Running, it’s something an athlete do to win a medal, something the foals do while playing or to put it simple, something you do when a simple trot it isn’t enough. Like when you are running for your life, and depending on your lifestyle, for how long can you maintain the speed.
That was Fluttershy though, when she was running from a timberwolf in the middle of the Everfree forest

mlp fim belongs to hasbro