These practices bring control over the respiratory impulses which form one of the channels of the flow of autonomic nerve impulses. Holding of the breath for a prolonged and comfortable time is an essential technique of Pranayam. However, in the initial practice, the breath holding phase is completely avoided and an emphasis is put on the breath holding phase is completely avoided and an emphasis is put on the controlled inspiration and expiration with a time ratio of 1:2 between them. The expiratory phase is not affected in its slow and controlled inspiration.
There are many varieties of Pranayama which use different permutations and combinations of breathing techniques through one or two nostrils or sometimes inspiration through the mouth.
The three phases of Pranayama, namely Controlled Inspiration, Controlled Retention, and Controlled Expiration are technically known as Puraka, Kumbhaka, and Rechaka respectively.
The main purpose of Pranayama is to gain control over the autonomic nervous system and through it influence the mental function. It is useful in higher yogic practices like meditation.