Ergonomic issues in ewe cheese production: reliability of the Strain Index and OCRA Checklist risk assessments

Occupational ergonomists often use a variety of methods to identify jobs that are considered at high risk for the development of work-related musculoskeletal illnesses. The Strain Index (SI) and the Occupational Repetitive Actions (OCRA) Checklist are two popular upper limb risk assessment tools used in many industries, including the agro-food industry. Both methods are based on similar biomechanical, physiological and epidemiologic principles, but their approach to quantification and estimation of risk factor magnitude is quite different. The purpose of this study was to assess the inter-method reliability of SI and OCRA Checklist. Methods: Twenty-one jobs were video recorded in a Sardinian cheese manufacturing facility. Eight raters were recruited to assess job exposures to physical risk factors using the SI and OCRA Checklist. Inter-method reliability was characterized using proportion of overall agreement, Cohen’s kappa, and Spearman and Pearson correlations. Results: Strain Index and the OCRA Checklist assessments produced generally reliable results, classifying the risk of 35 of 42 (83%) job exposures similarly. Conclusions: The OCRA Checklist and SI risk assessments are reliable upper limb measures of physical work exposures. Both measures appear useful for assessing risk of upper limb disorders of work tasks in the agro-food industry. However, the SI is specific to disorders of the distal upper limb and perhaps most useful for assessing risk in work primarily involving the wrist and fingers. Whereas the OCRA Checklist, which includes an assessment of the shoulder, may be more appropriate for evaluating jobs that also require extended periods of reaching and shoulder activity.