Avaliação de pegas e sobrecarga dos membros superiores durante o manuseio de caixas : aspectos biomecânicos e perceptuais
Silva, Luciana Cristina da Cunha Bueno
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Manual material handling (MMH) is a common task in occupational environments and has been associated with musculoskeletal disorders at low back and upper limbs. Studies have shown that the correct hand/box coupling can minimize the risks for upper limb disorders, suggesting the use of handles as a way to reduce the physical demand required by the task. However, even when the boxes have handles, the workers not always use them during handling, suggesting the need for new boxes and handles designs. In order to improve the knowledge in this area, this thesis was composed by three studies: the first study was exploratory and the main objective was to descriptively and objectively evaluate how experienced workers performed cardboard boxes handling activities in an industry setting. The range of movements for wrists, forearms and elbows were objectively evaluated through electrogoniometry. The boxes had already received an ergonomic intervention, implemented six months before the data collection. The ergonomic intervention evaluated was the insertion of cutout handles in the cardboard boxes. The main results indicated that the way the worker grasps the box is crucial to the upper limbs movements during handling tasks. Thus, one hypothesis was that the positioning of the hands close to the bottom face would give workers greater control and biomechanical advantage regarding the load. In this sense, the second and third studies were performed. These studies had been carried out both experimentally in a laboratory setting, and followed the same data collection methodology. Inclinometers and electromyography equipments were added to the data collection. The aim of the second study was to evaluate a new prototype cardboard, developed as an alternative design to the one evaluated in the first study. The results showed that cardboard prototypes were resistant for reuse in internal transport, comfortable and safer for wrist and elbow movements, as well had promoted a reduced muscle demand on electromyography activity for wrist extensors and biceps brachii, when compared to the commercial boxes. Considering that the cardboard boxes are limited to the transportation of dried products, it is suggested the need for new boxes designs using other types of materials. In this sense, new plastic prototypes have been developed. The aim of the third study was: to compare the common commercial boxes with plastic prototypes boxes regarding their effect on upper limb posture, muscle electrical activity and perceived pleasantness of volunteers about their perception of upper limbs comfort during handling tasks. The prototypes allowed changes in handle position (top and bottom) and inclination (0 °, 15° and 30°). The prototypes with handles positioned at 30° were positive for the elbow flexion, shoulders elevation and ulnar deviation of the wrists. The results of present thesis showed that the best box to be used depends on conditions such as the type of conveyed material and height of the handling surfaces at the work environments. The evaluated prototypes showed good durability and costeffective, and can be used in industrial environments, especially for internal transportation. The studies have increased our understanding of safer conditions and more comfortable grips, promoted safer movements and required less electrical muscle activity when compared to commercial boxes. In future studies, we suggest that individuals with experience in manual handling tasks were also evaluated and new joints and muscle groups are also evaluated.