To me it just looks like torture. I might be slightly rotund but I reckon I am as fit as a flee and I hardly ever break into a sweat. Yoga is about balancing energy. And I realise that the main difference between what I consider a yoga class to be and an exercise class, is that the yoga class will leave you coming out with more energy. The exercise class will leave you depleted.
I think there is a mistaken belief that you have to push your body to the limits to be doing anything good for it. I differ. You should be nurturing and looking after your body. If you are doing too much it is against the spirit of non-violence. Non-violence doesn't just mean refraining from bashing someone on the nose. It also means not being violent to your body and pushing it too far.
So maybe it is time to try a yoga class?