[kdotsky]

It's not pain that makes them tap. When a submission move is fully "locked in", they simply know there is nothing they can do to stop they're arm/leg/ankle/knee from being broken in the next few seconds. It's just training.

I trained with the Militech camp for several months. I saw a guy get his ankle broken in an ankle lock during very light practice sparring. He obviously didn't feel much pain, nor did he have reason to try to resist it. It just happened accidentally, which is why you're trained to just tap out.

The first time I got put in an arm bar while sparring the guy watching jumped in because I did not react to it quick enough (it didn't hurt). After a while you just react to situations by their actual level of danger rather than their level of pain. For example, while an opponent grinds his knee into your head with most of his weight, it may be very painful but you just "think I'm fine, no real danger". You get put in armbar and you think "armbar, too late for countermove, time to tapout" when you possibly don't feel much pain.

The pain threshold these guys have is by far enough to withstand an armbar (not that it's smart). They probably feel much worse pain in other parts of the match.

BTW if you want to see some *serious* UFC, try to find UFC 1-4. It's nothing like what you see today.