I've had a concussion, getting decked coming over the middle playing some pickup football with friends and landed on the back of my head. It can hurt a bunch. I cried like a little girl for about a whole minute, and then a minute later had no memory of it.
I remember a few years ago taking a rocket of a soccer ball to the noggin that I didn't see coming. I dropped like a sack of potatoes after a brief black out. I not-so-wisely continued playing.
While the memory of the shot is clear as day I was a mess the next day. I could barely walk straight and my vision was all jacked up a long with my equilibrium.
I have had 2 concussions, one not so bad and the other awful. One, I was in high school and ( please do not laugh) riding a unicyle, I fell off and caught the back of my head on a picnic table. At the time I was working at an amusement park called Kings Island, and I was out of it for less then a minute. They took me to medical and said I had a concussion and would miss the rest of the summer contract becuase they wouldnt let me ride again. It hurt, but it hurt more losing my summer job.
Then when I was in my twenties I was struck in the back of my head with an aluminum bat ( it was a mistake). That hurt like hell. I had this high pitched 'whine' in my ears and saw some interesting 'lights'. And I was unsteady for a day or two afterwards. Couldn't drive, etc..Loss of appetite, all that stuff.
I cant imagine what guy like these and MMA fighters and boxers go through having these things over and over again....