Lifting Tasks Research Articles

Einfluss eines passiven Exoskeletts zur Rückenunterstützung auf die subjektive körperliche Beanspruchung und subjektive Beschwerdewahrnehmung bei simulierten Tätigkeiten mit statischer Oberkörpervorneigung und dynamischen Hebebewegungen

Influence of a passive trunk exoskeleton on subjective physical strain and perceived discomfort during simulated tasks with static trunk flexion posture and dynamic lifting Objective: The influence of a passive back-supporting exoskeleton on perceived physical strain and discomfort was investigated in two occupational tasks. Methods: Thirty-six men (average age 26 years) performed simulated occupational tasks with and without the Laevo® exoskeleton in a balanced and randomised within-subject design. One of the activities was a dynamic lifting task (2 x 5 lifting processes, 11.6 kg load), which was performed with and without exoskeleton in a stoop (stretched knees) and squat position (flexed knees). The second activity was a 90-second sorting task with a static and 40° flexed upper body posture. Subjective physical strain was recorded by the “physical demand” dimension of the NASA-TLX questionnaire, discomfort by an 11-level numeric rating scale. The localisation of discomfort was also reported. The differences between the conditions with and without exoskeleton were analysed for both tasks and lifting postures (stretched vs. flexed knees). Results: With exoskeleton, there was always a small reduction in perceived physical strain levels (p < 0.05). Discomfort was rare, low and mainly in the lower back. For the sorting task with exoskeleton, the median level of discomfort intensity was one point lower (p < 0.05) than without exoskeleton. The frequency of discomfort was also lower with exoskeleton. There were no differences in the intensity of discomfort during dynamic lifting. When the exoskeleton was applied during lifting with stretched knee joints, the frequency of discomfort was slightly reduced; no differences occurred with flexed knee joints. Conclusion: The main potential of the studied exoskeleton appears to lie in activities with a static bent upper body posture. Longitudinal studies with a randomised controlled design are necessary to evaluate whether the possible potential described here is relevant to the prevention of work-related back complaints. Keywords: workplace design – back pain – assistive device

Beyond the mechanical lens: Systemic inflammatory responses to repetitive lifting under varying loads and frequencies

ObjectiveCurrently, low back disorder (LBD) research focuses primarily on mechanical variables to assess whether task demands exceed tissue capacity; however, it is important to assess how other nonmechanical variables affect tissue capacity in a time-dependent manner. The current investigation sought to explore physiological responses to an acute lifting task, as lifting has been implicated as a risk factor in the development of LBDs. MethodsTwelve participants completed two sessions of 2 h of repetitive symmetrical lifting from floor to knuckle height under two conditions, matched for total external work (Low Force High Repetition (LFHR) and High Force Low Repetition (HFLR)). Full-body kinematics and ground reaction forces were measured throughout. Interleukin 6 (IL-6) and interleukin 8 (IL-8), markers of systemic inflammation, were assessed from blood sampling at Baseline, 0, 4 and 24 h post-lifting on both days. Dual x-ray absorptiometry (DEXA) scans were also performed on participants to quantify body composition. ResultsSignificant load (HFLR and LFHR) * time (Baseline, 0, 4, 24 h) interaction effects were found for both IL-6 and IL-8, where the LFHR condition resulted in greater responses at 0 and 4 h post-lifting. ConclusionsThis was the first study of its kind to concurrently measure peak and cumulative spinal moments and their relationship to systemic inflammation in both sexes, while strictly controlling for confounding variables (e.g. physical activity, caloric intake, body composition, etc.). Greater levels of IL-6 and IL-8 were seen in the LFHR condition, likely due to the greater cumulative spinal moments in this condition.

Multi-Objective Optimization Method for Posture Prediction of Symmetric Static Lifting Using a Three-Dimensional Human Model

Background: The development of virtual human models has recently gained considerable attention in biomechanical studies intending to design for ergonomics. The computer-based simulations of virtual human models can reduce the time and cost of the design cycle. There is an increasing interest in finding the realistic posture of the human body with applications in prototype design and reduction of injuries in the workplace. Objectives: This paper presents a generic method based on a multi-objective optimization (MOO) for posture prediction of a sagittal-plane lifting task. Methods: Improved biomechanical models are used to formulate the predicted posture as a MOO problem. The lifting task has been defined by seven performance measures that are mathematically represented by the weighted sum of cost functions. Specific weights are assigned for each cost function to predict both stoop and squat type postures. Some inequality constraints have been used to ensure that the virtual human does not assume a completely unrealistic configuration. Results: The method can predict the hand configuration effectively. Simulations reveal that predicting a squat posture requires the minimization of certain objective functions, while these measures are less significant for the prediction of a stooped posture. Conclusions: In this study, a MOO-based posture prediction model with a validation process is presented. We employed a three-dimensional model to evaluate the applicability of using a combination of seven performance measures to the posture prediction of symmetric lifting tasks. Results have been compared with the available empirical data to validate the simulated postures. Furthermore, the assigned weights are obtained for a range of percentiles from 50% male to 90% female according to the postures obtained by 3D SSPPTM software.

Spatiotemporal Modeling of Lifting Task Scheduling for Tower Cranes With a Tabu Search and 4-D Simulation

Effective lifting task scheduling for tower cranes is beneficial for the smooth operation of a construction project. Previous studies have often ignored workspace availability for lifting task scheduling. Consequently, the pre- and post-lifting processes that are primarily caused by material preparation and transfer times at the supply and demand points were not considered. Therefore, an intuitive and effective way to display more element information of lifting tasks and more complex relationships among lifting tasks is required. To solve these problems, this study proposes a spatio-temporal modeling of lifting task scheduling for tower cranes, which consists of a lifting task scheduling optimization model with a tabu search and a lifting task scheduling display method with 4D simulation. The concept of the proposed spatio-temporal modeling is demonstrated by an example with 28 lifting tasks and two tower cranes. The results show that the average total time of the optimized lifting task scheduling, taking into consideration the material preparation and transfer times at the supply and demand points, can be reduced by 25.82%. In addition, the element information and relationship of lifting tasks can be clearly presented using the proposed display method with 4D simulation.

A new approach for ergonomic risk assessment integrating KEMIRA, best–worst and MCDM methods

In this study, a new three-phase ergonomic risk assessment approach was proposed for manual lifting tasks to determine which worker has the highest ergonomic risk level considering two criteria sets as lifting-related criteria and human-related criteria. In the first phase, Modified Kemeny Median Indicator Ranks Accordance (KEMIRA-M) and a novel two-dimensional best–worst method (BWM) integration were proposed for weighting ergonomic risk criteria in two sets. In this way, weighting procedure of KEMIRA-M was advanced by the proposed two-dimensional BWM in a consistent manner and subjectivity in determining the best and the worst criteria in traditional BMW was prevented by using KEMIRA-M. Thus, the weaknesses of both methods have been developed. In the second phase, the rankings of workers were determined via utilizing multi-objective optimization on the basis of simple ratio analysis, multi-objective optimization by ratio analysis (MOORA) ratio, MOORA reference point and complex proportional assessment to see how worker rankings differ despite using the same advanced weighting approach based on KEMIRA-M and two-dimensional BWM integration. Finally, to aggregate these different ranking results, technique of precise order preference was applied. In this way, different viewpoints of each ranking approach can be reflected on a single worker’s priority. The applicability of the proposed ergonomic risk assessment approach was demonstrated with a real application in tube manufacturing.

Comparative assessment of manual load lifting tasks by three methods: KIM-LHC, WISHA and Snook tables: A case study in printing industry

Introduction: today, musculoskeletal disorders are considered as a serious threat for workers, and one of the main activities, which lead to these problems, is lifting. Moreover, workers in printing industry are widely involved in inappropriate postures and lifting loads. The aim of this study was to compare the results of assessment of lifting tasks with KIM-LHC, WISHA and Snook tables in printing industry. Materials and Methods: In this cross-sectional study, a total number of 58 employees (64 tasks in total) from a printing industry staff in Tehran were evaluated with three observational methods of KIM-LHC, WISHA and Snook tables, and the final scores and necessary action levels were determined for them. Furthermore, statistical data were analyzed by SPSS (ver.22) software using Chi-square and Fisher exact tests. Results: Results showed that the prevalence of lower limbs musculoskeletal discomforts was high. Comparing the results of load lifting assessment with WISHA and KIM-LHC methods showed that there was a significant relationship between these two methods (p=0.005). Moreover, there was a significant relationship between the results of assessment through the WISHA and Snook tables methods (p=0.006), and finally the comparison of load lifting assessment results with KIM-LHC and Snook tables showed a significant relationship between these two methods (p=0.046). Conclusion: According to the results of this study, there was a high correlation between the results of these three methods, and they can be used as an alternative in printing industry for assessment of the load lifting task.

The effect of age, prolonged seated work and sex on posture and perceived effort during a lifting task

The purpose of this investigation was to determine the effect of prolonged seated work, lift task, age and sex on normalized lumbar angles, thoracic angles, perceived effort and duration of lifts. A total of 17 young and 17 mature participants were recruited with an average (standard deviation) age of 23.8 (5.0) years and 63.7 (3.9) years, respectively. Participants completed 3 different floor to knuckle lifts before and following 90 min of seated work. The lifts included; (i) 7 kg symmetrical, (ii) 4.5 kg symmetrical and (iii) 4.5 kg asymmetrical. Prolonged seated work and age interacted to affect normalized peak lumbar angles (p = 0.0469) where older adults adopted 56(15)% flexion after seated work compared to 67(16)% among younger adults. Older adults took significantly longer to complete the lifting tasks compared to younger adults while age did not affect perceived effort across lifting tasks. Older workers may require age specific interventions given age specific responses.

Altered Proprioceptive Feedback Influences Movement Kinematics in a Lifting Task.

Movement control process can be considered to take place on at least two different levels: a high, more cognitive level and a low, sensorimotor level. On a high level processing a motor command is planned accordingly to the desired goal and the sensory afference, mainly proprioception, is used to determine the necessary adjustments in order to minimize any discrepancy between predicted and executed action. On a lower level processing, the proprioceptive feedback later employed in high level regulations, is generated by Ia sensory fibers positioned in muscle main proprioceptors: muscle spindles. By entraining the activity of these spindle fibers through 80Hz vibration of triceps distal tendon, we show the intriguing possibility of inducing kinematics adjustments due to negative feedback corrections, during a lifting task.

Immediate effects of using insoles with various wedges on activation and co-contraction indices of selected trunk muscles during load lifting

Trunk muscles play an important role during load lifting and contract to control trunk stability. The aim of present study was to investigate immediate effects of using various insole wedges on activation and co-contraction indices of selected trunk muscles during load lifting. Thirty able-bodied males completed load lifting task using nine various insole wedges. The results showed these significant differences: for normalized mean amplitude of RA muscle between posterior and anterior-medial wedges and for QL muscle between posterior and lateral wedges, for normalized peak amplitude of RA muscle between posterior and anterior-medial wedges, for median frequency of LES muscle between anterior-medial and anterior-lateral wedges, and for co-contraction of RA/TES, RA/LES and RA/MU between posterior and anterior-medial wedges (P = 0.001). These findings should be considered during designation of shoe or insole for work environments. Future studies need to assess other biomechanical aspects of using various insole wedges during work-related tasks.

Task-Contingent Persistence is Related to Better Performance-Based Measures in Patients with Chronic Musculoskeletal Pain.

Purpose Pacing, avoidance, and overdoing are considered the three main behavioral strategies, also labeled activity patterns. Their relationship with functioning of patients with chronic pain is debated. The purpose of this study was to measure the influence of activity patterns on lifting tasks commonly used in daily life. Method We performed a monocentric observational study and included patients performing Functional Capacity Evaluation (FCE). Avoidance, pacing, and persistence were assessed with using the Patterns of Activity Measures–Pain (POAM-P). Maximal safe performance was measured for floor-to-waist, waist-to-overhead, horizontal lift, and carrying with dominant-hand tests according to the FCE guidelines. Descriptive statistics, associations of POAM-P subscales with various sociodemographic variables, and correlations are presented. Standard multiple linear regression models were applied to measure the associations between FCE tests and POAM-P subscales, adjusting for the following potential confounders: age, gender, body mass index (BMI), pain severity, trauma severity, localization of injury, and education. Results Persistence was significantly positively associated with performance on the 4 FCE tests: floor-to-waist (coefficient = 0.20; p=0.001), waist-to-overhead (coefficient = 0.13; p=0.004), horizontal lift (coefficient = 0.31; p ≤ 0.001), and dominant-handed lifting (coefficient = 0.19; p=0.001). Pacing was found to have a negative influence on the carrying dominant-hand test (coefficient = –0.14; p=0.034), and avoidance was not found to have an influence on the 4 FCE tests. Conclusion This study shows that task-persistence pattern is positively associated with physical performance in FCE, whereas pacing can have a negative influence on some tests.

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

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

Influence of creep deformation on sub-regional lumbar spine motion during manual lifting

Prolonged or repetitive spine flexion induces creep deformation of posterior spine tissues allowing for increased intervertebral motion beyond ‘normal’ limits, which may influence sub-regional (intersegmental) spine motion during subsequent manual lifting tasks. Using spine skin-surface kinematics, intersegmental lumbar spine motion was recorded over 20 minutes of prolonged static spine flexion and a subsequent manual lifting task (2 lifts every 3 minutes, 30 minutes total) in 14 participants. Results demonstrated that mid to lower lumbar intersegmental levels (i.e. L2/L3 to L4/L5) experienced the greatest overall creep deformation and range of motion during both prolonged flexion and manual lifting; however, overall range of motion during manual lifting was unaffected. Additionally, creep deformation did not completely recover within 30 minutes. Future work should continue to investigate the influence of this residual creep, as well as how overall creep deformation impacts spine neuromuscular control and stability, and ultimately the development of low back disorders. Practitioner summary: Mid to lower lumbar spine levels (i.e. L2/L3 to L4/L5) experienced the greatest creep deformation and range of motion during both prolonged flexion and manual lifting. Repeated lifting following prolonged flexion may limit creep recovery; however, overall lifting kinematic motion remained unchanged.

Markerless Vision-Based One Cardboard Box Grasping using Dual Arm Robot

Nowadays, robots are indispensable in industry, especially logistics industry, to replace human employees performing heavy lifting tasks. Introducing robots prevents musculoskeletal disorders that are common in ageing workforce. We designed and implemented a dual arm robot to grasp cardboard boxes of different dimensions using a hydrid force/position control. In a first step, the position of the cardboard was estimated using markers and ARtags, and an integrated camera. However this solution showed some limitation, because it is not possible to place ARtag on every cardboard of a logistic warehouse. In this paper, we propose a new method to estimate one cardboard box position based on vision without the need of markers at all. Our method explores the advantages of the RGBD integrated camera through the use of strong features and perspective geometry. Our method is very adequate to the case of one cardboard box due to the simplicity of its geometric shape. The experiments show that our method is fast, robust and precise, and of course is better suited to the logistics warehouse environment than the marker estimation procedure for palletization applications.

Kinematic and kinetic functional requirements for industrial exoskeletons for lifting tasks and overhead lifting

The aim of this study was to sample human kinematics and kinetics during simulated tasks to aid the design of industrial exoskeletons. Twelve participants performed two dynamic tasks; a simulated lifting task and an overhead lifting task. Based on the current data, to completely assist a worker with lifting loads up to 15 kg, hip actuators would need to supply up to 111 Nm of extensor torque at speeds up to 139°/s of extension velocity and 26°/s of flexion velocity. The actuators should allow the hip to extend to 11° and flex to 95°, and supply a power of 212 W. To completely assist workers lifting a 3 kg load overhead, actuators assisting shoulder flexion would need to supply up to 20 Nm of flexor torque at speeds up to 21°/s of extension velocity and 116°/s of flexion velocity. The actuators should also allow 67° of shoulder flexion and supply a power of 27 W. Practitioner summary: There is increasing interest in developing exoskeletons for industrial applications. This study details relevant kinetic and kinematic exposures for common production tasks, which can be used to inform functional requirements of industrial exoskeletons.AbbreviationsWMSD(s)work-related musculoskeletal disordersMMHmanual materials handlingDOFdegrees of freedomBLEEXBerkeley lower extremity exoskeletonLED(s)light emitting diodeRelrelativeHighlightsThis study sampled joint kinematic and kinetic activity to inform design of industrial exoskeletons.The study presents sample values to two types of common industrial tasks across the major joints as are often assisted.We also indicate considerations on which joints should be considered to be actively assisted.

A voice activated bi-articular exosuit for upper limb assistance during lifting tasks

Abstract Humans are favoured to conventional robotics for some tasks in industry due to their increased dexterity and fine motor skills, however, performance of these tasks can result in injury to the user at a cost to both the user and the employer. In this paper we describe a lightweight, upper-limb exosuit intended to assist the user during lifting tasks (up to 10kg) and while operating power tools, which are common activities for industrial workers. The exosuit assists elbow and shoulder flexion for both arms and allows for passive movements in the transverse plane. To achieve the design criteria an underactuated mechanism has been developed, where a single motor is used to assist two degrees of freedom per arm. In the intended application, the hands are generally busy and cannot be used to provide inputs to the robot, therefore, a voice-activated control has been developed that allows the user to give voice commands to operate the exosuit. Experiments were performed on 5 healthy subjects to assess the change in Muscular Activation (MA), inferred through Electromyography (EMG) signals, during three tasks: i) lifting and releasing a load; ii) holding a position and iii) manipulating a tool. The results showed that the exosuit is capable of reducing EMG activity (between 24.6% and 64.6%) and the recognition rate (94.8%) of the voice recognition module was evaluated.

How does LBP influence muscle activity during a cyclical dynamic lifting task?

How does LBP influence muscle activity during a cyclical dynamic lifting task?

Are there differences in lifting technique between those with and without low back pain? A systematic review

Background and aims To systemically review the literature to compare freestyle lifting technique, by muscle activity and kinematics, between people with and without low back pain (LBP). Methods Five databases were searched along with manual searches of retrieved articles by a single reviewer. Studies were included if they compared a freestyle lifting activity between participants with and without LBP. Data were extracted by two reviewers, and studies were appraised using the CASP tool for case-control studies. Results Nine studies were eligible. Heterogeneity did not allow for meta-analysis. Most studies (n = 8 studies) reported that people with LBP lift differently to pain-free controls. Specifically, people with LBP lift more slowly (n = 6 studies), use their legs more than their back especially when initiating lifting (n = 3 studies), and jerk less during lifting (n = 1 studies). Furthermore, the four larger studies involving people with more severe LBP also showed that people with LBP lift with less spinal range of motion and greater trunk muscle activity for a longer period. Conclusions People with LBP move slower, stiffer, and with a deeper knee bend than pain-free people during freestyle lifting tasks. Interestingly, such a lifting style mirrors how people, with and without LBP, are often told how to lift during manual handling training. The cross-sectional nature of the comparisons does not allow for causation to be determined. Implications The changes described may show embodiment of cautious movement, and the drive to protect the back. There may be value in exploring whether adopting a lifting style closer to that of pain-free people could help reduce LBP.

Analysing the effect of wearable lift-assist vest in squat lifting task using back muscle EMG data and musculoskeletal model.

The most common disorders of the musculoskeletal system are low back disorders. They cause significant direct and indirect costs to different societies especially in lifting occupations. To reduce the risk of low back disorders, mechanical lifting aids have been used to decrease low back muscle forces. But there are very few direct ways to calculate muscle forces and examine the effect of personal lift-assist devices, so biomechanical models ought to be used to examine the quality of these devices for assisting back muscles in lifting tasks. The purpose of this study is to examine the effect of a designed wearable lift-assist vest (WLAV) in the reduction of erector spinae muscle forces during symmetric squat lifting tasks. Two techniques of muscle calculation were used, the electromyography-based method and the optimization-based model. The first uses electromyography data of erector spinae muscles and its linear relationship with muscle force to estimate their forces, and the second uses a developed musculoskeletal model to calculate back muscle forces using an optimization-based method. The results show that these techniques reduce the average value of erector spinae muscle forces by 45.38 (± 4.80) % and 42.03 (± 8.24) % respectively. Also, both methods indicated approximately the same behaviour in changing muscle forces during 10 to 60 degrees of trunk flexion using WLAV. The use of WLAV can help to reduce the activity of low back muscles in lifting tasks by transferring the external load effect to the assistive spring system utilized in it, so this device may help people lift for longer.

Sex differences in upper limb musculoskeletal biomechanics during a lifting task

Women experience higher prevalence of work-related upper limb musculoskeletal disorders compared to men. Previous studies have investigated the biological, kinematic and electromyographic sex-related differences during a lifting task but the actual differences in musculoskeletal loads remain unknown. We investigated the sex differences in three musculoskeletal indicators: the sum of muscle activations, the sum of muscle forces and the relative time spent beyond a shear-compression dislocation ratio. A musculoskeletal model was scaled on 20 women and 20 men lifting a 6 or 12kg box from hip to eye level. Women generated more muscle forces and activations than men, regardless of the lifted mass. Those differences occurred when the box was above shoulder level. In addition, women might spend more time beyond a shear-compression dislocation ratio. Our work suggests higher musculoskeletal loads among women compared to men during a lifting task, which could be the result of poor technique and strength difference.

A Mobile Application to Measure Trunk Flexion Angles in Lifting Tasks

Occupational The aim of this project was to develop and test an application capable of quickly and repeatedly measuring trunk flexion angles during sagittal plane lifting tasks. The developed application uses the built-in accelerometer in mobile devices to approximate trunk flexion angle, as the user follows an operator as they perform a lift. A black line is superimposed over the camera feed, allowing the user to approximate the angle of inclination of a line connecting the operator’s seventh cervical and first sacral vertebrae—thereby estimating the trunk flexion angle. The magnitude of this angle and its velocity have been linked to the development of occupational low back pain; thus the application provides ergonomists a more refined means of screening tasks beyond currently available survey tools.