Right now the number of people practicing yoga is growing in a big way. This could be simply because the scientific community is slowly beginning to recognize the depth and dimension of what this is. But if improper, distorted kind of yoga spreads, in fifteen years’ time, scientific studies will clearly come out and tell you in how many ways it is harmful to human beings, and that will be the downfall.
There are certain dimensions of this that are almost absent in the world today. It is there in some places, but generally in the known places, it is absent. It is important that we bring back classical yoga as it was. If it is taught in a proper atmosphere with a certain sense of humility and inclusiveness about the whole process, it is a really fantastic process of shaping your system into a fantastic vessel, a fabulous device to receive the Divine.
It is a very powerful way of living. Power, not over somebody else; it’s all about power to access life.

http://isha.sadhguru.org/mission/isha-yoga/isha-hata-yoga-school/the-science-of-hatha-yoga/