"Sneeze: 2.9g
Slap on back: 4.1g
Hop off step: 8.1g
Plop down in chair: 10.1g"

The sneeze may have some validity if it is a violent sneeze. Most aren't. But the others do not have any validity. There are too many variables that are not considered. I have seen these kinds of comments online. Some of the justifications / math calculations leave a lot top be desired.

Nobody should be afraid of a hug. That is nonsense. Even a pat on the back is no big deal unless you have whiplash issues with your neck and the pat actually caused your body to jerk forward. Not likely. Even then, the problem would be your neck, not your head.

"But then I read on here that some can re-concuss themselves by just a simple bumpy car ride."

The bumpy car ride refers to strong bumps that continue and are such that if you tried to talk, you would not be able to. "How ow ow ow are are are you you you do do ing ing ?" Get the idea ? Maybe like a series of speed bumps ten feet or so apart that lasted for a minute or so of driving. The more common issue would be badly potholed rural/mountain roads that just shake your teeth out. Very few people experience these. And, when they do, they slow way down because the ride is just too uncomfortable for even a healthy brain.

There are rare situations where one might get a severe jolt hitting a bump. These usually require a trip to the wheel alignment shop. As I said, RARE. And usually more of a neck issue.

keep in mind that tires can only generate about 1 to 1.5 G's of stopping force before they skid and lose traction. So, those breaking actions are not even close to a sub-concussion threshold.

Regarding sub-concussive impacts. One at a time, they are no big deal. If you suffer 20 during a 2 hour football practice and do it 5 days a week for a season, I would be concerned.

My neck is very sensitive so I have learned to lean my head and shoulders forward if the road gets bumpy.

So, stop worrying about these little bumps and contacts and get on with your life. If you are going to 'play' around, just stay away from the head board.

btw, I bet there is more movement jerking away from an attempted hug that the hug could ever impart.