Influences of backpack loading on recovery from anterior and posterior losses of balance: An exploratory investigation

Backpacks are common devices for carrying external posterior loads. However, relatively little is known about how these external loads affect the ability to recover from balance loss. In this exploratory investigation, 16 young adults (8 female, 8 male) performed forward and backward lean-and-release balance recovery trials, while wearing a backpack that was unloaded or loaded (at 15% of individual body weight). We quantified the effects of backpack loading on balance recovery in terms of maximum recoverable lean angles, center-of-mass kinematics, and temporal-spatial stepping characteristics. Mean values of maximum lean angles were 20° and 9° in response to forward and backward perturbations, respectively. These angles significantly decreased when wearing the additional load for only backward losses of balance. During backward losses of balance, the additional load decreased peak center-of-mass velocity and increased acceleration by ∼10 and 18% respectively, which was accompanied by ∼5% faster stepping responses and steps that were ∼9% longer, 11% higher, and had an ∼10% earlier onset. Thus, wearing a backpack decreases backward balance recovery ability and changes backward recovery stepping characteristics.

Perceived benefits, barriers, perceptions, and readiness to use exoskeletons in the construction industry: Differences by demographic characteristics

Exoskeletons (EXOs) are a promising wearable intervention to reduce work-related musculoskeletal disorder risks among construction workers. However, the adoption of EXOs may differ with demographic characteristics. Survey data (n = 361) were collected from construction industry stakeholders and a summation score method was used to summarize respondent's benefits and barriers to EXO use, along with perceptions and readiness to use. Responses were stratified by race (White vs. non-White), sex (male vs. female), and age (<47 years vs. ≥47 years). Both a higher Benefits score and a higher Perceptions score were significantly and positively associated with a higher Readiness to Use score. There were also significant differences in perceived barriers to EXO use by race and sex. These results demonstrate substantial interest in EXO use but also emphasize the need to ensure proportionate access to the potential benefits of EXO technology.

Wearing a back-support exoskeleton alters lower-limb joint kinetics during single-step recovery following a forward loss of balance

We assessed the effects of a passive, back-support exoskeleton (BSE) on lower-limb joint kinetics during the initiation and swing phases of recovery from a forward loss of balance. Sixteen (8M, 8F) young, healthy participants were released from static forward-leaning postures and attempted to recover their balance with a single-step while wearing a BSE (backXTM) with different levels of support torque and in a control condition. The BSE provided ∼ 15-20 Nm of external hip extension torque on the stepping leg at the end of initiation and beginning of swing phases. Participants were unable to generate sufficient hip flexion torque, power, and work to counteract this external torque, although they sustained hip flexion torque for a more prolonged period, resulting in slightly increased hip contribution to positive leg work (compared to control). However, net positive leg work, and the net contribution of hip joint (human + BSE) to total leg work decreased with BSE use. While all participants had changes in hip joint kinetics, a significant compensatory increase in ankle contribution to positive leg work was observed only among females. Our results suggest that BSE use adversely affects reactive stepping by decreasing the stepping leg kinetic energy for forward propulsion, and that the relative contributions of lower-limb joints to total mechanical work done during balance recovery are altered by BSE use. BSEs may thus need to be implemented with caution for dynamic tasks in occupational settings, as they may impair balance recovery following a forward loss of balance.

Occupational arm-support and back-support exoskeletons elicit changes in reactive balance after slip-like and trip-like perturbations on a treadmill

The purpose of this study was to investigate the effects of arm- and back-support exoskeletons on reactive balance after slip-like and trip-like perturbations on a treadmill. Twenty-eight participants used two arm-support exoskeletons and two back-support exoskeletons with support (i.e., assistive joint torque) activated or deactivated. In each exoskeleton condition, as well in as a control without any exoskeleton, participants were exposed to 12 treadmill perturbations during upright standing. The exoskeletons did not significantly increase the probability of a failed recovery after the perturbations compared to wearing no exoskeleton, but did elicit effects on kinematic variables that suggested balance recovery was more challenging. Moreover, reactive balance differed when wearing back-support and arm-support exoskeletons, and when wearing an activated exoskeleton compared to a deactivated exoskeleton. Together, our results suggest these exoskeletons may increase the risk of slip- and trip-induced falls. The potential mechanisms of this increased risk are discussed and include the added mass and/or motion restrictions associated with wearing these exoskeletons. Our results do not support the assistive hip/back extension moment provided by back-support exoskeletons adversely affecting fall risk.

Trunk postural control during unstable sitting among individuals with and without low back pain: A systematic review with an individual participant data meta-analysis

INTRODUCTION

Sitting on an unstable surface is a common paradigm to investigate trunk postural control among individuals with low back pain (LBP), by minimizing the influence lower extremities on balance control. Outcomes of many small studies are inconsistent (e.g., some find differences between groups while others do not), potentially due to confounding factors such as age, sex, body mass index [BMI], or clinical presentations. We conducted a systematic review with an individual participant data (IPD) meta-analysis to investigate whether trunk postural control differs between those with and without LBP, and whether the difference between groups is impacted by vision and potential confounding factors.

METHODS

We completed this review according to PRISMA-IPD guidelines. The literature was screened (up to 7th September 2023) from five electronic databases: MEDLINE, CINAHL, Embase, Scopus, and Web of Science Core Collection. Outcome measures were extracted that describe unstable seat movements, specifically centre of pressure or seat angle. Our main analyses included: 1) a two-stage IPD meta-analysis to assess the difference between groups and their interaction with age, sex, BMI, and vision on trunk postural control; 2) and a two-stage IPD meta-regression to determine the effects of LBP clinical features (pain intensity, disability, pain catastrophizing, and fear-avoidance beliefs) on trunk postural control.

RESULTS

Forty studies (1,821 participants) were included for the descriptive analysis and 24 studies (1,050 participants) were included for the IPD analysis. IPD meta-analyses revealed three main findings: (a) trunk postural control was worse (higher root mean square displacement [RMSdispl], range, and long-term diffusion; lower mean power frequency) among individuals with than without LBP; (b) trunk postural control deteriorated more (higher RMSdispl, short- and long-term diffusion) among individuals with than without LBP when vision was removed; and (c) older age and higher BMI had greater adverse impacts on trunk postural control (higher short-term diffusion; longer time and distance coordinates of the critical point) among individuals with than without LBP. IPD meta-regressions indicated no associations between the limited LBP clinical features that could be considered and trunk postural control.

CONCLUSION

Trunk postural control appears to be inferior among individuals with LBP, which was indicated by increased seat movements and some evidence of trunk stiffening. These findings are likely explained by delayed or less accurate corrective responses.

SYSTEMATIC REVIEW REGISTRATION

This review has been registered in PROSPERO (registration number: CRD42021124658).

Teleoperator-Robot-Human Interaction in Manufacturing: Perspectives from Industry, Robot Manufacturers, and Researchers

OCCUPATIONAL APPLICATIONSIndustrial robots have become an important aspect in modern industry. In the context of human-robot collaboration, enabling teleoperated robots to work in close proximity to local/onsite humans can provide new opportunities to improve human engagement in a distributed workplace. Interviews with industry stakeholders highlighted several potential benefits of such teleoperator-robot-human collaboration (tRHC), including the application of tRHC to tasks requiring both expertise and manual dexterity (e.g., maintenance and highly skilled tasks in sectors including construction, manufacturing, and healthcare), as well as opportunities to expand job accessibility for individuals with disabilities and older individuals. However, interviewees also indicated potential challenges of tRHC, particularly related to human perception (e.g., perceiving remote environments), safety, and trust. Given these challenges, and the current limited information on the practical value and implementation of tRHC, we propose several future research directions, with a focus on human factors and ergonomics, to help realize the potential benefits of tRHC.

Understanding contributing factors to exoskeleton use-intention in construction: a decision tree approach using results from an online survey

Work-related musculoskeletal disorders (WMSDs) are a major health concern in the construction industry. Occupational exoskeletons (EXOs) are a promising ergonomic intervention to help reduce WMSD risk. Their adoption, however, has been low in construction. To understand the contributing factors to EXO use-intention and assist in future decision-making, we built decision trees to predict responses to each of three EXO use-intention questions (Try, Voluntary Use, and Behavioural Intention), using online survey responses. Variable selection and hyperparameter tuning were used respectively to reduce the number of potential predictors and improve prediction performance. The importance of variables in each final tree was calculated to understand which variables had a greater influence. The final trees had moderate prediction performance. The root node of each tree included EXOs becoming standard equipment, fatigue reduction, or performance increase. Important variables were found to be quite specific to different decision trees. Practical implications of the findings are discussed.Practitioner summary: This study used decision trees to identify key factors influencing the use-intention of occupational exoskeletons (EXOs) in construction, using online survey data. Key factors identified included EXOs becoming standard equipment, fatigue reduction, and performance improvement. Final trees provide intuitive visual representations of the decision-making process for workers to use EXOs.

Three passive arm-support exoskeletons have inconsistent effects on muscle activity, posture, and perceived exertion during diverse simulated pseudo-static overhead nutrunning tasks

Arm-support exoskeletons (ASEs) are an emerging technology with the potential to reduce physical demands during diverse tasks, especially overhead work. However, limited information is available about the effects of different ASE designs during overhead work with diverse task demands. Eighteen participants (gender-balanced) performed lab-based simulations of a pseudo-static overhead task. This task was performed in six different conditions (3 work heights × 2 hand force directions), with each of three ASEs and in a control condition (i.e., no ASE). Using ASEs generally reduced the median activity of several shoulder muscles (by ∼12-60%), changed working postures, and decreased perceived exertion in several body regions. Such effects, though, were often task-dependent and differed between the ASEs. Our results support earlier evidence of the beneficial effects of ASEs for overhead work but emphasize that: 1) these effects depend on the task demands and ASE design and 2) none of the ASE designs tested was clearly superior across the tasks simulated.

A pilot study investigating motor adaptations when learning to walk with a whole-body powered exoskeleton

Evidence is emerging on how whole-body powered exoskeleton (EXO) use impacts users in basic occupational work scenarios, yet our understanding of how users learn to use this complex technology is limited. We explored how novice users adapted to using an EXO during gait. Six novices and five experienced users completed the study. Novices completed an initial training/familiarization gait session, followed by three subsequent gait sessions using the EXO, while experienced users completed one gait session with the EXO. Spatiotemporal gait measures, pelvis and lower limb joint kinematics, muscle activities, EXO torques, and human-EXO interaction forces were measured. Adaptations among novices were most pronounced in spatiotemporal gait measures, followed by joint kinematics, with smaller changes evident in muscle activity and EXO joint torques. Compared to the experienced users, novices exhibited a shorter step length and walked with significantly greater anterior pelvic tilt and less hip extension. Novices also used lower joint torques from the EXO at the hip and knee, and they had greater biceps femoris activity. Overall, our results may suggest that novices exhibited clear progress in learning, but they had not yet adopted motor strategies similar to those of experienced users after the three sessions. We suggest potential future directions to enhance motor adaptations to powered EXO in terms of both training protocols and human-EXO interfaces.

A passive leg-support exoskeleton adversely affects reactive balance after simulated slips and trips on a treadmill

Occupational exoskeletons have become more prevalent as an ergonomic control to reduce the physical demands of workers. While beneficial effects have been reported, there is relatively little evidence regarding potential adverse effects of exoskeletons on fall risk. The purpose of this study was to investigate the effects of a leg-support exoskeleton on reactive balance after simulated slips and trips. Six participants (three females) used a passive, leg-support exoskeleton that provided chair-like support in three experimental conditions (no exoskeleton, low-seat setting, high-seat setting). In each of these conditions, participants were exposed to 28 treadmill perturbations from an upright standing posture simulating a backward slip (0.4-1.6 m/s) or a forward trip (0.75-2.25 m/s). The exoskeleton increased the probability of a failed recovery, and adversely affected reactive balance kinematics, after simulated slips and trips. After simulated slips, the exoskeleton decreased initial step length 0.039 m, decreased mean step speed 0.12 m/s, anteriorly displaced touchdown position of the initial recovery step by 0.045 m, and decreased PSIS height at initial step touchdown by 1.7 % sof its standing height. After simulated trips, the exoskeleton increased trunk angle at step 2.4 degrees, and decreased initial step length 0.033 m. These effects appeared to result from the exoskeleton inhibiting regular stepping motion due to its posterior placement on the lower limbs, added mass, and mechanical constraints on participant movement. Our results suggest care may be needed among leg-support exoskeleton users when at risk of slips or trips and motivate potential exoskeleton design modifications to reduce fall risk.

Recovering from Laboratory-Induced slips and trips causes high levels of lumbar muscle activity and spine loading

Slips, trips, and falls are some of the most substantial and prevalent causes of occupational injuries and fatalities, and these events may contribute to low-back problems. We quantified lumbar kinematics (i.e., lumbar angles relative to pelvis) and kinetics during unexpected slip and trip perturbations, and during normal walking, among 12 participants (6F, 6 M). Individual anthropometry, lumbar muscle geometry, and lumbar angles, along with electromyography from 14 lumbar muscles were used as input to a 3D, dynamic, EMG-based model of the lumbar spine. Results indicated that, in comparison with values during normal walking, lumbar range of motion, lumbosacral (L5/S1) loads, and lumbar muscle activations were all significantly higher during the slip and trip events. Maximum L5/S1 compression forces exceeded 2700 N during slip and trip events, compared with ∼ 1100 N during normal walking. Mean values of L5/S1 anteroposterior (930 N), and lateral (800 N) shear forces were also substantially larger than the shear force during the normal walking (230 N). These observed levels of L5/S1 reaction forces, along with high levels of bilateral lumbar muscle activities, suggest the potential for overexertion injuries and tissue damage during unexpected slip and trip events, which could contribute to low back injuries. Outcomes of this study may facilitate the identification and control of specific mechanisms involved with low back disorders consequent to slips or trips.

Estimating lumbar spine loading when using back-support exoskeletons in lifting tasks

Low-back pain (LBP) continues as the leading cause of work-related musculoskeletal disorders, and the high LBP burden is attributed largely to physical risk factors prevalent in manual material handling tasks. Industrial back-support exoskeletons (BSEs) are a promising ergonomic intervention to help control/prevent exposures to such risk factors. While earlier research has demonstrated beneficial effects of BSEs in terms of reductions in superficial back muscle activity, limited evidence is available regarding the impacts of these devices on spine loads. We evaluated the effects of two passive BSEs (BackX™ AC and Laevo™ V2.5) on lumbosacral compression and shear forces during repetitive lifting using an optimization-based model. Eighteen participants (gender-balanced) completed four minutes of repetitive lifting in nine different conditions, involving symmetric and asymmetric postures when using the BSEs (along with no BSE as a control condition). Using both BSEs reduced estimated peak compression and anteroposterior shear forces (by ∼8-15%). Such reductions, however, were task-specific and depended on the BSE design. Laevo™ use reduced mediolateral shear forces during asymmetric lifting (by ∼35%). We also found that reductions in composite measures of trunk muscle activity may not correspond well with changes in spine forces when using a BSE. These results can help guide the proper selection and application of BSEs during repetitive lifting tasks. Future work is recommended to explore the viability of different biomechanical models to assess changes in spine mechanical loads when using BSEs and whether reasonable estimates would be obtained using such models.

An Indoor Fall Monitoring System: Robust, Multistatic Radar Sensing and Explainable, Feature-Resonated Deep Neural Network

Indoor fall monitoring is challenging for community-dwelling older adults due to the need for high accuracy and privacy concerns. Doppler radar is promising, given its low cost and contactless sensing mechanism. However, the line-of-sight restriction limits the application of radar sensing in practice, as the Doppler signature will vary when the sensing angle changes, and signal strength will be substantially degraded with large aspect angles. Additionally, the similarity of the Doppler signatures among different fall types makes it extremely challenging for classification. To address these problems, in this paper we first present a comprehensive experimental study to obtain Doppler radar signals under large and arbitrary aspect angles for diverse types of simulated falls and daily living activities. We then develop a novel, explainable, multi-stream, feature-resonated neural network (eMSFRNet) that achieves fall detection and a pioneering study of classifying seven fall types. eMSFRNet is robust to both radar sensing angles and subjects. It is also the first method that can resonate and enhance feature information from noisy/weak Doppler signatures. The multiple feature extractors - including partial pre-trained layers from ResNet, DenseNet, and VGGNet - extracts diverse feature information with various spatial abstractions from a pair of Doppler signals. The feature-resonated-fusion design translates the multi-stream features to a single salient feature that is critical to fall detection and classification. eMSFRNet achieved 99.3% accuracy detecting falls and 76.8% accuracy for classifying seven fall types. Our work is the first effective multistatic robust sensing system that overcomes the challenges associated with Doppler signatures under large and arbitrary aspect angles, via our comprehensible feature-resonated deep neural network. Our work also demonstrates the potential to accommodate different radar monitoring tasks that demand precise and robust sensing.

A novel approach to quantify the assistive torque profiles generated by passive back-support exoskeletons

Industrial exoskeletons are a promising ergonomic intervention to reduce the risk of work-related musculoskeletal disorders by providing external physical support to workers. Passive exoskeletons, having no power supplies, are of particular interest given their predominance in the commercial market. Understanding the mechanical behavior of the torque generation mechanisms embedded in passive exoskeletons is, however, essential to determine the efficacy of these devices in reducing physical loads (e.g., in manual material handling tasks). We introduce a novel approach using a computerized dynamometer to quantify the assistive torque profiles of two passive back-support exoskeletons (BSEs) at different support settings and in both static and dynamic conditions. The feasibility of this approach was examined using both human subjects and a mannequin. Clear differences in assistive torque magnitudes were evident between the two BSEs, and both devices generated more assistive torques during trunk/hip flexion than extension. Assistive torques obtained from human subjects were often within similar ranges as those from the mannequin, though values were more comparable over a narrow range of flexion/extension angles due to practical limitations with the dynamometer and human subjects. Characterizing exoskeleton assistive torque profiles can help in better understanding how to select a torque profile for given task requirements and user anthropometry, and aid in predicting the potential impacts of exoskeleton use by incorporating measured torque profiles in a musculoskeletal modeling system. Future work is recommended to assess this approach for other occupational exoskeletons.

Effects of Back-Support Exoskeleton Use on Lower Limb Joint Kinematics and Kinetics During Level Walking

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 (backX^TM) 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.

Exploratory Field Testing of Passive Exoskeletons in Several Manufacturing Environments: Perceived Usability and User Acceptance

OCCUPATIONAL APPLICATIONSResults 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.

Usability, User Acceptance, and Health Outcomes of Arm-Support Exoskeleton Use in Automotive Assembly: An 18-month Field Study

OBJECTIVE

Examine arm-support exoskeleton (ASE) user experience over time, identify factors contributing to ASE intention-to-use, and explore whether ASE use may influence the number of medical visits.

METHODS

An 18-month, longitudinal study with ASE (n = 65) and control groups (n = 133) completed at nine automotive manufacturing facilities.

RESULTS

Responses to six usability questions were rather consistent over time. ASE use perceived effective in reducing physical demands on the shoulders, neck, and back. Perceived job performance, and overall fit and comfort, appeared to be key determinants for ASE intention-to-use. Based on medical visits among both groups, ASE use may decrease the likelihood of such visits.

CONCLUSIONS

These field results support the potential of ASEs as a beneficial ergonomic intervention, but also highlight needs for further research on ASE designs, factors driving intention-to-use, and health outcomes.

Effects of back-support exoskeleton use on gait performance and stability during level walking

BACKGROUND

Back-support exoskeletons (BSEs) are a promising intervention to mitigate physical demands at work. Although growing evidence indicates that BSEs can reduce low-back physical demands, there is limited understanding of potential unintended consequences of BSE use, including the risk of falls.

RESEARCH QUESTION

Does using a BSE adversely affect gait performance and stability, and are such effects dependent on specific BSE external torque characteristics?

METHODS

Twenty participants (10 M, 10 F) completed five level over-ground walking trials and a five-minute treadmill walking trial while wearing a BSE (backX™) with three different levels of external torque (i.e., no torque, low torque, and high torque) and in a control (no-exoskeleton) condition. Spatiotemporal gait patterns, stride-to-stride gait variability measures, required coefficient-of-friction (RCoF), and minimum foot clearance (MFC) were determined, to assess gait performance. Gait stability was quantified using the maximum Lyapunov exponent (MLE) of trunk kinematics and the margin-of-stability (MoS).

RESULTS

Using the backX™ with high supportive torque decreased slip risk (7% decrease in RCoF) and slightly improved trunk stability (3% decrease in MLE). However, it also decreased step length (1%), increased step width (10%) and increased gait variability (8-19%). Changes in MoS were complex: while MoS at heel strike decreased in the AP direction, it increased in the ML direction. There was a rather large decrease in MoS (26%) in the ML direction during the swing phase.

SIGNIFICANCE

This is the first study to quantify the effects of wearing a passive BSE with multiple supportive torque levels on gait performance and stability during level walking. Our results, showing that the external torque of the BSE may adversely affect gait step width, variability, and dynamic stability, can contribute to better design and practice guidelines to facilitate the safe adoption of BSEs in the workplace.

Effects of using a whole-body powered exoskeleton during simulated occupational load-handling tasks: A pilot study

Whole-body powered exoskeletons (WB-PEXOs) can be effective in reducing the physical demands of heavy occupational work, yet almost no empirical evidence exists on the effects of WB-PEXO use. This study assessed the effects of WB-PEXO use on back and leg muscle activities during lab-based simulations of load handling tasks. Six participants (4M, 2F) completed two such tasks (load carriage and stationary load transfer), both with and without a WB-PEXO, and with a range of load masses in each task. WB-PEXO use reduced median levels of muscle activity in the back (∼42-53% in thoracic and ∼24-43% in lumbar regions) and legs (∼41-63% in knee flexors and extensors), and mainly when handling loads beyond low-moderate levels (10-15 kg). Overall, using the WB-PEXO also reduced inter-individual variance (smaller SD) in muscle activities. Future work should examine diverse users, focus on finding effective matches between WB-PEXO use and specific tasks, and identify applications in varied work environments.

An exploratory study comparing three work/rest schedules during simulated repetitive precision work

The pattern of work and rest can influence both physical fatigue and task performance in manual operations. However, there is relatively limited evidence regarding the influences of specific work/rest schedules in tasks requiring high repetitiveness and precision demands, along with relatively low exertion levels. Eighteen participants completed an exploratory study that simulated such tasks, to compare the effects of three distinct work/rest schedules (i.e. short frequent [short] and long infrequent breaks [long], and a self-selected schedule) on muscle fatigue, task performance (in terms of accuracy and speed), and preference. Schedules with long or self-selected breaks generally induced less muscle fatigue, compared with the short break condition. Participants preferred the self-selected condition the most and the long-break condition the least. The different schedules tested did not influence task performance. A self-selected schedule may be beneficial for repetitive precision task, to achieve a balance across muscle fatigue, task performance, and individual preference. Practitioner summary: Influences of three work/rest schedules (i.e. short and long breaks, and a self-selected schedule) on fatigue, performance, and preference were explored during repetitive precision tasks. Schedules with long or self-selected breaks induced less muscle fatigue and none of the three schedules influenced performance. A self-selected schedule was the most preferred.

Effects of an arm-support exoskeleton on perceived work intensity and musculoskeletal discomfort: An 18-month field study in automotive assembly

BACKGROUND

Exoskeleton (EXO) technologies are a promising ergonomic intervention to reduce the risk of work-related musculoskeletal disorders, with efficacy supported by laboratory- and field-based studies. However, there is a lack of field-based evidence on long-term effects of EXO use on physical demands.

METHODS

A longitudinal, controlled research design was used to examine the effects of arm-support exoskeleton (ASE) use on perceived physical demands during overhead work at nine automotive manufacturing facilities. Data were collected at five milestones (baseline and at 1, 6, 12, and 18 months) using questionnaires. Linear mixed models were used to understand the effects of ASE use on perceived work intensity and musculoskeletal discomfort (MSD). Analyses were based on a total of 41 participants in the EXO group and 83 in a control group.

RESULTS

Across facilities, perceived work intensity and MSD scores did not differ significantly between the EXO and control groups. In some facilities, however, neck and shoulder MSD scores in the EXO group decreased over time. Wrist MSD scores in the EXO group in some facilities remained unchanged, while those scores increased in the control group over time. Upper arm and low back MSD scores were comparable between the experimental groups.

CONCLUSION

Longitudinal effects of ASE use on perceived physical demands were not found, though some suggestive results were evident. This lack of consistent findings is discussed, particularly supporting the need for systematic and evidence-based ASE implementation approaches in the field that can guide the optimal selection of a job for ASE use.

Effects of back-support exoskeleton use on trunk neuromuscular control during repetitive lifting: A dynamical systems analysis

Back-support exoskeletons (BSEs) are a promising ergonomic intervention to mitigate the risk of occupational low back pain. Although growing evidence points to the beneficial effects of BSEs, specifically in reducing low-back physical demands, there is limited understanding of potential unintended consequences of BSE use on neuromuscular control of the trunk during manual material handling (MMH). We quantified the effects of two passive BSEs (BackX™ AC and Laevo™ V2.5) on trunk dynamic stability and movement coordination during a repetitive lifting task. Eighteen participants (gender-balanced) completed four minutes of repetitive lifting in nine different conditions, involving symmetric and asymmetric postures when using the BSEs (along with no BSE as a control condition). Maximum Lyapunov exponents (short-term: λ_max-s; long-term: λ_max-l) and Floquet multipliers (FM_max) were respectively calculated to quantify the local dynamic and orbital stability of thorax and pelvis trajectories. Thorax-pelvis segmental coordination was also quantified using the continuous relative phase. Wearing the Laevo™ significantly increased λ_max-s for the pelvis (by ~ 8%) and FM_max for the thorax and pelvis (by ~ 5-10%). Use of either BSE decreased the in-phase coordination pattern for the thorax-pelvis coupling (by ~ 15%). These results suggest that BSE use can compromise neuromuscular control of the trunk, and caution should thus be used in selecting a suitable BSE for use in a given MMH task. Future work is needed, however, to assess the generalizability of different BSE design approaches in terms of unintended short-term and long-term effects on trunk neuromuscular control.

Classifying diverse manual material handling tasks using a single wearable sensor

The use of inertial measurement units (IMUs) for monitoring and classifying physical activities has received substantial attention in recent years, both in occupational and non-occupational contexts. However, a "user-friendly" approach is needed to promote this approach to quantify physical demands in actual workplaces. We explored the use of a single IMU for extracting information about different manual material handling (MMH) tasks (i.e., specific type of task performed, and associated duration and frequency), using a bidirectional long short-term memory network for classification. Classification performance using single IMUs placed on several body parts was compared with performance using multiple IMU configurations (2, 3, and 17 IMUs). Overall, the use of a single sensor led to satisfactory results (e.g., median accuracy >97%) in classifying MMH tasks and estimating task duration and frequency. Limited benefits were obtained using additional sensors, and several sensor locations yielded similar outcomes. Classification performance, though, was relatively inferior for push/pull vs. other tasks.

Understanding the experiences of self-injurious behavior in autism spectrum disorder: Implications for monitoring technology design

OBJECTIVE

Monitoring technology may assist in managing self-injurious behavior (SIB), a pervasive concern in autism spectrum disorder (ASD). Affiliated stakeholder perspectives should be considered to design effective and accepted SIB monitoring methods. We examined caregiver experiences to generate design guidance for SIB monitoring technology.

MATERIALS AND METHODS

Twenty-three educators and 16 parents of individuals with ASD and SIB completed interviews or focus groups to discuss needs related to monitoring SIB and associated technology use.

RESULTS

Qualitative content analysis of participant responses revealed 7 main themes associated with SIB and technology: triggers, emotional responses, SIB characteristics, management approaches, caregiver impact, child/student impact, and sensory/technology preferences.

DISCUSSION

The derived themes indicated areas of emphasis for design at the intersection of monitoring and SIB. Systems design at this intersection should consider the range of manifestations of and management approaches for SIB. It should also attend to interactions among children with SIB, their caregivers, and the technology. Design should prioritize the transferability of physical technology and behavioral data as well as the safety, durability, and sensory implications of technology.

CONCLUSIONS

The collected stakeholder perspectives provide preliminary groundwork for an SIB monitoring system responsive to needs as articulated by caregivers. Technology design based on this groundwork should follow an iterative process that meaningfully engages caregivers and individuals with SIB in naturalistic settings.

Trunk-pelvic coordination during unstable sitting with varying task demand: A methodological study

Unstable sitting is used commonly to evaluate trunk postural control (TPC), typically via measures based on center-of-pressure (CoP) time series. However, these measures do not directly reflect underlying control/movement strategies. We quantified trunk-pelvis coordination during unstable sitting using vector coding (VC) and correlated such coordination with CoP-based outcomes across varying task demands. Thirteen uninjured individuals (11 male/2 female) sat on an unstable chair at four instability levels, in a random order, defined relative to the individual gravitational gradient (∇G): 100, 75, 60, and 45%∇G. VC assessed trunk-pelvic coordination, and coupling angles classified movements as: 1) anti-phase, 2) in-phase, 3) trunk-phase, or 4) pelvic-phase. With decreasing %∇G (i.e., increasing instability), we found: increased anti-phase movement in the sagittal and frontal planes; decreased in-phase movement in the sagittal and frontal planes; and increased in-phase and pelvic-phase movement in the transverse plane. In the sagittal and frontal planes, we observed significant weak-to-moderate correlations between anti-phase and in-phase movements (0.288 < |ρ| < 0.549). Correlations between CoP-based measures and pelvic-phase and trunk-phase movements were typically weak and/or non-significant (|ρ| < 0.318). VC techniques discriminated between levels of instability during unstable sitting, identifying in-phase coordination (stiffening strategy) at lower instability levels and anti-phase coordination at higher instability levels. Compared to CoP-based measures, trunk coordination outcomes during unstable sitting provide measures of TPC that more directly quantify underlying movement strategies. These results can also serve as a baseline for future work investigating populations with impaired TPC (e.g., individuals with low back pain or limb loss).

Effects of two passive back-support exoskeletons on postural balance during quiet stance and functional limits of stability

While occupational back-support exoskeletons (BSEs) are considered as potential workplace interventions, BSE use may compromise postural control. Thus, we investigated the effects of passive BSEs on postural balance during quiet upright stance and functional limits of stability. Twenty healthy adults completed trials of quiet upright stance with differing levels of difficulty (bipedal and unipedal stance; each with eyes open and closed), and executed maximal voluntary leans. Trials were done while wearing two different BSEs (SuitX™, Laevo™) and in a control (no-BSE) condition. BSE use significantly increased center-of-pressure (COP) median frequency and mean velocity during bipedal stance. In unipedal stance, using the Laevo™ was associated with a significant improvement in postural balance, especially among males, as indicated by smaller COP displacement and sway area, and a longer time to contact the stability boundary. BSE use may affect postural balance, through translation of the human + BSE center-of-mass, restricted motion, and added supportive torques. Furthermore, larger effects of BSEs on postural balance were evident among males. Future work should further investigate the gender-specificity of BSE effects on postural balance and consider the effects of BSEs on dynamic stability.

Impacts of different fabric scissor designs on physical demands and performance in simulated fabric cutting tasks

While there is wide evidence that the occupational use of hand tools increases the risk of musculoskeletal disorder, evidence is limited regarding manual scissors, commonly used by custom tailors for bespoke garment production. We assessed whether scissor design impacts physical demands (muscle activity, perceived discomfort, and wrist posture) and task performance (quality and perceived efficiency). Twenty-four novice volunteers each completed simulated cutting tasks in 24 conditions involving the factorial combinations of four scissor designs (SD), three workstation heights, and two fabric types. SD significantly affected all outcome measures, and differences between SDs were consistent across workstation heights and fabric types. Two wide-handles scissors appeared superior overall, which may be related to the distinct grip type employed with this type of design. These results suggest that careful scissor selection has the potential to both reduce injury risk and enhance performance during fabric cutting tasks, though future testing is needed under more realistic conditions.

Assessing the potential for "undesired" effects of passive back-support exoskeleton use during a simulated manual assembly task: Muscle activity, posture, balance, discomfort, and usability

Back-support exoskeletons (BSEs) are wearable systems designed to reduce physical demands on the back, but which could have undesired effects beyond this design intention. Participants (n = 18) used two commercial BSEs to complete a brief (~15-20 s) simulated manual assembly task in varying conditions, with outcome measures that included: working posture, activity levels in "secondary" muscle groups (shoulders and thighs), perceived balance, discomfort, and usability. Using a BSE led to small and inconsistent changes in working postures (e.g., < ~14° change in lumbar flexion), muscular activity in the secondary muscle groups (<±2% of maximum voluntary isometric contractions), or perceived balance. Limitations in movement were reported for both BSEs, however, along with moderate levels of discomfort. Task-specific responses were evident for all outcome measures, though these depended on the specific BSE used and differed between genders in many cases. Future work should focus on interactions between a given user, BSE design, and task conditions.

Multi-level modeling with nonlinear movement metrics to classify self-injurious behaviors in autism spectrum disorder

Self-injurious behavior (SIB) is among the most dangerous concerns in autism spectrum disorder (ASD), often requiring detailed and tedious management methods. Sensor-based behavioral monitoring could address the limitations of these methods, though the complex problem of classifying variable behavior should be addressed first. We aimed to address this need by developing a group-level model accounting for individual variability and potential nonlinear trends in SIB, as a secondary analysis of existing data. Ten participants with ASD and SIB engaged in free play while wearing accelerometers. Movement data were collected from > 200 episodes and 18 different types of SIB. Frequency domain and linear movement variability measures of acceleration signals were extracted to capture differences in behaviors, and metrics of nonlinear movement variability were used to quantify the complexity of SIB. The multi-level logistic regression model, comprising of 12 principal components, explained > 65% of the variance, and classified SIB with > 75% accuracy. Our findings imply that frequency-domain and movement variability metrics can effectively predict SIB. Our modeling approach yielded superior accuracy than commonly used classifiers (~ 75 vs. ~ 64% accuracy) and had superior performance compared to prior reports (~ 75 vs. ~ 69% accuracy) This work provides an approach to generating an accurate and interpretable group-level model for SIB identification, and further supports the feasibility of developing a real-time SIB monitoring system.

Biomechanical assessment of two back-support exoskeletons in symmetric and asymmetric repetitive lifting with moderate postural demands

Two passive back-support exoskeleton (BSE) designs were assessed in terms of muscular activity, energy expenditure, joint kinematics, and subjective responses. Eighteen participants (gender-balanced) completed repetitive lifting tasks in nine different conditions, involving symmetric and asymmetric postures and using two BSEs (along with no BSE as a control condition). Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity (by ~9-20%) and reduced energy expenditure (by ~8-14%). Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. Participants reported lower perceived exertion using either BSE yet raised concerns regarding localized discomfort. Minimal changes in lifting behaviors were evident when using either BSE, and use of both BSEs led to generally positive usability ratings. While these results are promising regarding the occupational use of BSEs, future work is recommended to consider inter-individual differences to accommodate diverse user needs and preferences.

A head-worn display ("smart glasses") has adverse impacts on the dynamics of lateral position control during gait

BACKGROUND

Head-worn displays (e.g., "smart glasses") are an emerging technology to provide information, and in many situations they might be used while walking. However, little evidence exists regarding the effects of head-worn displays on walking performance. We found earlier that "smart glasses" had smaller adverse effects on measures of gait variability in the anterior-posterior direction vs. other types of information displays. Participants, however, complained about motion sickness and perceived instability while using smart glasses.

RESEARCH QUESTION

Were the participants' complaints a result of adverse effects of the smart glasses on the dynamics of lateral stepping and gait stability?

METHODS

Twenty individuals walked on a treadmill in four different conditions; single-task walking, and three dual-task walking conditions, the latter using smart glasses, smartphone, and a paper-based system to provide secondary cognitive tasks. We assessed the dynamics of lateral stepping and gait stability using the goal equivalent manifold and maximum Lyapunov exponent, respectively.

RESULTS

The dynamics of the lateral stepping were more adversely affected using smart glasses compared to the other types of information displays. However, stability measures revealed that the participants were more unstable when they used the smartphone and paper-based system.

SIGNIFICANCE

Promising results in terms of stability and adaptability suggest that head-worn display technology is a potentially useful alternative to smartphones and other types of information displays for reducing the risk of a fall. Results regarding perceptions of instability and a loss of control over lateral stepping, however, imply that this technology requires further development prior to real-work implementations.

Modelling performance during repetitive precision tasks using wearable sensors: a data-driven approach

In modern manufacturing systems, especially assembly lines, human input is a critical resource to provide dexterity and flexibility. However, the repetitive precision tasks common in assembly lines can have adverse effects on workers and overall system performance. We present a data-driven approach to evaluating task performance using wearable sensor data (kinematics, electromyography and heart rate). Eighteen participants (gender-balanced) completed repeated cycles of maze tracking and assembly/disassembly. Various combinations of input data types and classification algorithms were used to model task performance. The use of the linear discriminant analysis (LDA) algorithm and kinematic data provided the most promising classification performance. The highest model accuracy was found using the LDA algorithm and all data types, with respective levels of 62.4, 88.6, 85.8 and 94.1% for predicting maze errors, maze speed, assembly/disassembly errors and assembly/disassembly speed. The presented approach provides the possibility for real-time, on-line and comprehensive monitoring of system performance in assembly-lines or similar industries. Practitioner summary: This paper proposed models the repetitive precision task performance using data collected from wearable sensors. The use of the LDA algorithm and kinematic data provided the most promising classification performance. The presented approach provides the possibility for real-time, on-line and comprehensive monitoring of system performance in assembly lines or similar industries. Abbreviations: AD: anterior deltoid; BB: biceps brachii; ECR: extensor carpi radialis; ECU: extensor carpi ulnaris; FCR: flexor carpi radialis; FCU: flexor carpi ulnaris; FN: false negatives; FP: false positives; HR: heart rate; HRR: heart rate reserve; IMUs: inertial measurement units; kNN: k-nearest neighbors; LDA: linear discriminant analysis; MD: medial deltoid; MF: median power frequency; MNF: mean power frequency; MVIC: maximum voluntary isometric contraction; nRMS: normalized root-mean-square amplitudes; PD: posterior deltoid; RandFor: random forests; RHR: resting heart rate; RMS: root-mean-square amplitudes; sEMG: surface electromyographic; SVM: support vector machines; TB: triceps brachii medial; TN: true negatives; TP: true positives; t-SNE: t-distributed Stochastic Neighbor Embedding; UT: upper trapezius.

Perturbation-based balance training targeting both slip- and trip-induced falls among older adults: a randomized controlled trial

BACKGROUND

Falls are the leading cause of injuries among older adults. Perturbation-based balance training (PBT) is an innovative approach to fall prevention that aims to improve the reactive balance response following perturbations such as slipping and tripping. Many of these PBT studies have targeted reactive balance after slipping or tripping, despite both contributing to a large proportion of older adult falls. The goal of this randomized controlled trial was to evaluate the effects of PBT targeting slipping and tripping on laboratory-induced slips and trips. To build upon prior work, the present study included: 1) a control group; 2) separate training and assessment sessions; 3) PBT methods potentially more amenable for use outside the lab compared to methods employed elsewhere, and 4) individualized training for older adult participants.

METHODS

Thirty-four community-dwelling, healthy older adults (61-75 years) were assigned to PBT or a control intervention using minimization. Using a parallel design, reactive balance (primary outcome) and fall incidence were assessed before and after four sessions of BRT or a control intervention involving general balance exercises. Assessments involved exposing participants to an unexpected laboratory-induced slip or trip. Reactive balance and fall incidence were compared between three mutually-exclusive groups: 1) baseline participants who experienced a slip (or trip) before either intervention, 2) post-control participants who experienced a slip (or trip) after the control intervention, and 3) post-PBT participants who experienced a slip (or trip) after PBT. Neither the participants nor investigators were blinded to group assignment.

RESULTS

All 34 participants completed all four sessions of their assigned intervention, and all 34 participants were analyzed. Regarding slips, several measures of reactive balance were improved among post-PBT participants when compared to baseline participants or post-control participants, and fall incidence among post-PBT participants (18%) was lower than among baseline participants (80%). Regarding trips, neither reactive balance nor fall incidence differed between groups.

CONCLUSIONS

PBT targeting slipping and tripping improved reactive balance and fall incidence after laboratory-induced slips. Improvements were not observed after laboratory-induced trips. The disparity in efficacy between slips and trip may have resulted from differences in dosage and specificity between slip and trip training.

TRIAL REGISTRATION

Name of Clinical Trial Registry: clinicaltrials.gov Trial Registration number: NCT04308239. Date of Registration: March 13, 2020 (retrospectively registered).

Comparison of Treadmill Trip-Like Training Versus Tai Chi to Improve Reactive Balance Among Independent Older Adult Residents of Senior Housing: A Pilot Controlled Trial

BACKGROUND

There is growing interest in using perturbation-based balance training to improve the reactive response to common perturbations (eg, tripping and slipping). The goal of this study was to compare the efficacy of treadmill-based reactive balance training versus Tai Chi performed at, and among independent residents of, older adult senior housing.

METHODS

Thirty-five residents from five senior housing facilities were allocated to either treadmill-based reactive balance training or Tai Chi training. Both interventions were performed three times per week for 4 weeks, with each session lasting approximately 30 minutes. A battery of balance tests was performed at baseline, and again 1 week, 1 month, 3 months, and 6 months post-training. The battery included six standard clinical tests of balance and mobility, and a test of reactive balance performance.

RESULTS

At baseline, no significant between-group differences were found for any balance tests. After training, reactive balance training participants had better reactive balance than Tai Chi participants. Maximum trunk angle was 13.5° smaller among reactive balance training participants 1 week after training (p = .01), and a reactive balance rating was 24%-31% higher among reactive balance training participants 1 week to 6 months after training (p < .03). Clinical tests showed minimal differences between groups at any time point after training.

CONCLUSION

Trip-like reactive balance training performed at senior housing facilities resulted in better rapid balance responses compared with Tai Chi training.

Supporting Surgical Teams: Identifying Needs and Barriers for Exoskeleton Implementation in the Operating Room

OBJECTIVE

The objective of this study was to identify potential needs and barriers related to using exoskeletons to decrease musculoskeletal (MS) symptoms for workers in the operating room (OR).

BACKGROUND

MS symptoms and injuries adversely impact worker health and performance in surgical environments. Half of the surgical team members (e.g., surgeons, nurses, trainees) report MS symptoms during and after surgery. Although the ergonomic risks in surgery are well recognized, little has been done to develop and sustain effective interventions.

METHOD

Surgical team members (n = 14) participated in focus groups, performed a 10-min simulated surgical task with a commercial upper-body exoskeleton, and then completed a usability questionnaire. Content analysis was conducted to determine relevant themes.

RESULTS

Four themes were identified: (1) characteristics of individuals, (2) perceived benefits, (3) environmental/societal factors, and (4) intervention characteristics. Participants noted that exoskeletons would benefit workers who stand in prolonged, static postures (e.g., holding instruments for visualization) and indicated that they could foresee a long-term decrease in MS symptoms with the intervention. Specifically, raising awareness of exoskeletons for early-career workers and obtaining buy-in from team members may increase future adoption of this technology. Mean participant responses from the System Usability Scale was 81.3 out of 100 (SD = 8.1), which was in the acceptable range of usability.

CONCLUSION

Adoption factors were identified to implement exoskeletons in the OR, such as the indicated need for exoskeletons and usability. Exoskeletons may be beneficial in the OR, but barriers such as maintenance and safety to adoption will need to be addressed.

APPLICATION

Findings from this work identify facilitators and barriers for sustained implementation of exoskeletons by surgical teams.

Biomechanical Evaluation of Passive Back-Support Exoskeletons in a Precision Manual Assembly Task: "Expected" Effects on Trunk Muscle Activity, Perceived Exertion, and Task Performance

OBJECTIVE

To assess the efficacy of two different passive back-support exoskeleton (BSE) designs, in terms of trunk muscle activity, perceived low-back exertion, and task performance.

BACKGROUND

BSEs have the potential to be an effective intervention for reducing low-back physical demands, yet little is known about the impacts of different designs in work scenarios requiring varying degrees of symmetric and asymmetric trunk bending during manual assembly tasks.

METHOD

Eighteen participants (gender balanced) completed lab-based simulations of a precision manual assembly task using a "grooved pegboard." This was done in 26 different conditions (20 unsupported; 6 supported, via a chair), which differed in vertical height, horizontal distance, and orientation.

RESULTS

Using both BSEs reduced metrics of trunk muscle activity in many task conditions (≤47% reductions when using BackX™ and ≤24% reductions when using Laevo™). Such reductions, though, were more pronounced in the conditions closer to the mid-sagittal plane and differed between the two BSEs tested. Minimal effects on task completion times or ratings of perceived exertion were found for both BSEs.

CONCLUSION

Our findings suggest that using passive BSEs can be beneficial for quasi-static manual assembly tasks, yet their beneficial effects can be task specific and specific to BSE design approaches. Further work is needed, though, to better characterize this task specificity and to assess the generalizability of different BSE design approaches in terms of physical demands, perceived exertion, and task performance.

APPLICATION

These results can help guide the choice and application of passive BSE designs for diverse work scenarios involving nonneutral trunk postures.

Effects of Two Passive Back-Support Exoskeletons on Muscle Activity, Energy Expenditure, and Subjective Assessments During Repetitive Lifting

OBJECTIVE

The aim of this study was to explore the efficacy of two different passive back-support exoskeleton (BSE) designs during repetitive lifting in different postures.

BACKGROUND

Although BSEs have been proposed as a potential intervention for reducing physical demands, limited information is available about the impacts of different exoskeleton designs in diverse work scenarios.

METHOD

Eighteen participants (gender-balanced) performed lab-based simulations of repetitive lifting tasks. These tasks were performed in 12 different conditions, involving two BSEs and a control condition, two levels of lifting symmetry (symmetric and asymmetric), and two postures (standing and kneeling). Outcome measures described muscle activity and energy expenditure, along with perceived discomfort, balance, and usability.

RESULTS

Using both BSEs significantly reduced peak activity of the trunk extensor muscles (by ~10%-28%) and energy expenditure (by ~4%-13%) in all conditions tested. Such reductions, though, were task dependent and differed between the two BSEs. In most of the tested conditions, using BSEs positively affected subjective responses regarding perceived exertion and usability.

CONCLUSION

Our results suggest that the beneficial effects of a BSE are task specific and depend on the specific BSE design approach. More work is needed, though, to better characterize this task specificity and to determine the generalizability of BSE effects on objective and subjective outcomes for a wider range of conditions and users.

APPLICATION

Our results provide new evidence to guide the selection and application of passive BSE designs in diverse lifting tasks.

Detecting and Classifying Self-injurious Behavior in Autism Spectrum Disorder Using Machine Learning Techniques

Traditional self-injurious behavior (SIB) management can place compliance demands on the caregiver and have low ecological validity and accuracy. To support an SIB monitoring system for autism spectrum disorder (ASD), we evaluated machine learning methods for detecting and distinguishing diverse SIB types. SIB episodes were captured with body-worn accelerometers from children with ASD and SIB. The highest detection accuracy was found with k-nearest neighbors and support vector machines (up to 99.1% for individuals and 94.6% for grouped participants), and classification efficiency was quite high (offline processing at ~ 0.1 ms/observation). Our results provide an initial step toward creating a continuous and objective smart SIB monitoring system, which could in turn facilitate the future care of a pervasive concern in ASD.

IDENTIFYING BARRIERS AND FACILITATORS OF EXOSKELETON IMPLEMENTATION IN THE OPERATING ROOM

Introduction

Members of the surgical team experience musculoskeletal (MS) symptoms that impact occupational health. Although the prevalence of MS symptoms in this population is well-recognized, limited interventions with sustained success exist for the operating room (OR) environment. The purpose of this work was to determine the facilitators of and barriers to exoskeleton technology in the OR, as a potential intervention to reduce upper-body MS pain and discomfort for surgical team members.

Methods

After providing informed consent, participants completed a two-part study: focus groups and a simulated laparoscopic skills task while wearing a passive arm-support exoskeleton (Levitate AirFrameTM). Seven surgical residents, four surgical technicians, and two attending surgeons participated in this study. A script including questions on technology adoption, supporting workers tasks/job, and safety and health (adapted from Kim et al., 2016) was used to guide each focus group. Content analysis of the focus groups was completed by three study team members to identify relevant themes from participants’ responses, and two raters coded all remaining sessions. Subsequently, nine participants completed repetitions of the Fundamentals of Laparoscopic Surgery peg transfer task for 10 minutes wearing the noted exoskeleton. Afterwards, their overall impressions of the exoskeleton were assessed using the System Usability Scale (SUS; Brooke, 1996).

Results/Discussion

Four main themes related to the adoption of exoskeletons in the OR were identified: characteristics of individuals, benefits, barriers, and intervention characteristics. Theme 1: Characteristics of individuals. It was noted that implementation of exoskeletons would require a champion at an institution to spearhead the efforts. Additionally, individual curiosity and awareness of MS ergonomics problems were found as facilitators of adoption. Theme 2: Benefits. Expected long-term benefits of an exoskeleton were mentioned. Specifically, stakeholders anticipated a decrease in MS symptoms and expected that it would help with workforce retention and prevention of early retirement. The user role that was identified to most benefit from exoskeletons were the surgical assistants ( n = 9). Theme 3: Barriers. Seven categories of barriers were found. Safety and sterility were major concerns in the OR. Main concerns included ensuring that the arm cuffs were not in the area of surgical scrub (i.e., below the elbows) and the added bulk to wear inside the surgical gown. Furthermore, the factors of familiarity, perception, buy-in, and immediate results were noted to influence the use of an exoskeleton. Theme 4: Intervention characteristics. The theme of intervention characteristics was identified separately from benefits and barriers, as the categories in this theme could either help facilitate or hinder the adoption of exoskeletons in the OR. Workers reported that investment, specifically monetary, and maintenance of the equipment would likely influence wide-spread adoption. Usability of the exoskeleton was indicated as having a large influence on adoption. Workers in all roles noted that whether they adopt the exoskeleton during surgical procedures would depend on usability. The mean SUS score for the exoskeleton tested was 82.2 out of 100 ( SD = 7.9), which was within the acceptable range of usability. Passive exoskeleton technology has the potential to minimize MS symptoms and fatigue for the surgical team (Liu et al., 2018). The current work identified themes for adopting exoskeletons in the OR, and thus builds a better understanding of facilitators of and hinderances to stakeholders using this technology. Exoskeletons were suggested as having the potential to improve workforce retention and decrease MS symptoms. These results suggest that the use of arm-support exoskeletons can be valuable, though barriers such as cost and team member buy-in need to be addressed. Acknowledgements. This work was supported by Cooperative Agreement T42 OH008455, funded by the Centers for Disease Control and Prevention. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC or DHHS. The exoskeleton used in this study was loaned by the Levitate company; the company had no involvement in study design, analysis, or interpretation, nor the decision for publication.

Effects of exoskeleton design and precision requirements on physical demands and quality in a simulated overhead drilling task

We compared three passive exoskeleton designs in a mock drilling task under three precision requirements levels, defined by required hole sizes, in terms of physical demands (perceived exertion and muscular activation) and quality. The investigated designs were: 1) an upper-body exoskeleton mainly supporting the shoulder; and both 2) full-body, and 3) upper-body exoskeletons, each with connected supernumerary arms. At a fixed pace, participants (n = 12) repeated "drilling" two same-sized holes for 2 min. A fairly consistent result across exoskeleton designs was that higher precision demands increased some muscle activation levels and deteriorated quality. Designs with supernumerary arms led to the largest reductions in quality and increased physical demands overall, mainly in the low back. The shoulder-focused exoskeleton reduced shoulder demands but appeared to reduce quality with the highest precision requirement. Although future work is needed under more diverse/realistic scenarios, these results might be useful to (re)design occupational exoskeletons.

A Reactive Balance Rating Method That Correlates With Kinematics After Trip-like Perturbations on a Treadmill and Fall Risk Among Residents of Older Adult Congregate Housing

Background

A growing number of studies are using modified treadmills to train reactive balance after trip-like perturbations that require multiple steps to recover balance. The goal of this study was thus to develop and validate a low-tech reactive balance rating method in the context of trip-like treadmill perturbations to facilitate the implementation of this training outside the research setting.

Methods

Thirty-five residents of five senior congregate housing facilities participated in the study. Participants completed a series of reactive balance tests on a modified treadmill from which the reactive balance rating was determined, along with a battery of standard clinical balance and mobility tests that predict fall risk. We investigated the strength of correlation between the reactive balance rating and reactive balance kinematics. We compared the strength of correlation between the reactive balance rating and clinical tests predictive of fall risk with the strength of correlation between reactive balance kinematics and the same clinical tests. We also compared the reactive balance rating between participants predicted to be at a high or low risk of falling.

Results

The reactive balance rating was correlated with reactive balance kinematics (Spearman's rho squared = .04-.30), exhibited stronger correlations with clinical tests than most kinematic measures (Spearman's rho squared = .00-.23), and was 42%-60% lower among participants predicted to be at a high risk for falling.

Conclusion

The reactive balance rating method may provide a low-tech, valid measure of reactive balance kinematics, and an indicator of fall risk, after trip-like postural perturbations.

Relative Effort while Walking Is Higher among Women Who Are Obese, and Older Women

PURPOSE

Individuals who are obese, and older individuals, exhibit gait alterations that may result, in part, from walking with greater effort relative to their maximum strength capacity. The goal of this study was to investigate obesity-related and age-related differences in relative effort during gait.

METHODS

Four groups of women completed the study, including 10 younger healthy-weight, 10 younger obese, 10 older healthy-weight, and 9 older obese women. The protocol included strength measurements at the hip, knee, and ankle in both flexion and extension, and gait trials under self-selected and constrained (1.5 m·s gait speed and 0.65-m step length) conditions. Relative effort was calculated as the ratio of joint torques during gait, and strength from a subject-specific model that predicted strength as a function of joint angle.

RESULTS

Relative effort during self-selected gait was higher among women who were obese in knee extension (P = 0.028) and ankle plantar flexion (P = 0.013). Although both joint torques and strength were higher among women who were obese, these increases in relative effort were attributed to greater obesity-related increases in joint torques than strength. Relative effort was also higher among older women in hip flexion (P < 0.001) and knee extension (P = 0.008), and attributed to age-related strength loss. Results were generally similar between self-selected and constrained gait, indicating the greater relative effort among women who were obese and older women was not attributed to differences in gait spatiotemporal characteristics.

CONCLUSIONS

Women who were obese, as well as older women, walk with greater relative effort. These results may help explain the compromised walking ability among these individuals.

Classifying Diverse Physical Activities Using "Smart Garments"

Physical activities can have important impacts on human health. For example, a physically active lifestyle, which is one of the most important goals for overall health promotion, can diminish the risk for a range of physical disorders, as well as reducing health-related expenditures. Thus, a long-term goal is to detect different physical activities, and an important initial step toward this goal is the ability to classify such activities. A recent and promising technology to discriminate among diverse physical activities is the smart textile system (STS), which is becoming increasingly accepted as a low-cost activity monitoring tool for health promotion. Accordingly, our primary aim was to assess the feasibility and accuracy of using a novel STS to classify physical activities. Eleven participants completed a lab-based experiment to evaluate the accuracy of an STS that featured a smart undershirt (SUS) and commercially available smart socks (SSs) in discriminating several basic postures (sitting, standing, and lying down), as well as diverse activities requiring participants to walk and run at different speeds. We trained three classification methods—K-nearest neighbor, linear discriminant analysis, and artificial neural network—using data from each smart garment separately and in combination. Overall classification performance (global accuracy) was ~98%, which suggests that the STS was effective for discriminating diverse physical activities. We conclude that, overall, smart garments represent a promising area of research and a potential alternative for discriminating a range of physical activities, which can have positive implications for health promotion.

Using smart garments to differentiate among normal and simulated abnormal gaits

Detecting and assessing an individual's gait can be important for medical diagnostic purposes and for developing and guiding follow-on rehabilitation protocols. Thus, an accurate, objective gait classification system has the potential to facilitate earlier diagnosis and improved clinical decision-making. Systems using smart garments represent an emerging technology for physical activity assessment and that may be relevant for gait classification. The objective of this study was to assess the accuracy of one such system - comprised of commercial instrumented socks and a custom instrument shirt - for differentiating among normal gait and four distinct simulated gait abnormalities. Eleven participants completed an experiment in which they completed several gait trails on a single day. Gait types were classified using diverse modeling approaches (K-nearest neighbors, linear discriminant analyses, support vector machines, and artificial neural networks). High classification accuracy could be obtained, both when classification models were developed and tested using data from each participant separately and grouped together, particularly using the k-nearest neighbor method (>98% accuracy). Some gaits were more often "confused" with other gaits, especially when they shared underlying kinematic aspects. These results support the potential of using "smart" garments for detecting and identifying abnormal gaits, and for future implementation in diagnosis and rehabilitation.

Using a smart textile system for classifying occupational manual material handling tasks: evidence from lab-based simulations

Physical monitoring systems represent potentially powerful assessment devices to detect and describe occupational physical activities. A promising technology for such use is smart textile systems (STSs). Our goal in this exploratory study was to assess the feasibility and accuracy of using two STSs to classify several manual material handling (MMH) tasks. Specifically, commercially-available 'smart' socks and a custom 'smart' shirt were used individually and in combination. Eleven participants simulated nine separate MMH tasks while wearing the STSs, and task classification accuracy was quantified subsequently using several common models. The shirt and socks, both individually and in combination, could classify the simulated tasks with greater than 97% accuracy. Thus, using STSs appears to have potential utility for discriminating occupational physical tasks in the work environment. Practitioner summary: A smart textile system could classify diverse MMH tasks with high accuracy. This technology may help in developing future ergonomic exposure assessment systems, with the goal of preventing occupational injuries.