An Investigation of the Effect of Trunk Musculature on the Lumbar Spine Injury During a High-Speed Frontal Central Crash

Motor vehicle crashes have been a leading cause of fatalities and injuries worldwide. Owing to new protection systems, the occurrence of injuries has been decreasing in recent years. On the contrary, the incidence of lumbar spine injuries in frontal crashes has been increasing as a function of the vehicle model year. However, only a few studies focused on lumbar spine injuries in vehicle crashes. Therefore, the mechanism of lumbar spine injuries has not been understood thoroughly. Muscle contraction is one of the factors that influence the risk of lumbar spine injuries as occupants tend to brace their muscles during a vehicle crash. Greater muscle contraction, especially anticipatory muscle contraction, may contribute to bony injury. This study aimed to investigate the effect of lumbar muscle activation and the timing of muscle activation on the lumbar spine injury risk during a high-speed frontal central crash by utilizing a finite element human body model. The study implemented lumbar musculature on two versions of the validated models against the experimental results from a previous study. Sixteen simulations with 8 of each version were set up. These 8 simulations included: fully activated at 0ms, 40ms, and 80ms; half activated at 0ms, 40ms, and 80ms; no activation and no muscle. The model was seated in a simplified vehicle seat extracted from a common vehicle model and was in a frontal pole/tree (central) crash scenario with an initial speed of 56km/h. Each simulation ran for 150ms and forces on vertebrae L1, L3 and L5 were collected. The results showed the lumbar spine forces increased with the muscle activation level and decreased with the timing of the muscle activation. This suggested that the anticipatory powerfully braced lumbar muscles had a higher risk to induce lumbar spine injuries. Since it is impossible to train occupants to avoid bracing in anticipation of a frontal crash, this study focuses the attention on enhanced protection for the lumbar region of vehicle occupants in the future