Asanas (in Sanskrit meaning ‘convenient positions of the body’), the physical exercises used within the Hatha Yoga system, first of all affect the musculoskeletal system that performs the locomotor functions, moving and balancing the body within the space. The condition and the function of bones, muscles, ligaments and joints is subject to monitoring and control from the central nervous system, which peripheral part is composed by a large amount of various types of receptors. These are the muscles spindles in muscles, the Golgi tendon spindles in ligaments, and another 4-5 types of receptors that they figure out in joints. Thus, we have an extensive receptor field, «the body of the muscular sense» that provides adaptive response of the organism to the environment.
The substratum of the «muscular body» is represented by the aforementioned muscle and joint spindles that come as the peripheral part of the so-called gamma-motor system responsible for the formation and regulation of the most common motor responses of the phase and tonic type. In scope of this system the afferent impulses (the signals coming from muscles) partially switch onto the spinal cord motor neurons and from here the signal goes along the efferent (motor) pathways back to the muscle causing the corresponding action. Another part of the same afferent impulses go to the medulla oblongata (the fibers of the first order) along the ascending pathways. Hence originate the second-order fibers (the so-called medial loop) that end within the ventro-basal complex of the thalamus. From these nuclei there originate the neurons of the third order that are sent to the cerebral cortex, the somatosensory fields in the anterior central gyrus.
Thus we receive a system that can quite soundly operate on several levels. When a rapid response in a stressful situation is required, in terms of a sudden impact, when the level and the speed of the stimulus affecting the muscle are substantial enough, the reflex shall retreat into the spinal cord providing a protective response in scope of emergency conditions. In this situation the action shall be of stereotypical character (the example of it is a well-known knee-jerk response to stimulation of one’s tendon). No new reflexes shall be thus formed. This comes in contrast to the situation when the reaction to the stimulus is formed in terms of a slow response. In such a case the response shall involve all levels of the central nervous system and the whole somatosensory system that combines the impulses coming not only from the musculoskeletal system, but also from the receptor fields of the skin, vestibular apparatus, visual system, acoustic apparatus and other structures. The mobilization of such a large number of structures is necessary for formation of a new way to responding to the situation — the so-called dynamic stereotype — the system of spatiotemporal relationships between organs and systems (the P. K. Anokhin’s reafferent concept, the N. A. Bernstein’s concept of the reflex ring).
Hence comes a very interesting fact — it is this very slow performance of asanas, with slow “coming into” the pose and slow “going out” of it that enables the involvement of a large number of receptors and systems which purposes at and results in conscious establishment of a new movement stereotype. This is one of most essential differences of yoga exercises that distinguishes it among other various types of gymnastics.
There are also some interesting results of the studies performed by J.M. Petit et al. (1962). Having studied the EMG data for respiratory muscles-the antagonists they have found that in scope of fast work (rapid breathing) the muscles do function in alignment, while in terms of slow performance their dis-coordination can be observed. That is, the usual stereotyped movements do “dissolve” thus making way to the possibility of forming new interactions that are more effective in terms of their functionality. The performance of asanas in the same very slow mode also enables the correction of non-adaptive static and dynamic patterns, the so called pathogen arcs formed during one’s previous life. Most part of adults have these pathogenic arcs that are based upon disharmony in one’s emotional sphere, the traumatic experiences of the past, etc. (The simplest manifestation of pathogenic arc is the contraction of facial muscles (the aggression mask) or arms in one’s attempt to take mulabandha (a yoga exercise that comes to deliberate contraction of the perineal muscles) – A.G. Safronov “Yoga: Psychology, Psychosomatics, Bioenergetics”)).
Such practice of asanas when performed regularly promotes training of the nervous system, formation of some degree of nervous processes’ flexibility in generation of new, diverse and sustainable interneuronic links.
The asanas «appeal» to this very cortical part of CNS that is young in terms of evolution. It increases the amount of strong-willed, conscious processes within the human psyche structure and promotes working out one’s awareness, gives a practicing person the possibility of earning an important quality — the ability to change the behavioral patterns not subject to the environment that changes us “forcefully” but of our own accord that is based upon the current needs of our development. And this already comes as the art of managing our body and mind.
On the one hand, the practice of asanas should be regular so that the generated dynamic stereotypes could become established; on the other hand the complex should be constantly replenished with new, unusual positions, since in the reflex centers there can be observed the phenomenon of habituation — weakening of the reactivity, “habit formation” in respect of the stimulus.