This will give a tutorial on how the mechanics of a fast kick looks. You will still need some strength in your legs to develop fast twitch muscles or power muscles to be able to go faster. The relaxed technique shown here should allow those who have already trained their legs to kick.
about ROUNDHOUSE KICK
A roundhouse kick (also known as swinging kick or a power angle kick but often confused with the round kick) is a kick in which the attacker swings his or her leg around in a semicircular motion, striking with the front of the leg or foot.
This type of kick is utilized in many different martial arts and is popular in both non-contact and full-contact martial arts competitions. The kick has many variations based on stance, leg movement, striking surface, and the height of the kick.
The taekwondo roundhouse kick, known as dollyŏ chagi, is performed by first drawing the knee straight up in a “chamber” position. This chamber, identical to the chamber of many taekwondo kicks (front kick, side kick, etc.) is utilized so that the opponent cannot guess which kick will be thrown.
This differentiates it from muay Thai and other roundhouse kicks, which tend to incorporate rotation before or during the rising of the knee. The knee is then rotated so that it is nearly parallel to the ground (counterclockwise for the right leg roundhouse) and the kicking hip is simultaneously rotated towards the opponent.
The rotation of the hip, combined with the snapping of the leg forward, gives the kick its power. The striking surface is the instep or the ball of the foot. In this way taekwondo differs from Chinese sanshou, where the striking surface is the shin. This is also called an “off the line” or “rear leg” roundhouse kick.
The roundhouse kick can also be thrown from the rear leg towards the target and strike with the lower shin or the instep. This method is to get a quick strike on the opponent before they see it coming. The kick is swung and then snapped in front of the practitioner to give them more power and velocity. The taekwondo kicking method is unique on its own.
A similar kick is the front leg roundhouse, or “fast kick.” To begin the front leg roundhouse kick, the leading leg is chambered, then rotated and snapped towards the opponent in the manner described above. The fast kick version is done by skipping forward with the rear leg, moving the kicker towards the opponent while simultaneously chambering and snapping the front leg roundhouse.
This method was used by early American full-contact karateka Bill Wallace, a student of taekwondo as well as karate, to great effect. The front leg kick is generally weaker than the rear leg roundhouse because the hip does not rotate as far; however, it is also generally faster because the leg travels a shorter distance before striking the opponent.