Los Angeles - Tai chi is already known as a good low-impact exercise for older people. Now a recent study suggests it offers benefits beyond improving fitness and balance: It may help prevent shingles, a painful skin condition.

Researchers found older people who performed the slow, graceful movements of tai chi had a better immune response against the virus that causes shingles than those who only got health education, according to the most rigorous test to date.

It's unclear how tai chi, an ancient Chinese martial art that has become increasingly popular in the West, affects the immune system. But health experts were encouraged by the positive results.

"The message is that older people need to maintain healthy behavior," said Andrew Monjan of the National Institute on Aging, which helped fund the research. "It's nothing that our mothers haven't told us, but we're seeing it certainly holds up to scientific inquiry."

The study appears in the April issue of the Journal of the American Geriatrics Society and was led by Dr. Michael Irwin of the University of California, Los Angeles.

Shingles is a painful skin rash that can pop up in people who have had chickenpox. The chickenpox virus can remain dormant in the body and resurface as shingles years later. It usually starts with pain and itching on the skin that later turns into an irritating rash.

An estimated 1 million Americans are afflicted with shingles every year and it commonly occurs in people 50 years old and older.

The UCLA study involved 112 healthy adults, ages 59 to 86, who have had previous cases of chickenpox.

Half of them took tai chi classes three times a week for three months and the rest attended health education classes where they were taught good diet habits and stress management. Then both groups were vaccinated with a chickenpox vaccine. Researchers took periodic blood tests before and after vaccination to determine their level of immunity against shingles.

After six months, the tai chi group had nearly twice the level of immunity against shingles than the education group.

Those who performed tai chi before vaccination had an immune response that was similar to what a vaccine would produce in a younger population. Tai chi combined with the vaccine showed a 40 percent increase in immunity than the vaccine alone, researchers found.

The results weren't surprising to tai chi instructor Howard Chuck, who owns a tai chi academy in Sunnyvale, Calif.

Although none of his students are trying to ward off shingles, Chuck said the exercise is popular among his older people who prefer tai chi's meditation aspects.

"Tai chi requires a lot of mind power not just muscle power," he said.