The Mandarin term "tai chi chuan" literally translates as "supreme ultimate boxing" or "boundless fist". The concept of the "supreme ultimate" is the symbol of the Taijitu meant to show the principles of Yin and Yang duality of Taoist philosophy. Thus, tai chi theory and practice evolved in agreement with many of the principles of Chinese philosophy and Taoism in particular. Tai chi training first and foremost involves learning solo routines, known as forms (“…�H taolu). Paradoxically, while the image of tai chi chuan in popular culture is typified by exceedingly slow movement, many tai chi styles (including the three most popular, Yang, Wu and Chen) have secondary forms of a faster pace. The other half of traditional tai chi training (though many modern schools disregard it entirely) are partner exercises known as pushing hands, as well as martial applications of the postures of the form. Tai chi chuan was created as a form of traditional Chinese martial arts of the Neijia (soft or internal) branch. Since the first widespread promotion of tai chi's health benefits by Yang Chengfu in the early Twentieth century, it has developed a worldwide following among people with little or no interest in martial training for its benefit to health and health maintenance. Some call it a form of moving meditation, as focusing the mind solely on the movements of the form purportedly helps to bring about a state of mental calm and clarity. Besides general health benefits and stress management attributed to tai chi training, aspects of Traditional Chinese medicine are taught to advanced tai chi students in some traditional schools.[citation needed] Some martial arts, especially the Japanese martial arts, utilize a uniform for students during practice. Tai chi chuan schools do not generally require a uniform, but both traditional and modern teachers often advocate loose, comfortable clothing and flat-soled shoes.[1] [2] The physical techniques of tai chi chuan is described in the tai chi classics (a set of writings by traditional masters) as being characterized by the use of leverage through the joints based on coordination in relaxation, rather than muscular tension, in order to neutralize or initiate attacks. The slow, repetitive work involved in the process of learning how that leverage is generated gently and measurably increases and opens the internal circulation: (breath, body heat, blood, lymph, peristalsis, etc.).