On Tue, 3 May 2011 15:06:29 -0700 (PDT), in rec.bicycles.tech Chalo
wrote:

In my observation, hand and wrist injures are relatively common in
headers off of normal bikes. Concussions really aren't.

Injuries are quite common in all forms of collisions. I've seen
injuries when an ice skater collided with a Zamboni. I did my
residency at Ben Taub in Houston and I saw lots of closed head trauma
from traffic mishaps involving all kinds of vehicles and concussions
really are common... half a dozen in a shift wouldn't be out of the
ordinary evening.

If you choose not to wear a helmet, that's your business; however,
please don't suggest that closed head injury from blunt force trauma
is rare because ERs see them like clockwork.