Tai chi chuan (also rendered as tàijíquán) was a Human art of self-defense and exercise that originated in China. This martial art used relaxed strikes and throws to thwart the strength of an opponent. One of its principles was "stillness in movement". Will Riker's double Thomas once demonstrated his knowledge of tai chi, noting its similarity to the Klingon martial art mok'bara. (TNG: "Second Chances" )