This movement hyperextends and hyperflexes the neck muscles. The muscles, ligaments, bones and nerves of the neck are severely strained.
Whiplash is a common injury.
In the United States every year more than a million people are injured this way. Whiplash is hard to diagnose. Frequently X-rays and other tests don't reveal any structural damage. If you think you have whiplash, see your healthcare provider to minimize the damage and speed up the healing. Take care to preserve the normal curve of the neck when wearing a support.