When a murder of crows join in the apocalyptic uprising of their brethren, the only sane thing to do is run. The same goes if you find yourself in a dark, empty library and a headless man appears. And sure, these things would never really happen outside of the minds of Alfred Hitchcock or Stephen King, but in the world of fiction, they mastered the art of the racing heart.
Even as a simple spectator to those chase scenes, your muscles likely tense up with the biological urge to run the opposite direction. That’s because what happens to your body while watching a scary movie isn’t all that different from what happens when you go for a casual run. And even if you’re not terrified while doing so, there’s still a bit of that fight or flight mechanism in exercise. Adrenaline, also known as epinephrine, is one of the hormones that mobilizes us.