The Pranas have many special actions in Yogic practices. On a spiritual level, Samana Vayu governs the space within the heart (antar hridyakasha) in which the true Self, the Atman dwells as a fire with seven flames, governs the central internal space or antariksha. Samana regulates Agni with fuel, which must burn evenly. Without the peace and balance of Samana we cannot return to the core of our being or concentrate the mind.
Vyana governs the movement of Prana through the Nadis, keeping them open, clear, clean and even in their functioning. Apana protects us from negative astral influences and false teachers. Prana itself gives us the proper aspiration for our spiritual development.
Udana governs our growth in consciousness and takes the mind into the state of sleep and into the after death realms. Udana also governs the movement up the shushumna.
The mind moves with Udana Vayu. This takes us to the states of dream and deep sleep. After death it leads the soul to the astral and causal planes. Udana is often the most important Prana for spiritual growth.
As we practice Yoga the subtle aspects of these Pranas begin to awaken. This may cause various unusual movements of energy in body and mind, including the occurrence of various spontaneous movements or kriyas. We may feel new expanses of energy (subtle Vyana), great peace (subtle Samana), a sense of lightness or levitation (subtle Udana), deep groundedness and stability (subtle Apana), or just heightened vitality and sensitivity (subtle Prana).
Working On Prana
Proper nutrition brings about the increase of Prana on a physical level. This also requires proper elimination. In Ayurvedic thought the Prana from the food is absorbed in the large intestine, particularly in the upper two-thirds of this organ, which is not simply an organ of elimination. For this reason Apana Vayu is the most important Prana for physical health.
The Vedas say that mortals eat food with Apana, while the Gods eat food with Prana. The mortals are the physical tissues. The immortals are the senses. These take in food via Prana itself. Right food sustains Apana. Right impressions support Prana. For this not only outer factors like contact with nature, but also practices like rituals and visualizations are important, as well as sensory therapies involving color, sounds or aromas.