Originally Posted by
MMACH 5
I think you are equating rotational injury with head rotation. These aren't the same thing. Rotational injury has to do with parts of the brain and their differing densities accelerating and decelerating at different rates, causing nerve axons to tear and damage. Someone feel free to interject, if I'm explaining this incorrectly.
That's over complicated: your brain just should not rotate in its skull. That simple.
Interestingly, beside being the major cause of serious brain damage, rotational injuries are also cummulative (think of boxers and NFL.) So that guy who falls his bike a lot and avoids scalp cuts by wearing a helmet might, quite seriously, be making a bad trade off...
But, honestly, rotation is something of a red herring: virtually all serious cyclist head injuries come from fast hits by cars, and they do so much damage that any sort of helmet you can wear is irrelevant. The only smart safety measures are those that aim at not being hit. The reason why anti-rotation helmets matter is sports use - bmx, crit racing, downhill - where a participant might fall off quite frequently and where (obviously) no cars are involved. And of course it matters in motorcycling, because motorcycle helmets are tough enough to survive hits at more than 12mph.