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.