What is āsanas?

In Patañjali Yoga Sūtra, āsana is introduced through the sūtra “Sthira-sukham āsanam.” Āsana is described as that which is stable and comfortable. The purpose of āsana is not simply to perform different physical postures, but to make the body stable and comfortable for spiritual practice.

Āsana is important because when a person sits for sādhana, the body should remain stable for the required period of practice. If one cannot sit properly even for a few minutes and continues moving the legs, head, hands, or body, the āsana is not stable. When the āsana becomes stable, it supports the practitioner in remaining seated during sādhana.

The purpose of āsana is therefore connected with the practice of remaining steady and comfortable while sitting.
The body should become sufficiently stable that the practitioner can remain seated for a period of time without being disturbed by unnecessary movements.

The discussion also emphasizes that āsana should not be understood only through the large number of physical postures commonly associated with yoga.
The important point is that the āsana should support sādhana. The practice is described as moving from effort towards effortlessness.

Patañjali’s description of āsana is further connected with the idea of freedom from the disturbance of the pairs of opposites. Once āsana becomes established, heat and cold and other such opposites should not become obstacles in the practice.