Be careful when studying the technique of top sprinters and then trying to emulate it. You can easily fall into a trap because there’s a big difference between how it looks and how it feels. This is the single most important thing I learned from my brief training time with Charlie. Simply step down. All you should feel are your legs moving up and down in front of your body. The rest happens too fast to feel it (or at least it should). It almost feels like you’re just stamping your feet up and down.
Same thing with arm drive. Pull the arm down in front of your body, not back. Think vertical motion with the arms and legs.