Got a question about running? You're in the right place. Every Tuesday, world-renowned coach, author and athlete Hal Higdon posts and answers athlete questions here. You can submit your question by joining the discussions on Hal Higdon's Virtual Training Bulletin Boards.
When I started running, I used to overstride, landing too far forward, running at about 10:00 per mile. I shortened my stride primarily because of what I read on a running forum and as a way to avoid injury. Using this relatively short stride length, with heels barely kicking up, I reached a best 5-K pace of about 6:40 per mile. I feel now that running faster at the same stride length is causing me to put in a lot more effort per stride. Should I increase stride length? Does it come naturally, or do I have to consciously focus on it? Now that I'm faster, I wonder if I shouldn't lengthen again by allowing my heels to kick up further.
Let me begin by first cautioning you: Don’t trust all the information you can find in Internet running forums—and that includes this one. Having said that, it seems that your experiment in changing stride length has been successful—so far. A knowledgeable coach standing by the side of the track might have been able to examine your form and gotten you to where you are faster, but sometimes we need to find our own way.
I have seen beginning runners make major changes in their running form en route to becoming experienced runners. But most often these changes have come naturally. As these new runners became more fit, and as they strengthen once weak muscles, they find they can move their legs in ways once thought impossible. I'm not certain speeding up the process by tinkering with the way the body works, does much good. And it can get you in trouble.
Why not stop worrying about form and see what happens as you run at different speeds, both in training and in races? If you under-stride, you may waste energy pitter-patting. If you over-stride, it can slow you down more than speed you up. Good luck with your form experiments, but try not to be obsessed with them, and don’t be afraid to consult with a knowledgeable coach who can watch you in person.