Action scenes are a critical component of most genre novels, whether you're writing epic or urban fantasy, world-hopping science fiction, or gritty detective noir. But how do we write realistically about a bar brawl, or gun fight, or a sword fight, or a castle siege, if we've never been in one? Should we throw physics and physiology out the window or keep a handle on reality? How does a regular human respond when placed in harm's way?