MODELLING THE VERTEBRAL COLUMN MECHANICS IN WEIGHT LIFTING

Abstract

INTRODUCTION The vertebral column performs, throughout the life of the individual, a heavy mechanical load resisting role which often leads to painful complaints and damage. This work describes the application of a numerical model of the vertebral column to the calculation of the biomechanical stresses developed in it during the performance of a 2000 N weight lifting task. METHODS The mechanical response of the vertebral column to loading is simulated with the help of an kinematical model which replicates the configurations the former takes up throughout the performance of any postural task. The corresponding geometrical data is passed on to a finite element numerical package which computes the internal forces, moments and stresses occurring all along the entire spinal structure RESULTS AND DISCUSSION Figure 1 is the screen image of the kinematical model corresponding to an intermediate posture during the lifting of a 2000 Newton load. The weight lifting performer is filmed, a set of time equidistant frames are digitized with a frame grabber and the kinematical model is fitted to each of then by adjusting the corresponding values of its fifteen control parameters. The three windows on the right show the values of the axial and shear forces and of the bending moments in each of the vertebrae of the lumbar and dorsal regions. These forces and bending moments'" exceed the limits beyond which lesions may occur, namely. 150 Nm for the bending moments and 640 N for the shear forces, respectively. CONCLUSIONS The results illustrate a method for evaluating the mechanical stresses occurring during the performance of a physical task in sports and which, thus makes possible the assessment of the corresponding risk factors.