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.     

Analysis and improvement of work postures in the building industry: application of the computerised OWAS method

Awkward work posture is associated with the development of musculo-skeletal disorders. Previous workplace investigations in new building construction have shown that physical work affects workers' health in 46% of jobs. There is, however, a need for detailed analysis of jobs having physical workload and ergonomics problems. OWAS (Ovako Working Posture Analysing System) is a simple observation method for postural analysis, but there has been no study of its use in the building construction industry. The work described here examined (a) the use of the OWAS method to analyse work postures in building construction, (b) the development of a portable computer system for the OWAS method, (c) improvement of work postures identified as poor, and (d) use of the results as part of the ergonomics training programme of the company. Suggestions for work redesign measures are given.     

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.     

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.     

Perception and visualization of human posture information for computer-aided ergonomic analysis

This article reports three experiments that examined the effects of photographic method, computerized visualization scheme, and posture complexity on posture perception and specification for computer-aided ergonomic analysis. The subjects were presented with photographs of working postures, and were required to manipulate human forms generated by an ergonomics software program to match the postures in the photographs. The first experiment showed a clear advantage of using a three-dimensional (3-D) human form graphic with two photographs when complex, asymmetric postures were analysed. However, the use of a 3-D human graphic display and two photographs jeopardized the subjects' posture specification performance when simple, symmetric postures were analysed. The results of the second and the third experiment demonstrated the importance of achieving congruency between photographic and computer display perspectives in improving posture specification performance. Implications for ergonomic job analysis and ergonomics software design are discussed.     

An analysis of experts' ratings of ergonomic stress

Experts in the field of industrial ergonomics are frequently called upon to visit workplaces in order to evaluate and rate ergonomic stressors which may cause fatigue, discomfort, or injury. The objective of this study was to evaluate the extent of agreement among experts' perceptions of four categories of ergonomic stress: materials handling (e.g., lifting), upper extremity activities, posture, and energy expenditure.

A panel of five experts observed ten jobs in manufacturing and warehouse facilities. A three-point scale (1 = insignificant stress, 2 = moderate stress, 3 = high stress) was used to rate the jobs in each of the four stress categories. In addition, lifting stresses on each job were analyzed using methods described in the NIOSH Work Practices Guide for Manual Lifting. The resulting data were analyzed to determine the level of expert consensus and the level of agreement with the NIOSH results.

In general, there was a high level of consensus among the experts. Perfect agreement (identical ratings by all five experts) was obtained for 30 percent of the experts' scores; while consensus agreement (identical ratings by three or more experts) was obtained for 87.5 percent of the scores. In general, the experts' perceptions agreed with the NIOSH ratings of lifting stress. On a few jobs, however, the expert panel considered lifting stresses to be greater than predicted by the NIOSH ratings.     

Modernization of a laundry processing plant: is it really an improvement?

An ergonomics assessment was conducted in a modern, automated hospital-based laundry to investigate workers' complaints of musculoskeletal aches and pains and general fatigue. Numerous job stressors were identified requiring ergonomic solutions, including prolonged standing, excessive manual handling of transport units, non-adjustability of workstations, work pacing, awkward postures, lack of job rotation and excessive repetition of tasks. Associated health and safety issues such as noise, sharps, equipment maintenance and sanitation were also addressed. Potential mechanisms for repetitive strain injuries were substantiated and solutions for problematic areas were presented to management and the union for implementation. It was concluded that human factors must be taken into consideration when designing automated laundry systems to avoid mismatches resulting in potential injury to workers.     

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.     

The effects of shoulder posture on neck and shoulder musculoskeletal loading and discomfort during smartphone usage

While using their smartphone, users tend to adopt awkward neck and shoulder postures for an extended duration. Such postures impose the risk of MSDs on those body parts. Numerous studies have been undertaken to examine neck posture; however, few studies have investigated shoulder postures. This study examined various shoulder postures during smartphone use and their effect on neck and shoulder kinematics, muscle loading, and neck/shoulder discomfort. Thirty-two asymptomatic young adult smartphone users randomly performed texting tasks for 3 min at four different shoulder flexion angles (15°, 30°, 45°, and 60°), while maintained a neck posture in the neutral position (0° neck flexion angle). Measures were taken of neck and shoulder muscle activity of the cervical erector spinae (CES), anterior deltoid (AD), upper trapezius (UT) and lower trapezius (LT), and kinematic data (angle, distance and gravitational moment). Results showed AD and LT muscle activity significantly increased when the shoulder flexion angle increased with an opposite effect on CES and UT. A recommended shoulder posture was identified as 30° flexion, as this yielded the best compromise between activation levels of the four muscles studied. This angle also induced the lowest neck/shoulder discomfort score. The findings suggest smartphone users hold their device at approximately 30° shoulder flexion angle with their neck in a neutral posture to reduce the risk of shoulder and neck musculoskeletal disorders when smartphone texting.Relevance to industrySmartphone use in the manufacturing and service industries is an integral part of work and useful means of communication tool. Awkward postures during extensive smartphone use impose an increased risk of both neck and shoulder musculoskeletal disorders. Shoulder flexion angles need consideration when making recommendations about safe work postures during smartphone use.     

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.     

Using ergonomic digital human modeling in evaluation of workplace design and prevention of work‐related musculoskeletal disorders aboard small fishing vessels

This article seeks to present methods for preventing work‐related musculoskeletal disorders of Spanish fishermen and for redesigning the workplace aboard small fishing vessels. To achieve its objective, the research project was designed in four steps. First, the equipment and procedures for catching, handling, and storing fish were studied. Second, the work postures of all the fishermen were simulated and assessed by using an ergonomic digital human modeling system (ManneQuin Pro). Third, the work environment design aboard vessels was modified on the basis of acceptable simulated work postures to prevent repetitive movements, awkward working postures, and lower back biomechanical stresses. In the fourth step, ergonomic design parameters were provided to vessel designers. © 2011 Wiley Periodicals, Inc.     

Interaction with a smartphone under different task and environmental conditions: Emergence of users’ postural strategies

Nowadays, interactions with smartphones are constantly increasing. These devices are used in a wide variety of situations by performing various tasks. The purpose of this study is to determine whether one or more strategies emerge when subjects freely send message and browse on the web in three environmental conditions: sitting with or without support and standing. Therefore, a hierarchical cluster analysis (HCA) was applied to the angular parameters of the neck and trunk as well as to the distance between the face and the telephone. These 3D motion analysis data were also processed taking into account the ergonomic recommendations from the Rapid Upper Limb Assessment in order to qualify the postural strategies highlighted by the HCA. The findings showed that there are three different postural strategies adopted by the subjects especially in the sagittal plane: a first one involves the neck without implying the trunk; a second one strongly mobilizes the trunk flexion without involving the neck; and a third postural strategy which combines these two behaviors. These three postural strategies depend on the environmental condition. Indeed, the postural strategy involving the trunk is associated with the presence of a support while the one involving the neck only appears in conditions without support. It is also observed that smartphone users mainly adopt harmful postures, whether due to excessive flexion of the neck, trunk or both. Even when subjects place themselves in the least harmful postures, there are always risks of musculoskeletal disorders in the short or long term.     

The feasibility of repositioning ability as a tool for ergonomic evaluation: effects of chair back inclination and fatigue on head repositioning

Poor posture has been suggested as one of the main factors contributing to the high prevalence of neck pain in video display unit (VDU) users, but no clear association between pain and any particular resting neck posture has been found. Postural awareness of the neck, as indicated by the repositioning accuracy, may therefore be an appropriate measure and potentially useful assessment tool. The objective of this study is to examine whether posture and fatigue affect the head repositioning ability in typical VDU usage. A group of 20 healthy participants reproduced a normal comfortable posture for forward, upright and backward chair back inclinations in random order both before and after fatigue of the upper trapezius muscles. Ten repetitions of the posture were recorded for 2 s each, and the angular and translational deviations from the original head position were measured with regard to the external environment (head in space repositioning) and with regard to the trunk (head on trunk repositioning). Analysis by repeated measures ANOVA showed significant effects and interactions of fatigue and chair back inclination on the repositioning errors in the sagittal plane, which typically showed systematic trends towards certain postures rather than random errors around a mean position. While further work is required to examine the ergonomic impact of impaired repositioning ability, head repositioning is sensitive to ergonomic factors such as seating configuration and fatigue, and may therefore be a useful tool for evaluation of static working postures.     

Risk assessments of work-related musculoskeletal disorders among the TFT-LCD manufacturing operators

The thin film transistor liquid crystal display (TFT-LCD) industry is one of the major industries in Taiwan, yet few studies addressed its work-related musculoskeletal disorders (WMSDs). Thus, this study aims to evaluate the risk of WMSDs among the operators of a TFT-LCD manufacturing company in Taiwan by using the subjective questionnaire and ergonomic assessment tools. First, the NMQ survey was conducted among 393 operators, accounting for 94% of all operators in the TFT-LCD plant. The results showed that the prevalence of WMSDs was 31.8%. Among the various body parts, the highest prevalence of WMSDs was found in neck and shoulders (20.4%), while upper limbs were with the lowest prevalence (9.2%). Besides, the prevalence of WMSDs tends to be affected by both work factors and operator factors. Those who were more experienced, working in day shift and involved in the Array process tend to have a higher prevalence of WMSDs. Further, female and domestic operators reported a higher prevalence of WMSDs than male and foreign operators. Moreover, the jobs of 50 employees were analyzed using ergonomic assessment tools including OSHA MSDs, BRIEF, OWAS, 3D SSPP, and NIOSH lifting equation. The findings indicated that inadequate working height, restricted working space, awkward postures, overweight load, and high repetition were the major risk factors of WMSDs. Thus, countermeasures such as redesigning the workstations and material handling carts, proactive training of manual material handling, and providing safety clearance are recommended to enhance the occupational health and safety of the TFT-LCD operators.     

The feasibility of repositioning ability as a tool for ergonomic evaluation: effects of chair back inclination and fatigue on head repositioning

Poor posture has been suggested as one of the main factors contributing to the high prevalence of neck pain in video display unit (VDU) users, but no clear association between pain and any particular resting neck posture has been found. Postural awareness of the neck, as indicated by the repositioning accuracy, may therefore be an appropriate measure and potentially useful assessment tool. The objective of this study is to examine whether posture and fatigue affect the head repositioning ability in typical VDU usage.

A group of 20 healthy participants reproduced a normal comfortable posture for forward, upright and backward chair back inclinations in random order both before and after fatigue of the upper trapezius muscles. Ten repetitions of the posture were recorded for 2 s each, and the angular and translational deviations from the original head position were measured with regard to the external environment (head in space repositioning) and with regard to the trunk (head on trunk repositioning). Analysis by repeated measures ANOVA showed significant effects and interactions of fatigue and chair back inclination on the repositioning errors in the sagittal plane, which typically showed systematic trends towards certain postures rather than random errors around a mean position.

While further work is required to examine the ergonomic impact of impaired repositioning ability, head repositioning is sensitive to ergonomic factors such as seating configuration and fatigue, and may therefore be a useful tool for evaluation of static working postures.     

The use of mirrors during an assembly task: a study of ergonomics and productivity

Industrial assembly tasks often require awkward, sustained neck and/or shoulder postures that can lead to increased musculoskeletal discomfort and reduced productivity. The aim of this study was to investigate the effects of mirror and periscope visual aids as ergonomic interventions designed to eliminate awkward postures of the cervicobrachial region during assembly tasks. Participants simulated a simple assembly task by using a cordless screwdriver to drive screws into a pre-tapped aluminium block. Trials of 15 min were run for each of four distinct assembly workstation configurations: industry standard (in-line screwdriver, work at elbow height, no visual aid); pistol grip (pistol grip screwdriver, work at shoulder height, no visual aid); mirror (in-line screwdriver, work at elbow height, single mirror visual aid); and periscope (in-line screwdriver, work at elbow height, two-mirror visual aid system). Muscular activity, discomfort, body posture, productivity and operator subjective assessment were recorded to determine the effects of the visual aid interventions. The results show that when comparing the interventions to the industry standard condition, there was a 45% reduction in average cervical erector spinae activity, a 90% reduction in average neck flexion angle and a 72% reduction in neck discomfort with the interventions. When comparing these interventions to the pistol grip condition there was an 80% reduction in activity of the dominant side deltoid, a 92% reduction in shoulder flexion angle and an 81% decrease in shoulder discomfort with the interventions. Productivity was greatest in the industry standard configuration followed by the pistol grip (9% lower), the periscope (13% lower) and the mirror (23% lower) configurations. A follow-up study that compared the productivity of the periscope configuration with that of the industry standard configuration showed that within a 4-h work period this productivity differential decreased by over 33%.     

Technical Note: The use of mirrors during an assembly task: a study of ergonomics and productivity

Industrial assembly tasks often require awkward, sustained neck and/or shoulder postures that can lead to increased musculoskeletal discomfort and reduced productivity. The aim of this study was to investigate the effects of mirror and periscope visual aids as ergonomic interventions designed to eliminate awkward postures of the cervicobrachial region during assembly tasks. Participants simulated a simple assembly task by using a cordless screwdriver to drive screws into a pre-tapped aluminium block. Trials of 15 min were run for each of four distinct assembly workstation configurations: industry standard (in-line screwdriver, work at elbow height, no visual aid); pistol grip (pistol grip screwdriver, work at shoulder height, no visual aid); mirror (in-line screwdriver, work at elbow height, single mirror visual aid); and periscope (in-line screwdriver, work at elbow height, two-mirror visual aid system). Muscular activity, discomfort, body posture, productivity and operator subjective assessment were recorded to determine the effects of the visual aid interventions. The results show that when comparing the interventions to the industry standard condition, there was a 45% reduction in average cervical erector spinae activity, a 90% reduction in average neck flexion angle and a 72% reduction in neck discomfort with the interventions. When comparing these interventions to the pistol grip condition there was an 80% reduction in activity of the dominant side deltoid, a 92% reduction in shoulder flexion angle and an 81% decrease in shoulder discomfort with the interventions. Productivity was greatest in the industry standard configuration followed by the pistol grip (9% lower), the periscope (13% lower) and the mirror (23% lower) configurations. A follow-up study that compared the productivity of the periscope configuration with that of the industry standard configuration showed that within a 4-h work period this productivity differential decreased by over 33%.     

Occupational ergonomics research and applied contextual design implementation for an industrial shop-floor workstation

The aim of this original research article is to identify the occurrence of work-related ergonomics risk factors, in order to implement context specific human centered design interventions in the injection molding shop-floor workstations of plastic furniture manufacturing factories within the framework of industrially developing countries. Questionnaire study, postural assessment tools, computer aided design, digital human modeling and simulation, and basic work study techniques were used. Plastic processing industry is highly fragmented, consisting of small, medium scale enterprises with tremendous growth potential. Occupational design ergonomics research in the injection molding plastic furniture manufacturing shop-floor workstations is very scarce in industrially developing countries. Shop-floor workers are affected by prevalent awkward working postures and consequent body part discomforts. Useful and easily implementable accessories/fixtures with convenient design features were conceptualized. Virtual ergonomics evaluation of the workstation with proposed accessories/fixtures showed significant reduction of awkward working postures. Physical prototypes of the proposed fixtures were constructed and real human trials were performed in the factories. Time study indicated reduction in operator cycle time when compared with time taken before design modifications. Research methodology, results and design solutions described from an ergonomics perspective would definitely serve as a helpful guide for existing as well as upcoming factories in the injection molded plastic furniture manufacturing industry of industrially developing countries and further similar research endeavors.     

A discomfort survey in a poultry-processing plant

The relationship of musculoskeletal pain and discomfort due to awkward work postures, forces, static loading and over-use is widely accepted as an indicator of poor job design. A discomfort survey was conducted in a poultry-processing plant to help to prioritize areas for ergonomics intervention and to determine whether regions of discomfort relate to types of task performed. The survey form was basic, to accommodate illiteracy, and was administered to 699 employees. Demographic data and job information were recorded. The employee rated job satisfaction and overall discomfort, shaded areas of discomfort on a body diagram and rated the intensity of the discomfort for each area. The jobs were coded into four mutually exclusive categories: hand tool, hand manipulation, material handling and mixed task. A discomfort index (DI) combined the number of shaded areas with intensity. Of the 65% who reported discomfort, the back had the highest mean maximum intensity followed by the arm, contrary to prevalence ranking of body regions. In the light of the findings, the benefit of rotation in a plant requiring major redesign is questioned. Results unexpectedly highlighted women who reported arm discomfort with more than one job, and who performed manual material-handling tasks, to have a significant discomfort problem, which indicates the breadth of ergonomics intervention required in the poultry environment. Surprisingly, no other effects of task were found. The survey provided useful indications of ergonomics issues in areas not identified by medical records.