I've often wondered how singers who tour manage to scream night after night and not be in constant pain. For instance, I always go back to thinking about Kurt Cobain. Nirvana toured a lot when they were around. Their biggest hit was "Smells Like Teen Spirit", a constant screaming song. To perform that song every single night on a tour with the same energy HAD to be painful. The energy was certainly contagious, at least based on the energy of the audience, so Cobain probably felt pumped up enough to scream through a show. Then afterwards he was probably in pain, popped some pain killers which caused stomach problems and the rest is history.
I'd love to have been able to hear Cobain discuss that issue of constant screaming. Of course, some of these "screamo" bands today scream even more than Nirvana did. Perhaps we could hear from one of them someday. This is something I've always thought about.