The purpose of this study is to predict the physical motion of the human body under pre-crash conditions. Low speed front impact tests on human volunteers were conducted using a linear-motor sled with the rigid seat, steering wheel and seat-belt. During the experiments, the subject's physical motion, acceleration, and EMG signals were recorded. When the subject's muscles were initially relaxed, muscle responses were observed to start activation at around 130ms after the onset of acceleration. Furthermore, the head-neck-torso accelerations were strongly influenced by the muscle activity after the impact. The major body region such as head, neck and pelvis were constrained by the related muscle.