After my head injury I had the same symptoms as you describe. Could not pick up stuff from the ground or bend over to tie my shoe lace.

I looked into the matter and from what I understand it could be the autoregulation system of the brain that is not working properly. This means that the brains ability to keep the blood pressure constant at different heart rates, working positions etc. is compromised.

According to some theories this is also the reason why many people with PCS is unable to exercise after their head injury. The increase of blood pressure brings back symptoms by irritating or damaging the healing nerve tissue.

I tried to get rid of these symptoms myself by following the buffalo university regulated exercise regimen.

It actually worked for me and these symptoms are pretty much gone today, but I also managed to relapse a few times because i was too eager to exercise.

So its is quite important to keep within the bounds of the pulse rate limits.

I think this forum has several threads on the subject if interested.

-Glasshead