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Classification and Quantification of Human Error in Manufacturing: A Case Study in Complex Manual Assembly. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11020749] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Manual assembly operations are sensitive to human errors that can diminish the quality of final products. The paper shows an application of human reliability analysis in a realistic manufacturing context to identify where and why manual assembly errors occur. The techniques SHERPA and HEART were used to perform the analysis of human reliability. Three critical tasks were selected for analysis based on quality records: (1) installation of three types of brackets using fasteners, (2) fixation of a data cable to the assembly structure using cushioned loop clamps and (3) installation of cap covers to protect inlets. The identified error modes with SHERPA were: 36 action errors, nine selection errors, eight information retrieval errors and six checking errors. According to HEART, the highest human error probabilities were associated with assembly parts sensitive to geometry-related errors (brackets and cushioned loop clamps). The study showed that perceptually engaging assembly instructions seem to offer the highest potential for error reduction and performance improvement. Other identified areas of action were the improvement of the inspection process and workers’ provision with better tracking and better feedback. Implementation of assembly guidance systems could potentially benefit worker’s performance and decrease assembly errors.
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Kelson DM, Mathiassen SE, Srinivasan D. Trapezius muscle activity variation during computer work performed by individuals with and without neck-shoulder pain. APPLIED ERGONOMICS 2019; 81:102908. [PMID: 31422258 DOI: 10.1016/j.apergo.2019.102908] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 07/18/2019] [Accepted: 07/22/2019] [Indexed: 06/10/2023]
Abstract
This study aimed at determining the extent to which individuals with neck-shoulder pain and non-symptomatic individuals differ in muscle activation patterns, when performing computer work, as quantified by exposure variation analysis (EVA). As a secondary aim, we also aimed to quantify the day-to-day reliability of EVA variables describing trapezius muscle activation in a non-symptomatic control group. Thirteen touch-typing computer users (pain: n = 5, non-symptomatic: n = 8) completed three pre-selected computer tasks in the laboratory. Upper trapezius muscle activity was recorded using electromyography and analyzed using EVA with five amplitude and five duration categories. Individuals with neck-shoulder pain spent less time at low amplitudes and exhibited longer uninterrupted periods of muscle activation compared to their non-symptomatic counterparts. Thus, non-symptomatic workers tended to switch between exposure levels more often than individuals with pain. For a majority of EVA variables, ICCs ranged from 0.6 to 0.9, and between-days coefficients of variation were between 0.4 and 2.2.
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Affiliation(s)
- Denean M Kelson
- Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA, 24060, USA
| | - Svend Erik Mathiassen
- Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Gävle, Sweden
| | - Divya Srinivasan
- Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA, 24060, USA.
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Wahlström J, Bergsten E, Trask C, Mathiassen SE, Jackson J, Forsman M. Full-Shift Trunk and Upper Arm Postures and Movements Among Aircraft Baggage Handlers. ANNALS OF OCCUPATIONAL HYGIENE 2016; 60:977-90. [DOI: 10.1093/annhyg/mew043] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 06/05/2016] [Indexed: 12/30/2022]
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Abstract
This chapter discusses mechanical stressors that are believed to be associated with work-related musculoskeletal disorders. It starts with an introduction to work-related musculoskeletal disorders (particularly those with high incidences in workplaces, such as disorders of low back, neck/shoulder, hand/wrist, elbow, and knee) in high-risk industries, and those mechanical stressors (such as high forces, awkward postures, high repetitions, excessive contact stress, and harmful human vibrations) in workplaces that are responsible for these disorders. Quantification methods of these mechanical stressors are then discussed. Although various quantification methods such as self-report, observational technique, and direct measurement are discussed, details are focused on many of those well-published observational techniques used by practitioners to assess risk levels of these mechanical stressors in jobs. These methods can quantify job mechanical stressors and provide risk level indications that can be used by practitioners to facilitate their decision making. These methods can also be used to evaluate the improvements of ergonomics interventions by comparing the risk levels quantitatively before and after the interventions.
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Mathiassen SE, Hallman DM, Lyskov E, Hygge S. Can cognitive activities during breaks in repetitive manual work accelerate recovery from fatigue? A controlled experiment. PLoS One 2014; 9:e112090. [PMID: 25375644 PMCID: PMC4222971 DOI: 10.1371/journal.pone.0112090] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 10/13/2014] [Indexed: 11/18/2022] Open
Abstract
Neurophysiologic theory and some empirical evidence suggest that fatigue caused by physical work may be more effectively recovered during “diverting” periods of cognitive activity than during passive rest; a phenomenon of great interest in working life. We investigated the extent to which development and recovery of fatigue during repeated bouts of an occupationally relevant reaching task was influenced by the difficulty of a cognitive activity between these bouts. Eighteen male volunteers performed three experimental sessions, consisting of six 7-min bouts of reaching alternating with 3 minutes of a memory test differing in difficulty between sessions. Throughout each session, recordings were made of upper trapezius muscle activity using electromyography (EMG), heart rate and heart rate variability (HRV) using electrocardiography, arterial blood pressure, and perceived fatigue (Borg CR10 scale and SOFI). A test battery before, immediately after and 1 hour after the work period included measurements of maximal shoulder elevation strength (MVC), pressure pain threshold (PPT) over the trapezius muscles, and a submaximal isometric contraction. As expected, perceived fatigue and EMG amplitude increased during the physical work bouts. Recovery did occur between the bouts, but fatigue accumulated throughout the work period. Neither EMG changes nor recovery of perceived fatigue during breaks were influenced by cognitive task difficulty, while heart rate and HRV recovered the most during breaks with the most difficult task. Recovery of perceived fatigue after the 1 hour work period was also most pronounced for the most difficult cognitive condition, while MVC and PPT showed ambiguous patterns, and EMG recovered similarly after all three cognitive protocols. Thus, we could confirm that cognitive tasks between bouts of fatiguing physical work can, indeed, accelerate recovery of some factors associated with fatigue, even if benefits may be moderate and some responses may be equivocal. Our results encourage further research into combinations of physical and mental tasks in an occupational context.
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Affiliation(s)
- Svend Erik Mathiassen
- Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Gävle, Sweden
- * E-mail:
| | - David M. Hallman
- Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Gävle, Sweden
| | - Eugene Lyskov
- Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Gävle, Sweden
| | - Staffan Hygge
- Department of Building, Energy and Environmental Engineering, University of Gävle, Gävle, Sweden
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Barbieri DF, Srinivasan D, Mathiassen SE, Nogueira HC, Oliveira AB. The ability of non-computer tasks to increase biomechanical exposure variability in computer-intensive office work. ERGONOMICS 2014; 58:50-64. [PMID: 25345757 DOI: 10.1080/00140139.2014.965753] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Postures and muscle activity in the upper body were recorded from 50 academics office workers during 2 hours of normal work, categorised by observation into computer work (CW) and three non-computer (NC) tasks (NC seated work, NC standing/walking work and breaks). NC tasks differed significantly in exposures from CW, with standing/walking NC tasks representing the largest contrasts for most of the exposure variables. For the majority of workers, exposure variability was larger in their present job than in CW alone, as measured by the job variance ratio (JVR), i.e. the ratio between min-min variabilities in the job and in CW. Calculations of JVRs for simulated jobs containing different proportions of CW showed that variability could, indeed, be increased by redistributing available tasks, but that substantial increases could only be achieved by introducing more vigorous tasks in the job, in casu illustrated by cleaning.
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Affiliation(s)
- Dechristian França Barbieri
- a Laboratory of Clinical and Occupational Kinesiology (LACO), Department of Physical Therapy , Federal University of São Carlos , Washington Luiz Road, km 235, SP310, 13565-905 São Carlos , Brazil
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A comparison of cluster-based exposure variation and exposure variation analysis to detect muscular adaptation in the shoulder joint to subsequent sessions of eccentric exercise during computer work. J Electromyogr Kinesiol 2014; 24:192-9. [DOI: 10.1016/j.jelekin.2013.12.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 09/16/2013] [Accepted: 12/05/2013] [Indexed: 11/18/2022] Open
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Luger T, Bosch T, Veeger D, de Looze M. The influence of task variation on manifestation of fatigue is ambiguous - a literature review. ERGONOMICS 2014; 57:162-174. [PMID: 24552472 DOI: 10.1080/00140139.2014.885088] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/19/2013] [Accepted: 01/09/2014] [Indexed: 06/03/2023]
Abstract
Task variation has been proposed to reduce shoulder fatigue resulting from repetitive hand-arm tasks. This review analyses the effect of task variation, both 'temporal (i.e. change of work-rest ratio)' and 'activity (i.e. job rotation)' variation, on physiological responses, endurance time (ET) and subjective feelings. Pubmed was searched and complemented with references from selected articles, resulting in 17 articles. Temporal variation had some positive effects on the objective parameters, as blood pressure decreased and ET increased, and on the subjective feelings, as perceived discomfort decreased. The observed findings of activity variation showed both positive and negative effects of increased activity variation, while hardly any effects were found on electromyography manifestations of fatigue. In conclusion, the evidence for positive effects of increasing the level of variation is scarce. The number of studies on variation is limited, while in most studies the findings were not controlled for the amount or intensity of work.
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Affiliation(s)
- Tessy Luger
- a MOVE Research Institute Amsterdam , Faculty of Human Movement Sciences , VU University Amsterdam, Van Der Boechorststraat 9, 1081 BT, Amsterdam , The Netherlands
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van der Beek AJ, Mathiassen SE, Burdorf A. Efficient assessment of exposure to manual lifting using company data. APPLIED ERGONOMICS 2013; 44:360-365. [PMID: 23069188 DOI: 10.1016/j.apergo.2012.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 08/29/2012] [Accepted: 09/11/2012] [Indexed: 06/01/2023]
Abstract
The objective of this study, based on an extensive dataset on manual materials handling during scaffolding, was to explore whether routinely collected company data can be used to estimate exposure to manual lifting. The number of manual lifts of scaffold parts while constructing/dismantling scaffolds was well predicted by the number of scaffolders in the team and the type of worksite, in combination with company data of either the number of scaffold parts or the scaffold volume. The proportion of explained variance in the number of lifts ranged from 77% to 92%, depending on the variables in the model. Data on scaffold parts and scaffold volume can easily be obtained from the company's administration, since this is its usual paperwork supporting logistics and customer invoicing, respectively. We conclude that company data can be a promising source of information for ergonomic practitioners and researchers, to support assessment of manual lifting in scaffolding.
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Affiliation(s)
- Allard J van der Beek
- Department of Public and Occupational Health, EMGO Institute for Health and Care Research, VU University Medical Center, Van der Boechorststraat 7, P.O. Box 7057, NL-1007 MB, Amsterdam, The Netherlands.
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Samani A, Mathiassen SE, Madeleine P. Cluster-based exposure variation analysis. BMC Med Res Methodol 2013; 13:54. [PMID: 23557439 PMCID: PMC3623884 DOI: 10.1186/1471-2288-13-54] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 03/24/2013] [Indexed: 11/17/2022] Open
Abstract
Background Static posture, repetitive movements and lack of physical variation are known risk factors for work-related musculoskeletal disorders, and thus needs to be properly assessed in occupational studies. The aims of this study were (i) to investigate the effectiveness of a conventional exposure variation analysis (EVA) in discriminating exposure time lines and (ii) to compare it with a new cluster-based method for analysis of exposure variation. Methods For this purpose, we simulated a repeated cyclic exposure varying within each cycle between “low” and “high” exposure levels in a “near” or “far” range, and with “low” or “high” velocities (exposure change rates). The duration of each cycle was also manipulated by selecting a “small” or “large” standard deviation of the cycle time. Theses parameters reflected three dimensions of exposure variation, i.e. range, frequency and temporal similarity. Each simulation trace included two realizations of 100 concatenated cycles with either low (ρ = 0.1), medium (ρ = 0.5) or high (ρ = 0.9) correlation between the realizations. These traces were analyzed by conventional EVA, and a novel cluster-based EVA (C-EVA). Principal component analysis (PCA) was applied on the marginal distributions of 1) the EVA of each of the realizations (univariate approach), 2) a combination of the EVA of both realizations (multivariate approach) and 3) C-EVA. The least number of principal components describing more than 90% of variability in each case was selected and the projection of marginal distributions along the selected principal component was calculated. A linear classifier was then applied to these projections to discriminate between the simulated exposure patterns, and the accuracy of classified realizations was determined. Results C-EVA classified exposures more correctly than univariate and multivariate EVA approaches; classification accuracy was 49%, 47% and 52% for EVA (univariate and multivariate), and C-EVA, respectively (p < 0.001). All three methods performed poorly in discriminating exposure patterns differing with respect to the variability in cycle time duration. Conclusion While C-EVA had a higher accuracy than conventional EVA, both failed to detect differences in temporal similarity. The data-driven optimality of data reduction and the capability of handling multiple exposure time lines in a single analysis are the advantages of the C-EVA.
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Affiliation(s)
- Afshin Samani
- Laboratory for Ergonomics and Work-related Disorders, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg East 9220, Denmark.
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Jonker D, Rolander B, Balogh I, Sandsjö L, Ekberg K, Winkel J. Rationalisation in public dental care--impact on clinical work tasks and mechanical exposure for dentists--a prospective study. ERGONOMICS 2013; 56:303-313. [PMID: 23419089 DOI: 10.1080/00140139.2012.760751] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
UNLABELLED Swedish dentistry has been exposed to frequent rationalisation initiatives during the last half century. Previous research has shown that rationalisation often results in increased risk of developing work-related musculoskeletal disorders, thus reducing sustainability in the production system. In this prospective study, we assessed mechanical exposures among Swedish dentists in relation to specific rationalisations of clinical dental work during a six-year period. Body postures and movements of 12 dentists were assessed by inclinometry synchronised to video recordings of their work. No rationalisation effects could be shown in terms of a reduction in non-value-adding work ('waste'), and at job level, no major differences in mechanical exposure could be shown between baseline and follow-up. CONCLUSION The present rationalisation measures in dentistry do not seem to result in rationalisation at job level, but may potentially be more successful at the overall dental system level. PRACTITIONER SUMMARY In contrast to many previous investigations of the mechanical exposure implications of rationalisation, the present rationalisation measures did not increase the level of risk for dentists. It is highlighted that all occupations involved in the production system should be investigated to assess production system sustainability.
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Affiliation(s)
- D Jonker
- National Centre for Work and Rehabilitation Department of Medical Health Sciences, Linköping University, Linköping, SE 55185, Sweden.
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Palmerud G, Forsman M, Neumann WP, Winkel J. Mechanical exposure implications of rationalization: a comparison of two flow strategies in a Swedish manufacturing plant. APPLIED ERGONOMICS 2012; 43:1110-1121. [PMID: 22575494 DOI: 10.1016/j.apergo.2012.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 03/30/2012] [Accepted: 04/02/2012] [Indexed: 05/31/2023]
Abstract
The aim of this case study was to (1) investigate differences in mechanical exposure (i.e. mechanical forces arising in the body of the operator) between two production strategies: long-cycle parallelised flow assembly (OLD) and conventional serial flow assembly (NEW), and (2) estimate potential changes in job exposure as a consequence of waste reduction when rationalising a line system. Data on postures, movements and whole body exposure were collected during an ordinary working shift, by means of video recordings synchronised to direct technical measurements of six professional operators. The results revealed the machine paced NEW system to have slower movements with less time spent in movements of high velocity compared to the self-paced OLD system. No significant differences were found between time-median posture levels. 'Disturbances' in the NEW system offered lower mechanical risk exposures compared to direct assembly work. Modelling the removal of wasteful 'disturbances' revealed both an increase in risk-implying fast movements and decrease in recovery-implying periods at low velocity - effectively isolating a work intensification. This study helps expose the complex relationship between rationalizations and mechanical exposure for system operators.
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Affiliation(s)
- Gunnar Palmerud
- Occupational and Environmental Medicine, University of Gothenburg, Sweden
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Mathiassen SE, Wahlström J, Forsman M. Bias and imprecision in posture percentile variables estimated from short exposure samples. BMC Med Res Methodol 2012; 12:36. [PMID: 22443348 PMCID: PMC3359227 DOI: 10.1186/1471-2288-12-36] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 03/25/2012] [Indexed: 11/24/2022] Open
Abstract
Background Upper arm postures are believed to be an important risk determinant for musculoskeletal disorder development in the neck and shoulders. The 10th and 90th percentiles of the angular elevation distribution have been reported in many studies as measures of neutral and extreme postural exposures, and variation has been quantified by the 10th-90th percentile range. Further, the 50th percentile is commonly reported as a measure of "average" exposure. These four variables have been estimated using samples of observed or directly measured postures, typically using sampling durations between 5 and 120 min. Methods The present study examined the statistical properties of estimated full-shift values of the 10th, 50th and 90th percentile and the 10th-90th percentile range of right upper arm elevation obtained from samples of seven different durations, ranging from 5 to 240 min. The sampling strategies were realized by simulation, using a parent data set of 73 full-shift, continuous inclinometer recordings among hairdressers. For each shift, sampling duration and exposure variable, the mean, standard deviation and sample dispersion limits (2.5% and 97.5%) of all possible sample estimates obtained at one minute intervals were calculated and compared to the true full-shift exposure value. Results Estimates of the 10th percentile proved to be upward biased with limited sampling, and those of the 90th percentile and the percentile range, downward biased. The 50th percentile was also slightly upwards biased. For all variables, bias was more severe with shorter sampling durations, and it correlated significantly with the true full-shift value for the 10th and 90th percentiles and the percentile range. As expected, shorter samples led to decreased precision of the estimate; sample standard deviations correlated strongly with true full-shift exposure values. Conclusions The documented risk of pronounced bias and low precision of percentile estimates obtained from short posture samples presents a concern in ergonomics research and practice, and suggests that alternative, unbiased exposure variables should be considered if data collection resources are restricted.
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Affiliation(s)
- Svend Erik Mathiassen
- Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Gävle, Sweden.
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Jonker D, Rolander B, Balogh I, Sandsjö L, Ekberg K, Winkel J. Mechanical exposure among general practice dentists in Sweden and possible implications of rationalisation. ERGONOMICS 2011; 54:953-60. [PMID: 21973006 DOI: 10.1080/00140139.2011.606919] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The present study investigates the dental work in terms of time distribution and mechanical exposure in value-adding work (VAW) and non-VAW. Further rationalisation of dental work would typically involve an increase in the proportion of VAW. Information on mechanical exposure within the classes of VAW and non-VAW may be used to predict possible implications of rationalisation. Sixteen dentists were investigated. Using a data logger, postures and movements were continuously recorded for each subject during the 4 h of work, which included the 45 min of video recording. Time distribution and mechanical exposure for the six different work activities identified were evaluated from the video recordings, using a loss analysis technique. VAW, which comprised 54% of the total working time, generally implied significantly more constrained mechanical exposures as compared with non-VAW. The results suggest that future rationalisation of dental work, involving a reduction of non-VAW, may increase the risk of developing musculoskeletal disorders. Statement of Relevance: The present study illustrates the potential effects of rationalisation on biomechanical exposures for dentists. The results highlight the significance of integrating ergonomic issues into the rationalisation process in dentistry in addition to ordinary workstation and tool design improvements performed by ergonomists.
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Affiliation(s)
- D Jonker
- National Centre for Work and Rehabilitation, Department of Medical Health Sciences, Linko¨ping University, Linköping, Sweden.
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Westgaard RH, Winkel J. Occupational musculoskeletal and mental health: Significance of rationalization and opportunities to create sustainable production systems - A systematic review. APPLIED ERGONOMICS 2011; 42:261-296. [PMID: 20850109 DOI: 10.1016/j.apergo.2010.07.002] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 07/09/2010] [Accepted: 07/11/2010] [Indexed: 05/29/2023]
Abstract
This literature review aims to identify occupational musculoskeletal and mental health effects of production system rationalization as well as organizational-level measures that may improve health outcome ("modifiers" in this review). A short review of the effect of ergonomic interventions is included as background and rationalization is discussed as a theoretical concept. Indicator variables for occupational musculoskeletal and mental health and related risk factors are presented. Variables with a generalized format were allowed in the literature searches (e.g., job satisfaction and absenteeism were accepted as risk factor and health indicator, respectively), suitable for the research fields of work sociology, organization science, human resource management (HRM) and economics research. One hundred and sixty-two studies of rationalization effects on health and risk factors and 72 organization-level modifier results were accepted into the final database. Entries were sorted by rationalization strategy and work life sector, and trends in outcome (positive, mixed, no effect, or negative effect on health and risk factors) were determined. Rationalizations have a dominant negative effect on health and risk factors (57% negative, 19% positive); the most negative effects were found for downsizing and restructuring rationalizations in general (71 studies negative, 13 positive) and for the health care sector in particular (36 studies negative, 2 positive). The rationalization strategy High Performance Work System (HPWS) was associated with the highest fraction positive outcome studies (6 of 10 studies). Other rationalization strategies (lean practices, parallel vs. serial production and mechanization level) reported intermediate results, in part dependent on work life sector, but also on the year when studies were carried out. Worker participation, resonant management style, information, support, group autonomy and procedural justice were modifiers with favourable influence on outcome. It is concluded that production system rationalization represents a pervasive work life intervention without a primary occupational health focus. It has considerable and mostly negative influence on worker health, but this can be reduced by attention to modifiers. The results create a basis for new priorities in ergonomic intervention research.
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Affiliation(s)
- R H Westgaard
- Department of Industrial Economics and Technology Management, Norwegian University of Science and Technology, Trondheim, Norway.
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Dempsey PG, Mathiassen SE, Jackson JA, O'Brien NV. Influence of three principles of pacing on the temporal organisation of work during cyclic assembly and disassembly tasks. ERGONOMICS 2010; 53:1347-1358. [PMID: 20967657 DOI: 10.1080/00140139.2010.520745] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A study was conducted to investigate the influence of different approaches to arranging the pace and temporal organisation of repetitive assembly and disassembly tasks on both average performance and its variability and to compare assembly and disassembly times derived with psychophysical methods to a more traditional methods-time measurement (MTM) approach. The conditions studied were a traditional assembly line arrangement, where assemblies were started at a pace of 110 MTM (repeated on two occasions), a batch condition, where subjects were required to complete 36 assemblies within the total amount of time allowed at 110, MTM and a psychophysical condition, where subjects were allowed to choose their pace (repeated on two occasions). Overall, the results suggest that the mean time spent working in each cycle (the 'on-time') remained fairly constant across conditions, while the idle 'off-time' in between on-times was shorter and of less varied duration in the more autonomous batch and psychophysical conditions. During the second psychophysical (self-paced) condition, subjects completed a significantly higher number of assemblies than during the 110 MTM line condition. The higher pace was achieved through reduction in mean off-times and the potential implications for musculoskeletal risk are discussed. STATEMENT OF RELEVANCE: Higher levels of autonomy over work pace, which intuitively would be beneficial from an ergonomics standpoint, actually led to subjects selecting to organise work such that off-times (idle times) were reduced. In contrast, active 'on' times were not affected much by autonomy. These results point to a reason that piecework would be associated with increased risk for musculoskeletal disorders.
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Affiliation(s)
- Patrick G Dempsey
- Liberty Mutual Research Institute for Safety, Hopkinton, Massachusetts, USA.
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Patrick Neumann W, Dul J. Human factors: spanning the gap between OM and HRM. INTERNATIONAL JOURNAL OF OPERATIONS & PRODUCTION MANAGEMENT 2010. [DOI: 10.1108/01443571011075056] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Mathiassen SE, Paquet V. The ability of limited exposure sampling to detect effects of interventions that reduce the occurrence of pronounced trunk inclination. APPLIED ERGONOMICS 2010; 41:295-304. [PMID: 19793578 DOI: 10.1016/j.apergo.2009.08.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 06/23/2009] [Accepted: 08/03/2009] [Indexed: 05/28/2023]
Abstract
Ergonomics interventions often focus on reducing exposure in those parts of the job having the highest exposure levels, while leaving other parts unattended. A successful intervention will thus change the form of the job exposure distribution. This disqualifies standard methods for assessing the ability of various exposure measurement strategies to correctly detect an intervention's effect on the overall job exposure of an individual worker, in particular for the safety or ergonomics practitioner who with limited resources can only collect a few measurements. This study used a non-parametric simulation procedure to evaluate the relationship between the number of measurements collected during a self-paced manufacturing job undergoing ergonomics interventions of varying effectiveness, and the probability of correctly determining whether and to which extent the interventions reduced the overall occurrence of pronounced trunk inclination, defined as an inclination of at least 20 degrees . Sixteen video-recordings taken at random times on multiple days for each of three workers were used to estimate the time distribution of each worker's exposure to pronounced trunk inclination. Nine hypothetical ergonomics intervention scenarios were simulated, in which the occurrence of pronounced trunk inclination in the upper 1/8, 1/4, and 1/2 of the job exposure distribution was reduced by 10%, 30% and 50%. Ten exposure measurement strategies were explored, collecting from one to ten pre- and post-intervention exposure samples from an individual worker. For each worker, intervention scenario and sampling strategy, data were bootstrapped from the measured (pre-intervention) and simulated (post-intervention) exposure distributions to generate empirical distributions of the estimated intervention effect. Results showed that for the one to three intervention scenarios that had the greatest effect on the overall occurrence of trunk inclination in the job, one to four pre- and post-intervention measurements, depending on worker, were sufficient to reach an 80% probability of detecting that the intervention did, indeed, have an effect. However, even for the intervention scenario that had the greatest effect on job exposure, seven or more samples were needed for two of the three workers to obtain a probability larger than 50% of estimating the magnitude of the intervention effect to within +/-50% of its true size. For almost all interventions affecting 1/8 or 1/4 of the job, limited exposure sampling led to low probabilities of detecting any intervention effect, let alone its correct size.
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Neumann WP, Eklund J, Hansson B, Lindbeck L. Effect assessment in work environment interventions: a methodological reflection. ERGONOMICS 2010; 53:130-7. [PMID: 20069488 DOI: 10.1080/00140130903349914] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This paper addresses a number of issues for work environment intervention (WEI) researchers in light of the mixed results reported in the literature. If researchers emphasise study quality over intervention quality, reviews that exclude case studies with high quality and multifactorial interventions may be vulnerable to 'quality criteria selection bias'. Learning from 'failed' interventions is inhibited by both publication bias and reporting lengths that limit information on relevant contextual and implementation factors. The authors argue for the need to develop evaluation approaches consistent with the complexity of multifactorial WEIs that: a) are owned by and aimed at the whole organisation; and b) include intervention in early design stages where potential impact is highest. Context variety, complexity and instability in and around organisations suggest that attention might usefully shift from generalisable 'proof of effectiveness' to a more nuanced identification of intervention elements and the situations in which they are more likely to work as intended. STATEMENT OF RELEVANCE: This paper considers ergonomics interventions from perspectives of what constitutes quality and 'proof". It points to limitations of traditional experimental intervention designs and argues that the complexity of organisational change, and the need for multifactorial interventions that reach deep into work processes for greater impact, should be recognised.
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Affiliation(s)
- W P Neumann
- Department of Mechanical and Industrial Engineering, Ryerson University, Canada.
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Wells R, Mathiassen SE, Medbo L, Winkel J. Time--a key issue for musculoskeletal health and manufacturing. APPLIED ERGONOMICS 2007; 38:733-44. [PMID: 17379179 DOI: 10.1016/j.apergo.2006.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 11/13/2006] [Accepted: 12/11/2006] [Indexed: 05/14/2023]
Abstract
Time is a key issue for both ergonomists and engineers when they engage in production system interventions. While not their primary purpose, the actions of engineers have major effects on biomechanical exposure; possibly of much greater magnitude than many ergonomics interventions. This paper summarises the aims, actions and tools of engineers and ergonomists, emphasising time-related outcomes. Activities of the two groups when attempting to manipulate time aspects of work may be contradictory; engineers wishing to improve production and ergonomists aiming at better health as well as contributing to production. Consequently, tools developed by ergonomists for assessing time aspects of work describe rest patterns, movement velocities or daily duration of exposures, while engineering tools emphasise time-efficient production. The paper identifies measures that could be used to communicate time-relevant information between engineers and ergonomists. Further cooperation between these two stakeholders as well as research on the topic are needed to enable ergonomists to have a larger impact on the design of production systems.
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Affiliation(s)
- Richard Wells
- Kinesiology Department, University of Waterloo, Waterloo, Canada.
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Neumann W, Winkel J, Medbo L, Magneberg R, Mathiassen S. Production system design elements influencing productivity and ergonomics. INTERNATIONAL JOURNAL OF OPERATIONS & PRODUCTION MANAGEMENT 2006. [DOI: 10.1108/01443570610678666] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Mathiassen SE. Diversity and variation in biomechanical exposure: what is it, and why would we like to know? APPLIED ERGONOMICS 2006; 37:419-27. [PMID: 16764816 DOI: 10.1016/j.apergo.2006.04.006] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Trends in global working life suggest that the occurrence of jobs characterized by long-lasting low-level loads or repetitive operations is increasing. More physical "variation" is commonly believed to be a remedy against musculoskeletal disorders in such jobs. One aim of the present paper was to shortly review the validity of this conviction. An examination of the available epidemiologic literature pointed out that the effectiveness of initiatives like job rotation or more breaks is weakly supported by empirical evidence, and only for short-term psychophysical outcomes. Only a limited number of studies have been devoted to physical variation, and concepts and metrics for variation in biomechanical exposure are not well developed. Thus, as a second objective, the paper proposes a framework for investigating and evaluating aspects of exposure variation, based on explicit definitions of variation as "the change in exposure across time" and diversity as "the extent that exposure entities differ". Operational methods for assessing these concepts are also discussed.
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Affiliation(s)
- Svend Erik Mathiassen
- Centre for Musculoskeletal Research, University of Gävle, P.O. Box 7629, SE 90712 Umeå, Sweden.
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Bao S, Spielholz P, Howard N, Silverstein B. Quantifying repetitive hand activity for epidemiological research on musculoskeletal disorders--part I: individual exposure assessment. ERGONOMICS 2006; 49:361-80. [PMID: 16690565 DOI: 10.1080/00140130500520214] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
An exposure measurement approach is described for quantifying repetitive hand activity of individual workers in a prospective epidemiological study on work-related upper extremity musculoskeletal disorders. A total of 733 subjects were involved in this study at the baseline. Hand activities were quantified by force and repetition. Force levels were measured by workers' self-reports, ergonomists' estimates based on observation and measurements with instrumentation. Repetition levels were measured by detailed time-motion analyses using two repetitive hand activity definitions and ergonomists' estimates using scales for the American Conference of Governmental Industrial Hygienists hand activity level and the Strain Index. Results showed that the present exposure assessment approach seems to be able to quantify force level and repetitiveness of hand activities. Repetitive hand activity is quantified differently depending on whether forceful hand exertion or repetitive muscle activity is used as the definition. These hand activity definitions may quantify different physical exposure phenomena. Individual exposure assessment is important in epidemiological research of musculoskeletal disorders as there are interactions between the individual subjects and the measured parameters. These interactions may vary between exposure parameters.
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Affiliation(s)
- S Bao
- Safety & Health Assessment & Research for Prevention (SHARP) Program, Washington State Department of Labor and Industries, P.O. Box 44330, Olympia, WA 98504, USA.
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Kazmierczak K, Mathiassen SE, Forsman M, Winkel J. An integrated analysis of ergonomics and time consumption in Swedish 'craft-type' car disassembly. APPLIED ERGONOMICS 2005; 36:263-73. [PMID: 15854569 DOI: 10.1016/j.apergo.2005.01.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Revised: 01/04/2005] [Accepted: 01/30/2005] [Indexed: 05/03/2023]
Abstract
Car disassembly is at the edge of extensive rationalization due to increased legislative demands for recycling. This study focused on (1) assessing current mechanical exposures (physical work loads) for comparison with future rationalised systems, with particular emphasis on time aspects, (2) analysing disassembly work in terms of time consumption and exposures in constituent tasks as defined by a loss analysis technique, and (3) predicting the consequences of car disassembly rationalisation for mechanical exposures. The study showed that disassembly implied pronounced circulatory loads, and that more walking and higher lumbar peak loads were found than in studies of assembly work. Value-adding tasks comprised 30% of the total working time, and implied higher postural exposures for the head, arm, trunk and wrist, as well as less opportunities to recover, as compared to non-value-adding tasks. Organisational-type rationalization can be expected to increase the time spent in value-adding work, thus increasing local exposures for the average worker, while a concurrent increase in mechanization level might reduce circulatory exposures, the amount of walking, and peak lumbar loads.
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Affiliation(s)
- Karolina Kazmierczak
- National Institute for Working Life, Box 8850, SE-40272 Gothenburg, Sweden; Department of Design Sciences, Lund Technical University, Sweden.
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Möller T, Mathiassen SE, Franzon H, Kihlberg S. Job enlargement and mechanical exposure variability in cyclic assembly work. ERGONOMICS 2004; 47:19-40. [PMID: 14660216 DOI: 10.1080/0014013032000121651] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cyclic assembly work is known to imply a high risk for musculoskeletal disorders. To have operators rotate between work tasks is believed to be one way of decreasing this risk, since it is expected to increase variation in mechanical and psychological exposures (physical and mental loads). This assumption was investigated by assessing mechanical exposure variability in three assembly tasks in an electronics assembly plant, each on a separate workstation, as well as in a 'job enlargement' scenario combining all three stations. Five experienced operators worked for 1 h on each station. Data on upper trapezius and forearm extensor muscle activity were obtained by means of electromyography (EMG), and working postures of the head and upper arms were assessed by inclinometry. The cycle-to-cycle variance of parameters representing the three exposure dimensions: level, frequency and duration was estimated using ANOVA algorithms for each workstation separately as well as for a balanced combination of all three. For a particular station, the variability of trapezius EMG activity levels relative to the mean was higher than for extensor EMG: between-cycles coefficients of variation (CV) about 0.15 and 0.10, respectively. A similar relationship between CV applied to the parameter describing frequency of EMG activity. Except for head inclination levels, the between-cycles CV was larger for posture parameters than for EMG. The between-cycles variance increased up to six fold in the job enlargement scenario, as compared to working at only one station. The difference in mean exposure between workstations was larger for trapezius EMG parameters than for forearm extensor EMG and postures, and hence the effect of job enlargement on exposure variability was more pronounced for the trapezius. For some stations, job enlargement even implied less cycle-to-cycle variability in forearm extensor EMG parameters than working at that station only. Whether the changes in exposure variability associated with job enlargement were sufficient to imply a decreased risk for musculoskeletal disorders is not known.
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Affiliation(s)
- Therése Möller
- Department of Work and Health, National Institute for Working Life, SE-113 91 Stockholm, Sweden
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Mathiassen SE, Möller T, Forsman M. Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task. ERGONOMICS 2003; 46:800-824. [PMID: 12745980 DOI: 10.1080/0014013031000090125] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Data on exposure variability is an important remedy for designing and interpreting studies of occupational ergonomics. The present study aimed at retrieving the within- and between-subjects variance of several mechanical exposure parameters in a repeated, short-cycle task. Seven experienced operators repeatedly secured joints using two types of hand-held nutrunners. The joints were placed in three different locations on a rack, simulating automotive assembly. Bilateral muscle activity from the upper trapezius and the lower arm extensors, as well as head and upper arm inclination was continuously monitored. Exposure levels and their variance components were assessed in several data subsets using ANOVA. The results were interpreted in terms of statistical precision and power, and discussed as markers of important ergonomic qualities. A substantial exposure variability was found within and between subjects in all joint locations and for both tools. For mixed work across tools and locations, the necessary number of subjects to arrive at a group mean exposure with 95% confidence limits corresponding to +/- 10% of the mean ranged between 8 and 158, with posture recordings tending to require smaller populations than muscle activity recordings. Within-subject variance increased 2- to 37-fold, depending on exposure parameter, when work was 'enlarged' from securings with a specified location and tool to a mix of all locations and tools. Systematic differences between subjects in variability and responsiveness to 'work enlargement' indicated individualized motor control strategies. The results illustrate the importance of exposure variability data to the design of proper measurement strategies. They also suggest that the sizes of exposure variability per se can be interpreted as operational indices of what is thought to be important ergonomic risk indicators, such as the 'sameness' of repeated operations and the allowance for flexible working techniques.
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Mathiassen SE, Burdorf A, van der Beek AJ. Statistical power and measurement allocation in ergonomic intervention studies assessing upper trapezius EMG amplitude. A case study of assembly work. J Electromyogr Kinesiol 2002; 12:45-57. [PMID: 11804811 DOI: 10.1016/s1050-6411(01)00028-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The present study aimed at exploring the statistical power of ergonomic intervention studies using electromyography (EMG) from the upper trapezius muscle. Data from a previous study of cyclic assembly work were reanalyzed with respect to exposure variability between subjects, between days, and within days. On basis of this information, the precision and power of different data collection strategies were explored. A sampling strategy comprising four registrations of about two min each (i.e. two work cycles) for one day per subject resulted in coefficients of variation between subjects on the 10-, 50-, and 90-APDF-percentiles of 0.44, 0.31, and 0.29, respectively. The corresponding necessary numbers of subjects in a study aiming at detecting a 20% exposure difference between two independent groups of equal size were 154, 78, and 68, respectively (p< or = 0.05, power 0.80). Multiple measurement days per subject would improve power, but only to a marginal extent beyond 4 days of recording. Increasing the number of recordings per day would have minor effects. Bootstrap resampling of the data set revealed that estimates of variability and power were associated with considerable uncertainty. The present results in combination with an overview of other occupational studies showed that common-size investigations using trapezius EMG percentiles are at great risk of suffering from insufficient statistical power, even if the expected intervention effect is substantial. The paper suggests a procedure of how to retrieve and use exposure variability information as an aid when studies are planned, and how to allocate measurements efficiently.
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Affiliation(s)
- Svend Erik Mathiassen
- Division of Production Ergonomics, School of Technology and Society, Malmö University, SE-20506 Malmö, Sweden.
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Karsh BT, Moro FBP, Smith MJ. The efficacy of workplace ergonomic interventions to control musculoskeletal disorders: A critical analysis of the peer-reviewed literature. THEORETICAL ISSUES IN ERGONOMICS SCIENCE 2001. [DOI: 10.1080/14639220152644533] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Hägg GM, Luttmann A, Jäger M. Methodologies for evaluating electromyographic field data in ergonomics. J Electromyogr Kinesiol 2000; 10:301-12. [PMID: 11018440 DOI: 10.1016/s1050-6411(00)00022-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Surface electromyography (SEMG) is an important tool for work load assessment in ergonomics. Several different approaches using amplitude as well as frequency parameters give fruitful information depending on question at issue in the laboratory as well as in field studies. One basic factor determining the choice of analysis method is whether the SEMG is interpreted as an indicator of forces/torques or pure muscular activation. Two methods for occupational SEMG data reduction representing two different approaches to SEMG applications in ergonomics, Exposure Variation Analysis (EVA), and Joint Analysis of EMG Spectrum and Amplitude (JASA), applied on the same SEMG recording from three muscles during urology surgeon work, have been compared. The EVA method categorised the three muscle recordings as too static with no EMG gaps while the JASA method identifies fatigue in two of the three recordings. The practical relevance of these findings is discussed.
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Affiliation(s)
- G M Hägg
- Programme for Ergonomics, National Institute for Working Life, SE-112 79, Stockholm, Sweden.
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Mathiassen SE, Winkel J. Physiological comparison of three interventions in light assembly work: reduced work pace, increased break allowance and shortened working days. Int Arch Occup Environ Health 1996; 68:94-108. [PMID: 8720279 DOI: 10.1007/bf00381241] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
An industrial assembly task known to imply a high risk for shoulder-neck disorders was simulated in the laboratory. Eight females (aged 22-32 years) were trained to manage industrial work pace (120 according to the methods-time measurement system, MTM). They carried out seven work protocols at different days with different combinations of work pace (120 or 100 MTM), break allowance (20 min of active or passive breaks added every 2 h), and duration of the working day (2, 4 or 6 h). During 6 h of work at 120 MTM the electromyographic (EMG) amplitude from the upper trapezius muscle increased by about 11%, the EMG zero crossing rate decreased by about 2.5%, and perceived fatigue increased by about 4 CR10 scale units. When work pace was reduced to 100 MTM, the upper trapezius EMG amplitude decreased by 20% and became less variable. Heart rate decreased by about 10 bpm, perceived fatigue decreased by about 1 CR10 scale units, and shoulder tenderness was reduced by about 5%. However, the work task could still not be performed in a physiological steady state. Added breaks, whether active or passive, had no apparent effects on upper trapezius load during work or on physiological responses. Recovery of EMG, maximal strength, heart rate and blood pressure sensitivity, and tenderness was complete 4 h after work, independent of the preceding work conditions. These findings suggest that a limitation of the daily duration of assembly work may be more effective in limiting acute fatigue than reduced work pace or increased break allowance.
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Affiliation(s)
- S E Mathiassen
- Division of Applied Work Physiology, National Institute for Working Life, Solna, Sweden
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