Modeling of the Effect of Backpack Load Position on the Lumbar Spine Curvature

Aims: The aim of the study was to propose a simulated model for predict the lumbar spine curvature in standing from a healthy subject with a loaded backpack.
Study Design and Methodology: The anthropometric data of a schoolboy were used, and then the model was built in BRG. Life MOD (ver. 2007, Biomechanics Research Group, Inc., USA) based on these data. The backpack was loaded at 10, 15 and 20% of subject’s Body weight (BW) (stage 1). Then, three boxes (4, 4 and 12 Kg in weight) were attached in the backpack (stage 2). They were arranged in the sagittal, frontal and transversal planes and the position of the heavier weight was changed at each phase.
Results: Regression analysis between our numerical predictions of stage 1 and similar experimental literature led to a correlation gradient of 0.88 and 0.91 for L3-S1-horizon and T12-L3-S1 angles, respectively. The predicted G and H angles peaks at stage 2 were observed when the heavier box was in frontal plane at left or right side.
Conclusion: This study demonstrated the feasibility of obtaining a range of variable boundary conditions (e.g. altered due to changing the location of the heavier box) and applying a simplified three-dimensional model that can predict lumbar spine curvature changes in relatively short solution time.