Many orthopedic injuries have been reported with different kinds of postures. Moreover some posters can cause nerve damage, impotence etc.
So one must practice yoga carefully and under guidance of a Guru
Now this only refers to asana or posture
The other aspect of yoga is pranayama. This past is even more dangerous. That’s why Yogananda and Vivekananda described it very cautiously. They talk about holding breath more on outside because it is safer.
However pranayam is one of the biggest step in cleansing, reaching Samadhi and destroying past karma. It is very subtle and the only part that is revealed is the part with breath. However, prana is not breathing. It is a source of energy.
There are 2 prana. Universal and the one present in body. Each of them has 5 main divisions and then each of them has 5 more subdivisions. They are not of use for most people ( not of use to know). The universal prana has all the known energies – from solar, atomic, wind etc. They are connected to the prana of the body. And that is why we are susceptible to outside forces. But like the hydrostatic paradox or the lever system, like Vivekananda said, the prana of the body can affect the universe too!
That’s why pranayam is important. But it is not holding the breath but a little more
Now this wonderful technique was discovered by Patanjali a thousands of years ago. It is wonderful and the best way to get to God. Depending on the type of pranayam you do, it can be called “kriya yoga”
There are 8 types of pranayam. The 9 type is ultra secret and is known as kevali. The other 8 types at surya bhedan, shitli , shitkari, bhastrika, ujjai , bhramri, plavani, Some people call Anilom vilom or kapal Bhaati as pranayam. But that is not true. This wrong information started in the recent times by a certain popular misconception
Now in order for pranayam to be successful, the door or path to go within must be open. This requires a Guru. Otherwise if you try to hold the breath , or slow breathing, it can cause headaches, constipation, eye problems, impotence and other sexual dysfunction, chest pain, etc. these things are often irreversible!
So one should never attempt to do these things without a Guru. Now if you do a search on the the net, you will find many people who claim to know the pranayam. What they might describe, often inaccurately, is the breathing part. The critical inner changes are not talked about
The different manifestation, are described in shiv Swarodaya, and a few other books that are nit in print. Yogananda gave an outstanding description but it is poorly understood by most. Reason being the inner door has not been opened. How can you understand the different dimension ? Yogananda and Sri Yukteshwar said, make pranayam your religion. Nothing more is to be done. You can reach there very fast
There are certain rules to be followed with it. Diet control. Overwhelming work or exercise no matter how much you love it, will prevent any progress. One should talk very little. Not meeting or touching people is very helpful.
But you can learn these things from your Guru. All I can caution is don’t do it without a Guru. In the long run it can cause damage when practiced without a Guru
Even those with a Guru often miss the subtleties and cannot progress. One must stay in communication and ask for guidance frequently This one technique, although most powerful, has been lost. People think they know it but the truth is the dynamic power for success is missing. This is what Krishna said, when this is lost, he will come back
Human life is precious. People lose it without making any strides. Even the Bible talks about Pranayam but in a slanted way. It is better to learn how to silence the mind than enter in debates
The best descriptions of this has been given by Brahmananda, anwar, Akho, etc. they are all great enlightened people all within last few centuries.