On either side of the (astral or energetic, not physical) spine there is an energetic nerve channel, or nadi : ida on the left and pingala on the right. Energy automatically moves up the ida nadi, and down the pingala nadi, along with the breath.
When prana, or energy, travels upward through the ida nadi, the breath is automatically drawn into the lungs. As a result, the mind is drawn outward to the world of the senses. This upward movement, taking place outside the deeper channel of the sushumna, signifies an affirmation of temporal, not of eternal – of external, not internal – values. [ref name=”aas13″]The Art and Science of Raja Yoga, Swami Kriyananda. Step Twelve, “The Anatomy of Yoga.”[/ref]