Estimating pedestrian walking speed at street crossings using the YOLOv4 and deep SORT algorithms: Proof of principle.

There is evidence that existing standards for signal timing do not provide enough time for many pedestrians to safely cross intersections. Yet, current methods for studying this problem rely on inefficient manual observations. The objective of this work was to determine if the YOLOv4 and Deep SORT computer vision algorithms have the potential to be incorporated into automated measurement systems to measure and compare pedestrian walking speeds at one-stage and two-stage street crossings captured in birds-eye-view video. Walking speed was estimated for 1018 pedestrians at single-stage (591 pedestrians) and two-stage (427 pedestrians) street crossings. Pedestrians in the one-stage crossing were found to be significantly slower than pedestrians who crossed the two-stage crossing in one signal (1.19 ± 0.50 vs. 1.31 ± 0.49 m/s, p < 0.001). This proof of principle study demonstrated that the YOLOv4 and Deep SORT approaches are promising for estimating pedestrian walking speed.

Efficacy of Installation of Temporary Bathing Transfer Aids by Older Adults.

Grab bars facilitate bathing and reduce the risk of falls during bathing. Suction cup handholds and rim-mounted tub rails are an alternative to grab bars. The objective of this study was to determine whether older adults could install handholds and tub rails effectively to support bathing transfers. Participants installed rim-mounted tub rails and suction cup handholds in a simulated bathroom environment. Installation location and mechanical loading performance were evaluated. Participant perceptions during device installation and a bathing transfer were characterized. While 85% of suction cup handholds met loading requirements, more than half of participants installed the suction cup handhold in an unexpected location based on existing guidance documents. No rim-mounted tub rails were successfully installed. Participants were confident that the devices had been installed effectively. Suction cup handholds and rim mounted tub rails are easy to install, but clients may need additional guidance regarding where, and how to install them.

A comparison of minimum segment models for the estimation of centre of mass position and velocity for slip recovery during a bathtub transfer task.

BACKGROUND: Exploring the use of minimum marker sets is important for balancing the technical quality of motion capture with challenging data collection environments and protocols. While minimum marker sets have been demonstrated to be appropriate for evaluation of some motion patterns, there is limited evidence to support model choices for abrupt, asymmetrical, non-cyclic motion such as balance disturbance during a bathtub exit task. RESEARCH QUESTION: How effective are six models of reduced complexity for the estimation of centre of mass (COM) displacement and velocity, relative to a full-body model. METHODS: Eight participants completed a bathtub exit task. Participants received a balance perturbation as they crossed the bathtub rim, stepping from a soapy wet bathtub to a dry floor. Six reduced models were developed from the full, 72-marker, 12 segment 3D kinematic data set. Peak displacement and velocity of the body COM, and RMSE (relative to the full-body model) for displacement and velocity of the body COM were determined for each model. RESULTS: Main effects were observed for peak right, left, anterior, posterior, upwards and downwards motion, and peak left, anterior, posterior, upwards and downwards velocity. Time-varying (RMSE) was smaller for models including the thighs than models not containing the thighs. In contrast, inclusion of upper arm, forearm, and hand segments did not improve model performance. The model containing the sacrum marker only consistently performed the worst across peak and RMSE metrics. SIGNIFICANCE: Findings suggest a simplified centre of mass model may adequately capture abrupt, asymmetrical, non-cyclic tasks, such as balance disturbance recovery during obstacle crossing. A reduced kinematic model should include the thighs, trunk and pelvis segments, although models that are more complex are recommended, depending on the metrics of interest.

Biomechanical Demands and User Preference Associated with Wall-Mounted and Rim-Mounted Grab Bars.

Background. Grab bars are used to support bathing tasks. Sometimes, temporary rim-mounted grab bars may be preferred over permanent wall-mounted grab bars. Purpose. We compared postural requirements, applied loads, and user perceptions between two configurations of rim-mounted grab bars, a vertical wall-mounted grab bar, and a no-grab bar condition. Method. Ten adults entered and exited a simulated bathing environment. Trunk flexion was evaluated via 3D kinematics, while load cells mounted to the grab bars facilitated the evaluation of applied loads. Participants rated each condition on perceived safety, comfort, effectiveness, and ease of use. Findings. Rim-mounted grab bars resulted in greater trunk flexion and greater applied loads and were less favorably perceived. Implications. The rim-mounted grab bars included in this study may induce challenging postural demands and loading scenarios, and occupational therapists should consider whether they meet the needs of their clients.

Effect of Handrail Height and Age on Trunk and Shoulder Kinematics Following Perturbation-Evoked Grasping Reactions During Gait.

OBJECTIVE: To characterize the effect of handrail height and age on trunk and shoulder kinematics, and concomitant handrail forces, on balance recovery reactions during gait. BACKGROUND: Falls are the leading cause of unintentional injury in adults in North America. Handrails can significantly enhance balance recovery and help individuals to avoid falls, provided that their design allows users across the lifespan to reach and grasp the rail after balance loss, and control their trunk by applying hand-contact forces to the rail. However, the effect of handrail height and age on trunk and shoulder kinematics when recovering from perturbations during gait is unknown. METHOD: Fourteen younger and 13 older adults experienced balance loss (sudden platform translations) while walking beside a height-adjustable handrail. Handrail height was varied from 30 to 44 inches (76 to 112 cm). Trunk and shoulder kinematics were measured via 3D motion capture; applied handrail forces were collected from load cells mounted to the rail. RESULTS: As handrail height increased (up to 42 inches/107 cm), peak trunk angular displacement and velocity generally decreased, while shoulder elevation angles during reaching and peak handrail forces did not differ significantly between 36 and 42 inches (91 and 107 cm). Age was associated with reduced peak trunk angular displacements, but did not affect applied handrail forces. CONCLUSION: Higher handrails (up to 42 inches) may be advantageous for trunk control when recovering from destabilizations during gait. APPLICATION: Our results can inform building codes, workplace safety standards, and accessibility standards, for safer handrail design.

Grab Bar Use Influences Fall Hazard During Bathtub Exit.

OBJECTIVE: This study evaluated the hazard (risk of unrecovered balance loss and hazardous fall) and strategies associated with grab bar use, compared to no grab bar use, during unexpected balance loss initiated whilst exiting a bathtub. BACKGROUND: While independent bathing is critical for maintaining self-sufficiency, injurious falls during bathing transfer tasks are common. Grab bars are recommended to support bathing tasks, but no evidence exists regarding fall prevention efficacy. METHOD: Sixty-three adults completed a hazardous bathtub transfer task, experiencing an unpredictable external balance perturbation while stepping from a slippery bathtub to a dry surface. Thirty-two were provided a grab bar, while 31 had no grab bar available. Slips and grab bar use were recorded via four video cameras. Slip occurrence and strategy were identified by two independent video coders. RESULTS: Participants who had a grab bar were 75.8% more likely to recover their balance during the task than those who did not have a grab bar. Successful grab bar grasp was associated with balance recovery in all cases. Attempts to stabilize using other environmental elements, or using internal strategies only, were less successful balance recovery strategies. Grab bar presence appeared to cue use of the environment for stability. Proactive grasp and other strategies modified grasping success. CONCLUSION: Grab bars appear to provide effective support for recovery from unexpected balance loss. Grab bar presence may instigate development of fall prevention strategies prior to loss of balance. APPLICATION: Bathroom designs with grab bars may reduce frequency of fall-related injuries during bathing transfer tasks.

Consumer perspectives on grab bars: A Canadian national survey of grab bar acceptability in homes.

Given the prevalence and severity of bathroom falls and injuries across age groups, there is growing interest in policy-level approaches to bathroom fall prevention. Grab bars reduce fall risk during bathing transfers and improve bathing accessibility for adults of all ages and abilities. However, they are frequently absent from bathing environments, even in the homes of individuals who have a specific need for a grab bar. While mandatory bathroom grab bar installation has been suggested, it is unclear whether this would be supported by Canadians. The purpose of this study was to characterize Canadian public perceptions on the installation and use of grab bars in home bathrooms. We surveyed 443 Canadians about whether they currently had a grab bar and their perspectives on grab bar policy. 65.4% of respondents did not have a grab bar. However, 88.5% of respondents would allow a grab bar to be installed in their bathroom at no cost to them, only 11.5% of respondents would object to grab bar installation becoming mandatory in new builds, and 85.6% of respondents would use a grab bar if it were installed in their bathroom. Responses were affected by age (in four groups: 18-39, 40-59, 60-79, and 80+ years), self-reported impairment, and home ownership status. Older adults, respondents who reported having impairments, and home owners were more likely to respond favorably toward grab bars. Based on these results, the majority of Canadians would respond positively to policy mandating bathroom grab bars in new homes.

The Effect of Handrail Cross-Sectional Design and Age on the Speed and Quality of Reach-To-Grasp Reactions to Recover Balance.

OBJECTIVE: To determine the effect of handrail cross-section on the speed and quality of reach-to-grasp movements following balance loss in younger and older adults. BACKGROUND: Grasping a handrail is a common strategy for balance recovery. For handrails to be effective, the design must enable fast and accurate reactive grasping. Little is known about the effect of handrail cross-section on the timing or quality of the reach-to-grasp movement following balance loss. METHODS: Twenty-four younger and 16 older adults experienced incrementally increasing magnitudes of perturbations in the forward and backward direction until they were no longer able to recover balance. We analyzed the last trial where the participant could recover using only the handrail, without stepping or relying on the harness, the maximum withstood perturbation (MWP). Seven handrail cross-sections were tested. RESULTS: Handrail cross-section did not affect the speed or timing of the reach-to-grasp reaction for younger or older adults. However, handrail cross-section affected the MWP, the grip types used, and the likelihood of making an error or adjustment when grasping. The greatest MWP and fewest errors occurred with 1.5" round handrails. CONCLUSION: The absence of common strategies for accurately grasping complex shapes (reaching more slowly), combined with the higher frequency of errors with larger handrails, suggests that both older and younger adults prioritized quickly reaching the handrail over prehension during reach-to-grasp balance reactions. APPLICATION: This work provides new insights on the effect of age and handrail cross-sectional design on reach-to-grasp reactions to recover balance, which can inform safer handrail design standards.

The effect of handrail cross-sectional design and age on applied handrail forces during reach-to-grasp balance reactions.

Handrails have been shown to reduce the likelihood of falls. Despite common use, little is known about how handrail shape and size affect the forces that people can apply after balance loss, and how these forces and the corresponding ability to recover balance depend on age. Following rapid platform translations, 16 older adults and 16 sex-matched younger adults recovered their balance using seven handrail cross-sections varying in shape and size. Younger adults were able to withstand higher perturbations, but did not apply higher forces, than older adults. However, younger adults achieved their peak resultant force more quickly, which may reflect slower rates of force generation with older adults. Considering handrail design, the 38 mm round handrails allowed participants to successfully recover from the largest perturbations and enabled the highest force generation. Conversely, tapered handrails had the poorest performance, resulting in the lowest force generation and withstood perturbation magnitudes. Our findings suggest that the handrail cross-sectional design affects the magnitude of force generation and may impact the success of recovery. Our findings can inform handrail design recommendations that support effective handrail use in demanding, balance recovery scenarios.

Increasing the contrast of tread edge highlighters improves stair descent safety in older adults with simulated visual impairment.

Falls during stair descent are dangerous and costly. Contrasting tread edge highlighters improve measures of stair safety, however the necessary contrast level of these interventions has not been investigated. Thirteen older adults (67.7 ± 5.5 years) completed stair descent trials under normal (300lx) and low (30lx) lighting conditions, blurred and normal vision, and four different contrast levels (0%, 30%, 50%, 70%) between the tread edge highlighter and the neighbouring tread surface. Cadence and heel clearance decreased for 0% contrast compared to 50% and 70% contrast conditions, but contrast had no effect on foot overhang. Blurred vision was observed to be a greater factor influencing biomechanical measures of fall risk than low ambient lighting. Results suggest higher contrast highlighters improve measures of safety, even more so during simulated vision impairment, and that at least 50% contrast difference provides adequate visual information for safer stair ambulation.

A kinematic analysis of balance recovery following an unexpected forward balance loss during stair descent.

Falls during stair descent pose a major health concern. A stronger understanding of recovery from balance loss during stair descent is needed to guide fall prevention strategies and environmental design. We characterized balance recovery strategies, trunk and center-of-mass (COM) kinematics, and handrail use following unexpected forward balance loss during stair descent, and the effect of perturbation magnitude on these outcomes. Eighteen young adults experienced a rapid platform translation during stair descent to disrupt balance. Deception was used to reduce anticipation. All participants used compensatory stepping to recover balance, and most applied forces to the handrail in multiple directions. Higher perturbation magnitude resulted in higher COM velocity and handrail forces, more frequent incomplete steps, and quicker step contact time. Our findings provide a foundation for understanding balance recovery on stairs. The findings emphasize the importance of designing stairways that enable compensatory stepping, and handrails that permit adequate force generation in multiple directions to facilitate balance recovery on stairs.

Determining the effect of stair nosing shape on foot trajectory during stair ambulation in healthy and post-stroke individuals.

Stair design can influence the risk of stair falls. Stair nosings are intended to provide greater foot accommodation, although to date little is known about how the nosing shape can affect foot trajectory during stair ambulation. This study investigates the impact of different nosing shapes (round, square, tapered, and no nosing) on foot clearance and overhang measures during stair ascent and descent among healthy and post-stroke older adults. Slower cadence in ascent and descent, and greater foot overhang during descent highlighted the increased risk of stair falls for persons with chronic stroke. For both healthy and post-stroke participants, the tapered and round nosing shapes resulted in the largest horizontal foot clearance, and smallest foot overhang, respectively. However, given the greater step-to-step variability detected with round nosings, the tapered nosing presents as the safest choice among all evaluated designs. The results of this work can be used to inform architectural and accessible design standards for a safer built environment.

Hand-rung forces after a ladder climbing perturbation.

The hands are believed to be important for arresting falls from ladders. Yet, there is a paucity of kinetic data for the hand-handhold interface during recovery from a ladder climbing perturbation. This study quantified the hand-rung forces utilized after ladder climbing perturbations and the factors (upper body strength, fall severity, reestablished foot placement) contributing to hand-rung force. A ladder rung was released under the foot of the participants to simulate a climbing misstep perturbation. Hand-rung forces after the perturbation were quantified from load cells connected to two ladder rungs. Mean peak hand-rung force magnitudes were found to range between 46% and 84% of the climber's body weight. These magnitudes approached and, in some cases, exceeded individuals' grasping capacity. Individual upper body strength was not found to consistently contribute to hand-rung force, but increased hand-rung force was clearly linked with greater fall severity after an ascending perturbation. Individuals that reestablished foot placement after an ascending perturbation utilized lower hand-rung forces. Therefore, this study suggests hand-rung force to be dependent on circumstances of the falling event (fall severity, reestablished foot placement) as opposed to the climber's capability of producing upper body force. This knowledge highlights the importance of handhold and ladder designs for arresting a falling event, and is critical to inform ladder fall interventions such as designing handholds that resist high forces and permitting steps that enable reestablished foot placement.

Characterizing the demands of backward balance loss and fall recovery during stair descent to prevent injury.

Understanding the demands of balance recovery on stairs is important for developing strategies to prevent falls on stairs. This study characterized recovery strategies and whole-body movement following unexpected backward balance loss during stair descent in twelve young adults. Following balance loss, peak downward COM velocity was approximately double that experienced during non-perturbation stair descent. Participants used several balance recovery strategies: harness reliance (n = 1), no grasping reaction (n = 3), and grasping some environmental feature (n = 8). Of the five participants who used the handrail, four demonstrated grasping errors. Peak resultant handrail forces ranged from 24.2N to 238.3N. The results highlight the challenge of balance recovery during stair descent, showing that some people will use any available surface to arrest a fall. Our findings serve as a benchmark to understand the impact of stair-related interventions on fall recovery.

Effect of handrail height and age on the timing and speed of reach-to-grasp balance reactions during slope descent.

We investigated the effect of handrail height on the timing and speed of reach-to-grasp balance reactions during slope descent, in fourteen younger and thirteen older adults. Participants walked along an 8° slope mounted to a robotic platform. Platform perturbations evoked reach-to-grasp reactions. Handrail height did not significantly affect handrail contact time (i.e., time from perturbation onset to handrail contact) or movement time (i.e., time from EMG latency to handrail contact). Participants appeared to compensate for the increased hand-handrail distance with higher rails via increased peak upward hand speed, and decreased vertical handrail overshoot. Aging was associated with slower EMG latency, reduced hand acceleration time, and increased hand deceleration time. Our findings suggest that participants were not disadvantaged by higher handrails from reach-to-grasp timing or speed perspectives, and that other metrics (e.g., center-of-mass control after grasping) may be more important when evaluating handrail designs for balance recovery.

Use of handrails for balance and stability: Characterizing loading profiles in younger adults.

Well-designed handrails significantly enhance balance recovery, by allowing users to apply high forces to the rail and stabilize their center of mass. However, data on user-applied handrail forces during balance recovery are limited. We characterized the peak forces that 50 young adults applied to a handrail during forward and backward falling motions; quantified effects of handrail height (34, 38, 42 inches) and position prior to balance loss (standing beside the rail with or without hand contact, or facing the handrail with two-handed contact); and examined the relationship between handrail forces and individual mass. The testing environment consisted of a robotic platform that translated rapidly to destabilize participants, and a height-adjustable handrail that was mounted to the platform. Our findings support our hypotheses that starting position and handrail height significantly affect peak handrail forces in most axes. The highest handrail forces were applied when participants faced the handrail and grasped with two hands. In these cases, increased handrail height was associated with increased anterior forces and decreased downward, upward and resultant forces. As hypothesized, peak handrail forces correlated strongly with individual weight in most axes. Implications of these findings for handrail design are discussed.

Influence of handrail height and fall direction on center of mass control and the physical demands of reach-to-grasp balance recovery reactions.

The ability to maintain and recover center of mass (COM) and trunk control after a destabilization is critical for avoiding falls and fall-related injuries. Handrails can significantly enhance a person's ability to recover from large destabilizations, by enabling the person to grasp and apply high forces to the rail to stabilize their COM. However, the influence of handrail height and falling direction on COM control and the demands of grasping are unknown. We investigated the effect of handrail height (34, 38, 42 in.) and fall direction (forward, backward) on COM and trunk control, and the corresponding physical demands of reach-to-grasp balance reactions. Thirteen young adults were destabilized with platform perturbations, and reached to grasp a nearby handrail to recover balance without stepping. COM kinematics and applied handrail forces were collected. COM control was evaluated in terms of: (1) COM range and peak displacement, velocity and momentum in all Cartesian axes; and (2) trunk angular displacement, velocity and momentum in the roll and pitch axes. The physical demands of grasping were estimated via resultant handrail impulse. Compared to forward-directed falling, backward-directed falling was generally associated with greater peak COM and trunk angular displacement, velocity and momentum, along with greater handrail impulse. Higher handrails generally resulted in reduced peak COM and trunk angular displacement, velocity and momentum, as well as reduced handrail impulse. These results suggest that higher handrails may provide a stability advantage within the range of handrail heights tested, with better COM control achieved with lower physical demands of grasping.

Effect of Bathroom Aids and Age on Balance Control During Bathing Transfers.

Bathroom assistive devices are used to improve safety during bathing transfers, but biomechanical evidence to support clinical recommendations is lacking. This study evaluated the effectiveness of common bathroom aids in promoting balance control during bathing transfers. Twenty-six healthy adults (12 young, 14 older) stepped into and out of a slippery bathtub while using a vertical grab bar on the side wall, a horizontal grab bar on the back wall, a bath mat, a side wall touch, or no assistance. Balance control was characterized using center of pressure measures and showed greater instability for older adults. The vertical grab bar and wall touch resulted in the safest (best controlled) transfers. The bath mat provided improved balance control in the axis parallel to the bathtub rim but was equivalent to no assistance perpendicular to the rim, in the direction of obstacle crossing. These results can support clinical recommendations for safe bathing transfers.

Passive restraint reduces visually induced motion sickness in older adults.

Virtual environments such as those used in video games and driving/flight simulators are used for entertainment and training, but are often associated with visually induced motion sickness (VIMS). In this study, we asked whether passive restraint of the head and torso could reduce VIMS in younger and older adults. Twenty-one younger (18-35 years) and 16 older (65 + years) healthy adults engaged in a simulated driving task using a console video game while seated. On different days, participants completed 2 conditions: (a) in the unrestrained condition, participants were seated in a chair without a backrest and were free to move and (b) in the restrained condition, participants' head and torso were passively restrained to the backrest and headrest of the seat using tense elastic strips. Before and after exposure to the driving game, we measured standing postural sway with eyes closed. VIMS severity was quantified using the Fast Motion Sickness Scale and the Simulator Sickness Questionnaire. Results showed that older (but not younger) participants who became sick in the unrestrained condition reported significantly less VIMS when they were passively restrained. The present findings suggest that passive restraint may be useful to reduce, but not fully prevent, VIMS, particularly in older adults. (PsycINFO Database Record

The Evaluation of Vertical Pole Configuration and Location on Assisting the Sit-to-Stand Movement in Older Adults with Mobility Limitations.

Grab-bars and transfer poles are common sit-to-stand aids for mobility limited older adults. This study investigated differences in kinetics and kinematics to characterize the lower-limb strength and dynamic balance requirements across different pole configurations and positions in nine mobility limited older adults. Poles were varied by location (near and far) and configuration (single vertical pole, double vertical poles, vertical pole with a horizontal bar). Results indicated that the far pole condition resulted in increased trunk (p < 0.001) and hip flexion (p < 0.01 and < 0.0001 for contralateral and ipsilateral sides, respectively), and a reduced peak vertical force applied to the pole (p < 0.001). Peak extension moments at the hip and knee were unchanged, and, therefore, pole position had no effect on task demands. Placing the pole unilaterally introduced a small kinetic asymmetry, which significantly increased peak knee extension moments on the ipsilateral side (p < 0.05). Finally, dynamic balance was relatively unchanged across pole conditions. These findings offer novel insight into pole use and the effect of varying pole location and configuration in a sample of older adults with mobility impairment, and provide the basis for future work.