Physical abuse of children by shaking usually is not an isolated event.
Many shaken infants show evidence of previous trauma.
Frequently, the shaking has been preceded by other types of abuse. However, the primary factor is the proportionately large size of the adult relative to the child. The shaking causes the infant's head to whip forward and backward from the chest to the back. The infant's chest is compressed, and the arms and legs move about with a whiplash action. At the completion of the assault, the infant may be limp and either not breathing or breathing shallowly.