Taekwondo is characterized by its emphasis on head-height kicks, jumping and spinning kicks, and fast kicking techniques. In fact, World Taekwondo Federation sparring competitions award additional points for strikes that incorporate jumping and spinning kicks.[7] To facilitate fast, turning kicks, taekwondo generally adopts stances that are narrower and hence less-stable that the broader, wide stances used by martial arts such as karate. The tradeoff of decreased stability is believed to be worth the commensurate increase in agility. This emphasis on speed and agility is a defining characteristic of taekwondo, and has its origins in analyses undertaken by Choi Hong Hi. In his early biomechanical analyses of martial arts, Choi observed that (based on Newtonian physics) the power of a strike increases quadratically with the speed of the strike, but increases only linearly with the mass of the striking object. In other words, speed is more important than size in terms of generating power. This principle was incorporated into the early design of taekwondo and is still used. [2] [8]