I'm working with elite running coach Brad Hudson on a book entitled Run Faster from 5K to the Marathon, which will be published by Random House next year. One of Brad's signature training methods is steep hill sprints: very short (8-10 seconds) sprints up a very steep hill. He has his runners do 8 or 10 of them at a time, once or twice a week, at the end of an easy run. They are meant to increase stride power and running-specific strength.
I've started to incorporate steep hill sprints into my training for the California International Marathon. To avoid injury, I began with one (as Brad himself recommends), then advanced to two, and just today I did a set of three. I have a strong feel they are going to be quite beneficial, but quite apart from the anticipated physical benefits, I am just loving the experience of running at top speed. I can't remember the last time I sprinted before I started doing these hill sprints. It's such an exhilarating feeling to hold nothing back.
As small children, we only ran at top speed. Then we became "runners" and forgot how to sprint. It's kind of sad. I am coming to believe that everyone who calls himself or herself a runner should sprint a little.