In Ashtanga Vinyasa Yoga we teach that by mastering the third limb, asana — we can then provide a firm foundation from where we can explore the other limbs. These branches support each other. Asana practice must be established for proper practice of pranayama and is a key to the development of the yamas and niyamas. Once these first four externally oriented limbs are firmly rooted, the last four internally oriented limbs will gradually evolve over time.

There are 3 groups of sequences in the Ashtanga Vinyasa Yoga method. The primary series (yoga chikitsa) detoxifies and realigns the body. The intermediate series (Nadi shodhana) purifies the nervous system by opening and clearing the energy channels. The advanced series A,B,C,D (Sthira bhaga) integrating the strength and grace of the practice. 

Ashtanga Yoga practiced in its correct sequential order gradually leads the practitioner to a vibrantly healthy body and mind. Each posture and sequence is in preparation for the next, developing the strength, flexibility and balance required to move further into the practice. 
For more information on Ashtanga Yoga www.KPJAYI.org