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Typically, the simplest and most cost-efficient ergonomic solution to offset the rising costs of low back injuries is to reduce the box weight that is lifted. However, there is limited research on how a worker interacts with the box. In the present study, we quantify the utility of reducing the weight that is lifted - specifically, how changes in the box weight affect trunk kinematics, trunk moments, and ultimately, spinal loads. In the experiment, 15 participants lifted a variety of box weights (from 9.1 to 41.7 kg) from knee height, carried it a distance of 5 feet (1.5 m), and placed it on a shelf at elbow height. For the lower weights, small increases in box weight (3-9 kg) were offset by the trunk dynamics (sagittal velocity), resulting in no difference in spinal loads. At the same time, spinal loads were found to be significantly higher for weights above 25 kg. Thus, when making ergonomic changes (reduction of box weight), it is important to consider how workers will interact with the box. These results indicate that purely weight-based ergonomic controls might not sufficiently reduce the risk of low back disorders. Furthermore, this study provides additional evidence of the utility of using more complex spinal load models (dynamic, multiple muscle models) when evaluating highly dynamic and complex tasks. [ABSTRACT FROM AUTHOR]

Most biomechanical assessments of spinal loading during industrial work have focused on estimating peak spinal compressive forces under static and sagittally symmetric conditions. The main objective of this study was to explore the potential of feasibly predicting three-dimensional (3D) spinal loading in industry from various combinations of trunk kinematics, kinetics, and subject-load characteristics. The study used spinal loading, predicted by a validated electromyography-assisted model, from 11 male participants who performed a series of symmetric and asymmetric lifts. Three classes of models were developed: (a) models using workplace, subject, and trunk motion parameters as independent variables (kinematic models); (b) models using workplace, subject, and measured moments variables (kinetic models); and (c) models incorporating workplace, subject, trunk motion, and measured moments variables (combined models). The results showed that peak 3D spinal loading during symmetric and asymmetric lifting were predicted equally well using all three types of regression models. Continuous 3D loading was predicted best using the combined models. When the use of such models is infeasible, the kinematic models can provide adequate predictions. Finally, lateral shear forces (peak and continuous) were consistently underestimated using all three types of models. The study demonstrated the feasibility of predicting 3D loads on the spine under specific symmetric and asymmetric lifting tasks without the need for collecting EMG information. However, further validation and development of the models should be conducted to assess and extend their applicability to lifting conditions other than those presented in this study. Actual or potential applications of this research include exposure assessment in epidemiological studies, ergonomic intervention, and laboratory task assessment. [ABSTRACT FROM AUTHOR]