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Characterizing the Impact of Baseline Cognitive Status on Dual Task Performance: An Analysis of Postural and Cognitive Outcomes While Backward Protective SteppingJanuary 2020 (has links)
abstract: INTRODUCTION: As people age, they become increasingly susceptible to falls, particularly when their attention is divided. Cognitive domains such as executive functioning and processing speed also decline over time and are associated with falls. A critical aspect to reducing falls are reactive steps, which are used to recover balance after a perturbation. Characterizing the relationship between cognition, dual tasking, and prioritization is necessary in order to decrease fall risk in older adults. Thus, the purpose of this analysis was to determine the effects of baseline cognitive status on dual task interference and prioritization of postural and cognitive tasks while reactive stepping. METHODS: 30 participants (Parkinson's disease (PD) n=16, healthy controls (HC) n=14) were divided into two groups based on their baseline cognitive status: the high-cog group (n=18) or the low-cog group (n=12). All participants experienced 7 perturbation trials where they were solely tasked with reactive stepping, 2 cognitive trials where they were solely tasked with verbally responding to an auditory Stroop test, and 7 trials that combined the two tasks. Cognitive and protective stepping performance was calculated for dual task interference and prioritization across groups. RESULTS: There were no outcome variables that showed the log-cog group performing worse than the high-cog group from single to dual task conditions. While examining the dual task interference between groups, the only significant outcome was that the low-cog group exhibited a subtle improvement in their step length performance under dual task conditions while the high-cog group did not. When comparing the prioritization scores, there was no statistically significant difference in prioritization between the high-cog and low-cog group. Albeit not significant across groups, the prioritization score for all outcomes was negative, indicating a stepping prioritization under dual task conditions for both groups. This analysis provides preliminary evidence that baseline cognitive status does not significantly affect dual task interference nor prioritization while reactive step dual tasking. While these effects should be treated with caution, these results would suggest that baseline cognitive status may not play a critical role in dual task interference or attentional allocation in both people with PD and healthy older adults. / Dissertation/Thesis / Masters Thesis Exercise and Wellness 2020
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Impact of an Ankle Foot Orthosis on Reactive Stepping in Healthy Young Adults Using a Lean-and-Release ParadigmTwohy, Kyra Elizabeth 01 September 2020 (has links)
No description available.
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Push Recovery: A Machine Learning Approach to Reactive SteppingHorton, Jennifer Leigh 04 September 2013 (has links)
No description available.
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Assessing the Effects of Exoskeleton Use on Balance and Postural StabilityPark, Jangho 30 September 2021 (has links)
There is emerging evidence for the potential of occupational back-support exoskeletons (BSEs) to reduce physical demands, and thereby help control/prevent the risk of overexertion injuries associated with manual material handling. However, it is important to understand whether BSEs also introduce any unintended safety challenges. One potential risk associated with BSE use is increased risk of falls, since their extra weight, rigid structure, and external hip extension torque may increase demands on the postural control system. However, there is currently limited evidence on whether, and to what extent, BSE use alters postural stability and/or fall risk. The primary goal of this work was to understand the effects of exoskeleton use, and quantify the effects of exoskeleton design parameters, on balance and postural stability, with a focus on passive BSEs used for repetitive lifting work. A comprehensive evaluation of BSE use was performed under controlled laboratory conditions, focusing on three classes of human activity that form the basis of maintaining postural balance in diverse real-life scenarios: maintenance of a specified posture, voluntary movement, and reaction to an external perturbation.
The first study demonstrated that during quiet bipedal stance, BSE use increased median frequency and velocity of the center of pressure in the anterior-posterior direction. In the second study on level walking, BSE use caused an increase in gait step width and gait variability, and decrease in the margin of stability. BSE use with high supportive torque led to adapted gait patterns in early-stance phase. Hip range of motion and peak hip flexion velocity also decreased, and participants exhibited different strategies to increase mechanical energy for propelling the leg in late-stance phase: these effects increased with increasing torque applied by the exoskeleton. In the final study, BSE use did not alter the maximal lean angle from which individuals could successfully execute single step balance recovery, following a forward loss of balance. However, several recovery responses were negatively affected by BSE use, including increased reaction time, impeded hip flexion, and reduced margin of stability in the high-torque condition.
This is the first systematical investigation to quantify the effects of passive BSEs with multiple supportive torque levels on balance and postural stability. While exoskeleton effects on static balance were minimal, more substantial changes in gait spatiotemporal parameters, hip joint kinematics, and dynamic margins of stability were observed in the later studies. Our results indicate that postural stability deteriorated with exoskeleton use in dynamic conditions, and provide mechanistic insight into how stability is altered by different exoskeleton design factors such as added mass, restricted range of motion, and external hip extension torque. While our results are suggestive of increased fall risk, especially in the high-torque condition, fall risk in real life is moderated by a complex combination of individual and environmental conditions. Future work should consider more complex, realistic tasks and also include a more diverse sample that is studied under longer exposure durations, to further elucidate these findings. Our characterizations of a wide variety of postural responses as a function of exoskeleton torque settings are expected to contribute to improving both design and practice guidelines to facilitate the safe adoption of BSEs in the workplace. / Doctor of Philosophy / Occupational back-support exoskeletons (BSEs) – wearable mechanical systems designed to support, augment, and/or assist back extension – are expected to serve as an alternative workplace intervention to control and prevent overexertion injuries related to manual material handling tasks. While recent studies have shown the beneficial effects of BSE use in terms of physical load reduction on the low back, some concerns have also been raised on unexpected or unintended effects of exoskeletons. One potential risk associated with exoskeleton use is increased risk of falls, since a BSE's extra weight, rigid structure, and external hip extension torque are expected to place increased demands on the postural control system. Increase in fall risk is a critical safety concern, as occupational falls are a serious problem in terms of injuries, medical/industrial cost, and lost work time.
However, there exists limited evidence on whether the use of a BSE alters postural stability and/or increases fall risk. Hence, the goal of our study was to quantify the effects of BSE use on postural stability in various conditions related to real-life scenarios, such as standing balance, walking stability and how one would respond to a loss of balance following an external perturbation.
Our results showed that during quiet standing, BSE use slightly increased postural sway. In level walking tasks, BSE use had adverse effects on step length, step width, and dynamic stability. Furthermore, wearing a BSE with high supportive torque led to adapted gait patterns in early-stance phase, whereas participants showed different strategies to increase mechanical energy for propelling the leg in late-stance phase. In the final study investigating single step balance recovery following a forward loss of balance, we found that BSE use negatively affects balance recovery, mainly by impeding hip flexion.
Thus, our work suggests that exoskeleton use can deteriorate balance and/or postural stability in situations of static standing, voluntary walking, and reacting to an external perturbation, thereby potentially leading to an increase in fall risk. These effects may be more pronounced among specific population sub-groups such as older workers, and may also affect individuals more severely under conditions of stress or fatigue. Hence, future studies must include more rigorous testing of BSE use using a variety of challenging and realistic scenarios, and also include more diverse population samples. The findings from this work are expected to contribute to improving design and practice guidelines to facilitate the safe adoption of BSEs in the workplace.
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