Response of Neck Muscles to Rear Impact in the Presence of Bracing

In this research, cervical muscle behavior in rear impact accidents was investigated. Specifically, cervical muscle forces and muscle lengthening velocities were investigated with respect to cervical injuries. Variation of the onset time for muscle activation, variation of muscle activation level and variation of rear impact pulses were considered. The human body simulation computer program, MADYMO and anthropometric numerical human model were used to evaluate the neck. The factors mentioned above were examined with specific data being obtained from several different literature sources.

Cervical muscles were separated into three groups, the sternocleidomastoideus, the flexor muscle group and the extensor muscle group. Longuscolli and spleniuscapitis were selected to represent the flexor muscle and extensor muscle groups respectively. The values and trends of the muscle forces and lengthening velocities are investigated in each muscle group. Known experimentally measured resting force values of three neck muscles were used to calculate the minimum force applied by all the muscle in the neck. The magnitude of bracing, the timing of onset of bracing and the timing of the impact acceleration all have an effect on muscle force, muscle lengthening velocity and head displacement. The flexor muscles appear to be more significant during rearward head excursion and the extensor muscles are more active during head-neck rebound. In the absence of specific injury criteria for cervical soft tissue, insight is given into the forces and other parameters that may relate to injury.