I am asking this because as a person who has a history of concussions, a few days ago I moved my head very quickly in an attempt to avoid hitting it to the wall. I managed to avoid hitting the wall but in return the movement the I did to avoid collision was so rapid that it eventually caused relapse of some of concussion symptoms I used to suffer such as headache, mental rigidity, etc.

I tried to measure the acceleration involved in my head's sudden movement by using accelerometer of my tablet computer mimicking the same movement with my hand when holding the device. It seems that there is no way my head was subjected to more than 5G for 50-100ms which is nothing compared to the accelerations occur in MVA's..

I just can't understand how come sth like this can bring back all the symptoms all of a sudden. Isn't the in-built protection mechanism of my brain same as the that of normal people?