The usefulness of kicks in self-defense and actual combat has been debated. Some, like Bruce Lee, have commented that the leg, thanks to its size and weight, is a more powerful weapon than the arm. Because the leg is longer than the arm, kicks tend to keep an opponent at a distance and to surprise him or her with their range.
On the other hand, stance is very important in any combat system, and any attempt to deliver a kick will necessarily compromise one's stability of stance. The practicality of kicks is thus a question of the tradeoff between the power that can be delivered vs. the cost incurred to balance. Since combat situations are fluid, understanding this tradeoff and making the appropriate decision to adjust to each moment is key.
The high kicks practiced in modern martial arts or the flying/jumping kicks performed in synthesis styles are primarily performed for conditioning or aesthetic reasons. The proponents have viewed that some high front snap kicks are effective for striking the face or throat, particularly against charging opponents, and flying kicks can be effective to scare off attackers. Some contrasting views have stated that high kicks are completely ineffective as it would be much quicker and more probable to be able to strike the throat, nose or face with a palm strike for the face or a claw hand to strike at or choke the throat. It has been noted that high kicks (and other complicated kicks for that matter) can be almost impossible to perform in an actual confrontation due to the adrenal shock that one experiences in a stressful situation. This "adrenal dump" as it is called by some experts, causes the body to lose the ability of fine motor control, which is what many modern high kicks require to perform. Additionally, high kicks nearly always expose the groin, inviting a swift kick to the area from an agile opponent. As a result, the use of high kicks in defensive situations is considered risky at best for anyone but highly skilled martial artists. It should be further noted, that many styles use a more vulnerable stance (circular stance) that exposes the groin constantly (as noted by Bruce Lee for example in his defense manuals). Linear stance such as in Shotokan Karate, Wado Karate and most other original forms of Karate and Te fighting do not expose the groin. Taekwondo, Jeet Kune Do, and Shotokan Karate share nearly identical stances in terms of the initial attack and even after basic attacks (roundhouse, front kick, etc.). As with the varieties of kicks themselves, the choice of stance reflects a tradeoff between speed, commitment, power, range, balance, and maneuverability. Some self defence experts only condone the use of kicks as an intimidation or distraction tool, scaring off the attacker or distracting them so other techniques can be used. ( see Geoff Thompsons "real kicking" and "the fence" ) and even then only advocate the use of kicks to the lower abdomen at the highest.
The general consensus is that for most defense and combat applications, simple kicks aimed at vulnerable targets below the chest (self defence experts such as author and teacher Marc Macyoung claim that kicks should be aimed no higher than the waist/stomach) may be highly efficient, but should be executed with a degree of care. Thus, the fighter should not compromise their balance while delivering a kick, and retract the leg properly to avoid grappling. The front kick could be aimed at the groin/pelvis area when attacking, or to the waist/stomach area when being used defensively, knees and shins, inflicting respectable damage. The defensive side kick is a great move for stopping a blitzing opponent. The roundhouse kick performed at low level may be effective due to its power, and the vulnerability of many of its targets ( knees, ribs etc.) since attacking leg muscles will often cripple opponent's mobility, however the technique still throws a fighter's balance off and leaves them vulnerable. It is often recommended to build and drill simple combinations that involve attacking different levels of opponents. A common example would be distracting an opponent's focus via a fake jab, following up with a powerful attack at the opponent's legs and punching. Further, since low kicks are inherently quicker and harder to see and dodge in general they are often emphasized in a street fight scenario.
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