Pranayama is regarded lengthy or subtle according to its three components, the external, the internal and the steady; the retention processes are modified by the regulations of space, time and number.
When the breath is expired, it is Rechaka, the first kind of Pranayama. When the breath is drawn in, it is the second, termed Puraka. When it is suspended, it is the third kind, called Kumbhaka. Kumbhaka is retention of breath. Kumbhaka increases the period of life. It augments the inner spiritual force, vigour and vitality.