The mild exercise at the joints and the muscles around, stimulates the proprioceptors which brings about mild stretch reflex.

This not only increases the blood circulation around the joints but also improves the tone of their muscles. 

The slow movements and the maintenance of the aasana in a relaxed way requires little muscular activity and therefore consumes minimal energy. 

The heart rate, respiration rate remains in the normal range thus putting no extra burden on the cardio-respiratory mechanism.

In aasanas 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 aasanas like Vakrasana, Ardhya-matsyendrasana, Matsyasana, it locks and holds, and thus helps the muscles to remain stretched. In Bhujangasana, Shalabhasana, Dhanurasana etc. an effort to maintain the posture, gives rise to stretching of the muscles against some resistance. 

This increases the muscular tension which is important if one wishes to increase the muscular tone. 

Thus a proper selection of a set of aasanas could be utilized to correct the tone in the reciprocal group of muscles. 

It would be easily noted that the exercise of the trunk portion is more emphasized in corrective aasanas. i.e. the action of aasana is more centered upon the vertebral column, visceral organs and the nerve (endings) roots in this region. 

The circulation is increased and the nerves are toned up as they get fresh nourishment. The strengthening of the nerves in the viscera including the spinal cord and the branches of ANS is necessary to enable the practitioner to withstand powerful action of Kundalini.

It has been seen experimentally that the autonomic balance is brought about by practicing various corrective aasanas. 

Cultural aasanas provide the best possible movements for the spinal column, i.e.:

 (i) Forward bending (flexion)-Paschimottanasana and Yogamudra
(ii)   Backward bending (extension)- Bhujangasana,
       Dhanurasana, Ushtrasana, Matsyasana, Naukasana
(iii)    Lateral bending on right and left sides; Chakrasana as
       developed by Swami Kuvalayananda, Konasana.
(iv)   Rotation of spine in vertical axis-Vakrasana as
       developed by Swami Kuvalayananda, Matsyendrasana 
(v)   Topsy-Turvy and balancing against gravity- Sarvangasana,
       Shirshasana, Viparitakarni, Mayurasana, Kukkutasana,
       Bakasana.

The static stretching of the spinal column increases the blood circulation around the spine which tones up its muscles. 

The trunk movements are also slow and therefore each vertebra is moved gradually, and freely in its natural range of movement. 

As the nutrition is improved due to increased circulation around the joints, the toxic waste products are also efficiently removed. This prevents stiffening of joints and increases  mobility. 

The vertebral column is bent, stretched or rotated in all the directions in various degrees, in different aasanas. This exercise and the improved circulation around the spine render it flexible and elastic. 

This prevents rigidity of its joints. In growing children above 12 years of age, the practice of aasanas can influence the growth and development of their body due to the static stretching. 

In Sarvangasana, the head is completely bent and the arteries of the cervical spine are stretched. The chin-lock position of the head presses the soft tissues, jugular veins and thyroid gland and causes temporal redistribution of the flow of blood.

When the aasana is released, the pressure is relieved and the reactive increase in the blood supply probably causes the effective mixing of thyroid hormone with blood circulation.

In most of the aasanas the abdominal area is influenced. During the maintenance phase of the aasanas, the abdominal cavity undergoes pressure changes which are reflected on the visceral organs like stomach, colon, urinary bladder and lungs etc.

If the breathing is allowed to be continued while maintaining the aasanas, there is an alternate positive and negative pressure on the viscera.

If the breath is held during maintenance of aasana either after inhalation or exhalation, the positive and negative pressures are also maintained for some time. These pressures and consequent stretching of the walls of visceral organs stimulate visceroceptors which are sensitive to stretching.

The sensory impulses from these receptors reach the autonomic nervous centers and bring about a stretch reflex.

This helps in maintaining the optimum tone in the walls of the visceral organs which are made up of smooth muscles.

Emotions can influence the muscular tone of the visceral organs. So when the tone is balanced through alternate pressure and stretch mechanism, the emotional stability would definitely be established, particularly when the cerebral cortex is not allowed to interfere. 

Increased visceral circulation and the alternate positive and negative pressure changes brought about in the abdominal and the pelvic region promote and preserve the health of  endocrine glands. 

Disappointment or depression results in total or partial flexion of the body while exciting and stimulating situation causes an extension of the body. That is, the attitude of the body is related to the emotional or psychological factors which contribute to the development of one's personality. 

Typical postural patterns of cultural aasanas if practiced judiciously, would definitely remove minor functional and structural defects in these factors to render balanced and admirable personality. 

Thus one might experience emotional stability even after a few month's practice of aasanas. 

The regulation of posture depends on the muscle tone of the skeletal muscles. Muscle tone is influenced by emotions, as they disturb the cerebellum-hypothalamus functional axis.

If the corrective aasanas are practiced in an effortless (relaxed) and comfortable manner, the cortical activity does not interfere with this functional axis and that is why new emotional tensions cannot disturb the individual.

On the contrary, due to passive stretch reflex mechanism the muscle tone is reduced considerably which in turn decrease the existing emotional tension. The individual feels peaceful and pleasant. 

In topsy-turvy postures, due to upside down position of the body, the cardiovascular reflex mechanisms are stimulated. 

Now the venous return becomes very easy as the gravitational force is not working against it; on the other hand, the downward flow of blood is facilitated greatly due to the gravity. Brain receives sufficient quantity of blood easily which makes the nervous tissues refreshed.

In this condition, in order to prevent forceful blood flow towards the brain, a new pattern of reflex mechanism is set for the circulation in the upper extremity.

This conditioning of the baroreceptors and stretch receptors not only checks the forceful circulation in the brain during the posture but also maintains the blood pressure at the required level for other day-to-day activities of the body.

These topsy-turvy as well as the balancing aasanas stimulate vestibular organs of balance and improve their function.

Balancing against the gravity requires one's constant attention as well as a steady mind. Regular training of these organs in this way, in balancing aasanas, reflect upon the mind, rendering it increasingly stable, better concentrated. 

This is mainly due to the fact that the external sensory inputs or the internal thought processes are greatly reduced when one is aware of the function of balance. 

Thus these aasanas re-condition various muscles, joints, tendons, secretory and reflex mechanisms to make the body and mind.

Suitable for higher yogic practices.