Do We Have This One?
It seems in just about every single work of fiction with even one action scene in it, no character ever gets the inclination to limber up a little bit before they start kicking ass and taking names. While one could chalk it up to Willing Suspension of Disbelief, some works of fiction (like Dragonball) do it fairly unobtrusively, if not on an entirely consistent basis. In reality, the characters should end up being tired, sore, and even getting cramps in the middle of their awesome martial arts poses.
Just about any shonen manga ever, with the exception on those with a martial arts focus, where the characters will usually stretch before a match.
Any American action movie ever.