In our most recent Self-Defense class we worked on using the center. It is an easy concept to understand, while also being one of the most difficult concepts to practice.
The premise is that if you are being attacked or are fending off an attack you want your opponent off balance and off center. You never want your opponent squarely over his base of power and at the same time, you want to remain over yours.
What comes into play is learning how to gauge distance, how to use your body and learning how to apply torque and twisting movements as well as when to take a step back, forward or to either side. Everything we do in self defense uses the concept of centering. When an arm is presented, if you allow the attacker to keep his arm close to his center, this provides leverage and makes it difficult to apply the correct biomechanical response to your advantage. When the same arm is moved away from the center, it becomes much easier to apply force and reinforce the biomechanics of the body, this allows for an easier execution of the self defense technique.
Likewise if you are being attacked, you should remain over your center and control where your balance and power are derived from. Remembering that much if not all of the power is generated from your hips using torque, centering becomes even more important. A lack of awareness in this area will result in poorly executed techniques and a lack of power in strikes.
Remember to always stay centered.
strong spirit-strong mind-strong body
Sensei Orlando