Ergonomic effects of a management-based rationalization in assembly work — a case study

doi:10.1016/0003-6870(95)00063-1

Applied Ergonomics

Volume 27, Issue 2, April 1996, Pages 89-99

https://doi.org/10.1016/0003-6870(95)00063-1 Get rights and content

Abstract

Due to unsatisfactory productivity, a large company in the Swedish manufacturing industry decided to rationalize their assembly system. The intended rationalization comprised several changes with deliberate ergonomic implications. The main aim of the present study was to evaluate the impact of the rationalization on the physical work load of the operators. The work load was assessed before and after the changes using expert observations, company records and direct technical measurements. The results indicate that the intervention led to only minor changes in muscle load, body postures and movement patterns. Several of the planned initiatives were never implemented, e.g. teaching the workers multiple skills and designing work stations at which a major part of the assembly sequence could be performed. This was mainly due to a policy revision caused by changes in the market situation. In spite of the company's original intentions, the revised production system contained only minor ergonomic improvements. Thus, the realization of the ergonomic potential in a rationalization seems to depend on management culture, as well as factors outside the company.

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Cardiovascular disease (CVD) is the leading cause of death worldwide. Health and safety hazards and risk factors in the workplace are associated with occupational CVD, though inconsistent evidence of causal associations represents a knowledge gap. The assessment of physical load on the cardiovascular system in relation to work different risk factors and occupational groups is necessary, if preventative measures for occupational CVD are to be better tailored to workers’ needs.
The pertinent literature reports the use of different objective and subjective metrics to evaluate the cardiovascular load (CVL). We aimed to identify how cardiovascular stress is assessed in the workplace and to bring together related evidence-based recommendations for preventative measures. Hence, we systematically searched the Google Scholar database for corresponding publications to a) gather metrics used to assess CVL, b) summarize the related risk factors investigated, c) report the occupational groups and activities targeted in these studies, and d) compile recommendations resulting from these studies.
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This finding was similar to other industrial workers’ studies that have been conducted. For instance, sewing machine assemble workers had a median 50th percentile flexion/extension angle of 14° (BaoM. S. E and Winkel, 1996), material pickers in car assembly workers 14° (Christmansson et al., 2002), and craft-type car disassembly workers 10.1° (Kazmierczak et al., 2005). The 90th percentile is frequently used as an estimate of peak exposures encountered during a task or work shift (Kazmierczak et al., 2005), (Trask et al., 2006).
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Excessive standing may also cause the joints in the spine, hips, knees and feet to become stiff or locked (Balasubramanian et al., 2009). Bao et al. (1996) followed optimization and rationalization processes of a big production firm dealing with ergonomics of production processes. Their aim was to evaluate the ergonomic impact of workloads before the planned improvements and to compare them with the future state of the line.
Earlier studies have demonstrated the strong relationships between manual assembly work with a high repetition level and the presence of repetitive strain injuries (RSI) or repetitive motion illnesses (RMI). Moreover, recent works have also correlated the high physical load level in assembly lines with an increased number of quality defects in finished products. Thus, the ergo-quality level of a manual workstation needs to be carefully monitored not only to respond to the legislation but first of all to ensure a high system productivity level in the medium-term perspective. The objective of this study was to develop and test a new easy-to-use postural assessment tool and its performance in a car component assembly system. The results show the promising potential of the methodology particularly when compared with the well-known OCRA method.
Mechanical stress
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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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The aim of this study was to compare the capability of a cluster-based exposure variation (C-EVA) with a conventional exposure variation analysis (EVA) to detect muscular adaptation in the shoulder joint to subsequent sessions of eccentric exercise (ECC). Eleven healthy subjects performed work with a computer mouse for 10 min at three instants, i.e., before, immediately after, and 24 h after ECC. The subjects repeated an identical procedure one week after the first session. Surface electromyography was recorded from descending and ascending part of the trapezius, deltoid anterior, and serratus anterior muscles. EVA and C-EVA were performed and their marginal distributions were extracted. A principal component analysis was applied to the marginal distributions of both EVA and C-EVA. Principal component difference was computed by subtraction of the corresponding principal components before the ECC from immediately after and 24 h after the ECC. The first component extracted from C-EVA revealed an interactive effect between the sessions of ECC and instants whereas this effect was absent using the conventional EVA. The current study highlights the importance of a multivariate approach to analyze the potentially important changes in muscular activity in response to the repeated bout effect.

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Special issue paperErgonomic effects of a management-based rationalization in assembly work — a case study

Abstract

Applied Ergonomics

Int J Ind Ergon

Measurement of postural angles during work

Ergonomics

A worksite method for shoulder muscle fatigue measurements using EMG, test contractions and zero crossing technique

Ergonomics

Measurement and evaluation of local muscular strain in the shoulder during constrained work

J Hum Ergol

What is value-based management?

McKinsey Quarterly

Variation in shoulder-neck activity — physiological, psychophysical and methodological studies of isometric exercise and light assembly work

A comprehensive program package — MUFDAP — for analyzing data from ergonomic studies

Special issue paper
Ergonomic effects of a management-based rationalization in assembly work — a case study