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
