Tai chi, a traditional, slow-moving form of Chinese martial art, is known to increase flexibility and improve balance. Now, new research suggests it's better than more vigorous aerobic exercises for lowering blood pressure in people with prehypertension.

Prehypertension is blood pressure that's higher than normal but doesn't quite reach the level of high blood pressure, or hypertension. It's considered a warning sign that heart disease may be ahead, and it raises the risk of having a heart attack.

The new findings, published in the journal JAMA Network Open, add to a large body of research pointing to health benefits from tai chi, a wellness practice that combines slow, gentle movements and postures with mindfulness. It's often called meditation in motion.

In the study, researchers in China randomly assigned 342 adults with prehypertension to one of two interventions. The average age of participants was 49. Roughly half the people participated in supervised aerobic exercise, including jogging, climbing stairs, brisk walking and cycling. The other half was trained to practice tai chi. Both groups got hourlong sessions four times a week.

After 12 months, those in the tai chi group saw bigger drops in their blood pressure than those in the aerobic exercise group. What's more, nearly 22% of the people who practiced tai chi saw their blood pressure fall to within normal range, compared with nearly 16% of people in the aerobic exercise group. And fewer patients in the tai chi group went on to develop hypertension than in the aerobic exercise group.

Previous research has found that tai chi is more effective than brisk walking at lowering blood pressure, fasting blood sugar levels and perceived stress in people who have hypertension.

So what is it about tai chi that helps lower blood pressure? The practice tends to elicit more of a response from the parasympathetic nervous system, says Ruth Taylor-Piliae, a professor at the University of Arizona's College of Nursing, who was not involved in the study. The parasympathetic nervous system is the network of nerves that relaxes your body after periods of stress or danger.

"It [tai chi] kind of helps to just relax everything, and I think it's that response that's working towards lowering blood pressure," says Taylor-Piliae, whose research focuses on how mind-body interventions such as tai chi can benefit older adults with cardiovascular disease. "I think it's the meditative quality of it."

She notes a large body of evidence has now shown the benefits of tai chi on blood pressure. The practice is appealing as a form of exercise because it is low impact and requires little space or equipment.

"I think the beauty of tai chi is that you don't have to have a special gym membership, you don't have to have special clothing," Taylor-Piliae says. "Once you learn tai chi, you can do it anytime, anyplace, anywhere. And it does kind of provide that calming, relaxing" effect.

Studies have also shown that practicing tai chi can help reduce the risk of falls, improve balance and walking speed in older adults, and reduce depression and anxiety.

Evidence suggests it can also help protect against cognitive decline and even boost memory. But you have to practice it consistently to reap the most benefit.

"You have to have enough 'dose' of tai chi," Taylor-Piliae says. "You can't just do it one hour, one time."

This story was edited by Jane Greenhalgh.