Often called "moving meditation" or "the art of creating energy," tai chi began as a martial art in China about 2,000 years ago. Over the past century, it has become extremely popular as an exercise for older adults and is practiced by millions of Chinese each morning in parks throughout the country.

But tai chi's graceful movements are so slow and deliberate that researchers from Johns Hopkins University in Baltimore assumed it wouldn't have much impact on blood pressure. So in a study of the effect of moderate exercise on hypertension, they assigned the control group to learn tai chi.

To their surprise, tai chi appeared to lower blood pressure in older adults nearly as much as moderate-intensity aerobic exercise.

"We were expecting to see significant changes in the aerobic exercise group and minimal changes in the tai chi group," assistant professor of medicine Deborah R. Young reported at a recent American Heart Association conference. After 12 weeks, however, the tai chi group's average systolic blood pressure had fallen by 7 millimeters of mercury, compared with an average of 8.4 millimeters of mercury in the aerobic exercise group.

The researchers studied 62 sedentary men and women, aged 60 and older, whose systolic blood pressure was in the "high normal" to "mild hypertension" range. Half the group was randomly assigned to a 12-week program of brisk walking and low-impact aerobics. The other half, which was the "control" group, learned tai chi. Both groups exercised four times a week for 30 minutes per session. And in both groups, blood pressure began to drop after just six weeks of exercise.