Head kinematics and cervical muscle response during sagittal and frontal seated perturbations

This thesis is an investigation of head kinematic and cervical muscle responses to frontal, rear, right, and left low-velocity whiplash perturbations. Rear perturbations elicited the shortest EMG and kinematic onset latencies compared to the other directions, resulting in a "condensed" response. Average SCM amplitude was greatest during rear perturbations (~30% MVC) and had a relatively small average onset latency of 30 ms ('relative to the onset of head motion'). The peak magnitude of the linear and rotational head accelerations were the greatest during rear perturbations. Frontal perturbations resulted in a relatively "delayed" response resulting in an average SCM onset latency of 143 ms. Left and right perturbations demonstrated similar kinematics, similar SCM amplitudes (~10% MVC) and average onset latencies (55 ms and 65 ms). Overall, left and right perturbations elicited similar kinematic and EMG responses. Frontal and rear perturbations elicited variable kinematic and EMG responses, with the responses during rear perturbations being most associated with injury risks. These findings are consistent with the increased incidence of injury associated with rear impact collisions.