Ergonomic Risk Assessment of an Industrial Workstation Applying Motion Capture System

RULA (rapid upper limb assessment) is a survey method developed for use in ergonomics investigations of workplaces where work-related upper limb disorders are reported. This tool requires no special equipment in providing a quick assessment of the postures of the neck, trunk and upper limbs along with muscle function and the external loads experienced by the body. A coding system is used to generate an action list which indicates the level of intervention required to reduce the risks of injury due to physical loading on the operator. It is of particular assistance in fulfilling the assessment requirements of both the European Community Directive (90/270/EEC) on the minimum safety and health requirements for work with display screen equipment and the UK Guidelines on the prevention of work-related upper limb disorders.

Physical exposure to risks for potential work-related musculoskeletal injuries has been assessed using a variety of methods, including pen and paper based observation methods, videotaping and computer-aided analysis, direct or instrumental techniques, and various approaches to self-report assessment. These methods are critically reviewed in this paper. The applications of these techniques in ergonomic and epidemiologic studies are considered, and their advantages and shortcomings are highlighted. Finally, a strategy that considers both the ergonomics experts' view and the practitioners' needs for developing a practical exposure assessment tool is then discussed.

A common way to conduct practical risk assessments is to observe a job and report the observed long term risks for musculoskeletal disorders. The aim of this study was to evaluate the inter- and intra-observer reliability of ergonomists' risk assessments without the support of an explicit risk assessment method. Twenty-one experienced ergonomists assessed the risk level (low, moderate, high risk) of eight upper body regions, as well as the global risk of 10 video recorded work tasks. Intra-observer reliability was assessed by having nine of the ergonomists repeat the procedure at least three weeks after the first assessment. The ergonomists made their risk assessment based on his/her experience and knowledge. The statistical parameters of reliability included agreement in %, kappa, linearly weighted kappa, intraclass correlation and Kendall's coefficient of concordance. The average inter-observer agreement of the global risk was 53% and the corresponding weighted kappa (Kw) was 0.32, indicating fair reliability. The intra-observer agreement was 61% and 0.41 (Kw). This study indicates that risk assessments of the upper body, without the use of an explicit observational method, have non-acceptable reliability. It is therefore recommended to use systematic risk assessment methods to a higher degree.