The concentration principle is the mind-body connection to your workout. As you exercise you are concentrating on the movement. You become aware and connected to the muscles used and stabilized in each exercise. As you concentrate on moving your body you will become stronger, more flexible and efficient.
The roll up is a good example of how this principle comes into play. As you roll up, you are concentrating on deepening your abdominals to lift your body. As you roll down to the mat you are focusing on keeping your abdominal engaged to lower slowly vertebra by vertebra onto the mat.
The concentration principle can be used in everyday activities anytime from sitting at your desk to picking up a grocery bag. When sitting on a chair you are aware of your back upright, shoulders back and relaxed. When picking up groceries, you focus on bending your knees to lower the reach.
Establishing a mind body connection to movement will lead to more balance and graceful movements in life.