International standards on mental work-load--the ISO 10,075 series.
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After a short review of the history and an introduction into the background of standardization in the field of mental work-load an overview over the ISO 10,075 series of standards on ergonomic principles related to mental work-load is given. The review also presents relationships of these standards with some other ergonomic standards and some of the problems associated with standardization in the field of mental work-load. The stress-strain model, the concepts and the terminology used in ISO 10,075 are presented in the overview, together with the basic ideas and the frame of reference of the design guidelines provided by ISO 10,075-2. An outline of the state of discussion and possible developments of a working draft for ISO 10,075-3 on diagnostic methods concludes the presentation of the international standards on mental work-load. (+info)
Measurement of fatigue in industries.
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Fatigue of workers is a complex phenomenon resulting from various factors in technically innovated modern industries, and it appears as a feeling of exhaustion, lowering of physiological functions, breakdown of autonomic nervous balance, and decrease in work efficiency. On the other hand industrial fatigue is caused by excessive workload, remarkable alteration in working posture and diurnal and nocturnal rhythms in daily life. Working modes in modern industries have changed from work with the whole body into that with the hands, arms, legs and/or eyes which are parts of the body, and from physical work to mental work. Visual display terminal (VDT) work is one of the most characteristic jobs in the various kinds of workplaces. A large number of fatigue tests have already been adopted, but it is still hard to draw a generalized conclusion as to the method of selecting the most appropriate test battery for a given work load. As apparatus for fatigue measurement of VDT work we have developed VRT (Visual Reaction Test) and the Portable Fatigue Meter. Furthermore, we have presented immune parameters of peripheral blood and splenic T cells for physical fatigue. (+info)
Effects of direction of rotation in continuous and discontinuous 8 hour shift systems.
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OBJECTIVES: Previous research has produced conflicting evidence on the relative merits of advancing and delaying shift systems. The current study assessed the effects of the direction of shift rotation within 8 hour systems, upon a range of measures including sleep, on shift alertness, physical health, and psychological wellbeing. METHODS: An abridged version of the standard shiftwork index which included retrospective alertness ratings was completed by four groups of industrial shiftworkers on relatively rapidly rotating 8 hour systems (n=611). Two groups worked continuous systems that were either advancing or delaying; the other two groups worked discontinuous systems that were either advancing or delaying. RESULTS: Few effects were found of direction of rotation on chronic measures of health and wellbeing, even when the systems incorporated "quick returns" (a break of only 8 hours when changing from one shift to another). This was despite the use of measures previously shown to be sensitive to the effects of a broad range of features of shift systems. However, advancing continuous systems seemed to be associated with marginally steeper declines in alertness across the shift (F (3,1080)=2.87, p<0.05). They were also associated with shorter sleeps between morning shifts (F (1,404)=4.01, p<0.05), but longer sleeps between afternoons (F (1,424)=4.16, p<0.05). CONCLUSIONS: The absence of negative effects of advancing shifts upon the chronic outcome measures accorded with previous evidence that advancing shifts may not be as harmful as early research indicated. However, this interpretation is tempered by the possibility that difficult shift systems self select those workers most able to cope with their deleterious effects. The presence of quick returns in advancing continuous systems seemed to impact upon some of the acute measures such as duration of sleep, although the associated effects on alertness seemed to be marginal. (+info)
Neuroendocrine reactivity and recovery from work with different physical and mental demands.
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OBJECTIVES: The purpose of this study was to examine the extent to which the type or nature (physical, mental or mixed mental and physical) of work and work characteristics is related to the course of neuroendocrine reactivity and recovery from work. METHODS: Neuroendocrine reactivity and recovery were studied by measuring the urinary excretion of adrenaline, noradrenaline, and cortisol during and after 3 workdays, 1 consecutive day off, and a baseline day. The assessment was made in 3 groups of Dutch male workers (N=60) who differed in the nature (mental, physical, and combined mental and physical demands) of their work. Multilevel analyses were performed to fit linear mixed-effects models for each hormone. RESULTS: Main or interaction effects with time of day were found between the workers in combined mental and physical work and the 2 other groups of workers for cortisol, adrenaline, and noradrenaline excretion. In addition, the baseline levels of the 3 hormones were higher in the workers with combined mental and physical work when compared with the other 2 groups. The excretion rates during the workdays were higher than those on the day off, but a trend towards mobilizing less activity was found from the 1st to the 3rd workday. Job demands were negatively related to cortisol excretion. Job control and social demands at work did not affect the excretion rates of the hormones. CONCLUSIONS: Unfavorable effects on cortisol and adrenaline reactivity or recovery was found for workers with combined mental and physical demands when compared with workers doing mainly mental or mainly physical work. The results of the present study are in accordance with the cognitive activation theory and the allostatic load model. (+info)
Fatigue in the Danish general population. Influence of sociodemographic factors and disease.
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OBJECTIVE: To measure the levels of fatigue in the general population, and to examine how disease and sociodemographic factors influence fatigue. DESIGN: Cross sectional questionnaire study in the Danish general population. SUBJECTS: A random, age stratified sample of 1608 people aged 20-77 with an equal gender distribution (response rate 67%). MAIN OUTCOME MEASURES: Five fatigue scales from the questionnaire Multidimensional Fatigue Inventory: General Fatigue, Physical Fatigue, Reduced Activity, Reduced Motivation and Mental Fatigue. RESULTS: Fatigue scores were skewed towards absence of fatigue. The General Fatigue and Physical Fatigue scales showed the highest fatigue levels while the Reduced Motivation scale showed lowest levels. Gender differences in fatigue scores were small, but the variability among women was higher-that is, more women had high scores. A multiple linear regression analysis showed that respondents of low social status and respondents with a depression had high fatigue scores on all scales, independent of other factors. Chronic somatic disease had an independent direct effect on Mental Fatigue, but for the rest of the scales, the effect of somatic disease depended on age, gender and/or whether the person was living alone. For example, General and Physical Fatigue decreased with age among healthy people, whereas scores on these scales increased with age among those with a somatic disease. CONCLUSIONS: Physical and mental diseases play essential parts for the level of fatigue and as modulators of the associations between sociodemographic factors and fatigue. These interactions should be taken into account in future research on fatigue and sociodemographic factors and when data from clinical studies are compared with normative data from the general population. (+info)
Longitudinal study of associations between perceived health status and self reported diseases in the French Gazel cohort.
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STUDY OBJECTIVE: Although perceived health status is an indicator widely used in epidemiological studies, its relation to various diseases is not well known. The objective of this study is to examine these relations in detail. DESIGN: Marginal models used for a longitudinal study of the association between three health scales and 47 diseases among 12 164 men and 44 diseases among 4415 women. SETTING: French Gazel cohort during the period from 1991 to 1996. MAIN RESULTS: The general health status scale was significantly associated with 43 diseases among men, and 31 among women. Some of these significantly associated diseases were physical (for example, cancer and cerebrovascular accident) and others, psychological (for example, depression). The mental fatigue scale was more specifically associated with psychological disorders, including sleep problems, depression, and nervous diseases. Moreover, modifications in subjects' assessment of their health from one year to the next were generally associated with modifications in reported diseases. CONCLUSION: Although the mechanism that relates the presence of a disease to perceived health status remains in question, these results show clearly that there is a close association between these two domains that justifies the use of perceived health as a proxy for self reported diseases. (+info)
Excessive fatigue and weight gain among cleanroom workers after changing from an 8-hour to a 12-hour shift.
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OBJECTIVES: This study attempted to clarify the health effects of implementing a 12-hour shift in place of the traditional 8-hour shift in work in a clean room in an electronic parts producing factory. METHODS: Health-check records during a year or longer before and after the shift change were reviewed regarding subjective symptoms, height, body weight, and blood pressure for 189 male workers who had moved to a 12-hour shift and for 16 male workers who remained on an 8-hour shift. RESULTS: The workers changing to a 12-hour shift showed significant increases in subjective symptoms, particularly psychological symptoms defined as related to fatigue and bodyweight gain, 1 kg on average, in the year after the shift change. Increased symptoms and body weight remained high even another year later. The workers remaining in the 8-hour shift did not show significant changes in symptoms or body weight during the observation. No changes in blood pressure were observed in relation to the shift move. CONCLUSIONS: The results suggested that implementing a 12-hour shift caused marked psychological fatigue and unhealthy weight gain among some cleanroom workers and that the adaptation to the new work shift did not seem easy for these workers. Working in a clean room can be considered a job in which special caution is needed regarding increased fatigue when a compressed working schedule is implemented. Attention should also be paid to possible weight gain among persons working 12-hour shifts. (+info)
Shift work and disturbed sleep/wakefulness.
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Of the many health-related effects of shift work, disturbed sleep is the most common. This review describes the main observed effects of the three principal shifts (night, morning and afternoon) on patterns of sleep and wakefulness. The mechanism of sleep disruption in relation to circadian rhythms and the specific impact of aspects of shift organization (speed and direction of rotation) are discussed. The most troublesome acute symptoms are difficulty getting to sleep, shortened sleep and somnolence during working hours that continues into successive days off. These are only partially amenable to amelioration by manipulating shift patterns. However, there is no clear indication that chronic sleep problems result from long-term shift work. (+info)