I had some extreme problems with back and neck pain beginning when I was thirty years old. Chiropractors, doctors and massage therapists barely helped at all. After about four years of pain, driving me out of my carpentry career, I found a book on yoga in the library. No chanting of mantras or meditation involved as others seem to think is part of it.
It was scary at first because the slightest moves (outside of yoga) were very painful. But within two weeks my pain was greatly reduced and at the end of the book (about six weeks) I was stronger and more flexible than I had ever been in my life and the muscle spasms were about 90% reduced.
I only continued doing yoga for a year or so but the benefits have lasted more than a decade. If I were a little more disciplined and kept it up there is no telling how much better shape I might be in now.
Stretching is fine, its the emptying of the mind that poses a spiritual risk.
That shouldn't be a concern since that is not possible. Entirely unrelated to doing yoga I became a Tibetan Buddhist and have practiced Vajrayana tantric meditation for over twelve years now. I was told to begin with that trying to "empty the mind" isn't possible and should not be attempted. I now know for myself that it isn't possible and is not part of Buddhist meditation. I am fairly certain it isn't practiced by Hindus either. The idea is a fantasy concocted by westerners.
I should have also said that practicing hatha yoga (the physical stretching exercises) has no meditation practice to it at all. It is a concentration exercise in and of itself which is similar to some meditation practices.