There "ain't nothin' wrong with yoga asanas "... but the real question is whether yoga by itself goes far enough in helping you attain spiritual progress.
And by spiritual progress I mean the REAL stuff -- advanced spiritual states and samadhi realizations that involve no thought, chi transformations, and all sorts of advanced physical and esoteric kung-fu.
Yoga is great for stretching your muscles and increasing your flexibility. It's a wonderful remedy for back pain, as study after study keeps demonstrating. There are too many benefits to mention them all. But will yoga bring you to samadhi or spiritual enlightenment?
Hardly.
Here's the scoop. Yes, yoga is fantastic. So is Pilates. So are the flexibility exercises of Scott Sonnon, which can lead you to becoming even more flexible than a yoga guru in 1-2 years time. Bodywork is also great, and so are the soft martial arts, but none of these things will totally open up your chi channels.
Hence, no real spiritual progress. Spiritual progress in terms of samadhi states, mind you. Don't go twisting things and say I said they were useless, not god, don't change your body and so forth. Physical exercises do not produce samadhi, PERIOD. That's what we're talking about here.
When you open up your chi channels and cultivate your chi, that flooding of chi throughout your body softens your tissues and leads to real flexibility. It also leads to better health, longevity and REAL meditation progress. If you want to see someone who is soft and flexible, go find a master who has meditated correctly for several years and you'll understand what the softening of chi can do for your body. It can change your blood, chi channels, flesh, bone marrow, tendons, bones, air and reshape your entire body so that it looks like those beautiful statues of male and female Buddhas you find in Asia.
You see, it all depends upon opening up your chi channels and not losing your chi, while cultivating a peaceful or "empty"mind that doesn't throw up obstructions to the natural circulation of your chi.
Now yoga helps with flexibility. Pilates helps with flexibility. But without that something extra, they never lead you to anything more than a mundane result.
Meditation is that something extra, in particular emptiness meditation, which is why all the sages and spiritual schools emphasize it. It's the cure for health problems (chi passing through an are will tend to cure it), longevity (if you cultivate your chi you are cultivating your life force, hence longevity), and spiritual progress (because chi and consciousness are linked, and purified chi means a more purified or spiritual consciousness).
So how do you make yoga more effective for the spiritual path? By combining it with breathing practices geared toward opening up your chi channels, and with meditation. Don't practice yoga WITHOUT also practicing meditation and breath work. Otherwise you're leaving money on the table -- millions of dollars, so-to-speak.
I have met countless yoga teachers, from India no less, who have extremely flexible bodies and "no chi" whatsoever. Why? Because yoga was all physical form to them rather than a means of spiritual cultivation. They didn't practice meditation and they had no clue that they want to be opening up their chi channels. Some of them even had "dirty chi" just like martial artists who don't know how to cultivate emptiness.
Now if you combine yoga with breathing methods and meditation, you're on your way, but if you don't then it's just another physical exercise that leads to decline.
So remember, if you are going to practice yoga, try to combine it with breathing practices and meditation. Otherwise you're getting very little of the maximum benefits available. The 9-bottled wind breathing practice will open up your chi channels and as to meditation, there are so many options available on the website.
"Meditation for Beautiful Skin" has a bunch of meditations and exercises you can try.
And if you want real flexibility training, beyond what yoga can possibly give you, check into the work of Scott Sonnon, which are the flexibility training methods of Eastern Europe. You see from the East we have yoga and the martial arts, from the West we have bodywork, and from Eastern Europe we have the Sonnon exercises. It's all good, and you use whatever you want according to your needs. But the additive that really supercharges all these practices is breath work and meditation.
Remember that!
So get the message straight. For some reason, people never READ anymore and tend not to use their noggins. They read things into what isn't there. Exercise is fantastic for you. Yoga is great, Pilates great, Spirotonics great, gyrotonics great, rebounding great, Sonnon stuff great, flexibility workouts great,Kung-fu great, sports visualization great, ... but you will never achieve samadhi with physical practice. Never. True spiritual practice is cultivating the samadhi, dhyana and the Tao. If anyone says that physical practice is the route to the Tao and can get you into the genuine spiritual states we always talk about, they're just nuts. To cultivate your chi and samadhi, you must go higher, you must cultivate meditation and in particular, reach the state where your mind and chi become one, and in that unification your chi channels open and you attain the worriless state of no-thought.
So YES practice martial arts, yoga, and all sorts of kung-fu exercises or stretching. But remember to add meditation tot he mix, and follow the standard practices of (1) emptiness meditation or non-clinging, (2) cessation and contemplation, (3) dis-identification with the body, and (4) merit making.