Take the sheer power and versatility of a top athlete. add the strength and endurance of a heavyweight boxer and somehow pack it all into the poised and graceful frame of a prima ballerina. Then you might just have someone who could rehearse and dance Swan Lake without injury. Q.E.D. spent six weeks with the Northern Ballet Theatre to see just how far dancers have to punish their bodies before we can admire their seemingly effortless elegance on stage. With five of the company injured and dancing in considerable pain from the outset, it was going to be a real struggle to open at Glyndebourne on schedule....