Though it may seem as though yoga is just moving the body into shapes, the true depth of yoga is a spiritual discipline outlined in the the 8-limbs.
The Yoga Sutras
II.29 The 8 Limbs are abstentions, observances, posture, breath control, disengagement of the senses, concentration, meditation, and absorption.
The 8 Limbs
1. Yamas - Abstinence, External Disciplines
2. Niyamas - Observances, Internal Disciplines
3. Asana - Postures
4. Pranayama - Breath Regulation
5. Pratyahara - Withdrawal of the Senses
6. Dharana - Concentration
7. Dhyana - Meditation
8. Samadhi - Bliss, Absorption
Note:
The word Ashtanga translates to 8-limbs
