In rear-end collisions the anterior neck muscles are exposed to eccentric contractions beyond their biological limit as the head is forced into a hyper-extended position. The deep anterior neck muscles undergo micro trauma. This micro trauma can result in inhibition of these muscles, which will reduce their ability to act as deep stabilizers of the cervical spine.
When the deep stabilizers are not functioning effectively the larger superficial muscles take on the role of stabilizing the neck. These muscles are not suited to constant low level contraction required for stabilization and develop active and latent trigger points.
Several studies have shown that persons involved in whiplash have greater difficulty relaxing their muscles in between tasks, especially when exposed to low bio-mechanical loads (1,2 references below).
Release of tight, overworked superficial muscles is needed alongside gentle strengthening of the deep stabilizing muscles of the neck for lasting relief.