Whiplash is also known as Cervical Acceleration Deceleration or (CAD). It often occurs with a rear end collison which causes the vehicle to move forward from the impact. When this occurs the torso is shoved back into the seat, which loads the seatback. As a result, both the neck and head rise upwards, coming in contact with the headrest. Due to the position of the headrest, whiplash can occur. According to Dr. Brian Stemper (a Biomedical engineer at the Medical College of Wisconsin) " Whiplash injuries occur before the head rotates as its moving backward relative to the thorax; the key is the relationship between the head and the chest, Injuries tend to occur in the beginning phases of a car accident, he added, and women are five to percent more susceptible to the injury because of the flexibility in their cervical spines."