Pranayam has been derived from two Sanskrit words ..Pran and Ayam. It means, to expand the Pranic energy of the body. Normally it is understood only as a respiration technique of inhaling and exhaling . It is true that the level of Oxygen increases in the body through Pranayam, but the meaning is not limited to this. As per Tarka Sastram "Sareeraantah sanchaaree Vaayuhu Praanascha" 'Pran is a life-giving energy which is subtler than Oxygen and is present everywhere. In Pranayam, special breathing techniques are used to encourage that very vital force.Our lifestyle deeply effects the Pranic forces. Our actions, sleep, Diet, Thought, Senses..etc. All have an effect on our Pancha Pranas (ie. Praana Vaayu , Apaana Vaayu , Samaana Vaayu, Udaana Vaayu , Vyaana Vaayu ) . Irregularity in our lifestyle depletes Pranic Energy and leads to Pranic Blockages. That is why people feel the loss of energy from time to time. Sri Kriya leads to ailments in Organs and muscles. The various modulations of Sri Kriya practices help expand this forces and balance the Five types of Pranas in the body.
Yoga is not a religion. It is a Science. Science of well-being, Science of youthfulness, Science of Spirituality, Science of integrating body, mind and soul.