Yoga is a traditional and cultural science of India. Apart from yoga, India has contributed other sciences like Sanskrit grammar, mathematics, kama sutra, and Ayurveda to the humankind.Ayurveda includes yoga as a part of an ideal lifestyle and maintenance of health (swastha vritta). Lord Krishna has explained in the Bhagvad Gita various faculties of yoga. Yoga is further explored in the great treatise, Dnyaneshwari written by Saint Dnyaneshwar. Yoga literally means `union` or `to join`, i.e., union with the divine consciousness.
Each and every yoga appears like different types of yoga due to their different methods and techniques but the main objective of all of them is liberation, salvation or to attain samadhi, the highest state of chitta (consciousness) by controlling its urittis (tendencies, desires) arising in it, out of attachment with the materialistic world, so as to merge into the divine principle (absolute consciousness). Yoga is one of the six great philosophies of India and is an experiential science. Yoga is a part of the Indian lifestyle. Practice of yoga as daily ritual can bring great deal of peace of mind and joy. Since yoga brings about suitable changes in the behavioural pattern and the attitude of a person, the personal relationship at home and in the society are also improved.
Although the system of yoga is not developed for the purpose of treatment, it has been observed through the applied research that the regular practice of yoga not only controls these diseases but also promotes and maintains the healthy condition of body and mind and prevents the disease process. Yoga is not an alternative to any conventional therapy but it definitely supports the healing process. The popularity of yoga lies in its therapeutic value. Yoga has a potential to tranquilize and balance the mind, which is the key in the management of stress disorders.
The yoga asanas have a healing process that tranquil the mind as well. This is linked to the proper functioning of the organs of the human body. There are particular yoga asanas for particular mal functioning of human organs and cure. The effect of yoga on digestive system is vast. Almost all the asanas as well as kriyas influence stomach, colon, urinary bladder and the liver. Dhauti is mainly related to oesophagus and stomach while Basti is concerned with the anus, rectum and the colon. In addition to that, the external sphincters of the anus are contracted and relaxed alternately in Ashwini mudra.
Yoga has a great impact in the blood circulation system. Many asanas e.g., Shirshasana, Sarvangasana, Viparita karni, Hansana, Mayurasana, few pranayamas like Ujjayi pranayama and Bhastrika pranayama as well as uddiyan, nauli kriya, Jalandhar bandha specially influence the blood circulation. As a result of increased muscular work during exercise, carbon dioxide is produced in larger amount, which accumulates speedily in the joints, muscles and blood. Demand of oxygen is also increased but before chemoreceptors come into action, the receptors in the joints and muscles are stimulated due to increased muscular contractions. Receptors in the joints send impulses to the respiratory center and bring about an increase in the rate and depth of respiration. When chemoreceptors are stimulated, the inspiratory center becomes highly active.
The rate of respiration increases. Excess carbon dioxide is expelled out of the body and the level of carbon dioxide is lowered to normal. Besides the gaseous exchange, respiration also contributes to the awareness or alertness of the individual.
Changes in the respiratory pattern and consequent gaseous imbalance such as hypoxia (lack of adequate oxygen) may result in altered state of awareness. Various components of the respiratory cycle show variation from person to person due to shifting of awareness and the mental state. These components are, rate and depth of respiration, the ratio of movements of chest to the abdomen, pauses, jerks at any point in the breath, ratio of the duration of inhalation and exhalation. Yoga has pointed out the relationship between the irregularities in the breathing and disturbances or disorders of physical and psychological functions and vice versa.
Besides supplying the oxygen, respiratory system also contributes to the state of consciousness, awareness and attention. The Pranayama is like a bridge between the physical existence and the mental activity. Due to emotional impact muscle tone is affected which in turn disturbs the functions of the body. If asanas are performed in a relaxed way the coordination between the nervous and the muscular systems increases, the muscle tone is corrected and thus the emotions are balanced. When the muscles are relaxed, the muscle tone is reduced and at this moment there is no scope for worries and tensions. Main objective of asana, pranayama, bandhas and mudra is to strengthen the nervous system so as to counter-balance the spiritual power of kundalini, when awakened.
Emotions, hormones of the endocrine glands, behaviour and mental health are deeply correlated with each other. When the function of these glands is maintained at the optimum level by practicing asanas, bandhas and mudras regularly, physical and mental health are maintained automatically. A regular yoga practitioner experiences a feeling of happiness, contentment and a peaceful state of mind all the time and therefore, stress is never felt. Yoga also helps in maintaining the homeostasis. Therefore one can control psychosomatic diseases like diabetes or asthma with the help of yogic practices. However, a suitable change in the lifestyle and diet control is also essential for such results. Moreover, the influence of yogic practices on the endocrine glands is more evident in females than in males. It is observed by some women that the menstrual cycle may be accelerated or delayed when they start yogic practices particularly uddiyana bandha, kapalbhati, nauli, dhanurasana, halasana, yoga mudra, etc.
Flexibility, suppleness and efficiency in the movements of the body depend on the strength and capacity of the joints. By regular practice of asanas the flexibility of the joints can be increased. Learning and regular practice of asanas in young age offer not only the flexibility but also a proper development of the bones and the joints. Children can increase their height by practicing asanas regularly. The spine is made healthy and stronger with the help of a regular training through exercises and asanas.
By practicing asanas the stability, health and suppleness can be achieved. In nutshell, the main objective of asanas is to promote and maintain perfect health. They re-establish a harmonious functioning of the body and mind as one integrated whole. This reduces stress, strain and tensions arising out of interaction with the external disturbances. Practicing yoga also helps to overcome the internal disturbances like tremor and instability (angamejayatva) by reconditioning the psycho-physiological mechanisms and to prepare one for higher yogic practices like dhyana. Thus, yoga helps to bring about equilibrium in overall functions at the emotional, behavioural and perceptual level. This helps to attain stability and peace of mind as well as a sense of well-being. It also helps to maintain an optimum muscular tone in the body. This provides the best organic vigour to the individual.
Moreover, in asanas like Paschimottanasana and Halasana the relaxation in the final posture allows gravity to act as a stretching force and the muscles are passively stretched. In asanas like Vakrasana, Ardhamatsyendrasana, Matsyasana, the locks and holds help the muscles to remain moderately stretched. In Bhujangasana, Salabhasana, Dhanurasana etc., in an effort to maintain the posture, the muscles are stretched against some resistance from the joints and the tendons. It would be easily noted that the exercise of the trunk portion is more emphasized in corrective asanas. The action of these asanas is more centered upon the vertebral column, particularly the lumbar region, visceral organs and the nerve endings (roots) in this region. Here, the alternate positive and negative pressure gradient will increase the blood circulation. It has been seen experimentally that the autonomic balance is established by practicing various corrective asanas.
Cultural asanas provide best possible movements for the spinal column like (1) forward-bending (flexion) as in Paschimottanasana and Yogamudra, (2) backward-bending (extension) as in Bhujangasana, Dhanurasana, Ushtrasana and Matsyasana, (3) lateral bending on right and left sides, as in Konasana and Chakrasana (4) rotation of the spine in vertical axis in Matsyendrasana and Vakrasana and (5) topsy-turvy and balancing against gravity as in Sarvangasana, Shirshasana, Viparita karani, Mayurasana, Kukkutasana and Bakasana. The static stretching of the spinal column increases the blood circulation around the spine that tones up its muscles. The nutrition is improved due to increased circulation around the joints and the toxic waste products are also removed effectively. This prevents the stiffening of the joints and increases their mobility. The vertebral column is bent, stretched or rotated in all the directions in various degrees, in different asanas. This exercise and the improved circulation around the spine render it flexible and elastic. The rigidity of the spinal joints is reduced. Growing children above eight and below eighteen years of age, have been found to increase their height by practicing asanas in which the static stretching is maximum.
In most of the asanas the abdominal region is influenced. During the maintenance phase of the asanas the pressure in the abdominal cavity changes, this is reflected on the visceral organs like stomach, colon, urinary bladder, etc. If the normal breathing is continued while maintaining the asanas there is an alternate positive and negative pressure on these visceral organs. If the breath is retained during the maintenance of asana either after inhalation or exhalation, the positive or negative pressures are also maintained for that much duration. This not only changes the blood circulation in that area but also stimulates the visceroreceptors due to stretching of the walls of these organs. The sensory impulses from these receptors will bring about stretch reflexes in the smooth muscles of visceral organs and maintain their optimum tone. Scientific studies have revealed that asanas like Paschi-mottanasana, Padahastasana, Halasana, Dhanurasana, Ustrasana influence the nostril dominance and both the nostrils function more or less equally. This is due to decongestion of the mucosal membrane in the nostrils.
Thus, these asanas recondition various neuromuscular units; including joints, tendons, and other reflex mechanisms and make the body suitable for higher yogic practices.
Meditative asanas provide broad triangular base for the body, formed by two femurs and the pelvis. This broad base gives firm foundation to the body and makes it steady and stable. Even if one looses the body sense during meditation, he remains balanced due to subconscious control of the posture by the lower brain centers.