स्थिर सुखमासनम् ।
Sthira sukham asanam.
-Patanjali Yoga Sutra II:46
This aphorism gives us an idea about the main characteristic feature of asana. It says, asana is that which contributes to stability and comfort. Here stability does not mean the stability of body only but the stability of both the body and mind. Even if we remain stable in asana, we may remain mentally unstable due to various disturbing sensory inputs. Only the stability of both the body and the mind together would lead us to the sense of well-being.
It also does not mean that any position or posture of the body which is easy to attain and comfortable to maintain stably, is an asana. In that case perhaps sleeping (recumbent) position would have been the best asana, being easiest and most stable one. Since the word asana is related more with the sitting condition and also with the stability as well as the feeling of well-being it indicates the conscious state of the individual and not the sleeping condition. Therefore any postural pattern, particularly in a sitting condition, leading towards physical and mental stability as well as a sense of well being is an asana.
Asana is often transalated as posture. Even though Asana is not simply a posture, it is more then that - how it is acquired and controlled. Standing posture, sitting posture and a recumbent (lying) posture are three basic postures, characteric of human being, developed during the evolution.
We can also acquire certain basic psoture of animals and birds, because of our motor skills. By assuming such postures voluntarily, we may activate certain special area or the sub-cortical brain centers of coordination.
किरात तदासनम् स्थैर्यम् आरोग्यं चांगलाघवम् |
Kurvat tadasana sthairyam arogyam changalaghavam.
-Hathapradipika I:17
By practicing asanas the stability, health and suppleness be achieved. In nutshell we can say that,
Yoga is essentially a path to get liberated from all the bondages. However, medical research in recent years has uncovered many physical and mental benefits that Yoga offers, corroborating the experiences of millions of practitioners. A small sampling of research shows that:
A few dietary guidelines can ensure that the body and mind are flexible and well-prepared for Yoga practice. A vegetarian diet is usually recommended, and for a person over 30 years, two meals a day should suffice, except in cases of illness or very high physical activity or labour.