A multi-methodological study of the effects of lean manufacturing practices on work-related musculoskeletal disorder risk factors and other injuries

The purpose of this research is to advance the understanding of how lean manufacturing practices affect work characteristics and risk factors for work-related musculoskeletal disorders (WMSDs). There is little empirical work to date that critically examined lean manufacturing job design, physical risk factors for WMSDs, and the relationship between the two. This research used several methodological approaches to (1) determine if there is a direct and measurable relationship between lean manufacturing and WMSD risk exposure; (2) determine if there is a difference in work characteristics between exemplar lean and traditional manufacturing environments that affects WMSD risk factors; and (3) get insights into how the exemplar lean organizations manage and integrate productivity, ergonomics, and safety. Three studies were conducted using various sample sizes (i.e. 30, 112, and 71 jobs) at manufacturing sites with various degrees of leanness (i.e. from exemplar lean to traditional using lean tools). Force, repetition and posture [of the low back, shoulder and wrist] were the WMSD risk factors examined for each study.; Degree of leanness was assessed at both the job level and the plant level. At the job level, value-added and non-value added work content were used as proxies for leanness. At the plant level, leanness was assessed based on the extent to which the work site effectively implemented lean production techniques and principles that increase material flow and quality, and reduce non-value added processes - such as just-in-time material delivery, standardized work, and work team involvement in continuous improvement and problem solving activities. Neither stressful postures nor high hand forces were found to be associated with measures of leanness. Repetition was mixed for the studies---in one case repetition was no different and in one case it was slightly higher for jobs with high lean scores than those with low lean scores. Organizational practices that aided in achieving higher levels or productivity without compromising safety ranged from proactive monitoring of jobs by safety specialists to production worker involvement in continuous improvement activities.