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Occupational Exoskeletons: Overview of Their Benefits and Limitations in Preventing Work-Related Musculoskeletal Disorders
Abstract
Occupational Applications
There is a growing interest in industry towards the use of occupational exoskeletons, with claimed efficiency in reducing physical demands at work. In this paper, we review existing evidence regarding the benefits and risks of using these technologies to attenuate the injury mechanisms for occupational musculoskeletal disorders (MSDs). More specifically, we focus on the underlying mechanisms of low back pain and shoulder tendinopathies, since these are the conditions targeted by the current use of exoskeletons for occupational application. While the potential for occupational exoskeletons to attenuate muscular demand in the back or upper limbs appears fairly promising, we conclude that the current state of knowledge does not allow for an unreserved endorsement of the use of these technologies for the prevention of MSD. Unwanted consequences of using exoskeletons during handling tasks are also discussed here, such as postural strains and modified kinematics. Several gaps in current knowledge are also highlighted, notably related to the impacts of physical assistance on neuromuscular coordination and joint movements, the occurrence of muscle fatigue, and chronic physiological adaptations.
Technical Abstract
Background: To address the prevalence of work-related musculoskeletal disorders (MSDs) in physically demanding tasks, research is now focusing on new approaches, such as the use of exoskeletons. Purpose: Based on the available evidence underlying the claimed efficiency of occupational exoskeletons in reducing biomechanical strains at work, the aim of this paper is to relate the claimed effectiveness of exoskeletons at reducing muscle demand to the pathophysiological mechanisms underlying MSDs. A further aim is to analyse the literature to highlight the main deficiencies in current knowledge, in order to guide the research necessary to develop future generations of exoskeletons. Methods: A narrative review was completed, based on an electronic literature search, considering occupational applications of exoskeletons from January 1980 to January 2019. Results: Thirty articles, each of which evaluated the effects of occupational exoskeletons on physical workload, were considered relevant to discuss with respect to the pathophysiological origins of MSDs. We found 22 studies that were directly related to back-assistive exoskeletons. Studies mainly focused on back muscle activity, but additional factors contributing to low back pain were also considered (muscle fatigue, spine loading, perceived pain, and posture). Eight papers were directly related to upper-limb exoskeletons. Conclusion: Within the scope of the specific task for which exoskeleton use has been designed, exoskeletons have been found to have clear potential in limiting local muscular demands. However, the current state of knowledge does not support an unreserved endorsement for using these technologies for MSD prevention. Additional research is needed to better understand posture and movement control mechanisms, when the postural and/or upper limb muscular chains are assisted. The impacts of movement assistance on neuromuscular coordination and joints kinematics also need to be clarified. Several other questions remain to be examined, in particular related to the occurrence of muscle fatigue and chronic adaptations.
... Die bei cLBP am häufigsten angewendeten Therapien sind körperliche Übungen, manuelle Therapie, Psychotherapien, wie kognitive Verhaltenstherapie (KVT), Medikationsmanagement, gezielte interventionelle Verfahren, Edukation und Selbstmanagement [9,47,48,54,58]. Viele dieser Therapien haben ähnlich geringe bis moderate Therapieeffekte, zudem besteht eine hohe Variabilität im individuellen Ansprechen. ...
... Vier Arten von Bewegungstherapie wurden bewertet: (1) Gehtraining, (2) körperliche Übungen allgemein, gewöhnlich eine Kombination von Kraft-und Ausdauertraining, (3) Übungen zur motorischen Kontrolle ("motor control exercise") und (4) Übungen in bevorzugter Bewegungsrichtung. Allgemein fanden sich eine moderate Evidenzstärke und moderate Effektgrößen für die meisten Übungsformen, wobei keine spezifische Übungsform anderen überlegen war [6,11,18,29,37,51,52,55,56,58,61]. Die Effektgröße körperlicher Übungen verbesserte sich bei Kombination mit KVT [29], manueller Therapie [61] oder Entscheidungsfindungsstrategien für eine auf den einzelnen Patienten zugeschnittene Behandlung (beispielsweise Implementierung eines Entscheidungsbaums, um den Behandlern die Wahl der für die Patienten besten Übung zu erleichtern) [6,55]. ...
... Die Effektgröße körperlicher Übungen verbesserte sich bei Kombination mit KVT [29], manueller Therapie [61] oder Entscheidungsfindungsstrategien für eine auf den einzelnen Patienten zugeschnittene Behandlung (beispielsweise Implementierung eines Entscheidungsbaums, um den Behandlern die Wahl der für die Patienten besten Übung zu erleichtern) [6,55]. Mind-Body-Interventionen, wie Qigong oder Yoga unter Einbeziehung von Bewegung, wurden von der Arbeitsgruppe nicht begutachtet; diese Übungen haben -wie andere Übungsformen -einen moderaten Effekt, allerdings stellt die Ausweitung des Angebots für einen breiten klinischen Einsatz eine Herausforderung dar [58,63]. Nach Bewertung der Bandbreite an Bewegungstherapien für cLBP empfahl die Arbeitsgruppe einen protokoll-und klassifikationsbasierten Ansatz, angeleitet von Physiotherapeuten oder Chiropraktikern, und eine integrierte Entscheidungsfindung basierend auf der Patientenvorstellung, statt eine bestimmte Übungsform vorzuschlagen. ...
Chronic low back pain (cLBP) is highly prevalent in the United States and globally, resulting in functional impairment and lowered quality of life. While many treatments are available for cLBP, clinicians have little information about which specific treatment(s) will work best for individual patients or subgroups of patients. The Back Pain Research Consortium, part of the National Institutes of Health Helping to End Addiction Long-termSM (HEAL) Initiative, will conduct a collaborative clinical trial, which seeks to develop a personalized medicine algorithm to optimize patient and provider treatment selection for patients with cLBP.
The primary objective of this article is to provide an update on evidence-based cLBP interventions and describe the process of reviewing and selecting interventions for inclusion in the clinical trial.
A working group of cLBP experts reviewed and selected interventions for inclusion in the clinical trial. The primary evaluation measures were strength of evidence and magnitude of treatment effect. When available in the literature, duration of effect, onset time, carryover effect, multimodal efficacy, responder subgroups, and evidence for the mechanism of treatment effect or biomarkers were considered.
The working group selected 4 leading, evidence-based treatments for cLBP to be tested in the clinical trial and for use in routine clinical treatment. These treatments include (1) duloxetine, (2) acceptance and commitment therapy, (3) a classification-based exercise and manual therapy intervention, and (4) a self-management approach. These interventions each had a moderate to high level of evidence to support a therapeutic effect and were from different therapeutic classes.
... Exoskeletons have also been categorized by the body part they are designed to support, such as the back, upper-limb, lower-limb, or full-body [4,5]. Active or passive occupational back exoskeleton devices aim to prevent back MSDs from providing assistance to the spine during tasks involving forward bending [3,6]. ...
... Theurel and Desbrosses (2019) [6] reviewed and confirmed the effectiveness of passive back exoskeletons to reduce lumbar muscular demand but also reported inconsistent results. For instance, from 10% to around 50% reductions in back muscle activity have been reported in manual handling tasks [7] and during static postures [8,9]. ...
... For instance, from 10% to around 50% reductions in back muscle activity have been reported in manual handling tasks [7] and during static postures [8,9]. These large differences might be attributed to different factors, such as the design of the exoskeleton or the level of assistance [6]. Additional harmful effects have been observed with the use of exoskeletons: discomfort, heat, reduced range of motion [10], or larger postural oscillations [11]. ...
Soft back exoskeletons are aimed at reducing musculoskeletal effort during manual handling tasks, contributing to the prevention of low back disorders like lumbar strains and sprains or intervertebral disk problems. However, large differences in their biomechanical effects are observed in the literature. A possible explanation could be the lack or disparity of familiarization protocols with the exoskeleton. The aim of this experimental study was to characterize the familiarization process with a soft back-support occupational exoskeleton and determine the time needed to stabilize biomechanical variables. Participants carried out 6 familiarization sessions of 1 h to the CORFOR® soft back-exoskeleton. Joint kinematics, postural stability, exoskeleton pressure perception, muscle activity, and performance were measured at the beginning of the first session and at the end of each session during stoop and squat liftings. Results showed that back kinematics, performance, and exoskeleton pressure perception changed during the first sessions and stabilized after sessions 3 or 4, depending on the variable. The authors recommend a familiarization protocol for the CORFOR® soft back-exoskeleton of 4 sessions of 1 h duration. This recommendation could help CORFOR® users, for instance, in the automotive industry, the food retail industry, or the agriculture field.
... Powered or active exoskeletons are wearable robots designed to assist human movements by enhancing the physical capacity of a person [1][2][3][4]. They are currently developed for applications in medical therapy [4][5][6], support of patients with movement disorders [1,4], as well as in occupational contexts [2,3]. ...
... Powered or active exoskeletons are wearable robots designed to assist human movements by enhancing the physical capacity of a person [1][2][3][4]. They are currently developed for applications in medical therapy [4][5][6], support of patients with movement disorders [1,4], as well as in occupational contexts [2,3]. In the latter case, it is hypothesized that occupational exoskeletons can effectively prevent musculoskeletal diseases by assisting the workers in handling excessive loads or by increasing their endurance, thereby limiting muscular fatigue and associated diseases [1,3,7]. ...
... They are currently developed for applications in medical therapy [4][5][6], support of patients with movement disorders [1,4], as well as in occupational contexts [2,3]. In the latter case, it is hypothesized that occupational exoskeletons can effectively prevent musculoskeletal diseases by assisting the workers in handling excessive loads or by increasing their endurance, thereby limiting muscular fatigue and associated diseases [1,3,7]. ...
The design of human-machine interfaces of occupational exoskeletons is essential for their successful application, but at the same time demanding. In terms of information gain, biosensoric methods such as surface electromyography (sEMG) can help to achieve intuitive control of the device, for example by reduction of the inherent time latencies of a conventional, non-biosensoric, control scheme. To assess the reliability of sEMG onset detection under close to real-life circumstances, shoulder sEMG of 55 healthy test subjects was recorded during seated free arm lifting movements based on assembly tasks. Known algorithms for sEMG onset detection are reviewed and evaluated regarding application demands. A constant false alarm rate (CFAR) double-threshold detection algorithm was implemented and tested with different features. Feature selection was done by evaluation of signal-to-noise-ratio (SNR), onset sensitivity and precision, as well as timing error and deviation. Results of visual signal inspection by sEMG experts and kinematic signals were used as references. Overall, a CFAR algorithm with Teager-Kaiser-Energy-Operator (TKEO) as feature showed the best results with feature SNR = 14.48 dB, 91% sensitivity, 93% precision. In average, sEMG analysis hinted towards impending movements 215 ms before measurable kinematic changes.
... Another important aspect of active exoskeletons is the reduction of energy consumed by the user during work activities, which allows a decrease in both effective effort, as demonstrated by the decrease in metabolic consumption, and perceived effort [25]. Finally, active exoskeletons allow the attenuation of intense and repeated stresses on joints to prevent tendinopathies [26]. The negative effects on health from active exoskeletons are few, with the most important one not referring to a particular case but applicable to many Many active exoskeletons allow a reduction of loads on the body part they assist, without transferring the weight to other parts such as joints, as they have actuators that provide energy and contribute to lifting loads. ...
... Another important aspect of active exoskeletons is the reduction of energy consumed by the user during work activities, which allows a decrease in both effective effort, as demonstrated by the decrease in metabolic consumption, and perceived effort [25]. Finally, active exoskeletons allow the attenuation of intense and repeated stresses on joints to prevent tendinopathies [26]. The negative effects on health from active exoskeletons are few, with the most important one not referring to a particular case but applicable to many application fields, which is the transfer of loads from the shoulder to the waist. ...
... Passive exoskeletons, like active exoskeletons, can reduce acute and repetitive pressures on arm muscles to avoid tendinopathies [26]. Finally, passive exoskeletons allow greater movement stability, improving the user's balance and comfort [37]. ...
This paper examines occupational exoskeletons and their effects on workers. The study includes a thorough evaluation of the current literature on occupational exoskeletons, with an emphasis on the impact of these devices on workers’ health and the safety, performance and users’ subjective perceptions. The aim of the study was to gain knowledge of how exoskeletons affect the workers and to identify practical suggestions for practitioners. The findings of the study suggest that exoskeletons can have both positive and negative effects on workers. Some users claimed enhanced comfort and decreased fatigue, whilst others reported discomfort and suffering. The study highlights the importance of considering the individual needs and preferences of workers when selecting and implementing exoskeletons in the workplace, with a focus on health, safety, performance and user acceptance. Based on the findings, the paper presents suggestions for employers and practitioners to ensure the effective and safe use of exoskeletons in occupational settings. These recommendations cover areas such as the assessment of workplace requirements, the selection and fit of exoskeletons, the optimization of design and ergonomics and the evaluation of performance. The paper concludes by highlighting the need for further research in this area, particularly in the areas of long-term use.
... This might also be influenced by fatigue. Exoskeletons can reduce muscle fatigue by assisting with tasks that would otherwise require high levels of effort (20). Exoskeletons are designed to provide mechanical support and assist wearers in performing physically demanding tasks, such as lifting heavy objects or maintaining strenuous postures. ...
... A third explanation addresses the level of support. The review by Theurel and Desbrosses (20) showed that the use of a passive exoskeleton might induce unexpected consequences on the coordination between agonist and antagonist muscles. According to the findings by Kermavnar et al. (34), we were not able to determine a reduction in the activation of the M. erector spinae, but Walter et al. (35) found comparable results regarding the lack of significance between working with and without a passive exoskeleton with significant benefits of an active exoskeleton. ...
Introduction: Tasks performed at or above head height in industrial workplaces
pose a significant challenge due to their association with musculoskeletal
disorders. Upper-body exoskeletons have been identified as a potential solution
for mitigating musculoskeletal loads and fighting against excessive muscular
fatigue. However, the influence of such support on fine motor control, as well
as on cognitive-motor interference, has received limited attention thus far.
Therefore, this crossover randomized study aimed to investigate the impact
of the use of a passive upper-body exoskeleton in the presence of muscular
fatigue or not. Additionally, focusing on differences between single (ST) and dual
(DT) industrial tasks consisting of overhead speed and accuracy exercises.
Methods: In both scenarios, N = 10 participants (5 male/5 female) engaged in
an overhead precision task using a nail gun to precisely target specific areas on
three differently sized regions, based on Fitts’ law paradigm (speed-accuracy
trade-off task). This was done with and without the passive upper-body
exoskeleton, before and immediately after a fatiguing exercise of shoulder and
leg muscles. In addition, a second task (dual-task, DT) was carried out in which
the occurrence of an auditory signal had to be counted. The main outcomes
were muscular activation of the shoulder girdle as well as the time to perform
speed-accuracy tasks of different difficulty indexes (calculated by means of Fitts’
law).
Results and discussion: In the absence of fatigue, the exoskeleton did not affect
the speed-accuracy trade-off management of participants in the single task,
but it did in the dual-task conditions. However, after muscle fatigue, the speed-
accuracy trade-off was differently affected when comparing its execution with
or without the exoskeleton. In general, the dual task resulted in longer times
to perform the different tasks, whether it was with or without the exoskeleton.
Furthermore, the use of the exoskeleton decreased muscle activity, which is
associated with less physical effort, but only significantly for the M. deltoideus
and M. trapezius when compared by tasks. Overall, these study findings
highlight the potential supportive effects of using an upper-body exoskeleton
for industrial overhead tasks.
... the National safety council recently reported an estimated $164 billion in expenditure due to such work-related injuries (Nsc 2020). exoskeletons are a wearable technology of increasing interest in the occupational domain, as they are designed to support users while performing work tasks and reduce physical workload by providing external forces to body segments (de looze et al. 2016;Nussbaum et al. 2019;theurel and Desbrosses 2019). ...
... however, to the best of our knowledge, there have been no systematic investigations of differences in exoskeleton effectiveness across age, which might be important considering that the participation rates of older age groups in the workforce have been steadily increasing in the last two decades, and this trend is further projected to increase (Dubina et al. 2021). Recent systematic reviews and position papers have also begun to raise wider ethical concerns on the limited demographics represented in current exoskeleton studies (Pote et al. 2023;søraa and Fosch-Villaronga 2020;theurel and Desbrosses 2019) this research with limited participant representation forms the current evidence basis informing exoskeleton technology design, including critical design features such as sizing, assistance mechanisms, and humanexoskeleton interface, which could broadly impact exoskeleton usefulness and adoptability. thus, to be equitable in accessibility and usefulness across a broad range of users, it is important to expand the study of exoskeleton effectiveness and use across different age and gender groups (alemi et al. 2020;Madinei et al. 2020aMadinei et al. , 2020bNussbaum et al. 2019), as well as understand age and gender differences in willingness to adopt exoskeletons. ...
We investigated age and gender differences in the perception and use of soft (Apex) vs. rigid (Paexo Back) passive back-support exoskeletons (BSE) for repetitive lifting and lowering. A gender-balanced sample of 20 young (18-30 years) and 16 old (45-60 years) individuals were recruited. In the first session, participants' self-reported maximum acceptable load (MAL) was assessed using a psychophysical approach. Changes in muscle activity and kinematics due to BSE use in repetitive lifting/lowering tasks were also assessed. Overall, both BSEs increased MAL (by ∼7%), and reduced trunk extensor muscle activity across all groups (by ∼7-18%), compared to the control condition. Both BSEs promoted more squatting postures, increased quadriceps muscle activity (by ∼34%) and abdominal muscle activity during asymmetric tasks (by 5-20%). Some age and gender differences were significant, particularly for the trunk kinematics when using the Apex. Future work should include more diverse user groups in studying willingness to adopt BSEs and characterising their consequent effects on the body.
... This makes it more likely that exoskeletons are adopted rather than deserted after an initial period of testing. Although various frameworks based on existing technology acceptance models for industrial exoskeletons with potential end users [83], a grounded framework is still lacking. ...
... Even though it is difficult to justify the effectiveness of exoskeletons, due to the lack of long-term experimental tests (more than 3 months), and the need for standardized products, evaluation protocols, and regulations, these devices bring both benefits and limitations [83,84]. Some studies have highlighted the potential and effectiveness of exoskeletons in reducing muscle demand and addressing the pathophysiological mechanisms underlying MSDs during load handling tasks, static bending postures, and elevating postures. ...
Manual handling tasks, both in daily activities and at work, require high dexterity and the ability to move objects of different shapes and sizes. However, musculoskeletal disorders that can arise due to aging, disabilities, overloading, or strenuous work can impact the natural capabilities of the hand with serious repercussions both in working and daily activities. To address this, researchers have been developing and proving the benefits of wrist exoskeletons. This paper, which is Part II of a study on wrist exoskeletons, presents and summarizes wearable wrist exoskeleton devices intended for use in rehabilitation, assistance, and occupational fields. Exoskeletons considered within the study are those available either in a prototyping phase or on the market. These devices can support the human wrist by relieving pain or mitigating fatigue while allowing for at least one movement. Most of them have been designed to be active (80%) for higher force/torque transmission, and soft for better kinematic compliance, ergonomics, and safety (13 devices out of 24, more than 50%). Electric motors and cable transmission (respectively 11 and 9 devices, out of 24, i.e., almost 50% and 40%) are the most common due to their simplicity, controllability, safety, power-to-weight ratio, and the possibility of remote actuation. As sensing technologies, position and force sensors are widely used in all devices (almost 90%). The control strategy depends mainly on the application domain: for rehabilitation, CPM (control passive motion) is preferred (35% of devices), while for assistance and occupational purposes, AAN (assistance-as-needed) is more suitable (38% of the devices). What emerges from this analysis is that, while rehabilitation and training are fields in which exoskeletons have grown more easily and gained some user acceptance (almost 18 devices, of which 4 are available on the market), relatively few devices have been designed for occupational purposes (5, with only 2 available on the market) due to difficulties in meeting the acceptance and needs of users. In this perspective, as a result of the state-of-the-art analysis, the authors propose a conceptual idea for a portable soft wrist exoskeleton for occupational assistance.
... EXOs are quite promising, given that an EXO can assist the wearer during various physical activities by providing on-body support (e.g., external joint torques) and can reduce exposure to high physical demands. Recent systematic reviews have reported both beneficial and some potentially adverse effects of using an EXO during various job tasks, including those relevant to construction, while highlighting that these effects depend on the specific EXO designs used and task conditions (B€ ar et al. 2021;Kermavnar et al. 2021;Theurel and Desbrosses 2019). Despite the promise of EXO technologies as an intervention in construction, actual adoption of EXOs in the workplace has been limited (Crea et al. 2021). ...
... Worker opinions on expected benefits, specifically fatigue reduction and work performance gains, were key influential variables in all the decision trees developed here. This finding emphasises the need for effective and efficient selection of EXOs that best suit individual construction workers and work tasks, especially given that the effectiveness and subjective experiences of using an EXO are specific to EXO designs and task characteristics (e.g., Kermavnar et al. 2021;Ojelade et al. 2023;Theurel and Desbrosses 2019), as well as individual characteristics such as gender (Madinei et al. 2020). Improved EXO selection could ensure that construction workers (as EXO users) experience the benefits of EXOs while minimising potential adverse effects (resulting from poor EXO selection or task/EXO mismatch). ...
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.
... Manual material handling tasks like repetitive lifting/lowering are ever present in multiple industries (Theurel & Desbrosses, 2019), and known to cause musculoskeletal disorders (MSDs). MSDs of the lower back alone account for 39% of all cases (BLS, 2016). ...
... Past studies have shown their effectiveness through reduced energy expenditure, back muscle activity and perceived exertion/discomfort (Madinei et al., 2020a(Madinei et al., , 2020b(Madinei et al., , 2021Park et al., 2021). While a majority of prior work has included subjective and objective measures of exoskeleton effectiveness among young individuals (Theurel & Desbrosses, 2019), differences in exoskeleton perceptions, use strategies, and effectiveness across age and gender groups have not been systematically explored. In our study, we investigated age and gender differences in the perceptions and use of a soft and rigid type passive EXO for 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.
... In the context of ergonomic interventions, EXOs are wearable mechanical structures that can augment, physically assist, and reduce exposure to physical demands, thereby having the potential to alleviate muscle fatigue, pain from long working hours, and help maintain performance (Theurel & Desbrosses, 2019). EXOs have received increasing attention in recent years for occupational use, as evidence for EXO effectiveness has been obtained through several controlled laboratory simulations of industrially relevant tasks (Bär et al., 2021;Kermavnar et al., 2021). ...
... Many studies conducted in laboratory and industrial settings have demonstrated the effectiveness of EXOs for specific tasks (e.g., see Nussbaum et al., 2019;Theurel & Desbrosses, 2019), but the factors affecting adoption/ implementation of them in manufacturing industries are not yet completely understood. Although previous studies have sought stakeholder perceptions of EXO technologies, most of these studies have captured the opinions of stakeholders that have only "seen" such EXOs demonstrated. ...
... Previous studies observed that the use of occupational back-support exoskeletons can decrease the activity of back muscles during handling tasks, but also led to kinematic alterations [3][4][5][6]. However, the magnitude of these effects seems to depend on the characteristics of the exoskeleton, such as its technology (passive versus active) [4,7] or even its design (textile versus rigid, for example) [8], as well as the characteristics of the tasks performed (e.g., static tasks involving the maintenance of trunk flexion versus dynamic tasks that put the trunk in motion) [4,[9][10][11] and the population studied [9,11,12]. ...
... Muscular and kinematic adaptations may not be similar due to possible functional limitations [34]. Finally, this study focused on trunk extensor activation and trunk kinematics, while the use of active systems could yield consequences beyond the assisted muscles and/or joints, as demonstrated for passive systems [5,6]. This point is very important in the prevention of occupational accidents and diseases, where one of the fundamentals is to not displace the risk. ...
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.
... Assistive technologies for the upper limb are generally dependent on the use of tactile and kinesthetic feedback in order to facilitate, or correct the user's movements [1,2]. Robotic exoskeletons are a particular case, in that they involve fixation of a mechanical structure to the user's body. ...
... While a number of previous studies have examined the role of upper limb exoskeletons on object handling, this work has been principally oriented towards the benefits of an assistive device on the physical demands of the user [2,18,19]. The potential consequences upon those sensory capacities necessary for adaptive tool use behaviors have been largely overlooked. ...
Upper limb exoskeletons may confer significant mechanical advantages across a range of tasks. The potential consequences of the exoskeleton upon the user’s sensorimotor capacities however, remain poorly understood. The purpose of this study was to examine how the physical coupling of the user’s arm to an upper limb exoskeleton influenced the perception of handheld objects. In the experimental protocol, participants were required to estimate the length of a series of bars held in their dominant right hand, in the absence of visual feedback. Their performance in conditions with an exoskeleton fixed to the forearm and upper arm was compared to conditions without the upper limb exoskeleton. Experiment 1 was designed to verify the effects of attaching an exoskeleton to the upper limb, with object handling limited to rotations of the wrist only. Experiment 2 was designed to verify the effects of the structure, and its mass, with combined movements of the wrist, elbow, and shoulder. Statistical analysis indicated that movements performed with the exoskeleton did not significantly affect perception of the handheld object in experiment 1 (BF01 = 2.3) or experiment 2 (BF01 = 4.3). These findings suggest that while the integration of an exoskeleton complexifies the architecture of the upper limb effector, this does not necessarily impede transmission of the mechanical information required for human exteroception.
... From a physiological point of view, Bär et al. [29] in their review found that the utilization of an exoskeleton in M&L tasks seem to reduce the user's acute physical stress and strain in the exoskeleton-supported region. However, Theurel and Desbrosses [30] reviewed 30 articles trying to relate the claimed ability of the exoskeletons to reduce the muscular effort to the pathophysiological mechanisms underlying musculoskeletal disorders, concluding that there is not enough evidence to support an unreserved endorsement of these devices to prevent musculoskeletal disorders. Passive exoskeletons are indicated as more accessible for large industrial use due to their simplicity and lower cost compared to active ones [19]. ...
... Managers could use these two parameters to better assess the exoskeleton deployment in factories and logistic facilities in the near future even if this approach is time-consuming and requires longer testing times and several efforts by companies. However, the literature analysis highlights the potential of passive exoskeletons to limit local muscular activations, but it is not sufficient to unreservedly promote passive exoskeletons as a WRMSD prevention technology and more research is needed in this direction [30]. 4. ...
The human-centered workplace design philosophy and the operator 5.0 concepts are gaining ground in modern industries moving through the personalization of the operators’ workplace for improving workforce well being and capabilities. In such a context, new assistive technologies, such as passive exoskeletons, are good candidates to be wisely adopted in manufacturing and logistics systems. A growing interest in these devices has been detected over the last years, both from an academic and company perspective, with an increasing number of design solutions and tests according to their field of application. Aiming to investigate the current state of the art, we propose a literature review focused on passive exoskeletons for manufacturing and logistics (M&L) systems. We categorize the exoskeletons assessment in relation to the M&L tasks in which they are applied to give the reader an easy and direct insight into the exoskeleton performance in real settings. Further, the impact of the exoskeleton deployment from an efficiency perspective and its cost-effectiveness evaluation are provided. Finally, a maturity heat map is proposed to track the maturity level of different exoskeletons by focusing on a set of scientific and industrial domains. A discussion and a future research agenda are also provided by focusing on the managerial implications of investing in these devices.
... Les exosquelettes offrent un espoir légitime dans le champ de la prévention des TMS. Des études récentes ont montré des bénéfices de l'utilisation des exosquelettes notamment la diminution de l'activité musculaire, l'effort musculaire perçu, la perception de la fatigue et l'augmentation des performances du travailleur [11,12]. Cependant, nombre de ces études ont été réalisées en laboratoire, ne reflétant ainsi qu'une partie du travail réel [12,13]. ...
... Des études récentes ont montré des bénéfices de l'utilisation des exosquelettes notamment la diminution de l'activité musculaire, l'effort musculaire perçu, la perception de la fatigue et l'augmentation des performances du travailleur [11,12]. Cependant, nombre de ces études ont été réalisées en laboratoire, ne reflétant ainsi qu'une partie du travail réel [12,13]. Une démarche d'acquisition d'exosquelette peut se solder par un échec si elle n'a pas été suffisamment préparée et étudiée [14,15]. ...
... Numerous studies have focused on ergonomic risk analysis and the effect of physical assistance devices, such as occupational exoskeletons. However, these studies are mostly conducted in laboratory settings (Baltrusch et al., 2019;Theurel and Desbrosses, 2019;De Bock et al., 2022). Laboratory assessments provide controlled environments for detailed biomechanical and physiological measurements, isolating the exoskeleton's effects from other variables and allow for precise and repeatable measurements (Baltrusch et al., 2019). ...
To enhance physical capabilities of workers who regularly perform physically demanding tasks involving heavy lifting and awkward postures, various tools and occupational exoskeletons can be used. Most of the studies aiming to explore the efficiency of these tools and exoskeletons have been performed in confined and controlled laboratory spaces, which do not represent the real-world work environment. This study aimed to compare the outcome of biomechanical assessment of using a back support exoskeleton and assistive tools (Lever and Jake) in the procedure of a high demanding manual material handling task versus the results found by performing the same task in a laboratory. Ten able-bodied participants and ten able-bodied utility workers performed the same manhole removal task in-lab and in-field, respectively, with the aid of an exoskeleton and Lever and Jake tools. Muscle activity and Rapid Entire Body Assessment (REBA) scores were recorded using surface electromyography and inertial measurement units, respectively and compared between in-lab and in-field trials. The field experiments indicated significant differences (p < 0.05) in normalized muscle activity across most muscles when compared to laboratory data. These results revealed how muscle activity is affected by the controlled lab setting compared to real-world field conditions. However, REBA scores indicate similar ergonomic implications regardless of the utilization of exoskeletons or tools. These findings underscore that real-world field assessments are crucial for evaluating ergonomic risks and effects of occupational exoskeletons and tools to account for environmental factors and workers’ skills in ergonomic evaluations of this nature.
... Future research should focus on conducting welldesigned randomized controlled trials and longitudinal studies to gather robust evidence on the impact of exoskeletons on nurses' quality of work life, patient outcomes, and healthcare system sustainability. Long-term studies that assess the durability of exoskeletons, their effects on work-related injuries, fatigue, and job satisfaction are crucial for building a stronger evidence base [60]. Additionally, ongoing collaboration between researchers, engineers, healthcare professionals, and manufacturers is needed to refine and improve exoskeleton technology. ...
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.
... If the wearer is a worker, if the considered activity is work-related, and if the assisted joint is the back, exoskeletons are referred to as occupational Back Support Exoskeletons (oBSEs), [2]. Laboratory studies have documented how oBSEs can effectively reduce back muscle activation, with the associated potential to reduce back injuries [3][4][5][6][7].These benefits can be linked with potential ergonomic and productivity improvements [8,9], and new methods are being developed to update classical ergonomic risk evaluation tools (e.g, the NIOSH Lifting Index, [10]) to include the benefits linked with oBSE usage [11,12]. To provide assistance, oBSEs can rely either on purely mechanical elements or on active actuators. ...
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.
... Concerning rehabilitation, they can be used to improve gait and upper limb control during daily activities for those who have suffered a stroke or a spinal cord injury [1]- [4]. Exoskeletons can also be used to decrease the biomechanical load on the body [5], thus contributing to preventing the onset of MSDs when the workspace cannot be adapted to improve ergonomics [6], although more evidence is needed [7], [8]. In such situations, integrating the human intention into the exoskeleton's control loop is necessary to ensure safe, appropriate, and intuitive assistance [9]. ...
In the field of robotic exoskeleton control, it is critical to accurately predict the intention of the user. While surface electromyography (EMG) holds the potential for such precision, current limitations arise from the absence of robust EMG-to-torque model calibration procedures and a universally accepted model. This paper introduces a practical framework for calibrating and evaluating EMG-to-torque models, accompanied by a novel nonlinear model. The framework includes an in situ procedure that involves generating calibration trajectories and subsequently evaluating them using standardized criteria. A comprehensive assessment on a dataset with 17 participants, encompassing single-joint and multi-joint conditions, suggests that the novel model outperforms the others in terms of accuracy while conserving computational efficiency. This contribution introduces an efficient model and establishes a versatile framework for EMG-to-torque model calibration and evaluation, complemented by a dataset made available. This further lays the groundwork for future advancements in EMG-based exoskeleton control and human intent detection.
... Additionally, some respondents considered EXOs a potential opportunity to expand the pool of construction workers, either for those whose aging or musculoskeletal injuries resulted in their reduced work assignments or leaving of the workforce entirely. In both cases, our results are consistent with previous findings that suggest EXOs as an intervention to meet physical requirements of a job could contribute to a larger, healthier population of construction workers Mahmud et al., 2022;Theurel and Desbrosses, 2019). By promoting long-term retention, employers may avoid both losing valuable, experienced workers and the costs that come with recruiting and training new workers (Schwatka et al., 2012). ...
... Repetitive heavy duties tasks can produce muscle fatigue, cause joint and posture disorders as mentioned, for example, in [1][2][3]. Robotic solutions have been proposed to assist workers who perform tasks that require muscular effort, as reported, for example, in [4][5][6]. There is a wide range of several types of exoskeletons specifically de-signed for various assistive tasks. ...
This paper proposes a new upper-limb exoskeleton to reduce worker physical strain. The proposed design is based on a novel PRRRP (P-Prismatic; R-Revolute) kinematic chain with 5 passive Degrees of Freedom (DoF). Utilizing a magnetic spring, the proposed mechanism includes a specially designed locking mechanism that maintains any desired task posture. The proposed exoskeleton incorporates a balancing mechanism to alleviate discomfort and spinal torsional effects also helping in limb weight relief. This paper reports specific models and simulations to demonstrate the feasibility and effectiveness of the proposed design. An experimental characterization is performed to validate the performance of the mechanism in terms of forces and physical strain during a specific application consisting of ceiling-surface drilling tasks. The obtained results preliminarily validate the engineering feasibility and effectiveness of the proposed exoskeleton in the intended operation task thereby requiring the user to exert significantly less force than when not wearing it.
... Musculoskeletal disorders (MSDs) are currently one of the most prevalent disorders in the world. MSDs is a health problem involving the skeletal muscle system due to poor working posture, unorganized workstations, and lacking attention to ergonomic aspects (Theurel & Desbrosses, 2019;Zeverdegani et al., 2022;Zulkarnain et al., 2021). Work-related Musculoskeletal Disorders (WMsDs) is a term used to define MSDs, which are related or caused by work environment activities. ...
In a developing country like Indonesia, where the majority of the population is working in the informal sectors, there is a need for ergonomic tool intervention, which is low cost, and easy in terms of manufacturability with locally available materials. The rapid growth of motorcycle sales in Indonesia has stimulated the growth of motorcycle repair workshops. However, some of the non-authorized repair workshops ignore the occupational safety of the mechanics. This study aims to develop a motorcycle workbench as a tool for maintenance work to reduce musculoskeletal disorders (MSDs). The present study used Research and Development (R&D) with the ADDIE model combined with an ergonomic approach. The research subjects were 4 mechanics from one private workshop. Data was collected using interview, observation, and questionnaire techniques. The MSDs data was analyzed using Nordic Musculoskeletal Questionnaire (NMQ). The ergonomic risk factors were analyzed using Rapid Upper Limb Assessment (RULA) and Ovako Work Posture Analysis System (OWAS). The result showed an improvement in the work posture of mechanics. The MSDs complaint decreased based on NMQ Score. Furthermore, the RULA score and OWAS score also decreased. Thus, the development of the motorcycle workbench succeeded in reducing the MSDs complaint and improving mechanics’ occupational safety.
... Différentes études ont montré que l'utilisation d'un exosquelette permettrait une réductio n des contraintes musculosquelettiques (de Looze et al., 2016 ;Theurel & Desbrosses, 2019). Ces études n'ont pas spécifiquement étudié les tâches d'intervention chez les SP . ...
En France, plus de 80% des maladies professionnelles sont des troubles musculosquelettiques , et les sapeurs-pompiers (SP) sont particulièrement à risque. Notre objectif était de tester les effets de la solution exosquelette pour ce corps de métier. Cette étude compare deux conditions de réalisation d'une tâche de désincarcération par des SP : avec et sans exosquelette. L'impact est évalué sur l'activité musculaire des membres supérieurs (EMG), sur les ressources cognitives (NASA-TLX), et sur l'acceptation (questionnaire). Les résultats n'ont montré quasiment aucune différence au niveau musculaire, et pour la charge cognitive, seulement une fatigue physique ressentie plus faible avec l'exosquelette, ce qui nous conduit à parler d'effet placebo du port de l'exosquelette. L'évaluation de l'acceptation de l'exosquelette semble être globalement favorable. Cependant, des limites à cette étude sont discutées, notamment celles liées à la taille et aux caractéristiques de notre échantillon.
... In order to respect ergonomic principles, and to reduce the mechanical exposure of workers and their physical load, the use of exoskeletons has become a valuable tool, although at the moment there are no standards on the use of exoskeletons in an industrial environment (Poggensee et al, 2021). In short, and for all of the above, it is evident that any action that implies an improvement in working conditions constitutes a preventive measure of the first order to be considered within the field of ergonomics applied to prevent the appearance of work-related musculoskeletal disorders (Theurel et al, 2019), and that their implementation should be considered taking into account different applicability criteria. ...
To reduce the mechanical exposure of workers and their physical load, the use of exoskeletons has become nowadays a valuable preventive tool, although their implementation should be considered taking into account different applicability criteria. The implantation of exoskeletons in companies must follow the principles of preventive activity. The aim of this study is to design an effective management process, integrating the need for these equipment and the way in which they will be selected and implemented. A literature search using PUBMED, Web of Science and Scopus was carried out to investigate the challenges in the implantation of exoskeletons in companies, focusing on selection, evaluation and the validation process of exoskeletons.Results show that, before considering the implementation of the use of an exoskeleton, the job must be assessed and the risk factors correctly identified. After selecting a particular exoskeleton model, it is essential to validate it with objective parameters. Having passed the final validation, a test process about the use of the exoskeleton in the workplace must be designed to achieve reliable results. Also, is important to analyze the possible risks derived from the use of the exoskeletons. An effective process to implant exoskeletons leads to the optimization of man-machine integration and an increase in productivity in the company. In any case, exoskeletons are currently in a process of constant improvement, both in design and functionality, so it seems necessary to establish the bases to advance in their legal standardization.
... Exoskeletons are being developed for use in industrial applications to reduce musculoskeletal injuries, worker strain, and fatigue from performing repetitive and laborious tasks (de Looze et al., 2016;Lowe et al., 2019;Theurel and Desbrosses, 2019). These technologies represent a unique type of wearable technology because, not only are humans interacting with these machines on both a physical and cognitive level, the human and machine are physically and cognitively interdependent, which necessitates a high level of collaboration and coordination (Pons, 2008;Ronsse et al., 2011). ...
Introduction: Wearable I robots such as exoskeletons combine the strength and precision of intelligent machines with the adaptability and creativity of human beings. Exoskeletons are unique in that humans interact with the technologies on both a physical and cognitive level, and as such, involve a complex, interdependent relationship between humans and robots. The aim of this paper was to explore the concepts of agency and adaptation as they relate to human-machine synchrony, as human users learned to operate a complex whole-body powered exoskeleton.
Methods: Qualitative interviews were conducted with participants over multiple sessions in which they performed a range of basic functional tasks and simulated industrial tasks using a powered exoskeleton prototype, to understand their expectations of the human-technology partnership, any challenges that arose in their interaction with the device, and what strategies they used to resolve such challenges.
Results: Analysis of the data revealed two overarching themes: 1) Participants faced physical, cognitive, and affective challenges to synchronizing with the exoskeleton; and 2) they engaged in sensemaking strategies such as drawing analogies with known prior experiences and anthropomorphized the exoskeleton as a partner entity in order to adapt and address challenges.
Discussion: This research is an important first step to understanding how humans make sense of and adapt to a powerful and complex wearable robot with which they must synchronize in order to perform tasks. Implications for our understanding of human and machine agency as well as bidirectional coadaptation principles are discussed.
... For people with disabilities in their lower extremities, exoskeletons on wheels have been developed whose novel design supports the postural transition in the change of movement from sitting to standing and vice versa, providing a greater degree of user independence [77]. ...
This review aims to characterize the current landscape of exoskeletons designed to promote medical care and occupational safety in industrial settings. Extensive exploration of scientific databases spanning industries, health, and medicine informs the classification of exoskeletons according to their distinctive attributes and specific footholds on the human physique. Within the scope of this review, a comprehensive analysis is presented, contextualizing the integration of exoskeletons based on different work activities. The reviewers extracted the most relevant articles published between 2008 and 2023 from IEEE, Proquest, PubMed, Science Direct, Scopus, Web of Science, and other databases. In this review, the PRISMA-ScR checklist was used, and a Cohen's kappa coefficient of 0.642 was applied, implying moderate agreement among the reviewers; 75 primary studies were extracted from a total of 344. The future of exoskeletons in contributing to occupational health and safety will depend on continued collaboration between researchers, designers, healthcare professionals , and industries. With the continued development of technologies and an increasing understanding of how these devices interact with the human body, exoskeletons will likely remain valuable for improving working conditions and safety in various work environments.
... Exoskeletons result in reduced muscle activity and discomfort during work tasks within mechanics, manufacturing, and construction work (McFarland and Fischer, 2019;van der Have et al., 2022). The decrease in biomechanical load during MMH could also result in a slower development of muscle fatigue (Theurel and Desbrosses, 2019). Yet, several limitations of using exoskeletons have been underlined. ...
Occupational exoskeletons contribute to diminish the biomechanical load during manual work. However, familiarization to the use of exoskeletons is rarely considered, which may lead to failure of acceptance and implementation. In this study, ten logistic workers underwent a 5-week progressive familiarization to a passive shoulder exoskeleton, while ten workers acted as controls. Tests pre and post the familiarization applied measurements of muscle activity and kinematics of back, neck, and shoulder, perceived effort, and usability-ratings of the exoskeleton. Exoskeleton use resulted in lower muscle activity of anterior deltoid (13-39%) and upper trapezius (16-60%) and reduced perceived effort. Additionally, it induced an offset in shoulder flexion and abduction during resting position (8-10°). No conclusions on familiarization could be drawn due to low adherence to the protocol. However, the emotions of the workers towards using the exoskeleton decreased making it questionable whether the shoulder exoskeleton is suitable for use in the logistics sector.
... The existing design and evaluation methods of exoskeletons can be broadly classified as empirical/experimental or modelling/simulation (Fritzsche et al., 2021). Researchers have used the empirical approach to investigate many different aspects of exoskeletons such as effectiveness and limitations in preventing MSDs (Theurel and Desbrosses, 2019), impacts on physical workload , and structural complexity (Voilque et al., 2019). In contrast, modelling methods examine different aspects of exoskeletons via various computer simulations that imitate operations of human bodies and exoskeletons (Fritzsche et al., 2021;Zhang et al., 2021), which can predict the internal joint reaction forces and torques of exoskeleton users. ...
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.
... However, these studies mainly focused on the areas of performance [15] and biomechanical parameters [16]. Thus, studies have demonstrated a positive effect of Exos on physiological demands [11,16,17]. Previous studies have investigated restrictions in the freedom of movement caused by Exos via subjective queries [6,15] or have used a combination of recorded movement data and EMG measurements to assess changes in physical strain [16]. ...
p>The ergonomic configuration of processes is becoming increasingly important, especially considering the changing demographics and increasing shortage of skilled workers. Exoskeletons are widely discussed as a means of protecting employees from overstraining at the level of personal protective measures. The field of industrial exoskeletons research is still relatively new and has many unanswered questions. For example, there have not yet been sufficient studies on the influence of exoskeletons on the movements of employees.
This publication discusses the effects of exoskeletons in manual processes. For this purpose, exemplary physical activities are carried out in a pilot study by a subject collective, whereby the tasks are executed with and without an exoskeleton. During the execution, a motion capturing system is used to record the movement data. Different back-supporting exoskeletons are taken into account in the study. The evaluation is based on the joint angles of the participants while performing tasks with and without exoskeletons.
It is shown that the use of exoskeletons has a significant effect on the movement patterns, with a distinction made between rigid and soft support structures.</p
... However, these studies mainly focused on the areas of performance [15] and biomechanical parameters [16]. Thus, studies have demonstrated a positive effect of Exos on physiological demands [11,16,17]. Previous studies have investigated restrictions in the freedom of movement caused by Exos via subjective queries [6,15] or have used a combination of recorded movement data and EMG measurements to assess changes in physical strain [16]. ...
p>The ergonomic configuration of processes is becoming increasingly important, especially considering the changing demographics and increasing shortage of skilled workers. Exoskeletons are widely discussed as a means of protecting employees from overstraining at the level of personal protective measures. The field of industrial exoskeletons research is still relatively new and has many unanswered questions. For example, there have not yet been sufficient studies on the influence of exoskeletons on the movements of employees.
This publication discusses the effects of exoskeletons in manual processes. For this purpose, exemplary physical activities are carried out in a pilot study by a subject collective, whereby the tasks are executed with and without an exoskeleton. During the execution, a motion capturing system is used to record the movement data. Different back-supporting exoskeletons are taken into account in the study. The evaluation is based on the joint angles of the participants while performing tasks with and without exoskeletons.
It is shown that the use of exoskeletons has a significant effect on the movement patterns, with a distinction made between rigid and soft support structures.</p
... Various authors mentioned the effect of changed movement patterns and lifting style, specifically trunk flexion and inclination, on back muscle activity and loads on the lumbar spine Zhang et al., 2016;Alemi et al., 2019;Koopman et al., 2019). These adaptions in movement pattern due to exoskeleton use can be highly individual (Theurel and Desbrosses, 2019), but might have a strong impact on the supportive effect of the devices, and should therefore be considered carefully during the introduction and application of exoskeletons in a workplace environment. ...
Musculoskeletal disorders constitute the leading work-related health issue. Mechanical loading of the lower back contributes as a major risk factor and is prevalent in many tasks performed in logistics. The study aimed to compare acute effects of exoskeletons with different functional mechanisms in a logistic task. Twelve young, healthy individuals participated in the study. Five exoskeletons with different functional mechanisms were tested in a logistic task, consisting of lifting, carrying, and lowering a 13 kg box. By using electromyography (EMG), mean muscle activities of four muscles in the trunk were analyzed. Additionally, kinematics by task completion time and range of motion (RoM) of the major joints and segments were investigated. A main effect was found for Musculus erector spinae , Musculus multifidus , and Musculus latissimus dorsi showing differences in muscle activity reductions between exoskeletons. Reduction in ES mean activity compared to baseline was primarily during lifting from ground level. The exoskeletons SoftExo Lift and Cray X also showed ES mean reduction during lowering the box. Prolonged task duration during the lifting phase was found for the exoskeletons BionicBack, SoftExo Lift, and Japet.W. Japet.W showed a trend in reducing hip RoM during that phase. SoftExo Lift caused a reduction in trunk flexion during the lifting phase. A stronger trunk inclination was only found during lifting from the table for the SoftExo Lift and the Cray X. In conclusion, muscle activity reductions by exoskeleton use should not be assessed without taking their designed force paths into account to correctly interpret the effects for long-term injury prevention.
... Since LHD is developed slowly, the conservative treatment for LHD requires slow treatment in medicine, an external auxiliary technology is urgently needed to alleviate the pain of patients in the rehabilitation process. Studies have found that the use of a back support exoskeleton can reduce the activation of lower back muscles, which further reduces the risk of injury [6], [7], [8]. Exoskeleton robot can imitate the biological exoskeleton. ...
Low back pain has been torturing people around the world as a common and chronic disease, the main inducement of which is lumbar disc herniation (LDH). To alleviate patients’ pain noninvasively, this paper proposes a new lumbar spinal rehabilitation exoskeleton. This exoskeleton is composed of two bands connected by four motor-driven piston pushrods, where the range of band can be adjusted to adapt to people with different waistlines. The four pushrods provide support forces to hold the upper body to relieve the burden of lumbar. The joints between pushrods and band are universal pairs and spherical pairs. The whole structure can be regarded as a parallel robot, thus the supporting and waist tracking performance can be determined by motion control effect of pushrods. Considering the motor torque of pushrods is limited, in this paper, a saturated sliding mode control scheme is proposed. Meanwhile, an extended state observer (ESO) is employed to estimate the external disturbance and internal uncertainties, then the estimates of perturbations will be compensated by the feedback scheme. Furthermore, to enhance the disturbance-tracking performance of the ESO an integrated sliding mode observer is proposed to compensate the tracking errors of ESO. The stabilities of controller and observers are proved by Lyapunov stability theory. Finally, a simulation and two experiments are conducted to verify the performance of the proposed controller and the new exoskeleton. The simulation results show that the novel/new controller can drive the new exoskeleton to move along with the desirable trajectory to support the upper body so that alleviating the burden of waist. The results of myoelectricity experiments also show favorable effectiveness of exoskeleton on supporting upper body in different postures.
Note to Practitioners
—this article was inspired by the concerns of low back pain that many people are suffering. Most existing rehabilitation robots tend to focus on supporting lower body and arms, while back-support rehabilitation robots are barely seen. Although we can see a few upper-body supporting robots in sporadic papers, these studies have not proposed a good control scheme yet. Besides, it is difficult to find a rehabilitation robot with simple structure as well as conforming to ergonomics. To resolve the shortcomings of the structure of existing robots and control models, we proposed a completely new rehabilitation robot with novel mechanical structure. Meanwhile, a new saturated sliding mode and novel integrated observer are employed in the position-force control system to enhance the stability and controllability of the whole robot control system. Then, some elaborately designed experiments are conducted to test the proposed robot and the control system. Numerical results demonstrate that the proposed method can significantly increase the trajectory tracking performance and alleviate low back pain.
... The use of exoskeletons is increasingly seen as a solution to prevent the appearance of MSDs [11]. An exoskeleton can be defined "as a wearable, external mechanical structure that enhances the power of a person" [12]. ...
(1) Background: Healthcare workers are highly affected by work-related musculoskeletal disorders, particularly in the lower back, neck and shoulders, as their occupational tasks expose them to biomechanical constraints. One solution to prevent these musculoskeletal disorders may be the use of a passive exoskeleton as it aims to reduce muscle solicitation. However, few studies have been carried out directly in this field to assess the impact of the use of a passive upper limb exoskeleton on this population. (2) Methods: Seven healthcare workers, equipped with electromyographic sensors, performed a tool cleaning task with and without a passive upper limb exoskeleton (Hapo MS, Ergosanté Technologie, France). Six muscles of the upper limbs were analysed, i.e., anterior deltoid, biceps brachii, pectoralis major, latissimus dorsi, triceps brachii and longissimus thoracis. A subjective analysis of the usability of the equipment, the perception of effort and discomfort, was also carried out using the System Usability Scale and the Borg scale. (3) Results: The longissimus thoracis was the most used muscle during this task. We observed a significant decrease in the muscular solicitation of the anterior deltoid and latissimus dorsi when wearing the exoskeleton. Other muscles were not significantly impacted by the device. (4) Conclusions: the passive exoskeleton used in this study allowed the reduction in muscular load on the anterior deltoid and latissimus dorsi without negative effects on other muscles. Other field studies with exoskeletons are now necessary, particularly in hospitals, to increase our knowledge and improve the acceptability of this system for the prevention of musculoskeletal disorders.
This study investigates the biomechanical impact of a passive Arm-Support Exoskeleton (ASE) on workers in wool textile processing. Eight workers, equipped with surface electrodes for electromyography (EMG) recording, performed three industrial tasks, with and without the exoskeleton. All tasks were performed in an upright stance involving repetitive upper limbs actions and overhead work, each presenting different physical demands in terms of cycle duration, load handling and percentage of cycle time with shoulder flexion over 80°. The use of ASE consistently lowered muscle activity in the anterior and medial deltoid compared to the free condition (reduction in signal Root Mean Square (RMS) −21.6% and −13.6%, respectively), while no difference was found for the Erector Spinae Longissimus (ESL) muscle. All workers reported complete satisfaction with the ASE effectiveness as rated on Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST), and 62% of the subjects rated the usability score as very high (>80 System Usability Scale (SUS)). The reduction in shoulder flexor muscle activity during the performance of industrial tasks is not correlated to the level of ergonomic risk involved. This preliminary study affirms the potential adoption of ASE as support for repetitive activities in wool textile processing, emphasizing its efficacy in reducing shoulder muscle activity. Positive worker acceptance and intention to use ASE supports its broader adoption as a preventive tool in the occupational sector.
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.
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.
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.
The prevalence of work-related musculoskeletal disorders is a common issue in many occupations involving manual handling activities. In order to aid manual workers in reducing the burden on the musculoskeletal system, various wearable robotic technologies have been developed over the years. An increase in research work on wearable technologies has been observed, particularly in the last decade. In that context, this article presents a comprehensive review and a bibliometric analysis of the recorded occupational exoskeletons for manual handling since 2010. The review is aimed at identifying the paradigm shifts of research in the recent past and associating the trends pertaining to the applications, mechanisms, and control systems in the development of wearable devices for manual handling. The scope of the review limits itself to active and passive exoskeletons designed to support the upper extremity, lower extremity, and spine for performing load lifting, load carrying, or static holding. The analysis of the results revealed the emerging trends with the aim of providing researchers with areas for improvement and suggestions for different clusters of devices.
In recent years, exoskeleton test methods for industrial exoskeletons have evolved to include simulated laboratory and field environments. Physiological, kinematic, and kinetic metrics, as well as subjective surveys, are used to evaluate exoskeleton usability. In particular, exoskeleton fit and usability can also impact the safety of exoskeletons and their effectiveness at reducing musculoskeletal injuries. This paper surveys the state of the art in measurement methods applied to exoskeleton evaluation. A notional classification of the metrics based on exoskeleton fit, task efficiency, comfort, mobility, and balance is proposed. In addition, the paper describes the test and measurement methods used in supporting the development of exoskeleton and exosuit evaluation methods to assess their fit, usability, and effectiveness in industrial tasks such as peg in hole, load align, and applied force. Finally, the paper includes a discussion of how the metrics can be applied towards a systematic evaluation of industrial exoskeletons, current measurement challenges, and future research directions.
Wearable robots are becoming a valuable solution that helps injured, and elderly people regain mobility and improve clinical outcomes by speeding up the rehabilitation process. The XoSoft exosuit identified several benefits, including improvement of assistance, usability, and acceptance with a soft, modular, bio-mimetic, and quasi-passive exoskeleton. This study compares two assistive configurations: (i) a bilateral hip flexion (HA, hips-assistance) and (ii) a bilateral hip flexion combined with ankle plantarflexion (HAA, hips-ankles-assistance) with the main goal of evaluating compensatory actions and synergetic effects generated by the human- exoskeleton interaction. A complete description of this complex interaction scenario with this actuated exosuit is evaluated during a treadmill walking task, using several indices to quantify the human-robot interaction in terms of muscular activation and fatigue, metabolic expenditure, and kinematic motion patterns. Evidence shows that the HAA biomimetic controller is synergetic with the musculature and performs better concerning the other control strategy. The experimentation demonstrated a metabolic expenditure reduction of 8% of Metabolic Equivalent of Task (MET), effective assistance of the muscular activation of 12.5%, a decrease of the muscular fatigue of 0.6% of the mean frequency, and a significant reduction of the compensatory actions, as discussed in this work. Compensatory effects are present in both assistive configurations, but the HAA modality provides a 47% reduction of compensatory effects when considering muscle activation.
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.
Wearable robotics, also called exoskeletons, have been engineered for human-centered assistance for decades. They provide assistive technologies for maintaining and improving patients’ natural capabilities towards self-independence and also enable new therapy solutions for rehabilitation towards pervasive health. Upper limb exoskeletons can significantly enhance human manipulation with environments, which is crucial to patients’ independence, self-esteem, and quality of life. For long-term use in both in-hospital and at-home settings, there are still needs for new technologies with high comfort, biocompatibility, and operability. The recent progress in soft robotics has initiated soft exoskeletons (also called exosuits), which are based on controllable and compliant materials and structures. Remarkable literature reviews have been performed for rigid exoskeletons ranging from robot design to different practical applications. Due to the emerging state, few have been focused on soft upper limb exoskeletons. This paper aims to provide a systematic review of the recent progress in wearable upper limb robotics including both rigid and soft exoskeletons with a focus on their designs and applications in various pervasive healthcare settings. The technical needs for wearable robots are carefully reviewed and the assistance and rehabilitation that can be enhanced by wearable robotics are particularly discussed. The knowledge from rigid wearable robots may provide practical experience and inspire new ideas for soft exoskeleton designs. We also discuss the challenges and opportunities of wearable assistive robotics for pervasive health.
With mechanical loading as the main risk factor for LBP in mind, exoskeletons are designed to reduce the load on the back by taking over a part of the required moment. The present study assessed the effect of a passive exoskeleton on back and abdominal muscle activation, hip and lumbar flexion and on the contribution of both the human and the exoskeleton to the L5/S1 net moment, during static bending at five different hand heights. Two configurations of the exoskeleton (LOW & HIGH) differing in angle-torque characteristics were tested. L5/S1 moments generated by the subjects were significantly reduced (15–20% for the most effective type) at all hand heights. LOW generated 4–11 Nm more support than HIGH at 50%, 25% and 0% upright stance hand height and HIGH generated 4–5 Nm more support than LOW at 100% and 75%. Significant reductions (11–57%) in back muscle activity were found compared to WITHOUT for both exoskeletons for some conditions. However, EMG reductions compared to WITHOUT were highly variable across subjects and not always significant. The device allowed for substantial lumbar bending (up to 70°) so that a number of participants showed the flexion-relaxation phenomenon, which prevented further reduction of back EMG by the device and even an increase from 2% to 6% MVC in abdominal activity at 25% hand height. These results indicate that flexion relaxation and its interindividual variation should be considered in future exoskeleton developments.
The objective of this study was to assess the effect of a passive trunk exoskeleton on functional performance for various work related tasks in healthy individuals.
18 healthy men performed 12 tasks. Functional performance in each task was assessed based on objective outcome measures and subjectively in terms of perceived task difficulty, local and general discomfort.
Wearing the exoskeleton tended to increase objective performance in static forward bending, but decreased performance in tasks, such as walking, carrying and ladder climbing. A significant decrease was found in perceived task difficulty and local discomfort in the back in static forward bending, but a significant increase of perceived difficulty in several other tasks, like walking, squatting and wide standing. Especially tasks that involved hip flexion were perceived more difficult with the exoskeleton.
Design improvements should include provisions to allow full range of motion of hips and trunk to increase versatility and user acceptance.
The aim of this study was to evaluate the effect of an industrial exoskeleton on muscle activity, perceived musculoskeletal effort, measured and perceived contact pressure at the trunk, thighs and shoulders, and subjective usability for simple sagittal plane lifting and lowering conditions. Twelve male participants lifted and lowered a box of 7.5 kg and 15 kg, respectively, from mid-shin height to waist height, five times, both with and without the exoskeleton. The device significantly reduced muscle activity of the Erector Spinae (12%-15%) and Biceps Femoris (5%). Ratings of perceived musculoskeletal effort in the trunk region were significantly less with the device (9.5%-11.4%). The measured contact pressure was highest on the trunk (91.7 kPa-93.8 kPa) and least on shoulders (47.6 kPa-51.7 kPa), whereas pressure was perceived highest on the thighs (35-44% of Max LPP). Six of the users rated the device usability as acceptable. The exoskeleton reduced musculoskeletal loading on the lower back and assisted with hip extensor torque during lifting and lowering. Contact pressures fell below the Pain Pressure Threshold. Perceived pressure was not exceptionally high, but sufficiently high to cause discomfort if used for long durations.
Goal:
The purpose of this study was: (i) to design and fabricate a biomechanically-assistive garment which was sufficiently lightweight and low-profile to be worn underneath, or as, clothing, and then (ii) to perform human subject testing to assess the ability of the garment to offload the low back muscles during leaning and lifting.
Methods:
We designed a prototype garment which acts in parallel with the low back extensor muscles to reduce forces borne by the lumbar musculature. We then tested 8 healthy subjects while they performed common leaning and lifting tasks with and without the garment. We recorded muscle activity, body kinematics, and assistive forces.
Results:
The biomechanically-assistive garment offloaded the low back muscles, reducing erector spinae muscle activity by an average of 23-43% during leaning tasks, and 14-16% during lifting tasks.
Conclusion:
Experimental findings in this study support the feasibility of using biomechanically-assistive garments to reduce low back muscle loading, which may help reduce injury risks or fatigue due to high or repetitive forces.
Significance:
Biomechanically-assistive garments may have broad societal appeal as a lightweight, unobtrusive and cost-effective means to mitigate low back loading in daily life.
An additional mechanical mechanism for a passive parallelogram-based exoskeleton arm-support is presented. It consists of several levers and joints and an attached extension coil spring. The additional mechanism has two favourable features. On the one hand it exhibits an almost iso-elastic behaviour whereby the lifting force of the mechanism is constant for a wide working range. Secondly, the value of the supporting force can be varied by a simple linear movement of a supporting joint. Furthermore a standard tension spring can be used to gain the desired behavior. The additional mechanism is a 4-link mechanism affixed to one end of the spring within the parallelogram arm-support. It has several geometrical parameters which influence the overall behaviour. A standard optimisation routine with constraints on the parameters is used to find an optimal set of geometrical parameters. Based on the optimized geometrical parameters a prototype was constructed and tested. It is a lightweight wearable system, with a weight of 1.9 kg. Detailed experiments reveal a difference between measured and calculated forces. These variations can be explained by a 60 % higher pre load force of the tension spring and a geometrical offset in the construction.
This paper presents a design of a passive spine exoskeleton which implements a “push–pull” external assistive strategy. The spine exoskeleton was designed for reducing the risk of back injury. It applies a pulling force on thoracic region and a pushing force on lumbar region during spine flexion/extension. The design was inspired by previous simulation work, where the results highly supported benefits of the push–pull strategy on reducing the back muscular efforts and bending moment for the sagittal spine flexion/extension. A passive physical prototype was designed and constructed to test the push–pull strategy on human subjects. Three subjects were able to repeat the identical dynamic spine flexion and extension tasks with the spine exoskeleton prototype. The surface electromyography showed a reduction of up to 24% at lumbar and 54% at thoracic level muscle for the human subjects wearing the exoskeleton suit to accomplish the same static tasks without any external assistance. The muscle force and intervertebral bending moment were estimated to be reduced by up to 479 N and 36 N · m, respectively.
The aim of this review was to provide an overview of assistive exoskeletons that have specifically been developed for industrial purposes and to assess the potential effect of these exoskeletons on reduction of physical loading on the body. The search resulted in 40 papers describing 26 different industrial exoskeletons, of which 19 were active (actuated) and 7 were passive (non-actuated). For 13 exoskeletons, the effect on physical loading has been evaluated, mainly in terms of muscle activity. All passive exoskeletons retrieved were aimed to support the low back. Ten-forty per cent reductions in back muscle activity during dynamic lifting and static holding have been reported. Both lower body, trunk and upper body regions could benefit from active exoskeletons. Muscle activity reductions up to 80% have been reported as an effect of active exoskeletons. Exoskeletons have the potential to considerably reduce the underlying factors associated with work-related musculoskeletal injury. Practitioner Summary: Worldwide, a significant interest in industrial exoskeletons does exist, but a lack of specific safety standards and several technical issues hinder mainstay practical use of exoskeletons in industry. Specific issues include discomfort (for passive and active exoskeletons), weight of device, alignment with human anatomy and kinematics, and detection of human intention to enable smooth movement (for active exoskeletons).
Cumulative trauma disorders due to performance of repetitive tasks account for more than 50% of all occupational illnesses in the United States today. Employees affected by these disorders frequently experience substantial pain and functional impairment that may require a change in occupation. For the employer, these injuries result in loss of productivity and increased costs in the form of higher medical expenses and disability payments for injured workers. Successful treatment of work-related repetitive tissue injuries depends on early diagnosis and appropriate therapy. Prevention requires identifying sites and tasks that place employees at risk of injury and supporting efforts to develop safer work environments.(JAMA. 1992;267:838-842)
Overhead work is an important risk factor for upper extremity (UE) musculoskeletal disorders. We examined the potential of a mechanical arm and an exoskeletal vest as a wearable assistive device (WADE) for overhead work. Twelve participants completed 10 minutes of simulated, intermittent overhead work, using each of three payloads (1.1, 3.4 and 8.1 kg) and with/without the WADE. Ratings of perceived discomfort (RPDs) and electromyography (EMG) were obtained for the upper arms, shoulders and low back. Using the WADE, UE RPDs decreased by ∼50% with the heavier payloads, whereas smaller (∼25%) and non-significant increases in low-back RPDs were found and were relatively independent of payload. Changes in RPDs with WADE use were consistent with physical demands indicated by EMG, though EMG-based differences in fatigue were less apparent. Participants generally preferred using the WADE, particularly with heavier payloads. These results supported the potential utility of a WADE as an intervention for overhead work. Practitioner Summary: A wearable assistive device for overhead work reduced physical demands on the upper extremity and had high acceptance, though some evidence suggested increased demands at the low back. While some design needs were found and field-testing is needed, this may be a useful practical intervention.
Narrowing of the subacromial space has been noted as a common feature of rotator cuff (RC) tendinopathy. It has been implicated in the development of symptoms and forms the basis for some surgical and rehabilitation approaches. Various radiological methods have been used to measure the subacromial space, which is represented by a two-dimensional measurement of acromiohumeral distance (AHD). A reliable method of measurement could be used to assess the impact of rehabilitation or surgical interventions for RC tendinopathy; however, there are no published reviews assessing the reliability of AHD measurement.
The aim of this review was to systematically assess the evidence for the intrarater and inter-rater reliability of radiological methods of measuring AHD, in order to identify the most reliable method for use in RC tendinopathy.
An electronic literature search was carried out and studies describing the reliability of any radiological method of measuring AHD in either healthy or RC tendinopathy groups were included. Eighteen studies met the inclusion criteria and were appraised by two reviewers using the Quality Appraisal for reliability Studies checklist.
Eight studies were deemed to be of high methodological quality. Study weaknesses included lack of tester blinding, inadequate description of tester experience, lack of inclusion of symptomatic populations, poor reporting of statistical methods and unclear diagnosis. There was strong evidence for the reliability of ultrasound for measuring AHD, with moderate evidence for MRI and CT measures and conflicting evidence for radiographic methods. Overall, there was lack of research in RC tendinopathy populations, with only six studies including participants with shoulder pain.
The results support the reliability of ultrasound and CT or MRI for the measurement of AHD; however, more studies in symptomatic populations are required. The reliability of AHD measurement using radiographs has not been supported by the studies reviewed.
Our aim was to provide a quantitative assessment of the exposure-response relationships between work-related physical and psychosocial factors and the occurrence of specific shoulder disorders in occupational populations.
A systematic review of the literature was conducted on the associations between type of work, physical load factors, and psychosocial aspects at work, on the one hand, and the occurrence of tendinitis of the biceps tendon, rotator cuff tears, subacromial impingement syndrome (SIS), and suprascapular nerve compression, on the other hand. Associations between work factors and shoulder disorders were expressed in quantitative measures as odds ratio (OR) or relative risk (RR).
The occurrence of SIS was associated with force requirements >10% maximal voluntary contraction (MVC), lifting >20 kg >10 times/day, and high-level of hand force >1 hour/day (OR 2.8-4.2). Repetitive movements of the shoulder, repetitive motion of the hand/wrist >2 hours/day, hand-arm vibration, and working with hand above shoulder level showed an association with SIS (OR 1.04-4.7) as did upper-arm flexion > or =45 degrees > or =15% of time (OR 2.43) and duty cycle of forceful exertions > or =9% time or duty cycle of forceful pinch >0% of time (OR 2.66). High psychosocial job demand was also associated with SIS (OR 1.5-3.19). Jobs in the fish processing industry had the highest risk for both tendinitis of the biceps tendon as well as SIS (OR 2.28 and 3.38, respectively). Work in a slaughterhouse and as a betel pepper leaf culler were associated with the occurrence of SIS only (OR 5.27 and 4.68, respectively). None of the included articles described the association between job title/risk factors and the occurrence of rotator cuff tears or suprascapular nerve compression.
Highly repetitive work, forceful exertion in work, awkward postures, and high psychosocial job demand are associated with the occurrence of SIS.
To describe and discuss the process used to write a narrative review of the literature for publication in a peer-reviewed journal. Publication of narrative overviews of the literature should be standardized to increase their objectivity.
In the past decade numerous changes in research methodology pertaining to reviews of the literature have occurred. These changes necessitate authors of review articles to be familiar with current standards in the publication process.
Narrative overview of the literature synthesizing the findings of literature retrieved from searches of computerized databases, hand searches, and authoritative texts.
An overview of the use of three types of reviews of the literature is presented. Step by step instructions for how to conduct and write a narrative overview utilizing a 'best-evidence synthesis' approach are discussed, starting with appropriate preparatory work and ending with how to create proper illustrations. Several resources for creating reviews of the literature are presented and a narrative overview critical appraisal worksheet is included. A bibliography of other useful reading is presented in an appendix.
Narrative overviews can be a valuable contribution to the literature if prepared properly. New and experienced authors wishing to write a narrative overview should find this article useful in constructing such a paper and carrying out the research process. It is hoped that this article will stimulate scholarly dialog amongst colleagues about this research design and other complex literature review methods.
The scientific literature on work-related back disorders was reviewed to identify consistent risk factors and to determine the strength of the association between the two. Thirty-five publications were selected with quantitative information. Lifting or carrying loads, whole-body vibration, and frequent bending and twisting proved to be the physical load risk factors consistently associated with work-related back disorders. Job dissatisfaction and low job decision latitude proved to be important, but the evidence was not consistent across different studies and study designs. The epidemiologic studies illustrated the importance of several confounders, especially age, smoking habits, and education. In this review, gender, height, weight, exercise, and marital status were consistently not associated with back disorders in occupational populations.
This systematic review assessed aspects of physical load during work and leisure time as risk factors for back pain. Several reviews on this topic are available, but this one is based on a strict systematic approach to identify and summarize the evidence, comparable with that applied in the clinical literature on the efficacy of intervention for back pain. A computerized bibliographical search was made of several data bases for studies with a cohort or case-referent design. Cross-sectional studies were excluded. A rating system was used to assess the strength of the evidence, based on the methodological quality of 28 cohort and 3 case-referent studies and the consistency of the findings. Strong evidence exists for manual materials handling, bending and twisting, and whole-body vibration as risk factors for back pain. The evidence was moderate for patient handling and heavy physical work, and no evidence was found for standing or walking, sitting, sports, and total leisure-time physical activity.
We compared different passive exoskeletal designs in terms of physical demands (maximum acceptable frequency = MAF, perceived discomfort, and muscular loading) and quality in a simulated overhead drilling task, and the moderating influence of tool mass (∼2 and ∼5 kg). Three distinct designs were used: full-body and upper-body exoskeletons with attached mechanical arms; and an upper-body exoskeleton providing primarily shoulder support. Participants (n = 16, gender-balanced) simulated drilling for 15 min to determine their MAF, then maintained this pace for three additional minutes while the remaining outcome measures were obtained. The full-body/upper-body devices led to the lowest/highest MAF for females and the lowest quality. The shoulder support design reduced peak shoulder muscle loading but did not significantly affect either quality or MAF. Differences between exoskeleton designs were largely consistent across the two tool masses. These results may be helpful to (re)design exoskeletons to help reduce injury risk and improve performance.
Personal “protective” equipment has been recommended in agricultural tasks. The plastic mulching process is often required in commercial farming. On-body personal assist suits (PAS) affect heart rate, muscles, trunk movement, and user acceptance. In this study, 8 male and 6 female subjects performing 3-min digging tasks were evaluated. Electrocardiograph, electromyography of the right and left upper trapezius and (L3) lumbar erector spinae, and motion data were simultaneously recorded using a multichannel telemetry system. In the task's final minute, the workload was decreased using PAS in males, although the average workload did not change. Males achieved a more stable acceleration pattern using PAS as compared to females. 86% females experienced discomfort in the crotch area; therefore, we recommend that hip straps be modified to increase user acceptance. For a typical agricultural forward-bending task, such as digging, PAS can significantly reduce strain (p < 0.05) on lower back muscles (L3).
The aim of this study was to evaluate the effect of a passive upper body exoskeleton on muscle activity, perceived musculoskeletal effort, local perceived pressure and subjective usability for a static overhead task. Eight participants (4 male, 4 female) held a load (0 kg and 2 kg) three times overhead for a duration of 30 s each, both with and without the exoskeleton. Muscle activity was significantly reduced for the Biceps Brachii (49%) and Medial Deltoid (62%) by the device for the 2 kg load. Perceived effort of the arms was significantly lower with the device for the 2 kg load (41%). The device did not have a significant effect on trunk or leg muscle activity (for the 2 kg load) or perceived effort. Local perceived pressure was rated below 2 (low pressure levels) for all contact areas assessed. Half of the participants rated the device usability as acceptable. The exoskeleton reduced muscle activity and perceived effort by the arms, and had no significant negative effect on the trunk and lower body with regards to muscle activity, perceived effort and localised discomfort.
This paper proposes the design of an electrically-powered waist assistive exoskeleton wire-driven only by one actuator and its control method. The developed exoskeleton is intended to reduce muscle fatigue and further prevent back-injury of industrial workers who undergo repeated, intensive waist motions. Considering requirements specially for industrial purposes, system performances related to cost, weight, operational time, and system endurance & maintainability of the robot have to be specially pursued. Therefore, reduction in the number of actuators without deteriorating the robot’s main function can be an effective approach. Along with this concept, only the single actuator mounted on the back part of the robot is proposed to simultaneously drive both legs by wire through a differential gear mechanism. The applied differential mechanism allows natural motions generally observed in human walking with almost zero mechanical impedance, but the waist motion for lifting-up heavy objects can be assisted by the powered extension of both legs. A current control algorithm embedded in a micro-controller is specially designed to achieve objectives of the robot.
In order to evaluate the waist assistance provided by the developed robot, activation signals of electromyography (EMG) on main muscles of working wearers related to waist motions were measured. Further, the usability was evaluated using the responses of a questionnaire survey. Thus, the proposed method for waist assistance by a singular actuator is verified to be conclusively effective.
Work-related low back pain is a serious socioeconomic problem. This study examined whether HAL for Care Support, which is a newly developed wearable robot, would decrease lumbar fatigue and improve lifting performance during repetitive lifting movements. Eighteen healthy volunteers (11 men, 7 women) performed repetitive stoop lifting movements of a cardboard box weighing 12 kg as many times as possible. The first lifting trial was executed without HAL for Care Support, and the second was with it. We evaluated the VAS of lumbar fatigue as the lumbar load and the number of lifts and the lifting time as lifting performance. Without HAL for Care Support, the mean VAS of lumbar fatigue, the number of lifts and lifting time were 68 mm, 60 and 230 s; with HAL for Care Support, they were 51 mm, 87 and 332 s, respectively. Both lifting performance measures were significantly improved by using HAL for Care Support (Fig. 2). A power analysis showed that there was sufficient statistical power for the VAS of lumbar fatigue (0.99), the number of lifts (0.92), and lifting time (0.93). All participants performed their repetitive lifting trials safely. There were no adverse events caused by using HAL for Care Support. In conclusion, the HAL for Care Support can decrease lumbar load and improve the lifting performance during repetitive stoop lifting movements in healthy adults.
Use of exoskeletal vests (designed to support overhead work) can be an effective intervention approach for tasks involving arm elevation, yet little is known on the potential beneficial impacts of their use on physical demands and task performance. This laboratory study (n = 12) evaluated the effects of a prototype exoskeletal vest during simulated repetitive overhead drilling and light assembly tasks. Anticipated or expected benefits were assessed, in terms of perceived discomfort, shoulder muscle activity, and task performance. Using the exoskeletal vest did not substantially influence perceived discomfort, but did decrease normalized shoulder muscle activity levels (e.g., ≤ 45% reduction in peak activity). Drilling task completion time decreased by nearly 20% with the vest, but the number of errors increased. Overall, exoskeletal vest use has the potential to be a new intervention for work requiring arm elevation; however, additional investigations are needed regarding potential unexpected or adverse influences (see Part II).
Adopting a new technology (exoskeletal vest designed to support overhead work) in the workplace can be challenging since the technology may pose unexpected safety and health consequences. A prototype exoskeletal vest was evaluated for potential unexpected consequences with a set of evaluation tests for: usability (especially, donning & doffing), shoulder range of motion (ROM), postural control, slip & trip risks, and spine loading during overhead work simulations. Donning/doffing the vest was easily done by a wearer alone. The vest reduced the max. shoulder abduction ROM by ∼10%, and increased the mean center of pressure velocity in the anteroposterior direction by ∼12%. However, vest use had minimal influences on trip-/slip-related fall risks during level walking, and significantly reduced spine loadings (up to ∼30%) especially during the drilling task. Use of an exoskeletal vest can be beneficial, yet the current evaluation tests should be expanded for more comprehensiveness, to enable the safe adoption of the technology.
This study aimed to assess the physiological consequences of using an upper limb exoskeleton during manual handling task, as muscle activity, upper limb kinematics, postural balance and cardiac cost. Participants performed three tasks (load lifting (LIFT), carrying (WALK) and stacking-unstacking (STACK)) with (EXOS) and without (FREE) an exoskeleton. During LIFT and STACK, the activity of the deltoid anterior muscle was significantly lower for EXOS than for FREE. During LIFT, the activity of the triceps brachii (TB) and tibialis anterior muscles significantly increased for EXO. The TB muscle activity significantly decreased for EXOS during WALK. The cardiac cost tended to increase with the use of the exoskeleton during LIFT, compared to FREE. The upper limb kinematics significantly differed between the EXOS and FREE conditions for all tasks. The benefits of the upper limb exoskeleton to reduce shoulder flexor muscle activity has been demonstrated, while broader physiological consequences have also been evidenced as increased antagonist muscle activity, postural strains, cardiovascular demand, and modified kinematics.
The objective of this study was to investigate biomechanical loading to the low back as a result of wearing an
exoskeletal intervention designed to assist in occupational work. Twelve subjects simulated the use of two
powered hand tools with and without the use of a Steadicam vest with an articulation tool support arm in a
laboratory environment. Dependent measures of peak and mean muscle forces in ten trunk muscles and peak and mean spinal loads were examined utilizing a dynamic electromyography-assisted spine model. The exoskeletal device increased both peak and mean muscle forces in the torso extensor muscles (p < 0.001). Peak and mean compressive spinal loads were also increased up to 52.5% and 56.8%, respectively, for the exoskeleton condition relative to the control condition (p < 0.001). The results of this study highlight the need to design exoskeletal interventions while anticipating how mechanical loads might be shifted or transferred with their use.
Exoskeletons may form a new strategy to reduce the risk of developing low back pain in stressful jobs. In the present study we examined the potential of a so-called passive exoskeleton on muscle activity, discomfort and endurance time in prolonged forward-bended working postures. Eighteen subjects performed two tasks: a simulated assembly task with the trunk in a forward-bended position and static holding of the same trunk position without further activity. We measured the electromyography for muscles in the back, abdomen and legs. We also measured the perceived local discomfort. In the static holding task we determined the endurance, defined as the time that people could continue without passing a specified discomfort threshold. In the assembly task we found lower muscle activity (by 35-38%) and lower discomfort in the low back when wearing the exoskeleton. Additionally, the hip extensor activity was reduced. The exoskeleton led to more discomfort in the chest region. In the task of static holding, we observed that exoskeleton use led to an increase in endurance time from 3.2 to 9.7 min, on average. The results illustrate the good potential of this passive exoskeleton to reduce the internal muscle forces and (reactive) spinal forces in the lumbar region. However, the adoption of an over-extended knee position might be, among others, one of the concerns when using the exoskeleton.
Objective: To determine whether physical and psychosocial load at work influence sickness absence due to low back pain.
Methods: The research was a part of the study on musculoskeletal disorders, absenteeism, stress, and health (SMASH), a 3 year prospective cohort study on risk factors for musculoskeletal disorders. Workers from 21 companies located throughout The Netherlands participated in the part of this study on sickness absence due to low back pain. The study population consisted of 732 workers with no sickness absences of 3 days or longer due to low back pain in the 3 months before the baseline survey and complete data on the reasons for absences during the follow up period. The mean (range) period of follow up in this group was 37 (7–44) months. Physical load at work was assessed by analyses of video recordings. Baseline information on psychosocial work characteristics was obtained by a questionnaire. Data on sickness absence were collected from company records. The main outcome measure was the rate of sickness absences of 3 days or longer due to low back pain during the follow up period.
Results: After adjustment of the work related physical and psychosocial factors for each other and for other potential determinants, significant rate ratios ranging from 2.0 to 3.2 were found for trunk flexion, trunk rotation, lifting, and low job satisfaction. A dose-response relation was found for trunk flexion, but not for trunk rotation or lifting. Non-significant rate ratios of about 1.4 were found for low supervisor support and low coworker support. Quantitative job demands, conflicting demands, decision authority, and skill discretion showed no relation with sickness absence due to low back pain.
Conclusions: Flexion and rotation of the trunk, lifting, and low job satisfaction are risk factors for sickness absence due to low back pain. Some indications of a relation between low social support, either from supervisors or coworkers, and sickness absence due to low back pain are also present.
In a preliminary investigation of 45 middle aged adult subjects, 20 with low-back pain (LBP) and 25 with healthy backs (HB), balance responses (body sway) were measured under different sensory conditions with computerized force plate stabilometry. Compared with HB subjects, in the most stable and then the least stable balance positions, the LBP subjects demonstrated significantly greater postural sway, kept their center of force (COF) significantly more posterior, and were significantly less likely to be able to balance on one foot with eyes closed. Based on subjective observations, the LBP subjects were more likely to fulcrum about the hip and back to maintain uprightness in challenging balance tasks compared with healthy controls who maintained their fulcrum for the COF around the ankle. Research is needed to determine the incidence of balance problems in LBP patients compared with controls. Effective physical therapy assessment and treatment of LBP patients may require attention to postural alignment, strength, flexibility, joint stability, balance reactions, and postural strategies.
In PSA Peugeot Citroen factories, high precision requirements of workstations make them being manual. One of the main goal of the car manufacturer is to minimize the pain of workers while maintaining high efficiency of production lines. Consequently, assisting operators with an exoskeleton is a potential solution for improving ergonomics of painful workstations while respecting industrial constraints. To determine ergonomic performances of an exoskeleton, human joint angles and torques, ground reaction forces, and duration of operations are analysed for eight subjects performing a representative screwing task. Experiments were performed using ABLE upper-limb exoskeleton, developed by the French Atomic Energy Commission (CEA), which has the functionality to compensate arm and tools loads. Results show a clear reduction of the sum of the joints torques, up to 38.9%, given by ABLE supply and invite to make concrete the use of exoskeletons in car assembly lines.
Relevance to industry
In industries, workers performing manual operations are subjected to musculoskeletal disorders (MSD). The usage of robotic devices such as exoskeletons might then be a relevant solution to reduce workers pain and prevent MSD. The paper describes how to assess ergonomic performances of such robotic devices for a future usage in industry.
The purpose of this study was to determine if an on-body personal lift assistive device (PLAD)1 affected oxygen consumption during a continuous lifting task and to investigate if any effect could be explained by differences in muscle activity or lifting technique. The PLAD, worn like a back-pack, contains a spring-cable mechanism that assists the back musculature during lifting, lowering, and forward bending tasks. Males (n = 15) lifted and lowered a box loaded to 10% of their maximum back strength at 6 times/minute for 15-minutes using a free-style technique under two conditions: wearing and not wearing the PLAD. Oxygen consumption was collected continuously for the first condition; then the participants rested until their heart rates returned to resting levels before repeating the protocol for the second condition. Knee flexion was monitored using Liberty sensors at the hip, knee, and ankle. EMG of the thoracic and lumbar erector spinae (TES, LES), biceps femoris, rectus femoris and gluteus maximus were gathered using a Bortec AMT-8 channel system. VO2 measures were averaged across the duration (15 min) for each condition. Results showed no differences between oxygen consumption during the PLAD and no PLAD conditions. When wearing the PLAD, the TES demonstrated an 8.4% EMG reduction when lowering the box while the biceps femoris showed a 14% reduction while lifting the box. Knee angles, used as a proxy for stoop or squat lifts, were highly variable for both conditions. In conclusion, the PLAD had no effect on oxygen consumption and, therefore, neither workers nor employers should increase the tasks demands when wearing this ergonomic aid.
Relevance to industry
While the PLAD reduced musculoskeletal effort required by back musculature, loads or rates of lifting should not be increased since there is no change in the overall physical demand of the task.
The exoskeleton robot system is a brand new type of human-robot cooperation system. It fully combines human intelligence and robot power so that robot intelligence and human operator’s power are both enhanced. Therefore, it achieves a high-level performance that neither robots nor humans could achieve separately. This paper describes the basic exoskeleton concepts from biological systems to human-robot intelligent systems. It is followed by an overview of the development history of exoskeleton systems and their two main applications: human power assistance and human power augmentation. Besides the key technologies in exoskeleton systems, the research is presented from several viewpoints of the biomechanical design, system structure modeling, human-robot interaction, and control strategy.
Objective: To identify factors associated with rotator cuff syndrome (RCS) among active workers.
Methods: Seven hundred thirty-three workers in 12 worksites participated in a cross-sectional study with individual structured physical and psychosocial health interviews, physical examinations, and exposure assessments of biomechanical factors. Work organization, including job content or structural constraints, was assessed at the departmental level. Multivariable logistic modeling was used.
Results: Fifty-five subjects (7.5%) had RCS. Cases were more likely to report low job security (P < 0.04) and to have very high job structural constraints (P < 0.03). Age and body mass index were marginally significant. Upper arm flexion ≥ 45° ≥ 15% of time and either duty cycle of forceful exertions ≥9% time (odds ratio = 2.43, 95% CI = 1.04 to 5.68) or forceful pinch >0% [odds ratio = 2.66, 95% CI = 1.26 to 5.59] were significant risk factors.
Conclusions: Long duration of shoulder flexion and forceful exertion (especially pinch) in a job are significant risk factors for RCS. Work organization may impact physical and psychosocial exposures and should be further explored.
A prior laboratory study found that when wearing a weight transfer device in the stooped posture, trunk flexions were reduced, and subjects who did not experience flexion-relaxation of the erector spinae had reduced back muscle activity. Whole-body musculoskeletal models, which included individual passive torso stiffness and anthropometry, were implemented to predict loads in the passive tissues of the back and the leg joints. Results predicted that when wearing the device in the stooped posture, compression and shear forces at the L5-S1 level were reduced by 13% and 12% respectively. Internal loads in the leg joints were reduced between 10% and 31%. Much of the reduction in joint loads may be a result of the device's ability to limit torso flexion during stoop, rather than a transferring of load. While these results show possible benefit in the short-term, further study is needed on the long-term effects to determine if the device is an effective intervention for those who use the stooped posture routinely.
Repetitive work in the stooped posture is a known risk factor for developing low back disorders (LBDs); regardless, the stooped posture is widespread throughout the world in the agriculture, construction, and mining industries. An on-body weight transfer device was tested as a possible intervention for reducing the risk of developing LBDs. Eighteen subjects (11 male and 7 female), with no history of LBDs, performed stooped posture tasks in the laboratory. Surface electromyograms of the erector spinae, rectus abdominis, biceps femoris, and tibialis anterior muscles were recorded. Bodily joint flexions were measured with a combination of inclinometers and electrogoniometers. When wearing the device in the stooped posture, biceps femoris activity and lumbar flexion were significantly reduced. Subjects who did not experience flexion-relaxation had a significant reduction in lumbar erector spinae activity. By reducing back muscle activity, and by limiting lumbar flexion, the device could reduce the risk of developing LBDs for those who work while adopting the stooped posture. The device may also be beneficial for those with existing LBDs. Follow up field studies are needed to confirm the long-term potential benefits of such an intervention approach.
We have been developing a wearable robot that directly and physically supports human movement. A ldquomuscle suitrdquo for the arm that will provide muscular support for the paralyzed or those otherwise unable to move unaided is one example. Whereas low back pain is one of the most serious issue for the manual worker and in this paper, we focus on developing the support system for forward tilting of the upper body. In this paper, the concept and mechanical structure of the support system is shown. From the experimental result to keep forward tilting posture with load indicates our system is very effective for keeping forward tilting posture and it becomes clear that more than 60% reduction of muscular power is possible.
This paper presents ABLE, an innovative exoskeleton for the upper limb currently under development at CEA-LIST Interactive Robotics Unit. Its distinctive high performance mechanical transmissions - screw and cable patented arrangement - and its integrated architecture makes it the very first of its category. The first 4 axis model is described here but more complete models are already planned: a 7 axis model as well as portable versions. Its back-drivable, high efficiency, low inertia actuators provide a high capacity (around 40 N continuous effort at the hand) and allow hybrid force-position control without requiring any force sensor. Its first application is currently a research program in rehabilitation (BRAHMA project) and professional use is already in view. Assistance tasks for disabled persons (carrying a bottle) are also typical tasks to be performed by ABLE as well as intuitive telerobotics, haptic device for VR, and sport training, etc. Furthermore, its versatility and simple design allow industrial versions to become soon available.
Chronic low back pain (CLBP) is a major clinical problem with a substantial socio-economical impact. Today, diagnosis and therapy are insufficient, and knowledge concerning interaction between musculoskeletal pain and motor performance is lacking. Most studies in this field have been performed under static conditions which may not represent CLBP patients' daily-life routines. A standardized way to study the sensory-motor interaction under controlled motor performance is to induce experimental muscle pain by i.m. injection of hypertonic saline. The aim of the present controlled study was to analyze and compare electromyographic (EMG) activity of and coordination between lumbar muscles (8 paraspinal recordings) during gait in 10 patients with CLBP and in 10 volunteers exposed to experimental back muscle pain induced by bolus injection of 5% hypertonic saline. When the results are compared to sex- and age-matched controls, the CLBP patients showed significantly increased EMG activity in the swing phase; a phase where the lumbar muscles are normally silent. These changes correlated significantly to the intensity of the back pain. Similar EMG patterns were found in the experimental study together with a reduced peak EMG activity in the period during double stance where the back muscles are normally active. Generally, these changes were localized ipsilaterally to the site of pain induction. The clinical and experimental findings indicate that musculoskeletal pain modulates motor performance during gait probably via reflex pathways. Initially, these EMG changes may be interpreted as a functional adaptation to muscle pain, but the consequences of chronic altered muscle performance are not known. New possibilities to monitor and investigate altered motor performance may help to develop more rational therapies for CLBP patients.
This paper provides an overview of recent occupational injury and disease statistics from Western Australia, with a particular focus on manual handling injuries. The mechanisms for data collection and the limitations of the data sets are discussed. Information is presented to demonstrate the trends in injury data over an eight-year period. Breakdowns of estimates of new compensation cases by nature of injury, bodily location and mechanism of injury are discussed. The distribution of cases by age, gender and industry is also described. The implications of these data are discussed.Relevance to industryWhilst acknowledging their limitations, data sets such as that described here are useful for industry by providing an estimate of the scope and nature of the problem. Manual handling injuries are widely acclaimed as a persistent and common ergonomics problem. The added understanding of the problem afforded by such statistics assists with the recognition, assessment and control of the risks contributing to manual handling injuries. The statistics also provide benchmarks for organisation and industry comparisons.
A personal lift assist device (PLAD) was designed with passive elastic elements that act with a similar line of action to the spine muscles and reduce the extension moment experienced during lifting activities. The purpose of this paper was to evaluate the device's ability to reduce fatigue during a repetitive lifting task. Women (n = 12) lifted a box load representing 20% maximal extensor strength repetitively (12 lift/lowers per minute) for 45 min while electromyography (EMG) was recorded from the lumbar and thoracic erector spinae, and cardiovascular measures were monitored. Subjects were also tested on strength and endurance tests prior to, and after lifting. The increase in EMG RMS amplitude from the start until the end of the lifting session was significantly lower when wearing the PLAD for the TES (91% vs 3%) and the LES (104% vs 16%). The median frequency (MF) drop was also significantly lower when wearing the PLAD for TES and LES. The PLAD delayed the onset of fatigue in women by requiring less muscular effort.Relevance to industryThere are numerous industries that still require repetitive manual materials handling tasks to be performed by humans. Repetitive lifting fatigues the musculature involved and may lead to an increased risk of injury. The PLAD reduced fatigue on several measures. This device appears to have potential for industries where women perform repetitive, fatiguing lifts.
Rotator cuff syndrome (RCS) is a major health problem among workers. The aim of the study was to examine the risk factors for RCS among workers exposed to various levels of shoulder constraints.
From 3710 workers, representative of a French region`s working population, trained occupational physicians diagnosed a total of 142 cases of RCS among men and 132 among women between 2002-2005. Diagnoses were established by standardized physical examination while personal factors and work exposure were assessed by self-administered questionnaires. Statistical associations between RCS and personal and work-related factors were analyzed for each gender using logistic regression modeling.
The personal risk factors for RCS were age [odds ratio (OR) for 1-year increment 1.07, 95% confidence interval (95% CI) 1.05-1.09, among men and 1.08, 95% CI 1.06-1.10, among women] and diabetes mellitus (OR 2.9, 95% CI 1.0-8.6, among women). The work-related risk factors were (i) sustained or repeated arm abduction (≥ 2 hours/day) >90 degrees among men (OR 2.3, 95% CI 1.3-3.9) and >60 degrees among women (OR 1.8, 95% CI 1.0-3.2) or both conditions among men (OR 2.0, 95% CI 1.1-3.7) and women (OR 3.6, 95% CI 1.8-7.3); (ii) high repetitiveness of the task (≥ 4 hours/day) among men (OR 1.6, 95% CI 1.0-2.4) and women (OR 1.7, 95% CI 1.1-2.5); (iii) high perceived physical demand among men (OR 2.0, 95% CI 1.3-3.1); (iv) high psychological demand among men (OR 1.7, 95% CI 1.2-2.5); and (v) low decision authority among women (OR 1.5, 95% CI 1.0-2.3).
Personal (ie, age) and work-related physical (ie, arm abduction) and psychosocial factors were associated with RCS for both genders in this working population.
The personal lift-assist device (PLAD) is a non-motorised, on-body device that acts as an external force generator using the concept of stored elastic energy. In this study, the effect of the PLAD on the lifting kinematics of male and female lifters was investigated using principal component analysis. Joint kinematic data of 15 males and 15 females were collected using an opto-electronic system during a freestyle, symmetrical-lifting protocol with and without wearing the PLAD. Of the 31 Principal Components (PCs) retained in the models, eight scores were significantly different between the PLAD and no-PLAD conditions. There were no main effects for gender and no significant interactions. Results indicated that the PLAD similarly affected the lifting kinematics of males and females; demonstrating significantly less lumbar and thoracic flexion and significantly greater hip and ankle flexion when wearing the PLAD. These findings add to the body of work that suggest the PLAD may be a safe and effective ergonomic aid. STATEMENT OF RELEVANCE: The PLAD is an ergonomic aid that has been shown to be effective at reducing low back demands during manual materials handling tasks. This body of work establishes that the PLAD encourages safe lifting practices without adversely affecting lifting technique.
The personal lift-assist device (PLAD) is an on-body ergonomic aid that reduces low back physical demands through the restorative moment of an external spring element, which possesses a mechanical advantage over the erector spinae. Although the PLAD has proven effective at reducing low back muscular demand, spinal moments, and localized muscular fatigue during laboratory and industrial tasks, the effects of the device on the neuromuscular control of spinal stability during lifting have yet to be assessed. Thirty healthy subjects (15M, 15F) performed repetitive lifting for three minutes, at a rate of 10 lifts per minute, with and without the PLAD. Maximum finite-time Lyapunov exponents, representing short-term (λ(max-s)) and long-term (λ(max-l)) divergence were calculated from the measured trunk kinematics to estimate the local dynamic stability of the lumbar spine. Using a mixed-design repeated-measures ANOVA, it was determined that wearing the PLAD did not significantly change λ(max-s) (μ(NP)=0.335, μ(P)=0.321, p=0.225), but did significantly reduce λ(max-l) (μ(NP)=0.0024, μ(P)=-0.0011, p=0.014, η(2)=0.197). There were no between-subject effects of sex, or significant interactions (p>0.720). The present results indicated that λ(max-s) was not statistically different between the device conditions, but that the PLAD significantly reduced λ(max-l) to a negative (stable) value. This shows that subjects' neuromuscular systems were able to respond to local perturbations more effectively when wearing the device, reflecting a more stable control of spinal movements. These findings are important when recommending the PLAD for long-term industrial or clinical use.
It is generally thought that exercise is beneficial to alleviate pain. However, prolonged movement may lead to the development of painful injuries, because of the overload of low-threshold motor units. Especially in individuals with a pain condition, exercise prescription and the impact of fatigue is less clear. This may be because of the dual effects, aggravation and relief, which fatigue has on pain. The purpose of this review is to ascertain the relation between pain and the motor system, both in the development and management of pain. Recent studies show that fatigue alters pain-induced increases in corticomotor excitability and leads to within and between-muscle adaptations. Studies of acute pain have shown complex adaptations such as increased movement variability, which may be because of a search for motor solutions to prolong overall task performance. In contrast, chronic pain seems to limit movement duration, speed, and variability which could be protective in the short term but also counterproductive over time. Owing to these adaptations in movement strategies, pain chronicity may help to dictate exercise prescription. For example, the correct dosage of multimuscle, dynamic exercises would act to promote movement variability. Thus, it seems that exercise involving the use of different movement strategies could be effective in helping people to obtain exercise-induced benefits while avoiding injury and pain reaggravation.
The purpose of this study was to investigate the effectiveness and user acceptability of a Personal Lift-Assist Device (PLAD) at an automotive manufacturing facility, with operators who perform an on-line assembly process requiring forward bending and static holding. Surface EMG data were collected at six sites on the low back and abdomen, and an accelerometer was used to measure trunk inclination. Use of the PLAD significantly reduced the thoracic and lumbar erector spinae activity and EMG-predicted compression at the 10th, 50th, and 90th APDF percentile levels (p < or = 0.05), without significantly increasing rectus abdominus activity or trunk flexion. Similarly, ratings of perceived exertion were found to be significantly lower when wearing the PLAD (p = 0.006). Subjective opinions were positive, with 8/10 subjects indicating they would wear the device everyday. With slight changes, workers felt that the PLAD could be beneficial at reducing forces and discomfort in similar industrial or manual materials handling tasks that place excessive physical demands on the low back.
The PLAD (personal lift assistive device) was designed to reduce the lumbar moment during lifting and bending tasks via elastic elements. This investigation examined the effects of modulating the elastic stiffness. Thirteen men completed 90 lifts (15 kg) using 6 different PLAD stiffnesses in stoop, squat and freestyle lifting postures. The activity of 8 muscles were recorded (latissimus dorsi, thoracic and lumbar erector spinae, rectus abdominis, external oblique, gluteus maximus, biceps femoris and rectus femoris), 3D electromagnetic sensors tracked the motion of each segment and strain gauges measured the elastic tension. EMG data were rectified, filtered, normalized and integrated as a percentage of the lifting task. The highest PLAD tension elicited the greatest reduction in erector spinae activity (mean of thoracic and lumbar) in comparison to the no-PLAD condition for the stoop (37%), squat (38%), and freestyle (37%) lifts, while prompting comparable reductions in gluteus maximums and biceps femoris activity. The highest PLAD stiffness also elicited the greatest reduction in the integrated L4/L5 flexion moment for the stoop (19.0%), squat (18.4%) and freestyle (17.4%) lifts without changing peak lumbar flexion. Each increase in PLAD stiffness further reduced the muscle activity of the posterior chain and the dynamic lumbar moment.
In a preliminary investigation of 45 middle aged adult subjects, 20 with low-back pain (LBP) and 25 with healthy backs (HB), balance responses (body sway) were measured under different sensory conditions with computerized force plate stabilometry. Compared with HB subjects, in the most stable and then the least stable balance positions, the LBP subjects demonstrated significantly greater postural sway, kept their center of force (COF) significantly more posterior, and were significantly less likely to be able to balance on one foot with eyes closed. Based on subjective observations, the LBP subjects were more likely to fulcrum about the hip and back to maintain uprightness in challenging balance tasks compared with healthy controls who maintained their fulcrum for the COF around the ankle. Research is needed to determine the incidence of balance problems in LBP patients compared with controls. Effective physical therapy assessment and treatment of LBP patients may require attention to postural alignment, strength, flexibility, joint stability, balance reactions, and postural strategies.
In an era of automation, mechanization, and miniaturization, manual materials handling continues to constitute an occupational hazard of serious consequences. The "safe lifting method" attempts to reduce lifting stresses through proper positioning of individuals with respect to the weight being lifted. It does not consider any job/work modification, nor does it prescribe any specific capabilities of individuals assigned to the jobs. Through several examples, the pitfalls that may result from indiscriminate applications of the method to encompass all jobs under all situations are illustrated. (C)1982 The American College of Occupational and Environmental Medicine