OK, I've been riding for the last 20 years including the mountain bike craze from start to finish.

I didn't have a lot of money to put into bicycles for a long time so I ended up with older stuff often that failed at inappropriate times. I crashed A LOT.

One thing I noticed. When I wore a helmet I often would hit my head. I don't know whether this was because the helmet makes your head heavier and your neck muscles aren't used to this (which is my guess) or whether you just don't worry about hitting your head when you're wearing a helmet (which would be suggested by the theory of risk compensation). Whatever, wearing a helmet = hitting head fairly often.

When I wasn't wearing a helmet I NEVER hit my head. And I crashed about as often both ways.

My suspicion is that God knew what he was doing when he designed the human body and it tends to protect the head when there isn't an inch and a half of crap hanging off of it.

In the crashes I never conciously worried about hitting my head or not so it wasn't a case as in motorcycle crashes which usually happen a lot slower (believe it or not) and you have time to think about how you're going to crash.

The point is that people who claim that their helmet saved them from head injuries may be missing the point that perhaps the helmet CAUSED the head to strike in the first place. I won't go any further than to suggest that.