There have always been different approaches to yoga. Some people have called their system traditional yoga, scientific yoga, holistic yoga, and so on. Swami Sivananda called his yoga integral yoga, encompassing all the aspects of yoga for the homogeneous growth of the human nature, body, mind, emotions and spirit. Sri Swami Satyananda, called his yoga integral yoga, but with a stronger inclination towards scientific experience and experiment.
In the time of Swami Sivananda and Swami Satyananda such labelling was necessary. When Swami Sivananda was teaching yoga, fifty years ago, people had no concept of what yoga was. He decided to bring yoga out from a mystical environment to an environment suited to the people of that time, according to their needs. Swami Satyananda took this concept of yoga one step further. In order to validate previous yogic traditions, he emphasized the role of scientific research.
The term ‘classical yoga' describes a combination of traditional and scientific yoga. Tradition and science in the present-day environment evoke different kinds of images. Definitely, science is not equipped to validate all the claims of yoga due to the lack of scientific knowledge to interpret those claims. Science cannot measure the subtle prana, not even with Kirlian photography. It can measure the electrical emissions, the positive and negative fields of the body, but there is no equipment to measure subtle states of energy.
Science cannot measure kundalini or chakras. Attempts have been made and they are not useless. However, they have only defined a fraction of the entire area. Science does not have the equipment or the level of knowledge to experiment with yoga. One can experiment with pranayama for it deals with the breath and with asanas as they stimulate, alter and affect the function and performance of the internal body organs and systems. With some equipment one may measure muscle tension, breath and pulse rate, blood pressure and brain waves.
However, it will be difficult to measure or validate the claims of yogis in relation to mudras and bandhas as they stimulate the subtle fields of energy. There will be difficulty in experimenting with states of meditation and samadhi. Modern psychology has not even been able to clearly define consciousness or what the functions, attributes and experiences of the unconscious are.
Keeping this in mind, a synthesis between traditional yoga and scientific yoga has to develop. This synthesis is the classical yoga in which the concepts, theories and principles behind the yogic techniques, areas of experience, nature and personality must be known. It will take time to scientifically see the truth in these concepts. In the meantime, with whatever scientific knowledge is available, one must try to understand the traditional language and concepts and express that in modern language. So much can be done now. Therefore, the system of yoga which is being taught at Bihar School of Yoga has been named classical yoga, representing tradition and science.
—1996, Ganga Darshan, Munger