| 1. |
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| 2. |
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| 3. |
- Abeysekera, John, et al.
(författare)
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The identification of factors in the systematic evaluation of slip prevention on icy surfaces
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 28:5, s. 303-313
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Tidskriftsartikel (refereegranskat)abstract
- Slips and falls on icy roads often result in fractures or sprains and is a major problem in Nordic countries. Walking trials by 25 subjects wearing four types of winter shoes on five different icy walking surfaces provided subjective and objective measures of tendency to slip and number of slips, respectively. Since friction is a major determinant of a slip, the influence of material spread on icy surfaces, the surface temperatures and the shoe soling characteristics versus the Coefficient of Friction (COF) of the shoes were measured. Sand and gravel on icy roads had positive effects on improving COF. The study revealed that the aetiology of slips and falls is multi-faceted and attempts to solve the problem must adopt a systems approach. Perception of risk, aging, training, experience and postural balance are other factors to be considered in preventing slips and falls. Future research should concentrate on the degree of impact of each factor to the aetiology of slips and falls, which can help to decide priority action in preventing slips and falls.
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| 4. |
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| 5. |
- Christmansson, Marita, et al.
(författare)
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A case study of a principally new way of materials kitting—an evaluation of time consumption and physical workload
- 2002
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier. - 0169-8141 .- 1872-8219. ; 30:1, s. 49-65
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a materials kitting case study, using an alternative method for materials kitting: the traditional picker-to-material principle was replaced with a material-to-picker approach. The study was made in a materials supply workshop of an automobile plant shortly after this kitting process had been introduced. The materials kitting was video recorded and the material pickers’ physical exposure was assessed using ambulatory equipment to make an integrated registration of muscular activity, work postures and movements. The material pickers assessed work situations perceived as physically stressful. The materials kitting showed improved productivity as compared with other kitting methods. The study indicated that the work situation offered pickers low levels of physical exposure. The picking work was rather light but involved great repetitiveness in arm movements. The material pickers experienced the work as repetitive and having some physically stressful work situations. The integrated analyses showed: (1) that exposure in picking operations was similar to, but could be distinguished from, other work activities and (2) that picking from one type of storage package, Euro pallets, resulted in higher exposure than picking from plastic containers. More studies are needed on the implications of exposure levels in materials picking.
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| 6. |
- Gao, Chuansi, et al.
(författare)
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The effect of footwear sole abrasion on the coefficient of friction on melting and hard ice
- 2003
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 31:5, s. 323-330
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Tidskriftsartikel (refereegranskat)abstract
- Footwear sole wear by natural use or artificial abrasion either increases or decreases slip resistance on floors with and without lubricant. The objectives of this paper were to study the effect of footwear sole abrasive wear on slip resistance on ice with respect to temperature, and to compare the slip resistance of abraded soles on melting and hard ice with that on lubricated steel plate. The kinetic coefficient of friction (COF) of nine pairs of footwear were measured with the stationary step simulator developed at the Finnish Institute of Occupational Health, before and after the new footwear soles were artificially abraded. Two-way factorial ANOVA showed that the abrasion of nine pairs of footwear had no significant effect on COF on melting ice (Mean COF with abrasion=0.056, std=0.0158, COF without abrasion=0.055, std=0.0205, P=0.805). On hard ice, however, the COF of abraded soles measured (mean COF=0.244) was significantly higher than without abrasion (mean COF=0.180,p<0.001), and than abraded soles on lubricated steel (mean=0.137,p<0.001). There is statistical significance between the three types of surfaces (P<0.001). On hard ice, regardless of abrasion, curling footwear with crepe rubber soling showed significantly higher COF (mean=0.343 after abrasion, 0.261 before abrasion) than other types (P<0.001). The results indicate that artificially abraded footwear is more slip resistant than new one for use on hard ice. The abrasion requirement could be specified if developing a new standard to measure COF on ice in the future. Of the footwear measured, the curling footwear with crepe rubber soling performed best in terms of slip resistance property. Therefore, Crepe rubber soling is highly recommended for use on hard ice. Melting ice is much more slippery, in which sole abrasion does not improve slip resistance. Thus, additional measures should be taken to reduce slip and fall risk. Relevance to industrySlipping and falling accidents are common on surfaces covered with snow, ice, melting snow, melting ice or the mixed in winter for outdoor workers and pedestrians. Understanding of the friction at the interface can help footwear industry design slip resistant products, to help outdoor workers choose appropriate protective equipment, and to provide safe work practice for industries involving outdoor work.
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| 7. |
- Geng, Qiuqing, et al.
(författare)
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Change in contact temperature of finger touching on cold surfaces
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 27:6, s. 387-391
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with human fingers touching cold surfaces of four materials (aluminium, steel, nylon and wood) at different surface temperatures (-20°C, -15°C, -10°C, -4°C, 0°C and 2°C). Contact finger skin-surface interface temperature and subjective responses on thermal and pain sensations were determined during touching. Type of material and their surface temperature clearly affected the contact cooling of the finger. Individual variation in finger contact cooling was significant. Contact temperature limits for human fingers touching cold surfaces are suggested according to the experimental results. In addition, time to reach a critical temperature (7°C, 5°C or 0°C) when contacting a cold metallic surface is discussed.
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| 8. |
- Hanson, Lars, et al.
(författare)
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A control handling comfort model based on fuzzy logics
- 2003
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier. - 0169-8141 .- 1872-8219. ; 31:2, s. 87-100
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Tidskriftsartikel (refereegranskat)abstract
- The car interior is a complex man–machine interface. Poor interior design contributes to traffic accidents as well as discomfort and disorders in professional and long distance drivers. When buying a car comfort is for many customers an important factor. Consequently, car interior comfort besides safety is of great importance when designing cars. Comfort is a subjective feeling and hard to model mathematically. The aim of this paper is to show the feasibility with fuzzy logics to model relations between human perception, human characteristics and workplace structure. A model where drivers’ perceived comfort when handling interior controls is in relation to anthropometrics and control positions are used as illustration. A series of control reach studies in simulated car driving was used for the development of a comfort model. Combined with a human simulation program the comfort model may be used by car designers at an early stage of the design process for evaluation of design concepts aiming at reachable and manageable controls in a safe and comfortable interior. The comfort model illustrates that fuzzy logics provides a constructive way of turning qualities into mathematics.Relevance to industry: Fuzzy logics provide the opportunity to model physical parameters from the human and the technical system together with human perceptions. Such model can be combined for instance with human simulation tool and reduce ergonomic tests in real physical environments.
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| 9. |
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| 10. |
- Karlqvist, Lena, et al.
(författare)
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Self-reported working conditions of VDU operators and associations with musculoskeletal symptoms : a cross-sectional study focussing on gender differences
- 2002
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 30:4-5, s. 277-294
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to describe working conditions and the prevalence of musculoskeletal symptoms among male and female VDU operators, and to assess associations between work-related physical and psychosocial exposures and neck and upper limb symptoms by gender. The study population comprised a variety of occupations from both private and public sectors. Data on physical and psychosocial exposures were collected by questionnaires, as were data on musculoskeletal symptoms. Univariate associations between exposures and symptoms affecting the neck and upper limbs were estimated by calculating the prevalence ratios with 95% confidence intervals. We also assessed the potential excess odds ratio attributable to interaction between gender and, one by one, exposure variable. Women (n=785) used the computer on average 3.9 h/day and men (n=498) 3.6. Variation of different work tasks was lower among females than among males. Nineteen per cent of the women and 12% of the men did >3 h of continued computer work without breaks (>10 min) at least twice a week. Twice as many women as men experienced high job strain (high demands and low decision latitude). A higher proportion of women than men reported symptoms 3 days the preceding month from the upper body, irrespective of body region. For many of the studied exposures the prevalence of symptoms in one or several body regions was increased with increasing exposure, indicating exposure-response relationships. Duration of computer work was associated with symptoms among both men and women. Only among men, duration of work with a non-keyboard computer input device was associated with symptoms. Only among women, job strain was associated with symptoms. Time pressure was associated with higher prevalence of symptoms among women. Among men, time pressure was associated with lower prevalence of symptoms. Thus, the associations differed between the genders. Women experienced higher prevalence of symptoms than men in all body regions and they were more often exposed to physical and psychosocial conditions that in previous studies have been considered harmful, than men.
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| 11. |
- Kuklane, Kalev, et al.
(författare)
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A field study in dairy farms : thermal condition of feet
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 27:1, s. 367-373
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Tidskriftsartikel (refereegranskat)abstract
- The study aimed to find out the problems connected with feet during work in cold loose housing barns in wintertime. Thirteen dairy farms and 20 workers were studied. Skin temperatures and subjective responses were collected, and at the end of a work period the subjects filled in a questionnaire about the workday. The foot skin temperatures were measured on dorsal foot and second toe. Most of the workers used rubber boots. The ambient temperature outdoors varied from +5 to -11°C. Indoor temperatures could be the same as outdoors (cold barns and fodder storage) but also close to +30°C (milk room). The lowest mean foot and toe skin temperatures were 24.1±2.6°C and 16.0±1.4°C. The lowest measured values were 20.1°C and 12.8°C, respectively. The toe temperatures were on average 7.3°C colder than foot temperatures (mean 28.8°C). The low foot skin temperature was well related to cold sensation. Low toe temperatures fitted well with wetness sensation. On average the thermal sensation of feet over the work period was neutral. The lowest ratings were cold (-2). The combination of various environmental factors in farms complicates finding of perfect footwear for work. Recommendations on the choice of footwear and their care are given.
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| 12. |
- Medbo, Lars, 1957
(författare)
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Assembly Work Execution and Materials Kit Functionality in Parallel Flow Assembly Systems
- 2003
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Ingår i: International Journal of Industrial Ergonomics. - 1872-8219 .- 0169-8141. ; 31:4, s. 263-281
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on materials kit functionality - usefulness of the materials kit in respect of operators' handling of materials and cognition during assembly work. That is, how the materials kit facilitates assembly work as well as promotes learning. This analysis comprises video recordings of nine automobiles in total from the closed down Volvo Uddevalla plant; a plant with parallel flow, long cycle time assembly work, where the materials supply was designed to facilitate the assembly work. To evaluate the usefulness of a materials kit from an assembly point of view, its configuration was related to the observed assembly work, and the level of structural congruence was estimated in order to judge to what extent the materials kit actually supported the assembly work. Briefly summarised, by using an analysis method in the form of 'signal component' methodology, this analysis showed that the assembly work proved to be almost identical when there were no technical differences between the layouts. It was thus assumed that it is possible to design materials kits in accordance with the observed assembly work, even though the materials kits configuration in the case study was not fully optimised and the stipulated work patterns were not in agreement with the observed work patterns. The ideal situation is that the operator picks components from one materials container at a time; however, it turned out that the operators picked from nearly two materials containers simultaneously. Relevance to industry Parallel flow, long cycle time assembly systems call for knowledge about conformity in the execution of assembly work within a work group. This paper reports on a case study focusing on the possibility to design common materials kits and assembly instructions, which in turn influences e.g. materials supply and learning times. © 2003 Elsevier Science B.V. All rights reserved.
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| 13. |
- Piamonte, D.P.T., et al.
(författare)
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Understanding small graphical symbols : A cross-cultural study
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 27:6, s. 399-404
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Tidskriftsartikel (refereegranskat)abstract
- Graphical symbols such as icons or pictograms as interfaces in modern technological devices have become quite common. Although generally designed in western countries, their use can be found worldwide from audio-visual appliances to computers and computer-related devices. A basic ergonomic principle is to involve the potential users in the design and evaluation stages especially when the user groups are quite diverse. This study was part of an international project on evaluating telecommunication symbols. One of the major objectives was to test different graphical symbols (of the videophone), designed, and tested in Western Europe using subject groups from Asia, Europe, and the United States. This paper would discuss the major portions of the tests involving US and Swedish subjects. Performance indices used were hits, certainties, confusions, and semantic differential ratings. They were useful in analysing how the symbols were recognised, confused, and perceived by different subject groups. They also helped detect differences between groups which otherwise seemed to have similar test results. The results showed differences in patterns of ratings, which may be culturally linked and could help determine aspects of symbol design and usage that may be more helpful in designing instructions, learning aids, etc. Awareness of such subject bias and their implications are important on how one interprets the test results.Relevance to industryThe study outcome can be very helpful for industries in designing and evaluating candidate graphical symbols across various types of consumer products for worldwide use. Copyright © 2001 Elsevier Science B.V.
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| 14. |
- Trapenskas, Donatas, et al.
(författare)
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Localization performance of binaurally recorded sounds with and without training
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141 .- 1872-8219. ; 27:6, s. 405-410
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Tidskriftsartikel (refereegranskat)abstract
- One of the problems associated with listening to binaurally recorded sound events is localization confusions. The main objective of this investigation was to find out whether a short training session prior to listening to binaural recordings through headphones would facilitate correct spatial perception of the sound field. Focus was on the localization of the sound stimuli in median plane. Sound signals were recorded with an artificial head in three different conditions namely, anechoic, highly reverberant and moderately reverberant. Fourteen subjects participated in the listening tests. All subjects were required to localize all virtual sound stimuli under two different conditions. The first condition had a short training session binaurally recorded in the same environments as preceeding sound stimuli, and only sound stimuli recorded in the same environment were presented. The second condition did not have a training session, and sound stimuli recorded in different environments were presented. Results showed that a short training session prior to listening to binaurally recorded sounds through headphones was useful as it facilitated localization performance. The biggest effect was in reduced amount of sounds perceived inside the head. It was most pronounced for sound stimuli recorded in anechoic environment.
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| 15. |
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| 16. |
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| 17. |
- Newell, Theresa M., et al.
(författare)
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Prevalence of musculoskeletal disorders among orthodontists in Alberta
- 2004
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 33:2, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- Ergonomic problems have been noted among the hazards in the dental workplace. Many surveys have suggested that dental professionals may suffer from musculoskeletal disorders (MSDs) of the low back and neck as well as other MSDs. This survey aimed to look deeper into MSDs among orthodontists and provide a starting point to direct ergonomic intervention. The standardized Nordic questionnaire was mailed out to all registered orthodontists in Alberta, Canada. There was a 52.4% response rate from a sample of 61. Seventy-two percent of the respondents were male and 28% were female. The results showed low back trouble to be the most prevalent MSD (59%), followed by neck (56%), and shoulder trouble (47%). There was no significant differences in MSD prevalence between gender (p > 0.4), and no correlations existed between age, years of work, and number of hours of practice per week (p > 0.3). These results were consistent with other studies surveyed on dental professionals for the number and type of MSDs present. Further attention should be directed towards risk factors and ergonomic intervention.
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| 18. |
- Piedrahíta, Hugo, et al.
(författare)
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Musculoskeletal symptoms in cold exposed and non-cold exposed workers
- 2004
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 34:4, s. 271-278
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Tidskriftsartikel (refereegranskat)abstract
- A cross-sectional epidemiologic study was carried out to explore the relationship between musculoskeletal symptoms and cold exposure in a large meat processing company in Colombia. All workers in the packing areas (n=162) were recruited: 50 workers from very cold areas (+2°C) and 112 workers from less severely exposed areas (range +8°C to +12°C). Thermal environmental conditions were measured in both areas. By Standardized Nordic Questionnaire, there was a high prevalence of musculoskeletal symptoms among the more exposed workers, especially for low back, neck and shoulders. The prevalence ratios for neck and low back symptoms interfering with usual work were 11.2 (95% CI 1.3–93.4) and 4.5 (95% CI 1.6–12.4), respectively. Job features that could not be addressed in this study included work shift (day versus night), adequacy of thermal protective clothing, type of contract with the company and psychosocial conditions at work. The association between cold exposure and musculoskeletal problems is plausible but the mechanism is still obscure and there is a need for further research, both experimental and epidemiologic (preferably cohort studies).
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| 19. |
- Christmansson, M, et al.
(författare)
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A case study of a principally new way of materials kitting - an evaluation of time consumption and physical workload
- 2002
-
Ingår i: International Journal of Industrial Ergonomics. - : Elsevier. - 0169-8141. ; 30:1, s. 49-65
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a materials kitting case study, using an alternative method for materials killing: the traditional picker-to-material principle was replaced with a material-to-picker approach. The Study was made in a materials supply workshop of an automobile plant shortly after this kitting process had been introduced. The materials kitting was video recorded and the material pickers' physical exposure was assessed using ambulatory equipment to make an integrated registration of muscular activity, work postures and movements. The material pickers assessed work situations perceived as physically stressful. The materials kitting showed improved productivity as compared with other kitting methods. The study indicated that the work situation offered pickers low levels of physical exposure. The picking work was rather light but involved great repetitiveness in arm movements. The material pickers experienced the work as repetitive and having some physically stressful work situations. The integrated analyses showed: (1) that exposure in picking operations was similar to, but could be distinguished from, other work activities and (2) that picking from one type of storage package, Euro pallets, resulted in higher exposure than picking from plastic containers. More studies are needed on the implications of exposure levels in materials picking.
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| 20. |
- Hanson, Lars, et al.
(författare)
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A control handling comfort model based on fuzzy logics
- 2003
-
Ingår i: International Journal of Industrial Ergonomics. - 0169-8141. ; 31:2, s. 87-100
-
Tidskriftsartikel (refereegranskat)abstract
- The car interior is a complex man-machine interface. Poor interior design contributes to traffic accidents as well as discomfort and disorders in professional and long distance drivers. When buying a car comfort is for many customers an important factor. Consequently, car interior comfort besides safety is of great importance when designing cars. Comfort is a subjective feeling and hard to model mathematically. The aim of this paper is to show the feasibility with fuzzy logics to model relations between human perception, human characteristics and workplace structure. A model where drivers' perceived comfort when handling interior controls is in relation to anthropometrics and control positions are used as illustration. A series of control reach studies in simulated car driving was used for the development of a comfort model. Combined with a human simulation program the comfort model may be used by car designers at an early stage of the design process for evaluation of design concepts aiming at reachable and manageable controls in a safe and comfortable interior. The comfort model illustrates that fuzzy logics provides a constructive way of turning qualities into mathematics.
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| 21. |
- Juul-Kristensen, B, et al.
(författare)
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Physical workload during manual and mechanical deboning of poultry
- 2002
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141. ; 29:2, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- The physical workload after the introduction of new technology, i.e. mechanical versus manual deboning of poultry was studied with respect to force requirements, work postures and repetitive movements of the hand. Thirteen healthy women were studied during manual and mechanical deboning using electromyography (EMG), force recordings, observer based force ratings and electrogoniometers. The muscular activity was significantly higher in Extensor Carpi Ulnaris (ECU), Flexor Carpi Ulnaris (FCU), and Flexor Digitorum Superficialis (FDS) during cutting-the most strenuous task of manual deboning-than during mechanical deboning. Estimated cutting forces were 6.3 and 20.7 N (median and peak levels). Extreme wrist postures were more frequent during cutting, but peak acceleration and repetition-calculated from spectral analysis of the goniometer signal-were higher during mechanical deboning. In general the introduction of new technology, i.e. mechanical deboning had only marginal effects on the risk factors associated with work related musculoskeletal disorders during poultry processing. Mechanical deboning moderately reduced peak forces, but the muscular activity remained high, and in addition higher levels of acceleration and repetition rates were introduced. Observer based estimations of the hand forces correlated in these work tasks well with the mean peak EMG level of the relevant muscles.
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| 22. |
- Stal, M, et al.
(författare)
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The effect on workload by using a support arm in parlour milking
- 2003
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141. ; 32:2, s. 121-132
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Tidskriftsartikel (refereegranskat)abstract
- Swedish agriculture is currently undergoing radical changes with respect to the working environment. New production milking systems may alter the physical workload and thus have an effect on the development of musculoskeletal disorders. Earlier studies have shown that there is a manifest risk of suffering injury to the forearm, wrist and hand during machine milking especially during the attaching task (when holding the milking cluster in one hand while attaching the four teat-cups to the udder). High degrees of dorsiflexion and deviation of the wrist in combination with peak values of muscle activity in the forearm during milking might contribute injuries to the wrist and hand. Large-scale milk production increases the time spent performing the tasks involved. As a consequence, the cumulative engagement in extreme positions and rapid movements, and high level of muscular load on the upper extremities will also increase. The aim of this study was to investigate the impact of the workload on the milker's forearm, wrist and hands resulting from using the prototype of a device designed to facilitate the attaching task. The device is constructed as a support arm where the milking cluster is suspended in order to reduce the workload. The study was carried out in a loose-housing system where the cows come to be milked in a parlour. Eleven milkers participated in the study. The muscle activity in the biceps and the forearm flexors, as well as positions and movements of the wrists were measured by electromyography and electrogoniometry. The attaching task was measured both with and without the device. When the prototype was used only a minor decrease in the muscular load on the holding side was recorded. Surprisingly, the effect on the wrist positions and movements was small. This marginal effect could be due to the fact that all the milkers were used to milking without the support arm and despite the training period, they were unable to make full use of the device.
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| 23. |
- Ahsberg, E, et al.
(författare)
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Shiftwork and different dimensions of fatigue
- 2000
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Ingår i: INTERNATIONAL JOURNAL OF INDUSTRIAL ERGONOMICS. - 0169-8141. ; 26:4, s. 457-465
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
- Neumann, Patrick, et al.
(författare)
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Trunk posture: reliability, accuracy, and risk estimates for low back pain from a video based assessment method
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141. ; 28, s. 355-365
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Tidskriftsartikel (refereegranskat)abstract
- It has been recently reported that both dynamic movement characteristics, as well as the duration of postures adopted during work, are important in the development of low back pain (LBP). This paper presents a video-based posture assessment method capable of measuring trunk angles and angular velocities in industrial workplaces. The interobserver reliability, system accuracy, and the relationship of the measured exposures to the reporting of low back pain are reported. The video analysis workstation consisted of a desktop computer equipped with digital video capture and playback technology, a VCR, and a computer game type joystick. The operator could then use a joystick to track trunk flexion and lateral bending during computer-controlled video playback. The joystick buttons were used for binary input of twisting. The inter-observer reliability for peak flexion and percentage of time spent in posture category variables were excellent (ICC>0.8). Lower reliability levels were observed for peak and average velocity and movement related variables. The video analysis system time series data showed very high correlation to the criterion optoelectronic imaging system (r ¼ 0:92). Root mean square errors averaged 5.81 for the amplitude probability distribution function data. Trunk flexion variables including peak level, peak velocity, average velocity indicators, and percent time in flexion category indicators all showed significant differences between cases and controls in the epidemiological study. A model consisting of the measures peak trunk flexion, percent time in lateral bend and average lateral bending velocity emerged after multivariable analysis for relationship to low back pain.
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| 29. |
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| 30. |
- Wartenberg, Constanze, et al.
(författare)
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The effect of assembly tolerance on performance of a tape application task: A pilot study
- 2004
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Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141. ; 33:4, s. 369-379
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Tidskriftsartikel (refereegranskat)abstract
- Task characteristics such as visual and manual demands influence the postures employed and the muscular load during task execution. According to ergonomic experts at a car assembly plant, these demands are difficult to predict during product and production development and can easily be underestimated. One such task with combined visual and manual demands is the application of deco-tape to the door frame of cars. This precision task requires the exact manual positioning of the tape and a careful visual control in order to continuously adjust alignment and to check for any air bubbles fastened under the tape. This task has to be carried out within limited time determined by the pace of the assembly line, thus requiring both high precision and a certain speed. The present study aimed at the question: how do different degrees of assembly tolerance affect the execution of a precision assembly task? Deco-tape fixation was transformed into an experimental task in order to study the effect of different degrees of precision demands. Ten subjects without previous assembly experience completed 60 experimental trials each. In each trial a tape was affixed in an area indicated on a frame. Thirty trials required high precision with minimal assembly tolerance-that is the tape was affixed in an area that had the same width as the tape. The remaining 30 trials were carried out with lower precision demands-the indicated area provided an assembly tolerance of 3 mm at a tape width of 19 mm. Task completion time, the movement path of the right hand and head, and the occurrence of quality deficiencies were registered. The study showed strong effects of the change in assembly tolerance on the speed, postural behaviour and movement paths during task execution: Tasks with high precision demands required significantly longer completion times. Higher precision demands lead to a working posture with less variation in the distance between the right hand and head. During tasks with high precision, the movement path of the right hand was less economic-with smaller movement cycles of shorter duration-all owing for a more frequent control of results. It was concluded that precision demands play an important role for the speed, working posture and movement path during an assembly task. Considering these effects and their potential implication for the muscular load during task execution, it seems important to consider task characteristics such as precision demands in detail when designing products for assembly. A careful consideration of these task characteristics is essential when using simulation tools such as mannequins in extended phases of future product development processes. Relevance to industry Current ergonomic guidelines often focus on the physical layout of a workplace, while task characteristics such as visual and manual demands are considered to a lesser extent. However, these task characteristics may play an important role for assembly workers' postural behaviour and the muscular load during work. Increasing use of simulation tools instead of physical prototypes in the product and production development process makes it even more difficult to evaluate task characteristics such as precision demands. On this background, more knowledge about the effect of task characteristics on working posture and assembly paths is needed. The present pilot study provides a detailed analysis of the effect of different precision demands on the work posture and execution of an assembly task-deco-tape fixation. (C) 2003 Elsevier B.V. All rights reserved.
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