Effects of industrial back-support exoskeletons on body loading and user experience: an updated systematic review

Equivalent weight: Application of the assessment method on real task conducted by railway workers wearing a back support exoskeleton

Commonly used risk indexes, such as the NIOSH Lifting Index, do not capture the effect of exoskeletons. This makes it difficult for Health and Safety professionals to rigorously assess the benefit of such devices. The community requires a simple method to assess the effectiveness of back-support exoskeleton's (BSE) in possibly reducing ergonomic risk. The method introduced in this work is termed "Equivalent Weight" (EqW) and it proposes an interpretation of the effect built on the benefit delivered through reduced activation of the erector spinae (ES). This manifests itself as an apparent reduction of the lifted load perceived by the wearer. This work presents a pilot study where a practical application of the EqW method is used to assess the ergonomic risk in manual material handling (MMH) when using a back support exoskeleton (StreamEXO). The results are assessed by combining observational measurements from on-site testing with five different workers and quantitative measures of the muscle activity reduction achieved during laboratory evaluation with ten workers. These results will show that when lifting, lowering, and carrying a 19 kg load the StreamEXO can reduce risk by up to two levels (from "high" to "low") in the target sub-tasks. The Lifting index (LI) was reduced up to 64% when examining specific sub-tasks and the worker's movement conduction.

Reconstruction of occluded pelvis markers during marker-based motion capture with industrial exoskeletons

Industrial back support exoskeletons are a promising solution to alleviate lumbar musculoskeletal strain. Due to the complexity of spinal loading, evaluation of EMG data alone has been considered insufficient to assess their support effects, and complementary kinematic and dynamic data are required. However, the acquisition of marker-based kinematics is challenging with exoskeletons, as anatomical reference points, particularly on the pelvis, are occluded by exoskeleton structures. The aim of this study was therefore to develop and validate a method to reliably reconstruct the occluded pelvic markers. The movement data of six subjects, for whom pelvic markers could be placed while wearing an exoskeleton, were used to test the reconstructions and compare them to anatomical landmarks during lifting, holding and walking. Two separate approaches were used for the reconstruction. One used a reference coordinate system based on only exoskeleton markers (EXO), as has been suggested in the literature, while our proposed method adds a technical marker in the lumbar region (LUMB) to compensate for any shifting between exoskeleton and pelvis. Reconstruction with EXO yielded on average an absolute linear deviation of 54 mm ± 16 mm (mean ± 1SD) compared to anatomical markers. The additional marker in LUMB reduced mean deviations to 14 mm ± 7 mm (mean ± 1SD). Both methods were compared to reference values from the literature for expected variances due to marker placement and soft tissue artifacts. For LUMB 99% of reconstructions were within the defined threshold of 24 mm ±9 mm while for EXO 91% were outside.

Evaluating adaptiveness of an active back exosuit for dynamic lifting and maximum range of motion

Back exosuits deliver mechanical assistance to reduce the risk of back injury, however, minimising restriction is critical for adoption. We developed the adaptive impedance controller to minimise restriction while maintaining assistance by modulating impedance based on the user's movement direction and nonlinear sine curves. The objective of this study was to compare active assistance, delivered by a back exosuit via our adaptive impedance controller, to three levels of assistance from passive elastics. Fifteen participants completed five experimental blocks (4 exosuits and 1 no-suit) consisting of a maximum flexion and a constrained lifting task. While a higher stiffness elastic reduced back extensor muscle activity by 13%, it restricted maximum range of motion (RoM) by 13°. The adaptive impedance approach did not restrict RoM while reducing back extensor muscle activity by 15%, when lifting. This study highlights an adaptive impedance approach might improve usability by circumventing the assistance-restriction trade-off inherent to passive approaches.Practitioner summary: This study demonstrates a soft active exosuit that delivers assistance with an adaptive impedance approach can provide reductions in overall back muscle activity without the impacts of restricted range of motion or perception of restriction and discomfort.

The effects of an upper limb exoskeleton on gait performance and stability

Upper limb exoskeletons (ULEs) are emerging as workplace tools to alleviate workload and prevent work-related musculoskeletal disorders during lifting tasks. However, their introduction raises concerns about potential instability and increased fall risk for workers. This study investigates gait performance and stability parameters implications of ULE use. Fifteen participants performed a carrying task with different loads (0, 5, 10, 15 kg), both with and without the use of an ULE. Spatiotemporal gait parameters, Required Coefficient of Friction (RCoF), Minimum Foot Clearance (MFC), and Margin of Stability (MoS) were analysed. The findings indicate that while the ULE does not significantly alter most gait parameters or slip risk, it may negatively impact trip risk. Furthermore, while mediolateral stability remains unaffected, anteroposterior stability is compromised by ULE usage. These insights are critical for ensuring the safe implementation of ULEs in occupational settings.

Biomechanical analysis of different back-supporting exoskeletons regarding musculoskeletal loading during lifting and holding

Industrial back support exoskeletons (BSEs) are a promising approach to addressing low back pain (LBP) which still affect a significant proportion of the workforce. They aim to reduce lumbar loading, the main biomechanical risk factor for LBP, by providing external support to the lumbar spine. The aim of this study was to determine the supporting effect of one active (A1) and two passive (P1 and P2) BSEs during different manual material handling tasks. Kinematic data and back muscle activity were collected from 12 subjects during dynamic lifting and static holding of 10 kg. Mean and peak L5/S1 extension moments, L5/S1 compression forces and muscle activation were included in the analysis. During dynamic lifting all BSEs reduced peak (12-26 %) and mean (4-17 %) extension moments and peak (10-22 %) and mean (4-15 %) compression forces in the lumbar spine. The peak (13-28 %) and mean (4-32 %) activity of the back extensor muscles was reduced accordingly. In the static holding task, analogous mean reductions for P1 and P2 of L5/S1 extension moments (12-20 %), compression forces (13-23 %) and muscular activity (16-23 %) were found. A1 showed a greater reduction during static holding for extension moments (46 %), compression forces (41 %) and muscular activity (54 %). This pronounced difference in the performance of the BSEs between tasks was attributed to the actuators used by the different BSEs.

Multidisciplinary collaboration on exoskeleton development adopting user-centered design: a systematic integrative review

Purpose: The world population is ageing, along with an increasing possibility of functional limitations that affect independent living. Assistive technologies such as exoskeletons for rehabilitative purposes and daily activities assistance maintaining the independence of people with disabilities, especially older adults who wish to ageing-in-place. The purpose of this systematic integrative review was threefold: to explore the development team compositions and involvement, to understand the recruitment and engagement of stakeholders, and to synthesise reported or anticipated consequences of multidisciplinary collaboration.Methods: Databases searched included PubMed, CINAHL Plus, PsycINFO, Web of Science, Scopus, and IEEE Xplore. A total of 34 studies that reported the development of exoskeleton adopting user-centered design (UCD) method in healthcare or community settings that were published in English from 2000 to July 2022 were included.Results: Three major trends emerged from the analysis of included studies. First, there is a need to redefine multidisciplinary collaboration, from within-discipline collaboration to cross-discipline collaboration. Second, the level of engagement of stakeholders during the exoskeleton development remained low. Third, there was no standardised measurement to quantify knowledge production currently.Conclusion: As suggested by the synthesised results in this review, exoskeleton development has been increasing to improve the functioning of people with disabilities. Exoskeleton development often required expertise from different disciplines and the involvement of stakeholders to increase acceptance, thus we propose the Multidisciplinary Collaboration Appraisal Tool to assess multidisciplinary collaboration using the UCD approach. Future research is required to understand the effectiveness of multidisciplinary collaboration on exoskeleton development using the UCD approach.IMPLICATIONS FOR REHABILITATIONGlobal trend of population ageing causes a higher risk of disability in older adults who require rehabilitation and assistance in daily living.Assistive technologies such as exoskeletons have the potential to contribute to rehabilitation training and daily activity assistance demand closer multidisciplinary collaboration.A Multidisciplinary Collaboration Appraisal Tool using user-centered design approach (MCAT) is proposed to understand the effectiveness as well as limitations and barriers associated with multidisciplinary collaboration in developing exoskeletons.

Exoskeleton technology in nursing practice: assessing effectiveness, usability, and impact on nurses' quality of work life, a narrative review

The use of exoskeletons in nursing practice has gained attention as a potential solution to address the physical demands and risks associated with the profession. This narrative review examines the effectiveness, usability, and impact of exoskeleton technology on nurses' quality of work life. The review focuses on the reduction of physical strain and fatigue, improved posture and body mechanics, enhanced patient care, usability and acceptance factors, and the broader impact on work life. The effectiveness of exoskeletons in reducing physical strain and fatigue among nurses is supported by evidence showing decreased muscle activation and reduced forces exerted on the body. The usability and acceptance of exoskeletons are critical considerations, including device comfort and fit, ease of use and integration into workflows, user experience and training, compatibility with the work environment, and user feedback for iterative design improvements. The implementation of exoskeletons has the potential to positively impact nurses' work life by reducing work-related injuries, improving physical well-being, enhancing job satisfaction, and promoting psychological and psychosocial benefits. Additionally, the use of exoskeletons can lead to improved patient care outcomes. Challenges and future directions in the field of exoskeleton technology for nurses include cost and accessibility, adaptability to nursing specialties and tasks, long-term durability and maintenance, integration with personal protective equipment, and ethical considerations. Addressing these challenges and considering future research and development efforts are crucial for the successful integration of exoskeleton technology in nursing practice, ultimately improving nurses' quality of work life and patient care delivery.

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.

The effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading during squat and stoop lifts

Back support exosuits aim to reduce tissue demands and thereby risk of injury and pain. However, biomechanical analyses of soft active exosuit designs have been limited. The objective of this study was to evaluate the effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading in participants performing stoop and squat lifts of 6 and 10 kg crates, using participant-specific musculoskeletal models. The exosuit did not change overall trunk motion but affected lumbo-pelvic motion slightly, and reduced peak compressive and shear vertebral loads at some levels, although shear increased slightly at others. This study indicates that soft active exosuits have limited kinematic effects during lifting, and can reduce spinal loading depending on the vertebral level. These results support the hypothesis that a soft exosuit can assist without limiting trunk movement or negatively impacting skeletal loading and have implications for future design and ergonomic intervention efforts.

Benchmarking commercially available soft and rigid passive back exoskeletons for an industrial workplace

Low-back pain is a common occupational hazard for industrial workers. Several studies show the advantages of using rigid and soft back-support passive exoskeletons and exosuits (exos) to reduce the low-back loading and risk of injury. However, benefits of using these exos have been shown to be task-specific. Therefore, in this study, we developed a benchmarking approach to assess exos for an industrial workplace at Hankamp Gears B.V. We assessed two rigid (Laevo Flex, Paexo back) and two soft (Auxivo Liftsuit 1.0, and Darwing Hakobelude) exos for tasks resembling the workplace. We measured the assistive moment provided by each exo and their respective influence on muscle activity as well as the user's perception of comfort and exertion. Ten participants performed four lifting tasks (Static hold, Asymmetric, Squat, and Stoop), while their electromyography and subjective measures were collected. The two rigid exos provided the largest assistance during the Dynamic tasks. Reductions in erector spinae activity were seen to be task-specific, with larger reductions for the two rigid exos. Overall, Laevo Flex offered a good balance between assistive moments, reductions in muscle activity, as well as user comfort and reductions in perceived exertion. Thus, we recommend benchmarking exos for intended use in the industrial workplace. This will hopefully result in a better adoption of the back-support exoskeletons in the workplace and help reduce low-back pain.

Dynamic and Static Assistive Strategies for a Tailored Occupational Back-Support Exoskeleton: Assessment on Real Tasks Carried Out by Railway Workers

This study on occupational back-support exoskeletons performs a laboratory evaluation of realistic tasks with expert workers from the railway sector. Workers performed both a static task and a dynamic task, each involving manual material handling (MMH) and manipulating loads of 20 kg, in three conditions: without an exoskeleton, with a commercially available passive exoskeleton (Laevo v2.56), and with the StreamEXO, an active back-support exoskeleton developed by our institute. Two control strategies were defined, one for dynamic tasks and one for static tasks, with the latter determining the upper body's gravity compensation through the Model-based Gravity Compensation (MB-Grav) approach. This work presents a comparative assessment of the performance of active back support exoskeletons versus passive exoskeletons when trialled in relevant and realistic tasks. After a lab characterization of the MB-Grav strategy, the experimental assessment compared two back-support exoskeletons, one active and one passive. The results showed that while both devices were able to reduce back muscle activation, the benefits of the active device were triple those of the passive system regarding back muscle activation (26% and 33% against 9% and 11%, respectively), while the passive exoskeleton hindered trunk mobility more than the active mechanism.

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.

Effects of a Passive Back-Support Exosuit on Postural Control and Cognitive Performance During a Fatigue-Inducing Posture Maintenance Task

OBJECTIVE

To evaluate the effectiveness of passive back-support exosuit on postural control and cognitive performance during a fatigue-inducing posture maintenance task.

BACKGROUND

Wearable support systems (exoskeletons/exosuits) reduce physical demands but may also influence postural control and cognitive performance by reducing muscular fatigue.

METHOD

Eighteen participants visited on two different days to test an exosuit system and performed dual-task cognitive assessments based on human information processing (information acquisition, information integration, and action implementation) while maintaining a 35° trunk flexion posture for 16 minutes. Center-of-pressure (CoP), cognitive performance, and perceived workload were recorded, while erector spinae muscle activity was captured to quantify muscle fatigue.

RESULTS

The exosuit was effective in reducing erector spinae muscle fatigue during the static posture maintenance task (61% less in Δmedian frequency: -9.5 Hz (EXO-Off) versus -3.7 Hz (EXO-On)). The fatigue-inducing task increased CoP velocity as a function of time (29% greater: 9.3 mm/sec (pre) versus 12.0 mm/sec (post)), and exosuit use decreased CoP velocity (23% less: 12.1 mm/sec (EXO-Off) versus 9.4 mm/sec (EXO-On)). The exosuit was also effective at mitigating cognitive degradation, as evidenced by a higher hit-to-signal ratio (8% greater: 81.3 (EXO-Off) versus 87.9 (EXO-On)) in the information integration task and reducing perceived workload in all stages of human information processing.

CONCLUSION

Exosuit provided benefits of postural control and information integration processing during a 16-min static posture maintenance task.

APPLICATION

Torso exoskeletons/suits can have positive implications for occupations with concurrent physical and cognitive demands.

Using a Passive Back Exoskeleton During a Simulated Sorting Task: Influence on Muscle Activity, Posture, and Heart Rate

OBJECTIVE

To evaluate using a back exoskeleton in a simulated sorting task in a static forward bent trunk posture on muscle activity, posture, and heart rate (HR).

BACKGROUND

Potentials of exoskeletons for reducing musculoskeletal demands in work tasks need to be clarified.

METHODS

Thirty-six healthy males performed the sorting task in 40°-forward bent static trunk posture for 90 seconds, in three trunk orientations, with and without exoskeleton. Muscle activity of the erector spinae (ES), biceps femoris (BF), trapezius descendens (TD), rectus abdominis (RA), vastus laterals (VL), and gastrocnemius medialis was recorded using surface electromyography normalized to a submaximal or maximal reference electrical activity (%RVE (reference voluntary electrical activity)/%MVE). Spine and lower limb postures were assessed by gravimetric position sensors, and HR by electrocardiography.

RESULTS

Using the exoskeleton resulted in decreased BF muscle activity [-8.12%RVE], and minor changes in ES [-1.29%MVE], RA [-0.28%RVE], VL [-0.49%RVE], and TD [+1.13%RVE] muscle activity. Hip and knee flexion increased [+8.1°; +6.7°]. Heart rate decreased by 2.1 bpm. Trunk orientation had an influence on BF muscle activity.

CONCLUSION

Using the back exoskeleton in a short sorting task with static trunk posture mainly reduced hip extensor muscle activity and changed lower limb but not spine posture. Implications of using a back exoskeleton for workers' musculoskeletal health need further clarification.

APPLICATION

The detected changes by using the Laevo® illustrate the need for further investigation prior to practical recommendations of using exoskeletons in the field. Investigating various work scenarios in different kind of workers and long-term applications would be important elements.

Influence of a passive exoskeleton on kinematics, joint moments, and self-reported ratings during a lifting task

It was found that the Auxivo LiftSuit reduced the load on the back and hip muscles when lifting heavy loads, but its effect on lower body kinematics, joint moments, and self-reported ratings was unclear. The purpose of this study was to assess the effect of this passive lift-exoskeleton design, on lower body kinematics, joint moments, and self-reported ratings during lifting of heavy loads. Twenty healthy subjects performed lifting of heavy loads with and without the exoskeleton under surveillance of a motion capture system. Medium and maximum level adjustments of the exoskeleton, as well as no exoskeleton use were analyzed. Our results indicate significant reduction (p <.01) in pelvis segment tilt and hip flexion ROM with the exoskeleton at maximum level adjustment in males during lifting. Lumbosacral flexion moment ranges were significantly decreased (p <.013) with the exoskeleton at maximum and medium level adjustment in males during lifting. The general user impressions were mostly positive, with participants reporting that it was easier to perform the task with the exoskeleton than without it (p <.0.001), and preferring and recommending the exoskeleton for the task. Although our findings may suggest negative effects of the Auxivo LiftSuit in males and females due to a ROM restriction and loose fit, respectively, it does not mean that the Auxivo LiftSuit is not useful for lifting tasks. Further design improvements are required to allow full range of motion of hips and pelvis, as well to provide better adjustment and level of support in female users.

Evaluating cognitive and physical work performance: A comparative study of an active and passive industrial back-support exoskeleton

Occupational back-support exoskeletons, categorized as active or passive, hold promise for mitigating work-related musculoskeletal disorders. However, their impact on combined physical and cognitive aspects of industrial work performance remains inadequately understood, especially regarding potential differences between exoskeleton categories. A randomized, counterbalanced cross-over study was conducted, comparing the active CrayX, passive Paexo Back, and a no exoskeleton condition. A 15-min dual task was used to simulate both cognitive and physical aspects of industrial work performance. Cognitive workload parameters included reaction time, accuracy, and subjective measures. Physical workload included movement duration, segmented in three phases: (1) walking to and grabbing the box, (2) picking up, carrying, and putting down the box, and (3) returning to the starting point. Comfort of both devices was also surveyed. The Paexo significantly increased movement duration in the first segment compared to NoExo (Paexo = 1.55 ± 0.19 s; NoExo = 1.32 ± 0.17 s; p < .01). Moreover, both the Paexo and CrayX increased movement duration for the third segment compared to NoExo (CrayX = 1.70 ± 0.27 s; Paexo = 1.74 ± 0.27 s, NoExo = 1.54 ± 0.23 s; p < .01). No significant impact on cognitive outcomes was observed. Movement Time 2 was not significantly affected by both exoskeletons. Results of the first movement segment suggest the Paexo may hinder trunk bending, favoring the active device for dynamic movements. Both devices may have contributed to a higher workload as the movement duration in the third segment increased compared to NoExo.

Exoskeleton Usability Questionnaire: a preliminary evaluation questionnaire for the lower limb industrial exoskeletons

Exoskeleton robots are a promising solution to reduce musculoskeletal disorders (MSDs) in different work environments, but a specific usability scale for evaluating them is lacking. This study aimed to develop and verify a preliminary Exoskeleton Usability Questionnaire (EUQ) for the lower limb exoskeletons by creating a draft survey questionnaire from existing questions in prior studies. An experiment was conducted with 20 participants who performed a specific task while wearing three lower limb robots and provided subjective feedback using the developed questionnaire. Data were analysed using exploratory and confirmatory factor analysis (CFA), resulting in a usability evaluation questionnaire for exoskeleton robots clustered into four main factors: mobility, adjustability, handling and safety. This study's findings are expected to be useful in evaluating the usability of the lower limb exoskeletons in both general production sites and agricultural work, which can aid in reducing the prevalence of lower limb MSDs.Practitioner Summary: This study developed a preliminary subjective usability evaluation questionnaire for exoskeleton robots. The questionnaire is clustered into four main factors: mobility, adjustability, handling and safety. These findings provide a valuable tool for assessing exoskeleton usability, potentially reducing musculoskeletal disorders (MSDs) in various work environments.

Quantifying the effectiveness of a passive trunk-support exosuit at reducing erector spinae muscle fatigue during a quasi-static posture maintenance task

The objective of this study was to explore the effectiveness of a passive back-support exosuit at reducing low back muscle fatigue during an 18-minute trunk posture maintenance task. On two separate days sixteen participants performed an 18-minute trunk posture profile that reflected trunk flexion postures observed during a challenging vascular surgery procedure. On one day they performed the procedure with the support of the exosuit, on the other day without. Test contractions were performed every three minutes to capture the time-dependent electromyographic activity of the bilateral erector spinae muscles. Time domain (amplitude) and frequency domain (median frequency) measures of erector spinae muscle fatigue were assessed. Results revealed that the exosuit significantly reduced the measures of erector spinae muscle fatigue in terms of both amplitude (6.1%) and median frequency (5.3%), demonstrating a fatigue reduction benefit of the exosuit in a realistic surgical posture maintenance task.

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.

Assessment of Muscle Coordination Changes Caused by the Use of an Occupational Passive Lumbar Exoskeleton in Laboratory Conditions

The introduction of exoskeletons in industry has focused on improving worker safety. Exoskeletons have the objective of decreasing the risk of injury or fatigue when performing physically demanding tasks. Exoskeletons' effect on the muscles is one of the most common focuses of their assessment. The present study aimed to analyze the muscle interactions generated during load-handling tasks in laboratory conditions with and without a passive lumbar exoskeleton. The electromyographic data of the muscles involved in the task were recorded from twelve participants performing load-handling tasks. The correlation coefficient, coherence coefficient, mutual information, and multivariate sample entropy were calculated to determine if there were significant differences in muscle interactions between the two test conditions. The results showed that muscle coordination was affected by the use of the exoskeleton. In some cases, the exoskeleton prevented changes in muscle coordination throughout the execution of the task, suggesting a more stable strategy. Additionally, according to the directed Granger causality, a trend of increasing bottom-up activation was found throughout the task when the participant was not using the exoskeleton. Among the different variables analyzed for coordination, the most sensitive to changes was the multivariate sample entropy.

Effect of trunk flexion angle and time on lumbar and abdominal muscle activity while wearing a passive back-support exosuit device during simple posture-maintenance tasks

Quantifying the trunk flexion angles at which wearable support systems (exoskeletons/exosuits) provide substantial trunk extension moment during posture maintenance tasks (such as those seen in surgical environments) can provide a deeper understanding of this potential intervention strategy. Understanding how time (i.e. adaptation/learning) might impact the reliance on wearable support is also of value. Sixteen participants were asked to maintain specific trunk flexion angles (range 0-60°) with and without an exosuit system while erector spinae and rectus abdominis muscle activity were captured using surface electromyography. The effects of the exosuit showed a statistically significant (p < 0.007) effect on the activity of the erector spinae muscles at 10-60°-an effect that became 'large' (Cohen's d = 0.84) after 20° of trunk flexion. There were no meaningful time-dependent trends in the levels of muscle activation indicating there was no adaptation/learning effect of the exosuit in the task studied.Practitioner summary: This study examined the effectiveness of a back-support exosuit as a function of trunk flexion angle and time of use. The results revealed that the exosuit significantly reduced erector spinae muscle activity beyond 20° of trunk flexion but did not show a meaningful adaption/learning effect.Abbreviations: LBP: low back pain; EMG: electromyography; NEMG: normalized electromyography; IMU: inertial measurement unit; ES: erector spinae; RA: rectus abdominis; MVC: maximum voluntary contraction; FFT: Fast Fourier Transform.

Simulation of passive exotendon assistive device for agricultural harvesting task

This study proposes and investigates the feasibility of the passive assistive device to assist agricultural harvesting task and reduce the Musculoskeletal Disorder (MSD) risk of harvesters using computational musculoskeletal modelling and simulations. Several passive assistive devices comprised of elastic exotendon, which acts in parallel with different back muscles (rectus abdominis, longissimus, and iliocostalis), were designed and modelled. These passive assistive devices were integrated individually into the musculoskeletal model to provide passive support for the harvesting task. The muscle activation, muscle force, and joint moment were computed with biomechanical simulations for unassisted and assisted motions. The simulation results demonstrated that passive assistive devices reduced muscle activation, muscle force, and joint moment, particularly when the devices were attached to the iliocostalis and rectus abdominis. It was also discovered that assisting the longissimus muscle can alleviate the workload by distributing a portion of it to the rectus abdominis. The findings in this study support the feasibility of adopting passive assistive devices to reduce the MSD risk of the harvesters during agricultural harvesting. These findings can provide valuable insights to the engineers and designers of physical assistive devices on which muscle(s) to assist during agricultural harvesting.

Effect of wearable chair on gait, balance, and discomfort of new users during level walking with anterior loads

INTRODUCTION

Walking with anterior loads is common in industrial scenarios, but as exoskeletons are increasingly used in work environments to alleviate musculoskeletal disorders (MSDs), this new "human-robot" system composed of the human body and exoskeleton may be associated with new risks and harm that warrant further investigation. Therefore, this study will discuss the effect of a wearable chair on the gait, balance, and discomfort of new users with different weights of anterior loads during level walking.

METHOD

Twenty-two healthy subjects (sex balanced) participated in the experiment. Each exposure comprised one of two exoskeleton states (with/without) and four load conditions: No carried load, carrying an empty box (0.3 kg), 5%Body Weight (BW), and 10%BW. The order of exoskeleton states and load conditions was randomly assigned. Using an eight-camera motion capture system to record the entire movement. And the subjective discomfort and perceived balance after each exposure were recorded on an 11-point numeric rating scale, respectively. Using SPSS 26.0 software (IBM Inc., Chicago) to conduct statistical analyses.

RESULTS

Level walking with a wearable chair in different load conditions significantly affected gait parameters (like cadence) and gait balance. The perceived balance decreased with the exoskeleton, consistent with objective results. For subjective discomfort, wearing the exoskeleton significantly impacted global discomfort. Also, it increased the local discomfort of the shoulders, waist, thighs, shanks, and feet/ankles.

CONCLUSIONS

For new users, the risk of losing balance or falling may be increased when wearing an exoskeleton for non-target task behaviors (level walking/anterior load), and caution is recommended when the anterior load exceeds 5% BW.

PRACTICAL APPLICATION

The proposed strategy for assessing human gait, balance, and discomfort in wearable chairs may be applied during the iterative design of the product. These controls will help develop training programs and implementation guidelines for this exoskeleton type.

Numerical investigation of intra-abdominal pressure and spinal load-sharing upon the application of an abdominal belt

Chronic low back pain patients may experience spinal instability. Abdominal belts (ABs) have been shown to improve spine stability, trunk stiffness, and resiliency to spinal perturbations. However, research on the contributing mechanisms is inconclusive. ABs may increase intra-abdominal pressure (IAP) and reduce paraspinal soft tissue contribution to spine stability without increasing spinal compressive loads. A finite element model (FEM) of the spine inclusive of the T1-S1 vertebrae, intervertebral discs (IVDs), ribcage, pelvis, soft tissues, and abdominal cavity, without active muscle forces was developed. An identical FEM with an AB was developed. Both FEMs underwent trunk flexion. Following validation, the models' intervertebral rotation (IVR), IAP, IVD pressure, and tensile stress in the multifidus (MF), erector spinae (ES), and thoracolumbar fascia (TLF) were compared. The inclusion of an AB resulted in a 3.8 kPa IAP increase, but a decreased average soft tissue tensile stress of 0.28 kPa. The TLF withstood the majority of tension being transferred across the paraspinal soft tissues (>70 %). The average IVR in the AB model decreased by 10 %, with the lumbar spine experiencing the largest reduction. The lumbar IVDs of the AB model likewise showed a 31 % reduction in average IVD pressure. Using an AB improved trunk bending stiffness, primarily in the lumbar spine. Wearing an AB had minimal effect on reducing tensile stress in theES. The skewed stress distribution towards the TLF suggests its large contribution to spine stability and the potential advantage in unloading the structure when wearing an AB, measured herein at8 %.

Modelling for design and evaluation of industrial exoskeletons: A systematic review

Industrial exoskeletons are developed to relieve workers' physical demands in the workplace and to alleviate ergonomic issues associated with work-related musculoskeletal disorders. As a safe and economical alternative to empirical/experimental methods, modelling is considered as a powerful tool for design and evaluation of industrial exoskeletons. This systematic review aims to provide a comprehensive understanding of the current literature on the design and evaluation of industrial exoskeletons through modelling. A systematic study was conducted by general keyword searches of five electronic databases over the last two decades (2003-2022). Out of the 701 records initially retrieved, 33 eligible articles were included and analyzed in the final review, presenting a variety of model inputs, model development, and model outputs used in the modelling. This systematic review study revealed that existing modelling methods can evaluate the biomechanical and physiological effects of industrial exoskeletons and provide some design parameters. However, the modelling method is currently unable to cover some of the main evaluation metrics supported by experimental assessments, such as task performance, user experience/discomfort, change in metabolic costs etc. Standard guidelines for model construction and implementation, as well as validation of human-exoskeleton interactions, remain to be established.

A Smart, Textile-Driven, Soft Exosuit for Spinal Assistance

Work-related musculoskeletal disorders (WMSDs) are often caused by repetitive lifting, making them a significant concern in occupational health. Although wearable assist devices have become the norm for mitigating the risk of back pain, most spinal assist devices still possess a partially rigid structure that impacts the user's comfort and flexibility. This paper addresses this issue by presenting a smart textile-actuated spine assistance robotic exosuit (SARE), which can conform to the back seamlessly without impeding the user's movement and is incredibly lightweight. To detect strain on the spine and to control the smart textile automatically, a soft knitting sensor that utilizes fluid pressure as a sensing element is used. Based on the soft knitting hydraulic sensor, the robotic exosuit can also feature the ability of monitoring and rectifying human posture. The SARE is validated experimentally with human subjects (N = 4). Through wearing the SARE in stoop lifting, the peak electromyography (EMG) signals of the lumbar erector spinae are reduced by 22.8% ± 12 for lifting 5 kg weights and 27.1% ± 14 in empty-handed conditions. Moreover, the integrated EMG decreased by 34.7% ± 11.8 for lifting 5 kg weights and 36% ± 13.3 in empty-handed conditions. In summary, the artificial muscle wearable device represents an anatomical solution to reduce the risk of muscle strain, metabolic energy cost and back pain associated with repetitive lifting tasks.

Objective and subjective evaluation of a passive low-back exoskeleton during simulated logistics tasks

Musculoskeletal disorders remain the most common work-related health problem in the European Union. The most common work-related musculoskeletal disorder reported by workers is backache, especially in the logistics sector. Thus, this article aims to evaluate the effects of a commercial passive low-back exoskeleton during simulated logistics tasks. Thirty participants were recruited for this study. Typical logistics tasks were simulated in a laboratory environment. Cross-over research design was utilized to assess the effects of the exoskeleton on heart rate, trunk inclination, trunk acceleration, throughput, and perceived exertion. Also, usability and acceptance were obtained using a custom questionnaire. We found mostly non-significant differences. Effects on throughput varied widely between workplaces. Usability ratings were poor and acceptance moderate. The study suggests that a holistic evaluation and implementation approach for industrial exoskeletons is necessary. Further, prior to exoskeleton implementation, workplace adaptation might be required.

Reducing Back Exertion and Improving Confidence of Individuals with Low Back Pain with a Back Exosuit: A Feasibility Study for Use in BACPAC

OBJECTIVE

Low back pain (LBP) is hallmarked by activity limitations, especially for tasks involving bending. Back exosuit technology reduces low back discomfort and improves self-efficacy of individuals with LBP during bending and lifting tasks. However, the biomechanical efficacy of these devices in individuals with LBP is unknown. This study sought to determine biomechanical and perceptual effects of a soft active back exosuit designed to assist individuals with LBP sagittal plane bending. To understand patient-reported usability and use cases for this device.

METHODS

Fifteen individuals with LBP performed two experimental lifting blocks once with and without an exosuit. Trunk biomechanics were measured by muscle activation amplitudes, and whole-body kinematics and kinetics. To evaluate device perception, participants rated task effort, low back discomfort, and their level of concern completing daily activities.

RESULTS

The back exosuit reduced peak back extensor: moments by 9%, and muscle amplitudes by 16% when lifting. There were no changes in abdominal co-activation and small reductions maximum trunk flexion compared to lifting without an exosuit. Participants reported lower task effort, back discomfort, and concern about bending and lifting with an exosuit compared to without.

CONCLUSIONS

This study demonstrates a back exosuit not only imparts perceptual benefits of reduced task effort, discomfort, and increased confidence in individuals with LBP but that it achieves these benefits through measurable biomechanical reductions in back extensor effort. The combined effect of these benefits implies back exosuits might be a potential therapeutic aid to augment physical therapy, exercises, or daily activities.

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.

Evaluation of U.S. Army Soldiers wearing a back exosuit during a field training exercise

Back overuse injuries are a significant problem in the U.S. Army, responsible for nearly a quarter of musculoskeletal injuries. Back exosuits are wearable devices that relieve musculoskeletal strain, make lifting easier, and could potentially reduce Soldier overuse injuries. But published studies have not evaluated exosuits during realistic field operations to assess acceptability to Soldiers. We tested a back exosuit on field artillery Soldiers during a field training exercise. Afterward, Soldiers completed a survey to quantify their satisfaction, intent to use, and performance impact of the exosuit. Feedback was overwhelmingly positive: Approximately 90% of Soldiers reported that exosuits increased their ability to perform their duties, and 100% said that if the exosuit were further developed and made available to them, they would be likely to wear it. These numerical survey results indicated that exosuits can provide a practical and acceptable way to assist lifting and augment physical performance during realistic Army operations without interfering with other duties.

Manufacturing Industry Stakeholder Perspectives on Occupational Exoskeletons: Changes after a Brief Exposure to Exoskeletons

OCCUPATIONAL APPLICATIONSMultiple occupational exoskeletons have been developed recently with potential to reduce physical demands, muscle fatigue, and risk of over-exertion injuries in manufacturing, yet there are currently challenges in practical, large-scale deployment. We explored how stakeholder perceptions of exoskeletons were affected by exposure to passive arm- and back-support exoskeletons. Our outcomes indicate that even brief exposure to exoskeletons can positively influence worker and stakeholder perceptions on the usefulness and safety of exoskeletons. However, worker concerns about device usability and acceptability in the field were not mitigated by such brief exposure. This work may help manufacturing industry stakeholders understand what technology-adoption factors need further consideration when planning for exoskeleton deployment.

Effects of the Auxivo CarrySuit occupational exoskeleton when carrying front and side loads on a treadmill

Low-cost exoskeletons can effectively support workers in physically demanding jobs, but most such exoskeletons have been developed to support repetitive lifting or uncomfortable static postures. Very few low-cost exoskeletons have been designed to support walking while carrying heavy objects, which would be beneficial for jobs such as moving furniture and warehouse work. This paper thus presents a single-session lab evaluation of the Auxivo CarrySuit, a low-cost upper-body exoskeleton designed for carrying objects that would normally be held with the arms. Twenty participants carried four loads (box or two bags, 20 or 40 lb total weight) for 2 min each on a treadmill with and without the CarrySuit. Across all loads, the CarrySuit significantly reduced the mean electromyogram of the middle trapezius (partial eta-squared = 0.74 - from 16.1% to 8.8% of maximum voluntary contraction value) and anterior deltoid (partial eta-squared = 0.26 - from 3.0% to 1.1% of maximum voluntary contraction value) with no corresponding increase in lower back muscle activation. Furthermore, maximum heart rate and Ratings of Perceived Exertion were also reduced by the CarrySuit, and discomfort was shifted from the upper body to the legs. While arm EMG was not measured, it is likely that it was also reduced due to the unloading of the arms. The CarrySuit can thus be considered beneficial in the short term, though longer-term evaluations with actual workers are needed to determine practical benefits.

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.

Integrating Exosuit Capabilities into Clothing to Make Back Relief Accessible to Workers Unserved by Existing Exoskeletons: Design and Preliminary Evaluation

OCCUPATIONAL APPLICATIONSWe developed a method for integrating back-assist exosuit capabilities into regular clothing to make musculoskeletal relief accessible to more workers. We demonstrated proof-of-concept that this uniform-integrated exosuit can be effective and usable. Existing occupational exosuits are standalone accessories worn on top of a user's clothing and are not suitable for all workers. Our newly developed sub-class of exosuit could be beneficial to workers who alternate between bending, lifting, and sitting tasks, or to those in customer- or patient-facing jobs where it is important for wearable technology to be discreet.

Quality, productivity, and economic implications of exoskeletons for occupational use: A systematic review

The objective of this systematic review was to synthesize the current state of knowledge on the quality and productivity of workers and their work while wearing exoskeletons, as well as the economic implications of exoskeletons for occupational use. Following the PRISMA guidelines, six databases were systematically searched for relevant journal articles, written in English, and published since January 2000. Articles meeting the inclusion criteria had their quality assessed using JBI's Checklist for Quasi-Experimental Studies (Non-Randomized Experimental Studies). A total of 6,722 articles were identified and 15 articles focusing on the impact of exoskeletons on quality and productivity of exoskeleton users while performing occupational tasks were included in this study. None of the included articles evaluated the economic implications of exoskeletons for occupational use. This study revealed several quality and productivity measures (e.g., endurance time, task completion time, number of errors, number of task cycles completed) used to evaluate the impact of exoskeletons. The current state of the literature suggests that quality and productivity impacts of exoskeleton use are dependent on task characteristics that should be considered when adopting exoskeletons. Future studies should evaluate the impact of exoskeleton use in the field and on a diverse pool of workers, as well as its economic implications to better support decision-making in the adoption of exoskeletons within organizations.

Impact of a passive upper-body exoskeleton on muscle activity, heart rate and discomfort during a carrying task

OBJECTIVE

The goal of this study was to compare erector spinae muscle fatigue, upper limb muscle activity, body areas discomfort, and heart rate during a 10-min carrying task with and without a passive upper-body exoskeleton (CarrySuitⓇ) while considering sex influences.

BACKGROUND

Passive exoskeletons are commercially available to assist lifting or carrying task. However, evidence of their impact on muscle activity, fatigue, heart rate and discomfort are scarce and/or do not concur during carrying tasks.

METHOD

Thirty participants (16 females and 14 male) performed a 10-min, 15kg load-carrying task with and without the exoskeleton in two non-consecutive days. Heart rate, and erector spinae, deltoid, biceps and brachioradialis muscle activity were recorded during the carrying tasks. In addition, erector spinae electromyography during an isometric hold test and discomfort ratings were measured before and after the task.

RESULTS

While without the exoskeleton upper limb muscle activity increased or remained constant during the carrying task and showing high peak activation for both males and females, a significant activity reduction was observed with the exoskeleton. Low back peak activation, heart rate and discomfort were lower with than without the exoskeleton. In males muscle activation was significantly asymmetric without the exoskeleton and more symmetric with the exoskeleton.

CONCLUSION

The tested passive exoskeleton appears to alleviate the physical workload and impact of carrying heavy loads on the upper limbs and lower back for both males and females.

Manipulating device-to-body forces in passive exosuit: An experimental investigation on the effect of moment arm orientation using passive back-assist exosuit emulator

Passive exosuits have been vastly researched in the past decade for lifting tasks to alleviate the mechanical loading on the spine and reduce the lower back muscle activities in lifting tasks. Despite promising advantages of exosuits, factors such as comfort directly influence the user's acceptability of such body-worn devices. Exosuits' routing/anchoring points, which transmit device-to-body forces, remain the leading cause of discomfort among users. In the present study, we sought to investigate the effect of the routing element, that is, the "moment arm," in altering the device-to-body forces and perceived discomfort. We first presented a simplified human-exosuit model to establish insight into the effect of the moment arm on the device-to-body forces acting at the shoulder (FS) and waist (FW). Further, an experimental investigation was conducted on 10 participants with six different exosuit moment arm configurations (C1, C2, C3, C4, C5, and C6) to investigate their effect on the device-to-body forces, perceived discomfort, and muscle activity using a passive back-assist exosuit emulator in a lifting/lowering task. Configuration C4 was found to be most beneficial in reducing device-to-body forces at the shoulder and waist by up to 44.6 and 22.2%, respectively, during lifting. Subjective scores also comprehended with the device-to-body forces, indicating that C4 produces significantly less discomfort for participants. The outcome of the study illustrates the importance of selecting an appropriate moment arm configuration for passive back support exosuits in alleviating the device-to-body forces and perceived discomfort.

A Systematic Review on Lower-Limb Industrial Exoskeletons: Evaluation Methods, Evidence, and Future Directions

Industrial tasks that involve frequent sitting/standing transitions and squatting activities can benefit from lower-limb industrial exoskeletons; however, their use is not as widespread as their upper-body counterparts. In this review, we examined 23 articles that evaluated the effects of using Wearable Chair (WC) and Squat-assist (SA) exoskeletons. Evaluations mainly included assessment of muscular demands in the thigh, shank, and upper/lower back regions. Both types of devices were found to lessen muscular demands in the lower body by 30-90%. WCs also reduced low-back demands (~ 37%) and plantar pressure (54-80%) but caused discomfort/unsafe feeling in participants. To generalize outcomes, we suggest standardizing approaches used for evaluating the devices. Along with addressing low adoption through design upgrades (e.g., ground and body supports/attachments), we recommend that researchers thoroughly evaluate temporal effects on muscle fatigue, metabolic rate, and stability of wearers. Although lower-limb exoskeletons were found to be beneficial, discrepancies in experimental protocols (posture/task/measures) were discovered. We also suggest simulating more realistic conditions, such as walking/sitting interchangeability for WCs and lifting loads for SA devices. The presented outcomes could help improve the design/evaluation approaches, and implementation of lower limb wearable devices across industries.

Trends in Robotics Research in Occupational Safety and Health: A Scientometric Analysis and Review

Robots have been deployed in workplaces to assist, work alongside, or collaborate with human workers on various tasks, which introduces new occupational safety and health hazards and requires research efforts to address these issues. This study investigated the research trends for robotic applications in occupational safety and health. The scientometric method was applied to quantitatively analyze the relationships between robotics applications in the literature. The keywords "robot", "occupational safety and health", and their variants were used to find relevant articles. A total of 137 relevant articles published during 2012-2022 were collected from the Scopus database for this analysis. Keyword co-occurrence, cluster, bibliographic coupling, and co-citation analyses were conducted using VOSviewer to determine the major research topics, keywords, co-authorship, and key publications. Robot safety, exoskeletons and work-related musculoskeletal disorders, human-robot collaboration, and monitoring were four popular research topics in the field. Finally, research gaps and future research directions were identified based on the analysis results, including additional efforts regarding warehousing, agriculture, mining, and construction robots research; personal protective equipment; and multi-robot collaboration. The major contributions of the study include identifying the current trends in the application of robotics in the occupational safety and health discipline and providing pathways for future research in this discipline.

Side-effects and adverse events of a shoulder- and back-support exoskeleton in workers: A systematic review

INTRODUCTION

While the biomechanical effects of exoskeletons are well studied, research about potential side-effects and adverse events are limited. The aim of this systematic review was to provide an overview of the side-effects and adverse events on shoulder- and back-support exoskeletons during work tasks.

METHODS

Four in-field studies and 32 laboratory studies were included in this review, reporting on n = 18 shoulder exoskeletons, n = 9 back exoskeletons, n = 1 full body with a supernumerary arm, and n = 1 combination of shoulder and back exoskeleton.

RESULTS

The most frequent side-effect reported is discomfort (n = 30), followed by a limited usability of the exoskeleton (n = 16). Other identified side-effects and adverse events were changes in muscle activity, mobility, task performance, balance and posture, neurovascular supply, gait parameters and precision. An incorrect fit of the exoskeleton and the decreased degrees of freedom are most often reported as causes of these side-effects. Two studies did not find any side-effects. This review also showed that there are differences in the occurrence of side-effects in gender, age, and physical fitness. Most studies (89%) were conducted in a laboratory setting. Most studies (97%) measured short-term effects only. Psychological and social side-effects or adverse events were not reported. Side-effects and adverse events for active exoskeletons were understudied (n = 4).

CONCLUSION

It was concluded that the evidence for side-effects and adverse events is limited. If available, it mainly consists of reports of mild discomfort and limited usability. Generalisation is limited because studies were conducted in lab settings and measured short term only, and most participants were young male workers.

Using systems thinking-based risk assessment methods to assess hazardous manual tasks: a comparison of Net-HARMS, EAST-BL, FRAM and STPA

Formal risk assessment is a component of safety management relating to hazardous manual tasks (HMT). Systems thinking approaches are currently gaining interest for supporting safety management. Existing HMT risk assessment methods have been found to be limited in their ability to identify risks across the whole work system; however, systems thinking-based risk assessment (STBRA) methods were not designed for the HMT context and have not been tested in this area. The aim of this study was to compare the performance of four state-of-the-art STBRA methods: Net-HARMS, EAST-BL, FRAM and STPA to determine which would be most useful for identifying HMT risks. Each method was independently applied by one of four analysts to assess the risks associated with a hypothetical HMT system. The outcomes were assessed for alignment with a benchmark analysis. Using signal detection theory (SDT), overall STPA was found to be the best performing method having the highest hit rate, second lowest false alarm rate and highest Matthews Correlation Coefficient of the four methods.Practitioner summary: A comparison of four systems thinking risk assessment methods found that STPA had the highest level of agreement with the benchmark analysis and is the most suitable for practitioners to use to identify the risks associated with HMT systems.

Active exoskeleton reduces erector spinae muscle activity during lifting

Musculoskeletal disorders (MSD) are a widespread problem, often regarding the lumbar region. Exoskeletons designed to support the lower back could be used in physically demanding professions with the intention of reducing the strain on the musculoskeletal system, e.g., by lowering task-related muscle activation. The present study aims to investigate the effect of an active exoskeleton on back muscle activity when lifting weights. Within the framework of the study, 14 subjects were asked to lift a 15 kg box with and without an active exoskeleton which allows the adjustment of different levels of support, while the activity of their M. erector spinae (MES) was measured using surface electromyography. Additionally, the subjects were asked about their overall rating of perceived exertion (RPE) during lifting under various conditions. Using the exoskeleton with the maximum level of support, the muscle activity was significantly lower than without exoskeleton. A significant correlation was found between the exoskeleton's support level and the reduction of MES activity. The higher the support level, the lower the observed muscle activity. Furthermore, when lifting with the maximum level of support, RPE was found to be significantly lower than without exoskeleton too. A reduction in the MES activity indicates actual support for the movement task and might indicate lower compression forces in the lumbar region. It is concluded that the active exoskeleton supports people noticeably when lifting heavy weights. Exoskeletons seem to be a powerful tool for reducing load during physically demanding jobs and thus, their use might be helpful in lowering the risk of MSD.

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.

Exploring the relationship between kinematic variability and fatigue development during repetitive lifting

To investigate the variability-fatigue and repeaters-replacers hypotheses, motor variability (MV) and indicators of fatigue were assessed during repetitive lifting. Eighteen participants performed sequential repetitive bouts of lifting divided into a short bout, and three phases of a prolonged bout until volitional fatigue (or until a 1-h time limit). Whole-body kinematics were collected to calculate variability in three-dimensional joint angles and in continuous relative phase (CRP) of sagittal joint angle couplings, which were summed for the upper and lower body, and whole-body. Excellent individual consistency (ICC = 0.95-0.97) was demonstrated across lifting bouts as fatigue developed. Therefore, strong evidence was obtained for MV as an individual trait in support of the repeaters-replacers hypothesis. Associations were found for endurance and baseline effort with lower body variability, while no associations were found for rate of fatigue. Thus, some support was found for the variability-fatigue hypothesis which suggests that repeaters are less fatigue-resistant than replacers.

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.

Design and validation of a novel online platform to support the usability evaluation of wearable robotic devices

Wearable robotic devices (WRD) are still struggling to fulfill their vast potential. Inadequate daily life usability is one of the main hindrances to increased technology acceptance. Improving usability evaluation practices during the development of WRD could help address these limitations. In this work, we present the design and validation of a novel online platform aiming to fill this gap, the Interactive Usability Toolbox (IUT). This platform consists of a public website that offers an interactive, context-specific search within a database of 154 user research methods and educational information about usability. In a dedicated study, the effect of this platform to support usability evaluation was investigated. Twelve WRD experts were asked to complete the task of defining usability evaluation protocols for two specific use cases. The platform was provided to support one of the use cases. The quality and composition of the proposed protocols were assessed by (i) two blinded reviewers, (ii) the participants themselves, and (iii) the study coordinators. We showed that using the IUT significantly affected the proposed evaluation focus, shifting protocols from mainly effectiveness-oriented to more user-focused studies. The protocol quality, as rated by the external reviewers, remained equivalent to those designed with conventional strategies. A mixed-method usability evaluation of the platform yielded an overall positive image, with detailed suggestions for further improvements. The IUT is expected to positively affect the evaluation and development of WRD through its educational value, the context-specific recommendations supporting ongoing benchmarking endeavors, and highlighting the value of qualitative user research.

IMU-based human activity recognition and payload classification for low-back exoskeletons

Nowadays, work-related musculoskeletal disorders have a drastic impact on a large part of the world population. In particular, low-back pain counts as the leading cause of absence from work in the industrial sector. Robotic exoskeletons have great potential to improve industrial workers' health and life quality. Nonetheless, current solutions are often limited by sub-optimal control systems. Due to the dynamic environment in which they are used, failure to adapt to the wearer and the task may be limiting exoskeleton adoption in occupational scenarios. In this scope, we present a deep-learning-based approach exploiting inertial sensors to provide industrial exoskeletons with human activity recognition and adaptive payload compensation. Inertial measurement units are easily wearable or embeddable in any industrial exoskeleton. We exploited Long-Short Term Memory networks both to perform human activity recognition and to classify the weight of lifted objects up to 15 kg. We found a median F1 score of [Formula: see text] (activity recognition) and [Formula: see text] (payload estimation) with subject-specific models trained and tested on 12 (6M-6F) young healthy volunteers. We also succeeded in evaluating the applicability of this approach with an in-lab real-time test in a simulated target scenario. These high-level algorithms may be useful to fully exploit the potential of powered exoskeletons to achieve symbiotic human-robot interaction.

Exoskeletons: A challenge for development

The development of exoskeletons is currently a lengthy process full of challenges. We are proposing a framework to accelerate the process and make the resulting exoskeletons more user-centered. The needed accomplishments in science are described in an effort to lay the foundation for future research projects. Since the early 2000s, exoskeletons have been discussed as an emerging technology in industrial, medical, or military applications. Those systems are designed to support people during manual tasks. At first, those systems lacked broad acceptance. Many models found their niches in ongoing developments and more diverse systems entering the market. There are still applications that are in dire need of such assistance. Due to the lack of experience with body-worn robotics, the development of such systems has been shaped by trial and error. The lack of legacy products results in longer development times. In this paper, a process to generate a framework is presented to display the required research to enable future exoskeleton designers. Owing to their proximity to the user's body, exoskeletons are highly complex systems that need sophisticated subsystems, such as kinematic, control, interaction design, or actuators, to be accepted by users. Due to the wide variety of fields and high user demands, a synchronized multidisciplinary effort is necessary. To achieve this, a process to develop a modular framework for exoskeleton design is proposed. It focuses on user- and use-case-centered solutions for matching kinematics, actuation, and control. To ensure the usefulness of the framework, an evaluation of the incorporated solutions is required.

Opportunities and challenges in the development of exoskeletons for locomotor assistance

Exoskeletons can augment the performance of unimpaired users and restore movement in individuals with gait impairments. Knowledge of how users interact with wearable devices and of the physiology of locomotion have informed the design of rigid and soft exoskeletons that can specifically target a single joint or a single activity. In this Review, we highlight the main advances of the past two decades in exoskeleton technology and in the development of lower-extremity exoskeletons for locomotor assistance, discuss research needs for such wearable robots and the clinical requirements for exoskeleton-assisted gait rehabilitation, and outline the main clinical challenges and opportunities for exoskeleton technology.

Industrial exoskeletons from bench to field: Human-machine interface and user experience in occupational settings and tasks

Objective

Work-related musculoskeletal disorders (WRMSDs) are considered nowadays the most serious issue in the Occupational Health and Safety field and industrial exoskeletons appear to be a new approach to addressing this medical burden. A systematic review has been carried out to analyze the real-life data of the application of exoskeletons in work settings considering the subjective responses of workers.

Methods

The review was registered on PROSPERO. The literature search and its report have been performed following the PRISMA guidelines. A comprehensive literature search was performed in PubMed, EMBASE, Web of Science, and Scopus.

Results

Twenty-four original studies were included in the literature review; 42% of the papers retrieved included automobilist industry workers, 17% of the studies evaluated the use of exoskeletons in logistic facilities, and 17% of articles involved healthcare. The remaining six papers recruited farmers, plasterers, wasting collectors, construction workers, and other workmen. All the papers selected tested the use of passive exoskeletons, supporting upper arms or back. Usability, perceived comfort, perceived exertion and fatigue, acceptability and intention to use, occupational safety and health, and job performance and productivity were the main topic analyzed.

Conclusion

Exoskeletons are not a fix-all technology, neither for workers nor for job tasks; they tend to show more of their potential in static activities, while in dynamic tasks, they can obstacle regular job performance. Comfort and easiness of use are the key factors influencing the user's experience. More research is needed to determine the most effective and safe ways to implement exoskeleton use in occupational settings.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=275728, identifier CRD42021275728.