Developing an Occupation-Based Ergonomic Evaluation

With the right assessment, training, management support, and processes Web- based ergonomics training offers a more flexible and effective.
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Ergonomics tools, digital human model, product development process, Digital Prototyping, virtual ergonomics, Ergotyping. Due to demographic change, less young workers are available and the overall number of workers will decrease. The length of absenteeism, especially due to musculoskeletal disorders, increases with higher age. The range of performance between individuals grows wider although there are exceptions for different capabilities and elderly workers.

Therefore, a capability-appropriate workplace design is necessary to meet physical workplace demands in the manufacturing industry and in order to preserve the workability of the workforce. The human-centred design process was used to provide a design solution that meets the needs of the … workplace designers. The design solutions are evaluated three times.

Ergonomics Evaluation — FIEUW Occupational Therapy

The high number of capabilities with a wide range of individual performance can be best captured and represented in a database. Therefore, a database is developed in which relevant physical manufacturing capabilities are collected and processed for workplace designers. Based on this information, design solutions for a prospective capability-appropriate workplace design can be derived relative to the age structure of the manufacturing plant.

This gives the workplace designer propositions on how to plan their workplaces so as to avoid excessive stress and musculoskeletal disorders in the employees. Elderly worker, work-related capabilities, database for workplace design. The increasing amount of available data in digital working environments raise considerable usability challenges.

Beyond the trend for automation of such processes, strategic decisions still depend on humans in the loop who have to perceive, understand and process increasingly complex information and to make quick and correct decisions with considerable consequences for the effectiveness of the production process. This work is concerned with a baseline experiment in which effects of data presentations and information complexity on speed and accuracy were studied taking table reading for inventory control as an example.

In addition, learnability effects were assessed. Results show a significant effect of all factors on task performance. With increasing information complexity decision speed is considerably decreased. Operators' perceptual speed modulates performance. Low perceptual speed in conjunction with insufficient data presentation results in significantly lower task performance.

Who may benefit from an ergonomics evaluation?

Usability and user-centered information displaying is of vital importance for efficient operators' performance and to balance mental workload. The findings contribute to an understanding of the effects of single factors in combination for mental workload and may lead to better managerial decisions concerning the design of working conditions e. Usability, performance, speed, accuracy, table reading, inventory control, tabular data. For editorial issues, like the status of your submitted paper or proposals, write to editorial iospress.

For editorial issues, permissions, book requests, submissions and proceedings, contact the Amsterdam office info iospress. You are viewing a javascript disabled version of the site. Please enable Javascript for this site to function properly. Select this link to jump to content Menu. Select this link to jump to navigation Occupational Ergonomics - Volume 12, issue 3. Purchase individual online access for 1 year to this journal. The journal will publish peer-reviewed original papers, covering a variety of occupational ergonomics issues including, but not limited to: Emphasis will be on reflection of the recent increase in health and safety in the workplace and related job redesign requirements.

The journal aims to: Articles will not be confined to research areas, but will comprise a balanced mixture of basic and applied research, literature reviews, case studies, short communications and book reviews in the broad area of occupational ergonomics and safety. Recommend this journal Editorial board Submissions. The reports of clock time in the diaries were synchronised with the abduflex recordings. Investigators in ergonomic epidemiology are recommended to consider the prospects of task based exposure assessment carefully before placing resources at obtaining task information.

A source dataset was defined for each occupational group fig 1. The two exposure variables were chosen according to prevailing hypotheses about the pathogenesis of shoulder disorders, 30— 32 and in order to reflect the basic dimensions of exposure—that is, duration, level, and frequency. The exposure variables were calculated for the whole working day and for each task occurring during the day.

If a subject performed a given task more than once during the day, the recordings from the task were pooled.

Source dataset bottom boxes for machinists, car mechanics, and house painters. Summary statistics were derived by calculating the arithmetic mean across days for each subject, and subsequently averaging these individual specific mean exposures to obtain occupational group mean values. The set of task exposure means formed the TEM used for estimation below. Exposure variances between subjects and between days within subjects were estimated for each task and for the entire job using restricted maximum likelihood algorithms in a one way random effects model SAS 6. For each participant, a specific TEM was constructed using exposure data from all other subjects in the occupational group, in order to simulate the situation that the subject had not himself contributed to the TEM.

If a task had been performed by only one subject, the measured mean job exposure for the group was used instead of the missing task exposure, again omitting the subject considered. For each diary day, the job exposure was modelled by weighted averaging of task exposures in the TEM, using the task proportions from the diary as weights. Validation designs have been suggested as tools for maximising the precision of estimated group means in relation to invested resources.

In our case, both measured job exposures and task based estimates were available for subjects in the validation sample. Within this sample, linear least squares regression was used to determine the relation between task based and measured individual mean job exposures for one to four days of data collection SAS 6. For these subjects only task based job exposure estimates were available which were assumed to be calibrated using the validation sample regression.

OT-V Episode 7: Ergonomics At Work!

We explored the precision of the combined group mean by solving equation 1 for different sizes of the validation and diary-only samples, using the source datasets to obtain squared correlation coefficients and empirical values of s S 2 for one to four measurement days per subject. For comparison, we estimated the precision of a group mean obtained by direct measurements, only.

The standard error of the mean was calculated according to:. The equation was solved for 1 to subjects, and empirical values of s S 2 for one to four measurement days per subject were used to investigate the effect of increasing the number of days. Table 1 shows characteristics of the subjects in the three source datasets.

Tables 2—4 present data material, mean exposure, and exposure variability at job and task levels for machinists, car mechanics, and house painters, respectively. For both exposure variables, the house painters showed the highest mean exposure and the machinists the lowest. At the job level, we found considerable exposure variability between subjects as well as between days within subjects, and the relative size of these two variance components differed between groups.

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In each occupational group, tasks differed in mean exposure. The task distribution varied substantially between individuals, as shown by the wide range in the percentage of daily measurement time spent in each task. Among house painters and car mechanics a few days were found with no breaks, but in most of these cases the diary contained periods without task specification.

In general, the within-task exposure variability was considerable compared to the variability at the job level. Data material, mean exposure, and exposure variability at job and task levels for machinists. Data material, mean exposure, and exposure variability at job and task levels for car mechanics. Data material, mean exposure, and exposure variability at job and task levels for house painters.

Tables 5—7 present measured group mean exposures and associated overall variances between subjects, s S 2. As expected, s S 2 tended to decrease when more days were included in the individual mean job exposure estimates. The tables also show the results of linear regression of measured on task based individual mean job exposures cf fig 2. His deviating results could not be ascribed to errors in his diaries and measurement data.

The same was true of an outlying car mechanic. Mean daily exposure, exposure variability in the job, and results of linear regression analyses of measured on task based individual mean job exposures according to number of days with data collection per subject for machinists. Mean daily exposure, exposure variability in the job, and results of linear regression analyses of measured on task based individual mean job exposures according to number of days with data collection per subject for car mechanics.

Mean daily exposure, exposure variability in the job, and results of linear regression analyses of measured on task based individual mean job exposures according to number of days with data collection per subject for house painters. As expected, the precision of the group mean increased—that is, the standard error decreased, when more subjects with measured job exposures were included. The effect of increasing the number of measurement days per subject was far less pronounced.

Inclusion of subjects with task based exposure estimates improved the precision of the group mean only marginally beyond what was obtained on the basis of the directly measured subjects in the validation sample. The investigated approach combined personal task proportions from diaries with exposure data from a collective TEM.

Task based estimation of job exposure turned out to be unsuccessful. Consequently, only a negligible gain in precision of group mean exposures could be obtained by adding subjects with task based exposure estimates to a sample of subjects who were directly monitored, as suggested in validation designs. Numerous ergonomic studies have classified tasks in biomechanical terms such as the proportion of daily working hours with hands above shoulder level.

However, natural task categories may not contrast much in exposure. The diaries worked well in practice. Periods without task specification occurred infrequently, and the option of inserting supplementary tasks in the diaries was rarely used. In addition, the contrasts between task exposures were large when compared to other studies where jobs have been divided into their constituent tasks. Task proportions also varied between individuals cf tables 2—4 as a further indication that task based exposure estimation could be successful.

The task based estimates turned out to be very imprecise. The predictive ability of the task based estimates might have been better if tasks with large exposure variation could have been split into sub-tasks. Another possible improvement could be to cluster tasks a posteriori according to their empirical exposure. This introduced errors in the estimated job exposures, not only because task durations were imprecise, but also because task exposures were extracted according to the diary timeline. Also, the task sequences were relatively long which further reduced the significance of this source of error.

More exact information on task schedules could have been obtained by observing the subjects, 46 but then, in the present study, indirect exposure assessment would have been more expensive than direct measurements. Information about individual task occurrences could also have been pursued in production records.

However, the quality of such data might not be superior to diary information, and comparable records were not available for the three occupational groups. Due to the consecutive measurement schedule, the amount of data for a particular task was proportional to its occurrence in the occupation. While proportional sampling can be an efficient strategy for determination of mean task exposures in individuals, 17 it also implies uncertain exposures for rare tasks. Additional data collection for selected rare tasks might have been appropriate.

However, we believe that none of the possible improvements discussed above would substantially change the performance of the task based strategy. The use of a collective TEM to model job exposure across subjects has been explored in a study of energy expenditure using a validation sample. A squared correlation coefficient of 0. However, the study comprised 27 subjects from 21 occupations which could be expected to differ considerably in exposure even without examination of tasks—for example, a librarian versus a carpenter. The results of the present study suggest that a job exposure matrix would have served equally well to estimate the exposures of the study subjects, and that the efforts invested in obtaining and using task information were probably not very efficient.

This possibility was not discussed by the authors.

In a study of tank terminal workers, task based modelling across subjects was performed using a collective TEM constructed as part of the study. Based on this, it was concluded that estimation of physical load could be improved by task based exposure assessment. However, this interpretation did not consider the fact that collective mean task exposures mask the variability between and within subjects performing a particular task. Other ergonomic studies have evaluated the alternative approach of using personal task exposures to estimate exposure across days within subjects.

In a study of cleaners and office workers, direct measurements were performed for one whole working day per subject, and estimated job exposures were obtained using averaged task proportions across 10 diary days for each participant. However, the analyses did not take into account that the predictive ability of task based estimation across days is reduced by variability of task exposures between days cf tables 2—4. In this respect, the results concerned modelling of exposure across days, although no account was made for day-to-day variability.

However, the evaluation was based on subjects from occupational groups which differed considerably in exposure. As discussed above, this implied that the study did not assess the benefit of task based exposure assessment in excess of what would have been obtained by job based exposure assessment disregarding tasks—that is, by interviewing subjects about the overall exposure in their jobs. Based on the discussion above, we suspect that the lack of success of task based estimation is not confined to the occupational settings investigated in the present study.

On the other hand, studies from other areas of occupational epidemiology suggest that task information may be valuable for exposure assessment within an occupational group if the exposure contrast between tasks is very large and if individuals within a job have thoroughly different work roles. The precision of a group mean obtained by direct measurements on a number of subjects could be only marginally improved by adding subjects for whom only task based job exposure estimates were available. This was a consistent finding in three occupational groups representing a wide range of work tasks and job exposure levels.

The result questions the use of task based exposure assessment in ergonomic investigations aiming at precise group mean values, including group based studies of exposure-response relations.

Ergonomics Evaluation

The finding of weak correlations between estimated and measured job exposures also suggests that task based job exposure estimates may not be superior to estimates based on occupation in exposure-response studies adopting an individual approach to exposure assessment. Therefore, we recommend investigators in ergonomic epidemiology to consider the prospects of task based exposure assessment carefully before placing resources at obtaining task information.

The project was funded by the Danish Rheumatism Association grant no. You will be able to get a quick price and instant permission to reuse the content in many different ways. Skip to main content. We use cookies to improve our service and to tailor our content and advertising to you. More info You can manage your cookie settings via your browser at any time. To learn more about how we use cookies, please see our cookies policy. Log in via OpenAthens. Log in using your username and password For personal accounts OR managers of institutional accounts. Forgot your log in details?


  1. Who may benefit from an ergonomics evaluation?.
  2. North America.
  3. William Faulkner: Shmoop Biography.

Register a new account? Forgot your user name or password? Search for this keyword. Latest content Current issue Archive Authors About. Log in via Institution. Task based exposure assessment in ergonomic epidemiology: TEM, task exposure matrix CNC, computer operated numerically controlled stress mechanical occupational medicine shoulder Accurate and precise exposure data are essential in occupational epidemiology. Data collection The survey was conducted from August to February Policy implications Investigators in ergonomic epidemiology are recommended to consider the prospects of task based exposure assessment carefully before placing resources at obtaining task information.

View inline View popup. Conclusion The precision of a group mean obtained by direct measurements on a number of subjects could be only marginally improved by adding subjects for whom only task based job exposure estimates were available. Acknowledgments The project was funded by the Danish Rheumatism Association grant no. Assessment of physical work load in epidemiologic studies: Ergonomics ; Effect of measurement error on epidemiological studies of environmental and occupational exposures.

Occup Environ Med ;