The meditator’s goal, on the Hindu spiritual path of Raja Yoga, is to first become aware of energy and then to familiarize himself with it. Next he learns to harness this energy so it does not all flow out of him. Once this is done, his task is to withdraw this energy. As he withdraws this energy, he needs to draw it into and concentrate it in a central location. That central location is the spine.
The spine is the powerhouse of his life and he gathers this accumulated energy here. As he pulls the energy into his spine, he centers his awareness. Where his energy is flowing is where his awareness is going. He feels centered.