One of the main power principles in Kenpo Karate is known as Back-up Mass. Back-up Mass occurs when your weight is directly behind and moving in line with your weapon and strike. The simplest example is stepping through with a punch. The best analogy is a freight train colliding into an object. It is a way to maximize power by using most of your body and weight with a strike.
One of the techniques that exemplifies Back-up Mass is Gift of Destruction. It is against an unfriendly handshake; meaning, the attacker shakes your hand to distract you, because really he intends to punch you. You immediately step in with your left foot, pull on his right hand with your right hand and strike his elbow joint with your left hand; this extends his right arm and turns him to cancel his width zone to nullify his back-up weapon, his left hand. At the same time you drive a knee into the groin, which causes pain and bends him over to cancel him by getting his mind on the pain, getting a nerve reaction and breaking his height zone; you are still in his center-line so you must break the height zone to cancel his back-up weapons. You then check this right arm with your left and land with an inward elbow to the face.
The main point of this technique is that you are basically running into the guy the whole time; so not only have you cancelled his width zone when you pull on his arm and turn him, cancelled his height zone by kneeing him in the groin, but you’ve also penetrated and cancelled his depth zone by charging into him and driving in the knee and the elbow. It is a fast move that is meant to totally overpower the adversary.
Let’s look at the technique.
James shakes Joe’s hand, really with the intention of punching him.
To cancel the back-up weapon, Joe pulls on the right arm, while striking the elbow with his left and kneeing James in the groin. This is Opposing Forces–the right arm goes back, the left in, and the knee out and into the groin.
Joe lands into James with an elbow to the face. Notice here that the movement is all forward and that the weapon goes in while the foot goes down.
So, as you can see, in this technique, your weight is moving forward in line with your weapons as you totally disrupt the attacker’s depth zone and cancel him. Totally a power move and Back-up Mass technique.