I think it really depends on the Yoga class and who is teaching it and how.
I am not very flexible and have lower back issues but I loved playing golf. I took some beginners Yoga classes at my gym, a class that was taught by a person with a background in physical therapy and someone who understood back issues. It was really more about learning to stretch into positions and hold them while remaining relaxed and breathing deeply and thus increasing core stability and balance. I also took classes she taught on core stability and she incorporated Swiss stability balls and both classes dove tailed nicely with the physical therapy sessions my orthopedic had sent me to (“back school” as he called it) and while the physical therapist didn’t call it Yoga, she did teach me to do some stretches that very closely resembled some Yoga poses like Downward Dog, Bridge Pose, Seated Twist, Child’s Pose and Cat Pose and doing those each morning and each evening before bed or after playing golf or exercising really helped me not get stiff and sore and along with the Swiss Ball exercises greatly increased my core stability and flexibility and balance and therefore helped mitigate my back issues and back pain.
There was nothing Hindu-ish or “spiritual” about the Yoga classes I went to, there was no chanting, although there were a few groans, mostly from me. ;), The instructor didn’t even use the Namaste phrase although she did play music by Enya and lit a few scented candles, the closest she came to any sort of “meditation” was when starting and ending the class – “breathe deeply and think about good and calming things”. FWIW, I also took a Tai Chi class at this same gym that was conducted in the warm water pool and it was a great workout but not so stressful on my now aging joints.
Now I’m sure there are many Yoga classes that do incorporate a lot of “spiritualism” and meditation and references to Hinduism and Eastern or New Age philosophies that I can understand that many Christians would find offensive. But I think it’s also a stretch (pardon the pun) to claim that the moves, positions and stretches of Yoga in and of themselves are from Satan. There are Christian Yoga practitioners and Yoga like alternatives; there is Scripture Yoga and Holy Yoga and Praise Moves that incorporate the positive physical aspects of Yoga and the poses and substitute the more traditional Yoga meditations and chanting with Christian prayer and scripture. Perhaps not everyone’s cup of tea but I’m just saying that Yoga in and of its self is not “evil”.
I know some folks who are into very into running. Personally while I prefer to walk the golf course rather than ride a cart, I like fast walking and trail walking and will even incorporate a bit of jogging into it, but for me to run full out, either I have to be on fire or someone has to be chasing me. But a few of my friends who got into running had the goal of running in a Marathon (or 5k) and many of them accomplished that goal and good for them. But if one was to get picky, one could say that participating in a Marathon or even weight lifting is paying homage to ancient Greek pagan mythology and Gods. And then there is swimming and surfing – men and women swimming together and not “fully” clothed – oh the horrors! ; ),
to a number of knuckleheads on this thread, it doesn't matter how it is being taught, it's the fact that it's "whatever" based........
Logic and rationality are slowly escaping this site........
I have had many different yoga instructors and they all offer something different in the way they teach.
If it is Spiritual to get the kinks out of tight muscles .. then Yoga is spiritual :-)