Let's say you are in a war-situation, and both you and your opponent are out of bullets. When I was in the army, I learned that the most efficient way to kill your opponent would be to kick him in the balls until he was incapacitated by the pain (one or two good hits in the nuts), then finish him off by some means.
I have since doubted this claim: Would you really notice the pain in such a situation? I imagine it works in a surprise attack, but is it efficient when the body is in a fight-mode and full of adrenaline? If no, how long does it take to reach such a mode where you don't feel pain from when you are mentally aware that your life is in danger?
In particular, what triggers the no-pain-mode? Is it physical or psychological, controllable etc?
What exactly happens to the body when you are in a fight-mode? There are lots of rumours of huge strength increasing. For example, women lifting cars when their baby is trapped underneath, etc.) Is there any scientific studies showing that people become able to lift heavier objects than normal?