BOSTON (Reuters) - The slow, flowing movements of tai chi are better for relieving pain and other symptoms of fibromyalgia than conventional stretching exercises, doctors reported on Wednesday.

The improvements continued throughout the three months of lessons for 33 volunteers receiving the movement and breathing exercises, study leader Dr. Chenchen Wang of the Tufts University School of Medicine in Boston said in a telephone interview.

"Week by week they changed. The pain and depression improved, and a lot of people were depressed," said Wang, whose study is published in the New England Journal of Medicine.

"They feel better. People said it changed their life. Only two or three feel it didn't help."

Although they said the study should be repeated with a larger group to see if, for example, the enthusiasm of the instructor played a role, Dr. Gloria Yeh and her colleagues at Beth Israel Deaconess Medical Center in Boston said it might be time to give tai chi a chance.

"Aside from reductions in pain, patients in the tai chi group reported improvements in mood, quality of life, sleep, self-efficacy and exercise capacity," Yeh's team wrote in a commentary in the same journal.

"The potential efficacy and lack of adverse effects now make it reasonable for physicians to support patients' interest in exploring these types of exercises, even if it is too early to take out a prescription pad and write 'tai chi,'" they wrote.

Fibromyalgia, which may affect 200 million people worldwide, is difficult to diagnose and hard to treat, with no clear guidelines for symptoms that include pain, fatigue, stiffness and sleep difficulties.

There is evidence that it may be caused by a heightened sensitivity to pain and patients often turn to alternative therapies such as tai chi, yoga, acupuncture or massage.

Tai chi originated as a Chinese martial art that focuses on slow, graceful movements, breathing and relaxation in an effort to move a hypothetical energy throughout the body.

Volunteers in the tai chi group took 60-minute classes twice a week for three months from a tai chi master and were encouraged to practice at least 20 minutes per day.

Another group got health lectures and stretching classes, comparable to what people do when they wake up in the morning. "This was not real exercise," Wang said. Further tests comparing exercise to tai chi are planned.

To assess the effectiveness of both treatments, the Wang team used several assessment tools, including one that measured fibromyalgia symptoms on a 100-point scale. The people taking tai chi saw their scores improve by an average of 28 points, compared to a nine-point improvement in the stretching group.

Researchers should test the technique with a larger group for a longer period, compare different styles, and see if it is better than other forms of exercise, such as yoga, Yeh said.