Asana is the use of very specific physical postures. This is the foundation from which everything else is built. In fact, without the other techniques being applied, Hatha Yoga is little more than step or gymnastics. Only through the use of asana, vinyasa, bandha, pranayama, and drushti can the ultimate benefits of yoga be gained.
In yoga there are hundreds of postures. This is essential in order to penetrate the complex, and subtle depths of our neuromuscular system. Basic postures work more superficially. The more complex the posture, the more deeply you work. It is counter productive to try, and master the more complex ones before the basic tensions have been released by the more simple Asanas.
Sure, you might be able through strength, or flexibility, determination, or relentlessness to attain the shape of the pose. But this like everything, has its price. You will never obtain the freedom that is so much a part of the yoga experience. You are simply imposing new patterns of force, hardness and tension on old. It is essential that you work the other way: layer by layer, stripping away wall after wall that we have built up throughout our lives.
Every muscle, every organ, joint, and nerve is likely to be impregnated more, or less, with some kind of tension. Everyone has their own particular pattern. But, almost all of us suffer from some sort of restricted functioning of our bodies. Mentally this can manifest itself as anxiety, worry, obsessiveness, and the like.
On a physical level you can experience hardness in the muscles, tightness in the joints, dullness in the nerves, stagnation in the capillaries, and veins. All combine to limit our range of physical, perceptual, emotional, and intuitive responsiveness. It is imperative to dissolve the restricting tensions in order to make available responsiveness,
Asana will challenge the muscles, and joints to access their full potential. When that potential is realized, blood, and nerve impulses can flow freely. Each Asana challenges a different network of cells in muscles, tendons, ligaments, and organs. One by one they work systematically into every part of the body.
To master a specific Asana means to release a specific pattern of neuromuscular relationships from all tension. It also means to supply certain muscles, glands, and organs with oxygen, glucose, minerals, and energy through the blood flow.
To release even one of these patterns takes time, and constant, consistent repetition. Repetition of the actions of the Asana, including asana, vinyasa, bandha, pranayama, and drushti, over, and over again. It takes time to replace old habits with new. If there is discontinuity in this repetition the old pattern will reassert itself. Consistent means to activate the Asana always in the same manner, involving the correct, judicious use of asana, vinyasa, bandha, pranayama, and drushti.
As tension begins to leave us, we have an epiphany. Something of great magnitude is revealed. This is that the body, and mind cannot be functionally separated. What we find is that each area of physical resistance, (tension, stagnation, dullness, hardness, weakness, irritation) embodies an emotional pattern. When the habituated, physical pattern begins to be released, the emotional pattern begins to emerge. This means that Asana can, and inevitably will, bring about an emotional release.
If we do not apply all the techniques this very important process can also be hindered by our practice. If concerned only with alignment, developing heat, or powerful breathing, it is easy to override this process which forces the emotional pattern deeper. Approach the postures with the deliberation of asana (alignment), the fluidity of vinyasa, the subtlety of bandha, the rhythm of pranayama, and the attentiveness of drushti. Then the underlying emotional pattern will be challenged and released.