Self-assessed and directly measured occupational physical activities--influence of musculoskeletal complaints, age and gender

This study compares questionnaire assessed physical activity with direct technical measurements among cleaners and office workers, stratified regarding age, gender and self-reported neck/shoulder complaints. During two full working days number of steps was recorded by a pedometer, sitting/standing positions by a posimeter and heart rate by a Sport-Tester. In addition the subjects kept a work task diary for 10 days. There were high intra-individual variations in exposure between the days. Subjects with complaints rated their exposure higher than those without, although they in fact showed lower direct measured exposure. This may imply underestimation of exposure-effect relationships. Rate of perceived exertion showed low correlation with heart rate ratio within the two occupational groups, but high, 0.64 when the two groups were combined. Age and complaints explained 31% of the variance for the cleaners.     

Direct measurements and systematic observations of physical workload among medical secretaries, furniture removers and male and female reference populations

The aim of this investigation was to collect quantitative information about the occurrence of manual materials handling and working postures in working life. Direct technical recordings and systematic observations by trained ergonomists were used throughout a whole working day on 12 male furniture removers, 13 female medical secretaries, 27 males and 45 females randomly sampled from the working population in the Stockholm area. A quantitative job exposure profile was obtained by weighting together exposure data obtained by observation of tasks occurring during a normal working week. The results showed no major differences in physical exposures between the male and female reference populations. The medical secretaries spent less time than the female population kneeling/squatting and longer time than any other group with repetitive hand movements. Exposure data for task and job should be clearly distinguished.     

Task exposures in an office environment: a comparison of methods

Task-related factors such as frequency and duration are associated with musculoskeletal disorders in office settings. The primary objective was to compare various task recording methods as measures of exposure in an office workplace. A total of 41 workers from different jobs were recruited from a large urban newspaper (71% female, mean age 41 years SD 9.6). Questionnaire, task diaries, direct observation and video methods were used to record tasks. A common set of task codes was used across methods. Different estimates of task duration, number of tasks and task transitions arose from the different methods. Self-report methods did not consistently result in longer task duration estimates. Methodological issues could explain some of the differences in estimates seen between methods observed. It was concluded that different task recording methods result in different estimates of exposure likely due to different exposure constructs. This work addresses issues of exposure measurement in office environments. It is of relevance to ergonomists/researchers interested in how to best assess the risk of injury among office workers. The paper discusses the trade-offs between precision, accuracy and burden in the collection of computer task-based exposure measures and different underlying constructs captures in each method.     

Work organisation and gender among hospital cleaners in Quebec after the merger of 'light' and 'heavy' work classifications

In Québec, Canada, cleaning tasks were once divided into 'light' or 'heavy' cleaning, assigned respectively to women and men. These categories are being merged; in principle, both genders are assigned the same tasks. Activity analysis using observations and interviews examined work activity of male and female cleaners in two hospitals. In one hospital, work activity could be compared before (time 1) and after the work reorganisation (time 2). Some gender segregation of tasks appeared to have persisted at time 2, in both hospitals. Some route assignments contained components that were difficult for all cleaners, especially women of average strength. Only about one-third of the recommendations for improvement made at time 1 had been carried out by time 2, 12 years later. In a low-status job, it may be hard to meet equality, health and efficiency goals because commitment to improving equipment and worksite design may be lacking. PRACTITIONER SUMMARY: Current attempts to desegregate jobs should be accompanied by attention to physical job demands in order to protect employee health and access to equal employment. The study also shows the need to follow up ergonomic interventions, particularly in low-status jobs such as cleaning, where recommendations can be forgotten.     

An evaluation of classification algorithms for manual material handling tasks based on data obtained using wearable technologies

With recent progress in wearable measurement systems, physical exposures can be feasibly assessed at high precision in the workplace. Such systems, however, generally lack contextual information for a given job (e.g. task type, duration). To extract such information, we explored three classification algorithms to classify manual material handling (MMH) tasks during a simulated job in a laboratory, using several combinations of outputs from commercially available inertial motion capture and in-shoe pressure measurement systems. A total of 10 participants completed three replications of four cycles of a simulated job. Precision and recall values of ≥ ～90% and 80%, respectively, and errors in estimated task duration of < ～14%, could be achieved across the MMH task examined. Classification performance, however, varied between classification algorithms, input data sets and task types. Overall, combining wearable technology with task classification could be an effective approach for field-based exposure assessment, though field-testing is needed to demonstrate the applicability of this method.

Practitioner Summary: Combining wearable technologies with task classification was explored to extract exposure context, specifically task type and duration. Results supported that task classification can facilitate the use of wearable technologies in field-based exposure assessment, specifically by aiding in task identification from within the rather large data sets obtained from these technologies.     

Assessment of duration and frequency of work tasks by telephone interview: reproducibility and validity

Quantitative estimation of physical work load requires breakdown of jobs into smaller entities. The objective was to study the inter-rater reproducibility of the contents, frequency and duration of work tasks assessed by telephone interview. Two researchers interviewed 18 industrial workers with an interval of from 2 to 3 weeks in a balanced and blinded design. Altogether 114 tasks were identified, 68 of which were recorded by both interviewers. The tasks were classified into regularly occurring (n = 34) and occasional (n = 80). The outcome was the total duration of the tasks per day computed from the data on frequency and duration. Validity of the interview was studied against prestructured diaries filled in by nine workers. The interviewers' assessments of the overall contents of the tasks were rated as 'similar' or 'very similar' for 17 of the 18 workers. Both interviewers detected all 34 regularly occurring tasks. The intraclass correlation coefficient (ICC) of the total duration between the interviewers was 0.81 for regularly occurring tasks. ICCs of the total duration between the diary and the two interviewers were 0.90 and 0.91. However, in many cases the workers could not give a numerical value for duration or frequency. A telephone interview can be used as a first step in exposure assessment in epidemiological studies on risk factors of musculoskeletal disorders. These results show that a single telephone interview can give reproducible and valid information of the frequency and duration of tasks occurring daily. For occasional tasks interview methods should be developed further.     

Work routinization and implications for ergonomic exposure assessment

Jobs in many modern settings, including manufacturing, service, agriculture and construction, are variable in their content and timing. This prompts the need for exposure assessment methods that do not assume regular work cycles. A scheme is presented for classifying levels of routinization to inform development of an appropriate exposure assessment strategy for a given occupational setting. Five levels of routinization have been defined based on the tasks of which the job is composed: 1) a single scheduled task with a regular work cycle; 2) multiple cyclical tasks; 3) a mix of cyclical and non-cyclical tasks; 4) one non-cyclical task; 5) multiple non-cyclical tasks. This classification, based primarily on job observation, is illustrated through data from a study of automobile manufacturing workers (n = 1200), from which self-assessed exposures to physical and psychosocial stressors were also obtained. In this cohort, decision latitude was greater with higher routinization level (p < 0.0001), and the least routinized jobs showed the lowest self-reported exposure to physical ergonomic stressors. The job analysis checklist developed for non-routinized jobs is presented, and limitations of the task analysis method utilized in the study are discussed. A work sampling approach to job analysis is recommended as the most efficient way to obtain a comparable unbiased exposure estimate across all routinization levels.     

Assessment of duration and frequency of work tasks by telephone interview: reproducibility and validity

Quantitative estimation of physical work load requires breakdown of jobs into smaller entities. The objective was to study the inter-rater reproducibility of the contents, frequency and duration of work tasks assessed by telephone interview. Two researchers interviewed 18 industrial workers with an interval of from 2 to 3 weeks in a balanced and blinded design. Altogether 114 tasks were identified, 68 of which were recorded by both interviewers. The tasks were classified into regularly occurring (n=34) and occasional (n= 80). The outcome was the total duration of the tasks per day computed from the data on frequency and duration. Validity of the interview was studied against prestructured diaries filled in by nine workers. The interviewers' assessments of the overall contents of the tasks were rated as ‘similar’ or ‘very similar’ for 17 of the 18 workers. Both interviewers detected all 34 regularly occurring tasks. The intraclass correlation coefficient (ICC) of the total duration between the interviewers was 0.81 for regularly occurring tasks. ICCs of the total duration between the diary and the two interviewers were 0.90 and 0.91. However, in many cases the workers could not give a numerical value for duration or frequency. A telephone interview can be used as a first step in exposure assessment in epidemiological studies on risk factors of musculoskeletal disorders. These results show that a single telephone interview can give reproducible and valid information of the frequency and duration of tasks occurring daily. For occasional tasks interview methods should be developed further.     

Equal task,equal exposure? Are men and women with the same tasks equally exposed to awkward working postures?

The aim of the study was to determine whether men and woman with equal tasks perform these tasks in the same way. Video recordings of 37 male and 43 female workers in six task groups were observed, from which data regarding frequency and duration of exposure to awkward postures were derived. These data were also compared to self-reported exposures. The results showed that when level, duration and frequency of exposure were analysed at the same time, men and women had slightly different exposure patterns. However, these differences were not found when duration and frequency were analysed separately. From the questionnaires it appeared that men and women generally report similar exposures, but they seemed to over-report their exposure compared to the observed exposures. It is concluded that gender differences in exposure to awkward postures within the same task were small at most and cannot explain the female excess in musculoskeletal symptoms.     

The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in diary farming, using ambulatory heart rate and oxygen consumption measurements. The rate of perceived exertion was estimated with Borg scale. The maximal oxygen consumption was measured in the laboratory. The study group consisted of eight male and 15 female farmers. The handling of feed and manure was the heaviest work task in dairy farming. The aerobic capacity (VO2 max) of female farmers (26 +/- 3 ml/min/kg) was below average, and their work required over 50% of VO2 max during most of the tasks. The VO2 max of male farmers (32 +/- 10 ml/min/kg) was moderate, and most work tasks required below 50% of VO2 max. The mean heart rate in dairy farming tasks was 99 beats min-1 in men and 116 beats min-1 in women. However, according to the rate of perceived exertion, the mean experienced the same work tasks as subjectively more heavy than did the women. The physical strain of female farmers in dairy farming seems to be too high because of heavy work tasks and relatively low VO2 max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

The ability of non-computer tasks to increase biomechanical exposure variability in computer-intensive office work

Postures and muscle activity in the upper body were recorded from 50 academics office workers during 2 hours of normal work, categorised by observation into computer work (CW) and three non-computer (NC) tasks (NC seated work, NC standing/walking work and breaks). NC tasks differed significantly in exposures from CW, with standing/walking NC tasks representing the largest contrasts for most of the exposure variables. For the majority of workers, exposure variability was larger in their present job than in CW alone, as measured by the job variance ratio (JVR), i.e. the ratio between min–min variabilities in the job and in CW. Calculations of JVRs for simulated jobs containing different proportions of CW showed that variability could, indeed, be increased by redistributing available tasks, but that substantial increases could only be achieved by introducing more vigorous tasks in the job, in casu illustrated by cleaning.     

The use of continuous exposure data for predicting CTS in fish processing operators

Carpal tunnel syndrome (CTS) remains one of the most commonly reported and studied work related musculoskeletal disorders. Categorical representations of exposures has been critical in identifying associations between risk factors and CTS, however, quantification of exposure—response relationships require using continuous exposure data. Also, few interactions between risk factors, especially between risk factor categories, have been investigated. The objectives of this study were to investigate the utility of using continuous exposure data and to identify interaction effects of risk factors, both within and between risk factor categories, for predicting CTS. A cross sectional study was performed at a fish processing facility in which 53 participants were evaluated during normal task performance. Due to task asymmetry, each hand was considered separately, providing 106 hands for analysis. Direct measurement and a questionnaire were used to quantify exposures to common occupational and personal risk factors. Stepwise logistic regression analysis was performed to identify three models for predicting CTS and assess predictive ability using: occupational risk factors only (three-way interactions considered), personal risk factors only (two-way interactions considered), and a mixed model considering two-way interactions across risk factor categories and previously identified significant interactions. Models including only occupational or personal risk factors were moderately accurate overall (73% and 77% respectively), but were not sensitive in differentiating between CTS cases and non-cases (39% and 33% respectively). The mixed model was found to be accurate (88%) and sensitive (78%), though only one interaction effect was included. The results of this study illustrate the importance of using continuous exposure data, especially in job tasks where exposures to occupational risk factors is similar, when differentiating between high and low risk job tasks.     

The use of continuous exposure data for predicting CTS in fish processing operators

Carpal tunnel syndrome (CTS) remains one of the most commonly reported and studied work related musculoskeletal disorders. Categorical representations of exposures has been critical in identifying associations between risk factors and CTS, however, quantification of exposure-response relationships require using continuous exposure data. Also, few interactions between risk factors, especially between risk factor categories, have been investigated. The objectives of this study were to investigate the utility of using continuous exposure data and to identify interaction effects of risk factors, both within and between risk factor categories, for predicting CTS. A cross sectional study was performed at a fish processing facility in which 53 participants were evaluated during normal task performance. Due to task asymmetry, each hand was considered separately, providing 106 hands for analysis. Direct measurement and a questionnaire were used to quantify exposures to common occupational and personal risk factors. Stepwise logistic regression analysis was performed to identify three models for predicting CTS and assess predictive ability using: occupational risk factors only (three-way interactions considered), personal risk factors only (two-way interactions considered), and a mixed model considering two-way interactions across risk factor categories and previously identified significant interactions. Models including only occupational or personal risk factors were moderately accurate overall (73% and 77% respectively), but were not sensitive in differentiating between CTS cases and non-cases (39% and 33% respectively). The mixed model was found to be accurate (88%) and sensitive (78%), though only one interaction effect was included. The results of this study illustrate the importance of using continuous exposure data, especially in job tasks where exposures to occupational risk factors is similar, when differentiating between high and low risk job tasks.     

Variation at work: alternations between physically and mentally demanding tasks in blue-collar occupations

Abstract

The aims of this questionnaire study were to describe the occurrence and desired number of alternations between mental and physical tasks in industrial and non-industrial blue-collar work, and determine to which extent selected personal and occupational factors influence these conditions. On average, the 122 participating workers (55 females) reported to have close to four alternations per day between mental and physical tasks, and to desire more alternations than they actually had. They also expressed a general preference for performing a physical task after a mental task and vice versa. In univariate regression models, the desired change in task alternations was significantly associated with gender, age, occupation, years with current work tasks and perceived job control, while occupation was the only significant determinant in a multiple regression model including all factors. Our results suggest that alternations between productive physical and mental tasks could be a viable option in future job rotation.

Practitioner Summary: We addressed attitudes among blue-collar workers to alternations between physically and mentally demanding tasks. More alternations were desired than those occurring in the job, and workers preferred performing a physical task after a mental and vice versa. Alternating physical and mental tasks could, thus, be a viable option in job rotation.     

The relationship between shoulder torques and the perception of muscular effort in loaded reaches

The objective of this study was to define the quantitative relationship between external dynamic shoulder torques and calibrated perceived muscular effort levels for load delivery tasks, for application in job analyses. Subjects performed a series of loaded reaches and, following each exertion, rated their perceived shoulder muscular effort. Motion and task physical requirements data were processed with a biomechanical upper extremity model to calculate external dynamic shoulder torques. Calculated torque values were then statistically compared to reported calibrated perceived muscular effort scores. Individual subject torque profiles were significantly positively correlated with perceived effort scores (r2 = 0.45-0.77), with good population agreement (r2 = 0.50). The accuracy of the general regression model improved (r2 = 0.72) with inclusion of factors specific to task geometry and individual subjects. This suggests two major conclusions: 1) that the perception of muscular shoulder effort integrates several factors and this interplay should be considered when evaluating tasks for their impact on the shoulder region; 2) the torque/perception relationship may be usefully leveraged in job design and analysis.     

The impact of team task and job engagement on the transfer of tacit knowledge in e-business virtual teams

This research focuses on the initiative to integrate team task and job engagement as related to the transfer of tacit knowledge. The aim of this study is to investigate if team task and job involvement enhances the overall work efficiency through transfer of tacit knowledge between e-business virtual teams. We develop a model that is based on the relationship between tacit degree of knowledge, job engagement, team tasks, and their effect on knowledge transfer. The conceptual model is validated with the data collected from a survey. The results indicate that the tacit knowledge does not have a positive effect on team tasks and job engagement, and the team tasks and job engagement have a significant positive effect on knowledge transfer. In addition, the study found that team tasks and job engagement have mediating effects in the process of tacit knowledge transfer. Also, we discuss the theoretical and practical implications and contributions of this study.     

Integration of task networks and cognitive user models using coloured Petri nets and its application to job design for safety and productivity

Changes of task demands due to unforeseen events and technological changes can cause variations in job design such as modifications to job procedures and task allocation. Failure to adapt to job design variations can lead to human errors that may have severe consequences for system safety. Existing techniques for task modelling cannot adequately model how task networks can be adapted to changing work conditions and task demands. Therefore, there is a need to integrate task networks with cognitive user models that indicate how operators process information, make decisions, or cope with suspended tasks and errors. The work described here presents a tool for integrating task and cognitive models using coloured Petri nets. The cognitive user model comprises two modules of attention management (selective and divided attention), a module of memory management of suspended tasks and a module of work organization. Performance Shaping Factors (e.g., workload, fatigue and mental-tracking load) are calculated at any point in time to take into account the context of work (e.g., competing activities, errors and suspended tasks). Different types of human error can be modelled for rule-based behaviours required in proceduralized work environments. Simulation analysis and formal analysis techniques can be applied to process control tasks to verify job procedures, workload management strategies and task allocation schemes in response to technological changes and unfamiliar events.     

Task performance in heat: a review

A wide array of variable conditions, tasks, subject populations, etc., have been included in studies that have produced data on perceptual motor performance in the heat. This paper uses a methodology for comparing these studies, regardless of the inherent differences, which allows determination of whether thermal effects are dominant enough to persist through diverse combinations of variables. Approximately 160 individual studies of perceptual motor performance reported in the literature were summarized based on thermal level, duration of exposure and the type of task performed. Results indicated no dominant effect of duration of exposure to the heat and no dominant effect of thermal level on mental/cognitive tasks. For perceptual motor tasks other than very simple or mental tasks, an onset of performance decrement was noted in the 30-33°C WBGT range of temperature. This temperature level is consistent with the Recommended Exposure Limits for work in the heat at low levels of metabolic heat.     

Job enlargement and mechanical exposure variability in cyclic assembly work

Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level, frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known.