This has to be a photo manipulation. If someone is balancing on one foot, standing on your stomach, the weight would push in on your flesh, regardless of how strong your stomach muscles are. That said, it's a really neat image. Whatever the woman on top is wearing bothers me, though. Jeans legs with a short denim skirt? Jeans with the crotch cut out? I don't understand.
I guess I'm the only one who wants to understand clearly....is this photo manipulation of one model, or is this a real photo of two models really "doing" this? Because to me, that makes a difference in the appreciation of the image, which is really cool