Winds of Yoga

The Vayus - or winds are subtle forms of energy

Prana Vayu

governs the chest and respiration

Apana Vayu

governs the lower abdomen and elimination

Samana Vayu

stokes the gastric fire and aids digestion

Udana Vayu

which dwells in the thoracic cavity and governs intake of air and food

and Viyana Vayu

which pervades the entire body and distributes energy from food and breath.

from the Introduction of Light on Yoga