Characterizing trunk muscle activations during simulated low-speed rear impact collisions

Influence of muscle activation on lumbar injury under a specific +Gz load

PURPOSE

The present study aimed to analyze the influence of muscle activation on lumbar injury under a specific +Gz load.

METHODS

A hybrid finite element human body model with detailed lumbar anatomy and lumbar muscle activation capabilities was developed. Using the specific +Gz loading acceleration as input, the kinematic and biomechanical responses of the occupant's lower back were studied for both activated and deactivated states of the lumbar muscles.

RESULTS

The results indicated that activating the major lumbar muscles enhanced the stability of the occupant's torso, which delayed the contact between the occupant's head and the headrest. Lumbar muscle activation led to higher strain and stress output in the lumbar spine under +Gz load, such as the maximum Von Mises stress of the vertebrae and intervertebral discs increased by 177.9% and 161.8%, respectively, and the damage response index increased by 84.5%.

CONCLUSION

In both simulations, the occupant's risk of lumbar injury does not exceed 10% probability. Therefore, the activation of muscles could provide good protection for maintaining the lumbar spine and reduce the effect of acceleration in vehicle travel direction.

Characterizing Lumbar Spine Kinematics and Kinetics During Simulated Low-Speed Rear Impact Collisions

BACKGROUND

Recent work has demonstrated that low back pain is a common complaint following low-speed collisions. Despite frequent pain reporting, no studies involving human volunteers have been completed to examine the exposures in the lumbar spine during low-speed rear impact collisions.

METHODS

Twenty-four participants were recruited and a custom-built crash sled simulated rear impact collisions, with a change in velocity of 8 km/h. Randomized collisions were completed with and without lumbar support. Inverse dynamics analyses were conducted, and outputs were used to generate estimates of peak L4/L5 joint compression and shear.

RESULTS

Average (SD) peak L4/L5 compression and shear reaction forces were not significantly different without lumbar support (compression = 498.22 N [178.0 N]; shear = 302.2 N [98.5 N]) compared to with lumbar support (compression = 484.5 N [151.1 N]; shear = 291.3 N [176.8 N]). Lumbar flexion angle at the time of peak shear was 36° (12°) without and 33° (11°) with lumbar support.

CONCLUSION

Overall, the estimated reaction forces were 14% and 30% of existing National Institute of Occupational Safety and Health occupational exposure limits for compression and shear during repeated lifting, respectively. Findings also demonstrate that, during a laboratory collision simulation, lumbar support does not significantly influence the total estimated L4/L5 joint reaction force.

Model-Aided Design of a Rear-Impact Collision Testing System for In Vivo Investigations

A collision testing device used to simulate rear-end impacts on human volunteers was developed and validated. The testing device was designed using impact parameters obtained from real crash-test-derived vehicle-to-vehicle rear-end collisions. Experimental results show the proposed testing device achieves repeatable impact parameters well within the reported ranges of real vehicle-to-vehicle rear-end impact simulations reported in the literature. In particular, the device was able to produce a 7.66 (0.30) km/h delta-v collision with a duration of 111.6 (6.2) ms, and a 4.75 (0.29) g peak acceleration.