As the brain crashes into the skull, it can cause concussions, impairment and death, he said.
Heading the ball is not a primary cause, studies have determined, because the impact is not of sufficient force to send the brain crashing into the skull.
One obvious difference is that Afghan and Iraq veterans are much more likely to have been exposed to blasts, whose shock waves send the brain crashing into the skull.
Those waves can not only throw a soldier dozens of feet in the air into other objects — causing a conventional concussion as the brain crashes inside the skull — but may also subject brain tissue to sudden pressure variations that can cause similar damage.
But the difference is that the first player saw that he was about to be hit and tensed his neck, which limited the sharp back-and-forth jolt of the head that sends the brain crashing against the sides of the skull.
These impacts, in combination and under various conditions, can cause the brain to crash into the skull and cause stretching and shearing of brain tissue.
The brain can crash into the inside of the skull through a wide range of forces, some arriving straight to the head and others suddenly rotating it.
Only a few of more than 50 players interviewed at the tournament came close to defining the injury: a blow to the head that causes the brain to crash into the skull.
The suspicion, healthy to a point, arises because we know that computers, like brains, can crash when they are overloaded.
It investigates the relationship between the extent of neurofibrillary tangles (NFT), a hallmark of Alzheimer's disease in the brain, and particular crash situations.
