The back kick is an extremely powerful and potentially lethal weapon. It can be much more powerful than a roundhouse kick, carrying over 1,500 lbs. of force upon impact. However, proper execution is more difficult. The primary challenges to the back kick are accuracy and power.
The accuracy of a back kick can be vastly improved by distance. Closer distance is ideal to minimize the chance of missing your target. The closer distance from the target, the better the probability of accurate execution given the wider angle closer distance provides.
The above mentioned challenge of accuracy needs to be complemented with power. As one gets closer to improve accuracy there is less room for momentum to generate power. The challenge is to harness power even from close distance so as to maximize the fore of the kick.
Physics teaches us that force equals mass times acceleration (f=m*a). Greater distance allows for greater acceleration. As it relates to the back kick, the method to achieve greater acceleration from close distance is to raise and bend the knee to about waist level (chambering) before releasing the kick. With chambering, the acceleration is vastly increased. As a result, the power of the back kick, assuming equal body weight (i.e.mass) will increase proportionately with the higher acceleration you are able to generate.
With related practice combining both close distance and clambering, the power back kick will have tremendous force and can become a valuable weapon to add to your arsenal.
— Written by Master Yoo; edited by Hyun Sa Shin Min and Chun Shim