ABSTRACT
When tasks are rotated, two mathematical models are used to calculate the final OCcupational Repetitive Action (OCRA) indicators and Timing Assessment Computerized Strategy scores for postures: the time-weighted average and them ultitask complex. These models are applied to assess the final risk score for exposure to biomechanical overload of the upper limbs due to task rotation and to achieve an overall evaluation of the degree of exposure to the various tiring postures making up one or more tasks. In order to calculate the final exposure score when a job involves several repetitive postures and/or tasks, this mathematical model assigns a weight to: the total duration of the task or a series of tasks performed during the shift and/or the time frame considered. The corresponding specific durations of the individual tasks performed in the shift, expressed as time fractions with respect to constant time exposures.
