Mathematical and empirical proof of principle for an on-body personal lift augmentation device (PLAD)

Effects of a lumbar exoskeleton that provides two traction forces on spinal loading and muscles

In workplaces with prolonged or repetitive stooping, disc herniation due to excessive pressure at the lumbar L5/S1 joints has been a difficult condition to prevent and treat in the field of lower back pain. Previous research on lumbar exoskeletons mainly focused on the impact of assistive torque on muscle activation, overlooking the fact that providing assistive torque is not the optimal approach when bending over with a low load. Instead, using traction force to reduce disc pressure is a more adaptable method to mitigate the risk of intervertebral disc herniation. In this paper, a novel lumbar exoskeleton mechanism is proposed. The exoskeleton principle is similar to a lever arranged on the torso, which provides two types of traction forces using a single compression spring with a lower support moment and higher traction performance. Subsequently, a kinetic simulation model covering passive physiologic tissues and spring stiffness was developed to determine the optimal range of traction forces for a given load, to predict the disc pressure and muscle activation at optimal traction forces. Eight subjects were invited to wear the exoskeleton for stooping and lifting tests under extreme loads, using myoelectric sensors to measure muscle activation. The results confirm that optimal traction force effectively reduces L5/S1 disc pressure without additionally increasing muscle activation. The exoskeleton in this study provides an alternative idea for the design of lumbar exoskeletons adapted to light load stooping.

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

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

Effects of an occupational soft-back exoskeleton during order picking: a field study in logistics

The use of exoskeletons is increasingly considered as a solution to reduce workers' exposure to physical risk factors, such as low-back disorders. The aim of this study was to evaluate the effects of the CORFOR® occupational soft-back exoskeleton on trunk muscle activity and kinematics during an order picking manual task performed in the field. 10 workers, with at least 4 weeks' experience using the exoskeleton, performed a 1.5-hour order picking task with and without the exoskeleton. Trunk muscle activity, upper-body kinematics and the exoskeleton's acceptance were assessed. Erector spinae muscle activity was significantly reduced by 7.5% with the use of the exoskeleton. Moreover, trunk flexor muscles activity, trunk kinematics, or low-back pain were not affected. Further, the acceptance of the exoskeleton was rated as favourable. Thus, at least in the test company, the integration of the CORFOR® exoskeleton for order picking tasks is promising.

Effects of a soft back exoskeleton on lower lumbar spine loads during manual materials handling: a musculoskeletal modelling study

The aim of this study was to append a passive soft back exoskeleton to a validated musculoskeletal model and assess its effectiveness in reducing lumbar loads. Fifteen participants lifted a box, with and without wearing a CORFOR® exoskeleton. A full body OpenSim model was used to estimate lumbar joint moments and reaction forces, as well as low back muscles forces. Wearing the exoskeleton reduced the peak flexion moment, muscles forces, as well as peak compressive and shear forces. This musculoskeletal modelling study shows that wearing the exoskeleton may reduce lumbar spine loads and may contribute to prevent low back disorders.

Musculoskeletal models determine the effect of a soft active exosuit on muscle activations and forces during lifting and lowering tasks

Exosuits have the potential to mitigate musculoskeletal stress and prevent back injuries during industrial tasks. This study aimed to 1) validate the implementation of a soft active exosuit into a musculoskeletal model of the spine by comparing model predicted muscle activations versus corresponding surface EMG measurements, and 2) evaluate the effect of the exosuit on peak back and hip muscle forces. Fourteen healthy participants performed squat and stoop lift and lower tasks with boxes of 6 and 10 kg, with and without wearing a 2.7 kg soft active exosuit. Participant-specific musculoskeletal models, which included the exosuit, were created in OpenSim. Model validation focused on the back and hip extensors, where temporal agreement between EMG and model estimated muscle activity was generally strong to excellent (average cross-correlation coefficients ranging from 0.84 to 0.98). Root mean square errors of muscle activity (0.05-0.10) were similar with and without the exosuit, and compared well to prior model validation studies without the exosuit (average root mean square errors ranging from 0.05 to 0.19). In terms of performance, the exosuit reduced the estimated peak erector spinae forces during lifting and lowering phases across all lifting tasks but reduced peak hip extensor muscles forces only in a squat lift task of 10 kg. These reductions in total peak muscle forces were approximately 1.7-4.2 times greater than the corresponding exosuit assistance force, which were 146 ± 19 N and 102 ± 14 N at the times of peak erector spinae forces in lifting and lowering, respectively. Overall, the results support the hypothesis that exosuits reduce soft tissue loading, and thereby potentially reduce fatigue and injury risk during manual materials handling tasks. Incorporating exosuits into musculoskeletal models is a valid approach to understand the impact of exosuit assistance on muscle activity and forces.

Can a Novel Light Weight Minimal Support Lifting Exoskeleton Modify Lifting Movement in People without Low Back Pain?

Low back pain (LBP) is a major contributor to lifting-related disabilities. To minimize the risk of back pain, emerging technologies known as lifting exoskeletons were designed to optimize lifting movements. However, it is currently unknown whether a minimally supportive exoskeleton can alter the lifting movement in people without LBP. This study aims to investigate if wearing a novel lightweight exoskeleton that minimally supports the back, hip, and knee can alter the lifting range of motion and movement variations in people without LBP. This study also aims to investigate if wearing this novel exoskeleton can result in a reliable between-day lifting movement. In two separate sessions (each one week apart), fourteen participants lifted a box (that weighed 10% of their body weight) ten times, once while wearing an exoskeleton and once while not wearing an exoskeleton. Wearing the novel exoskeleton during lifting produced moderate-high, test-retest reliability (Trunk: ICC3,1 = 0.89, 95% CI [0.67, 0.96], SEM = 9.34°; Hip: ICC3,1 = 0.63, 95% CI [0.22, 0.88], SEM = 2.57°; Knee: ICC3,1 = 0.61, 95% CI [0.23, 0.87], SEM = 2.50°). Wearing an exoskeleton significantly decreased the range of motion of the knee (F1,4 = 4.83, p = 0.031, ηp2 = 0.06). Additionally, wearing an exoskeleton significantly decreased hip (diff = 8.38, p = 0.045) and knee (diff = -8.57, p = 0.038) movement variability; however, wearing an exoskeleton did not decrease the movement variability of the body's trunk (diff = 0.60, p = 1.00). Therefore, minimally supported lifting through the use of exoskeletons can modify movement in people without LBP and produce reliable lifting movements. Wearing the novel exoskeleton is also desirable for monitoring lifting movements. Future studies should investigate the use of sensors and IMU to monitor lifting movement at work with the least amount of intrusion on an individual's movement.

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

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

Effects of an exoskeleton on muscle activity in tasks requiring arm elevation: Part I - Experiments in a controlled laboratory setting

BACKGROUND

Long-term work with elevated arms, or overhead work, is a risk factor for musculoskeletal complaints and disorders. Upper-limb exoskeletons are a promising tool for reducing occupational workload when working with hands above shoulder level.

OBJECTIVE

The purpose of this study was to assess the effects of upper-limb exoskeleton on muscular and physical strain and perceived exertion during dynamic work at four different shoulder joint angles. Further, we evaluated if there are any negative effects associated with the use of exoskeleton.

METHODS

A total of 15 student participants performed dynamic work in laboratory setting with and without an exoskeleton at four different shoulder angles: 60, 90, 120 and 150 degrees. Muscle electrical activity from 8 muscles of the upper body, perceived exertion, and heart rate were measured during the work task, and grip strength, muscle stiffness, tone, and elasticity from six muscles, m. deltoideus physiological cross-sectional area and muscle fiber pennation angle, and nerve conduction velocity were measured before and after the work task.

RESULTS

Based on the results, the use of exoskeleton significantly reduced the muscle activity of the upper limb, shoulder, and back muscles. The reduction was most significant when the arm elevation was 120°, and in m. deltoideus muscle activity. RPE was also positively affected indicating reduction in workload when using exoskeleton.

CONCLUSION

The results suggest that the use of upper limb exoskeleton has potential to reduce physical workload during overhead work and, consequently, reduce the risk for work-related musculoskeletal disorders.

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

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

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

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

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

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

Design and ergonomic assessment of a passive head/neck supporting exoskeleton for overhead work use

Overhead work is an important risk factor associated with musculoskeletal disorders of the neck and shoulder region. This study aimed to propose and evaluate a passive head/neck supporting exoskeleton (HNSE) as a potential ergonomic intervention for overhead work applications. Fourteen male participants were asked to perform a simulated overhead task of fastening/unfastening nut in 4 randomized sessions, characterized by two variables: neck extension angle (40% and 80% of neck maximum range of motion) and exoskeleton condition (wearing and not wearing the HNSE). Using the HNSE, significantly alleviated perceived discomfort in the neck (p-value = 0.009), right shoulder (p-value = 0.05) and left shoulder (p-value = 0.02) and reduced electromyographic activity of the right (p-value = 0.005) and left (p-value = 0.01) sternocleidomastoid muscles. However, utilizing the exoskeleton caused a remarkable increase in right (p-value = 0.04) and left (p-value = 0.05) trapezius electromyographic activities. Performance was not significantly affected by the HNSE. Although the HNSE had promising effects with respect to discomfort and muscular activity in the static overhead task, future work is still needed to investigate its effect on performance and to provide support for the generalizability of study results.

A Lower-Back Exoskeleton with a Four-bar Linkage Structure for Providing Extensor Moment and Lumbar Traction Force

Lower back pain and related injuries are prevalent and serious problems in various industries, and high compression force to the lumbosacral (L5/S1) region has been known as one of the key factors. Previous research on passive lower back exoskeletons focused on reducing lumbar muscle activation by providing an extensor moment. Additionally, lumbar traction forces can reduce the compression force, and is a common treatment method for lower back pain in clinics. In this paper, we propose a novel passive lower back exoskeleton that provides both extensor moment and lumbar traction force. The working principle of the exoskeleton, extending the coil springs during lumbar flexion, and its design criteria regarding the amount of each force element were provided. The kinematic model explained its operation, and the dynamic simulation estimated its performance and validated its satisfaction with the design criteria. The biomechanical model provided a brief insight into the expected exoskeleton's effect on the reduced lower back compression force. Ten subjects performed static holding and dynamic lifting tasks, and the generated force elements in two directions, parallel and perpendicular to the trunk, were evaluated using a force sensor and electromyography sensors, respectively. The experiment demonstrated a pulling force opposite to the direction of intradiscal pressure and reduced erector spinae activation. This implies the effect of wearing the exoskeleton to decrease the intervertebral pressure during static back bending or heavy lifting tasks.

Methodologies for evaluating exoskeletons with industrial applications

Industrial exoskeletons are globally developed, explored, and increasingly implemented in industrial workplaces. Multiple technical, physical, and psychological aspects should be assessed prior to their daily application in various occupational environments. The methodology for evaluating these aspects is not standardised and differs in terms of focussed research objectives, used types of analyses, applied testing procedures, and use cases. The aim of this paper is to provide a matrix comparing the prevalence of different types of analyses combined with their respective research objective(s). A systematic review in the database 'Web of Science' identified 74 studies, mainly in laboratory settings, with a focus on short-term effects as well as with male-dominated samples being low representative for industrial workforces. The conducted evaluation methodologies are further discussed and compared in terms of testing procedure, sample, and research objectives. Finally, relevant aspects for prospectively evaluating industrial exoskeletons in a more harmonised and comprehensive way are suggested. Practitioner summary: Industrial exoskeletons are still inconsistently and insufficiently evaluated in scientific studies, which might hamper the comparability of systems, threaten the human health, and block an iterative system optimisation. Thus, a comprehensive evaluation methodology is needed with harmonised and multicriteria types of analyses.

An ergonomic assessment tool for evaluating the effect of back exoskeletons on injury risk

Low back disorders (LBDs) are a leading injury in the workplace. Back exoskeletons (exos) are wearable assist devices that complement traditional ergonomic controls and reduce LBD risks by alleviating musculoskeletal overexertion. However, there are currently no ergonomic assessment tools to evaluate risk for workers wearing back exos. Exo-LiFFT, an extension of the Lifting Fatigue Failure Tool, is introduced as a means to unify the etiology of LBDs with the biomechanical function of exos. We present multiple examples demonstrating how Exo-LiFFT can assess or predict the effect of exos on LBD risk without costly, time-consuming electromyography studies. For instance, using simulated and real-world material handling data we show an exo providing a 30 Nm lumbar moment is projected to reduce cumulative back damage by ∼70% and LBD risk by ∼20%. Exo-LiFFT provides a practical, efficient ergonomic assessment tool to assist safety professionals exploring back exos as part of a comprehensive occupational health program.

Low-Cost Force Sensors Embedded in Physical Human-Machine Interfaces: Concept, Exemplary Realization on Upper-Body Exoskeleton, and Validation

In modern times, the collaboration between humans and machines increasingly rises, combining their respective benefits. The direct physical support causes interaction forces in human-machine interfaces, whereas their form determines both the effectiveness and comfort of the collaboration. However, their correct detection requires various sensor characteristics and remains challenging. Thus, this paper presents a developed low-cost sensor pad working with a silicone capsule and a piezoresistive pressure sensor. Its measurement accuracy is validated in both an isolated testing environment and a laboratory study with four test subjects (gender-balanced), and an application integrated in interfaces of an active upper-body exoskeleton. In the material-testing machine, it becomes apparent that the sensor pad generally features the capability of reliably determining normal forces on its surface until a certain threshold. This is also proven in the real application, where the measurement data of three sensor pads spatially embedded in the exoskeletal interface are compared to the data of an installed multi-axis load cell and a high-resolution flexible pressure map. Here, the consideration of three sensor pads potentially enables detection of exoskeletal support on the upper arm as well as "poor" fit conditions such as uneven pressure distributions that recommend immediate system adjustments for ergonomic improvements.

Benchmarking occupational exoskeletons: An evidence mapping systematic review

OBJECTIVES

To provide an overview of protocols assessing the effect of occupational exoskeletons on users and to formulate recommendations towards a literature-based assessment framework to benchmark the effect of occupational exoskeletons on the user.

METHODS

PubMed (MEDLINE), Web of Science database and Scopus were searched (March 2, 2021). Studies were included if they investigated the effect of one or more occupational exoskeletons on the user.

RESULTS

In total, 139 eligible studies were identified, encompassing 33, 25 and 18 unique back, shoulder and other exoskeletons, respectively. Device validation was most frequently conducted using controlled tasks while collecting muscle activity and biomechanical data. As the exoskeleton concept matures, tasks became more applied and the experimental design more representative. With that change towards realistic testing environments came a trade-off with experimental control, and user experience data became more valuable.

DISCUSSION

This evidence mapping systematic review reveals that the assessment of occupational exoskeletons is a dynamic process, and provides literature-based assessment recommendations. The homogeneity and repeatability of future exoskeleton assessment experiments will increase following these recommendations. The current review recognises the value of variability in evaluation protocols in order to obtain an overall overview of the effect of exoskeletons on the users, but the presented framework strives to facilitate benchmarking the effect of occupational exoskeletons on the users across this variety of assessment protocols.

Multijoint passive elastic spine exoskeleton for stoop lifting assistance

In the task of carrying heavy objects, it is easy to cause back injuries and other musculoskeletal diseases. Although wearable robots are designed to reduce this danger, most existing exoskeletons use high-stiffness mechanisms, which are beneficial to load-bearing conduction, but this restricts the natural movement of the human body, thereby causing ergonomic risks. This article proposes a back exoskeleton composed of multiple elastic spherical hinges inspired by the biological spine. This spine exoskeleton can assist in the process of bending the body and ensure flexibility. We deduced the kinematics model of this mechanism and established an analytical biomechanical model of human–robot interaction. The mechanism of joint assistance of the spine exoskeleton was discussed, and experiments were conducted to verify the flexibility of the spine exoskeleton and the effectiveness of the assistance during bending.

Challenges and solutions for application and wider adoption of wearable robots

The science and technology of wearable robots are steadily advancing, and the use of such robots in our everyday life appears to be within reach. Nevertheless, widespread adoption of wearable robots should not be taken for granted, especially since many recent attempts to bring them to real-life applications resulted in mixed outcomes. The aim of this article is to address the current challenges that are limiting the application and wider adoption of wearable robots that are typically worn over the human body. We categorized the challenges into mechanical layout, actuation, sensing, body interface, control, human-robot interfacing and coadaptation, and benchmarking. For each category, we discuss specific challenges and the rationale for why solving them is important, followed by an overview of relevant recent works. We conclude with an opinion that summarizes possible solutions that could contribute to the wider adoption of wearable robots.

Systematic Review of Back-Support Exoskeletons and Soft Robotic Suits

Lower back pain and musculoskeletal injuries are serious concerns for workers subjected to physical workload and manual material handling tasks. Spine assistive exoskeletons are being developed to support the spine and distribute the spine load. This article presents a detailed up-to-date review on the back support exoskeletons by discussing their type (Active/Passive), structure (Rigid/Soft), power transmission methods, weight, maximum assistive force, battery technologies, tasks (lifting, bending, stooping work), kinematic compatibility and other important features. This article also assesses the back support exoskeletons in terms of their ability to reduce the physical load on the spine. By reviewing functional and structural characteristics, the goal is to increase communication and realization among ergonomics practitioners, developers, customers, and factory workers. The search resulted in reviewing 34 exoskeletons of which 16 were passive and 18 were active. In conclusion, back support exoskeletons have immense potential to significantly reduce the factors regarding work-related musculoskeletal injuries. However, various technical challenges and a lack of established safety standards limit the wide adaptation of exoskeletons in industry.

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

This study is an updated systematic review of papers published in the last 5 years on industrial back-support exoskeletons. The research questions were aimed at addressing the recent findings regarding objective (e.g. body loading, user performance) and subjective evaluations (e.g. user satisfaction), potential side effects, and methodological aspects of usability testing. Thirteen studies of active and twenty of passive exoskeletons were identified. The exoskeletons were tested during lifting and bending tasks, predominantly in laboratory settings and among healthy young men. In general, decreases in participants' back-muscle activity, peak L5/S1 moments and spinal compression forces were reported. User endurance during lifting and static bending improved, but performance declined during tasks that required increased agility. The overall user satisfaction was moderate. Some side effects were observed, including increased abdominal/lower-limb muscle activity and changes in joint angles. A need was identified for further field studies, involving industrial workers, and reflecting actual work situations. Practitioner summary: Due to increased research activity in the field, a systematic review was performed of recent studies on industrial back-support exoskeletons, addressing objective and subjective evaluations, side effects, and methodological aspects of usability testing. The results indicate the efficiency of exoskeletons in back-load reduction and a need for further studies in real work situations. Abbrevaitions: BB: biceps brachii; BF: biceps femoris; CoM: centre of mass; DA: deltoideus anterior; EMG: electromyography; ES: erector spinae; ES-C: erector spinae-cervical; ESI: erector spinae iliocostalis; ESI-L: erector spinae iliocostalis-lumborum; ESL: erector spinae longissimus; ES-L: erector spinae-lumbar; ESL-L: erector spinae longissimus-lumborum; ESL-T: erector spinae longissimus-thoracis; ES-T: erector spinae-thoracic; GM: glutaeus maximus; LBP: low back pain; LD: latissimus dorsi; LPD: local perceived discomfort scale; LPP: local perceived pressure scale; MS: multifidus spinae; MSD: musculoskeletal disorder; M-SFS: modified spinal function sort; NMV: no mean value provided; OA: obliquus abdominis (internus and externus); OEA: obliquus externus abdominis; OIA : obliquus internus abdominis; RA: rectus abdominis; RF: rectus femoris; RoM: range of motion; SUS: system usability scale; T: trapezius (pars Ascendens and Descendens); TA: trapezius pars ascendens; TC: mid-cervical trapezius; TD: trapezius pars descendens; VAS: visual analog scale; VL: vastus lateralis; VM: vastus medialis.

Human pressure tolerance and effects of different padding materials with implications for development of exoskeletons and similar devices

In this study, we assessed pressure tolerance in 16 healthy participants at the thigh, chest, and pelvic area, using different surfaces (1 cm², 20 cm² and different components, used in exoskeleton design), and the effects of different padding materials. Our results showed substantial variability in pressure tolerance among the participants, as well as lower pressure tolerance in females. Regarding the force applied with the exoskeleton components, male participants had higher discomfort threshold (230.3 ± 44.9 N compared to females (116.1 ± 24.6 N) in the chest area. For the applications with 20 cm² surface, the males also showed higher pain threshold at the thigh (89.3 ± 41.8 N vs. 34.6 ± 27.2 N) and the pelvis (97.6 ± 37.0 N vs. 56.1 ± 29.5 N). All padding materials increased pressure tolerance for 10-38% (p < 0.001), but little differences between materials were observed.

Design, modeling, and demonstration of a new dual-mode back-assist exosuit with extension mechanism

Occupational exoskeletons and exosuits have been shown to reduce muscle demands and fatigue for physical tasks relevant to a variety of industries (e.g. logistics, construction, manufacturing, military, healthcare). However, adoption of these devices into the workforce has been slowed by practical factors related to comfort, form-factor, weight, and not interfering with movement or posture. We previously introduced an un-motorized, low-profile, dual-mode exosuit comprised of textile and elastic materials to address these adoption barriers. Here we build upon this prior work by introducing an extension mechanism that increases the moment arm of the exosuit while in engaged mode, then collapses in disengaged mode to retain key benefits related to being lightweight, low-profile, and unobstructive. Here we demonstrate both analytically and empirically how this extensible exosuit concept can (i) reduce device-to-body forces (which can improve comfort for some users and situations), or (ii) increase the magnitude of torque assistance about the low back (which may be valuable for heavy-lifting jobs) without increasing shoulder or leg forces relative to the prior form-fitting exosuit. We also introduce a novel mode-switching mechanism, as well as a human-exosuit biomechanical model to elucidate how individual design parameters affect exosuit assistance torque and device-to-body forces. The proof-of-concept prototype, case study, and modeling work provide a foundation for understanding and implementing extensible exosuits for a broad range of applications. We envision promising opportunities to apply this new dual-mode extensible exosuit concept to assist heavy-lifting, to further enhance user comfort, and to address the unique needs of last-mile delivery workers.

Kinematic effects of a passive lift assistive exoskeleton

The VT-Lowe's exoskeleton was designed to help support the back during repetitive lifting tasks. This study focused on the kinematic differences between lifting with and without the exoskeleton (With-Exo and Without-Exo) over three different lifting styles (Freestyle, Squat, and Stoop) and two different box weights (0% and 20% of bodyweight). Twelve young and healthy males (Age 23.5 +/- 4.42 years; Height 179.33 +/- 6.37 cm; Weight 80.4 +/- 5.59 kg) participated in this study. Variables analyzed include the ankle and knee angles and angle between the Shoulder-Hip-Knee (SHK); the shoulder, elbow, and wrist heights; and the lifting speed and acceleration. The relationships between the torso angle, SHK angle, center of mass of the torso, torso torque, box height, as well as electromyography (EMG) data from a related study were also analyzed. On average, wearing the exoskeleton resulted in a 1.5 degree increase in ankle dorsiflexion, a 2.6 degree decrease in knee flexion, and a decrease of 2.3 degrees in SHK angle. Subjects' shoulder, elbow, and wrist heights were slightly higher while wearing the exoskeleton, and they lifted slightly more slowly while wearing the exoskeleton. Subjects moved more quickly while bending down as compared to standing up, and with the 0% bodyweight box as compared to the 20% bodyweight box. The values for Freestyle lifts generally fell in between Squat and Stoop lift styles or were not significantly different from Squat. EMG data from the leg muscles had relationships with torso torque while the back and stomach muscles showed no significant relationships.

Passive Trunk Exoskeleton Acceptability and Effects on Self-efficacy in Employees with Low-Back Pain: A Mixed Method Approach

Purpose Determinants of successfully introducing passive exoskeletons in the working environment to decrease mechanical loading on the back, are acceptability of the device to management and employees, including self-efficacy of employees when using the device. Therefore, the aim of this study was to assess self-efficacy of employees with low-back pain when using an exoskeleton and the acceptability of such a device to these employees and their managers. Methods We used a mixed method approach. We quantitatively assessed the change in self-efficacy of 17 employees with low-back pain when performing daily activity tasks with the exoskeleton, using the modified spinal function sort (M-SFS). Qualitatively, we conducted a focus group with employees and a double interview with two managers to add more insight and understandings into changes in self-efficacy and to discuss challenges of implementing an exoskeleton in the working environment. Results Self-efficacy significantly increased by 7% when using the exoskeleton. Employees acknowledged the flexibility of the exoskeleton being advantageous to current static external lifting devices, which confirmed the increase of self-efficacy in both static and dynamic tasks. Individual data showed that the increase in self-efficacy was largest for participants, being greatly restricted by their low-back pain. In the focus group, employees confirmed that they are mostly open to wearing the exoskeleton if they suffer from low-back pain. Conclusion If potential challenges, e.g. visibility and potential refusal of wearing an exoskeleton are considered in the implementation strategy, acceptability of and self-efficacy in using the passive trunk exoskeleton would be further improved, potentially contributing to reduced risk of low-back pain.

Short-Term Effects of a Passive Spinal Exoskeleton on Functional Performance, Discomfort and User Satisfaction in Patients with Low Back Pain

Purpose Low back pain (LBP) remains a major worldwide healthcare issue. Recently, spinal exoskeletons were proposed as a potentially useful solution for LBP prevention and vocational reintegration for people who perform heavy load lifting, repetitive movements or work in prolonged static postures. The purpose of this study was to investigate how patients with LBP respond to the novel passive SPEXOR exoskeleton regarding functional performance, discomfort and general user impression. Methods Fourteen patients, with low to moderate LBP (2-7 on a 0-10 scale), performed 12 functional tasks with and without the exoskeleton. In addition to objective performance measures, participants subjectively assessed the level of local low back discomfort, task difficulty and general discomfort on a 0-10 visual analogue scales. Results The SPEXOR exoskeleton had favourable effects on performance and local discomfort during prolonged static forward bending. Minor reductions in performance were observed for sit-stand and ladder climbing tasks. The discomfort associated with the exoskeleton was generally low to moderate (median < 4), except for the 6-min walk test (median = 4.5), which is likely due to the weight of the device and obstruction of upper limb movement. The general impressions were mostly positive, with good adjustability, low interference with the movement and moderate support reported by the participants. Conclusion The SPEXOR exoskeleton is potentially useful for LBP prevention or management, however, further improvements are needed to provide higher levels support during heavy load lifting.

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

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

Review of Current Spinal Robotic Orthoses

Osteoporotic spine fractures (OSF) are common sequelae of osteoporosis. OSF are directly correlated with increasing age and incidence of osteoporosis. OSF are treated conservatively or surgically. Associated acute pain, chronic disabilities, and progressive deformities are well documented. Conservative measures include a combination of initial bed rest, analgesia, early physiotherapy, and a spinal brace (orthosis), with the aim for early rehabilitation to prevent complications of immobile state. Spinal bracing is commonly used for symptomatic management of OSF. While traditional spinal braces aim to maintain the neutral spinal alignment and reduce the axial loading on the fractured vertebrae, they are well known for complications including discomfort with reduced compliance, atrophy of paraspinal muscles, and restriction of chest expansion leading to chest infections. Exoskeletons have been developed to passively assist and actively augment human movements with different types of actuators. Flexible, versatile spinal exoskeletons are designed to better support the spine. As new technologies enable the development of motorized wearable exoskeletons, several types have been introduced into the medical field application. We have provided a thorough review of the current spinal robotic technologies in this paper. The shortcomings in the current spinal exoskeletons were identified. Their limitations on the use for patients with OSF with potential improvement strategies were discussed. With our current knowledge of spinal orthosis for conservatively managed OSF, a semi-rigid backpack style thoracolumbar spinal robotic orthosis will reduce spinal bone stress and improve back muscle support. This will lead to back pain reduction, improved posture, and overall mobility. Early mobilization is an important part of management of patients with OSF as it reduces the chance of developing complications related to their immobile state for patients with OSF, which will be helpful for their recovery.

Design and preliminary evaluation of a flexible exoskeleton to assist with lifting

We present a passive (unpowered) exoskeleton that assists the back during lifting. Our exoskeleton uses carbon fiber beams as the sole means to store energy and return it to the wearer. To motivate the design, we present general requirements for the design of a lifting exoskeleton, including calculating the required torque to support the torso for people of different weights and heights. We compare a number of methods of energy storage for exoskeletons in terms of mass, volume, hysteresis, and cycle life. We then discuss the design of our exoskeleton, and show how the torso assembly leads to balanced forces. We characterize the energy storage in the exoskeleton and the torque it provides during testing with human subjects. Ten participants performed freestyle, stoop, and squat lifts. Custom image processing software was used to extract the curvature of the carbon fiber beams in the exoskeleton to determine the stored energy. During freestyle lifting, it stores an average of 59.3 J and provides a peak torque of 71.7 Nm.

Reliability of a battery of tests for functional evaluation of trunk exoskeletons

Recently, several spinal exoskeletons were developed with the aim to assist occupational tasks such as load-handling and work in prolonged static postures. While the biomechanical effects of such devices has been well investigated, only limited feedback to the developers is usually provided regarding the subjective perceptions of the end-users. The aim of this study was to present a novel battery of tests, designed to assess functional performance and subjective outcomes during the use of assistive trunk exoskeletons, and to assess its test-retest reliability. The battery of tests consists of 12 different simple functional tasks. Twenty participants were included in an intra-session reliability test and repeated the tests within 7-10 days to assess inter-session reliability. They were wearing a novel passive spinal exoskeleton during all trials. The outcomes included quantitative and subjective measures, such as performance time and rating of discomfort and perceived task difficulty. The majority of the outcome measures were reliable within session and between sessions (ICC or α > 0.80). Systematic effects were observed in a few tasks, suggesting that familiarization trials will be needed to minimize the learning effects. The novel battery of tests could become an important easy-to-use tool for functional testing of the spinal exoskeletons in addition to more specific biomechanical and physiological testing. Further studies should address the reliability of the present battery of tests for assessing specific populations, such as low back pain patients and explore how to minimize systematic effects that were observed in this study.

Perspectives of End Users on the Potential Use of Trunk Exoskeletons for People With Low-Back Pain: A Focus Group Study

OBJECTIVE

The objective of this study was to identify criteria to be considered when developing an exoskeleton for low-back pain patients by exploring the perceptions and expectations of potential end users.

BACKGROUND

Psychosocial, psychological, physical load, and personality influence incidence of low-back pain. Body-worn assistive devices that passively support the user's trunk, that is exoskeletons, can decrease mechanical loading and potentially reduce low-back pain. A user-centered approach improves patient safety and health outcomes, increases user satisfaction, and ensures usability. Still, previous studies have not taken psychological factors and the early involvement of end users into account.

METHOD

We conducted focus group studies with low-back pain patients (n = 4) and health care professionals (n = 8). Focus group sessions were audio-recorded, transcribed, and analyzed, using the general inductive approach. The focus group discussions included trying out an available exoskeleton. Questions were designed to elicit opinions about exoskeletons, desired design specifications, and usability.

RESULTS

Important design characteristics were comfort, individual adjustability, independency in taking it on and off, and gradual adjustment of support. Patients raised concerns over loss of muscle strength. Health care professionals mentioned the risk of confirming disability of the user and increasing guarded movement in patients.

CONCLUSION

The focus groups showed that implementation of a trunk exoskeleton to reduce low-back pain requires an adequate implementation strategy, including supervision and behavioral coaching.

APPLICATION

For health care professionals, the optimal field of application, prevention or rehabilitation, is still under debate. Patients see potential in an exoskeleton to overcome their limitations and expect it to improve their quality of life.

Classification of Lifting Techniques for Application of A Robotic Hip Exoskeleton

The number of exoskeletons providing load-lifting assistance has significantly increased over the last decade. In this field, to take full advantage of active exoskeletons and provide appropriate assistance to users, it is essential to develop control systems that are able to reliably recognize and classify the users' movement when performing various lifting tasks. To this end, the movement-decoding algorithm should work robustly with different users and recognize different lifting techniques. Currently, there are no studies presenting methods to classify different lifting techniques in real time for applications with lumbar exoskeletons. We designed a real-time two-step algorithm for a portable hip exoskeleton that can detect the onset of the lifting movement and classify the technique used to accomplish the lift, using only the exoskeleton-embedded sensors. To evaluate the performance of the proposed algorithm, 15 healthy male subjects participated in two experimental sessions in which they were asked to perform lifting tasks using four different techniques (namely, squat lifting, stoop lifting, left-asymmetric lifting, and right-asymmetric lifting) while wearing an active hip exoskeleton. Five classes (the four lifting techniques plus the class "no lift") were defined for the classification model, which is based on a set of rules (first step) and a pattern recognition algorithm (second step). Leave-one-subject-out cross-validation showed a recognition accuracy of 99.34 ± 0.85%, and the onset of the lift movement was detected within the first 121 to 166 ms of movement.

Impact of two postural assist exoskeletons on biomechanical loading of the lumbar spine

This study evaluated loading on the low back while wearing two commercially available postural assist exoskeletons. Ten male subjects lifted a box from multiple lift origins (combinations of vertical height and asymmetry) to a common destination using a squatting lifting technique with and without the use of either exoskeleton. Dependent measures included subject kinematics, moment arms between the torso or weight being lifted and the lumbar spine, and spinal loads as predicted by an electromyography-driven spine model. One of the exoskeletons tested (StrongArm Technologies™ FLx) reduced peak torso flexion at the shin lift origin, but differences in moment arms or spinal loads attributable to either of the interventions were not observed. Thus, industrial exoskeletons designed to control posture may not be beneficial in reducing biomechanical loads on the lumbar spine. Interventions altering the external manual materials handling environment (lift origin, load weight) may be more appropriate when implementation is fesible.

Feasibility of a Biomechanically-Assistive Garment to Reduce Low Back Loading During Leaning and Lifting

GOAL

The purpose of this study was: 1) to design and fabricate a biomechanically-assistive garment which was sufficiently lightweight and low-profile to be worn underneath, or as, clothing, and then 2) 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 eight 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.

Passive Back Support Exoskeleton Improves Range of Motion Using Flexible Beams

In the EU, lower back pain affects more than 40% of the working population. Mechanical loading of the lower back has been shown to be an important risk factor. Peak mechanical load can be reduced by ergonomic interventions, the use of cranes and, more recently, by the use of exoskeletons. Despite recent advances in the development of exoskeletons for industrial applications, they are not widely adopted by industry yet. Some of the challenges, which have to be overcome are a reduced range of motion, misalignment between the human anatomy and kinematics of the exoskeleton as well as discomfort. A body of research exists on how an exoskeleton can be designed to compensate for misalignment and thereby improve comfort. However, how to design an exoskeleton that achieves a similar range of motion as a human lumbar spine of up to 60° in the sagittal plane, has not been extensively investigated. We addressed this need by developing and testing a novel passive back support exoskeleton, including a mechanism comprised of flexible beams, which run in parallel to the spine, providing a large range of motion and lowering the peak torque requirements around the lumbo-sacral (L5/S1) joint. Furthermore, we ran a pilot study to test the biomechanical (N = 2) and functional (N = 3) impact on subjects while wearing the exoskeleton. The biomechanical testing was once performed with flexible beams as a back interface and once with a rigid structure. An increase of more than 25% range of motion of the trunk in the sagittal plane was observed by using the flexible beams. The pilot functional tests, which are compared to results from a previous study with the Laevo device, suggest, that the novel exoskeleton is perceived as less hindering in almost all tested tasks.

A Real-Time Lift Detection Strategy for a Hip Exoskeleton

Repetitive lifting of heavy loads increases the risk of back pain and even lumbar vertebral injuries to workers. Active exoskeletons can help workers lift loads by providing power assistance, and therefore reduce the moment and force applied on L5/S1 joint of human body when performing lifting tasks. However, most existing active exoskeletons for lifting assistance are unable to automatically detect user's lift movement, which limits the wide application of active exoskeletons in factories. In this paper, we propose a simple but effective lift detection strategy for exoskeleton control. This strategy uses only exoskeleton integrated sensors, without any extra sensors to capture human motion intentions. This makes the lift detection system more practical for applications in manufacturing environments. Seven healthy subjects participated in this research. Three different sessions were carried out, two for training and one for testing the algorithm. In the two training sessions, subjects were asked to wear a hip exoskeleton, controlled in transparent mode, and perform repetitive lifting and a locomotion circuit; lifting was executed with different techniques. The collected data were used to train the lift detection model. In the testing session, the exoskeleton was controlled in order to deliver torque to assist the lifting action, based on the lift detection made by the trained algorithm. The across-subject average accuracy of lift detection during online test was 97.97 ± 1.39% with subject-dependent model. Offline, the algorithm was trained with data acquired from all subjects to verify its performance for subject-independent detection, and an accuracy of 97.48 ± 1.53% was achieved. In addition, timeliness of the algorithm was quantitatively evaluated and the time delay was <160 ms across different lifting speeds. Surface electromyography was also measured to assess the efficacy of the exoskeleton in assisting subjects in performing load lifting tasks. These results validate the promise of applying the proposed lift detection strategy for exoskeleton control aiming at lift assistance.

Biomechanical evaluation of exoskeleton use on loading of the lumbar spine

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.

Towards low back support with a passive biomimetic exo-spine

Low-Back Pain (LBP) affects a large portion of the working population. Preventive exoskeletons have been proposed to reduce the moments on the lower back, specifically around the lumbosacral (L5/S1) joint. High correlation has been shown, between reducing the moments around the L5/S1 joint and intervertebral compression forces, which in turn have been identified as a risk factor for developing LBP. However, most passive back support exoskeletons use rigid plates or stiff beams to support the spine that limit the range of motion of the wearer. A large range of motion and versatility are especially desirable for industrial applications. To overcome these limitations, a passive biomimetic exo-spine has been designed, modelled and an initial prototype tested. Its potential to allow for a large range of motion, whilst at the same time limiting the most extreme and potentially harmful postures has been shown.

Physiological consequences of using an upper limb exoskeleton during manual handling tasks

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.

Exoskeletons for industrial application and their potential effects on physical work load

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).

INVESTIGATION ON A DEVELOPED WEARABLE ASSISTIVE DEVICE (WAD) IN REDUCTION LUMBAR MUSCLES ACTIVITY

A new wearable assistive device (WAD) was developed to decrease required force on the lumbar spine in static holding tasks. In order to obtain moments on lumbar spine in two conditions, with and without WAD, a biomechanical static model was used for estimation of external moments on lumbar spine. The results of biomechanical models indicated that there was a reduction in the lumbar moment ranging from 20% to 43% using WAD depending on the load and flexion angle. A total of 15 male healthy subjects were tested to experimentally verify the predicted reduction of external moments on the spine by wearing WAD. Normalized electromyography (EMG) of the right and left lumbar and thoracic erector spinae (LES, TES), latissimus dorsi (LD), external oblique (EO), internal oblique (IO) and rectus abdominus (RA) muscles were monitored at three lumbar flexion positions (0°, 30° and 60°) in symmetric posture with three different loads (0, 5 and 15 kg) in two conditions of with and without WAD. The effects of WAD and load were significant for all muscles but the interaction effects were only significant for extensor muscles groups (p < 0.016). Results of statistical analysis (ANOVA) on the normalized EMG while wearing WAD indicated that the muscle activity of right and left LES, TES and LD muscles significantly decreased (p < 0.001). This reduction for right LES, TES, LD muscles at 15 kg load and 60° trunk flexion were 23.2%, 30% and 27.8%, respectively which were in good agreement with the biomechanical model results.