Browsing by Author "Kim, Sun Wook"

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    Assessing the Effects of Exoskeleton Use on Balance and Postural Stability
    Park, Jangho (Virginia Tech, 2021-09-30)
    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.
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    Assessing the Relationship between Occupational Injury Risk and Performance: the Efficacy of Adding Adjustability and Using Exoskeletons in the Context of a Simulated Drilling Task
    Alabdulkarim, Saad A. (Virginia Tech, 2017-11-16)
    Work-related musculoskeletal disorders (WMSDs) continue to occur despite an increasing understanding of the risk factors that initiate these disorders. Ergonomics is commonly seen as a health and safety approach that has no influence on performance, a perspective potentially hindering intervention proposals in practice. Highlighting potential performance benefits can facilitate intervention cost-justification, along with the traditional focus on reducing exposure to injury risk. The main objective of this research was to examine the dual influences (i.e., on performance and injury risk) of two distinct types of interventions: adding adjustability, as a commonly advocated approach when considering ergonomics early in the (re)design phase to change task demands; and using exoskeletons to enhance worker capacity. A simulated drilling task was used, which was considered informative as it entailed diverse demands (precision, strength, and speed) and permitted quantifying two dimensions of task performance (productivity and quality). The dual influences of three levels of workstation adjustability were examined first; increasing adjustability improved performance, with this benefit occurring only when a given level of adjustability also succeeded in reducing ergonomic risk. Across examined conditions, several significant linear associations were found between risk (e.g., Strain Index score) and performance metrics (e.g., completion time), further supporting an inverse relationship between these two outcomes. The dual influences of three distinct passive exoskeletal designs were investigated/compared subsequently, in a simulated overhead drilling task and considering the potential moderating effects of tool mass and precision requirements. Specific designs were: full-body (Full) and upper-body (Arm) exoskeletons with attached mechanical arms; and an upper-body (Shl) exoskeleton providing primarily shoulder support. Both designs with mechanical arms increased static and median total muscle activity while deteriorating quality. The Shl design reduced shoulder loading while increasing dominant upper arm loading and deteriorating quality in the highest precision requirements. Influences of both increasing precision and tool mass were fairly consistent across the examined designs. As such, no single design was obviously superior in both physical demands and performance. Although future work is needed under more diverse/realistic scenarios, these results may be helpful to (re)design interventions that achieve dual benefits on performance and injury risks.
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    Behavioral Monitoring to Identify Self-Injurious Behavior among Children with Autism Spectrum Disorder
    Garside, Kristine Dianne Cantin (Virginia Tech, 2019-03-25)
    Self-injurious behavior (SIB) is one of the most dangerous behavioral responses among individuals with autism spectrum disorder (ASD), often leading to injury and hospitalization. There is an ongoing need to measure the triggers of SIB to inform management and prevention. These triggers are determined traditionally through clinical observations of the child with SIB, often involving a functional assessment (FA), which is methodologically documenting responses to stimuli (e.g., environmental or social) and recording episodes of SIB. While FA has been a "gold standard" for many years, it is costly, tedious, and often artificial (e.g., in controlled environments). If performed in a naturalistic environment, such as the school or home, caregivers are responsible for tracking behaviors. FA in naturalistic environments relies on caregiver and patient compliance, such as responding to prompts or recalling past events. Recent technological developments paired with classification methods may help decrease the required tracking efforts and support management plans. However, the needs of caregivers and individuals with ASD and SIB should be considered before integrating technology into daily routines, particularly to encourage technology acceptance and adoption. To address this, the perspectives of SIB management and technology were first collected to support future technology design considerations (Chapter 2). Accelerometers were then selected as a specific technology, based on caregiver preferences and reported preferences of individuals with ASD, and were used to collect movement data for classification (Chapter 3). Machine learning algorithms with featureless data were explored, resulting in individual-level models that demonstrated high accuracy (up to 99%) in detecting and classifying SIB. Group-level classifiers could provide more generalizable models for efficient SIB monitoring, though the highly variable nature of both ASD and SIB can preclude accurate detection. A multi-level regression model (MLR) was implemented to consider such individual variability (Chapter 4). Both linear and nonlinear measures of motor variability were assessed as potential predictors in the model. Diverse classification methods were used (as in Chapter 3), and MLR outperformed other group level classifiers (accuracy ~75%). Findings from this research provide groundwork for a future smart SIB monitoring system. There are clear implications for such monitoring methods in prevention and treatment, though additional research is required to expand the developed models. Such models can contribute to the goal of alerting caregivers and children before SIB occurs, and teaching children to perform another behavior when alerted.
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    Biomechanical Assessment and Metabolic Evaluation of Passive Lift-Assistive Exoskeletons During Repetitive Lifting Tasks
    Alemi, Mohammad Mehdi (Virginia Tech, 2019-09-16)
    Work-related musculoskeletal disorders (WMSDs) due to overexertion and consequently the low back pain (LBP) are one of the most prevalent sources of nonfatal occupational injuries and illnesses in all over the world. In the past several years, the industrial exoskeletons especially the passive ones have been proposed as alternative intervention and assistive devices, which are capable of reducing the risk of WMSDs and LBP. However, more research is warranted to validate the applicability of these exoskeletons. In addition, because the majority of previous studies have been limited to specific lifting tasks using only one type of lift assistive exoskeleton, more research is needed to examine the effect of alteration of different lift-assistive exoskeletons on reducing the activity of back muscles and metabolic reduction. The main objective of this dissertation is to render an overview of three studies that attempt to improve the literature by providing comprehensive biomechanical evaluations and metabolic assessments of three passive lift-assistive exoskeletons (VT-Lowe's Exoskeleton (developed in ARLab at VT), Laevo and SuitX). This dissertation has been composed of three related studies. The first study aimed to investigate and examine the capability of a novel lift assistive exoskeleton, VT-Lowe's exoskeleton, in reducing the peak and mean activity of back and leg muscles. Findings revealed that the exoskeleton significantly decreased the peak and mean activity of back muscles (IL(iliocostalis lumborum) and LT(longissimus thoracis)) by 31.5% and 29.3% respectively for symmetric lifts, and by 28.2% and 29.5% respectively for asymmetric lifts. Furthermore, the peak and mean EMG of leg muscles were significantly reduced by 19.1% and 14.1% during symmetric lifts, and 17.4% and 14.6% during asymmetric lifts. Interestingly, the VT-Lowe's exoskeleton showed higher reduction in activity of back and leg muscles compared to other passive lift-assistive exoskeletons available in the literatures. In the second study, the metabolic cost reduction associated with the use of VT-Lowe's exoskeleton during freestyle lifting was theoretically modelled, validated and corresponding metabolic savings were reported. The metabolic cost and the oxygen consumption results supported the hypothesis that the VT-Lowe's exoskeleton could significantly reduce the metabolic demands (~7.9% on average) and oxygen uptake (~8.7% on average) during freestyle lifting. Additionally, we presented a prediction model for the metabolic cost of exoskeleton during repetitive freestyle lifting tasks. The prediction models were very accurate as the absolute prediction errors were small for both 0% (< 1.4%) and 20% (< 0.7%) of body weight. In the third study, the biomechanical evaluation, energy expenditure and subjective assessments of two passive back-support exoskeletons (Laevo and SuitX) were examined in the context of repetitive lifting tasks. The experimental lifting tasks in this study were simulated in a laboratory environment for two different levels of lifting symmetry (symmetric vs. asymmetric) and lifting posture (standing vs. kneeling). Results of this study demonstrated that using both exoskeletons during dynamic lifting tasks could significantly lower the peak activity of trunk extensor muscles by ~10-28%. In addition, using both exoskeletons could save the energy expenditure by ~4-13% in all conditions tested by partially offsetting the weight of the torso. Such reductions were, though, task-dependent and differed between the two tested exoskeletons. Overall, the results of all three studies in this dissertation showed the capability of passive lift-assistive exoskeletons in reducing the activity of back and leg muscles and providing metabolic savings during repetitive lifting tasks.
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    Biomechanics-Based Optimization for Exoskeleton Design
    Hook, Melanie Lynn (Virginia Tech, 2023-05-24)
    The goal of this thesis is to use biomechanical data describing shoulder motion to determine optimal parameters to assist in the design of a 5 DOF active shoulder exoskeleton. This thesis will provide a proof of concept on optimization techniques using motion data using a simplified 3 DOF model to facilitate future work implementing a full 5 DOF model. Optimization will be performed to determine the link lengths and, consequently, the locations of the joints of the exoskeleton by considering the human's workspace to maximize range of motion and promote user safety by minimizing collisions of the exoskeleton with the user and with the exoskeleton itself. The thesis will detail the development of computational models of the human and proposed exoskeleton, the processing of experimental data used to estimate the human's capabilities, optimization, and future work. This work will contribute to a large-scale NSF-funded project of building an upper body exoskeleton emulator. The emulator will promote the widespread adoption of exoskeletons in industry by providing a test-bed to streamline the rapid design of various assistance profiles for various users and tasks.
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    Development and Assessment of Smart Textile Systems for Human Activity Classification
    Mokhlespour Esfahani, Mohammad Iman (Virginia Tech, 2018-09-13)
    Wearable sensors and systems have become increasingly popular for diverse applications. An emerging technology for physical activity assessment is Smart Textile Systems (STSs), comprised of sensitive/actuating fiber, yarn, or fabric that can sense an external stimulus. All required components of an STS (sensors, electronics, energy supply, etc.) can be conveniently embedded into a garment, providing a fully textile-based system. Thus, STSs have clear potential utility for measuring health-relevant aspects of human activity, and to do so passively and continuously in diverse environments. For these reasons, STSs have received increasing interest in recent studies. Despite this, however, limited evidence exists to support the implementation of STSs during diverse applications. Our long-term goal was to assess the feasibility and accuracy of using an STS to monitor human activities. Our immediate objective was to investigate the accuracy of an STS in three representative applications with respect to occupational scenarios, healthcare, and activities of daily living. A particular STS was examined, consisting of a smart socks (SSs), using textile pressure sensors, and smart undershirt (SUS), using textile strain sensors. We also explored the relative merits of these two approaches, separately and in combination. Thus, five studies were completed to design and evaluate the usability of the smart undershirt, and investigate the accuracy of implementing an STS in the noted applications. Input from the SUS led to planar angle estimations with errors on the order of 1.3 and 9.4 degrees for the low-back and shoulder, respectively. Overall, individuals preferred wearing a smart textile system over an IMU system and indicated the former as superior in several aspects of usability. In particular, the short-sleeved T-shirt was the most preferred garments for an STS. Results also indicated that the smart shirt and smart socks, both individually and in combination, could detect occupational tasks, abnormal and normal gaits, and activities of daily living with greater than 97% accuracy. Based on our findings, we hope to facilitate future work that more effectively quantifies sedentary periods that may be deleterious to human health, as well as detect activity types that may be help or hinder health and fitness. Such information may be of use to individuals and workers, healthcare providers, and ergonomists. More specifically, further analyses from this investigation could provide strategies for: (a) modifying a sedentary lifestyle or work scenario to a more active one, and (b) helping to more accurately identify occupational injury risk factors associated with human movement.
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    Development and Evaluation of Methods to Assess Physical Exposures in the Workplace
    Kim, Sun Wook (Virginia Tech, 2012-12-06)
    Work-related musculoskeletal disorders (WSMDs) are an important health concern in the workplace.  Accurately quantifying the level of physical exposures (i.e., kinematics and kinetics) is essential for risk assessments, developing and/or testing interventions, and improving estimates of exposure-response relationships.  Such exposures ideally should be quantified in situ, while workers interact with the actual work environment to complete their tasks.  However, in practice, relatively crude and/or time-consuming methods are often used, including self-reports, observational methods, and simple instrumentation, since directly assessing physical exposures is challenging in the workplace, and typically resource prohibitive. Inertial motion capture (IMC) and in-shoe pressure measurement (IPM) systems are emerging wearable technologies, and they can, respectively, facilitate monitoring of body kinematics and external forces on the body in the workplace.  Thus, this research examined the potential of such technologies in exposure assessments, and evaluated them in comparison to mature laboratory systems (i.e., optical motion capture system and force platform) or direct observation.  Performance of an IMC system was evaluated during several manual material handling (MMH) tasks, in terms of estimated body kinematics and kinetics at selected body parts.  A practical issue, regarding calibrating the IPM system in the field, was addressed by defining an ad hoc global coordinate system using a force platform.  Several regression models were developed for estimating center-of-pressure location and ground reaction forces.  Given that outputs from the IMC and the IPM systems are numerically fine-grained, but generally lack contextual information about a given job, task classification approaches were explored to automatically identify task types and their time proportions in a job. Overall, the outcomes from these studies demonstrated the potential of the IMC and the IPM systems for measuring physical exposures in the workplace.  However, estimation of physical exposures using these systems requires further improvements in some cases.  This research provided groundwork for future rapid and direct assessments of physical exposures in the workplace, and which needs to be expanded and validated in future efforts.
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    Effects of back-support exoskeleton use on lower limb joint kinematics and kinetics during level walking
    Park, Jang-Ho; Lee, Youngjae; Madinei, Saman; Kim, Sun Wook; Nussbaum, Maury A.; Srinivasan, Divya (Springer, 2022-04-27)
    We assessed the effects of using a passive back-support exoskeleton (BSE) on lower limb joint kinematics and kinetics during level walking. Twenty young, healthy participants completed level walking trials while wearing a BSE (backXTM) with three different levels of hip-extension support torque (i.e., no torque, low, and high) and in a control condition (no-BSE). When hip extension torques were required for gait-initial 0-10% and final 75-100% of the gait cycle-the BSE with high supportive torque provided ~ 10 Nm of external hip extension torque at each hip, resulting in beneficial changes in participants' gait patterns. Specifically, there was a ~ 10% reduction in muscle-generated hip extension torque and ~ 15-20% reduction in extensor power. During the stance-swing transition, however, BSE use produced undesirable changes in lower limb kinematics (e.g., 5-20% increase in ankle joint velocity) and kinetics (e.g., ~ 10% increase in hip flexor, knee extensor, and ankle plantarflexor powers). These latter changes likely stemmed from the need to increase mechanical energy for propelling the leg into the swing phase. BSE use may thus increase the metabolic cost of walking. Whether such use also leads to muscle fatigue and/or postural instability in long-distance walking needs to be confirmed in future work.
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    Effects of Occupational Exoskeletons on Responses to Simulated Slips and Trips
    Dooley, Stephen Joseph (Virginia Tech, 2023-07-26)
    Occupational exoskeletons are designed to reduce workplace injury risk by decreasing work demands. Due to their relatively recent development, there has been limited research into potential unintended and undesirable consequences of wearing them. The goal of this thesis was to investigate the effects of exoskeleton use on reactive balance in response to simulated slips and trips. Five representative exoskeletons were investigated including leg-, back, and shoulder-support exoskeletons. This thesis consists of two studies: a smaller study investigating one exoskeleton and a larger one investigating multiple exoskeletons. Participants stood on a specialized treadmill, then abruptly and unexpectedly changing treadmill belt speed to simulate trip-like forward losses of balance or slip-like backward losses of balance. The results of the first study showed that a passive leg-support exoskeleton adversely reactive balance for both slips and trips. The results of the second study showed that back-support exoskeletons had a greater adverse effect on reactive balance compared to shoulder-support exoskeletons for both slips and trips. These exoskeletons affected reactive balance due to their interaction with stepping kinematics and movement constraints. This thesis provides important information that can be used to warn users of potential increased fall risks and inform exoskeleton manufacturers who may be able to modify designs to reduce any additional fall risk.
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    Evaluation of Markerless Motion Capture to Assess Physical Exposures During Material Handling Tasks
    Ojelade, Aanuoluwapo Ezekiel (Virginia Tech, 2024-03-12)
    Manual material handling (MMH) tasks are associated with the development of work-related musculoskeletal disorders (WMSDs). Minimizing the frequency and intensity of handling objects is an ideal solution, yet MMH remains an integral part of many industry sectors, including manufacturing, construction, warehousing, and distribution. Physical exposure assessment can help identify high-risk tasks, guide the development and evaluation of ergonomic interventions, and contribute to understanding exposure-risk relationships. Physical exposure can be evaluated using self-assessment, observational methods, and direct measurements. Nevertheless, implementing these methods in situ can be challenging, time consuming, expensive, and infeasible or inaccurate in many cases. Thus, there is a critical need to improve physical exposure assessments to protect workers and save costs. This dissertation assessed the accuracy of a markerless motion capture system (MMC) to quantify physical exposures during MMH tasks using three studies. Specifically, the first study investigated the performance of an MMC system, together with machine learning algorithms, for classifying diverse MMH tasks during a simulated complex job. In the second study, the feasibility of predicting dynamic hand forces was determined, using alternative measures, such as kinematics from MMC and/or in-sole pressure systems, coupled with a machine learning algorithm. Finally, in the third study, we systematically evaluated MMC for assessing biomechanical demands, by comparing outputs from a full-body musculoskeletal model driven by kinematic and kinetics from gold standard input and estimates derived from the MMC and in-sole pressure measurement system. Overall, the findings of these studies demonstrated the potential of using MMC to classify several common occupational tasks and to estimate the associated biomechanical demands for a given worker (automatically and with minimal physical contact). Additionally, the methods developed here can help stakeholders rapidly assess an individual worker's exposure to physical demands during diverse tasks.
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    Exploratory field testing of passive exoskeletons in several manufacturing environments: perceived usability and user acceptance
    Schwerha, Diana; McNamara, Nathan; Kim, Sun Wook; Nussbaum, Maury A. (2022-04-22)
    OCCUPATIONAL APPLICATIONS: Results of the current exploratory study suggest that use of an exoskeleton (EXO) has the potential to be accepted by workers as an intervention in diverse manufacturing environments. Also evident were that the major factors contributing to EXO-use-intention are perceived comfort, task-technology fit, perceived safety, and perceived usefulness. A user's perception of perceived usability may be established by using an exoskeleton during actual job tasks, yet some aspects of perceived usability likely require multiple exposures to an EXO for an accurate assessment. Many negative comments regarding EXO use were related to physical constraints (e.g., restricted movements, bulkiness), and to the EXO interface (e.g., straps, cuff designs), suggesting a need for further research on EXO design to minimize discomfort. In practice, there is likely value in having workers use and explore candidate EXOs during their actual job, both to accurately assess the usefulness of an EXO and to find the most effective EXO.
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    Influence of gender and obesity on motor performance, neuromuscular control and endurance in older adults
    Duan, Xu (Virginia Tech, 2018-01-23)
    The rapid growth of an older demographic is an increasing concern around the world. Older people have been reported to suffer from physiological and neuromuscular declines in several systems including skeletal muscles, central nervous system, cardiovascular processes and respiratory function. These age-related changes are often reflected through impairments in functional performance of occupational tasks as well as activities of daily living. This may make an older population more prone to musculoskeletal disorders and injuries. In addition, health problems and injury risks are likely amplified by factors such as obesity. Obesity has emerged as a serious health concern in the United States in recent decades. However, obesity-related changes in performance and motor control as well as how they will be modified by gender, specifically among older adults, are still largely unexplored. As motor variability has recently been reported to be associated with fatigue development and may have the potential to reveal underlying mechanisms of neuromuscular control, the main goals of this study were to investigate the influence of gender and obesity on motor performance, neuromuscular control and endurance in the elderly, by examining differences in motor variability during intermittent submaximal isometric exertions of the knee and hand. Fifty-two older participants with age over 65 were recruited into four groups: obese male (9), obese female (13), non-obese male (15) and non-obese female (15). The obese groups consisted of those whose BMI was greater than 30 kg/m2. Participants were asked to perform intermittent (15s on and 15s off) isometric handgrip and knee extensions at 30% MVC until exhaustion. Force and muscle activations of the Vastus Lateralis, Rectus Femoris, Extensor Carpi Radialis and Flexor Carpi Radialis muscles were collected through the endurance task. Motor variability was quantified using the coefficient of variation (CV) and sample entropy (SaEn) of the surface electromyography (EMG) and force signals. Motor variability during exercise differed both between males and females, and between obese and non-obese people, reflecting different motor strategies employed in order to prolong endurance. Overall, across all individuals, we observed a significant positive correlation between cycle-to-cycle variability of knee extensor muscle activation during the baseline period of the task and endurance time. As for gender differences, males exhibited longer endurance times than females, and seemed to achieve that through utilizing a motor strategy involving a more variable (higher CV) and less complex (lower SaEn) agonistic muscle activity. Since this was accompanied by a lower fluctuation in the force signal (lower CV) and a higher complexity of force (SaEn), we interpreted this to be a motor strategy involving more variable recruitment of synergistic and antagonistic motor units during the knee extension task to prolong endurance time, among males compared to females. As for obesity differences, there were no obesity-related changes in endurance time. However, obese individuals exhibited a greater cycle-to-cycle variability that was positively correlated with endurance time during the knee extension task, indicating a larger alteration in the recruitment of motor units across successive contractions, which contributed to comparable endurance time and performance with their non-obese counterparts. During the hand-grip tasks, variabilities in force and muscle activity followed similar trends as the knee extension task. However, there were no significant gender or obesity differences in endurance time, and there also weren't any significant correlations between any of the dependent variables with endurance time. Thus, this study was a basic investigation into changes in motor variability and how it was associated with the development of fatigue among older adults; and the potential influences of gender and obesity on the relationships. Two tasks of high relevance to both occupational life and activities of daily living, i.e. knee extension and hand-grip were considered. Our findings enhance the theoretical understanding of the underlying neuromuscular control patterns and their relationship with fatigue for different individuals. Given that both aging and obesity rates are rising continuously and becoming a substantial health and safety problem especially in the occupational environment, the results from this study are both timely and critical for practical design applications, especially by recognizing the importance of having a variable motor pattern in task performance, even among older adults.
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    Investigating the Relationship Between Objective and Subjective Measures of Physical Demand During Passive Exoskeleton Use
    Kelley, Sydney Aelish (Virginia Tech, 2023-10-24)
    Passive exoskeletons hold promise in reducing the risk of work-related musculoskeletal disorders, however further research is essential before widespread adoption can occur. This study explores the feasibility of using subjective measures of physical demand in place of costly and less practical objective measures. Normalized electromyography (nEMG) data and ratings of perceived exertion (RPE) were collected from seven different studies conducted by the Occupational Ergonomics and Biomechanics Lab (OEB lab). Employing a repeated measures three-way ANOVA, we assessed the influence of nEMG, gender, and exoskeleton type on RPE. Additionally, mean nEMG and RPE from seven passive exoskeleton-based studies conducted outside the OEB lab were assessed in order to determine if the findings from the OEB lab existed across other research environments. The results demonstrated a general positive linear trend between nEMG and RPE for both the individual and mean results. Substantial inconsistencies emerged when considering the influence of gender, exoskeleton type, and task conditions on the relationship between nEMG and RPE. These discrepancies underscore the need for more in-depth research into this topic, specifically investigating the effects of gender and exoskeleton design.
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    Non-Treadmill Trip Training – Laboratory Efficacy, Validation of Inertial Measurement Units, and Tripping Kinematics in the Real World
    Lee, Youngjae (Virginia Tech, 2024-06-05)
    Trip-induced falls are a leading cause of injuries among adults aged 65 years or older. Perturbation-based balance training (PBT) has emerged as an exercise-based fall prevention intervention and shown efficacy in reducing the risk of trip-induced falls. The broad goal of my PhD research was to advance the application of this so-called trip training through three studies designed to address existing knowledge gaps. First, trip training is commonly conducted with the aid of costly specialized treadmills to induce trip-like perturbations. An alternative version of trip training that eliminates the need for a treadmill would enhance training feasibility and enable wider adoption. The goal of the first study was to compare the effects of non-treadmill training (NT), treadmill training (TT), and a control (i.e., no training) on reactive balance after laboratory-induced trips among community-dwelling older adults. After three weeks of the assigned intervention, participants were exposed to two laboratory-induced trips while walking. Results showed different beneficial effects of NT and TT. For example, NT may be more beneficial in improving recovery step kinematics, while TT may be more beneficial in improving trunk kinematics, compared to the control. While the first study showed the effects of PBT on laboratory-induced trips, little is known about how such training affects responses to real-world trips. Responses to real-world trips may be captured using wearable inertial measurement units (IMUs), yet IMUs have not been adequately validated for this use. Therefore, the goal of the second study was to investigate the concurrent validity of IMU-based trunk kinematics against the gold standard optical motion capture (OMC)-based trunk kinematics after overground trips among community-dwelling older adults. During two laboratory-induced trips, participants wore two IMUs placed on the sternum and shoulder, and OMC markers placed at anatomical landmarks of the trunk segment. Results showed that IMU-based trunk kinematics differed between falls and recoveries after overground trips, and exhibited at least good correlation (Pearson's correlation coefficient, r > 0.5) with the gold standard OMC-based trunk kinematics. The goal of the third study was then to explore differences in tripping kinematics between the laboratory and real world using wearable IMUs among community-dwelling older adults. Participants were asked to wear three IMUs (for sternum and both feet) and a voice recorder to capture their responses to real-world losses of balance (LOBs) during their daily activities for three weeks. Results showed a higher variance in laboratory-induced trips than real-world trips, and the study demonstrated the feasibility of using IMUs and a voice recorder to understand the underlying mechanisms and context of real-world LOBs. Overall, this work was innovative by evaluating a non-treadmill version of trip training, establishing the validity of IMUs in capturing kinematic responses after overground trips, and applying IMUs and a voice recorder to assess tripping kinematics in the real world. The results from this work will advance the use of PBT to reduce the prevalence of trip-induced falls and to investigate the real-world effects of such trip training in future studies.
  • Physiological Linkage Between Autistic and Non-autistic Adult Dyads During Collaborative Tasks
    Kim, Sun Wook; Fok, Megan; Wang, Manhua; Theodat, Anabelle; Baker, Brian; Jeon, Myounghoon; Scarpa, Angela (2022-09-28)
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    Quantifying the Reliability of Performance Time and User Perceptions Obtained from Passive Exoskeleton Evaluations
    Noll, Alexander Baldrich Benoni (Virginia Tech, 2024-08-16)
    Work-related musculoskeletal disorders (WMSDs) cost US industries billions annually and reduce quality of life for those afflicted. Passive exoskeletons (EXOs) have emerged as a potential intervention to reduce worker exposures to WMSD risk factors. As EXO adoption is rising, EXO manufacturers are designing and producing new EXOs in accordance with growing demand. However, there are no standardized EXO evaluation protocols and EXO use recommendations, due in part to insufficient information on the reliability of EXO evaluation measures. The purpose of this thesis was to quantify the reliability of common EXO evaluation measures, using both traditional approaches a more advanced statistical approach (i.e., Generalizability Theory), while also identifying potential effects of EXO type, work task, and individual differences. This work used data from a recently completed EXO evaluation study, conducted in Virginia Tech's Occupational Ergonomics and Biomechanics Lab. Forty-two total participants completed simulated occupational tasks, in two separate experimental sessions on different days, while using an arm-support EXO (ASE) and a back-support EXO (BSE). Several outcome measures reached excellent within-session reliability within four trials for many tasks considered. Between-session reliability levels were lower than within-session levels, with outcome measures reaching moderate-to-good reliability for most tasks. Interindividual differences accounted for the largest proportion of variance for measurement reliability, followed by the experimental session. For all tasks, outcome measures reached excellent dependability levels, with many achieving excellent levels within five total trials. Inconsistencies observed in between-session reliability levels and dependability levels suggest that additional training and EXO familiarity may affect measurement reliability of outcome measures differently for some tasks, unique to each EXO type. These discrepancies emphasize the importance for additional research into this topic. Overall, the current findings indicate that many of the commonly used EXO evaluation measures are reliable and dependable within five trials and one experimental session, providing a potential foundation for standardized EXO assessment protocols.