[QUOTE=Minimac;1110658]Solved!

According to her, rotating/shaking your head from side to side, rapidly or not, cannot under any circumstance cause a concussion unless it happened in a car crash with rear end collision. It requires a lot more force than a quick shaking, even if it is followed by a sudden change in rotation!

QUOTE]

She's WRONG.

Not about not being able to get concussed from a routine shaking. That's correct - and you have nothing to worry about.

She is, however, GROSSLY overestimating the force required to cause a closed head injury.

There are DOCUMENTED cases (does your doc read journals? ) of headbangers sustaining concussions. Similarly, a lot of hockey players suffer DOCUMENTED concussions from checks that jerk their necks back and forth, without their head ever coming into contact with the ice, glass, etc...