When is a body shape merely a body shape, and what transforms it into an asana?

It is the suffusion of the body with the breath, of bringing the quality of the breath to the shape, to the movement, that transforms a shape into an asana, a body movement into the practice of yoga. This is what fundamentally differentiates yoga from exercise, and what gives it the power to integrate mind and body. Why? Because making conscious the subconscious act of breathing, and bringing it to bear on the quality of a physical movement requires the conscious mind, the subconscious, and the physical body to engage with each other in an intricate dance that is yoga.

Try it now: Stand up, place your feet parallel and hip-distance apart. Close your eyes, and become aware of your breath. Feel how the breath changes the shape of your body as you inhale and exhale. Feel the front of your chest expand as you inhale, and your shoulder blades slide down the back slightly. Now translate that movement of the chest and the shoulder blades into the arms. Does an inhale encourage an external rotation of the arms? Experiment. On the exhale, also translate the movement of the torso into the arms. With each exhale, allow the arms to return to their neutral position, and allow them to lift again with the next inhale. Repeat this about 20 times, breathing as slowly, deeply, and smoothly as you can, without straining. Keep exaggerating the arm movement as it emerges from the breath until a full inhale lifts your arms fully overhead. Keep repeating the arm movement, and begin to spread your awareness down into your feet as you inhale and lift the arms, and notice whether that creates an even more complete connection between your breath, your mind, and your entire body. On the last exhale, release the arms back down, and stand with your eyes closed for a few more breaths, spreading your awareness throughout your body.