There seems to be a wide range of opinion on the ability to change running mechanics. I am off the opinion that you change running mechanics. This was reinforced to me yesterday when I was watching the baseball team that I work with do some running. Because of Christmas vacation I had not seen them in awhile, the head coach was doing the running so I was able to stand a little further back and observe. The changes in running mechanics were nothing short of astounding. It stood out in contrast to the players who had just come out from football.
That being said it is not an easy process, it is time consuming and demands tremendous focus and attention. It is not just about doing sprint drills, in fact that is a minor part of it. I think it is matter of making connections. Proper strengthening throughout the kinetic chain is crucial. For nearly thirty years I have used the same system- PAL System™ an acronym for Posture, Arm Action and Leg Action. We use that to analyze the mechanics and then attack the areas where the athlete must focus to improve. I never stray very far from the whole action. There are specific drills for each component, but those drills are quite simple and never really isolate, they just highlight an area.
It takes time. How much time? In general I would say six weeks to see significant changes. After that it requires constant attention to maintain the changes. Also it is important to recognize that each athlete has a movement signature, a little personal quirk that is essentially a movement fingerprint. I have learned to ignore those most of the time, because they do not significantly impact running form and they are tough to eradicate.
Proper strength training and Plyometric work play a huge role. I will talk about that in another post. In summary if you take a systematic approach based on sound biomechanical and motor learning principles running mechanics can be significantly improved.