Showing papers in "Applied Ergonomics in 1992"

Questionnaire development: an examination of the Nordic Musculoskeletal questionnaire.

Abstract: This paper describes the outcome of user trials of the Nordic Musculoskeletal Questionnaire which encompassed the views of the following groups: data entry clerks, technical staff, administrative clerks and 481 subjects employed in 10 supermarkets. A significant number of improvements was identified, especially concerning its wording, layout and administration. This has led to a standardized version being produced for use in studying the prevalence of reported symptoms in many types of occupational groups.

Employee stress and health complaints in jobs with and without electronic performance monitoring.

Abstract: Current applications of electronic performance monitoring based on job design theories that consider worker performance rather than stress issues are likely to generate unsatisfying and stressful jobs (Smith et al, 1986). This study examines critical job design elements that could influence worker stress responses in an electronic monitoring context. A questionnaire survey of employees in telecommunications companies representative of each region in the United States examined job stress in directory assistance, service representative and clerical jobs with specific emphasis on the influence of electronic monitoring of job performance, satisfaction and employee health. Useable surveys were received from 745 employees representing seven operating companies and AT & T; a response rate of about 25%. The results of this survey indicated that employees who had their performance electronically monitored perceived their working conditions as more stressful, and reported higher levels of job boredom, psychological tension, anxiety, depression, anger, health complaints and fatigue. It is postulated that these effects may be related to changes in job design due to electronic performance monitoring.

Human error identification in human reliability assessment. Part 1: Overview of approaches

Abstract: This paper reviews a number of approaches which can be used to identify human errors in human-machine systems. These approaches range from simple error classifications to sophisticated software packages based on models of human performance. However, the prediction of human behaviour in complex environments is far from being an easy task itself, and there is significant scope for improvement in human error identification ‘technology’. This first paper in a series of two reviews the available techniques of human error identification, highlighting their strengths and weaknesses. The second paper will review the validation of such approaches, and likely future trends in this area of human reliability assessment.

Back pain in nurses: epidemiology and risk assessment.

Abstract: It is widely recognized that back pain is a serious problem within the nursing profession. This paper commences with a review of epidemiological data concerning the magnitude of this problem: first, with regard to the excess prevalence of back pain in nurses (as compared with the general population); second, with regard to the impact of back pain in terms of sickness absence, and labour turnover; and third, with regard to the association between back pain and patient handling. There follows a formalized assessment of the level of risk inherent in a number of common patient-handling procedures. (This is based upon a new analysis of a number of existing sources of data which have not been gathered together before.) For each procedure, intra-abdominal pressure (IAP) is calculated as a function of patient weight and the level of risk is measured in terms of the probability of a criterion level of 45 mmHg (6.0 kPa) being violated. The paper concludes with a discussion of the implications of these findings for an ergonomic approach to the design of safe systems of work.

Eye movement and pupillary response indices of mental workload during visual search of symbolic displays.

Abstract: Eye movement and pupillary response measures (in addition to search time and accuracy) were collected as indices of visual workload during two experiments designed to evaluate the addition of colour coding to a symbolic tactical display. Displays also varied with regard to symbol density and the type of information participants were required to abstract from the display. These variables were factorially manipulated to examine the effects of colour coding in conditions of varying difficulty. In Experiment 1 (n = 8), search time and the number of eye fixations were affected by all variables and in a similar manner; fixation dwell time and the pupillary response dissociated from the other measures. Compared to monochrome displays, colour coding facilitated search (reduced search time, but not accuracy) during exhaustive search, but had no effect during self-terminating search. Experiment 2 (n = 8) was a replication of Experiment 1 with a pseudo-search control condition added to examine further the pupillary response measures: in particular, to assess the effects of the physical parameters of the displays, and to verify the findings of Experiment 1. Pupillary response measures were sensitive to the information processing demands of the search task, not merely to the physical parameters of the display. Further, the search time, accuracy, and eye movement results from the active search condition generally replicated Experiment 1, but the fixation dwell time data did not. These between-study differences were interpreted as indicating the importance of participant search strategy.

Human error identification in human reliability assessment. Part 2: Detailed comparison of techniques.

Abstract: This is the second part of a two-part review of human error identification (HEI) approaches in human reliability assessment (HRA). Part 1 reviewed the probabilistic risk assessment (PRA) context in which HRA occurs, and then detailed 12 HEI techniques which have evolved in the field of HRA. Part 2 attempts to compare the way these techniques perform against a range of criteria relevant to HEI theoretical and empirical validity, and practical usefulness in applied HRA. It is hoped that these comparisons will help assessors in the selection of techniques for practical applications. The comparisons also point to research and development needs in the area of applied HEI.

An evaluation of a weightlifting belt and back injury prevention training class for airline baggage handlers.

Abstract: This study evaluated the efficacy of a commercially available weightlifting belt in relation to reduction of lumbar injury incident rate and severity of injuries over an 8-month period. The study used 642 baggage handlers working for a major airline company as participants. Four treatment groups were randomly selected: a group receiving the belt only, a group receiving a 1 h training class only, a group receiving both a belt and a 1 h training class, and a control group receiving nothing. Two treatment groups were added which contained participants who discontinued use of the belt prior to the end of an 8-month study period. Results indicated that there were no significant differences for total lumbar injury incident rate, restricted workday case injury incident rate, lost workdays and restricted workdays rate, and worker's compensation rates. There was, however, a marginal significant difference for lost workday case injury incident rate. Groups with participants who wore the belt for a while then discontinued its use had a higher lost day case injury incident rate than did either the group receiving training only or the control group. Compliance was an overriding factor as the belt questionnaire response indicated that 58% of participants in the belt groups discontinued use of the belt before the end of 8 months. Comments made on the survey forms indicated that the belt was too hot. Similarly, comments suggested that the belt rubbed, pinched, and bruised ribs. Based on these results, the weightlifting belt used for this study cannot be recommended for use in aid of lifting during daily work activities of baggage handlers. Results indicate that use of the belts may, in fact, increase the risk of injury when not wearing a belt following a period of wearing a belt. As industries are experimenting with the use of belts, it is recommended that great care be taken in any further evaluation and close attention directed towards injuries which occur when not wearing the belt following a period of wearing the belt (ie, off-the-job injuries).

Working postures and activities of lorry drivers: a reliability study of on-site observation and recording on a pocket computer.

Abstract: Poor working postures are associated with the development of musculoskeletal disorders. Many different observation methods have been developed to analyse working posture and activity. TRAC (Task Recording and Analysis on Computer) enables the observer to choose and define the variables and the categories within variables to be recorded at the workplace and analysed afterwards. In this study, inter-observer reliabilities were determined for the variables that were essential to ensure accurate recording of both working posture and activity of lorry drivers. The pre-set standard for observer reliability was not reached before the number of variables was decreased: the variables concerning activities and load handled were omitted in favour of those concerning body posture. As a result of this reliability study an improved application of TRAC is proposed. For the purpose of recording all selected variables a second observer is introduced, so that two observers work simultaneously at the working site. The first observer pays attention only to working postures and the second observer records, among other things, activities. An additional program has been written to combine the variables of both observers for subsequent analysis. This enables us to investigate the relation between activity, appliances or goods being handled, and the corresponding working postures. The second observer records on a real-time basis and provides accurate information on the duration and sequence of activities. It is considered that this twofold application of TRAC is an important contribution to the accurate analysis of workplaces.

Measurement of trunk bending during work by direct observation and continuous measurement

Abstract: An observational method and a continuous measurement technique were simultaneously applied to record bending of the trunk during work. In a group of 16 workers performing dynamic tasks a significant correlation (r = 0.57) was found between the two methods. A similar result was observed among 14 sedentary workers (r = 0.62). Although significant correlations between direct observation and continuous recording techniques were present, large differences were found between data obtained from individual subjects. The results cast doubt on the validity of assessments of percentage of worktime with bent trunk at an absolute level using only one measurement method. It is suggested that greater consideration has to be given in future studies to the reliability of measurement of postural load due to trunk bending.

Stress, computer-based work monitoring and measurement systems: A conceptual overview.

Abstract: The design and implementation of computer-based work monitoring systems can result in changes in the organization, job and task. Electronic performance monitoring (EPM) systems are one type of change based on principles of work simplification and work rationalization. In this new work arrangement, control and coordination functions are allocated to the computer. The supervisor becomes a monitor of information and primarily provides negative performance feedback to the employee. The employee is constrained in his/her ability to use either job resources or social resources to meet the greater demands resulting from the system controlling the pace of work. It is proposed that these work arrangements provoke stress responses in employees that can result in short-term illness and potentially long-term changes in health status. Information enriched work environments are proposed as an alternative. These new work arrangements could improve job resources and social resources to manage job demands and reduce the potentially damaging stress responses. To provide a frame of reference we focus on the impact of EPM systems on the organizational and job elements involved in provoking individual stress responses. The impact of EPM systems on individual health is described using a psychosocial stress framework. Ergonomics interventions discussed include: participation in the design process; allocation of control and coordination functions between the computer and the employee; development of feedback systems; and work measurement and the development of performance appraisal systems.

Two key factors that belong in a macroergonomic analysis of electronic monitoring: Employee perceptions of fairness and the climate of organizational trust or distrust.

Abstract: Two microergonomic elements not usually discussed in treatments of electronic monitoring of VDT clerical work are employee perceptions of fairness (in work standards and measurement process) and the overall climate of employee trust in management. The author's field studies found these factors serving as major mitigating or intensifying elements in the stress that clerical employees can experience when they perform intensive heavy-duty VDT applications, and as central variables in distinguishing beneficial from harmful monitoring programmes. A case study involving change in supervisory monitoring policies for 200 customer service agents at one of Federal Express Corporation's telecommunication call centres in the USA in 1985–86 demonstrates how a Unit Head at a non-union company long known for its positive employee relations policies installed monitoring practices that the call agents considered unfair and a breach of the company's traditional climate of employee-employer trust. Employee protests, when communicated to top management, led to discarding the unilaterally-instituted and quantity-oriented monitoring policy and replacing it with a consensually-developed supervisory monitoring system balancing quality and quantity elements in a way that satisfied both employees and management. The present system of supervisory monitoring of customer service work at Federal Express (1991) enjoys broad employee support, suggesting that a fair system of monitoring, applied in an environment of earned trust between employees and employer, can meet critical productivity and quality interests of employers in clerical VDT work without creating harmful employee stress and discontent. It also suggests that empirical investigation of the fairness and trust factors represents an important and practical area of research in a macroergonomic analysis of employee monitoring programs and impacts.

When is light work heavy? Components of the physical workload of sewing machine operators working at piecework rates

Abstract: Epidemiologists have associated the job of sewing machine operators with a high incidence of musculoskeletal and other health problems, despite its classifications as light work according to energy expenditure criteria. An ergonomic analysis was undertaken in a trouser factory in order to describe components of the physical load of this work: force exerted, repetitions, time allocation and postures. Work activity of ten operators was observed and timed in situ, and forces were measured with a dynamometer. The time required to sew one seam is very short, 10–15 s per trouser leg. This short cycle is repeated more than 1500 times during the work day, involving quasi-continuous movements of the same parts of the body. The fact that movements are repeated so many times means that small details of the task assume a great importance. During the work day, a substantial force is exerted, only part of which can be measured with current technology. By these measurements, operators lift an average 406.1 kg of trousers per day and exert an average total force of 2858.4 kg with the upper limbs and 24 267.9 kg with the lower limbs. The work posture is static: seated with upper back curved and head bent over the sewing machine. Movements of the upper limbs involve abduction and adduction of the shoulders while exerting a force. For the same task, there is considerable variation in the dimensions of workstations. Interviews were conducted to determine the types of musculoskeletal complaints. The components of work activity could be treated to these complaints and to existing epidemiological data on musculoskeletal problems among sewing machine operators. This type of detailed examination can be applied by health and safety personnel to identify task components which could be changed to minimize the probability of musculoskeletal problems.

Operator stress and monitoring practices.

Abstract: This study attempted to identify the major sources of work-related stress among telephone operators, with special emphasis on computer monitoring and telephone surveillance. A cross-sectional random sample of over 700 telephone operators participated in a questionnaire survey (response rate = 88%). The survey included items designed to measure perceived stress, management practices, specific job stressors and monitoring preferences. Call-time pressure items were most strongly linked to job stress by operators, with 70% reporting that difficulty in serving a customer well and still keeping call-time down contributed to their feelings of stress to a large or very large extent. About 55% of operators reported that telephone monitoring contributed to their feelings of job stress. If given the opportunity, 44% of operators stated they would prefer not to be monitored by telephone at all, while 23% stated they would prefer some monitoring; 33% had no preference. The setting of inappropriate individual-call-time objectives, which may be consistently unachievable for some operators and which create conflict between management demands for quantity and quality and also between workers values concerning quality and productivity demands, appears to be the most stress-inducing aspect of the job. In terms of telephone surveillance, the issues of timeliness and specificity of feedback appear to be less important than call-time pressure.

Electronic performance monitoring: A review of research issues.

Abstract: The research literature on electronic performance monitoring (EPM) has attributed different outcomes to monitoring, including improved worker performance, reduced job satisfaction and increased job stress. A variety of research methods (case study, cross-sectional and laboratory designs) has been utilized to study these effects of EPM. In this paper, these methods are reviewed, and the results of several studies are summarized. The existing literature often does not clearly specify what is meant by monitoring. Future research on outcomes associated with monitoring should describe carefully the type of monitoring technology and system used - who does the monitoring, when it is done, and what aspect of performance is monitored. It is further suggested that future EPM research should describe in greater detail the work environment, the job tasks, and the organizational climate of monitored and non-monitored workers to determine whether these groups are comparable with respect to these factors, and that observed outcomes are not misattributed to EPM.

A review of physical exercises recommended for VDT operators.

Abstract: This paper presents an evaluation of exercises that have been recommended for the prevention of musculoskeletal discomfort among VDT/office workers. 127 individual exercises were analysed for their suitability for performance in VDT workplaces. Additionally, each exercise was judged in terms of its safety and its compliance with principles of physiotherapy. Results showed that, in the majority of cases, the prepared instructions for the exercises were satisfactory and the exercises could be readily performed at the workstation. However, over a third of the exercises were conspicuous and potentially embarrassing to perform, and half would significantly disrupt the work routine. Additionally, a number of the exercises posed potential safety hazards, exacerbated biomechanical stresses common to VDT work, or were contraindicated for persons with certain health problems. These findings suggest a need for greater attention to both the practical and the therapeutic aspects of exercises promoted for VDT users.

An experimental comparison of test and symbols for in-car reconfigurable displays.

Abstract: As cars become more sophisticated, there is a corresponding increase in the range of information which needs to be presented to drivers. This increased information load is beyond the scope of conventional technology; space requirements on the dashboard limit the number of displays, which can be employed. The study reported in this paper is based on the premise that centralized information presentation could be employed for in-car warming systems. Forty subjects were tested on a computer-based task, in which they had to rate the urgency of displayed information. The information was presented in one of four formats: symbols only, symbols plus title, symbols plus action, or symbol, title and action. Results show that the most effective type of display for urgency rating was symbol plus action, and that symbol, title and action produced the fastest reaction times. These results are considered in terms of previous research, and implications for the design of in-car warnings are discussed.

A review and reappraisal of electronic performance monitoring, performance standards and stress allowances.

Abstract: There is a growing trend toward electronic performance monitoring (EPM) to track the performance of workers engaged in computer-based tasks. Despite the possible productivity advantages of this approach to work management, the use of EPM may produce stress through work overload, negative computer feedback, loss of incentive pay and threat of job loss. These stress effects are most likely to occur among workers who have difficulty meeting work standards (eg, forms processed per hour) enforced through EPM. A stress allowance is proposed as a new category of work allowance for adjusting EPM work standards so as to minimize imbalances between task demands and the worker's resources to adapt.

Predicting garment pattern dimensions from photographic and anthropometric data

Abstract: Traditional linear measurements (lengths and circumferences taken over the body surface with a tape measure) were compared with measurements of frontal and lateral view photographs for usefulness in determining pattern dimensions for the upper torso of the female body form. The statistical regression models developed indicated that, while linear measurements provided slightly more accuracy in predicting a few of the pattern dimensions, the photographic measurements were more accurate in predicting others, particularly pattern angles. Photographic measurements hold promise as an alternative to the more intrusive linear measurements for predicting pattern dimensions.

Anthropometry for a mix of different populations.

Abstract: Anthropometric data available in the literature refers to certain nationalities. In a substantial number of countries, a mixture of individuals of different races live in a particular city or even a community. Anthropometrists should address the users of the intended system irrespective of their ethnic background. A case study for the community of King Fahd University for Petroleum and Minerals (KFUPM) in Saudi Arabia is presented. Nineteen body dimensions of 408 subjects affiliated with KFUPM are reported and compared with other studies. The theme to design for the user population is emphasized.

Effective vehicle width in self-paced tracking.

Abstract: In self-paced tracking tasks, such as driving, the speed is related to the lateral tolerance. This lateral tolerance has been varied in two ways in previous studies by changing the track width for constant vehicle width and vice versa. The current study used both an automobile driving task and a computer/mouse task to show that these two ways of varying lateral tolerance did not produce equivalent results. Subjects behaved as if vehicle width were less important than track width. Speeds and errors both increased as vehicle width increased for a constant lateral tolerance. This could have safety consequences when driving in confined spaces.

Technical characteristics of overhead cranes influencing the vibration exposure of the operators.

Abstract: The study was undertaken to determine the technical factors responsible for the generation of vibration and shocks in overhead cranes and therefore responsible for complaints by the workers. Vibration measurements were made on the floor and on the seat of the cabin on 21 cranes. Vibration levels were correlated with the characteristics of the cranes. The study showed that vibration accelerations increased with the span of the crane and were very dependent upon the state of the runway. The type of speed regulation and the position of the cabin also play a significant role. The suspension systems of the cabin and the seat are clearly inadequate to give significant reduction of the vibration. In several cases, it was even shown to amplify the vibration in the most critical frequency range. These results should be taken into account by designers as well as maintenance services in order to prevent the development of vibration at the source.

Posture, performance and discomfort in pregnancy.

Abstract: This study examined changes in posture, discomfort and performance during various stages of pregnancy. Twelve subjects performed a typing task in the second and third trimesters of pregnancy. Posture was measured using goniometry and comfort was assessed using body-mapping techniques. The subjects showed a marked increase in their angles of trunk inclination and a general increase in discomfort between the second and third trimesters of their pregnancies. All body parts were found to be more uncomfortable in the third trimester and the largest changes occurred in the low back and lower legs. Advancing pregnancy had no effect on typing performance.

Chernobyl operators: criminals or victims?

Abstract: The blame for the 1986 Chernobyl disaster has been variously attributed to the operating personnel, the plant management, the design of the reactor, and the lack of adequate safety information in the Soviet nuclear industry. This paper considers a number of design faults, operational shortcomings and human errors that combined in the accident. It examines the sequence of events leading up to the accident, design problems in the reactor and cooling rods, and the course of the accident itself. It considers the ergonomics aspects, and expresses the view that the main cause of the accident was inadequate human-machine interaction. Finally, it stresses the continuing inadequacies of the Soviet nuclear system, and emphasizes that unless the ergonomics lessons are fully learned, a similar disaster could still occur.

Estimation of heat stress in Tanzania by using ISO heat stress indices.

Abstract: The aim of this study was to evaluate the usefulness of the ISO heat stress standards in estimating the heat stress and strain in workplaces in Tanzania. Another aim was to select and to develop simplified methods for measuring physiological parameters in developing countries. The methods were tested in four hot factories and at a construction site. It seems that in tropical working environments the climatic conditions for which the ISO 7933 standard is applicable are too narrow. For instance, the mean skin temperature was incorrectly estimated by ISO 7933. An approximate analysis of the working situation can nevertheless be carried out by assuming the mean skin temperature to be 34.5 °C. During the study, heat stress and strain were not as high as expected; deep body temperatures were usually lower than 38 °C, sweat rates lower than 400 g/h and heart rates below 100 beats/min for about 72% of the measuring time. This is due to the job rotation of the workers and the long rest periods, because the number of workers is large in the factories, and the weather was not at its hottest during the survey.

Performance on a prototype keyboard with ternary chorded keys.

Abstract: Ten subjects learned to operate a ternary chorded keyboard which took them, on average, just over three hours. After an additional 10 h of use, they were inputting an average 70 characters/min with an accuracy of better than 97%. The individual performances were quite different and variable, but throughout rapidly improved. The experiments indicated that people are able to memorize 59 chords, and to execute them quickly, with surprising facility.

Synthesized or digitized? A guide to the use of computer speech.

Abstract: In addition to technical and cost determinants, a range of human factors issues governs the appropriateness of synthesized or digitized speech for a particular system. For example, since synthesized messages are created textually, they may reflect the rules and habits of written language, rather than spoken language. This may cause listeners some difficulty interpreting the intended meaning of the message. Moreover, the different speech media place constraints upon techniques of message creation editing, transmission and reception. Synthesized speech is easy to edit in terms of lexical content, but the production of sophisticated prosodic features can be problematic. In contrast, unedited digitized speech will normally have appropriate prosodic cues and because of this will be difficult to edit. The influence of these factors is examined and illustrations of both good and poor practice are given. The paper concludes with a decision criteria checklist for speech output devices.

Work environment functions in small enterprises in Sweden.

Abstract: In Sweden, a governmental commission has formed new strategies concerning the work environment with the aims of reducing employee absenteeism and re-employing those individuals who have already left employment as a result of bad working conditions. The main features in this new approach are: strengthening of the legislation; a responsibility for work injury costs; and a distinct rehabilitation responsibility. In this paper the authors discuss how these proposals suited the constraints and facilities of small enterprises, employing less than 50 persons. The results are based on interviews carried out with company directors, safety representatives and labour inspectors. The interviews revealed that the company directors had a negative attitude towards both the strengthening of legislation and responsibility for work injury costs. It was also revealed that the small companies lack both knowledge of how a good environment can be created and the state of their own work environment. It seems that the small companies cannot handle work environment questions in a systematic way without comprehensive education and training or without seeking expert assistance outside the company.

This button makes you go up: three-year-olds and the Nintendo controller.

Abstract: Forty three-year-old children used the Nintendo controoler in a simple cursor-placement task, with two different software interfaces. The directional interface required children to map specific directions of movement on to specific buttons on the controller. The non-directional interface simply advanced the cursor in a clockwise direction to the next placement location, regardless of the specific directional button pressed. Results indicate that while the youngest three-year-old children find the non-directional interface slightly easier to use, older three-year-olds are more successful with the directional interface. In addition, all three-year-olds actually experienced problems using the simpler, non-directional interface - and problems increased with age. The results are discussed with reference to designing appropriate interfaces for the wide variety of skill levels present in the pre-school population.

On the merits of ancient Chinese eye acupressure practices.

Abstract: Chinese schoolchildren and adults with strenuous visual tasks routinely perform massage-and-pressure exercises on selected acupressure points around the eyes. This practice, taught by the Jing-Luo school of acupuncture for more than 4000 years, is claimed to prevent and cure myopia and other afflictions thought to result from visual close work. A four-week pilot experiment was carried out with the aim of designing a proper study on the possible short-term benefits of eye acupressure programmes. Questionnaire data revealed that the subjects did experience various eye/vision symptoms as a result of the 90 min experimental task. This could not be verified by the measurements of accommodation precision and critical flicker fusion, nor could any beneficial effects of acupressure be seen over the four experimental weeks.

The effect of appraisers in estimating metabolic rate with the Edholm scale.

Abstract: A study was made of the appraisers' effect on the estimation of metabolic rate with the Edholm scale and a table of the ISO 7243 heat stress standard. The appraisers, five experienced and five inexperienced persons, estimated the metabolic rate of three different work tasks from videotapes. Analysis of variance indicated significant ( p ) differences in the appraisers' recordings of the activities. The appraisers were grouped according to the similarity of the estimated values they gave. The groups thus contained both experienced and inexperienced appraisers, and it was not possible to classify the appraisers into experienced and inexperienced groups according to their earlier experience. The metabolic rates according to the Edholm scale were higher than according to the ISO 7243 table. The differences in metabolic rates given by the individual observers varied from 38 to 118 W/m2. The variations in the estimation of metabolic rates were greater when the Edholm scale was used. This variation caused considerable variation also in the predicted mean vote, PMV index. It is recommended that the appraisers be selected carefully, because it is not possible to know whether a randomly selected appraiser is an ‘average’ or an ‘extreme’ appraiser without a test. Before conducting extensive field surveys where several appraisers estimate the metabolic rates, it would be useful to arrange training in order to calibrate the levels of the Edholm scale as well as ISO method among the appraisers because training clearly unified the estimation.