The front kick is the easiest kick to perform and it is usually the first kick taught new students, so it will be discussed first and in detail. Many of the things discussed under the front kick may also apply to other types of kicks.
Front Snap Kick
Foot position. The foot is angled forward, with the toes curled backward
Striking Surface. Strike with the ball of foot
Leg Position. Chamber the knee up high, fully extend the leg , and re-chamber the knee to the high position.
Usage. Use the kick to score or to setup a hand attack.
Movement. To kick, raise the knee quickly, keeping the leg inward toward center line to protect the groin. Keep the guard up and avoid hunching the shoulders or allowing elbows to move away from the body.
Re-chamber immediately to maintain balance. Keep your center of mass over the support foot. Power comes from the thrusting action, not from a forward movement of the center of mass. The thrusting action possesses a great deal of momentum and tends to pull the body after it, causing a forced forward step, so retract the kicking foot quickly into a stable state of balance. If you must step forward, step outside the opponent's lead foot so you will not be vulnerable to a foot sweep.
The kicking motion may begin by lifting the kicking foot with the sole parallel to the floor or by raising the heel first and then springing the foot upward off the ball of the foot. The springing action is quicker but the correct foot shape is not attained until later in the kicking motion.
Kick snap/thrust forward from the knee, so knee must be chamber to a height so that the thigh points at the intended target.
The support foot may remain stationary or twist into the kick. The kick is more powerful without the twist but the twist adds range and presents less of the body as a target. To increase range and power, allow your supporting foot to be dragged forward by the force of the kicking action. When kicking a heavier opponent, this forward movement resists the recoil from the impact more effectively than would kicking from a rigid stance.
Motion, The ball of foot is applied to the target by either a snapping or thrusting motion. For the snap kick, the knee is pointed at the target and the lower leg is snapped into the kick with a thrusting motion. The knee must be raised high enough that the foot does not just slide up the surface of the target. For the thrust kick, the knee rises higher than the target and then drops as the foot extends and the hip is thrust behind the kick. Although the leg and knee may move in many directions, the foot itself moves in a straight line from the floor to the target.
Direction. Most people think of a front kick as being executed toward the front, but, unless you are righting from a basic front stance, you will actually be executing the front kick toward the side. For example, think of firing a lead leg front kick from a back stance. The kick is actually firing out to the side.
Contact. The traditional front kick uses the ball of the foot to strike the opponent. This is an effective way to kick, since the striking area is small. It focuses the power, and the padding on the sole of the foot protects the bones of the foot from injury. To kick this way, the foot is angled forward and the toes are angled backward to protect them. When the toes are angled backward, they will naturally flex backward even more as impact is made. Pointing the foot and pulling the toes back by muscular action slows the kick because it stiffens the movement of the knee joint. A compromise is to pull the toes back only enough to prevent them from striking first and then letting them flex as needed. The instep of the kicking foot should line up with the shin. Dropping the heel too low causes ankle to flex and it may collapse, causing injury during a hard impact. Practice correct foot position by standing on the balls of the feet with the heels held high. Some styles, such as Uechi-ryu, actually use the big toe as the striking area for the front kick, but this is dangerous to the kicker. The heel may also be used as the striking area. The toes point upward or outward and the heel is pushed forward.
Variations. Front kick may be performed with the leading or trailing foot. Since there is little hip twist and less acceleration distance, the leading leg kick is faster but less powerful than the trailing leg version. However, it is useful for checking an onrushing opponent since the opponent supplies much of the impact force. With the lead leg kick, be prepared to project weight forward, otherwise recoil may drive you backwards. Jumps may be added to front kick.
I once had a Korean instructor who would fire a front kick toward your face, let his foot drop down to your chest, use his toes to grab the front of your uniform, and then pull you in range for a series of hand attacks. He could use his toes as easily as you used your fingers.
Front Thrust Kick
Same as front kick except instead of the foot snapping into the target, the foot is thrust through the target. Instead of the leg snapping from the hip, the hip is thrust forward to push the foot into and through the target. The front thrust kick is not as powerful as the front kick, since it applies its force over a longer period, but it is effective when used attack the target while also pushing the opponent away to give you more room to use other more powerful techniques.
Angular Front Kick
Used to stop, intercept, or check an incoming kick before, or just after, it is executed.
Foot position. The foot is vertical, but twisted outward.
Striking Surface. Strike with the sole of the foot.
Leg Position. Use some chamber, leg snaps and hooks outward, and then re-chamber.
Usage. Use it to kick inner thigh of an attempted side kick.
Movement. Performed similar to a twist kick or a low outside crescent kick, except foot is twisted so sole of foot makes contact.