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The current issue and full text archive of this journal is available at www.emeraldinsight.com/0144-3577.htm

The effects of lean production on worker job stressRobert ContiSchool of Management, Bryant University, Smitheld, Rhode Island, USA

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Jannis AngelisWarwick Business School, Coventry, UK

Cary CooperLancaster University Management School, Lancaster University, Lancaster, UK

Brian FaragherManchester Business School, Manchester, UK, and

Colin GillInstitute for Manufacturing, University of Cambridge, Cambridge, UKAbstractPurpose This empirical paper seeks to address the neglected work condition aspect of lean production (LP) implementation, specically the relationship between LP and worker job stress. Design/methodology/approach The Karasek job stress model was used to link shopoor practices to expected worker stress. The model incorporates the effects of job demands (physical and psychological), job control and social support. The study employs management and worker questionnaires, management interviews and structured plant tours. The response variable is total worker job stress the sum of the physical and mental stress levels. The independent variable for the rst question is the degree of lean implementation at the sites. Findings The results are based on 1,391 worker responses at 21 sites in the four UK industry sectors. About 11 tested practices are signicantly related to stress and an unexpected non-linear response of stress to lean implementation is identied. Results indicate that LP is not inherently stressful, with stress levels signicantly related to management decisions in designing and operating LP systems. Practical implications The hypotheses tests shed light on the relationships between LP practices and job stress, and reveal a signicant managerial inuence on stress levels. The regression model shows the scale and signicant lean practices of this inuence, with the work practices explaining 30 percent of job stress variations. The stress reduction and stress control opportunities identied in the study show the potential for designing and operating effective lean systems while also controlling stress levels. Originality/value This is the rst known multi-industry empirical study of the relationship of job stress to a range of lean practices and to the degree of lean implementation. Keywords Lean production, Stress, Work study Paper type Research paper

The authors wish to thank the Engineering and Physical Sciences Research Council (EPSRC) for funding our study, the University of Cambridge Institute for Manufacturing for administrative support, Professor Rick Delbridge, of Cardiff University, for proposing the blame hypothesis, and the other peer reviewers for their suggestions. The authors also wish to thank the anonymous journal reviewers for their insights and suggestions.

International Journal of Operations & Production Management Vol. 26 No. 9, 2006 pp. 1013-1038 q Emerald Group Publishing Limited 0144-3577 DOI 10.1108/01443570610682616

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Introduction Lean production (LP) is rooted in the Toyota Production System (TPS) of post World War II Japan (Ohno, 1988). It diffused globally, initially as just-in-time production (JIT), arguably becoming the competitive standard for products assembled from discrete parts. Diffusion was aided by the International Motor Vehicle Project (IMVP), which coined the term LP to describe evolved JIT (Womack et al., 1990). LP can simultaneously reduce costs and improve quality. The IMVP showed that, on average, lean built cars required one-third fewer hours and had one-third fewer defects than those from mass production. A study of 253 US manufacturers by Fullerton et al. (2003) concludes:The evidence provides empirical support to the premise that rms that implement and maintain JIT manufacturing systems will reap sustainable rewards as measured by improved nancial performance.

These accounts are countered by evidence of high stress in LP. (Lewchuck, et al., 2001; Bruno and Jordan, 2002; Brenner, et al., 2004), raising the question: Is lean production deterministically stressful, with benets gained at the expense of workers?. We address this question by measuring the relationships between job stress and both the degree of lean implementation in the workplace and the work practices employed. Job stress Cranwell-Ward (1998, p. 285) describes the prevailing view of stress:It (stress) is widely viewed today as the physiological and psychological reaction which occurs when individuals meet a threat or challenge and the individuals perception, whether consciously or subconsciously, is that it is beyond their immediate capacity.

Repeated exposure to this condition can result in strains that cause physical reactions (such as insomnia), emotional reactions (such as depression), and mental reactions (such as forgetfulness). We measured stress using the ASSET questionnaire. ASSET subscales are described by Johnson and Cooper (2003), in an investigation of its construct validity. ASSET is based on prevailing stress models, and employs two subscales that assess physical health and psychological well-being. This provides the exibility of either making separate measurements of physical and psychological stress or combining the two as a measure of total stress. Our study objective was to assess the effects of LP on total job stress, so we summed the two scale values. The ability to use our data to separately explore the physical and mental job stress responses is a future research opportunity. Stress coping skills can alter the perception of stress and stress responses. While programs to enhance coping skills can be helpful, Cartwright and Cooper (2002) emphasise that growing research evidence suggests that the most effective way in which organisations can reduce workplace stress is by eliminating or modifying the sources of stress inherent in the work environment. Our study is designed to help identify these sources. Lean production characteristics and job stress The architects of the TPS, Ohno and Shingo, dene its essence in complementary ways. Ohno (1981, p. 1) states that the fundamental doctrine of the TPS is the total elimination of waste, with waste dened as any activity not adding customer value.

Shingo (1989, p. 3) emphasises high value-added production ow and denes seven wastes that are ow barriers. These barriers are addressed by a set of integrated techniques, or elements, that evolved as part of the TPS and LP. Table I denes a set of ten key elements, with supporting references. LP operates with balanced, synchronised material ow. The elements of Table I aid in achieving this ow with minimum use of wasteful contingencies of material, people and machinery. This improves performance but increases the intensity of work the proportion of work time actually spent performing production tasks. Increased intensity increases job demands and the potential for job stress. Also, poka-yoke foolproof product and process designs, used to improve quality, also de-skill production tasks reducing worker job control. However, LP has offsetting stress reduction characteristics. The frustration of assembling ill-tting parts is largely eliminated by the use of foolproof designs (Womack et al., 1990, p. 101). Reductions in inventory make the factory easier to navigate and locate parts. Repetitive ow lets workers develop a favourable rhythm for their tasks (Baldamus, 1961). Improvement projects offer workers the opportunity to use their creativity and experience. Improved quality and costs can generate pride and a sense of job security. (Koenigsaecker, 2000). Most lean characteristics depend on management decisions, so it is likely that job stress depends heavily on management policies and practices. Effects of stress Stress affects both individuals and organisations. Kvarnstrom (1997), of the International Labour Organisation, reports that stress may impair individual health and the ability to cope with working and social situations, causing work performance and relationship strains. For organisations, stress causes absenteeism, increased medical costs and higher turnover. Cox et al. (2000) report that 50-60 percent of all lost working days are stress related. In Britain, this amounted to about 20 million lost working days in 2001, more than 30 times greater than industrial action losses. Stress-related illnesses now exceed back problems as Britains most common workplace ailment, costing industry 370 million yearly. A survey of 630 UK trade union safety representatives (Sparks and Cooper, 1997) showed that 66 percent named stress as the main health concern for workers. Lean production job stress literature There is extensive and contradictory research on lean stress. Several studies are ethnographic analyses of Japanese auto plants in the USA: Toyota (Parker and Slaughter, 1988), Mazda (Fucini and Fucini, 1990), Suburu/Isuzu (Graham, 1995) and Mitsubishi (Bruno and Jordan, 2002) They depict fast paced, high intensity, high stress environments. However, accepting their observations as typical of LP is questionable. After six months working as a covert observer at a single Suburu-Isuzu plant, Graham (1995, p. 154) generalises that The Japanese model (LP) is not equipped to deliver on its promises to its workers. During a corporations quest to maximise prots, workers simply become expendable. Studies like Grahams provide rich details and insights not possible with survey research, but they lack the statistical validly to generalise their results.

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LP element Set-up reduction

LP element denition

References with pages

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Inventory and waste reduction Kanban pull signals

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