On any early morning in China, millions of people, most of the old, gather in parks to exercise. There are several types of traditional exercise that are regarded not only as ways to take care of one's body, but also as therapy.     The most common type of exercise is taijiquan, the so-called shadow boxing. Another, perhaps less familiar to Westerners, is qigong, which is often translated as breathing therapy. The two main types of qigong are separated into" hard" and " soft". Soft qigong is more of a meditative type, mostly breathing exercises and fairly simple non-stressful movements. Hard qigong on the other hand, is more intense and is practiced to cultivate great strength, serious stamina and almost super-human abilities (supposedly).     A basic tenet of soft qigong is the concept of "holding the ball". This is a simple position which is seen in many different forms of qigong. The basic idea is that you picture a ball in front of you and you place your hands on either side of the ball so that you are holding it up.    The aim is to create a circuit of qi. Energy circulates throughout your body and by creating this circuit with your arms you can exercise the flow ball for a while your hands start to get warm. If you are doing it correctly, after a little while you should feel like the ball is expanding and contracting. You then move your hands farther apart, back in, then out again.    By going through the movements over and over, you condition your body while, at the same time, relaxing your mind. This, combined with movements specially formulated to increase qi flow (including lots of ball-holding), creates a veritable qi feast in your system.    Today, an estimated 70 million people in China practice qigong on a daily basis. The continued popularity of qigong represents a healthy interest in exercise.