Biomechanical overload in multiple tasks with weekly and annual cycle: practical experiences in the field of cleaning and packaging of fruit.

Abstract

The OCRA method is the reference method chosen in ISO (ISO 11228-3) and CEN (EN 1005-5) standards regarding risk assessment and management of upper limbs repetitive movements and exertions. The method consists of two specific tools (OCRA index and OCRA checklist). In this paper special attention will be devoted to the procedures for the analysis of multiple repetitive tasks.

When computing the OCRA index (checklist score) considering the presence of more than one repetitive task, a “traditional” procedure has been previously proposed. This approach, whose results could be defined as “time weighted average”, seems to be appropriate when considering rotations among tasks that are performed almost once every hour. On the contrary, when rotation among repetitive tasks is less frequent the “time weighted average” approach could result into an underestimation of the exposure level. For those scenarios an alternative approach is based on a concept that the most stressful task is the minimum starting point. A peculiar procedure allows to exactly estimate the resulting index within this range of minimum to maximum values. It is possible to apply this approach also for job rotation with weekly or monthly or annual cycle typical of agriculture, supermarket, cleaning sectors. This paper shows criteria and results in two working situation: cleaning (weekly cycle) and packaging of fruit (annual cycle).