As far as I understand it - everone's different. Most people have a usual threshold of: Hit your wrist on a door-knob whilst passing through: "Ouch" Hitting a knee on a stem: "AAAAAAAAAAAAAH!" And sit out for 5/10 minutes. A hefty bail involving you landing a fair way away from where your bike ends up: Not riding for quite a while... sometimes get a little dizzy/dodgey vision etc. Being in a head on car crash: Pass out/mild shock/serious pain. Personally - I've brutalised myself into accepting normal levels of pain, and think nothing of what most people would be really hurt by... but as SOON as the pain exceeds that threshold, I go into a mild form of shock* really easy - yet I come out of it dead quick. (This is where the boundary lies... I didn't get any shock, but it BLOODY hurt.) *By "mild shock", I mean mild nausea, slight tunnel vision, and feeling generally unwell - not blacking out, or anything so much as you described. I know some people who struggle to withhold the pain of tipping over the bars, but Krisboats - on the other hand - just completely ignores the fact that he should be experiancing some sort of pain I guess each person's pain tolerance is down to them - but even then, there'll always be anomalies to the rule.