Back-support Exoskeletons Research Articles

Innovations in Ergonomic Risk Assessment and Intervention in Material Handling

This review paper delves into the complex facets of ergonomic risk evaluation and reduction across various industrial sectors. The focus is on identifying the hazards linked to manual labor, especially those contributing to physical risks and musculoskeletal disorders among workers, and proposing inventive solutions to mitigate these threats. The review brings together insights from different studies, emphasizing the application of automation, virtual modeling, Kinect-based evaluations, and other innovative tools in repetitive tasks and material handling operations. It also explores the usage of back-support exoskeletons, observational checklists, and workspace redesigns to decrease risks in construction, manufacturing, vegetable transportation, clothing accessories, and other sectors. The development of risk assessment frameworks for specific roles such as container terminal operators and the examination of musculoskeletal disorders in diverse worker demographics, including older female farmers and factory workers, are also featured. The comprehensive approach of the journal sets the stage for future research, aiming to further reduce the prevalence of musculoskeletal disorders through continued innovation and cross-sector collaboration.

Comparison of active and passive back-support exoskeletons for construction work: range of motion, discomfort, usability, exertion and cognitive load assessments

PurposeLow back disorders are more predominant among construction trade workers than their counterparts in other industry sectors. Floor layers are among the top artisans that are severely affected by low back disorders. Exoskeletons are increasingly being perceived as ergonomic solutions. This study aims to compare the efficacy of passive and active back-support exoskeletons by measuring range of motion, perceived discomfort, usability, perceived rate of exertion and cognitive load during a simulated flooring task experiment.Design/methodology/approachIn this study eight participants were engaged in a repetitive timber flooring task performed with passive and active back-support exoskeletons. Subjective and objective data were collected to assess the risks associated with using both exoskeletons. Descriptive statistics were used for analysis. Scheirer-Ray-Hare test and Wilcoxon signed-rank test were adopted to compare the exoskeleton conditions.FindingsThe results show no significant differences in the range of motion (except for a lifting cycle), perceived level of discomfort and perceived level of exertion between the two exoskeletons. Significant difference in overall cognitive load was observed. The usability results show that the active back-support exoskeleton made task execution easier with less restriction on movement.Research limitations/implicationsThe flooring task is simulated in a laboratory environment with only eight male participants.Originality/valueThis study contributes to the scarce body of knowledge on the usage comparison of passive and active exoskeletons for construction work.

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.

Dynamic assessment for low back-support exoskeletons during manual handling tasks.

Exoskeletons can protect users' lumbar spine and reduce the risk of low back injury during manual lifting tasks. Although many exoskeletons have been developed, their adoptability is limited by their task- and movement-specific effects on reducing burden. Many studies have evaluated the safety and effectiveness of an exoskeleton using the peak/mean values of biomechanical variables, whereas the performance of the exoskeleton at other time points of the movement has not been investigated in detail. A functional analysis, which presents discrete time-series data as continuous functions, makes it possible to highlight the features of the movement waveform and determine the difference in each variable at each time point. This study investigated an assessment method for exoskeletons based on functional ANOVA, which made it possible to quantify the differences in the biomechanical variables throughout the movement when using an exoskeleton. Additionally, we developed a method based on the interpolation technique to estimate the assistive torque of an exoskeleton. Ten men lifted a 10-kg box under symmetric and asymmetric conditions five times each. Lumbar load was significantly reduced during all phases (flexion, lifting, and laying) under both conditions. Additionally, reductions in kinematic variables were observed, indicating the exoskeleton's impact on motion restrictions. Moreover, the overlap F-ratio curves of the lumbar load and kinematic variables imply that exoskeletons reduce the lumbar load by restricting the kinematic variables. The results suggested that at smaller trunk angles (<25°), an exoskeleton neither significantly reduces the lumbar load nor restricts trunk movement. Our findings will help increasing exoskeleton safety and designing effective products for reducing lumbar injury risks.

Long-term effects and user acceptance of back-support exoskeletons in the workplace

The aim of our study was to evaluate the long-term effects of back-support exoskeletons (BSEs) in occupational settings. Valuable insights were gained through repeated in-depth interviews with occupational safety professionals over a one-year period regarding the use and impact of BSEs over a one-year period. The results highlight a significant lack of user acceptance, primarily due to movement restrictions and discomfort. Passive BSEs (PassEXOs) were reported to be sometimes uncomfortable, restricting mobility and causing pressure point discomfort, while quasipassive soft BSEs (SoftEXO) received more positive feedback. In addition, factors such as proper fit, adjustability, hygiene maintenance, and the ease of donning and doffing were identified as key determinants of employee acceptance of BSEs. By gaining a deeper understanding of these factors, organisations can facilitate a successful and sustainable integration of BSE technology into the workplace.

Impact of social influence on construction workers' intention-to-use exoskeletons

PurposeLow back disorder is one of the most prevalent and costly injuries in the construction industry. Back-support exoskeletons are increasingly perceived as promising solutions. However, the intended benefits of exoskeletons may not be realized if intention-to-use the device is low. Social influence could increase intention-to-use exoskeletons. This study aims to evaluate the impact of social influence on construction workers' intention-to-use back-support exoskeletons.Design/methodology/approachA field study involving 37 construction workers was conducted, with workers who used exoskeleton for one week, and their peers and supervisors. Data were collected using questionnaires and semi-structured interviews, and analyzed using descriptive statistics and thematic analysis, respectively.FindingsThe workers felt that the exoskeleton is easy to use and the functions are well integrated. Workers' intention-to-use exoskeleton was mainly influenced by employers providing and requiring the use of the device. The attitude of the workers and the perception of peers and supervisors did not have a significant impact on workers' intention-to-use exoskeleton, whereas the subjective norm of construction workers had a positive impact on the intention-to-use exoskeletons.Research limitations/implicationsThe study involved only 37 workers, including 15 workers who used the exoskeleton, and 14 peers and 8 supervisors of the workers.Originality/valueThis study contributes to existing knowledge on the influence of social influence on intention-to-use exoskeletons. The study also highlights how exoskeleton designs and the construction workplace can influence behavioral intention-to-use exoskeletons.

Control of a Back-Support Exoskeleton to Assist Carrying Activities.

Back-support exoskeletons are commonly used in the workplace to reduce low back pain risk for workers performing demanding activities. However, for the assistance of tasks differing from lifting, back-support exoskeletons potential has not been exploited extensively. This work focuses on the use of an active back-support exoskeleton to assist carrying. A control strategy is designed that modulates the exoskeleton torques to comply with the task assistance requirements. In particular, two gait phase detection frameworks are exploited to adapt the exoskeleton assistance according to the legs' motion. The control strategy is assessed through an experimental analysis on ten subjects. Carrying task is performed without and with the exoskeleton assistance. Results prove the potential of the presented control in assisting the task without hindering the gait movement and improving the usability experienced by users. Moreover, the exoskeleton assistance significantly reduces the lumbar load associated with the task, demonstrating its promising use for risk mitigation in the workplace.

How does perceived usefulness of an exoskeleton change with virtual reality training?

We investigated how novices’ perception of exoskeleton usefulness changes with different types of exposure to an exoskeleton; and when the biomechanical benefits and limitations of potential exoskeleton use are presented to them. Twenty young, healthy participants completed this study. The three types of informational exposures to a back-support exoskeleton (BSE) were: (1) Information-based, (2) Virtual Reality (VR)-based, and (3) hands-on experience (lifting a box using the BSE), where users virtually and physically completed various lifting/lowering tasks set at shoulder, waist, and ankle heights in symmetric and asymmetric positions. After every trial in each exposure, perceived usefulness was obtained. Overall, perceived usefulness ratings generally varied with major task variables (load, lift height, and trunk angle). The VR-based exposure appeared to clarify the specific circumstances under which the BSE was perceived to be useful and reduced extreme biases (positive or negative) that individuals may have developed prior to trying on a BSE.

Effects of Back-support Exoskeletons on Task Performance and Perceived Exertion During Construction-related Tasks: Differences related to Experience

The effects of three Back-support Exoskeletons (BSEs) on task performance (completion time) and perceived exertion were examined during simulated construction tasks. Forty participants (20 novices) completed the tasks using no BSE and three BSEs, each with two support settings (On and Off). There were significant main and interaction effects of Experience level on both outcome measures. Using BSEs negatively affected task performance for some tasks, though these effects were smaller among experienced participants. Interestingly, using BSEs inconsistently affected perceived physical effort, possibly due to the characteristics of the tasks, BSE designs, and experience levels. These results indicate that the effects of BSE on task performance and perceived physical effort are specific to experience level, BSE designs, and task demands. Further study is needed to better understand how to generalize these results to the actual work population.

Differences in kinematics and resulting lumbar spinal forces during repetitive lifting tasks: Simulation versus estimation of the effects of wearing a back-support exoskeleton

We explored the feasibility of using biomechanical simulations to predict altered spinal forces resulting from wearing a back-support exoskeleton (BSE) during repetitive lifting tasks. Twenty (10M, 10F) young, healthy participants completed repetitive lifting task, while wearing a BSE (‘with EXO’) and without wearing a BSE (‘without EXO’). Spinal forces were estimated by applying the BSE torque profile to body kinematics measured in ‘with EXO’ condition, while spinal forces were simulated by applying the same torque profile to body kinematics measured in ‘without EXO’ condition. Simulated compression force was higher than estimated compression force, probably due to lower trunk flexion angle in ‘without EXO’ condition. Such differences were larger among women than among men. However, simulated shear force was comparable with estimated shear force. Future works further need to compare simulated and estimated spinal forces for different BSEs (e.g., soft BSE), asymmetric lifting tasks, and different age group.

Comparison of soft vs. rigid back support exoskeletons through psychophysical and biomechanical approaches during load handling

As occupational exoskeletons are approaching real world implementation, perceptions about use and their effectiveness may differ across diverse age/gender groups, and device design. A soft and rigid type back-support exoskeleton (EXO) were evaluated in terms of selfrated maximum acceptable load (MAL), usability/social perceptions, and biomechanical outcomes during simulated manual material handling tasks. Thirty-six female and male participants from two age groups (18- 30 and 45-60 years) completed repetitive lifting and lowering tasks. Overall, both EXOs significantly improved participants’ MAL by ~6-7%, reduced peak trunk angle by 3-5 degrees, and reduced peak trunk extensor muscle activity by 9 - 13% . Participants generally reported both the EXOs as being useful, easy to use, and safe. This first systematic consideration of diverse age groups using a psychophysics approach in the context of passive occupational EXO use in laboratory settings contributes to bridging the gap between lab and field studies in exoskeleton implementations.

Reliability Analysis of Task Performance and Subjective Measures for Assessment of Occupational Exoskeletons

Use of occupational exoskeletons (EXOs), an emerging intervention, has attracted great interest from various industries. To facilitate their industry adoption, emphasis has been placed on the standardization of EXO assessment, but little effort has been made to improve experimental efficiency and effectiveness. Therefore, we investigated the within-session reliability of task performance (completion time) and subjective outcome measures when using arm- and back-support EXOs during donning/doffing and cart pushing/pulling tasks. Twenty-four participants replicated 10 trials of these tasks in each of two sessions, with each participant randomly assigned to one of two EXO groups. Within-session reliability increased with the number of trials and in Session 2 (vs. Session 1). Many outcome measures achieved excellent reliability, though the number of trials required for this varied across outcome measures, tasks, and EXO types. These findings can assist in the efficient design of future studies to assess the effects of EXO use.

Biomechanical Consequences of Using Passive and Active Back-Support Exoskeletons during Different Manual Handling Tasks.

The aim of this study was to assess, for both men and women, the consequences of using different back-support exoskeletons during various manual material tasks (MMH) on the activity of back muscles and trunk kinematics. Fifteen men and fourteen women performed MMH involving a 15 kg load (a static task, a symmetric lifting task, and an asymmetric lifting task). Four exoskeleton conditions were tested: without equipment (CON) and with three exoskeletons passive (P-EXO), and active (A-EXO1 and A-EXO2)). The electromyographic activity of the lower trapezius (TZ), latissimus dorsi (LD), erector spinae (ES), gluteus maximus (GM), and biceps femoris (BF) muscles was recorded. Trunk kinematics were evaluated to provide average thoracic, lumbar, and hip angles. The use of the P-EXO decreased the activity of LD, GM, and BF from -12 to -27% (p < 0.01) compared to CON, mostly during the static task. The A-EXO1 and A-EXO2 reduced the muscle activity of all studied muscles from -7 to -62% (p < 0.01) compared to CON and from -10 to -52% (p < 0.005) compared to the P-EXO, independently of the modalities of the experimental tasks. A statistical interaction between the sex and exoskeleton was only observed in a few rare conditions. Occupational back-support exoskeletons can reduce trunk extensor muscle activity compared to no equipment being used. However, these reductions were modulated by the exoskeleton technology (passive vs. active), design (weight and anthropomorphism), and the modalities of the task performed (static vs. dynamic). Our results also showed that the active exoskeletons could modify the trunk kinematics.

Effects of a Passive Back Support Exoskeleton when Lifting and Carrying Lumber Boards.

Passive back support exoskeletons, which support the human trunk using elements like springs and elastic bands, have demonstrated positive results in laboratory-based studies, but have seen significantly less field testing. As an intermediate step between generic lab evaluations and field tests, we conducted a single-session lab evaluation of the HeroWear Apex exoskeleton with mockup construction tasks: 20 adult men (without extensive construction experience) lifted, carried and raised lumber boards (265 cm length, up to 18 kg total load). The exoskeleton significantly reduced mean erector spinae electromyograms, with effect sizes (Cohen's d) ranging from -0.2 to -0.55 - corresponding to reductions of 5-25% relative to noexoskeleton electromyogram values. In asymmetric carrying tasks, the exoskeleton provided more assistance to the more heavily loaded erector spinae muscle. Additionally, in lifting tasks, the exoskeleton decreased trunk/hip flexion/extension range of motion and increased knee range of motion, indicating changes in lifting strategy. These results indicate potential exoskeleton benefits for lumber board carrying and will serve as the basis for further evaluations with workers in the field.Clinical Relevance- This study establishes that a passive back exoskeleton reduces erector spinae electromyograms by 525% when lifting and carrying lumber boards used in construction work.

Real-time lumbosacral joint loading estimation in exoskeleton-assisted lifting conditions via electromyography-driven musculoskeletal models

Lumbar joint compression forces have been linked to the development of chronic low back pain, which is specially present in occupational environments. Offline methodologies for lumbosacral joint compression force estimation are not commonly integrated in occupational or medical applications due to the highly time-consuming and complex post-processing procedures. Hence, applications such as real-time adjustment of assistive devices (i.e., back-support exoskeletons) for optimal modulation of compression forces remains unfeasible. Here, we present a real-time electromyography (EMG)-driven musculoskeletal model, capable of estimating accurate lumbosacral joint moments and plausible compression forces. Ten participants performed box-lifting tasks (5 and 15 kg) with and without the Laevo Flex back-support exoskeleton using squat and stoop lifting techniques. Lumbosacral kinematics and EMGs from abdominal and thoracolumbar muscles were used to drive, in real-time, subject-specific EMG-driven models, and estimate lumbosacral joint moments and compression forces. Real-time EMG-model derived moments showed high correlations (R2 = 0.76 - 0.83) and estimation errors below 30% with respect to reference inverse dynamic moments. Compared to unassisted lifting conditions, exoskeleton liftings showed mean lumbosacral joint moments and compression forces reductions of 11.9 - 18.7 Nm (6 - 12% of peak moment) and 300 - 450 N (5 - 10%), respectively. Our modelling framework was capable of estimating in real-time, valid lumbosacral joint moments and compression forces in line with in vivo experimental data, as well as detecting the biomechanical effects of a passive back-support exoskeleton. Our presented technology may lead to a new class of bio-protective robots in which personalized assistance profiles are provided based on subject-specific musculoskeletal variables.

Evaluation of concrete workers' interaction with a passive back-support exoskeleton

PurposeConcrete workers perform physically demanding work in awkward postures, exposing their backs to musculoskeletal disorders. Back-support exoskeletons are promising ergonomic interventions designed to reduce the risks of back disorders. However, the suitability of exoskeletons for enhancing performance of concrete workers has not been largely explored. This study aims to assess a passive back-support exoskeleton for concrete work in terms of the impact on the body, usability and benefits of the exoskeleton, and potential design modifications.Design/methodology/approachConcrete workers performed work with a passive back-support exoskeleton. Subjective and qualitative measures were employed to capture their perception of the exoskeleton, at the middle and end of the work, in terms of discomfort to their body parts, ease of use, comfort, performance and safety of the exoskeleton, and their experience using the exoskeleton. These were analyzed using descriptive statistics and thematic analysis.FindingsThe exoskeleton reduced stress on the lower back but caused discomfort to other body parts. Significant correlations were observed between perceived discomfort and usability measures. Design modifications are needed to improve the compatibility of the exoskeleton with the existing safety gears, reduce discomfort at chest and thigh, and improve ease of use of the exoskeleton.Research limitations/implicationsThe study was conducted with eight concrete workers who used the exoskeleton for four hours.Originality/valueThis study contributes to existing knowledge on human-wearable robot interaction and provides suggestions for adapting exoskeleton designs for construction work.

Performance and effectiveness of a passive back-support exoskeleton in manual material handling tasks in the construction industry

Performance and effectiveness of a passive back-support exoskeleton in manual material handling tasks in the construction industry

Evaluation of the physiological benefits of a passive back-support exoskeleton during lifting and working in forward leaning postures

Musculoskeletal disorders affecting the back are highly prevalent in fields of occupation involving repetitive lifting and working in forward leaning postures. Back-support exoskeletons are developed to relieve workers in physically demanding occupations. This study investigates the physiological effects of a lightweight exoskeleton which provides support through textile springs worn on the back. We hypothesized that wearing such a passive back-support exoskeleton reduces muscle activity of the back and hip muscles, while not influencing abdominal muscle activity and movement kinematics during typical occupational tasks.We collected electromyography data from the main back and hip muscles as well as whole body kinematics data via optical motion tracking during a set of relevant weight lifting tasks corresponding to typical work conditions. In our sample of 30 healthy volunteers, wearing the exoskeleton significantly reduced muscle activity, with reductions up to 25.59% during forward leaning and 20.52% during lifting in the main back and hip muscles (Erector Spinae at thoracic and lumbar level and Quadratus Lumborum). Simultaneously, no changes in knee and hip range of motion were observed. The stretch of the textile springs correlated with the body mass index and chest circumference of the wearer, and depended on posture, but not on the lifted load.The LiftSuit exoskeleton relieved back and hip muscles during typically straining occupational tasks, while biomechanical parameters were preserved. This suggests that passive lift-support exoskeletons can be safely used to relieve workers during lifting and forward leaning tasks.

A Statistical Parametric Mapping Analysis Approach for the Evaluation of a Passive Back Support Exoskeleton on Mechanical Loading During a Simulated Patient Transfer Task

This study assessed the effectiveness of a passive back support exoskeleton during a mechanical loading task. Fifteen healthy participants performed a simulated patient transfer task while wearing the Laevo (version 2.5) passive back support exoskeleton. Collected metrics encompassed L5-S1 joint moments, back and abdominal muscle activity, lower body and back kinematics, center of mass displacement, and movement smoothness. A statistical parametric mapping analysis approach was used to overcome limitations from discretization of continuous data. The exoskeleton reduced L5-S1 joint moments during trunk flexion, but wearing the device restricted L5-S1 joint flexion when flexing the trunk as well as hip and knee extension, preventing participants from standing fully upright. Moreover, wearing the device limited center of mass motion in the caudal direction and increased its motion in the anterior direction. Therefore, wearing the exoskeleton partly reduced lower back moments during the lowering phase of the patient transfer task, but there were some undesired effects such as altered joint kinematics and center of mass displacement. Statistical parametric mapping analysis was useful in determining the benefits and hindrances produced by wearing the exoskeleton while performing the simulated patient transfer task and should be utilized in further studies to inform design and appropriate usage.

Variable-Damper Control Using MR Fluid for Lower Back Support Exoskeleton

Even with proper lifting techniques, fatigue can cause many debilitating injuries. Exoskeleton lumbar support devices help prevent these injuries for workers and improve their overall performance. In this article, we present a study on the performance of a semiactive lower back support exoskeleton. The device is powered by a spring–damper mechanism that utilizes a magnetorheological fluid to add a resistive force to the hip joint. The braking force of the device showed a range between 100 and 900 N depending on the compression stroke, coil current, and actuation speed. Muscle activation of the latissimus dorsi, erector spinae, and gluteus maximus was reduced. The analysis based on a biomechanical model showed a power reduction of 40% at the hip joint in the bending phase, and a total reduction of 20% during the entire lifting cycle. The automatic control system using only embedded sensors showed successful and stable functioning but had excessive delays in the activation of the device.