What is pranayama and why do we practice it

Pranayama is one of 8 disciplines mentioned in the Yoga Sutras of Patanjali. As a practice it evolves from a discipline of watching the breath - breath as object; to a more refined practice where the breath is observed to provide evidence of manomaya kosa (mental emotional body). Finally breath can be applied as an instrument to affect the condition of mind. Within Iyengar methodology, pranayama is recognised as the gateway to pratyahara (internalisation of the senses of perception). Asana, pranayama and pratyahara can all be practised and refined in terms of technique and skill and together these three disciplines bring the outcomes of dharana, dhyana and samadhi (concentration, meditation and transformation).