Abstract

This paper includes the biomechanical determination and assessment of lumbar load during asymmetrical bi-manual materials handling tasks which involve lateral turning of the body, trunk inclination, and sagittal flexion and lateral bending of the spine. Diagonal lifting tasks were analysed for different values for load weight (0-40 kg) and task duration (0.75-1.5 s). Whereas a constant grasp height of 15 cm was assumed, the height for releasing the load differed (50, 100, 150 cm). A dynamic spatial human model (The Dortmunder) was used for calculating the torque in the sagittal, frontal, and transversal planes through the lumbosacral joint and for determining the compressive and the sagittal and lateral shear force at the L5-S1 disc. During diagonal lifting of loads, lumbosacral torque in the sagittal plane is considerably larger than the lateral bending and torsional torque components. The shorter the time for task execution, the higher the resultant dynamic effects and, in consequence, the higher the lumbar load. Lumbosacral compression and shear increase with increasing load-release heights due to higher acceleration and retardation of body and load when the same grasp position and task duration are assumed. The maximum load-bearing capacity of the lumbar spine was determined on the basis of strength data for isolated lumbar segments provided in the literature. The compressive strength falls within the same range as the compressive forces calculated for asymmetrical lifting of loads up to 40 kg. Verf.-Referat (gekuerzt)