Evaluation of ergonomic approach and musculoskeletal disorders in two different organizations in a truck assembly plant

The aim of this study was to assess the ergonomic physical exposure, organizational and psychosocial factors in a truck assembly plant for two different cycle times (11 min and 8 min). A self-reported questionnaire was applied to evaluate subjective physical exposure, organizational and psychosocial factors by operators in two organization of an assembly process. The initial cycle time was 11 min (system A) and the new was 8 min (system B). The same work and assembly tasks had to be completed in both systems. However, the organization and distribution of the tasks and workstations were reorganized. The results of the questionnaire showed that subjective estimation by the operators regarding ergonomic risk factors was better in the new organization and self-reported WR-MSDs symptoms were fewer. However, exposure to risk factors and WR-MSDs symptoms was not statistically different between two cycle times. The findings provide better understanding of how organizational changes can modify ergonomic exposure in manufacturing assembly industries. Effective interventions are thus not only engineering solutions but also organizational and administrative adaptations.     

Differences in functional performance of the shoulder musculature with obesity and aging

The workforce includes an increasing number of workers who are obese and/or older, which may lead to higher rates of workplace injuries. We examined the main and interactive effects of obesity and age on strength and functional performance during sustained isometric exertions involving shoulder flexion in two postures. Four groups of eight participants each (non-obese (18.5 < BMI < 25 kg/m²) young (18–25 years), non-obese older (50–65 years), obese (30 < BMI < 40 kg/m²) young, and obese older) completed static endurance tasks in each posture, at fixed target levels of shoulder moment. Shoulder strength was ∼25% higher with obesity and equivalent between age groups. Both obesity and age affected endurance time, with the obese and younger groups both having shorter endurance. Obesity and age did not have an interactive effect on endurance time and the results were inconclusive regarding acute fatigue effects for individuals who are older and obese. Further work is needed under more realistic task conditions, to explore the likely complex effects of these individual differences.     

Assimilation and use of ergonomic knowledge by nonergonomists to improve jobs in two electrical product assembly plants

This article describes the results of an analysis of the assimilation of ergonomic knowledge by nonergonomists during participatory ergonomics projects whose aim is the prevention of work-related musculoskeletal disorders (WMSDs). In two plants producing electrical consumer products and telecommunications equipment, ergonomic groups were established and trained. The groups analyzed seven working situations resulting in 50 implemented proposals. A reduction in WMSD risk factors was observed. The analysis of the assimilation of ergonomic knowledge by the groups and their members was based on two sources: analysis of the groups' working sessions, and independent interviews of group members. The results show that group members master most phases of the formalized ergonomic analysis. The interviews revealed that several factors influence knowledge transfer: prior training and organizational status of the group members, the didactic method used, company culture, support by management, and attitudes of coworkers. © 1997 John Wiley & Sons, Inc.     

SEE: A proactive strategy-centric and deep learning-based ergonomic risk assessment system for risky posture recognition

Work-related musculoskeletal disorders (WMSDs) are serious workplace injuries that put workers' safety at risk. However, traditional WMSD assessments are based on the human-evaluation strategy (HES), requiring human intervention. Proactive strategy (PAS)-oriented WMSDs assessments collect data using posture data tags and special semi-human–machine equipment to improve efficiency and reduce human efforts to capture specific postures in a real-world setting. Meanwhile, more research on applying artificial intelligence-based pose machines for musculoskeletal risk assessment in various workplaces is needed. Hence, this study proposed a holistic posture acquisition and ergonomic risk analysis model with the PAS-oriented philosophy for developing a smartphone-based and workplace-based risk assessment system for WMSDs. The Convolutional Pose Machines (CPM) method was combined with a rapid entire body assessment method for the system's design. Finally, the smart ergonomic explorer (SEE) system includes three subsystems: an automotive scene capturer, an ergonomic risk level calculator, and a risk assessment reporter. A musculoskeletal risk assessment experiment with 13 poses was also carried out to validate the SEE system and compare its accuracy with manual evaluation. The result shows good agreement with the REBA score, with an average proportion agreement index (P0) of 0.962 and kappa of 0.82. It indicates that the proposed system can not only accurately analyze the working posture, but also accurately evaluate the total REBA scores. This study is hoped to provide practical advice and implications for achieving a more effective empirical response for WMSD assessment.     

Comparing the effects of two school workstations on spine positions and mobility, and opinions on the workstations – A 2-year controlled intervention

A wide variety of conventional design workstations are used in schools and workstations have often been described as inappropriate for children's body dimensions. The present study aimed to investigate the effects of saddle chairs and desks with comfort curve for the body on schoolchildren's spine positions and mobility and opinions of workstations compared to conventional workstations. During the first 12-month study period, the number of participants was 98, 48 in the intervention and 50 in the control group. Since the older control group (9th graders, n = 29) decided against participation after the first 12 months, the number of participants in the entire follow-up of 24 months, was 47 (27 intervention and 20 control participants). During the follow-up, the intervention group used new chairs and desks while the controls used conventional workstations. Spine positions and mobility were measured and both groups completed a questionnaire, concerning opinions of workstations. The results indicated that no difference between groups was found when comparing workstation effects on spine positions and mobility during the whole follow-up. Schoolchildren preferred the ergonomic workstations to the conventional workstations during the first year (p < 0.001), but no difference was seen during the second year.

Relevance to industry

: The present results indicated that new design workstations had no effects on spine positions compared to conventional workstations. However, some intra-group positive effects were observed among intervention group. Therefore, the authors believe further development of both school workstations and school environment should be encouraged to ensure better long-term back health in children.     

Low back injury risks during construction with prefabricated (panelised) walls: effects of task and design factors

New technology designed to increase productivity in residential construction may exacerbate the risk of work-related musculoskeletal disorders (WMSDs) among residential construction workers. Of interest here are panelised (prefabricated) wall systems (or panels) and facilitating an ongoing effort to provide proactive control of ergonomic exposures and risks among workers using panels. This study, which included 24 participants, estimated WMSD risks using five methods during common panel erection tasks and the influences of panel mass (sheathed vs. unsheathed) and size (wall length). WMSD risks were fairly high overall; e.g. 34% and 77% of trials exceeded the ‘action limits’ for spinal compressive and shear forces, respectively. Heavier (sheathed) panels significantly increased risks, although the magnitude of this effect differed with panel size and between tasks. Higher levels of risk were found in tasks originating from ground vs. knuckle height. Several practical recommendations based on the results are discussed.

Statement of Relevance:Panelised wall systems have the potential to increase productivity in residential construction, but may result in increased worker injury risks. Results from this study can be used to generate future panel design and construction processes that can proactively address WMSD risks.     

Low back injury risks during construction with prefabricated (panelised) walls: effects of task and design factors

New technology designed to increase productivity in residential construction may exacerbate the risk of work-related musculoskeletal disorders (WMSDs) among residential construction workers. Of interest here are panelised (prefabricated) wall systems (or panels) and facilitating an ongoing effort to provide proactive control of ergonomic exposures and risks among workers using panels. This study, which included 24 participants, estimated WMSD risks using five methods during common panel erection tasks and the influences of panel mass (sheathed vs. unsheathed) and size (wall length). WMSD risks were fairly high overall; e.g. 34% and 77% of trials exceeded the 'action limits' for spinal compressive and shear forces, respectively. Heavier (sheathed) panels significantly increased risks, although the magnitude of this effect differed with panel size and between tasks. Higher levels of risk were found in tasks originating from ground vs. knuckle height. Several practical recommendations based on the results are discussed. STATEMENT OF RELEVANCE: Panelised wall systems have the potential to increase productivity in residential construction, but may result in increased worker injury risks. Results from this study can be used to generate future panel design and construction processes that can proactively address WMSD risks.     

Protein profiling of low-density lipoprotein from obese subjects

Although obesity and high levels of low-density lipoprotein (LDL) are well-known risk factors for cardiovascular disease, the precise role(s) of different LDL constituents in obesity has not been explored. In the present study, we compared the LDL proteome of healthy control adults (body mass index<25) and obese subjects (body mass index>30). LDL was isolated by density-gradient ultracentrifugation and proteins were separated with 2-D PAGE, quantified, and identified by peptide mass fingerprinting using MALDI-TOF MS. A new LDL-associated protein was identified as transthyretin and found to be significantly more abundant in LDL from the obese subjects. In addition, LDL from the obese subjects contained relatively more α(1) -antitrypsin, apo J, apo C-II, than LDL from controls, and also more of an acidic isoform (pI/Mr; 5.2/23 100) of apo A-I. On the other hand, the relative amounts of apo A-IV and the major isoform of apo A-I (pI/Mr; 5.3/23 100) were significantly less in LDL from the obese subjects. Apo E was less and non-sialylated apo C-III more abundant in LDL from obese men than control men, while there were no such differences between LDL from obese and control women. These findings illustrate that obesity is not only associated with increased LDL-cholesterol levels but also with alterations in the LDL protein composition. The presence of transthyretin in LDL from obese subjects may reflect over-nutrition and affect the lipid metabolism in obesity.     

Paddling upstream: a contextual analysis of implementation of a workplace ergonomic policy at a large newspaper

Efforts to implement workplace ergonomic programs aimed at reducing the burden of work-related musculoskeletal disorders (WMSD) have to address multiple physical and psychosocial aspects of work environments yet often contextual factors limit their success. We describe the processes involved in an ergonomic program to reduce neck and upper limb WMSDs at a large Canadian newspaper. Using qualitative data collection and analysis methods, we illustrate the impact of key contextual characteristics of: (1) the program (management commitment, union involvement, experience and skill of program leaders, and researcher involvement); (2) the organization (drive for productivity, management control, organizational culture); and (3) the broader social context (economic climate, nature of newspaper work, technology and nature of WMSD). We argue for increased attention to identification and response to the contextual factors affecting program implementation in order to more successfully address upstream determinants of WMSD.     

Ergonomic,job task,and psychosocial risk factors for work‐related musculoskeletal disorders among teleservice center representatives

A cross‐sectional study was conducted to evaluate the association between work‐related musculoskeletal disorders (WRMDs) and work conditions, perceived exhaustion, job dissatisfaction, and job‐stress issues at two teleservice centers (TSCs). The study covered teleservice representatives who respond to toll‐free calls for assistance. The work involves a computer or manual search for information, and data entry using keyboards. One facility had upgraded the furniture at the workstations; the other facility had not. A questionnaire survey among 114 teleservice representatives and an ergonomic evaluation were conducted to determine WRMDs and their risk factors and perceived job stress. A high prevalence of symptoms of WRMDs was found at both TSCs. Suboptimal ergonomic conditions were associated with neck, shoulder, elbow, and back WRMDs, as well as with increased job dissatisfaction. Perceived increased workload variability and lack of job control were associated with the occurrence of neck and back WRMDs, respectively. WRMDs were more frequently reported by teleservice representatives at the center with older furniture and suboptimal ergonomic conditions. WRMDs may be prevented by improving ergonomic conditions at workstations and addressing work‐organization elements.     

Obesity does not reduce maximum acceptable weights of lift

The maximum acceptable weights of lift (MAWL) of obese and non-obese participants were empirically investigated. Three obesity levels were considered: non-obese (18.5 kg/m(2)< or= body mass index (BMI)or= 40 kg/m(2)). Ten male and 10 female participants were recruited for each obesity level. The participants determined their MAWL for 18 different lifting task conditions (six lifting frequencies x three lifting heights). An analysis of variance (ANOVA) was conducted to determine the effects of obesity level, gender, lifting height, lifting frequency and their interactions on MAWL. Overall, the ANOVA results indicated that obesity does not reduce MAWL, and thus, suggested that the existing MAWL data can be used to accommodate both general and obese workers. However, further studies based on the biomechanical and physiological approaches are required to provide more complete understanding of obesity effects on lifting tolerance limits.     

The impact of ergonomic work environment exposures on the risk of disability pension: Prospective results from DWECS/DREAM

The objectives were to identify the impact of ergonomic work environment exposures on the risk of disability pension. A representative sample of 8475 employees of the total working population in Denmark were interviewed regarding work environment exposures and followed in a national register with data on granted disability pension. For women, approximately 34% of the disability pension cases were attributable to ergonomic work environment exposures. For men, 21% of the disability pension cases were attributable to ergonomic work environment. Ergonomic work environment, especially physically demanding work, working with hands lifted and repetitive work, are areas of intervention at the workplace that can facilitate and prolong labour market participation. The study provides estimates for the association between ergonomic exposures at work and administrative, cost-related measures of work disability in a large population-based longitudinal cohort study over 14 years. Approximately 21% for men and 34% for women of the disability pension cases were attributable to ergonomic work environment exposures.     

Can we simulate the biomechanical effects of exoskeletons prior to workstation implementation? Application of the Forces ergonomic method

Increasingly, exoskeletons are becoming a valuable tool for prevention technicians to promote occupational health and reduce the risk of musculoskeletal disorders in industry. However, the effective implementation of industrial exoskeletons is a complex challenge. Deciding whether these devices are the optimal solution to the detected ergonomic risks at a specific workstation is not straightforward. This study presents the modelling of three commercial passive exoskeletons, one for lumbar and two for shoulder risk reduction, to be considered in the musculoskeletal risk assessment of industrial workstations. The presented modelling considers the forces and moments applied by exoskeletons to the body using the Forces ergonomic method, providing the musculoskeletal risk for each joint based on inertial motion capture data registered at each workstation. This approach is exemplified on simulated and actual production workstations. The results reveal that the modelling application allows an objective understanding of the biomechanical effects of exoskeletons. Modelling establishes a predictive tool to assess and make decisions regarding the suitability of the exoskeleton prior to implementation at a workstation.     

Ergonomics study and analysis of workstations in Tunisian mechanical manufacturing

The workers’ performance in the mechanical manufacturing sector is the main factor for the improvement of productivity and quality. At present, it seems that the available information on the ergonomics and the working environment of the mechanical manufacturing actors is scarce. This study deals with the relationship between the working method and the workstation in injection mold manufacturing. An original methodology, based on the survey of operators using participatory ergonomic tools, is proposed in order to evaluate the ergonomic performance of 3 workstations: milling, turning, and drilling. The surveys concerned 3 operators. Obtained results showed that ergonomics play a key role in improving mechanical manufacturing. The results obtained from the analysis showed that ergonomics has a key role in the quality of the various tasks performed by operators. Using the Rapid Entire Body Assessment (RULA) and Rapid Entire Body Assessment (REBA) investigation tools, the examination of the workstations revealed 4 machining operations and 12 operator postures that have a direct influence on the performance of all machining stations. In addition, data from the analysis conducted on injection mold manufacturing revealed that neither the workstations were ergonomic nor the operators complied with the ergonomic rules. Based on the results obtained, a new standardized score is proposed for the RULA and REBA calculations. This score was applied and validated through another study conducted in a leaf spring manufacturing plant. The results of these studies were concretized by proposing the digital factory where CATIA software was used for the virtual design of the ergonomic workstations and their environments.     

Sex differences in upper limb 3D joint contributions during a lifting task

Sex-related differences in work technique may contribute to increasing the risk of musculoskeletal joint disorders among women. In lifting tasks, sex differences have been reported for the trunk and lower limb, although women present a higher prevalence of shoulder disorders. We investigated sex differences in the upper limb technique during a lifting task. Trunk and upper limb kinematics were recorded in 27 women and 27 men lifting a box (6 or 12?kg) from hip to eye level. Work technique was quantified through the three-dimensional contribution of each joint to overall box height. The glenohumeral joint showed a higher contribution in women with a 6?kg box and wrist and elbow joints did with a 12?kg box, compared to men at either 6 or 12?kg. Sex differences occurred systematically above shoulder level. Our results argue for careful consideration of sex during ergonomic intervention, particularly during the overhead task.

Practitioner Summary: We investigated the sex-related differences in upper limb technique during lifting tasks. Results highlight a sex-specific kinematic strategy above the shoulder level on the glenohumeral joint and on the wrist and elbow joints. To help reduce women’s shoulder disorders in overhead task, ergonomic interventions should account for those differences.

Abbreviations: DoF: degree-of-freedom; WR/EL: wrist and elbow; GH: glenohumeral; SC/AC: sternoclavicular and acromioclavicular; TR/PE: pelvo-thoracic     

Obesity effect on male active joint range of motion

Despite the prevalence of obesity, how obesity affects human physical capabilities is not well documented. As an effort toward addressing this, the current study investigated the obesity effect on joint range of motion (RoM) based on data collected from 20 obese and 20 non-obese males. In total, 30 inter-segmental motions occurring at the shoulder, elbow, knee and ankle joints and lumbar and cervical spine areas were examined. The obesity effect was found to be non-uniform across the joint motions. Obesity significantly reduced RoM for nine of the 30 motions: shoulder extensions and adductions, lumbar spine extension and lateral flexions and knee flexions. The largest significant RoM reduction was 38.9% for the left shoulder adduction. The smallest was 11.1% for the right knee flexion. The obesity-associated RoM reductions appear to be mainly due to the mechanical interposition and obstruction of inter-segmental motions caused by excess fat in the obese body.

Statement of Relevance: Currently, obesity is prevalent worldwide and its prevalence is expected to increase continually in the near future. This study empirically characterised the obesity effects on joint RoM to provide better understanding of the physical capabilities of the obese. The study findings will facilitate designing man–artefact systems that accommodate obese individuals.     

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.     

Passive stiffness changes in the lumbar spine and effect of gender during prolonged simulated driving

Gender differences in lumbar and pelvic posture have been reported previously in prolonged sitting, both in an office chair and automobile seat. To date, it is not known whether these postural exposures during prolonged driving affect the passive lumbar spine flexion stiffness. The purpose of this study was to examine time-varying responses of passive lumbar spine stiffness, lumbar spine and pelvic postures during a 2 h simulated driving trial. Secondary goals investigated the influence of gender on lumbar spine stiffness, discomfort scores and seat pressure profiles. Twenty (10 males, 10 females) subjects were recruited to complete a 2 h simulated driving task. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of 2 h. During driving there was a time-varying difference in the lumbar flexion angles adopted by the gender groups. A significant interaction (p = 0.0458) was found for gender and time with women being found to sit significantly different than males in the second hour of driving exhibiting greater maximum lumbar flexion (60.0% ROM (±1.27) than men 50.0% ROM (±1.5). Both men and women demonstrated similar passive stiffness changes characterized by an initial increase in transitional zone stiffness after 1 h (+0.1 Nm/degree for males and +0.3 Nm/degree for females, p = 0.2372). Over 2 h of driving there was a non-significant trend of genders to respond differently to the seated exposure. Specifically transitional zone stiffness was found to increase in males (0.86 (SD 0.31) to 0.92 (SD 0.31) Nm/degree) and decrease in females (0.81 (SD0.88) to 0.73 (SD 0.52) Nm/degree) (p = 0.1178). Differences in lumbar posture and passive stiffness over 2 h of simulated driving were demonstrated between genders in this study.Relevance to industryGender specific ergonomic interventions should be investigated for the automobile seat. Additionally, the changes in passive stiffness induced by prolonged seated exposures could introduce altered low back kinematics in activities performed after a long car ride. Lifting scenarios such as luggage unloading or parcel delivery are common activities immediately after driving. The altered stiffness of the lumbar spine in these activities could have potential ergonomics and injury related implications for both the general population and professional drivers.     

Ergonomic studies in computer-aided design

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.