Human body and Hath yoga are deeply connected. Hatha Yoga is designed to gain in-depth understanding of our body and to unleash its power and strength to obtain our higher selves. To a Hath Yogi, the body is not a mere mass of living matter, but a mystic bridge between the spiritual and the physical being. Hatha-yoga is often regarded as physical or bodily yoga. Such an over simplistic view is mistaken if that is all hatha is considered to be; but it is certainly the case that hatha-yoga works very much "with" and "through" the body, and that its conceptual isolation of the body is crucial to Hatha`s theory and practice. This conceptualization, which involves whole `subtle` physiological dimension-forms, should be understood properly.

Hatha Yoga does not seek mere transcendental experiences. Its objective is to transform the human body to make it a worthy vehicle for Self-realization. According to a yogic philosophy, the body, mind and senses constitute instruments or tools for the respective processes of experiencing the world and realizing our true nature. If these instruments are to work efficiently then it is important that the yogi maintains them in the best possible condition, and, furthermore, endeavours to strengthen and purify them to the utmost.

According to the Yoga-Sutra achieving this goal results in beauty, gracefulness, strength, and robustness. Such a condition is said to proceed from sanyama (control) upon the `gross` and `subtle` elements. This implies that bodily perfection is viewed as a consequence of meditative discipline, although the relation between the two should perhaps be better understood as one of mutual enhancement. Physical upliftment assists the spiritual one and vice versa.

Impact of Hatha Yoga on Body Cells
Hatha Yoga teaches that the physical body is built up of small cells each cell containing within it a miniature life which controls its action. These lives on the other hand have small bits of intelligence which allow the cells to do their work in a proper manner. The small cells of human body are under the control of the central system and readily obey their orders consciously or unconsciously. The process of digestion, assimilation etc shows the intelligence of the cells either separately or collectively in groups. Each atom of a living body according to the Yogi is a living being which has its own independent life. Cells in human body are the ones which carry on the work of continual regeneration. It has been said that in order to perform all the different actions the cells need a supply of Prana. The cells are able to get the supply of Prana from the nourishment they derive from the food which they have.

In order to supply adequate Prana to the cells it is necessary that the body is kept in a proper condition and the yogis believe that Hatha Yoga is a way to keep the body in a healthy condition.

Impact of Hatha Yoga on the Respiratory System
Breathing according to Hatha Yoga is the most important activity of the body. This is because all the other functions of the body depend on breathing. Moreover it is said that without the exercise of breathing man is not able to survive. But at the same time it should be remembered that correct habits of breathing are more important for continued vitality and freedom from disease. Hatha Yogis believe that breathing should be practised in such a manner as to the state whereby the individual is able to bring about control on his body and is in a state to send any amount of Prana or vital energy to any part of the body. Proper breathing to a large extent depends on the contraction and relaxation of muscles and controlling the muscles actually enables an individual to master the science of breathing.

The Yogis of Hatha Yoga have classified respiration into four general methods namely High Breathing, Mid Breathing, Low Breathing and Yogi Complete Breathing. It has also been said that the exercise of Complete Breathing that are practiced by the Hatha Yogis helps the individuals to acquire a proper health and also helps them to be free from all kinds of diseases.

Impact of Hatha Yoga on the Digestive System
Hatha Yoga also has an impact on the digestive system as well. It has been said that if the digestive system works in a proper manner the individual is able to absorb the Prana in a more effective manner from the food that he intakes. And if the Prana from the food is absorbed in an effective manner the Prana or the vital energy is transmitted to all the parts of the body and the body works in a more effective manner. Hatha Yoga assists in the proper working of the digestive system of individuals and hence circulates Prana in the body in an effective manner.

Of the ten main types of prana, it is prana and apana that are regarded as the `highest agents`, and hence it is the operations of these two which hatha-yogis are most concerned to bring under their control. It is the ordinary tendency of apanas the governor of excretory functions to flow down-wards and out of the body, while prana flows upwards and is expelled with the breath. By means of the specially designed postures (asanas), bodily `seals` and locks` (Mudras and bandhas), and breath-retentions (Kumbhaka), the yogi aims to prevent the escape of this vital force and to unify and retain it within the central channel of Sushumna Nadi.

Nadi is the feminine form of "Nada", both terms denoting a tube, stalk or channel. Such channels may include veins, arteries, nerve fibres and other bodily vessels, but, in the context of yoga physiology, Nadi refers specifically to conduits of prana. The number of nadis in the subtle matrix permeating the human organism is given variously in the manuals of hatha-yoga ranging averagely on 300,000 to being uncountable, like the veins of an asvattha leaf. The theory of Nadi also incorporates the conception of `tides` or `currents` of prana. They are the carrier of this vital energy, and pathway of Kundalini Shakti when evoked. The study of this aspect of vital force is often termed "svara-yoga", svara meaning `sound` and referring both to the subtle sound made by prana as it passes in and out of the body and to the prana it-self.

Kundalini Energy
Kundalini means `she who is coiled` and Shakti means `power`. Therefore, Kundalini-Shakti stands for the `coiled` or `spiral power`, often also known as `Serpent power`. This is the powerful force which when evoked transcends our being and self. Understanding these vital cosmic forces are a must for any Yogi to deal with the infinite potential in a human body, that when stirred up cause them to cross all the barriers and reach enlightenment.

Kundalini is a force so powerful as to be considered the source of all manifestation. There is more than one specific locus in the bodily matrix that harbours a strong potential for stimulating or accessing that force, and one or other of such loci may be the object of attention in particular hatha techniques. The presence of a range of `power access points` could be one reason for disagreements in hatha texts concerning Kundalini`s initial location. The aim of hatha-yoga is to first purify the nadis to facilitate the improved flow of prana, and then to induce the arousal and upward-movement of Kundalini. The activation of this otherwise latent but extremely powerful force is bound to create a profound transformation of the yogi. Not to mention his sublimation of his or her ordinary sense of identity.

Several interpreters have attempted to relate the phenomena of the subtle bodily matrix to those with physical anatomy of human body and in the context of modern biological science. While the chakras are not to be identified with the physical plexuses of the nervous system, they are nevertheless connected with, and in a physical sense represented by them. Many have gone further and have indeed tried to draw an equation between the nadis and chakras on the one hand, and the Fibres and plexuses of the physical nervous system on the other. The web of nadis can be equated with the physical nervous system, the chakras with `clusters of intersecting nerves` and prana with nerve energy.