Sushumna

sushumna, which corresponds in the physical body to the spine. Sushumna nadi lies dormant in most people and becomes active with yogic practices, especially pranayama which focuses on working with the energy body.  HYP pg 493 describes the importance of sushumna nadi, calling it “the main freeway from the depths of the earth to the heights of heaven”.

When the breath flows equally in both nostrils, sushumna is said to be flowing equally – eg danda