Exploring the challenges of avoiding collisions with virtual pedestrians using a dual-task paradigm in individuals with chronic moderate to severe traumatic brain injury.

BACKGROUND: Individuals with a moderate-to-severe traumatic brain injury (m/sTBI), despite experiencing good locomotor recovery six months post-injury, face challenges in adapting their locomotion to the environment. They also present with altered cognitive functions, which may impact dual-task walking abilities. Whether they present collision avoidance strategies with moving pedestrians that are altered under dual-task conditions, however, remains unclear. This study aimed to compare between individuals with m/sTBI and age-matched control individuals: (1), the locomotor and cognitive costs associated with the concurrent performance of circumventing approaching virtual pedestrians (VRPs) while attending to an auditory-based cognitive task and; (2) gaze behaviour associated with the VRP circumvention task in single and dual-task conditions. METHODOLOGY: Twelve individuals with m/sTBI (age = 43.3 ± 9.5 yrs; >6 mo. post injury) and 12 healthy controls (CTLs) (age = 41.8 ± 8.3 yrs) were assessed while walking in a virtual subway station viewed in a head-mounted display. They performed a collision avoidance task with VRPs, as well as auditory-based cognitive tasks (pitch discrimination and auditory Stroop), both under single and dual-task conditions. Dual-task cost (DTC) for onset distance of trajectory deviation, minimum distance from the VRP, maximum lateral deviation, walking speed, gaze fixations and cognitive task accuracy were contrasted between groups using generalized estimating equations. RESULTS: In contrast to CTLs who showed locomotor DTCs only, individuals with m/sTBI displayed both locomotor and cognitive DTCs. While both groups walked slower under dual-task conditions, only individuals with m/sTBI failed to modify their onset distance of trajectory deviation and maintained smaller minimum distances and smaller maximum lateral deviation compared to single-task walking. Both groups showed shorter gaze fixations on the approaching VRP under dual-task conditions, but this reduction was less pronounced in the individuals with m/sTBI. A reduction in cognitive task accuracy under dual-task conditions was found in the m/sTBI group only. CONCLUSION: Individuals with m/sTBI present altered locomotor and gaze behaviours, as well as altered cognitive performances, when executing a collision avoidance task involving moving pedestrians in dual-task conditions. Potential mechanisms explaining those alterations are discussed. Present findings highlight the compromised complex walking abilities in individuals with m/sTBI who otherwise present a good locomotor recovery.

Performance during dual-task walking in a corridor after mild traumatic brain injury: A potential functional marker to assist return-to-function decisions.

Objective: To compare the performance of participants with mTBI and healthy control on locomotor-cognitive dual-tasks in a corridor with limited technology.Design: Prospective study of twenty participants with mTBI (10 women; 22.10 ± 2.97 years; 70.9 ± 22.31 days post-injury), and 20 sex- and age-matched control participants (10 women; 22.55 ± 2.72 years).Methods: Participants performed six different dual-tasks combining locomotor tasks (level-walking, obstacle-crossing, and tandem gait) and cognitive tasks (counting backwards and verbal fluency). Symptoms and neuropsychological performance were also assessed.Results: No differences between groups were found for symptoms and neuropsychological measures. For gait speed, the group effect was not significant, but a significant group X cognitive task interaction was found, revealing a tendency toward slower gait speed in the mTBI group during dual-task conditions. A significantly greater dual-task cost for gait speed was found for the mTBI group. Although no statistically significant differences in cognitive performance were observed during dual-tasks, the mTBI group subjectively reported being significantly less concentrated.Conclusion: The present study revealed that in persons who seem to have well recovered after mTBI, on average 71 days post-injury, alterations in gait are detectable using a simple, "low-tech," corridor-based dual-task walking assessment.

Virtual reality-based assessment of cognitive-locomotor interference in healthy young adults.

BACKGROUND: A recent literature review emphasized the importance of assessing dual-task (DT) abilities with tasks that are representative of community ambulation. Assessing DT ability in real-life activities using standardized protocols remains difficult. Virtual reality (VR) may represent an interesting alternative enabling the exposure to different scenarios simulating community walking. To better understand dual-task abilities in everyday life activities, the aims of this study were (1) to assess locomotor and cognitive dual-task cost (DTC) during representative daily living activities, using VR, in healthy adults; and 2) to explore the influence of the nature and complexity of locomotor and cognitive tasks on DTC. METHODS: Fifteen healthy young adults (24.9 ± 2.7 years old, 8 women) were recruited to walk in a virtual 100 m shopping mall corridor, while remembering a 5-item list (DT condition), using an omnidirectional platform and a VR headset. Two levels of difficulty were proposed for the locomotor task (with vs. without virtual agent avoidance) and for the cognitive task (with vs. without items modification). These tasks were also performed in single task (ST) condition. Locomotor and cognitive DTC were measured by comparing performances in ST and DT conditions. Locomotor performance was characterized using walking speed, walking fluidity, and minimal distance between the participant and the virtual agent during avoidance. Cognitive performance was assessed with the number of items correctly recalled. Presence of DTC were determined with one-sample Wilcoxon signed-rank tests. To explore the influence of the tasks' complexity and nature on DTC, a nonparametric two-way repeated measure ANOVA was performed. RESULTS: No locomotor interference was measured for any of the outcomes. A cognitive DTC of 6.67% was measured (p = .017) while participants performed simultaneously both complex locomotor and cognitive tasks. A significant interaction between locomotor task complexity and cognitive task nature (p = .002) was identified on cognitive DTC. CONCLUSIONS: In challenging locomotor and cognitive conditions, healthy young adults present DTC in cognitive accuracy, which was influenced by the locomotor task complexity task and the cognitive task nature. A similar VR-based protocol might be used to investigate DT abilities in older adults and individuals with a stroke.

Design and Accuracy of an Instrumented Insole Using Pressure Sensors for Step Count.

Despite the accessibility of several step count measurement systems, count accuracy in real environments remains a major challenge. Microelectromechanical systems and pressure sensors seem to present a potential solution for step count accuracy. The purpose of this study was to equip an insole with pressure sensors and to test a novel and potentially more accurate method of detecting steps. Methods: Five force-sensitive resistors (FSR) were integrated under the heel, the first, third, and fifth metatarsal heads and the great toe. This system was tested with twelve healthy participants at self-selected and maximal walking speeds in indoor and outdoor settings. Step counts were computed based on previously reported calculation methods, individual and averaged FSR-signals, and a new method: cumulative sum of all FSR-signals. These data were compared to a direct visual step count for accuracy analysis. Results: This system accurately detected steps with success rates ranging from 95.5 ± 3.5% to 98.5 ± 2.1% (indoor) and from 96.5 ± 3.9% to 98.0 ± 2.3% (outdoor) for self-selected walking speeds and from 98.1 ± 2.7% to 99.0 ± 0.7% (indoor) and 97.0 ± 6.2% to 99.4 ± 0.7% (outdoor) for maximal walking speeds. Cumulative sum of pressure signals during the stance phase showed high step detection accuracy (99.5 ± 0.7%⁻99.6 ± 0.4%) and appeared to be a valid method of step counting. Conclusions: The accuracy of step counts varied according to the calculation methods, with cumulative sum-based method being highly accurate.

Validity of Instrumented Insoles for Step Counting, Posture and Activity Recognition: A Systematic Review.

With the growing interest in daily activity monitoring, several insole designs have been developed to identify postures, detect activities, and count steps. However, the validity of these devices is not clearly established. The aim of this systematic review was to synthesize the available information on the criterion validity of instrumented insoles in detecting postures activities and steps. The literature search through six databases led to 33 articles that met inclusion criteria. These studies evaluated 17 different insole models and involved 290 participants from 16 to 75 years old. Criterion validity was assessed using six statistical indicators. For posture and activity recognition, accuracy varied from 75.0% to 100%, precision from 65.8% to 100%, specificity from 98.1% to 100%, sensitivity from 73.0% to 100%, and identification rate from 66.2% to 100%. For step counting, accuracies were very high (94.8% to 100%). Across studies, different postures and activities were assessed using different criterion validity indicators, leading to heterogeneous results. Instrumented insoles appeared to be highly accurate for steps counting. However, measurement properties were variable for posture and activity recognition. These findings call for a standardized methodology to investigate the measurement properties of such devices.

Modeling spatial navigation in the presence of dynamic obstacles: a differential games approach.

Obstacle circumvention strategies can be shaped by the dynamic interaction of an individual (evader) and an obstacle (pursuer). We have developed a mathematical model with predictive and emergent components, using experimental data from seven healthy young adults walking toward a target while avoiding collision with a stationary or moving obstacle (approaching head-on, or diagonally 30° left or right) in a virtual environment. Two linear properties from the predictive component enable the evader to predict the minimum distance between itself and the obstacle at all times, including the future intersection of trajectories. The emergent component uses the classical differential games model to solve for an optimal circumvention while reaching the target, wherein the locomotor strategy is influenced by the obstacle, target, and the evader velocity. Both model components were fitted to a different set of experimental data obtained from five poststroke and healthy participants to derive the minimum predicted distance (predictive component) and obstacle influence dimensions (emergent component) during circumvention. Minimum predicted distance between evader and pursuer was kept constant when the evader was closest to the obstacle in all participants. Obstacle influence dimensions varied depending on obstacle approach condition and preferred side of circumvention, reflecting differences in locomotor strategies between poststroke and healthy individuals. Additionally, important associations between model outputs and observed experimental outcomes were found. The model, supported by experimental data, suggests that both predictive and emergent processes can shape obstacle circumvention strategies in healthy and poststroke individuals. NEW & NOTEWORTHY Obstacle circumvention during goal-directed locomotion is modeled with a new mathematical approach comprising both predictive and emergent elements. The major novelty is using differential games solutions to illustrate the dynamic interactions between the individual as an evader and the approaching obstacle as a pursuer. The model is supported by experimental evidence that explains the behavior along the continuum of locomotor adaptation displayed by healthy subjects and individuals with stroke.

Substituting anticipatory locomotor adjustments online is time constrained.

Two crucial, multi-articular strategies for anticipatory locomotor adjustments (ALA) are knee flexor generation to step over obstacles and hip flexor generation to step up. While lower limb control can be adapted online to modify an already planned obstacle avoidance, or to avoid the sudden appearance of an obstacle, it is not known whether a planned ALA can be substituted by different one online. The present objective was to study such ALA substitutions at two specific timepoints: the final planning stage and the initiation of ALA execution. Ten healthy, young adults (22.0 ± 1.7 years; 5 males) walked in a Virtual Environment (VE) representing the laboratory within a head mounted display. Two blocks of trials, one involving an initial VE with an obstacle (OB) and the other an initial VE with a platform (PL) (heights of 15% of lower limb length for both), were presented, where the initial VE could remain unchanged or be randomly switched between them at one of the two timepoints. The final VE always corresponded to the real environment. Lead limb kinematics, joint kinetics and energetics, as well as electromyography were measured. Repeated measures ANOVAs were used to compare across conditions. Foot clearance, knee flexor generation, and hip flexor generation all changed in the expected directions for the final VEs when requiring early substitution, but not when switched late. These findings show that volitional, locomotor strategies may be substituted at the end of the ALA planning phase, but not once execution is initiated.

Body-foot geometries as revealed by perturbed obstacle position with different time constraints.

This study examined the geometrical relationships between the feet, pelvis and an environmental obstruction when crossing an obstacle with unexpected changes to its position. Nine healthy young adults stepped over an obstacle 19 cm high with their right leg leading. The obstacle could be static or advanced at either lead (early detection) or trail (late detection) foot contact prior to clearance to force an adaptive reorganization of body-foot geometry and foot proximity to the obstacle. Stride length, minimum foot clearance over the obstacle, and foot-obstacle horizontal proximity before and after clearance were measured along with the relative position of the pelvis to each foot at eight points (four for each foot) during approach and clearance: heel contacts before and after crossing the obstacle, maximum foot heights and foot clearances. With early obstacle movement, trail limb stride length before crossing was lengthened, but foot proximity was still far from the final obstacle position. Clearance was less affected for the trail foot as compared to the lead foot. Proximity of the lead limb following clearance was the same for both early and late perturbations and closer than for the static obstacle condition. For relative body-foot positioning, significant differences were found only in the anterior-posterior direction. Following obstacle displacement, body-foot geometry was initially adapted, but then re-established to static obstacle values with an apparent focus on a balance geometry with the forward placed foot establishing new contact. These findings support an overall balance geometry that can be temporarily adjusted and coordinated with foot proximity to the obstruction to maintain continual gait and safe clearance.

Research Priorities for Optimizing Long-term Community Integration after Brain Injury.

OBJECTIVE: This paper reports on a funded summit, which convened a multidisciplinary group of experts to provide consensus on the research priorities necessary for improving long-term community integration of individuals with traumatic brain injury (TBI) and their caregivers. METHODS: The 2-day summit was directed using the World Café Methodology, to engage stakeholders and collaboratively arrive at a consensus on the problems to be targeted in research. Participants (n=54), drawn from two Canadian provinces, included an interdisciplinary group of researchers, clinicians, representatives from brain injury associations, individuals with TBI, and caregivers. In small groups, participants discussed challenges to long-term community integration and potential initiatives that would address these barriers. Field notes from the discussions were analyzed using qualitative content analysis. RESULTS: The consensus on prioritized research directions included developing interventions to optimize the functioning and participation of individuals with TBI, reducing caregiver burden, and evaluating how emerging technology can facilitate delivery of care. CONCLUSIONS: The World Café Methodology was an effective method for developing research priorities. The breadth of expertise of participants and the collegial environment allowed for the identification of a broad perspective on important future research directions with potential to enhance the long-term community integration of individuals with brain injury.

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.

Using dual task walking as an aid to assess executive dysfunction ecologically in neurological populations: A narrative review.

Within rehabilitation, clinical assessment plays a crucial role in diagnosis, prognostication and making decisions about return to function. The ecological validity of the assessment of executive dysfunction has become a particular focus in neuropsychology and is gaining interest in mobility research and neurological rehabilitation of acquired brain injury or degenerative neurological diseases. In this narrative review, we look at how the task of walking and the inseparable cognitive demands and interference of the surrounding environment are exploited in dual task walking (DTW) paradigms to expose executive dysfunction. While quite a number of studies and reviews have recently focused on the utility of DTW for gait assessment, particularly to assess fall risk, very little consideration has been given to the level of ecological validity required. This paper directly addresses this issue with discussion of evidence and lacunas related to task, personal and technological factors that should be addressed in order to exploit fully DTW paradigms as an ecological assessment tool.

Executive dysfunction following a mild traumatic brain injury revealed in early adolescence with locomotor-cognitive dual-tasks.

OBJECTIVE: To compare gait parameters between children in early adolescence (EA) with and without a mild traumatic brain injury (mTBI) during dual-task walking (DTW). METHODS: Children in EA with mTBI (n = 14; six girls) were compared to those without (n = 13; five girls) while walking in different combinations of obstacle avoidance and cognitive dual-tasks. Gait speed and fluidity and their related dual-task costs (DTC) were analysed along with foot clearance and proximity to the obstacle. RESULTS: No group effects were found for gait speed, proximity or clearance, but were found for fluidity DTC, specifically during the dual Stroop task and when crossing the deeper obstacle. There were also group differences for fluidity during the planning of obstacle avoidance for the narrow obstacle combined with the verbal fluency task and the deep obstacle with no cognitive task. Finally, gait fluidity showed group differences across unobstructed dual-task situations. CONCLUSIONS: Gait fluidity may be a more sensitive variable than gait speed for revealing executive dysfunction following mTBI in EA. Assessing DTW in level walking also seems to show a potential to reveal executive dysfunctions in this age group. These results provide direction for future research on clinical assessment using DTW post-mTBI in adolescents.

Acute Physical Exercise Affects Cognitive Functioning in Children With Cerebral Palsy.

Little is known about the effects of acute exercise on the cognitive functioning of children with cerebral palsy (CP). Selected cognitive functions were thus measured using a pediatric version of the Stroop test before and after maximal, locomotor based aerobic exercise in 16 independently ambulatory children (8 children with CP), 6-15 years old. Intense exercise had: 1) a significant, large, positive effect on reaction time (RT) for the CP group (preexercise: 892 ± 56.5 ms vs. postexercise: 798 ± 45.6 ms, p < .002, d = 1.87) with a trend for a similar but smaller response for the typically developing (TD) group (preexercise: 855 ± 56.5 ms vs. postexercise: 822 ± 45.6 ms, p < .08, d = 0.59), and 2) a significant, medium, negative effect on the interference effect for the CP group (preexercise: 4.5 ± 2.5%RT vs. postexercise: 13 ± 2.9%RT, p < .04, d = 0.77) with no significant effect for the TD group (preexercise: 7.2 ± 2.5%RT vs. postexercise: 6.9 ± 2.9%RT, p > .4, d = 0.03). Response accuracy was high in both groups pre- and postexercise (>96%). In conclusion, intense exercise impacts cognitive functioning in children with CP, both by increasing processing speed and decreasing executive function.

Efficacy of virtual reality-based intervention on balance and mobility disorders post-stroke: a scoping review.

Rehabilitation interventions involving virtual reality (VR) technology have been developed for the promotion of functional independence post stroke. A scoping review was performed to examine the efficacy of VR-based interventions on balance and mobility disorders post stroke. Twenty-four articles in the English language examining VR game-based interventions and outcomes directed at balance and mobility disorders were included. Various VR systems (customized and commercially available) were used as rehabilitation tools. Outcome measures included laboratory and clinical measures of balance and gait. Outcome measures of dynamic balance showed significant improvements following VR-based interventions as compared to other interventions. Further, it was observed that VR-based intervention may have favorable effects in improving walking speed and the ability to deal with environmental challenges, which may also facilitate independent community ambulation. VR-based therapy thus has the potential to be a useful tool for balance and gait training for stroke rehabilitation. Utilization of motor learning principles related to task-related training may have been an important factor leading to positive results. Other principles such as repetition, feedback etc. were used in studies but were not explored explicitly and may need to be investigated to further improve the strength of results. Lastly, robust study designs with appropriate attention towards the intensity and dose-response aspects of VR training, clear study objectives and suitable outcomes would further aid in determining evidence-based efficacy for VR game-based interventions in the future.

Real-time modulation of visual feedback on human full-body movements in a virtual mirror: development and proof-of-concept.

BACKGROUND: Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. However, existing systems have generally not implemented realistic full-body avatars and/or a scaling of visual movement feedback. We developed a "virtual mirror" that displays a realistic full-body avatar that responds to full-body movements in all movement planes in real-time, and that allows for the scaling of visual feedback on movements in real-time. The primary objective of this proof-of-concept study was to assess the ability of healthy subjects to detect scaled feedback on trunk flexion movements. METHODS: The "virtual mirror" was developed by integrating motion capture, virtual reality and projection systems. A protocol was developed to provide both augmented and reduced feedback on trunk flexion movements while sitting and standing. The task required reliance on both visual and proprioceptive feedback. The ability to detect scaled feedback was assessed in healthy subjects (n = 10) using a two-alternative forced choice paradigm. Additionally, immersion in the VR environment and task adherence (flexion angles, velocity, and fluency) were assessed. RESULTS: The ability to detect scaled feedback could be modelled using a sigmoid curve with a high goodness of fit (R2 range 89-98%). The point of subjective equivalence was not significantly different from 0 (i.e. not shifted), indicating an unbiased perception. The just noticeable difference was 0.035 ± 0.007, indicating that subjects were able to discriminate different scaling levels consistently. VR immersion was reported to be good, despite some perceived delays between movements and VR projections. Movement kinematic analysis confirmed task adherence. CONCLUSIONS: The new "virtual mirror" extends existing VR systems for motor and pain rehabilitation by enabling the use of realistic full-body avatars and scaled feedback. Proof-of-concept was demonstrated for the assessment of body perception during active movement in healthy controls. The next step will be to apply this system to assessment of body perception disturbances in patients with chronic pain.

A preliminary study to identify locomotor-cognitive dual tasks that reveal persistent executive dysfunction after mild traumatic brain injury.

OBJECTIVE: To identify different combinations of physical (level, obstacle avoidance, stepping down) and cognitive (visual, mental) demands within a locomotor navigational context that best discriminates between persons with mild traumatic brain injury (MTBI) and control subjects for an eventual clinical tool to assess residual executive dysfunction. DESIGN: Group comparison study. SETTING: Rehabilitation facility. PARTICIPANTS: Volunteer sample (N=14) of persons with MTBI (n=7) (6 women; age, 20±1.6 y) and a comparison group (n=7) of subjects without neurologic problems (6 women; age, 22.4±1.4 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait speed (m/s) and dual-task cost calculated as the relative change in gait speed from single (no cognitive task) to dual tasks for the same gait condition. RESULTS: There were significant interactions between groups and cognitive tasks and between groups and cognitive and physical tasks for gait speed. Specifically, the MTBI group walked slower than control subjects in the dual-task conditions when stepping over an obstacle combined with each cognitive task. When gait speed was measured as dual-task costs, group differences were more evident, except for stepping down. CONCLUSIONS: These preliminary results suggest that both absolute gait speed and calculated dual-task costs during the combination of stepping over an obstacle with a simultaneous cognitive task are sensitive to revealing executive dysfunction in persons with MTBI. Gait speed can be easily measured in the clinic to provide important information to make diagnoses and decide about return to play or function. Continued work building on these preliminary results is needed toward the development of a clinical tool.

Altered integrated locomotor and cognitive function in elite athletes 30 days postconcussion: a preliminary study.

OBJECTIVE: To begin to understand changes in locomotor navigation in elite athletes following concussion. METHODS: Clinical measures and gait analysis were undertaken on average 37.33 days (SD = 4.8) postconcussion for 6 athletes as well as for a control group of athletes matched for age, sex, and team. The locomotor task consisted of walking at a self-selected speed along an unobstructed or obstructed path with and without a visual interference task. The trends for 4 dependent variables were described (2 for gait behavior and 2 for cognitive behavior). A principal component analysis was used to reduce data to root sources of variance among these variables. General group differences were tested with Wilcoxon matched-pairs tests on factorial scores. RESULTS: Athletes with concussion were symptom free at the time of testing and their neuropsychological test results were not different from those of athletes in the control group. However, when the laboratory data between paired groups were compared, descriptive analyses suggested potential group differences in navigating the obstacle. The simultaneous Stroop task appeared to present difficulty for both groups. A significant group effect was found on the component of the factorial analysis that was highly loaded with both gait and cognitive variables (minimum clearance, Stroop task errors, and cognitive dual-task costs), generally supporting the descriptive analyses by suggesting that athletes with concussion do not navigate the targeted complex environments like the control group. CONCLUSIONS: Athletes with concussion appear to still show navigational deficits in environments well after being considered fully recovered according to current return-to-play protocols. Although still preliminary and requiring further study, the present findings suggest that functional assessment within complex environment contexts could be considered before sending athletes back to play following a concussion, even in the absence of postconcussion symptoms or with normal clinical outcomes.

Relationship Between Dual-Task Walking and Level of Conflict Between Gait and Concurrent Tasks in Adolescents.

This study aimed to determine the role of resource conflict in dual-task (DT) effects on gait and concurrent tasks in children and adolescents. Gait was evaluated with and without concurrent tasks (visual-manual, visual-vocal and auditory-vocal). The roles of condition (single vs dual) and type of concurrent task in DT effect were tested by Repeated Measured of ANOVA. Relative changes from single to DT conditions were compared using One-Way ANOVA. There were significant reductions in gait speed, cadence, and stride length, and increases in double support time, step time and variability in step time, and no change in variability in stride length, step width, and concurrent task performance from single to DT conditions. DT effects on gait parameters and concurrent tasks were comparable across DT conditions.

Avoidance behaviours while circumventing to the left or right of someone with different shoulder widths and facing directions: How do side, width, or orientation matter?

BACKGROUND: Collision avoidance during locomotion is influenced by a variety of situational factors. When circumventing around an inanimate object, the amount of clearance is dependent on the side of avoidance. When avoiding other pedestrians, individuals most often choose to walk behind a moving pedestrian, and avoid people differently depending on their body size. However, side of avoidance has not been evaluated with human obstacles, nor facing direction of a stationary pedestrian, nor the size of a single pedestrian. Therefore, the aim of this study is to evaluate these knowledge gaps concurrently. RESEARCH QUESTION: How do people avoid a collision to the left-side or right-side of a single stationary pedestrian (interferer) of varying shoulder width and orientation? METHODS: Participants (n = 11) walked along a 10 m pathway towards a goal, while a stationary interferer stood 6.5 m from the start. The interferer faced one of three directions relative to the participant (orientation); forward, leftward, or rightward, with either their normal shoulder width or enlarged width created by wearing football shoulder pads. Participants were explicitly instructed as to which side of the interferer to avoid (forced-left vs forced-right). Each participant completed 32 randomized avoidance trials. Centre of Mass separation at the time of crossing was used to examine individual's avoidance behaviours. RESULTS: Results revealed no effect of interferer width, but a significant side of avoidance effect, where the centre of mass separation between the participant and interferer at the time of crossing was smallest when participants avoided to their left. SIGNIFICANCE: Findings suggest that changing the facing direction or artificially increasing the shoulder width of a stationary interferer will not affect one's avoidance behaviours. However, an asymmetry in side of avoidance is maintained similar to that observed in obstacle avoidance behaviours.

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.