Asana, literally, means a posture. By common usage, the term is most often used for the postures which form a part of yoga. To make that more clear, sometimes these postures are called yogasanas. Asanas are classified into three categories depending upon whether they are meant primarily for relaxation, physical exercise, or meditation. In this discussion, we shall restrict ourselves to the asanas which are primarily meant to give us some physical exercise. A typical asana begins with a starting position. From this position, the person goes towards the final posture through a series of slow, gentle and graceful movements. After reaching the final posture, the person holds the posture for 10-15 seconds, or longer. The final posture is a position of intense but enjoyable stretch. One of the requirements in the final posture is that the person should be stable and comfortable. After staying in this position for 10-15 seconds, the person returns, once again through slow and graceful movements, to a relaxed position. The person may spend some time in relaxation before going to the next asana. In other words, there are three stages in the asana – initial position (relaxed); final posture (stretch), which is maintained for a while; and return to a relaxed position. The transition from the first stage to the second, and that from the second stage to the third may be synchronized with breathing. How to enter into a posture, and how to come out of it, are at least as important as the posture itself. That is why, asanas are best learnt personally from a competent teacher rather than from a book.
One of the unique features of asanas is that although they involve physical exercise, they are not tiring; in fact, at the end of a session of asanas, the person feels rejuvenated. This happens due to a variety of reasons. First, asanas involve no jerky movements. Secondly, stretch alternates with relaxation. Thirdly, the sequence of asanas is so arranged that every pose is followed by a counter-pose. If a posture involves bending forwards, the next asana involves bending backwards. Thus the stretch produced by one asana is neutralized by the next one. Finally, postures are interspersed with relaxation, and the session ends with relaxation.
It is natural to compare asanas with other forms of physical exercise such as walking, jogging, swimming and sports. In contrast with asanas, most of the other exercises are tiring. Secondly, a set of judiciously selected 15-20 asanas gives comprehensive exercise to every joint and muscle, whereas other exercises may involve a relatively limited group of muscles. Hence asanas are, in general, better than other exercises with respect to improvement in flexibility of the body and coordination of movements. Thirdly, although the intensity of exercise in asanas is low, the improvement in fitness is comparable to that achieved by other far more intense exercises. This happens because the breathing excursions and fluctuations in abdominal and thoracic pressures in yogic postures are comparable to those in intense exercises, and therefore the improvement achieved in functioning of the heart and lungs is also comparable. However, lower intensity of exercises means that asanas do not burn too many calories, and therefore cannot contribute as much to weight loss as some vigorous exercises. Finally, asanas are done with full consciousness. Therefore they lead to an enhanced sensitivity to the goings-on in the body, leading to early detection of fluctuations in well-being, and avoidance of accidents. Asanas also have some practical advantages as compared to other exercises. Because of their gentle nature, injury is unlikely. Secondly, if there is pain in some part of the body, it may still be possible to do at least those postures which do not hurt. Therefore, the regularity of practice is generally not affected by minor aches and pains. Finally, asanas can be done at home, even in night pajamas, in any weather, and need no equipment.
Asanas are a part of yoga, and yoga is a spiritual discipline. What is the link between these physical practices and spirituality? While it is true that yoga is a system primarily designed for spiritual growth, spiritual growth cannot be achieved in a vacuum. It is by living a life consciously directed by the goal of spiritual growth that we can get closer to the goal. One of the requirements of life driven by spiritual growth (or any other goal) is that our instruments for living should be in good shape. Body is the principal instrument of life. Keeping it healthy is therefore important for living a life of purpose. When the purpose is spiritual growth, keeping the body healthy becomes not just important; it becomes a sacred duty. Therefore, asanas should be done with the attitude that we are doing them to keep the body healthy, and that we want to be healthy so that this body can be a fit instrument for doing what God has sent us to this world for. This is the spirit behind the prayer with which a session of asanas generally begins and ends. It is only when asanas are done with this attitude that they become yogasanas. Without this attitude, asanas are just physical exercises; with this attitude, even other exercises like walking become a part of yoga.