The daily work load of refuse collectors working with three different collecting methods: a field study

The daily work load of 116 Dutch (male) refuse collectors working with polythene bags, two-wheeled mini-containers and large four-wheeled containers was studied. To this end a time analysis of the tasks and activities in the real working situation was made and the postures and the physiological work load of the collector working with the three different methods was assessed. Manual materials handling and the corresponding working postures were studied by means of observations. Heart rate (HR) was continuously recorded during the working day. Furthermore, to enable the assessment of the work load during refuse collecting as a percentage of the maximal oxygen uptake ([Vdot]O₂max) every refuse collectors' relationship between HR and oxygen uptake was measured during a simulation of the tasks and activities in the laboratory. The range in total working time of the refuse collectors was large. Most time is spent on the task ‘loading’; this lasted on average about 5?h. The mean number of handled objects for the three refuse collecting methods is 1500 bags, 500 mini-containers and 120 large containers respectively. The mean amount of collected refuse per collector of bags and mini-containers is about 11000kg. For the collectors of the large containers it is 27% higher, namely about 14000kg. The mean weight of one object for the bags, mini-container and large container is 7, 22 and 110?kg respectively. The straight posture was the most common in refuse collecting by bags. The posture flexed at the trunk and bent forwards or backwards occurred often while pushing and pulling containers. However, the refuse collectors of the large containers pushed and pulled for shorter periods during a working day in comparison with collectors of the mini-containers. Criteria for energetic overload were set at a mean energy expendiiure of 30% [Vdot]O₂ max and an energy expenditure of 50% [Vdot]O₂ max or more for a maximum of 60?min per day. According to these limits the energetic work load of the collectors of bags was indicated as being too high. In order to formulate guidelines in terms of mechanical and energetic load it is necessary to measure more accurately these loads during refuse collecting activities.     

Effect of the number of two-wheeled containers at a gathering point on the energetic workload and work efficiency in refuse collecting

The effect of the number of two-wheeled containers at a gathering point on the energetic workload and the work efficiency in refuse collecting was studied in order to design an optimal gathering point for two-wheeled containers. Three sizes of gathering points were investigated, i.e. with 2, 16 and 32 two-wheeled containers at a gathering point. The collecting of two-wheeled containers was simulated in a test circuit. The energetic workload was quantified by the parameters oxygen uptake (l min⁻¹), heart rate (beats min⁻¹) and perceived exertion. The work efficiency was quantified as the time it took to collect 32 two-wheeled containers per time period. The maximum acceptable amount of two-wheeled containers collected during an 8-h working day was estimated using the energetic criterion of a maximum oxygen uptake of 30% VO_2max. The size of the gathering point had no effect on the oxygen uptake, heart rate or perceived exertion. However, the number of two-wheeled containers per collecting period (work efficiency) and the maximum acceptable amount during an 8-h working day were higher in the conditions with 16 and 32 two-wheeled containers at a gathering point compared to the condition with the 2 two-wheeled containers at a gathering point.     

Use of the CABS methodology to assess biomechanical stress in commercial crab fishermen

Commercial fishing is a job characterized by long hours in an unpredictable, dynamic natural environment and variable demands placed on the musculoskeletal system, requiring strength, coordination, and endurance. The focus of this project was in the quantification of the biomechanical stresses placed on the lumbar spine during the work activities of commercial crab fishermen. The continuous assessment of back stress (CABS) methodology was used to develop distributions describing the amount of time that each of the crew members on a two- or three-man crabbing crew spend at various levels of low back stress. The results of this analysis, expressed in terms of time-weighted histograms, show significant inter and intra-crewmember variability in the stress measures during regular daily work activities. For the three man crew, the captain has relatively low stress levels throughout the work day, while the mate performs high force (up to 30 kg), dynamic exertions while pulling the crab pots from the water up into the boat and high loads (20-40 kg) during the loading and unloading of the boat in the morning and evening, respectively. The third man of the crew experiences static awkward postures (forward flexed postures held for up to 5 min at a time) as he sorts and packs the crabs. For the two-man crew, the results show a more even distribution of the high stress activities between the crewmembers. The application of the results of this analysis for prioritization of work tasks for ergonomic intervention is discussed.     

The physical and physiological workload of refuse collectors

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (Fmax) and the maximal aerobic power (VO2max) of 23 refuse collectors were measured in the laboratory. Fmax was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (+/- 127)N. VO2max was measured running on a treadmill; the mean value was 43.3 (+/- 0.8)ml O2 per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fmax and a mean energy expenditure of 30% VO2max and an energy expenditure of 50% VO2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.     

The physical and physiological workload of refuse collectors

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (F_max) and the maximal aerobic power( [Vdot]O_2max of 23 refuse collectors were measured in the laboratory. F_max was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (± 127)N. VO_2max was measured running on a treadmill; the mean value was 43-3 (±0-8) ml O₂ per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fm? and a mean energy expenditure of 30% VO_2max and an energy expenditure of 50% VO_2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.     

Guidelines for energetic load in three methods of refuse collecting

The energetic load and guidelines were formulated for energetic load in three methods of refuse collecting. These methods were collecting refuse in polythene bags (in a city area and in a suburb), in two-wheeled mini-containers and in large four-wheeled containers. To determine the energetic load of the collecting methods, these collecting methods were simulated in the laboratory. The simulation protocols were based on data such as weight of the handled materials, and the frequency and duration of the most prominent refuse collecting activities as found in the preliminary field study. During the execution of the protocols the heart rate and oxygen uptake were continuously recorded. The maximal oxygen uptake was determined during a continuous running protocol on a treadmill. The energetic load was expressed in terms of percentage of the maximal oxygen uptake. As the limit for the energetic load a value of 30% of the maximal oxygen uptake during an 8-h working day was chosen. The limit for energetic overload was exceeded for the maximal oxygen uptake for refuse collecting with polythene bags in a city area (44·5%), collecting with bags in a suburb (37·2%) and with mini-containers. The percentage of the maximal oxygen uptake for collecting with large containers was 28·4%, which was below the limit for the energetic load of 30%. Guidelines were formulated for the relevant occupational field terms: maximal amount of collecting hours and maximal amount of collected refuse per collector per hour. The guidelines were formulated in percentiles (P₉₀ and P₇₅). This means that 90 and 75% of the refuse collecting population in The Netherlands will be prevented from having an energetic overload above the limit of 30% of the maximal oxygen uptake.     

Musculoskeletal symptoms among commercial fishers in North Carolina

Musculoskeletal symptoms were reported by 215 fishermen followed at 6-month intervals over 18 months. Exposure information was collected through field observation and in-depth ethnographic interviews allowing potential ergonomic stressors to be identified and catalogued by task and stage of work. Symptoms causing work interference in the last 12 months were reported by 38.5% of the cohort at baseline. Low back symptoms were the most common cause of work impairment (17.7%), followed equally by pain in the hands or wrists and shoulders (7%). Symptoms in any body region were more likely to have been reported among individuals who did not fish full-time and those who worked other jobs part or all year had significantly lower symptom prevalence; both likely reflect a healthy worker effect. A number of ergonomic stressors were identified in all stages of fishing with exposure variability dictated by some unpredictable factors such as weather; but also by type of boat, gear, crew size, and level of experience. Reducing ergonomic exposures associated with work among these traditional workers is important, regardless of whether they directly cause or contribute to their musculoskeletal symptoms, or aggravate existing pathology.     

Conceptions of dentists and dental nurses about ergonomics

Abstract

Sixty-eight dentists and 90 dental nurses, all working in a municipal dental care programme in the city of Helsinki, Finland, were surveyed by a questionnaire about their knowledge of and attitudes towards ergonomics. Thirty-three per cent of the dentists and 36% of the dental nurses were of the opinion that they were at present working according to ergonomic principles. Fifty-one per cent of the dentists and 45% of the nurses could not indicate any ergonomic problem in their place of work. Of the remainder the dental unit was mentioned by 62% of the dentists, and own or counterpart's working posture and habits by 44% of the nurses as the most frequent ergonomic problem. Training in dental ergonomics during undergraduate studies was significantly more general among the nurses than the dentists. Ergonomic knowledge and attitudes were found to correlate with each other, as well as knowledge of ergonomics with training in ergonomics and ergonomic working style, but only among the nurses. The results indicate that a dental team needs functionally-designed dental equipment and instruction in ergonomic principles applied to dentistry.     

Ergonomic Criteria for Occupational and Public Health Surveys

Abstract

Ergonomic criteria express how load causes strain. Epidemiological studies are needed to establish these criteria and these can be further utilized in studying the effects of work on health. For establishing criteria, the exposure to the agent under study should be expressed in quantitative terms. Health-related subjective or objective end-points are available for many types of strain, it is important to indicate the confounding variables, both in regard to the work environment and to the workers studied. In some areas, ergonomic criteria are already used for standard setting. The slate of the art is reviewed for noise, vibration, muscle and tendon syndromes, heart rate and accidents.

With improving occupational health, the end-points available for ergonomic criteria shift from ill-health in the direction of well-being. Further research on ergonomic criteria is required for the purposes of standard setting. A systematic collection and evaluation of ergonomic criteria should be organized as an international effort.

Critères Ergonomiques Destinés aux Enquêtes de Médecine du Travail et de Santé Publique.

Ergunomische Kriterien für Beruffliche und Öffentliche Gesundheitsüberwachungen.     

Routing electric meter readers

Electric utility companies employ a crew of workers who periodically visit and read the electric meters of each customer in their service area. Each reader is transported by auto from a central office to the first customer on his work list. At the end of his work shift time limit the reader is free to leave the area possibly returning home or to the central office by public bus. Taking a graph that corresponds to the city network of streets meter readers must traverse each street while moving from house to house. It is possible that dead heading may be required—back tracking over a street that has already been covered. A working tour is an open path whose reading time plus deadheading time does not exceed the work limit. The problem is to find the minimum number of working tours. Stating the problem in this manner gives us an optimization problem closely related to the M-Chinese postman problem—an edge oriented routing problem. After presenting some background on this type of problem a heuristic procedure is used to solve an example from the City of Beersheva. The solution provides a 40% reduction in the number of working tours. The paper ends with a discussion of the solution, and provides conditions under which the algorithm should have practical utility.     

Cross-sectional study of risk factors for symptoms in the neck and shoulder area

Abstract

This study was performed in order to evaluate how individual characteristics, as well as ergonomic, organizational and psychosocial factors in the work situation are associated with early symptoms in the neck and shoulder area. Nine hundred randomly drawn subjects of the working population in a semi-rural community in Sweden were mailed a questionnaire comprising the Nordic questionnaire on musculoskeletal symptoms, questions on ergonomic, organizational and psychosocial work conditions, life style factors, and background factors. The total response rate was 73% ( n = 637). Questions on ergonomic work conditions and on organizational and psychosocial work conditions provided the measures of exposure. Prevalence ratios (PR) were calculated for symptoms in the neck and shoulder area as reported by 303 subjects. Significant determinants for early symptoms were being a female and being an immigrant, as were repetitive movements demanding precision. High work pace, low work content and work role ambiguity were significant organizational risk factors while life style characteristics did not appear as risk factors. The results suggest that symptoms are signals not only of ergonomic deficiencies in the work situation, but in particular of work organizational conditions. Special attention should be given to the work conditions of women and immigrants in preventive interventions.     

The influence of task design on upper limb muscles fatigue during low-load repetitive work: A systematic review

Ergonomic interventions such as increased scheduled breaks or job rotation have been proposed to reduce upper limb muscle fatigue in repetitive low-load work. This review was performed to summarize and analyze the studies investigating the effect of job rotation and work-rest schemes, as well as, work pace, cycle time and duty cycle, on upper limb muscle fatigue. The effects of these work organization factors on subjective fatigue or discomfort were also analyzed. This review was based on relevant articles published in PubMed, Scopus and Web of Science. The studies included in this review were performed in humans and assessed muscle fatigue in upper limbs. 14 articles were included in the systematic review. Few studies were performed in a real work environment and the most common methods used to assess muscle fatigue were surface electromyography (EMG). No consistent results were found related to the effects of job rotation on muscle activity and subjective measurements of fatigue. Rest breaks had some positive effects, particularly in perceived discomfort. The increase in work pace reveals a higher muscular load in specific muscles. The duration of experiments and characteristics of participants appear to be the factors that most have influenced the results. Future research should be focused on the improvement of the experimental protocols and instrumentation, in order to the outcomes represent adequately the actual working conditions.Relevance to industryIntroducing more physical workload variation in low-load repetitive work is considered an effective ergonomic intervention against muscle fatigue and musculoskeletal disorders in industry. Results will be useful to identify the need of future research, which will eventually lead to the adoption of best industrial work practices according to the workers capabilities.     

Working conditions of Iranian hand-sewn shoe workers and associations with musculoskeletal symptoms

The working conditions and the prevalence of self-reported musculoskeletal symptoms among 180 Iranian hand-sewn shoe workers were evaluated in this cross-sectional study. Data were collected using both questionnaire (for assessing musculoskeletal symptoms and associated risk factors) and direct observations of posture (by the Rapid Upper Limb Assessment [RULA] method). The prevalence and severity of symptoms was very high among the study population. The mean RULA grand score of 6.2 indicates that in most cases the workers' postures at their workstations need to be investigated and some changes are required immediately. Multiple logistic regression models indicated that the job experience, daily working hours, duration of continuous work without breaks, feeling pressure due to work and working postures were significantly associated with musculoskeletal symptoms of different body regions. The results are discussed in terms of their implications for hand-sewing tasks. These findings can help to better understand the working conditions of those jobs involving hand-sewing operation and highlight the potential for ergonomic interventions to reduce musculoskeletal symptoms among these working groups.

Practitioner Summary: Working conditions of hand-sewn shoe workers and their musculoskeletal symptoms were investigated. The prevalence and severity of musculoskeletal symptoms was very high among the study population. Poor working postures, feeling pressure due to work, long duration of work without breaks and prolonged daily working hours were positively associated with musculoskeletal symptoms.     

A Study of Computerized Offices in Greece: Are Ergonomic Design Requirements Met?

In this study, an investigation was conducted into the extent to which ergonomic requirements for work on computers are met in Greek office workstations. The ergonomic requirements considered were those included in Council Directive 90/270/EEC (1990) of the European Union and the ISO 9241 (1997) standard. 593 office workstations were assessed using an assessment tool consisting of 70 assessment points. The assessment results show that the ergonomic requirements that are independent of the specific characteristics of individual work spaces and environments (e.g., design standards for seats, monitors, and input devices) are adequately met. Ergonomic requirements that should take into consideration the specific characteristics and constraints of individual work content, work spaces, and environments (e.g., requirements dealing with workplace layout, environmental conditions, software, and work organization) are inadequately met. Based on these results, issues are indicated on the effort ergonomists should focus to improve working conditions in computerized offices.     

Designing better shift systems

The results of some intervention studies on the effects of the change from weekly rotating to quicker rotating shift systems are presented. Consequently, the following recommendations for the design of shift systems according to physiological, psychological and social criteria are discussed: (1) Nightwork should be reduced as much as possible. If this is not possible, quickly rotating shift systems are preferable to slowly rotating ones. Permanent nightwork does not seem to be recommendable for the majority of shiftworkers. (2) Extended workdays (9-12 hours) should only be contemplated when the nature of work and the workload are suitable for extended working hours, and the shift system is designed to minimize the accumulation of fatigue and toxic exposure is limited. (3) An early start for the morning shift should be avoided. Flexible working time arrangements can be achieved in all shift systems. The highest flexibility is possible in the so-called 'time autonomous groups'. (4) Quick changeovers (e.g. from night shift to afternoon shift on the same day) should be avoided. The number of consecutive working days should be limited to five-seven. Every shift system should include some free weekends with at least two consecutive days off. (5) The forward rotation (phase delay, clockwise rotation: morning/evening/night shift) would seem to be most preferred.     

海铁联运港口混合作业模式下轨道吊与集卡协同调度

在集装箱海铁联运港口中,铁路作业区作为连接铁路运输和水路运输的重要节点,其装卸效率将影响集装箱海铁联运的整体效率。首先,对比分析了“船舶-列车”作业模式和“船舶-堆场-列车”作业模式的特点,并结合海铁联运港口实际作业情况提出了混合作业模式。然后,以轨道吊完工时间最短为目标构建混合整数规划模型,既考虑了班列和船舶的作业时间窗约束,又考虑了轨道吊间干扰和安全距离、轨道吊和集卡接续作业和等待时间等现实约束。针对遗传算法在局部搜索能力方面的不足,将启发式规则与遗传算法相结合设计了求解轨道吊与集卡协同调度问题的混合遗传算法（HGA）,并进行了数值实验。实验结果验证了所提模型和混合算法的有效性。最后通过设计实验分析集装箱数量、岸边箱占比、轨道吊数量和集卡数量对轨道吊完工时间和集卡完工时间的影响,发现同等集装箱数量下岸边箱占比提高时,应通过增加轨道吊数量来有效缩短完工时间。     

The design of shift systems

All shift systems have advantages and drawbacks. There is no single ‘optimum shift system’ which can be used in industry or commerce at all work places. However, there are shift systems which are more favourable, and others which are less favourable, in the context of physiological, psychological, and social recommendations for the design of shift systems. This article discusses the following recommendations:

(1) Nightwork should be reduced as much as possible. If this is not possible, quickly rotating shift systems are preferable to slowly rotating ones. Permanent nightwork does not seem to be advisable for the majority of shiftworkers.

(2) Extended workdays (9-12 h) should only be contemplated, if the nature of work and the workload are suitable; the shift system is designed to minimize the accumulation of fatigue; there are adequate arrangements for cover of absentees; overtime will not be added; toxic exposure is limited; and if it is likely that a complete recovery after work and a high acceptance of the working time arrangement are possible.

(3) An early start for the morning shift should be avoided. In all shiftsystems flexible working time arrangements- are realizable. The highest flexibility is possible in ‘time autonomous groups’.

(4) Quick changeovers (e.g., from night to afternoon shift at the same day or from afternoon to morning shift) must be avoided. The number of consecutive working days should be limited to 5-7 days. Every shift system should include some free weekends with at least two successive full days off.

(5) The forward rotation of shifts (phase delay, clockwise rotation) would seem to be recommendable at least in continuous shift systems.

Besides the design of a shift system, implementation strategy is of particular importance for the acceptance of the shift system.     

Development of an ergonomic evaluation facility for Indian tractors

The design of tractors manufactured in low-income countries like India has not changed much in the past two decades, especially from an ergonomic point of view. Moreover, in these countries tractors are used for transportation purposes in addition to farming operations. Therefore, the design criteria for these tractors need to be different from those in high-income countries. This paper describes the development of an ergonomic facility for improvement of tractor design. An ergonomic evaluation facility has been developed consisting of a work place envelope for the Indian population, a layout measuring device and an ergonomic rig. This facility can be used for comparative evaluation of the display and control layouts of different tractors in order to develop an optimum layout. The ergonomic rig has the facility to simulate the improved layout for subjective evaluation.     

Musculoskeletal disorders among visual display terminal workers: individual,ergonomic, and work organizational factors

A number of individual, ergonomic, and organizational factors of presumed importance for the occurrence of musculoskeletal disorders were investigated in a group of 260 visual display terminal (VDT) workers. The cross-sectional study utilized medical and workplace investigations as well as questionnaires. The results were subjected to a multivariate analysis in order to find the major factors associated with various upper-body muscular problems. Several such factors were identified for each investigated type of musculoskeletal problem. Some were related to the individual: age, gender, woman with children at home, use of spectacles, smoking, stomach-related stress reactions, and negative affectivity. Organizational variables of importance were opportunities for flexible rest breaks, extreme peer contacts, task flexibility, and overtime. Identified ergonomic variables were static work posture, hand position, use of lower arm support, repeated work movements, and keyboard or VDT vertical position.     

Visually deficient working conditions and reduced work performance in office workers: Is it mediated by visual discomfort?

IntroductionThe main purpose of this cross-sectional study was to investigate whether visual discomfort acts as a mediating factor between perceived visual ergonomic working conditions and self-rated visual performance among office workers who carry out administrative tasks and computer-based work at the Swedish Tax Agency.MethodsA questionnaire was sent to 94 office workers addressing: 1) perceived visual quality of the visual display units; 2) prevalence of eye symptoms; and 3) self-rated visual performance. Eighty-six persons (54 women (63%), 31 men (36%), and 1 of unspecified sex) answered the questionnaire. Multiple regression analysis investigated the association between visual ergonomic working conditions and visual performance, both with and without visual discomfort as a mediator.ResultsThe group mean of the Indexed survey questions indicated a reasonably good quality of visual ergonomic working conditions, a relative absence of eye symptoms, and acceptable self-rated visual performance. Results from multiple regression analysis showed a significant association between perceived visual ergonomic working conditions and self-rated visual performance (r² = 0.30, β = 0.327, p < 0.01). When visual discomfort was used as a mediator, the association between perceived visual ergonomic working conditions and self-rated visual performance remained the same (r² = 0.32, β = 0.315, p < 0.01).DiscussionIt was remarkable to discover that self-rated visual performance was independent of visual discomfort. Possible explanations include exposure factors not included in the current study, such as dry air and sensory irritation in the eyes, psychosocial stress, time spent performing near work activities, or time exposed to visually deficient working conditions.Relevance to industryThe strong connection between satisfaction with visual ergonomic working conditions and productivity in this study has implications for workplace profitability and staff satisfaction. If productivity is enhanced by better visual ergonomic working conditions, then managers of workplaces may be able to improve work outcomes by optimizing the physical work environment.