I do something similar, therapy for a physical problem that I have. I use meditation music while doing the stretches and also control my breathing, I think the end result is much like you would get with yoga. I also practice straight meditation.
The two have helped me enormously. Both have been proven to lower blood pressure and reduce stress, cost very little or nothing and have no negative side effects. I feel much stronger and more flexible since starting the program, and have normal blood pressure with no medication. I am able to bend down and put my hands flat on the ground, not bad for 61. I have a business fixing up old furniture and I used to worry I would hurt myself with all the lifting, but I don't have any problems now.
It's sad that the Watchtower demonizes these practices, but I don't think they want people to be mentally and physically healthy, then they wouldn't need the Watchtower, lol. While they are used as part of a religious practice by some, they aren't actually religious in of themselves, and the idea that meditation leaves the mind vulnerable to demonic attack is ludicrous of course.
Think how much healthier everyone would be if they spent the hours they waste at the kingdom hall doing yoga instead!