I think yoga is a brilliant form of exercise, I'm not particularly that good at it and find I get acid reflux in stances such as "downward dog" if I stay in that position too long, as for "head stands" I don't think I will ever get to that stage. I have a friend who has been doing it for years, in fact she left teaching to concentrate on her yoga classes which have grown over the years, she thinks it would be good to be taught in schools. I like the breathing and clearing the mind concept, although I don't manage to do that at all well. I haven't been for a while but I intend going back, my gym has something called "body balance" which is quite gentle and incorporates elements of yoga and pilates so I might try that as well.