If you're looking to increase your speed, the folks over at Runner's World say that one of the best ways to develop power and speed is to run 10 seconds uphill — as fast as you possibly can.
"The best way to recruit fast-twitch muscle fibers is to run at max intensity," says Brad Hudson, coach to distance running stars. "The best way to build leg strength is hill running. So we run all-out up a steep hill. But we keep it to 10 seconds to avoid producing lactate and becoming fatigued." Running no more than 10-second repeats also reduces injury risk by limiting your fast-running time. And hills by their nature lessen the risk of injury because the slope shortens the distance you have to "fall" or land, reducing impact.
So if you're looking to speed up, head for the hills or pump up the incline on your treadmill anywhere from six to 10 percent grade. I like to do it at the end of my workout, so I don't poop out early on because it's a tough 10 seconds. Try it out and let me know how it's working for you.