(Shared it in its entirety directly from http://sharathjois.com/the-practice/)
Ashtanga Yoga is an ancient system of Yoga that was taught by Vamana Rishi in the Yoga Korunta. This text was imparted to Sri T. Krishnamacharya in the early 1900’s by his Guru Rama Mohan Brahmachari, and was later passed down to Pattabhi Jois during the duration of his studies with Krishnamacharya, beginning in 1927.
The following are aspects that Pattabhi Jois emphasizes as the main components of Ashtanga Yoga.
Vinyasa: Vinyasa means breathing and movement system. For each movement, there is one breath. For example, in Surya Namskar there are nine vinyasas. The first vinyasa is inhaling while raising your arms over your head, and putting your hands together; the second is exhaling while bending forward, placing your hands next to your feet, etc. In this way all asanas are assigned a certain number of vinyasas.
The purpose of vinyasa is for internal cleansing. Breathing and moving together while performing asanas makes the blood hot, or as Pattabhi Jois says, boils the blood. Thick blood is dirty and causes disease in the body. The heat created from yoga cleans the blood and makes it thin, so that it may circulate freely. The combination of the asanas with movement and breath make the blood circulate freely around all the joints, taking away body pains. When there is a lack of circulation, pain occurs. The heated blood also moves through all the internal organs removing impurities and disease, which are brought out of the body by the sweat that occurs during practice.
Sweat is an important by product of vinyasa, because it is only through sweat that disease leaves the body and purification occurs. In the same way that gold is melted in a pot to remove its impurities, by the virtue of the dirt rising to the surface as the gold boils, and the dirt then being removed, yoga boils the blood and brings all our toxins to the surface, which are removed through sweat. If the method of vinyasa is followed, the body becomes healthy and strong, and pure like gold.
After the body is purified, it is possible to purify the nervous system, and then the sense organs. These first steps are very difficult and require many years of practice. The sense organs are always looking outside, and the body is always giving into laziness. However, through determination and diligent practice, these can be controlled. After this is accomplished, mind control comes automatically. Vinyasa creates the foundation for this to occur.
Tristhana: This means the three places of attention or action: posture, breathing system and looking place. These three are very important for yoga practice, and cover three levels of purification: the body, nervous system and mind. They are always performed in conjunction with each other.
Asanas purify, strengthen and give flexibility to the body. Breathing is rechaka and puraka, that means inhale and exhale. Both the inhale and exhale should be steady and even, the length of the inhale should be the same length as the exhale. Breathing in this manner purifies the nervous system. Dristhi is the place where you look while in the asana. There are nine dristhis: the nose, between the eyebrows, navel, thumb, hands, feet, up, right side and left side. Dristhi purifies and stabilizes the functioning of the mind.
For cleaning the body internally two factors are necessary, air and fire. The place of fire in our bodies is four inches below the navel. This is the standing place of our life force. In order for fire to burn, air is necessary, hence the necessity of the breath. If you stoke a fire with a blower, evenness is required so that the flame is not smothered out, or blown out of control.
The same method stands for the breath. Long even breaths will strengthen our internal fire, increasing heat in the body which in turn heats the blood for physical purification, and burns away impurities in the nervous system as well. Long even breathing increases the internal fire and strengthens the nervous system in a controlled manner and at an even pace. When this fire is strengthened, our digestion, health and life span all increase. Uneven inhalation and exhalation, or breathing too rapidly, will imbalance the beating of the heart, throwing off both the physical body and autonomic nervous system.
An important component of the breathing system is mula and uddiyana bandha. These are the anal and lower abdominal locks which seal in energy, give lightness, strength and health to the body, and help to build a strong internal fire. Without bandhas, breathing will not be correct, and the asanas will give no benefit. When mula bandha is perfect, mind control is automatic.
The six poisons: A vital aspect of internal purification that Pattabhi Jois teaches relates to the six poisons that surround the spiritual heart. In the yoga shastra it is said that God dwells in our heart in the form of light, but this light is covered by six poisons: kama, krodha, moha, lobha, matsarya, and mada. These are desire, anger, delusion, greed, envy and sloth. When yoga practice is sustained with great diligence and dedication over a long period of time, the heat generated from it burns away these poisons, and the light of our inner nature shines forth.
This forms the practical and philosophic basis of Ashtanga Yoga as taught by Sri K. Pattabhi Jois and R. Sharath Jois.
About R. Sharath Jois-
Sharath was born on September 29, 1971 in Mysore, India to Saraswathi Rangaswamy, daughter of ashtanga master Sri K. Pattabhi Jois. Growing up in a house full of yoga practitioners, Sharath learned his first asanas at age seven and experimented with postures from the primary and intermediate series until he turned fourteen. Though he spent the next three years focused on his scholastic education, earning a diploma in electronics from JSS in Mysore, Sharath knew that he would one day follow the ashtanga path blazed by his mother and legendary grandfather.
Sharath embarked on his formal yoga study at the age of nineteen. He would wake every day at 3:30 a.m. and cross the town of Mysore to his grandfather’s Lakshmipuram yoga shala. There, he would first practice and then assist his guru, Pattabhi Jois, a routine of dedication he has followed for many years.
Today, Sharath’s sincere devotion and discipline to the study and practice of yoga compels him to rise six days a week at 1:00 a.m. to complete his practice before the first students arrive at the K. Pattabhi Jois Ashtanga Yoga Institute, where he serves as Director.
Sharath is Pattabhi Jois’s only student who has studied and continues to practice the complete six series of the ashtanga yoga system. He presently resides in Mysore with his wife Shruthi, daughter Shraddha, and son Sambhav.