PATH: a work sampling-based approach to ergonomic job analysis for construction and other non-repetitive work

A high prevalence and incidence of work-related musculoskeletal disorders have been reported in construction work. Unlike industrial production-line activity, construction work, as well as work in many other occupations (e.g. agriculture, mining), is non-repetitive in nature; job tasks are non-cyclic, or consist of long or irregular cycles. PATH (Posture, Activity, Tools and Handling), a work sampling-based approach, was developed to characterize the ergonomic hazards of construction and other non-repetitive work. The posture codes in the PATH method are based on the Ovako Work Posture Analysing System (OWAS), with other codes included for describing worker activity, tool use, loads handled and grasp type. For heavy highway construction, observations are stratified by construction stage and operation, using a taxonomy developed specifically for this purpose. Observers can code the physical characteristics of the job reliably after about 30 h of training. A pilot study of six construction laborers during four road construction operations suggests that laborers spend large proportions of time in nonneutral trunk postures and spend approximately 20% of their time performing manual material handling tasks. These results demonstrate how the PATH method can be used to identify specific construction operations and tasks that are ergonomically hazardous.     

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.     

Ergonomic effects of a management-based rationalization in assembly work - a case study

Due to unsatisfactory productivity, a large company in the Swedish manufacturing industry decided to rationalize their assembly system. The intended rationalization comprised several changes with deliberate ergonomic implications. The main aim of the present study was to evaluate the impact of the rationalization on the physical work load of the operators. The work load was assessed before and after the changes using expert observations, company records and direct technical measurements. The results indicate that the intervention led to only minor changes in muscle load, body postures and movement patterns. Several of the planned initiatives were never implemented, e.g. teaching the workers multiple skills and designing work stations at which a major part of the assembly sequence could be performed. This was mainly due to a policy revision caused by changes in the market situation. In spite of the company's original intentions, the revised production system contained only minor ergonomic improvements. Thus, the realization of the ergonomic potential in a rationalization seems to depend on management culture, as well as factors outside the company.     

A checklist for evaluating ergonomic risk factors resulting from awkward postures of the legs, trunk and neck

A one-page checklist for determining the presence of ergonomic risk factors associateed with awkward postures of the lower extremities, trunk and neck was developed and evaluated as part of a joint labor-management ergonomics intervention program. This checklist was used by plant personnel at four work sites to assess the postural requirements on 335 cyclical (i.e., work-cycle duration less than five minutes) manufacturing and warehouse jobs. In addition, results generated by the checklist were compared to the results of ergonomic analyses performed by persons with advanced training in occupational ergonomics.

Workers were observed using awkward postures for most of the jobs in the survey. Awkward postures of the lower extrimities were relatively uncommon, occuring in 25 percent or less of the jobs. Awkward postures of the trunk and neck were common, occuring in more than 70 percent of the jobs. Results generated by the checklist were generally in agreement with results generated by the experienced ergonomists; however, the checklist was found to be more sensitive in identifying the presence of awkward postures.

The checklist was found to be an effective rapid-screening instrument for identifying cyclical jobs that expose workers to potentially harmful postures. However, the checklist methodology did not include sufficient documentation of work methods to identify the specific job attributes associated with these exposures. Furthermore, the checklist was not used to evaluate non-cyclical jobs (e.g., maintenance and skilled trades).     

Personalized method for self-management of trunk postural ergonomic hazards in construction rebar ironwork

Construction rebar workers face postural ergonomic hazards that can lead to work-related Lower Back Disorders (LBDs), primarily due to their prolonged awkward working postures required by the job. In a previous study, Wearable Inertial Measurement Units (WIMUs)-based Personal Protective Equipment (PPE) was developed to alert workers when their trunk inclination holding time exceeded acceptable thresholds as defined in ISO standard 11226:2000. However, subsequent field testing identified PPE was ineffective for some workers because the adopted ISO thresholds were not personalized and did not consider differences in individual’s response to postural ergonomic hazards. To address this problem, this paper introduces a worker-centric method to assist in the self-management of work-related ergonomic hazards, based on data-driven personalized healthcare intervention. Firstly, personalized information is gathered by providing each rebar ironworker a WIMU-based personalized mobile health (mHealth) system to capture their trunk inclination angle and holding time data. Then, the captured individual trunk inclination holding times are analyzed by a Gaussian-like probability density function, where abnormal holding time thresholds can be generated and updated in response to incoming trunk inclination records of an individual during work time. These abnormal holding time thresholds are then adapted to be used as personalized trunk inclination holding time recommendations for an individual worker to self-manage their working postures, based on their own trunk inclination records. The proposed worker-centric method to assist in the self-management of ergonomic postural hazards leading to LBDs was field tested on a construction site over a three-month duration. The results of the paired t-tests indicate that posture scores evaluated by the Ovako Working Posture Analysis System (OWAS) significantly decrease when the personalized recommendation is applied, while increase again when the personalized recommendation is removed. Based on data-driven personalized healthcare intervention, the results demonstrate the significant potential of the proposed worker-centric self-management method for rebar workers in preventing and controlling postural ergonomic hazards during construction rebar ironwork.     

Kinematics differences between obese and non-obese workers during vertical handling tasks

Obesity is highly prevalent in the workforce but little is known about its effects on musculoskeletal disorders risk factors, such as the posture adopted during work activity. Vertical Handling Tasks (VHT), including manual lifting and lowering loads, are quite frequent in industrial settings and are considered to be a major cause of Work-Related Musculoskeletal Disorders (WMSD). Therefore, the main objective of this study is to compare and analyse the strategies and postures adopted during VHT between obese and non-obese subjects. A kinematics study with the VICON® system was conducted within a convenience sample of 8 non-obese (4 women and 4 men) and 8 obese (4 women and 4 men) volunteers participants. Different occupational conditions were tested over 8 trials of VHT. When developing VHT, the obese group presents kinematics significant differences (p < 0.05), compared with non-obese, namely: a decrease in the duration of the tasks, an increase in the horizontal distance between the load and the body worker, and an increase of the trunk sagittal flexion. This study demonstrates that obese individuals are exposed to a higher level of WMSD risk, during VHT performance.Relevance to industryThe findings are relevant to ergonomic workstations/job design for obese workers. This study defends that obesity can be a WMSD risk factor during VHT frequently found in industry, pointing to the need of companies to include this factor during ergonomic interventions on workstations and to adopt obesity prevention measures.     

Development of ergonomic posture recognition technique based on 2D ordinary camera for construction hazard prevention through view-invariant features in 2D skeleton motion

Outdoor tasks operated by construction workers are physically demanding, requiring awkward postures leading to pain, injury, accident, or permanent disability. Ergonomic posture recognition (EPR) technique could be a novel solution for ergonomic hazard monitoring and assessment, yet non-intrusiveness and applicability in complex outdoor environment are always critical considerations for device selection in construction site. Thus, we choose RGB camera to capture skeleton motions, which is non-intrusive for workers compared with wearable sensors. It is also stable and widely used in an outdoor construction site considering various light conditions and complex working areas. This study aims to develop an ergonomic posture recognition technique based on 2D ordinary camera for construction hazard prevention through view-invariant features in 2D skeleton motion. Based on captured 2D skeleton motion samples in the test-run, view-invariant features as classifier inputs were extracted to ensure the learned classifier not sensitive to various camera viewpoints and distances to a worker. Three posture classifiers regarding human back, arms, and legs were employed to ensure three postures to be recognized simultaneously in one video frame. The average accuracies of three classifiers in 5-fold cross validation were as high as 95.0%, 96.5%, and 97.6%, respectively, and the overall accuracies tested by three new activities regarding ergonomic assessment scores captured from different camera heights and viewpoints were 89.2%, 88.3%, and 87.6%, respectively. The developed EPR-aided construction accident auto-prevention technique demonstrated robust accuracy to support on-site postural ergonomic assessment for construction workers’ safety and health assurance.     

The work load of warehouse workers in three different working systems

An investigation was conducted in five companies in the distribution branch. These companies were divided into three different working systems, i.e., highly mechanized (HM), moderately mechanized (MM), and slightly mechanized (SM). The three systems differed in logistics and kind of appliances used. The purpose of this study was to compare the three working systems with different degrees of mechanization concerning the time spent on tasks, activities during the working day, postures that occurred, physiological work load, perceived exertion and recovery from work. To investigate the different tasks, activities and working postures, 50 warehouse workers, originating from the three working systems, were observed by means of a direct observation method, called: ‘TRAC’. To investigate the physiological work load the heart rate was recorded continuously during the working day and related to the individually determined relation between heart rate and oxygen uptake. This relation was constructed with the results of a cycle ergometer test done in the laboratory. During lunch and at the end of the working day the warehouse workers filled in a questionnaire concerning their perceived exertion and recovery from work.

In the slightly mechanized system more time was spent with the trunk flexed more than 75° as compared with the other two systems. This posture was very common during lifting of objects, and lifting was done more often in this system than in the other systems. In the MM system the warehouse workers had the highest estimated oxygen uptake and reported the highest perceived exertion at the end of the working day. The workers in the HM system had a shorter working day and had less problems with recovery from work than the workers of the other two systems. Poor working postures like rotation and lateroflexion were commonly found in the HM working system. An important explanation was the difference in time spent driving an electric car. This activity was done mostly in the HM system. In conclusion, the HM system was considered most favourable when it concerned work load and recovery from work. The appliances used in the HM system, and especially the electric car, need to be designed according to ergonomic guidelines to avoid poor working postures.     

Effect of sampling interval on the reliability of ergonomic analysis using the Ovako working posture analysing system (OWAS)

In industry, the Ovako working posture analysing system (OWAS) is applied using different sampling intervals. However, it has not yet been established what influence the sampling interval has on the reliability of the data collection. For this purpose, the sampling interval of an existing ergonomic analysis of working postures using OWAS with 20,601 observations was varied between 2 and 90 s to investigate the effects of deviation from the original sampling interval of 1 s. Based on these comprehensive industrial data, which was statistically analyzed with regression analyses, it can be concluded that in the ergonomic analysis of working postures using OWAS, direct observations should have a sampling interval of 20 s, and video-based observations should have a sampling interval of 10 s or less.Relevance to industryThe Ovako working posture analysing system (OWAS) is a practical and frequently selected method for the ergonomic analysis and evaluation of working postures. However, the selection of a suitable method is as least as important as the definition of a sampling strategy providing reliable values obtained through observation. For this reason we investigated the effect of the sampling interval and recommend using 20 s for direct observations and 10 s or less for video-based observations.     

Long-duration assessment of upper arm posture and motion and their association with perceived symptoms among bakery workers

Awkward shoulder postures have been suggested to be a cause of shoulder discomfort among bakery workers. This study aimed at long-duration assessment of upper arms posture and motion and their association with perceived symptoms among bakery workers. Among workers in three types of bread systems, fifty-seven bakers were randomly selected. The self-reported rates for the perceived severity and frequency of shoulder discomfort were collected through questionnaires. Working postures and movements of the shoulders during work were continuously recorded with inclinometry measurements for three hours. Percentage of time spent with the upper arm right elevated more than 60° was significantly correlated with the perceived discomfort rate in the right shoulder for all bakery workers (r = 0.48 to 0.63, p ≤ 0.05). A significant correlation was found between angular velocity with the perceived discomfort intensity for right upper arm.(r = 0.60 to 0.87, ≤0.005) of all workers in the three baking systems. Physical exposure in bakers was characterized by significantly more awkward postures and the percentage of time spent with the upper arms elevated more than 60°. The current findings can facilitate more informed decisions with respect to both engineering (e.g.ergonomic workstation and tool design) and administration (e.g. work organization) control strategies.     

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.     

Analysis of working postures in hammering tasks on building construction sites using the computerized OWAS method

The main objectives of this study were to identify the most problematic postures in hammering tasks performed at building construction sites through application of the computerized OWAS method, and to develop recommendations for improvement of working method and workplaces. Eighteen construction workers, with mean age of 41.6, from three construction companies participated in the field study. The hammering tasks observed during the two-month period included roof boarding, concrete form preparation, clamping support braces, assembling roof frames, roof joisting, shelter form preparation, and fixing fork clamps. Three different types of hammer, including a small Fiskar's hammer, a Fiskar's construction hammer, and a Rocket hammer, were used by the workers. Of all the observations, poor working postures were observed most frequently in roof joisting (12.4% of all observations within the task), followed by concrete form preparation (8.6%), and construction of frames for the roof (7.5%). Overall, out of 593 different postures analysed, a total of 7.8% of postures adopted by the workers during various hammering tasks were classified into OWAS categories III or IV, indicating that these postures should be corrected either soon or immediately. The computerized OWAS method for postural data analysis proved to be a very useful way to reduce postural load of dynamic hammering tasks, and allowed for efficient application of the original OWAS method.     

A software‐based method for ergonomic posture assessment in automotive preproduction planning: Concordance and difference in using software and personal observation for assessments

This article describes the pilot study for testing a system for ergonomic posture assessment. 1 The software‐based approach for ergonomic assessment is based on motion capturing work tasks using realistic mock‐ups of the assembly environment. The approach for ergonomic assessment reduces the expenditure of time for evaluation. This may lead to considerable ergonomic aspects during the early stages of production planning. A comparative test between human observers and the software system was carried out. The test of the system focuses on correct recognition of postures from the motion data and compares the computer‐based evaluation with the results of a manual analysis carried out by a human observer. The tests indicate sufficient results for the automated assessment, especially for the arm and leg postures. But there is still some potential for further improvement of the recognition accuracy of the back postures. © 2011 Wiley Periodicals, Inc.     

Ergonomic evaluation of work table for waste sorting tasks using digital human modelling

Waste sorting facilities rely heavily on plentiful human labour, and the lack of adequately designed work systems leads to musculoskeletal disorders among the workers. The present research explores the ergonomic design aspects of a cost-effective intervention, a work table for waste sorting in developing countries. This study evaluates the appropriate range of work height for the sorting tasks and proper location of hoppers to drop the sorted items. The ergonomic assessment was conducted by simulating postures involved in sorting tasks in a virtual environment and performing a biomechanical evaluation of the static postures by digital human modelling. Thirty male subjects from Indian population simulated the postures of sorting tasks. The compressive force at L4/L5 intervertebral disc, shoulder flexion moment, shoulder abduction moment, and elbow flexion moment were taken as the indicative parameters of the subject's physical workload. The appropriate table height was marginally lower than the elbow height of the subject and within 4 cm. The preferred hopper position was on the floor adjacent to the worker compared with the hopper on the top of the table.     

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.     

Comparison of ergonomic risk assessment outputs from OWAS and REBA in forestry timber harvesting

Globally, work-related (musculoskeletal disorders (MSDs) are one of the most important health problems encountered by ergonomists. Forest work, especially logging harvesting, is traditionally recognized as one of the most difficult types of physical work and has distinct characteristics. Harvesting works in forestry are composed of the following work stages: logging, skidding, and loading. This study aimed to examine risk factors of MSDs associated with different work postures during harvesting under variable external conditions by comparing work stages using the Ovako Working posture Assessment System (OWAS) and Rapid Entire Body Assessment (REBA). A statistically significant difference was observed between the two methods. While the difference in risk to the musculoskeletal system was statistically significant in different work stages using REBA, logging and skidding were assigned to the same risk level using OWAS. Easy-to-use ergonomic hand tools should be developed that are suitable for working conditions and help reduce MSD risk in forestry workers.     

Continuous assessment of back and upper arm postures by long-term inclinometry in carpet weavers

Awkward back and shoulder postures have been suggested to be a cause of back and shoulder discomfort in carpet weavers. This study aimed at continuous assessment of the upper arm and back postures and estimation of biomechanical load subtasks using inclinometers during 4 h.Median of trunk flexion angle in weavers was 18° and 13° during knotting and compacting subtasks, respectively. The weavers worked with arms elevated greater than 45° for %4.5 of the work time. The average cumulative compression load for males and females were estimated at 22 MN-S and 13 MN-S, respectively.In addition to poor workstation design, constrained posture of the trunk and low elevation and velocity for both arms may be the main risk factors for developing fatigue and disorders in the back and shoulder regions among carpet weavers. Therefore, any ergonomic interventions should be focused on reducing trunk flexion and the constrained postures of weavers.     

Ergonomics of posture--review of various problems of standing and sitting posture

Medical and ergonomic field studies indicate that bad standing and sitting postures are sometimes accompanied by pains in muscle and connective tissues of tendons, joint capsules and ligaments. There is evidence that such pains can become the symptoms of chronic diseases attributed to rheumatic disorders. Recent orthopaedic research revealed that inadequate standing and sitting postures provoke excessive increases of intradiscal pressure. These orthopaedic findings, together with ergonomic investigations on sitting behaviour and somatic troubles, provide good bases for the construction of rest chairs and work seats.     

Ergonomic studies in computer-aided design

Abstract

This paper describes the results of an ergonomic survey on interactive graphics workstations for computer-aided design (CAD). A work-sampling study was carried out to characterize the use of keyboard, digitizer tablet and video display. Subjective impressions of CAD software, CAD hardware and health aspects were collected by means of a questionnaire. Working methods and working postures were recorded on videotape. The two most important differences in comparison with other office terminals are: (i) dynamic working methods result in an absence of constrained postures in CAD operators and allow full-body exercise; (ii) CAD operators spend more time (46–68 per cent of working hours) viewing the video display than the average office terminal operator. Some ergonomic recommendations have been deduced for the construction of CAD terminals, as well as for the ergonomic improvement of existing workstations.