Last summer when I started running regularly again with the idea of participating in races, every run was done at the same speed. Think of the person running just in front of the sag wagon in the last mile of a marathon. That was about my speed and probably what my form looked like. More of a lumber than a run.
While I have not gained much actual quickness in the last year or so, I have developed the ability to run at different paces for different types of runs. The first to develop was the "sprint" for speed work of 200 - 400 meters, with walk breaks in between. This is where I learned that you can pick your feet up off the ground while running.
Lately, I have been doing longer tempo style runs and have found a third gear. I can go a little faster than my long run lumber, but not as fast as my "sprint". I have found a middle speed. Incredible. This is another reason that I love triathlon, and running specifically. You are always finding something new within yourself. I wonder what else is in there?