Reliable exposure assessment strategies for physical ergonomics stressors in construction and other non-routinized work

The objective of this research was to provide guidelines for the reliable assessment of ergonomics exposures in non-routinized work. Using a discrete-interval observational sampling approach, two or three observers collected a total of 5852 observations on tasks performed by three construction trades (iron workers, carpenters and labourers) for periods of several weeks. For each observation, nine exposure variables associated with awkward body postures, tool use and load handling were recorded. The frequency of exposure to each variable was calculated for each worker during each of the tasks on each of the days. ANOVA was used to assess the importance of task in explaining between-worker and within-worker variability in exposures across days. A statistical re-sampling method (bootstrap) was used to evaluate the reliability of exposure estimates for groups of workers performing the same task for different sampling periods. Most exposures were found to vary significantly across construction tasks within trade, and between-worker exposure variability was generally smaller than within-worker exposure variability within task. Bootstrapping showed that the reliability of the group estimates exposure for the most variable exposures within task tended to improve as the assessment periods approached 5 – 6 d, with marginal improvements for longer assessment periods. Reliable group estimates of exposure for the least variable exposures within task were obtained with 1 or 2 d of observation. The results of this study demonstrate that an initial estimate of the important environmental or task sources of exposure variability can be used to develop an efficient sampling strategy that provides reliable estimates of ergonomics exposures during non-routinized work.     

A multilayered ergonomic intervention program on reducing musculoskeletal disorders in an industrial complex: A dynamic participatory approach

Work-related musculoskeletal disorders (WMSDs) are closely identified with common complaints in different workplaces. This study aimed to implement an intervention program through which ergonomic measures were dynamically localized in industry. An interventional study, including three basic layers, namely, training workshops, participatory ergonomics (PE), and workstation redesign was fulfilled in an Iranian steel manufacturing complex from 2017 to 2020. A steering committee (SC) was formed following several meetings held for clarification of the project to the management team. The SC members then attended four organized workshops managed by an ergonomics specialist. Afterwards, the basics of ergonomics were transferred to action groups. After developing ergonomic assessment tools, the ergonomic problems were prioritized and numerous positive changes were made by the action groups. The findings of the tailored checklists revealed a load of WMSDs risk factors. All the three layers of the program were implemented as initiated. Ergonomics training workshops were then held and significant differences were observed between the participants' pre/posttest mean scores in all workshops (p < 0.001). Moreover, PE measures were exercised at all levels of the organization inducing enthusiastic motivation of the workforce to consider ergonomic requirements in the workplace. Consequently, the workers' innovative ideas and the managerial support yielded diverse workstation redesigns due to a growth in either the workers' ergonomics awareness or participatory culture grounding. A multilayered ergonomic intervention was implemented in this study. In conclusion, a multifaceted long-term follow-up intervention program could be applied to enhance workers’ health status and to raise system productivity.     

A generic algorithm for computing optimal ergonomic postures during working in an industrial environment

The present study tries to decrease the risk of work-related musculoskeletal disorders for industry workers by proposing a generic algorithm that recommends an optimal ergonomic posture for accomplishing tasks in an industrial environment. In the case of a dangerous ergonomic pose, the optimization algorithm starts by heuristically changing it to a more ergonomic one. Each recommended posture's feasibility is tested with an inverse kinematic method that can predict the worker's behavior for accomplishing a task. This iterative optimization procedure continues until the optimal ergonomic pose for the worker is achieved. The algorithm's validity is tested in thirteen cases, people with different gender (50 percent male, 50 percent female) aged between 20 and 35, and different height and body morphologies. According to studies, there is a connection between musculoskeletal disorders and the wrong posture for accomplishing tasks in industries. We suggest an optimization algorithm that can indicate the worker the optimal ergonomic pose by considering task constraints in real-time.     

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n=1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.     

Reliable exposure assessment strategies for physical ergonomics stressors in construction and other non-routinized work

The objective of this research was to provide guidelines for the reliable assessment of ergonomics exposures in non-routinized work. Using a discrete-interval observational sampling approach, two or three observers collected a total of 5852 observations on tasks performed by three construction trades (iron workers, carpenters and labourers) for periods of several weeks. For each observation, nine exposure variables associated with awkward body postures, tool use and load handling were recorded. The frequency of exposure to each variable was calculated for each worker during each of the tasks on each of the days. ANOVA was used to assess the importance of task in explaining between-worker and within-worker variability in exposures across days. A statistical re-sampling method (bootstrap) was used to evaluate the reliability of exposure estimates for groups of workers performing the same task for different sampling periods. Most exposures were found to vary significantly across construction tasks within trade, and between-worker exposure variability was generally smaller than within-worker exposure variability within task. Bootstrapping showed that the reliability of the group estimates exposure for the most variable exposures within task tended to improve as the assessment periods approached 5-6 d, with marginal improvements for longer assessment periods. Reliable group estimates of exposure for the least variable exposures within task were obtained with 1 or 2 d of observation. The results of this study demonstrate that an initial estimate of the important environmental or task sources of exposure variability can be used to develop an efficient sampling strategy that provides reliable estimates of ergonomics exposures during non-routinized work.     

Physical ergonomic hazards in highway tunnel construction: overview from the Construction Occupational Health Program

This report provides an overview of physical ergonomic exposures in highway construction work across trades and major operations. For each operation, the observational method “PATH” (Posture, Activity, Tools and Handling) was used to estimate the percentage of time that workers spent in specific tasks and with exposure to awkward postures and load handling. The observations were carried out on 73 different days, typically for about 4 h per day, covering 120 construction workers in 5 different trades: laborers, carpenters, ironworkers, plasterers, and tilers. Non-neutral trunk postures (forward or sideways flexion or twisting) were frequently observed, representing over 40% of observations for all trades except laborers (28%). Kneeling and squatting were common in all operations, especially tiling and underground utility relocation work. Handling loads was frequent, especially for plasterers and tilers, with a range of load weights but most often under 15 pounds. The results of this study provide quantitative evidence that workers in highway tunnel construction operations are exposed to ergonomic factors known to present significant health hazards. Numerous opportunities exist for the development and implementation of ergonomic interventions to protect the health and safety of construction workers.     

In-field instrumented ergonomic risk assessment: Inertial measurement units versus Kinect V2

Musculoskeletal disorders are a major category of nonfatal work-related diseases in the industry. Therefore, various risk factor assessment methods, such as Rapid Upper Limb Assessment (RULA), were proposed for preventing musculoskeletal disorders in industrial environments. Nevertheless, RULA measurements based on workers' self-report or external rater observation are subjective and suffer from low repeatability. Thus, the objective of this paper is to investigate the accuracy and reliability of (1) a wearable technology (using inertial measurement units) and (2) a marker-less optical technology (using Kinect V2) for RULA risk assessment tool against motion-capture cameras (reference) for different manual material handling tasks. The obtained RULA scores were compared against the reference system using the proportion agreement index (Po) and Cohen's Kappa coefficient (κ). The wearable technology showed a “substantial” agreement (κ > 0.6) with the motion-capture cameras. The marker-less technology showed inconsistency in the agreement with the motion-capture cameras ranging from “fair” (κ < 0.4) to “moderate” (κ > 0.4) agreements, caused by both self-occlusion and object occlusion. Therefore, wearable technology showed to be more suitable than marker-less optical technology for in-field ergonomic risk assessment.     

Biomechanical analysis of upper trapezius,erector spinae and brachioradialis fatigue in repetitive manual packaging tasks: Evidence from Chinese express industry workers

This study aims to assess the effects of repetitive motion-induced fatigue during manual packaging on kinematics and muscle activity of the arm, back and shoulder. Eighteen participants performed a 60-min manual packaging task. Electromyography median frequency of RUT, RES, LES and RB decreased by 13.2% (p < 0.05), 12.8% (p < 0.05), 11.3% (p < 0.05) and 21% (p < 0.001), respectively over time. The head flexion and the right upper arm flexion angles significantly (p < 0.001) differed among different packaging sizes, and similar results were observed for left upper arm flexion and rotation. The trunk and pelvis angles significantly (p < 0.05) differed over time under three kinds of packaging. The results showed there was an increase in the rating of perceived exertion from 8.56 to 16.94 (p<0.01) during the task. The outcomes of this study indicate repetitive movements in the manual packaging task resulted in elevated prevalence of muscle discomfort in packaging workers, especially the right brachioradialis. Interventions such as specific work: rest ratios, workplace redesign should be explored to relieve muscle fatigue and discomfort.Relevance to industryFor workers performing repetitive manual packaging tasks, biomechanical analysis of different muscles groups can help in developing appropriate ergonomic interventions.     

Assessing the ergonomic exposures for drywall workers

Objective

The study was conducted to assess the ergonomic exposures to risk factors that may lead to the reported musculoskeletal injuries (especially back, neck and wrist injuries) of drywall workers.

Methods

A hierarchical taxonomy for construction of drywall panel hanging (drywall panel fitting and installation) was developed with activities defined within the interior wall systems tasks (drywall panel, studs and insulation). Exposures were characterized for the drywall panel work with the PATH (Posture, Activity, Tools, and Handling) work-sampling observation method. Data on working postures were collected for three main body parts: legs, arms and trunk. Activities performed for each task, tools used, and manually handled loads were also recorded for each observation.

Results

The study identified several ergonomic exposures in interior systems construction. Several risk factors were especially prevalent in the drywall panel installation task: awkward body postures such as overhead arm posture, trunk flexion, and handling of heavy drywall panels. Some tasks were observed to have combinations of these musculoskeletal risk factors, such as drywall panel installation, where the workers lifted heavy drywall panels in awkward body postures. In addition, a safety hazard frequently resulted when a worker's foot was poorly supported on a ladder while lifting heavy drywall panels to hang them on the ceiling or upper wall.

Conclusion

The drywall panel installation task poses a severe threat to the safety and musculoskeletal health of the drywall workers. Much of this could be eliminated by reducing the burden of handling heavy and bulky drywall panels.

Relevance to industry

The construction industry is well-documented to have high rates of injury and musculoskeletal disorders. Design of appropriate interventions requires specific knowledge of which tasks and activities involve the highest levels of exposure to relevant factors. Assessment of such factors in drywall panel hanging has provided data that will be useful to evaluate the ergonomics efficacy of future changes in task processes or tools. Feasible solutions appear to exist; effectiveness trials and worker input are needed in order to evaluate whether they could eliminate the observed exposures.     

考虑工人路径的多智能体强化学习空间众包任务分配方法

针对工人和任务进行匹配是空间众包研究的核心问题之一,但已有的方法通常会忽略工人路径对任务分配结果产生的影响.传统的任务分配方法存在计算速度慢、适用范围小和协作效果不突出等问题.对此,从空间众包平台的角度出发研究面向路网的空间众包任务分配问题,以任务完成时间最短为目标,提出考虑工人路径规划的基于多智能体强化学习的QMIX-A*算法,缩短任务的平均完成时间,进而提高用户的满意度.大量的数值仿真研究验证了QMIX-A*的有效性和稳定性,为空间众包服务平台的任务分配与路径优化策略的选择提供决策支持.     

Physiology-based dynamic muscle fatigue model for upper limbs during construction tasks

Due to physically demanding construction tasks, workers frequently suffer from significant levels of muscle fatigue that can cause diverse detrimental effects on safety, health, and productivity. In this regard, evaluating the level of muscle fatigue prior to work is essential to take proper preventive actions before severe fatigue takes place. Although previous research efforts have quantified muscle fatigue using surveys, instruments, and mathematical models, most of them do not take into account irregularly varying muscle activation and fatigue recovery during a task. They are thus limited, especially for construction tasks that have varying forces and intermittent idling/resting periods. This study thus proposes a physiology-based modeling approach to computationally model and empirically validate dynamic muscle fatigue generation and recovery for construction workers through laboratory testing. Specifically, a muscle fatigue estimation model for upper limbs based on System Dynamics, which is a differential equation-based continuous simulation, is developed based on fundamental physiological mechanisms of the accumulation and clearance of intramuscular metabolites during muscle exertion and their effects on muscle contractile processes. Then the model is refined and validated through laboratory experiments. The results demonstrated the immense potential for the developed elbow and shoulder models to evaluate workers' muscle fatigue in upper limbs under varying workloads. The contribution of this study is to provide an analytic tool for understanding the physiological mechanisms of muscle fatigue and estimating workers' muscle fatigue levels during construction tasks, which can help to design appropriate interventions prior to work, thereby reducing undesirable results from muscle fatigue.     

Effects of work experience and exertion height on static lifting strengths and lift strategies of experienced and novice female participants

In this study, 46 female experienced workers and inexperienced novices (23 each) were recruited to determine their maximum lifting strength at 15 exertion heights between 10 and 150 cm from the floor. The results revealed that the experienced workers' strengths at all 15 heights exhibited relatively little fluctuation, and were approximately 50–70 N lower than those of novices when heights were ≤50 cm. No differences in strengths were observed at 60–150 cm between the groups. The experienced workers tended to adopt a consistently deep squat at lower heights (≤50 cm) and a more erect posture with stiffened arms at higher heights (≥70 cm), resulting in lower L4/L5 disc compression forces and shoulder moments than in novices, respectively. In contrast to the lifting techniques adopted by experienced workers to effectively avoid overloading, the findings suggest that novice female workers who lack experience should be cautious and trained for performing lifting tasks.     

Musculoskeletal complaints among nurses related to patient handling tasks and psychosocial factors--based on logbook registrations

The aims were to evaluate the inter-method reliability of a registration sheet for patient handling tasks, to study the day-to-day variation of musculoskeletal complaints (MSC) and to examine whether patient handling tasks and psychosocial factors were associated with MSC.Nurses (n = 148) fulfilled logbooks for three consecutive working days followed by a day off. Low back pain (LBP), neck/shoulder pain (NSP), knee pain (KP), psychosocial factors (time pressure, stress, conscience of the quality of work) and patient transfers and care tasks were reported.The logbook was reliable for both transfer and care tasks. The numbers of nurses reporting MSC and the level of pain increased significantly during the three working days (15%-30% and 17%-37%, respectively) and decreased on the day off. Stress and transfer task were associated with LPB and transfer tasks were associated with KP.Our results confirm a relationship between work factors and MSC and indicate that logs could be one way to obtain a better understanding of the complex interaction of various nursing working conditions in relation to MSC.     

Stimulating and sustaining interest in a language course: An experimental comparison of Chatbot and Human task partners

Novel technology can be a powerful tool for enhancing students' interest in many learning domains. However, the sustainability and overall impact of such interest is unclear. This study tests the longer-term effects of technology on students' task and course interest. The experimental study was conducted with students in foreign language classes (n = 122): a 12-week experimental trial that included pre- and post-course interest, and a sequence of task interest measures. Employing a counterbalanced design, at three week intervals students engaged in separate speaking tasks with each of a Human and “Chatbot” partner. Students' interest in successive tasks and in the course (pre-post), were used to assess differential partner effects and course interest development trajectories. Comparisons of task interest under different partner conditions over time indicated a significant drop in students' task interest with the Chatbot but not Human partner. After accounting for initial course interest, Structural Equation Modelling indicated that only task interest with the Human partner contributed to developing course interest. While Human partner task interest predicted future course interest, task interest under Chatbot partner conditions did not. Under Chatbot partner conditions there was a drop in task interest after the first task: a novelty effect. Implications for theory and practice are discussed.     

Effect of an on-body ergonomic aid on oxygen consumption during a repetitive lifting task

The purpose of this study was to determine if an on-body personal lift assistive device (PLAD)¹ affected oxygen consumption during a continuous lifting task and to investigate if any effect could be explained by differences in muscle activity or lifting technique. The PLAD, worn like a back-pack, contains a spring-cable mechanism that assists the back musculature during lifting, lowering, and forward bending tasks. Males (n = 15) lifted and lowered a box loaded to 10% of their maximum back strength at 6 times/minute for 15-minutes using a free-style technique under two conditions: wearing and not wearing the PLAD. Oxygen consumption was collected continuously for the first condition; then the participants rested until their heart rates returned to resting levels before repeating the protocol for the second condition. Knee flexion was monitored using Liberty sensors at the hip, knee, and ankle. EMG of the thoracic and lumbar erector spinae (TES, LES), biceps femoris, rectus femoris and gluteus maximus were gathered using a Bortec AMT-8 channel system. VO2 measures were averaged across the duration (15 min) for each condition. Results showed no differences between oxygen consumption during the PLAD and no PLAD conditions. When wearing the PLAD, the TES demonstrated an 8.4% EMG reduction when lowering the box while the biceps femoris showed a 14% reduction while lifting the box. Knee angles, used as a proxy for stoop or squat lifts, were highly variable for both conditions. In conclusion, the PLAD had no effect on oxygen consumption and, therefore, neither workers nor employers should increase the tasks demands when wearing this ergonomic aid.     

The benefits of an additional worker are task-dependent: assessing low-back injury risks during prefabricated (panelized) wall construction

Team manual material handling is a common practice in residential construction where prefabricated building components (e.g., wall panels) are increasingly used. As part of a larger effort to enable proactive control of ergonomic exposures among workers handling panels, this study explored the effects of additional workers on injury risks during team-based panel erection tasks, specifically by quantifying how injury risks are affected by increasing the number of workers (by one, above the nominal or most common number). Twenty-four participants completed panel erection tasks with and without an additional worker under different panel mass and size conditions. Four risk assessment methods were employed that emphasized the low back. Though including an additional worker generally reduced injury risk across several panel masses and sizes, the magnitude of these benefits varied depending on the specific task and exhibited somewhat high variability within a given task. These results suggest that a simple, generalizable recommendation regarding team-based panel erection tasks is not warranted. Rather, a more systems-level approach accounting for both injury risk and productivity (a strength of panelized wall systems) should be undertaken.     

Predicting real-world ergonomic measurements by simulation in a virtual environment

Virtual reality techniques have been increasingly used for ergonomic applications. However, it is always important to know whether the results obtained in a virtual environment (VE) are representative of a real environment (RE) ones. This paper presents our preliminary experimental results on the relationship between ergonomic measurements in VE and RE for some typical “drilling” tasks. The same tasks were carried out by thirty male manufacturing factory workers in both VE and RE. Five evaluation indices - three objective (elbow angle, maximum force capacity reduction, and task completion time) and two subjective (BPD - Body Part Discomfort and RPE - Rated Perceived Exertion) - were used to evaluate the similarities between VE and RE for the selected “drilling” tasks. Four of these indices (all except elbow angle) were significantly higher (p < 0.05) in VE than in RE, which indicates that subjects experienced more discomfort and grew fatigued more quickly in VE. However, linear correlations (Pearson’s rho: 0.635-0.807) between VE and RE were found for two of the five indices (BPD and maximum force capacity reduction).

Relevance to industry

Using digital mock-ups and virtual reality simulations, industrial work activities can be evaluated to identify potential ergonomic problems during an early design stage, which reduces design time and costs, increases quality and improves customer satisfaction. A validated linear relationship can provide a reference for work design in virtual reality.     

Office workers' computer use patterns are associated with workplace stressors

This field study examined associations between workplace stressors and office workers' computer use patterns. We collected keyboard and mouse activities of 93 office workers (68F, 25M) for approximately two work weeks. Linear regression analyses examined the associations between self-reported effort, reward, overcommitment, and perceived stress and software-recorded computer use duration, number of short and long computer breaks, and pace of input device usage. Daily duration of computer use was, on average, 30 min longer for workers with high compared to low levels of overcommitment and perceived stress. The number of short computer breaks (30 s–5 min long) was approximately 20% lower for those with high compared to low effort and for those with low compared to high reward. These outcomes support the hypothesis that office workers' computer use patterns vary across individuals with different levels of workplace stressors.     

Risk assessment of cheese processing tasks using the Strain Index and OCRA Checklist

The purpose of this study was to conduct and compare two ergonomic risk assessment methods often used in occupational health research and practice: the Strain Index (SI) and Occupational Repetitive Actions (OCRA) Checklist. Seven raters used the SI and OCRA Checklist to assess task-level physical exposures to the upper extremity of workers performing 21 cheese-manufacturing tasks. Of the total task exposures assessed with both methods, nearly half (49.1%) were classified as hazardous using the OCRA Checklist while 60.2% were classified as hazardous using the SI. Although the underlying injury risk characterization constructs of the SI and OCRA Checklist differ, the results indicated that the SI and OCRA Checklist often classified job tasks into similar risk categories. The differences in risk classifications determined by the SI and OCRA Checklist for job tasks were likely related to the definition of variables measured by these assessment methods as well as the complexity of tasks evaluated. By design, the SI is specific to the distal upper extremity while the OCRA Checklist accounts for the entire upper extremity including the shoulder. When conducting risk assessments of industrial work tasks, the choice of analysis tools should be based on the purpose of the assessment and the complexity of task functions. Both the SI and OCRA Checklist yield risk assessment ratings that are similar for cheese processing tasks.     

Relationships between maximum holding time and ratings of pain and exertion differ for static and dynamic tasks

Ratings of perceived discomfort (0 to 10 scale) have been used to estimate relative maximum holding times (%MHT), particularly for static tasks. A linear 1:10% ratio has been described, where a rating of 5 corresponds to 50%MHT. It is unknown whether this linear ratio is valid for dynamic tasks. Additionally, whether pain or exertion are the primary predictors of discomfort is not clear. Thus, the goal of this study was to investigate both pain and exertion ratings during static (50% maximum; N = 42) and dynamic (75% maximum; N = 34) elbow flexion tasks until failure. Gender, self-reported physical activity, and peak torque were also assessed. Pain and exertion ratings reasonably matched the 1:10% ratio during the static task but not during the dynamic task. Exertion related more strongly to MHT than pain in both tasks. Neither gender nor activity level appeared to influence perceptual ratings, but peak torque explained approximately 20% of the variance in MHT.