I remember as a kid I had these dreams. I was chased by kids bigger and badder than me. Try as I might, I could not run faster than running in slow motion. It was very similar to a lucid dream (scroll back to L is for Lucid Dream) where I was awake in my dream.
The major difference was that I could not make a conscious effort to run faster and escape. Maybe this falls in the category of a nightmare; awake in the middle of a dream with imminent danger but not having the ability to change anything.
One general consensus here is anxiety. Your legs push you forward throughout your life and there is resistance to your progress. You are in a situation where an intrusive force is disrupting your otherwise peaceful world, sometimes even mocking you, and you have no control over it. At least at the moment. Life changes often for the better. You just have to go through trials and tribulations and learn how to overcome.
Honorable Mention Race, Recurring Dreams and Red
Tomorrow S is for Sleep Paralysis
Question Have you had a similar dream where there was a force resisting your progress?