I have suffered at least 14 concussions. Only ONE caused me to say, "I'm going to pay for this one." Oddly, I never had symptoms after the first few minutes so I did not pay for that one.

I have bumped my head many times. I know when I suffered a concussion by the immediate symptoms. Delayed symptoms without immediate symptoms are meaningless to me.

I have serious anxiety issues. Just not from worry about head bumps. Over-stimulation sends my brain into a tizzy that can take hours of recovery. I have rescue meds for the worst times but have not needed them in many years because I have learned to moderate over-stimulation.

Bumpers absorb 5 mph, by law. The thin padding in a head rest reduces impact force greatly. Do the physics of 5 mph impact with different deflections.

I've done those calculations. It is amazing how 1/4 inch, even 1/8th inch of deflection reduces acceleration/deceleration values. Hit the headrest with your hand and watch how far it moves. I bet it moves 1 inch.

Do the calculations of the force required to have 60 Gs of acceleration/deceleration with 1/2 inch of deflection. It will be worth your time.

I have never been concerned about cognitive effects. I've suffered the cognitive and memory effects of concussion/mTBI since 1965. They cause some challenges but as one neuro said, I overcome those struggles with work-arounds. He assessment of my brain dysfunction caused him to ask, "How do you function with such a dysfunctional brain?" Then, he looked at my intelligence factors and said. "I see. You use your intelligence to overcome your dysfunctions."

90 out of 100 average bears have better memory functions than me. I have better smarts than 95 out of 100 bears. I use those smarts to deal with the memory and cognitive challenges.

I know what works well and what does not. I don't fret the bad. I just find other ways to get things done.

I am more concerned about headaches. Two of my last 4 concussions caused head aches that were chronic for over 6 months.

Whiplash can cause almost all of the symptoms of a concussion by interrupting blood flow and such. Whiplash does not cause long term cognitive/memory problems.