One time in the Navy I walked into a low-hanging fire sprinkler valve. It hurt so bad I wound up down on one knee, and I don't remember actually GOING down to the knee. For a few seconds, I couldn't do anything else and for several seconds more I didn't do anything except pull myself together. Afterward, I analyzed in HERO terms and found that the game is pretty accurate:
Assuming that all my stats were baseline, I figured that what happened is that I did a move-through on the ship (and failed to do any knockback, of course). That does STR damage plus a velocity bonus that I wasn't moving fast enough to get, so I did 2d6 Physical to the ship and got the same damage in return. Assuming average results, I took 2 Body and 7 Stun, reduced to 0 Body and 5 Stun by my natural 2 PD. After applying x2 Stun for the hit location and another x2 Stun for taking damage out of combat, my total damage taken was 0 Body and 20 Stun. With my CON of 10, I was Stunned but not unconscious. My "next phase" was consumed by recovering from being stunned, and then I voluntarily "took a recovery" on all my actions until I had my Stun back.
TL;DR: head injuries hurt and I'm a nerd.