| A series of experimental sagittal plane lifting studies were performed to gain an understanding of how different parameters such as speed of lift, lifting technique, fatigue and the weight lifted affects the loads on the lumbar spine. A dynamic analysis of human lifting was performed to predict the lumbar moments during the lift. The models used in these studies began the analysis at the foot floor interface (bottom up analysis), in contrast to beginning the analysis at the hand load interface and working downward (top down analysis). A top down analysis usually ignores the involvement of the lower extremities during lifting and models the trunk as a rigid body independent of the trunks ability to bend and flex while lifting.;Lifting while twisting was also analyzed. An algorithm which corrected the error in human motion position data, obtained with optoelectronics, was developed. The algorithm enabled the kinematic data (angular velocity and acceleration) needed for 3-D modeling to be obtained. The algorithm was able to reduce the error in the position data by 25-50%. After the position data was corrected with the algorithm a lifting study involving twisting was performed. Moments at the lumbar spine were predicted using a three dimensional dynamic model. While the rotational moment was relatively small compared to the flexion and lateral bending moment, it was the most sensitive to the speed of the lifting task.;This investigation indicated that a change in the parameters studied, when lifting using an unprescribed lifting technique, brought about a change in the lifting technique either in the form of changing the lifting speed, posture or by loading one joint to unload another. We have speculated that these changes were a result of the subjects attempt to make the lift as comfortable as possible. The degree of comfort may be dictated by the metabolic cost or by the subject's strength. Changes in the lifting technique seemed independent of whether the new technique would have been proper or improper. |
