While practicing I like to use the spine as a boney landmark indicating 'center' or middle of my body. While inverted or simply lying on the floor in a gentle twist I can try and use my internal eye to sense this intricate structure and where it is positioned in hope of playing fair with my left side and right side. What blows my mind is the feeling that overcomes the body while doing this. Energy is unlocked. Breath moves more freely. Dare I say that both ida and pingala nadi are able to move more autonomously yet in perfect harmony through sushumna? Perhaps!