of qigong is typically more on health or meditation than martial applications. Internally the main difference is the flow of qi. In qigong, the flow of qi is held at a gate point for a moment to aid the opening and cleansing of the channels. In tai chi, the flow of qi is continuous, thus allowing the development of power by the practitioner. Partnered practice Tai chi's martial aspect relies on sensitivity to the opponent's movements and center of gravity, which dictate appropriate responses. Disrupting the opponent's center of gravity upon contact is the primary goal of the martial t'ai-chi ch'üan student. The sensitivity needed to capture the center is acquired over thousands of hours of first yin (slow, repetitive, meditative, low-impact) and then later adding yang (realistic, active, fast, high-impact) martial training through taolu (forms), tuishou (pushing hands), and sanshou (sparring). Tai chi trains in three basic ranges: close, medium and long. Pushes and open-hand strikes are more common than punches, and kicks are usually to the legs and lower torso, never higher than the hip, depending on style. The fingers, fists, palms, sides of the hands, wrists, forearms, elbows, shoulders, back, hips, knees, and feet are commonly used to strike. Targets are the eyes, throat, heart, groin, and other acupressure points. Chin na, which are joint traps, locks, and breaks are also used. Most tai chi teachers expect their students to thoroughly learn defensive or neutralizing skills first, and a student must demonstrate proficiency with them before learning offensive skills. Martial schools focus on how the energy of a strike affects the opponent. A palm strike that looks to have the same movement may be performed in such a way that it has a completely different effect on the opponent's body. A palm strike that could simply push the opponent backward, or instead be focused in such a way as to lift the opponent vertically off the ground, changing center of gravity; or that it could project the force of the strike into the opponent's body with the intent of causing internal damage. Most development aspects are meant to be covered within the partnered practice of tuishou, and so, sanshou (sparring) is not commonly used as a method of training, although more advanced students sometimes practice by sanshou. Sanshou is more common to tournaments such as wushu tournaments. Weapon practice Tai chi practices involving weapons also exist. Weapons