Back in the 1960s I worked in a factory putting together cars. That's about when they started adding head rests to help cut down on whiplash injuries. I'm long since retired but it doesn't seem like there are fewer people with whiplash after car accidents. Am I right?

You are. Whiplash injuries still account for a large part of the costs associated with road traffic accidents. The exact mechanism for whiplash injury is unclear. The head restraints added to all passenger vehicles in 1969 were meant to reduce how far back the head could extend. At that time it was thought that hyperextension was the cause of whiplash.

The head restraints were not found to reduce whiplash-related injuries after all. Then it was proposed that muscle contraction and the forceful motion forward might be the problem. Air bags may help with this but many times the air bags don't deploy.

Today's advanced technology is helping researchers examine neck motion under different conditions. Comparing changes in the neck under normal motion versus under the load of an accident may bring some new answers.