Showing papers in "Ergonomics in 1994"
TL;DR: A model of human trust in machines is developed, taking models of trust between people as a starting point, and extending them to the human-machine relationship, providing a framework for experimental research on trust on trust a...
Abstract: Today many systems are highly automated. The human operator's role in these systems is to supervise the automation and intervene to take manual control when necessary. The operator's choice of automatic or manual control has important consequences for system performance, and therefore it is important to understand and optimize this decision process. One important determinant of operators' choice of manual or automatic control may be their degree of trust in the automation. However, there have been no experimental tests of this hypothesis until recently, nor is there a model of human trust in machines to form a theoretical foundation for empirical studies. In this paper a model of human trust in machines is developed, taking models of trust between people as a starting point, and extending them to the human-machine relationship. The resulting model defines human trust in machines and specifies how trust changes with experience on a system, providing a framework for experimental research on trust a...
787 citations
TL;DR: It is concluded that invalid exposure assessment may, to a large extent, explain the lack of quantitative data on relationships between mechanical exposures and musculoskeletal disorders.
Abstract: Ergonomic epidemiology is a rapidly increasing field of research providing data on the occurrence of musculoskeletal disorders and possible risk factors. The present paper states, on the basis of a literature overview, that physical work load (mechanical exposure) is poorly denned and measured in most studies on ergonomic epidemiology. On this background the paper: (1) suggests adjustments of mechanical exposure concepts and terminology; (2) concludes that invalid exposure assessment may, to a large extent, explain the lack of quantitative data on relationships between mechanical exposures and musculoskeletal disorders; and (3) suggests some guidelines for future quantitative assessments of mechanical exposure in large populations.
489 citations
TL;DR: It is indicated that work-related UE musculoskeletal disorders are relatively common among telecommunication workers who use VDTs, and evidence that the psychosocial work environment is related to the occurrence of these disorders is added.
Abstract: The relationship between workplace factors and work-related upper extremity musculoskeletal disorders (UE disorders) was assessed in a cross-sectional study of 533 telecommunication employees utilizing video display terminals (VDTs). Cases of UE disorders were defined using symptom questionnaires and physical examinations. Data on demographics, individual factors (medical conditions and recreational activities), work organization and practices, and psychosocial aspects of work, including electronic performance monitoring (EPM), were obtained by questionnaire. Associations between workplace factors and UE disorders were assessed by multiple logistic models generated for each of the four UE areas (neck, shoulder, elbow, hand/wrists). One-hundred and eleven (22%) participants met our case definition for UE disorders. Probable tendon-related disorders were the most common (15% of participants). Probable nerve entrapment syndromes were found in 4% of participants. The hand/wrist was the area most affected, 12%...
328 citations
TL;DR: It is concluded that the questionnaire approach gives a fairly good picture of the neck/upper extremity status of a working female population, however, a clear view of the size of a problem is obtained only by a detailed clinical examination, particularly as regards the neck, elbows and hands, for which the questionnaire gave an underestimate.
Abstract: To study the usefulness of a screening questionnaire for neck/upper extremity complaints, 165 women in either repetitive industrial, or mobile and varied work, were studied by the questionnaire and by a detailed clinical physical examination. A total of 94 subjects recorded complaints in the questionnaire. In 140 subjects findings were recorded at the examination. Most subjects with findings at the clinical examination of shoulders reported complaints in the questionnaire (sensitivity 80%). For the other anatomical regions, the sensitivity was rather low (42-65%). For all regions, most subjects without findings reported no complaints (specificity 77-97%). A total of 75 subjects were given clinical diagnoses according to a set of predetermined diagnostic criteria. The capacity of the questionnaire to identify diagnoses of shoulders was higher (sensitivity 92%) than for the other regions (66-79%). Of subjects who did not qualify for diagnosis, a majority (specificity 71-81%) did not report complaints in the questionnaire. We conclude that the questionnaire approach gives a fairly good picture of the neck/upper extremity status of a working female population. However, a clear view of the size of a problem is obtained only by a detailed clinical examination, particularly as regards the neck, elbows and hands, for which the questionnaire gave an underestimate.
245 citations
TL;DR: The possible causes of musculoskeletal pain in VDT workers and strategies to minimize it are discussed and workstation, chair, and keyboard design is reviewed, and recommendations to improve user comfort are made.
Abstract: This paper discusses the possible causes of musculoskeletal pain in VDT workers and outlines strategies to minimize it. The paper reviews workstation, chair, and keyboard design, and makes recommendations to improve user comfort. Also discussed is worker selection, training, posture, conditioning, and rest breaks. Short term musculoskeletal discomfort is experienced by many VDT operators in the telecommunications industry and chronic disability may result in the long term. It is important that the ergonomist and office manager work together to improve the working conditions in this important occupational area.
223 citations
TL;DR: In this article, the ability to follow a car in front, as measured by coherence and reaction time to speed variations, offers such a measure of attention and perception performance as well as the ability of the driver to follow the vehicle in front.
Abstract: The measurement of impairing effects on driving performance by such external factors as alcohol, medicinal drugs, or mobile telephoning, etc., is extended with a new test. Most existing methods of measuring impairing effects in the actual driving environment have the drawback that, irrespective of high sensitivity, they measure driving skills that are involved in only a very low percentage of accident causes, i.e., accidents after motor-response or eye-hand co-ordination errors. Since in accident causation, attention and perception errors predominate over response errors, on-road studies should examine specifically deterioration in attention and perception. The ability to follow a car in front, as measured by coherence and reaction time to speed variations, offers such a measure of attention and perception performance.
194 citations
TL;DR: Three investigations were carried out to examine the concurrent validity and the reliability of a portable dynamometer (Takei Kiki Kogyo) for the measurement of back and leg strength.
Abstract: Three investigations were carried out to examine the concurrent validity and the reliability of a portable dynamometer (Takei Kiki Kogyo) for the measurement of back and leg strength. First, leg extension strength of 19 subjects was measured using the Takei dynamometer and compared to the isometric knee extension strength of the dominant (right) leg measured using a computer-controlled dynamometer (Lido Active, Davis, CA). The back extension strength of 18 subjects was also compared between the two dynamometers. Second, back and leg strengths of 36 subjects, aged 19-30 years, were measured twice using the Takei dynamometer. Six days separated the test and retest. Third, back and leg strengths of four subjects, aged 21-30 years, were measured at six different times of the solar day. Significant relations (p 0.05). A small (4.5%) but significant difference was found between the test (1057.2 +/- 309.9 N) and retest (1106.2 +/- 334.4 N) mean values for back strength (p < 0.05). A time of day effect was evident for back and leg strength (p < 0.05); on average the peak times occurred at 16:53 h and 18:20 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
173 citations
TL;DR: Investigation of data obtained from official aircraft accident investigation reports found aircraft accident reports can be a useful source of information about cognitive failures if probed with an information processing approach to human failure in the aircraft cockpit.
Abstract: The present studies were undertaken to investigate the applicability of an information processing approach to human failure in the aircraft cockpit. Using data obtained from official aircraft accident investigation reports, a database of accidents and incidents involving New Zealand civil aircraft between 1982 and 1991 was compiled. In the first study, reports were coded into one of three error stages proposed by Nagel (1988) and for the presence of any of 61 specific errors noted by Gerbert and Kemmler (1986). The importance of decisional factors in fatal crashes was noted. Principal components analysis suggested the presence of five different varieties of human failure. In the second study, a more detailed error taxonomy derived from the work of Rasmussen (1982) was applied to the data. Goal selection errors emerged as the most frequent kind of cognitive error in fatal accidents. Aircraft accident reports can be a useful source of information about cognitive failures if probed with an appropria...
166 citations
TL;DR: An empirical study of the cognitive processes of semi-expert electronics engineers pursuing real-world design projects, which indicated that subjects were implementing a highly systematic design strategy which deviated only a small amount from a top-down, depth-first procedure.
Abstract: In this paper we report an empirical study of the cognitive processes of semi-expert electronics engineers pursuing real-world design projects. Extensive diary and interview data were analysed so as to reveal the organization of on-going design activity and the goals that were motivating behaviour. Our analyses indicated that subjects were implementing a highly systematic design strategy which deviated only a small amount (12%) from a top-down, depth-first procedure. Some of this deviation could be accounted for by social demands impinging on the individual designer, and whilst there was also evidence of 'opportunistic' deviation from a structured design approach, this did not appear to be a significant feature of our subjects' behaviour. We present a model of the design process as a set of production rules which describe an abstract 'design schema' for electronic engineering. This design schema embodies processes which control and co-ordinate problem-understanding and problem-structuring activity as well as the essentially top-down, depth-first pursuit of design solutions. The schema also allows for flexibility in the design process, permitting subjects to cope with contingencies arising through social influences and performance breakdowns. A further aspect of the design schema is that it encapsulates a 'satisficing' procedure which reflects a principle that dominated our engineers' solution-search and evaluation activity - they characteristically focused exclusively on initial, satisfactory (but usually sub-optimal) solution concepts rather than comparing alternatives with the aim of optimizing choices. We conclude our discussion by recommending facilities that we feel computer-based design aids should offer users if they are to be genuinely useful adjuncts to design activity.
163 citations
TL;DR: It was concluded, that at low load levels common in working life, MPF and subjective scores seem to provide different fatigue information and the MPF did not seem to work as a valid estimator of muscle fatigue at this low load level.
Abstract: In order to relate EMG signs of localized muscle fatigue to subjectively perceived muscle fatigue, a study was undertaken on 20 healthy volunteers exposing their right trapezius muscle by raising the arm to 90 degrees of abduction. Every person performed two contractions: 0 kg hand load during 5 min and 2 kg hand load during 2.5 min. Surface EMG was recorded and analysed with respect to RMS amplitude and mean power frequency (MPF). Subjective muscle fatigue was estimated with a psychophysical rating scale (Borg's CR-10 Scale). At high load level we found a significant correlation between MPF and the CR-scores (r = -0.46), but at low load level there was no correlation. At high load level there was a linear decrease of MPF with increasing load dose, but at low load level the MPF did not change, despite significant subjective fatigue. There was a linear rise of the CR-score with increasing load dose, more pronounced at high load level. It was concluded, that at low load levels common in working life, MPF and subjective scores seem to provide different fatigue information. Moreover, the MPF did not seem to work as a valid estimator of muscle fatigue at this low load level. Caution is recommended if it is to be used in static low-load situations.
157 citations
TL;DR: Mood states of confusion, vigour, and fatigue were affected significantly by the sleep deprivation regimen, but there was no significant effect of sleep loss or anger, tension, and depression.
Abstract: This study examined the effects of partial sleep deprivation on submaximal and maximal weight-lifting tasks and on subjective states pre- and post-activity. Eight male subjects (aged 18-24 years) were restricted to a nightly ration of 3 h sleep for 3 successive nights after baseline measures on the first day. A 4 day period where normal sleep was permitted fulfilled a control condition, the normal and sleep-deprived conditions being counterbalanced and separated by 10 days. The weight-lifting tasks consisted of biceps curl, bench press, leg press, and dead lift. For each exercise a submaximal load, corresponding to a fixed value on a category ratio scale of exertion, was determined for 20 repetitions; the maximal lift for that exercise was then obtained. A profile of mood states and subjective sleepiness were determined at each test occasion, tests being conducted in the evening of each day. There was no significant effect of sleep loss on performance of maximal biceps curl (p 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: This paper assessed perceptions of hazard levels associated with three signal words, CAUTION, WARNING, and DANGER, combined with four background colours, white, yellow, orange, and red.
Abstract: This study assessed perceptions of hazard levels associated with three signal words, CAUTION, WARNING, and DANGER, combined with four background colours, white, yellow, orange, and red. In general, DANGER was perceived as indicating the highest level of hazard, WARNING, an intermediate level, and CAUTION, the lowest level. Greatest consistency was found for DANGER. There was a small but significant amount of disagreement about the relative amounts of hazard represented by CAUTION and WARNING. White, yellow, orange, and red were also perceived as being associated with successively greater levels of hazard. Greatest consistency was found for DANGER with a red background. There was little agreement about the best colours to be associated with CAUTION and WARNING. Ratings on scales of seriousness of injury and probability of injury show that people perceive CAUTION and WARNING to be much closer to each other than to DANGER.
TL;DR: The authors' observations showed long periods of strenuous working postures for ' mouse' operators compared to 'non-mouse' operators, and further investigations need to be carried out on the effects of word-processing techniques and to develop ergonomic work station designs for the 'mouse' and other non-keyboard input devices.
Abstract: Work postures and movements of the upper limb were analysed for 12 'mouse' operators and 12 'non-mouse' computer operators employed in word-processing work. Measurements were carried out during correction of a given text. 'Mouse' operators spent 64% of the working time with the operative wrist deviating more than 15 degrees towards the ulnar side, while 'non-mouse' operators spent 96% of the time with the corresponding wrist in neutral position towards radial deviation. The rotation in the shoulder was at all times in neutral position towards inward rotation for 'non-mouse' operators, while 'mouse' operators worked 81% of the time with the shoulder rotated outward more than 30 degrees. 'Mouse' operators corrected a longer text during the given time. Our observations showed long periods of strenuous working postures for 'mouse' operators compared to 'non-mouse' operators. We believe that further investigations need to be carried out on the effects of word-processing techniques and to develop ergonomic work station designs for the 'mouse' and other non-keyboard input devices.
TL;DR: Higher vibration levels, as well as firmer handgrips, resulted in higher absorption of energy, while the constitution of the hand and arm affected the energy absorption to a larger extent.
Abstract: A possible basis for the risk assessment for hand-transmitted vibration may be to determine the amount of energy absorbed in the human hand and arm. In the present study, the mechanical energy absorption in the hand-arm system was measured within the frequency range of 4 to 1000 Hz. The study was carried out on ten healthy subjects during exposure to sinusoidal vibration. The influence of various experimental conditions, such as vibration direction (X h , Y h , Z h ), grip force (25ndash;75 N), vibration level (8–45 mm/Srms), and hand-arm posture were studied. The outcome shows that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimulus. Higher vibration levels, as well as firmer handgrips, resulted in higher absorption of energy. Varying hand-arm postures had only a small influence on the amount of absorbed energy, while the constitution of the hand and arm affected the energy absorption to a larger extent
TL;DR: In this article, a study of 708 second generation Caucasian N. American (NA) and 513 Japanese and Korean (JK) male subjects was conducted to determine normative data with respect to forefoot shape and dimension.
Abstract: The kinanthropometric aspects of comfort of fit of sport shoes has not been subjected to any great scrutiny. It is suggested that comfort of fit is largely determined by the match of foot shape to shoe shape and consequently there is a need for normative data that describe foot shape, dimension and proportion for discrete populations. A study of 708 second generation Caucasian N. American (NA) and 513 Japanese and Korean (JK) male subjects was conducted to determine normative data with respect to forefoot shape and dimension. A series of 2 height, 7 length, 1 breadth and 1 girth measures of the right foot bearing full body weight was recorded using a modified Mitutoyo digital caliper interfaced with a micro-processor. Substantial differences were noted in the incidence of digital patterning. The relative proportion of digital patterns I (1 > 2 > 3 > 4 > 5) and II (2 > 1 > 3 > 4 > 5) were NA 76.09%, 23.91%; JK 50.80% and 49.20% respectively. The distance between the pternion and the distal extremity of the second digit expressed as a percentage of the maximum foot length (MFL) was found to be 98.60% (NA) and 99.60% (JK). In addition, the distance between the pternion and the distal extremity of the fifth digit relative to MFL was 82.60% (NA) and 85.00% (JK). The implication of these data is that the anterior margin of the JK foot makes a less acute angle with the long axis of the foot than the NA population. Additional information with respect to foot breadth leads to the conclusion that the shape of the JK forefoot differs from that of the NA, with the implication that unique shoe lasts for both populations are required for optimal shoe comfort.
TL;DR: A modified five point scale of perceived exertion, sequentially numbered 1 to 5, was created to simplify the complicated and time-consuming procedures using conventional methods of measuring energy expenditure, or even heart rate responses, during work of very short duration, especially in field situations.
Abstract: A simple and rapid method of determining occupational workload among Indian women performing manual activities was developed based on the strong relationship between physiological responses and subjective feeling of exertion. A modified five point scale of perceived exertion, sequentially numbered 1 to 5, was created to simplify the complicated and time-consuming procedures using conventional methods of measuring energy expenditure, or even heart rate responses, during work of very short duration, especially in field situations. The scale denotes physiological workload: 1: very light; 2: light; 3: moderately heavy; 4: heavy; and 5: very heavy. A job-classification table based on energy expenditure and heart rate responses is also proposed, and different household activities such as grinding masalas, dish washing, sweeping, mopping, ironing, storing water, etc. have been graded accordingly.
TL;DR: The results indicated that the combination of a prophylactic nap and caffeine was more effective in maintaining nocturnal alertness and performance than was the nap alone.
Abstract: After a normal baseline night of sleep and a morning of baseline test performance, 24 young adult male subjects returned to bed from 16:00-20:00 prior to a 24 h period of sleep loss. Twelve subjects received caffeine 200 mg at 01:30 and 07:30. Performance tests (correctly completed addition problems, vigilance sensitivity, and logical reasoning correct responses) all indicated maintenance of baseline performance levels in the caffeine group after administration of caffeine while performance declined in the placebo group. Similar results were found for the Multiple Sleep Latency Test and Oral Temperature, which both remained near baseline levels throughout the observation period in subjects receiving caffeine. The results indicated that the combination of a prophylactic nap and caffeine was more effective in maintaining nocturnal alertness and performance than was the nap alone. Of more interest was the fact that the group which was given the combination of nap and caffeine was able to maintain alertness and performance at very close to baseline levels throughout a 24 h period without sleep.
TL;DR: The data indicate a high overall frequency of occupational back pain, similar to other studies in Europe, and the comparison between the two hospitals suggests factors associated with the disorder: work tasks and particularly nurses/patients ratio are more important factors than age and length of exposure.
Abstract: Nursing staff members of a urban general hospital (GH) and a small oncological department (OD) were surveyed to determine the prevalence of occupational related musculoskeletal disorders (MSDs), the specific disabilities, accidents at work, and working time lost. All subjects had a medical examination to evaluate osteoarthicular disease and selected cases were invited to X-ray examinations. The purpose of this study was to compare MSDs in the two groups of nurses working in two hospitals with different work organization in the same geographical area, Pordenone in Italy. In the previous year 48% GH and 33% OD nurses reported back pain due to work, 29.4 and 16.1% respectively have had X-ray or orthopaedic examinations, 19.2% and 9.1% had been away from work because of back pain. All these differences are statistically significant. The analysis of musculoskeletal pain sites and working tasks in the two hospital workers shows no differences in distribution. Great difference exists when analysing the numbers of patients assisted by a nurse: 0.57 and 1.27 nurse/patients respectively in GH and OD. Our data indicate a high overall frequency of occupational back pain, similar to other studies in Europe. The comparison between the two hospitals suggests factors associated with the disorder: work tasks and particularly nurses/patients ratio are more important factors than age and length of exposure. Different work distribution, shift organization, a better ratio between nurses and patients, an improvement of equipment provision, and specific nurse-training with application of ergonomic methods could improve work efficiency radically and decrease injury rates.
TL;DR: The finding that the CS has good psychometric properties when used on samples of students was replicated and extended to a smaller sample of individuals working on rotating shifts and scores were found to be stable over time and did not change when subjects were exposed to night- and shiftwork.
Abstract: Prompted by some discrepancies in the report detailing the development of the Composite Scale (CS) of Morningness (Smith et al. 1989) this study replicated the examination of the psychometric properties of the CS on a large sample (n = 424) of health science students. It was confirmed that the mean and range of CS scores previously reported were in error. The finding that the CS has good psychometric properties when used on samples of students was replicated and extended to a smaller (n = 35) sample of individuals working on rotating shifts. CS scores were found to be stable over time and did not change when subjects were exposed to night- and shiftwork.
TL;DR: Girth measures provide serial information across the foot in the coronal plane to complete comprehensive data on the three dimensional shape of the foot.
Abstract: A comprehensive series of variables that describe the essential three dimensional characteristics of the human foot is presented together with descriptive statistics derived from a diverse civilian population (n = 1197), representing a wide age range (18-85 years) and randomly selected in terms of physical demands placed upon the foot in the course of a normal working day. The paper illustrates the effect of linear scaling of the first, second and fifth digit lengths upon forefoot shape. The ratio of the pternion to metatarsale tibiale and fibulare lengths determine the angle and position of the axis across the metatarsal-phalangeal joint (MPJ). The height of the hallux, MPJ, dorsum, and arch are shown to vary independently from all other variables and in conjunction with akropodion to dorsum length and dorsum to distal heel length, provide the necessary information for describing the characteristics of the foot in the sagittal plane. Girth measures provide serial information across the foot in the corona...
TL;DR: In this article, the effects of environmental and biomechanical factors of the shoe-floor interface on DCOF measures using a new slip resistance testing device were investigated using shoe material, floor type, and contaminant.
Abstract: Slip resistance measurements are used by industry, shoe/floor manufacturers, and the legal profession as a criterion for determining slip potentials of various environments. Whilst static coefficients of friction (COF) of a shoe-floor interface have been used traditionally, dynamic COF(DCOF) measures have been shown to be more relevant to the biomechanics of slips and falls. Recently, new devices have become available that better incorporate the biomechanics of foot movement into DCOF measurement. The purpose of this study was to investigate the effects of environmental and biomechanical factors of the shoe-floor interface on DCOF measures using a new slip resistance testing device. The environmental factors chosen were shoe material, floor type, and contaminant. The biomechanical factors were heel velocity, vertical force, and shoe angle. The results showed that of the biomechanical factors, heel velocity had largest effects on the DCOF. However, contaminant condition was an important interaction. Increa...
TL;DR: The data show that poor working postures in the nursing profession not only occur during patient handling activities but also during tasks like 'administration', which suggests that focusing on patient-handling in order to determine the load on the musculoskeletal system would lead to an underestimation of the total working posture load of nurses.
Abstract: The working postures of Dutch nurses (n = 18) in an orthopaedic ward and a urology ward were observed using the Ovako Working posture Analysis System (OWAS). During observation, both working postures and activities were recorded. A specially developed computer program was used for data analysis. By means of this program, it was possible to calculate the working posture load for each activity and the contribution of a specific activity to the total working posture load. This study shows that some activities of the nurses in both wards were performed with poor working postures. In the orthopaedic (resp. urology) ward two (resp. one) out of 19 observed postures of parts of the body were classified as Action Category 2. Moreover, 20% (resp. 16%) of the so-called typical working postures was classified in Action Category 2. This suggests, that in both wards working postures that are slightly harmful to the musculoskeletal system, occur during a substantial part of the working day. Differences between both wards with respect to working posture load and time expenditure were determined. Activities causing the workload to fall into OWAS higher Action Categories were identified. The data show that poor working postures in the nursing profession not only occur during patient handling activities but also during tasks like 'administration'. Focusing on patient-handling (i.e., lifting patients) in order to determine the load on the musculoskeletal system would therefore lead to an underestimation of the total working posture load of nurses.
TL;DR: There were significant group differences in work related effects on the eyes' ciliary and extraocular muscles and on subjective symptoms, indicating that not only visual symptoms but also muscle pain in the head, neck, and upper back regions may result from near-point induced oculomotor strain.
Abstract: Two studies, one experimental and one clinical, are presented. Study I examines the effect of three hours of continuous VDT work (text-editing) on a set of optometric and health-related variables in an experimental design with two matched groups, one experimental (n = 18) and one control group (n = 19). Doing the same keyboard activities for 3 h as the experimental group, the control group was looking out of a window instead of at the display while working (distance viewing). There were significant group differences in work related effects on the eyes' ciliary and extraocular muscles and on subjective symptoms, indicating that not only visual symptoms but also muscle pain in the head, neck, and upper back regions may result from near-point induced oculomotor strain. Study II shows the health effect of optical corrections on symptomatic VDT workers (n = 14). There is a significant pre-post reduction in symptoms, indicating that visual anomalies contribute to work-related symptoms. The results of both studi...
TL;DR: This study tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work with the simultaneous recording and on-line analysis of heart rate and physical activity.
Abstract: This study, using 12 train drivers on a high speed track and 11 drivers on a mountain track, tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work. With the simultaneous recording and on-line analysis of heart rate and physical activity, the emotional component in terms of the so-called additional heart rate was separated from the physical component. Mental workload was calculated by the heart rate variability and by shifts in the T-wave amplitude of the ECG. Speed of the train, mode of driving, and stress of the situation were rated by two observers who accompanied the drivers in the cabin. During speeds up to 100 km/h as compared to standstills no heart rate changes occurred, but with speeds from 100 km/h up to 200 km/h heart rate decreased indicating a monotony effect. However, heart rate variability, and T-wave amplitude indicated higher mental load during driving in most speed categories. Starting the train and coming to a halt showed greater emotional workload as compared to moving. Observer ratings of stress and subjective ratings of stress by the drivers revealed several discrepancies. Discrepancies were also seen between workload as indicated by the physiological parameters, and corresponding stress ratings by the observers or by the drivers.
TL;DR: The results from this study indicate that the static trapezius load must be kept at a minimum; a Median arm flexion should be less than 15 degrees and a median arm abduction less than 10 degrees seems to approach an acceptable arm position; and a forward median flexion of the back of less than 20 degrees seems not to lead to a higher rate of low back pain for workers with long periods of employment.
Abstract: This paper is a summary of several papers published in different journals and conference proceedings. The contents deal with the incidence of load related musculoskeletal illness of female workers exposed to various workloads. Furthermore, the changes in workload due to improved workplace design and the effect on the incidence of musculoskeletal illness was evaluated. The sick-leave due to musculoskeletal illness was reduced from 5·3% to 3·1% and the reduction in turn-over from 30·1% to 7·6%. The cost and the benefits of this ergonomic intervention were analysed, and showed that an investment of NOK. 350 000 produced total savings of NOK. 3 200 000. Postural load was assessed by recording electromyography (EMG) on the upper part of musculus trapezius, postural angles of the upper arm and flexion/extension of the head and back. A quantitative relationship was found between the static trapezius load and the development of musculoskeletal sick-leave, related to the length of employment. Indications were foun...
TL;DR: The effects of three frequently rotating shifts in an irregular sequence on the daily activities of 239 Japanese female hospital nurses were studied by the time-budget method and a strong positive correlation between total sleep time (including day sleep) and the length of the interval between two consecutive shifts was found.
Abstract: The effects of three frequently rotating shifts in an irregular sequence on the daily activities of 239 Japanese female hospital nurses were studied by the time-budget method. The nurses recorded their daily activities for several consecutive days. The questionnaire was returned by 80·8% of the participants, and recordings of 1016 days were analysed. A two-way analysis of variance clarified that the shift combination influenced the daily activities. The most distinct result was that nurses spent significantly more time on free-time activities on the day when they worked the night shift followed by the evening shift than they did on the day when they worked any other shift combination. Nurses offset sleep deprivation either by sleeping during the day before and after working the night shift (82–100%) or by sleeping 2 to 4 h later in the morning after working the evening shift and on days off. There was a strong positive correlation between total sleep time (including day sleep) and the length of the interv...
TL;DR: The Ergonomics Society Lecture Presented at the EGS Annual Conference, Edinburgh, 13-16 April 1993 as mentioned in this paper, was the first one to advocate safety in the oil industry.
Abstract: (1994). Promoting safety in the oil industry. The Ergonomics Society Lecture Presented at the Ergonomics Society Annual Conference, Edinburgh, 13-16 April 1993. Ergonomics: Vol. 37, No. 12, pp. 1999-2013.
TL;DR: Flexion/extension acceleration values from this study can serve as preliminary motion benchmarks that establish relative risk levels of CTDs for hand-intensive, highly repetitive jobs that do not require hand tools.
Abstract: One of the major research voids in the study of occupational hand/wrist cumulative trauma disorders (CTDs) is the lack of quantification of the relationship between the known kinematic risk factors, such as wrist angle and repetition, and CTD risk. A previously published article in this journal (Marras and Schoenmarklin 1993) reported the descriptive results from a quantitative surveillance study performed in industry in which worker's wrist motions were monitored on the factory floor. The wrist motion components that were monitored on each subject were position, velocity, and acceleration measures in each plane of movement (radial/ulnar, flexion/extension, and pronation/supination). The objective of this article was to form a metric that associates the degree of incidence of hand/wrist CTDs with those types of wrist motions that were significant in the earlier paper. Of all the kinematic parameters measured, multivariate analysis of the motion data revealed that acceleration in the flexion/extension plane discriminated the best between groups of low and high incidence rates of CTDs. The epidemiological association between flexion/extension acceleration and CTD incidence rate is compatible with results from empirical studies and theoretical models in the physiologic and biomechanical literature. The flexion/extension acceleration values from this study can serve as preliminary motion benchmarks that establish relative risk levels of CTDs for hand-intensive, highly repetitive jobs that do not require hand tools. Industrial practitioners can use this methodology, along with other accepted tools, to enhance ergonomic assessments of jobs.
TL;DR: Motivation is evaluated as a task-related factor causing the development of psychologically mediated ('psychogenic') shoulder-muscle tension in four separate experiments using a visual display unit based complex reaction-time task.
Abstract: This paper evaluates motivation as a task-related factor causing the development of psychologically mediated (‘psychogenic’) shoulder-muscle tension. In four separate experiments using a visual display unit (VDU) based complex reaction-time task, motivation was established by means of continuous feedback on the level of performance (relative to a preset target performance level) or by means of a money reward for good performance. In all experiments motivation improved the performance, but an increase in the psychogenic shoulder-muscle tension was only observed in the money-reward condition. It is discussed whether this difference in the muscle-tension response is due to changes in the subjects' attitude unrelated to performance or due to a superior performance in the money-reward condition.
TL;DR: Five two- person manual lifting techniques were evaluated as to the amount of physical exertion required of the nurses; the barrow lift appeared to be the most strenuous one; the Australian lift resulted in low compressive forces and a moderate level of perceived exertion.
Abstract: In the present laboratory study five two-person manual lifting techniques were evaluated as to the amount of physical exertion required of the nurses. Ten female volunteers served as nurses; two healthy volunteers (weight: 55 kg and 75 kg) served as passive patients. The working postures and motions were recorded on videotape. The data thus obtained were used in a anatomical-biomechanical analysis. The perceived exertion by the nurses was measured as well. In almost all situations the compressive forces on the nurse's spine exceeded their acceptable limit of 3425 N. Differences between the lifting techniques were most obvious when the 55 kg patient was lifted. Ratings of the perceived exertion (RPE scores) were higher in symmetrical handling than in asymmetrical handling. The three techniques using asymmetrical hand positions produced less subjective stress. RPE scores and rotation of the back were negatively correlated. Rotating the back when moving a patient from one side to the other seems to ease the task. On the whole, the results of the biomechanical evaluation are in line with the subjective perception of the nurses. In both instances the barrow lift appeared to be the most strenuous one; the Australian lift resulted in low compressive forces and a moderate level of perceived exertion.