Analysis of the influence of position on the loadings of the lumbar spine

Objective: To evaluate the influence of position on lumbar loadings. Methods: Ten healthy participants were recruited for the study. A motion analysis system was used to collect kinematic data, a force platform measured ground reaction force, and spherical reflective markers were attached into the upper, low extremities and trunk of each participant during lumbar flexion, extension, left bending and left axial rotation. The marker’s data and ground reaction force data were input to Open Sim and the compression and shear force in each segment of the lumbar spine was calculated. Results: In each position, the compression force and shear force from L1-L2, L2-L3, L3-L4 to L4-L5 increased gradually, but compared with L4-5 segment, the values in L5-S1 segment were decreased. In each segment, there were significant differences in compression and shear forces among flexion, extension, left lateral bending and left axial rotation (p<0.05). The compression forces presented with the largest values in flexion, followed by lateral bending, extension, and left axial rotation, and the shear force presented with the largest value in flexion, followed by left axial rotation, extension and left lateral bending. Conclusion: In the lumbar spine L4-5 and L5-S1 segment support more loadings than other segments, especially during flexion and axial rotation.