Case Studies of Ergonomic Interventions in Automotive Parts Distribution Operations

Ergonomic job analysis, intervention design, and intervention implementation are essential components of an ergonomics program designed to reduce worker exposure to risk factors associated with musculoskeletal disorders. As part of a 4-year study to reduce overexertion injuries in the service parts division of a major automaker, intervention case studies were identified that could be used at multiple facilities across the division. Interventions were developed and implemented. The three case studies include 1) self-elevating powered vehicle for transporting parts throughout the facility and for reaching to high bin locations; 2) lift and tilt pallet jacks for packing small parts into large bin-like containers; and 3) single-level telescoping conveyor used for delivering hand-held totes for subsequent sorting operations. Several analysis methods were used to assess worker exposure before and after intervention implementation (biomechanical analysis, posture analysis, worker interviews, and activity analysis). Following implementation, a decrease in exposure to risk factors for musculoskeletal disorders was documented. Worker interviews revealed acceptance and agreement that risk factors associated with the targeted tasks were reduced. Each case study includes a description of the implementation hurdles and can serve as both primary and secondary prevention of musculoskeletal disorders. Future work should document worker health and/or symptom changes as well as changes in risk factor exposure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45011/1/10926_2004_Article_496314.pd

Use of computer aided drafting for analysis and control of posture in manual work

Computer aided design (CAD) in conjunction with digitised anthropometric manikins can be used for analysis and control of stressful work postures, one of the most frequently cited occupational risk factors of upper extremity cumulative trauma disorders. This paper describes the use of macros for manipulating manikins and workstation components and for designing the workplace. AutoCAD, a popular computer aided design software package, was used to demonstrate the feasibility of these concepts. Specifically, macros are used for drawing work equipment using parametric designs, manipulating manikins and analysing jobs. In comparing the macros to the use of primitive CAD commands, the macros not only decrease the amount of time needed to create workstation components, but they also make the task easier for the user and decrease the risk of errors. Despite the limitation of anthropometric data and manikins, CAD is an effective method for identifying postural stresses and redesigning the workstation to control the identified stresses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28529/1/0000326.pd

The strengths and limitations of lecture-based training in the acquisition of ergonomics knowledge and skill

A common approach to training designers of workplaces to incorporate ergonomic considerations in their designs is a two- to five-day course based primarily on lectures by experts. A quiz, designed to test the acquisition of ergonomics factual knowledge and skill in judging the degree of physical stress in various job configurations, was given to 147 participants before and after four days of a five-day short course based principally on lectures by university faculty and staff. The major findings were as follows. First, there was a considerable lack of factual knowledge and a high level of error in judging the level of stress prior to the training. Second, the training increased participants' factual knowledge but had little impact on their ability to accurately judge levels of stress in slides depicting real work situations. Third, participants' knowledge and skills before the training and their improvement as a result of the training were unrelated to prior education or training in ergonomics or experience with repetitive, manual work. These results are interpreted in light of prior research on design of effective health and safety training.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28698/1/0000518.pd

A Cross-Sectional Assessment of the ACGIH TLV for Hand Activity Level

The ACGIH Worldwide Threshold Limit Value (TLV) for hand activity “considers average hand activity level or “HAL” and peak hand force.” We report cross-sectional data that assess the validity of the TLV with respect to symptoms and selected upper extremity musculoskeletal disorders among workers. The prevalence of symptoms and specific disorders were examined among 908 workers from 7 different job sites in relation to the TLV. Worker exposures were categorized as above the TLV, above the TLV Action Limit but below the TLV, or below the TLV Action Limit. Symptoms in the distal upper extremities did not vary by TLV category. Tendonitis in the wrist/hands/fingers did not vary by TLV category, but elbow/forearm tendonitis was significantly associated with TLV category. All measures of carpal tunnel syndrome were associated with TLV category. In all instances, prevalence of symptoms and specific disorders were substantial in jobs that were below the TLV action limit, suggesting that even at “acceptable” levels of hand activity, many workers will still experience symptoms and/or upper extremity musculoskeletal disorders, which may be important in the rehabilitation and return to work of injured workers. Future analyses need to examine the incidence of symptoms and upper extremity musculoskeletal disorders prospectively among workers in relation to the TLV for hand activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45015/1/10926_2005_Article_874.pd

Analysis of the third national health and nutrition examination survey (NHANES III) using expert ratings of job categories

Background Few epidemiologic studies have addressed the exposure–response relationships between work activities and symptomatic knee osteoarthritis (OA). This analysis used data from a national survey and ergonomists' ratings to address this issue. Methods Interview and knee X-ray data were obtained from the Third National Health and Nutrition Examination Survey. Occupational ratings were obtained using ergonomists. A weighted logistic regression was used. Results Among men, a significant exposure–response relationship was found between symptomatic knee OA and kneeling. In both genders, there was a significant trend in heavy lifting and severe symptomatic knee OA. Approximately 20.7% of knee OA can be attributed to kneeling >14% of the workday among men. Conclusions The significant exposure–response relationships suggest that modest reductions in certain occupational activities can reduce the burden of knee OA. The study was limited by unvalidated expert ratings. Research is needed to identify hazardous characteristics of work activities and to clarify exposure–response relationships. Am. J. Ind. Med. 51:37–46, 2008. © 2007 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57516/1/20512_ftp.pd

Examination of the effect of tool mass and work postures on perceived exertion for a screw driving task

Eighteen subjects with industrial work experience drove screws into perforated sheet metal at three vertical (64, 114 and 165 cm) locations with a pistol-shaped tool, and at two horizontal (13 and 63 cm) work locations using an in-line tool. Both air-powered tools were varied in mass (1, 2 and 3 kg). Subjects drove screws using each tool mass at all work locations. After driving 25 screws at a particular work location/tool mass combination, subjects assessed their perceived exertion for that condition using the Borg ten-point ratio rating scale and completed a body part discomfort survey. Both tool mass and work location were significant factors in determining the ratings. As tool mass increased, so did the ratings of perceived exertion (18% to 100%). The lowest ratings of perceived exertion were at 114 cm on the vertical surface and at 13 cm on the horizontal surface. For the vertical surface, the body part discomfort data revealed that the low back and the right arm were often cited as uncomfortable at 64 cm, the right arm was identified as uncomfortable at 114 cm, and the right arm and the chest were cited as uncomfortable at 165 cm. For the horizontal surface, at both 13 cm and 63 cm, the neck and the right arm were identified as uncomfortable.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30647/1/0000289.pd

Medical Management and Rehabilitation in the Workplace: Emerging Issues

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45004/1/10926_2004_Article_223619.pd

Predictors of Upper Extremity Discomfort: A Longitudinal Study of Industrial and Clerical Workers

Upper extremity discomfort associated with work activity is common with a prevalence of over 50% in many settings. This study followed a cohort of 501 active workers for an average of 5.4 years. Cases were defined as workers who were asymptomatic or had a low discomfort score of 1 or 2 at baseline testing and went on to report a discomfort score of 4 or above on a 10-point visual analog scale. This change is considered clinically significant. Controls had a low baseline discomfort score and continued to have a low discomfort rating throughout the study. The risk factors found to have the highest predictive value for identifying a person who is likely to develop a significant upper extremity discomfort rating included age over 40, a BMI over 28, a complaint of baseline discomfort, the severity of the baseline discomfort rating and a job that had a high hand activity level (based upon hand repetition and force). The risk profile identified both ergonomic and personal health factors as risks and both factors may be amenable to prevention strategies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45012/1/10926_2005_Article_871.pd

A Longitudinal Study of Industrial and Clerical Workers: Predictors of Upper Extremity Tendonitis

Upper extremity tendonitis (UET) associated with work activity is common but the true incidence and risk factors can best be determined by a prospective cohort study. This study followed a cohort of 501 active workers for an average of 5.4 years. Incident cases were defined as workers who were asymptomatic at baseline testing and had no prior history of UET and went on to be diagnosed with an UET during the follow-up period or at the follow-up evaluation. The incident cases were compared to the subset of the cohort who also had no history of an UET and did not develop tendonitis during the study. The cumulative incidence in this cohort was 24.3% or 4.5% annually. The factors found to have the highest predictive value for identifying a person who is likely to develop an UET in the near future included age over 40, a BMI over 30, a complaint at baseline of a shoulder or neck discomfort, a history of CTS and a job with a higher shoulder posture rating. The risk profile identifies both ergonomic and personal health factors as risks and both categories of factors may be amenable to prevention strategies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45013/1/10926_2005_Article_872.pd