When a vehicle stops suddenly in a crash or is struck from behind, a seat belt will keep a person's body from being thrown forward. But the head may snap forward, then backward, causing whiplash.

In addition to car accidents, whiplash can be caused by roller coasters and other amusement park rides, sports injuries, or being punched or shaken. (Whiplash is one of the hallmarks of shaken baby syndrome .)

You may feel pain and stiffness in your neck for the first few days following a whiplash injury. Then you feel better, but the pain and stiffness may come back several days later.

The discomfort you feel may involve surrounding muscle groups in your head, chest, shoulders, and arms.

• Try over-the-counter pain relievers like aspirin, acetaminophen, or ibuprofen.
• For at least 2 to 3 weeks, avoid activities that bring on or worsen your pain and stiffness. Don't lift or carry anything heavy or participate in sports.
• If you have pain when you move your head or the pain involves your shoulders or arms, your doctor may recommend a soft neck collar or short-term prescription drug to relax the muscles.

Call your doctor if:

• Neck pain and stiffness comes back after it had resolved.
• The pain spreads to your shoulders or arms.
• You have pain when you move your head.
• You have numbness, tingling, or weakness in your arms.

Headrests in your car can reduce the severity of neck pain from a car accident. Make sure that the headrest is positioned properly for your height.

If you do get whiplash, learn proper stretching exercises once your neck has healed. This reduces the chance that neck pain or stiffness will come back.

Ferri FF. Ferri's Clinical Advisor: Instant Diagnosis and Treatment. St. Louis, Mo: Mosby; 2005: 896-897.

Goetz CG, Pappert EJ. Textbook of Clinical Neurology. 2nd ed. Philadelphia, Pa: Saunders; 2003.

Marx JA, Hockberger RS, Walls RM, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002:125,606.