Father, my opinion based on testimonies of ex-yoga practitioners, on the book "The Gurus, the Young Man, and Elder Paisios" and other books is that one should stay away from yoga as far as possible.
And why should one do asanas when he could do stretchings, aerobics and anything similar?
The argument presented in the testimonies I have read is that with yoga, we can't separate the physical exercises from the spiritual stuff.
Maybe they are wrong, but why should we take any chance?
Forgive me if I offended anyone.
I think it is possible to separate the two.
For example, I often do "Yoga for Regular Guys," a program created by former pro wrestler Diamond Dallas Page. He royally screwed up his back in the ring from a bad fall and was told he would have trouble walking again and his career was over. His wife did yoga in that ethereal "spiritual" California way and encouraged him to do it, as well. Page, being the macho "down to earth" tough guy, found it really hard to even consider doing something so "sissy" but gave it a shot and, in the end, developed with his fitness doctor a purely physical program of stretching and iso-metric and iso-kinetic exercise that is entirely devoid of spiritual content which allowed him to get back into the ring and win the title (btw, I know wrestling is fake, but you have to be able to perform well in order to go anywhere in the industry, and that means being healthy and fit and able to take a fall well)
The YRG program is still very recognizably "yoga". When I was first diagnosed with acute sciatica, I tried the regular yoga dvds sold by all sorts of Guru-types and found much of the prattling spiritual advice in them insulting to my intelligence as well as to my faith. Yet the exercises themselves helped. I could not, however, continue to practice along with the dvds even with the sound off because I knew what was being said at any given moment. A chance reading of a newspaper article about a local Gulf War Vet who, like Page, was told he would have trouble walking but, through the YRG program, is now running marathons, pointed me in that direction. It has exactly what I need from a yoga program: structure and physical guidance devoid of Hindu spiritual content. At the end of each session, one is taught to lie still and relax one's body for five to ten minutes, which is a perfect time to pray in one's own words, thanking God for your physical health and all the material benefits He bestows on us.
Disclaimer: I am not affiliated with any business organization which sells YRG in any way. I'm only an avid fan.