Comparison of prediction models for the compression force on the lumbosacral disc

The main objective of this research was to compare three representative methods of predicting the compressive forces on the lumbosacral disc: LP-based model, double LP-based model, and EMG-assisted model. Two subjects simulated lifting tasks that are frequently performed in the refractories industry of Korea, in which vertical and lateral distances, and weight of load were varied. To calculate the L5/S1 compressive forces, EMG signals from six trunk muscles were measured, and postural data and locations of load were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here, whereas the compressive forces from the two LP-based models were only significantly affected by weight of load. In addition, low lifting index (LI) values were observed for relatively high L5/S1 compressive forces from the EMG-assisted model, suggesting that the 1991 NIOSH lifting equations may not fully evaluate the risk of dynamic asymmetric lifting tasks.