It's easy to tell people to make exercise part of their daily routine. It's not so easy to tell them what to do. Some folks like to run marathons or climb mountains. But if you would rather care for your body without risking life or limb or increasingly creaky joints, you might consider Tai Chi Chuan, the ancient martial art that looks like a cross between shadow boxing and slow-motion ballet. Tai Chi combines intense mental focus with deliberate, graceful movements that improve strength, agility and-particularly important for the elderly-balance. Practitioners praise Tai Chi's spiritual and psychological benefits, but what has attracted the attention of Western scientists lately is what Tai Chi does for the body. In many ways, researchers are just catching up to what tens of millions of people in China and Chinatowns around the rest of the world already know about Tai Chi. Scientists at the Oregon Research Institute in Eugene reported that Tai Chi offers the greatest benefit to older men and women who are healthy but relatively inactive. Previous studies have shown that Tai Chi practiced regularly helps reduce falls among healthy seniors. The next step, from a scientific point of view, is to determine whether Tai Chi can help those who are already frail. There are several styles of Tai Chi, but most of them start with a series of controlled movements, or forms, with names like Grasping the Sparrow's Tail and Repulse the Monkey. There are many good how-to books to get you started, or you can choose from among the growing number of classes offered at rec centers and health clubs in the U. S. and around the world. (These have the added benefit of combining instruction with a chance to meet new people.) Either way, the goal is to move at your own pace. As Tai Chi Cultural Center in Los Altos, California puts it, 'Pain is no gain.' It can take a few months for the effects to kick in, but when they do they can act as a gateway to a new lifestyle. 'Once people start feeling better, they often become more active in their daily life,' says Dr. Karim Khan, a family-practice and sports physician at the University of British Columbia. Any form. of exercise, of course, can do only so much. 'For older individuals, Tai Chi will not be the end-all,' says William Haskell, an expert in chronic-disease prevention at Stanford University. 'But Tai Chi plus walking would be a very good mixture.' Younger people probably need more of an aerobic challenge, but they can benefit from Tai Chi's capacity to reduce stress. The best thing about Tai Chi is that people enjoy it, so they are more likely to stick with it long enough to get some benefit. It helps when something that's good for you is also fun. Tai Chi movements can improve all the following EXCEPT______.