Evaluation risks of biomechanical overload during the manual vineyard pruning by using measured values of the effort

Several analytical methods have been developed to determine and quantify the risk from exposure to biomechanical overload of the upper limbs. The subjective estimates of the force applied by the workers during the assessment of muscle-skeletal risk exposure in the vineyard manual pruning appear critical. Some recent research has been carried out using a sensorized scissor to obtain measures of the handling effort used, in place of the estimates expressed by workers (Schillaci et al., 2010; Romano et al., 2010). This research proposes a preliminary study of an experimental methodology in order to replace subjective opinions with instrumental values obtained by using electromyography (EMG) in assessing the risk of muscle-skeletal overloading of the upper limbs during manual vineyard pruning. The OCRA method (Colombini and Occhipinti, 1996, 2005) is the procedure recommended the international standard (ISO 11228-3) for risk assessment from overload due to upper limbs repetitive movements. The Borg CR10 scale is usually used to evaluate the subjective perception of the strain in relation to the amount of the strain. In this research, we have used the results laboratory tests that used EMG performed by a sample of pruners on different vine cultivators with different branch diameters and with different scissors. Using the surface EMG it was possible to highlight the actions taken by each muscles involved in the technical actions. The measurements of the EMG acquired were compared with the measurements of the MVC (maximum voluntary contraction) on the activity and the subject examined. From the data processing recorded during the laboratory operations, represented by percentage of intensity compared to the relative MCV, a value was obtained for the strength for each muscle analyzed during the activity and for an intensity scale of the strength. The values of “strength” acquired have been used to calculate the risk through the OCRA index. The results obtained were compared with the workers opinions about the subjective perception of the strain and with the results of previous research (Schillaci et al., 2010; Romano et al., 2010). The EMG tests have shown the involvement of the muscular districts involved giving new ideas about risk assessment in pruning operations.