Vyana vayu, or "omnipresent air," is the prana vayu that integrates all vayus. Vyana vayu helps to balance the other four vayus, and is present throughout the body. It is not associated with any one area of the body, but rather the entire body, and even extends outward into the area surrounding the body, also known as the aura.

Nourishing and expansive, vyana governs the movement of prana through the nadis—the 72,000 energy channels that flow throughout the body. Vyana also dictates the flow of blood and nutrients through the circulatory system, the flow of chemical and electrical impulses through the nervous system, the movement of fluid through the lymphatic system, the movement of muscles and joints, and even the flow of thoughts and emotions. Truly, vyana brings it all together. 

When vyana is out of balance, everything feels out of balance—mentally, emotionally, and physically. Certainly each vayu contributes to overall balance in the body, but without vyana to coordinate them all, balance cannot be achieved. Like an orchestra without its conductor, it just won’t sound the same. Similarly, you won’t feel up to par unless vyana is well-balanced. 

Overall, a balanced yoga practice will help vyana to flourish. Standing poses are particularly beneficial, because they involve movement of every part of the body, from the center outward. Warrior poses, Trikonasana (Triangle Pose), and Utkatasana (Chair Pose) are excellent balancers of vyana. In addition, the vyana-balancing pranayama practice of nadi shodhana (alternate nostril breathing) will also be beneficial. 

A regular yoga practice, complete with asana (postures), pranayama (breathwork), meditation, and moral contemplation, will work together to bring about overall balance—vyana being the driving force behind all of it. Thus we have the underpinnings—the very mechanisms—that demonstrate how yoga helps us find balance. 
