Chinese martial arts, which are called kung fu or gung fu and wushu , are a number of fighting styles that have developed over the centuries in China. These fighting styles are often classified according to common traits, identified as "families" (; ), "sects" (; ) or "schools" (; ) of martial arts. Examples of such traits include Shaolinquan physical exercises involving animal mimicry, or training methods inspired by Chinese philosophies, religions and legends. Styles that focus on qi manipulation are called internal (; ), while others that concentrate on improving muscle and cardiovascular fitness are called "external" (; ). Geographical association, as in northern (; ) and "southern" (; ), is another popular classification method.