Restricted Sprint?

[The Raining Brains]

If you are running away from something then eventually your fatigue is going to have some kind of bearing on your speed. The sprint should not run out but perhaps gradually slow down slightly so that the monster eventually gains on you if you fail to escape. The warning sign being your character's out-of-breath panting. Then, once you stop and are no longer in sight of the monster, your ability to sprint would be temporarily disabled until youve been given sufficient time to rejuvenate. It would maintain realism but also discourage players from abusing the sprint function.

It would have to be handled with subtlety though.