Wednesday, December 5, 2007

Hatha Yoga and Science

This article is dedicated to Hatha Yoga practitioners, students and those who think they want but are unable to learn Hatha Yoga for whatever reasons.

1. Why practice Hatha Yoga? How to practice Hatha Yoga correctly and why Hatha Yoga should be practiced the way it is taught by competent teachers? These are the questions I will try to answer in a simplistic way to the extent I understand the subject. It will be beyond me for more details.

2. Purposes of Hatha Yoga: Practiced correctly, Hatha Yoga has these benefits: Physical Flexibility and Strength, Balance or stability, Awareness of the self at different levels.

3. Hatha Yoga is not a mere physical exercise; it has to be practiced with the Body, Mind and Breath coordinated.

4. Flexibility: stretching muscles increases its suppleness and length, both increases joint flexibility and hence body flexibility. But the speed with which and the extent to which the muscles can be safely stretched have limits. Stretching too fast causes body to stiffen up. Stretching too far causes the muscles to start trembling and resist the stretch. Hence in Hatha Yoga, we stretch slowly to our comfortable capacity and sustain the stretch for a few breaths.

5. Strength: Muscle tone improves when we concentrate on repetitive movements of short ranges of motions.

6. Awareness: Yoga is always practiced with full attention of the mind. Constant observation of the body sensation, habitual postures and movements, habitual exertion, emotional states, breathing pattern, thought patterns in Yoga practice trains the mind for close observation and enables us to know ourselves at different levels of the self and to correct imbalance of our body as well as incorrect postures or practice.

7. Balance: Hatha Yoga exercises are mainly stretching or postures. Postures cause stretching as well as relaxation. Some postures when practiced with mind and breath coordinated, improves body balance not only in the overall frame of the body, but also amongst and within parts of the body. Balance of body depends on, among other things, muscular strength and integrity, nervous conditions which may be affected by emotional states, sensory perception etc.


8. To understand how and why Yoga works, one should recognize that Yoga is a Science. In Yoga, you use your own bodies as the Laboratories and apparatus and your mind as the scientists. You learn to observe yourselves and improve your movements as well as your precision in your observations.

9. So, keep your mind here and now on the space occupied by your body. In the process, you will note that, for example, inhalation assists elevation whereas exhalation assists going into a posture. So, observe carefully the relationship between breath and efficiency of movements and learn to make use of the breath to assist your movements.

10. Shift from one posture to another smoothly and slowly, clearly understanding the entire process. Respect pain and other strong sensations and conditions. Decide to avoid pain, which is a warning sign of impending physical harm or damage.


11. To know scientifically why Hatha Yoga has the benefits described, let us have a brief look at our nervous systems and muscles and their relationship.

12. Central and Peripheral Nervous Systems

a. Central Nervous System: the brain and the spinal cord.
b. Peripheral Nervous System: all other parts of the entire nervous system


13. Central Nervous System can further be divided into
i. Somatic Nervous System and
ii. Autonomic Nervous System

14. Autonomic Nervous System can further be subdivided into
i. Sympathetic Nervous System
ii. Parasympathetic Nervous System
iii. Enteric Nervous System

15. Somatic Nervous System comes under our conscious control. It innervates skeletal muscle and receives sensory information about pain, touch, vision and audition.

16. Autonomic Nervous Systems largely work independent of our will or conscious control or the somatic system. We should not confuse autonomic with automatic. We can breathe automatically by courtesy of our somatic nervous System. The Somatic and the Autonomic Nervous Systems interact with each other and we constantly depend on such smooth interactions.

17. Sympathetic Nervous System arouses and prepares us globally for emergency and is stimulated by stresses. It also quiets down the body latter when it is sedated by breathing or relaxation techniques. The Sun Salutation is a good Hatha Exercise to stimulate Sympathetic Nervous System and Corpse to calm it down.


18. Parasympathetic Nervous System, in contrast, is organ specific and does not work globally. It manages the functions of many internal organs and structures for us at the unconscious level.

19. The Enteric Nervous System is new to many. It supervises the digestion and propulsion of food through the bowel and manages other bowel functions. And it is found to be related to emotional states but not enough is yet known. It is important to relaxation.

20. Neurons: 100 billion in the brain alone. They are the basic structural and functional units of the nervous systems. Neurons have several components. A nucleated cell body that supports growth and development. Cellular extensions that receive and transmit information. There are two types of extensions: dendrites and axons. Dendrites receive information. Axons transmit information in the form of nerve impulses to other sites. There are many dendrites and only one axon per neuron.

21. Three types of neurons are important in Hatha Yoga:

a. Sensory neurons: carry the flow of sensation from the peripheral nervous system to the central nervous system and consciousness.
b. Motor neurons: carry instructions from the brain and spinal cord into the peripheral nervous system and from there to muscles and glands.
c. Inter-neurons: interposed between sensory and motor neurons and transmit our will and volition to the motor neurons.

22. Volition: Actual initiation of the ON and OFF commands from the cerebral cortex and other regions of our Central Nervous System that are responsible for commanding our action.

23. Reflexes are opposed to volition: Reflex is response that bypasses high centers of consciousness, e.g. cerebral cortex. For speedy reaction, the information is passed to the spinal cord and decision is made there without referring to the cerebral cortex. There are dozens of reflexes, three of which are important in Yoga.

24. Myotatic stretch reflex: Better known as knee jerk. They are found all over the body, but especially active in antigravity muscles. They should be minimized to avoid muscle shortening that limits stretch. That is why you move into a posture slowly if your aim is lengthening muscles and increasing flexibility.

25. Clasp knife reflex: Also a stretch reflex. Its end result causes the target muscle to relax rather than contract. Incoming axon does not terminate at motor neuron but at inhibitory interneuron. This reflex can be used to advantage in flexibility exercise.

26. Flexion reflex: This is a kind of Pain reflex. It not only activates flexor muscles but also relax extensor muscles, to make the flexion easy.

27. Muscle movements: By itself, muscle contracts or relaxes. Muscle does not pull itself though it may relax and allows to be lengthened when pulled by an external force. Muscle contracts when the motor neurons impinge impulses on it on command from the Central Nervous System. The strength of the contraction depends on the rate of impulses reaching the muscle. When there is no nervous impulse, the muscle relaxes.

28. In hatha practice, we cause the muscles to shorten or lengthen. Shortening is generally concentric. Concentric shortening takes place when muscle fibers stimulated by nerve impulses responded by the entire muscle shortening. Lengthening, however, is generally eccentric. Whenever a muscle increases in length under tension while resisting gravity by contracting some of its fibers, this is called eccentric lengthening. Note that gravity is an external force that can cause relaxed muscles to lengthen.

29. Stretch receptors are pain receptors found in the bellies of muscles. When muscles are stretched by external forces too fast or too far, the receptors are triggered off and muscles start to contract as a self defense mechanism to resist the stretching which may lead to muscle tear.

30. Isotonic exercise strictly refers to shortening of muscles under a constant load but the term is now used loosely to denote exercises involving movement under moderate or minimal resistance. Raising and lowering a book in your hand repetitively is an isotonic exercise. Isotonic exercise increases strength.

31. Isometric exercise involves holding still under substantial resistance. Holding a book without raising it or allowing it to fall is an isometric exercise of the same muscles. After 15 seconds or so, the stretched muscles start to relax and lengthen if the stretch is within comfortable limits. Otherwise the stretch receptors will be triggered off to resist the stretch.


32. To gain flexibility, you stretch slowly and within your comfortable capacity and sustain the stretch for a few breaths which last for more than the 15 seconds or so required for motor neurons to stop impinging nerve impulses on the muscle tissues concerned thus allowing them to relax and lengthen under the stretch without triggering the stretch receptors or go slowly into a posture which results in a moderate stretch. The individual muscle fibers can growth also in length by the addition of sarcomeres.

33. To gain strength, you have to work up the motor neurons to keep on firing nerve impulses to the muscles tissue concerned to contract the tissues and this can be achieved by repetitive movements of short ranges of motions. The strength of the contraction is proportional to the rate of nerve impulse impinging on the muscle fiber.

34. The above two exercises are done with volition, that is, within the conscious control of your cerebral cortex. What happen if you simply toss your body parts without conscious control? You may activate reflexes which may not work towards your objective. Reflexes are controlled from your spinal cord, not from your cerebral cortex, the higher consciousness.

35. But this does not mean reflexes are always counter productive. Some of them can be productive but you need to select the right ones to activate to your advantage. You must know yourself better and use the knowledge to advance your objectives.

36. Balance requires not only flexibility and strength, but also keen senses and training. Flexibility enables you to arrange your body parts in a balanced architecture, strength allows you to maintain such architecture even under limiting conditions and your senses guide you in doing so and training gives your efficiency in doing so quickly and with little effort.

37. The act of breathing is a somatic act of skeletal muscles. When we breathe consciously, we command from the cerebral cortex; when we don’t, the command shifts to the medulla and pons at the brain stem. These lower centers of respiration manage somatic aspects of breathing automatically.

38. The Sensory limb of Autonomic Nervous System carries information on oxygen and carbon dioxide levels in the blood etc to the respiration centers. This is the important link between Somatic and Autonomic Nervous Systems in respiration. There are also other ways in which breathing is affected by the autonomic mechanisms.

39. Quiet breathing influence the autonomic circuits that slow heart beats and reduce blood pressure, producing calm and sense of balance.

40. To relax, all these aspects must be tackled. First skeletal muscular relaxation, which depends on somatic activities, requires the sympathetic system be quiet down, the parasympathetic system is not busy managing house keeping, the Enteric system is not digesting food or concern with regrets of past, anxiety for future, fear of the unknown or a overly joyful mood of the present.


41. We normally end a Hatha session with Systematic Relaxation in the Corpse. Corpse posture keeps muscles still and allows the motor neurons to stop firing impulses and thus allows the muscles to relax. But muscles can be aroused by mental activity too. Keeping the mind working on simple task focuses it and over time the mind also quiets down.

42. There are obvious warning signs to excess in physical exercises, but not in breathing exercises. The traditional warnings are many. It seems that the rhythm and record of breath resonate throughout the body. It seems to accentuate whatever is in the mind, good or bad.

43. Deep relaxation also should not be overdone. Motor neurons get lazy and you may lose your capacity to control them. Or even worse, you do not get feedback of this happening. Practice relaxation, therefore, not more than twice a day of no more than 20 minutes per session.

By Hiew 2007

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