In the science of Ayurveda the human body has been divided into six main parts: the head, the chest, the two arms and the two legs. The head is the seat of knowledge, the heart that of devotion, the arms and the legs are for action. The path of Yoga combines these three- body, mind & the soul- which act in unison. Therefore Yoga is the foundation for all the other paths.
In short Yoga leads to the purification of the body, the mind and the intellect. Practice of asana brings firmness to the body, eliminates the Rajo guna or the oscillating character of the mind and makes the mind steady. This practice gives health, poise, mobility and immunity from disease.
Prana is air, breath, the very life force ayama means expansion of its length and breadth and volume. Thus the systemic lengthening of inhalation and exalation and the pause in between breath control. Pranayama is breath control, the end product being mental calm and tranquility of the nervous system. The body and the mind become tolerant. With proper breath control the pulse becomes steady and regular, the body achieves suppleness and the complexion becomes radiant.
The sadhaka sustains and maintains the focus of attention throughout the above concentration, unbounded by time and space, it becomes dhyana or meditation. In such a state of deep concentration and steady flow of meditation, the body, the breath, the mind, the intellect, and the ego all lose their individual existence and merge into one single state of Being.
The body is often considered as our vehicle, without this we cannot experience anything. When the body is weak, shaky or in pain, meditation is impossible. A sound and healthy body is thus the very first stage in meditation.