Abstract
Introduction: Low back pain is a problem of great magnitude, reaching about 85% of the population. Thus, the load that the spine is subjected in daily activities is the focus of current research in ergonomics. Tasks involving trunk flexion and handling heavy loads have been associated with a high incidence of injuries in the lumbar spine. Despite of the differences in kinematic and electromyographic characteristics of symptomatic and asymptomatic subjects have been investigated in the literature, studies that evaluate the relationship of these characteristics with experience in work has not been carried out. There is also a lack of accurate measuring equipment to assess the exposure of the lumbar spine in the real environment. Given the importance of determining the actual exposure which workers are subjected to propose preventive measures further studies are justified in this direction. Objectives: This study aims to: 1. To compare the movements of the spine and muscle activation in individuals experienced and inexperienced with and without low back pain during the simulated task of handling loads; 2. To compare two systems of recording back movements, the registration system by camera (Qualisys, ProReflex MCU, Sweden) and inclinometer (Logger Tecknologi HB, Akarp, Sweden). Methods: Two groups of subjects will be recruited, one composed of individuals with no experience in the manual handling and other experts. The definition of cases will be carried out from a physical assessment proposed by Ohlsson et al. (1994) and the Nordic Musculoskeletal Questionnaire. The experimental handling will be done at a pace of 12 handlings per minute, with the initial height of the ground and as final hip height of the subject. The deposition area of the box is at 90° from the initial position. The load will be 11.3 kg, which has been recommended for individuals undergoing return to work after injury in the lumbar spine. Will be used electromyography to evaluate the electrical activity of lumbar muscles (DelSYS, United States), optics capture for kinematic analysis (Qualisys, Sweden) and inclinometer (Logger Tecknologi, Sweden). The collection will be performed synchronously. For the analysis of differences in muscle activity and kinematic pattern between subjects experienced or inexperienced with and without pain, a multivariate analysis of variance (MANOVA) can be applied. The root mean square (RMS) of the differences between the system and Qualisys inclinometry will be calculated. In addition, the Pearson correlation between the data generated by the system Qualisys and inclinometer will be performed. For the interpretation of these results, will be considered the strength of the coefficient, the confidence interval of the correlation and statistical significance of the difference between the measures assessed by a test T. Assumptions: The movements of the spine and muscle activation will exhibit different patterns in experienced and inexperienced workers with and without low back pain during the simulated task of handling loads. The inclinometer will present similar results to the registry system imaging (Qualisys) used as reference. Relevance: It is expected to understand how the lumbar spine of individuals behaves while handling loads in a controlled environment. And what is the difference in this behavior in experts with or without pain for those subjects without experience. And, from the comparison of the systems of recording back movements, indicate the use of a portable device that can evaluate the lumbar movements in the workplace. The study is relevant for the identification of factors associated to low back pain, aiding the evaluation and proposing of interventions in the real environment more effectively.
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