Interventions to Promote More Effective Balance-Recovery Reactions in Industrial Settings: New Perspectives on Footwear and Handrails

“Change-in-support” balance-recovery reactions that involve rapid stepping or reaching movements play a critical role in preventing falls. Recent geriatrics studies have led to new interventions to improve ability to execute these reactions effectively. Some of these interventions have the potential to reduce fall risk for younger persons working in industrial settings. In this paper, we review research pertaining to two such interventions: 1) balance-enhancing footwear insoles designed to improve stepping reactions, and 2) proximity-triggered handrail cueing systems designed to improve reach-to-grasp reactions. The insole has a raised ridge around the perimeter that is intended to improve balance control by providing increased stimulation of sensory receptors on the footsole in situations where loss of balance may be imminent. The cueing system uses flashing lights and/or verbal prompts to attract attention to the handrail and ensure that the brain registers its location, thereby facilitating more rapid and accurate grasping of the rail if and when sudden loss of balance occurs. Results to date support the efficacy of both interventions in geriatric populations. There is also some evidence that these interventions may improve balance control in younger persons; however, further research is needed to confirm their efficacy in preventing falls in industrial settings

The application of implementation science for pressure ulcer prevention best practices in an inpatient spinal cord injury rehabilitation program

To implement pressure ulcer (PU) prevention best practices in spinal cord injury (SCI) rehabilitation using implementation science frameworks

Determining the visual angle of objects in the visual field: An extended application of eye trackers

Many eye-tracker systems display the point of central gaze fixation on video images of the viewed environment. We describe here a method for determining the visual angles of objects located in the periphery. Such data are needed to study the potential contributions of peripheral vision during cognitive and motor tasks.This work was supported by the Canadian Institutes of Health Research (CIHR) Grant #MOP-13355. The work of E. C. King was also supported by a CIHR Canada Graduate Scholarships Master’s Award and graduate scholarships from the Toronto Rehabilitation Institute and University of Toronto (Vision Science Research Program, and Institute of Biomaterials and Biomedical Engineering)

Stepping to recover balance in complex environments: is online visual control of the foot motion necessary or sufficient?

Rapid step reactions evoked by balance perturbation must accommodate constraints on limb motion imposed by obstacles and other environmental features. Recent results suggest that the required visuospatial information (VSI) is acquired and stored “proactively”, prior to perturbation onset (PO); however, the extent to which “online” (post-PO) visual feedback can contribute is not known. To study this, we used large unpredictable platform perturbations to evoke rapid step reactions, while subjects wore liquid crystal goggles that occluded vision: (1) prior to PO (forcing use of online-VSI), (2) after PO (forcing use of stored-VSI), or (3) not at all (normal-VSI). Subjects stood behind a barrier in which the location of a narrow slot, through which the foot had to be moved during forward step reactions, was varied unpredictably between trials. Within subjects who were able to do the task (6 of 8 young adults tested), responses in stored-VSI and normal-VSI trials were very similar. However, in online-VSI trials, the foot-off time for the step through the slot was delayed (by ∼50 ms, on average). Presumably, this delay allowed more time to acquire and process online-VSI regarding the required foot trajectory, yet subjectswere still more likely to select the “wrong” foot (contralateral to the slot location) and to contact the barrier while moving the foot through the slot, in online-VSI trials. These results suggest a critical role for stored-VSI during the earliest phase of the step, in selecting the step limb and planning the initial trajectory. Online acquisition and processing of the required VSI may be too slow to allow effective control of this early phase, particularly in situations where the demands for accurate foot motion are high.This study was supported by an operating grant (#MOP-13355) from the Canadian Institutes of Health Research (CIHR)

Gaze behavior governing balance recovery in an unfamiliar and complex environment

Visuospatial information regarding obstacles and other environmental constraints on limb movement is essential for the successful planning and execution of stepping movements. Visuospatial control strategies used during gait and volitional stepping have been studied extensively; however, the visuospatial strategies that are used when stepping rapidly to recover balance in response to sudden postural perturbation are not well established. To study this, rapid forward stepping reactions were evoked by unpredictable support-surface acceleration while subjects stood amid multiple obstacles that moved intermittently and unpredictably prior to perturbation onset (PO). To prevent predictive control, subjects performed only one trial (their very first exposure to the perturbation and environment). Visual scanning of the obstacles and surroundings occurred prior to PO in all subjects; however, gaze was never redirected at the obstacles, step foot or landing site in response to the perturbation. Surprisingly, the point of gaze at time of foot-contact was consistently and substantially anterior to the step-landing site. Despite the apparent absence of 'online' visual feedback related to the foot movement, the compensatory step avoided obstacle contact in 10 of 12 young adults and 9 of 10 older subjects. The results indicate that the balance-recovery reaction was typically modulated on the basis of visuospatial environmental information that was acquired and continually updated prior to perturbation, as opposed to a strategy based on 'online' visual control. The capacity to do this was not adversely affected by aging, despite a tendency for older subjects to look downward less frequently than young adults.Supported by the Canadian Institutes of Health Research and the Ontario Neurotrauma Foundation

A novel handrail cueing system to prevent falls in older adults

Balance-recovery reactions that involve rapid reaching movements to grasp a handrail for support can play a critical role in preventing falls. To execute these reactions, the central nervous system (CNS) requires visuospatial information (VSI) about the handrail location. However, the urgent need to react rapidly may limit ability to acquire this information after loss of balance occurs. Instead, it appears that the CNS may continually monitor the environment and store salient VSI for use if and when a loss of balance occurs. Age-related deficits in visual attention may impair ability to use grasping reactions to recover balance by impeding the acquisition, processing and storage of required VSI. To counter this problem, we have developed a proximity-triggered handrail cueing system (patent pending) that provides a visual cue (flashing lights) and/or verbal cue (“attention, use the handrail”) so as to attract attention to the handrail. The cueing system comprises light-emitting diodes mounted inside a translucent black railing, speakers inserted into the handrail mounting fixtures, and a photocell that triggers the cueing as the person approaches. To test the system, grasping reactions were evoked as subjects walked along an extended (2x6 m) motion platform configured to simulate an office environment (including a stair, handrail and visual distracters). The platform was triggered to move suddenly and unexpectedly when the subject was adjacent to the handrail. Pilot results (21 subjects) showed that the rail was grasped more frequently when there was a verbal cue (67%) or a visual cue (40%), compared to conventional-handrail trials (10%)

Gaze Behavior of Older Adults in Responding to Unexpected Loss of Balance while Walking in an Unfamiliar Environment: a Pilot Study

AbstractPurposeRapid reach-to-grasp balance-recovery reactions play a critical role in preventing falls. Recent young-adult studies suggest these reactions may be guided using stored visuo-spatial information from the central field, and that peripheral vision may also play an important role. This study used gaze recordings to examine the visual control of reach-to-grasp reactions in older adults.MethodsA motion platform was configured to simulate a “real-life” environment that included a handrail. Subjects performed an activity that required walking to the end of the platform, which was triggered to move suddenly and unexpectedly as they approached the handrail. Twelve healthy older adults (64-79 years old) were tested and compared to 12 healthy young adults (22-30 years old) tested as part of another study.ResultsOlder adults were more than twice as likely as young adults to react to the platform perturbation by grasping the handrail (10/12 versus 4/12), despite being much less likely to visually fixate the handrail after entering the new environment. Grasping errors were remarkably common (5/10 older, 2/4 young), but there was no consistent relationship to the preceding gaze behavior.ConclusionOlder adults were highly dependent on using a handrail to recover balance, but commonly failed to direct overt visual attention to the rail after entering the unfamiliar environment. The failure to fixate the rail required the reaching movement to be guided using peripheral vision. Further research is needed to determine whether grasping errors can be prevented via interventions that either attract overt attention to the handrail or improve processing of peripheral-field information

The moveable handhold: a new paradigm to study visual contributions to the control of balance-recovery reactions

Balance-recovery reactions that involve rapid step or reach-to-grasp movements are prevalent and functionally important responses to instability. Successful use of these reactions to recover balance in daily life requires a capacity to modulate the reaction to deal with the continual variation in environmental constraints that occurs as the person moves, i.e. location of objects that can obstruct limb movements or serve as handholds to grasp. The most direct approach to study this involves applying balance perturbations as subjects move within a visually complex environment; however, this approach does not allow precise control over kinematic variables or visual inputs, and is susceptible to strong learning effects. We have therefore developed an alternate approach, wherein the subject is stationary and the relative motion between subject and constraints that normally occurs as a result of ambulation is instead introduced via movement of the surrounding obstacles or handholds. We previously developed a motor-driven "obstacle-mover" to manipulate constraints on step reactions, and now describe an analogous approach to study reach-to-grasp reactions, using a motor-driven "handhold-mover". We anticipate that this paradigm will provide new opportunities to probe CNS control of upright stance, by providing a sensitive indicator of limitations in the neuromusculoskeletal systems. It can also be used to test perturbation-evoked reactions in seated subjects, thereby allowing testing or training of persons who are unable to stand and use of techniques (e.g. TMS, EEG) that can be difficult to perform in free-standing subjects.This study was funded by grant no. MOP-13355 from the Canadian Institutes of Health Research (CIHR). K.C.C. held scholarships from the Ontario Graduate Scholarships in Science & Technology program, University of Toronto [Institute of Biomaterial and Biomedical Engineering (IBBME) and Vision Science Research Program (VSRP)] and Toronto Rehabilitation Institute (TRI). S.M.M. held postdoctoral awards from the Ontario Neurotrauma Foundation (ONF) and University of Toronto [CIHR Strategic Training in Health Care, Technology and Place (HCTP)]. E.C.K. held scholarships from the CIHR, University of Toronto (IBBME and VSRP) and TRI. J.Y.T. held scholarships from the Natural Sciences and Engineering Research Council of Canada, University of Toronto (HCTP) and TRI. C.Y.S. held a postdoctoral award from the ONF

Gaze behavior of older adults in responding to unexpected loss of balance while walking in an unfamiliar environment: a pilot study

Purpose: Rapid reach-to-grasp balance-recovery reactions play a critical role in preventing falls. Recent young-adult studies suggest these reactions may be guided using stored visuo-spatial information from the central field, and that peripheral vision may also play an important role. This study used gaze recordings to examine the visual control of reach-to-grasp reactions in older adults. Methods: A motion platform was configured to simulate a “reallife” environment that included a handrail. Subjects performed an activity that required walking to the end of the platform, which was triggered to move suddenly and unexpectedly as they approached the handrail. Twelve healthy older adults (64-79 years old) were tested and compared to 12 healthy young adults (22-30 years old) tested as part of another study. Results: Older adults were more than twice as likely as young adults to react to the platform perturbation by grasping the handrail (10/12 versus 4/12), despite being much less likely to visually fixate the handrail after entering the new environment. Grasping errors were remarkably common (5/10 older, 2/4 young), but there was no consistent relationship to the preceding gaze behavior. Conclusion: Older adults were highly dependent on using a handrail to recover balance, but commonly failed to direct overt visual attention to the rail after entering the unfamiliar environment. The failure to fixate the rail required the reaching movement to be guided using peripheral vision. Further research is needed to determine whether grasping errors can be prevented via interventions that either attract overt attention to the handrail or improve processing of peripheral-field information.This study was funded by operating grant #MOP-13355 from the Canadian Institutes of Health Research (CIHR). S.M.M. held a summer internship award from the Ontario Neurotrauma Foundation and a CIHR Strategic Training Post-Doctoral Fellowship in Health Care, Technology and Place. E.C.K. held scholarships from the CIHR, the Toronto Rehabilitation Institute, and the University of Toronto (Institute of Biomaterials and Biomedical Engineering, and Vision Science Research Program)

Does the 'eyes lead the hand' principle apply to reach-to-grasp movements evoked by unexpected balance perturbation?

A fundamental principle that has emerged from studies of natural gaze behavior is that goal-directed arm movements are typically guided by a saccade to the target. In this study, we evaluated a hypothesis that this principle does not apply to rapid reach-to-grasp movements evoked by sudden unexpected balance perturbations. These perturbations involved forward translation of a large (2x6m) motion platform configured to simulate a 'real-life' environment. Subjects performed a common 'daily-life' visuo-cognitive task (find a telephone and make a call) that required walking to the end of the platform, which was triggered to move as they approached a handrail mounted alongside the travel path. A deception was used to ensure that the perturbation was truly unexpected. Eleven of 18 healthy young-adult subjects (age 22-30) reached to grasp or touch the rail in response to the balance perturbation. In support of the hypothesis, none of these arm reactions was guided by concurrent visual fixation of the handrail. Seven of the 11 looked at the rail upon first entering the environment, and hence may have used "stored" central-field information about the handrail location to guide the subsequent arm reaction. However, the other four subjects never looked directly at the rail, indicating a complete reliance on peripheral vision. These findings add to previous evidence of distinctions in the CNS control of volitional and perturbation-evoked arm movements. Future studies will determine whether similar visuo-motor behavior occurs when the available handhold is smaller or when subjects are not engaged in a concurrent visuo-cognitive task.This work was supported by operating grant #MOP-13355 from the Canadian Institutes of Health Research (CIHR). E.C.K. held scholarships from CIHR, the Toronto Rehabilitation Institute, and the University of Toronto (Institute of Biomaterials and Biomedical Engineering and the Vision Science Research Program). S.M.M. held a summer internship award from the Ontario Neurotrauma Foundation and a CIHR Strategic Training Post-Doctoral Fellowship in Health Care, Technology and Place