If you subscribe to my youtube channel, you might have seen this about a week ago. It's a video of me sprinting with some frame by frame commentary and analysis. The point of the video is to show how the arms and legs are intricately linked.
Too often, we all try and work on running form in isolation (which is why Drills are no good), when in reality we need to look at it as a whole. The various segments of the body do not work in isolation as if we were doing butt kicks. Instead, it's an entire integrated whole where the various segments interact and can influence subsequent movements or other segments. In addition to isolating segments when doing form work, many also isolate segments when analyzing form. Most of us coaches have a checklist of things that should be happening (footstrike, arm angles, shin angles, body position, etc.) and if one of those things is incorrect, we focus solely on that segment. For instance, if the runner is reaching out with his lower leg and heel striking, when we work on form we focus entirely on getting the foot down sooner. Instead, the foot being out in front could be a symptom, not the problem. Often times, what comes out as being visually "incorrect" is often a symptom of a problem elsewhere.
In this video, I'll show one example of how the arms and legs interact. In this case, an incorrect lower leg movement is a symptom of something going on in the arms. If we only focused on the legs, I couldn't correct it no matter what I tried because it isn't the cause, it is merely a symptom. That's why we need to take a whole body approach to movement.