In traditional front and side kicks, the body is upright and the knee rises before the foot is thrust or snapped outward. Sport kicks incorporate moving footwork and the kicks start from the knee. The knee is held close-in to protect against an opponent's kick and the body does not move much during a kick. The idea is to kick quickly and powerfully without telegraphing intentions. With the knee held in close and turned slightly to cover the groin, more speed is available. In fact, the kicking leg may be used offensively and defensively at the same time. For instance, a practitioner might deflect an oncoming front kick with an upraised leg, which immediately turns into an offensive kicking leg, enabling him or her to defend and attack with the same action.
Traditional front kicks are wide open so kickers are exposed to a quick counterattack. In the sport front kick, the knee is instantly brought up and turned slightly inward to protect the body.
Traditional side kicks require the knee to be cocked into kicking position and the fighter leans forward toward the target as he or she kicks, leaving an opening for a counterstrike. In sport side kicks, the knee comes up at an angle that is directed away from the target as the kicker turns his or her body toward his opponent for protection. This allows the kicker to put all of his or her body's power and momentum into the kick.