BASIC PREMISES :- The last half of the twentieth century saw many schools of hatha yoga take root in the West. Some are based on authentic oral traditions passed down through many generations of teachers. Some are pitched to meet modern needs and expectations but still consistent with the ancient art, science, and philosophy of yoga. Still others have developed New Age tangents that traditionalists view with suspicion. Picture this title placed near the exit of your local bookstore: Get Rich, Young, and Beautiful with Hatha Yoga. I’ve not seen it, but it would hardly be surprising, and I have to admit that I would look carefully before not buying it….. Given human differences, the many schools of hatha yoga approach even the most basic postures with differing expectations, and yoga teachers find themselves facing a spectrum of students that ranges from accomplished dancers and gymnasts to nursing home residents who are afraid to lie down on the floor for fear they won’t be get back up. That’s fine; it’s not a problem to transcend such differences, because for everyone, no matter what their age or level of expertise, the most important issue in hatha yoga is not flexibility and the ability to do difficult, but awareness—awareness of the body and the those who read this book, awareness of the anatomical and physiological principles that underlie each posture. From this awareness comes control, and from control comes grace and beauty. Even postures approximated by beginning students can carry the germ of poise and elegance. MOVEMENT AND POSTURE:- The first organizing principle underlying human movement and posture is our existence in a gravitational field. Imagine its absence in a spacecraft, where astronauts float unless they strapped in place, and where outside the vessel little backpack rockets propel them from one work site to another. To get exercise, which is crucial for preventing loss of bone calcium on long voyages, they most work out on machines bolted to the floor. They can’t do the three things most of us depend on: walking, running, and lifting. If they tried to partner up for workouts, all they could do is jerk one another back & forth. And even hatha yoga postures would be valueless; they would involve little more relaxing and squirming around. Back on earth, it is helpful to keep recalling how the force of gravity dominates our practice of hatha yoga. We tend to overlook it, forgetting that it keeps us grounded in the most literal possible sense. When we lift up into the cobra, the locust, or the bow postures, we lift parts of the body away from the ground against the force of gravity. In the shoulderstand the force of gravity holds the shoulders against the floor. In a standing posture we would collapse if we did not either keep antigravity muscles active or lock joints to remain erect. And even lying supine, without the need either to balance or to activate the antigravity muscles, we make use of gravity in other creative ways, as when we grasp our knees, pull them toward the chest, roll from side to side, and allow our body weight to massage the back muscles against the floor. THE VESTIBULAR SYSTEM, SIGHT, & TOUCH:- So far we seen how motor neurons drive the musculoskeletal system, how association neurons channel our will to the motor neurons, and how sensory input from muscles, tendons, and pain receptors participate with motor neurons in simple reflexes. But that’s only the beginning. Many other sources of sensory input also affect motor function. Some of the most important are the vestibular sense, sight, and touch. BREATHING:- Yogis know nothing of physiology, at least in terms that would have been helpful to 17th & 18th century European scientists and physicians like John Mayow, but for a long time they have made extraordinary claims about the value of studying the breath. They say flatly, for example, that the breath is the link between the mind and the body, and that if we can control our respiration we can control every aspect of our being. This is the endpoint, they tell us, that begins with simple with simple hatha yoga breathing exercises. Every aspect of our being? That’s a lot, by any standard. No matter: even though such comments may stimulate our curiosity, their pursuit is outside the scope of this book. Our objective here is to pursue studies in breathing as far as they can be tested objectively and experientially, and then to discuss some of the relationships between yoga and respiration that can be correlated with modern biomedical science: how different patterns of breathing affect us in different ways, why this is so, and what we can learn from practice and observation. THE SOMATIC AND AUTONOMIC SYSTEMS:- The way we breathe affects far more than our posture, and can best explore those remifications by looking at the two great functional divisions of the nervous system—somatic and at the tissues and organs they each oversee. The somatic nervous system is concerned with everything from the control of skeletal muscle activity to conscious sensations such as touch, pressure, pain, vision, and audition. For the autonomic nervous system, think first of regulation of blood pressure, viscera, sweat glands, digestion, and elimination—in fact, any kind of internal function of the body that you have little or no interest in trying to manage consciously. This system is concerned with sensory input to the brain from internal organs—generally more for autonomic reflexes than inner sensations—as well as for motor control of smooth muscle in the walls of internal organs and blood vessels, cardiac muscle in the wall of the heart, and glands (figs. 10.4a—b). Both systems are involved in breathing.