The term Asana is sometimes translated with “pose”, but this is not a proper word to explain what Asana is. A “pose” is not a natural position of the body: it can be an artificial position that is assumed for expressing an emotion or a thought.
The asanas on the contrary have nothing “to express”: on the face there is not some “expression” during the practice of the Asana. A “pose”, assumed for some seconds, can conduct to a physical and mental effort. The Asana doesn’t produce tiredness on any level: contrarily, a feeling of comfort is experienced after the session is finished.
Another term that is reported for the Asana is “exercise.” This however is inaccurate: an Asana is not a simple physical exercise. The physical exercise involves fatigue as it happens in body-building. And the expression “physical exercise” gives the idea of rapid and forced, repeatedly performed movements of the whole body or of part of it. The Asanas are primarily of static nature: there are no repetitions, neither tension, neither muscular fatigue.
The Asanas can be defined only as postural models. The posture required by a given Asana must slowly be achieved, then it must be maintained staying firm, and finally must be slowly discarded with sweetness of movements. In the different Asanas the whole body and mind are involved through particular neuromuscular mechanisms in the execution: this fact gradually brings some specific changes in the whole personality of the individual.
What is essential is therefore the postural model that the Asana implicates: to it partakes the function to educate the body and mind, preparing them to the more advanced yogic practices of pranayama, dharana and dhyana. The phase of movement of the asana is not important. Every Asana implicates two phases: (a) dynamic phase; (b) static phase. In the execution of the Asana some movement is necessary, to assume the Asana and to return to the initial position.
These movements must be slow, secure, soft and without jerks, so that there is no tension or tiredness. The breath must stay normal: in the phase of movement of the Asana there is no voluntary control of breath. As a rule the body has to find the correct respiratory rhythm during the phase of movement.
The static phase, once that the posture has been assumed, must be maintained staying immovable for a certain time, without effort or uneasiness: there must not be undue tensions in any part of the body. In this phase, nevertheless, the awareness of breath or concentration on a mental image of a vast ocean is required, so to avoid that the mind is disturbed from the flow of thoughts or from any emotion. At the end of the phase of maintenance the Asana has to be accomplished in a slow and gradual way.