Exposição biomecânica durante o manuseio de caixas em ambiente real e simulado com trabalhadores industriais
Nogueira, Helen Cristina
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Musculoskeletal risks involving manual box handling can be minimized with the adoption of preventive approaches such as the inclusion of handles in boxes. However, the literature indicates the acquisition of motor skills over working time, can also be a protective factor in development of musculoskeletal disorders. Thus, the study 1 aimed to evaluate the physical load of the upper arms and upper back between 37 novice and 21 experienced subject during handling a new box design compared to commercial ones. The order of surfaces to handle (places to boxes depositions – floor and shoulder levels) and the type of box was randomized. In addition to direct measures (electrogoniometry, inclinometry and electromyography) subjective scales were used to assess the comfort and perceived effort. In general, both experienced and inexperienced subjects had lower biomechanics load handling non-commercial boxes compared to commercial ones. However, the inexperienced subjects demonstrated greater reductions in physical overload during the handling of non-commercial boxes, being more advantageous the recommendation of these boxes for this user profile. In the real work setting, handling boxes is highly rotating mainly in developing countries. Thus, interventions focus on boxes could help the workers, who may have different levels of experience with the job. However, the real work environment involves other tasks besides handling box, and tasks distribution over time could minimize the handling risks. In this way, the study 2 has been proposed to assess the physical exposure in real environment, where in addition to handling box workers perform other activities, aiming to identify the representative handling task in the total work exposure. The biomechanical exposure was assessed from muscular electrical activity of trapezius and upper limb movement recordings during a period of 4 hours to the work routine. The results showed that handling box task required the greater activation of the trapezius in relation to other activities, particularly in peak loads (percentiles 90 and 99 APDF - Amplitude Probability Distribution Function). Effect size calculations have identified the magnitude of the difference between the tasks is large, particularly in peak loads. In relation to the total job, handling box differed by greater amplitudes of upper back forward flexion and left arm elevation postures. Thus, the handling task requires interventions to decrease the physical load in a real work environment in order to promote occupational health, as identified in simulated environment by other studies. The conclusions of this thesis are related to the importance of considering the profile of workers' experience and the need to assessment work exposure involving all tasks performed, emphasizing the importance of studies involving workers in the real working environment.