk yaw, and visually focused on the VP for a greater percentage of time. Thus, lack of limb movements of another pedestrian resulted in more cautious circumvention control and OA needed more time to process visual information with greater visual attention focused on the VP. Age-related changes could translate to a greater risk of falls in OA populations with reduced balance and mobility that could limit community ambulation.

The Effect of Human Settlement Pedestrian Environment on Gait of Older People: An Umbrella Review

Older people are limited by the pedestrian environment in human settlements and are prone to travel difficulties, falls, and stumbles. Furthermore, we still lack systematic knowledge of the pedestrian environment affecting the gait of older people. The purpose of this review is to synthesize current evidence of effective human settlement pedestrian environments interfering with gait in older people. The systematic effects of the human settlement pedestrian environment on gait in older people are discussed. Databases such as Web of Science, Medline (via PubMed), Scopus, and Embase were searched for relevant studies up to June 2022. The literature was screened to extract relevant evidence from the included literature, assess the quality of the evidence, and analyze the systematic effects of the pedestrian environment on gait in older people. From the 4297 studies identified in the initial search, 11 systematic reviews or meta-analysis studies were screened, from which 18 environmental factors and 60 gait changes were extracted. After removing duplicate elements and merging synonymous features, a total of 53 relationships between environmental factors and gait change in older people were extracted: the main human settlement pedestrian environmental factors affecting gait change in older people in existing studies were indoor and outdoor stairs/steps, uneven and irregular ground, obstacles, walking path turns, vibration interventions, mechanical perturbation during gait, and auditory sound cues. Under the influence of these factors, older people may experience changes in the degree of cautiousness and conservatism of gait and stability, and their body posture performance and control, and muscle activation may also be affected. Factors such as ground texture or material, mechanical perturbations during gait, and vibration interventions stimulate older people's understanding and perception of their environment, but there is controversy over the results of specific gait parameters. The results support that human settlements' pedestrian environment affects the gait changes of older people in a positive or negative way. This review may likely contribute evidence-based information to aid communication among practitioners in public health, healthcare, and environmental construction. The above findings are expected to provide useful preference for associated interdisciplinary researchers to understand the interactions among pedestrian environments, human behavior, and physiological characteristics.

Effects of Enriched Physical Activity Environments on Balance and Fall Prevention in Older Adults: A Scoping Review

The incidence of falling, due to aging, is related to both personal and environmental factors. There is a clear need to understand the nature of the major risk factors and design features of a safe and navigable living environment for potential fallers. The aim of this scoping review was to identify studies that have examined the effectiveness of environments, which promote physical activity and have an impact on falls prevention. Selected studies were identified and categorized into four main topics: built environment, environment modifications, enriched environments, and task constraints. The results of this analysis showed that there are a limited number of studies aiming to enhance dynamic postural stability and fall prevention through designing more functional environments. This scoping review study suggests that the design of interventions and the evaluation of an environment to support fall prevention are topics for future research.

Age-related changes in gaze sampling strategies during obstacle navigation

BACKGROUND

Appropriate coordination of gaze behavior and body motion is essential for navigating cluttered environments. This is often complicated by having to contend with a concurrent secondary task, like engaging in a conversation or looking for relevant landmarks. However, there is little evidence of how aging and multitasking affects how gaze is deployed during obstacle navigation to guide our movements.

RESEARCH QUESTION

How do gaze patterns differ between young and older adults when navigating around a series of obstacles under dual-task conditions?

METHODS

17 young adults and 17 older adults navigated around vertically-oriented obstacles in isolation (i.e., single-task condition) and while engaging in a concurrent backward-counting or visual search task (i.e., dual-task conditions). In the visual search condition, participants had to identify the location of an object (i.e., a black shape on a tile) along the perimeter of the pathway, simulating a landmark. We quantified the spatial-temporal pattern of gaze to obstacles relative to body position, as well as the frequency and duration of gaze fixations to obstacles, route-planning features, and landmarks.

RESULTS

We found that older adults transferred gaze away from obstacles earlier and contacted obstacles more frequently than young adults. However, the proportion of fixation number and duration to obstacles did not differ between groups in any condition. In addition, older adults had to allocate gaze to landmarks to a greater extent in the visual search condition-at the expense of fixating route-planning areas-to maintain similar search performance in the dual-task condition compared to the single-task condition.

SIGNIFICANCE

Older adults use different gaze strategies and have greater difficulty under dual-tasking conditions than young adults when navigating around a series of obstacles. We suggest that deficits in visual working memory and/or divided attention may explain these results.

Gaze and motor behavior of people with PD during obstacle circumvention

The aim of this study was to analyze the motor and visual strategies used when walking around (circumvention) an obstacle in patients with Parkinson's disease (PD), in addition to the effects of dopaminergic medication on these strategies. To answer the study question, people with PD (15) and neurologically healthy individuals (15 - CG) performed the task of obstacle circumvention during walking (5 trials of unobstructed walking and obstacle circumvention). The following parameters were analyzed: body clearance (longer mediolateral distance during obstacle circumvention of the center of mass -CoM- to the obstacle), horizontal distance (distance of the CoM at the beginning of obstacle circumvention to the obstacle), circumvention strategy ("lead-out" or "lead-in" strategy), spatial-temporal of each step, and number of fixations, the mean duration of the fixations and time of fixations according to areas of interest. In addition, the variability of each parameter was calculated. The results indicated that people with PD and the CG presented similar obstacle circumvention strategies (no differences between groups for body clearance, horizontal distance to obstacle, or obstacle circumvention strategy), but the groups used different adjustments to perform these strategies (people with PD performed adjustments during both the approach and circumvention steps and presented greater visual dependence on the obstacle; the CG adjusted only the final step before obstacle circumvention). Moreover, without dopaminergic medication, people with PD reduced body clearance and increased the use of a "lead-out" strategy, variability in spatial-temporal parameters, and dependency on obstacle information, increasing the risk of contact with the obstacle during circumvention.

Locomotor circumvention strategies are altered by stroke: II. Postural Coordination

Background

Locomotor strategies for obstacle circumvention require appropriate postural coordination that depends on sensorimotor integration within the central nervous system. It is not known how these strategies are affected by a stroke. The objective of this study was to contrast postural coordination strategies used for obstacle circumvention between post-stroke participants (n = 12) and healthy controls (n = 12).

Methods

Participants walked towards a target in a virtual environment (11 × 8 m room) with cylindrical obstacles that were stationary or approaching from head-on, or diagonally 30° left/right.

Results

Two stepping strategies for obstacle circumvention were identified: 1) side step: increase in step width by the foot ipsilateral to the side of circumvention; 2) cross step: decrease in step width by the foot contralateral to the side of circumvention. The side step strategy was favoured by post-stroke individuals in circumventing stationary and head-on approaching obstacles. In circumventing diagonally approaching obstacles, healthy controls generally veered opposite to obstacle approach (>60% trials), whereas the majority of post-stroke participants (7/12) veered to the same side of obstacle approach (V_same). Post-stroke participants who veered to the opposite side (V_opp, 5/12) were more independent and faster ambulators who favoured the side step strategy in circumventing obstacles approaching from the paretic side and cross step strategy for obstacles approaching from the non-paretic side. V_same participants generally favoured the side step strategy for both diagonal approaches. Segmental rotation amplitudes and latencies were largest in the V_same group, and significantly greater in post-stroke participants than controls for all obstacle conditions. All participants initiated circumvention with the feet followed by the pelvis and thorax, demonstrating a caudal-rostral sequence of reorientation.

Conclusion

Postural coordination strategies for obstacle circumvention were altered post stroke, depending on the residual or restored functional abilities. Segmental re-orientations are also affected by the motion and direction of obstacle.

Visuo-locomotor control in persons with spinal cord injury in a manual or power wheelchair for direction change and obstacle circumvention

Many individuals, such as persons with spinal cord injury (SCI), rely on wheeled locomotion involving manual (MWC) or power (PWC) wheelchairs to navigate their environments. Yet, visuo-locomotor control underlying WC navigation in experienced users is not well understood. The objective of this study was to compare the visuo-locomotor control between MWC and PWC in individuals with SCI while changing direction and circumventing an obstacle. Participants with SCI using a MWC (n = 12, 38.5 ± 10.7 years) or a PWC (n = 10, 47.8 ± 8.6 years) were asked to maneuver their chair straight ahead, while changing direction 45° to the right, and while circumventing an obstacle to the right, all at self-selected speeds. Speed, minimal clearance, point of deviation, temporal body and WC coordination, relative timing of segment rotations and visual behavior were analyzed. There was no main effect of group for speed, clearance and point of deviation. During direction change, the head always led body and wheelchair reorientation while an "en bloc" strategy was used for circumventing obstacle for both groups. In straight-ahead locomotion, participants predominantly fixed their gaze on the end target. During direction change and obstacle circumvention, participants fixated more on the future path and the obstacle for both WC modes. Overall, specific gaze behavior depended on environmental demands. While MWC and PWC users adopt similar navigational strategies and visuo-locomotor coordination while changing direction and circumventing obstacle, there were some differences in the amount of head rotation that could be related to a counter-movement used more by PWC users.

The effects of object height and visual information on the control of obstacle crossing during locomotion in healthy older adults

In order to safely avoid obstacles, humans must rely on visual information regarding the position and shape of the object obtained in advance. The present study aimed to reveal the duration of obstacle visibility necessary for appropriate visuomotor control during obstacle avoidance in healthy older adults. Participants included 13 healthy young women (mean age: 21.5±1.4years) and 15 healthy older women (mean age: 68.5±3.5years) who were instructed to cross over an obstacle along a pressure-sensitive pathway at a self-selected pace while wearing liquid crystal shutter goggles. Participants were evaluated during three visual occlusion conditions: (i) full visibility, (ii) occlusion at T-1 step (T: time of obstacle crossing), and (iii) occlusion at T-2 steps. Toe clearances of both the lead and trail limb (LTC and TTC) were calculated. LTC in the occlusion at T-2 steps condition was significantly greater than that in other conditions. Furthermore, a significant correlation was observed between LTC and TTC in both groups, regardless of the condition or obstacle height. In the older adult group alone, step width in the occlusion at T-2 steps condition increased relative to that in full visibility conditions. The results of the present study suggest that there is no difference in the characteristics of visuomotor control for appropriate obstacle crossing based on age. However, older adults may exhibit increased dependence on visual information for postural stability; they may also need an increased step width when lacking information regarding their positional relationship to obstacles.

Constraints on perception of information from obstacles during foot clearance in people with chronic stroke

The aim of this study was to examine effects of different types of task constraints on coupling of perception and action in people with chronic stroke when crossing obstacles during a walking task. Ten participants with hemiplegic chronic stroke volunteered to walk over a static obstacle under two distinct task constraints: simple and dual tasks. Under simple task constraints, without specific instructions, participants walked at their preferred speed and crossed over an obstacle. Under dual task constraints, the same individuals were required to subtract numbers whilst walking. Under both distinct task constraints, we examined emergent values of foot distance when clearing a static obstacle in both affected and unaffected legs, measured by a 3D motion tracking system. Principal component analysis was used to quantify task performance, and discriminant analysis was used to compare gait performance between task constraints. Results suggested that patients, regardless of affected body side, demonstrated differences in perception of distance information from the obstacle, which constrained gait differences in initial swing, mid-swing, and crossing phases. Furthermore, dual task constraints, rather than hemiplegic body side, were a significant discriminator in patients' perceptions of distance and height information to the obstacle. These findings suggested how performance of additional cognitive tasks might constrain perception of information from an obstacle in people with chronic stroke during different phases of obstacle crossing, and thus may impair their adaptive ability to successfully manoeuvre around objects.

Timed Up and Go test: Comparison of kinematics between patients with chronic stroke and healthy subjects

Understanding locomotor behavior is important to guide rehabilitation after stroke. This study compared lower-limb kinematics during the walking and turning sub-tasks of the Timed Up and Go (TUG) test in stroke patients and healthy subjects. We also determined the parameters which explain TUG sub-task performance time in healthy subjects. Biomechanical parameters were recorded during the TUG in standardized conditions in 25 healthy individuals and 29 patients with chronic stroke using a 3D motion-analysis system. Parameters were compared between groups and a stepwise regression was used to indicate parameters which explained performance time in the healthy subjects. The percentage difference in step length between the last and first steps was calculated, during walking sub-tasks for each group. Speed, cadence, step length, percentage paretic single support phase, percentage non-paretic swing phase, peak hip extension, knee flexion and ankle dorsiflexion were significantly reduced in the Stroke group compared to the Healthy group (p<0.05). In the Healthy group, step length and cadence explained 91% of variance for Go and 86% for Return (walking sub-tasks), and none of the parameters explained the Turn. Previous study in patients with stroke showed that the same parameters explained the variance during the walking sub-tasks and balance-related parameters explained the Turn. The present results showed that step length was differently modulated in each group. Thus the locomotor behavior of patients with stroke during obstacle circumvention is quite specific in light of the results obtained in healthy subjects.

Review of safety and mobility issues among older pedestrians

Although old people make up an extremely vulnerable road-user group, older pedestrians' difficulties have been studied less extensively than those of older drivers, and more knowledge of this issue is still required. The present paper reviews current knowledge of older-adult problems with the main components of pedestrian activity, i.e., walking and obstacle negotiation, wayfinding, and road crossing. Compared to younger ones, old pedestrians exhibit declining walking skills, with a walking speed decrease, less stable balance, less efficient wayfinding strategies, and a greater number of unsafe road crossing behaviors. These difficulties are linked to age-related changes in sensorial, cognitive, physical, and self-perception abilities. It is now known that visual impairment, physical frailty, and attention deficits have a major negative impact on older pedestrians' safety and mobility, whereas the roles of self-evaluation and self-regulation are still poorly understood. All these elements must be taken into consideration, not only in developing effective safety interventions targeting older pedestrians, but also in designing roads and cars. Recent initiatives are presented here and some recommendations are proposed.

Strategies for obstacle crossing in older adults with high and low risk of falling

[Purpose] Tripping is a frequent cause of falls among aging adults. Appropriate limb movements while negotiating obstacles are critical to trip avoidance. The aim of our study was to investigate the mechanics of obstacle crossing in older adults at low or high risk of falling. [Subjects and Methods] Twenty community-dwelling adults aged ≥55 years, were evaluated with the Tinetti Balance and Gait scale and classified as being at high or low risk of falling. Between-group comparisons of kinematics were evaluated for obstacle heights of 10%, 20%, and 30% of leg length. [Results] The high-risk group demonstrated greater toe-obstacle clearance of the leading leg. Increasing obstacle height led to increased maximal toe-obstacle clearance, toe-obstacle distance, and shortened swing phase of the leading limb. Adaptation of clearance height was greater for the trailing leg. Individuals at high risk of falling demonstrated less symmetry between the leading and trailing legs and a narrower step width, features that increase the likelihood of tripping. [Conclusion] Kinematic parameters of obstacle clearance, including the symmetry index described in our study, could provide clinicians with a quick screening tool to identify patients at risk of falling and to evaluate outcomes of training programs.

Acquiring visual information for locomotion by older adults: a systematic review

Developments in technology have facilitated quantitative examination of gaze behavior in relation to locomotion. The objective of this systematic review is to provide a critical evaluation of available evidence and to explore the role of gaze behavior among older adults during different forms of locomotion. Database searches were conducted to identify research papers that met the inclusion criteria of (1) study variables that included direct measurement of gaze and at least one form of locomotion, (2) participants who were older adults aged 60 years and above, and (3) reporting original research. Twenty-five papers related to walking on a straight path and turning (n=4), stair navigation (n=3), target negotiation and obstacle circumvention (n=13) and perturbation-evoked sudden loss of balance (n=5) were identified for the final quality assessment. The reviewed articles were found to have acceptable quality, with scores ranging from 47.06% to 94.12%. Overall, the current literature suggests that differences in gaze behavior during locomotion appear to change in late adulthood, especially with respect to transfer of gaze to and from a target, saccade-step latency, fixation durations on targets and viewing patterns. These changes appear to be particularly pronounced for older adults with high risk of falling and impaired executive functioning.

Sensorimotor and psychosocial correlates of adaptive locomotor performance in older adults

OBJECTIVE

To identify sensorimotor and psychosocial factors independently associated with an inability to perform adaptive walking tasks in older adults.

DESIGN

Cross-sectional cohort study.

SETTING

Population-based older cohort.

PARTICIPANTS

Community-living elderly (N=720; age ≥65y) who could walk 7m at self-selected normal speed.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Walking performance was assessed in 4 walking tests: fast walking, obstacle crossing, narrow-based walking, and walking while talking. Possible correlates of the inability to perform the walking test included knee extensor strength, lower limb coordination, Cumulative Somatosensory Impairment Index (CSII), visual acuity and contrast sensitivity, cognition, depression, personal mastery, social support, and years of education.

RESULTS

The results of binary logistic regression analyses, adjusted for demographics and self-selected normal speed, demonstrated that poor knee extensor strength was associated with an inability to perform tasks demanding an increase in walking speed (fast walking and obstacle crossing). Both poor lower limb coordination and higher CSII were significantly associated with failure in tests that demanded precise control over foot placement (obstacle crossing and narrow-based walking). Higher CSII was associated with failure in all tests except in the walking while talking. In contrast, poor cognition was associated with an inability to perform walking while talking. Poor personal mastery was the only variable that was associated with failure in all walking tests.

CONCLUSIONS

The results demonstrated a systematic and coherent pattern in these associations and indicated possible sensorimotor and psychological parameters that should be specifically investigated and should be intervened if a patient reports a difficulty/inability in walking in certain situations.

Human locomotion through a multiple obstacle environment: strategy changes as a result of visual field limitation

This study investigated how human locomotion through an obstacle environment is influenced by visual field limitation. Participants were asked to walk at a comfortable pace to a target location while avoiding multiple vertical objects. During this task, they wore goggles restricting their visual field to small (S: 40°×25°), medium (M: 80°×60°), large (L: 115°×90°), or unlimited (U) visual field sizes. Full-body motion capture was used to extract for each trial the mean speed, pathlength, mean step width, magnitude of head rotation and head mean angular speed. The results show that compared with the U condition, the M and L conditions caused participants to select a wider path around the obstacles without slowing down or altering step width. However, the S condition did slow down the participants, and increased both their step width and path length. We conclude that only for the S condition, balancing problems were substantial enough to spend more energy associated with increased step width. In all cases, participants choose to optimize safety (collision avoidance) at the cost of spending more energy.