Doctors in Boston report that the traditional Chinese martial art Tai Chi appears to have health benefits for older patients with chronic health conditions.

Tai Chi is a martial art in slow motion so slow that it hardly seems martial at all. Practitioners move from one posture to the next at the speed of a snail, breathing deeply and relaxing.

Tai Chi is centuries old and practiced to promote good health, concentration, memory, balance, digestion, and flexibility. It is also thought to reduce anxiety and depression.

Does it really work?

Physician Wang Chenchen of the Tufts-New England Medical Center in Boston says a review of several U.S. and Chinese studies shows that it seems do some good, although she notes that the quality of many of the studies is poor.

"From this evidence, we conclude that Tai Chi appears to have psychological and physical benefits," she said. "It also appears to be safe for old adult people with chronic conditions."

Dr. Wang and her colleagues reviewed nearly 50 studies conducted in the United States and China that evaluated Tai Chi's health impact mostly on elderly people. She says the strongest evidence shows that the martial art helps keep the elderly steady and prevents falls and broken bones, one of the most common reasons old people are hospitalized

"From our review of the articles, we find that Tai Chi is very safe and effective for balance, also for flexibility," she said.

Other studies that Dr. Wang's team evaluated indicated that Tai Chi practitioners experienced improved heart and lung fitness whether they had been healthy at the start of the research or had heart problems, such as heart attack, heart bypass surgery, or high blood pressure.

The research also suggested that Tai Chi reduced arthritis symptoms as well as stress and anxiety.

Dr. Wang says the research hints that one need not be elderly to benefit. One study looked at children aged nine to 11, while another examined young adults.

"For primary school students nine to 11, they also find Tai Chi good for reduced anxiety at school," said Dr. Wang. "Another study found that Tai Chi improved sleeping quality for 20-24 year old [people]."

But Dr. Wang, a native of Nanjing, China, says most of the studies had limitations or biases that impair their findings, especially those conducted in China. Only a few used rigorous scientific methods. At best, she says, the combination of results is suggestive of Tai Chi's benefits on health, but not definite proof.

"It's very difficult to draw conclusions," she said. I"t's very difficult to say Tai Chi really works. We still don't know yet. We need a good study to show the benefits."

Dr. Wang's article appears in the Archives of Internal Medicine, published by the American Medical Association.