Nothing would motivate me more to run than knowing zombies were hot on my trail and hungry for brains! Apparently I am not alone in thinking this way. Check out this web site for "Run For Your Lives! a 5K Obstacle Course". As the name implies, there are zombies scattered throughout the course that are hell bent on catching you and taking you out of the game. It souns like a blast - in fact I am pretty sure that I have talked about this kind of thing before, so I am glad that somebody somewhere is listening!
Check out their video - the only thing that scares me is the fact that these would be fast moving zombies too!