How to increase both fast and slow twitch muscle?

I want to be a very fast sprinter. I also need to be a strong long distance runner. There's all this hoo-haw going around about fast twitch v. slow twitch muscle fibers and that you build one for long distance and the other for short distance. Furthermore, if you run long distance, it will start to damage your sprints. Is there an efficient way (or at least any ol' way) i should train so that i can get the most out of both sprinting and long distance?