Depends where too, one clean shot to the jaw will knock you down from the trauma but won't do as much as a shot to the temple which obviously moves the brain more.

more shots = move movement too... teh damage is caused because the skill moves and the brain doesn't (sort of like if you walk to the back of a bus... the bus is moving but you're not, keep walking and you'll bang into te back seats :P) so the more movement the more the brain bangs off the skull.