Atlas must have felt this way after a day of shouldering the weight of the world -- drained, bleary-eyed and suffering from the agony of a stiff neck.

Sore neck muscles are a common result of everyday stress. One out of every 10 Americans will suffer from neck pain at least once in their lifetime, according to Erwin Gonzalez, director of physical medicine and rehabilitation at Beth Israel Medical Center in New York.

There are 10 muscle groups in the neck that help support the head, which weighs about 15 pounds. Stress causes the trapezius -- a large, diamond-shaped muscle that extends from the back of the skull to the middle of the torso -- to tighten up.

"When people are tense, they contract the muscles in the upper and middle part of the trapezius," said Gonzalez. "This pulls on the neck and spine and causes a lot of tension within the muscle."

Prolonged contraction of a muscle creates a knot or spasm, which causes a sharp pain at the base of the neck.

"A spasm can last from days to weeks and may prevent people from moving their head in one direction," said Rafael Lopez, assistant professor of orthopedic surgery at George Washington University Medical Center.

Pain that lasts more than 72 hours or radiates to the shoulder, down the arm or to the back of the head should be reported to a doctor, Lopez said.

Relieving muscle tension may be easier than eliminating the initial stress. Exercise, massage and biofeedback -- a visualization technique where a person imagines the muscles contracting and releasing -- are all useful.

Just shrugging the shoulders and stretching is helpful. Beth Israel's Gonzalez recommends isometric exercises -- a method where one set of muscles is tensed against another set or against an immovable object. Place the palm of the hand on the forehead and press for about six seconds. Then rotate the palm to the left side of the head, the back and the right side. Repeat the contraction six to 12 times.

In addition to stress, whiplash injuries are another cause of neck pain. The injury, either a pulled muscle or torn ligament, usually occurs when the weight of the head is forcibly thrown backward and forward during an automobile accident. There are about 257,000 whiplash injuries reported annually, according to the National Highway Traffic Safety Administration.

Headrests play a vital role in preventing whiplash. When a person is sitting upright in a car, the headrest should be two inches from the back of the head. If the headrest is positioned at the level of the neck, it can cause a more severe injury, said George Washington's Lopez. -- Wendy Melillo