There are few things in life that motivate you as well as impending death does, and there are few things in fiction that personify death as well as zombies do. Take those two arguments and apply them to someone needing motivation to get in shape and you have a powerful force indeed.
That’s the idea behind Run For Your Lives, the zombie 5K run that’s been sweeping North America for almost the last year. You can run as either a survivor or a zombie. Survivors carry red scarves, and they, well, run for their lives. If the zombies get a survivors’ scarf, the survivor becomes a zombie and is tasked with taking down survivor participants. Either way, you end up running your 5K, and you probably have a lot more fun than you would on a typical 5K. (Unless you’re into that kind of thing, I suppose!)